Welding, also known as fusion welding, is a manufacturing process and technology that can connect metals or other thermoplastic composite materials (such as plastics) by heating, high temperature, or high pressure. There are three welding methods:

1. Fusion welding. Heat the workpiece to form a molten pool. After cooling and solidification, the molten pool can be connected, and filler materials can be added if necessary. It is suitable for pressureless welding of various metals and alloys in the enterprise.

2. Pressure welding. Pressure must be applied to the welded parts during welding, which belongs to various metal materials and certain metal material processing.

3. Brazing. Using metal structural materials with a melting point lower than the parent material can be used as brazing material, wetting the parent material with liquid solder, filling the joint gap, diffusing the parent material, and realizing the welding of the connected weldment. It is suitable for the welding of various active materials in the enterprise and the welding of different metals or uneven materials.

The welding temperature of low-carbon steel straight seam steel pipes is controlled at 1250 degrees to 1460 degrees, which can meet the requirements of 3 to 5 mm steel pipe wall thickness.

When the input heat resource is insufficient, the welding edge of the heated straight seam steel pipe cannot reach the required welding working temperature, and the metal industrial structure can remain firm, forming an insoluble or molten metal; when the input heat is too large, the edge of the weld is heated to exceed the welding environment temperature, resulting in weld overheating or the formation of molten droplets.

The common feature of various pressure welding methods is the use of pressure without filler materials during the welding process. Most pressure welding methods, such as diffusion welding, high-frequency welding, cold pressure welding, etc. There is no melting process, so there is no problem of alloy element combustion loss and harmful elements invading the weld, which simplifies the welding process and improves the safety and sanitation conditions of welding. At the same time, due to the relatively low heating temperature, short heating time, and small heat impact. Many materials that are difficult to weld by fusion welding can often be welded into high-quality joints with the same strength as the parent material by pressure welding.