Studies on the mechanical properties of TMCP steel weldments in low temperature and hydorgen environments.

• Main Authors: Chang, Shuo-Che, 張碩哲
• Other Authors: S.L.I. Chan
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/51570496921720597009

碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 85 === The goal of this experiment is to study the effects of microstructure and alloying additions on the mechanical properties of TMCP (Thermo Mechanical Control Process) steels and its weldments in the low temperature and hydrogen environments. Because of their low carbon equivalent, the weldability and fracture toughness of TMCP steels are usually satisfactorily. The results have been compared to that controlled rolled SM490C steel. With suitable alloying elements addition, high heat input welding can be employed to join these steels, and the heat-affected zones can meet the toughness requirement even for low temperature service. In the first part of this experiment, different mechanical testing methods (Impact and Tensile) were used to study the differences between TMCP and SM490C steels and weldments on the low temperature mechanical properties. The results indicate that TMCP steels and weldments are better than SM490C on the impact toughness. The ductile to brittle transition temperature of SM490C is approximately 0℃, much higher that of TMCP (-40℃). Low temperature tensile tests show that the parent metals and the weldments of both steels have an excellent property. When the temperature was decreased gradually, the tensile and yield strength increased ,but their ductility remained unchanged. In the second part, electrochemical hydrogen charging was adopted to review the resistance of TMCP and SM490C steels to hydrogen environments. The results indicate that TMCP steels and weldments have an excellent ductility than SM490C in the transverse and longitudinal rolling direction. At a current density brew than 20mA/cm2, however, the ductility loss of TMCP steel was higher than that of SM490C steel.