CN107937824B - Nickel-saving 7Ni steel for ultralow temperature environment and heat treatment process thereof - Google Patents
Nickel-saving 7Ni steel for ultralow temperature environment and heat treatment process thereof Download PDFInfo
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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Abstract
The invention discloses nickel-saving 7Ni steel used in an ultralow temperature environment and a heat treatment process thereof, belonging to the technical field of low-temperature steel. The nickel-saving type 7Ni steel comprises the following components: ni: 7.00-7.60%; c: 0.02-0.06%; si: 0.03-0.80%; mn: 0.10-0.90%; cr: 0.30-0.60%; the balance of Fe and inevitable impurities. The steel adopts QLT heat treatment, and specifically comprises a high-temperature quenching process, a two-phase zone sub-temperature quenching process and a tempering process, wherein the process comprises a multi-step process. The nickel-saving type 7Ni steel has excellent strong plasticity combination and excellent low-temperature toughness, the performance of the steel reaches a proper level of 9Ni steel, the steel can be used as structural steel in an ultralow-temperature environment, the manufacturing cost is reduced, and the steel has very good economic applicability.
Description
Technical Field
The invention relates to the technical field of low-temperature steel, in particular to nickel-saving 7Ni steel used in an ultralow-temperature environment and a heat treatment process thereof.
Background
As a clean and efficient energy source, the demand for Liquefied Natural Gas (LNG) is rapidly increasing worldwide. Liquefied natural gas is liquid formed by cooling natural gas to-162 ℃ at normal pressure, and the liquefied natural gas has 1/625 of the original gaseous volume and is very convenient to store and transport. At present, the global demand of LNG is increased at a speed of about 8% every year, Asia is increased at a higher speed in the coming years, China becomes one of five natural gas imports and consuming countries around the world, the consumption of domestic natural gas is increased by more than 10% every year, and the consumption of the natural gas in China reaches 2000 billion cubic meters by 2020. The LNG industry is receiving more and more attention in our country, and in addition to the established receiving bases, in the coming years, more than ten LNG receiving bases including dozens of large LNG storage tanks are built in coastal cities.
Since LNG storage and transportation temperatures are-162 ℃, this requires that materials used to construct LNG storage tanks must have good low temperature impact toughness and good combination of strong plasticity. The 9Ni steel is an important steel grade required by LNG storage and transportation equipment, and with the rapid development of the LNG industry, the demand of the 9Ni steel is increased continuously. However, with the large consumption of nickel resources, the proportion of nickel alloying cost to 9Ni steel cost is increasing, so that the cost of nickel-based low-temperature steel is increasing continuously, and nickel saving becomes an important subject. Therefore, Nile-saving type 7Ni steel capable of replacing 9Ni steel is developed by Nippon Sumitomo metal company, the low-temperature toughness of the Nile-saving type 7Ni steel reaches 9Ni steel level by optimizing component design and adopting a reasonable TMCP process, and the Nile-saving type 7Ni steel is practically applied to manufacturing of LNG storage tanks. Currently, 7Ni steel has been incorporated into Japanese Industrial Standards (JIS) under the designation SL7N590 and written as an example of 2736&2737 in ASME standard, and will be incorporated as grade a841G in the future in ASTM standard. In addition, the American Petroleum Institute (API), BS \ EN, ISO are also promoting the standard certification work of this nickel-saving steel. However, in China, research on nickel-saving type 7Ni steel is still in the beginning, and further research and investigation is necessary.
Disclosure of Invention
The invention aims to provide nickel-saving type 7Ni steel used in an ultralow temperature environment and a heat treatment process thereof, wherein the nickel-saving type 7Ni steel can be used in a low temperature environment of more than 196 ℃ below zero, and has high toughness, high plasticity and high strength; meanwhile, the low-temperature steel reduces the nickel alloying cost, and on the premise of saving nickel resources, the low-temperature performance of the low-temperature steel can still meet the requirements of LNG engineering steel and reach the level equivalent to the mechanical property of 9Ni steel.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a nickel-saving type 7Ni steel used in ultralow temperature environment is characterized in that: the nickel-saving 7Ni steel comprises the following chemical components in percentage by weight:
ni: 7.00-7.60%; c: 0.02-0.06%; si: 0.03-0.80%; mn: 0.10-0.90%; cr: 0.30-0.60%; the balance of Fe and inevitable impurities.
