Overseas pipeline welding construction has experienced the development process of manual welding and automatic welding.

Manual welding is mainly downward welding with cellulose electrodes and downward welding with low hydrogen electrodes.

In terms of automatic pipeline welding, there is a pipeline flash butt welding machine developed by the former Soviet Union, which welded tens of thousands of kilometers of large-diameter pipelines during the former Soviet Union.

Its distinctive features are high efficiency and strong adaptability to the environment.

The CRC multi-head gas shielded pipeline automatic welding system developed by the American CRC company consists of three parts: a pipe end beveling machine, an internal seamer and internal welding machine combination system, and an external welding machine.

So far, the cumulative length of welded pipelines worldwide has exceeded 34,000km.

France, the former Soviet Union and other countries have also researched and applied similar automatic welding technology inside and outside pipelines. This technical direction has become the mainstream of automatic welding technology for large-diameter pipelines in the world today.

my country's steel pipeline girth welding technology has experienced several major changes. In the 1970s, traditional welding methods and low-hydrogen electrode manual arc welding upward welding technology were adopted. In the 1980s, manual arc welding downward welding was promoted. The welding technology is downward welding with cellulose electrodes and low-hydrogen electrodes. In the 1990s, self-shielded flux-cored wire semi-automatic welding technology was applied. Today, all-position automatic welding technology has been fully promoted.

Manual arc welding includes the application of cellulose electrodes and low hydrogen electrodes.

Manual arc welding upward welding technology is the main welding method in pipeline construction in my country in the past. It is characterized by a large gap between the nozzles. The arc resting method is used during the welding process. The thickness of each weld layer Larger, welding efficiency is low.

Manual arc welding downward welding is a welding technology introduced from abroad in the 1980s. It is characterized by a small gap between the nozzles. The welding process is completed by using high current, multi-layer, and rapid welding methods. , suitable for flow operations and with high welding efficiency.

Since the thickness of each welding layer is thin, the toughness of the girth welding joint can be improved through the heat treatment of the rear welding layer on the front welding layer.

The manual arc welding method is flexible, simple and adaptable. The organic combination of downward welding and upward welding methods and the good root welding adaptability of cellulose electrodes are still the preferred choice for automatic welding in many situations. Methods cannot replace it.

Self-protected flux-cored wire semi-automatic welding technology has been applied to pipeline construction since the 1990s, and is mainly used for filling and covering.

It is characterized by high deposition efficiency, good forming in all positions, strong environmental adaptability, and easy mastery by welders. It is an important welding process for pipeline construction.

With the improvement of the strength grade of steel pipes used in pipeline construction, and the increase of pipe diameter and wall thickness, automatic welding technology has gradually begun to be applied in pipeline construction.

Pipeline automatic welding technology has great potential in the application of large-diameter, thick-walled pipeline construction due to its advantages of high welding efficiency, low labor intensity, and the welding process is less affected by human factors.

However, my country's automatic pipeline welding technology is in its infancy, the problem of automatic root welding has not yet been solved, and supporting facilities such as pipe end bevel shaping machines are not yet mature, which have hindered the large-scale application of automatic welding technology.