A collision-resistant steel plate for butane pressure vessels and its manufacturing method

Abstract

A collision-resistant steel plate for butane pressure vessels, comprising the following components (wt%): C: 0.10–0.20%, Si: 0.20–0.45%, Mn: 1.60–1.80%, Al: 0.025–0.045%, P≤0.015%, S≤0.005%, V: 0.065–0.085%, Nb: 0.027–0.045%. The process involves: smelting, casting into a billet, heating the billet, rough rolling, finish rolling, cooling, normalizing, and stress relief. The static yield strength Rel of this invention is 460–500 MPa, and the dynamic yield strength Re is 510–760 MPa; the tensile strength is 610–700 MPa; the yield ratio is ≤0.85; and the static elongation after fracture A is 29–41% and the dynamic elongation after fracture A... d The strength-ductility product is 18995–27798 MPa·% at 28–41%; the drop hammer tear (DWTT) energy is 15–19 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 is 3.57–3.89 kJ, and the grain size of ferrite does not exceed 0.008 μm.

Description

Technical Field

[0001] This invention relates to a pressure vessel steel and its manufacturing method, specifically to an impact-resistant butane pressure vessel steel plate and its manufacturing method. Background Technology

[0002] This invention relates to steel materials and manufacturing methods for mobile pressure vessels such as road vehicle cryogenic liquefied gas tank cars, railway liquefied gas tank cars, and marine tank container bodies. In particular, it relates to a steel plate with high strength-ductility product (tensile strength multiplied by elongation after fracture) and high impact resistance properties that effectively inhibits damage such as collisions to tank bodies transporting flammable and explosive hazardous chemicals, and its manufacturing method.

[0003] Butane is a colorless gas with a slightly unpleasant odor. It is used as a foaming agent in the chemical industry, as a high-calorific-value fuel in glass shell processing, machinery manufacturing, and textile printing and dyeing. It can also be used as a lighter fluid, instrument calibration gas, and fuel gas, making it an important chemical raw material. It is classified as flammable and explosive. However, currently, there are no specific technologies for addressing the characteristics of steel materials used in collision protection, the material's resistance to collision 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 the transportation of mobile pressure vessels. For steel materials used in mobile pressure vessels transporting hazardous chemicals, the design must not only consider the safety of personnel in the transport vehicles but also the safety of the media transported and stored in these pressure vessels during and after a collision.

[0004] From the perspective of existing technology, most technical literature on collision avoidance performance and technical performance indicators mainly focuses on the safety of automotive steel. The safety of automotive steel is primarily based on human safety, with detailed designs for the material's collision and energy absorption characteristics. However, the storage containers currently used in transportation are basically a matter of matching static strength and high toughness, or a design that improves strength and toughness by combining the strength and toughness of the base material with welding materials and methods. This presents significant safety risks. When a pressure vessel transporting butane, a hazardous chemical, is involved in a collision, it will deform severely, causing a rapid increase in internal pressure. When this pressure exceeds the dynamic yield strength of the steel used in the container or the deformation exceeds the limit, the tank will rupture, leading to an explosion upon contact with air. Simultaneously, the leaked butane gas can cause anesthesia and mild irritation to people near the transport vehicle, resulting in acute poisoning, and pollutes the surrounding environment. As searched:

[0005] 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%. The document states that ensuring the safety of butane-carrying pressure vessels in collisions is very difficult. While the material described in the invention can guarantee safety during routine ethane transport, its dynamic yield strength and dynamic elongation at fracture are crucial properties for butane tank materials. This invention only guarantees the static mechanical properties of the material under normal transport conditions, not the dynamic yield strength and dynamic elongation at fracture, which are unique safety attributes of butane tank materials. Therefore, it cannot guarantee that the physical properties of the butane 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. Consequently, it cannot guarantee the safety of moving pressure vessels in collisions.

