Welding 4140 PH bucket pins

Date 10-13-2015 02:43

I need to weld a collar onto a 3" dia. bucket pin (4140 PH) about 21" long. I'm using A36 (0.5" thick) for the collar, and making a 1.5" plug weld to connect the collar/flange to the end of the pin. After consulting the Lincoln Bible, I decided on using 309L filler (had a bunch leftover) and a 500° preheat on the end of the pin. I filled up the plug weld in around 12 passes or so, keeping my interpass temp around 500°. These will be used on a compactor like this one.
I just sent the first two off, and have 10 more to do, but I wanted to ask the experts about my process. The collar just keeps the pin from falling out, but I always get paranoid about Q&T alloy steel. Is this approach reasonable or fubar?

By 803056

Date 10-13-2015 19:50

If it works, why question success.

Al

By devo

Date 10-13-2015 21:37

Thanks Al

By Superflux (****)

Date 10-14-2015 01:58

Pretty much the way we used to do in the "Coal Hole" I worked in, except we were only using 300° preheat.

By mcostello (**)

Date 10-14-2015 02:59

Is more preheat a bad thing?

By welderbrent (*****)

Date 10-14-2015 05:35

It is just as harmful to preheat too high as it is too low. Both ends of the spectrum need careful observation especially with certain grades of steel.

Brent

By marktski (**)

Date 10-14-2015 16:06

At a nameless OEM of mining equipment, we used 450 preheats on 4130 regularly.
500 on 4140 won't hurt. I always went by the rule that if you stay below 800 degrees,
you shouldn't harm (most)steel at all. Correct me if I'm wrong.

By Superflux (****)

Date 10-17-2015 03:54

marktski

Not to agree or disagree with the 800° hypothesis after all, welding occurs at MUCH higher temperatures. I've heard many "rules of thumb", such as 100° per inch of thickness and that magnetizing will destroy the temper.
I've used a qualified procedure with Hastelloy and 4140 that had a 600° preheat.
Years ago (1970's) when high performance bicycles were in their infancy and aluminum was too costly for most riders/buyers, these custom frames were made of 4130 under the assumption that no post weld heat treat was necessary and only the Olympians required the benefit of aerospace alloys.
After all that long windedness, it boils down to what Al said... basically, why mess with success?