An article to give you a comprehensive understanding of commonly used welding methods

Welding is the core processing technology in the fields of modern manufacturing, steel structures, pipes, sheet metal, auto repair, and special equipment. According to the physical nature of the welding process, it is mainly divided into three categories: fusion welding, pressure welding, and brazing. The following is a detailed dismantling of the most commonly used welding methods in the industry, including principles, process characteristics, applicable materials, advantages and disadvantages, and on-site applications.

Fusion welding is a welding method that heats the welding part to a molten state without applying pressure, and relies on the cooling and crystallization of the molten metal to form a weld. It is also the most commonly used type in industry, construction sites, and maintenance.

1. Manual Arc Welding (Rod Arc Welding / Hand Arc Welding)

Basic Principle	The high temperature of the arc generated between the welding rod and the workpiece is used to melt the welding rod and base metal, and form a strong weld after cooling. The equipment is simple, with AC/DC welding machine as the core.
Core Features	The equipment is portable, the cost is extremely low, and the location is not limited. It can be operated indoors and outdoors, at high altitudes, and in the field; it is flexible in operation and can weld seams in all positions.
Applicable Materials	Ordinary carbon steel, low alloy steel, cast iron, some stainless steel; not suitable for ultra-thin plates and high-precision welds.
Applicable Scenarios	Steel structure workshops, steel frame construction, equipment maintenance, pipeline repair, infrastructure projects, agricultural machinery and automobile repairs, and temporary component welding.
Advantages	Cheap equipment, easy to carry, strong wind resistance, good weld toughness, and extremely versatile.
Disadvantages	Low production efficiency, rough appearance of welds, large spatter, lots of smoke and dust, high technical requirements for welders, and thin plates are easy to burn through.
Practical Key Points	Select the corresponding welding rod according to the base material and control the current; bevel the thick plate and perform multi-layer and multi-pass welding; pay attention to wind, fire and arc burn prevention.

2. Argon Arc Welding (TIG Welding / Tungsten Inert Gas Shielded Welding)

Basic Principle	Use tungsten electrode as the electrode to generate arc, and at the same time, argon gas is introduced to isolate the air and protect the molten pool from oxidation. The welding can be completed by filling wire or self-melting. It is divided into DC argon arc welding and AC argon arc welding.
Core Categories	DC argon arc welding → welding carbon steel, stainless steel, alloy steel; AC argon arc welding → specializing in welding aluminum and aluminum alloys.
Applicable Materials	Stainless steel, aluminum alloy, copper, titanium alloy, thin-walled pipe fittings, high-precision metals.
Applicable Scenarios	Pressure pipes, pressure vessels, stainless steel products, door and window sheet metal, kitchen utensils, precision machinery, boilers, instruments, non-ferrous metal welding. The pipeline industry often refers to argon electric welding, which is argon arc welding base + hand arc welding filling cover.
Advantages	Beautifully formed welds, no spatter, small welding deformation, extremely high quality welds, good air tightness, suitable for thin parts and all-position welding.
Disadvantages	Slow welding speed, high cost, high equipment price, poor wind resistance, and cannot operate in outdoor windy environments.

Important Reminder: Argon arc welding is the preferred primer process for special equipment, pressure pipes, and pressure vessels. It has fewer internal defects in the weld and a high flaw detection pass rate. It is an essential skill for high-end welding positions.

3. Carbon Dioxide Gas Shielded Welding (CO₂ Welding / Gas Shielded Welding)

Basic Principle	The welding wire is used to automatically feed the wire, the base material and the welding wire are melted by the arc, and the carbon dioxide gas is continuously introduced into the molten pool to protect it. It is a semi-automatic fusion welding.
Applicable Materials	Low carbon steel, low alloy high-strength steel, mainstream welding method for ordinary structural parts; generally not used for high-demand stainless steel and non-ferrous metals.
Applicable Scenarios	Automobile manufacturing, engineering machinery, containers, steel structures, frames, shelves, greenhouses, batch sheet metal parts, and assembly line production.
Advantages	High welding efficiency, large penetration, low cost, wide current adjustment range, suitable for continuous operations on thick plates and long welds.
Disadvantages	Large spatter, average weld formation, weak windproof ability, low temperature and strong wind environment, easy to produce pores, and large amount of smoke and dust.

4. Submerged Arc Welding

Basic Principle	The arc is covered by granular flux and burns under the flux layer to complete the welding. Most of them are fully automatic/semi-automatic equipment.
Applicable Scenarios	Thick steel plate splicing, large steel structures, pressure vessel cylinders, long straight welds, shipyards, and heavy machinery mass production.
Advantages	Large current, extremely deep penetration, stable weld quality, no arc, less smoke and dust, high degree of automation, suitable for thick plate and large welds.
Disadvantages	The equipment is bulky, can only weld long straight welds in flat positions, has poor flexibility, and is not suitable for small parts, short welds, and special-shaped workpieces.

During the pressure welding process, the workpiece is heated or not heated, and the contact surfaces of the two metals are tightly combined to form a connection by applying pressure, and there is no filler metal in the whole.

1. Resistance Welding (Spot Welding, Projection Welding, Seam Welding)

Basic Principle	Use electric current to generate resistance heat through the workpiece contact surface, heat the metal to a plastic state, and pressurize to complete the welding at the same time.
Spot Welding	Most commonly used; two point electrodes press the workpiece to form a local welding spot. Mostly used for overlapping thin plates.
Applicable Scenarios	Batch processing of automobile bodies, home appliance casings, sheet metal parts, shelves, barbed wire, and hardware products.
Advantages	Extremely fast, high degree of automation, small deformation, no need for welding wires and electrodes, low cost, suitable for mass production on the assembly line.
Disadvantages	Only suitable for overlapping thin plates, poor sealing, unable to withstand large loads, and high power equipment.

2. Friction Welding

Basic Principle	Two workpieces are used to generate heat through high-speed friction with each other. After the end face reaches the plastic state, it is instantly upset and pressurized to complete the welding.
Applicable Scenarios	Shaft workpieces, cutting tools, drill pipes, valve rods, and dissimilar metal docking.
Advantages	High weld strength, stable quality, high efficiency, no pollution, and can weld some dissimilar metals.
Disadvantages	The equipment is highly specialized and is only suitable for rotationally symmetrical workpieces.

During brazing welding, the base metal does not melt, only the solder with a lower melting point is melted, the liquid solder fills the joint gap, and the connection is completed after cooling. It is divided into two categories: hard soldering and soft soldering.

1. Soft Soldering (Tin Soldering)

Solder	Tin-lead alloy, lead-free solder; melting point lower than 450℃.
Applicable Scenarios	Electronic circuit boards, wire connectors, small precision electrical appliances, instrument circuits.
Features	Low temperature, no deformation of the workpiece, simple operation, low joint strength; only used for weak current and light load connections.

2. Brazing (Brazing / Silver Soldering)

Solder	Copper-based, silver-based solder; melting point higher than 450℃. Commonly used equipment: oxygen acetylene flame, high frequency induction equipment.
Applicable Scenarios	Copper pipes, air conditioning and refrigeration pipes, cutting tools, carbide cutter heads, and hardware fittings.
Advantages	The joint has good sealing performance, high strength, and small deformation of the workpiece. It is suitable for thin-walled pipe fittings and dissimilar metal connections.
Disadvantages	Average high temperature resistance, cannot withstand severe impact and heavy load.

Summary of Selection Guide