STT Lincoln Electric

Wave Form Controlled Technology™ •GMAW Pu P ulse •Power Mode •Rapid Arc

•STT

Agenda

1.

Introduction

2.

STT STT proc pr ocess ess

a)

Background Background current

b)

Initial short ing

c)

Pinch curr c urre ent

d)

Secont curr c urre ent reduction reducti on

e)

Peak current

f)

Tailout

3.

STT visualization

4.

STT setting setti ngs s and guidelines gui delines

5.  Ap  A p p l i c ati at i o n - aus au s t eni en i t i c s t ain ai n l ess es s . Cr-Mo Cr -Mo l o w all al l o y ed 6.

STT vs. TIG TIG, aus austenit tenitic ic stainle stainl ess, welding weldi ng time ti me

7.

Comparing Comparin g STT STT to CV, CV, quality qualit y

8.

Welding fumes

9.

Possible ossi ble appli applications cations

10. Summa umm ary – benefits 11. FCW for austenitic & duplex d uplex sta st ainless

Introduction

Con onve vent ntio iona nall CV  Arc v o l t age/W ag e/Wel eld d i n g c u r r ent en t 50

100

150

200

250

300

350

35 30 25

Fill ROOT

20

Spray arc

15 10 5 0

Short arc

Globular Transfer 

SG2 1.0 SG21.0m 1.0mmmm 1.0m 80/20 80/20MIX-gas MIX-gas

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Alternatives

Wave Form Controlled ™ Alternatives  Arc voltage/Welding current 50

100

150

200

250

300

350

35 30 25

Fill ROOT

20

Pulse / Spray

15 10 5

Power Mode®

Pulse

RapidArc™

STT®

0

Lincoln Lincoln Electric Electric Alternatives Alternatives to to offer  offer 

STT Process

STT

STT principle

Good Goodfusion fusionand and setting settingof of the the proper properarc arclength length

OOveral veralheat heat

input input(wetting) (wetting)

Movie Reason Reasonfor forlower  lower  spatter spatterin inSTT STT

STT Process

Background current – Arc current level prior to shorting to the weld pool. – Contributes to the overall heat input – Keeps arc lit

Background current (T0 - T1): This is the current level of the arc prior to shorting to the weld pool. It is a steady-state current level, between 50 and  100 A

STT Process

Initial Shorting

– Response to the “arc voltage” detector sensing that the arc has shorted – Current is reduced even further at actual ball/weld puddle contact – Extremely low current promotes ball wetting instead of repelling – Reason for lower spatter in STT

Ball time: When the electrode initially shorts (at the background current), the "arc voltage" detector   provides a signal that the "arc" is shorted. The  background current is futher  reduced to 10 A for  approxiametly 0.75 milliseconds. This time interval is referred to as the  ball time.

STT Process

Pinch Current

– High current is applied immediately after the initial short – Current increases, causing the molten droplet to separate from the electrode – STT electronically calculates when droplet separation is to occur and reduces the current before this happens, eliminating the explosive spatter.

Pinch mode (T2 - T3): Following the ball time, a high current is applied to the shorted electrode in the form of an increasing, dual slope ramp. This accelerates the transfer of molten metal from the electrode to the weld pool by applying electronic pinch forces.

STT Process

Second Current Reduction

– Current is quickly reduced before electrode separates, eliminating spatter – STT circuitry re-establishes the welding arc at a low current level

The dv/dt calculation: This calculation is included within the  pinch mode. It is the calculation of the rate of change of the shorted electrode voltage vs. time. When this calculation indicates that a specific dv/dt value has been attained, indicating that fuse separation is about to occur, the current is reduced to 50 A in microseconds. (Note, this event occurs before the shorted  electrode separates. T4indicates the separation has occurred, but at a low current.

STT Process

Peak Current

– High current is applied immediately after the arc is reestablished – Arc is momentarily broadened, producing high heating of the plate, insuring good fusion and setting the proper arc length

Plasma boost (T5 - T6): This mode follows immediately the separation of the electrode from the weld pool. It is the period of  high arc current where the electrode is quickly "melted   back." (The geometry of the melted electrode at this point is very irregular.)

STT Process

Tailout

– Current is reduced from peak to background level – Reduces agitation of the weld puddle –  This control is a coarse heat control

Plasma (T6 - T7): This is the  period of the cycle where the arc current is reduced from  plasma boost to the  background current level.

movie

Movie

Peak & Background Current

STT settings Peak current •Providing the energy to set the arc length. •Setting according wire diameter and composition. •Pressure in both ways; wire and weld bead. Peak current = arc pressur e & length

Low High Back ground current •Providing the “overall heat” •More or less wetting. •Most used control on the STT.

