Anti-collision pressure vessel steel for storing and transporting trifluoromethane and production method thereof

Abstract

The application discloses an anti-collision pressure container steel for storing and transporting trifluoromethane, which is characterized by the following components and wt%: C: 0.10-0.20%, Si: 0.15-0.40%, Mn: 0.70-1.15%, Al: 0.015-0.025%, P: ≤0.015%, S: ≤0.005%, V: 0.015-0.035%, and Nb: 0.010-0.022%. The application comprises the following steps: after smelting and casting into a blank, the cast blank is heated; rough rolling; finish rolling; cooling; normalizing; and stress relief. The static yield strength Rel of the application is 245-350 MPa, the dynamic yield strength Re is 315-555.5 MPa, the tensile strength is 400-520 MPa, the yield strength ratio is ≤0.85, the static elongation after fracture A is 31-41%, the dynamic elongation after fracture A is 30-40%, the product of strength and plasticity is 13950-21320 MPa%, the drop weight tear test (DWTT) energy is 19-21 kJ, the absorbed energy of the steel plate is 2.5-3.1 KJ when the collision speed is 5-50 m / s and the collision displacement is 1.5 m, and the grain size of ferrite is not more than 0.035 μm. d The application discloses an anti-collision pressure container steel for storing and transporting trifluoromethane, which is characterized by the following components and wt%: C: 0.10-0.20%, Si: 0.15-0.40%, Mn: 0.70-1.15%, Al: 0.015-0.025%, P: ≤0.015%, S: ≤0.005%, V: 0.015-0.035%, and Nb: 0.010-0.022%. The application comprises thefollowing steps: after smelting and casting into a blank, the cast blank is heated; roughrolling; finish rolling; cooling; normalizing; and stress relief. The static yield strength Rel ofthe application is 245-350 MPa, the dynamic yield strength Re is 315-555

Description

Technical Field

[0001] This invention relates to a pressure vessel steel and its production method, specifically to a collision-resistant pressure vessel steel for storing and transporting trifluoromethane and its production method. Background Technology

[0002] Trifluoromethane is a non-flammable gas primarily used as a refrigerant, fire extinguishing agent, propellant, plasma etching agent, and solvent in supercritical fluid extraction. It is an important chemical raw material. When a collision occurs, the steel tanks used in mobile pressure vessels transporting the hazardous chemical trifluoromethane deform, causing severe deformation of the tank body. This deformation leads to a rapid increase in internal pressure. When the pressure exceeds the material's dynamic yield strength or the deformation itself, it can cause a fire or explosion of the hazardous gas or liquid inside the tank, simultaneously polluting the surrounding environment. These collision-induced accidents and their cascading effects are characteristics not typically considered in the design of steel used in conventional automobiles.

[0003] Trifluoromethane is primarily transported to its users in storage containers. During transport, accidents such as tank tipping, overturning, and collisions are unavoidable. In the event of such an accident, the container storing boron trichloride will deform, leading to a rapid increase in internal pressure. If this pressure exceeds the dynamic yield strength of the steel used in the storage container or the deformation exceeds the pressure, the container will crack. Simultaneously, the leaked trifluoromethane gas will pollute the surrounding environment and may even pose an explosion hazard due to contact with air.

[0004] Existing steel materials used for trifluoromethane storage containers do not address the dynamic mechanical properties of the steel during collisions. They lack consideration of collision-resistant material properties, resistance to fracture and tearing under high strain rates during collision deformation, and the high energy absorption capacity of the tank within a certain distance after a collision. This severely restricts the improvement of safety design technology for mobile pressure vessel transportation. Most technical literature focuses on the safety of automotive steel, which is primarily designed based on human safety factors, detailing the material's collision and energy absorption characteristics. However, for steel materials used in mobile pressure vessels transporting hazardous chemicals, the design must consider not only the safety of personnel in the transport vehicle but also the safety of the transported and stored medium during and after a collision—a aspect that cannot be verified in automotive steel material design.

