A method for manufacturing an outer wall wear-resistant seamless steel pipe and an outer wall wear-resistant seamless steel pipe

Abstract

The present invention relates to a method for manufacturing a seamless steel pipe with an outer wall, and belongs to the field of steel manufacturing. The method includes steelmaking, tube blank manufacturing, annular furnace heating, perforation, continuous rolling, tension reduction or sizing, and online quenching steps. The quenching is an online quenching step, which includes: after the final rolling of the steel pipe, the water pressure and flow rate of each group of water rings on the online quenching equipment are adjusted to achieve centralized cooling, so that more than 95% of the martensitic structure is generated within 1.5 mm from the outer wall of the steel pipe; the roller speed of the steel pipe conveying in the online quenching cooling zone is adjusted to adjust the quenching cooling temperature gradient in the direction of the steel pipe wall thickness, indirectly control the depth of the hardened layer, and regulate the ratio of martensite to non-martensitic structure in the direction of the steel pipe wall thickness; it also relates to a seamless steel pipe with an outer wall. The method of the present invention can obtain a seamless steel pipe with an outer wall that is hard on the outside and tough on the inside.

Description

Technical Field

[0001] The invention relates to the field of steel, and in particular to a method for manufacturing a seamless outer wall wear-resistant steel pipe and a seamless outer wall wear-resistant steel pipe manufactured based on the method. Background Art

[0002] Wear-resistant seamless steel pipes are widely used in power, metallurgy, mining, chemical and other industries, mainly for conveying abrasive granular materials such as sand, stone, coal powder, ash and slag. On the one hand, the conveyed abrasive materials require the inner wall of the wear-resistant pipe to have high hardness and excellent wear resistance. On the other hand, in order to prevent low-stress brittle cracking during service, the wear-resistant pipe is usually required to have certain plasticity and toughness. In order to coordinate and solve the contradiction between high hardness and certain plasticity and toughness, the industry currently mainly adopts the methods of quenching the inner wall of steel pipes, and nesting tough outer pipes + wear-resistant inner pipes to produce wear-resistant pipes.

[0003] In addition to the above uses, when the wear-resistant pipe is used in special scenarios such as boiler water pipes, its inner wall conveys water, oil or gas medium, and the outer wall is in contact with hard particles or solids, which requires the outer wall to have good wear resistance. In order to improve the wear resistance of the outer wall of the steel pipe, common methods include surfacing a wear-resistant layer on the surface, chrome plating, etc., which are costly, have low production efficiency and are not environmentally friendly.

[0004] The main published patents about outer wall wear-resistant seamless steel pipes are as follows:

[0005] The Chinese utility model patent with publication number CN212226263U and publication date December 25, 2020, entitled "A high-performance pressure-resistant and wear-resistant composite steel pipe" provides a high-performance pressure-resistant and wear-resistant composite steel pipe. It is characterized in that it includes a pressure-resistant inner pipe and a wear-resistant outer pipe, and an interlayer is provided between the pressure-resistant inner pipe and the wear-resistant outer pipe, the interlayer is filled with a rubber buffer layer, a support structure is arranged at the end of the interlayer, and the outer surface of the wear-resistant outer pipe is coated with a wear-resistant coating.

[0006] The Chinese utility model patent with publication number CN210440696U and publication date May 1, 2020, and titled "A Wear-Resistant Seamless Steel Pipe" provides a wear-resistant seamless steel pipe. It is characterized in that it includes an outer base pipe and an inner liner pipe, the inner liner pipe is arranged inside the outer base pipe, and is characterized in that: a reinforcement pipe is arranged between the outer base pipe and the inner liner pipe, the reinforcement pipe includes an outer reinforcement pipe, an inner reinforcement pipe and a reinforcement ring sheet, the reinforcement ring sheet is evenly sleeved on the inner reinforcement pipe, the reinforcement ring sheet is connected to the inner wall of the outer reinforcement pipe, the inner liner pipe is arranged inside the inner reinforcement pipe, and the outer side of the outer base pipe is provided with a wear-resistant layer.

[0007] The wear-resistant seamless steel pipes disclosed in the above patents all adopt a composite structure of inner and outer pipes, which has a complex structure and high production cost. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a new method for manufacturing a wear-resistant seamless steel pipe with an outer wall and a wear-resistant seamless steel pipe with an outer wall manufactured based on the method. The method of the present invention obtains a wear-resistant seamless steel pipe with an outer wall having the characteristics of being hard on the outside and tough on the inside through process adjustment.

