Austenitic stainless steel material for liquid hydrogen spherical tank and preparation method thereof

Abstract

The invention discloses an austenitic stainless steel material for a liquid hydrogen spherical tank. The stainless steel material comprises the following chemical components in percentage by mass: 0.008%-0.080% of C, 0.20%-0.80% of Si, 4.00%-10.00% of Mn, 10.5%-13.5% of Ni, 1.00%-3.00% of Mo, less than or equal to 0.050% of Al, 0.20%-0.40% of N, 0.0007%-0.0030% of O, 20.0%-25.0% of Cr, 0.10%-0.20% of Nb, 0.10%-0.20% of V, less than or equal to 0.20% of Ti, less than or equal to 0.01% of P, less than or equal to 0.004% of S and the balance of iron and impurities. The invention further discloses a preparation method of the stainless steel material. The invention solves the problem that the existing austenitic stainless steel limits the size increase of the liquid hydrogen tank.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid hydrogen storage material preparation methods, and in particular relates to an austenitic stainless steel material for a liquid hydrogen spherical tank. The present invention also relates to a preparation method of the stainless steel material. Background Art

[0002] In the context of global green and low-carbon transformation, clean energy represented by hydrogen energy is welcoming important development opportunities, and liquid hydrogen has obvious advantages in the storage and transportation of the hydrogen energy industry. In the introduction period of commercialization of the hydrogen energy industry, it is a general trend to actively develop liquid hydrogen production technology and equipment manufacturing. At the same time, this puts forward higher requirements for the storage and transportation of liquid hydrogen.

[0003] The existing steel plates for liquid hydrogen storage spherical tanks are made of 304L and 316L austenitic stainless steels with excellent toughness at ultra-low temperatures (-273°C) and low brittle fracture. They are relatively weak (yield strength ≥ 210MPa) and are not suitable for large (10,000m 3 When manufacturing liquid hydrogen spherical tanks (above), the required steel plate thickness will reach more than 40mm, which significantly increases the manufacturing cost and welding difficulty. Although the yield strength of 9Ni steel for low temperature given in the national standard GB / T2450-2017 "Nickel alloy steel plate for low temperature pressure vessels" is ≥585MPa, which is significantly higher than 304L and 316L austenitic stainless steel, it can only be used in working conditions ≥-196℃, such as the liquid natural gas temperature zone. It is not tough enough in the liquid hydrogen temperature zone (≤-273℃) and cannot be used. Summary of the invention

[0004] The first object of the present invention is to provide an austenitic stainless steel material for a liquid hydrogen spherical tank, which solves the problem of low strength of 304L and 316L steel plates used in existing spherical tanks for storing liquid hydrogen.

[0005] The second object of the present invention is to provide a method for preparing austenitic stainless steel material for liquid hydrogen spherical tanks, which solves the problem that the existing austenitic stainless steel with low yield strength limits the increase in the size of liquid hydrogen tanks.

[0006] The first technical solution adopted by the present invention is: the liquid hydrogen spherical tank is made of austenitic stainless steel material, and the chemical composition of the stainless steel material is composed of the following components in mass ratio:

[0007] C: 0.008% - 0.080%, Si: 0.20% - 0.80%, Mn: 4.00% - 10.00%, Ni: 10.5% - 13.5%, Mo: 1.00% - 3.00%, Al: ≤0.050%, N: 0.20% - 0.40%, O: 0.0007% - 0.0030%, Cr: 20.0% - 25.0%, Nb: 0.10% - 0.20%, V: 0.10% - 0.20%, Ti: ≤0.20%, P: ≤0.01%, S: ≤0.004%, and the balance is iron and impurities.

[0008] The characteristics of the first technical solution adopted in the present invention further lie in:

[0009] Preferably, the chemical composition of the stainless steel material consists of the following components by mass ratio:

[0010] C: 0.020% - 0.060%, Si: 0.40% - 0.60%, Mn: 6.00% - 8.00%, Ni: 11.0% - 13.0%, Mo: 1.50% - 2.50%, Al: ≤0.050%, N: 0.25% - 0.35%, O: 0.001% - 0.0025%, Cr: 21.5% - 24.5%, Nb: 0.15% - 0.20%, V: 0.15% - 0.20%, Ti: 0.15% - 0.20%, P: 0.005% - 0.008%, S: 0.0001% - 0.003%, and the balance is iron and impurities.

