heat treating a tig welded piece

Ryan Minchew

Ryan Minchew

Joined
Sep 29, 2005
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580
I was wondering if anyone knew where I could find out what happens to a weld that has been heat treated? Does it become brittle and possibly what the shear and tensile strengths are? I am hoping to weld 4140, 4130, or some stainless steels and have them heat treated after they are tig welded. I will weld 4140 to 4140 and such it won't be 2 different types. I just need to make sure my idea is not going to work and that I'm not making brittle welds. Thanks for any help or advice.
 
I know that when some makers weld a mild steel tang onto a knife they do it after heat treat. Then they heat the weld to temper it so it's not too brittle.

If your doing this before heat treat then I would think that you would be ok since the weld will get heat treated and tempered as the rest of the knife.

Typically the weld is stronger than the parts being welded together.
 
First pick a welding rod recommended for those alloys .For hardened steel a preheat and post heat is a good idea, 400 F is OK.
 
Don Hanson III said:
I would think normalizing is a good idea after welding also.
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That and a compatible filler rod should make it work. You know you could cut off a thin sliver of the origin steel (grind down a bit if need be) and actually use it for filler.Make sure you have enough argon to keep it sheilded and when you stop welding back off the arc, but keep the argon on the puddle till it cools a bit.
Jim
 
If you have a really good TIG machine it will give a pre and post flow of argon. Mine does not give a post flow so I just cycle the foot pedal to stop the arc and restart the flow. Just another method. Backing off works too I just don't like the flare.
 
ib2v4u said:
That and a compatible filler rod should make it work. You know you could cut off a thin sliver of the origin steel (grind down a bit if need be) and actually use it for filler.Make sure you have enough argon to keep it sheilded and when you stop welding back off the arc, but keep the argon on the puddle till it cools a bit.
Jim
Click to expand...


I've not tried tig welding before I didn't know if it was possible to weld using the same material. This is a project I probably will have to farm out. I appreciate the help guys.
 
With tig you are using a piece of tungsten surrounded by a ceramic "cup" the cup has a flow of argon in it to keep a nutral atmosphere. When you fire the arc up you are creating a very hot plasma arc. The tungsten is not consumed. What you do have is a tremendously hot heat source you can focus very well. Usually the weld is made by melting the surface of the parent pieces filling an v with filler rod. The filler can be any metal that is compatable to the parent. If 2 pieces of say D2 were butted together tightly I could run down the crack and melt them together. Problem is there would be no real depth to the weld. To get a full penetration weld I need a groove and as I melt the parent pieces I need some filler to fill the groove. If I had a piece of d2 wire, small square stock what ever, as long as I can easily melt enough off to fill the groove I am good. The process will burn off a bit of the carbon though. You could take a forged 1084 blank clean it up and then tig spots and lines or what ever of nickel or even thin pieces of 15n20 on the blank it would resemble damascus. PS I have a bunch of near pure nickel tig wire. Someday it will be play time.
 
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