High-strength steel pipe and method for manufacturing the same

Abstract

The application discloses a high-strength steel pipe and a preparation method thereof. The chemical composition of the high-strength steel pipe is as follows: C: 0.08-0.18%, Mn: 0.6-1.5%, Si: 0.20-0.40%, Cu: 0.15-0.40%, Mo: 0.05-0.15%, B: 0.006-0.015%, Ni: 0.15-0.30%, P: less than or equal to 0.010%, S: less than or equal to 0.010%, and the rest is Fe and inevitable impurities. The application is suitable for the manufacturing field of high-strength steel pipes, and can prepare seamless steel pipes with high strength, high plasticity and toughness, high fine grain and good welding performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of steel materials, and particularly relates to a high-strength steel pipe and a preparation method thereof. BACKGROUND

[0002] With the strengthening of infrastructure construction in China, the domestic crawler crane market continues to grow. The skeleton of the crawler crane is the key part of the load, transfer, lifting heavy objects, which is generally welded by 3-12m seamless steel pipe. High-strength steel pipe is a new type of walking part developed to simulate metal crawler belts, which has good longitudinal flexibility and transverse rigidity, and also has the advantages of small ground pressure, good adhesion, small vibration, low noise, good wet ground passing performance, no damage to the road, high speed, light weight and the like. However, the types and contents of gold elements in the high-strength steel pipe commonly used at present are relatively large, and the toughness and welding performance are correspondingly reduced while the strength is improved, and the carrying capacity is relatively low.

[0003] At present, the prior art 1 (CN202110238781.8) discloses a high-performance online quenching high-strength steel pipe and a production method thereof. The chemical composition of the high-performance online quenching high-strength steel pipe includes, by mass fraction: C: 0.1-0.3%, Si: 0.1-0.8%, Mn: 0.4-2.0%, P: 0.001-0.015%, S: 0.001-0.015%, Al: 0.001-0.05%, Ti: 0.005-0.05%, O: 0.001-0.01%, N: 0.003-0.012%, B: 0.0005-0.005%, Ca+Mg: 0.001-0.01%, and B+Ca+Mg: 0.002-0.012%, and the balance is Fe and inevitable impurities. However, the alloy elements in the patent are not only more and have high content, which will lead to resource waste and a substantial increase in the cost of steel, and it is difficult to be popularized and applied on a large scale in practice. The prior art 2 adopts steel plate rolling and then welding, such as high-strength steel pipe for pipeline pipe with excellent low-temperature toughness and high-strength steel plate for pipeline pipe and their manufacturing method (CN200780024813.2). The high-strength steel plate for pipeline pipe with excellent low-temperature toughness is formed into a tubular shape, and the butt joint is welded, and then the pipe is expanded, which leads to the existence of weld and heat-affected zone in the steel pipe itself, and reduces the service life of the steel pipe. Therefore, a high-strength seamless steel pipe with high strength, good low-temperature impact toughness and good welding performance is needed to be developed to meet the needs of the crawler crane. SUMMARY

[0004] Objective: To solve the problems of the prior art, the present application provides a high-strength steel pipe and a preparation method thereof. According to the actual needs, the chemical composition of the high-strength steel pipe is optimized, the strength of the steel is improved by adding manganese, boron and nickel elements in proportion, and the corrosion resistance of the steel is improved by using copper elements.

[0005] Technical solution: To solve the above technical problems, the technical solution adopted by the present application is:

[0006] In a first aspect, the present application provides a high-strength steel pipe, which has the following chemical composition and mass percentage: C: 0.08-0.18%, Mn: 0.6-1.5%, Si: 0.20-0.40%, Cu: 0.15-0.40%, Mo: 0.05-0.15%, B: 0.006-0.015%, Ni: 0.15-0.30%, P≤0.010%, S≤0.010%, and the balance being Fe and unavoidable impurities.

