Welding is a welding in the welding process will workpiece interface is heated to a molten state, without the pressure to complete. Welding, heat welding two workpieces interface will be rapidly heated to melt, the formation of the molten pool. Bath to move forward with the heat source, cooling to form a continuous weld the two workpieces become one.

Welding process, the air hot bath direct contact with the oxygen in the atmosphere will be metal oxide and a variety of alloying elements. Atmospheric nitrogen and water vapor into the molten pool, but also in the subsequent cooling process in the formation of pores in the weld, folder slag, cracks and other defects, deterioration in weld quality and performance.

In order to improve the welding quality, it has developed a variety of protection methods. For example, the gas shielded arc welding is isolated from the atmosphere with gases such as argon, carbon dioxide, in order to protect the welding arc and weld pool rate; and if steel Aluminium Welding Electrodes drug skin deoxy oxygen affinity of ilmenite powder electrode beneficial elements manganese, silicon, etc. can be protected from oxidation into the bath and after cooling for high-quality weld.

Bonding under high pressure so that the two workpiece combination between atoms in the solid state to achieve, also known as solid-state welding. The bonding process is resistance butt welding, when the current through the connection end of the two workpieces, and the department to become one due to resistance is very large and the rise in temperature, when heated to a plastic state, the effect of axial pressure connection.

The common feature of a variety of bonding methods to exert pressure in the welding process without filler material. The majority of bonding methods such as diffusion welding, high frequency welding, cold pressure welding and so the melting process, and thus the beneficial alloying elements like welding as burning, invasive and harmful elements in the weld, thus simplifying the welding process, also welding safety and health conditions improved. As the heating temperature is lower than welding, the heating time is short, and thus the heat-affected zone. Difficult to fusion welded materials, often with pressure welding and high-quality connectors into the parent material of equivalent strength.

Brazing is lower than the workpiece melting point metal material for brazing the workpiece and the filler metal is heated to above the melting point of brazing, lower than the melting point temperature of the workpiece, the use of liquid solder wetting workpiece to fill the interface gap with the workpiece to achieve interdiffusion between atoms in order to achieve a method of welding.

Formed by welding to connect the two to connect the joints of the body known as the weld. Weld on both sides of the welding by the welding heat, and the changes in the organization and performance in this area is called the heat-affected zone. Welding materials, welding current, welding, the workpiece material is different in the weld and heat affected zone after welding may overheat, embrittlement, hardening or softening, the weldment performance degradation and deterioration of the weldability. This requires adjustment of the welding conditions, welded pieces of interface preheat before welding, insulation when welding and post weld heat treatment can improve the welding quality of the weldment.

In addition, welding is a rapid local heating and cooling process, the welding zone due to the binding of the workpiece body around to free expansion and contraction, after cooling will produce welding stress and deformation in weldments. Important product after welding to eliminate welding stresses, the correction of welding deformation.

Modern welding technology has been able to weld the internal and external defects, mechanical properties equal even higher than the body is connected weld. The mutual position of the welding body in space known as welded joints, the strength of the joints affected by weld quality, but also its geometry, dimensions, by force and working conditions. The basic form of joint butt, lap, T-connected (positive transfer), and corner joints.

Cross-sectional shape of the butt joint weld, decided to be welded before welding, the thickness and the two connected side of the groove. When welding thick steel plates, in order to penetration at the Edge out of the groove of a variety of shapes, in order to more easily into the Welding Rod or wire. Groove in the form of single-sided welding groove and on both sides of the welding groove. Choosing the form of a groove, in addition to ensure that penetration should also be considered to facilitate welding filler metals less welding deformation is small and the groove processing costs low.

Dramatic changes in the thickness of the two steel plates butt in order to avoid cross-section caused by severe stress concentration, often thick edge gradually thinning to achieve the thickness of the two connected edges. Static strength and fatigue strength of butt joints than other joints. Connection to the alternating, shock load or low temperature and high pressure container, often give priority to the use of a butt joint welding.

Preparatory work before the lap joint welding, assembly, welding deformation and residual stress is smaller, and thus is often used in the structure of the site installation of joints and unimportant. In general, the lap joint is not suitable for alternating loads, corrosive medium, high or low temperature conditions to work.

T-joints and corner joints is usually due to the structural needs. T-connector on the penetration fillet weld characteristics similar to the fillet weld lap joints. Will become when the weld and external direction perpendicular to the front of fillet weld, then weld the shape of the surface can cause varying degrees of stress concentration; fillet weld penetration by force and butt joints.

Low-angle connector carrying capacity, is generally not used alone, penetration, or both inside and outside fillet weld when improved, used for closed-shaped structure around the corner.