Welded steel wire(low and medium carbon)

We need more specific information the type/grade of wire. Is it cold drawn? you say (galvanized) zinc should not be welded with or to. The zinc evaporates during welding and migrates into the weld structure weakening it. As you have found out it becomes brittle always plate up after the welding process. I answered this very same question a couple of days ago. ZINC should never come near a welding process.

The wire is cold drawn and the wire grade is from a SAE1020 steel. The problem is we have to weld it because it is join. The wire break occured after hot dip galvanizing.

If I'm clear on this, you have a 5 mm rod being drawn through a series of dies to get to your final size. How many steps, and what is the draft per step? are you exceeding the available ductility in one of these steps? Are the dies matched in bearing length, or did somebody slip in a 'replacement' to get the line running.

Is there any sign of residual hot roll scale on the rod under the plating?

What are the die angles in the dies, and are you ABSOLUTELY CERTAIN THAT YOU DO NOT HAVE A ring in one, which negates the angles and results in internal ruptures do to lack of flow. ALso, in addition to the lube on the rod, are you SURE that you have complete and unobstructed flow of oil or whatever you are using to each die?

milo

I had to chime in after reading the other responses. I too work with cold drawn welded wire and suggest you first look at the setup of welder itself. Are you running a resistive welding setup? If so look at your weld itself. Are you getting excessive blowout? Not enough fusion taking place between the 2 wires? Can you see signs of the current not passing directly from the positive electrode through the wires to the ground electrode? Remember current takes the least resistive path to ground. Ensure that it is through the product and not a secondary path. Also ensure that your spring force, heat & hold settings are sufficient and that the stroke length of the head is correct. Otherwise there is no squeeze. As far as testing of the welds go, I am assuming that you are welding crossed wire, then I would suggest a shear or torque test sampling of your welds. We weld sheets and rolls and always check the tensile strength & elasticity of wire coming out of wire draw, as well as, the shear strength on the 1st & last roll/sheet on an order. This way you try to catch the problem before sending it out to the galvanizer. Hope this has helped.

Sonave- Nice post. With out knowing where in the process that the break is occurring, all bets are off. If its breaking before drawing or in the die, then the weld quality may be the issue as you pointed out. If its breaking after the initial die or during drawing and straightening, then there may be die issues in addition to weld quality. If it is breaking after galvanizing, well thats a whole 'nother story. Your advice to look at the process of welding is good advice, and upon further reflection- something rare on these rush to post public forums- seems to be the most likely possibility- the welds aren't staying together to keep his machines running continuously. Further information on the process and where failure is occurring will help us all better understand the problem and solutions.

Nice job.

milo