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

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Conventional Short Circuit Transfer

Traditional Short Circuit Transfer click on picture to run video

STT Process Research Began July,1985 Purpose Develop a semi - automatic “short circuiting” welding process which eliminates spatter when using 100% CO2 shielding gas.

Working Prototype January,1987 STT Process Working Prototype January,1987 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 STT Process Working Prototype January,1987 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

STT Process STT Welding Arc

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

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

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.

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

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

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

Surface Tension Transfer

STT Process High speed video of STT arc click on picture to run video

STT Process High speed video of STT arc click on picture to run video

Sheet Metal Welding With STT STT Process Sheet Metal Welding With STT Traditional CV Short Arc Welding Welding with STT

Commercial System Introduced at Essen 1993 STT Process Commercial System Introduced at Essen 1993 Process Requires Current and Voltage Sensing High Speed Switching System Rapid Control of Output Rapid Response Power Source

Basic Transformer Design Reactor Selects Output Welding Current Inductance Coil Smoothes / Filters DC Output Transformer Single Phase Input High Volts High Amps Low Amps Low Volts Bridge Rectifier Changes AC to DC

Inverter Technology DC - Smooth High Voltage Low Amperage AC - 20,000+ Hz High Voltage Low Amperage DC - Smooth Low Voltage High Amperage AC - 50/60 Hz High Voltage Low Amperage DC - Rippled High Voltage Low Amperage AC - 20,000+ Hz Low Voltage High Amperage DC - Rippled Low Voltage High Amperage

Analog Power Source with Analog Feeder

Digital Power Source and Digital Feeder, Software Controlled

Build it Yourself

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

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

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

STT Process STT open root (viewed from inside of pipe) click on picture to run video

Open Root Welding With STT STT Process Open Root Welding With STT Benefits Welded open root ligament or thickness is large ~ 0.22” (5.6mm) Large ligament eliminates burn through on next weld pass. 0.22” (5.6mm)

STT on Pipe

With Good Root Fusion

STT Process 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 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

Open Root Welding With STT STT Process Open Root Welding With STT Single-sided welding

Open Root Welding With STT STT Process Open Root Welding With STT

PROCESS CERTIFICATION STT Process 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

Dual Process Capabilities Optimize Quality and Productivity by allowing process changes in same station

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

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

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 36.2 Minutes 113.7 Minutes $132.65 STT Root, Balance FCAW 17.0 Minutes 46.9 Minutes $54.72