How To Weld Carbon Seamless Steel Pipes?

Preparation before welding

Before welding carbon seamless steel pipes, sufficient preparation is required first. This includes cleaning impurities such as oil and rust on the surface of the steel pipe to ensure the quality of the welded joint. At the same time, it is also necessary to check whether the size and specifications of the steel pipe meet the requirements to avoid mismatches during welding. For some special applications, such as hydraulic tubes or boiler tubes, the accuracy and material properties need to be strictly controlled.

Choose a suitable welding process

According to factors such as the material, thickness and use requirements of carbon seamless steel pipes, it is very important to choose a suitable welding process. Common welding processes include manual arc welding, gas shielded welding, submerged arc welding, etc.

1. Manual arc welding

This is a commonly used welding method that melts and connects the electrode and steel pipe metal together through the high temperature generated by the arc. It is simple to operate and has strong adaptability. It is suitable for welding of small scale and simple structures. It can be used for welding in various positions, such as welding with some pup joints and valve connection parts, but the welding quality is greatly affected by the welder's technical level.

2. Submerged arc welding

Use welding wire as electrode to weld under the flux layer. High welding efficiency, good weld quality, small welding deformation, but the equipment is more complicated. It is suitable for straight seam welding in large-scale and high-efficiency production. It is commonly used in the manufacturing process of heat exchanger tubes and large carbon steel pipe structures.

3. Gas shielded welding

Use inert gas or active gas as the protective medium, such as carbon dioxide gas shielded welding. The welding speed is fast, the weld is beautiful, and there is less spatter during welding. However, it has high requirements for the welding environment to prevent gas mixing from affecting the welding quality. It is suitable for occasions with high requirements for weld quality.

4. Argon arc welding

Using pure argon as the shielding gas can effectively prevent oxidation and nitridation during welding, and the welding quality is high. It is especially suitable for occasions with high requirements for welding quality, such as casing pipe welding in the chemical and petroleum industries, but the cost is high.

Operation steps

1. Beveling

According to the wall thickness of the steel pipe and the welding process requirements, a suitable bevel is made at the part to be welded. This helps to ensure the penetration and forming quality of the weld.

2. Butt joint and positioning

Butt the two carbon seamless steel pipes to be welded together and fix them with clamps or other tools to ensure that they will not move or misalign during the welding process.

3. Preheating and slow cooling

For thicker-walled steel pipes or when using high-energy density welding methods, it may be necessary to preheat the steel pipe to reduce welding stress and prevent cracks. Similarly, slow cooling after welding is completed is also beneficial.

4. Welding operation

According to the selected welding process, weld in accordance with the corresponding operating specifications. Pay attention to controlling parameters such as welding current, voltage, speed, etc. to ensure the quality and beauty of the weld.

5. Weld cleaning and inspection

After welding is completed, clean the weld to remove welding slag and other impurities. Then perform visual inspection and internal quality inspection (such as X-ray flaw detection, etc.) on the weld to ensure that the weld is defect-free and meets the requirements.

Inspection standards for completed welding

After welding is completed, the weld joints of carbon seamless steel pipes need to be strictly inspected. This includes appearance inspection, dimensional measurement, mechanical property testing, and non-destructive testing. Only when all inspection indicators meet the requirements can the welded joint be judged as qualified.

Summary

In summary, the welding method of carbon seamless steel pipe involves multiple links and steps, which requires welders to have rich professional knowledge and practical experience. Through correct operation methods, reasonable process selection and strict inspection standards, the welding quality and safety of carbon seamless steel pipe can be ensured.

Read more: Seamless Steel Pipe Sizes or ERW vs seamless pipe in weight calculation