Processing method for LNG storage tank heads

Abstract

This application provides a method for processing LNG storage tank heads, comprising: determining the number of stamping passes N for the LNG storage tank head based on the target head diameter, wherein N is positively correlated with the target head diameter, N≥2, and the stamping deformation amount of each stamping pass is X, 5%≤X≤10%; hot stamping the high-manganese steel sheet according to the number of stamping passes to obtain a blank; and warm spinning the blank to obtain the LNG storage tank head. This method can avoid cracking and springback problems in the LNG storage tank head and facilitates the control of the head's dimensional accuracy.

Description

Technical Field

[0001] This application relates to the field of end cap processing, and more particularly to a method for processing end caps for LNG storage tanks. Background Technology

[0002] Clean energy is essential for the sustainable development of modern society. In recent years, the production and trade of liquefied natural gas (LNG) have become increasingly active globally, emerging as a new hotspot in the world's oil and gas industry. This necessitates the construction of numerous LNG storage facilities for the storage and transportation of LNG.

[0003] Traditional LNG storage tank end caps are constructed using materials such as Invar alloy, 9Ni steel, aluminum alloy, and austenitic stainless steel, but these materials are relatively expensive. In recent years, high-manganese steel has gained significant attention due to its low price and excellent ductility and toughness. High-manganese steel is inexpensive, possesses good low-temperature resistance and wear resistance, making it ideal for storing liquefied natural gas.

[0004] However, high-manganese steel is prone to cracking, springback, and difficulty in controlling dimensional accuracy during the processing and forming of LNG storage tank heads, which affects the actual performance of LNG storage tank heads. Summary of the Invention

[0005] This application provides a processing method for LNG storage tank heads to solve the problems of cracking, springback, and difficulty in controlling dimensional accuracy that easily occur when high manganese steel is used in the processing and forming of LNG storage tank heads in related technologies, thereby affecting the actual performance of LNG storage tank heads.

[0006] This application provides a method for processing end caps for LNG storage tanks, comprising the following steps:

[0007] Based on the target diameter of the LNG storage tank end cap, determine the number of stamping passes N for the LNG storage tank end cap, where N is positively correlated with the target end cap diameter, N≥2, and the stamping deformation amount of each stamping pass is X, where 5%≤X≤10%.

[0008] The high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank;

[0009] The blank is subjected to warm spinning treatment to obtain the end cap for LNG storage tank.

[0010] According to an embodiment of this application, determining the number of stamping passes for the LNG storage tank end cap based on the target end cap diameter includes:

[0011] When the target end cap diameter for LNG storage tanks is >3000mm, 4≤N≤6;

[0012] When the target end cap diameter for LNG storage tanks is ≤3000mm, 2≤N≤4.

[0013] According to an embodiment of this application, a high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank, comprising:

[0014] In the first stamping pass, the high manganese steel sheet is hot stamped using a heating-stamping-heating method.

[0015] In any stamping pass other than the first stamping pass and the Nth stamping pass, the high manganese steel sheet is hot stamped by stamping first and then heating.

[0016] In the Nth stamping pass, the high manganese steel sheet obtained in the (N-1)th stamping pass is stamped and straightened to obtain a blank.

[0017] According to embodiments of this application, a hot stamping process is employed to heat-stamp-heat-surge high-manganese steel sheets, including:

[0018] The high-manganese steel sheet is fed into a heating furnace;

[0019] The furnace is preheated using a first heating rate, and after the furnace reaches the preheating target temperature, it is heated using a second heating rate, wherein the second heating rate is greater than the first heating rate.

[0020] After the temperature in the heating furnace reaches the first preset temperature range, the heating furnace is subjected to the first heat preservation treatment.

[0021] The high-manganese steel sheet is sent out of the heating furnace for stamping.

[0022] The high-manganese steel sheet after stamping is fed into a heating furnace, and the furnace is subjected to a second heat preservation treatment, wherein the time of the second heat preservation treatment is shorter than the time of the first heat preservation treatment.

[0023] According to embodiments of this application, a hot stamping process is performed on high-manganese steel sheets using a method of stamping followed by heating, including:

[0024] The high-manganese steel sheet is sent out of the heating furnace for stamping.

