Economical hydrigen gas transportation pipeline steel, and production method

Abstract

An economical hydrogen gas transportation pipeline steel comprises the following components in percentage by weight: 0.03-0.08% C. 0.15% or less Si, 0.53-1.19% Mn, 0.012% or less P. 0.0015% or less S, 0.010-0.080% Ti, 0.025-0.048% Al, 0.0045% or less N, and 0.002% or less O. A method comprises: casting a steel into a slab after smelting; heating the slabs; rough rolling; finishing rolling; cooling; and coiling. The yield strength of the steel of the present invention is 298-507 MPa, heat treatment is not needed, the production and manufacturing processes are shortened, and overall energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present invention relates to a pipeline steel and a production method, particularly to a hydrogen gas transportation pipeline steel and a production method.BACKGROUND

[0002] Hydrogen, as a rapidly developing clean energy source, is expected to significantly increase its share in the future energy mix. It is predicted that by 2050, China's total hydrogen consumption will reach 60 million tons. Given that pipeline transportation is the most economical method for long-distance hydrogen delivery, the market demand for hydrogen transportation steel will be substantial.

[0003] To ensure the safe long-distance transportation of hydrogen, materials must exhibit excellent resistance to hydrogen embrittlement. This requires appropriate composition design, high purity, and low segregation of the steel, along with minimal microstructural and residual stresses, ensuring uniform performance throughout the material.Searching Reveals:

[0004] Chinese patent application No. 202111089004.8 discloses a method for producing an L360QS hydrogen conveying pipeline steel. The steel includes the following chemical components: 0.07%-0.10% C, 0.20%-0.30% Si, 0.80%-0.90% Mn, 0.008% or less P, 0.0015% or less S, 0.025%-0.035% Alt, 0.010%-0.020% Nb, 0.015%-0.020% Ti, 0.10-0.15% Cr, 0.0005% or less B, and 0.16%-0.19% Pcm, the balance being Fe and unavoidable impurities. According to the normalized L360QS steel produced in this document, a steel plate has uniform and stable properties, and a difference between the same plates is within 40 MPa; the steel has a yield strength of 380-420 MPa, a tensile strength of 480-560 MPa, an elongation A50 of 45-70%, a yield ratio of 0.75 or less, an impact energy at −40° C. of 300-400 J, and a shear area percentage in a drop-weight tear test at −30° C. of 85-100%. The anti-HIC (Hydrogen-induced cracking) performance indicators CLR (Crack length ratio), CTR (Crack thickness ratio), and CSR (Crack sensitivity ratio) are all 0 in a solution A, and a reduction of area is more than 60%, and an elongation is more than 26% in an experiment with a concentration of 10 MPa H2. However, based on the design concept of conventional H2S corrosion-resistant steel, a low carbon+low manganese+low P and S composition design is adopted, and a normalizing+quenching and tempering or quenching and tempering process is adopted for production to meet the acid resistance requirements of low steel grade products, but its process cost is high and the requirements of high steel grade products are not met.

[0005] Chinese patent application No. 202210304498.5 discloses an L245S hydrogen conveying pipeline steel and a production method thereof. The steel includes the following chemical components: 0.03%-0.05% C, 0.20%-0.28% Si, 0.70%-1.0% Mn, 0.010% or less P, 0.0015% or less S, 0.020%-0.040% Alt, 0.020%-0.030% Nb, 0.006% or less Ca, 0.0005% or less B, and 0.08%-0.12% Pcm, the balance being Fe and unavoidable impurities. This document uses an on-line quenching+off-line tempering process to produce L245S, omitting a reheating process of off-line quenching. The process cost is low, the production cycle is short, the alloy content of the steel is low, and a steel plate has uniform and stable properties, and has good resistance to HIC (Hydrogen-induced cracking), SSCC (Sulfide stress corrosion cracking), and hydrogen embrittlement: in a hydrogen environment with a pressure of 6 MPa, the yield strength is 350-420 MPa, the tensile strength is 440-500 MPa, the reduction of area is more than 50%, and the elongation is more than 25%; the impact toughness is 300-400 J under an impact test at −20° C.; and a shear area percentage is more than 88% under a drop-weight test at −20° C. However, also based on the design concept of conventional H2S corrosion-resistant steel, a low carbon+low manganese+low P and S composition design is adopted, and a normalizing+quenching and tempering or quenching and tempering process is adopted for production to meet the acid resistance requirements of low steel grade products, resulting in higher process costs and not meeting the requirements of high steel grade products.SUMMARY

