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What Is Welding:welding Process Of Steel Pipe

what is welding:welding process of steel pipe

Welded steel tube, also known as welded pipe, is a steel pipe made of steel plate or strip steel after crimping and welding, and the length is generally 6 meters. Welded steel pipes have simple production process, high production efficiency, many varieties and specifications, and less equipment investment, but the general strength is lower than that of seamless steel pipes.

Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld. Classification by production method: process classification - arc welded pipe, electric resistance welded pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe.

Smaller diameter welded pipes use straight seam welding, and large diameter welded pipes are mostly spiral welded. According to the shape of the end of the steel pipe, it is divided into circular welded pipe and special-shaped (square, rectangular, etc.) welded pipe. According to different materials and uses, it is divided into welded steel pipes for mining fluid transportation, galvanized welded steel pipes for low-pressure fluid transportation, and electric welded steel pipes for belt conveyor idlers.

There are many weights of welded pipes, so what is the welding process?

Welding is a manufacturing process and technique for joining metals or other thermoplastic materials such as plastics by means of heat, high temperature or high pressure.

Welding is a local rapid heating and cooling thermal cycle process. This heating process makes the base metal rapidly melt to form a weld zone, and the base metal near the weld is subjected to a special thermal cycle and undergoes a solid phase transformation. That is, the change of organization makes the performance of this area change. This part is called the heat-affected zone.

In the heat-affected zone, due to the different distances from the center of the weld, the thermal cycle process experienced by different parts is also different.That is to say, the heating rate, peak temperature, holding time and cooling rate of each point in the center of the weld are different.Different phase transitions have taken place in the base metal at different positions in this area, and different microstructures are obtained, which affects the performance of this area, among which the peak temperature and cooling rate have the greatest influence.

In welding practice, the thermal cycle curves measured during welding according to different test points from the center of the weld show that.The heat-affected zone of the weld is the result of the solid-state phase transition of different contents due to the local rapid heating of the welding acting on the base metal at different positions.Among them, the properties of the coarse-grained region have the greatest change, and the structure and properties of the heat-affected structure mainly refer to the thermally-affected coarse-grained region, abbreviated as coarse-grained HAZ.

Classification of welding

1. Fusion welding - heating the workpiece to be joined to locally melt it to form a molten pool.After the molten pool is cooled and solidified, it is joined, and if necessary, fillers can be added to assist. It is suitable for welding of various metals and alloys without pressure.

2. Pressure welding - the welding process must apply pressure to the weldment, which belongs to the processing of various metal materials and some metal materials.

3. Brazing - use a metal material with a lower melting point than the base metal as the brazing filler metal, use the liquid brazing filler metal to wet the base metal, fill the joint gap, and diffuse with the base metal to connect the weldment. It is suitable for welding of various materials, and also suitable for welding of different metals or dissimilar materials.