10 replies to this topic

[Muda]

Is back welding wheel studs (hardened in this case) on the back of a hub (rear in this case) ever a proper procedure?
Would this change the strength or ductility of the metal?

[Jim Boemler]

What are you trying to accomplish?

[dstevens]

Welding hardened steel requires more attention than with mild steel. It will effect the material and will need to be treated after welding to ensure it doesn't weaken. It's a Varsity job. You'd need to use something like Eureka Marweld 250, DC TIG straight polarity, 100% argon. Likely to fubar it long term if you did MIG with something like ER70-S2.

I would (and did) go with press fit. Notwithstanding the complexities of welding hardened steels, the SM rules don't allow for that mod even for damage repair as it's not a recommended repair per the FSM.

To echo Jim, what are you trying to achieve?

[Muda]

Took a light nudge on the LR wheel early in the enduro this weekend (not my car). Rubber to wheel only. About and hour later co-driver came in with wheel coming off. All 4 hardened studs had broken. Examination revealed that studs had been back welded. Each broke just below the flange. Seemed to me that welding hardened steel would make it more brittle unless it was heat treated again. But I'm no metallurgist. Wondering if back welding is done by others (if so, for what purpose) or if the original owner of this hub just had no clue.

[dstevens]

The properties of metal are changed by welding even if the material isn't hardened. The extent depends on the material, filler and to a lessor degree, the process. It's possible (and very likely) that welding the material made it more brittle. In fact it's not uncommon. If he welded it without regard for the material or filler it could have compromised the part.

On edit: if you want to get your fabricator geek on here is a piece about the effects of welding on steel...

http://www.thefabric...ngthening-steel

[Keith Novak]

Seemed to me that welding hardened steel would make it more brittle unless it was heat treated again. But I'm no metallurgist.

Bingo. Can't say for sure that they broke after being welded because of the random local heat treatment, but it seems a great example why not to. I would have guessed either the lugs would become brittle at the area, or the hub could become brittle causing the holes to crack.

[Jim Boemler]

Probably true, but it begs my earlier question: What was the welding trying to accomplish? Why would anybody do it to begin with? Based on that issue, "clueless" gets my vote.

[Glenn]

Probably true, but it begs my earlier question: What was the welding trying to accomplish? Why would anybody do it to begin with? Based on that issue, "clueless" gets my vote.

Probably the studs were coming loose. Some studs need a small chamfor to completly seat against the hub, I have seen numerous times the stud loose after loostening the wheel lugs. Have broken several as a result. In one case we had to use a plazma cutter to get the wheel off the car, KILLED the wheel!!!!

[Muda]

Probably true, but it begs my earlier question: What was the welding trying to accomplish? Why would anybody do it to begin with?

The only thing I can figure is that the guy screwed up the holes so that the studs wouldn't press fit tightly and decided to secure them with a weld.

[Jim Boemler]

Glenn, if that's the case, they bought the wrong studs. Solution is to buy the right parts.

If he'd just tacked the stud in place, it probably wouldn't bother either part. Doing a full weld puts a LOT more heat into the parts.

[dstevens]

The only thing I can figure is that the guy screwed up the holes so that the studs wouldn't press fit tightly and decided to secure them with a weld.

The better way to fix that if you didn't want to buy a new one would be to fill the holes that are loose and re drill/bore them. Unless you have the equipment and chops it would be cheaper (and easier) to buy salvage uprights. If you had a stick welder, angle grinder and drill press with the right sized drill it wouldn't be too difficult.

Edit: new hub @ MSM is pretty reasonable...