Bimetal composite pipe is composed of two different metal materials, and the pipe layers are tightly combined by various deformation and connection technologies
Bimetal composite pipe is composed of two different metal materials, and the pipe layers are tightly combined by various deformation and connection technologies, so that the two materials are combined into one and a new type of metal composite pipe is made. Generally, the design principle is that the base material meets the allowable stress of pipeline design, and the cladding resists corrosion or wear. Bimetal composite pipe has all the advantages of base layer and cladding layer. Compared with monolithic alloy pipe, it can reduce the cost, and composite pipe can improve the safety and reliability in chloride and/or acid environment which is sensitive to stress corrosion cracking of monolithic alloy pipe. With the development of industrial technology, the complication of environmental media and the intensification of world competition, many industries have higher and higher requirements for the comprehensive properties of metal pipes, so bimetal composite pipes and their production technology have developed rapidly.
Bimetal composite pipe can realize the complementary advantages of materials to a great extent, save alloy elements, reduce engineering costs, improve the corrosion resistance and wear resistance of the pipe and prolong the service life of the pipe on the basis of ensuring various properties of the original base pipe, and is a substitute product for pure stainless steel pipe, copper pipe or other corrosion-resistant alloy pipes. After years of research and promotion, composite pipes have been widely recognized in the fields with strong corrosion such as petroleum, petrochemical enterprises, nuclear industry, medicine and food processing. They can also be compounded with wear-resistant metals through inner layers, thus meeting the requirements of high-wear working environments such as pulverized coal in power plants, mineral powder in mines and tailings slurry transportation.
With people's focus on health, the hygiene of drinking water is becoming more and more important. Qualified drinking water has to be transported from waterworks to thousands of households through a long pipeline, and excellent pipeline is the primary factor to ensure drinking water hygiene. Nowadays, most water pipelines are the ordinary metal pipes whose inner walls are subject to anticorrosion treatment, including plastic spraying and epoxy coating. Although the nominal anticorrosion materials are food grade, the analysis of chemical substances is inevitable after a long time, which leads to the decline of drinking water quality. Moreover, due to the aging of anticorrosive materials, the actual service life of pipelines can not reach the design life. However, the stainless steel material has good stability and will not be resolved into water, thus ensuring the long-term hygiene of drinking water and the service life of pipelines. However, the pure stainless steel pipe is expensive and the investment is large, which restricts the use of drinking water pipes. The bimetal composite pipe, however, has solved the practicability and economy properly, so that it will be widely used in drinking water pipes in the future, and has great market potential.
Nowadays, there are two main manufacturing processes for composite pipes:
1. Lining composite
The thin-walled stainless steel pipe is sleeved into the carbon steel pipe, and then the two materials are tightly attached in two ways: 1. Metallurgical composite: The two materials are metallurgically composited together by the high pressure of underwater blasting, the bonding strength of metallurgical composite is very high, and the two materials will not be peeled off; 2. Mechanical composite: By the methods of water pressure, spinning and drawing, the two materials are bonded together, but the bonding force is much lower than that of metallurgical composite.
Metallurgical composite has many advantages, but it is difficult for general enterprises to implement it because of its complex process and huge investment.
The investment of mechanical composite is less, but the composite strength is low and the application occasions are limited.
The production method of lining composite is single production, so that the output is relatively low and the price is relatively expensive.
Lining composite technology flow:
A. Base pipe: Procurement-Sandblasting treatment of inner wall-Offline ultrasonic flaw detection-Waiting.
B. Liner: mill production-Offline X-ray flaw detection-Offline ultrasonic flaw detection-Waiting.
C. Compounding: Jacketing machine-Hydraulic (spinning) compounding-Flat chamfering-Pipe end sealing for welding-Spraying labels-Finished product collection.
If spinning composite technology is applied, hydrostatic test is required, and hydrostatic composite can be used for both purposes without hydrostatic test.
2. Internal composite
By purchasing steel coils that have been metallurgically compounded in steel mills, using special continuous production mills and special welding technology for welding, the production of composite pipes is continuously carried out.
The advantage of the production method is that the metallurgical composite with difficult manufacturability is completed in large steel mills, and the pipe factory directly buys composite steel plates and steel coils for production. The production method of steel pipes gets rid of the manual mode, which is suitable for industrial production and has large output. The disadvantage is that the price of composite steel plate and steel coil is more expensive than that of two layers of steel pipe sleeved together. The inner composite mill is divided into spiral composite mill and straight seam composite mill. The straight seam composite mill is suitable for pipes with pipe diameter below 630, while the spiral composite mill is suitable for pipes with pipe diameter above 219.
Technology flow of straight composite pipe mill: Coiling-Uncoiling-Uncoiling and leveling-Edge milling-Straight seam forming-Welding-Sizing and straightening-Sizing and cutting-X-ray inspection-Hydrostatic test-Offline ultrasonic inspection-Flat chamfering-Weighing and measuring length spraying mark-Finished product collection.
Technology flow of spiral composite pipe mill: Coiling-Uncoiling-Uncoiling and levelling-Edge milling-Delivery-Guide plate-Spiral forming-Welding-External welding-Internal welding-Sizing and straightening-Flat chamfering-Hydrostatic test and diameter expansion-X-ray inspection-Offline ultrasonic inspection-Weighing and measuring length and spraying labels-Finished product collection.