[0005] Search results:

[0006] Chinese Patent Publication No. CN112746222B discloses "A 355MPa-grade impact-resistant steel plate," which adopts a low-to-medium carbon alloy system of 0.07-0.10% C, 1.0-1.6% Mn, and micro-0.001-0.1% Ti+Cu+Ni. The target performance steel plate is obtained using a controlled rolling and controlled cooling process. The steel plate microstructure consists of ferrite, pearlite, and a small amount of bainite, with a high-angle grain boundary content ≥50%. The material has a yield strength ≥355MPa, tensile strength ≥490MPa, and elongation after fracture ≥55%. The cleavage fracture unit size is ≤10μm, and the fracture fiber rate is ≥80%. Using this material can only guarantee safety during the routine transportation of boron trichloride tanks. However, the material's dynamic yield strength and dynamic elongation after fracture are crucial characteristics for ensuring the safety of trifluoromethane tank materials. This material can only guarantee the static mechanical properties of the material under normal transportation conditions, but cannot guarantee the safety of the material during trifluoromethane tank transportation, as these are unique safety attributes. It cannot guarantee that the physical properties of the trifluoromethane contained in the material will not change significantly in the event of a collision, nor can it guarantee the dynamic mechanical properties of the material after a collision. Therefore, it cannot guarantee the safety of moving pressure vessels in collisions.

[0007] Chinese Patent Publication No. CN115287431A discloses "A Low-Temperature Marine Steel Plate with Excellent Plasticity and Its Manufacturing Method". It uses a medium-low carbon 0.08-0.10%C-0.8~1.50%Mn+microalloyed Ti+Nb alloy and adopts a controlled rolling and controlled cooling process to obtain a steel plate with target performance, resulting in a ferrite + bainite two-phase microstructure. The material has a yield strength ≥355MPa, tensile strength >490MPa, impact energy at -60℃ >200J, and elongation after fracture >33%. Using this material can only guarantee safety during the routine transportation of boron trichloride tanks. However, the material's dynamic yield strength and dynamic elongation after fracture are crucial characteristics for ensuring the safety of trifluoromethane tank materials. This material can only guarantee the static mechanical properties of the material under normal transportation conditions, but cannot guarantee the safety of the material during trifluoromethane tank transportation, as these are unique safety attributes. It cannot guarantee that the physical properties of the trifluoromethane contained in the material will not change significantly in the event of a collision, nor can it guarantee the dynamic mechanical properties of the material after a collision. Therefore, it cannot guarantee the safety of moving pressure vessels in collisions.

[0008] Document WO2022171081A discloses "A Collision-Resistant and Crack-Resistant Steel for Ship Hull Structures and Its Manufacturing Method," which uses a low-carbon steel composition of 0.06-0.12% C, 1.3-1.7% Mn, and micro-Ti (0.005-0.012%), supplemented with Mg+Ca pure steel treatment technology. It employs controlled rolling and controlled cooling, followed by normalizing heat treatment to obtain a steel plate with the target performance. The microstructure of the steel plate is ferrite + pearlite. The material has a yield strength ≥315MPa, tensile strength 440~570MPa, CTOD ≥1.5mm at -60℃, NDTT ≤70℃, uniform elongation ≥18%, and total elongation A5 ≥38%. However, the composition and manufacturing process of this steel cannot guarantee the safety of moving pressure vessels in collisions. Using this material can only guarantee safety during the routine transportation of trifluoromethane tanks. However, the material's dynamic yield strength and dynamic elongation after fracture are crucial characteristics for ensuring the safety of trifluoromethane tank materials. This material can only guarantee the static mechanical properties of the material under normal transportation conditions, but cannot guarantee the safety of the material during the transportation of trifluoromethane tanks, as these are unique safety attributes. It cannot guarantee that the physical properties of the trifluoromethane contained in the material will not change significantly in the event of a collision, nor can it guarantee the dynamic mechanical properties of the material after a collision. Therefore, it cannot guarantee the safety of moving pressure vessels in collisions. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by providing a material with a thickness of 6–35 mm, a static yield strength Re of 245–350 MPa, a dynamic yield strength Re of 315–555.5 MPa, a tensile strength of 400–520 MPa, a yield-to-tensile ratio ≤0.85, a static elongation at fracture A of 31–41%, and a dynamic elongation at fracture A0.1. d The steel is a collision-resistant pressure vessel steel for storing and transporting trifluoromethane, with a strength-ductility product of 13950–21320 MPa·% and a drop hammer tear (DWTT) energy of 19–21 kJ. When the impact velocity is 5–50 m / s and the impact displacement is 1.5 m, the energy absorbed by the steel plate after the impact is 2.5–3.1 kJ, and the ferrite grain size does not exceed 0.035 μm.

