EFFECT OF WELD HEAT INPUT ON THE MECHANICAL CHARACTERISTICS OF Cr-Mo STEEL BARS USING THE MIG WELDING PROCEDURE

Abstract

The impact of weld heat input on the mechanical characteristics of this steel was investigated in this study. The weld sample was an ASTM A304 grade A Flat Bar with a thickness of 5.00 millimetres. With the use of a data logger, a K-type thermocouple was installed in the drilled holes to measure the temperature fields at each of the places throughout the welding operation. The welding sample was created by varying three process parameters in the MIG welding process. Welding current, weld passes, and point of interest thermocouple position away from the weld centreline are the parameters. The experiment was designed using Taguchi's L9 orthogonal array to limit the number of experimental runs (DOE). To study the influence of weld heat input, the samples were subjected to mechanical and microstructure testing. The hardness test revealed that when the weld pass on the weld zone, HAZ, and base metal increases, the hardness value falls. The tensile test finding indicated that the tensile strength of samples 80A and 100A rises as the weld pass increases, however sample 60A decreases as the weld pass increases. The impact resistance increased when the weld pass was increased, according to the findings of the impact tests. The distance away from the weld centreline of the region subjected to a certain peak temperature increases as weld heat input increases, according to the weld thermal cycle. The value of the temperature fields increases dramatically as the heat source passes through the specific cross-section, where thermocouples are positioned. Later on, the temperature begins to drop at a slower rate. It's also obvious that when the distance between the measurement point and the weld centreline grows, the temperature drops.