[0009] One of the purposes of the present invention is to provide a method for manufacturing an outer wall wear-resistant seamless steel pipe, which controls the phase change in the wall thickness direction of the steel pipe by controlling the online quenching process, thereby ensuring that low-temperature transformation structure martensite is generated within a certain thickness inside the outer wall of the steel pipe, and the part other than the hardened martensite layer is medium-temperature transformation bainite structure or even high-temperature transformation ferrite + pearlite structure, thereby obtaining an outer wall wear-resistant seamless steel pipe with the characteristics of hard outside and tough inside.

[0010] In order to achieve the above-mentioned invention object, the present invention specifically provides a method for manufacturing an outer wall wear-resistant seamless steel pipe, which includes steelmaking, tube blank manufacturing, annular furnace heating, perforation, continuous rolling, stretching or sizing and quenching, wherein the quenching is an online quenching step, which includes:

[0011] In the first step, after the steel pipe is finally rolled, the water pressure and flow rate of each group of water rings on the online quenching equipment are adjusted to achieve centralized cooling, so that more than 95% of the martensite structure is generated within 1.5 mm from the outer wall of the steel pipe;

[0012] The second step is to adjust the roller speed of the steel pipe conveying in the online quenching and cooling zone, adjust the quenching and cooling temperature gradient in the direction of the steel pipe wall thickness, indirectly control the depth of the hardened layer, and regulate the ratio of martensite and non-martensite structure in the direction of the steel pipe wall thickness.

[0013] In the first step, the online quenching equipment is controlled so that the start-cooling temperature of the online quenching is ≥ the Ar3 temperature of the steel grade + 40°C.

[0014] In the first step, the total number of online quenching water rings opened is controlled to remain constant, and all water rings of different specifications / materials are opened.

[0015] In the first step, the water pressure and flow rate of each water ring in the online quenching are controlled to be constant, the water pressure in a single water ring is ≥0.45MPa, and the flow rate of a single water ring is ≥125m 3 / h.

[0016] In the second step, the roller speed V (m / s) of the steel pipe conveying in the online quenching and cooling zone and the steel pipe wall thickness T (mm) are controlled to satisfy the following corresponding relationship:

[0017] If 8≤T<12V=1.8±0.5;

[0018] If 12≤T<16V=1.6±0.5;

[0019] If 16≤T<20V=1.4±0.5;

[0020] If 20≤T<25V=1.3±0.5;

[0021] If 25≤T<30V=1.2±0.5;

[0022] If 30≤T≤40V=1.0±0.5.

[0023] In the second step, the temperature of the outer wall of the steel pipe out of the cooling zone is controlled to be ≤Ms temperature-120°C.

[0024] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, the pipe blank is manufactured by directly casting smelted molten steel, or by forging or rolling after casting.

[0025] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, when the tube blank is heated in the annular furnace, the heating temperature is in the temperature range of 1200-1300° C., and the insulation time is 1-4 hours.

[0026] Another object of the present invention is to provide an outer wall wear-resistant seamless steel pipe based on the above manufacturing method. In the outer wall wear-resistant seamless steel pipe, its alloy composition system is C-Si-Mn-Cr, wherein 0.5%≤C≤0.7%, 0.2%≤Si≤0.3%, 0.5%≤Mn≤0.85%, and 0.3%≤Cr≤0.9%. At the same time, in order to meet the hardenability requirements of the steel pipe, the contents of C, Mn and Cr elements in the steel meet the following requirements: Cep=C+Mn / 6+Cr / 5≥0.75%; an outer wall wear-resistant seamless steel pipe prepared by the above method has the following characteristics: ① The proportion of martensite within 1.5mm of the outer wall (quenching side) of the steel pipe is ≥95%; ② The 50% martensite zone of the steel pipe (depth of hardened layer) is between 1 / 2 and 2 / 3 of the wall thickness, that is, the steel pipe is hardened from 1 / 2 to 2 / 3 of the depth from the outer wall to the inside, and has good wear resistance. The remaining wall thickness is not hardened and maintains a certain toughness; ③ The impact absorption energy Kv8 of the inner wall sample of the steel pipe is ≥32J (the test parameters are 20°C, longitudinal, and the sample size is 10mm*10mm*55mm).

