Metal Question, Cold Vs Hot Rolled
- Thread starter sterno
- Start date
Cold rolled steel is low carbon steel. Hot rolled steel is also low carbon steel.
"Cold rolled" steels is made from hot rolled steel by running it through rollers to break up the oxides on the outside and then "pickling" it in acid to remove the deposits. Cold rolling breaks up the grain structure of hot rolled steel. Some old time machinists preferred hot rolled steel because they felt the grain structure provided more strength than cold rolled.
Heat treating (hardening, drawing) to produce strength is dependent upon enough carbon in the steel to allow it to change from ferrite into austinite and then in to martinsite. Neither hot or cold rolled steel has enough carbon to do this. They can however become "half hard" with a sub-zero quench (liquid nitrogin...not likely to be used outside a lab or a manufacturing facility). Both can be "case hardened" by heating to red heat and adding carbon with some product like Kasinite, but this will only produce a hardness that is only a few thousandths thick.
Cold rolled steel is easier on machining cutting tools than hot rolled, unless you get underneath the oxide on the first cut.
Most gun parts require some degree of heat treat or require some property that prohibits the use of cold or hot rolled low carbon steels for most gun parts, but not all.
Pocketfisherman
New member
Cold Rold is also significantly harder on the Rockwell scale then Hot Rolled. The surface is less porous, slower to oxidize, but it is also more brittle than hot rolled. A lot of parts are made from hot rolled because it is a lot easier to bend, cut or machined, and then heat treated after the fact for hardening. It does not much matter which is used, it is the end result of the product, and quality put into the manufacturing and/or hardening of the parts during that process. Cold Rolled can also be annealed to soften it, machined, and then hardened again too, but that's expensive in terms of the energy costs to do so.
O-1 (oil hardening drill rod), W-1 (water hardening drill rod), are the too most common that can be hardened and drawn to the desired amount of strengh and hardness.
http://www.onlinemetals.com/steelguide.cfm
You want tool steel:
http://www.onlinemetals.com/toolsteelguide.cfm
http://www.onlinemetals.com/steelguide.cfm
You want tool steel:
http://www.onlinemetals.com/toolsteelguide.cfm
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Common 1018 cold or hot rolled steels cannot be hardened, come in a soft state...does not have to be annealed, or can it be.
See links above relative to hot and cold rolled steel and the carbon content. Steels that contain .20% carbon will not harden with heat and quenching with normal means.
Tool steels (which can be heat treated) are not usually refered to as: hot or cold rolled steel.
I found an online supplier that answered alot of my questions. Thanks for the responses!
I'm pretty familiar with metalworking/blacksmithing/foundry processes, I just don't know that much about the different steels. All the stuff I've worked on before didn't really call for anything special so I just used hot rolled.
I'm pretty familiar with metalworking/blacksmithing/foundry processes, I just don't know that much about the different steels. All the stuff I've worked on before didn't really call for anything special so I just used hot rolled.
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Ok, so let me speculate for a second...
Lets say I was going to fabricate every part on a single-shot pistol chambered in a low pressure round, like say, .22lr.
Would it be safe for me to use hot rolled steel, case hardened, for the internals (Hammer, sear, trigger, firing pin, etc.)? Would I be safer using tool steel for the barrel and breech block?
Lets say I was going to fabricate every part on a single-shot pistol chambered in a low pressure round, like say, .22lr.
Would it be safe for me to use hot rolled steel, case hardened, for the internals (Hammer, sear, trigger, firing pin, etc.)? Would I be safer using tool steel for the barrel and breech block?
Bill DeShivs
New member
You would be safer using tool steel for all the parts. Most makers use 4140.
asskickinpeanuts
New member
steel
My understanding of steel (at least sheet):Carbon content is a function of the heat/grade (or recipe) of the melt for the steel at the mill. Hot rolled is softer because the grain structure is haphazard. Cold rolling aligns the grains, which is called work hardening, which increases the stiffness. Annealling after cold rolling allows the grains to randomly re-orient themselves. Thus, dead soft or fully annealed is soft like hot rolled. Tempering allows a certain amount of hardness to be imparted back to the steel, making it harder, depending on the amount of elongation after annealing.
Folks have made careers out of studying metallurgical properties and how to get them for different applications. More specific questions will indicate more specific answers. And yes, this opinion may be worth what you paid for it.
My understanding of steel (at least sheet):Carbon content is a function of the heat/grade (or recipe) of the melt for the steel at the mill. Hot rolled is softer because the grain structure is haphazard. Cold rolling aligns the grains, which is called work hardening, which increases the stiffness. Annealling after cold rolling allows the grains to randomly re-orient themselves. Thus, dead soft or fully annealed is soft like hot rolled. Tempering allows a certain amount of hardness to be imparted back to the steel, making it harder, depending on the amount of elongation after annealing.
Folks have made careers out of studying metallurgical properties and how to get them for different applications. More specific questions will indicate more specific answers. And yes, this opinion may be worth what you paid for it.
grymster2007
New member
I wouldn't use hot or cold rolled steel for most gun parts. High strength alloy steels such as 4140, 4340 and 4350 and many others would be appropriate for most parts. Tool steels, such as O1, A2, D2 might be good choices for parts subject to wear, but not practical for most applications.
W-1 is water quenching tool steel. If you quench it in oil rather than in water, it will not harden as much as if quenched in water. O-1, if quenched in water, is very likely to produce quench cracks and should only be quenched in quenching oil.
Water is a more sever quenching medium than oil. W-1 Steel, although intended to be water quenching, often will have quenching cracks and distortion even if you use the correct temperature for hardening (1333 degrees F.), and drawing.
Tempering is performed after quenching to soften the steel slightly from the very hard (and brittle) quenched state.
Without tempering it is possible for steel to be very hard but brittle to sharp loads.
Tempering is done by heating to a controlled temperature and allowing slow cooling, or sometimes another quench but at a lower temperature.
first, im not a metallurgist nor a gunsmith, just a lowly machinist. hot or cold rolled material is just how the material was formed and does not tell you what type of steel you have. cold rolled steel is most commonly the 10xx series steels,1018, 1020 and so on but that type of steel can also be hot rolled. see how it works? you choose the proper TYPE of steel for the job. everything ive read shows alloy steel,4140.4340 and 17-4 and 400 series stainless is used firearm parts, maybe a real gunsmith could verify this. by the way I do pretend to be a gunsmith but only on my guns
if you are really interested in the applications for the different types of steels get yourself a copy of the machinerys handbook. enough information to make your head explode, just try to get a used copy cause new ones are expensive.
if you are really interested in the applications for the different types of steels get yourself a copy of the machinerys handbook. enough information to make your head explode, just try to get a used copy cause new ones are expensive.
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grymster2007
New member
It's metallurgy.... two ells!.... pick up yur English in a bar didja?