In the nickel-saving 7Ni steel, the contents of impurity elements P and S are controlled as follows: p.ltoreq.0.010 wt.%; s is less than or equal to 0.005 wt.%.
The nickel-saving 7Ni steel also contains Mo and/or Nb; the Mo content is 0.1-0.20 wt.%, and the Nb content is 0.01-0.06 wt.%.
The preferable chemical components of the nickel-saving type 7Ni steel comprise the following three groups:
the component A comprises the following components in percentage by weight: ni: 7.00-7.60%, C: 0.02 to 0.06%, Si: 0.03-0.06%, Mn: 0.70-0.90%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Nb: 0.01-0.03%; the balance being Fe;
the component B comprises (wt%): ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10-0.20%; the balance being Fe;
the component C comprises the following components in percentage by weight: ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10 to 0.20%, Nb: 0.03-0.06%; the balance being Fe.
After the nickel-saving 7Ni steel with the chemical components is subjected to hot rolling and heat treatment, the thickness of the steel is 10-20 mm, the yield strength is higher than 590MPa, the tensile strength is higher than 680MPa, the elongation is higher than 20%, and the impact energy is higher than 100J at the low temperature of-196 ℃.
The preparation process of the nickel-saving type 7Ni steel used in the ultralow temperature environment comprises steel making, rolling and heat treatment; in the steelmaking process: deep desulfurization is carried out by adopting a molten iron K-S desulfurization technology, composite blowing is carried out at the top and the bottom of a converter, Ca-Si treatment is carried out in an LF heating furnace, and vacuum treatment and component fine adjustment are carried out in an RH vacuum furnace;
the rolling process comprises the following steps: heating the cast ingot to 1260-1300 ℃ before rolling, coating an anti-oxidation coating on the surface of the cast ingot, wherein the heating rate is 8-13 min/cm, keeping the temperature for 4 hours, and the initial rolling temperature in the rough rolling stage is not less than 1100 ℃; the thickness of the intermediate blank is 70-100 mm; the start rolling temperature of finish rolling is not more than 900 ℃, and the finish rolling temperature is 820-860 ℃;
the heat treatment process comprises the following steps: and carrying out QLT heat treatment on the air-cooled rolled steel to obtain the high-toughness, high-plasticity and high-strength low-temperature steel used in a low-temperature environment above 196 ℃ below zero. The heat treatment process (QLT heat treatment) specifically includes the steps of:
(1) quenching the rolled steel subjected to air cooling at a high temperature of above A3, wherein the temperature of A3 is 750-800 ℃;
(2) carrying out sub-temperature quenching on the steel subjected to high-temperature quenching in the step (1) at a two-phase region temperature of 630-780 ℃;
(3) tempering the steel subjected to the two-phase zone sub-temperature quenching in the step (2) at the temperature below A1, and water cooling, wherein the temperature of A1 is 620-650 ℃.
In the step (1), the high-temperature quenching temperature is 830-930 ℃, and the heat preservation time is 58-62 minutes; in the step (2), the temperature of the two-phase zone sub-temperature quenching is 690-710 ℃, and the heat preservation time is 58-62 minutes; in the step (3), the tempering temperature is 578-582 ℃, and the heat preservation time is 58-62 minutes.
The rolling process comprises the following steps: heating the cast ingot to 1260-1300 ℃ before rolling, coating an anti-oxidation coating on the surface of the cast ingot, wherein the heating rate is 8-13 min/cm, keeping the temperature for 4 hours, and the initial rolling temperature in the rough rolling stage is not less than 1100 ℃; the thickness of the intermediate blank is 70-100 mm; the start rolling temperature of finish rolling is not more than 900 ℃, and the finish rolling temperature of finish rolling is 820-860 ℃.
