Rail Wheel Factory In Plant Training Report

2011 In Plant Training Report

Submitted By o Yamani Praneeth o Venu. M o Salman Ali

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In Plant Training Report On

Railway Wheels and Axle Manufacturing Submitted By The Students Of Bachelor Of Engineering In Mechanical Engineering

In Plant Training Carried Out At

RAIL WHEEL FACTORY Yelhanka, Bangalore

Submitted By :Yamani Praneeth

1NT09ME114

Salman Ali

1NT09ME091

Venu. M

1NT09ME104

External Guide Mr. Prabhakar SSE / TTC

Nitte Meenakshi Institute Of Technology Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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Acknowledgement This In Plant Training would not have been possible without the support of many people. We wish to express our heartfelt gratitude to Shri DAYANANDA NAIK , PRINCIPAL/TTC who was abundantly helpful and offered invaluable assistance, support and guidance.

Deepest gratitude are also due to the section engineers without whose knowledge and assistance this training would not have been successful.

Special thanks also to our Head of Department Dr (Wg Cdr) P B Shetty for sharing the literature and invaluable assistance and permitting us to perform this training.

We also thank all the operators in shop floor of RWF who helped us to complete our training and guided us all the way. Lastly, we extend our gratitude to our families for their support and those who have directly or indirectly helped us to complete this training successfully.

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Abstract Indian Railways is the largest railway network in Asia. The wheels and axles for the entire Indian railways is manufactured and supplied by RWF (Rail Wheel Factory) Yelhanka, Bengaluru.

This report contains the brief procedure carried out in RWF to produce rail wheels and axles. The materials required for the productions, processing and also the test carried out on the components such that they do not undergo any damages during working

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Table of Contents Company History

•

Profile

•

Overview

•

Production

Wheel shop •

Forging Shop

•

Casting shop

•

Cleaning shop

Axle shop •

Forging

•

Machining

•

Assembly

Material Testing

•

Destructive testing

•

Non-destructive testing

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Company History Till early 1980s Indian Railways was importing about 55% of requirement of wheels and axles. Indigenous capacity was available only at Tata Iron & Steel Company [TISCO] and Durgapur Steel Plant [DSP]. The TISCO plant was technically not capable of meeting the changing requirement of wheels and axles for the new designs of rolling stock and production was discontinued. DSP was only able to partially meet Indian Railways’ needs. The cost of imports was high with prices rising in the world market. Financing of imports, delays in supplies and limited availability of foreign exchange adversely affected wagon production and rolling stock maintenance. It was in this context that in the early 1970s the Railway Ministry felt the necessity for setting up a new specialized Production Unit for manufacture of rolling stock wheels and axles as import substitute. The ultimate objective was that DSP and the Rail Wheel Factory [RWF, formerly Wheel & Axle Plant] should be able to totally meet Indian Railways requirement for standard wheels and axles so that their import could be stopped. An extensive study was made of the latest technology and equipment available globally possibility of collaboration and foreign exchange requirement. Based on this study the Rail Wheel Factory project was conceived in the mid-70s with IR deciding to: Adopt the cast wheel technology developed by M/S Griffin Wheel CO., USA for wheel manufacture. American Railroads have been using cast wheels for freight operations while European Railways use forged wheels. Adoption of cast wheel technology was found more suitable as the productivity of the plant is higher and cost of production lower as compared to forged wheels. The net saving in foreign exchange on wheel imports was estimated at Rs.8 Crores per annum. 

Undertake axle forging on special purpose Long Forging Machine followed by heat treatment furnaces with automated conveyors for movement of axles. 

Provide axle-machining facilities incorporating profile copying lathes, special purpose end machining equipment and a wheel set assembly complex with integrated engineering for handling and movement of axles. 

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Profile Rail Wheel Factory (earlier known as Wheel and Axle Plant) is situated in Bangalore, India. It is a state-of-the-art plant, meeting bulk of the requirement of wheels, axles and wheel sets for the Indian Railways. The spare capacity available is profitably utilised to meet the domestic demands for non-railway customers and exports. RWF strives to build successful and lasting relationships with its customers by consistently exceeding their expectations. Customer focus and quality remain our watchwords. The plant is certified to ISO-9001: 2000 and ISO-14001: 1994 standards by M/s. BVQI. It is also certified to confirm to the Quality Assurance Program of Association of American Railroads (AAR) in respect of manufacture of new wheels and axles. All products are subjected to stage and final inspection, starting from the chemical composition of the molten metal till the final inspection. This includes micro/macro properties of the material, Magnetic Particle Testing, Ultrasonic Testing, Hardness, warpage, dimensional parameters, surface finish etc. All their products are accompanied with a Quality Assurance Certificate and carry a warranty of one year from shipment. RWF has the full capability to design and manufacture any size of wheels, axles and wheelsets to suit individual customer’s special requirements.

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OVERVIEW The Indian Railways are one of the largest in the world under a single management. They employ the largest manpower as compared to any other enterprise in the country. They also own the heaviest assets and rail track length of over one-lakh kilometres and are operating the railways with nearly 5 300 locomotives, 39,000 passenger vehicles and 3.5 lakh freight cars. The size and magnitude of the railways can be better appreciated when we realize that their Railways run more than 1.5 lakh train kilometres every day carrying nearly one crore passengers and nearly 67 lakh tons of originating freight dally, there by earning over Rs.4 500 crores of revenue per annum. While on the one hand the Railways have been striving hard to meet the transport needs of the country and to provide more and more amenities, they have also been struggling to improve the health of the railways and to rehabilitate its aging assets. To achieve the astronomical results of performance mentioned above It Is Imperative that the railways explore all possibilities of the country becoming self-sufficient in all Inputs. Not only for repairs and rehabilitation of the aging rolling stock but also for manufacturing additional rolling stock to meet the Increasing demands the requirements of wheel and axle are also increasing. These are two of the heaviest components of the Railway Wagons and coaches, which play the most crucial role towards safety. . The foundation stone for the wheel unit of the Rail Wheel Factory at Bangalore was laid by the then Railway Minister Shri.Kamalapathl Trlpathi in October 1980. The task involved in putting up this plant at a huge Investment adopting the latest technology was really stupendous and It Is a matter very great pride not only for the railway men but also for the whole of the Nation that with the help Of Indian Engineers workers and Industry it has been possible to cast the first wheel In about 3 years’ time from the date of laying of the foundation stone. After detailed study, It was decided to adopt "Cast Steel Technology" for the manufacture of Wheel through the controlled pressure pouring technique developed by M/s. Griffin Wheel Co., USA and the "Long Forging Technology" for the manufacture of Axles, which has been mastered by M/s. GFM, Austria (Europe) A great advantage in adopting the Griffin Technology Is that the arising of scrap wheels, axles, rail and heavy sections of steel from the railways own system can be recycled to produce new wheels.

