CN117737607A - Ultralow-temperature steel for hydrogen energy storage and transportation equipment and preparation process thereof - Google Patents
Ultralow-temperature steel for hydrogen energy storage and transportation equipment and preparation process thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 56
- 239000010959 steel Substances 0.000 title claims abstract description 56
- 239000001257 hydrogen Substances 0.000 title claims abstract description 39
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 39
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000004146 energy storage Methods 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000005242 forging Methods 0.000 claims abstract description 283
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 73
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 24
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 20
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 238000001816 cooling Methods 0.000 claims description 53
- 238000003303 reheating Methods 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 20
- 239000007921 spray Substances 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 17
- 229910045601 alloy Inorganic materials 0.000 claims description 16
- 239000000956 alloy Substances 0.000 claims description 16
- 229910052786 argon Inorganic materials 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims 4
- 239000012071 phase Substances 0.000 abstract description 56
- 238000000034 method Methods 0.000 abstract description 26
- 230000008569 process Effects 0.000 abstract description 25
- 229910000734 martensite Inorganic materials 0.000 abstract description 14
- 230000009466 transformation Effects 0.000 abstract description 14
- 238000001953 recrystallisation Methods 0.000 abstract description 10
- 239000007790 solid phase Substances 0.000 abstract description 10
- 230000007704 transition Effects 0.000 abstract description 5
- 239000000463 material Substances 0.000 description 14
- 238000005259 measurement Methods 0.000 description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 13
- 238000010521 absorption reaction Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 238000005496 tempering Methods 0.000 description 8
- 238000007670 refining Methods 0.000 description 6
- 230000000717 retained effect Effects 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000001887 electron backscatter diffraction Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 229910021592 Copper(II) chloride Inorganic materials 0.000 description 1
- -1 CuCl2 saturated picric acid Chemical class 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 239000003949 liquefied natural gas Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Abstract
The ultralow-temperature steel for the hydrogen energy storage and transportation equipment and the preparation process thereof comprise the following chemical elements in percentage by mass: c: 0.06-0.1%, ni:6.5 to 10.5 percent of Mn:1.0 to 1.5 percent of Cr:0.8 to 1.5 percent of Si:0.3 to 0.5 percent of aluminum Al:0.3 to 0.5 percent and the balance of Fe element; on the basis of the components of the conventional Ni-based ultralow-temperature steel, the proportion is adjusted, the components are optimized, the grain refinement and dynamic recrystallization are promoted, and the low-temperature toughness of the steel is improved; applying an austenite plus forging process to densify and refine the parent phase austenite (fcc phase) grains, and then forming finer bcc phases (ferrite or martensite) from the refined parent phase through solid phase transformation; the grain ultra-refinement can obviously improve the low-temperature toughness of the steel, and the grain boundary is increased by the grain ultra-refinement treatment, so that crack propagation can be effectively prevented, the ductile-brittle transition temperature is reduced, and the low-temperature toughness is obviously improved.
Description
Technical Field
The invention belongs to the technical field of ultralow-temperature steel, and particularly relates to ultralow-temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof.
Background
The ultralow-temperature steel is mainly used for storing and transporting liquid hydrogen, liquefied natural gas, liquid nitrogen, liquid oxygen and the like, and has wide application in the fields of energy, chemical industry and the like. Important parts of hydrogen energy storage and transportation equipment, such as containers, pipelines and valves, are long-term service in low-temperature environments below-200 ℃, and are key equipment in the field of low-temperature industry. With the reduction of the use temperature, the steel material is changed from a ductile state to a brittle state, and if defects or load fluctuation exist at the moment, sudden brittle fracture can be caused, so that serious safety accidents are generated. In order to improve the safety of hydrogen energy storage and transportation equipment, containers, pipelines, valves and the like used in ultra-low temperature environments are generally manufactured by Ni-based low temperature steel. The content of residual austenite is increased by adding Ni element, so that the reverse transformation of austenite is promoted, and the low-temperature toughness is improved. In general, as the Ni content increases, the low-temperature toughness of Ni-based steel is gradually improved, and meanwhile, the Ni-based steel has enough strength, so that the good low-temperature resistance of hydrogen energy storage and transportation equipment can be ensured.
