What is welding?
Welding, also known as fusion, is a manufacturing process and technology that uses heating, high temperature or high pressure to join metals or other thermoplastic materials such as plastics.
There are many sources of energy for modern welding, including gas flames, arcs, lasers, electron beams, friction and ultrasound. In addition to being used in factories, welding can also be performed in a variety of environments, such as outdoors, underwater and in space. Welding can be dangerous to operators wherever it is, so appropriate protective measures must be taken when welding. Possible injuries to the human body caused by welding include burns, electric shock, visual impairment, inhalation of toxic gases, excessive ultraviolet radiation, etc.
Welding achieves the purpose of joining through the following three ways:
Fusion welding - heating the workpieces to be joined to partially melt them to form a molten pool, which is joined after the molten pool cools and solidifies. If necessary, molten fillers can be added to assist. It is suitable for welding of various metals and alloys without pressure.
Pressure welding - the welding process must apply pressure to the weldment, which belongs to the processing of various metal materials and partial metal materials.
Brazing - Use a metal material with a lower melting point than the parent material as the brazing material, use the liquid brazing material to wet the parent material, fill the joint gap, and diffuse with the parent material to achieve the connection of the welded parts. It is suitable for welding of various materials, and also suitable for welding of different metals or heterogeneous materials.
What is brazing?
Brazing refers to a welding method in which the gap of the solid workpiece is filled with liquid brazing material after the brazing material and the weldment with a lower melting point than the weldment are heated to the melting temperature of the brazing material at the same time. When brazing, the oxide film and oil stains on the contact surface of the parent material must be removed first, so as to facilitate the capillary to play a role after the brazing material melts, increase the wettability and capillary fluidity of the brazing material. According to the different melting points of the brazing material, brazing is divided into hard brazing and soft brazing.
Brazing has small deformation and smooth and beautiful joints. It is suitable for welding precise, complex and components composed of different materials, such as honeycomb structure plates, turbine blades, carbide tools and printed circuit boards. Before brazing, the workpiece must be carefully processed and strictly cleaned to remove oil stains and excessively thick oxide films to ensure the assembly gap of the interface. The gap is generally required to be between 0.01 and 0.1 mm.
Compared with fusion welding, the parent material does not melt during brazing, only the brazing material melts; compared with pressure welding, no pressure is applied to the weldment during brazing. The weld formed by brazing is called a brazing seam. The filler metal used for brazing is called a brazing filler.
Brazing process: The workpieces with cleaned surfaces are assembled together in an overlapping manner, and the brazing filler is placed near or between the joint gaps. When the workpiece and the brazing filler are heated to a temperature slightly higher than the melting point of the brazing filler, the brazing filler melts (the workpiece is not melted), and is sucked in and filled between the solid workpiece gaps by capillary action. The liquid brazing filler and the workpiece metal diffuse and dissolve each other, and a brazed joint is formed after condensation.
What is the difference between welding and brazing?
Welding is a method of connecting the workpieces by heating or pressurizing or both, with or without filler materials, so brazing is one of the welding methods.
As one of the three major welding process methods, brazing is different from fusion welding and pressure welding.
Fusion welding is the use of an external heat source (such as an arc) to locally heat and melt the area near the interface of the connected components (i.e., the parent material), and then cool to form a joint. During the welding process, both the parent material and the filler metal are melted, and the two are chemically combined. Such as: manual arc welding, CO2 welding, TIG welding, MIG welding, submerged arc welding, MAG welding, plasma welding, laser welding, electron beam welding, etc.
Pressure welding is to apply pressure to make the atomic spacing of the welded surface close to the lattice distance. No solder is used during welding, the metals to be connected are chemically or physically combined, the weld is narrow, and the heat-affected zone is small, including resistance welding (spot welding, seam welding), flash welding, friction welding, cold pressure welding, etc. Brazing is to achieve the connection of the brazed parts by molten metal (brazing material). The temperature of the brazing material is lower than the temperature of the parent material. During welding, the brazing material melts but the parent material does not melt, and the two are physically combined. It is customary to divide brazing and soldering at a welding temperature of 450°C. Brazing mainly includes flame brazing, induction brazing, furnace brazing, resistance brazing, etc.
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