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Productions Wheels RWF manufactures cast steel wheels by a controlled pressure pouring process. In this process, the raw material used is pedigree scrap (old used wheelsets, axles etc, rejected as unfit for use by the Railways). The scrap steel is melted in Ultra High Frequency Electric Arc furnace. The correct chemistry of molten metal steel is established through a Spectrometer. The wheels are eventually get cast in the graphite moulds, which are pre-heated and sprayed. After allowing for a pre-determined setting time the mould is spilt and the risers are automatically separated from the cast wheel. The wheel is then subjected to various heat treatments. The wheel undergoes the process of cleaning, checking, peening and various stages of inspections. The wheel produced by this process requires no machining except the precession boring of heats central hole (hub) where the axle has to be fitted.

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Axles RWF buys high-quality vacuum-degassed steel blooms from large-scale steelmakers. Axles are manufactured from billets cut from the blooms. These blooms are forged in a precision long-forging machine supplied from M/s GFM, Austria. The billets are heated in a rotary hearth furnace to forging temperatures. Billets then forged in axles on a special purpose long forging machine. The forged axles are gas cut to required length. The axles are heat treated through various heat treatment processes. The physical properties are confirmed before machining of the axles. The forged axles are machined on various machines. The operations include end machining, rough turning, finish turning, machining centres, grinding and burnishing. Internationally standardized tests (ultrasonic, magnetic particle, etc.) are used to confirm the quality of the axles.

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Wheel Sets The assembly of wheel sets is done on a highly automated wheel assembly complex. The wheel seat size of the axles is measured on an automated measuring unit and the dimensions are transferred to two wheel borers. Paired wheels are custom bored as per the wheel seat size to get correct interference fit. The wheels are then pressed on axle in a 300 T Wheel press.

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WHEEL SHOP

The first unit of Rail Wheel Factory is wheel shop where Railway wheels are produced. The wheels of a vehicle are the circular objects which are fixed underneath. It enables the vehicle to move along the ground. The railway’s wheels are circular objects made up of alloy steel and weigh about 500 kg. There is variety of railway wheels. All types are produced in the same manner but they differ in their dimensions. The wheel sits on the wheel seat of the axle. In rail wheel factory, the wheel shop is divided into 3 portions where different operations are performed on the wheel.

The Three parts are: 

Melting Shop



Casting Shop



Cleaning Shop

Each shop is explained further in detail.

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MELTING SHOP In the wheel shop of Rail Wheel Factory, the wheels are manufactured by casting process. For this process molten metal is required. Hence the first process for the manufacturing of railway wheels in the wheel shop is Melting of Metal scrap.

Melting is a process of converting the solid metal scrap into molten metal which can be used for casting any shaped solid or hollow structure. When the temperature is raised very high i.e., to a temperature above the melting point of that particular metal, under a very sophisticated environmental condition, the solid metal changes its phase into liquid. This is the basic principle of melting.

The furnace used in RWF for melting is ELECTRIC ARC type of furnace and the charge used for producing molten metal are rejected wheels, axles etc.

ELECTRIC ARC FURNACE: An electric arc furnace utilizes the heat produced by the electric arc generated between two conducting materials to melt the charge. It is used for melting cast iron and steels. High thermal efficiency, rapid heating, close temperature control and strict atmosphere are few characteristics of the furnace that lead to the production of good quality metal.

Direct arc electric type of furnace is used in RWF wheel shop whose construction is as follow:

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The Furnace consists of a heavy steel cylindrical shell with a spherical bottom lined with refractory of the furnace that supports the charge and the walls are lined with magnesite bricks.

The furnace is built on a tilting platform that facilitates tilting of furnace forward for pouring molten metal into ladles. The furnace can also be tilted backwards for inspection, charging metal, flux, deoxidiser etc. and for removal of slag through slag door. 

The roof of the furnace is made of steel lined inside with refractory bricks and can be clamped in position. Metal can also be charged from furnace roof. 

The roof is provided with 3 circular holes through which nonconsumable graphite electrodes are inserted. The electrodes can be raised and lowered by means of guides and are usually water cooled to dissipate heat. They are connected to 3-phase power supply. 

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Charge: The charge used for the production of railway wheels in RWF is: •

The rejected (damaged) axles from axle shop.

•

The rejected wheels from wheel shop.

•

Used axles and worn out wheels.

•

The chips formed during machining of axles

The main material composition of the scarp is alloy steels, carbon, manganese and silicon. Note: The composition for casting of wheels can be altered by re-carburising or decarburising the molten metal in the furnace in order to obtain the required wheel material composition.

Scrap(rejected wheels)

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Melting Process: Arc furnace works on the principle that, when an arc is struck between the electrodes and charge material, heat is generated due to the resistance offered by the metal charge. ❖Level the furnace, remove the roof mast lock pin, raise the electrode and then raise the roof of the furnace. ❖Charge approximately 900 to 1200kgs of claimed lime and 200 to250kgs of claimed petroleum coke/graphite powder. ❖ Charge scrap wheels or metal cakes/skull or risers with the help of magnet (2-2.5MT approximately) ❖ The electrodes are lowered down. On supplying the necessary current and voltage, an arc is produced between the electrode and the charge material. ❖ The gap between the electrode and charge is maintained by regulating the movement of electrodes so that the arc remains between them and bums continuously melting the charge material. The flux melts and forms a slag that floats on the surface of the liquid metal. The slag prevents oxidation, refines the metal and protects the furnace roof from excessive heat.

