Enhanced Surface Tension Transfer for Pipe Welding Harry Sadler Manager Military and Shipbuilding...

Enhanced Surface Tension Transfer for Pipe WeldingHarry Sadler

Manager Military and Shipbuilding Sales

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The business of The Lincoln Electric Company is manufacturing and selling The business of The Lincoln Electric Company is manufacturing and selling high quality welding equipment and consumables, and cutting equipment. Our high quality welding equipment and consumables, and cutting equipment. Our challenge is to meet the needs of our customers and to exceed their challenge is to meet the needs of our customers and to exceed their expectations. On occasion, purchasers may ask Lincoln Electric for advice or expectations. On occasion, purchasers may ask Lincoln Electric for advice or information about their use of our products. We respond to our customers information about their use of our products. We respond to our customers based on the best information in our possession at that time. Lincoln Electric based on the best information in our possession at that time. Lincoln Electric is not in a position to warrant or guarantee such advice, and assumes no is not in a position to warrant or guarantee such advice, and assumes no liability, with respect to such information or advice. We expressly disclaim any liability, with respect to such information or advice. We expressly disclaim any warranty of any kind, including any warranty of fitness for any customer’s warranty of any kind, including any warranty of fitness for any customer’s particular purpose, with respect to such information or advice. As a matter of particular purpose, with respect to such information or advice. As a matter of practical consideration, we also cannot assume any responsibility for updating practical consideration, we also cannot assume any responsibility for updating or correcting any such information or advice once it has been given, nor does or correcting any such information or advice once it has been given, nor does the provision of information or advice create, expand or alter any warranty with the provision of information or advice create, expand or alter any warranty with respect to the sale of our products.respect to the sale of our products.

Lincoln Electric is a responsive manufacturer, but the selection and use of Lincoln Electric is a responsive manufacturer, but the selection and use of specific products sold by Lincoln Electric is solely within the control of, and specific products sold by Lincoln Electric is solely within the control of, and remains the sole responsibility of, the customer.remains the sole responsibility of, the customer.

Customer Assistance Policy

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Conventional Short Circuit Transfer

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Traditional Short Circuit Transfer

click on picture to run video

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STT Process

• Purpose– Develop a semi - automatic “short

circuiting” welding process which eliminates spatter when using 100% CO2 shielding gas.

Research Began July,1985

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STT Process

• Major Achievements

– Reduced spatter in 100% CO2

– Developed capability to use larger diameter electrodes

– Reduced fumes– Ability to control the welding current

independent of the wire feed speed.

Working Prototype January,1987

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STT Process

• Results– The spatter reduction feature of the

technology also produced a very stable arc, especially at low currents. This is a big advantage when welding the open root on pipe in the 5G position

Working Prototype January,1987

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STT Process

STT Welding Arc

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STT Process

• Background current – Arc current level prior to shorting to the

weld pool.– Contributes to the overall heat input– Keeps arc lit

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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

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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.

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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

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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

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STT Process

• Tailout– Current is reduced from peak

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

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Surface Tension Transfer

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STT Process

• High speed video of STT arc


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STT Process

• High speed video of STT arc


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STT ProcessSheet Metal Welding With STT

Traditional CV Short Arc Welding

Welding with STT

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STT Process

• Process Requires– Current and Voltage Sensing– High Speed Switching System– Rapid Control of Output– Rapid Response Power Source

Commercial SystemIntroduced at Essen

1993

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ReactorReactorSelects Output Selects Output

Welding CurrentWelding Current

Bridge RectifierBridge RectifierChanges AC to DCChanges AC to DC

Inductance CoilInductance CoilSmoothes / FiltersSmoothes / Filters

DC OutputDC Output

TransformerTransformerSingle Phase InputSingle Phase Input

High VoltsHigh Volts High Amps High AmpsLow AmpsLow Amps Low VoltsLow Volts

Basic Transformer Design

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AC - 50/60 HzAC - 50/60 HzHigh VoltageHigh Voltage