[0011] Preferably, the nickel equivalent Ni of the stainless steel material eq is 30% - 50%, and Ni eq = Ni + 12.93C + 1.11Mn + 0.72Cr + 0.88Mo - 0.27Si + 0.19Nb + 0.53Cu + 0.9V + 7.55N.

[0012] Preferably, the metallographic structure of the stainless steel material contains an austenite phase with a volume fraction ≥70%; in the middle of the cross-section thickness parallel to the rolling direction and the thickness direction, the average grain size of the original austenite grains is 15μm - 25μm, and the average aspect ratio of the original austenite grains is 1 - 3; the room temperature yield stress is 450MPa - 710MPa, and the room temperature tensile strength is 690MPa - 810MPa.

[0013] Preferably, the average grain size of the austenite grains of the stainless steel material is 10μm - 20μm.

[0014] Preferably, the average effective grain size in the stainless steel material is 15μm - 25μm.

[0015] The second technical solution adopted by the present invention is: a preparation method of austenitic stainless steel material for liquid hydrogen spherical tanks, which is specifically implemented according to the following steps:

[0016] Step 1: Melt the steel with a predetermined chemical composition and manufacture a steel billet by continuous casting;

[0017] Step 2: Heat the steel billet obtained in Step 1, and perform hot rolling and water cooling;

[0018] Step 3: Perform heat treatments of intermediate heat treatment and tempering on the product of Step 2 in sequence.

[0019] The beneficial effects of the present invention are:

[0020] The present invention provides an austenitic stainless steel material for liquid hydrogen spherical tanks and a preparation method thereof. The high-strength austenitic stainless steel has a plate thickness of 4.5 mm to 45 mm, a nickel equivalent of 30% to 50%, and the metallographic structure contains an austenite phase with a volume fraction of ≥70%. The yield strength at room temperature is ≥450 MPa, and the fracture toughness K JQ ≥132 MPa·m 1 / 2 . This austenitic steel for low temperature has sufficient toughness at -253°C, and the yield stress at room temperature is above 450 MPa. When the austenitic stainless steel for low temperature of the present invention is used for liquid hydrogen spherical tanks, the plate thickness of the steel plate for the spherical tank can be thinner than that of traditional 304L or 316L austenitic stainless steels, which can realize the enlargement and light weight of liquid hydrogen spherical tanks, improve the fuel efficiency of liquid hydrogen transport ships, etc. In addition, compared with 9Ni steel for liquefied natural gas environment, the austenitic steel of the present invention has more excellent fracture toughness in the -253°C environment, and can better ensure the reliability of long-term service of large liquid hydrogen spherical tanks. Description of the Drawings

[0021] Figure 1 is a schematic transverse view of the metallographic structure of the austenitic stainless steel plate;

[0022] Figure 2 is a schematic longitudinal view of the metallographic structure of the austenitic stainless steel plate. Detailed Embodiments

[0023] The present invention will be described in detail below with reference to the drawings and embodiments.

[0024] The present invention provides an austenitic stainless steel material for liquid hydrogen spherical tanks, and the chemical composition of the stainless steel material is composed of the following components by mass ratio:

[0025] C: 0.008% - 0.080%, Si: 0.20% - 0.80%, Mn: 4.00% - 10.00%, Ni: 10.5% - 13.5%, Mo: 1.00% - 3.00%, Al: ≤0.050%, N: 0.20% - 0.40%, O: 0.0007% - 0.0030%, Cr: 20.0% - 25.0%, Nb: 0.10% - 0.20%, V: 0.10% - 0.20%, Ti: ≤0.20%, P: ≤0.01%, S: ≤0.004%, the balance being iron and impurities.

[0026] Preferably, the chemical composition of the stainless steel material consists of the following components by mass ratio:

[0027] C: 0.020% - 0.060%, Si: 0.40% - 0.60%, Mn: 6.00% - 8.00%, Ni: 11.0% - 13.0%, Mo: 1.50% - 2.50%, Al: ≤0.050%, N: 0.25% - 0.35%, O: 0.001% - 0.0025%, Cr: 21.5% - 24.5%, Nb: 0.15% - 0.20%, V: 0.15% - 0.20%, Ti: 0.15% - 0.20%, P: 0.005% - 0.008%, S: 0.0001% - 0.003%, the balance being iron and impurities.

