Powered by the welding power source, a strong and long-lasting gas discharge phenomenon occurs between the workpiece and the electrode. The arc arc is supplied by the welding power source, and a strong and long-lasting gas discharge phenomenon occurs between the workpiece and the electrode.
Necessary conditions for arc combustion Gas ionization and cathode electron emission.
Applicable scope of electrode arc welding Electrode arc welding is carried out by manual welding of welding rods, and can be used for multi-position welding such as flat welding, vertical welding, horizontal welding and overhead welding. In addition, because the electrode arc welding equipment is light and flexible, it can be welded in any place with power supply. Suitable for welding of various metal materials, various thicknesses and various structural shapes.
The safety characteristics of electrode arc welding: the no-load voltage of welding arc welding equipment is generally 50V-90V, and the safe voltage that the human body can withstand is 30V-45V. It can be seen that the manual arc welding equipment will cause human life. Danger, you must wear protective equipment when welding.
Classification of arc welding
Arc welding can be divided into manual arc welding, semi-automatic (arc) welding, and automatic (arc) welding. Automatic (arc) welding usually refers to automatic submerged arc welding - a protective layer of solder is applied to the soldering portion, and a solder wire made of filler metal is inserted into the solder layer to generate an arc with the solder metal, and the arc is buried under the solder layer. The heat generated by the arc melts the welding wire, the flux and the base metal to form a weld, and the welding process is automated. The most common use is manual arc welding.
The basic process of basic process manual arc welding is as follows:
a. Clean the welding surface before welding to avoid affecting the quality of arc ignition and welds.
b. Prepare the joint form (bevel type).
The function of the groove is to make the welding rod, welding wire or welding torch (the nozzle for spraying acetylene-oxygen flame during gas welding) can directly extend into the bottom of the groove to ensure the penetration, and facilitate the slag removal and facilitate the necessary swing of the welding rod in the groove. To get a good fusion.
The shape and size of the groove mainly depends on the material to be welded and its specifications (mainly thickness) as well as the welding method and weld form to be taken.
Common groove types in practical applications are:
Flange joints - for thin parts with a thickness <3mm;
Flat bevel - suitable for thinner parts of 3~8mm;
V-groove - suitable for workpieces with a thickness of 6~20mm (single-sided welding);
X-shaped groove - suitable for workpieces with a thickness of 12~40mm, and has a symmetrical and asymmetrical X-edge (double-sided welding);
U-shaped groove - suitable for workpieces with a thickness of 20~50mm (single-sided welding);
Double U-shaped groove - suitable for workpieces with a thickness of 30~80mm (double-sided welding).
The groove angle is usually 60~70°. The purpose of using the blunt edge (also called root height) is to prevent the weldment from burning through, and the gap is for the purpose of penetration.
The main parameters of the welding parameters of the main parameters of arc welding are:
The type of electrode (depending on the material of the base material), the diameter of the electrode (depending on the thickness of the weldment, the position of the weld, the number of weld layers, the welding speed, the welding current, etc.), the welding current, the number of weld layers, and the welding speed.
In addition to the above-mentioned ordinary arc welding, in order to further improve the welding quality, it is also adopted:
Gas shielded arc welding:
For example, argon arc welding using argon gas as a shielding gas for a welding zone, carbon dioxide welding using carbon dioxide as a shielding gas for a welding zone, etc., the basic principle is to continuously spray out the nozzle from the nozzle while welding with an arc as a heat source. The gas isolates the air from the molten metal in the weld zone to protect the arc and the liquid metal in the weld pool from atmospheric oxygen, nitrogen, hydrogen, etc., in order to improve the quality of the weld.
Tungsten argon arc welding:
The high-melting-point metal tungsten rod is used as an electrode for arcing during welding, and is under arc protection under argon gas protection. It is often used for stainless steel "target=_blank> stainless steel, high-temperature alloy and other strict welding.
Plasma arc welding:
This is a welding method developed by tungsten argon arc welding. The electromechanical "target=_blank> machine arc welding current size judgment in the nozzle hole
Small current:
The weld bead is narrow, the penetration depth is shallow, and it is easy to form too high, not fused, not welded, slag inclusion, pores, electrode sticking, arc breaking, no arc striking, etc.
Large current:
Wide weld bead, deep penetration, undercut, burn through, shrinkage hole, large splash, over burn, large deformation, weldment, etc.
Precautions for fire and explosion accidents during arc welding 1. No flammable or combustible materials shall be allowed within 10 meters of the welding site. The width of the working place shall be greater than 1 m. At the height of work, pay attention to the direction of the spark.
2. The welding unit should place the E-block generator (acetylene bottle) and oxygen at 10 meters away.
3. Store the flammable and explosive containers without welding. Under this circumstance, the residual gas must be removed first, and the combustible gas should be excluded. Only after the risk of explosion is confirmed can be welded. It is safer to check with a gas detector.
4. When welding pipes and containers, the hole cover and valve must be opened.
5. Ensure that the connection parts of welding equipment and rubber insulated cables are not loose, and the damaged parts are well insulated to prevent leakage and overheating.
6. It is strictly forbidden to use flammable and explosive pipes for welding circuits.
7. When using carbon dioxide gas cylinders and argon gas cylinders, the "Cylinder Safety Supervision Regulations" should be observed.
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