Wear-resistant seamless steel tube and preparation method thereof

Abstract

The invention provides a wear-resistant seamless steel tube and a preparation method thereof, and belongs to the technical field of seamless steel tubes, the wear-resistant seamless steel tube comprises an alloy and reinforced particles, the alloy comprises the following components by mass percentage: 14.5%-15.5% of Cr, 2.0%-2.4% of Mn, 0.12%-0.16% of C, 0.35%-0.45% of Mo, 0.18%-0.22% of Si, 0.16%-0.20% of Al, 0.08%-0.12% of V, 0.03%-0.05% of Ti, 0.025%-0.04% of Nb, 0.24%-0.26% of rare earth elements, and the balance Fe and inevitable impurities. By optimizing the element composition and proportion of the steel pipe, adding the rare earth element and the reinforced particles and performing specific quenching treatment on the material, the hardness and elongation of the seamless steel pipe are improved, and meanwhile, the service life of the seamless steel pipe pumped concrete is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field related to seamless steel pipes, and in particular relates to a wear-resistant seamless steel pipe and a preparation method thereof. Background Art

[0002] The existing seamless steel pipe is used as a pump pipe to transport concrete materials, and its service life is generally 30,000 to 50,000 cubic meters. Under high flow conditions, the durability of the pump pipe is even lower, which greatly affects the pumping efficiency of concrete.

[0003] Chromium can significantly improve the hardness and corrosion resistance of steel pipes, making them more resistant to wear. Especially when the mass fraction of chromium in the material exceeds 12%, it can produce a secondary hardening effect, further enhancing the hardness of the steel pipe; however, high chromium content will reduce the toughness of the steel pipe. When the pumping rate is too fast, the coarse aggregate in the concrete will rub and collide violently with the steel pipe, which can easily cause destructive cracks inside the steel pipe, affecting the service life of the seamless steel pipe. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a wear-resistant seamless steel pipe and a preparation method thereof.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 1.8-2.2% of the weight of the alloy. The alloy comprises the following components by mass percentage: Cr: 14.5-15.5%, Mn: 2.0-2.4%, C: 0.12-0.16%, Mo: 0.35%-0.45%, Si: 0.18-0.22%, Al: 0.16-0.20%, V: 0.08-0.12%, Ti: 0.03-0.05%, Nb: 0.025-0.04%, rare earth elements 0.24-0.26%, and the balance is Fe and unavoidable impurities.

[0009] The rare earth element is praseodymium.

[0010] The reinforcing particles are high carbon ferrochrome powder.

[0011] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0012] S1. Weigh the reinforcement particles and each alloy component according to the mass percentage, then smelt the alloy at a smelting temperature of 1600-1650° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1520-1580° C., add the reinforcement particles, and continue smelting for 1-1.5 hours to obtain molten steel;

[0013] S2, continuously casting the molten steel into round billets at a casting temperature of 1230-1250°C and keeping the temperature for 3-5 hours;

[0014] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1150-1190°C, rolling it through a tube rolling mill, the rolling temperature is 1100-1140°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 860-900°C;

[0015] S4. The rolled semi-finished steel pipe is quenched at 900°C to 940°C until the temperature is below 120°C, and then subjected to tempering heat treatment at 660°C to 680°C for 25 to 35 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0016] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace, heat it to 800-840℃, and cool it to below 80℃ by spraying water on the inner wall after it comes out of the furnace. Then temper it in the range of 150-250℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0017] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 10 to 30 r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 5 to 15°.

[0018] The quenching liquid comprises the following components according to weight percentage: 6-10% hydroxyethyl cellulose, 3-5% sodium lignin sulfonate, 0.6-1% triethanolamine, 18-22% composite auxiliary agent, and the balance is castor oil.

[0019] The composite auxiliary agent is a mixture of polyvinyl alcohol and aluminum oxide powder, and the mass ratio of the two is 10:1-3.

[0020] The particle size of the alumina powder is 2000 mesh.

[0021] The present invention has the following technical effects:

[0022] 1. Rare earth elements contain praseodymium, which can capture chromium in the alloy, enhance the diffusion ability of chromium in the alloy metallographic structure, reduce the enrichment of chromium in the plastic zone at the crack tip, and improve the plasticity of the steel pipe, thereby improving the crack phenomenon of the steel; high carbon ferrochrome powder can improve the hardenability of seamless steel pipes, improve the hardness and corrosion resistance of seamless steel pipes, and make the steel pipes have higher wear resistance and erosion resistance.