In recent years, various patent applications have been filed to control the toughness of Ni-based ultra-low temperature steels. For example, the patent application "a heat treatment process for improving the low-temperature impact toughness of 9Ni steel" (CN 104745770A) improves the low-temperature impact toughness of 9Ni steel through two-phase zone quenching, secondary normalizing and other processes, and optimizes the mechanical properties of 9Ni steel; the patent application discloses a toughening treatment process (CN 106893816B) for high-nickel low-carbon series steel, which combines a multi-pass heat treatment and a deep cooling treatment process, and improves the strength and the low-temperature toughness through carbide precipitation strengthening effect.
With the continuous development of hydrogen energy storage and transportation equipment, the requirements on low-temperature toughness, strength and safety are continuously improved. Under the principle of controllable cost (no increase of Ni content), the development of Ni-based ultralow-temperature steel with good technological performance, excellent low-temperature toughness and high strength is very critical. In general, the strength and toughness of steel materials are contradictory, and the higher the strength, the lower the toughness, and vice versa. In order to solve the problem, the invention develops ultralow-temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof on the basis of not increasing the content of Ni element according to the theory of crystal grain ultrafine, can reduce ductile-brittle transition temperature, remarkably improves low-temperature toughness and keeps good strength.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention aims to provide ultralow temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof, and according to a grain ultrafine theory, on the basis of not improving the content of Ni element, the ultralow temperature toughness of the ultralow temperature steel for the hydrogen energy storage and transportation equipment can be remarkably improved and good strength can be maintained by implementing different-temperature multistage thermal deformation and forging processes, so that grain ultrafine is realized on a microscopic scale, the uniformity of the grain is improved, the grain boundary is increased, crack expansion is effectively prevented, and the ductile-brittle transition temperature is reduced.
In order to achieve the above purpose, the specific technical scheme adopted by the invention is as follows:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c: 0.06-0.1%, ni:6.5 to 10.5 percent of Mn:1.0 to 1.5 percent of Cr:0.8 to 1.5 percent of Si:0.3 to 0.5 percent of aluminum Al:0.3 to 0.5 percent and the balance of Fe element.
A preparation process of ultralow-temperature steel for hydrogen energy storage and transportation equipment comprises the following specific steps:
step one, homogenizing: the mass percentages are as follows: c: 0.06-0.1%, ni:6.5 to 10.5 percent of Mn:1.0 to 1.5 percent of Cr:0.8 to 1.5 percent of Si:0.3 to 0.5 percent of aluminum Al:0.3 to 0.5 percent, and the rest of the Fe element sample is heated to 1100 to 1160 ℃ and is preserved for 120 to 180 minutes until the alloy element and the carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: forging the obtained single-phase austenite, wherein the forging temperature range is 850-1050 ℃, the forging ratio is 50-80%, the final forging temperature is 850-950 ℃, and then cooling to room temperature;
step three, austenitizing: reheating the sample after primary forging to 800-900 ℃, and preserving heat for 20-40 minutes;
step four, secondary forging: spray cooling the austenitized sample, and performing secondary forging when the sample is cooled to 50-100 ℃ below the A1 temperature line: the forging ratio is 50-70%, the forging direction is perpendicular to the one-time forging direction, the final forging temperature is 100 ℃ below the A1 temperature line, and water cooling is performed immediately to room temperature after the forging is finished;
step five, heating in a two-phase region: reheating the sample after secondary forging to a two-phase region of 50 ℃ above the A1 temperature line, and preserving heat for 15-30 minutes to obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 250-300 deg.c below the A1 temperature line, and three times of forging with forging ratio of 20-30% and final forging temperature of 300 deg.c below the A1 temperature line;
step seven, forging four times: immediately reheating the sample after the three times of forging to 50-100 ℃ below the A1 temperature line, preserving heat for 10-20 minutes, and performing four times of forging after the temperature is uniform: the forging temperature range is 100-150 ℃ below the A1 temperature line, the forging ratio is 50-70%, the forging direction is perpendicular to the three-time forging direction, the final forging temperature is 300 ℃ below the A1 temperature line, and the water cooling to room temperature is carried out immediately after the forging is completed.
The temperature line A1 is approximately 620-670 ℃.
