straigthening of railroad rails

huangyhg

straigthening of railroad rails
a huge coal stacker reclaimer on rails had foundation embankment settlement. we are going to remediate the foundations. the owner wants the rails to be salvaged but they have been bent out of tolerance. is there a practical way of straigthening heavy rails?
since even bigger than tolerance yet maybe not yet big in absolute value, maybe any attempts to reset the shape without heating may remain in the elastic realm at weather temperature, and hence deemed to fail.
so it seems application of heat and a mattress able to reduce the rails to the wanted shape under conditions of heated plasticity and coercion and to the wanted tolerance would be required.
i think the rail replacement must be quite costly if such kind of equipment is not available locally to be worth the effort os seeking one from afar.
then one needs to check what alterations the applied heat will cause in the rails and if they will remain within metallurgical and mechanical specifications and requirements.
my father is a an old railroad man and he would probably tell you to get new rail. a couple of problems.
1. you can heat the rail to bring it back to straight, but you will have a difficult time making it completely straight. it also requires condsideration into the air temperature. hot and cold temps can have a big impact on rail.
2. the rail may have been in this postion for quite some time and portions of it may have a tendancy to want to return to this shape. you need a good rail base to resist this stress. this affects the foundation and connects of the rail to the base or foundation. you might be able to cut the rail into smaller sections to help reduce these stresses.
i would probably recommend selling the rail for scrap and buying new rail.
thank you ishvaaag and beamer for your inputs.
i think heating high carbon steel will embrittle it making it more susceptible to future problems.
cold working would probably also not do as the rails are very heavy .
merry christmas
a paper by avent and mukai what you should know about heat straitening repair of damaged steel (engineering journal, q1 2001, aisc) addresses some of the issues regarding heat repair of damaged beam-shapes, column-shapes and channels but not rails.
i'd have thought the heat input required to staignten a rail would be excessive.
like the others i think replacing the damaged section is the way to go.  how much steel are you talking about?
the making, shaping and treating of steel, 9th edn., has a chapter 鈥楻ailroad-rail and rail-joint bar production.鈥?nbsp; this includes information on straightening rails, which is done cold using heavy presses.  a pair of presses, each having dies sloped to a straight centerline, plus support rollers on each side, is used.
regarding the metallurgy and effects of heating.  for rail weighing 91-120 lbs/yard, a representative composition is 0.67-0.80% c, 0.70-1.00% mn. 0.04% p (max) and 0.10-0.23% si.  after hot rolling, a controlled cooling is used to prevent shatter cracks.  the rails are allowed to cool under 1000of, then placed inside insulated chambers.  the controlled cooling between 725 and 300of (a minimum of 7 hours is required before reaching 300of) allows formation of a tough, strong, pearlitic microstructure.  
hardening of the top and wear edge, primarily for rail used in heavy wear regions such as curves, can be accomplished by heating with either an inverted u-shaped induction coil or gas burners, followed by compressed air quenching.  residual heat results in tempering to a brinell hardness between 321 and 388.  hardening of the rail web or base is undesirable.
although this information refers to 30+ years old u.s. practices, i would not expect significant functional differences.  without either the specific heavy equipment for cold straightening or for controlled cooling after hot working, i would strongly advise against straightening rails.  straightening by a manufacturer is a possibility, although less feasible if the rail has been partially hardened
check the costs.  i would really be suprised if removing the rails, shipping them to a press break,straightening the rails, shipping them back and reinstalling is cheaper than buying new.  scrap the old rail to a slavage yard and apply the slavaged dollars toward buying the new rail.  it is not only cheaper, but you and the owner will sleep better at night knowning that the freight will be riding on good rails.