Restricting the heat-affected zone during the plasma cutting of high-alloy steels

Abstract

A review of literature shows that the process of plasma cutting can be conducted within a wide range of technological parameters.^1–10 The most important parameters, which can be changed in the course of processing, are the intensity of current and the rate of feed. On the one hand, these parameters determine the quality of the cut surfaces, and, on the other, they indicate the quantity of heat supplied to the element being cut. The quantity of supplied heat affects, primarily, the width of the HAZ. Because of this, investigations were carried out to determine how the operational medium and the plasma-cutting parameters can affect the possibility of restricting the width of the heat-affected zone, which is of importance in the case of high-alloy steels. Bearing in mind the diversification in the grades and thicknesses of high-alloy steels and, therefore, a large number of tests which would have to be carried out, the investigation was restricted to a single, widely used in the industry, 8 mm thick 1H18N9T stainless steel. The work involved cutting out test specimens (160 × 40 mm) in different media (air and water) while using a range of process parameters (current intensity and rate of feed). On the cut-out specimens, measurements of deviation from perpendicularity were made and an assessment of surface classification was carried out in accordance with PN-EN ISO 9013:2003 Standard.¹¹ Out of the test specimens, additional testpieces of 40 × 50 mm were prepared and used for the metallographic, hardness and X-ray analyses.