The Effect Of Hydrogen On Mechanical Properties Of Austenitic Stainless Steel Welded Joint Prepared By The High Power Laser

Austenitic stainless steel has good corrosion resistance and non-magnetic, high toughness and plasticity, are widely used in the atmospheric pressure container and biological engineering, chemical engineering and other fields. In recent years, the application of stainless steel plate are more and more applied in the aerospace, medical equipment, the application of nuclear industry. Therefore, plate of stainless steel welding is becoming very important. Traditional welding method is difficult to guarantee the quality of thick plate welding of stainless steel, and laser welding has the incomparable virtues than the traditional welding and can effectively reduce weld defects.The research about stainless steel plate welding technology is needed by the industry in this context. At the same time, because of the thick plate stainless steel application environment is very bad in special environments, such as ocean, space, nuclear reactor, the hydrogen embrittlement tendency of the stainless steel plate are also required a degree of exploration and research.This paper analyzed the mechanism of laser welding and the influence of the parameters for the laser welding process. According to the general physical properties of austenitic stainless steel material, calculate the parameters which can make the thickness of 10 mm 304 austenitic stainless steel plate penetration, such as the laser power, welding speed and defocusing amount, the plan is needed for the welding. Using the method of single factor experiment which can weld the 10 mm thick of austenitic stainless steel plate by one side, through observing surface morphology of weld penetration, measuring the hardness of weld, making weld tensile samples for research of weld mechanical properties, it is concluded that when the welding process parameters at P = 4.5 KW, v = 4.5 mm/s, f=-2, 10 mm thick of austenitic stainless steel can get good welding joint.To study the effect of hydrogen on stainless steel welded joint mechanical properties, let the hydrogen into the weld tensile specimen by electrochemistry. It shows that hydrogen charging current “I” and hydrogen charging time “t” have an influence on the degree of hydrogen damage of tensile samples, exploring the parameters when the tensile samples have appeared at the height of hydrogen loss. Tensile samples of hydrogen current “I” range from 0.1 m A to 0.5 m A, hydrogen filling time “t” range form 24 h to 120 h, After filling the hydrogen, tensile test should be accomplished immediately, To observe the position of the tensile fracture and discuss which kind of the tensile specimen fracture is, analysis the tensile samples whether have hydrogen embrittlement. After a series of experiments, it is concluded that when the tensile samples in hydrogen charging current 0.5 m A, hydrogen filling time of 120 h, under the condition, the stainless steel weld have most serious hydrogen loss, tensile specimen fracture in the weld. By means of tensile test specimen fracture location and fractograph composition analysis, discussion group different components have different sensitivity to the hydrogen and the mechanism of hydrogen embrittlement of weld tissue.By means of metallographic microscope, microhardness tester, scanning electron microscope(SEM) analysis the austenitic stainless steel plate welded joint microstructure, hardness and mechanical properties and fracture morphology of tensile samples, and the testing results are analyzed and discussed.