4140 HT same as 4140 pre hard ?
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    Default 4140 HT same as 4140 pre hard ?

    I just read the 4140 pre hard thread and now I have a couple questions.
    Is the pre Hard the same thing as 4140 HT ? I've always thought it was but maybe I'm wrong ?
    What about HTSR ? is there another process involved with the HTSR or is stress relieving just a side benefit of the heat treat process ?
    Thanks

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    I think it is all one and the same thing, if you are thinking in terms of standard mill products. The heat treat cycle is supposed to begin with an annealed bar, then quenched, then tempered (stress relieved) to reduce the hardness and to help the crystalline structure to have adequate time to transform into a more stable form.

    Since the bar shapes are simple when quenched, there is going to be some differential in structure from the surface to the core of the bar. Machining the bar into an asymmetric shape is going to upset the existing balance of forces to some extent, and thus the warpage occurs. So the trick is to rough the shape several times and gradually machine the warped surfaces into straight surfaces. This requires clever setups to prevent inducing clamp induced distortions.

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    You might check out this thread. I got my terminology mixed up in it and it lead to a rather lengthy discussion.

    http://www.practicalmachinist.com/vb...hlight=4140+hT

    Walter A.

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    Walter, be careful referring people to that old post. There is some SERIOUS misinformation in the final post. (by some fellow typing in all caps).

    To the OP: 4140HT (Heat treated) and 4140 QT (Quenched and tempered) and 4140 HTSR (Heat treated & stress relieved) and 4140 Pre-Hard are all basically the same thing. They are generally in the range 0f 26-32 HRc. Movement during/after machining may or may not be problematic, depending on the amount and configuration of material to be removed from the original stock, as alluded to by Hu.

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    Isnt it sumtimes refered to as 4140 pre heat treated as well.or 4140PHT,I think but not sure(am asking)that it also is called 4150??? by maybe Alro Steel??
    Gw

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    Quote Originally Posted by eKretz View Post
    Walter, be careful referring people to that old post. There is some SERIOUS misinformation in the final post. (by some fellow typing in all caps).
    Correct.. the last post in the referenced post should be ignored.

    OK - Here is a chart with the composition of most Carbon Alloy Steels:
    http://www.admiralsteel.com/reference/alcomp.html

    Here is a decent description about alloy steels:
    http://www.steelforge.com/ferrous/alloysteel.htm

    The Wikipedia information:
    http://en.wikipedia.org/wiki/Low_alloy_steel

    And finally a list of almost all heat treatment processes:
    http://www.materialsengineer.com/E-H...t_of_Steel.htm

    Walter A.

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    Cuslog;

    You might also look up ASTM-A193 as this is usually what you get when you specify pre-hardened 4140. It machines nicely.

    Bear in mind that 4140 can be hardened well beyond R30-32c but then it won't be called ASTM-A193.

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    Quote Originally Posted by Greg White View Post
    Isnt it sumtimes refered to as 4140 pre heat treated as well.or 4140PHT,I think but not sure(am asking)that it also is called 4150??? by maybe Alro Steel??
    Gw
    4140, 4142, 4150, and 4160 are all available as HTSR. Lovejoy-type motor couplings are typically made from 4160HTSR.

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    Quote Originally Posted by eKretz View Post
    Walter, be careful referring people to that old post. There is some SERIOUS misinformation in the final post. (by some fellow typing in all caps).
    Heat treatment always seems to bring out some of the worst "information" of any subject that comes up.

    Shop I used to do a lot of repair work for calls me one afternoon about sawing some ~2.5" Inco 718 rounds. Stock was supposed to have been cut in 4 ft lengths prior to delivery. Their own horizontal saw was down awaiting some parts, which wasn't a big deal normally since it was used almost exclusively for maintenance while the bulk of their production started out as forgings from various aircraft alloys.

    I'm standing in the middle of the shop talking to the turning supervisor about the specific lengths to cut for best part yield since they're going to bar pull and part off the parts. A clown who's supposedly a mechanical engineer walks up to give his input. One of those yokels wearing a pair of dress slacks that stop about 4" above his shoetops, and a belt about a foot too long, buckled leaving the extra foot dangling like something half obscene.

    He chimes in to tell me I need to be real careful when I saw the stock so I don't get it too hot and "take the temper out of it". The turning supervisor rolls his eyes and adds, Yeah, don't let the saw blade get red hot or anything. I played along and told him in a real serious tone that I'd make sure and pour some water on it if I saw it changing colors.

    The supposed engineer was so clueless that the fact that we were both making jokes about his "advice" flew right over his head without ever slowing down. Considering every part going out the door of that shop goes into a jet engine, I found it real comforting to know such competent technical advice was available to the production staff

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    " A clown who's supposedly a mechanical engineer walks up to give his input. One of those yokels wearing a pair of dress slacks that stop about 4" above his shoetops, and a belt about a foot too long, buckled leaving the extra foot dangling like something half obscene."

    I've been a mechanical engineer for 20 yrs, and that's a good story. While I wouldn't say people like this proverbial "know it all" are common, there's always an element of that out there. True machine shop knowledge and craftsmanship are hit or miss for ME's; I know plenty who run small time shops and are quite adept, but just as many who couldn't turn a wrench to save their ass.

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    A new one for me a few years ago was the callout "4140 HRAR", which I was told is "Hot Rolled As Rolled" and apparently simply allowed to cool after hot rolling which made it 28-32 Rc. We have made many parts of this and I honestly cannot tell the diference betrween this and "4142", LaSalle steel's turned ground and polished (If I'm correct, my ignorance sometimes seems to know no bounds) which is also 4140 HT but with polished OD.
    I bow to the knowledge of those who possess it.

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    Quote Originally Posted by greasysmitty View Post
    " A clown who's supposedly a mechanical engineer walks up to give his input. One of those yokels wearing a pair of dress slacks that stop about 4" above his shoetops, and a belt about a foot too long, buckled leaving the extra foot dangling like something half obscene."

    I've been a mechanical engineer for 20 yrs, and that's a good story. While I wouldn't say people like this proverbial "know it all" are common, there's always an element of that out there. True machine shop knowledge and craftsmanship are hit or miss for ME's; I know plenty who run small time shops and are quite adept, but just as many who couldn't turn a wrench to save their ass.
    Good to get your opinion, 10 years late to the party..........

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    six wakc ago I culden't even spell enganer
    now I are one

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    Quote Originally Posted by 72bwhite View Post
    six wakc ago I culden't even spell enganer
    now I are one
    enganieer with a striped hat and greasy bibs!

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    Quote Originally Posted by partsproduction View Post
    A new one for me a few years ago was the callout "4140 HRAR", which I was told is "Hot Rolled As Rolled" and apparently simply allowed to cool after hot rolling which made it 28-32 Rc. We have made many parts of this and I honestly cannot tell the diference betrween this and "4142", LaSalle steel's turned ground and polished (If I'm correct, my ignorance sometimes seems to know no bounds) which is also 4140 HT but with polished OD.
    I bow to the knowledge of those who possess it.
    4140, in my world 41xx, HRAR, can come in at any hardness from 12 HRC to over 40HRC, with no consistency in any given length of bar or heat of material. This is not the same condition as used for T, P, & G materials.
    If it has to be to a specific yield strength and or hardness range, then it has to be Normalized, Quenched, and tempered to get the hardness or yield strength needed.


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