The environment fracture susceptibility of high-strength bainitic low alloy steels containing silicon

摘要

The mechanical properties and environment fracture susceptibility of two silicon contained bainitic steels with different carbon content have been investigated. The results show that the micro-hardness of the high-carbon (HC) (0.88C wt. %)steel sample and the low-carbon (LC) (0.33C wt. %) steel sample is HV 623±5 and HV 501±6,respectively. The yield stress,tensile strength,elongation and reduction in area of HC sample are 1818MPa,2110MPa,6.7 % and 18.7 %,respectively. The yield stress,tensile strength,elongation and reduction in area of LC sample are 1310MPa,1603MPa,12.4 %and 51.8 %,respectively. The Charpy V impact toughness of HC sample and LC sample is 13.3±0.4J and 51.3±1.3J,respectively. The fracture toughness of the HC steel and LC steel is 34.4MPa. m1/2 and 93.6MPa· m1/2,respectively. The pre-cracked WOL sample of HC steel can fracture delayed in air (RH=25% ～30%),humid air (RH=92 %) and water,the threshold stress intensity factors are KIE(A)=16.2MPa· m1/2,KIE(H)=I2.2MPa· m1/2,and KIE(W)=9.SMPa·m1/2,respec　tively. And the crack growth rate is 2.Smm/h,12.2mm/h,14.5mm/h,respectively. The pre-cracked WOL sample of LC steel does not fracture either in air or in wet air (RH=92%). But the pre-cracked WOL sample of LC steel can fracture delayed in water and the KIE(W)=3 1.5MPa· m1/2,the crack growth rate is 0.08 mm/h. The threshold stress intensity factor KIH of low-carbon-containing sample charged in the solution of 0.5 mol/L H2SO4+0.25g/L As2O3 with current density i=0.1mA/cm2 is 23.8MPa. m1/2. Its crack growth rate is 0.42 mm/h.