[0010] Measures to achieve the above objectives:

[0011] A collision-resistant pressure vessel steel for storing and transporting trifluoromethane, comprising the following components and weight percentages: C: 0.10–0.20%, Si: 0.15–0.40%, Mn: 0.70–1.15%, Al: 0.015–0.025%, P≤0.015%, S≤0.005%, V: 0.015–0.035%, Nb: 0.010–0.022%, with the remainder being Fe and unavoidable impurities; its steel properties are as follows: thickness 6–35 mm, static yield strength Rel 245–350 MPa and dynamic yield strength Re 315–555.5 MPa, tensile strength 400–520 MPa, yield ratio ≤0.85, static elongation after fracture A 31–41% and dynamic elongation after fracture A d The strength-ductility product is 13950-21320 MPa·% at 30-39%; the drop hammer tear (DWTT) energy is 19-21 kJ; when the impact velocity is 5-50 m / s and the impact displacement is 1.5 m, the energy absorbed by the steel plate after the impact is 2.5-3.1 kJ, and the grain size of ferrite does not exceed 0.035 μm.

[0012] Preferably, the weight percentage content of C is 0.10 to 0.15%.

[0013] Preferably, the weight percentage content of Si is 0.17 to 0.34%.

[0014] Preferably, the weight percentage content of V is 0.019 to 0.031%.

[0015] Preferably, the Nb content is 0.014 to 0.018% by weight.

[0016] A method for producing a collision-resistant pressure vessel steel for storing and transporting trifluoromethane, comprising the following steps:

[0017] 1) After smelting and casting into billets, the billets are heated to 1150-1240℃ at a heating rate of 4-12 min / cm.

[0018] 2) Perform rough rolling, controlling the initial rolling temperature to be no lower than 1050℃;

[0019] 3) Perform finishing rolling, and control the final rolling temperature to be no higher than 925℃; control the cumulative reduction rate of the last three passes to be no less than 30%;

[0020] 4) Cool the temperature to 550–590°C at a cooling rate of 0.90–4.80°C / s;

[0021] 5) Perform normalizing, controlling the normalizing temperature at 840–910℃, and hold at this temperature for the following duration:

[0022] (10~25min)+t×1min / mm

[0023] In the formula: t—represents the thickness of the hot-rolled plate, in mm;

[0024] 6) Stress relief: The stress relief temperature is controlled at 550-590℃, and the temperature is maintained at this temperature for 30-120 minutes.

[0025] Preferably, the temperature is controlled at a cooling rate of 1.8–4.2 °C / s to cool to 562–580 °C.

[0026] Preferably, the normalizing temperature is controlled at 850–890°C.

[0027] The role and mechanism of each raw material and main process in this invention

[0028] C: In this invention, carbon (C) is an indispensable element for improving the strength of steel, playing a role in solid solution strengthening. As the C content in steel increases, the Fe3C content in the steel increases, leading to improved yield strength and tensile strength. Specifically, for every 0.1% increase in C content, the tensile strength increases by approximately 90 MPa, and the yield strength increases by approximately 40-50 MPa. However, it is important to note that the C content should not be too high; as the C content increases, the elongation and impact toughness of the steel decrease. Research has found that a C content of no more than 0.20% in steel effectively improves its strength while remaining suitable for industrial production, thus enhancing its applicability and feasibility in industrial applications. Therefore, considering the influence of element C on the performance of pressure vessel steel plates in this technical solution, in order to improve the strength of the steel while being suitable for process production, the mass percentage content of C in the impact-resistant pressure vessel steel plates of this invention is controlled between 0.10 and 0.20%, preferably between 0.10 and 0.15%.