[0025] The high-manganese steel sheet after stamping is fed into the heating furnace, and the furnace temperature is controlled within the second preset temperature range.

[0026] The heating furnace is then subjected to a second insulation treatment.

[0027] According to an embodiment of this application, the first heating rate is 50°C / h-100°C / h.

[0028] According to an embodiment of this application, the preheating target temperature is 200°C.

[0029] According to an embodiment of this application, the second heating rate is 180°C / h-220°C / h.

[0030] According to an embodiment of this application, the first preset temperature range is 880℃-950℃.

[0031] According to an embodiment of this application, the first heat preservation treatment time is 25 min to 35 min.

[0032] According to an embodiment of this application, the second preset temperature range is 900℃-940℃.

[0033] According to an embodiment of this application, the second heat preservation treatment time is 10 min to 15 min.

[0034] According to an embodiment of this application, a blank is subjected to warm spinning treatment to obtain an end cap for an LNG storage tank, comprising:

[0035] The blank is placed into the heating furnace, and the furnace temperature is controlled within the third preset temperature range.

[0036] The heating furnace is subjected to a third insulation treatment;

[0037] The blank is sent out of the heating furnace for warm spinning treatment to obtain the end cap for LNG storage tank. The processing temperature of the warm spinning treatment is controlled within the fourth preset temperature range.

[0038] According to an embodiment of this application, the third preset temperature range is 300℃-400℃.

[0039] According to an embodiment of this application, the third heat preservation treatment time is 20-30 minutes.

[0040] According to an embodiment of this application, the fourth preset temperature range is 250℃-350℃.

[0041] According to an embodiment of this application, before hot stamping the high-manganese steel sheet according to the number of stamping passes, the method further includes:

[0042] Antioxidant treatment is applied to high manganese steel sheets.

[0043] According to the embodiments of this application, the Mn content of the high manganese steel sheet is 22.5%-25.5%.

[0044] According to the embodiments of this application, the tensile strength of the high manganese steel sheet is 800MPa-950MPa.

[0045] According to the embodiments of this application, the Charpy impact energy (KV) of high manganese steel sheet at -196°C is 60J-300J.

[0046] This application determines the number of stamping passes for LNG storage tank heads based on the target head diameter, wherein the number of stamping passes is positively correlated with the target head diameter, the number of stamping passes is greater than or equal to 2, and the stamping deformation amount of each stamping pass is ≤10%; subsequently, high-manganese steel sheets are hot-stamped according to the number of stamping passes to obtain a blank; finally, the blank is warm-spun to obtain the LNG storage tank head. This method has the following technical advantages:

[0047] During the processing of LNG storage tank heads, the number of stamping passes is determined based on the target head diameter. The deformation amount X of each stamping pass is controlled within 5% ≤ X ≤ 10%. This allows for adaptive adjustment of the number of stamping passes according to the head diameter, ensuring the stamping effect while avoiding excessive deformation during a single stamping. This helps prevent cracking and springback issues in LNG storage tank heads.

[0048] Hot stamping of high-manganese steel sheets based on the number of stamping passes can reduce the material's resistance to stamping deformation by heating. Furthermore, hot stamping of high-manganese steel sheets based on the number of stamping passes can improve the uniformity of deformation during the stamping process, which helps to further avoid cracking and springback problems in LNG storage tank heads and facilitates the control of the head's dimensional accuracy.

[0049] In addition, warm spinning of the blank can prevent the end cap from cracking due to temperature drop during spinning, effectively correct geometric errors generated during hot stamping, and eliminate residual stress, thereby improving the forming accuracy and surface quality of the end cap, further preventing cracking and springback problems in LNG storage tank end caps, and improving the accuracy of end cap dimensional control. Attached Figure Description

[0050] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0051] Figure 1 This is a flowchart of the processing method for the end caps of the LNG storage tank provided in this application.

[0052] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0053] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0056] Clean energy is essential for the sustainable development of modern society. In recent years, the production and trade of liquefied natural gas (LNG) have become increasingly active globally, emerging as a new hotspot in the world's oil and gas industry. This necessitates the construction of numerous LNG storage facilities for the storage and transportation of LNG.