REMOVAL OF SLAG: After the liquid metal has been achieved the desired temperature, the electrodes are raised to extinguish the arc and the furnace is tilted backwards to remove the slag. After 45-55minutes of arcing, start emptying the scrap through slag door with oxygen lancing pipe. Spread dolomite over the cleaned slag door. Clear slag door scrap. Remove full slag before the temperature is 1630 degree Celsius. If the slag is sluggish, shovel 25 -30kgs of fluorspar on the slag. ❖ Temperature must be controlled so that the maximum slag is removed by 1650 degree Celsius. Allow only thin layer of slag on the metal surface.

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❖ Care must be taken not to remove the metal through slag door throughout the slagging operation. Keeps the slag door clean by removing the slag metal jam using pipe or rod. ❖ After almost all first slag is removed add Ferro-manganese at around 1650 degree Celsius and 150kgs of reducing slag mixture into the furnace to make the slag reducing.

TAPPING OF MOLTEN METAL: ❖ Once the slag is taken out and the chemical composition of the molten metal is tested and is same as required lift the ladle from John Mohr Pit (JMP) with the help of crane and pours the molten metal to the ladle from the furnace. ❖ Insulation powder is thrown into ladles to prevent radiation loss of liquid metal.

❖ Excess molten metal which cannot be poured into the ladle may be emptied into pigging pot or dirt floor.

Note: The sample of molten metal is taken from the furnace at different temp. and is tested for its composition and there by its properties by spectrometer analysis. The composition is altered de-carburising or re-carburising of molten metal.

RE-CARBURISING OF METAL  Keep the required quantity of graphite powder ready in small quantities, filled in gunny bag; maintain the bath temp. around 1640 Celsius minimum

 Lower the electrode column into the molten bath, such that the electrode is just inside the bath. Introduce the graphite powder into the molten bath, near the electrode column through the slag door.

 Push the cake fallen on door inside the furnace metal bath by rabble. Put on the powder in whichever tap is required.  After 3-4 minutes of arcing, mix the bath thoroughly using metallic rabbles. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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 Insure that the bath is uniform and no graphite powder is floating on the top of the bath. Take the sample with the slag pre coated spoon from deep inside the bath. After 3-4 min take one more sample in the similar way.

DECARBURISING OF METAL :  The temperature of the metal must be maintained around 1630-1640 Celsius. Coat the front end of oxygen pipe with furnace slag.  Insert the slag coated oxygen lancing pipe into the bath through the slag door and blow the bath with oxygen at 5-6kg/cm depending on the carbon to be reduced. After the oxygen blowing add 10-15kg of Ferro silicon to take care of high oxidised metal, when necessary  Add 30-40kgs of Ferro manganese or silicon manganese to raise manganese level in the bath and to take care of extra oxygen in the metal. Put on power.  Mix the bath thoroughly with the rabble. After 3-4 min of arcing, take the sample from deep inside the bath for test. Again after 3-4 min take another check sample.

 The ladles are then taken into JMP from where the metal is poured into the cope and drag assembly for casting.

Note:  There are three electric arc furnaces in RWF and two JMP  For each heat the furnace produces 20tonnes of molten metal in a period of one hour , which is used to cast 30 Wheels  The furnace temp during melting is set to 1720 Celsius and during pouring into ladle; the temp of molten metal is around 1610 Celsius.

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CASTING SHOP: In this part of the wheel shop the molten metal is poured into cope and drag assembly, later the caste wheel is separated from cope and drag assembly and is made to undergo certain heat treatment process. CASTING: The casting process begins with pouring of molten metal into cope-drag assembly, a small period of air cooling and finally separating the cope-drag assembly to obtain the caste wheel.

❖ The ladle containing the molten metal placed in JMP is brought into the place of pouring and graphite powder is sprayed into molten metal to prevent temperature loss.

❖ Cope and drag made up of graphite material is assembled and it is also brought near the place of pouring. ❖ This cope-drag assembly is placed on the covering of the ladle which contains a centre circular hole. This hole houses the — pipe through which molten metal gets into the cope-drag assembly.

❖ When external air pressure is applied on the covering of the ladle, the liquid metal with high pressure comes out of the ladle through the centre — pipe and gets into the cavity present in cope-drag assembly.

❖ Once this cavity is filled with molten metal, a graphite stopper present in the cope and drag assembly will fall down to the bottom of the drag and prevents the further flow of liquid metal from ladle into cavity. Also it prevents the liquid metal flowing back to ladle from cavity.

❖ The pouring of molten metal for each wheel takes about 80 sec and 30-31 wheels can be cast in each heat. ❖ Once metal is poured, paddy husk is added to the assembly through riser holes to prevent sudden drop in temp of molten metal which otherwise would produce cracks in the surface of the wheels. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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❖ After 11 minutes of air cooling, the cope and drag assembly is split and the caste wheel is obtained which is placed In Kiln where the wheel is subjected to controlled air cooling. ❖ The separated cope and drag are sent separately and cleaned in various ways: First the metal present in sprue and riser are taken of the cope and later both cope and drag and sand washed to take out every little metal present and also to produce clean and finish surface so that it can be used for next casting.

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SPRUE WASHING: After the controlled air cooling the wheel coming out of the kiln is at a temperature of about 400-600 degree Celsius. It contains a little part of the runner and riser which is not removed during splitting. The part must be removed before the further cleaning of the wheel. This is done in 2 ways: 1.

Sprue grinding.

2.

Induction process by electrode.

SPRUE GRINDING



In this method, the excess sprue material is removed by using grinding wheel.



A grinding wheel mounted on the horizontal spindle is brought on the caste wheel and hence the excess material is removed by the abrasive action of the grinding wheel.

INDUCTION PROCESS



In this method a carbon electrode with copper coating is used to remove the excess sprue material.



Once the electric current is sent through the electrode it produces a strong electric arc between the carbon electrode and the wheel. The heat produced by this arc is more than enough to melt and vaporize the excess metal.

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NOTE:



The temperature of the wheel should not be less than 380 degree Celsius before entering sprue washing.



The long rod placed in the centre during casting is cut just before sprue wash by grinding plate.