[0006] This invention addresses the requirements for high-pressure hydrogen transportation pipelines by providing an economical hydrogen gas transportation pipeline steel with a yield strength of 298 to 507 MPa that requires no additional heat treatment, along with a production method thereof.

[0007] Measures to achieve the above object are as follows:

[0008] an economical hydrogen gas transportation pipeline steel includes the following components in percentage by weight: 0.03-0.08% C, 0.15% or less Si, 0.53-1.19% Mn, 0.012% or less P, 0.0015% or less S, 0.010-0.080% Ti, 0.025-0.048% Al, 0.0045% or less N, and 0.002% or less O, the balance being Fe and unavoidable impurities.

[0009] Preferably, the weight percentage content of Ti is 0.019-0.073%.

[0010] Preferably: the weight percentage content of S is 0.0012% or less.

[0011] Preferably: the weight percentage content of N is 0.0041% or less.

[0012] Further: 0.30% or less Cr or 0.20% or less Mo or 0.04% or less Nb or a combination of two or more thereof is added.

[0013] A method for producing the economical hydrogen gas transportation pipeline steel includes the steps of:

[0014] 1) Casting a steel into a slab after smelting, with composition adjustment controlled to be completed during a LF refining stage;

[0015] 2) Heating the slab, wherein the surface and average temperatures should be no less than 650° C. and 700° C., respectively, while ensuring that a phase transformation rate does not exceed 8% during charging a furnace. Alternatively, the slab may be cooled slowly by stacking to 500° C. or below before being charged into a furnace, in which case the phase transformation rate must exceed 92%. The heating temperature is controlled between 1200° C. and 1280° C., preferably for higher furnace charging temperatures to reduce energy consumption during heating.

[0016] 3) performing rough rolling, wherein a total reduction rate of the rough rolling is controlled to be not less than 80%, and a reduction rate of last two passes of the rough rolling is controlled to be not less than 23%;

[0017] 4) performing finishing rolling: wherein a total reduction rate of the finishing rolling is controlled to be 60-85%, and a reduction rate of last two passes is controlled to be 10% or less; and the final rolling temperature is controlled to be 860-920° C.;

[0018] 5) performing cooling, namely performing cooling at a cooling rate of 10-40° C. / s to the coiling temperature; and

[0019] 6) performing coiling, wherein the coiling temperature is controlled to be 550-700° C.

[0020] Further: preferably, a phase transformation rate of the slab is controlled to not exceed 5% when entering the furnace.

[0021] In the invention, the roles and mechanisms of each component and key processes are as follows:

[0022] Carbon (C): Primarily serves for solid solution strengthening to enhance the steel's strength. However, C is prone to segregation, which can lead to the formation of pearlite bands or M / A (martensite / austenite) bands. C is also a strong hardenability element, and excessive C can cause non-uniform phase transformation across the thickness during controlled cooling, both of which negatively impact hydrogen resistance. An optimal C content of 0.03-0.08% is specified. When Ti content is in the range of 0.04-0.08%, it consumes C, helping to mitigate segregation, and allows for an increase in C content to 0.05-0.08%.

[0023] Silicon (Si): In the invention, Si primarily provides solid solution strengthening and assists in desulfurization. However, excessive Si can lead to “tiger stripe” surface defects on the steel strip, causing inconsistent surface cooling efficiency and non-uniform phase transformations across the surface, both of which are detrimental to hydrogen resistance. Therefore, the Si content is limited to ≤0.15%.

