Steel for wear-resistant welded pipe, preparation method of steel and welded pipe

Abstract

The invention relates to the technical field of metal materials, and provides steel for a wear-resistant welded pipe, a preparation method of the steel and the welded pipe. The steel for the wear-resistant welded pipe is composed of the following components in percentage by mass: 0.04%-0.06% of C, 0.5%-0.8% of Si, 0.5%-1.0% of Mn, 3%-4% of Cu, 10.5%-12.5% of Cr, 3.5%-4.5% of Ni, 2.5%-4.5% of V, 0.1%-0.5% of Mo, 0.04%-0.08% of La, 0.01%-0.05% of Sm, less than or equal to 0.06% of P, less than or equal to 0.03% of S and the balance of Fe and other inevitable impurities, and Cr + Mo-La + Sm is more than or equal to 10.93% and less than or equal to 12.61%. By means of the technical scheme, the problem that in the related technology, steel for the welded pipe is insufficient in abrasion resistance is solved.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a wear-resistant welded pipe steel and a preparation method thereof and a welded pipe. Background Art

[0002] Steel has become a key material for building various infrastructure and industrial equipment due to its excellent comprehensive performance, and welded pipes are one of its important application areas. From urban water supply and heating pipelines, to the structural support of industrial plants, to the long-distance transportation of oil and natural gas, welded pipes provide a solid guarantee for the normal operation of society. However, in environments with friction and impact, such as ventilation ducts in mining, due to the harsh underground environment, the collision and friction of ore particles, the wear resistance of welded pipes is insufficient, and cracks, holes and other defects are prone to occur, resulting in premature damage to the pipeline and unable to meet long-term use requirements. The performance of welded pipes is closely related to the performance of the steel itself. Therefore, it is necessary to develop steel for welded pipes with higher wear resistance and 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 for welded pipe, a preparation method thereof and a welded pipe, which solves the problem of insufficient wear resistance of the steel for welded pipe in the related art.

[0004] The technical solution of the present invention is as follows: The invention provides a wear-resistant welded pipe steel, which 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%, 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%.

[0005] The mass percentage of carbon (C) is controlled at 0.04%~0.06%, which can not only ensure the strength basis of wear-resistant welded pipe steel, but also prevent excessive decrease in steel toughness due to excessive carbon content, thereby achieving a good balance between strength and toughness. After being made into welded pipes, wear-resistant welded pipe steel can maintain structural stability when subjected to pressure and wear.

[0006] The mass percentage of silicon (Si) is controlled at 0.5%~0.8%. Silicon mainly acts as a deoxidizer and strengthener in steel, which has a positive effect on the preparation and processing performance of steel for wear-resistant welded pipes.

[0007] The mass percentage of manganese (Mn) is controlled at 0.5%~1.0%, which can ensure the strength and hardenability of the steel. It can form manganese sulfide with sulfur, improve the hot processing performance of the steel, reduce hot brittleness, and enhance its applicability under complex working conditions after being made into welded pipes.

[0008] The mass percentage of copper (Cu) is controlled at 3%~4%. In some environments with corrosive media, it can effectively reduce the corrosion rate of steel. At the same time, the addition of copper can also ensure the strength of steel to a certain extent.

[0009] The mass percentage of nickel (Ni) is controlled at 3.5%~4.5%, which can improve the low-temperature performance of steel and enable the steel to maintain good mechanical properties in low-temperature environments.

[0010] The mass percentage of vanadium (V) is controlled at 2.5%~4.5%. Vanadium carbides are dispersed in the steel and can effectively hinder dislocation movement, thereby ensuring the hardness and wear resistance of the steel.

[0011] As a further technical solution, the wear-resistant welded pipe steel 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%, V2.5%~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 is Fe and other inevitable impurities, and Cr+Mo-La+Sm=12.19%, 3.37%≤Ni-Mo≤3.67%.

[0012] In the present invention, when the composition of the wear-resistant welded pipe steel satisfies the following relationship: Cr+Mo-La+Sm=12.19%, 3.37%≤Ni-Mo≤3.67%, the wear resistance of the welded pipe steel is further improved.

[0013] The present invention also proposes a method for preparing the wear-resistant welded pipe steel, comprising 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.

[0014] As a further technical solution, the smelting temperature is 1630-1680°C and the smelting time is 35-50 minutes.

[0015] As a further technical solution, the refining temperature is 1680~1730℃ and the time is 10~20min.

