A steel for wear-resistant welded pipes, its preparation method, and welded pipes

Abstract

The present invention relates to the technical field of metal materials, and provides a steel for wear-resistant welded pipes, a preparation method thereof, and a welded pipe. The steel for wear-resistant welded pipes is composed of the following components in mass percentage: C 0.04% - 0.06%, Si 0.5% - 0.8%, Mn 0.5% - 1.0%, Cu 3% - 4%, Cr 10.5% - 12.5%, Ni 3.5% - 4.5%, V 2.5% - 4.5%, Mo 0.1% - 0.5%, La 0.04% - 0.08%, Sm 0.01% - 0.05%, P ≤ 0.06%, S ≤ 0.03%, the balance being Fe and other inevitable impurities, and 10.93% ≤ Cr + Mo - La + Sm ≤ 12.61%. Through the above technical solution, the problem of insufficient wear resistance of the steel for welded pipes in the related art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and specifically, to a wear-resistant steel pipe for welding, its preparation method, and a welded pipe. Background Art

[0002] Steel, with its excellent comprehensive properties, has become a key material for constructing various infrastructure and industrial equipment. Welded pipes are one of its important application fields. From urban water supply and heating pipe networks to the structural supports in industrial plants and then to the long-distance transportation of oil and gas, welded pipes provide a solid guarantee for the normal operation of society. However, in environments with friction and impact, such as ventilation pipes in mine mining, due to the harsh underground environment and the collision and friction of ore particles, the wear resistance of welded pipes is insufficient, and defects such as cracks and holes are likely to occur, resulting in premature damage to the pipes and being unable to meet the long-term use requirements. The performance of welded pipes is closely related to the properties of the steel itself. Therefore, it is necessary to develop wear-resistant steel pipes for welding to improve the wear resistance of steel to meet the use requirements under different working conditions and extend the service life of welded pipes. Summary of the Invention

[0003] The present invention provides a wear-resistant steel pipe for welding, its preparation method, and a welded pipe, which solve the problem of insufficient wear resistance of the steel pipe for welding in the related art.

[0004] The technical solution of the present invention is as follows:

[0005] The present invention provides a wear-resistant steel pipe for welding, which is composed of the following components by mass percentage: C 0.04% - 0.06%, Si 0.5% - 0.8%, Mn 0.5% - 1.0%, Cu 3% - 4%, Cr 10.5% - 12.5%, Ni 3.5% - 4.5%, V 2.5% - 4.5%, Mo 0.1% - 0.5%, La 0.04% - 0.08%, Sm 0.01% - 0.05%, P ≤ 0.06%, S ≤ 0.03%, and the balance is Fe and other inevitable impurities, and 10.93% ≤ Cr + Mo - La + Sm ≤ 12.61%.

[0006] Controlling the mass percentage content of carbon (C) at 0.04% - 0.06% can not only ensure the strength basis of the wear-resistant steel pipe for welding but also prevent the excessive decrease of the toughness of the steel due to too high carbon content, thus achieving a good balance between strength and toughness. The wear-resistant steel pipe for welding can maintain structural stability when bearing pressure and wear after being made into a welded pipe.

[0007] Controlling the mass percentage content of silicon (Si) at 0.5% - 0.8%, silicon mainly acts as a deoxidizer and strengthener in the steel, which has a positive impact on the preparation and processing performance of the wear-resistant steel pipe for welding.

[0008] Controlling the mass percentage of manganese (Mn) within 0.5% - 1.0% can ensure the strength and hardenability of the steel. It can form manganese sulfide with sulfur, improve the hot working performance of the steel, reduce the phenomenon of hot brittleness, and enhance its applicability under complex working conditions after being made into welded pipes.

[0009] Controlling the mass percentage of copper (Cu) within 3% - 4% can effectively reduce the corrosion rate of the steel in some environments with corrosive media. At the same time, the addition of copper can also ensure the strength of the steel to a certain extent.