[0057] Traditional LNG storage tank end caps are constructed using materials such as Invar alloy, 9Ni steel, aluminum alloy, and austenitic stainless steel, but these materials are relatively expensive. In recent years, high-manganese steel has gained significant attention due to its low price and excellent ductility and toughness. High-manganese steel is inexpensive, possesses good low-temperature resistance and wear resistance, making it ideal for storing liquefied natural gas.

[0058] However, high-manganese steel is prone to cracking, springback, and difficulty in controlling dimensional accuracy during the processing and forming of LNG storage tank heads, which affects the actual performance of LNG storage tank heads.

[0059] In view of the above problems, this application provides a processing method for LNG storage tank end caps, which can avoid cracking and springback problems in LNG storage tank end caps and facilitate the control of the dimensional accuracy of the end caps.

[0060] This application provides a method for processing end caps for LNG storage tanks. Please refer to [link to relevant documentation]. Figure 1 It includes the following steps:

[0061] S100: Based on the target diameter of the LNG storage tank end cap, determine the number of stamping passes N for the LNG storage tank end cap, where N is positively correlated with the target end cap diameter, N≥2, and the stamping deformation amount of each stamping pass is X, 5%≤X≤10%;

[0062] S200: High manganese steel sheets are hot-stamped according to the number of stamping passes to obtain a blank;

[0063] S300: The blank is subjected to warm spinning treatment to obtain the end cap for LNG storage tank.

[0064] High-manganese steel is a high-strength steel with a tensile strength of ≥550MPa. Due to its poor plasticity, high-manganese steel exhibits significant work hardening. When processing high-manganese steel sheets using traditional cold stamping processes, problems such as cracking, springback, and difficulty in controlling dimensional accuracy easily occur. In addition, high-strength steel stamping processes generally require presses with larger tonnages, which can easily damage existing equipment. At the same time, the need for large-tonnage presses also increases the overall production investment cost.

[0065] Therefore, in the processing of LNG storage tank heads, by determining the number of stamping passes based on the target head diameter and controlling the stamping deformation X of each pass within 5% ≤ X ≤ 10%, the number of stamping passes can be adjusted adaptively according to the head diameter. This avoids excessive deformation during a single stamping while ensuring the stamping effect, thus helping to prevent cracking and springback problems in LNG storage tank heads.

[0066] Hot stamping of high-manganese steel sheets based on the number of stamping passes can reduce the material's resistance to stamping deformation by heating. Furthermore, hot stamping of high-manganese steel sheets based on the number of stamping passes can improve the uniformity of deformation during the stamping process, which helps to further avoid cracking and springback problems in LNG storage tank heads and facilitates the control of the head's dimensional accuracy.

[0067] In addition, warm spinning of the blank can prevent the end cap from cracking due to temperature drop during spinning, effectively correct geometric errors generated during hot stamping, and eliminate residual stress, thereby improving the forming accuracy and surface quality of the end cap, further preventing cracking and springback problems in LNG storage tank end caps, and improving the accuracy of end cap dimensional control.

[0068] The specific steps for S100 are as follows:

[0069] Based on the target diameter of the LNG storage tank end cap, determine the number of stamping passes N for the LNG storage tank end cap, where N is positively correlated with the target end cap diameter, N≥2, and the stamping deformation amount of each stamping pass is X, where 5%≤X≤10%.

[0070] By determining the number of stamping passes for the LNG storage tank end caps based on the target end cap diameter and controlling the stamping deformation X of each stamping pass to 5%≤X≤10%, the number of stamping passes can be adjusted adaptively according to the end cap diameter. Combined with a setting where the number of stamping passes N is greater than or equal to 2, excessive deformation during a single stamping can be avoided while ensuring the stamping effect, which helps to prevent cracking and springback problems in the LNG storage tank end caps.

[0071] In some embodiments, the stamping height of each stamping pass can be 120mm-150mm, thereby further avoiding excessive deformation during a single stamping by combining the stamping deformation amount setting, which helps to avoid cracking and springback problems in the end caps used for LNG storage tanks.

[0072] In some embodiments, determining the number of stamping passes for the LNG storage tank end cap based on the target end cap diameter includes:

[0073] When the target end cap diameter for LNG storage tanks is >3000mm, 4≤N≤6;

[0074] When the target end cap diameter for LNG storage tanks is ≤3000mm, 2≤N≤4.