[0028] C: is an austenite phase stabilizing element, which helps to improve the low-temperature brittleness of the material. However, when the content of C element is excessive, excessive precipitation of Cr-based carbides will occur, resulting in a decrease in low-temperature performance. Therefore, the content of C element is set at 0.008% - 0.080%, preferably 0.020% - 0.060%.

[0029] Si: is an austenite phase stabilizing element, which helps to improve the low-temperature brittleness of the material. However, when the content of Si element is excessive, it is easy to form metal intermetallic compounds containing Si element, which affects the low-temperature toughness of the alloy. Therefore, the content of Si element is set at 0.20% - 0.80%, preferably 0.40% - 0.60%.

[0030] Mn: is a low-cost austenite stabilizing element, which can increase the strength and low-temperature toughness of the alloy. If excessive, it will form coarse MnS inclusions, resulting in a significant decrease in the plastic working ability and toughness of the alloy. Therefore, the content of Mn element is set at 4.00% - 10.00%, preferably 6.00% - 8.00%.

[0031] Ni: is an austenite stabilizing element, which can improve both strength and low-temperature toughness. Ni is a high-cost metal and should not be added too much. Therefore, the content of Ni element is set at 10.5% - 13.5%, preferably 11.0% - 13.0%.

[0032] Mo: It can effectively improve the strength and corrosion resistance of austenitic stainless steel. However, the cost of Mo element is relatively high, and it is not advisable to add too much. Therefore, the range of Mo element is determined to be 1.00% - 3.00%, preferably 1.50% - 2.50%.

[0033] Al: It helps with deoxidation during alloy melting. However, excessive Al is likely to form intermetallic compounds, reducing the low-temperature toughness of the material. Therefore, the range of Al element is set to ≤0.050%.

[0034] N: It is an austenite phase stabilizing element. Adding N helps improve the low-temperature toughness, and N strengthens the austenite phase by forming Cr-based nitrides, thereby increasing the strength. However, excessive N promotes the excessive formation of Cr-based nitrides, reducing the low-temperature toughness of the material. Therefore, the range of N element is determined to be 0.20% - 0.40%, preferably 0.25% - 0.35%.

[0035] O: It forms oxides in the steel, significantly reducing the toughness of the austenite phase. However, excessively reducing the O content is likely to increase the melting cost. Therefore, the O content is controlled within 0.0007% - 0.0030%, preferably 0.001% - 0.0025%.

[0036] Cr: It is a necessary element for stainless steel to improve corrosion resistance and can also increase the strength of the alloy through solid solution strengthening. However, excessive addition of Cr will lead to the excessive precipitation of Cr-based carbonitrides, reducing the low-temperature toughness. Therefore, the range of Cr element is determined to be 20.0% - 25.0%, preferably 21.5% - 24.5%.

[0037] Nb: It improves the strength of the material through austenite solid solution strengthening or promoting the precipitation and dispersion strengthening of nitrides. When excessive Nb is added, the excessive precipitation of nitrides will lead to a significant decrease in low-temperature toughness. Therefore, the range of Nb element is determined to be 0.10% - 0.20%, preferably 0.15% - 0.20%.

[0038] V: It improves the strength of the material through austenite solid solution strengthening or promoting the precipitation and dispersion strengthening of nitrides. When excessive V is added, the excessive precipitation of nitrides will lead to a significant decrease in low-temperature toughness. Therefore, the range of V element is determined to be 0.10% - 0.20%, preferably 0.15% - 0.20%.

[0039] Ti: It improves the strength of the material through austenite solid solution strengthening or promoting the precipitation and dispersion strengthening of nitrides. When excessive Ti is added, the excessive precipitation of nitrides will lead to a significant decrease in low-temperature toughness. Therefore, the range of Ti element is determined to be ≤0.20%, preferably 0.15% - 0.20%.

[0040] P: Present as an impurity in stainless steel, excessive addition will reduce the hot forming performance, and strict control will lead to increased costs. Therefore, the range of P element is determined to be ≤0.010%, preferably 0.005% - 0.008%.

[0041] S: Precipitates at the austenite grain boundaries, reducing the toughness of the material, and strict control will lead to increased costs. Therefore, the range of S element is determined to be ≤0.004%, preferably 0.0001% - 0.003%.

[0042] Preferably, the nickel equivalent Ni of this stainless steel material eq is 30% - 50%, and the Ni equivalent calculation formula is Ni eq = Ni + 12.93C + 1.11Mn + 0.72Cr + 0.88Mo - 0.27Si + 0.19Nb + 0.53Cu + 0.9V + 7.55N. The metallographic structure contains an austenite phase with a volume fraction ≥70%, thus ensuring good low-temperature toughness.

