Resistive spot welding of AISI430 steel

[Karolys]

Hello there,
I am new to the forum. I graduated from KTU, have a bachelor degree in Mechanical Engineering, and now working as manufacturing engineer (my first two moths in this position, i also worked 6 months as design engineer before) in Lithuania in the small company producing stainless steel equipment. As you can imagine, i do not have too much experience.
I ran in to a problem at my work of weak spot welds of AISI 430 steel. We normally use AISI 304, and AISI 201 as economy steel, and sometimes where possible AISI430 instead.
As i know from the past, everything was good with the spot welds of all of these steels, but lately I got the information, that one of our products collapsed, and workers in the factory were also complaining about the weak spot welds of the AISI430 steel.
I ran a few tests with a different steel spot welds, put them under the press and measured pressure at their breaking points, which shows that the specimen of AISI430 breaks at on average 3.5 times less pressure applied (~5 kg/cm^2 to ~18kg/cm^2).

I can guess that there is some sort of a change in chemical composition of the steel, and I plan to inform my supply department for that, but anyway, as I want to improve, i need to know where the problem might be exactly.

My question would be, if anyone has ever faced same problem and maybe have a good knowledge in RSW, some links to sites, books, or just a plain answer here in forum? Spot welding quality dependance? Causes for these problems? Possible change in steel composition?

I could share pictures of my test results (how broken spot welds look like etc.)

Thanks in advance

[Kelly_Bramble]

Welcome to EE!

According to the attached document, welding AISI430 is not recommended.

Good luck!

430F.pdf

[Karolys]

Thanks for the reply.

According to a carbon equivalent, neither AISI304, nor AISI430 is recommended for RSW, cause the have pretty similar CE. It hardens metal around the weld, and it may crack easily. But we had selected various currents to weld, and still, result is far worse then welding same specimens of different steel. I would normally be OK just to know that it is not recommended to weld this steel, but we have been using it for 3 years now, and there haven't been any problems.

[Kelly_Bramble]

I would normally be OK just to know that it is not recommended to weld this steel, but we have been using it for 3 years now, and there haven't been any problems.

So then I would propose that something has changed... The equipment needs maintenance or replacement, the material is not what you think it is or the welding process has been changed. Could be a material cleaning issue, handling, or even environment.

[Karolys]

Thanks for the help,

i'll try to find out. Will start with the metal suppliers and suppliers of the welding equipment.