[0075] In this embodiment, by setting the target end cap diameter for LNG storage tanks to be >3000mm, the number of stamping passes N for LNG storage tank end caps is controlled to be 4≤N≤6. This allows large-diameter end caps with a diameter >3000mm to effectively reduce the amount of stamping deformation during a single stamping through multiple stamping passes, further preventing cracking and springback problems in LNG storage tank end caps. Furthermore, multiple stamping passes can avoid the need for large-tonnage presses, which helps to reduce processing costs.

[0076] Based on this, by setting the target end cap diameter for LNG storage tanks to ≤3000mm, and controlling the number of stamping passes N for LNG storage tank end caps to 2≤N≤4, production efficiency can be improved and energy consumption reduced while ensuring stamping effect. This avoids using excessive stamping passes for small-diameter end caps, which has insignificant benefits, and further optimizes process costs.

[0077] The S200 process is as follows: The high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank;

[0078] Hot stamping of high-manganese steel sheets based on the number of stamping passes can reduce the material's resistance to stamping deformation by heating. Furthermore, hot stamping of high-manganese steel sheets based on the number of stamping passes can improve the uniformity of deformation during the stamping process, which helps to further avoid cracking and springback problems in LNG storage tank heads and facilitates the control of the head's dimensional accuracy.

[0079] In some embodiments, the high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank, including:

[0080] In the first stamping pass, the high manganese steel sheet is hot stamped using a heating-stamping-heating method.

[0081] In any stamping pass other than the first stamping pass and the Nth stamping pass, the high manganese steel sheet is hot stamped by stamping first and then heating.

[0082] In the Nth stamping pass, the high manganese steel sheet obtained in the (N-1)th stamping pass is stamped and straightened to obtain a blank.

[0083] In practical applications, the high manganese steel sheet can be hot-stamped in the first stamping pass by heating-stamping-heating. This preheating process allows the high manganese steel sheet to be fully austenitized, reducing the resistance to stamping deformation and improving the forming effect of the sheet.

[0084] Furthermore, since the temperature of the high-manganese steel sheet decreases after each actual stamping operation, thereby increasing the resistance to stamping deformation, the high-manganese steel sheet can be heated again after the first stamping pass. This can be done in any stamping pass other than the first and Nth stamping passes, using a method of stamping first and then heating to perform hot stamping treatment on the high-manganese steel sheet. This ensures that the high-manganese steel sheet is fully austenitized by heating before each actual stamping operation, reducing the resistance to stamping deformation and further improving the forming effect of the sheet. It also improves the forming effect of the blank after the final hot stamping pass, avoiding cracks or springback problems in the blank.

[0085] Finally, the high-manganese steel sheet obtained from the (N-1)th stamping pass can be directly stamped and straightened in the Nth stamping pass to obtain a blank for subsequent processing steps.

[0086] In some embodiments, the high-manganese steel sheet is hot-stamped using a heating-stamping-heating method, including:

[0087] The high-manganese steel sheet is fed into a heating furnace;

[0088] The furnace is preheated using a first heating rate, and after the furnace reaches the preheating target temperature, it is heated using a second heating rate, wherein the second heating rate is greater than the first heating rate.

[0089] After the temperature in the heating furnace reaches the first preset temperature range, the heating furnace is subjected to the first heat preservation treatment.

[0090] The high-manganese steel sheet is sent out of the heating furnace for stamping.

[0091] The high-manganese steel sheet after stamping is fed into a heating furnace, and the furnace is subjected to a second heat preservation treatment, wherein the time of the second heat preservation treatment is shorter than the time of the first heat preservation treatment.

[0092] In this embodiment, when hot stamping high-manganese steel sheets are processed using a heating-stamping-heating method, the high-manganese steel sheets can be preheated in the heating furnace at a first heating rate before being fed into the furnace. After the furnace reaches the target preheating temperature, a second heating rate is used to heat the furnace, wherein the second heating rate is greater than the first heating rate. Using a slower first heating rate for preheating allows the sheet to be heated gradually from the surface to the core at a slower rate, resulting in more uniform heating of the entire sheet and avoiding deformation caused by rapid local heating, which would affect the stamping process.