Compared with the prior art, the invention has the beneficial effects that:
1. and (3) optimizing alloy components: on the basis of the components of the conventional Ni-based ultralow-temperature steel, the proportion is adjusted, the components are optimized, and the grain refinement and dynamic recrystallization are promoted. By tightly controlling C: 0.065-0.1%, reducing ductile-brittle transition temperature and improving low-temperature toughness; adding Ni:6.5 to 10.5 percent, reducing the critical point of an A1 temperature line (which is eutectoid transformation temperature and varies along with alloy components, A1 temperature line is approximately equal to 620 to 670 ℃ as shown in figure 1) and A3 (which is an inter-transformation temperature line of ferrite and austenite and varies along with alloy components, wherein A3 approximately equal to 680 to 730 ℃ as shown in figure 1) of the alloy, refining ferrite phase in the alloy, promoting austenite reverse transformation and obviously reducing ductile-brittle transformation temperature; cr is added: 0.8 to 1.5 percent, improves the stability of austenite, reduces the Ms point of martensite, and is beneficial to dynamic recrystallization; mn is added: 1 to 1.5 percent, and the austenite region in the steel is enlarged, thereby improving the toughness; adding Si:0.3 to 05 percent, can refine grains in steel, avoid coarse grains and improve the low-temperature toughness of the steel; adding aluminum Al:0.3 to 05 percent, aluminum AlN can be formed with N, and the low-temperature toughness of the steel is improved by refining grains.
2. Forging and dynamic recrystallization: the two processes are combined to obtain fine and uniform equiaxed grains. The forging ratio must be greater than 50% to increase dynamic recrystallization to provide the driving force. The forging temperature is critical to be selected and should be 100-150 ℃ below the A1 temperature line and above the C curve nose tip temperature, thereby being beneficial to realizing dynamic recrystallization. Dynamic recrystallization is affected by phase change driving force, nucleation rate and diffusion speed, and has high temperature and high diffusion speed, but the phase change driving force and nucleation rate are low, so that the dynamic recrystallization is difficult to finish; conversely, too low a temperature and low diffusion rate are unfavorable for dynamic recrystallization.
3. Forging and solid phase transformation: applying an austenite plus forging process to densify and refine the parent phase austenite (fcc phase) grains, and then forming finer bcc phases (ferrite or martensite) from the refined parent phase through solid phase transformation, so that the grains can be significantly refined; and then repeatedly carrying out an austenite+forging+solid phase transformation process, wherein newly formed mother phase grains are finer, so that subsequent bcc phase grains are continuously refined, and finally fine and uniform equiaxed grains are obtained, and the ultra-refinement of the grains is realized. Wherein, in order to avoid coarse austenite of the parent phase, the austenitizing temperature and the heating time of multiple cycles should be reduced in sequence.
4. Fine grain strengthening: grain refinement can simultaneously improve the strength, plasticity and toughness of the metal material. The finer and uniform crystal grains are, the more crystal grains are in unit volume, the less impurities are on unit crystal boundaries, the less deformation is dispersed on a single crystal grain when the material is deformed, the uniform deformation is realized, the crack propagation can be effectively prevented, and the higher the strength, the better the toughness and the plasticity of the material are. The grain ultra-refinement can obviously improve the low-temperature toughness of the steel, and the grain boundary is increased by the grain ultra-refinement treatment, so that crack propagation can be effectively prevented, the ductile-brittle transition temperature is reduced, and the low-temperature toughness is obviously improved.
Drawings
FIG. 1 is a schematic diagram of the preparation process of the present invention.
FIG. 2 is a grain orientation diagram (EBSD) of the ferrite-based bcc structure of the present invention.
Fig. 3 is a drawing of a parent phase austenite grain diagram (SEM).
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings.
Example 1:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c:0.08%, ni:9.8%, mn:1.1%, cr:1.2%, si:0.5%, aluminum Al:0.35% and the balance of Fe element.