[0006] Chinese patent publication CN115287431A discloses "A Low-Temperature Marine Steel Plate with Excellent Plasticity and Its Manufacturing Method." This method uses a medium-low carbon alloy (0.08-0.10% C, 0.8-1.50% Mn + microalloyed Ti + Nb) and employs controlled rolling and cooling processes to obtain the target performance steel plate. The resulting material has a ferrite + bainite two-phase microstructure, a yield strength ≥355MPa, a tensile strength >490MPa, an impact energy at -60℃ >200J, and an elongation after fracture >33%. However, achieving the safety of a butane-carrying pressure vessel in a collision, as described in this paper, presents significant challenges. Using this material can only guarantee safety during the routine transportation of ethane tanks. However, the dynamic yield strength and dynamic elongation after fracture are crucial characteristics for butane tank materials. This material can only guarantee the static mechanical properties of the material under normal transportation conditions, not the dynamic yield strength and dynamic elongation after fracture, which are unique safety attributes of butane tank materials. It cannot guarantee that the physical properties of the butane 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] Patent document WO2022171081A discloses "A Collision-Resistant and Crack-Resistant Steel for Ship Hull Structures and Its Manufacturing Method," which uses low-carbon steel (0.06-0.12% C, 1.3-1.7% Mn, 0.005-0.012% Ti), supplemented with Mg+Ca pure steel treatment technology, and 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%. This document presents a significant challenge in ensuring the safety of butane-carrying pressure vessels during collisions. Using this material can only guarantee safety during the routine transportation of ethane tanks. However, the dynamic yield strength and dynamic elongation after fracture are crucial characteristics for butane tank materials. This material can only guarantee the static mechanical properties of the material under normal transportation conditions, not the dynamic yield strength and dynamic elongation after fracture, which are unique safety attributes of butane tank materials. It cannot guarantee that the physical properties of the butane 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

[0008] This invention addresses the shortcomings of existing technologies in the steel used for mobile pressure vessels transporting hazardous liquid butane. It provides a steel with a static yield strength Rel of 460–500 MPa, a dynamic yield strength Re of 510–760 MPa, a tensile strength of 610–700 MPa, a yield-to-tensile ratio ≤0.85, and a static elongation at fracture A of 29–41% and a dynamic elongation at fracture A0.05. d The steel plate for impact-resistant butane pressure vessels has an energy density of 28-41%, a strength-ductility product of 18995-27798 MPa·%, a drop hammer tear (DWTT) energy of 15-19 kJ, and absorbs 3.57-3.89 kJ of ferrite after impact when the impact velocity is 5-50 m / s and the impact displacement is 1.5 m. The ferrite grain size does not exceed 0.008 μm.

[0009] Measures to achieve the above objectives:

[0010] A collision-resistant steel plate for butane pressure vessels, comprising the following components and weight percentages: C: 0.10–0.20%, Si: 0.20–0.45%, Mn: 1.60–1.80%, Al: 0.025–0.045%, P≤0.015%, S≤0.005%, V: 0.065–0.085%, Nb: 0.027–0.045%, with the remainder being Fe and unavoidable impurities; its steel plate properties are: thickness 6–35 mm, static yield strength Rel 460–500 MPa and dynamic yield strength Re 510–761 MPa, tensile strength 610–700 MPa, yield ratio ≤0.85, static elongation after fracture A 29–41% and dynamic elongation after fracture A d The strength-ductility product is 18995–27798 MPa·% at 28–41%; the drop hammer tear (DWTT) energy is 15–19 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 3.57–3.89 kJ, and the grain size of ferrite does not exceed 0.008 μm.

[0011] Preferably, the weight percentage content of V is 0.069 to 0.081%.

[0012] Preferably, the Nb content is 0.031 to 0.042% by weight.

[0013] A method for producing a collision-resistant steel plate for butane pressure vessels, comprising the following steps:

[0014] 1) After smelting and casting into billets, the billets are heated to 1190-1260℃ at a heating rate of 7-13 min / cm.

