Application of Ceramic Lined Composite Steel Pipe in Coal Pipeline
Experimental study on the application of ceramic-lined composite steel pipes in coal pipelines Du Zhongze Fu Hanguang (Xi'an University of Architecture and Technology, Beijing Metallurgical Energy-saving Industrial Company, Shanghai Branch) The principle of high-temperature synthetic ceramic-lined composite steel pipes was used to test the performance of composite steel pipes. Composite steel pipe ceramic layer of high hardness, good wear resistance, but the high porosity, low toughness in the aluminum heat agent by adding s2, can improve the density, improve corrosion resistance, Zr2 can be added to improve the fracture toughness applied to the coal pipeline, The use effect is very good. It is rumored that the coal-water mixture broken by the water gun in the full hydraulic coal mining shaft is conveyed to the horizontal coal water chamber from the chute in the roadway of the mining area without pressure, and then is pressured by the coal water pump and the coal conveying pipeline. Transportation to the ground coal preparation plant. In the raw coal transportation process, the coal conveying pipeline has become an important production facility. Because the coal slurry conveyed by the coal conveying pipeline contains vermiculite, and it is also a large-grained hydraulic lifting, the wear of the slurry conveying pipeline becomes a problem in pipeline transportation. Technical problems: Common seamless steel tubes, white cast iron tubes, alloy steel tubes, and diabase in pipelines cannot solve this problem fundamentally. The development of centrifugal self-propagating high-temperature synthetic ceramic-lined composite steel tubes has fundamentally solved the above problems. Its main features are: 1 smooth surface of the pipe, running resistance; 2 light weight, easy installation and transportation; 3 good wear resistance; 4 good impact resistance, easy to handle pipe accidents; 5 welding performance of pregnancy 1 self-propagation high-temperature synthesis Ceramic-lined composite steel pipe principle Centrifugal self-propagating high-temperature synthetic ceramic-lined composite steel pipe is based on the following principles of aluminothermic reaction. The Fe23 and A1 powders are uniformly mixed into a steel pipe in a certain proportion, fixed on a centrifuge, and the reactants are ignited when the number of revolutions of the centrifuge reaches a certain value; N—the rotation speed of the steel pipe, s-1; C-a ceramic; characterizes the compressive strength of the composite tube, the compression shear experiment characterizes the bond strength of the subscript m—a cermet layer to the transition layer crush strength e d 2 experimental method 2.1 manufacture of ceramic-lined composite steel tubes 1501 chemical pure A, Feft powder raw materials, dried at 150 °C X2h, according to the stoichiometric preparation, weighing fully mixed. Hot rolled seamless steel tube sample size Y130mm 2h drying, self-propagating ceramic-lined steel pipe synthesis experiments on a horizontal centrifuge. 2.2 Performance test of ceramic-lined composite steel pipes Ceramic-lined composite steel pipes were tested for their strength, hardness, fracture toughness, and other properties. The strength tests were mainly conducted through crushing and compression shear tests. The formula for the crush test was: A test tube length; t - a composite tube thickness; D - average diameter; k - a section coefficient. Pressure shear strength e determination formula is: Pm maximum pressure shear load. The fracture toughness was measured by the Vickers indentation method. The Vickers hardness indentation test was performed on a Browwell hardness tester model HW187.5. Loading load 294N, loading time 1Ch15s, loading speed 0.1mm/s Vickers hardness formula is 55.63d2, where d(mm) is the average length of the diagonal of the indentation. The length of the indentation and the length of the indentation in the outer corner of the indentation are measured under a quantitative metallographic microscope and the magnification is 400 times. The fracture toughness is calculated as follows: L4 is the length of the indentation tetragonal outside crack in mm) Five samples were measured and averaged. 3 Experimental results and analysis 3.1 Effect of Si2 on properties of composite steel pipe Si2 has influence on the density and hardness of composite steel pipe ceramic layer. See b for the effect of corrosion resistance and bonding strength. It can be seen that SO2 can significantly improve the density and bonding of ceramics. Strength, improve corrosion resistance, but reduce ceramic hardness. This is because the addition of Si2 has a significant effect on the thermal reaction of aluminum, which is mainly reflected in the decrease of reaction temperature and the prolongation of reaction time. Metallographic analysis shows that the relative amount of FeO.Al23 phase increases with the increase of S2 content. Because the reaction of A + Fe23 is carried out in two steps: b The impact of corrosion resistance and bonding strength SiOz on the performance of composite steel pipe 150h corrosion resistance