Gas welding and gas cutting

Gas welding is the use of heat to fuse and weld the metal together. The material itself has not changed. It is a physical change. The gas cutting is to pass the molten metal and then pass excess oxygen, let the hot metal react with oxygen to form metal oxide, and the metal and the newly formed metal are oxidized. The nature of the material is separated and separated, so that the purpose of cutting is achieved, so gas cutting is a chemical change.

There are two directions for gas welding operations:
(1) Left-hand welding: The welding wire and the welding torch move from the right end to the left end of the welding seam, the welding wire is in front of the welding torch, and the flame points to the portion to be welded of the welding piece. It is characterized by simple and convenient operation and is suitable for welding workpieces with thinner and lower melting points.

(2) Right-hand welding: The welding wire and the welding torch move from the left end to the right end of the welding seam, the welding wire is behind the welding torch, and the flame points to the welded portion of the welding piece. The feature is that the flame always covers the welded weld metal during the welding process, so that the molten pool is cooled slowly, which helps to improve the metal structure of the weld, and the heat is concentrated and the penetration depth is large, which is suitable for welding workpieces with large thickness. But the operation is hard to master.

The gas cutting process has three phases:
(1) Preheating: At the beginning of gas cutting, a gas flame (oxyacetylene flame or oxypropane flame) is used to preheat the workpiece to be cut to the burning temperature of the metal material—flame point (about 1100~1150°C for carbon steel) .

(2) Combustion: The high-speed cutting oxygen flow is sprayed, so that the metal that has reached the ignition point is intensely burned in the oxygen flow to form an oxide.

(3) Blowing slag: The oxide formed by the combustion of the metal is blown off by the oxygen stream to form a slit, which separates the metal and completes the cutting process.