Manufacturing method of seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline

Abstract

The invention discloses a manufacturing method of a seamless steel tube for an ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline, the raw material is a round tube blank of the seamless steel tube for L415QH hydrogen transportation, and the round tube blank comprises the following chemical components in percentage by mass: 0.05-0.07% of C; 0.25 to 0.35 percent of Si; 1.20% to 1.35% of Mn; 0.18 to 0.28 percent of Cr; 0.10 to 0.15% of Mo; 0.02 to 0.04 percent of V; less than or equal to 0.015% of P; s < = 0.003%; 0.01 to 0.02 percent of Ti; the content of RE is 0.0010 to 0.0020 percent; and the balance of iron and impurities. The technological process comprises the steps of pipe blank heating, perforating, continuous rolling, sizing, cooling, saw cutting, off-line heat treatment, flaw detection, water pressure detection, manual inspection and detection analysis. The product disclosed by the invention has the characteristics of low production cost, energy conservation, environmental protection, stable mechanical property of the steel pipe and good toughness performance matching.

Description

Technical Field

[0001] This invention belongs to the field of ferrous metal smelting and metal pressure processing technology, and particularly relates to a method for manufacturing a seamless steel pipe for ultra-low carbon rare earth L415QH pure hydrogen long-distance pipeline. Background Technology

[0002] Hydrogen energy boasts outstanding advantages such as convenient storage and transportation, diverse sources, and clean and environmentally friendly characteristics, making it a crucial component of the future energy structure. Many countries have prioritized hydrogen energy development as a key energy strategy. Hydrogen transportation is a vital link in hydrogen energy utilization, and safe and efficient hydrogen transportation technology is a prerequisite for the large-scale commercial development of hydrogen energy. This invention relates to a seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipelines, achieving economic reliability and stable performance, perfecting the high-end pipeline product series, enhancing product market competitiveness, and creating significant economic benefits for the company. Summary of the Invention

[0003] The purpose of this invention is to provide a method for manufacturing seamless steel pipes for ultra-low carbon rare earth L415QH pure hydrogen long-distance pipelines. After inspection and testing, the dimensional accuracy, surface quality, chemical composition, and mechanical properties meet the requirements for seamless steel pipes for L415QH hydrogen pipelines.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a method for manufacturing a seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipelines, comprising the following steps:

[0006] 1) Produce L415QH seamless steel round tube billets for hydrogen transportation with qualified chemical composition and quality, so that the carbon equivalent CEpcm in the steel is ≤0.19%;

[0007] 2) The round tube blank is loaded into the annular heating furnace and heated through three sections: preheating section, heating section and soaking section. The temperature of the preheating section is 650~950℃, the temperature of the heating section is 950~1200℃, and the temperature of the soaking section is 1220~1260℃.

[0008] 3) The round tube billet exits the annular heating furnace and is sent to the piercing mill for piercing. The consistency of the piercing mill body and the front and rear rolling center lines is ensured, and the temperature after piercing is ≥1130℃.

[0009] 4) The pierced tube is fed into the Ф460mmPQF hot continuous rolling mill for continuous rolling, ensuring that the temperature of the tube before entering the continuous rolling mill is ≥950℃.

[0010] 5) Depending on the wall thickness of the steel pipe, the sizing unit selects different numbers of frames for sizing to ensure that the temperature of the steel pipe after sizing is ≥850℃.

[0011] 6) After the steel pipes leave the sizing unit, they are air-cooled on the cooling bed. After being air-cooled to room temperature, they are sawed, flawed, and manually inspected.

[0012] 7) Perform quenching and tempering heat treatment on hot-rolled seamless steel pipes that meet the appearance and dimensions. The temperature of the holding section of the heating furnace is 920±10℃, and the holding time is 5-10 minutes. The temperature of the tempering furnace is 680±10℃, and the holding time is 5-10 minutes. Then, the pipes are taken out of the furnace and air-cooled.

[0013] 8) After heat treatment, seamless steel pipes undergo straightening, flaw detection, hydrostatic testing, and sampling, and are subjected to relevant tests. Samples are taken for chemical composition and mechanical property analysis.

[0014] The chemical composition of the seamless steel pipe by mass percentage is as follows: C 0.05-0.07%, Si 0.25-0.35%, Mn 1.10-1.20%, P≤0.010%, S≤0.003%, Cr 0.18-0.28%, Mo 0.10-0.15%, V 0.02-0.04%, Ti 0.01-0.02%, Re 0.001-0.002%, with the remainder being Fe and unavoidable impurities.

[0015] Furthermore, the production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 14.3mm × 12000mm.

[0016] Furthermore, the production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 15.9mm × 12000mm.

[0017] Furthermore, the production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 9.5mm × 11500mm.

