Brazing is a method of welding that uses a filler metal with a melting point lower than that of the workpiece. The workpiece and filler are heated to a temperature above the melting point of the filler but below that of the workpiece, allowing the liquid filler to wet the workpiece, fill the joint gap, and achieve atomic diffusion with the workpiece, thus completing the welding process.

The seam formed during welding between two connected bodies is called a weld seam. The areas on both sides of the weld seam are affected by welding heat during the process, leading to changes in structure and properties; this area is known as the heat-affected zone. Due to differences in materials, welding currents, etc., overheating, embrittlement, hardening, or softening may occur in the weld seam and heat-affected zone after welding, which can degrade the performance of the welded piece and worsen its weldability. This necessitates adjustments to welding conditions; preheating at the joint before welding, maintaining temperature during welding, and post-weld heat treatment can improve the quality of the welded piece.

Precautions

Additionally, welding is a localized rapid heating and cooling process. The welding area cannot freely expand and contract due to constraints from surrounding workpieces, resulting in welding stresses and deformations after cooling. Important products require the elimination of welding stresses and correction of welding deformations post-welding.

Modern welding technology can produce weld seams without internal or external defects, with mechanical properties equal to or even higher than those of the connected bodies. The relative positions of the welded bodies in space are referred to as weld joints. The strength at the joint depends not only on the quality of the weld seam but also on its geometric shape, size, load conditions, and working conditions. The basic forms of joints include butt joints, lap joints, T-joints (orthogonal joints), and corner joints.

The cross-sectional shape of a butt joint weld seam is determined by the thickness of the welded bodies before welding and the beveling form at both edges. When welding thicker steel plates, various shapes of bevels are created at the edges to facilitate easier insertion of rods or wires for complete penetration. Bevel forms include single-sided and double-sided bevels. When selecting a bevel form, factors such as ensuring complete penetration, ease of welding, minimal filler metal volume, small welding deformation, and low bevel processing costs should be considered.

When butt joining two steel plates of different thicknesses, to avoid severe stress concentration caused by abrupt changes in cross-section, it is common to gradually thin down the edge of the thicker plate until both edges are of equal thickness. The static strength and fatigue strength of butt joints are higher than those of other joints. In applications involving alternating or impact loads or in low-temperature high-pressure vessels, butt joints are often preferred for welding.

Lap joints have simple pre-welding preparation work and are easy to assemble; they exhibit less welding deformation and residual stress. Therefore, they are often used for field installation joints and less critical structures. Generally speaking, lap joints are not suitable for working under conditions involving alternating loads, corrosive media, high temperatures, or low temperatures.

T-joints and corner joints are typically used due to structural requirements. The characteristics of incomplete penetration in T-joint fillet welds are similar to those in lap joint fillet welds. When a weld seam is perpendicular to an external force direction, it becomes a face fillet weld; this can lead to varying degrees of stress concentration on the surface shape of the weld seam; fully penetrated fillet welds experience stress conditions similar to those in butt joints.

Corner joints have low load-bearing capacity and are generally not used alone; they only improve when fully penetrated or when there are fillet welds on both sides. They are mostly used at corners of closed structures.

Welded products are lighter than riveted parts, castings, and forgings; this can reduce weight for transportation vehicles and save energy. Welding has good sealing properties and is suitable for manufacturing various types of containers. Developing combined processing techniques that integrate welding with forging and casting can create large-scale economically reasonable cast-welded structures and forged-welded structures with high economic benefits. Using welding processes effectively utilizes materials; welded structures can employ different materials with varying properties at different locations to fully leverage each material's strengths for economic efficiency and quality. Welding has become an indispensable processing method in modern industry and is increasingly important.

In modern metal processing, welding has developed later than casting and forging processes but has progressed rapidly. The weight of welded structures accounts for about 45% of steel production; the proportion of aluminum and aluminum alloy welded structures is also continuously increasing.

Future welding processes need to develop new methods, equipment, and materials to further improve quality and safety reliability; this includes improving existing arc, plasma arc, electron beam, laser welding energies; utilizing electronic technology and control technology to enhance arc process performance; developing reliable lightweight arc tracking methods.

On the other hand, there should be an increase in mechanization and automation levels in welding; for example: achieving program control or digital control in welding machines; developing specialized machines that automate all processes from preparation through welding to quality monitoring; promoting and expanding CNC robotic arms and welding robots on automated production lines can enhance production levels while improving hygiene and safety conditions in welding.

Welding Equipment

1. Welding Machine

2. CO2 Shielded Welding Machine

3. Argon Arc Welding Machine

4. Resistance Welding Machine

5. Submerged Arc Welding Machine

6. Welding Wire

7. Flux

8. Welding Auxiliary Materials