Steel for X52MH hydrogen transmission pipeline and manufacturing method thereof

Abstract

The invention relates to the technical field of steel for hydrogen conveying pipelines, in particular to steel for an X52MH hydrogen conveying pipeline and a manufacturing method of the steel. The steel comprises the following chemical components in percentage by mass: 0.020%-0.045% of C, 0.11%-0.19% of Si, 1.05%-1.15% of Mn, less than or equal to 0.0010% of S, less than or equal to 0.008% of P, 0.015%-0.045% of Al, 0.020%-0.040% of Nb, 0.010%-0.020% of Ti, 0.015%-0.040% of V, less than or equal to 0.004% of N, less than or equal to 0.0015% of O, less than or equal to 0.0001% of H and the balance of Fe and other inevitable impurities. According to the composition design, Nb-V-Ti microalloy strengthening, low C and Mn and strict control over P, S and gas O, N and H are adopted, the slow tensile property of a smooth sample of the manufactured product in the 6.3 MPa pure hydrogen atmosphere is larger than or equal to 500 MPa, K1C is larger than or equal to 120 MPa.m < 0.5 >, the fatigue cycle number is 100 thousand times under the stress of 360 MPa, and steel is not fractured.

Description

Technical Field

[0001] The present invention relates to the technical field of steel for hydrogen pipelines, and in particular to an X52MH steel for hydrogen pipelines and a method for manufacturing the same. Background Art

[0002] With the deepening of the national energy strategy, hydrogen energy will soon be given the same legal status as traditional energy sources such as coal and oil. This major policy measure will comprehensively accelerate the coordinated development of the hydrogen energy industry chain. From the upstream hydrogen energy preparation to the midstream storage and transportation links, and then to the downstream hydrogenation station construction and terminal applications, all links in the hydrogen energy industry chain will usher in unprecedented development opportunities. Among them, hydrogen energy transportation is a key link connecting the upstream and downstream of the industry chain. Its technical route and economic efficiency directly affect the large-scale development of the hydrogen energy industry.

[0003] At present, pipeline hydrogen transportation has become the most economical and feasible way of hydrogen transportation with its significant cost advantage and high efficiency, providing important support for the large-scale commercial application of hydrogen energy. The traditional X52 pipeline steel design has high C content, imprecise P and S control, insufficient smelting purity and lax gas content control, which will lead to problems such as fracture in hydrogen environment.

[0004] As hydrogen transportation becomes more and more popular, a boom in hydrogen pipeline steel has started in China. Patent CN118703910 A discloses a hydrogen pipeline steel L360MH and its production method, wherein: C: 0.030-0.045%, Si: 0.05-0.10%, Mn: 0.70-0.90%, P≤0.012%, S≤0.0015%, Als: 0.020-0.040%, Ca: 0.0010-0.0025%, Nb: 0.010-0.040%, V: 0.010-0.030%, Ti: 0.005-0.025 %, Cu: 0.10-0.25%, Cr: 0.15-0.30%, Ni: 0.07-0.15%, N≤0.0080%, the balance is Fe and unavoidable impurities; Patent CN118460928A discloses a high-strength steel plate for hydrogen pipeline and its rolling method and application, wherein: C: 0.01%-0.03%, Si: 0.10%-0.30%, Mn: 0.50%-1.00%, P: 0.008%-0.012 %, S: 0.0010% ~ 0.0020%, Cr: 0.20% ~ 0.40%, Ni: 0.10 ~ 0.30%, Cu: 0.15% ~ 0.25%, Nb: 0.030% ~ 0.050%, Ti: 0.010% ~ 0.020%, Al: 0.020% ~ 0.040%, the balance is Fe and unavoidable impurities; Patent CN116145040A discloses a X52MH hydrogen-doped hydrogen pipeline steel and its production method, wherein: C :0.03%~0.04%, Si: 0.10%~0.25%, Mn: 1.0%~1.1%, P≤0.005%, S≤0.0010%, Alt: 0.015%~0.035%, Nb: 0.030%~0.040%, Ti: 0.010%~0.020%, Cr: 0.15~0.20%, Cu: 0.10%~0.15%, Ni: 0.10%~0.15%, the balance is Fe and unavoidable impurities. The above patents all adopt low C+Nb / Ti strengthening + C / Cu / Cr design, but alloying elements such as C, Cu, Cr and Ni may be segregated inside the steel, causing the aggregation of hydrogen atoms. When the concentration of hydrogen atoms exceeds the critical hydrogen pressure concentration at that position, there is a risk of secondary cracks forming, and problems are prone to occur during long-term hydrogen delivery. At the same time, the gas content, especially the H content, is not controlled in the design, which will also affect its performance in a hydrogen environment. Summary of the invention

