17-7PH Full Hard for Spring Clip

[globia]

I am making a very simple flat spring clip to hold in a heater. When installed it is just slightly bent. The material I would like to use is 17-7PH full hard. Can I use this material in the full hard condition without further heat treatment? The temperature of the heater will go up to approx. 400-450C but only a small portion of the clip will be in contact. I used 1095 blue spring steel for the prototype but I am concerned about corrosion with time.

 

[TVP]

Sounds feasible to me. Is there a specific issue regarding 17-7 that you are concerned about?

 

[globia]

I just wanted reassurance that the part will spring back when slightly bent and not conform. I know that 17-7PH in the annealed condition can be formed and then heat treated to CH900 to achieve spring properties but I have not worked with 17-7PH purchased in the full hard condition before. I also want to be sure the machinist will be able to cut to size (approx. .25 x .37 with a .125 hole) when in the full hard condition without a problem. If you have any insight on this I would greatly appreciate it. Thanks!

 

[israelkk]

According to MIL-HDBK-5J (MMPDS-01) This steel is supplied in Condition A for ease of forming and in Condition A is readily cold formed. Therefore, I think the annealed condition you refer to is not accurate. The "annealed" condition can never be heat treated to CH900. It can be treated to H900. To be heated to CH900 it has to be in the Condition C (heavily cold drawn before heat treated). I do not know what is full hard condition you refer to, may be you mean Condition C. To your statement "I just wanted reassurance that the part will spring back when slightly bent and not conform" this is not an engineering statement. You need to calculate the bending stresses as the result of the load or the deflection of the spring. No one can give you an honest answer without those calculations.

 

[israelkk]

According to MIL-HDBK-5J (MMPDS-01) I quote: "Heat Treatment — 17-7PH must be used in the heat-treated condition and should not be placed in service in Condition A or T."

 

[globia]

Thank you for pointing out the difference in Condition A and C. Basically all I wanted to find out is if 17/7-PH shim stock in Full Hard Temper (Rockwell C41-C48, ASTM A693) is suitable for a simple spring clip without further heat treatment (not a critical application at all). I did get confirmation from my material vendor. Thanks!

 

[swall]

What condition did the vendor state you would be receiving? That is what is important, not just the hardness.

 

[globia]

Condition C.