at room temperature corrosion weight evaluation of ceramic corrosion resistance; □ density, compression strength. The melting point is lower than the melting point of Al2O3, so after the crystallization of AfeO3, FeO.Al2O3 is distributed in the liquid phase between the Afcft dendrites and becomes a channel for gas discharge. With the increase of SiO2 content, not only the FeO.AI2O3 phase The relative amount increases, and a 2SO2 phase is formed again. This creates favorable conditions for gas discharge, so that the porosity of the ceramic is reduced, the density is increased, and the shear strength is improved. On the other hand, SiO2 is a thinner and can Lowering the reaction temperature, when the temperature drops faster, the gas can not be discharged in time, but the ceramic density reduction is due to the opposite effect of SO2 has two effects, so that the relationship between the relative density and SiO2 addition on the curve The main reason why SO2 significantly reduces the microhardness of ceramics is that the addition of SO2 changes the phase structure of the ceramic layer, reduces the amount of iron spinel (FeO.A12O3), and increases the number of Fe2SiO4 phases. SiO2 promotes the glass phase (FeO. The formation of AI2O3.4SiO2) was partitioned from the low-corrosion FeO.A12O3 distributed in the network in a-AI2O3, and it was not connected in the radial direction. Therefore, the addition of SiO2 promoted the corrosion resistance of the ceramic, but Excessive amount of FeO.AI2O3 with low corrosion resistance increases, and ceramic porosity increases, but corrosion resistance decreases. 3.2ZrO2 affects the toughness of ceramics The main drawback of ceramics is the large brittleness, and the SHS coating also has the problem of large brittleness. Although the brittleness of the SHS coating compounded with the metal matrix is ​​improved to a certain extent, this improvement is very limited. The SHS coating still cannot withstand large mechanical impacts, which seriously hinders its practical application to increase the toughness of the ceramic layer. Can improve the reliability of its work. The addition of appropriate amount of ZrO2 in the aluminum heat paste has the effect of refining the coating grains and improves the toughness of the ceramic layer. The fracture toughness increase is not obvious when the ZrO2 content is less than 1.5%, and the ZrO2 content is in the range of 3% to 6%. The toughness increases almost linearly. When the amount of ZrO2 added is 7.5%, the maximum fracture toughness value Kic=4.42MPa.m1/2 is obtained, which is more than twice that of the original coating. When the added amount of ZrO2 exceeds 7.5%, the fracture toughness tends to decrease. The reason is that a large amount of ZrO2 enters the SHS reaction system and absorbs heat, which leads to a decrease in the reaction temperature of the system, thereby reducing the density of the coating, resulting in a decrease in the toughness of the coating. 3.3 Properties of self-propagating high-temperature synthetic ceramic-lined composite steel pipes The performance of self-propagating high-temperature synthetic ceramic-lined composite steel pipes is shown in the attached table. It can be seen from the attached table that the ceramic-lined composite steel pipes have excellent wear resistance and high corrosion resistance. strength. 3.4 Application of self-propagating high-temperature synthetic ceramic-lined composite steel pipes Self-propagating high-temperature synthetic ceramic-lined composite steel pipes have been subjected to industrial tests on coal transportation pipes. The size of the coal transportation pipes is Y325mm20mm and the ceramic thickness is 5mm. The result shows that the ceramic lined composite steel pipe Has excellent wear resistance and corrosion resistance, ceramics in use without peeling. Compared with 16Mn seamless steel pipe, the service life is increased by 6~10 times, the cost is 12,000 yuan/t, and the cost of seamless steel pipe is 5,000 yuan/t. The use of self-propagating high-temperature synthetic ceramic lined composite steel pipe has significant economic benefits. Scheduled Ceramic Lined Composite Steel Pipes Performance Materials Hardness Ceramics Density Crushing Strength Compression Shear Strength Fracture Toughness Water Resistance Corrosion Resistance Relative Wear Resistance Force Coefficients Carbon Steel Tubes Ceramic Composite Tubes 4 Conclusions Self-propagating high-temperature synthesis and centrifugal techniques, In ordinary horizontal centrifuges, ceramic-lined composite steel pipes can be prepared. Ceramics and steel pipes combine well, ceramics have high hardness, good abrasion resistance, and high mechanical impact resistance. When preparing centrifugal self-propagating high-temperature synthetic ceramic-lined composite steel pipes, aluminum heat Adding SO2 to the agent can increase density and bond strength, improve corrosion resistance, but reduce ceramic hardness. When the fracture toughness of porcelain is 7.5%, the highest fracture toughness value is 4.42MPa.m1/2, which is more than twice that of the original coating. 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