[0007] In a second aspect, the present application provides a method for preparing a high-strength steel pipe, comprising the following steps:

[0008] S1) providing a raw steel billet, which has the following chemical composition and mass percentage: C: 0.08-0.18%, Mn: 0.6-1.5%, Si: 0.20-0.40%, Cu: 0.15-0.40%, Mo: 0.05-0.15%, B: 0.006-0.015%, Ni: 0.15-0.30%, P≤0.010%, S≤0.010%, and the balance being Fe and unavoidable impurities, and smelting the raw steel billet to obtain a smelted steel liquid;

[0009] S2) casting and hot extruding the smelted steel liquid, and then cooling it to below 50°C to obtain a steel pipe in the form of an extrusion;

[0010] S3) performing cold drawing twice on the obtained steel pipe to obtain a high-strength steel pipe.

[0011] In some embodiments, in step S1), the smelting employs secondary smelting, specifically including: smelting and refining the raw steel billet, cooling it, and then performing smelting and refining again to obtain a smelted steel liquid.

[0012] Further, in some embodiments, in step S2), the smelting employs vacuum induction smelting, and the refining employs ladle furnace refining.

[0013] In some embodiments, in step S2), the hot extrusion is performed at a temperature of 950-1100°C.

[0014] In some embodiments, in step S2), the smelting employs vacuum induction smelting, and the refining employs ladle furnace refining.

[0015] In some embodiments, in step S2), after the hot extrusion is completed, one or both of spraying and spraying cold air are employed for cooling.

[0016] In some embodiments, in step S2), the cold air is sprayed at 5-5℃.

[0017] In some embodiments, in step S3), the cold drawing force is 300-1000kN, and after the first cold drawing, a heating and holding treatment is performed, the heating temperature is 500-800℃, the holding time is 3-10min, the steel is cooled in a rapid quenching liquid at a cooling speed of >300℃ / s, and then the second cold drawing is performed.

[0018] In some embodiments, the high-strength steel pipe also has one or more of the following mechanical properties:

[0019] (1) tensile strength >1350Mpa;

[0020] (2) lower yield strength or specified plastic elongation strength >1270MPa;

[0021] (3) elongation after fracture >17.0%;

[0022] (4) impact energy at room temperature 229.5-262.5KV2 / J;

[0023] (5) impact energy at 20℃ 215.0-245.5KV2 / J;

[0024] (6) impact energy at-40℃ 115.5-152.5KV2 / J.

[0025] Beneficial effects: the high-strength steel pipe and the preparation method thereof provided by the application, by optimizing the chemical composition of the high-strength pipe, adding manganese, boron and nickel elements in proportion to improve the strength of the steel, using copper elements to improve the corrosion resistance of the steel, and through secondary smelting and cold drawing, a seamless high-strength steel pipe with high strength and plasticity is prepared, which reduces the process of rolling the steel plate into a pipe and then welding, reduces energy consumption and cost, is conducive to realizing industrialized production, and meets the comprehensive performance requirements of high-strength steel pipes in the domestic crawler crane market. The application has the following advantages:

[0026] a) by optimizing the different chemical compositions of the high-strength steel pipe and adding manganese, boron and nickel to enhance the strength of the steel, using copper elements to improve the corrosion resistance of the steel, and prolonging its service life;

[0027] b) using smelting, forging, hot extrusion and other preparation processes to improve the plasticity of the steel.

[0028] c) using cold drawing preparation process to improve the strength and toughness of the steel, reduce energy consumption and cost, and be conducive to realizing industrialized production.

[0029] d) the chemical composition ratio of the high-strength steel pipe can be adjusted according to actual needs to meet the needs of different types of engineering machinery equipment. Attached Figure Description

[0030] Figure 1 This is a grain size diagram of the high-strength steel pipe prepared in Example 1 of the present invention;

[0031] Figure 2 This is a grain size diagram of the high-strength steel pipe prepared in Example 2 of the present invention;

[0032] Figure 3 This is a grain size diagram of the high-strength steel pipe prepared in Example 3 of the present invention;

[0033] Figure 4 This is a microstructure image of the high-strength steel pipe prepared in Example 1 of the present invention;

[0034] Figure 5 This is a microstructure image of the high-strength steel pipe prepared in Example 2 of the present invention;

[0035] Figure 6 This is a microstructure diagram of the high-strength steel pipe prepared in Example 3 of the present invention. Detailed Implementation

[0036] Example 1

[0037] A high-strength steel pipe, based on the chemical composition by mass percentage, has the following composition: C: 0.10%, Mn: 1.4%, Si: 0.25%, Cu: 0.18%, Mo: 0.12%, B: 0.008%, Ni: 0.16%, P: 0.005%, S: 0.005%, with the remainder being Fe and unavoidable impurities.