HUB CUTTING:

The centre portion of the wheel, where the axle fits in, need to be bored in order to remove the caste portion from the wheel. This is done by up cutting process. 

The hole is initially bored for a diameter lesser than required during this process using Hub Cutting Machine. Hence the process is also called Hub cutting process.



The oxy-acetylene gas flame coming out of the nozzle at high pressure and velocity is used for hub cutting.



The part of the pipe inserted during casting remains inside the caste wheel after being cut at both the edges. This is called Pilot hole.



This hole is initially cleaned using pneumatic air, so that the hub cutting process can be begun from this portion.



The oxy-acetylene gas flame is first directed to the pilot hole and then moved along the radius and finally moved in a circular shape.



Hence the circular hub which is being cut falls after the arc completes a circle of required radius.

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NOTE:

• The nozzle of the machine need to be regularly changed to prevent hub not falling situation i.e., if insufficient flame is supplied for cutting due to defects in the nozzle, the hub is not completely cut through the whole depth of the wheel. Hence, the cut portion will not fall after complete circular path of the flame The distance of 8-12mm must be maintained between the nozzle tip and the back hub face for proper cutting action.

HEAT TREATMENT It is defined as an operation or combination of operations involving heating and cooling of a metal/alloy in solid state to obtain desirable conditions or proportions.

OBJECTIVES OE HEAT TREATMENT



To eliminate residual stresses that is present in the axle during forging and subsequent cooling.



To homogenize the structure of the metal of forging.



To impart, to the axle that degree of hardness, this makes it most easy to machine. To improve strength, toughness and other mechanical properties of the forged axle.



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NORMALISING: The wheels after hub cutting remain at a temperature of about 400 degree Celsius. It is now sent into the Rotary Hearth Furnace for Normalising process. Normalising process helps to maintain proper grain size which is the main requirement for various properties of the wheel •

The rotary hearth furnace used for normalising has 7 zones. First 4 zones are called as pre- heating zones, where the outer Layer of the wheel and a few inner layers get heated. • The next 3 zones are called Soaking zone where in the heat spreads uniformly including the core of the wheel. • The temperature of these zones varies for different types of Wheel. E.g.: for BOXN wheels Zone1 and 3 is 968 degree Celsius Zone 3 to 7 is 938 degree Celsius •

The fuel used in rotary hearth furnace is High Speed Diesel.

• Each wheel remains in rotary hearth furnace for a duration of 1.5 hours before coming out. • The temperature of the wheel coming out of the furnace is around 950 degree Celsius.

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Rotary Hearth Furnace

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QUENCHING: During the movement of the train, the rim portion of the wheel is in contact with the rail and hence it is this portion that is subjected to more wear and tear. Therefore this rim of the wheel must be harder than the other parts of the wheel. This hardening is done by quenching process. High pressure jet of water is made to fall only on the ream portion of the wheel for about 6-8 minutes. This increases the hardness of the ream portion up to a depth of 5-8mm.

TEMPERING:

Since the wheels are manufactured by casting process, there are chances of internal stresses being induced in the interior of the wheel. These stresses are very dangerous and may also damage the wheel during working. In order to remove these stresses from the wheels, they are sent into Draw Furnace where the wheel undergoes tempering process.

• The Draw furnace consists of 8 zones maintained at 500 degree Celsius each. • Each wheel once entered the Draw furnace remains inside for 2 hours before coming out of the furnace. • The Draw furnace in RWF is run using high speed Diesel and has a capacity of 40 wheels.

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HUB QUENCHING:

During the assembly of the wheels with axels there are chances of crack formations in the hub portion. Hence this portion needs to be hardened. This hardening of the hub portion is done by Quenching Process. High pressure jet of water is sprayed only on the interior of the hub during this process. Hence the hub portion becomes harder after this process and the chance of crack portion is totally reduced.

The wheel after hub quenching has a rough surface and is air cooled. The wheel need not be air cooled separately, they are sent into storage yard after hub quenching. Wheels are taken from storage yard as and when required and is subjected to further cleaning and finishing process.

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WHEEL FINAL PROCESS SHOP CLEANING: The Wheel coming out of the casting shop has a rough, uneven surface these wheels need to be cleaned and finished before its usage. This cleaning, finishing and certain tests are conducted in this cleaning shop. The operations carried out on the wheel in cleaning shop are discussed below:

SAND BLASTING/STEEL BLASTING:

The surface of the wheel may contain dirt, ashes and even dust particles formed during storing; also the wheels contain scales formed during heat treatment process. This unwanted dust must be removed In order to obtain a clean surfaced wheel. Steel blasting is the first process carried out in the cleaning shop. In this process, tiny spherical metal particles with high velocity are made to strike the surface of the wheel. Due to the impact of these particles the surface dust present on the wheel gets removed due to the abrasive action. Hence the surface cleaned wheel is obtained after this steel blasting process.

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After this steel blasting, the wheel is made to undergo two tests namely Ultra Sonic test and Magnaglo test. Only those wheels passed in these test are sent to further processing and the wheels with defects are sent back to machining accordingly. The rejected wheels are sent to scrap yard and is recycled.

WARPAGING:

The wheels during casting and heat treatment process remains at high temperature. During this high temperature there are chances of wheel undergoing a little bending. But this bending of wheels above certain limits is undesirable for the working of the wheel. 

The Warpaging process includes the balancing of the wheels from which the defects relating to the shape of the wheels can be detected.



If the detected defects in the shape like bending of wheels etc. are more than the limiting value, wheels are rejected.

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SHOT PEENING: 

Peening is a process very similar to steel blasting process.



Here tiny spherical steel particles are made to strike the surface of the wheel at high velocity.



In case there arc surface cracks, when the steel particle strikes the cracked surface at high velocity, they will fill the gap and help to remove the surface defects.



Peening process also removes the surface stresses.



Each wheel undergoes peening process for minimum of 1 minute.

HUB BORING: This is the rough boring operation carried out on the wheel before it is sent into assembly shop. During hub cutting, the centre hole generated is of a smaller diameter when compared to the required diameter. This hole need to be enlarged for the axle to fit in. This hole enlarging is done by the boring process o A square shaped carbide tool is used for this operation o The hole of 3mm lesser than the axle wheel seat diameter is produced during this process. o The hole produced has a rough surface finish.