[0027] Based on the above technical solution, the method of the present invention and the seamless steel pipe obtained based on the method have the following technical advantages compared with the prior art:

[0028] The manufacturing method of the present invention controls the phase change in the wall thickness direction of the steel pipe by controlling the online quenching process, thereby ensuring that the low-temperature transformation structure martensite is generated within a certain thickness inside the outer wall of the steel pipe, and the part except the hardened martensite layer is all medium-temperature transformation bainite structure or even high-temperature transformation ferrite + pearlite structure, thereby obtaining an outer wall wear-resistant seamless steel pipe with the characteristics of hard outside and tough inside. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a typical structure of the outer wall hardened layer of the embodiment of the present invention, which is martensite + a very small amount of residual austenite.

[0030] Figure 2 It is a typical unhardened tough structure of the inner wall of the embodiment of the present invention, which is pearlite + a small amount of ferrite structure. DETAILED DESCRIPTION

[0031] The outer wall wear-resistant seamless steel pipe and the manufacturing method thereof described in the present invention will be further explained and illustrated in combination with specific embodiments below. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0032] The present invention is a method for manufacturing a seamless steel pipe with an outer wall that includes some of the same seamless steel pipe manufacturing steps as the prior art, that is, they all include steelmaking, tube blank manufacturing, ring furnace heating, perforation, continuous rolling, tension reduction or sizing and quenching. As a feature of the present invention, the quenching is carried out by online quenching. In order to achieve the purpose of the above invention, the present invention focuses on the online quenching process of seamless steel pipes. After the study, it is found that: ① After the final rolling of the steel pipe, by adjusting the water pressure and flow rate of each group of water rings of the online quenching equipment, the effect of ultra-high-speed centralized cooling can be produced, ensuring that more than 95% of the martensitic structure is generated within 1.5 mm from the outer wall of the steel pipe, and the 1.5 mm distance from the outer wall here is 1.5 mm from the quenching side. ② By adjusting the roller speed of the steel pipe conveying in the online quenching cooling zone, the quenching cooling temperature gradient in the wall thickness direction of the steel pipe can be adjusted, thereby indirectly controlling the depth of the hardened layer and regulating the ratio of martensite / non-martensite structure in the wall thickness direction of the steel pipe. From the above research results, it can be known that by adjusting the online quenching process, the organizational proportion and final performance of the outer wall wear-resistant seamless steel pipe can be effectively adjusted.

[0033] The method of the present invention is mainly completed based on the above-mentioned understanding. In order to achieve the above-mentioned purpose, the present invention proposes a method for manufacturing an outer wall wear-resistant seamless steel pipe, the steps of which include: steelmaking, manufacturing tube blanks, annular furnace heating, perforation, continuous rolling, stretching or sizing, and online quenching. The online quenching steps are: ① Control the online quenching cooling temperature ≥ Ar3 temperature of the steel type + 40°C; ② Control the total number of online quenching water rings to remain constant. For different specifications / materials, all water rings are fully opened. In the embodiment, 42 water rings are selected; ③ Control the water pressure and flow rate of each water ring in the online quenching to be constant, the water pressure in the water ring is ≥ 0.45MPa, and the flow rate of a single water ring is ≥ 125m 3 / h; ④ Control the roller speed V and the steel pipe wall thickness T of the steel pipe conveying in the online quenching and cooling zone to meet the corresponding relationship listed in Table 1 below.

[0034] Table 1 Correspondence between roller speed V and steel pipe wall thickness T

[0035]

[0036] ⑤ Control the temperature of the outer wall of the steel pipe out of the cooling zone ≤ Ms temperature - 120℃; ⑥ After the steel pipe leaves the cooling zone, the finished product of the outer wall wear-resistant seamless steel pipe is directly obtained.

[0037] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, the step of manufacturing the tube blank can adopt the method of direct casting of smelted molten steel, or the method of forging or rolling after casting.

[0038] In a method for manufacturing a seamless steel tube with outer wall wear resistance of the present invention, the heating temperature of the tube blank in the annular furnace is in the temperature range of 1200-1300°C, and the holding time is 1-4 hours. If the heating temperature is too high or the holding time is too long, it is possible to cause coarse grains and damage the wear resistance. If the heating time is too short or the holding time is insufficient, the deformation performance of the tube blank may be poor.

[0039] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, the online quenching adopts the method of spraying water from the water ring to the outer wall of the steel pipe, while the inner wall of the steel pipe is not sprayed with water for cooling, that is, the method of single external cooling. Thus, a wear-resistant seamless steel pipe with outer wall hardness and inner toughness can be obtained.