[0023] The rare earth element praseodymium and high carbon ferrochrome powder work synergistically to improve the toughness of the steel pipe in the case of high chromium content, avoid and reduce the occurrence of cracks, and improve the corrosion resistance of the steel pipe and reduce the negative impact of cracks.

[0024] 2. Among the composite additives of the quenching liquid, polyvinyl alcohol has good thickening and film-forming ability. As a polymer, it can make the steel pipe have certain thermal insulation performance in the quenching liquid. Alumina has excellent thermal insulation and can prevent heat dissipation. The addition of polyvinyl alcohol can improve the suspension and dispersion ability of alumina powder and avoid the aggregation of alumina powder. The synergistic cooperation of the two can make the quenching liquid have higher thermal insulation and coating capabilities.

[0025] 3. The present invention adopts a specific quenching liquid to quench the steel pipe, so that the various structures in the steel pipe are significantly refined during the quenching process, avoiding the uneven distribution of the structure morphology of high-content chromium in the alloy.

[0026] By adding composite additives to the quenching liquid, a layer of ultra-low thermal conductivity film can be formed on the surface of the steel pipe when the quenching medium contacts the hot steel pipe, which can slow down the cooling rate of the steel pipe temperature to a certain extent, thereby maintaining a high hardness of the steel pipe while improving the toughness of the steel. On the other hand, the thicker the film formed on the surface of the steel pipe during the quenching process, the better its thermal insulation effect, and the slower the cooling rate of the steel pipe, thereby reducing the cracking tendency of the steel pipe during the quenching process, and ultimately effectively controlling the generation of cracks while maintaining high hardness and toughness of the steel pipe.

[0027] 4. The present invention optimizes the element composition and ratio of the steel pipe and adopts a specific preparation process to produce a high-performance seamless pipe, which improves the high requirements for the hardness, wear resistance and service life of the steel pipe in industrial production, and overcomes the technical difficulty in the prior art that seamless steel pipes are difficult to achieve high wear resistance and long service life under high concrete flow rates.

[0028] 5. The present invention improves the uneven distribution of the microstructure of high-content chromium in the alloy by adding rare earth elements and reinforcing particles and performing specific quenching treatment on the material, thereby improving the toughness of the steel and solving the technical problems of poor toughness and microcracks in seamless steel pipes prepared under high chromium content, and ultimately achieving high wear resistance of seamless steel pipes. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 2.0% of the alloy weight. The alloy comprises the following components by mass percentage: Cr: 15.0%, Mn: 2.2%, C: 0.14%, Mo: 0.40%, Si: 0.20%, Al: 0.18%, V: 0.10%, Ti: 0.04%, Nb: 0.03%, rare earth elements 0.25%, and the balance Fe and unavoidable impurities.

[0032] The rare earth element is praseodymium.

[0033] The reinforcing particles are high carbon ferrochrome powder.

[0034] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0035] S1. Weigh the reinforcement particles and each alloy component according to the mass percentage, then smelt the alloy at a smelting temperature of 1620° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1550° C., add the reinforcement particles, and continue smelting for 1.5 hours to obtain molten steel;

[0036] S2, continuously casting the molten steel into round billets at a casting temperature of 1240°C and keeping the temperature for 4 hours;

[0037] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1170°C, rolling it through a tube rolling mill, the rolling temperature is 1120°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 880°C;

[0038] S4. The rolled semi-finished steel pipe is quenched at 920°C to a temperature below 120°C, and then subjected to tempering heat treatment at 670°C for 30 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0039] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace and heat it to 820℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall. Then it is tempered within the range of 200℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0040] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 20r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 10°.

[0041] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 5:1.

[0042] The particle size of the alumina powder is 2000 mesh.

[0043] Example 2

[0044] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 1.8% of the weight of the alloy. The alloy comprises the following components by mass percentage: Cr: 14.5%, Mn: 2.0%, C: 0.12%, Mo: 0.35%, Si: 0.18%, Al: 0.16%, V: 0.08%, Ti: 0.03%, Nb: 0.025%, rare earth elements 0.24%, and the balance Fe and unavoidable impurities.