The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment specifically comprises the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.08%, ni:9.8%, mn:1.1%, cr:1.2%, si:0.5%, aluminum Al:0.35 percent of the sample with the rest of Fe element is put into an argon protection furnace to be heated to 1120 ℃, and the temperature is kept for 150 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking out the obtained single-phase austenite sample from the furnace, forging at 1000 ℃ and 60% of forging ratio, final forging at 850 ℃, primarily refining and densifying austenite grains, and then cooling to room temperature by water to obtain a structure mainly comprising martensite;
step three, austenitizing: reheating the sample after primary forging to 850 ℃, preserving heat for 30 minutes, and carrying out austenitizing treatment to obtain an austenite structure with fine microstructure, so as to avoid forming coarse grains;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to about 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the 'primary forging' direction, the forging ratio is 60%, the final forging temperature is 500 ℃, and the grains are dynamically recrystallized at the final forging temperature to obtain uniformly refined equiaxed grains; immediately cooling the forging to room temperature after the forging is finished, and obtaining a tissue taking fine lath martensite as a main material and retained austenite as an auxiliary material;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 700 ℃ (about 50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 20 minutes to avoid grain growth and obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging ratio of 30%; the temperature generates solid phase transformation to form ferrite and applies forging, so that the grain structure can be obviously refined;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three-time forging direction, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 60%, the water is cooled to room temperature immediately after the forging is finished, and the microstructure of a final sample is obviously refined.
After the above procedure, the sample of example 1 was tested. The orientation and size of the grains were observed by back scattered electron diffraction (EBSD), and as a result, the average size of the bcc structure grains was about 0.45 μm as shown in fig. 2; to measure the size of the parent austenite grains, example 1 was subjected to short tempering at 350 ℃ and polishing corrosion, and then the microstructure was observed by a Scanning Electron Microscope (SEM), as shown in fig. 3, and the average size of the parent austenite grains was about 6.5 μm. From this, it is known that the grains of both the parent austenite and bcc structure are significantly refined.
Mechanical property test:the ultra-fine treatment process is a pretreatment process, and is used for measuring the mechanical property of the final tempering state, and the ultra-fine sample is tempered at 560 ℃ for 2 hours. Measurement of "tempered" sample: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =201J; determination of tensile Strength R at room temperature m =857±15MPa, 40% improvement in low temperature toughness compared with the conventional process, 20% improvement in tensile strength.
Example 2:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c:0.1%, ni:10.5%, mn:1.5%, cr:1.5%, si:0.5%, aluminum Al:0.5 percent and the balance of Fe element.
The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment specifically comprises the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.1%, ni:10.5%, mn:1.5%, cr:1.5%, si:0.5%, aluminum Al:0.5 percent, and the balance of Fe element is put into an argon protection furnace to be heated to 1160 ℃, and the temperature is kept for 120 minutes until the alloy element and carbide are completely dissolved, thus obtaining uniform single-phase austenite structure;
step two, forging for the first time: taking out the obtained single-phase austenite sample from the furnace, forging at 1100 ℃, forging ratio 80%, final forging temperature 900 ℃, primarily refining and densifying austenite grains, and then cooling to room temperature by water to obtain a tissue mainly comprising martensite;
step three, austenitizing: reheating the sample after primary forging to 800 ℃, preserving heat for 40 minutes, and carrying out austenitizing treatment to obtain an austenite structure with fine microstructure, so as to avoid forming coarse grains;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the primary forging direction, the forging ratio is 70%, the final forging temperature is 500 ℃, and the grains are dynamically recrystallized at the final forging temperature to obtain uniformly refined equiaxed grains; immediately cooling the forging to room temperature after the forging is finished, and obtaining a tissue taking fine lath martensite as a main material and retained austenite as an auxiliary material;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 675 ℃ (50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 30 minutes to avoid grain growth and obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging rate of 25%; the temperature generates solid phase transformation to form ferrite and applies forging, so that the grain structure can be obviously refined;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three-time forging direction, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 50%, the water is cooled to room temperature immediately after the forging is finished, and the microstructure of a final sample is obviously refined.
Mechanical property test: measurement of "tempered" sample: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =158J; determination of tensile Strength R at room temperature m ＝935±15MPa。
Example 3:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c:0.06%, ni:6.5%, mn:1.1%, cr:0.8%, si:0.3%, aluminum Al:0.3 percent of Fe element and the balance of unavoidable impurities.
