My old boss said I'd never get a clean weld on a leaf spring without pre-heating

Back when I was just starting out, I was trying to fix a broken truck spring for a friend. My boss at the time, a guy named Carl, told me flat out that trying to weld 5160 without a proper pre-heat was a waste of time and would just crack. I didn't have a big rosebud torch then, just my little MIG welder, so I tried it anyway... and of course, it cracked right down the middle after it cooled. That was about three years ago. Last week, I finally got around to trying it again on a similar piece, but this time I borrowed a friend's oxy-acetylene setup and got the metal up to about 400 degrees first. The weld held perfectly and the repair is solid. It's a small thing, but it feels good to finally prove to myself that I can do it right. Anyone have a good rule of thumb for how hot you really need to get 5160 before you strike an arc?

2 comments

2 Comments

rosethompson13h ago

Man, that feeling of finally getting it right after a past failure is the best. Totally get why you'd want to prove it to yourself. That first crack must have been so frustrating, especially with Carl's voice in your head. Good on you for borrowing the gear and taking the time to do it proper. For 5160, I've always heard shoot for that 400-500 degree sweet spot, like you did, where a water drop sizzles but doesn't instantly boil off.

keithb5110h ago

Used to think that was overkill, but you're right.