Several years ago, I pulled some loads of rail frogs from a Frog and Switch Mfg. in Memphis,Tn. to a company just west of Bloomington, Ill. They were to be blast hardened and returned to be installated in new switches.
The company in Ill. used a plastic explosive laid in strips on the switch frogs, and then detonated them, in an enclosed cylindrical pipe like structure; I was told that it was the fastest way to increase the Rockwell Hardness of the steel. The idea was to increase the wearability of the switch frog when placed in use. My question is how widespread is this technique to increase hardness? Is it being used currently to improve wearability of rail steel? It seemed that the only location that it was used at was in the frogs[ apparently a place where there is much contact with wheels ,and an area of concern for track maintenance?]
Manganese steel casting inserts (and other exotic metals) are typically hardened this way along with almost all crossing frog inserts (diamonds). A quick way to tell if a frog has been explosive hardened is to see if a “Box-H” has been stamped at the heel or toe of the insert or in the middle of a crossing insert. Frogs with these type of inserts are referred to as being “rail bound” as in being held between at least two pieces of rail.
If a casting fails during explosive hardening, it spider webs like a piece of broken automotive glass. Pretty neat process to watch.
Conley Switch & Frog in Memphis? (Now part of Progress Rail)…
There seemed to be an unanswered part of the question “what is done to improve the wear of normal rail”. Head hardened rail is available but is normally only used in curves where the extra cost is justified.
The freshly rolled rail is inverted and dipped in an oil bath which rapidly cools the upper part of the head and results in a significant increase in hardness. This has to be done in controlled conditions and I think the rail is curved vertically a little on insertion and straightens out on cooling.
I have seen manganese steel rail used in similar situations (and I think the scream of the flanges on those rails was noticeably worse than on standard rails - really banshee like) but that was in the 1950s and early 1960s.
You want that frog insert hardened - Frogs are usually the most brittle things out there and take an incredibly severe pounding/ extreme impact loading over the flangeway gap.
So, by all means, make that thing as tough as economically possible. You are dollars ahead for doing it.
As for rail, M636 is mostly there. Vacuum treating, HiSi and improved rolling, grinding and cooling of the rail have improved the head hardness. If you can’t control the tonnage or extreme curvature (anything much over 2 degrees of curvature), then the head hardened stuff is a must.
You are exactly right. It was Conley, in Memphis, The folks that were doing the hardening were out in a cornfield[ literally] west of Bloomington, Il. It was a commercial fireworks manufacturing operation, they apparently did the hardening operation as an adjunct to that business. They used strips of plastic explosive ribbons [C-4, maybe?] laid out on the surfaces to be hardened, then they ‘shot’ the stuff in a cylindrical structure[ possibly an old tankcar body; that they packed with a loose gravel looking product to absorb the impact of the explosive action, which produced a mufffled but powerful blast. It was pretty interesting to see. When they were done we loaded the pieces back up and went back to Memphis. At that time [ about 8 years ago] they were pretty busy. It was a pretty interesting side to a railfan and one not a lot get to see.
Tom; The Bloomington facility was simply a couple of corrugated sheet metal sheds about fourty by eighty, open on one end, and a smaller building or two close by. The road to the place was about a half mile long, and wound through what was then a full stand of corn, about seven or eight feet high; the tank car looked like a large pipe closed on the outside end, but open under the easternmost shed. Put a few vehicles around it , and there you are. There was not even a sign about it on the road, you were directed to turn into the driveway of a farmhouse by the road and follow the lane back to the plant, which with the growth of the corn was impossible to see from the highway.
Our corporate “mothership” is right there in Bloomington, not far from State Farm’s campus. Gee, think the explosives people could do something about our unhelpful and none-to-bright accounting department?[}:)][}:)][}:)]
The frogs to be hardened were basicly constructed at the Memphis facility, of then, Conley Frog and Switch, now Pprogress Rail [ per Mudchicken]. The frogs alone, along with some prefabed rail points were transported by truck to the Bloomington facility, where the hardening process was done, and then transported back to be constructed into switches which were assembled and put on a switch rack car[ not sure of the exact designation,but the whole assembled switches could be transported to the placement site on these cars], or the switch parts alone, in a ‘kit’ format to the place for a field assembly.
I would think that if the hardening was done, “In Place,” the liability would be imense, as it would surely attract crowds. It is not a problem to simply lay down the plastic explosive to do the blast hardening, but can you imagine the NOISE! What a racket that would be… not to mention the flash, nothing short of spectacular…[}:)][}:)][}:)]