The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment specifically comprises the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.06%, ni:6.5%, mn:1.1%, cr:0.8%, si:0.3%, aluminum Al:0.3 percent, and the balance of Fe element is put into an argon protection furnace to be heated to 1100 ℃, and the temperature is kept for 180 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking out the obtained single-phase austenite sample from the furnace, forging at 1050 ℃ and 50% of forging ratio, final forging at 950 ℃ to obtain primarily refined and densified austenite grains, and then cooling the austenite grains to room temperature by water to obtain a structure mainly comprising martensite;
step three, austenitizing: reheating the sample after primary forging to 900 ℃, preserving heat for 20 minutes, and carrying out austenitizing treatment to obtain an austenite structure with fine microstructure, so as to avoid forming coarse grains;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to about 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the 'primary forging' direction, the forging ratio is 50%, the final forging temperature is 500 ℃, and the grains are dynamically recrystallized at the final forging temperature to obtain uniformly refined equiaxed grains; immediately cooling the forging to room temperature after the forging is finished, and obtaining a tissue taking fine lath martensite as a main material and retained austenite as an auxiliary material;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 720 ℃ (50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 15 minutes to avoid grain growth and obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging ratio of 20%; the temperature generates solid phase transformation to form ferrite and applies forging, so that the grain structure can be obviously refined;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three-time forging direction, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 70%, the water is cooled to room temperature immediately after the forging is finished, and the microstructure of a final sample is obviously refined.
Mechanical property test: measurement of "tempered" sample: measurement of Charpy impact absorption at low temperature-196 ℃Work A k =195J; determination of tensile Strength R at room temperature m ＝778±15MPa。
Example 4:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c:0.09%, ni:8.5%, mn:1.0%, cr:1.3%, si:0.4%, aluminum Al:0.5 percent of Fe element and the balance of unavoidable impurities.
The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment specifically comprises the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.09%, ni:8.5%, mn:1.0%, cr:1.3%, si:0.4%, aluminum Al:0.5 percent, and the balance of Fe element is put into an argon protection furnace to be heated to 1130 ℃, and the temperature is kept for 120 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking out the obtained single-phase austenite sample from the furnace, forging at 1050 ℃ and 50% of forging ratio, final forging at 900 ℃ to obtain primarily refined and densified austenite grains, and then cooling the austenite grains to room temperature by water to obtain a structure mainly comprising martensite;
step three, austenitizing: reheating the sample after primary forging to 860 ℃, preserving heat for 30 minutes, and carrying out austenitizing treatment to obtain an austenite structure with fine microstructure, so as to avoid forming coarse grains;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the primary forging direction, the forging ratio is 70%, the final forging temperature is 500 ℃, and the grains are dynamically recrystallized at the final forging temperature to obtain uniformly refined equiaxed grains; immediately cooling the forging to room temperature after the forging is finished, and obtaining a tissue taking fine lath martensite as a main material and retained austenite as an auxiliary material;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 710 ℃ (50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 15 minutes to avoid grain growth and obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging ratio of 30%; the temperature generates solid phase transformation to form ferrite and applies forging, so that the grain structure can be obviously refined;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 15 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three-time forging direction, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 60%, the water is cooled to room temperature immediately after the forging is finished, and the microstructure of a final sample is obviously refined.
Mechanical property test: measurement of "tempered" sample: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =166J; determination of tensile Strength R at room temperature m ＝873±15MPa。
Example 5:
the ultralow-temperature steel for the hydrogen energy storage and transportation equipment comprises the following chemical elements in percentage by mass: c:0.07%, ni:7.8%, mn:1.4%, cr:1.2%, si:0.5%, aluminum Al:0.4% and the balance of Fe element.
The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment specifically comprises the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.08%, ni:9.8%, mn:1.1%, cr:1.2%, si:0.5%, aluminum Al:0.35 percent of the sample with the rest of Fe element is put into an argon protection furnace to be heated to 1120 ℃, and the temperature is kept for 150 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking out the obtained single-phase austenite sample from the furnace, forging at 1000 ℃ and a forging ratio of 60%, final forging at 850 ℃, primarily refining and densifying austenite grains, and then cooling the austenite grains to room temperature by water to obtain a tissue mainly comprising martensite;
step three, austenitizing: reheating the sample after primary forging to 890 ℃, preserving heat for 30 minutes, and carrying out austenitizing treatment to obtain an austenite structure with fine microstructure, so as to avoid forming coarse grains;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the primary forging direction, the forging ratio is 60%, the final forging temperature is 500 ℃, and the grains are dynamically recrystallized at the final forging temperature to obtain uniformly refined equiaxed grains; immediately cooling the forging to room temperature after the forging is finished, and obtaining a tissue taking fine lath martensite as a main material and retained austenite as an auxiliary material;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 700 ℃ (about 50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 25 minutes to avoid grain growth and obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at final forging temperature 300 deg.c in forging ratio of 25%; the temperature generates solid phase transformation to form ferrite and applies forging, so that the grain structure can be obviously refined;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three-time forging direction, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 70%, the water is cooled to room temperature immediately after the forging is finished, and the microstructure of a final sample is obviously refined.
