The machine is working allwright some time, but after 10 pices, we are getting penetration defects, some time in the mittle og the welding, and other times in the HAZ zone, and we dont know why. The machine is working on the same parameter the hole time, we are not changing anything. The machine is a AC installation with 800 kVA at 50 % performance.
I'm assuming you mean defects in the weld called penetrators. Are you using shielding gas? If so what type? You indicated you are running up to 10 pieces. Is that in a 8 hour period. What is your typical productivity?
A consumable shielding gas would benefit your process. Basically penetrators are originated by the atmospheric oxygen combining with the molten material (resultant of flashing) and creating an oxide. Using an active shielding gas (lets say propane) on the outside of the part during flashing will minimize the oxygen at the faying surfaces. One warning: if you use propane in the ID (assuming the parts are hollow) you must be careful. If need be you can use an inert gas on the ID (Argon) to keep the threat of explosion to a minimum.
You can introduced by tubing (copper) that encompasses the circumference of the part adjacent to the flashing (sparking). Holes can be angled into the tubing in order to jet the propane into the faying surfaces. That way the tubing doesn't become too abused and the gas is consuming the oxygen. The gas is also introduced after the flashing starts and yes fire is visible during the weld.
That you will need to determine for your application. What one process uses may be too little or overkill for another. Try it at different flows and examine the welds.
You may need to furnish the type of steel or an ASTM # of the materials you are trying to join for someone to help you further.
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