The arc length is related to the type and thickness of covered electrode coating. However, short arcs, especially low hydrogen covered electrode, should be used as much as possible. Long arcs may cause blowholes. Short arc can prevent harmful gases such as O2 and N2 in the atmosphere from invading the weld metal and forming undesirable impurities such as oxides, which will affect the welding quality.

Second, the appropriate welding speed

Suitable welding speed depends on covered electrode diameter, coating type, welding current, heat capacity of welding object, structure beginning and other conditions, so it is impossible to make standard provisions.

Keeping proper welding speed, slag can cover the molten pool well. Make all kinds of impurities and gases in the molten pool have enough floating time to avoid slag inclusion and porosity in the weld. When welding, if the rod feeding speed is too fast, the shrinkage stress will increase when the welding part cools, which will cause the weld to crack.

Third, the welding temperature control

The temperature of molten pool directly affects the welding quality. The molten pool has high temperature, large molten pool, good fluidity and easy melting. But when it is too high, the molten iron will flow down easily, and the back surface formed by single-sided welding and double-sided welding will burn through easily, forming flash, which is difficult to control, reducing the plasticity of the joint and cracking easily in bending. When the temperature of molten pool is low, the molten pool is small, the color of molten iron is dark, and the fluidity is poor, which is easy to produce defects such as incomplete penetration, incomplete fusion and slag inclusion.

Extended data:

Welding standard specification

1. During welding and cutting operations, all flammable and explosive articles within the working environment 10m shall be cleaned, and attention shall be paid to whether there are flammable liquids and flammable gases in the trenches and sewers of the working environment, and whether it is possible to leak flammable and explosive substances into the trenches and sewers, so as to avoid disasters and accidents caused by welding slag and metal sparks.

2. When welding and cutting at high altitude, it is forbidden to throw covered electrode's head, and the lower part of welding and cutting operations should be isolated. After the operation is completed, you should carefully check and confirm that there is no fire hazard before leaving the site.

3. Gas cylinders that meet the requirements of relevant national standards and regulations should be used, and the storage, transportation and use of gas cylinders should strictly abide by the safety operation procedures.

4. Pipelines conveying combustible gas and combustion-supporting gas shall be installed, used and managed according to regulations, and operators and inspectors shall receive special safety technical training.

5. When welding and repairing fuel containers and pipelines, the welding and repairing methods shall be determined according to the actual situation. When implementing the replacement method, the replacement should be thorough, and the shadow of combustible substances should be strictly controlled in the work. When the pressureless replacement method is implemented, a certain voltage should be maintained as required. Oxygen content should be strictly controlled in the work. It is necessary to strengthen detection, pay attention to monitoring, and have safety organization measures.

Baidu encyclopedia-welding

Baidu encyclopedia-welding technology