This completes the manufacture of railway wheels. Thus the wheel after boring comes out of the wheel shop and is ready to be assembled along the axle and hence ready for working.

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AXLE SHOP The

second unit of RWF is axle shop where the railway axles are produced. An axle is a cylindrical rod on which the wheels of locomotives are seated and hence helps to maintain the distance between the 2 wheels. There is wide variety of axle for different type's vehicles. The railway axle is a long thick cylindrical rod made up of alloy steel and weighs about 500 kg, The axles mainly consists of 4 parts namely Body. Wheel seat. Dust guard and Journal. Major portion of the axle is the body whose length is fixed and is equal the distance to be maintained between two parallel wheels. Hence the length of the body which is the centre portion of the axle varies for different types of axle. The portion of the axle where the wheels of the train is fixed is the wheel seat. The diameter and the length of the wheel seat are completely based on the diameter of the bore in the wheel and its thickness. The curved portion between the wheel seat and the journal is the dust guard. The two ends of the axle are after the dust guard is called the journal. The journal is the main portion which is required in a perfect smooth finished surface state. The bearings of the train wheels occupy this place. In RWF the axle shop is divided into three portions where different operations are performed on the axle. The three portions - Forging shop, Machining shop and Assembly shop.

o The blooms are cut and are given the shape of axle by forging and later heat treated in the forging shop. o The axles to the required dimensions are machined in the machining shop. Certain tests done to check cracks. o The finished axles are assembled along with wheels in the assembly shop.

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FORGING SHOP Forging is the process that involves deforming of hot metal piece to a desired shape using compressive forces. The force may be impact type, like a blow from a hammer or a squeeze type, like that of Hydraulic press. In RWF the axle are produced by forging process. Here the long blooms are cut into small piece called billets which are later given the shape of the axle by forging. Forging, because of its inherent improvement in the grain size and introduction of uninterrupted grain flow in the finished Component has the following advantages: o o o o o o

Greater toughness and strength. Reduction of weight of the finished part Saving in the material. Elimination internal defects, such as cracks, porosity, blow holes etc. Ability to with stand unpredictable loads during service. Minimum machining to be done for the work piece.

CUTTING: The long bar with square cross section called Blooms are cut into small length pieces called Billets by Gas welding. The Billet Cutting machine is an automated machine with feed speed of approx. 20 mm/min and capacity of 9 Billets/hr. The fuel used is Oxy-Acetylene gas. The gas flame with a pressure of about 10 bar is directed on the work piece and cutting action is performed. The cutting is based on length to weight ratio. NOTE: One sample piece of the bloom from each batch is taken for testing. e.g. Loco-Axle (Diesel axle) Cut piece length- 975mm Length after forging- 2523mm

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HEATING: The billets after being cut must be heated so that it can be forged. The Rotary Health Furnace having four zones namely Pre-heating zone, heating zone, soaking zone 1 and soaking zone 2 is used for heating the billets to a temperature of about 1185 - 1200 degree Celsius. The billet first enters the pre-heating zone where the heating process begins. Further it moves to the heating zone. In the soaking zone 1 and 2 is the spread to the core of the work piece. The fuel used is High Speed Diesel (HSD). The pressure inside the RHF is set to 10 bar. The temperature of the flue gas coming out of RHF is around 600 degree Celsius.

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FORGING: The red hot billet is now sent to forging machine in order to obtain the required shape. Forging is the process that involves deforming of hot metal piece to a desired shape using compressive forces. The force may be impact type, like a blow from a hammer or a squeeze type, like that of Hydraulic press. For forging, the work piece is heated to a proper temperature so that it gains required plastic properties before deformation. The forging machine used here is a Long Forging Machine which consists of four hammers each of which exerts a pressure of , about 800 tons. The hammers operate through power and the pressure ; is applied using hydraulics. During operation the temperature of the billet will be around 1180- 1200 degree Celsius and at this temperature it is forged into the required axle shape. The hammers are made of special steel alloy and hence water is sprayed during operation so that the hammer does not wear out.

END CUTTING : The forged axle is of excess length than the required hence this excess material from both the ends is cut off using a gas torch. The end cutting machine consists of two gas torch whose centre distance can be adjusted depending up on the actual axle length. The required oxy-acetytene gas at high pressure is used to cut the axle which is still at a higher temperature (1000 degree Celsius). During operation, the two torches are fixed to a centre distance equal to the sum of required length, shrinkage length (1%) and the torch thickness and cutting performed. The high pressure (10 bar) gas flame is brought near the work piece which is held by stands. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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NOTE: Water is not used as the work piece is still in red hot condition and spraying may results in the formation of cracks. Once the excess material is cut off axle is then sent for stamping operation. In this process the stamping machine punches/ stamps the axle with numbers (unique for each axle) which includes different coding.

COOLING: After end cutting and stamping the axle is still at high temperature. In order to do further processing and enhance the properties of the axle, it must be cooled. Air cooling helps the axle to loose heat by radiation. During cooling the axles are placed on a bed. Each cooling bed is of 30 axle's capacity. Once the 30th axle is placed on the bed. it is air cooled for about 2hrs 25mins. Heat from the axle is radiated out and forms thermal equilibnum with the surroundings. Each axle after cooling is sent into The Normalizing Furnace.

Normalizing : Once the cooling is done the axles are sent into normalizing furnace. • Normalizing consists of heating steel about 40-50 degree Celsius above its upper critical temperature and if necessary holding it at that temperature for a short time and then cooling in still air for at room temperature. • The cooled axles once entered into the normalizing chamber are placed on the base of the furnace and fire is set on the sides of the furnace. The fuel used is high speed diesel (HSD). • The type of structure obtained by normalizing will depend largely on the thickness of cross section as this will affect the rate of cooling. Thin sections will give a much finer grain than thick sections

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Quenching: Not all types of axles require quenching. Only a few types of diesel axles are quenched in quenching agent (polymer oil) for a period of 30 mins depending on the carbon content present in the material of the particular axle. Quenching is defined as sudden cooling of heated steel (metal) by dipping in cooling agent or spraying cooling agent in order to obtain the work piece in a stable state which induces certain properties iike hardness etc to the work piece material. A mixture of polymer oil and water in the ratio 1:20 is used as quenching agent in forging shop of RWF. The axles which do not require quenching are sent directly to tempering chamber after normalizing. Diesel axles are sent into tempering chamber after quenching.

