Kingnero & Gtaw:
This is a bit off topic for this thread but you guys might find it interesting. It relates to Gtaw’s excellent post of 19AUG17, 14:59, in thread725-429054, RE: “HAZ and NDT in Piping,” and his last post here, and the way small unforseen things can really change the picture. And then, to toughness, hardness, brittleness and low cycle fatigue in my case, as they might be issues in this thread too. We were making CJP welds in 1.5 & 2" thk. by about 10' wide in HSLA stl. plates, butt welds, many passes, about 1/3 from one side and 2/3 from the other side, SAW, with a flux with some alloying constituents in it. We had used this wire and flux combination for years without any problems. But, this time they really bit me in the butt.
I got an early a.m. call at home before even starting for the office. At least I didn’t have to go back home to pack. We had a large depressed center flat car sitting in a rail yard on the east coast, with a several million dollar transformer sitting on it, and a large crack in the deck pl., in the lower transition area of the deck pl. What to do, could I bring a new railcar along with me when I came out to have a look, can you get here by noon, etc? I sure didn’t have any answers during those first morning phone calls. On seeing it, the crack seemed to originate in the above mentioned CJP butt weld, and went toward the center of the car and also up the transition. Fortunately, the crack was in a pretty favorable orientation w.r.t. the stress fields, so I had them drill some holes through the deck pl. at the crack tips, did a bunch of calculatin, thinkin and prayin and then told them we wouldn’t pay for transferring the load (+ 200ton, near the car’s load limit) to another car, even if we could find one quick enough, and told them it would be o.k. to move the load to its destination. The transformer manufacturer, the handling railroads, the car owner, and the power company were in a real twit. They wanted the transformer moved safely to its destination, on time, and certainly didn’t want any of the responsibility if the railcar caused any problems. We did buy some extra short term insurance for this move and our ill situated involvement in it. We got regular reports on the car’s progress during the rest of the trip, as to any additional crack growth (none) or other unusual conditions (none), and then had the car brought back to our plant.
We took samples out of the weld area and the two base metal pls. for testing. The weld looked good when we sectioned it, and it had been UT’ed during construction. But, chemistry and hardness, etc. at different levels in the weld showed increasing manganese and hardness in the outer passes of the welds. These multi-pass welds were precipitating some manganese out of the previous weld passes and out of the flux too and concentrating it more and more in the outer passes, and the more-so with more passes. The crack did seem to originate in the outer passes of the weld. We gouged out the crack and repaired it, and we replaced the top layer, or so, of weld passes in the butt weld. The metallurgists told us to switch to a neutral flux and the same welding wire for the multi-multi-pass welds and that seemed to solve the problem. At least I’m not aware of any more cracks like that one, on a fair bunch of railcars of that general design. We did do some testing and inspections of other cars in this group. These cars were only a few years old, and when you consider the cars don’t regularly run under max. loading/max. stress (max. cap’y.) and some percentage of the time they are running with no load or only 3/4 max. loads, etc. so this was hardly a high cycle fatigue problem, and not even particularly highly stressed in the crack region. But, in this case the hardness/brittleness of the weld seemed to do us in.
