[jruddat]

Hi all,
I was wondering which filler metal you might recommend for welding a normalized 4340 pipe to a normalized 4130 pipe of the same size (0.058" wall thickness). After welding the parts will be quenched at 1570°F and then tempered twice at 400°F. I was thinking that Eureka 130 might be a good choice given the need for heat treatment afterwards. The welded joint will need to be as strong as possible since the pipe will be operating under torque as high as 50–60 ft⋅lb.

Thanks,
Jack

[FWE]

Fun. Time for you to get the etchants and hardness testing machine out, along with some other toys, if you are really interested in the mechanical properties.

Looks like Eureka 130 is a 4130 rod so you will need to see what it does when heat treated, which is the way to maximum strength. Some interesting stuff on astmsteel.com; 4130 and 4340. Seems like you can just fit in the tempering window of each material, all depends what characteristics you are really after.

What is the pipe for? Driveshaft?

[jruddat]

The pipe It is for boring into trees, the 4340 portion being threaded and the 4130 being the main shaft. Eureka 130 is 33-38 HRC as welded and 48-52 HRC when fully hardened.

[FWE]

The plots below, from here, should give you an idea of how the properties of a 4130 weld can change with heat treatment. If you want an indication of what could happen then I hope this helps. In this instance, welding with matching filler requires some work to get right, hence why this is normally recommended.

[Poland308]

When you say boring into trees do you mean like a hole saw or like a screw? Very different torq profiles.