Manufacturing Process of Piston Rings and Cylinder Liners

MANUFACTURING PROCESS OF PISTON RINGS AND CYLINDER LINERS A Term paper Report Submitted by

G Madhusudhan Rao (158W5A0315) SK.K.Khamuruddin (158w5A0324) K Naveen Teja (148W1A0386) B Anusha (158W5A0325)

In partial fulfillment of the requirements For award of the degree of

BACHELOR OF TECHNOLOGY

With specialization in MECHANICAL ENGINEERING

Under the esteemed guidance of Mr. N Vijay Kumar, ME Associative Professor of ME Department

MECHANICAL ENGINEERING DEPARTMENT VELAGAPUDI RAMAKRISHNA SIDDHARTHA ENGINEERING COLLEGE VIJAYAWADA 500 007 APRIL 2017

Department of Mechanical Engineering

CERTIFICATE

MANUFACTURING PROCESS OF PISTON RINGS This is to certif y that the Term Paper Paper titled “ MANUFACTURING AND CYINDER LINERS” was prepared and presented by G Madhusudhan Rao(158W5A0315),

SK.K.Khamuruddin (158w5A0324), (158w5A0324), K Naveen Teja (148W1A0386), B Anusha(158W5A0325) of B.Tech., 6th Semester,Mechanical Semester,Mechanical Engineering in partial fulfillment of requirements for award of the Degree of Bachelor of Technology in Mechanical Engineering under the Jawaharlal Nehru Technological University Kakinada, Kakinada during the year 2016-17

TERM PAPER GUIDE

(N VIJAY KUMAR)

HEAD OF THE DEPARTMENT

(DR.N VIJAYA SAI)

Acknowledgement

We would like to articulate our profound gratitude and indebtedness to our guide Mr. N VIJAY KUMAR, ME, Associative Professor  who has always been a constant motivation and guiding factor throughout the Term Paper time in and out as well. It has been a great pleasure for us to get an opportunity to work under his guidance and complete the Term Paper successfully.

We wish to extend our sincere thanks to Dr. N.VIJAYA SAI, Professor and Head of the Mechanical Engineering Department, for his constant encouragement throughout the work.

We sincerely thank our principal Dr. A.V.Ratna Prasad  garu for his encouragement during the course of Term Paper. We thank one and all who have rendered help to us directly or indirectly in the completion of work.

G Madhusudhan Rao (158W5A0315) SK.K.Khamuruddin

(158w5A0324)

K Naveen Teja

(148W1A0386)

B Anusha

(158W5A0325)

DECLARATION

We hereby declare that the work is being presented in this Term Paper “MANUFACTURING PROCESS OF PISTON RINGS AND CYINDER LINERS”, submitted towards the partial fulfillment of requirements for the award of the degree of Bachelor of Technology in Mechanical Engineering in VR Siddhartha Engineering College, Vijayawada is an authentic record of our work carried out under the supervision of Mr. N VIJAY KUMAR, Associative Professor in Mechanical Department, V.R Siddhartha Engineering College, Vijayawada. Vijayawada. The matter embodied in this dissertation report has not been submitted by us for the award of any other degree. Furthermore, the technical details furnished in various chapters of this report are purely relevant to the above Term Paper.

G Madhusudhan Rao (158W5A0315) SK.K.Khamuruddin

(158w5A0324)

K Naveen Teja

(148W1A0386)

B Anusha

(158W5A0325)

ABSTRACT

A cylinder liner is a cylindrical component that is placed in an engine block. It is one of the most important functional parts to make up the interior of an engine and it gives a wear protective surface for piston and piston rings. It is used in petrol engine where combustion takes place. A piston ring is a split ring that fits into a groove that fits on the outer diameter of a piston in an IC engine. This paper involves involves Introduction to piston rings and cylinder cylinder liners, production of piston rings and cylinders, introduction to centrifugal casting, types of centrifugal casting, basic information about true centrifugal casting, process involved in production, molten metal preparation with materials, basic introduction on electromagnetic induction furnace  and its

features, machining process and various types of inspections done on the products. This paper also contains the information on the defects occurred while and before the production is done, there causes and remedies . This whole data was collected from industries visited. The main aim of the paper is to collect the basic information on production of piston rings, cylinder liners.

