Cutting Properties of Austenitic Stainless Steel by Using Laser Cutting Process without Assist Gas

Recently, laser cutting is used in many industries. Generally, in laser cutting of metallic materials, suitable assist gas and its nozzle are needed to remove the molten metal. However, because of the gas nozzle should be set closer to the surface of a workpiece, existence of the nozzle seems to prevent laser cutting from being used flexible. Therefore, the new cutting process, Assist Gas Free laser cutting or AGF laser cutting, has been developed. In this process, the pressure at the bottom side of a workpiece is reduced by a vacuum pump, and the molten metal can be removed by the air flow caused by the pressure difference between both sides of the specimen. In this study, cutting properties of austenitic stainless steel by using AGF laser cutting with 2？kW CO2 laser were investigated. Laser power and cutting speed were varied in order to study the effect of these parameters on cutting properties. As a result, austenitic stainless steel could be cut with dross-free by AGF laser cutting. When laser power was 2.0？kW, cutting speed could be increased up to 100？mm/s, and kerf width at specimen surface was 0.28？mm. 1. Introduction Laser cutting is one of the thermal cutting processes such as gas cutting and plasma cutting [1]. In laser cutting, as a focused laser beam melts or vapors a workpiece locally, it has the following features. First, width of cut kerf is narrower than that of the conventional cutting process. Second, laser cutting can achieve precision cut with small distortion. Therefore, laser cutting is applied in many industries such as automobile, aerospace, shipbuilding, and so on [2]. In laser cutting of metallic materials, molten metal is usually removed by using suitable assist gas at high pressure as shown in Figure 1 [3]. Thus, the special gas nozzle is needed to provide the assist gas such as oxygen, nitrogen, air, and so on. However, because of the gas nozzle should be moved closer to the position about 1？mm from the surface of a workpiece, it’s thought that existence of the nozzle causes lack of flexibility of laser cutting. For example, when the laser cutting of odd-shapes material pressed into shapes is intended, the gas nozzle may touch the material. Additionally, in the remote laser cutting studied in these days [4–6], gas nozzle using itself is difficult. From this viewpoint, it’s expected that the application range of laser cutting will expand by realizing without assist gas. Figure 1: Schematic of conventional laser cutting process of metallic materials with assist gas. For this reason, the new cutting process, Assist Gas Free