General question about hardening and tempering process
General question about hardening and tempering process
(OP)
To all,
I am in the process of evaluating the performance of an existing half hard tempered CRS bracket and I just realized that I don't have any information regarding the physical property of the material after the hardening process other than the hardness number. I know there is a relationship between BHN and UTS, but is there anything else? How about the yield strength? Would the Young's Modulus be affected in anyway?
Any help will be greatly appreciated.
Thomas Wong
Chicago
I am in the process of evaluating the performance of an existing half hard tempered CRS bracket and I just realized that I don't have any information regarding the physical property of the material after the hardening process other than the hardness number. I know there is a relationship between BHN and UTS, but is there anything else? How about the yield strength? Would the Young's Modulus be affected in anyway?
Any help will be greatly appreciated.
Thomas Wong
Chicago





RE: General question about hardening and tempering process
RE: General question about hardening and tempering process
RE: General question about hardening and tempering process
Be careful when using the word temper, since there are two meanings. One meaning is the heating process performed after austenitizing & quenching a hardenable steel alloy, so that the martensite is tempered to a more desirable microstructure. The other meaning is used to describe the condition of metals, for example, cold rolled-steel in the half hard temper or an aluminum alloy that has been processed to the T6 temper.
I believe it is this second meaning in which you are interested. If a metal sheet/strip is cold-rolled without subsequent annealing, it will be stronger/harder, but have less elongation and formability. Half-hard is not very precise, but it means that the steel has been cold-rolled so that the thickness has been reduced by a certain percentage. For low carbon steel, this means the hardness will be ~ 70-85 HRB, the approximate tensile strength is 380-520 MPa, and the elongation will be ~ 4-16%. Data is from ASM HANDBOOK Volume 1.
RE: General question about hardening and tempering process
That's about the information I have come across so far by browsing thru websites, and I think your message has clarified that for me. So, by refering a part half-hard really only mean the strip steel (before forming) has been rolled so that the thinkness has been reduced by a certain percentage to gain hardness and tensile strength and with no heat treating process involved? I guess I got the two mixed up, I always thought that the terms full-half, half-hard and quarter-half came from heat treatment processes.
So, this half-hard bracket I am studying has a higher UTS, higher hardness number but with no improvement in Young's Modulus or yield strength? I am not sure if I understand what it means when you say "elongation will be ~4-16%"
Thanks,
Thomas Wong
Chicago
RE: General question about hardening and tempering process
Elongation refers to the change in length of a sample that has been tensile tested to failure. The steel will stretch ~ 4-16% depending on the grade, amount of cold reduction, etc. The yield strength will be the stress required to cause permanent deformation and the ultimate tensile strength is the highest stress produced during the test. Refer to a text book or a perform a keyword search on Google for more information on tensile testing.