[0029] Si: In this invention, Si is mainly a deoxidizing element in the steelmaking process and has a certain solid solution strengthening effect. It should be noted that when the Si content in steel increases from 0.20% to 0.60%, the strength of the steel remains basically unchanged or increases slightly, while the toughness of the steel is significantly improved. Appropriately increasing the Si content in steel will increase the volume fraction of ferrite in the microstructure and refine the grains, thereby benefiting the toughness of the steel. Therefore, in the pressure vessel steel plate with good hot formability described in this invention, the mass percentage content of Si is controlled between 0.15% and 0.40%, preferably between 0.17% and 0.34% by weight.

[0030] Mn: In this invention, Mn has a significant effect on improving the strength of low-carbon and medium-carbon pearlitic steel. Adding 1% Mn to steel can increase the tensile strength of the steel by approximately 100 MPa. Mn has a significant effect on center segregation in the as-cast structure. Higher Mn content will result in a higher degree of center segregation in the as-cast steel, which seriously affects the low-temperature impact toughness, post-collision tear resistance, and elongation at high strain rates of the steel plate. In the impact-resistant pressure vessel steel plate described in this invention, the mass percentage of Mn is controlled between 0.70% and 1.15%.

[0031] Al: In this invention, Al is added as a deoxidation balancing element during the steelmaking process. Specifically, in the early stages of refining, the Al content in the molten steel needs to be controlled to no more than 0.035%. In the later stages of refining, the oxygen content in the steel is already controlled to a low level; if Al is added again, large-sized chain-like alumina inclusions will form in the molten steel, severely impairing the low-temperature toughness, impact tear resistance, and high strain rate elongation properties of the finished steel plate. Furthermore, adding Al in the later stages of refining will form a large amount of AlN in the steel. AlN easily precipitates during the casting of the molten steel into a continuous casting billet, reducing the hot plasticity of the billet and causing corner cracks or intergranular cracks on the surface or corners of the billet. Therefore, considering the impact of Al on the performance of pressure vessel steel plates in this technical solution, the mass percentage of Al in the impact-resistant pressure vessel steel plates described in this invention is controlled between 0.015% and 0.025%.

[0032] V: In this invention, V is a strong carbonitride forming element. Adding V to steel can significantly improve its strength. It can refine the grain size by forming carbide structures and promoting austenite grain growth, thereby increasing the room temperature strength of the steel. V not only promotes pearlite formation but also refines ferrite laths. Furthermore, when V is added to steel, the regular Fe3C cementite lamellae and pearlite clusters in the steel are blocked by V or carbonitride precipitates. This increases the number of cementite breakpoints in the pearlite lamellae, reduces the area of ​​the pearlite clusters, and causes the pearlite clusters to be inter-oriented. The pearlite lamellae become shorter and thinner, and the fragmentation of the pearlite lamellae increases. However, it should be noted that the V content in the steel should not be too high. When the V content is too high, the number and size of precipitates increase, which leads to a decrease in the toughness of the steel. Therefore, taking into account the various strengthening and toughening effects of V in steel, the mass percentage content of V in the impact-resistant pressure vessel steel plate of the present invention is controlled between 0.015% and 0.035%, preferably between 0.019% and 0.031% by weight.

[0033] Nb: In the impact-resistant pressure vessel steel plate described in this invention, the addition of an appropriate amount of Nb is to promote grain refinement of the steel rolling microstructure, improve the strength and toughness of the steel plate, and enhance its impact energy absorption and impact tear fracture resistance. Nb can effectively refine the microstructure during controlled rolling by inhibiting austenite recrystallization; moreover, Nb can effectively reduce the steel's overheat sensitivity and temper brittleness. Therefore, in the impact-resistant pressure vessel steel plate described in this invention, the mass percentage content of Nb is controlled between 0.010% and 0.022%, preferably between 0.014% and 0.018% by weight.