Introduction

Cylinder Liners Ever since its inception in 1960, the cylinder liner manufacturing activity at Cooper has grown from strength to strength. Today, the company is one of the top three cylinder liner manufacturers in the country, producing 2000 tons a month, and with expansion plans in the pipeline. Thanks to our extensive research in the area, the cen trifugally cast Cylinder Liners are manufactured with a special alloy cast iron with selective elements. Basically a cylinder liner i s a hollow cylindrical shape which acts as the enclosure in which the combustion takes place. Of course the word hollow does not employ that it is weak in strength for it is under the fluid pressure due to combustion and hence must withstand the high level of hoop stress induced in it. It provides good surface for the piston pi ston rings to slide along its length. Construction is done either by centrifugal casting in case of smaller liners and sand casting in case of larger liners. The inner surface of the cylinder liner is usually chrome plated to make it smooth but this smoothness also has its drawback that it does not allow oil to spread out properly thus affecting liner lubrication in a negative manner. The manner. The raw material comprises of combination of Pig Iron, Mild Steel, some iron scrap material and cast iron. The correct proportions have to be chosen for different vehicles depending on properties required by their matching components and as specified by the original equipment manufacturers. manufacturers. A small quantity is tested in a sample cup, for the Material composition. The other impurities such as Sulphur and Phosphorus are controlled to the permissible Levels. Slag material is removed before some additives like Nickel, Molybdenum, Chromium; Copper etc. are added in small quantities as recommended to develop desired strength, hardness and surface finish in the final product. Next, the molten metal is taken into ladles and poured into rotating die machines where it is cast centrifugally. After rough machining, every piece is thoroughly inspected for casting defects or cracks and for sufficient material thickness, wherever further machining is to be done. Then hardness is checked for each and every piece on a Brinell hardness tester. Finally they are dipped into special anti-corrosion agents to enhance shelf life and high workability.

Piston Rings A piston ring is a split ring that fits into a groove on the outer diameter of a piston a piston in a reciprocating engine such as an internal an internal combustion engine or steam or steam engine. The three main functions of piston rings in reciprocating engines are: 1. Sealing the combustion chamber so that there is minimal loss of gases to the crank case. 2. Improving heat transfer from the piston to the cylinder the cylinder wall. 3. Regulating engine oil consumption by scraping oil from the cylinder walls back to the sump. The gap in the piston ring compresses to a few thousandths of an inch when inside the cylinder bore. Piston rings are a major factor in identifying if an engine is two strokes or four strokes. Three piston rings suggest that it is a four stroke engine while two piston rings suggest that it is a two stroke engine. Most piston rings are made of a very hard and somewhat brittle cast brittle cast iron. When fitting new piston rings or breaking them in within an engine, the end gap is a crucial measurement. In order that a ring may be fitted fi tted into the "grooves" of the piston, it is not continuous but is broken at one point on its circumference. The ring gap may be checked by putting the ring into the bore/liner (squared to bore) and measuring with a feeler gauge. End gap should be within recommended limits for size of bore and intended "load" of engine. Metals expand with a rise in temperature, so too small a gap may result in i n overlapping or bending when used under hot running conditions (racing, heavy loads, towing) and, even at normal temperatures, a small ring gap may lead to ring gap closure, ring breakage, bore damage and possible seizure of the piston. Too large a gap may give unacceptable compression and levels of blow-by gases or oil consumption. When being measured measured in a used bore, it may indicate excessive bore wear or ring wear. During engine assembly, a piston-ring compressor is used to evenly squeeze the rings long enough to slide the piston into the cylinder. Rings are not a very expensive part, but fitting new ones is usually very costly. This is because to fit them, the mechanic must essentially take the whole engine apart. Therefore the labor costs are the major factor. Once going that far, one might as well correct many other problems found inside - so fitting f itting new rings is usually done as part of an entire engine rebuild/reconditioning.