[0040] In a method for manufacturing a seamless steel pipe with a wear-resistant outer wall of the present invention, in order to ensure the wear resistance of the outer wall of the steel pipe and prevent the appearance of undesirable structures such as proeutectoid ferrite on the outer wall of the steel pipe during the cooling process, the online quenching and cooling temperature should be maintained at above the Ar3 temperature of the steel grade + 40°C. The Ar3 temperature of the steel grade is a clear concept in this field, which refers to the starting temperature of the transformation of proeutectoid ferrite during the cooling transformation of supercooled austenite.

[0041] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, in order to ensure the wear resistance of the outer wall of the steel pipe, it is necessary to ensure that the martensitic structure of the outer wall of the steel pipe is fully transformed and fine, and ultra-high-speed centralized cooling is conducive to the martensitic phase transformation, reduces the proportion of residual austenite in the structure, and is conducive to the refinement of the martensitic structure. According to the technical solution of the present invention, the water pressure in a single water ring must be ≥0.45MPa during online quenching, and the flow rate of a single water ring must be ≥125m 3 / h to ensure the effect of ultra-high-speed centralized cooling.

[0042] In the manufacturing method of a wear-resistant seamless steel pipe with an outer wall of the present invention, in order to ensure the effect of "hard outside and tough inside" of the steel pipe, it is necessary to control the steel pipe to form a certain cooling rate gradient along the wall thickness direction, so that the steel pipe generates a non-martensitic structure in a certain area from the inner wall to the outside, and the non-martensitic structure includes a small amount of martensite + bainite, bainite, bainite + ferrite + pearlite, ferrite + pearlite structure, etc. When the roller speed V of the steel pipe conveyed in the online quenching and cooling zone and the steel pipe wall thickness T meet the corresponding relationship listed in Table 1, the 50% martensitic area (that is, the depth of the hardened layer) can be between 1 / 2 and 2 / 3 of the wall thickness of the steel pipe, that is, the steel pipe is hardened from 1 / 2 to 2 / 3 of the depth from the outer wall to the inside, and has good wear resistance, and the remaining part is not hardened and maintains a certain toughness. The hardening depth ratio fluctuates between 1 / 2 and 2 / 3 depending on the type of steel.

[0043] In the manufacturing method of the outer wall wear-resistant seamless steel pipe of the present invention, in order to ensure the wear resistance of the outer wall of the steel pipe and improve the hardening effect of the outer wall, it is necessary to control the temperature of the outer wall of the steel pipe out of the cooling zone ≤ Ms temperature -120°C. The low final cooling temperature is beneficial to increasing the proportion of martensite structure in the hardened layer.

[0044] Another object of the present invention is to provide an outer wall wear-resistant seamless steel pipe based on the above-mentioned manufacturing method, wherein the alloy component system of the outer wall wear-resistant seamless steel pipe is C-Si-Mn-Cr, wherein:

[0045] 0.5%≤C≤0.7%,

[0046] 0.2%≤Si≤0.3%,

[0047] 0.5%≤Mn≤0.85%,

[0048] 0.3%≤Cr≤0.9%.

[0049] At the same time, in order to meet the hardenability requirements of the steel pipe, the content of C, Mn and Cr elements in the steel meets the requirements: Cep = C + Mn / 6 + Cr / 5 ≥ 0.75%;

[0050] The outer wall wear-resistant seamless steel pipe prepared by the above manufacturing process has the following characteristics:

[0051] ① The proportion of martensite within 1.5mm from the outer wall (quenching side) of the steel pipe is ≥95%;

[0052] ② The 50% martensite area (hardened layer depth) of the steel pipe is between 1 / 2 and 2 / 3 of the wall thickness, that is, the steel pipe is hardened from 1 / 2 to 2 / 3 of the outer wall to the inside, with good wear resistance, and the remaining wall thickness is not hardened, maintaining a certain toughness;

[0053] ③The impact absorption energy of the inner wall sample of the steel pipe Kv8≥32J (20℃, longitudinal, sample size 10mm*10mm*55mm).

