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Please refer the picture it is not rust, it is some kind of red oxidation in the surface http://files.engineering.com/getfile.aspx?folder=b09a1c42-04b9-4a2f-b4b1-4d905641dccf&file=20171205_191015_resized.jpg

We are heat treating 52100 (100Cr6) material with salt quenching. After heat treatment we are observing red colour (powder like layer) on the surface of the parts. If i try of wipe of with cloth it gets removed, and it is not like rust. The process are Prewash ---- 860 C / 2 Hrs --- Salt quench...

No it does not crack. In quench press with out die only with quenching also it cracks.

Hi Maui, Reducing the oil flow did not help, upon further reduction we are getting NMTP. Undercut design change not possible. Will update you all after further trials. Thanks for all your ideas.

What is the expected risk if we take out the parts from quench at 100C and do an air cooling? Oil flash point is 175 C is there any risk of fire because if the part surface is at 100C then the core may be at higher temperature. So after some time the surface temp may increase and if it reaches...

Exit temp is 50 C. Quench time is 160 Sec. Ok let me try with reduced flow rate.

Hi Maui we have already tried by flipping the part upside down but no use and parts still cracked. Bottom oil flow is 300 LPM (this is to quench bore) and top flow 350 LPM (to quench OD) In our quench press we do not have pulsing facility. Do you suggest to reduce the oil flow and what is your...

Oh Thank You Maui nice paper & good informative. What will happen if we take out the parts from quenching at slightly higer temperature (may be at 100C surface temperature instead of 50C). So martensite formation in the core can be made uniform with the surface at the end. Will this help.

Thank You Maui. I have downloaded the paper will spend some time to read now. Thanks again.

Hi one more information parts with out undercut also is cracking the same way. What's your opinion on this?

Hi tbuelna can you please share your email id.

Thank You tbuelna, will try to make a sketch of die and send as soon. Thanks

Hi tbuelna yes you are right. Quench die is not restricting the oil flow to the undercut. Undercut is open to oil. I have shown a small sketch for understanding. And crack always on the top undercut area. Die is a taper die which sits on both top and bottom bore. Oil flow is from both top and...

We have done all the metallurgical tests No decarb / recarb Fine martensite Grain size 8 or finer No any segregation No GBO / NMTP Hardness - 64 HRc as quenched both core and surface.

I am facing quench cracking during plug hardening of ring with oil quench (`40C). Hardening temp at 830C. Ring is transfered to plugging press and quenched with oil. Material is A485-1, ring dia is 250mm and thickness is 23mm. Crack always in the same location of undercut. Any reasons / solution ?