DMR-249 A is an indigenously developed high strength low alloy steel for Indian ship building industry for making ship-hull and is extensively used in the construction of war ships and submarines. Welding electrodes c...DMR-249 A is an indigenously developed high strength low alloy steel for Indian ship building industry for making ship-hull and is extensively used in the construction of war ships and submarines. Welding electrodes conforming to SFA 5.5 AWS E8018 C1 has been indigenously developed for welding of this steel using shielded metal arc welding process. In the present study, susceptibility to hydrogen assisted cracking of DMR-249 A steel welds made using this electrode has been assessed using implant test. Implant tests were conducted using this electrode at two different levels of diffusible hydrogen, measured using gas chromatography technique. It is observed that both the steel and the welding consumable are not susceptible to hydrogen assisted cracking even with a high diffusible hydrogen level of 9 m L/100 g of weld metal. In implant tests, specimen did not fracture even after loading to stress levels higher than the yield strength of the base metal. The good resistance of this steel and the welding consumable, even with high levels of diffusible hydrogen, is attributed to absence of a susceptible microstructure in both the weld metal and heat affected zone. Hence, this study shows that, in the absence of a susceptible microstructure, hydrogen assisted cracking is unlikely to occur even if hydrogen level is high. It also confirms that in welding of DMR-249 A with indigenously developed E8018 C1 electrode, hydrogen assisted cracking is not a concern and no preheating is required to avoid it during welding.展开更多
Double torsion specimens were applied to study the subcritical crack growth of flabby and intricate ore in Jinchuan Ⅲ Mine. The relation between the subcritical crack velocity v and the stress intensity factor KI is ...Double torsion specimens were applied to study the subcritical crack growth of flabby and intricate ore in Jinchuan Ⅲ Mine. The relation between the subcritical crack velocity v and the stress intensity factor KI is obtained, and the fracture toughness KIC and the lower limit of stress corrosion K0 are determined respectively. The results of test show that the curves of lgKI—lgv and KI—lgv can be well linear, and the high discretion of data are caused by mineral composition, particle size and mechanical property of rock itself. In addition, the subcritical crack growth with stress corrosion of the ore is caused by the united function of two mechanisms, one is the tensile stress and the other is the material at the crack tip. Chemical reaction takes place between the materials and the corrosion medium in the environment and makes the chemical bond break. So, the obtained results provide reliable references for predicting the block caving velocity of the ore in Jinchuan Ⅲ Mine under high horizontal stress condition.展开更多
文摘DMR-249 A is an indigenously developed high strength low alloy steel for Indian ship building industry for making ship-hull and is extensively used in the construction of war ships and submarines. Welding electrodes conforming to SFA 5.5 AWS E8018 C1 has been indigenously developed for welding of this steel using shielded metal arc welding process. In the present study, susceptibility to hydrogen assisted cracking of DMR-249 A steel welds made using this electrode has been assessed using implant test. Implant tests were conducted using this electrode at two different levels of diffusible hydrogen, measured using gas chromatography technique. It is observed that both the steel and the welding consumable are not susceptible to hydrogen assisted cracking even with a high diffusible hydrogen level of 9 m L/100 g of weld metal. In implant tests, specimen did not fracture even after loading to stress levels higher than the yield strength of the base metal. The good resistance of this steel and the welding consumable, even with high levels of diffusible hydrogen, is attributed to absence of a susceptible microstructure in both the weld metal and heat affected zone. Hence, this study shows that, in the absence of a susceptible microstructure, hydrogen assisted cracking is unlikely to occur even if hydrogen level is high. It also confirms that in welding of DMR-249 A with indigenously developed E8018 C1 electrode, hydrogen assisted cracking is not a concern and no preheating is required to avoid it during welding.
基金Project(50274074) supported by the National Natural Science Foundation of China Innovated project of education(134375210) supported by Central South University
文摘Double torsion specimens were applied to study the subcritical crack growth of flabby and intricate ore in Jinchuan Ⅲ Mine. The relation between the subcritical crack velocity v and the stress intensity factor KI is obtained, and the fracture toughness KIC and the lower limit of stress corrosion K0 are determined respectively. The results of test show that the curves of lgKI—lgv and KI—lgv can be well linear, and the high discretion of data are caused by mineral composition, particle size and mechanical property of rock itself. In addition, the subcritical crack growth with stress corrosion of the ore is caused by the united function of two mechanisms, one is the tensile stress and the other is the material at the crack tip. Chemical reaction takes place between the materials and the corrosion medium in the environment and makes the chemical bond break. So, the obtained results provide reliable references for predicting the block caving velocity of the ore in Jinchuan Ⅲ Mine under high horizontal stress condition.