[0045] The rare earth element is praseodymium.

[0046] The reinforcing particles are high carbon ferrochrome powder.

[0047] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0048] S1. Weigh the reinforcement particles and each alloy component according to the mass percentage, then smelt the alloy at a smelting temperature of 1600° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1520° C., add the reinforcement particles, and continue smelting for 1 hour to obtain molten steel;

[0049] S2, continuously casting the molten steel into round billets at a casting temperature of 1230°C and keeping the temperature for 3 hours;

[0050] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1150°C, rolling it through a tube rolling mill, the rolling temperature is 1100°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 860°C;

[0051] S4. The rolled semi-finished steel pipe is quenched at 900°C to a temperature below 120°C, and then subjected to tempering heat treatment at 660°C for 25 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0052] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace, heat it to 800℃, and cool it to below 80℃ by spraying water on the inner wall after it comes out of the furnace. Then temper it within the range of 150℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0053] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 10r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 5°.

[0054] The quenching liquid comprises the following components by weight percentage: 6% hydroxyethyl cellulose, 3% sodium lignin sulfonate, 0.6% triethanolamine, 18% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 10:1.

[0055] The particle size of the alumina powder is 2000 mesh.

[0056] Example 3

[0057] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 2.2% of the weight of the alloy. The alloy comprises the following components by mass percentage: Cr: 15.5%, Mn: 2.4%, C: 0.16%, Mo: 0.45%, Si: 0.22%, Al: 0.20%, V: 0.12%, Ti: 0.05%, Nb: 0.04%, rare earth elements 0.26%, and the balance Fe and unavoidable impurities.

[0058] The rare earth element is praseodymium.

[0059] The reinforcing particles are high carbon ferrochrome powder.

[0060] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0061] S1. Weigh the reinforcement particles and each alloy component according to mass percentage, then smelt the alloy at a smelting temperature of 1650° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1580° C., add the reinforcement particles, and continue smelting for 1.5 hours to obtain molten steel;

[0062] S2, continuously casting the molten steel into round billets at a casting temperature of 1250°C and keeping the temperature for 5 hours;

[0063] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1190°C, rolling it through a tube rolling mill, the rolling temperature is 1140°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 900°C;

[0064] S4. The rolled semi-finished steel pipe is quenched at 940°C to a temperature below 120°C, and then subjected to tempering heat treatment at 680°C for 35 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0065] S5. Put the semi-finished steel pipe after natural cooling in S4 into a quenching and tempering furnace, heat it to 840℃, and after it comes out of the furnace, cool it to below 80℃ by spraying water on the inner wall, and then temper it within the range of 250℃ to eliminate the heat treatment stress to finally obtain the finished steel pipe.

[0066] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 30r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 15°.

[0067] The quenching liquid comprises the following components by weight percentage: 10% hydroxyethyl cellulose, 5% sodium lignin sulfonate, 1% triethanolamine, 22% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 10:3.

[0068] The particle size of the alumina powder is 2000 mesh.

[0069] Example 4

[0070] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 1.9% of the weight of the alloy. The alloy comprises the following components by mass percentage: Cr: 14.8%, Mn: 2.2%, C: 0.13%, Mo: 0.38%, Si: 0.19%, Al: 0.17%, V: 0.09%, Ti: 0.035%, Nb: 0.029%, rare earth elements 0.245%, and the balance Fe and unavoidable impurities.

[0071] The rare earth element is praseodymium.

[0072] The reinforcing particles are high carbon ferrochrome powder.

[0073] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0074] S1. Weigh the reinforcement particles and each alloy component according to mass percentage, then smelt the alloy at a smelting temperature of 1620° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1540° C., add the reinforcement particles, and continue smelting for 1.2 hours to obtain molten steel;

[0075] S2, continuously casting the molten steel into round billets at a casting temperature of 1235°C and keeping the temperature for 3.5 hours;

[0076] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1160°C, rolling it through a tube rolling mill, the rolling temperature is 1110°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 870°C;

[0077] S4. The rolled semi-finished steel pipe is quenched at 910°C to a temperature below 120°C, and then subjected to tempering heat treatment at 665°C for 28 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0078] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace and heat it to 810℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall. Then it is tempered in the range of 180℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0079] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 15r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 12°.

