Change in the ductility properties of 2.25 Cr–1 Mo steel during post-welding heat treatment

Abstract

A major problem associated with the use of steels at elevated temperatures in the chemical, petrochemical and power industries, is not only that of hydrogen embrittlement and creep, but also the loss of ductility related to the content of low-alloy trace elements. This phenomenon is known as temper embrittlement. Temper brittleness is associated with embrittlement due to heat treatment, rather than that due to a long period of exposure to high temperatures under working conditions. Since Polish technical literature does not have a term describing this phenomenon, the authors will use the expression ‘loss of ductility’ or ‘working brittleness’. This particular embrittlement is caused by the segregation of phosphorus, tin, antimony and arsenic on the grain boundaries of the primary austenite during prolonged working life, or a low rate of cooling of the steel within the temperature range of 550 to 350°C. It manifests itself in the lowering of the impact strength or in the rising of the brittle fracture transition temperature (Fig.1).