Heat Treating 4340 E AQ Steel
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Posted by: DougP ® 05/18/2004, 10:37:56 Author Profile Mail author Edit

My company recently machined some 4340 E AQ steel connecting rods and sent them out for heat treating. The material is 2 1/2" RD and 41" Long. Each rod has rolled threads at each end 2" length. When the parts were received back from the heat treater 17 of 23 had a crack, which was into the center of the part and the full length of the part. Each crack was identical, even to the arc at the end of each crack just prior to meeting with the threads. Could this be a problem with the heat treating process, the material (the certs were with material) or could it be the design. Your help would be greatly appreciated. Thanks. Doug

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Re: Heat Treating 4340 E AQ Steel
Re: Heat Treating 4340 E AQ Steel -- DougP	Post Reply	Top of thread	Forum

Posted by: isofilm ® 06/04/2004, 18:57:37 Author Profile Mail author Edit

Hi Doug, It sounds like the quenching rate was too high.  We specify the exact temperature vs. time profile from beginning to end, in addition to requiring an actual temperature record of each run. This keeps the honest people honest. Best regards, Daniel L. Thomas, CTO Novel Concepts, Inc. https://www.novelconceptsinc.com

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