The design principle of the invention is as follows:
the low-temperature steel has the element composition, wherein Ni is the most important alloy element in the low-temperature steel, and the proper amount of Ni is added, so that the temperature point of A1 can be reduced, and grains are refined. Ni is an important element for ensuring the stability of the reversed austenite because Ni is enriched in the reversed austenite during the heat treatment and the martensite transformation temperature point can be lowered due to the increased Ni content. When the content of Ni enriched in the reversed austenite is high enough, the high stability of the reversed austenite can still be maintained in a low-temperature environment of-196 ℃. When the reverse austenite is transformed into martensite, more energy is absorbed, stress concentration is reduced, and the crack tip is passivated, so that the crack can be effectively inhibited from expanding. Ni can also reduce the ductile-brittle transition temperature of steel and improve low-temperature toughness. In addition, the solid solution of Ni increases the cross-slip capability of the matrix and reduces the interaction of interstitial atoms and dislocations.
C can significantly improve the strength of steel and is one of the most economical strength-improving elements. However, low-temperature steel is basically low-carbon steel, and because the content of C is too high, toughness-brittleness is transformed into temperature rise, the low-temperature toughness of the steel is reduced, and the process properties such as welding and the like are damaged. The C content of the steel should be strictly controlled in consideration of both low-temperature toughness and weldability. Mn is an austenite stabilizing element, is beneficial to reversing the formation of austenite and can improve the strength of a matrix. The C content is reduced, the Mn/C ratio is improved, and the low ductile-brittle transition temperature can be obtained. The strength cannot meet the requirement when the Mn content is too low, and the toughness is influenced by forming large-size MnS inclusions when the Mn content is too high, so that the Mn needs to be controlled in a certain proper range. Si can inhibit P from being segregated in grain boundaries, can be dissolved in a matrix to generate a solid solution strengthening effect, and can improve the strength and the hardness of the matrix, but can reduce the toughness and the plasticity. Mo increases hardenability and increases strength and hardness of the steel, but too high Mo content results in a decrease in low-temperature toughness. Cr can improve the oxidation resistance and corrosion resistance of steel, and improve the strength, hardness and wear resistance, but can also reduce the plasticity and toughness of steel, so the Cr content is not suitable to be too high. Nb is a strong carbide forming element, can form an NbC or Nb (CN) precipitation phase in steel, pins grain boundaries, prevents austenite grains from growing, and improves the strength and the low-temperature toughness of the steel. However, too high a content of Nb results in too large a precipitate size, which adversely affects the properties of the steel.
For nickel-based low-temperature steel, in the smelting process, the content of impurity elements such as P, S and the like is controlled most importantly, the impurity elements have great influence on the low-temperature toughness of the steel, and the content of P, S in the steel is reduced as far as possible.
The QLT heat treatment is a high-temperature quenching, two-phase zone sub-temperature quenching and tempering process, and comprises a multi-step process. The low-temperature steel is subjected to first-step high-temperature quenching to obtain lath martensite; in the second step of heat preservation of the two-phase region, reverse transformation austenite cores are formed in part of martensite and are mainly distributed at the original austenite grain boundary and the martensite lath boundary; in the third step of tempering and heat preservation, the nucleated reversed austenite grows to form a film strip shape or granular and blocky reversed austenite. Then, the reversed austenite with higher stability is continuously retained in the structure in the process of water cooling to room temperature. And a small amount of reversed austenite with lower stability undergoes martensite transformation again to form new martensite, and the martensite is non-tempered martensite. Other martensite which does not generate reverse transformation is tempered to form tempered martensite. Compared with QT heat treatment, the adoption of QLT heat treatment can enable the structure of low-temperature steel to be more refined, can improve the quantity of stable reversed austenite in the steel and is beneficial to improving the low-temperature toughness of the steel.
The invention has the following advantages and beneficial effects:
1. the nickel-saving type 7Ni steel for the ultralow temperature environment has the same level low-temperature performance as the traditional 9Ni steel, and can be used as a low-temperature structural material for manufacturing an LNG storage tank.
2. The nickel-saving type 7Ni steel is structural steel for manufacturing low-temperature pressure vessels, can replace 9Ni steel, and becomes LNG engineering steel. Currently, 7Ni steel for LNG engineering has appeared in the japanese market and is put into practical use in LNG engineering, but 7Ni steel that can be used in LNG engineering has not appeared in the domestic market so far. Compared with 9Ni steel, the low-temperature steel reduces the Ni alloying cost, saves Ni resources, can meet the requirements of LNG engineering use, has low-temperature performance equivalent to that of the 9Ni steel, and has great application prospect.
