Stainless Steel HAZ Research Articles

Study the Effect of Welding Position and Plate Thickness to the Mechanical and Microstructural Properties of the TIG Dissimilar Metal Welded between Carbon Steel ASTM A36 and Stainless Steel 304 Plates

Dissimilar metal welding was mostly done to optimize the application and engineering requirements with economic considerations. Weld microstructures greatly influenced the mechanical properties of welded joints. The investigations were carried out to evaluate the microstructural and mechanical properties of dissimilar weldment between carbon steel ASTM A36 and austenitic stainless steel 304 with a variation of welding position (1G, 2G, 3G) and weld thickness (6 mm to 12 mm) joints by TIG welding. A detailed analysis was conducted on the weld zone composition, the microstructural, and mechanical properties. The results show that the welding position and thickness of the weld joints influenced the microstructure both in HAZ and weld metal. Size, distribution, and orientation of microstructure were improved and more uniform with increasing of welded joint thickness. In HAZ carbon steel, GB ferrite was dominant, especially for the flat welding position (1G), while for the horizontal position (2G) and the vertical welding position (3G) showed other structures such as Widmanstaten ferrite, hard-structures like martensite and bainite. In the region near the fusion line and the weld metal, the chemical composition changed due to thermal convection, diffusion, and macro-segregation caused by penetration of liquid metal carbon steel into the weld pool. SEM/EDS results indicated diffusion of carbon from carbon steel A36 to stainless steel 304 and formed the hard-structure along the fusion line. The mechanical test results showed that the tensile test breaking point occurred in the parent metal of carbon steel A36. The bending test results showed very high stress on the face side of the welding joint, and there are no cracks from the bending test result. Vickers hardness testing showed that the hardness distribution increased from the carbon steel HAZ to the stainless steel HAZ, and the maximum hardness has achieved the value of 297 Hv at the fusion line of stainless steel 304.

Mechanical Properties and Microstructure at Stainless Steel HAZ from Dissimilar Metal Welding After Heat Treatment Processes

Metallurgy of HAZ at both metals after dissimilar metal welding is important to be evaluated, because differences in metallurgical characteristics due to heating effect on bothHAZ might take place after the process. For the case of austenitic stainless steel, metallurgical aspects that should be considered after welding are the formation of chromium carbide (sensitization) and delta ferrite phase. In the present research, focus is given on the HAZ microstructure and hardness both after welding and post-heat treatment process. Microstructure observation was carried out by optical microscope and Scanning Electron Microscope (SEM), whereas hardness testing was carried out by micro-Vickers method. From this study, it can be concluded that the increase in heat treatment temperature can reduce the volume fraction of delta ferrite and chrome carbide precipitation, whereas hardness at the HAZ region decreases after the heat treatment.

Metallurgy and mechanical properties variation with heat input,during dissimilar metal welding between stainless and carbon steel

The present research focus on the metallurgy and mechanical aspect of dissimilar metal welding.One of the common parameters that significantly contribute to the metallurgical aspect on the metal during welding is heat input. Regarding this point, in the present research, voltage, current and the welding speed has been varied in order to observe the effect of heat input on the metallurgical and mechanical aspect of both welded metals. Welding was conducted by Gas Metal Arc Welding (GMAW) on stainless and carbon steel with filler metal of ER 309. After welding, hardness test (micro-Vickers), tensile test, macro and micro-structure characterization and Energy Dispersive Spectroscopy (EDS) characterization were performed. It was observed no brittle martensite observed at HAZ of carbon steel, whereas sensitization was observed at the HAZ of stainless steel for all heat input variation at the present research. Generally, both HAZ at carbon steel and stainless steel did not affect tensile test result, however the formation of chromium carbide at the grain boundary of HAZ structure (sensitization) of stainless steel, indicate that better process and control of welding is required for dissimilar metal welding, especially to overcome this issue.

Grain size distribution after similar and dissimilar gas tungsten arc welding of a ferritic stainless steel

In this study, gas tungsten arc welding of ferritic stainless steel and grain size distribution in heat affected zone of the welded samples were investigated. Both similar and dissimilar arc welding operations were considered where in dissimilar welding joining of stainless steel to mild steel was examined. In the first stage, a three-dimensional model was developed to evaluate temperature field during and after arc welding while the model was performed using finite element software, ANSYS. Then, the effects of welding heat input and dissimilarity of the joint on the weld pool shape and grain growth in HAZ of stainless steel was investigated by means of model predictions and experimental observations. The results show that the similar joint produces wider HAZ and considerably larger grain size structure while in the dissimilar welds, the low carbon part acts as an effective heat sink and prevents the grain growth in the stainless steel side as well reduces the welding maximum temperature.

Stress corrosion cracking of the AISI 316L stainless steel HAZ in a PWR nuclear reactor environment

Low-carbon alloy steels and stainless steels are widely used in the primary circuits of pressurized water reactor (PWR)-type nuclear reactors. Nickel alloys are employed in welding these materials due to their characteristics such as high mechanical and corrosion resistance and suitable thermal expansion coefficients. Over the last 30 years, stress corrosion cracking (SCC) has mainly been observed in the regions of welds between dissimilar materials that exist in these reactors. The objective of this work is to evaluate, for comparison purposes, the susceptibility to SCC of the heat-affected zone of austenitic stainless steel AISI 316L when subject to an environment that is similar to the primary circuit of a PWR nuclear reactor at temperatures of 303 and 325°C. To carry out this evaluation, the slow strain rate test was used. The results indicate that the SCC is heat activated and that at 325°C, the most significant weak fractures arising from SCC process can be seen.

Electrochemical Noise Analysis of 13 mass% Cr Stainless Steel HAZ by Solution Flow Type Micro-droplet Cell-Effect of Solution Concentration-

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Nd:yttritium–aluminum–garnet laser welding of copper to stainless steel

Systematic laser welding experiments were conducted on dissimilar metal of copper and 300 series stainless steel using a high average power Lumonics JK 701H Nd:yttritium–aluminum–garnet laser. The laser melt penetration depth and width in copper and stainless steel were evaluated as a function of the laser parameters. The results reveal that melting of copper demands much higher average power, shorter pulse duration, and lower welding speed than melting stainless steel. If the laser beam is focused on the interface of the joint or on the stainless steel side, the weld penetration in stainless steel is much deeper than that in copper and the weld formation is poor and solidification cracks emerge. Distributing heat input by positioning the laser beam with respect to the interface of the joint was explored. Good results were achieved while positioning the laser beam 0.4 mm on the copper side. Butt weld penetration can go up to 2.4 mm and fusion zone in both copper and stainless steel is evenly distributed. By adjusting welding parameters, weld defects such as shrinkage, porosity, solidification cracks, etc., can be eliminated. Although isolated hot crack clusters exist along the austenite grain boundary in stainless steel HAZ, the strength of the weld joint is higher than copper and high vacuum tight property can be achieved.