We were experiencing difficulties while joining copper to copper parts of a circuit breaker.The two parts are copper wire with rectangular cross-section about 6 to 8 sq. mm(0.009-0.012 sq. inches)and a copper cord with the same square. We employed solid tungsten electrodes. The problem was that either there wasn't a quality weld or the electrodes would squash the two parts. A partial solution was to set the welding time to one period(20 milliseconds)with high amperage, to increase the power of the transformer and to replace the solid tungsten electrodes with copper electrodes with tungsten tips. Now the two parts are easily joined but we can't achieve identical welds. The welds differ from each other. 1. What is most likely the reason for such a problem? 2. Could anybody suggest a possible solution? 3. If we set the weld time - half period - could this be a solution?

-- Stanislav Guenov (stan@isomatic.com), December 03, 1999

Answers

Problem: Welds differ from each other. Question: What is the most likely reason?

The most likely reason is a mechanical situation. One option could be the configuration of the parts when stacked up between the weld tips, or before welding, may not be the same. Maybe the copper cord was not positioned the same way each time; or maybe the cord was twisted from one time to the next. We are assuming that the weld control delivers the same current each time and that the weld pressure is the same each time. If the pressure / heat / time is not changing, the mechanics are all that's left to change, the mechanics being the physical condition of the parts to be welded.

Why not try exaggerating the physical conditions and observing the results? I expect the copper cord is the most likely to not present its self in the same condition for each weld. Are the parts being fixed prior to welding so that they lay the same way and have the same tension on them each time?

Question: Could - half period - be a solution? Probably not, but can you try it without much difficulty? You want to weld copper as "quickly" as possible to avoid the heat, keeping it from affecting the copper. However, you do not want to increase the voltage so much that the resistance has less heating affect. Remember that if the time is reduced, heat and pressure will most likely have to be increased so that the energy remains equal.

Bill Lucas, T.J. Snow Co.

-- Bill Lucas (welders@tjsnow.com), December 18, 1999.

An additional issue to look into is the condition of the weld head. If the weld head has poor "follow-up" welding forces can vary during formation of the weld. Rapid follow-up during a weld is provided by the low-inertia mechanism of the welding head. Follow-up is the ability of the welding head to follow the minute expansion and contraction of the weld during heating and cooling. This action maintains a constant forging action during the manufacture of the weld and insures consistent weld uniformity.

-- Bernie Wire (bw@microwelder.com), February 10, 2000.

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-- JASMIN PATEL (raj553421@yahoo.com), December 08, 2002.

send us sample or drawing.

-- jasmin (raj553421@yahoo.com), July 05, 2003.