[0034] P and S: In the impact-resistant pressure vessel steel plate described in this invention, P and S are both impurity elements in the steel. Only by smelting pure steel can the performance of the steel of this invention be guaranteed; therefore, the content of P and S elements in the steel must be controlled within a low range. Based on this, in the pressure vessel steel plate described in this invention, the P element content can be controlled to P≤0.015%, and the S element content can be controlled to S≤0.005%.

[0035] The reason why the present invention controls the heating rate at 4 to 12 min / cm to heat the billet to 1150 to 1240°C is that, under the condition of ensuring a suitable heating rate, it is possible to ensure that no heating cracks occur on the surface of the billet, and that the billet can be fully austenitized. Furthermore, the billet is heated without coarsening the austenite grains, thereby providing a heated billet with sufficiently low rolling deformation resistance for subsequent rolling.

[0036] The reason why the roughing rolling temperature is controlled to be no less than 1050℃ is that the roughing rolling temperature is to allow the billet to be fully deformed above the non-recrystallization temperature of austenite, and to break the grains within this roughing rolling temperature range, thereby achieving large deformation and smaller grain size in the high-temperature section of austenite, and providing sufficient temperature and thickness control parameters for subsequent finishing rolling temperature control.

[0037] The reason why this invention controls the finishing rolling temperature to be no higher than 925℃ and controls the cumulative reduction rate of the last three passes to be no less than 30% is to further reduce the austenite grains in the rough-rolled steel plate near the austenite non-recrystallization temperature. In order to ensure the mechanical properties of the finished steel plate, the cumulative reduction rate of the last three passes is controlled to be above 33% to ensure that the grain nucleation at the grain boundaries is increased during the transformation of deformed austenite to ferrite, thereby achieving the dual purpose of controlling the steel plate properties and the thickness of the finished product.

[0038] The reason why this invention cools to 550-590℃ at a cooling rate of 0.90-1.80℃ / s is because the temperature of the steel plate after finishing rolling is still at A... C1The purpose of controlling the cooling rate and the final cooling temperature range after finishing rolling is to rapidly reduce the temperature of the rolled steel plate to near or below the ferrite transformation temperature, thereby ensuring the required ferrite + pearlite structure of the finished steel plate and precisely controlling the rolled properties within a certain range.

[0039] The reason why the normalizing temperature is controlled at 840-910℃ and held at this temperature for a holding time according to the formula (10-25 min) + t × 1 min / mm is that the strength and plasticity of the rolled steel plate cannot reach the optimal match. By using reasonable normalizing heat treatment parameters, the strength and plasticity of the steel plate are optimized and the strength of the steel plate is controlled within a more precise range, thus ensuring the static mechanical properties and impact resistance of the steel plate material of this invention.

[0040] The reason why the stress relief temperature is controlled at 550-590℃ and held at this temperature for 30-120 minutes is that stress relief heat treatment can further eliminate the hard phase structure in the normalized heat-treated steel plate, appropriately reduce the strength of the steel plate, and reduce the internal stress caused by the rolling and cooling phase transformation and uneven phase transformation of the steel plate, thereby improving the collision safety characteristics of the steel of this invention when transporting hazardous chemicals.

[0041] Regarding the microstructure of the steel plate of this invention:

[0042] In this invention, the microstructure matrix is ​​composed of ferrite, pearlite, and bainite. Ferrite characteristics: ferrite volume percentage 82–90%, with the area ratio of ferrite grain boundary orientation difference in the 15–60° range being 71–78%; pearlite volume percentage: 10–14%; bainite percentage: 0.5–2.5%. Precipitation characteristics in the steel: precipitate size 15–30 nm; precipitate spacing 368–378 nm. When the material deformation is 10–15%, the geometrically required dislocation density in the steel is 2.4 × 10⁻⁶. 14 ~2.7×10 14 / m 2 .