Production of cylinder liners and piston rings: -  Generally centrifugal casting process is most widely used for production of cylindrical castings in which molten metal is poured at suitable temperature into rapidly rotating mould

Centrifugal casting The centrifugal casting process consists of pouring the molten metal at a suitable temperature into a rapidly rotating mould or die. It is essential that pouring temperature of molten metal should be high enough to enable it to reach the farthest point in the mould before solidification commence. The axis of rotation of mould may be horizontal, vertical or slightly inclined. The centrifugal force imparted to molten metal enables it to be picked up and held in contact with the rotating mould. The mould is allowed to rotate till the casting is completely solidified. Thus the outer shape of casting takes the shape of the inside of the mould and the bore of casting is truly circular and concentric with axis of rotation. The thickness of casting is determined by the quantity of molten metal poured, and the length by the length of mould between two end plates. In centrifugal casting, a permanent mold is rotated continuously about its axis at high speeds (300 to 3000 rpm) as the molten metal is poured. The molten metal is centrifugally thrown towards the inside mold wall, where it solidifies after cooling. The casting is usually a finegrained casting with a very fine-grained outer diameter, owing to chilling against the mould surface. Impurities and inclusions are thrown to the surface of the inside diameter, which can be machined away. Casting machines may be either horizontal or vertical-axis verti cal-axis Horizontal axis machines are preferred for long, thin cylinders, vertical machines for rings. Most castings are solidified from the outside first. This may be used to encourage directional solidification of the casting, and thus give useful metallurgical properties to it. Often the inner and outer layers are discarded and only the intermediary columnar zone is used. Centrifugal casting was the invention of Alfred Krupp, who used it to manufacture cast steel tyres for railway wheels in 1852.

Types of centrifugal casting:*True centrifugal casting *Semi centrifugal casting *Centrifuge (or) pressure casting -Basically cylinder liners and piston rings are produced by true centrifugal casting.

True Centrifugal Casting No core is used in this method; essentially all of the heat is extracted from the molten metal through the outer mould wall. The poor thermal conductivity of the air in contact with the internal diameter results in little heat loss from this direction. Thus, perfect directional solidification is obtained from outer surface to inner one and grain growth is typically columnar. Because of favorable thermal gradients, in addition to the outward centrifugal force acting upon the molten metal, each successive increment of metal to solidify is fed by the residual liquid metal in contact with it, until solidification is complete. Under proper conditions, shrinkage porosity is non-existent.

Process Involved In Production (a) Molten metal preparation (b) Casting (c) Machining (d) Inspection

Molten Metal preparation Molten metal is prepared by using electric induction furnace. The electric induction furnace is a type of melting furnace that uses electric currents to melt metal. Induction furnaces are ideal for melting and alloying a wide variety of metals with minimum melt losses, however, li ttle refining of the metal is possible. Material: pig iron, cast iron, iron scrap

Electromagnetic Induction Furnace An induction furnace is an electrical furnace in which the heat is applied by induction heating of metal. Induction furnace capacities range from less than one kilogram to one hundred tonnes capacity and are used to melt iron and steel, copper, aluminium and precious metals. The advantage of the induction furnace is a clean, energy-efficient and well-controllable melting process compared to most other means of metal melting. Most modern foundries use this type of furnace, and now also more iron foundries are replacing cupolas with induction furnaces to melt cast iron, as the former emit lots of dust and other pollutants. Since no arc or combustion is used, the temperature of the material is no higher than required to melt it; this can prevent loss of valuable alloying elements. The one major drawback to induction furnace usage in a foundry is the lack of refining capacity; charge materials must be clean of oxidation products and of a known composition and some alloying elements may be lost due to oxidation (and must be re-added to the melt). An induction furnace consists of a nonconductive crucible holding the charge of metal to be melted, surrounded by a coil of copper wire. A powerful alternating current flows through the wire. The coil creates a rapidly reversing magnetic field that penetrates the metal. The magnetic field induces eddy currents, circular electric currents, inside the metal, by electromagnetic induction. The eddy currents, flowing through the electrical resistance of the bulk metal, heat it by Joule heating. In ferromagnetic materials like iron, the material may also be heated by magnetic hysteresis, the reversal of the molecular magnetic dipoles in the metal. Once melted, the eddy currents cause vigorous stirring of the melt, assuring good mixing. An advantage of induction heating is that the heat is generated within the furnace's charge itself rather than applied by a burning fuel or other external heat source, which can be important in applications where contamination is an issue. Operating frequencies range from utility frequency (50 or 60 Hz) to 400 kHz or higher, usually depending on the material being melted, the capacity (volume) of the furnace and the melting speed required. Generally, the smaller the volume of the melts, the higher the frequency of the furnace used; this is due to the skin depth which is a measure of the distance an alternating current can penetrate beneath the surface of a conductor. For the same conductivity, the higher frequencies have a shallow skin depth— depth —that is less penetration into the