[0018] Furthermore, the chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.06%, Si 0.28%, Mn 1.15%, P 0.009%, S 0.002%, Cr 0.21%, Mo 0.11%, V 0.03%, Ti 0.012%, Re 0.0012%, with the remainder being Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.058%, Si 0.29%, Mn 1.14%, P 0.008%, S 0.001%, Cr 0.20%, Mo 0.13%, V 0.03%, Ti 0.011%, Re 0.0011%, with the remainder being Fe and unavoidable impurities.

[0020] Furthermore, the chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.064%, Si 0.27%, Mn 1.16%, P 0.008%, S 0.002%, Cr 0.19%, Mo 0.12%, V 0.03%, Ti 0.013%, Re 0.0013%, with the remainder being Fe and unavoidable impurities.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] ① The chemical composition adopts a C+Mn+Cr+Mo+V+Ti alloying system, which provides a combination of solid solution strengthening and grain refinement strengthening, thereby improving the strength and impact toughness of the material. The L415QH seamless steel pipe for hydrogen transportation is produced through ultra-low carbon alloying design and offline normalizing process, achieving low-carbon production. The product performance meets the requirements of Appendix A of GB / T9711 standard, with a carbon equivalent CEpcm ≤ 0.19%.

[0023] ② A low-temperature heating system is adopted. The round tube blank is loaded into the annular heating furnace and heated through three sections: preheating section, heating section and soaking section. The final soaking section temperature is 1220~1260℃, and the total heating time is controlled within 3.5 hours.

[0024] ③ Ensure that the temperature after piercing is ≥1130℃, the temperature entering the continuous rolling mill is ≥950℃, and the temperature exiting the sizing unit is ≥850℃. Temperature control is crucial in key processes. Through product heat treatment, the steel pipe exhibits excellent performance characteristics. Specific performance indicators are as follows:

[0025] Yield strength: 430~450MPa; Tensile strength: 550~580MPa; Yield-to-tensile ratio: ≤0.80; Elongation: ≥40%; Transverse impact value at -50℃: KV8≥200J / cm 2 Shear area ratio ≥85%; grain size: ≥9.0 grade.

[0026] This invention addresses the problems existing in the background technology by providing a "manufacturing method for an ultra-low carbon L415QH seamless steel pipe for hydrogen transportation," which effectively solves the aforementioned technical problems and achieves significant progress. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 This is a microscopic tissue photograph of Example 1;

[0029] Figure 2 This is a microscopic tissue photograph of Example 2;

[0030] Figure 3 This is a microscopic tissue photograph of Example 3. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to Examples 1 to 3.

[0032] The L415QH seamless steel round tube billet for hydrogen transportation has qualified chemical composition and quality, resulting in a carbon equivalent CEpcm of ≤0.19% in the steel.

[0033] The production process sequence is as follows: billet heating → piercing → continuous rolling → sizing → cooling → sawing → heat treatment → flaw detection → hydrostatic testing → manual inspection → testing and analysis.

[0034] The specific production process is briefly described below:

[0035] 1. Produce L415QH seamless steel round tube billets for hydrogen transportation with qualified chemical composition and quality, so that the carbon equivalent CEpcm in the steel is ≤0.19%;

[0036] 2. The round tube blank is loaded into the annular heating furnace and heated through three sections: preheating section, heating section, and soaking section. The temperature of the preheating section is 650-950℃, the temperature of the heating section is 950-1200℃, and the temperature of the soaking section is 1220-1260℃.

[0037] 3. The round tube billet exits the annular heating furnace and is sent to the piercing mill for piercing. Ensure the consistency of the piercing mill body and the front and rear rolling center lines, and ensure that the temperature after piercing is ≥1130℃.

[0038] 4. The pierced tube is fed into the Ф460mmPQF hot continuous rolling mill for continuous rolling, ensuring that the temperature of the tube before entering the continuous rolling mill is ≥950℃.

[0039] 5. Depending on the wall thickness of the steel pipe, the sizing unit selects different numbers of frames for sizing to ensure that the temperature of the steel pipe after sizing is ≥850℃.

[0040] 6. After the steel pipes leave the sizing unit, they are air-cooled on the cooling bed. After being air-cooled to room temperature, they are sawed, inspected for flaws, and manually checked.

[0041] 7. For hot-rolled seamless steel pipes with qualified appearance and dimensions, perform quenching and tempering heat treatment. The temperature of the holding section of the heating furnace is 920±10℃, and the holding time is 5-10 minutes. The temperature of the tempering furnace is 680±10℃, and the holding time is 5-10 minutes. Then, the pipes are taken out of the furnace and air-cooled.

[0042] 8. After heat treatment, seamless steel pipes undergo straightening, flaw detection, hydrostatic testing, and sampling, and are subjected to relevant tests. Samples are taken for chemical composition and mechanical property analysis.

[0043] Seamless steel pipes for hydrogen transportation, L415QH, with the following specifications (outer diameter × wall thickness × length): Ф457mm × 14.3mm × 12000mm (Example 1), Ф457mm × 15.9mm × 12000mm (Example 2), and Ф457mm × 9.5mm × 11500mm (Example 3), produced by offline normalizing process, were sampled and tested. The chemical composition analysis results (weight percentage content) are shown in Table 1, the mechanical property test results are shown in Table 2, the metallographic property test results are shown in Table 3, and the microstructure photographs are shown in [Table 4]. Figures 1-3 As shown.

