0 Preface The use of pipes to transport materials has the advantages of high efficiency, energy saving, low pollution and low losses. With the improvement of pump transportation technology and the development of transportation pipeline technology, the pipeline transportation of materials has developed rapidly. As there are many types of materials to be transported, long transportation distance, and increased transportation capacity, the pipeline transportation industry has increasingly higher requirements for pipeline materials. It is hoped that a variety of pipeline materials will be selected for the transportation of materials with different properties. The main performance indicators of pipeline materials are wear resistance, corrosion resistance, friction reduction and processability.
At present, the development direction of pipeline materials for material transportation is to improve wear resistance. The commonly used pipeline materials are as follows: Yu Fang (1972-), female, Shanxi Taiyuan, master, lecturer. Mainly engaged in teaching and scientific research in lifting transportation machinery, metallurgical machinery and computer-aided design.
Using high alloy casting, the advantages are high hardness and good wear resistance; the disadvantages are poor toughness, not easy to weld, poor workability, and high cost.
The inner wall of the steel pipe is lined with basalt (cast stone), ceramics, alloy cast iron, rubber and plastics. Its characteristics are that the outer layer can be processed and the connection is convenient, but the shortcomings are that the inner layer is fragile, easy to detach, difficult to construct, and high in cost.
It adopts high-density polyethylene and polyvinyl chloride extrusion molding, which is convenient in construction and low in cost, but it is not resistant to high temperature and high pressure, and is suitable for small-diameter material conveying pipes.
Made of low carbon steel, low price, easy installation and easy replacement, but fast wear and tear and poor economic efficiency.
The above-mentioned various types of pipeline transportation materials are mostly used for material transportation within industrial and mining enterprises. For large-diameter and long-distance material transportation, processed spiral welded pipes or straight welded pipes are usually used. Because people tend to focus on improving the wear resistance of pipeline materials, and neglect to improve the processability, the difficulty of processing and manufacturing pipelines and laying facilities is increased, and the cost of pipeline construction and maintenance limits the application of material pipeline transportation technology. Therefore, it is very necessary to seek material pipeline transportation materials with good wear resistance, corrosion resistance, friction reduction and processability.
1 Characteristics of bimetallic material pipelines Bimetallic pipes are functional materials. Different material combinations can be selected according to the physical and chemical properties and working conditions of the transported materials, so that the materials can maximize their potential. For example, for abrasive powder materials, such as mineral powder, alumina powder, etc., steel pipes made of wear-resistant alloy steel plates can be lined with ordinary carbon steel pipes as liners, so that the pipes have good wear resistance; for water Coal slurry, mud and other highly corrosive slurries can be made of corrosion-resistant materials such as stainless steel plates as lining materials combined with ordinary steel pipes to make corrosion-resistant bimetallic pipes. In addition, the bimetallic material conveying pipeline also has the following characteristics: due to the rolling finishing of the inner wall of the pipe, the roughness of the inner surface is reduced, the flow resistance of the material is greatly reduced, and the energy consumption of long-distance transportation is reduced .
The inner wall of the pipe was rolled, and the relative deformation was 15% to 25%. Cold work hardening increased the hardness of the inner metal material, thereby improving the wear resistance of the pipe.
The bimetallic tube is tightly coupled, has good overall strength, and can withstand certain bending deformation. Due to the low-carbon steel used in the outer tube, the weldability and workability are better. After the end surface treatment, it can be conveniently welded or flanged, and it is easy to install and repair the pipeline.
2 Production of bimetallic material conveying pipeline The bimetallic material conveying pipeline is composed of two layers of pipe materials. The inner layer of pipe material generally has a thickness of about 0.5 ~ 2mm. The outer layer of pipe material is a common fluid delivery pipe. There are two problems that need to be solved in the process of processing and manufacturing: the processing and manufacturing of the metal tube for inserting and the assembly and compounding of the double-layer metal tube.