[0016] As a further technical solution, the starting temperature of the hot rolling is 1110-1150°C, and the final rolling temperature is 900-920°C.

[0017] In the present invention, the starting rolling temperature of the hot rolling of the ingot is set to 1110-1150°C. At this temperature, the ingot has good plasticity and low deformation resistance, which is convenient for rolling processing. The final rolling temperature is controlled at 900-920°C, which can refine the grains and ensure that the steel can obtain good organizational structure and performance during the rolling process.

[0018] 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, kept at that temperature for 3-5 hours, and then cooled to room temperature at a rate of 50-70°C / min.

[0019] 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; 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.

[0020] In the present invention, segmented heat treatment is adopted during heat treatment, and through a specific heat treatment strategy, the wear resistance of the steel for the wear-resistant welded pipe is ensured while the strength is improved.

[0021] As a further technical solution, during the third stage of heat treatment, the first rate is greater than the second rate.

[0022] In the present invention, the first rate is set to be greater than the second rate during the third stage heat treatment, thereby further improving the strength of the steel for the wear-resistant welded pipe.

[0023] The present invention also provides a welded pipe, which is made from the wear-resistant welded pipe steel or the wear-resistant welded pipe steel made by the preparation method.

[0024] The working principle and beneficial effects of the present invention are: In the present invention, by reasonably proportioning and strictly controlling the content of each alloy element of the welded pipe steel, 10.93%≤Cr+Mo-La+Sm≤12.61% is controlled, the grains can be refined, the wear resistance of the welded pipe steel can be improved, and the welded pipe steel can be suitable for various engineering fields that require high wear resistance of pipes. DETAILED DESCRIPTION

[0025] The following will be combined with 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 part of the embodiments of the present invention, not all of the embodiments. 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.

[0026] Example 1 Steel for wear-resistant welded pipes, composed of the following components in mass percentage: C 0.05%, Si 0.68%, Mn 0.87%, Cu3.5%, Cr 11.8%, Ni 3.6%, V 3.2%, Mo 0.43%, La 0.068%, Sm 0.028%, P 0.05%, S 0.02%, the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=12.19%; The preparation method of steel for wear-resistant welded pipe comprises the following steps: S1. According to the composition of the steel for wear-resistant welded pipe, raw materials are melted at 1630°C for 50 minutes, refined at 1680°C for 20 minutes, and continuously cast to obtain ingots; S2. Hot rolling the ingot and heat treating it to obtain steel for wear-resistant welded pipe; wherein the starting rolling temperature of hot rolling is 1110°C and the final rolling temperature is 920°C; during heat treatment, the temperature is raised to 720°C at a rate of 70°C / min, kept at that temperature for 3h, and then cooled to room temperature at a rate of 70°C / min for heat treatment.

[0027] Example 2 Steel for wear-resistant welded pipes, composed of the following components in mass percentage: C 0.04%, Si 0.5%, Mn 0.5%, Cu3%, Cr 10.5%, Ni 3.5%, V 2.5%, Mo 0.5%, La 0.08%, Sm 0.01%, P 0.06%, S 0.03%, the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=10.93%; The preparation method of steel for wear-resistant welded pipe comprises the following steps: S1. According to the composition of the steel for wear-resistant welded pipe, raw materials are smelted at 1680°C for 35 minutes, refined at 1730°C for 10 minutes, and continuously cast to obtain ingots; S2. Hot rolling the ingot and heat treating it to obtain steel for wear-resistant welded pipe; wherein the starting rolling temperature of hot rolling is 1150°C and the final rolling temperature is 900°C; during heat treatment, the temperature is raised to 620°C at a rate of 80°C / min, kept at that temperature for 4 hours, and then cooled to room temperature at a rate of 60°C / min for heat treatment.

[0028] Example 3 Steel for wear-resistant welded pipes is composed of the following components in mass percentage: C 0.06%, Si 0.8%, Mn 1.0%, Cu4%, 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 is Fe and other inevitable impurities, and Cr+Mo-La+Sm=12.61%; The preparation method of steel for wear-resistant welded pipe comprises the following steps: S1. According to the composition of the steel for wear-resistant welded pipe, raw materials are melted at 1660°C for 45 minutes, refined at 1710°C for 16 minutes, and continuously cast to obtain ingots; S2. Hot rolling the ingot and heat treating it to obtain steel for wear-resistant welded pipe; wherein the starting rolling temperature of hot rolling is 1125°C and the final rolling temperature is 910°C; during heat treatment, the temperature is raised to 680°C at a rate of 75°C / min, kept at that temperature for 5h, and then cooled to room temperature at a rate of 50°C / min for heat treatment.