Tempering :

It is necessary to return towards equilibrium after quench hardening, by heating the steel to a temperature below the critical temperature. This is tempering. Tempering also reduces the internal stresses in the axles which may have induced during heating, forging or quenching.

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Axle Machining Shop The axle coming out of Forging Chamber are of dimension greater than required, only rough shape and have very rough surface. These axles cannot be used directly. Hence in order to obtain exact dimensional, required shape and a perfect surface finish machining has to be carried out. Metal cutting is a process of removing a layer of material from the metal blank by means of a tool, which is harder than the metal being cut. The layer of metal is removed is called as chip and this removal is due to plastic deformation or controlled fracture in the metal blank.

CUTTING TOOL: A cutting tool is hard metal piece used for the removal of metal layer during machining. It is made of material which is harder than the metal to be cut. Tools are usually made of High Speed Steel (HSS), Carbides, Ceramics, and Coated Carbides etc. Chip removal in the metal cutting process may be performed either by cutting tool having distinct cutting edges or by abrasives used in grinding wheels , abrasive sticks etc. These abrasives have a very large number of hard grains with sharp edges which remove metal from the work piece surface in such operations as grinding. Single point cutting tools having a wedge like shape; find a wide application on lathes and slotting machines. Multi point cutting tools have merely two or more single point cutting tools arranged together as a unit. Milling cutter, drill bit, grinding wheel, broaching tools are some of the examples.

CHIP FORMATION: In the process of metal cutting, as the cutting tool moves forward, The work piece material ahead of the tool passes through the shear Plane. The advancing tool removes the work piece metal along the shear Plane in the form of chips. The chips formed may be continuous chips, continuous chips with built-up edge or discontinuous chips. A continuous chip is formed when the workpiece material is ductile. Eg: Mild steel, copper etc • Continuous chips with built up edge are formed when alloy steels, tool steels etc are machined where large cutting forces are required. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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• When brittle materials like cast iron bronze etc are machined, discontinuous chips are formed. Continuous chips are desirable since it creates a smooth finish on the work piece, absorb less power,create less machining noise and enhance tool life.

NOTE: Most of the heat produced during cutting action is carried away by chips and hence prevents the tool from overheating.

COOLANTS: During metal cutting extensive heat is generated due to the friction between the tool and work piece Also, as the chips slides up the tool face, heat is generated due to friction at the contact points between chip and tool face. The excessive heat thus generated can damage the microstructure of both the cutting tool and the work piece. In order to reduce the effect of friction or heat generated,Cutting fluids are used. A cutting fluid or a coolant is a liquid, added to the cutting zone to reduce effects of friction between the tool- work and tool-chip interface by way of cooling and lubrication A cutting fluid must have high specific heat, thermal conductivity,good lubricating oil, non-corrosive, and non-toxic, odorless and must have low viscosity. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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A coolant may be oil based (containing petroleum) or chemical fluids containing synthetic oils etc. Machining of axles is carried out in various steps. It begins with initial rough turning followed by drilling, reaming, tapping, smooth turning and finally grinding. The different machining operations of axle are carried out either by conventional method or by programmed CNC machines in Rail Wheel

In the conventional method the operator needs to guide all the Operations such as loading, unloading, feed, speed etc. The movement of each carriage or tool operation can be controlled at any instant by the operator. The dimensional accuracy obtained is in milimeter (mm) range. In the Computer Numerical Control (CNC) machines a program is initialy designed for the different operations of the axle and is fed into the system which activates the machine. The operations are carried out automatically once the machine is switched ON. A few parameters can be varied in the fixed program. The dimensional accuracy up to 1 micron can be obtained. Finaly the exact dimensional perfect axles are subjected to different tests like Ultra Sonic test etc. This completes the production of an AXLE. Hence the axle coming out of the axle machining shop is ready for use and is sent to Assembly.

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STATION I : End Milling,Centering and Cup Turning The rough surface axle coming from the forging shop is sent to station 1 in the machining shop were End milling; centering and Cup turning operations are carried out. The forged axle after under going various heat treatment process will have excess length and this must be cut to the required length with little amount of tolerance which is left for further machining. This excess material is removed by milling operation. The excess material is removed at the ends of the axle hence called as end milling. Milling is a manufacturing process in which excess material from the work piece is removed by a rotating multi point cutting tool called milling cutter. The multipoint milling tool consists of number of inserts which does the actual cutting job. During operation the stationary work piece is brought near to the high speed rotating [350 rpm] milling cutter which removes the excess material. The inserts used for milling are made up of Carbide and have 4 cutting edges. Each edge may be used for operating of 70 axles. Centering is producing a centre hole in the axle in order to hold the work Piece in further machining processes. Centering is followed by Cup turning where the excess material is removed and given surface finish only at the ends. This is done in order to hold the job in the chuck in further machining. R Both the Centering tool and cup turning tool are made of High carbon Steel (HCS) and are place on same spindle. The speed and feed Spends on the material of the axle to be machined. The tool life of cntering tool is of 200 axles. All the above 3 processes are carried out on both ends simultaneously.

