The Process Influence on Strength Properties of an Austenitic Stainless Steel (254 SMO)

Abstract: This work has been performed at Outokumpu Stainless AB, QPE, in Degerfors where focus is on production of hot rolled tailor-made quarto plate in special stainless steel grades such as highly alloyed austenitics and duplex steel grades. After a period with low values in strength and a lot of deviations in tensile tests for the highly alloyed austenitic stainless steel, 254 SMO, there was a need to investigate what influence some parameters during process has on strength values. Process parameters during hot rolling and levelling have been examined to see if there is a connection between these and the strength. A statistical data base has been created to investigate the connection with strength. There has been experimental work involving two test plates in different dimensions to see how a double/extended heat treatment influence the sigma phase values and grain size, and if these can be connected to the strength values. The test plates have also been used to investigate how the position of the test coupon is affecting the tensile test result. Moreover, there have been tests performed in the cold plate leveller. The strength is a complex problem since there are many parameters that contribute to a variation in strength value. It is possible to see an influence from the investigated parameters, but their individual impact on strength varies. There are several indications in the results that the flatness seems to be a factor affecting the variation in strength. However, there is a need for more thorough investigations where the flatness can be measured to completely verify this