What is difference between HRA and CDA Steel
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Thread: What is difference between HRA and CDA Steel

  1. #1
    Gunco Regular smittygj's Avatar
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    Default What is difference between HRA and CDA Steel

    Question for the metalsmiths

    I'm getting ready to purchase some round bar stock to begin my .50 cal rifle project.

    Supplier has 4140 HRA steel and 4140 CDA steel.
    What is the difference between the two?

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    TOM1911's Avatar
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    IIRC: Hra is hot rolled and cda is cold drawn types. It probably wont make a difference if it is normalized.

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    wildmann43's Avatar
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    The "A" suffix would indicate "annealed", which is normalized, yes?

    The HRA will have some mill scale on it(looks like rust), while ths CDA will look relatively clean & oily when it arrives.

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    Gunco Regular smittygj's Avatar
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    Thanks Guys!

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    Gunco Member tac556's Avatar
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    My best Guess:
    HRA= Hot Rolled, Annealed
    CDA= Cold Drawn, Annealed

    Annealed is NOT the same as normalized. Two different processes. Annealed is the softest state that particular alloy can be in, although there are even sub categories for how long it is annealed, the temp used, etc.
    Not sure what is the difference in 4140, but in 4130 there is a 20% strength loss by going to annealed instead of normalized.

    If surface finish is important, use the cold drawn. It will have smoother surface, and also be dimensionally more correct. Hot Rolled steel typically will have more surface variation (scale) and it is not intended to be dimensionally perfect. Which is why CD steel costs more.

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    Gunco Regular twistedneck's Avatar
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    Annealed or normalized are usually not finished conditions. Both 4130 and 4140 (HR or CR) need to be quenched and tempered like cephus said. I think 4140 annealed is about 11Rc (off the scale low). so its only about 100BHN, or 50,000 PSI Ultimate strength..

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