[0024] Manganese (Mn): Mn contributes to both solid solution strengthening and increased hardenability. However, Mn belongs to a strong segregation element, and the segregation of Mn can reduce local phase transformation temperatures, exacerbating C segregation. Thus, the Mn content is carefully controlled within 0.53-1.19%.

[0025] Titanium (Ti): Ti provides grain refinement and precipitation strengthening. Being a strong carbide-forming element, Ti forms TiC precipitates, which consume C and help control C segregation. Additionally, finely dispersed Ti precipitated particles act as effective hydrogen traps, enhancing hydrogen resistance. An appropriate Ti content is 0.010-0.080%, with a preferred content of 0.019-0.073 wt. %.

[0026] Aluminum (Al): Al is primarily used as a deoxidizer, reducing the O content in the steel, and also serves to fix N. However, excessive Al can increase the size and quantity of inclusions and reduce the fluidity of molten steel. The recommended Al content is 0.025-0.048%.

[0027] Phosphorus (P), Sulfur(S), Nitrogen (N), and Oxygen (O): These elements are controlled due to their detrimental effects on hydrogen resistance. P tends to segregate at the center, S combines with Mn to form elongated inclusions, N can form large TiN inclusions when combined with Ti, and O increases the size and number of inclusions.

[0028] Chromium (Cr) and Molybdenum (Mo): When added, Cr and Mo primarily contribute to microstructure and grain refinement. Cr segregates similarly to Mn, so Cr content increases require a corresponding reduction in Mn. Mo has less tendency to segregate and can be added in moderate amounts; however, excessive Mo can lead to the formation of hard M / A phases, which should be avoided.

[0029] Niobium (Nb): Typically precipitates alongside Ti, contributing to both grain refinement and precipitation strengthening.

[0030] The invention maintains the slab surface temperature at no less than 650° C. and the average slab temperature at no less than 700° C. when entering the furnace, with the phase transformation rate controlled below 8%, and the heating temperature controlled between 1200° C. and 1280° C. These parameters are set because phase transformation occurs during slab cooling after cutting, where a temperature gradient exists across the slab thickness, causing variations in phase transformation time and proportion. Phase transformation results in microstructural unevenness. However, by keeping the overall phase transformation rate below 8%, microstructure uniformity is relatively maintained on the whole, minimizing inheritance of unevenness into subsequent rolling and controlled cooling processes. When the phase transformation rate falls between 8% and 92%, non-uniform microstructure and phase transformation are likely to carry over through rolling and controlled cooling, impacting the final structure and hydrogen resistance. If the phase transformation rate exceeds 92%, the microstructure essentially completes phase transformation, resulting in relative uniformity again of the microstructure, which minimizes impact on the microstructure in subsequent rolling and cooling processes. However, energy consumption during reheating will increase.

[0031] The total reduction rate during rough rolling is controlled to be no less than 80%, with the reduction rates of the last two passes of rough rolling each no less than 23%. This large deformation in the last two passes accumulates substantial strain in the microstructure, promoting static recrystallization and grain refinement during the transfer of the intermediate slab, which benefits microstructure uniformity in subsequent finishing rolling and controlled cooling.

[0032] In finishing rolling, the total reduction rate is controlled between 60% and 85%, with the reduction rate of the last two passes limited to ≤10%, and the final rolling temperature controlled between 860° C. and 920° C. A higher final rolling temperature, along with limiting the reduction rate in the last two passes, helps avoid phase transformation during rolling and prevents the formation of localized hard-phase bands on the surface, thereby reducing the risk of hydrogen blistering.

[0033] The cooling rate is controlled between 10° C. / s and 40° C. / s down to the coiling temperature, as an excessively high cooling rate may lead to non-uniform properties of the microstructure across the thickness of the slab, which is detrimental to hydrogen resistance. Additionally, rapid cooling can cause localized hard zones on the surface of the slab, increasing the risk of hydrogen blistering.

