Last edited 15 Feb 2019

Large-diameter seamless steel pipe welding preheating

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The difference between the main production of seamless steel pipe and the small diameter of the main production depends on the manufacturer's product range, but generally less than 200mm is small seamless.

Seamless steel tubes have hollow sections and are used in large quantities as pipelines for transporting fluids, such as petroleum, natural gas, gas, water and certain solid materials.

Compared with solid steel such as round steel, the steel pipe is lighter in weight for the same bending and torsional strength. It is an economical section steel and is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycles and so on. Steel frames and other steel scaffolding used in construction are used to manufacture ring-shaped parts, which can improve the material utilisation rate, simplify the manufacturing process, save materials and processing hours.

The technical term for heating large-diameter seamless steel pipe or the welded portion before welding is called preheating. This may be necessary when the ambient temperature around the welding area is too low.

The primary intent of large-diameter seamless steel pipe welding preheating is to reduce the cooling rate of the welded joint. Preheating can lower the cooling rate, but it does not substantially affect the the time at high temperature. Therefore, when welding large-diameter seamless steel tubes with a tendency to harden, the primary technical method for reducing the cooling rate and reducing the tendency of hardening is to preheat, rather than increase the line energy.

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