[0038] S1) Smelting: First, vacuum induction melting is carried out according to the composition ratio, followed by refining in an LF furnace. After cooling, steel billets are obtained. Then, the steel billets are vacuum induction melted again and refined in an LF furnace.

[0039] S2) Continuous casting and rolling: Molten steel is poured into a continuous casting machine to cast steel bars, which are then hot-extruded into tubular shapes at 1060℃ and cooled by spraying.

[0040] S3) Cold drawing: The hot-extruded steel pipe is cold-drawn once using a 400kN cold drawing machine, then held at 780℃ for 4 minutes, cooled with a rapid quenching liquid at a cooling rate of 500℃ / s, and finally cold-drawn again using a 600kN cold drawing machine to obtain a high-strength steel pipe.

[0041] Example 2

[0042] A high-strength steel pipe, according to the chemical composition in mass percent, C: 0.16%, Mn: 0.6%, Si: 0.35%, Cu: 0.35%, Mo: 0.06%, B: 0.012%, Ni: 0.25%, P: 0.005%, S: 0.008%, and the balance of Fe and inevitable impurities.

[0043] S1) Smelting: first vacuum induction smelting according to the component ratio, LF furnace refining, and after cooling, a billet is obtained, then the billet is vacuum induction smelted again, and LF furnace refining is performed;

[0044] S2) Continuous casting and rolling: the molten steel is poured into a continuous casting machine to cast a steel bar, hot extruded into a tubular shape at 1020°C, and then cooled using cold air at 0°C to -5°C.

[0045] S3) Cold drawing: the obtained hot extruded steel pipe is once cold drawn using a 600kN cold drawing machine, then cooled at 650°C for 8min using a cooling speed of 450°C / s rapid quenching liquid, and finally cold drawn using a 900kN cold drawing machine to obtain a high-strength steel pipe.

[0046] Example 3

[0047] A high-strength steel pipe, according to the chemical composition in mass percent, C: 0.14%, Mn: 1.0%, Si: 0.30%, Cu: 0.25%, Mo: 0.08%, B: 0.010%, Ni: 0.20%, P: 0.005%, S: 0.008%, and the balance of Fe and inevitable impurities.

[0048] S1) Smelting: first vacuum induction smelting according to the component ratio, LF furnace refining, and after cooling, a billet is obtained, then the billet is vacuum induction smelted again, and LF furnace refining is performed;

[0049] S2) Continuous casting and rolling: the molten steel is poured into a continuous casting machine to cast a steel bar, hot extruded into a tubular shape at 960°C, and then cooled to 400°C using cold air at 5°C to 0°C, and then cooled to room temperature using spray cooling.

[0050] S3) Cold drawing: the obtained hot extruded steel pipe is once cold drawn using a 500kN cold drawing machine, then cooled at 550°C for 5min using a cooling speed of 400°C / s rapid quenching liquid, and finally cold drawn using an 800kN cold drawing machine to obtain a high-strength steel pipe.

[0051] Example 4

[0052] A high-strength steel pipe, in terms of the chemical composition in mass percent, is C: 0.08%, Mn: 0.6%, Si: 0.40%, Cu: 0.40%, Mo: 0.15%, B: 0.015%, Ni: 0.30%, P: 0.005%, S: 0.008%, and the balance of Fe and inevitable impurities.

[0053] A high-strength steel pipe is prepared according to the scheme of Example 2.

[0054] Example 5

[0055] A high-strength steel pipe, in terms of the chemical composition in mass percent, is C: 0.18%, Mn: 1.5%, Si: 0.20%, Cu: 0.15%, Mo: 0.05%, B: 0.006%, Ni: 0.15%, P: 0.005%, S: 0.008%, and the balance of Fe and inevitable impurities.