melt. Lower frequencies can generate stirring or turbulence in the metal. A preheated, onetonne furnace melting iron can melt cold charge to tapping readiness within an hour. Power supplies range from f rom 10 kW to 42 MW, with melt sizes of 20 kg to 65 tonnes of metal respectively. An operating induction furnace usually emits a humor whine (due to fluctuating magnetic forces and magnetostriction), the pitch of which can be used by operators to identify whether the furnace is operating correctly or at what power level.

FEATURES OF INDUCTION FURNACE An electric induction furnace requires an electric coil to produce the charge. This heating coil is eventually replaced. The crucible in which the metal is placed is made of stronger materials that can resist the required heat, and the electric coil itself cooled by a water system so that it does not overheat or melt. The induction furnace can range in size, from a small furnace used for very precise alloys only about a kilogram in weight to a much larger furnaces made to mass produce clean metal for many different applications. The advantage of the induction furnace is a clean, energy-efficient and well-controllable melting process compared to most other means of metal melting. Foundries use this type of furnace and now also more iron foundries are replacing cupolas with induction furnaces to melt cast iron, as the former emit lots of dust and other pollutants. Induction furnace capacities range from less than one kilogram to one hundred tonnes capacity, and are used to melt iron and steel, copper, aluminium, and precious metals. The one major drawback to induction furnace usage in a foundry is the lack of refining capacity; charge materials must be clean of oxidation products and of a known composition, and some alloying elements may be lost due to oxidation (and must be re-added to the melt).

Casting Preparation by True Centrifugal Process

Machining Machining Process Description :

The casting are shot blasted and are sent to the machine shop for machining operation, the first operation is the roughing operation where casting skin is removed, this operations is performed on a custom designed vertical high speed turning cum boring machine. The machined liner is then turned on a CNC Turning Centre where all outer diameter and lengths are maintained, for Dry liners the next sequence of operations would be Rough Grinding, fine boring, Rough honing followed by Plateau honing and Finish grinding whereas for Wet Liners after CNC turning, fine boring followed by rough honing, fine CNC turning and plateau honing would be performed. Honing has been and will remain to be in the foreseeable future the only process available that could provide both the required surface roughness and the crosshatching in cylinder liners. The cross-hatching lay direction is needed to provide means for retaining lubricants. A cylinder liner has fairly intricate i ntricate surface requirements due to its complicated functions. It has to provide adequate surface roughness to resist wear and to store and retain lubricants during high temperatures, in addition to liner hardness, geometric dimensioning and tolerance to ensure other proper functions.

Fine Boring

Boring is the process which gives the final look of inner diameter. We perform boring operation on vertical machining center. This is fully computerized control machine. We also use special purpose boring machine which maintains dimension accuracy, taper, ovality and surface finish.

Outer Diameter Turning

It perform outer diameter of liner on Lathe machine, which is manually operated machine, gives high accuracy in dimensional parameters, surface roughness parameters and geometrical parameters. A main benefit of OD CNC Turing is to minimize cycle time, repeatability of quality and consistency product.

Grinding and Stage Inspection

Grinding is the process where super surface finish can be maintained on products. We have two type of grinding process center less grinding and cylindrical grinding. Grinding controls dimensional parameters, surface parameters and geometrical parameters.

Honing

Honing is the process where required hex pattern can be maintained in finish inner diameter. We use Plato honing process. The main benefits of Plato honing process is to achieve required quality parameters like surface finish

Inspection Visual inspection

It consists of inspecting the surface of the casting with naked eye or sometimes with a magnifying glass or microscope. It can only indicate surface defects such as blow holes, fusion, swells, external cracks, and mismatch. Almost all castings are subjected to certain degree of visual inspection. Dimensional inspection

It consists of inspecting the surface of the casting with naked eye or sometimes with a magnifying glass or microscope. It can only indicate surface defects such as blow holes, fusion, swells, external cracks, and mismatch. Almost all castings are subjected to certain degree of visual inspection.

