X60-grade high-niobium pipeline steel for hydrogen transportation as well as preparation method and application of X60-grade high-niobium pipeline steel

Abstract

The invention belongs to the technical field of pipeline steel, and particularly relates to X60-grade high-niobium pipeline steel for hydrogen transmission and a preparation method and application thereof. The X60-grade high-niobium pipeline steel for hydrogen transmission comprises 0.030%-0.055% of C, 0.08%-0.13% of Si, 0.90%-1.30% of Mn, 0.075%-0.120% of Nb, 0.010%-0.020% of V, 0.010%-0.020% of Ti, smaller than or equal to 0.035% of Al, smaller than or equal to 0.001% of S, smaller than or equal to 0.012% of P, smaller than or equal to 0.0050% of N, smaller than or equal to 0.0002% of H, smaller than or equal to 0.0030% of O and the balance Fe, and the range of CEpcm is 0.11%-0.14. The X60-grade high-niobium hydrogen transmission pipeline steel with extremely excellent hydrogen resistance can be obtained, the cost is relatively low, and heat treatment is not needed.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline steels, and in particular relates to an X60 grade high-niobium pipeline steel for hydrogen transmission, and a preparation method and application thereof. Background Art

[0002] Hydrogen energy is a clean secondary energy source that can be used as an efficient energy storage carrier. Due to the large differences in the physical properties of natural gas and hydrogen, high-pressure hydrogen causes the degradation of the relevant mechanical properties of pipeline steel. Therefore, the standard specifications for long-distance natural gas pipelines cannot be directly used for design and construction. New hydrogen pipelines face problems such as poor hydrogen resistance of pipeline steel materials in hydrogen environments, difficulty in determining process parameters, and lack of supporting standards. It is urgent to develop special steel for hydrogen transportation to meet the development needs of a hydrogen energy society.

[0003] The existing hydrogen pipeline steel technology does not significantly reduce the S, P, C, Mn, Si, Al and other elemental components that are prone to segregation at the same time; does not add micro-alloying elements such as high Nb, trace V and trace Ti at the same time; does not control the cooling rate of accelerated cooling to 15°C / s; does not refine the structure through a large rolling deformation, a low final rolling temperature and a fast cooling rate, and does not ensure that the grain size is greater than level 11; many existing hydrogen steel patents require tempering heat treatment; many hydrogen steel patents require the addition of Cu, Cr, Ni. The inventors of this application found that the simultaneous addition of Cu, Cr, and Ni that are prone to segregation will instead cause the hydrogen resistance of the pipeline steel to decrease. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides an X60 grade high niobium hydrogen transport pipeline steel and its preparation method and application. Through the present invention, an X60 grade high niobium hydrogen transport pipeline steel with extremely excellent hydrogen resistance can be obtained without heat treatment.

[0005] The technical solution provided by the present invention is as follows:

[0006] The invention discloses an X60 grade high niobium pipeline steel for hydrogen transportation, comprising the following components in weight percentage: C: 0.030-0.055%, Si: 0.08-0.13%, Mn: 0.90-1.30%, Nb: 0.075-0.120%, V: 0.010-0.020%, Ti: 0.010-0.020%, Al≤0.035%, S≤0.001%, P≤0.012%, N≤0.0050%, H≤0.0002%, O≤0.0030%, and the balance is Fe. The Cepcm range is 0.11-0.14.

[0007] The above X60 grade high niobium hydrogen transport pipeline steel has extremely excellent hydrogen resistance and good mechanical properties.

[0008] Preferably, X60 grade high niobium pipeline steel for hydrogen transport comprises the following components in weight percentage: C: 0.045%, Si: 0.11%, Mn: 1.17%, Nb: 0.091%, V: 0.017%, Ti: 0.018%, Al: 0.031%, S: 0.0008%, P: 0.008%, N: 0.0033%, H: 0.00009%, O: 0.0025%, and the balance is Fe.

[0009] The specific description of the functions and dosage selection of each component in X60 grade high niobium hydrogen pipeline steel is as follows:

[0010] S: S is an impurity element in steel and is very easy to segregate. The inventors of the present application found that the maximum segregation degree of S is 28.01. The segregation of S in pipeline steel will increase the sensitivity to hydrogen embrittlement in a high-pressure gaseous hydrogen environment. Therefore, the present invention controls the S content to ≤0.001%.