[0056] A high-strength steel pipe is prepared according to the scheme of Example 2.

[0057] Example 6

[0058] The chemical composition in Example 2 is used.

[0059] S1) Smelting: first vacuum induction smelting according to the component ratio, LF furnace refining, and after cooling, a billet is obtained, then the billet is vacuum induction smelted again, and LF furnace refining is performed;

[0060] S2) Continuous casting and rolling: the molten steel is poured into a continuous casting machine to cast a steel bar, hot extruded into a tubular shape at 1150°C, and then cooled using cold air at 0°C to -5°C.

[0061] S3) Cold drawing: the obtained hot extruded steel pipe is once cold drawn using a 600kN cold drawing machine, then cooled at a cooling rate of 450°C / s using a rapid quenching liquid at 650°C for 8min, and finally cold drawn using a 900kN cold drawing machine to obtain a high-strength steel pipe.

[0062] Example 7

[0063] The chemical composition in Example 2 is used.

[0064] S1) Smelting: first vacuum induction smelting according to the component ratio, LF furnace refining, and after cooling, a billet is obtained, then the billet is vacuum induction smelted again, and LF furnace refining is performed;

[0065] S2) Continuous casting and rolling: the molten steel is poured into a continuous casting machine to cast a steel bar, hot extruded into a tubular shape at 920°C, and then cooled using cold air at 0°C to -5°C.

[0066] S3) Cold drawing: the hot extruded steel tube is drawn once by a 600 kN cold drawing machine, then cooled at a cooling rate of 250 °C / s by a quenching liquid, and finally drawn by a 900 kN cold drawing machine to obtain the high strength steel tube.

[0067] Example 8

[0068] The chemical composition in Example 2 is used.

[0069] S1) Smelting: the steel is first smelted by vacuum induction smelting according to the component ratio, refined by a LF furnace, and then cooled to obtain a steel billet, and then the steel billet is smelted again by vacuum induction smelting, refined by a LF furnace;

[0070] S2) Continuous casting and rolling: the molten steel is poured into a continuous casting machine to cast a steel bar, and then hot extruded into a tubular shape at 920 °C, and then cooled by cold air at 0 °C to -5 °C.

[0071] S3) Cold drawing: the hot extruded steel tube is drawn once by a 600 kN cold drawing machine, then cooled at a cooling rate of 250 °C / s by a quenching liquid, and finally drawn by a 900 kN cold drawing machine to obtain the high strength steel tube.

[0072] Comparative Example 1

[0073] The chemical composition of the high strength steel tube in Comparative Example 1 is as follows: C: 0.16%, Mn: 0.3%, Si: 0.35%, Cu: 0.35%, Mo: 0.06%, B: 0.004%, Ni: 0.1%, P: 0.005%, S: 0.008%, and the rest is Fe and inevitable impurities.

[0074] The high strength steel tube is prepared according to the scheme of Example 2, and the difference from Example 2 is the content of manganese, boron, and nickel.

[0075] Comparative Example 2

[0076] The chemical composition of the high strength steel tube in Comparative Example 2 is as follows: C: 0.16%, Mn: 0.6%, Si: 0.35%, Mo: 0.06%, B: 0.012%, Ni: 0.25%, P: 0.005%, S: 0.008%, and the rest is Fe and inevitable impurities.

[0077] The high strength steel tube is prepared according to the scheme of Example 2, and the difference from Example 2 is that it does not contain Cu.

[0078] Comparative Example 3 (Example L of CN200780024813.2)

[0079] The detailed description is found in Example L of CN200780024813.2.

