I would appreciate any info that anyone has on the process of heat treating steels to harden them. For example if I were to buy a 4140 round, oil quenched and tempered, which will have a Rockwell C32 is it possible to heat treat that same round to a C60? And if so how is this accomplished? What if I needed only a C50 how does this change the process? Thanks in advance! [sig][/sig]
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Hardening of steels
- Thread starter kipp
- Start date
Dear KIPP
You want to harden and temper Aisi 4140 to various hardness levels.Pl write the the shape and dimension of the product you want to heattreat. I have the answer to your problems. Pl write to me in the following E-mail address,
Jayjit Bakshi. ( joyjit_b@hotmail.com)
Thanks-----Jayjit. [sig][/sig]
You want to harden and temper Aisi 4140 to various hardness levels.Pl write the the shape and dimension of the product you want to heattreat. I have the answer to your problems. Pl write to me in the following E-mail address,
Jayjit Bakshi. ( joyjit_b@hotmail.com)
Thanks-----Jayjit. [sig][/sig]
alpinecryo
Mechanical
Kipp,
To harden 4140 to higher Rockwell, you will need to anneal the steel and then repeat the heat treating cycle. You can expect to get decarbing, or scaling. Once 4140 is heat treated, you will need to turn some of the OD to get below the softer outer layer. To get a different hardness, you "draw" at a higher or lower temperature. If it would be helpful, you can e-mail me at dougb@alpinecryo.com I would be happy to talk to you. Doug Dougb
To harden 4140 to higher Rockwell, you will need to anneal the steel and then repeat the heat treating cycle. You can expect to get decarbing, or scaling. Once 4140 is heat treated, you will need to turn some of the OD to get below the softer outer layer. To get a different hardness, you "draw" at a higher or lower temperature. If it would be helpful, you can e-mail me at dougb@alpinecryo.com I would be happy to talk to you. Doug Dougb
I think the steel is coming to you in the normalized condition. The hardness you report would be very low for a quenched-and-tempered 4140.
The maximum hardness in a quenched steel depends on the carbon content of the martensite formed during the quench. The technical literature says that this maximum for an xx40 steel is HRC 60 --- before tempering. And, since 4140 is not a deep hardening steel, this hardness will be only on the surface and --- depending on the mass of the part --- a short distance below. After tempering --- almost always a very good idea --- at a temperature of 150C, you should expect to have (at the surface) a 0.2% yield strength of about 1460 MPa, an ultimate tensile strength of about 1970 MPa, an elongation to plastic instability of a little over 5%, a total elongation of something between 10 and 14%, and an HRC of 54.
You may have to re-think your choice of material.
The maximum hardness in a quenched steel depends on the carbon content of the martensite formed during the quench. The technical literature says that this maximum for an xx40 steel is HRC 60 --- before tempering. And, since 4140 is not a deep hardening steel, this hardness will be only on the surface and --- depending on the mass of the part --- a short distance below. After tempering --- almost always a very good idea --- at a temperature of 150C, you should expect to have (at the surface) a 0.2% yield strength of about 1460 MPa, an ultimate tensile strength of about 1970 MPa, an elongation to plastic instability of a little over 5%, a total elongation of something between 10 and 14%, and an HRC of 54.
You may have to re-think your choice of material.
Two of the answers are only partially correct.
1) You do not have to anneal before rehardening.
2) It is true that 4140 is not deep hardening compared to some steels 'richer' in alloy content. However, deep is a relative term. For example; 4140 is much deeper hardending than 1018 (cold finished 'mild' steel). The question of how deep cannot be answered without knowing the actual geometry of your part, type of quenchant (typically oil or water), extent of agitation during quenching and temperature of quenchant because depth of hardening depends not only upon cross section of part but also on mass of the part and the thermodynamics of the quenching process. That is why the first guy wants more info before he can appropriately answer your question.
If you have a 'relatively' small cross section, you can through harden to Rc60 and temper(or draw) back to Rc50. Even if you cannot through harden to Rc 60, you can still very likely achieve Rc 50 at the surface even with possibly a 3" cross section (I am guessing from way back memory).
Another question that needs to be answered is; what is your objective? Strength, wear resistance, or both.
Hope this helps
1) You do not have to anneal before rehardening.
2) It is true that 4140 is not deep hardening compared to some steels 'richer' in alloy content. However, deep is a relative term. For example; 4140 is much deeper hardending than 1018 (cold finished 'mild' steel). The question of how deep cannot be answered without knowing the actual geometry of your part, type of quenchant (typically oil or water), extent of agitation during quenching and temperature of quenchant because depth of hardening depends not only upon cross section of part but also on mass of the part and the thermodynamics of the quenching process. That is why the first guy wants more info before he can appropriately answer your question.
If you have a 'relatively' small cross section, you can through harden to Rc60 and temper(or draw) back to Rc50. Even if you cannot through harden to Rc 60, you can still very likely achieve Rc 50 at the surface even with possibly a 3" cross section (I am guessing from way back memory).
Another question that needs to be answered is; what is your objective? Strength, wear resistance, or both.
Hope this helps
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