[0011] Al: Al is the main deoxidizing element in steel, but it is also an element that is very easy to segregate. The inventors of this application found that the maximum segregation degree of Al is 7.18. At the same time, when the aluminum content in steel exceeds a certain amount, it is easy to cause a significant increase in large-sized aluminum oxide inclusions. Segregation and inclusions will increase the hydrogen embrittlement sensitivity of pipeline steel in a high-pressure gaseous hydrogen environment. Therefore, the present invention controls the Al content to ≤0.035.

[0012] C: C is an effective strengthening element, but it is an element that is very easy to segregate. The inventors of this application found that the maximum segregation degree of C is 6.45. An increase in C content will lead to aggravated segregation, resulting in increased hydrogen embrittlement sensitivity in a high-pressure gaseous hydrogen environment, and deterioration of welding performance. The present invention controls the C content to 0.030% to 0.055%.

[0013] Cr: Cr can improve strength and corrosion resistance, but the high-pressure gas hydrogen environment is different from the hydrogen sulfide corrosion environment, and it is not necessary to intentionally add elements to improve corrosion resistance. The Cr element is an element that is easily segregated. The inventor of this application found that the maximum segregation degree of Cr is 2.98. In order to improve the hydrogen embrittlement resistance of pipeline steel, Cr is not added in this application.

[0014] P: P is an impurity element in steel and is easy to segregate. The inventors of the present application found that the maximum segregation degree of P is 2.59. The segregation of P in pipeline steel will increase the sensitivity to hydrogen embrittlement in a high-pressure gaseous hydrogen environment. Therefore, the present invention controls the P content to ≤0.012%.

[0015] Si: Si is an effective strengthening element, but Si is an element that is very easy to segregate. The inventors of this application found that the maximum segregation degree of Si is 2.00. An increase in Si content will lead to aggravated segregation and increased hydrogen embrittlement sensitivity in a high-pressure gaseous hydrogen environment. The present invention controls the Si content to 0.08% to 0.13%.

[0016] Cu: Cu can improve strength and corrosion resistance, but the high-pressure gas hydrogen environment is different from the hydrogen sulfide corrosion environment, and it is not necessary to intentionally add elements to improve corrosion resistance. The Cu element is an element that is easily segregated. The inventor of this application found that the maximum segregation degree of Cu is 1.70. In order to improve the hydrogen embrittlement resistance of pipeline steel, Cu is not added in this application.

[0017] Ni: Ni can improve strength, toughness and corrosion resistance, but the high-pressure gas hydrogen environment is different from the hydrogen sulfide corrosion environment, and it is not necessary to intentionally add elements to improve corrosion resistance. Ni is an element that is easily segregated and is relatively expensive. The inventor of this application found that the maximum segregation degree of Ni is 1.65. In order to improve the hydrogen embrittlement resistance of pipeline steel, Ni is not added in this application.

[0018] Mn: Mn can improve the strength of pipeline steel and is inexpensive, but Mn is an element that easily segregates. The inventors of this application found that the maximum segregation degree of copper is 1.62. In order to improve the hydrogen embrittlement resistance of pipeline steel, the Mn content is controlled in this application to be 0.90-1.30%.

[0019] Microalloying elements Nb, V and Ti: Nb, V and Ti elements all have the effects of fine grain strengthening and precipitation strengthening. Nb, V and Ti have relatively small segregation tendencies. Compared with other alloying elements, only a small amount of Nb, V and Ti need to be added to the steel to obtain significant performance improvements. Nb, V and Ti elements can obtain a large number of nano-precipitate particles, which can not only improve the strength of pipeline steel, but also form hydrogen traps for pinning hydrogen atoms, greatly improving the hydrogen embrittlement resistance. V also has a significant effect on improving the softening of the heat affected zone of welding. This application increases the amount of Nb added to ensure that the strength of the steel can reach X60 grade. The Nb content in the steel is controlled within the range of 0.075-0.120%, the V content is controlled within the range of 0.010-0.020%, and the Ti content is controlled within the range of 0.010-0.020%. The synergistic effect of high Nb and a small amount of V and Ti elements is used to obtain a high-strength and high hydrogen resistance hydrogen transmission pipeline steel.