Coordinate measuring machine ( machine  (CMM CMM)) it is a device for measuring the physical geometrical characteristics of an object. This machine may be manually controlled by an operator or it may be computer controlled. Measurements

are defined by a probe attached to the third moving axis of this machine. Probes may be mechanical, optical, laser, or white light, among others. A machine which takes readings in six degrees of freedom and displays these readings in mathematical form is known as a CMM.

Description of CMM The typical 3D "bridge" CMM is composed of three axes, X, Y and Z. These axes are orthogonal to each other in a typical three-dimensional three -dimensional coordinate system. Each axis has a scale system that indicates the location of that axis. The machine reads the input from the touch probe, as directed by the operator or programmer. The machine then uses the X,Y,Z coordinates of each of these points to determine size and position with micrometer precision typically, A coordinate measuring machine (CMM) is also a device used in manufacturing and assembly processes to test a part or assembly against the design intent. By precisely recording the X, Y, and Z coordinates of the target, points are generated which can then be analyzed via regression algorithms for algorithms for the construction of features. These points are collected by using a probe that is positioned manually by an operator or automatically via Direct Computer Control (DCC). DCC CMMs can be programmed to repeatedly measure identical parts, thus a CMM is a specialized form of industrial robot These machines can be free-standing, handheld and portable.

DEFECTS

Blow:

Blow is relatively large cavity produced by gases which displace molten metal form.

Scar:

Due to improper permeability or venting, a scare is a shallow blow. It generally occurs on flat surf; whereas a blow occurs on a convex casting surface. A blister is a shallow blow like a scar with thin layer l ayer of metal covering it,

Scab:

This defect occurs when a portion of the face of a mould lifts or breaks down and the recess thus made is filled by metal. When the metal is poured into the cavity, gas may be disengaged with such violence as to break up the sand which is then washed away and the resulting cavity filled with metal. The reasons can be: - to fine sand, low permeability of sand, high moisture content of sand and uneven moulds ramming.

Blow holes:

Blow holes, gas holes or gas cavities are well rounded cavities having a clean and smooth surface. They appear either on the casting surface or in the body of a casting. These defects occur when an excessive evolved gas is not able to flow through the mould. So, it collects into a bubble at the high points of a mould cavity ad prevents the liquid metal from filling that space. This will result in open blows. Closed, cavities or gas holes are formed when the evolved gases or the dissolved gases in the molten metal are not able to leave the m ass of the molten metal as it solidifies and get trapped within the casting. These defects are caused by: i) Excessive moisture content (in the case of green sand moulds) or organic content of the sand, moisture on chills, chaplets or metal inserts, ii) Inadequate gas permeability of the molding sand (due to fine grain size of sand, high clay content, hard ramming), iii) Poor venting of mould, insufficient drying of mould and cores, cores not properly vented, high gas content of the molten metal, iv) Low pouring temperature and incorrect feeding of the casting etc.

Pin holes:

Pin holes are small gas holes either at the surface or just below the surface. When these are present, they occur in large numbers and are fairly uniformly dispersed over the surface.

This defect occurs due to gas dissolved in the alloy and the alloy not properly degassed.

Hot tear:

Hot tears are hot cracks which appear in the form of irregular crevices with a dark oxidized fracture surface. They arise when the solidifying met does not have sufficient strength

to

resist

tensile

forces

produced

during

solidification. They are chiefly from an excessively high temperature of casting metal, increased metal contraction incorrect design of the gating system and casting on the whole (causing portions of the casting to be restrained from shrinking freely during cooling which in turn causes excessive high intern resistance stresses), poor deformability of the cores, and non-uniform cooling which gives rise t internal stresses. This defect can be avoided by improving the design of the casting and by having a mould of low hot strength and large hot deformation.

