Effect Of Heat Treatment After Welding On The Organization And Overall Properties Of Joint Of2101Duplex Stainless Steel

As a new economical duplex stainless steel, LDX2101is an excellent structure-function material with low-cost, high strength, good corrosion resistance and has wide application prospect. Owing to two-phase structure and the high content of alloying elements such as Ni, Cr, the improper heat treatment and welding process in the manufacturing process may lead to the precipitation of harmful precipitates. During the welding process, the faster speed of thermal cycles causes the complex microstructural transformation, which result in the damage of the phase equilibria and the deterioration of the joint performance. Solution treatment can adjust the ratio of two phases, eliminate the precipitates, and improve the joint performance effectively. However, the role of solution treatment will be nothing if the temperature and cooling rate are not well defined. Therefore, the research in organizational characteristics and overall performance under different heat treatment conditions of2101duplex stainless steel welding joints had guiding significance for theory and practical production.In this paper, PAW+SMAW process was used in the welding for UNS S32101duplex stainless steel plate. Then the solution treatment at1050℃and aging treatment for various holding time for welded splice was performed, the sensitized temperature of joint was determined by impact test and chemical corrosion test. Then weld specimens aged at sensitized temperature for different time (10min,30min,60min). The microstructural evolutions and properties of welding joints were examined by OM, SEM, TEM, EDS and ferrite body analyzer; combined with Brinell hardness test, impact test and electrochemical corrosion test to establish a correspondence between the change of joint performance and organizational.Through the microstructure analysis of welding joint solution heat treated at1050℃, it showed that the welding joint no grain coarsening, two-phase balanced, not the precipitates generated, moderate hardness, low temperature impact toughness and excellent corrosion resistance. Thereful, a satisfactory welding joint can be obtained solution treated at1050℃. The welding joints after solution treatment have been aged at500℃,600℃,700℃,800℃,900℃respectively for30min, the test results show that, as the temperature increase, the impact toughness and corrosion resistance decreased first and then increased,700℃is the most sensitive temperature of the performance deterioration. Performance is better in HAZ than weld.The aging treatment of welding joint of LDX2101DSS was performed at700℃for various holding time. The results shows that a huge of Cr2N phase precipitate at a/a or α/γ interfaces and in ferrite grains in the joint metal including weld zone,HAZ and base metal. With increasing the aging time, Cr2N grow into the adjacent ferrite grains and its content increases. Its formation mechanism is a eutectoid reaction of aâ†'Cr2N+γ2.The precipitate phase formed in the weld joint causes an increase of hardness, but decreases severely the ductibility and impact toughness. The fracture becomes from ductile into brittle. Meanwhile, the corrosion resistance of the welding joint is directly influenced by the abundant Cr2N phases.