[0034] The coiling temperature is controlled between 550° C. and 700° C. to allow for coiling at a relatively high temperature. Slow cooling of a steel coil in air enables self-tempering, which further relieves phase transformation stress in the microstructure and enhances hydrogen resistance.

[0035] Compared with the prior art, this invention achieves a yield strength of 298-507 MPa without requiring heat treatment, thereby shortening the production process and reducing overall energy consumption.BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 is a metallographic structure diagram of the present invention.DETAILED DESCRIPTION

[0037] The invention is described in detail below:

[0038] Table 1 provides a list of the chemical compositions for each example and comparative example of the invention.

[0039] Table 2 presents the main process parameters for each example and comparative example of the invention.

[0040] Table 3 lists the performance characteristics of each example and comparative example of the invention.

[0041] The steels in the embodiments of the present invention are produced according to the following steps:

[0042] 1) After smelting, a steel is cast into a slab, with composition adjustment controlled to be completed during an LF (Ladle Furnace) refining stage.

[0043] 2) Heating the slab, wherein the surface and average temperatures should be no less than 650° C. and 700° C., respectively, while ensuring that a phase transformation rate does not exceed 8% during charging a furnace. The heating temperature is controlled between 1200° C. and 1280° C.

[0044] 3) Rough rolling is performed, with a total reduction rate of the rough rolling controlled at no less than 80%, and the reduction rate of the final two passes of rough rolling at no less than 23%.

[0045] 4) Finishing rolling is performed, with a total reduction rate of the finishing rolling controlled between 60% and 85%, and the reduction rate of the final two passes kept at ≤10%, The final rolling temperature is controlled within the range of 860° C. to 920° C.

[0046] 5) Cooling is conducted, cooling the steel to the coiling temperature at a cooling rate of 10-40° C. / s.

[0047] 6) Coiling is performed, with the coiling temperature controlled between 550° C. and 700° C.TABLE 1Value list of compositions in Embodiments and Comparative examples of the present invention (wt %)EmbodimentComparativeComparativeElement12345678910example 1example 2C0.0550.0530.0480.0770.0480.0510.0410.080.0560.0330.0730.113Si0.1360.0720.0850.150.0350.0780.0760.1430.0240.1260.050.26Mn0.880.641.190.551.121.061.140.530.731.010.721.34P0.0070.0070.0060.0090.0110.010.010.0070.0110.010.0180.015S0.00130.00080.00090.00080.00090.00150.00090.00060.00120.00150.00200.019Ti0.0360.0430.0560.0170.0740.0270.0230.0680.0150.0360.1050.028Al0.0310.0260.0250.0390.0370.0440.0290.0480.0440.0270.0310.021N0.00430.00220.00310.0030.00390.00350.00250.00420.00260.00450.00350.0051O0.0010.00130.00190.00070.00050.00090.00090.00030.00160.00190.0013 / Nb / / / / / 0.0140.025 / 0.028 / / / Mo / / / / / / / / / 0.15 / / Cr / / / / / 0.13 / 0.270.11 / / / TABLE 2List of main process parameters in Embodiments and Comparative examples of the present inventionSurfaceAveragePhaseReductiontemperaturetemperaturechange raterate ofCumulativeCumulativeof castof castof castCastlast tworeductionreductionblankblankblank beforeblankpasses ofrate ofrate ofFinalentering aentering aentering aheatingroughroughfinishingrollingCoolingCoilingfurnacefurnacefurnacetemperaturerollingrollingrollingtemperatureratetemperatureEmbodiment° C.° C.%° C.%%%° C.°C. / s° C.1810875<5%127223.181.770.4905356082670745<5%125623.681.377.8915206943810827<5%120125.781.566.7914256494769861<5%121125.583.968.3906336245718831<8%120524.382.676.6883266336786853<5%120123.683.584.6865335887113185>92% 122824.185.166.7861386588209294>92% 127823.584.663.8891325879109155>92% 121823.482.973.48802955210448559>92% 122024.485.377.886914570Comparative58164765%124319.784.480.183673584example 1Comparative63465155%129021.376.971.981955672example 2TABLE 3Performance list in Embodiments and Comparative examples of the present inventionHydrogen-Sulfide stressH2 ambientinducedcorrosionelongation / YieldTensileImpactcrackingcracking (SSCC)conventionalstrengthstrengthenergyDWTT-SA(HIC) inHydrogenunder 80%ambientEmbodimentMPaMPaat −20° C. Jat −15° C. %solution Abubblingstresselongation1365463300100%No cracksNoNo cracks100.32321448330100%No cracksNoNo cracks100.73408507312100%No cracksNoNo cracks98.24298423277 95%No cracksNoNo cracks97.95449572271100%No cracksNoNo cracks99.46456586372100%No cracksNoNo cracks98.17441583292100%No cracksNoNo cracks96.98483592313 95%No cracksNoNo cracks98.49488589355100%No cracksNoNo cracks98.810507608386100%No cracksNoNo cracks96.3Comparative589701124 67%CrackedYesCracked81.6example 1Comparative493544115 53%CrackedYesCracked85.7example 2As shown in Table 3, the designed product achieves excellent toughness and hydrogen resistance without the need for high-energy offline heat treatment. The elongation in a hydrogen environment reaches 96% or above of the elongation observed in standard conditions.This specific embodiment is merely an exemplary implementation and is not intended to limit the technical scope of the invention.