[0029] Example 4 The difference between this embodiment and embodiment 1 is that the steel for wear-resistant welded pipe is composed of the following components in 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%, and the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=12.19%.

[0030] Example 5 The difference between this embodiment and embodiment 1 is that the steel for wear-resistant welded pipe is composed of the following components in 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%.

[0031] Example 6 The difference between this embodiment and embodiment 1 is that the steel for wear-resistant welded pipe is composed of the following components in 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%.

[0032] Example 7 The difference between this embodiment and embodiment 6 is that the heat treatment is sequentially performed through the first stage heat treatment, the second stage heat treatment and the third stage heat treatment; The first heat treatment was heated to 450°C at a rate of 20°C / min and kept at this temperature for 0.8h; The second heat treatment was heated to 720°C at a rate of 40°C / min and kept at this temperature for 2.2h; The third heat treatment was performed by cooling the temperature to 400°C at a rate of 35°C / min, keeping the temperature for 2.5h, and then cooling to room temperature at a rate of 70°C / min.

[0033] Example 8 The difference between this embodiment and embodiment 6 is that the heat treatment is sequentially performed through the first stage heat treatment, the second stage heat treatment and the third stage heat treatment; The first heat treatment was heated to 450°C at a rate of 50°C / min and kept at this temperature for 0.8h; The second heat treatment was carried out by heating the temperature to 720°C at a rate of 70°C / min and keeping the temperature for 2.2h; The third heat treatment was performed by cooling the temperature to 400°C at a rate of 65°C / min, keeping the temperature for 2.5h, and then cooling to room temperature at a rate of 70°C / min.

[0034] Example 9 The difference between this embodiment and embodiment 6 is that the heat treatment is sequentially performed through the first stage heat treatment, the second stage heat treatment and the third stage heat treatment; The first heat treatment was heated to 450°C at a rate of 30°C / min and kept at this temperature for 0.8h; The second heat treatment was heated to 720°C at a rate of 50°C / min and kept at this temperature for 2.2h; The third heat treatment was performed by cooling the temperature to 400°C at a rate of 45°C / min, keeping the temperature for 2.5h, and then cooling to room temperature at a rate of 70°C / min.

[0035] Example 10 The difference between this embodiment and embodiment 6 is that the heat treatment is sequentially performed through the first stage heat treatment, the second stage heat treatment and the third stage heat treatment; The first heat treatment was heated to 450°C at a rate of 40°C / min and kept at this temperature for 0.8h; The second heat treatment was heated to 720°C at a rate of 60°C / min and kept at this temperature for 2.2h; The third heat treatment was performed by cooling the temperature to 400°C at a rate of 55°C / min, keeping the temperature for 2.5h, and then cooling to room temperature at a rate of 70°C / min.

[0036] Embodiment 11 The difference between this embodiment and embodiment 6 is that the heat treatment is sequentially performed through the first stage heat treatment, the second stage heat treatment and the third stage heat treatment; The first heat treatment was heated to 350°C at a rate of 40°C / min and kept at this temperature for 1.5h; The second heat treatment was carried out by heating the temperature to 620°C at a rate of 60°C / min and keeping the temperature for 3.5h; The third heat treatment was performed by cooling the temperature to 500°C at a rate of 55°C / min, keeping the temperature for 1.5h, and then cooling to room temperature at a rate of 70°C / min.

[0037] Example 12 The only difference between this embodiment and embodiment 11 is that in the third heat treatment, the temperature is lowered to 500°C at a rate of 55°C / min, kept at that temperature for 1.5 hours, and then cooled to room temperature at a rate of 55°C / min.

[0038] Embodiment 13 The only difference between this embodiment and embodiment 11 is that in the third heat treatment, the temperature is reduced to 500°C at a rate of 55°C / min, kept at that temperature for 1.5 hours, and then cooled to room temperature at a rate of 50°C / min.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the steel for wear-resistant welded pipe is composed of the following components in 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%, Sm0.028%, P 0.05%, S 0.02%, and the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=10.39%.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that the steel for wear-resistant welded pipe is composed of the following components in 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%, Sm0.028%, P 0.05%, S 0.02%, and the balance is Fe and other inevitable impurities, and Cr+Mo-La+Sm=13.39%.