[0020] O: O tends to increase the size and quantity of inclusions, which is not conducive to hydrogen resistance. In this application, the content of O is controlled to be ≤0.0030%.

[0021] N: N is easy to combine with Ti to form oversized TiN inclusions. At the same time, the increase of free N will also deteriorate the mechanical properties of the steel. This application determines that the N content in the steel is controlled at ≤0.0050%.

[0022] The present invention also provides a method for preparing X60 grade high niobium pipeline steel for hydrogen transmission, comprising the following steps: sequentially performing molten iron desulfurization, converter oxygen blowing decarburization, LF treatment, RH treatment, continuous casting, billet heating, rough rolling, finish rolling, and rapid cooling, wherein no heat treatment is required after the finish rolling step.

[0023] Preferably, during the heating of the ingot, the heating temperature of the heating furnace is 1190-1240° C., and the insulation time of the heating furnace is 130-160 min.

[0024] Preferably, in the rough rolling, the starting temperature of the rough rolling is 1000-1060°C, the outlet temperature of the rough rolling is 930-980°C; the reduction ratios of the two passes at the end of the rough rolling are both greater than 20%, and the cumulative reduction ratio of the rough rolling is greater than 80%.

[0025] Preferably, in the finishing rolling, the starting temperature of the finishing rolling is 910-950°C, the outlet temperature of the finishing rolling is 800-840°C, and the curling temperature is 525-585°C; the reduction rate of each finishing rolling pass is greater than 10%, and the cumulative reduction rate of the finishing rolling is greater than 65%.

[0026] Preferably: during the rapid cooling, the cooling rate is ≥15°C / s.

[0027] In the above technical solution:

[0028] LF is deep deoxidation and desulfurization treatment. The RH process is mainly to remove impurities such as H and N, and use Ca treatment to modify inclusions. Electromagnetic stirring or dynamic light pressure is used to improve the segregation of continuous casting billets, and the low-multiple rating of the casting billets is controlled within C1.0. The heating temperature of the heating furnace is 1190-1240℃. Slightly increasing the heating temperature promotes the full dissolution of micro-alloy elements such as Nb, V and Ti. The holding time of the heating furnace is 130-160min. The holding time is shortened and the grain boundary dragging effect of the Nb element is combined to refine the reheated austenite grain size. The rough rolling start temperature is 1000-1060℃, and the rough rolling outlet temperature is 930-980℃; the reduction rate of the last two passes of rough rolling is greater than 20%, and the cumulative reduction rate of rough rolling is greater than 80%. The finishing rolling start temperature is 910-950°C, the finishing rolling exit temperature is 800-840°C, and the curling temperature is 525-585°C; the finishing rolling reduction rate is greater than 10% per pass, and the finishing rolling cumulative reduction rate is greater than 65%. Under the condition of constant composition and segregation of the ingot, the cooling rate plays an important role in the control of pearlite banding, and the formation of banded structure can be suppressed by accelerated cooling. By comparing the changes in banded structure under different cooling rates, the inventors found that when the cooling rate increases from 2°C / s to 25°C / s, the banded structure is significantly controlled. The present invention preferably has an accelerated cooling rate of ≥15°C / s.

[0029] The present invention also provides X60 grade high niobium hydrogen transport pipeline steel prepared according to the above preparation method, with yield strength Rt0.5: 450-500MPa, tensile strength Rm: -540-600MPa, -20°C impact energy KV2≥320J, hardness HV10: 180-200, and cross-sectional shrinkage rate of 65% in a 6.3MPa hydrogen environment.

[0030] The present invention also provides an application of the X60 grade high niobium hydrogen transport pipeline steel for manufacturing The above large-diameter high-pressure hydrogen transmission pipeline is preferably used to make an X60-grade hydrogen transmission pipeline.

