Evaluation of Reheat Cracking Susceptibility in High Strength Austenitic Stainless Steels

In order to assess the susceptibility to reheat cracking of high-strength austenitic stainless steels of KA-SUS304J1HTB and KA-SUS310J1HTB, we established a reheat cracking simulated test method by using a stress relaxation test. A simulated HAZ leat Affected Zone) test specimen of KA-SUS304J1HTB fractured during stress relaxation at 650 degrees C when the strain exceeded 16.6%. On the other hand, an as-received test specimen of KA-SUS310J1TB fractured during stress relaxation at 650 degrees C when the strain was more than 10.3%. Subsequently, local reduction of area (RA) of the fractured simulated HAZ and as-received test specimens was measured. No appreciable local RA was observed in the vicinity of the fractured surface on both test specimens. Besides, test specimen with larger grain size was found out to be fractured in shorter time, as compared to test specimen with sTriall grain size. These findings were in close accordance with the previously reported characteristics of the reheat cracking cases. We then calculated the stress relaxation processes on the basis of experimental results by using Norton's creep law. The calculation results showed that simulated HAZ specimen of KA-SUS304J1HTB would not generate reheat cracking for more than 100,000 hours when the initial stress was equal to or below 300 MPa. However, reheat cracking would occur on KA-SUS310J1TB after only about 40,000 hours when the initial stress was 300 MPa. Compared to KA-SUS304J1HTB, KA-SUS310IJ1TB was more susceptible to reheat cracking.