2.1 Processing of metal pipe for lining The processing of metal pipe for lining is produced in a single piece. Different lining materials are selected according to the nature of the conveyed material, and the specifications of the inner pipe can be flexibly changed according to the size of the outer pipe. In order to ensure a smooth composite lining, the outer diameter of the inner layer pipe should be 0.5 ~ 2mm smaller than the inner diameter of the outer layer pipe. After the diameter of the inner layer pipe is determined, it should be ensured by the cutting shear accuracy of the sheet material. The size deviation is within 0.5mm. The sheet material is rolled and formed on a special steel pipe forming machine, and then spot welded with a spot welder, and then the weld seam is automatically welded by a specially developed metal pipe automatic welding machine. Welding adopts non-melting electrode argon gas shielded welding. In the case of ensuring penetration, the height of the weld should be as small as possible. After welding, the weld should be annealed and then flattened to make the weld have good ductility and the thickness is consistent with the thickness of the matrix.
The metal pipe automatic welding machine can automatically weld the butt longitudinal seam of the metal cylinder. The machine is composed of a frame, a workbench, a key-type pressing mechanism, a walking beam, a welding trolley, a power supply, a hydraulic system and a control system. Can weld Y50 ~ 400mmX0.5 ~ 2.5mmX100 ~ 6000mm carbon steel, alloy steel, stainless steel, titanium alloy, copper aluminum and other metal pipes.
2.2 Composite assembly of double-layer metal tubes There are various methods for compounding double-layer metal tubes, such as explosive compounding, thermal expansion compounding, and diameter reducing compounding. Most of these methods have the problems of complicated process, large equipment investment, high production cost, and not easy on-site construction. Therefore, they are not suitable for manufacturing material pipeline transportation pipes with relatively short service life. Tests have shown that it is suitable to use rolling drawing method to produce various specifications of material conveying pipes. Through the joint action of the inner rolling head and the outer layer tube, the inner layer metal tube produces greater plastic deformation and closely adheres to the inner wall of the outer layer tube. Its bonding strength can fully meet the requirements of the material delivery tube, and Can withstand a certain deformation without separation.
The main compounding process of the double-layer metal tube is as follows: Before the compounding process, the joint surface of the inner and outer layers of the tube should be treated, which mainly includes cleaning dirt, derusting, degreasing and texturing. The surface treatment is done by special machinery. The outer layer pipe is shot-blasted to remove the dirt and oxide on the inner surface at once; the inner layer pipe is brushed with a steel wire brush.
The two pipe materials after surface treatment should be assembled together immediately. In order to facilitate the rolling compound, the assembled pipe material can be swollen at one end to avoid slipping.
Rolling compounding is carried out on specially designed rotary drawing equipment. The equipment is composed of bed, tube material clamping device, main transmission device, rotary rolling head and traction device. When rolling compound, the assembled pipe material is loaded on the chuck, the size of the rolling head is adjusted, the main motor and the emulsion lubrication system are started, and then the traction motor is started to pull the rolling head through the pipe material.
After the pipe material is rolled and compounded, the end of the inner layer tube can be turned out, the end surface of the outer layer tube can be covered, and flat chamfering can be performed. If flange connection is used, the flange can be welded on both ends of the pipe material; if pipe joint connection is used, threads are processed on both ends of the pipe material.
3 Application Examples The alumina powder conveying pipeline of an aluminum processing plant is made of hot-milk seamless steel pipe for fluid transportation with a specification of Yl21mmX 6mm. The lined steel pipe is made of medium-carbon steel plate with a thickness of 2mm. Bimetallic pipe, flanged after pipe end treatment. The inner surface roughness of the pipe can reach Ral. 6 ~ 0.8, and the tensile strength after cold work hardening is 637 ~ 930MPa. As the inner surface of the pipe is increased in hardness and smoother, the frictional resistance of transportation is significantly reduced, which reduces the consumption of transportation energy , Extending the service life of the pipeline. Compared with ordinary pipes, the price is increased by about 40%, but the service life is increased by 3 to 4 times.
4 Conclusions In the field of pipeline transportation of materials, compared with ordinary fluid pipelines, bimetallic pipes have obvious advantages in reducing transmission resistance and improving service life; they are also superior to other wear-resistant pipelines in terms of processability and laying maintenance. . Therefore, bimetallic pipes are suitable for the pipeline transportation of materials. The popularization and use of such materials will greatly promote the development of pipeline transportation technology for materials. The problems that need to be solved at present are: â‘ Develop large-scale powerful rolling composite equipment; â‘¡Seek more suitable alloy sheet for inner tube production.
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