High-strength steel for welded pipe, preparation method thereof and welded pipe

Abstract

The invention relates to the technical field of welded pipe steel, and proposes a high-strength steel for welded pipe, a preparation method thereof and a welded pipe. The steel for welded pipe comprises a matrix and a reinforcement phase, wherein the matrix is ​​composed of the following elements by weight percentage: C 0.06%-0.10%, Cr 16%-18%, Si 0.7%-0.8%, Mn 1.5%-2%, Al 0.02%-0.05%, Ni 0.5%-0.7%, Cu 1.5%-2.0%, La 0.1%-0.2%, Nd 0.2%-0.3%, Co 0.2%-0.3%, Ti 0.1%-0.3%, Mo 2%-3%, and the rest is Fe and inevitable impurities; the reinforcement phase is composed of silicon carbide and AlCoCrFeNi high entropy alloy powder; the mass ratio of the matrix to the reinforcement phase is 100:0.5-1. Through the above technical scheme, the problem of low yield strength of steel for welded pipe in the related art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of welded pipe steel, and in particular to a high-strength steel for welded pipe and a preparation method thereof and a welded pipe. Background Art

[0002] Welded pipes are made of steel plates or steel strips that are welded after being curled and formed. They are widely used in many fields such as construction, engineering, and manufacturing to transport liquids, gases, and solids. The chemical element ratio and production process of steel used for welded pipes will directly affect the strength of the steel. At present, the strength of steel used for welded pipes is limited. In some complex working conditions or scenarios with high strength requirements, it may not meet the use requirements and is prone to deformation, breakage and other problems.

[0003] With the continuous development of industry, industrial equipment is becoming more and more diversified, and the requirements for welded pipes are getting higher and higher. Therefore, it is necessary to improve the strength of steel used for welded pipes, and then improve the strength of welded pipes to adapt to the application of different industrial scenarios and expand the scope of application. Summary of the invention

[0004] The present invention provides a high-strength welded pipe and a preparation method thereof, which solves the problem of low yield strength of the welded pipe in the related art.

[0005] The technical solution of the present invention is as follows: The invention provides a high-strength steel for welded pipe, comprising a matrix and a reinforcement phase, wherein the matrix is ​​composed of the following elements by weight percentage: C 0.06%-0.10%, Cr 16%-18%, Si 0.7%-0.8%, Mn 1.5%-2%, Al 0.02%-0.05%, Ni 0.5%-0.7%, Cu 1.5%-2.0%, La 0.1%-0.2%, Nd 0.2%-0.3%, Co 0.2%-0.3%, Ti0.1%-0.3%, Mo 2%-3%, and the rest is Fe and inevitable impurities; the reinforcement phase is composed of silicon carbide and AlCoCrFeNi high entropy alloy powder; and the mass ratio of the matrix to the reinforcement phase is 100:0.5-1.

[0006] As a further technical solution, the mass ratio of the sum of the masses of Co and Ti to the mass ratio of Cr is 6.4≤Cr / (6Co+4Ti)≤7.2, and the mass ratio of Co to Ti is Co / Ti=1.

[0007] Among the three chemical elements Cr, Co and Ti, Co can promote the solid solution of Cr in steel and enhance the solid solution strengthening effect of Cr. Cr can synergistically affect the formation of carbides in steel with Ti and improve the precipitation strengthening effect. Co can create more favorable conditions for the precipitation strengthening of Ti, for example, by adjusting the matrix structure state of the steel, the carbides or carbonitrides formed by Ti are more evenly and finely dispersed. By limiting the ratio of the three elements Cr, Co and Ti, their respective strengthening effects in steel can be fully exerted, and a good synergistic effect can be generated between each other, so that the steel for welded pipes has good strength. The mass ratio of Co and Ti and the mass ratio of Cr is preferably Cr / (6Co+4Ti)=6.8, and Co / Ti=1.

[0008] As a further technical solution, the median particle size of the AlCoCrFeNi high entropy alloy powder is 100 μm.

[0009] As a further technical solution, the median particle size of the silicon carbide is 45 μm.

[0010] As a further technical solution, the mass ratio of the silicon carbide to the CoCrNii high entropy alloy powder is 50:0.1~0.3.

[0011] As a further technical solution, the mass ratio of the silicon carbide to the AlCoCrFeNi high entropy alloy powder is 50:0.2.