[0005] The object of the present invention is to provide a X52MH hydrogen pipeline steel and a manufacturing method thereof, wherein the slow tensile strength of a smooth sample in a 6.3MPa pure hydrogen atmosphere is ≥500MPa, and K 1C ≥120MPa·m0.5 , the steel did not break after 100,000 fatigue cycles under 360MPa stress.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] In one aspect, the present invention provides an X52MH steel for hydrogen pipeline, the chemical composition and mass percentage of which are as follows:

[0008] C: 0.020% ~ 0.045%, Si: 0.11% ~ 0.19%, Mn: 1.05% ~ 1.15%, S: ≤0.0010%, P: ≤0.008%, Al: 0.015% ~ 0.045%, Nb: 0.020% ~ 0.040%, Ti: 0.010% ~ 0.020%, V: 0.015% ~ 0.040%, N: ≤0.004%, O: ≤0.0015%, H: ≤0.0001%, the rest is Fe and other unavoidable impurities.

[0009] In the chemical composition of the steel for hydrogen pipeline of the present invention, the C element is controlled at 0.020-0.045%. If the C content is too high, it will cause lattice distortion with ferrite, and although the strength is improved, the resistance to hydrogen embrittlement is reduced. Therefore, while reducing the C content, Nb, Ti, and V elements are added to form dispersed and fine compounds with the C element, which can form hydrogen traps to prevent hydrogen from enriching at the grain boundaries and significantly improve the resistance to hydrogen embrittlement. On the other hand, the grains are refined, the large-angle grain boundary area is increased, and the hydrogen resistance is improved. The hydrogen resistance is further improved by strictly controlling the gas O, N, and H contents.

[0010] In the above technical solution, further, the steel has a slow tensile strength of ≥500MPa and a cross-sectional shrinkage of ≥60% in a 6.3MPa pure hydrogen atmosphere, and K 1C ≥120MPa·m 0.5 .

[0011] In the above technical solution, further, the number of fatigue cycles of the steel under 6.3MPa pure hydrogen atmosphere and 360MPa stress is ≥100,000 times.

[0012] In the above technical solution, further, the metallographic structure of the steel is ferrite+pearlite.

[0013] Another aspect of the present invention provides a method for manufacturing the above-mentioned X52MH hydrogen pipeline steel, the method comprising the following steps:

[0014] (1) Steelmaking: Hot metal desulfurization pretreatment, phosphorus content of hot metal entering the converter is ≤0.14%, sulfur content is ≤0.005%, desulfurization slag cleaning area is greater than 95%, scrap steel is added, RH process vacuum degree is ≤2.6mbar, vacuum treatment time is maintained for ≥10min, calcium treatment is performed after RH treatment, and soft blowing time after calcium treatment is ≥15min;

[0015] (2) Continuous casting: The continuous casting billet is pile-cooled for 36 to 48 hours to ensure that the billet is slowly cooled;

[0016] (3) Hot rolling: The continuous casting billet is put into a heating furnace for 180-210 min, the furnace temperature is 1150-1180°C, the outlet temperature of the rough rolling R1 is 920-950°C, the outlet temperature of the rough rolling R2 is 970-990°C, the start temperature of the finishing rolling is 940-970°C, and the final rolling temperature is 805-835°C;

[0017] (4) Cooling and coiling: Use layer cooling water spray cooling, and then coiling after cooling.

