High-strength seamless steel tube

Abstract

The invention relates to the technical field of pipes, and provides a high-strength seamless steel pipe which is composed of the following components in percentage by weight: 0.2%-0.4% of C, 0.17%-0.27% of Si, 1.4%-1.6% of Mn, less than or equal to 0.03% of P, less than or equal to 0.01% of S, 1.1%-1.3% of Cr, 0.25%-0.35% of Mo, 0.015%-0.025% of Ti, 0.1%-0.2% of V, 0.02%-0.04% of Al and the balance of iron and inevitable impurities, and the ratio of C to (Mn + V + Ti) is 4.5-7.6: 1. Through the technical scheme, the problem of low strength of the seamless steel pipe in the related technology is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of pipes, and in particular to a high-strength seamless steel pipe. Background Art

[0002] Seamless steel pipe is a long strip of steel with a hollow cross-section and no seams around the perimeter. Due to its manufacturing process, the pipe wall has no welding seams. Compared with welded steel pipes, it has higher reliability and is widely used in the field of oil and natural gas transportation.

[0003] However, there are some problems in the application of seamless steel pipes at present. In terms of strength, the strength of some seamless steel pipes is relatively low. Low strength can easily cause deformation and rupture when subjected to greater pressure or external force. For example, in the transportation of oil and natural gas, if the pipeline strength is insufficient, it may cause leakage, which will not only waste resources, but also cause serious pollution to the environment and even cause safety accidents; in mechanical manufacturing, parts made of low-strength seamless steel pipes may not be able to withstand the stress during equipment operation, shortening the service life of the equipment and affecting production efficiency. Therefore, it is necessary to develop a seamless steel pipe with high strength. Summary of the invention

[0004] The present invention provides a high-strength seamless steel pipe, which solves the problem of low strength of the seamless steel pipe in the related art.

[0005] The technical solution of the present invention is as follows: The present invention proposes a high-strength seamless steel pipe, which is composed of the following components in weight percentage: C 0.2%~0.4%, Si 0.17%~0.27%, Mn 1.4%~1.6%, P≤0.03%, S≤0.01%, Cr 1.1%~1.3%, Mo 0.25%~0.35%, Ti 0.015%~0.025%, V 0.1%~0.2%, Al 0.02%~0.04%, and the balance is iron and inevitable impurities, wherein C:(Mn+V+Ti)=4.5~7.6:1.

[0006] As a further technical solution, the C:(Mn+V+Ti)=5.5:1.

[0007] The present invention also provides a method for preparing a high-strength seamless steel pipe, comprising the following steps: S1. Steelmaking: Mix the materials according to the target composition, and then continuously cast them into a solid cylinder after smelting; S2, rolling: heating the solid cylinder to 1080-1240°C and axially piercing the inner hole to obtain a hollow tube body, and then rolling and tension reducing the rough tube to obtain a smooth tube; S3. The smooth tube is sequentially quenched, tempered, straightened and flaw-detected to obtain a seamless steel tube.

[0008] As a further technical solution, the smelting temperature in S1 is 1560~1590℃.

[0009] As a further technical solution, the temperature of the rough pipe rolling in S2 is 1080~1240℃, and the temperature of the tension reducing is 780~880℃.

[0010] In the present invention, the temperature of the rough pipe rolling is limited to 1080-1240°C. Within this temperature range, the rough pipe has high plasticity and is easy to be processed into the desired hollow pipe shape, while ensuring that no defects such as cracks and tears are generated inside the material. The temperature of the tension reduction is limited to 780-880°C, which ensures that the steel pipe has good plasticity while achieving precise control of the outer diameter and wall thickness of the steel pipe.

[0011] As a further technical solution, the quenching in S3 includes the following steps: the light tube is heated to 600°C once, kept warm once, then heated to 880-960°C for a second time, kept warm twice, and then cooled to room temperature by water spray quenching.

[0012] As a further technical solution, the tempering temperature in S3 is 500-650° C., and the tempering insulation time is 30-90 min.

