CONTINUOUS COOLING SENSITIZATION OF TYPE-316 AUSTENITIC STAINLESS-STEEL

The continuous cooling sensitization (CCS) behavior of a high-carbon type 316 (UNS S31600) austenitic stainless steel has been quantified as a function of peak cycle temperature, cooling rate, and prior deformation. A critical peak temperature effect was observed such that maximum temperatures either above or below 950-degrees-C generally resulted in lower degree of sensitization (DOS) values. CCS development increased with decreasing cooling rates and occurred primarily in the critical range between 900 and 750-degrees-C. Peak cycle temperatures of 1,000 and 1,050-degrees-C suppressed carbide nucleation and sensitization development during cooling to lower temperatures. Prior deformation in the range of 5 to 20% significantly enhanced sensitization development with the measured DOS generally increasing as prior strain increased. Recovery was initiated in the strained materials when cycle peak temperatures reached or exceeded approximately 900-degrees-C and played an important role in reducing subsequent sensitization development. In certain cases, prior strain values of 20% were only as effective as 10% in enhancing sensitization development because of the effects of recovery.