[0010] Controlling the mass percentage of nickel (Ni) within 3.5% - 4.5% can improve the low - temperature performance of the steel, enabling the steel to maintain good mechanical properties in low - temperature environments.

[0011] Controlling the mass percentage of vanadium (V) within 2.5% - 4.5%, the carbides of vanadium are dispersed in the steel, which can effectively hinder the movement of dislocations, thus ensuring the hardness and wear resistance of the steel.

[0012] As a further technical solution, the steel for wear - resistant welded pipes consists of the following components by mass percentage: C 0.04% - 0.06%, Si 0.5% - 0.8%, Mn 0.5% - 1.0%, Cu 3% - 4%, Cr 10.5% - 12.5%, Ni 3.5% - 4.5%, V 2.5% - 4.5%, Mo 0.1% - 0.5%, La 0.04% - 0.08%, Sm 0.01% - 0.05%, P ≤ 0.06%, S ≤ 0.03%, and the balance is Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.19%, 3.37% ≤ Ni - Mo ≤ 3.67%.

[0013] In the present invention, when the components of the steel for wear - resistant welded pipes satisfy the following relational expressions: Cr + Mo - La + Sm = 12.19%, 3.37% ≤ Ni - Mo ≤ 3.67%, the wear resistance of the steel for welded pipes is further improved.

[0014] The present invention also provides a preparation method for the steel for wear - resistant welded pipes, which includes the following steps:

[0015] S1. Take raw materials according to the components of the steel for wear - resistant welded pipes for melting, refining, and continuous casting to obtain a billet;

[0016] S2. Hot - roll and heat - treat the billet to obtain the steel for wear - resistant welded pipes.

[0017] As a further technical solution, the temperature of the melting is 1630 - 1680 °C, and the time is 35 - 50 min.

[0018] As a further technical solution, the refining temperature is 1680~1730°C and the time is 10~20 min.

[0019] As a further technical solution, the starting rolling temperature of the hot rolling is 1110~1150°C and the finishing rolling temperature is 900~920°C.

[0020] In the present invention, the starting rolling temperature of the continuous casting billet for hot rolling is set to 1110~1150°C. At this temperature, the continuous casting billet has good plasticity and low deformation resistance, which is convenient for rolling processing. By controlling the finishing rolling temperature at 900~920°C, the grain can be refined, ensuring that the steel can obtain good organizational structure and performance during the rolling process.

[0021] As a further technical solution, during the heat treatment, the temperature is raised to 620~720°C at a rate of 70~80°C / min, held for 3~5 h, and then cooled to room temperature at a rate of 50~70°C / min.

[0022] As a further technical solution, the heat treatment includes a first-stage heat treatment, a second-stage heat treatment, and a third-stage heat treatment;

[0023] In the first-stage heat treatment, the temperature is raised to 350~450°C at a rate of 30~40°C / min and held for 0.8~1.5 h;

[0024] In the second-stage heat treatment, the temperature is raised to 620~720°C at a rate of 50~60°C / min and held for 2.2~3.5 h;

[0025] In the third-stage heat treatment, the temperature is lowered to 400~500°C at a first rate of 45~55°C / min, held for 1.5~2.5 h, and then cooled to room temperature at a second rate of 50~70°C / min.

[0026] In the present invention, sectional heat treatment is adopted during the heat treatment. Through a specific heat treatment strategy, while ensuring the wear resistance of the steel for the wear-resistant welded pipe, the strength is also improved.

[0027] As a further technical solution, during the third-stage heat treatment, the first rate is greater than the second rate.

[0028] In the present invention, setting the first rate greater than the second rate during the third-stage heat treatment further improves the strength of the steel for the wear-resistant welded pipe.

[0029] The present invention also provides a welded pipe made of the steel for the wear-resistant welded pipe described above or the wear-resistant welded pipe made by the preparation method described above.