[0093] Based on this, after reaching the preheating target temperature, a faster second heating rate is used to heat the furnace, which can shorten the heating time and reduce processing costs without affecting the heating effect.

[0094] Furthermore, after the temperature in the heating furnace reaches the first preset temperature range, performing a first heat preservation treatment on the heating furnace can further improve the heating uniformity of the sheet and enhance the overall heating effect of the sheet; while after the high manganese steel sheet is sent out of the heating furnace, it is stamped so that the sheet has been fully austenitized during the stamping process, reducing the resistance to stamping deformation, thereby further improving the forming effect of the sheet.

[0095] After the initial stamping of the high-manganese steel sheet, to ensure that the sheet is fully austenitized by heating before each subsequent stamping operation and to reduce its resistance to stamping deformation, the stamped high-manganese steel sheet can be sent back into the heating furnace for a second heat treatment. To minimize the risk of oxidation on the sheet surface affecting the quality of the finished product, the second heat treatment time can be controlled to be shorter than the first heat treatment time, avoiding excessive heating.

[0096] In some embodiments, the high-manganese steel sheet is hot-stamped using a method of first stamping and then heating, including:

[0097] The high-manganese steel sheet is sent out of the heating furnace for stamping.

[0098] The high-manganese steel sheet after stamping is fed into the heating furnace, and the furnace temperature is controlled within the second preset temperature range.

[0099] The heating furnace is then subjected to a second insulation treatment.

[0100] In this embodiment, in any stamping pass other than the first stamping pass and the Nth stamping pass, the heated high-manganese steel sheet obtained from the previous stamping pass can be stamped first. Then, the stamped high-manganese steel sheet is sent into a heating furnace, and the furnace temperature is controlled within a second preset temperature range. After that, the heating furnace is subjected to a second heat preservation treatment. This ensures that the high-manganese steel sheet is fully austenitized by heating before each actual stamping operation, reducing the resistance to stamping deformation and further improving the forming effect of the sheet. The second heat preservation treatment of the heating furnace can further improve the heating uniformity of the sheet and improve the overall heating effect of the sheet.

[0101] In some embodiments, the first heating rate is 50°C / h-100°C / h.

[0102] In some embodiments, the preheating target temperature is 200°C.

[0103] The target preheating temperature is 200℃, which can fully preheat the high manganese steel sheet, thereby effectively reducing the resistance to stamping deformation.

[0104] In some embodiments, the second heating rate is 180℃ / h-220℃ / h.

[0105] In some embodiments, the first preset temperature range is 880℃-950℃.

[0106] The first preset temperature range is 880℃-950℃, which can achieve full austenitization of the sheet, reduce the resistance to stamping deformation, and further improve the forming effect of the sheet.

[0107] In some embodiments, the first heat preservation treatment time is 25 min to 35 min.

[0108] The first heat preservation treatment time is 25-35 minutes, which can ensure that the material is fully heated and avoid oxidation on the surface of the material due to excessive heat preservation time.

[0109] In some embodiments, the second preset temperature range is 900°C-940°C.

[0110] The second preset temperature range of 900℃-940℃ can effectively heat the sheet after stamping, keep the sheet fully austenitized, reduce the resistance to stamping deformation, and improve the forming effect of the sheet.

[0111] In some embodiments, the second heat preservation treatment lasts for 10-15 minutes.

[0112] The second heat preservation treatment takes 10-15 minutes, which helps to ensure that the sheet is fully heated after stamping, while avoiding oxidation on the sheet surface due to excessive heat preservation time.

[0113] The S300 steps are as follows: The blank is subjected to warm spinning treatment to obtain the end cap for LNG storage tanks;

[0114] Warm spinning of the blank can also prevent the end cap from cracking due to temperature drop during spinning. It helps to effectively correct geometric errors generated during hot stamping and eliminate residual stress, thereby improving the forming accuracy and surface quality of the end cap. This further avoids cracking and springback problems in the end caps used in LNG storage tanks and improves the accuracy of dimensional control of the end caps.

[0115] In some embodiments, the blank is subjected to warm spinning to obtain a head for an LNG storage tank, comprising:

[0116] The blank is placed into the heating furnace, and the furnace temperature is controlled within the third preset temperature range.

