Classification and application of bimetallic composite pipe;
Stainless steel lined composite steel pipe is a branch of bimetallic composite pipe, which is composed of two kinds of metal pipes with different properties through special technology. It combines the advantages of two kinds of metal tubes and avoids their disadvantages. Making the best use of everything is a good metal pipe.
Bimetal composite pipe is divided into two kinds of composite interfaces: metallurgical composite, diffusion composite and mechanical composite. Now it has been used in electric power, coal, urban and rural construction, shipbuilding, petrochemical, machinery, nuclear industry and other industries.
Metallurgical compounding of (1) bimetallic composite pipe;
The metallurgical composite of bimetallic composite pipe is made by explosive composite, surfacing and double melting, and the two composite interfaces are metallurgically fused together. Features: composite interface bandwidth, fusion of two metals; Compound firmly; There is no boundary between heat conduction, sound conduction and electric conduction; Cold and hot contraction and expansion are consistent. As early as 1967, the stainless steel lined composite steel pipe compounded by this process was tested in Britain, and the stainless steel lined composite steel pipe with T3 10 stainless steel as the outer layer and 125 steel as the inner layer was successfully developed. High temperature strength and corrosion resistance to meet the requirements of power and pulp industry. Boiler manufacturers all over the world are interested in bimetallic pipes as superheated materials for advanced devices (such devices operate at high pressure of 80 ~ 89 kg/mm and high temperature of 593 ~ 650℃). 1976, this kind of stainless steel lined composite steel pipe was installed on the power generation boiler, which solved the corrosion problem of the outer furnace of the boiler tube and improved the corrosion resistance by 2 ~ 4 times.
(2) Diffusion (dispersion) recombination of bimetallic composite pipe:
Diffusion (dispersion) recombination of bimetallic composite pipe is a diffusion annealing at 1050℃ for 1 h ~ 4 h after mechanical recombination. Due to the diffusion of C atoms, a second phase is formed in the micro-region near the interface. With the extension of diffusion time, the distribution band of the second phase widens, the interfacial hardness and the interfacial shear strength increase, which can make the stainless steel inner tube and low carbon steel outer tube firmly close to metallurgical bonding. In the pulp industry, stainless steel lined composite steel pipe is used to overcome the serious corrosion caused by molten sulfuric acid/sulfide solution in the furnace. The suitable temperature is 250 ~ 550℃
(3) Mechanical compounding of bimetallic composite pipe:
Mechanical compounding of bimetallic composite pipe is the production method of the first generation stainless steel lined composite steel pipe. Generally, two separately manufactured steel pipes are inserted into the other, and then mechanically combined by cold rolling, die drawing, cold drawing and hydraulic cold expansion. The non-diffusion joint surface is limited to the heat exchanger of brewery and the heat exchanger tube of waste heat boiler of acetic acid plant in low thermal conductivity process below 250℃.
(4) Composite steel pipe lined with stainless steel:
Stainless steel lined composite steel pipe is composed of stainless steel inner pipe and galvanized steel pipe by cold rolling composite technology. Through the outward rolling of the combiner, the outer tube is elastically deformed and the inner tube is plastically deformed, resulting in interference fit and tight fit. The advantages of this composite technology are: high bonding strength and compactness, high molding rate, low energy consumption and high speed, which represents the level of mechanical composite technology today. He is divided into:
(1) Appropriate compounding: the bonding distance of the composite interface is more than 25μ measured by electron microscope, and the composite strength is more than 0.2 MPa, which conforms to the industrial standard of urban and rural construction CJ/T 192-2004 "Stainless Steel Lined Composite Steel Pipe". Flexible corrosive low-pressure pipeline used for water supply and drainage pipeline, pipeline direct drinking water pipeline, sprinkler fire pipeline, gas purification and liquid purification;
(2) Interference recombination: under electron microscope, the bonding distance of the composite interface is 5 ~ 25μ, and the composite strength is 2 ~ 4 MPa. SY/T6623-2005 Specification for Composite Steel Pipe with Internal Coating or Corrosion Resistant Alloy Lining implements the oil and gas industry standard;
(3) Overcompounding: the bonding distance of the composite interface is less than 5μ and the composite strength is greater than 4Mpa as measured by electron microscope.