3. According to the invention, the QLT process is used for the low-temperature steel, so that the structure of the steel is refined, the distribution of the reversed austenite in the steel is more dispersed and uniform, the low-temperature steel obtains enough quantity of reversed austenite with high stability, and the purpose of reducing the Ni content without obviously damaging the performance of the low-temperature steel is achieved.
Drawings
FIG. 1 is a schematic view showing the QLT heat treatment of nickel-saving type 7Ni steel of the present invention.
FIG. 2 is a SEM microstructure of the nickel-saving type 7Ni steel of example 1 after heat treatment.
FIG. 3 is a SEM microstructure of the nickel-saving type 7Ni steel of example 2 of the present invention after heat treatment.
FIG. 4 is a SEM microstructure of nickel-saving 7Ni steel of example 3 after heat treatment.
The specific implementation mode is as follows:
the present invention will be further illustrated by the following examples, which are to be construed as merely illustrative and not limitative of the remainder of the disclosure.
Example 1
The nickel-saving 7Ni steel for the ultralow temperature environment comprises the following chemical components in percentage by weight: ni: 7.00-7.60%, C: 0.02 to 0.06%, Si: 0.03-0.06%, Mn: 0.70-0.90%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Nb: 0.01-0.03%; the balance of Fe (one specific component is shown in the table 1); proportioning and smelting according to the proportion, and adopting a corresponding desulfurization technology to control the content of impurities; then, carrying out air cooling after multi-step hot rolling on the cast ingot, and ensuring the thickness of the intermediate blank to be 70-100 mm before finish rolling; the air-cooled rolled steel was subjected to QLT heat treatment (process parameters are shown in table 2), samples were taken from the heat-treated steel sheets as shown in fig. 1, and the microstructure of the samples was observed by a scanning electron microscope, and the specific microstructure was shown in fig. 2.
Example 2
The nickel-saving 7Ni steel for the ultralow temperature environment comprises the following chemical components in percentage by weight: ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10-0.20%; the balance of Fe (one specific component is shown in the table 1); proportioning and smelting according to the proportion, and adopting a corresponding desulfurization technology to control the content of impurities; then, carrying out air cooling after multi-step hot rolling on the cast ingot, and ensuring the thickness of the intermediate blank to be 70-100 mm before finish rolling; the air-cooled rolled steel was subjected to QLT heat treatment (process parameters are shown in table 2), samples were taken from the heat-treated steel sheets as shown in fig. 1, and the microstructure of the samples was observed by a scanning electron microscope, and the specific microstructure was shown in fig. 3.
Example 3
The nickel-saving 7Ni steel for the ultralow temperature environment comprises the following chemical components in percentage by weight: ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10 to 0.20%, Nb: 0.03-0.06%; the balance being Fe (one of the specific components is shown in Table 1). Proportioning and smelting according to the proportion, and adopting a corresponding desulfurization technology to control the content of impurities; then, carrying out air cooling after multi-step hot rolling on the cast ingot, and ensuring the thickness of the intermediate blank to be 70-100 mm before finish rolling; the air-cooled rolled steel was subjected to QLT heat treatment (process parameters are shown in table 2), samples were taken from the heat-treated steel sheets as shown in fig. 1, and the microstructure of the samples was observed by a scanning electron microscope, and the specific microstructure was shown in fig. 4.
Table 1 chemical composition of 7Ni steel smelted in examples 1-3 and compared to 9Ni steel (wt%)
TABLE 2 EXAMPLES 1-3 Heat treatment Processes of 7Ni steels melted and compared with 9Ni steels
| Numbering | Heat treatment process | Heat treatment System |
| 1 | QLT | 830℃×1h+690℃×1h+580℃×1h |
| 2 | QLT | 830℃×1h+690℃×1h+580℃×1h |
| 3 | QLT | 930℃×1h+710℃×1h+580℃×1h |
| 9Ni steel | QLT | 800℃×1h+670℃×1h+570℃×1h |
TABLE 3 room temperature tensile properties and Low temperature impact properties of heat treated 7Ni steels and 9Ni steels of examples 1-3
As can be seen from table 3, although the nickel content in the inventive 7Ni steel is reduced by about 2% compared to the 9Ni steel, the inventive 7Ni steel can have excellent properties of high toughness, high plasticity, high strength, no difference in tensile properties from the 9Ni steel, and a comparable level in low temperature toughness to the 9Ni steel through reasonable composition design and heat treatment process.