[0043] Preferably, in the middle of the cross-sectional thickness parallel to the rolling direction and the thickness direction of this stainless steel, the average grain size of austenite grains is 15μm - 25μm, and the average aspect ratio of the original austenite grains is 1 - 3 to ensure good low-temperature toughness; the room-temperature yield stress is 450MPa - 710MPa, and the room-temperature tensile strength is 690MPa - 810MPa.

[0044] Preferably, the fracture toughness K of this stainless steel material at -253°C JQ ≥132MPa·m 1 / 2 .

[0045] Preferably, the average grain size of austenite grains measured according to GB / T 6394-2017 "Method for Determining the Average Grain Size of Metals" of this stainless steel material is 10μm - 20μm.

[0046] Preferably, the average effective grain size in this stainless steel material is 15μm - 25μm, where the average effective grain size is obtained by extracting samples from the tempered stainless steel and measuring with an electron backscatter diffraction analyzer (EBSD). The effective grain is defined as the grain surrounded by grain boundaries with an orientation difference greater than 15°. Image processing of more than three effective grain regions gives an equivalent grain size, and the average value of the obtained equivalent grain sizes represents the average effective grain size.

[0047] Preferably, the thickness of the stainless steel material sheet is 4.5mm to 45mm.

[0048] The present invention also provides a preparation method for the austenitic stainless steel material used in liquid hydrogen spherical tanks, which is specifically implemented according to the following steps:

[0049] Step 1: Melt steel with a predetermined chemical composition and manufacture a steel billet by continuous casting;

[0050] Step 2: Heat the steel billet obtained in Step 1, perform hot rolling and water cooling;

[0051] Step 3: Sequentially perform intermediate heat treatment and tempering heat treatment on the product of Step 2.

[0052] Casting: When melting the austenitic stainless steel of this embodiment, set the temperature of the molten steel to 1680 °C and adjust the element amount; after melting, continuously cast the molten steel to manufacture a stainless steel billet.

[0053] Hot rolling: The stainless steel billet is hot rolled and then immediately water cooled. The cumulative rolling amount below 980 °C during hot rolling should be above 70%. On the one hand, it ensures that the original austenite grains are refined through sufficient recrystallization, and on the other hand, it reduces the spacing of the segregation bands of Ni existing in the steel billet, further promoting the refinement of austenite grains. The refined austenite grains are an effective guarantee for achieving the fracture toughness of materials at ultra-low temperatures (-273 °C). The present invention requires strict control of the rolling temperature and rolling amount. When the finishing temperature of hot rolling is lower than 680 °C, the deformation resistance increases and the mill load increases. In addition, if the finishing temperature of hot rolling is lower than 680 °C, the starting temperature of water cooling is lower than 540 °C, which will lead to a decrease in ultra-low temperature toughness and room temperature yield strength. Therefore, the finishing temperature of hot rolling is controlled above 680 °C. In addition, if the finishing rolling temperature of hot rolling exceeds 940 °C, abnormal growth of austenite grains is likely to occur due to high-temperature recovery and deformation texture, which is not conducive to ultra-low temperature toughness. Therefore, the finishing rolling temperature of hot rolling is below 940 °C. The preferred finishing rolling temperature of hot rolling is below 900 °C. After hot rolling, water cooling is carried out to near room temperature. The starting temperature of water cooling is set at 540 °C to 940 °C. Water cooling is carried out immediately after the end of hot rolling. The average cooling rate during water cooling is 2 °C / s or more, and the cooling stop temperature is 180 °C or less.

[0054] Intermediate heat treatment: The heating temperature of the intermediate heat treatment is set at 680 °C to 750 °C. When the heating temperature of the intermediate heat treatment (intermediate heat treatment temperature) is lower than 680 °C, the austenite phase transformation is incomplete. On the other hand, if the temperature of the intermediate heat treatment exceeds 680 °C, a metastable austenite phase is likely to form at room temperature. The holding time of the intermediate heat treatment is set at 30 minutes to 150 minutes. When the holding time is less than 30 minutes, the austenite phase transformation may be incomplete. If the holding time exceeds 150 minutes, carbide precipitation may occur. After the intermediate heat treatment, in order to avoid temper embrittlement, water cooling is carried out at a temperature below 1800 °C, and the cooling rate is not less than 15 °C / s.

