high silicon - flash-butt welding

[lukkaa]

Hello,
I would like to ask you for your opinion.

I have a high strength low alloy steel (0,2-0,25% C, Ni,Mo,Cr) with addition of silicon (about 1,3%). This steel is welded with flash-butt welding and carbon equivalent is satisfactory for this type of welding.
But I have read that silicon over 1% deteriorates a quality of weld joint.

What do you think? Do you have any experiences with this high silicon steel welding?

Thank you for any answer

 

[metengr]

lukkaa;
Here is some relatively simple advice, qualify the weld joint. You can design a pull test to evaluate the strength of the weld joint and surrounding base metal.

 

[lukkaa]

metengr,
Thanks for your reply. Yes You are right, but I didn't write that this steel doesn't exist. It is only a development project.
So I can try to image a pull test of this steel, but without any results.
So, as well as Thanks

 

[dbooker630]

High silicon can create an embrittled area after welding. I had a case with an unintentional addition of Si raised the hardness and reduced the ductility of the joint. You may want to consider a post-weld heat treat to evaluate against the as-welded part.

 

[redpicker]

It is going to be difficult to find much information that will be helpful. Flash welding is a rather unique welding process and has its own set of special problems.

I know that with ERW welds, silicon is often kept very low (<0.05%) to prevent a specific defect known as "hook cracks" in the weld zone. The flash welding process is similar to the ERW process in that it is a non-fusion welding process, but the thicknesses for flash welding are generally higher and ERW is generally a continuous process while Flash Welding is a per-piece process.

In contrast, as far as I know, silicon content is not restricted for friction welding. By "not restricted", I mean the content is in the 0.25-0.35% range. I mention this because friction welding is another non-fusion welding process and, in many ways, more similar to Flash welding than ERW is.

With the alloy content you mention, I a would assume a full post-weld heat treatment consisting of austenitizing (perhaps quenching) and tempering, otherwise, grain growth at the weld zone will cause a problem even if the silicon content does not. A proper post-weld heat treatment may restore weld integrity to adequate levels.

You might ask the producers of the flash welding equipment and/or flash welding processors. Give them the chemistry of the steels you are using and the mechanical properties you need to achieve (including a weld-line CVN) and see what they say. If there are no specific impact requirements, ask for a relatively low CVN requirement (say 10-15 Ft-Lbs). Of course, if you have specific CVN requirements, use those.

Off-hand, I really don't know if this silicon would be an insurmountable or not. You may just have to run some tests to see if the results will meet your requirements or not.

rp