[0080] Comparative Example 4 (Example 4 of CN202110238781.8)

[0081] A production method of high-performance online quenching high-strength steel pipe, comprising the following process steps:

[0082] S1) Smelting: molten iron and scrap steel (mass ratio, molten iron: scrap steel = 1:2) are smelted into molten steel by an electric furnace, and when the molten steel temperature reaches 1600-1700℃ and the carbon mass fraction in the molten steel is 0.03-0.15%, the phosphorus mass fraction is 0.001-0.015%, and the sulfur mass fraction is 0.005-0.025%, the molten steel is tapped, and a deoxidizing agent is added for pre-deoxidization to <50ppm of dissolved oxygen in the molten steel; the molten steel after pre-deoxidization is subjected to LF refining, and the refining process of temperature rise, slagging, bottom blowing, deoxidization and desulfurization, and inclusion removal is performed for 60min; the dissolved oxygen in the molten steel is controlled to be <20ppm, and the nitrogen content is <80ppm; a titanium-based cored wire is fed into the molten steel, the titanium-based cored wire is made of steel strip wrapped around alloy powder with a particle size of less than 3mm, and the chemical composition of the alloy powder includes, by mass fraction: Ti: 16%, Ca: 4%, Mg: 6%, N: 2%, O: 0.3%, Si: 50%, Al: 10%, and the balance is iron and impurity elements; the outer diameter of the titanium-based cored wire is 16mm, and the feeding speed is 120m / min; the ladle is bottom blown for 1min after feeding the wire, generating micron or sub-micron sized CaO, MgO, Ti2O3 oxides; the element content of the molten steel is adjusted according to the composition requirements of the high-performance online quenching high-strength steel pipe, and the molten steel is continuously cast into round billets

[0083] S2) Pipe rolling: the round pipe billet is heated to 1300℃ for 80min to obtain a heated pipe billet; the heated pipe billet is subjected to inclined piercing to obtain a pierced pipe; the pierced pipe enters a continuous rolling pipe mill for pipe rolling, and the finish rolling temperature is 1000℃ to obtain a continuously rolled rough pipe; the continuously rolled rough pipe is subjected to sizing rolling, and the finish rolling temperature is 970℃ to obtain a hot extruded steel pipe;

[0084] S3) Quenching: the hot extruded steel pipe is subjected to online quenching, the quenching open cooling temperature is 920℃, the cooling speed is 85℃ / s, the final cooling temperature is <200℃, and then the pipe is air cooled to room temperature on a cooling bed to obtain a high-performance online quenching high-strength steel pipe in the quenched state;

[0085] S4) tempering: the high-performance on-line quenched high-strength steel pipe in quenched state is subjected to a tempering heat treatment, the tempering temperature is 530℃, the tempering time is 120min, and the high-performance on-line quenched high-strength steel pipe in tempered state is obtained; the prepared high-performance on-line quenched high-strength steel pipe has the following chemical components in mass fraction: C: 0.24%, Si: 0.1%, Mn: 1.8%, P: 0.006%, S: 0.015%, Al: 0.02%, Ti: 0.006%, O: 0.001%, N: 0.01%, B: 0.003%, Ca: 0.0002%, Mg: 0.005%, Cr: 0.3%, Mo: 0.2%, and the balance of Fe and inevitable impurities. The prepared high-performance on-line quenched high-strength steel pipe contains Al2O3, MgO, CaO, CaS, MnS, Ti2O3, TiN and inevitable inclusions; the number of inclusions containing at least one of MgO, CaO, CaS, Ti2O3 and TiN with a size of 0.03-3μm in the steel is 1840 / mm2; according to the number of inclusion particles, 78% of the inclusions containing MgO or CaO in the steel also contain at least one of Al2O3, Ti2O3, TiN, CaS and MnS; the TiN in the steel is precipitated in single phase or is precipitated in combination with other inclusions, wherein the number of TiN existing in single phase precipitates accounts for 79%, and the average size is 36nm. The microstructure of the steel pipe is mainly martensite in quenched state, the content of martensite reaches 100%, wherein the average grain size of the original austenite is 27μm, and is divided by acicular ferrite; in quenched state, the yield strength is 1340MPa, the impact toughness at 0℃ is 47J, in tempered state, the yield strength is 1260MPa, and the impact toughness at 0℃ is 170J.

[0086] The tensile strength, lower yield strength or specified plastic elongation strength, elongation after fracture is determined according to GB / T 228.1-2021, the impact energy is determined according to GB / T 229-2020, the grain size is tested according to GB / T 6394-2017, the intercept method is selected; the microstructure is determined according to GB / T 13298-2015, the neutral salt spray test is determined according to GB / T 10125-2021, the salt spray deposition rate is 1.1-1.5mL(80cm 2 * h), the solution concentration is 49.00-49.95g / L, the collection solution PH value is 6.68-6.90, the working chamber temperature is 34.47-35.65℃, and the sample is tested in a hanging test mode, and the physical and mechanical properties are shown in Table 1.