[0041] Experimental Example 1 The wear resistance test of the wear-resistant welded pipe steels prepared in Examples 1 to 6 and Comparative Examples 1 to 2 was carried out respectively: an abrasive wear test was carried out according to standard ASTM-G65-15, using 40-70 mesh quartz sand, and a 2000r wear test was carried out at 25°C, and the wear weight loss = the weight of the sample before wear - the weight of the sample after wear. The results are shown in Table 1 below.

[0042] Table 1 Wear resistance test results

[0043] In comparative example 1, the content relationship of Cr, Mo, La, and Sm is Cr+Mo-La+Sm=10.39%, and the wear loss of the obtained steel is 0.796g; in comparative example 2, the content relationship of Cr, Mo, La, and Sm is Cr+Mo-La+Sm=13.39%, and the wear loss of the obtained steel is 0.800g; compared with comparative examples 1-2, the content relationship of Cr, Mo, La, and Sm in embodiments 1-3 is 10.93%≤Cr+Mo-La+Sm≤12.61%, and the wear loss of the steel for wear-resistant welded pipe finally obtained is below 0.700g. It can be seen that Cr can form a variety of carbides in steel and distribute them in the matrix of steel, which hinders the deformation and cutting of the material surface during wear and improves the wear resistance of steel. Mo can regulate the precipitation and growth of carbides, La and Sm can purify molten steel, but if there is too much La or the relationship with other element contents is not reasonably regulated, it may cause stress concentration due to the increased 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 content of Cr, Mo, La, and Sm and making the components of the four satisfy the relationship of 10.93%≤Cr+Mo-La+Sm≤12.61%, the element relationships are linked to each other, which significantly improves the wear resistance of steel for wear-resistant welded pipes.

[0044] Since Ni can reduce the critical cooling rate of steel, so that the grains have more time to nucleate and grow during the cooling process, thereby achieving grain refinement, and Mo regulates the growth of grains by segregation at the grain boundaries. Therefore, in order to further improve the wear resistance of steel, in Examples 5 to 6, on the basis of Cr+Mo-La+Sm=12.19%, 3.37%≤Ni-Mo≤3.67% is further limited, and the wear weight loss of the wear-resistant welded pipe steel finally obtained reaches less than 0.500g.

[0045] Experimental Example 2 According to the standard GB / T 228.1-2021 "Tensile test of metallic materials Part 1: Room temperature test method", the tensile strength test of the steel for wear-resistant welded pipe prepared in Examples 6 to 13 was carried out respectively, and the test results are shown in Table 2.

[0046] Table 2 Strength test results

[0047] In order to improve the strength of wear-resistant welded pipe steel and improve the uniformity of steel structure, in Examples 7 to 13 (compared with Example 6), a staged heat treatment is used in the process to increase the tensile strength of the wear-resistant welded pipe steel from 1880 MPa to more than 1994 MPa; At the same time, the heating rate and cooling rate of the heat treatment affect the uniform growth of grains and the movement of dislocations. In order to further improve the strength, the heating rate and cooling rate parameters during the heat treatment in Examples 9 to 11 (compared with Examples 7 to 8) are: the first stage of heat treatment is heated at a rate of 30 to 40 ° C / min, the second stage of heat treatment is heated at a rate of 50 to 60 ° C / min, and the third stage of heat treatment is cooled at a rate of 45 to 55 ° C / min. Finally, the tensile strength of the steel for wear-resistant welded pipe is further increased to more than 2090 MPa, effectively avoiding the defects of too high or too low heating rate and cooling rate, which are easy to cause large residual stress in the steel and are not conducive to obtaining high-strength steel.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should 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%, and the balance is Fe and other inevitable impurities, and 10.93%≤Cr+Mo-La+Sm≤12.61%.

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 3, characterized in that: During the heat treatment, the temperature is raised to 620-720° C. at a rate of 70-80° C. / min, kept at that temperature for 3-5 hours, and then cooled to room temperature at a rate of 50-70° C. / min.

8. The method for preparing steel for wear-resistant welded pipe according to claim 3, characterized in that: 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.

9. The method for preparing steel for wear-resistant welded pipe according to claim 8, characterized in that: During the third stage of heat treatment, the first rate is greater than the second rate.

10. 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 9.

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