Butt welding is a joining process used to join two parts together. The work acts as the electrode and the entire cross section is welded. After the parts are clamped and brought together with force a current is applied. The intention is to create heat using Joules Law H= I2rt at the joint surface with current flow.
As the joint heats up the force upsets the joint and a bulged area is formed. The current is stopped. The weld area cools under force and then the force is removed and the butt weld is complete. This differs from flash welding, where the current is applied before the two pieces come together. This creates the flash.
A very similar inquiry came in previously. That person was butt welding 0.500” diameter 1008 steel on a 30 KVA machine. The machine apparently was adequate. The issue was fine tuning the welding parameters. Your 4140 steel is stronger but could probably work on a similarly sized machine.
This question was answered earlier in another article in this blog:
“WE ARE BUTT WELDING 0.500” DIAMETER 1008 STEEL. HAVE TRIED SEVERAL FORCES, PULSES AND SLOPES WITH NO SUCCESS ON A 30 KVA WELDER. NEED SOME GUIDANCE”
Based on that article a 30 KVA welder probably is large enough for this butt-welding job.
The person making this inquiry has seen this finished product and questioned is it better to butt welded before or after the plating process?
A second question was could equipment be fabricated in house to perform the butt welding?
It is this authors belief never having seen this product, that the plating process is a post welding operation. Butt welding and the generated heat would severely distort physically disfigure the area of the butt weld. Material removal is likely required to resize the butt weld/upset area. Any pre butt weld plate and diamond in that area would have been ruined. If nickel plate is necessary in this area, at least a spot replate could be performed. The diamond would be missing for this short length.
It would be assumed this diamond tipped wire is being used to cut through some very difficult/hard materials and coolants will likely be present. A short welded length may not be a problem.
This cross section of steel is large and would probably not be a candidate for spot welding. Butt or flash welding would be a better choice. I am not aware of any chart available in the marketplace to offer power requirements or suggested schedules by cross section for this type of material.
If your facility has equipment in house or you can rent time somewhere, trial and error would be my suggestion. Always start trials at low power settings and work up to higher power levels for safety sake. When you begin to get some sort of welding hone in slowly to good results and record all welding conditions.
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