[0015] 2) Perform rough rolling, controlling the initial rolling temperature to be no lower than 1050℃;

[0016] 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 33%;

[0017] 4) Cool the material to 580-680°C at a cooling rate of 0.25°C / s to 5.0°C / s;

[0018] 5) Perform normalizing, controlling the normalizing temperature at 855–920℃, and hold at this temperature for the following duration:

[0019] (10~25min)+t×1min / mm

[0020] In the formula: t—represents the thickness of the hot-rolled plate, in mm;

[0021] 6) Stress relief: The stress relief temperature is controlled at 550-585℃, and the temperature is maintained at this temperature for 30-120 minutes.

[0022] Preferably, the temperature is controlled at a cooling rate of 0.84–4.8 °C / s to 580–670 °C.

[0023] Preferably, the normalizing temperature is controlled at 865–910°C.

[0024] The role and mechanism of each raw material and main process in this invention

[0025] C: In the impact-resistant pressure vessel steel plate described in this invention, C is one of the essential elements for improving the strength of steel, and C plays a role in solid solution strengthening. With the increase of C content in steel, the Fe3C content increases, and the yield strength and tensile strength of the steel improve. 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 should be noted that the C content in steel should not be too high; as the C content increases, the elongation and impact toughness of the steel decrease. Studies have found that when the C content in steel is no more than 0.20%, it can both improve the strength of the steel and make it suitable for industrial production operations, thus improving its applicability and feasibility in industrial production. Therefore, considering the influence of C on the performance of the pressure vessel steel plate in this technical solution, in order to improve the strength of the steel while being suitable for industrial production operations, the mass percentage of C in the impact-resistant pressure vessel steel plate described in this invention is controlled between 0.10% and 0.20%.

[0026] Si: In the impact-resistant pressure vessel steel plate described in this invention, Si is mainly a deoxidizing element during the steelmaking process and has a certain solid solution strengthening effect. It should be noted that when the Si content in the 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 the 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 of Si is controlled between 0.25% and 0.45%.

[0027] Mn: In the impact-resistant pressure vessel steel plate described in this invention, Mn has a significant effect on improving the strength of low-carbon and medium-carbon pearlitic steel. Adding 1% Mn to the 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 1.60% and 1.80%.

[0028] Al: In the impact-resistant pressure vessel steel plate described in this invention, Al is added as a deoxidation balancing element during the steelmaking process. Specifically, in the early refining stage, the Al content in the molten steel needs to be controlled at no more than 0.035%. In the later refining stage, 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 refining stage 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 the pressure vessel steel plate in this technical solution, the mass percentage of Al in the impact-resistant pressure vessel steel plate described in this invention is controlled between 0.025% and 0.045%.

[0029] V: In the impact-resistant pressure vessel steel plate described in this invention, V is a strong carbonitride forming element. Adding V to steel can greatly improve its strength. It can refine the grains by forming carbide structures and growing austenite grains, thereby improving the room temperature strength of the steel. V can not only promote the formation of pearlite, but also refine ferrite laths. In addition, when V is added to steel, the regular Fe3C cementite lamellae and pearlite clusters in the steel are blocked by V or carbonitride precipitates. The number of cementite breakpoints in the pearlite lamellae increases, the area of ​​the pearlite clusters becomes smaller, and the pearlite clusters are staggered in orientation. The length of the pearlite lamellae becomes smaller and thinner, and the degree of 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 in the steel is too high, the number and size of precipitates increase, which will lead 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 of V in the impact-resistant pressure vessel steel plate of the present invention is controlled between 0.065% and 0.085%.