[0080] The quenching liquid comprises the following components in weight percentage: 7% hydroxyethyl cellulose, 3.5% sodium lignin sulfonate, 0.7% triethanolamine, 19% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 20:3.

[0081] The particle size of the alumina powder is 2000 mesh.

[0082] Comparative Example 1

[0083] The only difference from Example 1 is that no rare earth element is added to the alloy composition.

[0084] A wear-resistant seamless steel pipe comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 2.0% of the alloy weight. The alloy comprises the following components by mass percentage: Cr: 15.0%, Mn: 2.2%, C: 0.14%, Mo: 0.40%, Si: 0.20%, Al: 0.18%, V: 0.10%, Ti: 0.04%, Nb: 0.03%, and the balance is Fe and unavoidable impurities.

[0085] The reinforcing particles are high carbon ferrochrome powder.

[0086] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0087] S1. Weigh the reinforcement particles and each alloy component according to the mass percentage, then smelt the alloy at a smelting temperature of 1620° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1550° C., add the reinforcement particles, and continue smelting for 1.5 hours to obtain molten steel;

[0088] S2, continuously casting the molten steel into round billets at a casting temperature of 1240°C and keeping the temperature for 4 hours;

[0089] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1170°C, rolling it through a tube rolling mill, the rolling temperature is 1120°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 880°C;

[0090] S4. The rolled semi-finished steel pipe is quenched at 920°C to a temperature below 120°C, and then subjected to tempering heat treatment at 670°C for 30 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0091] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace and heat it to 820℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall. Then it is tempered within the range of 200℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0092] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 20r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 10°.

[0093] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 5:1.

[0094] The particle size of the alumina powder is 2000 mesh.

[0095] Comparative Example 2

[0096] The only difference from Example 1 is that no reinforcing particles are added to the composition of the seamless steel pipe.

[0097] A wear-resistant seamless steel pipe, the component of which is an alloy. The alloy comprises the following components by mass percentage: Cr: 15.0%, Mn: 2.2%, C: 0.14%, Mo: 0.40%, Si: 0.20%, Al: 0.18%, V: 0.10%, Ti: 0.04%, Nb: 0.03%, rare earth elements 0.25%, and the balance Fe and unavoidable impurities.

[0098] The rare earth element is praseodymium.

[0099] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0100] S1. Weigh each component of the alloy according to mass percentage, then smelt the alloy at a smelting temperature of 1620° C. to obtain an alloy melt that meets the alloy composition requirements, and cool the temperature to 1550° C. to obtain molten steel;

[0101] S2, continuously casting the molten steel into round billets at a casting temperature of 1240°C and keeping the temperature for 4 hours;

[0102] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1170°C, rolling it through a tube rolling mill, the rolling temperature is 1120°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 880°C;

[0103] S4. The rolled semi-finished steel pipe is quenched at 920°C to a temperature below 120°C, and then subjected to tempering heat treatment at 670°C for 30 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0104] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace and heat it to 820℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall. Then it is tempered within the range of 200℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0105] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 20r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 10°.

[0106] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 5:1.

[0107] The particle size of the alumina powder is 2000 mesh.

[0108] Comparative Example 3

[0109] The only difference from Example 1 is that neither rare earth elements nor reinforcing particles are added to the composition of the seamless steel pipe.

[0110] A wear-resistant seamless steel pipe comprises an alloy, wherein the alloy comprises the following components by mass percentage: Cr: 15.0%, Mn: 2.2%, C: 0.14%, Mo: 0.40%, Si: 0.20%, Al: 0.18%, V: 0.10%, Ti: 0.04%, Nb: 0.03%, and the balance is Fe and unavoidable impurities.

[0111] A method for preparing a wear-resistant seamless steel pipe comprises the following steps:

[0112] S1. Weigh each component of the alloy according to mass percentage, then smelt the alloy at a smelting temperature of 1620° C. to obtain an alloy melt that meets the alloy composition requirements, and cool the temperature to 1550° C. to obtain molten steel;

[0113] S2, continuously casting the molten steel into round billets at a casting temperature of 1240°C and keeping the temperature for 4 hours;

[0114] S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1170°C, rolling it through a tube rolling mill, the rolling temperature is 1120°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 880°C;

[0115] S4. The rolled semi-finished steel pipe is quenched at 920°C to a temperature below 120°C, and then subjected to tempering heat treatment at 670°C for 30 minutes. After the tempering heat treatment, the steel pipe is straightened with temperature and cooled naturally.