[0013] As a further technical solution, the heating rate of the tempering in S3 is 5°C / min.

[0014] As a further technical solution, the straightening temperature in S3 is 400-500°C.

[0015] As a further technical solution, the heating rate of the first heating is less than the heating rate of the second heating, and the first insulation time is greater than the second insulation time.

[0016] As a further technical solution, the heating rate of the first heating is 3-5°C / min, and the heating rate of the second heating is 8-10°C / min.

[0017] As a further technical solution, the heating rate of the first heating is preferably 3°C / min, and the heating rate of the second heating is preferably 8°C / min.

[0018] In the present invention, during the heating process of quenching, different settings are made for the primary heating and secondary heating rates, the heating rate of the primary heating is less than the heating rate of the secondary heating, during the primary heating process, the lower heating rate provides sufficient time for the alloy elements to diffuse, and the slow heating causes the grain growth rate of the steel to be slower during the heating process, which helps to maintain fine initial grains, and the faster secondary heating rate can reduce the residence time of the steel pipe in the non-austenitizing temperature range, avoid abnormal grain growth at a lower temperature, and improve the wear resistance of the seamless steel pipe.

[0019] As a further technical solution, the first insulation time is 30 to 35 minutes, and the second insulation time is 15 to 20 minutes.

[0020] As a further technical solution, the first insulation time is preferably 30 minutes, and the second insulation time is preferably 20 minutes.

[0021] In the present invention, the primary insulation time and the secondary insulation time are reasonably set, and the primary insulation time is limited to be greater than the secondary insulation time. The longer primary insulation time helps to eliminate the temperature gradient and composition non-uniformity inside the steel pipe, making the structure more uniform. The short secondary insulation time ensures the homogenization of the austenite composition and the full solid solution of the alloy elements, while avoiding grain growth. The long primary insulation time and the short secondary insulation time cooperate with each other to create good structural transformation conditions for the steel pipe and improve the wear resistance of the seamless steel pipe.

[0022] The working principle and beneficial effects of the present invention are: In the present invention, the contents of impurity elements such as phosphorus and sulfur are strictly limited to reduce their adverse effects on the strength and toughness of steel. Silicon, as a deoxidizer, can improve the strength and hardness of steel while enhancing the oxidation resistance of steel. Aluminum can refine the grains and improve the strength of steel. By strictly controlling the mass relationship of carbon, manganese, titanium and vanadium, the synergistic effect of each element can be brought into play, which can not only give full play to the strengthening effect of carbon, but also further optimize the strength of steel through the regulation of the organization by other elements, thereby improving the strength of the seamless steel pipe. DETAILED DESCRIPTION

[0023] 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.

[0024] In the following examples and comparative examples: Example 1 A high-strength seamless steel pipe, composed of the following components in weight percentage: C 0.2%, Si 0.17%, Mn 1.4%, P 0.024%, S 0.008%, Cr 1.1%, Mo 0.25%, Ti 0.015%, V 0.1%, Al 0.02%, and the balance is iron and inevitable impurities; A method for preparing a high-strength seamless steel pipe comprises the following steps: S1. Steelmaking: Mix the materials according to the target composition, heat to 1560℃, melt and continuously cast to form a solid cylinder; S2, rolling: the solid cylinder is heated to 1080°C and the inner hole is axially penetrated to obtain a hollow tube body. After the rough tube is rolled at 1080°C, it is tension-reduced at 780°C to obtain a smooth tube; S3. Heat treatment: The light tube is heated to 880℃ at a heating rate of 3℃ / min, kept warm for 50min, then cooled to room temperature by water spray quenching, heated to 500℃ at a rate of 5℃ / min for tempering, kept warm for 90min, straightened at 400℃, and after flaw detection, a seamless steel tube is obtained.

