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Induction Annealing Bolt Shafts

A company contacted THE LAB at Ambrell to anneal bolt shafts with induction heating. They needed to heat 431 Stainless steel bolts to 1,850 ºF (1,010 ºC) and Inconel and 8740 alloy steel bolts to 1,000 ºF (538 ºC). THE LAB determined that an EASYHEATTM 3 kW, 150-400 kHz induction heating system with a three-turn helical induction heating coil would be the optimal solution for the client.

Initial tests were conducted to optimize the power delivered to the part. The three-turn helical coil was used to heat the shaft of the bolts for 10 to 12 seconds on the large bolts and 18 to 20 seconds on the smaller bolts using the same coil. This met the client’s timing objectives as did the results of the heating.


Ambrell induction is the preferred heating method for annealing for numerous organizations for a number of reasons. First off, induction is a rapid heating method. Additionally, induction delivers superior repeatability so the client will get the same result time after time. That repeatability can increase end product quality. Induction is also hands-free and flameless, which boosts workplace safety. Finally, the expertise of THE LAB with their free induction heating application testing was important to this client. THE LAB proposed a solution that met all of their objectives. 


To check out other annealing application notes from THE LAB at Ambrell, visit our annealing applications page. And, if you have an application, you should consider free applications testing, including our convenient Remote Lab Service. With Remote Lab Service, you can observe testing in our laboratory from the comfort and convenience of your office. 

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