Mechanical property test: measurement of "tempered" sample: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =172J; determination of tensile Strength R at room temperature m ＝822±15MPa。
Comparative example 1:
an ultralow-temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof adopt samples with the same components as those in the embodiment 1. Carrying out heat treatment according to the traditional processAnd (3) the superfine treatment process is not adopted. The key steps of the traditional process are as follows: (1) Putting the sample into an argon protection furnace, heating to 900 ℃, preserving heat for 60 minutes, and then quenching the sample to room temperature; (2) And (3) carrying out high-temperature tempering at 560 ℃ on the quenched sample, preserving heat for 120 minutes, and then cooling to room temperature in air. Mechanical property test: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =106J; determination of tensile Strength R at room temperature m =718±15MPa, and the mechanical properties are significantly reduced.
Comparative example 2:
an ultralow-temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof adopt samples with the same components as those in the embodiment 1. The heat treatment is carried out according to the traditional process without adopting an ultra-fine treatment process. The key steps of the traditional process are as follows: (1) Placing the sample into an argon protection furnace, heating to 800 ℃, preserving heat for 60 minutes, and then quenching to room temperature by water; (2) The sample is heated to 690 ℃ again, kept for 40 minutes, and then quenched to room temperature; (3) And (3) carrying out high-temperature tempering at 560 ℃ on the quenched sample, preserving heat for 120 minutes, and then cooling to room temperature in air. Mechanical property test: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =134J; determination of tensile Strength R at room temperature m =752±15MPa, and the mechanical properties are significantly reduced.
Comparative example 3:
an ultralow-temperature steel for hydrogen energy storage and transportation equipment and a preparation process thereof adopt samples with the same components as those in the embodiment 1. The main steps are ultra-fine treatment process, but each forging process is cancelled. For mechanical property testing, "tempered" sample test results: measurement of Charpy impact absorption work A at low temperature of-196 DEG C k =146J; determination of tensile Strength R at room temperature m =753±15MPa, and the mechanical properties are remarkably reduced.
The invention utilizes the grain refinement principle and combines the processes of alloy component optimization, forging and dynamic recrystallization, forging and solid phase transformation, and the like to develop the ultralow-temperature steel for the hydrogen energy storage and transportation equipment and the preparation process thereof, and the obtained beneficial effects are as follows:
(1) Microstructural grain ultra-refinement:
after the superfine treatment process, a tissue with martensite as a main component and retained austenite and ferrite as auxiliary components is obtained, and the grains are fine and uniform. The samples were subjected to EBSD observation, wherein the bcc structure grain orientation is as shown in FIG. 2, and the average bcc grain size is 0.3-0.8 μm.
After the sample is tempered at 350 ℃ for a short time and is corroded by a CuCl2 saturated picric acid solution, mother phase austenite grains are observed through SEM, and as shown in figure 3, the mother phase fcc austenite grains are refined to 5-8 mu m. From this, it is clear that after the grain refinement treatment, both the final bcc grains and the parent-phase fcc austenite grains are significantly refined, and the parent-phase fcc grains are the basis for further refinement of the subsequent grains.
(2) Improving low-temperature toughness and strength:
the ultra-low temperature steel grain ultra-refining treatment process for the hydrogen energy storage and transportation equipment developed by the invention is a pretreatment process, and mechanical property test and comparison are carried out after the subsequent conventional high-temperature tempering reaches a tempering state. Tempering at 580 deg.c for 2 hr, and measuring the mechanical performance. The low-temperature impact toughness of a sample in a tempering state is measured at the low temperature of minus 196 ℃, the highest Charpy impact absorption power can reach more than 200J, and the Charpy impact absorption power is improved by 45 percent compared with the traditional process; the tensile strength of the sample in the 'tempered state' measured at room temperature can reach more than 950MPa, and is improved by 30 percent compared with the traditional process.