[0030] 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 rolled microstructure and increase the large-angle grain boundary difference of ferrite grains in the steel, thereby improving the strength, toughness, impact energy absorption, and impact tear fracture resistance of the steel plate. Nb can effectively refine the microstructure by inhibiting austenite recrystallization during controlled rolling; moreover, Nb can effectively reduce the overheating sensitivity and temper brittleness of the steel. Therefore, in the impact-resistant pressure vessel steel plate described in this invention, the mass percentage of Nb is controlled between 0.027% and 0.045%.

[0031] 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, S, and O 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%.

[0032] The reason why the present invention controls the heating rate at 7-13 min / cm to heat the billet to 1190-1260℃ 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.

[0033] 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.

[0034] The reason why this invention controls the finishing rolling temperature to be no higher than 925℃ and the cumulative reduction rate of the last three passes to be no less than 33% 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.

[0035] The reason why this invention cools to 580-680℃ at a cooling rate of 0.25℃ / s to 5.0℃ / 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.

[0036] The present invention controls the normalizing temperature at 855–920°C and holds it at this temperature for the specified time according to the formula:

[0037] The process of (10~25min)+t×1min / mm is because 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 can be optimized and the strength of the steel plate can be controlled within a more precise range, thus ensuring the static mechanical properties and impact resistance of the steel plate material of this invention.

[0038] The reason why the stress relief temperature is controlled at 550-585℃ 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.

[0039] Regarding the microstructure of the steel plate of this invention:

[0040] The microstructure of the steel of this invention is ferrite + pearlite + bainite, wherein: the volume percentage of ferrite is 75-81%, and the area ratio of the orientation difference of ferrite grain boundaries of 15-60° is 75-81%; the volume percentage of pearlite is 17-21%, and the percentage of bainite is 0.4-4.5%.

[0041] The precipitate size in the steel ranges from 13 to 27 nm, and the spacing between the precipitates is from 330 to 350 nm. When the deformation of the steel plate is 10% to 15%, the geometrically required dislocation density in the steel is 3.75 × 10⁻⁶. 14 ~3.90×10 14 / m 2 .

[0042] The microstructure of steel plates is typically determined using an optical microscope with a nitric acid + 3% ethanol etching solution. However, when optical microscopy is insufficient, electron backscatter diffraction scanning electron microscopy (EBSD) can be used for identification. The volume fraction of the microstructure is equivalent to the area fraction within the measured field of view. The orientation difference of ferrite grain boundaries is observed using EBSD. 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 precipitate grain size and spacing.

[0043] For geometrically required dislocations, this invention differs from conventionally statistically distributed dislocations. The density of geometrically required dislocations is related to the average Burgers vector of deformation-induced dislocations. Geometrically required dislocations adapt to deformation incompatibilities, unlike statistically distributed dislocations, and these dislocations ensure that the degree of material deformation is maximized. Geometrically required dislocation density (ρ) GND The ρ is calculated using the intergranular orientation difference (θ), the unit length of the dislocation density analysis site (u), and the average Burgers vector (b) of the deformed material, all measured by EBSD. GND =2θ / (ub).

[0044] In the impact-resistant pressure vessel steel plate described in this invention, its 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 the steel plate. For the steel of this invention, the impact resistance performance is 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. For the steel plate of this invention, specific properties should meet the following data ranges: steel plate thickness range 6–35 mm, yield strength R… eL 460MPa, tensile strength R m Tensile strength: 610–700 MPa; yield strength ratio: ≤0.85; elongation after fracture (A): 25–43%. Strength-ductility product range: 18995–27798 MPa·%, where strength-ductility product = tensile strength (R... m () × Elongation after fracture (A); Drop hammer tear (DWTT) energy is 15-19 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 3.57-3.89 kJ.

[0045] 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 510–760 MPa and dynamic elongation at fracture of 29–41% 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 butane containers needs to be constrained, 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 butane within the tank remain largely unchanged during a collision, thus preventing significant deformation and alterations in the material's mechanical properties after impact.