[0030] The working principle and beneficial effects of the present invention are as follows:

[0031] In the present invention, by reasonably proportioning and strictly controlling the content of each alloy element of the steel for welded pipes, controlling 10.93% ≤ Cr + Mo - La + Sm ≤ 12.61%, the grain size can be refined, the wear resistance of the steel for welded pipes can be improved, and the steel for welded pipes is suitable for various engineering fields with high requirements for the wear resistance of pipes. Detailed implementation mode

[0032] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of the present invention.

[0033] Embodiment 1

[0034] The wear-resistant steel for welded pipes is composed of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 11.8%, Ni 3.6%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, and the balance is Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.19%;

[0035] The preparation method of the wear-resistant steel for welded pipes includes the following steps:

[0036] S1. Take raw materials according to the components of the wear-resistant steel for welded pipes, melt them at 1630 °C for 50 min, refine them at 1680 °C for 20 min, and continuously cast to obtain a billet;

[0037] S2. Hot-roll the billet and perform heat treatment to obtain the wear-resistant steel for welded pipes; among them, the starting rolling temperature of the hot rolling is 1110 °C, and the final rolling temperature is 920 °C; during the heat treatment, it is heated to 720 °C at a rate of 70 °C / min, held for 3 h, and then cooled to room temperature at a rate of 70 °C / min for heat treatment.

[0038] Embodiment 2

[0039] The wear-resistant steel for welded pipes is composed of the following components by mass percentage: C 0.04%, Si 0.5%, Mn 0.5%, Cu 3%, Cr 10.5%, Ni 3.5%, V 2.5%, Mo 0.5%, La 0.08%, Sm 0.01%, P 0.06%, S 0.03%, and the balance is Fe and other inevitable impurities, and Cr + Mo - La + Sm = 10.93%;

[0040] The preparation method of the wear-resistant steel for welded pipes includes the following steps:

[0041] S1. Take raw materials according to the components of the steel for wear-resistant welded pipes, melt them at 1680 °C for 35 min, refine them at 1730 °C for 10 min, and then continuously cast to obtain a casting blank.

[0042] S2. Hot-roll the casting blank and perform heat treatment to obtain the steel for wear-resistant welded pipes. Among them, the starting rolling temperature for hot rolling is 1150 °C, and the final rolling temperature is 900 °C; during heat treatment, it is heated to 620 °C at a rate of 80 °C / min, held for 4 h, and then cooled to room temperature at a rate of 60 °C / min for heat treatment.

[0043] Example 3

[0044] The steel for wear-resistant welded pipes is composed of the following components by mass percentage: C 0.06%, Si 0.8%, Mn 1.0%, Cu 4%, Cr 12.5%, Ni 4.5%, V 4.5%, Mo 0.1%, La 0.04%, Sm 0.05%, P 0.04%, S 0.03%, the balance being Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.61%;

[0045] The preparation method of the steel for wear-resistant welded pipes includes the following steps:

[0046] S1. Take raw materials according to the components of the steel for wear-resistant welded pipes, melt them at 1660 °C for 45 min, refine them at 1710 °C for 16 min, and then continuously cast to obtain a casting blank.

[0047] S2. Hot-roll the casting blank and perform heat treatment to obtain the steel for wear-resistant welded pipes. Among them, the starting rolling temperature for hot rolling is 1125 °C, and the final rolling temperature is 910 °C; during heat treatment, it is heated to 680 °C at a rate of 75 °C / min, held for 5 h, and then cooled to room temperature at a rate of 50 °C / min for heat treatment.

[0048] Example 4

[0049] The difference between this example and Example 1 is only that the steel for wear-resistant welded pipes is composed of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 11.8%, Ni 4.35%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, the balance being Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.19%.

[0050] Example 5

[0051] The difference between this embodiment and Embodiment 1 lies only in the steel for wear-resistant welded pipes, which is composed of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 11.8%, Ni 4.1%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, and the balance is Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.19%, Ni - Mo = 3.67%.