Back ground = Wetting

Tail out •In the same way as background •To be use with high travel speed •  Automation not for pipe welding

Application; Stainless preparation

Preparation; Stainless Tack weld with bar 

Tape

 Application: Pipe diameter 10” Position: Material: AISI 316L

x 8 mm G3

60°

3mm

Backing gas: 95%Ar 5%N2

Application Stainless pipe

Application: Stainless Root Pass STT Root LNM 316LSI 1,0mm Gas: Ar + 2%CO2 Peak 270A Background 80A WFS 168” /min Position 3GD

PULSE Fill LNM316LSI 1,0mm Gas: Ar + 2%Co2 22V, 175Amp Positi on 3GU (!)

Pulse CAP LNM316LSI 1,0mm Gas Ar + 2%CO2 22 V, 175Amps Positi on 3GU

Cor – a – Rosta

Welding stainless Example 7

Cor – a – Rosta wires are available in most used grades and  increased productivity justifies the move to premium quality wires!!!

Example 7

Gates for shipbuilding…

Example 7

n

n-1

10 mm

2 1

LNB

PA, 10 mm thick palte, gap 3-4mm, root 1,5, beveling V60 Bead# Method, wire

d, mm

I, A

U, V

Gas

Current, polarity

Welding Speed, mm/sek

HI kJ /mm

1

136, Cor – a Ar os ta 316L

1,2

155

24

M21

DC+

5,5-6

0,5

2 -n

136,

1,2

182

26

M21

DC+

5,5-6

0,65

Cor- a Rosta 316L

Overmaching corrosion resistance…

Remark

Application: Pipe welding

Application; Steel Root Pass  Application: Pipe diameter 6” Position: 60° Material: X42

x 10mm G3(D)

3mm

Fill Outershield 71E-H 1,2mm Gas: 80%Ar 20%Co2 26V, 215Amp Position 3GU

STT Root Supra MIG 1,0mm Gas: Ar + 20%CO2 Peak 280A Background 70A WFS 148”/min Position 3GD

CAP Outershield 71E-H 1,2mm Gas Ar + 20%CO2 26 V, 215Amps Position 3GU

Setting STT Procedures

STT Welding Parameter Guidelin e & Joint Configuration  Applicable for Un-, Low, & High Alloyed Mater ials (wire ø1.0 mm) Welding Positi on

Wall Thickness

1G / PA (Rotating)

5G Down / PG

< 3.5 mm

>3.5 mm Wall Thickness

Peak Curr ent

Backgrond Current

Wire Feed Speed

8 mm

260-270

65-85

360-420

Peak Current

Backgrond Current

Wire Feed Speed

230-240

45-55

290-330

250-260

50-65

320-360

Gas Selection

Shielding & Backing Gas Selection Table Mild & Low  Alloyed Steel ++

Regular 3xx Stainless Steel -

(Super) Duplex Stainless Steel -

Fully Austenitic Stainless Steel -

Nickel Alloys -

 Ar + 20% CO2 + He

+

-

-

-

-

 Ar + 2% CO2

-

++

+

+

-

 Ar + 28% He + 2%CO2

-

+*

++

++

-

 Ar + 30% He

-

-

-

-

+ ++

(+) (+) -

+ + ++

++ ++ -

+ + ++

+ + ++

 Ar + 20% CO2

 Ar + 28% He + 2%H2 Backing gas  Ar  N2 N2 + 5%H2 ++ + (+) *

First o ption Second o ption Optional Not recommended Recom mended when w all thick ness > 6 mm

LSW06/AvdS-DR

Procedure Comparison

Procedure Comparison 25 mm

25 mm

3-4 mm Material Welding Position Pipe Diamete

1.4462 (Duplex) 1G Rotating 25"

3-4 mm Material Welding Position Pipe Diamete

GMAW-STT Consumable Classification Diameter Shielding gas Flow Backing gas Stick-out Peak Current Background Current Arc voltage Wire Feed Speed Welding Time

LNM 4462 G 22 9 3 N L 1,2 mm 98% Ar +2% CO2 13 l/min 100% Ar 12 mm 280 A 80 A 100 "/min 6 minutes

1.4462 (Duplex) 1G Rotating 25"

GTAW Consumable Classification Diameter Shielding gas Flow Backing gas Stick-out Current

LNT 4462 W 22 9 3 N L 2,4 mm 100% 8 l/min 100% Ar -90 A

Arc voltage Wire Feed Speed Welding Time

11-13 V -22 minutes

Low Spatter, Defect Free Rootpass 

Welding Fume

Solid wire (MIG/MAG, TIG & STT)

   )   r   u   o    h    /   g    (   n   o    i   s   s    i

  m   e   e   m   u    F

Welding cu rrent (A)

STT: 50% reduction in fume emission versus conventional GMAW

Industry Segments

Markets where STT can be applied Oil & Gas Industry Cross Country Pipelines Power Generation Chemical Industry Pulp & Paper Industry Food & Dairy Industry

Base materials

 Applications with the STT process Pipe Root-pass Welding Mild- & Fine Grained Steel Low Alloyed Steel Creep Resistant Steel (qualified and certified in Poland) Standard 3xx-series Stainless Steel Fully Austenitic Stainless Steel (Super)Duplex Stainless Steel Nickel Alloys