[0046] Compared with the prior art, the present invention has a static yield strength Rel of 460-500 MPa and a dynamic yield strength Re of 510-760 MPa, a tensile strength of 610-700 MPa, a yield-to-tensile ratio ≤0.85, and a static elongation after fracture A of 29-41% and a dynamic elongation after fracture A d The strength-ductility product is 18995–27798 MPa·% at 28–41%; the drop hammer tear (DWTT) energy is 15–19 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 3.57–3.89 kJ, and the grain size of ferrite does not exceed 0.008 μm. Detailed Implementation

[0047] The present invention will now be described in detail:

[0048] Table 1 is a list of chemical components of the various embodiments and comparative examples of the present invention;

[0049] Table 2 is a list of the main process parameters for each embodiment and comparative example of the present invention;

[0050] Table 3 is a list of performance test results for each embodiment and comparative example of the present invention.

[0051] Table 4 is a list of the microstructure of each embodiment and comparative example of the present invention;

[0052] Table 5 is a list of dynamic performance test results for each embodiment and comparative example of the present invention.

[0053] The various embodiments of the present invention are produced according to the following steps.

[0054] 1) After smelting and casting into billets, the billets are heated to 1190-1260℃ at a heating rate of 7-13 min / cm.

[0055] 2) Perform rough rolling, controlling the initial rolling temperature to be no lower than 1050℃;

[0056] 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 33%;

[0057] 4) Cool the material to 580-680°C at a cooling rate of 0.25°C / s to 5.0°C / s;

[0058] 5) Perform normalizing, controlling the normalizing temperature at 855–920℃, and hold at this temperature for the following duration:

[0059] (10~25min)+t×1min / mm

[0060] In the formula: t—represents the thickness of the hot-rolled plate, in mm;

[0061] 6) Stress relief: The stress relief temperature is controlled at 550-585℃, and the temperature is maintained at this temperature for 30-120 minutes.

[0062] Table 1. List of chemical components (wt%) of various embodiments and comparative examples of the present invention.

[0063]

[0064]

[0065] Continued from Table 1

[0066]

[0067] Table 2. List of main process parameters for each embodiment and comparative example of the present invention.

[0068]

[0069] Continued from Table 2

[0070]

[0071]

[0072] Table 3. List of mechanical property test results for each embodiment and comparative example of the present invention.

[0073]

[0074]

[0075] Table 4 lists the microstructure of each embodiment and comparative example of the present invention.

[0076]

[0077]

[0078] Note:

[0079] Table 3 shows that the impact-resistant pressure vessel steel plates of Examples 1-9 have moderate mechanical properties and strong resistance to deformation, as indicated by the mechanical properties of the finished products.

[0080] To illustrate the deformation resistance of the impact-resistant pressure vessel steel plates of Examples 1-9 of the present invention, it is necessary to measure the microstructure and ferrite grain size of the impact-resistant pressure vessel steel plates of Examples 1-9 and the comparative steel plates of Comparative Examples 1-10, respectively. The test results are listed in Table 4.

[0081] The relevant performance testing conditions are as follows:

[0082] 1) Tensile property test: conducted at room temperature (20℃) and strain rate (0.0067s). -1 Under the specified conditions, the yield strength, tensile strength and elongation were tested according to GB228.1 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0083] 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".

[0084] 3) Testing of different metallographic structures in steel: The different metallographic compositions in steel are tested using DIN 50600 "Inspection of metallic materials - Metallographic micrographs - Image proportions and dimensions".

[0085] 4) Ferrite grain boundary orientation difference and geometrically required dislocation density test in steel: The ferrite grain boundary orientation difference and geometrically required dislocation density are tested using or with reference to YB / T 4677 "Determination of texture in steel by electron backscatter diffraction (EBSD) method".

[0086] As can be seen from Tables 3 and 4, the pressure vessel steel plates of Examples 1-9 exhibit significantly better overall impact resistance compared to the comparative steel plates of Examples 1-9. The impact-resistant pressure vessel steel plates of Examples 1-9 of this invention not only possess excellent comprehensive mechanical properties but also exhibit good resistance to deformation and strain strengthening.