Segregation

Centrifugal castings are under various forms of segregation thus Pushing less dense constituents at centre

Banding

Sometimes castings produce zones of segregated low melting point constituents such as eutectic phases and sulphide and oxide inclusions. Various theories explain this, one states vibration is the main cause of banding

Defects, Causes and There remedies for Casting process INTRODUCTION

Casting is a process which carries risk of failure occurrence during all the process of accomplishment of the finished product. Hence necessary action should be taken while manufacturing of cast product so that defect free parts are obtained. Mostly casting defects are concerned with process parameters. Hence one has to control the process parameter to achieve zero defect parts. For controlling process parameter one must have knowledge about effect of process parameter on casting and their influence on defect. To obtain this all knowledge about casting defect, their causes, and defect remedies one has to be analyse casting defects. Casting defect analysis is the process of finding root causes of occurrence of defects in the rejection of casting and taking necessary step to reduce the defects and to improve the casting yield. In this review paper an attempt has been made to provide all casting related defect with their causes and remedies. During the process of casting, there is always a chance where defect will occur. Minor defect can be adjusted easily but high rejected rates could lead to significant change at high cost. Therefore it is essential for die caster to have knowledge on the type of defect and be able to identify the exact root cause, and their remedies.

CASTING DEFECT CAN BE CLASSIFIED AS FOLLOWS:Filling related defect Shape related defect Thermal defect These defects are explained as follows.

Filling related defects Blowhole:-

Blowhole is a kind of cavities defect, which is also divided into pinhole and subsurface blowhole. Pinhole is very tiny hole. Subsurface blowhole only can be seen after machining. Gases entrapped by solidifying metal on the surface of the casting, which results in a rounded or oval blowhole as a cavity. Frequently associated with slags or oxides. The defects are nearly always located in the cope part of the mould in poorly vented pockets and undercuts.

Possible causes Resin-bonded sand:-

• Inadequate core venting • Excessive release of gas from core • Excessive moisture absorption by the cores • Low gas permeability of the core sand Clay-bonded Clay-bonded sand • Moisture content of sand too high, or water released too quickly • Gas permeability of the sand too low • Sand temperature too high • Bentonite content too high • Too much gas released from lustrous carbon produce Remedies Resin-bonded sand:-

• Improve core venting, provide venting channels, and ensure core prints are free of dressing • Reduce amounts of gas. Use slow-reacting slow -reacting binder. Reduce quantity of binder. Use coarser sand if necessary. • Apply dressing to cores, thus slowing down the rate of heating and reducing gas pressure. • Dry out cores and store dry, thus reducing absorption of water and reducing gas pressure. Clay-bonded sand • Reduce moisture content of sand. Improve conditioning of the sand. Reduce inert dust content. • Improve gas permeability. Endeavour to use coarser sand. Reduce Bentonite and carbon carrier content.

• Reduce sand temperature. Install a sand cooler cooler if necessary. Increase sand quantity. • Reduce Bentonite content. Use Bentonite with a high montmorillonite content, high specific binding capacity and good thermal stability. • Use slow-reacting slow-reacting lustrous carbon producers or carbon carriers with higher capacity for producing lustrous carbon. In the last instance, the content of carbon carriers in the moulding sand can be reduced Gas porosity:-

The gas can be from trapped air, hydrogen dissolved in aluminium alloys, moisture from water based die lubricants or steam from cracked cooling lines. Air is present in the cavity before the shot. It can easily be trapped as the metal starts to fill the cavity. The air is then compressed as more and more metal streams into the cavity and the pressure rises. When the cavity is full it becomes dispersed as small spheres of high pressure air. The swirling flow can cause them to become elongated.

Possible Causes:-

• Metal pouring temperature too low. • Insufficient metal fluidity e.g. carbon equivalent too low. • Pouring Pouring too slow. • Slag on the metal surface. • Interruption to pouring during filling of the mould. • High gas pressure in the mould arising from molding material having high moisture and/or volatile content and/or low permeability. • Lustrous carbon from the molding process. • Metal section too thin. • Inadequately pre-heated pre-heated metallic moulds. Remedies:-

• Increase metal pouring temperature. • Modify metal composition to improve fluidity. • Pour metal as rapidly as possible poss ible without interruption. Improve mould filling by modification to running and gating system. • Remove slag from metal surface. • Reduce gas pressure in the mould by appropriate adjustment adjustment to moulding material properties and ensuring