[0012] The present invention also proposes a method for preparing high-strength welded pipe steel, which is used to prepare the high-strength welded pipe steel, comprising the following steps: S1. Smelting according to the composition of the matrix to obtain molten steel; S2, adding the reinforcing phase to the molten steel, mixing, and casting to obtain a billet; S3. The billet is rolled and cooled to obtain high-strength steel for welded pipes.

[0013] As a further technical solution, in step S3, during the rolling, the starting rolling temperature is 1070-1100°C, and the finishing rolling temperature is 870-900°C.

[0014] As a further technical solution, in step S3, the cooling is divided into a first cooling stage and a second cooling stage, and the cooling rate of the first cooling stage is less than the cooling rate of the second cooling stage.

[0015] As a further technical solution, in step S3, during the cooling, a first cooling stage is first performed at a cooling rate of 10-15°C / s to 550-600°C, and then a second cooling stage is performed at a cooling rate of 15-25°C / s to 320-350°C.

[0016] As a further technical solution, in step S3, during the cooling, the material is first cooled to 580°C at a cooling rate of 12°C / s, and then cooled to 320°C at a cooling rate of 20°C / s.

[0017] The cooling rate of welded pipe steel during the cooling process affects the grain refinement and the tensile strength of the welded pipe steel. If the cooling rate is too high, a large amount of internal stress may be generated inside the steel, resulting in uneven shrinkage. If the cooling rate is too low, the grains of the steel may grow and the structure may become relatively coarse, resulting in a decrease in the tensile strength of the steel. The present invention, by limiting the cooling process, can better play the advantages of cooling, reduce coarse grains, promote grain refinement, and improve the tensile strength of the steel.

[0018] The present invention also proposes a welded pipe, which is obtained by welding a steel strip after coiling and forming, and the steel used for the steel strip is the steel prepared by the preparation method of the high-strength welded pipe steel or the high-strength welded pipe steel.

[0019] The working principle and beneficial effects of the present invention are: In the present invention, the strength of the welded pipe steel can be further improved by a reasonable ratio of multiple elements in the welded pipe steel. The addition of rare earth elements La and Nd can purify the grain boundary, refine the grain, reduce the grain boundary brittleness, and improve the strength and toughness of the steel. Ti is a strong carbide forming element, which can refine the grain and form TiC to enhance the precipitation strength; Mo can inhibit the enlargement of the grain and inhibit the decrease in the strength and toughness of the steel due to the coarse grain; the reinforcing phase composed of silicon carbide and AlCoCrFeNi high entropy alloy powder can hinder the dislocation movement, improve the interface bonding effect, and improve the strength of the welded pipe steel. Through the joint action of the elements and the reinforcing phase in the matrix, the strength of the material can be significantly improved. As the direct constituent material of the welded pipe, the welded pipe steel determines the basic bearing capacity of the welded pipe. High-strength welded pipe steel can improve the strength of the welded pipe to adapt to the application of different industrial scenes and expand the scope of application. DETAILED DESCRIPTION

[0020] 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.

[0021] Example 1 A high-strength welded pipe steel comprises a matrix and a reinforcement phase, wherein the matrix has the following elemental composition in weight percentage: C 0.06%, Cr 16%, Si 0.7%, Mn 1.5%, Al 0.02%, Ni 0.5%, Cu 1.5%, La 0.1%, Nd 0.2%, Co 0.2%, Ti 0.1%, Mo 2%, and the remainder is Fe and unavoidable impurities; The mass ratio of matrix to reinforcement phase is 100:0.5; the reinforcement phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yijin New Material Technology Co., Ltd.) with a mass ratio of 50:0.1; A method for preparing a high-strength welded pipe comprises the following steps: S1. Smelting according to the composition of the matrix to obtain molten steel; S2, adding the reinforcing phase to the molten steel, mixing, and casting to obtain a billet; S3. After rolling, the billet is cooled to 550°C at a cooling rate of 10°C / s, and then cooled to 350°C at a cooling rate of 25°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1070°C and the final rolling temperature is 870°C.