[0043] The microstructure of steel is typically determined using an optical microscope with a nitric acid + 3% ethanol etching solution. However, when the microstructure is difficult to discern with an optical microscope, electron backscatter diffraction scanning electron microscopy (EBSD) can be used for identification. The orientation difference of ferrite grain boundaries is observed using the EBSD method in metallography. The precipitates in steel are mainly NbC and VC, which are observed using a thin-film transmission electron microscope. The size and spacing of the precipitates are observed using a transmission electron microscope at 5000x magnification in 30 arbitrary fields of view. Images are obtained, and then image analysis software is used to determine the grain size and spacing of the precipitates from these images.

[0044] Geometrically required dislocations differ from statistically distributed dislocations in that their density is related to the average Burgers vector of deformation-induced dislocations. Geometrically required dislocations accommodate deformation incompatibilities, unlike statistically distributed dislocations, and these dislocations ensure that the material's deformation is maximized. The geometrically required dislocation density (ρ) GND) ρ is calculated using the intergranular orientation difference (θ) measured by EBSD, the unit length (u) of the analytical position of dislocation density, and the average Burgers vector (b) of the deformed material. GND =2θ / (ub).

[0045] In this invention, the properties are divided into basic tensile properties and impact resistance properties. Basic mechanical properties, such as yield strength, tensile strength, elongation, and elongation after fracture, are the conventional mechanical properties of steel plates. For the steel of this invention, the impact resistance properties are divided into the following dimensions: strength-ductility product characterizes the material's ability to undergo uniform plastic strain; drop hammer tear (DWTT) characterizes the material's resistance to tearing after impact; and impact absorption energy is the material's ability to absorb external impact energy when deformed after impact.

[0046] This invention focuses on dynamic yield strength and dynamic elongation after fracture, crucial characteristics of steel used in collision-resistant mobile pressure vessels. Previous designs for mobile pressure vessels only considered static yield strength and static elongation after fracture. However, during a collision, the mechanical behavior of the steel changes drastically compared to the conventional load-bearing environment. When a mobile pressure vessel collides, the tank material experiences deformation and strain rates exceeding those under static yield strength testing conditions, causing rapid and drastic changes in its mechanical properties. By focusing on key dynamic mechanical properties—dynamic yield strength and dynamic elongation after fracture—during a collision, the collision safety evaluation indicators for the mobile pressure vessel tank material can be incorporated into the initial design of the tank and transport vehicle. Furthermore, it enhances the safety of the mobile pressure vessel during transport, ensuring its safety throughout its entire lifecycle—a crucial aspect previously overlooked or neglected in the design of such materials. The dynamic yield strength of 315–555.5 MPa and the dynamic elongation at fracture of 30–39% defined in this invention are obtained through tests conducted under extreme road conditions in simulated existing transportation environments. For values ​​exceeding these limits, the material's dynamic mechanical properties will exhibit rapid plastic instability, leading to fracture or breakage. To ensure the aforementioned dynamic yield strength and elongation at fracture, the speed of vehicles transporting such hazardous chemicals needs to be restricted, and appropriate protective barriers or structures must be installed around the tank material to buffer the collision energy and momentum during impacts. This ensures that the physical and chemical properties of the hazardous chemicals within the tank do not change significantly during a collision, thus preventing large deformation and alterations in the material's mechanical properties after the impact.