[0018] In the above technical solution, further, in step (2), protective pouring is adopted in the whole continuous casting process, and the superheat is controlled to be ≤15°C.

[0019] In the above technical solution, further, in step (4), the cooling time is 10 to 20 seconds.

[0020] In the above technical solution, further, in step (4), the coiling temperature is 480-520°C.

[0021] The beneficial effects of the present invention are:

[0022] (1) The composition design of the present invention adopts Nb-V-Ti microalloy strengthening, low C and Mn, and strict control of P, S and gas O, N, H. The product manufactured has a smooth sample slow tensile performance of ≥500MPa, K in a 6.3MPa pure hydrogen atmosphere. 1C ≥120MPa·m 0.5 , the steel did not break after 100,000 fatigue cycles under 360MPa stress.

[0023] (2) The alloy elements such as Cu, Cr and Ni are not selected in the composition design of the present invention because Cu, Cr and Ni may be segregated in the structure, thereby causing the aggregation of hydrogen atoms and leading to the formation of secondary cracks.

[0024] (3) In the composition design of the present invention, Nb-V-Ti microalloy strengthening is adopted, and V can form precipitation strengthening, that is, it is conducive to the formation of hydrogen traps; it can also adsorb free C to prevent the aggregation of C and cause cracking in a hydrogen environment.

[0025] (4) The present invention reduces the C content in the steel, regulates the organizational morphology during the rolling process, reduces the appearance of banded structures, reduces the size of carbides, and improves the hydrogen resistance of the steel.

[0026] (5) The present invention strictly controls the contents of P, S and gases O, N and especially H, controls the vacuum degree during the smelting process, increases the processing time, increases the purity of the molten steel, reduces inclusions in the steel, and improves the hydrogen resistance of the steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The metallographic structure of the steel of Example 1;

[0028] Figure 2 This is the steel metallographic structure of Comparative Example 2. DETAILED DESCRIPTION

[0029] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0030] Example 1

[0031] The steel for the hydrogen pipeline in Example 1 has the alloying elements in the proportions shown in Table 1 (the balance is Fe and unavoidable impurities).

[0032] Table 1 Composition of steel in Example 1 %

[0033] Serial number C Si Mn P S Al Nb Ti V N O H Example 1 0.030 0.15 1.10 0.006 0.0009 0.029 0.030 0.015 0.024 0.0022 0.0011 0.00008

[0034] The method for manufacturing the above steel comprises the following steps:

[0035] (1) Hot metal desulfurization pretreatment: the phosphorus content of hot metal entering the converter is 0.11%, the sulfur content is 0.003%, the desulfurization slag cleaning area is 98%, scrap steel is added, the vacuum degree of the RH process is 0.8 mbar, the treatment time is 19 minutes, and calcium treatment is performed after RH treatment. The soft blowing time after calcium treatment is 22 minutes;

[0036] (2) The whole process of continuous casting adopts protective pouring, the superheat is 10℃, and the continuous casting billet is pile-cooled off the line for 48h to ensure the slow cooling of the billet;

[0037] (3) Hot rolling: The continuous casting billet is put into the heating furnace for 197 min, the furnace temperature is 1168°C, the outlet temperature of the rough rolling R1 is 924°C, the outlet temperature of the rough rolling R2 is 981°C, the finishing rolling temperature is 956°C, and the final rolling temperature is 815°C;

[0038] (4) Layer cooling water spray cooling is adopted, the cooling time is 17s, and coiling is carried out after cooling, and the coiling temperature is 500℃.

[0039] The performance indicators of the steel prepared in Example 1 under hydrogen and nitrogen environments are shown in Table 5.

[0040] like Figure 1 As shown, its metallographic structure is pearlite (small amount) + ferrite (large amount).

[0041] Example 2

[0042] The steel for the hydrogen pipeline of Example 2 has the alloying elements in the proportions shown in Table 2 (the balance is Fe and unavoidable impurities).

