Classification of Welding Processes in Hardware Processing
Welding is one of the core processes in hardware and sheet metal processing. Based on welding principles, process characteristics, and heat source types, it can be divided into the following major categories, each containing common specific processes suitable for different sheet metal materials, thicknesses, and processing requirements:
I. Fusion Welding
Core Principle: The joint of the workpiece is heated to a molten state without pressure (or with slight pressure), and after cooling, a weld is formed, achieving interatomic bonding. This is the most commonly used category in sheet metal processing.
Electric Arc Welding
Manual Electric Arc Welding (Shielded Metal Arc Welding)
Flexible operation, simple equipment, suitable for welding single pieces and small batches of non-standard sheet metal parts. It can weld materials such as carbon steel and stainless steel, but requires high welder skills.
Submerged Arc Welding
The electric arc burns under a layer of flux. It has high welding efficiency and stable weld quality, suitable for long straight welds or circumferential welds on medium and thick sheet metal, and is often used for mass-produced steel structural parts.
Gas Shielded Arc Welding
Targon Arc Welding (TIG/MIG)
TIG welding (non-consumable electrode) is suitable for precision welding of thin sheet metal parts, producing aesthetically pleasing welds; MIG welding (consumable electrode) is more efficient and suitable for welding medium and thick plates and non-ferrous metals (such as aluminum and copper), and is widely used in stainless steel sheet metal processing.
Carbon Dioxide Gas Shielded Welding (CO₂ welding): Low cost and fast welding speed, suitable for welding sheet metal parts of low-carbon steel and low-alloy steel, commonly used in mass production of engineering machinery, appliance casings, etc.
Gas Welding: Uses a flame from the combustion of a mixture of acetylene and oxygen as a heat source. The equipment is lightweight and suitable for welding thin steel plates and non-ferrous metals, but the heat is dispersed, resulting in greater deformation. Its application in precision sheet metal processing is gradually decreasing.
Electroslag Welding: Utilizes the resistance heat generated by current passing through liquid molten slag to melt the base material and welding wire. Suitable for thick plate welding, generally not used for conventional sheet metal parts.
II. Pressure Welding
Core Principle: Pressure is applied to the workpieces during welding, causing plastic deformation at the joint. Bonding is achieved through atomic diffusion. Some processes require heating.
Resistance Welding
Spot Welding: Current passes through the contact surfaces of the two workpieces, generating resistance heat. Pressure is applied to form a weld spot. Suitable for lap welding of thin sheet metal, such as the batch connection of appliance housings and automotive sheet metal parts, with extremely high efficiency.
Seam Welding: The electrodes are rollers, forming a continuous weld seam during welding. Suitable for welding sealed sheet metal parts (such as water tanks and fuel tanks).
Butt Welding: The end faces of two workpieces are joined together, heated, and then pressure is applied to weld them. Suitable for connecting profiles and bars, less commonly used for sheet metal parts.
Friction Welding: Utilizes the heat generated by friction between the contact surfaces of the workpieces, applying pressure to complete the welding. Suitable for butt welding of round and tubular sheet metal parts. The weld quality is stable with minimal deformation.
III. Brazing
Core Principle: Uses a filler metal with a melting point lower than the base metal. After heating, the filler metal melts and fills the joint gap, diffusing with the base metal to achieve connection. The base metal does not melt. **Hard Brazing:** Uses brazing filler metals with a melting point above 450℃ (e.g., copper-based, silver-based filler metals). It produces high-strength joints and is suitable for welding stainless steel and hard alloy sheet metal parts, such as cutting tools and heat exchangers.
**Soft Brazing:** Uses brazing filler metals with a melting point below 450℃ (e.g., tin-lead filler metals). It produces lower-strength joints and is commonly used for electrical connections in sheet metal parts (e.g., circuit boards and metal terminals).
IV. Special Welding: Welding processes for special materials or high-precision requirements, occasionally used in custom non-standard sheet metal work:
**Laser Welding:** Uses a laser beam as a heat source. Concentrated heat results in minimal welding deformation. Suitable for welding thin-walled, precision sheet metal parts (e.g., medical devices, electronic component housings). It can also weld dissimilar materials.
**Plasma Arc Welding:** Utilizes the high temperature of a plasma arc for welding. It has strong penetration and is suitable for sheet metal processing of thick plates or high-melting-point metals (e.g., titanium alloys).
Electron beam welding uses an electron beam as a heat source in a vacuum environment, resulting in welds with a large depth-to-width ratio and high quality, making it suitable for high-precision sheet metal welding in the aerospace field.
