Microstructure and mechanical properties of 2200 MPa grade ultra-high strength low alloy steels

Mechanical properties of two kinds of ultra-high strength low alloy clean steels with different silicon content under different heat treatment condition have been investigated.Effects of silicon content on mechanical properties of 2 200 MPa grade steels have been analyzed.It has been pointed out that the mixed microstructure comprising lath martensite,e carbide and a little amount of retained austenite is obtained after quenched and tempered at low temperature.0.5% carbon addition can increase the tensile strength of steels to 2 200 MPa,1.75% silicon addition results in an increase of about 100 MPa in tensile strength,it can improve the stability of tempering and maintain 2 200 MPa at the tempering temperature of 270 ℃.