Claims (10)
1. The ultralow-temperature steel for the hydrogen energy storage and transportation equipment is characterized by comprising the following chemical elements in percentage by mass: c: 0.06-0.1%, ni:6.5 to 10.5 percent of Mn:1.0 to 1.5 percent of Cr:0.8 to 1.5 percent of Si:0.3 to 0.5 percent of aluminum Al:0.3 to 0.5 percent and the balance of Fe element.
2. The preparation process of the ultralow-temperature steel for the hydrogen energy storage and transportation equipment is characterized by comprising the following specific steps of:
step one, homogenizing: the mass percentages are as follows: c: 0.06-0.1%, ni:6.5 to 10.5 percent of Mn:1.0 to 1.5 percent of Cr:0.8 to 1.5 percent of Si:0.3 to 0.5 percent of aluminum Al:0.3 to 0.5 percent, and the rest of the Fe element sample is heated to 1100 to 1160 ℃ and is preserved for 120 to 180 minutes until the alloy element and the carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: forging the obtained single-phase austenite, wherein the forging temperature range is 850-1050 ℃, the forging ratio is 50-80%, the final forging temperature is 850-950 ℃, and then cooling to room temperature;
step three, austenitizing: reheating the sample after primary forging to 800-900 ℃, and preserving heat for 20-40 minutes;
step four, secondary forging: spray cooling the austenitized sample, and performing secondary forging when the sample is cooled to 50-100 ℃ below the A1 temperature line: the forging ratio is 50-70%, the forging direction is perpendicular to the one-time forging direction, the final forging temperature is 100 ℃ below the A1 temperature line, and water cooling is performed immediately to room temperature after the forging is finished;
step five, heating in a two-phase region: reheating the sample after secondary forging to a two-phase region of 50 ℃ above the A1 temperature line, and preserving heat for 15-30 minutes to obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 250-300 deg.c below the A1 temperature line, and three times of forging with forging ratio of 20-30% and final forging temperature of 300 deg.c below the A1 temperature line;
step seven, forging four times: immediately reheating the sample after the three times of forging to 50-100 ℃ below the A1 temperature line, preserving heat for 10-20 minutes, and performing four times of forging after the temperature is uniform: the forging temperature range is 100-150 ℃ below the A1 temperature line, the forging ratio is 50-70%, the forging direction is perpendicular to the three-time forging direction, the final forging temperature is 300 ℃ below the A1 temperature line, and the water cooling to room temperature is carried out immediately after the forging is completed.
3. The process for preparing ultralow-temperature steel for hydrogen energy storage and transportation equipment according to claim 2, which is characterized in that: the temperature line A1 is approximately 620-670 ℃.
4. The ultralow temperature steel for hydrogen energy storage and transportation equipment according to claim 1, which is characterized by comprising the following chemical elements in percentage by mass: c:0.08%, ni:9.8%, mn:1.1%, cr:1.2%, si:0.5%, aluminum Al:0.35% and the balance of Fe element.
5. A process for preparing ultra-low temperature steel for hydrogen energy storage and transportation equipment according to claim 2 or 3, which is characterized by comprising the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.08%, ni:9.8%, mn:1.1%, cr:1.2%, si:0.5%, aluminum Al:0.35 percent of the sample with the rest of Fe element is put into an argon protection furnace to be heated to 1120 ℃, and the temperature is kept for 150 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking the obtained single-phase austenite sample out of the furnace, forging the single-phase austenite sample at a forging temperature of 1000 ℃ and a forging ratio of 60%, and performing final forging at a final forging temperature of 850 ℃, and then performing water cooling to room temperature;
step three, austenitizing: reheating the primary forging sample to 850 ℃, and preserving heat for 30 minutes;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the 'primary forging' direction, the forging ratio is 60%, the final forging temperature is 500 ℃, and immediately cooling to room temperature after the forging is completed;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 700 ℃ (50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 20 minutes to obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at final forging temperature of 300 deg.c and forging ratio of 30%;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three forging directions, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 60%, and the water is cooled to room temperature immediately after the forging is completed.