[0087] Table 1 Physical and mechanical properties of high-strength steel pipe

[0088]

[0089] As shown in Table 1, the high-strength steel pipe prepared by adjusting the chemical composition and optimizing the proportion in the embodiment of the application has the following performances: (1) tensile strength > 1350 MPa; (2) lower yield strength or specified plastic elongation strength > 1270 MPa; (3) elongation after fracture > 17.0%; (4) impact energy at room temperature 229.5-262.5 KV2 / J; (5) impact energy at 0°C 215.0-245.5 KV2 / J; (6) impact energy at -40°C 115.5-152.5 KV2 / J. The tensile strength, lower yield strength or plastic elongation strength, elongation after fracture, impact energy at room temperature, 0°C and -40°C are significantly improved relative to Comparative Examples 1-2 and Comparative Examples 3-4 (Prior Art 1-2), and the grain size is significantly reduced. It can be seen that, by adjusting the chemical composition and optimizing the proportion, the proportion of manganese, boron and nickel elements is adjusted to improve the strength of the steel (Comparative Example 1), and the copper element is increased to improve the corrosion resistance of the steel (Comparative Example 2), a seamless steel pipe with high strength, high plasticity and toughness, high fine grain and good welding performance is prepared by adopting the method of secondary smelting, rolling and cold drawing, and the microstructure thereof is tempered martensite + bainite + residual austenite.

[0090] In the above embodiments of the application, the serial numbers or sequences of the embodiments are only for description, and do not represent the advantages and disadvantages of the embodiments. The descriptions of the embodiments are each focused on, and the parts not described in detail in an embodiment can be referred to the relevant description of other embodiments. The technical means disclosed in the application scheme is not limited to the technical means disclosed in the above embodiments, and includes the technical scheme composed by any combination of the above technical features. The above has disclosed the application with the preferred embodiments, but it is not used to limit the application, and the technical scheme obtained by equivalent replacement or equivalent transformation falls within the protection scope of the application.

Claims

1. A method for producing a high-strength steel pipe, characterized by, The method comprises the following steps: S1) providing a raw steel billet, the chemical composition and mass percentage of the raw steel billet are as follows: C: 0.08-0.18%, Mn: 0.6-1.5%, Si: 0.20-0.40%, Cu: 0.15-0.40%, Mo: 0.05-0.15%, B: 0.006-0.015%, Ni: 0.15-0.30%, P≤0.010%, S≤0.010%, the rest being Fe and inevitable impurities; smelting the raw steel billet to obtain a smelted molten steel; S2) casting, hot extruding and then cooling to below 50℃ the smelted molten steel to obtain a steel pipe in the form of a steel tube; wherein the hot extrusion is performed at a temperature of 950-1100℃; after the hot extrusion, one or both of spraying and spraying cold air are used for cooling; S3) performing twice cold drawing on the obtained steel pipe to obtain a high-strength steel pipe, wherein the cold drawing uses a cold drawing force of 300-1000kN, after one cold drawing, one heating and holding treatment is needed, the heating temperature is 500-800℃, the holding time is 3-10min, rapid quenching liquid cooling is used, and the cooling speed is >300℃ / s, and then the second cold drawing is performed.

2. The method of producing a high-strength steel pipe according to claim 1, characterized by, In step S1), the smelting uses secondary smelting, specifically including: smelting and refining the raw steel billet, cooling, then smelting and refining again to obtain the smelted molten steel.

3. The method of producing a high-strength steel pipe according to claim 1 or 2, characterized by, The smelting uses vacuum induction smelting, and the refining uses ladle refining.

4. The method of producing a high-strength steel pipe according to claim 1, wherein The spraying of cold air uses spraying of cold air at 5-5℃.

5. A high-strength steel pipe, which is prepared by the method of any one of claims 1-4.

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