[0116] S5. Put the semi-finished steel pipe after natural cooling in S4 into the tempering furnace and heat it to 820℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall. Then it is tempered within the range of 200℃ to eliminate the heat treatment stress and finally obtain the finished steel pipe.

[0117] During quenching in step S4, the rolled steel pipe is placed on rollers, which drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process. The rotation speed of the steel pipe is 20r / s until it is completely immersed in the quenching liquid. In addition, the steel pipe has a certain inclination, and the inclination angle is 10°.

[0118] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is a mixture of polyvinyl alcohol and alumina powder, and the mass ratio of the two is 5:1.

[0119] The particle size of the alumina powder is 2000 mesh.

[0120] Comparative Example 4

[0121] The only difference from Example 1 is that no polyvinyl alcohol is added to the quenching liquid.

[0122] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is alumina powder.

[0123] The particle size of the alumina powder is 2000 mesh.

[0124] Comparative Example 5

[0125] The only difference from Example 1 is that no alumina powder is added to the quenching liquid.

[0126] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, 20% composite auxiliary agent, and the balance is castor oil. The composite auxiliary agent is polyvinyl alcohol.

[0127] Comparative Example 6

[0128] The only difference from Example 1 is that no polyvinyl alcohol and no alumina powder are added to the quenching liquid.

[0129] The quenching liquid comprises the following components by weight percentage: 8% hydroxyethyl cellulose, 4% sodium lignin sulfonate, 0.8% triethanolamine, and the balance is castor oil.

[0130] Performance testing:

[0131] Elongation test: Refer to GB / T 228.1 standard, process arc-shaped tensile specimens, and use a tensile testing machine to test the elongation of the finished steel pipe.

[0132] Hardness test: Refer to GB / T 230.1 standard and use digital Rockwell hardness tester to test the inner wall hardness of finished steel pipe.

[0133] Service life test conditions: concrete pumping speed is 3m / s;

[0134] The above test results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] The data of elongation, hardness and service life of the finished steel pipes in Examples 1-4 prove that the finished steel pipes prepared by the technical solution of the present invention have excellent toughness and long service life.

[0139] Comparative Example 1

[0140] The only difference from Example 1 is that no rare earth element is added to the alloy composition.

[0141] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 1 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Example 1.

[0142] Hardness and elongation are manifestations of the toughness of finished steel pipes. The higher the elongation and hardness, the better the toughness of the finished steel pipe. The above results show that when the mass fraction of chromium content in the steel pipe is higher than 12%, the addition of rare earth elements can improve the hardness and elongation of the finished steel pipe, and at the same time extend the service life of the finished steel pipe.

[0143] Comparative Example 2

[0144] The only difference from Example 1 is that no reinforcing particles are added to the composition of the seamless steel pipe.

[0145] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 2 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Example 1.

[0146] The reinforcing particles are high carbon ferrochrome powder. The above results show that the addition of reinforcing particles can improve the hardness and elongation of the finished steel pipe and extend the service life of the finished steel pipe.

[0147] Comparative Example 3

[0148] The only difference from Example 1 is that neither rare earth elements nor reinforcing particles are added to the composition of the seamless steel pipe.

[0149] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 3 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Comparative Examples 1 and 2.

[0150] As mentioned above, the reinforcing particles are high carbon ferrochrome powder. When rare earth elements are present, the addition of the reinforcing particles can synergistically improve the hardness and elongation of the finished steel pipe, while extending the service life of the finished steel pipe.

[0151] Comparative Example 4

[0152] The only difference from Example 1 is that no polyvinyl alcohol is added to the quenching liquid.

[0153] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 4 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Example 1.

[0154] The above results show that the addition of polyvinyl alcohol in the quenching liquid can improve the hardness and elongation of the finished steel pipe and extend the service life of the finished steel pipe.