6. The ultralow temperature steel for hydrogen energy storage and transportation equipment according to claim 1, which is characterized by comprising the following chemical elements in percentage by mass: 0.1%, ni:10.5%, mn:1.5%, cr:1.5%, si:0.5%, aluminum Al:0.5 percent and the balance of Fe element.
7. A process for preparing ultra-low temperature steel for hydrogen energy storage and transportation equipment according to claim 2 or 3, which is characterized by comprising the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.1%, ni:10.5%, mn:1.5%, cr:1.5%, si:0.5%, aluminum Al:0.5 percent, and the balance of Fe element is put into an argon protection furnace to be heated to 1160 ℃, and the temperature is kept for 120 minutes until the alloy element and carbide are completely dissolved, thus obtaining uniform single-phase austenite structure;
step two, forging for the first time: taking the obtained single-phase austenite sample out of the furnace, forging the single-phase austenite sample at 1100 ℃, forging the single-phase austenite sample at 80% and at 900 ℃, and then cooling the single-phase austenite sample to room temperature by water;
step three, austenitizing: reheating the sample after primary forging to 800 ℃, and preserving heat for 40 minutes;
step four, secondary forging: spray cooling the sample after austenitizing, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) and starting forging, wherein the forging deformation direction is vertical to the primary forging direction, the forging ratio is 70%, and the final forging temperature is 500 ℃; immediately cooling to room temperature after forging;
step five, heating in a two-phase region: reheating the sample after secondary forging to a 675 ℃ (50 ℃ above the A1 temperature line) two-phase region, and preserving heat for 30 minutes to obtain a uniform and fine ferrite and austenite two-phase structure;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging ratio of 25%;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three forging directions, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 50%, and the water is cooled to room temperature immediately after the forging is completed.
8. The ultralow temperature steel for hydrogen energy storage and transportation equipment according to claim 1, which is characterized by comprising the following chemical elements in percentage by mass: c:0.06%, ni:6.5%, mn:1.1%, cr:0.8%, si:0.3%, aluminum Al:0.3% and the balance of Fe element.
9. A process for preparing ultra-low temperature steel for hydrogen energy storage and transportation equipment according to claim 2 or 3, which is characterized by comprising the following steps:
step one, homogenizing: the mass percentages are as follows: c:0.06%, ni:6.5%, mn:1.1%, cr:0.8%, si:0.3%, aluminum Al:0.3 percent, and the balance of Fe element is put into an argon protection furnace to be heated to 1100 ℃, and the temperature is kept for 180 minutes until the alloy element and carbide are completely dissolved, thus obtaining a uniform single-phase austenite structure;
step two, forging for the first time: taking the obtained single-phase austenite sample out of the furnace, forging the single-phase austenite sample at 1050 ℃ and 50% of forging ratio and 950 ℃ of final forging temperature, and then cooling the single-phase austenite sample to room temperature by water;
step three, austenitizing: reheating the sample after primary forging to 900 ℃, and preserving heat for 20 minutes;
step four, secondary forging: spray cooling the austenitized sample, cooling to 600 ℃ (50-100 ℃ below the A1 temperature line) to start forging, wherein the forging deformation direction is vertical to the primary forging direction, the forging ratio is 50%, and the final forging temperature is 500 ℃, and immediately cooling to room temperature after the forging is completed;
step five, heating in a two-phase region: reheating the sample after the secondary forging to a 720 ℃ (50 ℃ above an A1 temperature line) two-phase region, and preserving heat for 15 minutes;
step six, forging for three times: spray cooling the heated sample in the two-phase region to 400 deg.c (250-300 deg.c below the A1 temperature line), and three times of forging at 300 deg.c and forging ratio of 20%;
step seven, forging four times: immediately reheating the sample after three times of forging to 600 ℃ (50-100 ℃ below the A1 temperature line), preserving the heat for 20 minutes, and carrying out four times of forging after the temperature is uniform: the forging direction is perpendicular to the three forging directions, the initial forging temperature is 600 ℃, the final forging temperature is 500 ℃, the forging ratio is 70%, and the water is cooled to room temperature immediately after the forging is completed.
10. The ultralow temperature steel for hydrogen energy storage and transportation equipment according to claim 1, which is characterized by comprising the following chemical elements in percentage by mass: c:0.09%, ni:8.5%, mn:1.0%, cr:1.3%, si:0.4%, aluminum Al:0.5 percent and the balance of Fe element.
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