[0022] Example 2 A high-strength welded pipe steel comprises a matrix and a reinforcement phase, wherein the matrix has the following elemental composition in weight percentage: C 0.08%, Cr 17%, Si 0.75%, Mn 1.8%, Al 0.04%, Ni 0.6%, Cu 1.8%, La 0.15%, Nd 0.25%, Co 0.25%, Ti 0.25%, Mo 2.5%, and the remainder is Fe and unavoidable impurities; The mass ratio of matrix to reinforcement phase is 100:0.5; the reinforcement phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yijin New Material Technology Co., Ltd.) with a mass ratio of 50:0.1; A method for preparing a high-strength welded pipe comprises the following steps: S1. Smelting according to the composition of the matrix to obtain molten steel; S2, adding the reinforcing phase to the molten steel, mixing, and casting to obtain a billet; S3. After rolling, the billet is cooled to 550°C at a cooling rate of 10°C / s, and then cooled to 320°C at a cooling rate of 25°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0023] Example 3 A high-strength welded pipe steel comprises a matrix and a reinforcement phase, wherein the matrix has the following elemental compositions in weight percentage: C 0.10%, 18%, Si 0.8%, Mn 2%, Al 0.05%, Ni 0.7%, Cu 2.0%, La 0.2%, Nd 0.3%, Co 0.3%, Ti 0.3%, Mo 3%, and the remainder is Fe and unavoidable impurities; The mass ratio of matrix to reinforcement phase is 100:1; the reinforcement phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yijin New Material Technology Co., Ltd.) with a mass ratio of 50:0.1; A method for preparing a high-strength welded pipe comprises the following steps: S1. Smelting according to the composition of the matrix to obtain molten steel; S2, adding the reinforcing phase to the molten steel, mixing, and casting to obtain a billet; S3. After rolling, the billet is cooled to 550°C at a cooling rate of 15°C / s, and then cooled to 350°C at a cooling rate of 25°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1100°C and the final rolling temperature is 900°C.

[0024] Example 4 The only difference compared with Example 2 is that, among the elements of the high-strength welded pipe steel, the Cr content is 16%.

[0025] Example 5 The only difference compared with Example 2 is that, among the elements of the high-strength welded pipe steel, the Cr content is 18%.

[0026] Example 6 Compared with Example 2, the only difference is that the reinforcing phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yijin New Material Technology Co., Ltd.) in a mass ratio of 50:0.2.

[0027] Example 7 Compared with Example 2, the only difference is that the reinforcing phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yijin New Material Technology Co., Ltd.) in a mass ratio of 50:0.3.

[0028] Example 8 Compared with Example 6, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 550°C at a cooling rate of 12°C / s, and then cool it to 320°C at a cooling rate of 25°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0029] Example 9 Compared with Example 6, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 550°C at a cooling rate of 15°C / s, and then cool it to 320°C at a cooling rate of 25°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0030] Example 10 Compared with Example 8, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 550°C at a cooling rate of 12°C / s, and then cool it to 320°C at a cooling rate of 20°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0031] Embodiment 11 Compared with Example 8, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 550°C at a cooling rate of 12°C / s, and then cool it to 320°C at a cooling rate of 15°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0032] Example 12 Compared with Example 10, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 580°C at a cooling rate of 12°C / s, and then cool it to 320°C at a cooling rate of 20°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0033] Example 13 Compared with Example 10, the only difference is step S3. In this embodiment, step S3 is: S3, after rolling the billet, cool it to 600°C at a cooling rate of 12°C / s, and then cool it to 320°C at a cooling rate of 20°C / s to obtain high-strength steel for welded pipes; during rolling, the starting rolling temperature is 1080°C and the final rolling temperature is 890°C.

[0034] Comparative Example 1 Compared with Example 2, the only difference is that the welded pipe steel of this comparative example does not contain a reinforcing phase, and the welded pipe steel is composed only of the following elements in weight percentage: C 0.08%, Cr 17%, Si 0.75%, Mn 1.8%, Al 0.04%, Ni 0.6%, Cu 1.8%, La 0.15%, Nd 0.25%, Co 0.25%, Ti 0.25%, Mo 2.5%, and the rest is Fe and unavoidable impurities.

[0035] Comparative Example 2 Compared with Example 2, the only difference is that the welded pipe steel in this comparative example includes a matrix and a reinforcement phase, and the matrix is ​​composed of the following elements in weight percentage: C 0.08%, Cr 19%, Si 0.75%, Mn 1.8%, Al 0.04%, Ni0.6%, Cu 1.8%, La 0.15%, Nd 0.25%, Co 0.25%, Ti 0.25%, Mo 2.5%, and the rest are Fe and inevitable impurities; wherein the mass ratio of the matrix to the reinforcement phase is 100:2.5; the reinforcement phase is composed of silicon carbide (median particle size 45 μm) and AlCoCrFeNi high entropy alloy powder (median particle size 100 μm, Beijing Yi Jin New Material Technology Co., Ltd.) in a mass ratio of 50:0.1.