[0155] Comparative Example 5

[0156] The only difference from Example 1 is that no alumina powder is added to the quenching liquid.

[0157] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 5 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Example 1.

[0158] The above results show that the addition of alumina powder in the quenching liquid can improve the hardness and elongation of the finished steel pipe and extend the service life of the finished steel pipe.

[0159] Comparative Example 6

[0160] The only difference from Example 1 is that no polyvinyl alcohol and no alumina powder are added to the quenching liquid.

[0161] It can be seen from Table 1 that the hardness, elongation and service life of the finished steel pipe prepared in Comparative Example 6 are lower than the hardness, elongation and service life of the finished steel pipe prepared in Comparative Examples 4 and 5.

[0162] The above results show that polyvinyl alcohol and alumina powder in the quenching liquid synergistically improve the hardness and elongation of the finished steel pipe, while extending the service life of the finished steel pipe.

[0163] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A wear-resistant seamless steel pipe, characterized in that: The invention comprises an alloy and reinforcing particles, wherein the reinforcing particles account for 1.8-2.2% of the weight of the alloy. The alloy comprises the following components by mass percentage: Cr: 14.5-15.5%, Mn: 2.0-2.4%, C: 0.12-0.16%, Mo: 0.35%-0.45%, Si: 0.18-0.22%, Al: 0.16-0.20%, V: 0.08-0.12%, Ti: 0.03-0.05%, Nb: 0.025-0.04% and 0.24-0.26% of rare earth elements, and the balance is Fe and unavoidable impurities.

2. A wear-resistant seamless steel pipe according to claim 1, characterized in that: The rare earth element is praseodymium.

3. The wear-resistant seamless steel pipe according to claim 1, characterized in that: The reinforcing particles are high carbon ferrochrome powder.

4. A method for preparing a wear-resistant seamless steel pipe according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Weigh the reinforcement particles and each alloy component according to the mass percentage, then smelt the alloy at a smelting temperature of 1600-1650° C. to obtain an alloy melt that meets the alloy composition requirements, cool it to 1520-1580° C., add the reinforcement particles, and continue smelting for 1-1.5 hours to obtain molten steel; S2, continuously casting the molten steel into round billets at a casting temperature of 1230-1250°C and keeping the temperature for 3-5 hours; S3, punching the obtained round billet to obtain a tube billet, the punching temperature is 1150-1190°C, rolling it through a tube rolling mill, the rolling temperature is 1100-1140°C, and sizing it through a sizing mill to obtain a semi-finished steel pipe, the sizing temperature is 860-900°C; S4, quench the semi-finished steel pipe at 900℃~940℃, quench to a temperature below 120℃, then perform tempering heat treatment at a temperature of 660℃~680℃, the tempering treatment time is 25~35min, and after the tempering heat treatment, perform warm straightening and natural cooling; S5. Put the semi-finished steel pipe after natural cooling in S4 into a tempering furnace and heat it to 800-840℃. After it comes out of the furnace, it is cooled to below 80℃ by spraying water on the inner wall, and then tempered in the range of 150-250℃ to obtain a wear-resistant seamless steel pipe.

5. The method for preparing a wear-resistant seamless steel pipe according to claim 4, characterized in that: In S4, during quenching, the rolled steel pipe is placed on rollers, and the rollers drive the steel pipe to rotate by rotating, so that the steel pipe keeps rotating during the quenching process when entering the quenching liquid. The rotation speed of the steel pipe is 10 to 30 r / s, and the steel pipe is immersed in the quenching liquid at an inclination angle of 5 to 15 degrees.

6. The method for preparing a wear-resistant seamless steel pipe according to claim 5, characterized in that: The quenching liquid comprises the following components in terms of weight percentage: 6-10% hydroxyethyl cellulose, 3-5% sodium lignin sulfonate, 0.6-1% triethanolamine and 18-22% composite auxiliary agent, and the balance is castor oil.

7. The method for preparing a wear-resistant seamless steel pipe according to claim 6, characterized in that: The composite auxiliary agent is a mixture of polyvinyl alcohol and aluminum oxide powder, and the mass ratio of the two is 10:1-3.

8. The method for preparing a wear-resistant seamless steel pipe according to claim 7, characterized in that: The particle size of the alumina powder is 2000 mesh.

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