Delayed Fracture Behavior of CrMo-Type High Strength Steel Containing Titanium

摘要

The delayed fracture behaviors of CrMo-type high strength steels containing different amount of titanium (0 to 0.10 percent) were studied. The steels were quenched at 880 deg C and tempered from 400 deg C to 650 deg C , and a wide range of tensile strength was obtained. The sustained load tensile test was carried out by using notched tensile specimens in Walpole solution. The experimental results showed that with higher strength, the Ti-microalloyed steels show higher resistance to delayed fracture compared with non-microalloyed steel due to titanium beneficial role and microstructure changes. The undissolved TiC is uniformly distributed as strong hydrogen traps, retarding or preventing the diffusion and accumulation of hydrogen to lower-interaction energy sites, such as prior austenite and martensite lath boundaries in stress concentration area. Meanwhile, the grain refining effect of titanium is also an important factor to improve the delayed fracture resistance of Ti-microalloyed steels. The characteristics of delayed fracture remain nearly the same with titanium addition.