Cooling Times of Odd alloyed Steel
Cooling Times of Odd alloyed Steel
(OP)
I would like to heat a piece of track work rail steel of the following profile to the following temperature distribution, all shown in the picture at the link.
This track work can be of that cross-section in the link above, but extruded up to 80 feet long and is made of a low-alloy steel with a pearlitic microstructure. I want to keep the pearlite microstructure, but I just want to heat about 3-4 feet in length of the rail extrusion to the temperature distribution shown in the above link. The chemical composition of the steel is shown in the below link.
If I were to heat the base of the rail (where it shows the temperature range to be 1000 to 1600 degrees Fahrenheit) to 1200 degrees Fahrenheit, and the head of the rail (where it shows the temperature range to be 650 to 850 degrees Fahrenheit) to 750 degrees Fahrenheit, how quickly could I bring the steel down to room temperature throughout its entire mass (72 degrees Fahrenheit) in the following quench scenarios while avoiding the formation of martensite in the steel?
1) Completely submerged in 72 degree Fahrenheit, still water.
2) Sitting on concrete at 60 degrees Fahrenheit in still air (observed to take 6-10 hours).
3) Cooled through application of water misting.
4) Sitting in front of a 48" diameter fan which produces 19500 CFM with the airflow running transverse to the length of the rail extrusion.
5) Cooled by direct application of liquid nitrogen (observed to take 12 minutes but unknown if the microstructure was changed).
Any advice in this realm would be much appreciated because I am very lost on this and I don't have any Jominy charts or anything to look at cooling rates or evaluate anything analytically for this specific type of steel.
Please and Thank You
This track work can be of that cross-section in the link above, but extruded up to 80 feet long and is made of a low-alloy steel with a pearlitic microstructure. I want to keep the pearlite microstructure, but I just want to heat about 3-4 feet in length of the rail extrusion to the temperature distribution shown in the above link. The chemical composition of the steel is shown in the below link.
If I were to heat the base of the rail (where it shows the temperature range to be 1000 to 1600 degrees Fahrenheit) to 1200 degrees Fahrenheit, and the head of the rail (where it shows the temperature range to be 650 to 850 degrees Fahrenheit) to 750 degrees Fahrenheit, how quickly could I bring the steel down to room temperature throughout its entire mass (72 degrees Fahrenheit) in the following quench scenarios while avoiding the formation of martensite in the steel?
1) Completely submerged in 72 degree Fahrenheit, still water.
2) Sitting on concrete at 60 degrees Fahrenheit in still air (observed to take 6-10 hours).
3) Cooled through application of water misting.
4) Sitting in front of a 48" diameter fan which produces 19500 CFM with the airflow running transverse to the length of the rail extrusion.
5) Cooled by direct application of liquid nitrogen (observed to take 12 minutes but unknown if the microstructure was changed).
Any advice in this realm would be much appreciated because I am very lost on this and I don't have any Jominy charts or anything to look at cooling rates or evaluate anything analytically for this specific type of steel.
Please and Thank You
RE: Cooling Times of Odd alloyed Steel
I probably still have them for european rail steel, but not on my server - will have to look through some of the old HDDs.
They will tell you the cooling rate and the final structure. However, you will certainly not end up with the same quality of steel as it comes from the mill!
Are you trying to mitigate the thermal deformation caused by thermite head repair by any chance?
RE: Cooling Times of Odd alloyed Steel
RE: Cooling Times of Odd alloyed Steel
Bob
RE: Cooling Times of Odd alloyed Steel
For example, if I had two pieces of rail steel with exactly the same composition which were both heated to 1200 degrees Fahrenheit, but one was cooled to 72 degrees Fahrenheit by submerging it in a dunk tank (which took 2 hours to cool it) and the other was cooled to 72 degrees Fahrenheit with liquid nitrogen (which took 12 minutes to cool); would the 2nd sample which was cooled more quickly retain more of the original hardness than the first sample which was cooled more slowly?
I suppose this is where I would need to take a look at hardness and cooling rate charts but I don't have any for this rail steel neither do I have any rules of thumb for the amount of mass in each section of the rail being cooled.
RE: Cooling Times of Odd alloyed Steel
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
RE: Cooling Times of Odd alloyed Steel
Bob
RE: Cooling Times of Odd alloyed Steel
RE: Cooling Times of Odd alloyed Steel
Bob
RE: Cooling Times of Odd alloyed Steel
RE: Cooling Times of Odd alloyed Steel
Bob
RE: Cooling Times of Odd alloyed Steel
I heat these rail in a furnace and let these rail air cool but it takes 6-10 hours, which inhibits throughput. I would like to speed things up as far as the heating and cooling times go while still accomplishing what needs to be done (making it malleable for lateral bending) and without significantly altering the properties of the rail.
I can induction heat every one of these and quickly cool it down with application of liquid nitrogen. This would be very fast and allow production of these rail to continue at an amazing pace.
I can heat them in an oven and sit them in a quench tank. This may not be as fast and I would have to re-route fluid flow lines to a tank and make room for a tank and a material flow plan for the rail to be moved into the tank, and setup the tank to have a set flow rate or to just be agitated, decide what quenchant is best, etc.
I can also heat them in a furnace and let them cool under fans. This will probably only be a little faster than letting them sit in open air and cool but a bit easier to maneuver in a material handling aspect.
There are a myriad of different approaches I can take. The heating time and time the rail is held at a specific temperature are not as important to me as the cooling time. I am mostly concerned with a way or a chart or rule of thumb; something that I can use to determine cooling times using different cooling times using different methods without ruining the rail. That way, I can better weigh my options.
RE: Cooling Times of Odd alloyed Steel
Agitated water is a faster quench than Liquid Nitrogen. The nitrogen boils on the surface and creates a gas layer that limits the cooling rate.
I do presume that you will be heating from the flange, and 1200F (maybe even 1250F) will be plenty safe from transforming the structure. Since the head will bend much easier it will only need to 600F or so to make it a little easier to form.
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P.E. Metallurgy