A Study on the Cut Surface Quality of Mild Steel Plate by Oxygen Plasma Arc Cutting.

Abstract

Oxygen plasma arc cutting characteristics and cut surface quality factors are discussed in this paper. It has been carried out to cut the SS400 workpieces with various plate thicknesses. Such measurements as top and bottom kerf widths, bevel angle, straightness, dross attached level and cut surface roughness are used to evaluate the cut surface quality. A new classification method of the dross attached level, by which the dross attached level is classified into three kinds of states, is put forward. Influence of cutting conditions on cut shape and cut surface state is investigated in detail. With the increase of cutting speed and the decrease of arc current, kerf width decreases, bevel angle increases, while straightness varies within a variation range of about 0.2 mm for the thicknesses of 3.2 to 8.0 mm. And compared with top kerf width, bottom kerf width more rapidly decreases. Moreover, with the increase of cutting speed, the cut surface roughness exhibits a slight drop regardless of arc current, and under the present conditions the smoother cuts of Rz less than about 40μm are obtained.It is proved that the dross attached state bears relation to not only cutting heat input, but also arc current and plate thickness. There are two dross attached areas, respectively, occurring under low and high cutting heat inputs. The heat input range obtaining the dross free cut varies with plate thickness. The dross free area gets wider when cutting current increases. Furthermore, it has been made clear that kerf width and bevel angle are approximately in linear proportion to the logarithm of cutting heat input for a given thickness, respectively. A vertical cut can be available under high cutting heat input.