[0055] Tempering: The stainless steel plate after intermediate heat treatment is tempered. Tempering helps to ensure a predetermined stable austenite phase. The tempering temperature is set at 500°C to 600°C. When the heating temperature of tempering is lower than 500°C, it is impossible to ensure that the volume fraction of austenite phase ≥ 70%, which may lead to insufficient ultra-low temperature toughness. The tempering holding time is set at 30 minutes to 150 minutes. When the residence time is less than 30 minutes, the austenite phase transformation may be incomplete, and stress-induced martensite transformation may occur during the manufacture of the curved stainless steel plate for liquid hydrogen spherical tanks, resulting in ultra-low temperature brittleness. When the holding time exceeds 150 minutes, there is a possibility of carbide precipitation causing brittleness.

[0056] According to the above manufacturing method, an austenitic steel plate with excellent ultra-low temperature toughness and high yield strength at room temperature, which can be used for storing liquid hydrogen spherical tanks, can be obtained.

[0057] The austenitic stainless steel of the present invention is not limited to the above manufacturing method, as long as it can ensure that the metallographic structure contains an austenite phase with a volume fraction ≥ 70% and the requirements of austenite grain size. The typical metallographic structure of the austenitic stainless steel of the present invention is as Figure 1 (transverse) and Figure 2 (longitudinal) shown.

[0058] First, the test methods in the examples are described as follows: The yield strength Rp 0.2 and tensile strength R m of the material are measured at room temperature according to GB / T228.1; the fracture toughness at -253°C is calculated by J integral (initiation toughness) using the method of GB / T 21143 and then converted to K JQ .

[0059] In the examples, the thickness of the austenitic stainless steel plates used is 15 mm.

[0060] Example 1

[0061] The chemical composition of the stainless steel material in this Example 1 consists of the following components by mass ratio:

[0062] C: 0.040%, Si: 0.52%, Mn: 6.81%, Ni: 12.2%, Mo: 2.23%, Al: 0.010%, N: 0.28%, O: 0.002%, Cr: 22.5%, Nb: 0.17%, V: 0.16%, Ti: 0.16%, P: 0.006%, S: 0.001%, and the rest is iron and impurities.

[0063] The Ni eq of this stainless steel material = 40%, the volume fraction of austenite phase is 83%, the average grain size is 14 um, the average effective grain size is 16 um, and the average aspect ratio of the original austenite grains is 1.2.

[0064] The mechanical property results of this stainless steel material are as follows: the yield strength R at room temperature p0.2 = 506 MPa, and the tensile strength R m = 765 MPa; the fracture toughness K at -253 °C JQ = 162 MPa·m 1 / 2 .

[0065] Example 2

[0066] The chemical composition of the stainless steel material in this Example 2 consists of the following components by mass ratio:

[0067] C: 0.078%, Si: 0.80%, Mn: 9.68%, Ni: 13.4%, Mo: 2.91%, Al: 0.050%, N: 0.40%, O: 0.003%, Cr: 24.4%, Nb: 0.20%, V: 0.17%, Ti: 0.10%, P: 0.008%, S: 0.004%, and the rest is iron and impurities.

[0068] For this stainless steel material, Nieq = 48%, the volume fraction of austenite phase is 77%, the average grain size is 18 μm, the average effective grain size is 22 μm, and the average aspect ratio of the original austenite grains is 1.3.

[0069] The mechanical property results of this stainless steel material are as follows: the yield strength R at room temperature p0.2 = 681 MPa, and the tensile strength R m = 776 MPa; the fracture toughness K at -253 °C JQ = 132 MPa·m 1 / 2 .

[0070] Example 3

[0071] The chemical composition of the stainless steel material in this Example 3 consists of the following components by mass ratio:

[0072] C: 0.007%, Si: 0.22%, Mn: 4.03%, Ni: 10.8%, Mo: 1.05%, Al: 0.005%, N: 0.25%, O: 0.001%, Cr: 20.2%, Nb: 0.13%, V: 0.12%, Ti: 0.13%, P: 0.003%, S: 0.0002%, and the rest is iron and impurities.

[0073] For this stainless steel material, Nieq = 32%, the volume fraction of austenite phase is 91%, the average grain size is 19 μm, the average effective grain size is 24 μm, and the average aspect ratio of the original austenite grains is 1.3.

