Although almost all metal materials have high reflectivity for infrared energy at room temperature, CO2 lasers emitting 10.6 um beams in the far infrared range have been successfully applied to laser cutting practice in many metals. The initial absorption rate of the metal to the 10.6um laser beam is only 0.5% to 10%, but when the focused laser beam with a power density exceeding 106w/cm2 is irradiated onto the metal surface, it can be quickly made in the microsecond time. The surface begins to melt. The absorption rate of most metals in the molten state rises sharply and generally increases by 60% to 80%.
(1) Carbon steel.
The modern laser cutting system can cut the maximum thickness of carbon steel plate up to 20MM. The slit of cutting carbon steel by oxidation melting and cutting mechanism can be controlled in a satisfactory width range. The slit of the thin plate can be narrowed to about 0.1MM.
(2) Stainless steel.
Laser cutting is an effective tool for the manufacturing industry that uses stainless steel sheets as the main component. Under the strict control of the heat input in the laser cutting process, the heat-affected zone of the trimming can be restricted to be small, so that the good corrosion resistance of such materials can be effectively maintained.
(3) Alloy steel.
Most alloy structural steels and alloy tool steels can achieve good trim quality by laser cutting. Even for some high-strength materials, straight, non-stick slash trimming is achieved as long as the process parameters are properly controlled. However, for high-speed tool steels and hot-die steels containing tungsten, there is corrosion and slag formation during laser cutting.
(4) Aluminum and alloys.
Aluminum cutting is a melt cutting mechanism, and the auxiliary gas used is mainly used to blow away the molten product from the cutting zone, and generally a good cut surface quality can be obtained. For some aluminum alloys, care should be taken to prevent intergranular microcracks on the surface of the slit.
(5) Copper and alloys.
Pure copper (copper) cannot be cut with a CO2 laser beam because of its high reflectivity. Brass (copper alloy) uses a higher laser power, and the auxiliary gas uses air or oxygen to cut thinner sheets.
(6) Titanium and alloys.
Pure titanium can be well coupled to the thermal energy of the focused laser beam. The chemical reaction is intense when the auxiliary gas is oxygen, and the cutting speed is fast, but it is easy to form an oxide layer on the trimming edge, which may cause overburning. For the sake of safety, it is better to use air as an auxiliary gas to ensure the quality of the cut.
The laser cutting quality of titanium alloy commonly used in aircraft manufacturing is good. Although there is a little stickiness at the bottom of the slit, it is easy to remove.
(7) Nickel alloy.
Nickel-based alloys are also called superalloys and come in many varieties. Most of them can perform oxidative melt cutting.