[0052] Embodiment 6

[0053] The difference between this embodiment and Embodiment 1 lies only in the steel for wear-resistant welded pipes, which is composed of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 11.8%, Ni 3.8%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, and the balance is Fe and other inevitable impurities, and Cr + Mo - La + Sm = 12.19%, Ni - Mo = 3.37%.

[0054] Embodiment 7

[0055] The difference between this embodiment and Embodiment 6 lies only in that during heat treatment, it undergoes the first-stage heat treatment, the second-stage heat treatment, and the third-stage heat treatment in sequence;

[0056] The first-stage heat treatment is heated to 450°C at a rate of 20°C / min and held for 0.8 h;

[0057] The second-stage heat treatment is heated to 720°C at a rate of 40°C / min and held for 2.2 h;

[0058] The third-stage heat treatment is cooled to 400°C at a rate of 35°C / min, held for 2.5 h, and then cooled to room temperature at a rate of 70°C / min.

[0059] Embodiment 8

[0060] The difference between this embodiment and Embodiment 6 lies only in that during heat treatment, it undergoes the first-stage heat treatment, the second-stage heat treatment, and the third-stage heat treatment in sequence;

[0061] The first-stage heat treatment is heated to 450°C at a rate of 50°C / min and held for 0.8 h;

[0062] The second-stage heat treatment is heated to 720°C at a rate of 70°C / min and held for 2.2 h;

[0063] The third-stage heat treatment cools down to 400 °C at a rate of 65 °C / min, holds for 2.5 h, and then cools to room temperature at a rate of 70 °C / min.

[0064] Example 9

[0065] The difference between this example and Example 6 is only that during the heat treatment, it undergoes the first-stage heat treatment, the second-stage heat treatment, and the third-stage heat treatment in sequence;

[0066] The first-stage heat treatment heats up to 450 °C at a rate of 30 °C / min and holds for 0.8 h;

[0067] The second-stage heat treatment heats up to 720 °C at a rate of 50 °C / min and holds for 2.2 h;

[0068] The third-stage heat treatment cools down to 400 °C at a rate of 45 °C / min, holds for 2.5 h, and then cools to room temperature at a rate of 70 °C / min.

[0069] Example 10

[0070] The difference between this example and Example 6 is only that during the heat treatment, it undergoes the first-stage heat treatment, the second-stage heat treatment, and the third-stage heat treatment in sequence;

[0071] The first-stage heat treatment heats up to 450 °C at a rate of 40 °C / min and holds for 0.8 h;

[0072] The second-stage heat treatment heats up to 720 °C at a rate of 60 °C / min and holds for 2.2 h;

[0073] The third-stage heat treatment cools down to 400 °C at a rate of 55 °C / min, holds for 2.5 h, and then cools to room temperature at a rate of 70 °C / min.

[0074] Example 11

[0075] The difference between this example and Example 6 is only that during the heat treatment, it undergoes the first-stage heat treatment, the second-stage heat treatment, and the third-stage heat treatment in sequence;

[0076] The first-stage heat treatment heats up to 350 °C at a rate of 40 °C / min and holds for 1.5 h;

[0077] The second-stage heat treatment heats up to 620 °C at a rate of 60 °C / min and holds for 3.5 h;

[0078] The third-stage heat treatment cools down to 500 °C at a rate of 55 °C / min, holds for 1.5 h, and then cools to room temperature at a rate of 70 °C / min.

[0079] Example 12

[0080] The difference between this embodiment and Embodiment 11 is only that in the third-stage heat treatment, the temperature is decreased to 500 °C at a rate of 55 °C / min, after holding for 1.5 h, it is cooled to room temperature at a rate of 55 °C / min.