[0054] Example

[0055] Using Examples A1-A8 and Comparative Examples B1-B6, the outer wall wear-resistant seamless steel pipes in the above Examples and Comparative Examples are prepared by the following steps:

[0056] (1) Smelting, the steel grade composition is controlled as shown in Table 1;

[0057] (2) Manufacturing of tube blanks: The tube blanks can be manufactured by direct casting of molten steel or by forging or rolling after casting;

[0058] (3) Ring furnace heating: heat the round tube to 1200-1300°C, and keep it at this temperature for 1-4 hours;

[0059] (4) Perforation;

[0060] (5) Continuous rolling;

[0061] (6) After being stretched or sized, the finished steel pipe specification is 244.8*24mm;

[0062] (7) Online quenching: The specific process data of the online quenching start-up temperature, the water pressure / flow rate of each water ring, the roller speed, etc. of each embodiment and comparative example are shown in Table 2;

[0063] Table 2 Mass percentage of chemical elements of Examples A1-A8 and Comparative Examples B1-B6 (wt%)

[0064]

[0065] It can be seen from Table 2 that the Cep value of Comparative Example B1 does not conform to the parameter range defined in the present invention.

[0066] Table 3 lists the specific parameters of the manufacturing method of Examples A1-A8 and Comparative Examples B1-B6, including heating temperature, holding time, cooling method, Ar3, cooling start temperature, water pressure, water volume, roller speed, Ms temperature and outer wall cooling zone exit temperature.

[0067] Table 3 Specific parameters of the embodiments and comparative examples

[0068]

[0069]

[0070] It can be further seen from Table 3 that the comparative example B2 adopts an immersion cooling method, which does not comply with the limitation of the present invention on the cooling method of the steel pipe, the start cooling temperature of the comparative example B3 is lower than the range defined in the present invention, the water pressure and water volume of the comparative example B4 are lower than the range defined in the present invention, the roller moving speed of the comparative example B5 is higher than the range defined in the present invention, and the temperature of the outer wall of the steel pipe out of the cooling zone of the comparative example B6 is higher than the range defined in the present invention.

[0071] Table 4 shows the microstructure and mechanical property parameters of the seamless steel pipes of Examples A1-A8 and Comparative Examples B1-B6 measured when they were placed on a cooling bed and air-cooled to room temperature.

[0072] Table 4

[0073]

[0074]

[0075] In Table 4 above, the metallographic structure test results are tested by the following method: After the seamless steel pipes made by different processes are sawn into sections, metallographic samples are cut from the middle part of the steel pipes, and metallographic structure analysis tests are performed after sample preparation. Figure 1 As shown, Figure 1 The typical structure of the outer wall hardened layer is martensite + a very small amount of residual austenite. Among them: the proportion of martensite within 1.5mm from the outer wall (quenching end) is quantitatively characterized by backscattered electron diffraction (EBSD), and the depth of the 50% martensite zone (hardened layer depth) is approximately replaced by the position where the hardness value of continuous points along the diameter direction changes sharply. For comparison, Figure 2 It is a typical unhardened tough structure of the inner wall, which is pearlite + a small amount of ferrite structure.

[0076] As shown in Table 4, the martensite ratio of the seamless steel pipes of Examples A1-A8 at 1.5 mm from the outer wall (quenching end) is higher than 95%, and the depth of the 50% martensite zone accounts for a ratio of the wall thickness between 1 / 2 and 2 / 3, which is better than the cross-sectional organization distribution of the steel pipes of Comparative Examples B1-B6. Not only does the steel pipe surface have good wear resistance, but the inner wall of the steel pipe also has a certain toughness. It can be used in fields that require wear resistance of the outer wall of the steel pipe, making full use of the waste heat during the manufacture of the seamless steel pipe, and the production process is convenient. Compared with the composite outer wall wear-resistant seamless steel pipe, the cost is lower.

[0077] It can also be seen from Table 4 that the Cep value of the alloying element in Comparative Example B1 is less than 0.75%, which makes the hardenability of the material insufficient, and the depth of the 50% martensite zone of the steel pipe is insufficient; the cooling method of Comparative Example B2 adopts immersion quenching, and the outer, middle and inner walls of the steel pipe are all quenched into martensite structure, and the toughness of the inner wall is insufficient, which does not meet the requirements of the present invention; the cooling temperature of Comparative Example B3 is lower than the range specified in the present invention, resulting in a large proportion of undesirable structures such as proeutectoid ferrite precipitating on the outer wall of the steel pipe, making the martensite structure ratio of the outer wall of the steel pipe less than 95%; Comparative Example B The quenching water pressure and flow rate of comparative example B4 are insufficient, resulting in insufficient cooling rate of the outer wall of the steel pipe, poor quenching, and the proportion of martensite within 1.5 mm from the outer wall (quenching end) of the steel pipe and the proportion of 50% martensite zone depth to wall thickness do not meet the requirements of the present invention; the roller speed of comparative example B5 is too fast, resulting in insufficient cooling rate of the outer wall of the steel pipe, and the proportion of 50% martensite zone depth to wall thickness does not meet the requirements of the present invention; the final cooling temperature of the outer wall of the steel pipe of comparative example B6 is too high, resulting in insufficient cooling of the outer wall of the steel pipe, and the proportion of martensite at 1.5 mm from the outer wall (quenching end) does not meet the requirements of the present invention.

