With the development and progress of science and technology, the welding problem of large-caliber plastic-coated steel pipes has been successfully developed. The connection method is bimetallic welding. 5cm~8cm long stainless steel sheet, thickness 0.8mm, material E309 or 304, the inner wall should be coated with epoxy resin. In actual welding applications, first use stainless steel wire for argon arc welding to make the base, the base thickness is one-third of the product wall thickness, and the outer layer is covered by electric welding. After welding, the inside and outside of the plastic-coated steel pipes do not need to use anti-corrosion methods. The outer layer is generally repaired with solvent-free repair fluid or brushed with several coats of paint. If the requirements are strict, 3PE anti-corrosion methods can be used directly.

The actual project application of bimetal welded internal and external plastic coated steel pipes has involved fire protection, water supply and drainage, chemical industry, petroleum, circulating water, marine systems, etc. Typical application projects include Jiangling Motors circulating water piping system, SAIC central air conditioning circulating water system, and Volkswagen The buried fire-fighting piping system of FAW plant, the fire-fighting and water supply and drainage piping system of Shanghai Metro. These projects all use bimetal welding, and have obtained the unanimous approval of the owner, design institute and construction unit, and achieved good equipment benefits at the same time.

The actual project application of bimetal welding inner and outer plastic coated steel pipes has involved fire fighting, water supply and drainage, chemical industry, petroleum, circulating water, marine systems, etc. Typical application projects include Jiangling Motors circulating water piping system, SAIC central air conditioning circulating water system, and Volkswagen The buried fire-fighting piping system of FAW plant, the fire-fighting and water supply and drainage piping system of Shanghai Metro, the water supply and drainage piping system of Hainan SDIC Vopak, etc. These projects all use bimetal welding, and have obtained the unanimous approval of the owner, design institute and construction unit, and achieved good equipment benefits at the same time.

The concept of bimetal welding was first proposed by Dr. Schneider, the head of the Holzminburg Steel Welding Laboratory in Hannover, Germany in the 1990s, and has been continuously developed by Singapore, Australia and other countries, but has not been applied to the pipeline field. Many domestic R&D units digested and transformed this core technology, and successfully produced bimetal welded plastic coated steel pipes, and applied them to engineering projects, such as the Shanghai Industrial and Commercial Bank of China Waigaoqiao Branch Project, the Liaoning Huludao Shipyard Project, etc. Wuxi Lisen Hotel, Guangyuan Airport. This fills up the domestic empty space.

The bimetal welded plastic-coated steel pipe discards the defects of high cost and low compressive strength of the original plastic-coated steel pipe. The damage of the steel pipe to the coating layer during welding construction is currently the best connection scheme for plastic-coated steel pipes, especially buried plastic-coated steel pipes.

The process is to line the inner wall of the steel pipe port before painting with a layer of stainless steel. The lining stainless steel is 5-10 mm. Generally, the plastic layer damaged by welding does not exceed 5-10 mm. After the stainless steel pipe is lined, it undergoes pre-treatment, The process of sandblasting and shot blasting, coating curing and other processes finally produces bimetallic welded plastic coated steel pipes. Before construction welding, a 20-30 degree break must be made. The bottom layer of the weld can be made by argon arc welding, or with stainless steel welding rod (304 or 314 stainless steel model). One, and then use carbon steel welding rod to weld the entire interface. Note that there are two points, one is beveling, and the other is that the stainless steel is fully welded to the inner wall of the steel pipe.