[0031] The beneficial effects of the present invention are as follows:

[0032] The present invention significantly reduces the S, P, C, Mn, Si, Al and other element components that are easily segregated in pipeline steel, and significantly improves the hydrogen embrittlement resistance of pipeline steel products in a high-pressure gaseous hydrogen environment; the strength of the steel is improved by adding high Nb, a small amount of V and Ti microalloying elements, which makes up for the insufficient strength problem caused by reducing the content of elements such as C, Mn, Si, etc. At the same time, the nanophase precipitated by the Nb, V and Ti microalloying elements can be used as a hydrogen trap to significantly improve the hydrogen resistance of the pipeline steel. During the reheating process of the ingot, the original austenite grain size is refined by controlling the heating temperature and heating time, and the organization is refined by a large rolling deformation, a low final rolling temperature and a fast cooling rate to ensure that the grain size is greater than level 11. Rapid cooling can also reduce the generation of banded organization in the steel, thereby obtaining an X60-grade high-niobium hydrogen transport pipeline steel with extremely excellent hydrogen resistance, and no heat treatment is required;

[0033] The X60 grade high niobium hydrogen transport pipeline steel of the present invention has the following characteristics: yield strength Rt0.5: 450-500MPa, tensile strength Rm: 540-600MPa, -20°C impact energy KV2≥320J, hardness HV10: 180-200, and section shrinkage rate of 65% in a 6.3MPa hydrogen environment, and has extremely excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the metallographic structure diagram of Example 2. DETAILED DESCRIPTION

[0035] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0036] Unless otherwise specified, the test methods used in the embodiments of the present invention are all conventional methods; the materials, reagents, etc. used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0037] The steel of each example was prepared as follows:

[0038] The processes are carried out in sequence: molten iron desulfurization, converter oxygen blowing decarburization, LF treatment, RH treatment, continuous casting, ingot heating, rough rolling, hot rolling and rapid cooling.

[0039] During the heating of the ingot, the heating temperature of the heating furnace is about 1215° C., and the insulation time of the heating furnace is about 145 minutes.

[0040] The starting temperature of rough rolling is 1060°C, and the outlet temperature of rough rolling is 955°C; the reduction rates of the last two passes of rough rolling are both greater than 20%, and the cumulative reduction rate of rough rolling is greater than 80%.

[0041] In the hot rolling of the rolling mill, the finishing rolling start temperature is about 930°C, the finishing rolling outlet temperature is about 820°C, and the curling temperature is about 555°C; the finishing rolling reduction rate for each pass is about 10%, and the cumulative finishing rolling reduction rate is about 65%.

[0042] During the rapid cooling, the cooling rate is about 15°C / s.

[0043] Performance comparison of X60 grade high niobium hydrogen pipeline steel

[0044] Table 1 shows the chemical composition of the embodiments and comparative examples, and Table 2 shows the mechanical properties and hydrogen resistance of the embodiments and comparative examples. The hydrogen resistance results of Comparative Example 2 and Comparative Examples 1-3 show that the technical route of reducing C and Mn while adding Cu, Cr, and Ni cannot significantly improve the hydrogen resistance of pipeline steel. The hydrogen resistance results of the embodiments and Comparative Examples 1 and 2 show that the present invention greatly reduces the S, P, C, Mn, Si, Al and other element components that are easily segregated in pipeline steel, and improves the strength of the steel by adding high Nb and a small amount of V and Ti microalloying elements. Combined with the optimized rolling and cooling process, X60-grade high niobium hydrogen transport pipeline steel with extremely excellent hydrogen resistance can be obtained, and there is no need to add alloying elements such as Cu, Cr, Ni, Mo, and no heat treatment is required, which has an excellent cost performance.

[0045] Table 1 Chemical compositions of the embodiments and comparative examples

[0046]

[0047] Table 2 Mechanical properties and hydrogen resistance of the embodiments and comparative examples

[0048]

[0049] like Figure 1 The crystal phase diagram of Example 2 is shown in FIG. As can be seen from the figure, the structure is polygonal ferrite + granular bainite + juvenile pearlite, the grain size is 11, the structure is uniform and fine, and the impact energy at -10℃ is 410J, which has good mechanical properties.

