Optimization of arc quenching parameters for enhancing surface hardness and line width in S45C steel using Taguchi method

Abstract

This study investigates the impact of arc length, current intensity, travel speed, and gas flow rate on surface hardness and line width during arc quenching process of S45C steel. The current intensity has the greatest influence on the surface hardness of S45C steel, followed by the travel speed, gas flow rate, and arc length. Using the Taguchi method, the optimal values of the parameters such as the arc length of 1.5 mm, the current intensity of 125 A, the travel speed of 250 mm/min and the gas flow rate of 12.5 l/min were calculated. The optimal surface hardness would be 379 HV, with a standard deviation of 46.4 HV. The current intensity is the most critical component in determining line width among these parameters. The arc length ranks second, followed by the TIG gun’s travel speed. The gas flow rate is the least significant factor. A longer arc length may result in a broader heat zone, which leads to a better line width. Increasing the arc length, current intensity, travel speed, and gas flow rate results in a similar pattern of surface hardness change caused by the low-heated and over-heated phenomena. The microhardness distribution showed a hardening zone of up to 2500 μm and a maximum hardness of 453 HV. The microstructure of arc quenching samples has three zones: hardening, heat-affected, and base metal. The hardening zone exhibits a martensite microstructure with a tiny needle shape and a residual austenite matrix.