• Adequate venting of  moulds  moulds and cores. • Eliminate lustrous carbon where applicable. • If possible, modify casting design to avoid thin sections. • Ensure metal moulds are adequately pre-heated pre-heated and use insulating coatings. Thermal defects Cracks or tears

Cracks can appear in die castings from a number of causes. Some cracks are very obvious and can easily be seen with the naked eye. Other cracks are very difficult to see without magnification. Possible causes

• Shrinkage of the casting within the die • Undercuts or damage in in die cavities • Uneven, or excessive, ejection forces • Thermal imbalance in the die • Insufficient draft in sections of the die • Excessive porosity in critical regions of the part • Product design not matched to the process • Inadequate die design Remedies

• Reduce dry strength, add saw dust/ coal dust • Reduce pouring temperature • Avoid superheating of metal • Use chills • Provide feeders • Avoid early knockout. Give sufficient cooling time. • Correct composition • Reduce sharp corners Shrinkage

Shrinkage defects occur when feed metal is not available to compensate for shrinkage as the metal solidifies. Shrinkage defects can be split into two different types: open shrinkage defects and closed shrinkage defects. Open shrinkage defects are open to the atmosphere, therefore as the shrinkage cavity forms air compensates. There are two types of open air defects: pipes and caved surfaces. Pipes form at the surface of the casting and burrow into the casting, while caved surfaces are shallow cavities that form across the surface

of the casting. Closed shrinkage defects, also known as shrinkage porosity, are defects that form within the casting. Isolated pools of liquid form inside solidified metal, which are called hot spots. The shrinkage defect usually forms at the top of the hot spots. They require a nucleation point, so impurities and dissolved gas can induce closed shrinkage defects. The defects are broken up into macro porosity and micro porosity (or micro shrinkage), where macro porosity can be seen by the naked eye and micro porosity cannot. Possible causes

The density of a die casting alloy in the molten state is less than its density in the solid state. Therefore, when an alloy changes phase from the molten state to the solid state, it always shrinks in size. This shrinkage takes place when the casting is solidifying inside a die casting die. At the centre of thick sections of a casting, this shrinkage can end up as many small voids known as ‘shrinkage porosity’. If the shrinkage porosity is small in i n diameter and confined to the very centre of thick sections it will usually cause no problems. However, if it is larger in size, or joined together, it can severely weaken a casting. It is also a particular problem for castings which need to be gas tight or water tight’. Remedies

The general technique for eliminating shrinkage porosity is to ensure that liquid metal under pressure continues to flow into the voids as they form. Defects by Appearance Metallic projection Joint flash or fins

Flat projection of irregular thickness, often with lacy edges, perpendicular to one of the faces of the casting. It occurs along the joint or parting line of the mold, at a core print, or wherever two elements of the mold intersect. Possible causes

Clearance between two elements of the mold or between mold and core; poorly fit mold joint. Remedies

Care in pattern making, molding and core making. Control of their dimensions; Care in core setting and mold assembly.

Cavities

Blowholes, pinholes, Smooth-walled cavities, essentially spherical, often not contacting the external casting surface (Blowholes). The defect can appear i n all regions of the casting. Possible causes

Blowholes and pinholes are produced because of gas entrapped in the metal during the course of solidification: Remedies

Make adequate provision for evacuation of air and gas from the mold cavity; Increase permeability of mold and cores.

Conclusions:After studying and analyzing cylinder liners and piston rings using some materials following conclusions were drawn a) The cylinder liner made up of titanium alloy is lighter than the existing cylinder l iners b) The analysis equivalent stress ( von mises ) but the titanium alloy is slightly less than cast iron alloy, which is currently used as cylinder liners c) Total deformation of titanium alloy is less than the current material ( cast iron alloy ) d) Thus, although the cost of titanium alloy is high, ti tanium alloy is safe to use as cylinder liner e) Piston rings of reciprocating engine have several functions apart from sealing gas pressure which effect performance of engine f) From literature it appears that piston ring can be designed using experimental, analytical and numerical techniques

Reference Industry visit, Lakshmi Chaitanya alloys Vijayawada E sources:- Wikipedia, lectures