[0074] The mechanical property results of this stainless steel material are as follows: the yield strength R at room temperature p0.2= 455 MPa, tensile strength R m = 693 MPa; fracture toughness K at -253 °C JQ = 135 MPa·m 1 / 2 .

[0075] Example 4

[0076] The chemical composition of the stainless steel material in this Example 4 consists of the following components by mass ratio:

[0077] C: 0.038%, Si: 0.49%, Mn: 1.80%, Ni: 12.5%, Mo: 2.31%, Al: 0.008%, N: 0.27%, O: 0.002%, Cr: 22.5%, Nb: 0.15%, V: 0.18%, Ti: 0.12%, P: 0.057%, S: 0.001%, and the rest are iron and impurities.

[0078] For this stainless steel material, Nieq = 35%, the volume fraction of austenite phase is 86%, the average grain size is 14 μm, the average effective grain size is 18 μm, and the average aspect ratio of the original austenite grains is 1.1.

[0079] The mechanical property results of this stainless steel material are: yield strength R at room temperature p0.2 = 388 MPa, tensile strength R m = 582 MPa; fracture toughness K at -253 °C JQ = 110 MPa·m 1 / 2 .

[0080] Example 5

[0081] The chemical composition of the stainless steel material in this Example 5 consists of the following components by mass ratio:

[0082] C: 0.042%, Si: 0.53%, Mn: 6.78%, Ni: 12.2%, Mo: 2.25%, Al: 0.008%, N: 0.01%, O: 0.002%, Cr: 22.4%, Nb: 0.13%, V: 0.25%, Ti: 0.11%, P: 0.055%, S: 0.001%, and the rest are iron and impurities.

[0083] For this stainless steel material, Nieq = 38%, the volume fraction of austenite phase is 83%, the average grain size is 11 μm, the average effective grain size is 16 μm, and the average aspect ratio of the original austenite grains is 1.3.

[0084] The mechanical property results of this stainless steel material are: yield strength R at room temperature p0.2 = 427 MPa, tensile strength R m = 644 MPa; fracture toughness K at -253 °CJQ = 118 MPa·m 1 / 2 。

[0085] Example 6

[0086] The chemical composition of the stainless steel material in this Example 6 consists of the following components by mass ratio:

[0087] C: 0.043%, Si: 0.53%, Mn: 6.82%, Ni: 12.0%, Mo: 2.30%, Al: 0.009%, N: 0.27%, O: 0.002%, Cr: 0.21%, Nb: 0.10%, V: 0.13%, Ti: 0.12%, P: 0.052%, S: 0.001%, and the rest is iron and impurities.

[0088] For this stainless steel material, Nieq = 24%, the volume fraction of austenite phase is 66%, the average grain size is 19 μm, the average effective grain size is 25 μm, and the average aspect ratio of the original austenite grains is 1.2.

[0089] The mechanical property results of this stainless steel material are: the room temperature yield strength R p0.2 = 368 MPa, the tensile strength R m = 567 MPa; the fracture toughness K at -253 °C JQ = 144 MPa·m 1 / 2 。

[0090] Comparative Example 1

[0091] The chemical composition of the 304L stainless steel material in this Comparative Example 1 consists of the following components by mass ratio:

[0092] C: 0.020%, Si: 0.41%, Mn: 1.75%, Ni: 9.33%, N: 0.01%, Cr: 18.42%, Cu: 0.15%, and the rest is iron and impurities.

[0093] For this stainless steel material, Nieq = 25%, the volume fraction of austenite phase is 98%, the average grain size is 15 μm, the average effective grain size is 18 μm, and the average aspect ratio of the original austenite grains is 1.1.

[0094] The mechanical property results of this stainless steel material are: the room temperature yield strength R p0.2 = 232 MPa, the tensile strength R m = 586 MPa; the fracture toughness K at -253 °C JQ = 137 MPa·m 1 / 2 。

[0095] Comparative Example 2

[0096] The chemical composition of the 316L stainless steel material in Comparative Example 2 is composed of the following components by mass ratio:

[0097] C: 0.031%, Si: 0.45%, Mn: 1.74%, Ni: 12.42%, Mo: 2.20%, N: 0.025%, Cr: 19.55%, Cu: 0.32%, and the balance is iron and impurities.

[0098] For this stainless steel material, Nieq = 31%, the volume fraction of austenite phase is 97%, the average grain size is 19 μm, the average effective grain size is 25 μm, and the average aspect ratio of prior austenite grains is 2.1.