[0025] Example 2 A high-strength seamless steel pipe, composed of the following components in weight percentage: C 0.3%, Si 0.22%, Mn 1.5%, P 0.022%, S 0.006%, Cr 1.2%, Mo 0.3%, Ti 0.02%, V 0.15%, Al 0.03%, and the balance is iron and inevitable impurities; A method for preparing a high-strength seamless steel pipe comprises the following steps: S1. Steelmaking: Mix the materials according to the target composition, heat to 1575℃, melt and continuously cast to form a solid cylinder; S2, rolling: the solid cylinder is heated to 1080℃ and the inner hole is axially penetrated to obtain a hollow tube body, and the rough tube is rolled at 1150℃ and then tension-reduced at 830℃ to obtain a smooth tube; S3. Heat treatment: The light tube is heated to 920℃ at a heating rate of 3℃ / min, kept warm for 50min, then cooled to room temperature by water spray quenching, heated to 575℃ at a rate of 5℃ / min for tempering, kept warm for 60min, straightened at 450℃, and after flaw detection, a seamless steel tube is obtained.

[0026] Example 3 A high-strength seamless steel pipe, composed of the following components in weight percentage: C 0.4%, Si 0.27%, Mn 1.6%, P 0.019%, S 0.005%, Cr 1.3%, Mo 0.35%, Ti 0.025%, V 0.2%, Al 0.04%, and the balance is iron and inevitable impurities; A method for preparing a high-strength seamless steel pipe comprises the following steps: S1. Steelmaking: Mix the materials according to the target composition, heat to 1590℃, melt and continuously cast to form a solid cylinder; S2, rolling: the solid cylinder is heated to 1080℃ and the inner hole is axially penetrated to obtain a hollow tube body, and the rough tube is rolled at 1240℃ and then tension-reduced at 880℃ to obtain a smooth tube; S3. Heat treatment: The light tube is heated to 960℃ at a heating rate of 3℃ / min, kept warm for 50min, then cooled to room temperature by water spray quenching, heated to 650℃ at a rate of 5℃ / min for tempering, kept warm for 30min, straightened at 500℃, and after flaw detection, a seamless steel tube is obtained.

[0027] Example 4 Compared with Example 2, the difference of Example 4 is that the weight percentage of C in the seamless steel pipe in this example is 0.36%.

[0028] Example 5 Compared with Example 2, the difference of Example 5 is that the weight percentage of C in the seamless steel pipe in this example is 0.22%.

[0029] Example 6 Compared with Example 2, the difference of Example 6 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, kept at this temperature for 30 minutes, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 20 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0030] Example 7 Compared with Example 2, the difference of Example 7 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 8°C / min, kept at this temperature for 30 minutes, then heated to 920°C at a heating rate of 3°C / min, kept at this temperature for 20 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0031] Example 8 Compared with Example 2, the difference of Example 8 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, kept at this temperature for 30 minutes, then heated to 920°C at a heating rate of 3°C / min, kept at this temperature for 20 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0032] Example 9 Compared with Example 2, the difference of Example 9 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 8°C / min, kept at this temperature for 30 minutes, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 20 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0033] Example 10 Compared with Example 2, the difference of Example 10 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, kept at this temperature for 20 minutes, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 30 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0034] Embodiment 11 Compared with Example 2, the difference of Example 11 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, kept at this temperature for 20 minutes, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 20 minutes, cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0035] Example 12 Compared with Example 2, the difference of Example 12 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, kept at this temperature for 30 minutes, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 30 minutes, then cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0036] Example 13 Compared with Example 2, the difference of Example 13 lies in step S3. In this embodiment, step S3 is as follows: the light tube is first heated to 600°C at a heating rate of 3°C / min, then heated to 920°C at a heating rate of 8°C / min, kept at this temperature for 50 minutes, then cooled to room temperature by water spray quenching, heated to 575°C for tempering, and kept at this temperature for 60 minutes.

[0037] Embodiment 14 Compared with Example 6, the difference of Example 14 is that the weight percentage of C in the seamless steel pipe in this example is 0.334%.

[0038] Comparative Example 1 Compared with Example 2, the difference between Comparative Example 1 is that the weight percentage of C in the seamless steel pipe in this comparative example is 0.1%.