[0081] Embodiment 13

[0082] The difference between this embodiment and Embodiment 11 is only that in the third-stage heat treatment, the temperature is decreased to 500 °C at a rate of 55 °C / min, after holding for 1.5 h, it is cooled to room temperature at a rate of 50 °C / min.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Embodiment 1 is only that the steel for wear-resistant welded pipes consists of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 10%, Ni 3.6%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, the balance being Fe and other inevitable impurities, and Cr + Mo - La + Sm = 10.39%.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Embodiment 1 is only that the steel for wear-resistant welded pipes consists of the following components by mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu 3.5%, Cr 13%, Ni 3.6%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, the balance being Fe and other inevitable impurities, and Cr + Mo - La + Sm = 13.39%.

[0087] Experimental Example 1

[0088] The wear resistance of the steel for wear-resistant welded pipes prepared in Embodiments 1 to 6 and Comparative Examples 1 to 2 was respectively tested: according to the standard ASTM-G65-15, an abrasive wear experiment was carried out, using 40 - 70 mesh quartz sand, and a 2000 r wear experiment was carried out at 25 °C. The wear loss weight = the weight of the specimen before wear - the weight of the specimen after wear. The results are shown in Table 1 below.

[0089] Table 1 Test Results of Wear Resistance

[0090]

[0091] In Comparative Example 1, the content relationship of Cr, Mo, La, and Sm is Cr + Mo - La + Sm = 10.39%, and the wear weight loss of the steel obtained is 0.796 g; in Comparative Example 2, the content relationship of Cr, Mo, La, and Sm is Cr + Mo - La + Sm = 13.39%, and the wear weight loss of the steel obtained is 0.800 g; compared with Comparative Examples 1 - 2, in Examples 1 - 3, the content relationship of Cr, Mo, La, and Sm is 10.93% ≤ Cr + Mo - La + Sm ≤ 12.61%, and the wear weight loss of the wear-resistant welded pipe steel finally obtained is below 0.700 g. It can be seen that Cr can form various carbides in the steel, which are distributed in the steel matrix, hinder the deformation and cutting of the material surface during wear, and improve the wear resistance of the steel. Mo can regulate the precipitation and growth of carbides, and La and Sm can purify the molten steel. However, if there is too much La or the content relationship with other elements is not reasonably regulated, it may cause stress concentration due to the increase in the formation of inclusions, which is not conducive to the stability of the phase structure in the steel and the improvement of wear resistance. Therefore, by regulating the contents of Cr, Mo, La, and Sm and making the components of the four satisfy the relational expression 10.93% ≤ Cr + Mo - La + Sm ≤ 12.61%, and the element relationships interact with each other, the wear resistance of the wear-resistant welded pipe steel is significantly improved.

[0092] Also, since Ni can reduce the critical cooling rate of the steel, enabling more time for nucleation and growth of grains during cooling to achieve grain refinement, and Mo regulates the growth of grains through segregation at the grain boundaries. Therefore, in order to further improve the wear resistance of the steel, in Examples 5 - 6, on the basis of Cr + Mo - La + Sm = 12.19%, 3.37% ≤ Ni - Mo ≤ 3.67% is further defined, and the wear weight loss of the wear-resistant welded pipe steel finally obtained reaches below 0.500 g.

[0093] Experimental Example 2

[0094] In accordance with the standard GB / T 228.1 - 2021 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature", the tensile strength tests were respectively carried out on the wear-resistant welded pipe steels obtained in Examples 6 - 13, and the test results are shown in Table 2.

[0095] Table 2 Strength test results

[0096]

[0097] In order to improve the strength of the wear-resistant welded pipe steel and enhance the uniformity of the steel structure, in Examples 7 - 13 (compared with Example 6), sectional heat treatment was adopted in the process, and the tensile strength of the wear-resistant welded pipe steel was increased from 1880 MPa to above 1994 MPa.