[0036] Comparative Example 3 Compared with Example 2, the only difference is that the reinforcing phase in this comparative example is only AlCoCrFeNi high entropy alloy powder.

[0037] Comparative Example 4 Compared with Example 2, the only difference is that the reinforcement phase in this comparative example is only silicon carbide.

[0038] Experimental Example 1 The yield strength of the steel for welded pipe in Examples 1 to 7 and Comparative Examples 1 to 4 was determined by the determination method in GB / T 228.1-2021 “Metallic Materials: Tensile Tests Part 1: Room Temperature Test Methods”. The determination results are shown in Table 1.

[0039] Table 1 Yield strength test results of welded pipe steel

[0040] The yield strength Rp0.2 of the steel for welded pipe in Examples 1 to 7 of the present invention is ≥718 MPa, which is higher than that in Comparative Examples 1 to 4, indicating that the steel for welded pipe of the present invention has excellent yield strength.

[0041] Experimental Example 2 The tensile strength of the steel for welded pipe in Example 6 and Examples 8 to 13 was determined by the determination method in GB / T 228.1-2021 “Metallic Materials: Tensile Tests Part 1: Room Temperature Test Method”. The determination results are shown in Table 2.

[0042] Table 2 Tensile strength test results of welded pipe steel

[0043] The tensile strength of the steel for welded pipe in Examples 8 to 13 of the present invention is ≥996 MPa, indicating that the steel for welded pipe of the present invention has excellent tensile strength.

[0044] 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 high strength welded pipe steel comprising a matrix and a reinforcement phase, characterized in that: The matrix is ​​composed of the following elements by weight percentage: C 0.06%~0.10%, Cr 16%~18%, Si 0.7%~0.8%, Mn 1.5%~2%, Al 0.02%~0.05%, Ni 0.5%~0.7%, Cu 1.5%~2.0%, La 0.1%~0.2%, Nd 0.2%~0.3%, Co 0.2%~0.3%, Ti0.1%~0.3%, Mo 2%~3%, and the rest is Fe and inevitable impurities; the reinforcement phase is composed of silicon carbide and AlCoCrFeNi high entropy alloy powder; the mass ratio of the matrix to the reinforcement phase is 100:0.5~1.

2. The high-strength welded pipe steel according to claim 1, characterized in that: The mass ratio of the sum of the masses of Co and Ti to the mass ratio of Cr is 6.4≤Cr / (6Co+4Ti)≤7.2, and the mass ratio of Co to Ti is Co / Ti=1.

3. The high-strength welded pipe steel according to claim 1, characterized in that: The median particle size of the AlCoCrFeNi high entropy alloy powder is 100 μm.

4. The high-strength welded pipe steel according to claim 1, characterized in that: The median particle size of the silicon carbide is 45 μm.

5. The high-strength welded pipe steel according to claim 1, characterized in that: The mass ratio of the silicon carbide to the AlCoCrFeNi high entropy alloy powder is 50:0.1-0.

3.

6. A method for preparing high-strength welded pipe steel, used for preparing a high-strength welded pipe steel as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Smelting according to the composition of the matrix to obtain molten steel; S2, adding the reinforcing phase to the molten steel, mixing, and casting to obtain a billet; S3. The billet is rolled and cooled to obtain high-strength steel for welded pipes.

7. The method for preparing high-strength welded pipe steel according to claim 6, characterized in that: In step S3, during the rolling, the starting rolling temperature is 1070-1100°C, and the finishing rolling temperature is 870-900°C.

8. The method for preparing high-strength welded pipe steel according to claim 6, characterized in that: In step S3, the cooling is divided into a first cooling stage and a second cooling stage, and the cooling rate of the first cooling stage is less than the cooling rate of the second cooling stage.

9. The method for preparing high-strength welded pipe steel according to claim 6, characterized in that: In step S3, during the cooling, a first cooling stage is performed at a cooling rate of 10-15°C / s to 550-600°C, and then a second cooling stage is performed at a cooling rate of 15-25°C / s to 320-350°C.

10. A welded pipe, characterized in that: The welded pipe is obtained by welding a steel strip after coiling and forming, and the steel used for the steel strip is the steel for high-strength welded pipe described in any one of claims 1 to 5 or the steel prepared by the preparation method of the high-strength welded pipe steel described in any one of claims 6 to 9.

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