Welding requirements for straight seam steel pipes

Straight seam steel pipe is a welded tube made of strip steel coil as raw material, extruded at regular temperature, and welded by automatic double-wire double-sided submerged arc welding process. The straight seam steel pipe sends the strip steel into the welded pipe unit, and after rolling by multiple rollers, the strip steel is gradually rolled up to form a circular tube blank with an opening gap. Adjust the reduction amount of the squeeze roller to control the gap between the weld seams at 1~3mm, and make the two ends of the weld joints flush. Steel pipe transportation is listed as one of the five major transportation industries along with railways, highways, water transportation and shipping. Straight seam steel pipes are more and more widely used in chemical industry, petroleum, electric power, metallurgy, city gas and heating systems, important tasks of high temperature, corrosion, bad and radioactive media. And the quantity and quality of straight seam steel pipe applications play an important role.

Steel pipes can be divided into round pipes and special-shaped pipes according to the shape of the cross-sectional area. Due to the condition that the circumference is equal, the circle area is large, and more fluid can be transported with a circular tube. In addition, when the ring section is subjected to internal or external radial pressure, the force is relatively uniform, so most steel pipes are round pipes.

The welding requirements of straight seam steel pipes are

1. The head-to-tail butt joint of strip steel adopts single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after being rolled into steel pipes.

2. The weld gap control device is used to meet the welding requirements, and the pipe diameter, misalignment and weld gap are strictly controlled.

3. Lincoln electric welding machine is used for single-wire or double-wire submerged arc welding for internal welding and external welding, so as to obtain stable welding quality.

4. Before forming, the strip steel is leveled, trimmed, planed, surface cleaned, transported and pre-bent.

5. Electric contact pressure gauges are used to control the pressure of the oil cylinders on both sides of the conveyor, so that the strip steel can be conveyed smoothly.

6. The raw materials are strip steel coil, welding wire and flux. Before putting into use, they must go through strict physical and chemical tests.

7. Use external control or internal control roll forming.

Straight seam steel pipes should include all straight seam steel pipes that use pressure to transport gas or liquid. From the perspective of stable production, it follows the name of straight seam steel pipe pressure vessel, so it is not a pressure pipeline in a simple sense. The possibility of accidents and the harmfulness of accidents define the scope of straight seam steel pipes. my country has clarified the scope of straight seam steel pipes and stipulated the definition of straight seam steel pipes. Pressure pipes use the corresponding pressure, used to transport gas or liquid tubular equipment, as a liquid medium with a temperature higher than or equal to the standard boiling point, and a pipe with a nominal diameter greater than 25mm. Straight seam steel pipe pressure equipment, in addition to causing its own explosion, may also cause explosions and fires due to medium leakage.

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