Weldability of 4140, 4340 to H13 2

[limey1]

The 4140 and 4340 would be hardened prior to welding. The components would be tack welded together, and are under varying compression forces (These are mating faces). Question is what type of welding rod would best fit this application ?

Cheers

 

[metengr]

limey1;
Why do you even want to weld after a hardening heat treatment? Why not before hardening using wed rod of similar chemical composition as the base metals you listed? This makes no sense and significantly increases your susceptibly to cracking either during or after welding. Also, the heat from welding will result in changed mechanical properties adjacent to the weld region.

So, with these reasons above, why do you want to weld after hardening????

 

[limey1]

Wether I use 4140 or 4340, It has to be heat treated before attaching it to the H13 component.(Cant heat treat H13 component) I would like to not heat treat at all but im getting some deformation from the standard 4340 and the print Im using calls for hardening. The Rockwell C is coming in below 20 and I need @ 44-48. Finding an alternate material then puts me in the old price/availability hole.

 

[metengr]

limey1;
Do you realize that for welding to H13 you need to preheat locally to at least 800 deg F? If you absolutely need to tack weld, I would recommend using an austenitic filler metal - 309 or Ni-base instead of a matching low alloy filler metal. The austenitic weld deposit will be lower strength but will be able to absorb residual stresses from weld shrinkage and to lessen the changes for cracking.

You also need to understand that welding to hardened H13 and 4140 and 4340 steels will require PWHT below the original tempering temperature used for hardening. This temperature should be 50 deg F below the original tempering temperature.

 

[arunmrao]

Valid issues raised by metengr. Using 309 or higher Ni based filller metal,may avoid some of the welding issues. However, the weld joint will be an area of low strength in the assembly. Will this be acceptable.
Also if you could describe some more,the application and relative sizes of the parts to be welded,better interaction could be possible.

I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
_____________________________________

 

[limey1]

"the weld joint will be an area of low strength in the assembly. Will this be acceptable".
Yes, the plate will only be tack welded at three points for retaining purposes.
Also, since yesterday, I found out that our supplier wasn't using 4340 hardened, as called for on the print. Some change was made many moons ago to go to a cheaper material, not hardened, which is why Im seeing the problems now. There was now update made to drawings etc. Slightly frustrating!! The application is on a 2000T Extrusion Press.

 

[arunmrao]

Thanks Limey1 for the clarification. I think you are safe adopting the less rigorous Ni based filler metal route.

I have just been reviewing a customer's drawing. The composition is for a low carbon steel (close to 1020),but it specifies Cr min 0.5% and maximum 0.2%. I am surprised!

I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
_____________________________________

 

[limey1]

Wouldnt 1040 get you more in the Cr min/max window the customer wants?