[0050] As shown in Table 2, in Example 1 to Example 3, the Nb content increases from 0.075% to 0.110%, which can further reduce the C and Mn contents in the steel, while ensuring that mechanical properties such as strength and impact remain unchanged, and the cross-sectional shrinkage rate in hydrogen increases slightly, that is, the hydrogen resistance increases slightly.

[0051] Combined with the above analysis, it can be seen that the technical route of reducing C and Mn while adding Cu, Cr, and Ni cannot significantly improve the hydrogen resistance of pipeline steel. The present invention greatly reduces the S, P, C, Mn, Si, Al and other element components that are easily segregated in pipeline steel, and improves the strength of steel by adding high Nb and a small amount of V and Ti microalloying elements. Combined with the optimized rolling cooling process, X60 grade high niobium hydrogen pipeline steel with extremely excellent hydrogen resistance can be obtained, and there is no need to add alloying elements such as Cu, Cr, Ni, Mo, and no heat treatment is required, which has an excellent cost performance.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A X60 grade high niobium hydrogen transport pipeline steel, characterized in that: The invention comprises the following components in weight percentage: C: 0.030-0.055%, Si: 0.08-0.13%, Mn: 0.90-1.30%, Nb: 0.075-0.120%, V: 0.010-0.020%, Ti: 0.010-0.020%, Al≤0.035%, S≤0.001%, P≤0.012%, N≤0.0050%, H≤0.0002%, O≤0.0030%, and the balance is Fe. The CEpcm range is 0.11-0.

14.

2. The X60 grade high niobium hydrogen transport pipeline steel according to claim 1, characterized in that: The alloy comprises the following components in weight percentage: C: 0.045%, Si: 0.11%, Mn: 1.17%, Nb: 0.091%, V: 0.017%, Ti: 0.018%, Al: 0.031%, S: 0.0008%, P: 0.008%, N: 0.0033%, H: 0.00009%, O: 0.0025%, and the balance is Fe.

3. A method for preparing X60 grade high niobium hydrogen transport pipeline steel according to claim 1 or 2, characterized in that: The following steps are involved: The steps of molten iron desulfurization, converter oxygen blowing decarburization, LF treatment, RH treatment, continuous casting, ingot heating, rough rolling, finish rolling and rapid cooling are carried out in sequence, wherein no heat treatment is required after the finish rolling step.

4. The method for preparing X60 grade high niobium hydrogen transport pipeline steel according to claim 3, characterized in that: During the heating of the ingot, the heating temperature of the heating furnace is 1190-1240° C., and the insulation time of the heating furnace is 130-160 min.

5. The method for preparing X60 grade high niobium hydrogen transport pipeline steel according to claim 3, characterized in that: In the rough rolling, the starting temperature of the rough rolling is 1000-1060° C., the outlet temperature of the rough rolling is 930-980° C.; the reduction ratios of the two passes at the end of the rough rolling are both greater than 20%, and the cumulative reduction ratio of the rough rolling is greater than 80%.

6. The method for preparing X60 grade high niobium hydrogen transport pipeline steel according to claim 3, characterized in that: In the finishing rolling, the starting temperature of the finishing rolling is 910-950°C, the outlet temperature of the finishing rolling is 800-840°C, and the curling temperature is 525-585°C; the reduction rate of each finishing rolling pass is greater than 10%, and the cumulative reduction rate of the finishing rolling is greater than 65%.

7. The method for preparing X60 grade high niobium hydrogen transport pipeline steel according to claim 3, characterized in that: During the rapid cooling, the cooling rate is ≥15°C / s.

8. An X60 grade high niobium pipeline steel for hydrogen transport prepared according to the preparation method according to any one of claims 3 to 7.

9. The X60 grade high niobium hydrogen transport pipeline steel according to claim 8, characterized in that: Yield strength Rt0.5: 450~500MPa, tensile strength Rm: 520~600MPa, -20℃ impact energy KV2≥320J, hardness HV10: 180~200, section shrinkage rate under 6.3MPa hydrogen environment is greater than 64%.

10. An application of the X60 grade high niobium hydrogen transport pipeline steel according to claim 1 or 2 or 8 or 9, characterized in that: Used for making The above large-diameter high-pressure hydrogen pipelines; Alternatively, it can be used to make X60-grade hydrogen pipelines.

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