Welding torch, also known as welding torch, is a tool for welding or preheating black or non-ferrous metal workpieces with oxygen and low-pressure acetylene as heat sources. It is the main tool for gas welding operation. The function of welding torch is to mix combustible gas and oxygen evenly according to a certain proportion, and spray it from welding nozzle at a certain speed to form a flame with a certain energy rate and composition, suitable for welding requirements and stable combustion. The quality of welding gun directly affects the welding quality of gas welding, so it is required that the welding gun should have good performance of adjusting the ratio of oxygen to combustible gas and the flame energy rate, so that the injection speed of mixed gas is equal to or greater than the combustion speed, thus making the flame burn stably. At the same time, the welding torch is required to be light in weight, convenient to operate and safe and reliable to use. Common models of spray-suction welding guns. H0 1-6, H0 1-20, etc. (In the model, H stands for welding torch, 0 stands for manual operation, 1 stands for spray suction type, and the suffix number represents the maximum thickness of welded low-carbon steel in mm). Each welding gun is equipped with five nozzles with different specifications, and each nozzle is engraved with different numbers 1, 2, 3, 4, 5. A small number of nozzles have a small aperture, and a large number of nozzles have a large aperture. The required welding nozzles can be selected according to the material and the thickness of the plate.