[0039] Comparative Example 2 Compared with Example 2, the difference of Comparative Example 2 is that the weight percentage of C in the seamless steel pipe in this comparative example is 0.5%.

[0040] Experimental Example 1 The seamless steel pipes prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were tested for yield strength according to the test method specified in GB / T 228.1-2021 "Tensile test of metallic materials - Part 1: Room temperature test method".

[0041] The test results are shown in Table 1: Table 1 Performance test results of Examples 1 to 5 and Comparative Examples 1 to 2

[0042] Compared with Comparative Examples 1 and 2, the yield strength of Example 2 is greater than that of Comparative Examples 1 and 2, indicating that when the composition of the seamless steel pipe is limited to C:(Mn+V+Ti)=4.5~7.6:1, the strength of the seamless steel pipe can be improved.

[0043] Experimental Example 2 The seamless steel pipes prepared in Examples 2 and 6 to 13 were tested for mass wear according to the test method specified in GB / T 12444-2006 "Metallic material wear test methods - Test ring-test block sliding wear test", with a maximum torque of 14 N·m, a rotation speed of 400 r / min, and a time of 15 min.

[0044] The test results are shown in Table 2: Table 2 Performance test results of seamless steel pipes obtained in Example 2 and Examples 6 to 14

[0045] Compared with Example 6, the wear amounts of Example 2 and Examples 7 to 14 are all greater than that of Example 6, indicating that when the heating rate of the first heating is less than the heating rate of the second heating, and the first insulation time is greater than the second insulation time, the wear resistance of the seamless steel pipe can be improved.

[0046] 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 seamless steel pipe, characterized in that: It is composed of the following components in weight percentage: C 0.2%~0.4%, Si 0.17%~0.27%, Mn 1.4%~1.6%, P≤0.03%, S≤0.01%, Cr 1.1%~1.3%, Mo 0.25%~0.35%, Ti0.015%~0.025%, V 0.1%~0.2%, Al 0.02%~0.04%, and the balance is iron and inevitable impurities, wherein C:(Mn+V+Ti)=4.5~7.6:

1.

2. The method for preparing a high-strength seamless steel pipe according to claim 1, characterized in that: The following steps are involved: S1, mixing the materials according to the target composition, smelting and continuous casting to form a solid cylinder; S2, heating the solid cylinder to 1080-1240° C. to axially penetrate the inner hole to obtain a hollow tube body, and then rolling and tension reducing the rough tube to obtain a smooth tube; S3. The smooth tube is sequentially quenched, tempered, straightened and flaw-detected to obtain a seamless steel tube.

3. The method for preparing a high-strength seamless steel pipe according to claim 2, characterized in that: The smelting temperature in S1 is 1560~1590℃.

4. The method for preparing a high-strength seamless steel pipe according to claim 2, characterized in that: The temperature of the rough pipe rolling in S2 is 1080-1240°C, and the temperature of the tension reducing is 780-880°C.

5. The method for preparing a high-strength seamless steel pipe according to claim 2, characterized in that: The quenching in S3 includes the following steps: the light tube is heated to 600°C for the first time, kept warm for the first time, then heated to 880-960°C for the second time, kept warm for the second time, and then cooled to room temperature by water spray quenching.

6. The method for preparing a high-strength seamless steel pipe according to claim 2, characterized in that: The tempering temperature in S3 is 500-650° C., and the tempering holding time is 30-90 min.

7. The method for preparing a high-strength seamless steel pipe according to claim 2, characterized in that: The straightening temperature in S3 is 400-500°C.

8. The method for preparing a high-strength seamless steel pipe according to claim 5, characterized in that: The heating rate of the first heating is less than the heating rate of the second heating, and the first heat preservation time is greater than the second heat preservation time.

9. The method for preparing a high-strength seamless steel pipe according to claim 5, characterized in that: The heating rate of the first heating is 3-5°C / min, and the heating rate of the second heating is 8-10°C / min.

10. The method for preparing a high-strength seamless steel pipe according to claim 5, characterized in that: The first insulation time is 30 to 35 minutes, and the second insulation time is 15 to 20 minutes.

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