[0043] Table 2 Composition of Example Steel %

[0044] Serial number C Si Mn P S Al Nb Ti V N O H Example 2 0.034 0.16 1.15 0.005 0.0008 0.025 0.028 0.012 0.028 0.0025 0.0010 0.00009

[0045] The method for manufacturing the above steel comprises the following steps:

[0046] (1) Hot metal desulfurization pretreatment: the phosphorus content of hot metal entering the converter is 0.09%, the sulfur content is 0.003%, the desulfurization slag cleaning area is 98%, scrap steel is added, the vacuum degree of the RH process is 0.8 mbar, the treatment time is 21 minutes, and calcium treatment is performed after RH treatment. The soft blowing time after calcium treatment is 21 minutes;

[0047] (2) The whole continuous casting process adopts protective pouring, the superheat is 11°C, and the continuous casting billet is pile-cooled off the line for 48 hours to ensure that the billet is slowly cooled;

[0048] (3) Hot rolling: The continuous casting billet is put into the heating furnace for 192 min, the furnace temperature is 1165°C, the outlet temperature of the rough rolling R1 is 935°C, the outlet temperature of the rough rolling R2 is 988°C, the finishing rolling temperature is 961°C, and the final rolling temperature is 820°C;

[0049] (4) Layer cooling water spray cooling is adopted, the cooling time is 20s, and coiling is carried out after cooling, and the coiling temperature is 520℃.

[0050] The performance indicators of the steel prepared in Example 2 under hydrogen and nitrogen environments are shown in Table 5.

[0051] Comparative Example 1

[0052] The steel for hydrogen pipeline in Comparative Example 1 has alloy elements in the proportions shown in Table 3 (the balance is Fe and unavoidable impurities).

[0053] Table 3 Comparative Example 1 Steel Composition %

[0054] Serial number C Si Mn P S Al Nb Ti V Cr Cu Ni Comparative Example 1 0.040 0.19 0.85 0.005 0.0008 0.018 0.032 0.018 0.030 0.31 0.16 0.15

[0055] The method for manufacturing the above steel comprises the following steps:

[0056] (1) Hot metal desulfurization pretreatment: the phosphorus content of hot metal entering the converter is 0.12%, the sulfur content is 0.005%, the desulfurization slag cleaning area is 98%, scrap steel is added, the vacuum degree of the RH process is 1.1 mbar, the treatment time is 15 minutes, and calcium treatment is performed after RH treatment. The soft blowing time after calcium treatment is 20 minutes;

[0057] (2) The whole continuous casting process adopts protective pouring, the superheat is 11°C, and the continuous casting billet is pile-cooled off the line for 48 hours to ensure that the billet is slowly cooled;

[0058] (3) Hot rolling: The continuous casting billet is put into the heating furnace for 252 min, the furnace temperature is 1222°C, the outlet temperature of the rough rolling R1 is 951°C, the outlet temperature of the rough rolling R2 is 994°C, the finishing rolling temperature is 1002°C, and the final rolling temperature is 863°C;

[0059] (4) Layer cooling water spray cooling is adopted, the cooling time is 19s, and coiling is carried out after cooling, and the coiling temperature is 521℃.

[0060] The performance indicators of the steel prepared in Comparative Example 1 under hydrogen and nitrogen environments are shown in Table 5.

[0061] Comparative Example 2

[0062] The steel for hydrogen pipeline in Comparative Example 2 has alloy element proportions as shown in Table 4 (the balance is Fe and unavoidable impurities).

