Papers by Keyword: Dissimilar Weld

Abstract: The influence of post weld heat treatments (PWHT) at 400°C, 600°C, 900°C on microstructures in heat affected zone (HAZ) of dissimilar welds between carbon steel and austenitic stainless steel was studied. As-welded condition, the fully Martensitic layer along the fusion line, Widmanstatten Ferrite, Bainite, Pearlite phases in the HAZ of carbon side and the fully austenitic zone in the weld metal can be observed. After PWHT, the microstructures of these zones were dramatically modified as a result of carbon diffusion from the carbon steel toward the weld metal. Decarburization of the base metal led to the formation of a zone with large Ferrite grains. Bainite or fine Pearlite were formed by carbon diffused to both the interfacial Martensite and the purely Austenite zone. The lowest hardness value in the decarburization zone was 92HV on average after PWHT at 900°C and the peak hardness value that was documented in the carburize zone with 366HV at 600°C. Carbides precipitation (M₂₃C₆, M₇C₃) were found in both the HAZ of carbon steel and austenitic stainless steel.

Abstract: The paper explores laser welding of high-strength CP-W^® 800 steel and forged steel. Dissimilar welds were produced with different welding parameters. Two welding beam diameters were used. The microstructure and mechanical properties of the resulting welds were examined. Metallographic sections were prepared and microhardness and tension tests were carried out. Fatigue tests were conducted on the weld specimens to map the effects of welding parameters on the fatigue behaviour of the dissimilar weld between the CP steel and the forged steel. Greater amount of heat input impairs the strength of the joint but improves its resistance to initiation of fatigue cracks.

Abstract: The paper presents results obtained during evaluation of dissimilar weld joints of creep-resistant steels. During high temperature exposure of dissimilar weld joints, alloying elements were redistributed across the weld interface. These diffusion effects can cause local changes of microstructure and have a direct effect on local mechanical properties in weld interface area. Carbon and nitrogen have the strongest influence on changes of mechanical properties of steels. . These local changes of mechanical properties have a strong influence on the reliability and the service live of the whole welded structures. The dissimilar joints of the austenitic steel/martenzitic steel type was studied. Laboratory weld joints were prepared and annealed at different temperatures for different time periods. Microhardness profiles across the weld interface were measured and the influence of long-term, high temperature exposure on the changes of local microhardness was evaluated. Results were compared with pseudo-binary phase diagrams and with the literature.

Abstract: This work studied the ball indentation test at room temperature to characterize the local tensile properties of bi-metallic weld joints. The weld specimens used were fabricated by joining between SA 508 Gr. 3 ferritic steel and Type 304LN stainless steel with Alloy 82 buttering on the ferritic steel side and Alloy 82/182 weld metal. The test results showed that yield stress (YS) of weld metal was slightly higher than that of Type 304 and smaller than that of SA508 Gr.3, and ultimate tensile stress (UTS) of weld metal was similar as those of Type 304 and SA508 Gr.3 base metals. Also, the values of YS and UTS of buttering layer (Alloy 82) were nearly same as those of weld metal. Heat-affected-zones (HAZs) showed higher YS and UTS values compared to their base metals.

Abstract: In a primary reactor cooling system, a dissimilar weld zone exists between cast stainless steel (CF8M) in a pipe and low-alloy steel (SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and 330
, while no effect is observed in SA508 cl.3. The aged specimens are prepared by an artificially accelerated aging technique maintained for 300, 1800 and 3600 hrs at 430
, respectively. The specimens for elastic-plastic fracture toughness tests are prepared two types, which notch is created in the center of deposited zone and the heat affected zone of CF8M. From the experiments, the plastic-elastic fracture toughness values (JIC) with the increase of aging time decrease as the notch is created in the HAZ of CF8M, while that is different slightly as the notch is created in the deposited zone. Also, JIC values in the deposited zones are smaller than the HAZ of CF8M at all aged specimens.

Abstract: A dissimilar weld zone exists between the pipe and nozzle in a primary reactor cooling system (RCS). Thermal aging is observed in cast stainless steel, CF8M used in a pipe as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and 330°C. No effect is observed in low-alloy steel. SA508 cl.3 is used in a nozzle. The artificially accelerated aging specimens are prepared to maintain for a temperature of 430°C for 300, 1800, and 3600hrs, respectively. Then, various mechanical tests such as hardness, tension, impact test, are performed in virgin and aged specimens in order to determine the existence of dissimilar weld zones. The specimens for elastic-plastic fracture toughness tests are prepared for one type, where a notch is created in the heat affected zone of CF8M. From the experiments, it was found that J-integral values decrease as age increases.

Abstract: In a primary reactor cooling system(RCS), a dissimilar weld zone exists between austenitic-ferritic duplex cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and 330°C, while no effect is observed in SA508 cl.3. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for 100, 300, 900, 1800 and 3600 hrs at 430°C, respectively. The various mechanical tests for the dissimilar weld zone are performed for virgin and aged specimens.