Effects of heat treatment on the mechanical properties and microstructures of four different heats of a precipitation hardening HSLA steel

Abstract

ASTM A710 is a high strength low alloy (HSLA) steel whose strength is a result of both a fine-grained microstructure and a dispersion of copper precipitates. For these reasons, the tensile and impact properties of an A710 plate depend both on the thermomechanical history of each plate and on its chemistry. Since plates shipped from steel suppliers are frequently heat treated under different conditions, it is difficult to know whether property differences are due to chemistry variations or to heat treatment variations or a combination of both. Heat-to-heat property differences should be determined for a specific, known heat treatment. This report describes the variability observed in the mechanical properties of four plates made from four different heats of steel that have received known and carefully controlled heat treatments at the National Bureau of Standards. The sensitivity of the resultant mechanical properties to heat treatment variations within each heat is reported here. Optical and transmission electron metallographic techniques were used to determine as-received and heat treated microstructures.