[0063] Table 4 Comparative Example 2 Steel Composition %

[0064] Serial number C Si Mn P S Al Nb Ti V Cr Cu Ni Comparative Example 2 0.070 0.15 1.47 0.010 0.0015 0.028 0.018 0.016 0.018 0.026 0.021 0.011

[0065] The manufacturing method thereof comprises the following steps:

[0066] (1) Hot metal desulfurization pretreatment: the phosphorus content of hot metal entering the converter is 0.15%, the sulfur content is 0.008%, the desulfurization slag cleaning area is 98%, scrap steel is added, the vacuum degree of the RH process is 1.0 mbar, the treatment time is 12 minutes, and calcium treatment is performed after RH treatment. The soft blowing time after calcium treatment is 24 minutes;

[0067] (2) The whole continuous casting process adopts protective pouring, the superheat is 13°C, and the continuous casting billet is pile-cooled off the line for 48 hours to ensure that the billet is slowly cooled;

[0068] (3) Hot rolling: The continuous casting billet is put into the heating furnace for 223 min, the furnace temperature is 1217°C, the outlet temperature of the rough rolling R1 is 968°C, the outlet temperature of the rough rolling R2 is 1065°C, the finishing rolling temperature is 1011°C, and the final rolling temperature is 845°C;

[0069] (4) Layer cooling water spray cooling is adopted, the cooling time is 21s, and coiling is carried out after cooling, and the coiling temperature is 528℃.

[0070] The performance indicators of the steel prepared in Comparative Example 2 under hydrogen and nitrogen environments are shown in Table 5.

[0071] like Figure 2 As shown, the metallographic structure is pearlite (little) + ferrite (large), and at the same time, a banded structure appears in the metallographic structure of Comparative Example 2, which weakens the hydrogen resistance.

[0072] Table 5 Performance test results of steel of Example 1-2 and Comparative Example 1-2

[0073]

[0074] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A X52MH steel for hydrogen pipeline, characterized in that: Its chemical composition and mass percentage are: C: 0.020% ~ 0.045%, Si: 0.11% ~ 0.19%, Mn: 1.05% ~ 1.15%, S: ≤0.0010%, P: ≤0.008%, Al: 0.015% ~ 0.045%, Nb: 0.020% ~ 0.040%, Ti: 0.010% ~ 0.020%, V: 0.015% ~ 0.040%, N: ≤0.004%, O: ≤0.0015%, H: ≤0.0001%, the rest is Fe and other unavoidable impurities.

2. The X52MH hydrogen pipeline steel according to claim 1, characterized in that: The steel has a slow tensile strength of ≥500MPa and a cross-sectional shrinkage of ≥60% for a smooth specimen in a 6.3MPa pure hydrogen atmosphere. 1C ≥120MPa·m 0.5 .

3. The X52MH hydrogen pipeline steel according to claim 1, characterized in that: The steel has a fatigue cycle number of ≥100,000 times under a stress of 360 MPa in a 6.3 MPa pure hydrogen atmosphere.

4. The X52MH hydrogen pipeline steel according to claim 1, characterized in that: The metallographic structure of the steel is ferrite+pearlite.

5. A method for manufacturing the X52MH hydrogen pipeline steel according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) Steelmaking: Hot metal desulfurization pretreatment, phosphorus content of hot metal entering the converter is ≤0.14%, sulfur content is ≤0.005%, desulfurization slag cleaning area is greater than 95%, scrap steel is added, RH process vacuum degree is ≤2.6mbar, vacuum treatment time is maintained for ≥10min, calcium treatment is performed after RH treatment, and soft blowing time after calcium treatment is ≥15min; (2) Continuous casting: The continuous casting billet is pile-cooled, and the pile-cooling time is 36 to 48 hours; (3) Hot rolling: The continuous casting billet is put into a heating furnace for 180-210 min, the furnace temperature is 1150-1180°C, the outlet temperature of the rough rolling R1 is 920-950°C, the outlet temperature of the rough rolling R2 is 970-990°C, the start temperature of the finishing rolling is 940-970°C, and the final rolling temperature is 805-835°C; (4) Cooling and coiling: Use layer cooling water spray cooling, and then coiling after cooling.

6. The manufacturing method according to claim 5, characterized in that: In step (2), protective pouring is adopted in the whole continuous casting process, and the superheat is controlled to be ≤15°C.

7. The manufacturing method according to claim 5, characterized in that: In step (4), the cooling time is 10 to 20 seconds.

8. The manufacturing method according to claim 5, characterized in that: In step (4), the coiling temperature is 480-520°C.

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