[0078] It should be noted that the above examples are only specific embodiments of the present invention, and the present invention is obviously not limited to the above examples, and there are many similar variations. All variations directly derived or associated from the contents disclosed by the technicians in this field should fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a seamless outer wall wear-resistant steel pipe, the method comprising steelmaking, tube blank manufacturing, annular furnace heating, perforation, continuous rolling, stretching or sizing, characterized in that: There is also an online quenching step, which includes: In the first step, after the final rolling of the steel pipe, the water pressure and flow of each group of water rings on the online quenching equipment are adjusted to achieve centralized cooling, so that more than 95% of the martensite structure is generated within 1.5mm from the outer wall of the steel pipe; the water pressure and flow of each water ring of the online quenching are controlled to be constant, the water pressure in a single water ring is ≥0.45MPa, and the flow of a single water ring is ≥125m 3 / h; The second step is to adjust the roller speed of the steel pipe conveying in the online quenching and cooling zone to control the quenching and cooling temperature gradient in the direction of the steel pipe wall thickness, indirectly control the depth of the hardened layer, and adjust the ratio of martensite and non-martensite structures in the direction of the steel pipe wall thickness, so that the 50% martensite area of ​​the steel pipe is between 1 / 2 and 2 / 3 of the wall thickness; control the roller speed V of the steel pipe conveying in the online quenching and cooling zone and the steel pipe wall thickness T to meet the following corresponding relationship: If 8≤T<12, V=1.8±0.5; If 12≤T<16, V=1.6±0.5; If 16≤T<20, V=1.4±0.5; If 20≤T<25, V=1.3±0.5; If 25≤T<30, V=1.2±0.5; If 30≤T≤40, V=1.0±0.5, where the unit of roller speed V is m / s and the unit of steel pipe wall thickness T is mm; In the produced outer wall wear-resistant seamless steel pipe, the alloy component system is C-Si-Mn-Cr, wherein 0.5%≤C≤0.7%, 0.2%≤Si≤0.3%, 0.5%≤Mn≤0.85%, 0.3%≤Cr≤0.9%, and at the same time, the content of C, Mn and Cr elements meets the requirements: Cep=C+Mn / 6+Cr / 5≥0.75%; The proportion of martensite within 1.5mm from the outer wall of the steel pipe is ≥95%.

2. The method for manufacturing a seamless steel pipe with outer wall wear-resistant according to claim 1, characterized in that: In the first step, the online quenching equipment is controlled so that the start-cooling temperature of the online quenching is ≥ the Ar3 temperature of the steel grade + 40°C.

3. The method for manufacturing a seamless outer wall wear-resistant steel pipe according to claim 1, characterized in that: In the first step, the total number of online quenching water rings opened is controlled to remain constant, and all water rings are opened.

4. The method for manufacturing a seamless outer wall wear-resistant steel pipe according to claim 1, characterized in that: In the second step, the temperature of the outer wall of the steel pipe out of the cooling zone is controlled to be ≤Ms temperature-120°C.

5. The method for manufacturing a seamless steel pipe with outer wall wear-resistant according to claim 1, characterized in that: The tube blank is manufactured by directly casting smelted molten steel, or by forging or rolling after casting.

6. The method for manufacturing a seamless outer wall wear-resistant steel pipe according to claim 1, characterized in that: When the tube billet is heated in the annular furnace, the heating temperature is in the temperature range of 1200 to 1300°C, and the holding time is 1 to 4 hours.

7. An outer wall wear-resistant seamless steel pipe produced by the manufacturing method according to any one of claims 1 to 6, characterized in that: In the outer wall wear-resistant seamless steel pipe, 50% of the martensite area of ​​the steel pipe is between 1 / 2 and 2 / 3 of the wall thickness, that is, the steel pipe is hardened at a depth of 1 / 2 to 2 / 3 from the outer wall to the inside; The impact absorption energy of the steel pipe inner wall sample Kv8 ≥ 32J, the sample size during the test is 10mm×10mm×55mm, the test temperature is 20℃, and the impact sample is processed along the longitudinal direction.

Images