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The coolant is used to reduce the heat generated during operation. Eg: For BOXN axle Feed (mm/min)

Speed (rpm)

End milling

270

350

Centering

60

350

Cup turning

135

350

STATION 2:- Rough Turning: Turning is a machining process used for the generation of external and conical surfaces on a rotating work piece by means of a single point traversing cutting tool. The process is performed on a lathe; where in the cutting tool is fed against a rotating work piece. The forged axle has scales and excess material on its surface. In order to remove this excess material rough turning is carried out through out the surface of the axle. The exact shape of the axle is obtained in this process and the surface of the machined axle after this operation is rough. During operation the axle is fixed between the chucks and made to rotate at a very high speed. The carbide tool having 8 cutting edged is fed against this rotating axle which removes the excess material in the form of chips. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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The material is removed from both the edged simultaneously i.e. the turning operation makes use of 2 tool at the same time in order to reduce the time of operation. In Rail Wheel Factory (RWF) axle machining shop rough turning is done by both CNC lathes and conventional lathe. In the CNC lathe the feed, the motion of the tool spindle/holder for each type of axle is programmed and fed into the computer which guides the cutting operation. Various parameters like length of the axle, feed, diameter of the axle, speed of rotation etc can be adjusted' altered by the operator as and when required.In the comentional lathe the tool holder is placed in the carriage and each lathe used for rough turning has 4 carriage's, two of which used for turning the body of axle while the other two for turning the wheel seat, dust guard and journal. The carriages are guided by the Templates which have the same shape as that of the axle to be machined. As tracer placed in the carriage traces the template, tool carriage and hence the tool moves along the same shape; hence the required shape is obtained on the axle. Each parameter like feed, speed, carriage movement etc can be controlled by the operator. The process can also be automated and can be stopped and adjusted at any point of time. NOTE: A dimensional accuracy up to I micron can be obtained in CNC machine while accuracy up to 1 mm can be obtained in conventional lathe.

STATION 3: Drilling. Reaming and Tapping After rough turning of the axle, threaded holes are drilled at the two ends surfaces in order to fix the bearing to the axle.

Drilling Drilling is a machining operation of producing a cylindrical hole in a solid work piece by means of a revolving tool called the Drill bit. Drill bit is also called as twist drill since it has sharp twisted edges formed around a cylindrical body. It is made up of HCS.

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In operation, the drill bit is held in the chuck of the machine and rotated by a spindle at high speed , With the help of the hand wheel or ty automatic means, the drill bit is forced to move against the rigidly clamped work piece. The hole is generated by the sharp cutting edges of the rotating drill bit while the excess material removed (chips) gets curled and escapes through the helical grooves provided in the drill bit Since the cutting action takes place inside the work piece, lot of heat is generated: this may cause damage to the tool as well as the work piece. Hence coolant is used to reduce the heat, Both the ends are drilled at the same time.

Reaming: Reaming is the operation of finishing a previously drilled hole to bring it to an exact size and to improve the surface finish of the hole. The operation is earned out using a multi tooth revolving tool caller Reamer, which consists of a set of parallel straight or helical cutting edges along the length of the cylindrical tool. This operation is carried out at a speed lower than drilling in order to obtain a good surface finish.

Tapping : Tapping is the operation of producing internal threads in a previously drilled hote by means of a tool called tap. The tap has threads cut on its periphery and is hardened to improve its properties,The threads cut on the tap form the replica of the threads to be produced in the work piece Taps are available in standard sizes. To generate a specific size thread in the work piece, a hole with diameter smaller than the size of the tap is first drilled using twist drill. To perform the tapping operation, the tool is held rigidly in the spindle and is rotated at a speed less than drilling operation. The rotating tap is fed slowly in the hole of the work piece to cut the material and produce threads.

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Note : All the three drilling,reaming and tapping tools are held in same spindle but speed is varied for respective operations. These tools are made up of HCS. Operations are carried out simultaneously on both sides.A continuos supply of coolant is required in order to reduce the heat production and wash away the chips.

STATION 4: SMOOTH TURNING The rough finish axle is now given a good surface finish by turning operation. A six edged carbide tool is fixed in the tool holder and is fed against the rotating work piece. The feed given is very less (approx .4mm/rev) in order to obtain the perfect finish. The axle dimensions are same as required dimension, with tolerance of about 3-5 microns.This operations givse finishing to the body of the axle, while the dust guard and the journal is finished by the grinding wheel.

STATION 5: GRINDING The journal is the most important part of the axle since this bearing is seated on it. Hence the journal is given a perfect finish.This is done by grinding. The shape of the grinding wheel is same as that of the axles,dust guard and journals shape. Hence for diff. axles different grinding wheel must be used. Two wheels are kept on both the ends to finish both the sides of the axles. They operate one after the other. In operation the workpiece comes near to the wheel and gets fixed. Now the high speed grinding wheel approaches the axle due to which very fine material layer is removed from the workpiece due to the action of abrasive particles fixed on the grinding wheel. In the same manner the other side of the axle is also fininshed.

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Assembly Shop After the grinding of the journal portion, ultrasonic testing is performed in assembly shop. Also the finished wheel with rough centre is smoothend in the assembly shop o In assembly shop, the wheel seat diameter is exactly measure to each axle and wheel for the particular axle is centre bored to the measured axle’s wheel seat diameter by the vertical boring machine using octagon shaped carbide tool. o After the smooth surface finish boring operation the two wheels for one particular axle are sent for pressing. o The two wheels are hydraulicaly pressed, so that the two wheels sit on the wheel seat of the axle by using pressing machine one wheel after the other. This combination of thwo wheels and an axle is called Wheel Set. o The pressure to be applied on the wheel for pressing each wheel varies on diff. properties. Some times castor oil is applied on the axle during pressing in order to reduce the pressure on the axle. o The wheel sets obtained is measure by various guages (eg. Offset guage).

In case the distance between wheels is to be altered or any other minor corrections need to be done is corrected by damping machine.

Once the wheel set is inspected,it is painted to prevent the surface of the axle from rusting and the journal is covered and then transported to place where rest of the body parts of the train is manufactured.

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TESTING OF MATERIALS Welds, casting's and forgings are tested for one or more following purposes. o To asses numerically the fundamental mechanical properties like ductility, malleability, toughness etc. o To determine data i.e force deformation values to draw upsets of specification upon which engineer can base his design, o To determine the surface or sub surface defects in process parts. o To check chemical composition. o To determine suitability of the material for a particular application. Tests on jobs can be broadly classified as 1.

Destructive tests:

After being destructively tested, the component or specimen either breaks or remains no longer useful for further use. E.g. tensile test, impact test etc. 2.

Non- Destruction tests

A component does not break in non destructive testing and even being tested so it can be used for the purpose for which it is made. E.g. magnetic particle inspection, ultrasonic testing etc.

