The Effect of Silicon on the Stress Corrosion Resistance of Low Alloy High Strength Steels^★

The effect of five levels of silicon, within the range 0.09% to 2.15%,⁽¹⁾ on the stress corrosion resistance of 4340 steel was established in 3.5% sodium chloride solution for two tensile strength ranges (280 to 300 ksi and 230 to 240 ksi). At the higher strength range, the threshold stress intensity K_ISCC was independent of silicon content, but the stress corrosion crack velocity was significantly retarded when the silicon content exceeded 1.5%. At the 230 to 240 ksi strength range, steels containing less than 1.5% silicon exhibited a higher K_ISCC threshold than steels of higher silicon content. Strength level had a significant effect on crack velocity characteristics.