Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part I - theoretical analysis

Abstract: A computational and experimental study was carried out to quantitatively understand the influence of the heat flow and the fluid flow in the transient development of the weld pool during gas tungsten arc (GTA) and laser beam welding of Type 304 stainless steel. Stationary gas tungsten arc and laser beam welds were made on two heats of Type 304 austenitic stainless steels containing 90 ppm sulfur and 240 ppm sulfur. A transient heat transfer model was utilized to simulate the heat flow and fluid flow in the weld pool. In this paper, the results of the heat flow and fluid flow analysis are presented.

Prediction for the austenite grain size in the presence of growing particles in the weld HAZ of Ti-microalloyed steel

Abstract: A model to predict the austenite grain size in a Ti-microalloyed steel weld heat affected zone (HAZ) was developed. Grain boundary mobility for the austenite grain growth was expressed as a function of aging temperature and alloying elements. By analyzing isothermal austenite grain growth behavior, the Zener coefficient of cubic TiN particle was measured. From quantification of the effect of grain boundary pinning by TiN particle and alloying elements on the grain boundary mobility, an isothermal grain growth model of Ti-microalloyed steel is presented. The predicted austenite grain sizes from the proposed model were in agreement with the experimental results. Finally, combining with the additivity rule, a general austenite grain growth model during the continuous welding thermal cycle was developed.

An experimental and theoretical study of heat-affected zone austenite reformation in three duplex stainless steels

Abstract: Three duplex grades, one molybdenum-free, one 22Cr type, and one super duplex grade, have been subjected to weld simulation treatments, and the resulting microstructures have been quantified by automatic image analysis techniques. Substantial differences between the duplex grades were observed with an increased ability to reform austenite with increased alloying content. A theoretical model has been applied, based upon the paraequilibrium concept elaborated by Hillert, and the paraequilibrium compositions of individual phases were calculated as a function of temperature using the THERMOCALC database. A model based on Cahns theory of grain boundary nucleated reactions has also been utilized to calculate the kinetics of the reaction. By using this model, the grain size effects could be included in the treatment. The results of the calculations were compared with experimental data, and the experimental results were reproduced using the same parameter set for the three materials, with the exception of the diffusion coefficient values which had to be adjusted. This adjustment has in a later study been verified experimentally. The results validate the model used and the physical relevance of using the paraequilibrium model. The appropriateness of a paraequilibrium approach is also supported by experimental evidence from weld metal compositions. It is shown that the nitrogen content of the alloys plays an important role, and a higher nitrogen content results in more efficient austenite reformation. This implies that the alloy nitrogen compositions should lie close to the upper specification limits for these materials and nitrogen losses should be avoided on welding since the material properties, both mechanical and corrosive, are strongly related to the austenite-ferrite phase ratio.