The microhardness

impact toughness

wear resistance

phases composition and microstructure of die steel for auto engine crankshaft forging of boroning process at 850 ~950 ℃ 3 ~6 h are studied. The research results show that the steel boronized at 925 ℃ for 4 h has better performance

that is the maximum HV microhardness value of tlie boronizing lay¬er 1712

the thickness of the boronizing layer 58.6 pjn

and the impact toughness value at 400 ℃ and 24 ℃ respectively 39 J • cm

-2

and 27 J • cm

-2

and the wear amount after 90 min friction test 6.7 mg of die steel. The phase composition shows that the main phase of the boronizing layer is Fe

2

B

while the boriding layer

transition layer and matrix microstructure are obviously observed in microstructure.