[0047] Compared with the prior art, the present invention has a static yield strength Rel of 245-350 MPa and a dynamic yield strength Re of 315-555.5 MPa, a tensile strength of 400-520 MPa, a yield-to-tensile ratio ≤0.85, and a static elongation after fracture A of 31-41% and a dynamic elongation after fracture A d The strength-ductility product is 13950-21320 MPa·% at 30-39%; the drop hammer tear (DWTT) energy is 19-21 kJ; when the impact velocity is 5-50 m / s and the impact displacement is 1.5 m, the energy absorbed by the steel plate after the impact is 2.5-3.1 kJ, and the grain size of ferrite does not exceed 0.035 μm. Detailed Implementation

[0048] The present invention will now be described in detail:

[0049] Table 1 is a list of chemical components of the various embodiments and comparative examples of the present invention;

[0050] Table 2 is a list of the main process parameters for each embodiment and comparative example of the present invention;

[0051] Table 3 is a list of performance test results for each embodiment and comparative example of the present invention;

[0052] Table 4 is a list of the microstructure of each embodiment and comparative example of the present invention;

[0053] Table 5 is a list of dynamic performance test results for each embodiment and comparative example of the present invention.

[0054] The various embodiments of the present invention are produced according to the following steps.

[0055] 1) After smelting and casting into billets, the billets are heated to 1150-1240℃ at a heating rate of 4-12 min / cm.

[0056] 2) Perform rough rolling, controlling the initial rolling temperature to be no lower than 1050℃;

[0057] 3) Perform finishing rolling, and control the final rolling temperature to be no higher than 925℃; control the cumulative reduction rate of the last three passes to be no less than 30%;

[0058] 4) Cool the temperature to 550–590°C at a cooling rate of 0.90–4.80°C / s.

[0059] 5) Perform normalizing, controlling the normalizing temperature at 840–910℃, and hold at this temperature for the following duration:

[0060] (10~25min)+t×1min / mm

[0061] In the formula: t—represents the thickness of the hot-rolled plate, in mm;

[0062] 6) Stress relief: The stress relief temperature is controlled at 550-590℃, and the temperature is maintained at this temperature for 30-120 minutes.

[0063] Table 1. List of chemical components (wt%) of various embodiments and comparative examples of the present invention.

[0064]

[0065]

[0066] Continued from Table 1

[0067]

[0068]

[0069] Table 2. List of main process parameters for each embodiment and comparative example of the present invention.

[0070]

[0071] Continued from Table 2

[0072]

[0073]

[0074] Table 3. List of mechanical property test results for each embodiment and comparative example of the present invention.

[0075]

[0076]

[0077] Table 4 lists the microstructure of each embodiment and comparative example of the present invention.

[0078]

[0079]

[0080] Table 5. List of dynamic performance test results for each embodiment and comparative example of the present invention.

[0081]

[0082]

[0083] The explanation is as follows:

[0084] 1. The performance testing methods in Table 3 are described below:

[0085] (1) Tensile property test: Tensile property test: Under the condition of room temperature 20℃, the strain rate is controlled at 0.0067s. -1 The yield strength, tensile strength and elongation values ​​were tested according to GB228.1 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0086] (2) Ferrite grain size test: The ferrite grain size was tested at room temperature according to GB / T 6394 "Method for determination of average grain size of metal".

[0087] 2. The performance testing methods in Table 4 are described below:

[0088] (1) Tensile property test: Under room temperature conditions, the strain rate was controlled at 0.0067 s. -1The yield strength, tensile strength and elongation values ​​were tested according to GB228.1 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0089] (2) Test of precipitate size and spacing in steel: The spacing of precipitates was tested using JY / T 0581 "General Rules for Analysis by Transmission Electron Microscopy" and YB / T 4676 "Analysis of Precipitates in Steel by Transmission Electron Microscopy".

[0090] (3) Testing of different metallographic structures in steel: The different metallographic compositions in steel were tested using DIN 50600 "Inspection of metallic materials - Metallographic micrographs - Image proportions and dimensions".

[0091] (4) Test of ferrite grain boundary orientation difference and geometrically required dislocation density in steel: The ferrite grain boundary orientation difference and geometrically required dislocation density are tested by means of or with reference to YB / T 4677 "Determination of texture in steel by electron backscatter diffraction (EBSD) method".