The foregoing embodiments and comparative examples are merely illustrative of the principles and capabilities of the present invention, and not all that is required is that one obtain additional embodiments in accordance with the present embodiments without the use of inventive faculty, and such additional embodiments are within the scope of the present invention.
Claims (3)
1. A nickel-saving type 7Ni steel used in ultralow temperature environment is characterized in that: the nickel-saving 7Ni steel comprises the following chemical components in percentage by weight:
ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10-0.20%; the balance being Fe;
or, the nickel-saving 7Ni steel comprises the following chemical components in percentage by weight:
ni: 7.00-7.60%, C: 0.02 to 0.10%, Si: 0.50-0.80%, Mn: 0.10-0.30%, P is less than or equal to 0.010%, S is less than or equal to 0.005%, Cr: 0.30-0.60%, Mo: 0.10 to 0.20%, Nb: 0.03-0.06%; the balance being Fe;
after hot rolling and heat treatment, the nickel-saving 7Ni steel has the thickness of 10-20 mm, the yield strength higher than 590MPa, the tensile strength higher than 680MPa, the elongation higher than 20% and the impact energy higher than 100J at the low temperature of-196 ℃.
2. The heat treatment process of nickel-saving type 7Ni steel for ultra-low temperature environment according to claim 1, wherein: rolling the smelted ingot into a steel plate with the thickness of 10-20 mm, air cooling, and then carrying out heat treatment, wherein the heat treatment process comprises the following steps:
(1) quenching the rolled steel subjected to air cooling at a high temperature of above A3, wherein the temperature of A3 is 750-800 ℃;
(2) carrying out sub-temperature quenching on the steel subjected to high-temperature quenching in the step (1) at a two-phase region temperature of 630-780 ℃;
(3) tempering the steel subjected to the two-phase zone sub-temperature quenching in the step (2) at the temperature below A1, and water cooling, wherein the temperature of A1 is 620-650 ℃.
3. The heat treatment process of nickel-saving type 7Ni steel for ultra-low temperature environment according to claim 2, wherein: in the step (1), the high-temperature quenching temperature is 830-930 ℃, and the heat preservation time is 58-62 minutes; in the step (2), the temperature of the two-phase zone sub-temperature quenching is 690-710 ℃, and the heat preservation time is 58-62 minutes; in the step (3), the tempering temperature is 578-582 ℃, and the heat preservation time is 58-62 minutes.
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| CN109385506A (en) * | 2018-12-11 | 2019-02-26 | 重庆世潮机械有限公司 | A kind of cylindrical die roll quenching technical |
| CN110129676A (en) * | 2019-05-27 | 2019-08-16 | 南京钢铁股份有限公司 | A kind of LNG storage tank 7Ni steel plate and production technology |
| CN111286586B (en) * | 2020-03-27 | 2021-10-26 | 中国科学院理化技术研究所 | Method for strengthening and toughening steel material |
| CN114657464A (en) * | 2022-03-03 | 2022-06-24 | 包头钢铁（集团）有限责任公司 | Rare earth nickel-saving 7Ni steel plate for LNG receiving station and production method thereof |
| CN115747652B (en) * | 2022-11-15 | 2023-06-23 | 北京科技大学 | Nb7 Ni-containing ultralow-temperature steel for nickel-saving LNG storage tank and heat treatment process thereof |
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| CN104674110A (en) * | 2015-02-09 | 2015-06-03 | 北京科技大学 | Lower temperature steel plate for pressure vessels and production method thereof |
| CN105543694A (en) * | 2015-12-29 | 2016-05-04 | 东北大学 | Preparation method of 7Ni steel plate for liquefied natural gas storage tank |
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| CN104674110A (en) * | 2015-02-09 | 2015-06-03 | 北京科技大学 | Lower temperature steel plate for pressure vessels and production method thereof |
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