[0098] Meanwhile, the heating rate and cooling rate of heat treatment affect the uniform growth of grains and the movement of dislocations. To further improve the strength, the heating rate and cooling rate parameters during heat treatment in Examples 9 to 11 (compared with Examples 7 to 8) are as follows: in the first-stage heat treatment, the temperature is raised at a rate of 30 to 40 °C / min, in the second-stage heat treatment, the temperature is raised at a rate of 50 to 60 °C / min, and in the third-stage heat treatment, the temperature is lowered at a rate of 45 to 55 °C / min. Finally, the tensile strength of the wear-resistant welded pipe steel is further increased to more than 2090 MPa, effectively avoiding the defects that too high or too low heating rate and cooling rate are likely to cause large residual stresses in the steel and are not conducive to obtaining high-strength steel.

[0099] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A steel for wear-resistant welded pipe, characterized in that: It is composed of the following components in mass percentage: C 0.04%~0.06%, Si0.5%~0.8%, Mn 0.5%~1.0%, Cu 3%~4%, Cr 10.5%~12.5%, Ni 3.5%~4.5%, V 2.5%~4.5%, Mo0.1%~0.5%, La 0.04%~0.08%, Sm 0.01%~0.05%, P≤0.06%, S≤0.03%, the balance is Fe and other inevitable impurities, and 10.93%≤Cr+Mo-La+Sm≤12.61%; The method for preparing the wear-resistant welded pipe steel comprises the following steps: S1. According to the composition of the steel for wear-resistant welded pipe, raw materials are melted, refined, and continuously cast to obtain ingots; S2, hot rolling and heat treating the ingot to obtain steel for wear-resistant welded pipe; The heat treatment includes a first stage heat treatment, a second stage heat treatment and a third stage heat treatment; The first heat treatment is to increase the temperature to 350-450°C at a rate of 30-40°C / min and keep the temperature for 0.8-1.5h; The second heat treatment is carried out by heating the temperature to 620-720°C at a rate of 50-60°C / min and keeping the temperature for 2.2-3.5h; The third stage heat treatment is to cool the temperature to 400-500°C at a first rate of 45-55°C / min, keep the temperature for 1.5-2.5h, and then cool the temperature to room temperature at a second rate of 50-70°C / min.

2. The wear-resistant welded pipe steel according to claim 1, characterized in that: It is composed of the following components in mass percentage: C 0.04%~0.06%, Si 0.5%~0.8%, Mn 0.5%~1.0%, Cu 3%~4%, Cr 10.5%~12.5%, Ni 3.5%~4.5%, V 2.5%~4.5%, Mo 0.1%~0.5%, La 0.04%~0.08%, Sm 0.01%~0.05%, P≤0.06%, S≤0.03%, and the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=12.19%, 3.37%≤Ni-Mo≤3.67%.

3. The method for preparing steel for wear-resistant welded pipe according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. According to the composition of the steel for wear-resistant welded pipe, raw materials are melted, refined, and continuously cast to obtain ingots; S2. hot rolling and heat treating the ingot to obtain steel for wear-resistant welded pipe.

4. The method for preparing steel for wear-resistant welded pipe according to claim 3, characterized in that: The smelting temperature is 1630-1680° C. and the smelting time is 35-50 min.

5. The method for preparing steel for wear-resistant welded pipe according to claim 3, characterized in that: The refining temperature is 1680-1730° C. and the refining time is 10-20 min.

6. The method for preparing steel for wear-resistant welded pipe according to claim 3, characterized in that: The hot rolling start temperature is 1110-1150°C, and the final rolling temperature is 900-920°C.

7. The method for preparing steel for wear-resistant welded pipe according to claim 1, characterized in that: During the third stage of heat treatment, the first rate is greater than the second rate.

8. A welded pipe, characterized in that: The wear-resistant welded pipe steel is made from the wear-resistant welded pipe steel according to any one of claims 1 to 2 or the wear-resistant welded pipe steel made by the preparation method according to any one of claims 3 to 7.

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