316L环型锻件，如何做冷加工来增加硬度

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一批316L环型锻件，外径675MM，内径585MM，高95MM，
客户要求硬度达到160HB以上，现在锻件已经粗加工成型，客户自己精加工，
但固溶（1050度）热处理后锻件硬度只有140左右，如何热处理增加硬度 或者 其它办法。

因为客户要精加工，所以提高表面硬度的办法 客户精加工后，所测硬度会降下来。
以下为客户的回复及我的提问，供大家帮我解决问题：

Dear Stephen,
We are going to have hardness requirement for 160HB in future orders.   Hence pl. continue your research & development to achieve hardness of minimum 160HB.   Our other supplier able to achieve higher hardness by giving higher Chrome & Nitrogen to the max allow as per std.
As per discussion with our Design Dept. I confirm herewith for this particular order we will accept minimum hardness 150HB.
Best Regards,
Vin Talekar
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Sent: Tuesday, December 22, 2009 4:24 PM

FOR ITEm 1 of PO IBC350314, the special requirement of HARDNESS is Min. 160HB.

I study the ASTM A182 F316 and VMS-034 REV09 standard,and do not find the requirement for the hardness in the both standards.

As far as i am concerned,for the stainless steel contented low carbon( i.e.F316/F316L/F304) the normal hardness is about 140HB.

It is very difficult to increase the hardness to 160HB by heat-treatment procedure.

The hardness value is 141HB on the test bar.

Tensile Strength=537Mpa

Yield Strength=241Mpa

Elongation=63.6%

Reduction of Area=73%

We try & test heat treatment for test bar several times, but the hardness value can not reach to 160HB.



Please kindly offer your comment!



Stephen