Destructive Testing Physical section will carry out various metallurgical tests on wheels, axles, consumables, maintenance spares accessories and failure investigations. The test shaft be carried on sample basis collected from the lot, to check the suitability of the product or component for its intended purposes or service, Based on the tests conducted on the samples collected from the materials can be assessed to its fitness to use further or not. Copyright ® Salman Ali Nitte Meenakshi Institute Of Technology

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Importance of These Test Tests are required to meet specifications. Specifications are drawn internationally to cut down the manufacturing costs and to avoid catastrophic online failure of the product. Specifications are prepared uased on some test parameters which in turn gives an idea of the component to serve the purpose. Ultimately the result is pre-assessed of the product behavior in service.

TESTS CARRIED OUT Since the wheels are produced by casting process, there is lot of stress induced during solidification of the molten metal. These are not good for working of wheels, hence to check the limiting stress tests are carried out.

CLOSURE TEST : Radial saw cut analysis technique is used to measure the bulk circumferential residual stress levels in rail road cast steel wheel. With this technique the opening or closure of the saw cut, at the flange tip is monitored as a function of the radial saw cut depth.

HARDNESS TEST : Hardness survey conducted on wheel slice cut from the cast wheel to asses the trend of hardening effect and its zone after Quenching of wheel Hardness pattern will be checked on the slice for every 30 mm approx. by using hardness tester.

TENSILE STRENGTH : In tensile testing, the ratio of maximum load to original cross sectional area is also called the ultimate strength. This test M give an idea of material strength obtained by proper process adopted of steel making and its effective heat treatment done. Test will be carried out by turning to the standard test method and breaking by using tensile testing machine.

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YIELD STRENGTH : The stress at which a material exhibits a specified deviation from proportionality of stress and strain. The test will conducted on integral part of UTS. This yield point is the first stress in a material, and usually less than maximum attainable stress at which an increase in strain occurs with out an increase in stress. This point will be noted down while doing UTS.

ELONGATION : In tensile testing the increase in gauge length is measured after the fracture of test specimen with in the gauge length. This test will be measured after breaking of the specimen. This will indicate the ductility of the material.

REDUCTION IN AREA : The difference, expressed as the percentage of the original area, between original cross sectional area and that after straining the specimen in tensile testing. This represents the ductility of the material.

GRAIN STRUCTURE : Grain size are reported in terms on number of grains per Unit area or volume average diameter, or as grain size number derived from area measurements. This will be done as per standard procedure method by using optical microscope at 100X and compared to known ASTM charts respectively. The structures of Polished and etched metals as revealed by a microscope at a magnification greater than 10X. This indicates the type of structure having the material. The test reveals the casting defects of the Material like porosity, shrinkage etc this test is done by surface Prepared and acid etched and viewed not by exceeding 10X magnifications.

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Impact Test: A test to determine the behaviour of the material when subjected to high rates of loading, usually in bending, tension or torsion. The loads that are suddenly applied to a structure are known as shock or impact load. One effect of this load is to produce stress waves. These loads produce rapid build up of stress and effect the resisting properties of the material. The property of a material is associated with work required to cause rupture. Most comonly used impact tests are – izod and charpy tests.

IZOD IMPACT TEST: The test consists of breaking by one blow from a swimnging hammer under specified conditions. A notched test piece gripped vertically with the bottom of the notch in the same plane as the upper face of the grip. The blow is struck at fixed position on the face having the notch. The energy is determined.

CHARPY IMPACT TEST: The test consists of breaking by one blow by a swinging hammer under specified conditions. The test piece is U-notched in the middle and supported at each end. The energy absorbed is determined from the impact value obtained.

HARDNESS: The term hardness is resistance to scratching, abrassion or cutting.the hardness tests are carried out for the purpose of checking physical condition of a product. These tests help to have a quality control of the product. The resistance of the metal is usually measured by indentation. Various hardness tests are employed such as brinnel, rockwell and vickers. This hardness determines the material characteristics.

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NON DESTRUCTIVE TESTING ULTRA SONIC TESTING The principle of this test is the velocity of Ultra Sonic Waves (high frequency sound waves) varies in different medium. In axle machine shop the Ultra Sonic Waves are made to pass through the axle. The velocity of these waves varies in different metal medium. When the waves are sent; if they come across metallic and non- metallic inclusions the velocity varies which can be detected through a computer connected to the ultra sonic testing machine. While propagating, if the waves come in contact with the cracks, they reflect without passing through them This change in wave signal is detected on the computer. The axles with cracks and non-metallic inclusions are if possible corrected else it's rejected. The ultra sonic testing is done twice in the axle machine Shop. First when axle comes out of STATION 1 (Le. after end milling, centering and cup turning). Here the waves are sent in horizontal direction from two end surfaces so that interna! vertical cracks can be detected. Second when the axle id out of rough turning. Here the waves are sent in vertical direction along the whole length so that lnternal horizontal cracks can be detected It is called Radial Ultrasonic Testing

NOTE : o For detecting vertical cracks the Ultra Sonic Waves must be sent into the work piece via a medium. And grease serves as a medium helping the waves to pass through the work piece from the source o For detecting horizontal cracks. water acts as medium for the waves to pass from the source to the axle Both tests are earned out for about 8-10 hrs

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MAGNETIC PARTICLE TESTING : This test is done to a completely finished axle just before it enters the assembly shop where assembling of wheel and axle takes place. This test is mainly to detect surface cracks. In this test, magnetic particle powder is mixed in oil and is poured on the body of the axle which is held in place by the chucks. DC current is used and the axle acts as a permanent magnet until the current flows through Then Ultra Violet rays are incident on the axle. If no surfaces Cracks are present then UV rays are reflected back else green light is effected. The axle with cracks are rejected or else sent to heat treatment depending up on the size of the crack.

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Generalised Working Chart (Wheel)

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Generalised Working Chart (AXLE)

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Bibliography 1 Manufacturing Process-I by Kestoor Praveen 2) Manufacturing Process-II by Kestoor Praveen. 3) Production Technology by O.P.Khanna and 4) Workshop Technology- by Hajra Chowdary. 5) Internet -- www.google.com -- http://www.rwf.indianrailways.gov.in/

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