stress relieving after finish machining?

[merkan]

i know that stress relieving is done after rough machining in order to avoid distortion while hardening.(by the way i am using vacuum hardening for my tools.i want to know whether it will be helpful or not if stress relieving is done after finish machining in order to avoid distortion.(without rough machining and stress relieving before finish machining)

 

[kenvlach]

A typical sequence is rough machine, harden (Q + T), near-finish machine, stress relieve (if necessary), and finish machine. Whether stress relief is needed depends upon the material (brittle? work hardens?), the nature of the final machining (creates heat or deforms? coolant/lubricant used?), whether the parts will be plated, and the application (loading and fatigue issues). For example, steel of hardness HRC 40 or higher which has been ground after heat treatment must be stress relieved prior to electroless nickel plating per AMS 2024. ASTM B733 is more strict (HRC 31), as is chromium plating per QQ-C-320, to avoid cold working which both increases hydrogen embrittlement susceptibility and lessens fatigue resistance.

Machinery’s Handbook, 25th Edn., p. 522 mentions stress relieving high-speed steel after sub-zero cooling treatment.

Stress relief in some cases improves corrosion resistance.

 

[funnelguy]

merkan, I think you will get a much better response on your query if you post it in the Machines & Machining engineering section of the Industrial/Manufacturing Engineers part of this forum.

I think the vacuum process can be very useful for reducing HT distortion. That assumes the process can get cooling rates adequate for your application. Best to discuss specifics with possible suppliers and look for insights there. Reputation is everything when dealing with this type of work, IMO.

The size, material and geometry of the part and nature and sequence of machining operations all have great effect on HT distortion. More specifics will help forum members assist you. Good luck!