What Is Gas Welding?

Gas welding, in English: oxygen fuel gas welding (referred to as OFW). A welding method that uses the flame generated by the mixed combustion of combustible gas and combustion-supporting gas as a heat source, melting the welding piece and the welding material to achieve inter-atomic bonding.

Gas welding is also called wind welding. PMA plasma brazing machine completely replaces the traditional brazing equipment, a new generation of brazing equipment that does not require oxygen, acetylene, liquefied gas, alcohol, gasoline combustible gas. Using IGBT inverter control principle, the flame is very stable during welding, the whole equipment is light and convenient, suitable for outdoor welding. The operation of the welding machine is simple, anyone who knows the welding machine can do it, no special training is needed, this product does not require flammable and explosive gases such as acetylene, and the safety performance is greatly improved. Just use electricity, some underdeveloped areas (no oxygen or acetylene, gasoline, etc.) use, etc.

advantage:

1 pair

Neutral flame: When O2 / C2H2 = 1 ~ 1.2, the flame formed by combustion. The flame structure can be divided into three parts: flame center, inner flame, and outer flame. The flame heart is composed of unburned oxygen and acetylene. The outer surface of the flame core is distributed with a layer of carbon particles generated by the decomposition of acetylene. The temperature is high (about 900 ° C), and the hot carbon particles emit bright white light, which is pointed and cone-shaped with a clear outline. The inner flame is mainly composed of acetylene and incompletely combusted products (H2 and CO). It has reducing properties, is blue-white, has an unclear outline, and has no obvious boundary with the outer flame. The temperature of the inner flame is very high, up to 3150 ° C. The outer flame is composed of CO2 and water vapor produced by complete combustion of CO and H2 and O2 in the air, and is oxidizing. The temperature of the outer flame is in the range of 1200-2500 ° C, and gradually changes from lilac to orange-yellow from the inside to the outside.
Oxidation flame: When O2 / C2H2> 1.2, the flame formed by combustion. The flame structure can be divided into two parts, the flame center and the outer flame. There is excess oxygen in the flame, forming an oxidizing oxygen-rich region outside the flame core. The flame heart is short and pointed, and it is blue-white. The outer flame is a purplish outer flame, which is shorter than the normal outer flame and the flame is straight.
Carbonized flame: When O2 / C2H2 <1, the flame formed by burning. Oxygen is not enough to completely burn acetylene, and excess acetylene is decomposed into carbon and hydrogen. Carbon will penetrate

During gas welding operation, the welding torque is generally held by the right hand, the thumb is located at the acetylene switch, and the index finger is located at the oxygen switch, so that the gas flow rate can be adjusted at any time. Holding the welding handle with the other three fingers, the basic operations of gas welding with the right hand holding the welding wire are: ignition, flame adjustment, welding and flameout.

1. When igniting, adjusting the flame and extinguishing the ignition, slightly open the oxygen valve, then open the acetylene valve, and ignite the flame with an open flame (available electron gun or low-voltage electric spark, etc.). The flame at this time is a carbonized flame, and then gradually open the oxygen valve to adjust the carbonized flame to a neutral flame. If you continue to increase oxygen (or reduce acetylene), you can get an oxidized flame. Ignition may continue. "Blasting" sound may occur continuously because the acetylene is not pure and the impure acetylene should be released to reignite. Sometimes it is difficult to ignite because the amount of oxygen is too large. At this time, the oxygen valve should be closed slightly. When igniting, do not point the hand holding the fire source directly at the welding nozzle or point at others to prevent burns. When it is necessary to turn off after welding, the acetylene valve should be closed first, and then the oxygen valve should be closed to avoid tempering and reduce smoke and dust.

2. Surfacing welding wave (1) The weldment is prepared to clean the oxide scale, rust, oil and dirt on the surface of the weldment with a wire brush, abrasive cloth, etc., so that the weldment is exposed on the metal surface.
(2) Welds generally start with a neutral flame for low-carbon steel, leftward welding. That is, the welding moment is to be welded from right to left, so that the flame is directed to the part to be welded. When the welding wire tip is located in front of and below the flame and welded together, due to the initial heating, the inclination angle of the welding moment should be larger (50 70), which is beneficial The workpiece is preheated, and the projection of the nozzle axis coincides with the weld. At the same time, the flame should be moved back and forth at the welding place to ensure that the welding zone is heated uniformly. After the weldment is melted from red into a bright and clear molten pool, the welding wire can be melted, and then the welding wire is immediately lifted up, and the flame moves forward uniformly to form a new molten pool.
(3) Normal welding In order to obtain high-quality and beautiful welds and control the heat of the weld pool, the welding moment and the welding wire should make uniform and coordinated movement; that is, the longitudinal movement along the weldment joint; the welding moment makes a lateral swing along the weld joint; The welding wire is fed in the direction of the vertical weld and moves up and down.
(4) Weld end When the end of the weld is welded, the angle between the welding moment and the weldment should be reduced due to poor heat dissipation at the end. (20 ~ 30 °), at the same time, increase the welding speed and add more welding wires to prevent the molten pool from expanding and forming burn-through.