> Not such a good idea with a riveted boiler.
> All of the rivets would relax as much as the
> rest of the boiler, and you would end up
> with the worldÂ’s largest garden sprinkler. I
> think our best bet here would be to treat
> them as gently as possible in use to avoid
> thermal shocks. The usual fire up slow, cool
> down slow, and donÂ’t run the injector for
> too long at a shot.

I hate to chime in again, but. Rivets will not relax under a stress relieving process. Their tensile strength will follow approximately the same temp. curve as the parent metal. Area of higher stress occur in the material being riveted as they are shock heated and rapidly cooled during the riveting process. These stresses are normally relieved as you mentioned by a slow fireup and avoiding further thermal shock. When alloy boilers are reriveted the area around the rivet changes in microstructure forming a very brittle matrix. This is what lead to cracking problems and early failures. To accomplish repairs successfully the affected areas must be heat treated (at temps considerably above steaming temps) to retemper these areas.


lamontdc@adelphia.net

A friend was in Strasburg several years ago when the 4-8-0 was a kit. He found a welder working on frame voids - something about hammering out the voids and welding in? Please explain the process you used and how it has held up in service. Might help the rest of us solve these problems.

Dave

irondave@bellsouth.net

My fault - I didn't spec a temperature range and Kelly probably envisioned a red hot boiler. I envisioned a kitchen oven enlarged.

Nice to have a metal expert on the board.

Dave

irondave@bellsouth.net

What years did locomotive builders use (or switch to) alloy boilers and what was that alloy? Are any in operation today?

thanks,
Ray

> I hate to chime in again, but. Rivets will
> not relax under a stress relieving process.

What does stress relieving do? Stress relieving involves heating a material to a temperature of 1100 degrees for a specified amount of time. An example would be boiler plate which is a P-1 material. Section I of the ASME Code specifies that steel up to 2" thick shall be held @ 1100 degrees for 1 hour per inch of thickness. Stress relieving does just what it says, it relieves the material of stresses. Rivets on the other hand are under stress by design. That's what keeps a riveted joint tight. As the rivet cools, it tries to shrink, thus putting tremendous pressure on the lapped plates. If you stress relieve a riveted boiler, you will relax or relieve all of the rivets so that they are no longer under tension. Instant sprinkling can. This is why you don't rivet a boiler with cold rivets. (Plus, they would be too hard to drive anyway.)

rick@strasburgrailroad.com

You are 100% correct and a full anneal will anneal everything. What we are talking about here is a treatment at much lower temperatures for a longer time to remove "spikes" of stress higher then the rivets from the fabrication.

lamontdc@adelphia.net

What he might have witnessed was Bill Sherwood replacing a section of a lower frame rail that was a casting defect from Baldwin. The section in question is about 3" x 4" and runs from one box pedestal to the next. When the frame was cast, this part must have been farthest from the inlet of the mold, as the steel flowed into this section from each end, and was cold enough that when the two streams met they just stopped and didnÂ’t knit together.

The result was a perfect ball-and-socket joint that we discovered with magna-flux ½ way down the length of the section. When cut out, the two pieces came right apart, the two rough cast ends fitting together perfectly.

Bill then welded in a short chunk of steel bar to replace what was missing. The hammering your friend saw was probably Bill air hammering his welds between each pass relieve them and minimize the welds pulling the frame together.

kelly@strasburgrailroad.com

Could have been but I distinctly remember him saying something about hammering all around flaws and having them "pop out" of the casting, followed by welding in the resulting cavities. Sounded odd to me at the time. Wouldn't grinding out flawed areas be the approach?

Dave

irondave@bellsouth.net

> Wouldn't grinding out
> flawed areas be the approach?

> Dave

You would think so. I can't say what your friend might have seen.

kelly@strasburgrailroad.com

> You would think so. I can't say what your
> friend might have seen.

Yeah, and he isn't a drinker. Wish I had paid more attention.

Dave

irondave@bellsouth.net