[0044] Table 1. Chemical composition analysis results (Wt.%) of L415QOH tube blank.

[0045] C Si Mn P S Cr Mo V Ti RE <![CDATA[CE pcm ]]> Example 1 0.060 0.28 1.15 0.009 0.002 0.21 0.11 0.03 0.012 0.001 0.115 Example 2 0.058 0.29 1.14 0.008 0.001 0.20 0.13 0.03 0.011 0.001 0.119 Example 3 0.064 0.27 1.16 0.008 0.002 0.19 0.12 0.03 0.013 0.001 0.118

[0046] Table 2. Mechanical property test results of L415QOH seamless steel pipes

[0047] <![CDATA[R t0.5 (MPa)]]> <![CDATA[R m (MPa)]]> <![CDATA[R t0.5 / R m ]]> A(％) <![CDATA[KV8(-50℃, horizontal, J / cm 2 )]]> Shear area ratio, % Example 1 438 563 0.78 40 245，257，256 100,100,100 Example 2 445 567 0.78 41 249，261，275 100,100,100 Example 3 448 569 0.78 40 254，270，261 100,100,100

[0048] Table 3 Metallographic Performance Test Results (Grade) of L415QH Seamless Steel Pipe

[0049]

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for manufacturing a seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipelines, characterized in that, Includes the following steps: 1) Produce L415QH seamless steel round tube billets for hydrogen transportation with qualified chemical composition and quality, so that the carbon equivalent CEpcm in the steel is ≤0.19%; 2) The round tube blank is loaded into the annular heating furnace and heated through three sections: preheating section, heating section and soaking section. The temperature of the preheating section is 650~950℃, the temperature of the heating section is 950~1200℃, and the temperature of the soaking section is 1220~1260℃. 3) The round tube billet exits the annular heating furnace and is sent to the piercing mill for piercing. The consistency of the piercing mill body and the front and rear rolling center lines is ensured, and the temperature after piercing is ≥1130℃. 4) The pierced tube is fed into the Ф460mmPQF hot continuous rolling mill for continuous rolling, ensuring that the temperature of the tube before entering the continuous rolling mill is ≥950℃. 5) Depending on the wall thickness of the steel pipe, the sizing unit selects different numbers of frames for sizing to ensure that the temperature of the steel pipe after sizing is ≥850℃. 6) After the steel pipes leave the sizing unit, they are air-cooled on the cooling bed. After being air-cooled to room temperature, they are sawed, flawed, and manually inspected. 7) Perform quenching and tempering heat treatment on hot-rolled seamless steel pipes that meet the appearance and dimensions. The temperature of the holding section of the heating furnace is 920±10℃, and the holding time is 5-10 minutes. The temperature of the tempering furnace is 680±10℃, and the holding time is 5-10 minutes. Then, the pipes are taken out of the furnace and air-cooled. 8) After heat treatment, seamless steel pipes undergo straightening, flaw detection, hydrostatic testing, and sampling, and are subjected to relevant tests. Samples are taken for chemical composition and mechanical property analysis. The chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.05-0.07%, Si 0.25-0.35%, Mn 1.10-1.20%, P≤0.010%, S≤0.003%, Cr 0.18-0.28%, Mo 0.10-0.15%, V 0.02-0.04%, Ti 0.01-0.02%, Re 0.001-0.002%, with the remainder being Fe and unavoidable impurities.

2. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 14.3mm × 12000mm.

3. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 15.9mm × 12000mm.

4. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The production specifications are: outer diameter of steel pipe × wall thickness of steel pipe × length of steel pipe = Ф457mm × 9.5mm × 11500mm.

5. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The chemical composition of the seamless steel pipe by mass percentage is as follows: C 0.06%, Si 0.28%, Mn 1.15%, P 0.009%, S 0.002%, Cr 0.21%, Mo 0.11%, V 0.03%, Ti 0.012%, Re 0.0012%, with the remainder being Fe and unavoidable impurities.

6. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.058%, Si 0.29%, Mn 1.14%, P 0.008%, S 0.001%, Cr 0.20%, Mo 0.13%, V 0.03%, Ti 0.011%, Re 0.0011%, with the remainder being Fe and unavoidable impurities.

7. The manufacturing method of the seamless steel pipe for ultra-low carbon rare earth-containing L415QH pure hydrogen long-distance pipeline according to claim 1, characterized in that, The chemical composition of the seamless steel pipe by weight percentage is as follows: C 0.064%, Si 0.27%, Mn 1.16%, P 0.008%, S 0.002%, Cr 0.19%, Mo 0.12%, V 0.03%, Ti 0.013%, Re 0.0013%, with the remainder being Fe and unavoidable impurities.

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