Types of Metal Welding
The difference between ordinary soldering and brazing and soldering is that soldering forms a connection by melting the solder with a lower melting point (lower than the melting point of the work piece itself) without heating to melt the work piece itself.
There are many energy sources for welding, including gas flames, arcs, lasers, electron beams, friction, and ultrasonic waves. In addition to being used in factories, welding can also be carried out in a variety of environments, such as field, underwater, and space. No matter where it is, welding may bring danger to the operator, so appropriate protective measures must be taken when welding. The possible injuries to the human body caused by welding include burns, electric shock, visual impairment, inhalation of toxic gas, excessive ultraviolet radiation, etc.
There are more than 40 metal welding methods, mainly divided into the following types:
Fusion welding is a method of heating the work piece interface to a molten state during the welding process and completing the welding without applying pressure. During fusion welding, the heat source quickly heats and melts the interface between the two work pieces to be welded to form a molten pool. The molten pool moves forward with the heat source. After cooling, a continuous weld is formed to connect the two work pieces into one.
During the welding process, if the atmosphere is in direct contact with the high-temperature molten pool, the oxygen in the atmosphere will oxidize the metal and various alloy elements. Nitrogen and water vapor in the atmosphere enter the molten pool, and defects such as pores, slag inclusions, and cracks are formed in the weld during the subsequent cooling process, which deteriorates the quality and performance of the weld.
In order to improve the welding quality, various protection methods have been developed. For example, gas-shielded arc welding is to use argon, carbon dioxide, and other gases to isolate the atmosphere to protect the arc from oxidation during welding to avoid defects; as in the case of steel welding, titanium oxide powder with a large affinity for oxygen is added to the electrode coating By deoxidizing, the beneficial elements manganese, silicon, etc. in the electrode can be protected from oxidation and enter the molten pool. After cooling, high-quality welds can be obtained.
Pressure welding is the combination of two work pieces in the solid-state under pressure, which is also called solid-state welding. The commonly used pressure welding process is resistance butt welding. When the current passes through the connection end of the two work pieces, the temperature rises due to the large resistance. When heated to a plastic state, the connection becomes integrated under the action of axial pressure.
The common feature of various pressure welding methods is to apply pressure during the welding process without adding filler material. Most pressure welding methods such as diffusion welding, high-frequency welding, cold pressure welding, etc. do not have a melting process, so there is no problem of burning of beneficial alloy elements like fusion welding, and the intrusion of harmful elements into the weld, thereby simplifying the welding process and Improved the safety and sanitary conditions of welding. At the same time, because the heating temperature is lower than the fusion welding and the heating time is short, the heat-affected zone is small. Many materials that are difficult to weld by fusion welding can often be welded into high-quality joints with the same strength as the base material by pressure welding.
Brazing is to use a metal material lower than the melting point of the work piece as the brazing material. The work piece and the brazing material are heated to a temperature higher than the melting point of the brazing material and lower than the melting point of the work piece. The liquid brazing material is used to wet the work piece, fill the interface gap, and realize the work with the work piece. The mutual diffusion of atoms to achieve welding.
It consists of an optical oscillator and the medium placed between the mirrors at both ends of the cavity of the oscillator. When the medium is excited to a high-energy state, it begins to generate light waves of the same phase and reflects back and forth between the two ends of the mirror, forming a photoelectric cross-talk effect, amplifying the light waves, and obtaining enough energy to start emitting laser light.
The laser can also be interpreted as a device that converts raw energy sources such as electrical energy, chemical energy, thermal energy, light energy, or nuclear energy into electromagnetic radiation beams of certain light frequencies (ultraviolet, visible, or infrared). The conversion form is easy to perform in some solid, liquid, or gaseous media. When these media are excited in the form of atoms or molecules, they produce a beam-laser with almost the same phase and almost a single wavelength. Due to the same phase and single wavelength, the different angles are very small, and the distance that can be transmitted before being highly concentrated to provide functions such as welding, cutting, and heat treatment is quite long.
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