The effect of austenitic treatment at 860 ~ 980 °C on microstructure of steel 30CrSiMnNiWMo (% :0. 28C

0. 74Mn

1. 04Si

2. 70Cr

1. 15Ni

0. 45Mo

1.04W

0. 07V

0. 05Al) and mechanical properties of steel tempered at 260 °C has been studied. Results show that there are a lot of carbide M6C in microstructure of steel 30Cr3SiMnNiWMo quenched at 860 ~ 920 °C led to slightly decrease toughness of tempered steel

and after quenched at 950 °C

the carbides in steel are basically dissolved and the original austenite grains of steel beginning coarsen led to de- crease strength of tempered steel ； with oil quenched at 920 ℃ for 1 h + tempered at 260 °C for 2 h

the steel 30Cr3SiMnNiWMo has lath martensite microstructure with minor residual austenite and un-dissolved carbides

so it has excellent strength and toughness i. e. UTS- 1 680 MPa

YS- 1 330 MPa

elongation- 13%

RA- 58. 3% and impact energy- 85 J.