[0092] 3. The performance testing methods in Table 5 are described below:

[0093] (1) Dynamic yield strength and dynamic elongation test: Under room temperature conditions, the strain rate was controlled at 0.01-30s. -1 The dynamic yield strength and dynamic elongation were tested according to GB228.1 "Metallic materials, tensile testing—Part 1: Test method at room temperature". The strain rate refers to the change in strain per unit time.

[0094] (2) DWTT tear test: The DWTT tear performance was tested using SY / T6476 "Drop hammer tear test method for pipeline steel pipe".

[0095] (3) Collision energy absorption test: The collision energy absorption test shall be conducted in accordance with BS / EN15227-2020 "Requirements for collision resistance of railway facilities and railway vehicle bodies".

[0096] As can be seen from Tables 3 to 5, the pressure vessel steel plate described in this invention has excellent performance. It not only has good resistance to deformation and strain rate strengthening, but also good resistance to impact tearing and impact absorption, and has a very broad application prospect.

[0097] This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.

Claims

1. A collision-resistant pressure vessel steel for storing and transporting trifluoromethane, comprising the following components and weight percentages: C: 0.10–0.145% or C: 0.20%, Si: 0.15–0.23%, Mn: 0.70–1.15%, Al: 0.015–0.024%, P≤0.015%, S≤0.005%, V: 0.015–0.017%, Nb: 0.010–0.014%, with the remainder being Fe and unavoidable impurities; its steel properties are: thickness 6–35 mm, static yield strength Rel 245–350 MPa and dynamic yield strength Re 315–555.5 MPa, tensile strength 400–520 MPa, yield ratio ≤0.85, static elongation after fracture A 31–41% and dynamic elongation after fracture A d At 30-39%, the strength-ductility product is 13950-21320 MPa·%; the drop hammer tearing (DWTT) energy is 19-21 kJ; when the impact velocity is 5-50 m / s and the impact displacement is 1.5 m, the energy absorbed by the steel plate after the impact is 2.5-3.1 kJ, and the ferrite grain size does not exceed 0.035 µm. Production method: 1) After smelting and casting into billets, the billets are heated to 1150-1240℃ at a heating rate of 4-7 min / cm or at a heating rate of 12 min / cm. 2) Perform rough rolling, controlling the initial rolling temperature at 950–1040℃; 3) Perform finishing rolling, controlling the final rolling temperature not to exceed 925℃; control the cumulative reduction rate of the last three passes to be not less than 30%; 4) Cool the temperature to 550–590°C at a cooling rate of 0.90–4.80°C / s; 5) Perform normalizing, controlling the normalizing temperature at 840–910℃, and hold at this temperature for the following duration: (10~25min) + t×1min / mm In the formula: t—represents the thickness of the hot-rolled plate, in mm; 6) Stress relief: The stress relief temperature is controlled at 550-590℃, and the temperature is maintained at this temperature for 30-120 minutes.

2. A method for producing a collision-resistant pressure vessel steel for storing and transporting trifluoromethane as described in claim 1, comprising the following steps: 1) After smelting and casting into billets, the billets are heated to 1150-1240℃ at a heating rate of 4-7 min / cm or at a heating rate of 12 min / cm. 2) Perform rough rolling, controlling the initial rolling temperature at 950–1040℃; 3) Perform finishing rolling, controlling the final rolling temperature not to exceed 925℃; control the cumulative reduction rate of the last three passes to be not less than 30%; 4) Cool the temperature to 550–590°C at a cooling rate of 0.90–4.80°C / s; 5) Perform normalizing, controlling the normalizing temperature at 840–910℃, and hold at this temperature for the following duration: (10~25min) + t×1min / mm In the formula: t—represents the thickness of the hot-rolled plate, in mm; 6) Stress relief: The stress relief temperature is controlled at 550-590℃, and the temperature is maintained at this temperature for 30-120 minutes.

3. The method for producing impact-resistant pressure vessel steel for storing and transporting trifluoromethane as described in claim 2, characterized in that: Cool to 562–580℃ at a controlled cooling rate of 1.8–4.2℃ / s.

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