The classification of the welding
Hebei
Metal welding, according to the characteristics of the process points have fusion welding, pressure welding and brazing three categories.
Welding is heated to melt in welding process, the workpiece interface state, do not add pressure to complete welding method. Fusion welding, the heat will stay two welding workpiece interface heat melting rapidly, forming molten pool. Molten pool with heat source moving forward, continuous weld is formed after cooling and connect the two artifacts as a whole.
In the process of welding, if direct contact with the molten pool of high temperature, atmospheric oxygen in the atmosphere will be metal oxide and various alloy elements. Into the molten pool, such as nitrogen, water vapor in the atmosphere will be in the subsequent cooling process in the formation of porosity in the weld defects such as cracks, slag inclusion, and deterioration of weld quality and performance.
In order to improve the welding quality, people developed various protection methods. Gas shielded arc welding is used, for example, argon, carbon dioxide and other gases from the atmosphere, in order to protect the welding arc and pool rate; And as steel welding, add affinity for oxygen in covering titanium iron powder of the solid, can protect the electrode in the beneficial elements such as manganese, silicon from oxidation and into the molten pool, cooled to obtain high quality welds.
Bonding is under the condition of pressure, make the two artifacts in solid state bonding between atoms, also called solid-state welding. Commonly used is the butt welding, pressure welding process when a current flows through the connection end of the two artifacts, it due to the resistance being very high temperatures, when heated to a plastic state under axial pressure is connected as a whole. The common characteristics of all kinds of pressure welding method is in the process of welding pressure and without filler material. Most bonding methods such as diffusion welding, high frequency welding, cold welding, such as no melting process, there is no useful alloying elements burning, such as welding and harmful elements into the problem of weld, simplifying the welding process, also improved the welding safety and health conditions. At the same time due to the heating temperature is lower than fusion welding, short heating time, thus small heat affected zone. Many difficult to melt welding welding materials, often can use pressure welding welded and the parent metal the same strength of high quality connectors.
Brazing is a metal material for the use of the low melting point than the workpiece solder, the workpiece heated to higher than the melting point solder, and filler metals is lower than the temperature of the melting point of workpiece, using liquid solder wetting artifacts, filling gaps and artifacts to realize mutual diffusion between atoms, so as to realize the welding method.
Welding formed when the connection of two connecting seam called welds. On either side of weld in welding when the welding heat effect, and microstructure and property changes, this area is called the heat affected zone. When welding for welding materials, welding current and different workpiece materials, after welding in the welding seam and heat affected zone may cause overheating, embrittlement, hardening or softening phenomenon, also make the weldment performance degradation, worsening weldability. Its need to adjust the welding conditions, the butt welding pieces of outlet preheating before welding, welding heat preservation and heat treatment after welding can improve the welding quality of welding.
