Study on Cold Cracking Susceptibility of Domestic T23 Steel Using Implant Tests

Under no preheating,preheating at 150℃ and preheating at 250℃,the critical fracture stresses of domestic T23 steel were determined by implant test,the fracture morphology and microstructure near fracture were observed,the welding cold crack sensitivity was analyzed.The results indicate that under the condition of no preheating,the critical fracture stress of T23 implant sample is higher than its yield strength,and the fracture surface is cleavage fracture and quasi-cleavage fracture,on which secondary cracks appear,with wattle martensite and lower bainite mixing in the coarse grain zone.When preheating temperature rises,the critical fracture stress increases,the proportional of lower bainite of coarse grain area is more,the martensite proportion reduces correspondingly,the secondary cracks of implant fracture decrease and cleavage plane becomes narrow.So,the plasticity of material is strengthened,the crack is blocked.The results show that domestic T23 steel has a weak cold crack sensitivity,and preheating can obviously improve the anti-cold crack ability.