[0087] In this invention, the pressure vessel steel plates of Examples 1-9 all have a yield strength between 460-498 MPa, a tensile strength between 610-700 MPa, an elongation between 25-43%, a strength-ductility product between 18995-27798 MPa·%, and a yield strength ratio in the range of 0.70-0.75.

[0088] Furthermore, it should be noted that, through observation of the microstructure of the pressure vessel steel plates of Examples 1-9, it can be seen that the matrix of the impact-resistant pressure vessel steel plates of Examples 1-9 is ferrite + pearlite + a small amount of bainite, and the volume percentage of ferrite is 75-81%, and the ferrite grain size is between 0.004 and 0.008 mm.

[0089] In summary, it can be seen that 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.

[0090] Table 5. List of dynamic performance test results for each embodiment and comparative example of the present invention.

[0091]

[0092]

[0093] To illustrate the deformation resistance of the impact-resistant pressure vessel steel plates of Examples 1-9 of the present invention, it is necessary to measure the dynamic yield strength, dynamic elongation, tearing performance, and impact absorption energy of the impact-resistant pressure vessel steel plates of Examples 1-9 and the comparative steel plates of Comparative Examples 1-9, respectively. The results are shown in Table 5.

[0094] The relevant performance testing conditions are as follows:

[0095] 1) The dynamic yield strength and dynamic elongation tests in Table 5 were all conducted at room temperature (20℃) and strain rates of 0.01-30 s. -1 Under the conditions, 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.

[0096] 2) The DWTT tear test in Table 5 is conducted using SY / T6476 "Drop Hammer Tear Test Method for Pipeline Steel Pipes".

[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 method for producing a collision-resistant steel plate for a butane pressure vessel, comprising the following steps: 1) After smelting and casting into billets, the billets are heated at a heating rate of [missing information]. The billet is heated to 1243-1260℃ at a heating rate of 7℃ / s or at a heating rate of 12-13℃ / s. 2) Perform rough rolling, controlling the initial rolling temperature at 1050~1092℃; 3) Perform finish rolling, controlling the final rolling temperature to 807~836℃; control the cumulative reduction rate of the last three passes to be no less than 33%; 4) Cool the material to 580~636℃ at a cooling rate of 0.25~5.0℃ / s; 5) Perform normalizing, controlling the normalizing temperature at 855–920℃, 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 550-585℃, and the temperature is maintained at this temperature for 30-120 minutes; The impact-resistant steel plate for butane pressure vessels comprises the following components and weight percentages: C: 0.10~0.20%, Si: 0.20~0.45%, Mn: 1.62~1.80%, Al: 0.025~0.045%, P≤0.015%, S≤0.005%, V: 0.065~0.085%, Nb: 0.027~0.045%, with the remainder being Fe and unavoidable impurities. Its steel plate properties: thickness 6~35mm, static yield strength Rel 460~500MPa and dynamic yield strength Re 510~760MPa, tensile strength 610~700MPa, yield-to-tensile ratio ≤0.85, static elongation after fracture A 29~41% and dynamic elongation after fracture A d The strength-ductility product is 18995-27798 MPa·% at 28-41%; the drop hammer tear (DWTT) energy is 15-19 kJ; when the collision velocity is 5-50 m / s and the collision displacement is 1.5 m, the energy absorbed by the steel plate after the collision is 3.57-3.89 kJ, and the grain size of ferrite does not exceed 0.008 µm.

2. The method for producing a collision-resistant steel plate for a butane pressure vessel as described in claim 1, characterized in that: The weight percentage content of V is 0.069~0.081%.

3. The method for producing a collision-resistant steel plate for a butane pressure vessel as described in claim 1, characterized in that: Controlled cooling However, the speed is 0.84~4.8℃ / s.

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