Low AmperageLow Amperage

DC - RippledDC - RippledHigh VoltageHigh Voltage


DC - SmoothDC - SmoothHigh VoltageHigh Voltage


AC - 20,000+ HzAC - 20,000+ HzHigh VoltageHigh Voltage


AC - 20,000+ HzAC - 20,000+ HzLow VoltageLow Voltage

High AmperageHigh Amperage

DC - RippledDC - RippledLow VoltageLow Voltage


DC - SmoothDC - SmoothLow VoltageLow Voltage


Inverter Technology

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Analog Power Source with Analog Feeder

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Digital Power Source and Digital Feeder, Software Controlled

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Build it Yourself

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STT Process, Analog Control

• Controls

– Wire feed speed

Adjusts deposition rate

– Peak Current

Controls the arc length

– Background Current

Fine heat input control

– Tailout

Coarse heat input control

– Hot Start

Controls the starting heat

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STT Process, Non-Synergic Digital Control

• Controls– Wire feed speed

• Adjusts deposition rate– Peak Current

• Controls the arc length– Background Current

• Fine heat input control– Tailout

• Coarse heat input control– Hot Start

• Controls the starting heat– Start/End Options

• Preflow, Run-in, Start Time, Crater, Burnback, Postflow

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STT Process, Synergic Digital Control

• Controls– Wire feed speed

• Adjusts deposition rate– Trim

• Adjust ball size and arc energy– Weld Mode/Arc Control

• Dynamically modifies Hot Start, Peak, Background, and Tailout Current

– Start/End Options• Preflow, Run-in, Start Time,

Crater, Burnback, Postflow

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STT Process

STT open root (viewed from inside of pipe)


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STT Process

• Benefits– Welded open root

ligament or thickness is large ~ 0.22” (5.6mm)

– Large ligament eliminates burn through on next weld pass.

Open Root Welding With STT

0.22” (5.6mm)

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STT on Pipe

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With Good Root Fusion

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STT Process

STT Replacing Short-arc

– No Lack of Fusion– Good Puddle Control– Consistent X-ray Quality Welds– Shorter Training Time– Low Fume Generation & Spatter

– 100% CO2 (on mild steel)

– Various gas mixtures

Process Advantages

STT Replacing TIG

– 4 Times Faster– Vertical Down Welding

Possible– Consistent X-ray Quality

Welds– Shorter Training Time– Welds Stainless, Nickel Alloys

and Mild Steel

– 100% CO2 (on mild steel)

– Various gas mixtures

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STT Process

Single-sided welding


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STT Process


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STT ProcessPROCESS CERTIFICATION

STT process may be used in the following variants of pipe welding:

•Root pass & basic coated electrode for other passes

•Root pass, semi-auto welding with Innershield for other passes

•For root, fill & cap passes of pipe up to 10 mm wall thickness

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Dual Process Capabilities

• Optimize Quality and Productivity by allowing process changes in same station

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U.S. Based Organizations with PUBLISHED Rules for qualification of Short Circuit Transfer Modes

• American Welding Society• American Bureau of Shipping• American Society of Mechanical Engineers• American Petroleum Institute• Any other code that references ASME SEC IX for

Procedure and Operator Qualification

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Welding Cost Analysis, Assumptions

• Labor and Overhead--$70/hr• Operating Factors

– GTAW—35%– SMAW—30%– STT—40%– FCAW—35%

• GTAW Root Pass at 1.7 ipm• SMAW Root Pass at 4.4 ipm• STT Root Pass at 5.5 ipm• Same Net Material Costs

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Eight Inch Schedule 40 A106B Pipe, 5G Position

Process Time at 100% Time at Operating Factor

Net Labor Cost per Joint

GTAW Root, Fill, and Cap

54.35 Minutes 155.3 Minutes $181.18

GTAW Root, Balance SMAW


STT Root, Balance FCAW


Enhanced Surface Tension Transfer for Pipe Welding Harry Sadler Manager Military and Shipbuilding...

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