[0099] The mechanical property results of this stainless steel material are as follows: the room temperature yield strength R p0.2 = 245 MPa, the tensile strength R m = 621 MPa; the fracture toughness K at -253 °C JQ = 142 MPa·m 1 / 2 .

[0100] Comparative Example 3

[0101] The chemical composition of the 9Ni steel material in Comparative Example 3 is composed of the following components by mass ratio:

[0102] C: 0.040%, Si: 0.52%, Mn: 6.81%, Ni: 12.2%, Mo: 2.23%, Al: 0.010%, N: 0.28%, O: 0.002%, Cr: 22.5%, Nb: 0.17%, V: 0.16%, Ti: 0.16%, P: 0.006%, S: 0.001%, and the balance is iron and impurities.

[0103] For this stainless steel material, Nieq = 40%, the volume fraction of austenite phase is 83%, the average grain size is 18 μm, the average effective grain size is 22 μm, and the average aspect ratio of prior austenite grains is 2.5.

[0104] The mechanical property results of this stainless steel material are as follows: the room temperature yield strength R p0.2 = 603 MPa, the tensile strength R m = 705 MPa; the fracture toughness K at -253 °C JQ = 98 MPa·m 1 / 2 .

[0105] From the above data, it can be seen that the tensile strength of the stainless steel material of the present invention is significantly better than that of 304L and 316L austenitic stainless steels, and the fracture toughness at -253 °C is significantly better than that of 9Ni steel, which can meet the performance requirements of large (above 10000 m 3 ) liquid hydrogen spherical tanks.

Claims

1. Austenitic stainless steel material for liquid hydrogen spherical tank, characterized in that, The chemical composition of the stainless steel material consists of the following components by mass ratio: C: 0.008% - 0.080%, Si: 0.20% - 0.80%, Mn: 4.00% - 10.00%, Ni: 10.5% - 13.5%, Mo: 1.00% - 3.00%, Al: ≤0.050%, N: 0.20% - 0.40%, O: 0.0007% - 0.0030%, Cr: 20.0% - 25.0%, Nb: 0.10% - 0.20%, V: 0.10% - 0.20%, Ti: ≤0.20%, P: ≤0.01%, S: ≤0.004%, and the balance is iron and impurities.

2. The austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, characterized in that, The chemical composition of the stainless steel material consists of the following components by mass ratio: C: 0.020% - 0.060%, Si: 0.40% - 0.60%, Mn: 6.00% - 8.00%, Ni: 11.0% - 13.0%, Mo: 1.50% - 2.50%, Al: ≤0.050%, N: 0.25% - 0.35%, O: 0.001% - 0.0025%, Cr: 21.5% - 24.5%, Nb: 0.15% - 0.20%, V: 0.15% - 0.20%, Ti: 0.15% - 0.20%, P: 0.005% - 0.008%, S: 0.0001% - 0.003%, and the balance is iron and impurities.

3. The austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, characterized in that, The nickel equivalent Ni of the stainless steel material eq is 30% to 50%, Ni eq = Ni + 12.93C + 1.11Mn + 0.72Cr + 0.88Mo - 0.27Si + 0.19Nb + 0.53Cu + 0.9V + 7.55N。 4. The austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, characterized in that, The metallographic structure of the stainless steel material contains an austenite phase with a volume fraction ≥70%; in the middle of the cross-section thickness parallel to the rolling direction and the thickness direction, the average grain size of the original austenite grains is 15μm - 25μm, and the average aspect ratio of the original austenite grains is 1 - 3; the room temperature yield stress is 450MPa - 710MPa, and the room temperature tensile strength is 690MPa - 810MPa.

5. The austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, characterized in that, The average grain size of the austenite grains of the stainless steel material is 10μm - 20μm.

6. The austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, wherein The average effective grain size in the stainless steel material is 15μm - 25μm.

7. The preparation method of the austenitic stainless steel material for liquid hydrogen spherical tanks according to claim 1, characterized in that, Specifically, it is implemented according to the following steps: Step 1: Melt the steel with a predetermined chemical composition and manufacture a steel billet by continuous casting; Step 2: Heat the steel billet obtained in Step 1, and perform hot rolling and water cooling; Step 3: Perform heat treatments of intermediate heat treatment and tempering on the product of Step 2 in sequence.

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