Effect of cyclic heat treatment on carbide evolution and impact toughness of 1Cr-0.5Mo steel

Abstract

The effects of the evolution behavior of carbide on impact toughness of 1Cr-0.5Mo steel during cyclic heat treatment were investigated by quantitative metallographic method and electrolytic extraction method with SEM,XRD,EPMA and low temperature impact test. The results show that with the increasing number of cyclic heat treatment, the lamellar carbides in the pearlite structure dissolve and spheroidize gradually, and the type of carbide also changes: M3C→M23C6. Increasing the number of cyclic heat treatments promotes the precipitation and connection of M23C6 along the grain boundaries, significantly deteriorates the impact toughness of 1Cr-0.5Mo steel.When the number of cyclic heat treatments reaches 4,the M23C6 grows to chain-like at the grain boundary and the impact toughness of 1Cr-0.5Mo steel can no longer meet the requirements. During the cyclic heat treatment, the average equivalent circle diameter of the overall carbide in 1Cr-0.5Mo steel shows a trend of decrease first and then increase because of the dissolution of lamellar carbides and the Ostwald ripening of carbides.

Keywords

• 1cr-0.5mo steel
• cyclic heat treatment
• pearlite
• carbide
• <i>m</i>₂₃c₆