Claims

1. An economical hydrogen gas transportation pipeline steel, characterized by comprising the following components in percentage by weight:0.03-0.08% C, 0.15% or less Si, 0.53-1.19% Mn, 0.012% or less P, 0.0015% or less S, 0.010-0.080% Ti, 0.025-0.048% Al, 0.0045% or less N, and 0.002% or less O, the balance being Fe and unavoidable impurities.

2. The economical hydrogen gas transportation pipeline steel according to claim 1, characterized in that the weight percentage content of Ti is 0.019-0.073%.

3. The economical hydrogen gas transportation pipeline steel according to claim 1, characterized in that the weight percentage content of S is 0.0012% or less.

4. The economical hydrogen gas transportation pipeline steel according to claim 1, characterized in that the weight percentage content of N is 0.0041% or less.

5. The economical hydrogen gas transportation pipeline steel according to claim 1, characterized in that 0.30% or less Cr or 0.20% or less Mo or 0.04% or less Nb or a combination of two or more thereof is added.

6. A method for producing the economical hydrogen gas transportation pipeline steel according to claim 1, characterized by the steps of:1) casting a steel into a slab after smelting, with composition adjustment controlled to be completed during a LF refining stage;2) heating the slab, wherein the surface and average temperatures should be no less than 650° C. and 700° C., respectively, while ensuring that a phase transformation rate does not exceed 8% during charging a furnace; alternatively, the slab may be cooled slowly by stacking to 500° C. or below before being charged into a furnace, in which case the phase transformation rate must exceed 92%; the heating temperature is controlled between 1200° C. and 1280° C.;3) performing rough rolling, wherein a total reduction rate of the rough rolling is controlled to be not less than 80%, and a reduction rate of last two passes of the rough rolling is controlled to be not less than 23%;4) performing finishing rolling: wherein a total reduction rate of the finishing rolling is controlled to be 60-85%, and a reduction rate of last two passes is controlled to be 10% or less; and the final rolling temperature is controlled to be 860-920° C.;5) performing cooling, namely performing cooling at a cooling rate of 10-40° C. / s to the coiling temperature; and6) performing coiling, wherein the coiling temperature is controlled to be 550-700° C.

7. The method for producing the economical hydrogen gas transportation pipeline steel according to claim 6, characterized in that a phase transformation rate of the slab is controlled to not exceed 5% when entering the furnace.

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