[0117] The heating furnace is subjected to a third insulation treatment;

[0118] The blank is sent out of the heating furnace for warm spinning treatment to obtain the end cap for LNG storage tank. The processing temperature of the warm spinning treatment is controlled within the fourth preset temperature range.

[0119] In this embodiment, before the blank is subjected to warm spinning treatment, the blank is first placed in a heating furnace, and the furnace temperature is controlled within a third preset temperature range. Then, the heating furnace is subjected to a third heat preservation treatment, which can heat the blank first, thereby avoiding a large temperature drop during the warm spinning process and thus preventing cracks, thereby improving the quality of the finished head.

[0120] Based on this, controlling the processing temperature of the warm spinning process within the fourth preset temperature range helps maintain the temperature stability of the blank during the warm spinning process, further avoids a large temperature drop during the warm spinning process, and improves the quality of the finished head.

[0121] In some embodiments, the third preset temperature range is 300℃-400℃.

[0122] In some embodiments, the third heat preservation treatment lasts for 20-30 minutes.

[0123] In some embodiments, the fourth preset temperature range is 250°C-350°C.

[0124] In some embodiments, when the third preset temperature range is 300℃-400℃ and the fourth preset temperature range is 250℃-350℃, the blank can be heated to near the processing temperature of warm spinning after heating, thereby further avoiding the temperature drop phenomenon during the warm spinning process and effectively improving the quality of the finished end cap.

[0125] In some embodiments, before hot stamping the high-manganese steel sheet according to the number of stamping passes, the method further includes:

[0126] Antioxidant treatment is applied to high manganese steel sheets.

[0127] In practical applications, high-manganese steel sheets can be subjected to anti-oxidation treatment before heating, such as coating the surface of the high-manganese steel sheets with an anti-oxidation coating to reduce the generation of iron oxide scale during the heating process, thereby improving the quality of the finished end caps.

[0128] In some embodiments, the high-manganese steel sheets and / or blanks may be subjected to anti-oxidation treatment before any step in the process flow that requires heating in the furnace, thereby further reducing the generation of iron oxide scale during the heating process and minimizing the impact of heating oxidation on the quality of the finished head.

[0129] In some embodiments, the blank may be trimmed and shot blasted before being warm-spinned, so that the finished head meets the specified process standards and actual design shape.

[0130] In some embodiments, after the finished head is obtained by hot spinning, the surface of the finished head can be further polished and the ends of the finished head can be trimmed so that the finished head meets the specified process standards and actual design shape.

[0131] In some embodiments, the Mn content of the high-manganese steel sheet is 22.5%-25.5%.

[0132] In some embodiments, the tensile strength of the high-manganese steel sheet is 800MPa-950MPa.

[0133] In some embodiments, the Charpy impact energy (KV) of the high-manganese steel sheet at -196°C is 60J-300J.

[0134] High-manganese steel materials that meet the above conditions have ultra-low temperature application characteristics. Compared with stainless steel and high-Ni alloys, they have excellent low-temperature volume stability, toughness, excellent weldability and high fatigue performance. Moreover, compared with stainless steel products, no deformation treatment is required to improve strength. Thus, their low-temperature resistance and wear resistance can be effectively utilized to achieve stable storage of liquefied natural gas.

[0135] High-manganese steel is prone to cracking, springback, and difficulty in controlling dimensional accuracy during the processing and forming of LNG storage tank heads, which affects the actual performance of LNG storage tank heads.

[0136] In the processing of LNG storage tank heads, this application determines the number of stamping passes for the LNG storage tank head based on the target head diameter, ensuring that the stamping deformation of each pass is ≤10%. This allows for adaptive adjustment of the number of stamping passes according to the head diameter, avoiding excessive deformation during a single stamping while ensuring the stamping effect. This helps prevent cracking and springback problems in LNG storage tank heads.

[0137] Hot stamping of high-manganese steel sheets based on the number of stamping passes can reduce the material's resistance to stamping deformation by heating. Furthermore, hot stamping of high-manganese steel sheets based on the number of stamping passes can improve the uniformity of deformation during the stamping process, which helps to further avoid cracking and springback problems in LNG storage tank heads and facilitates the control of the head's dimensional accuracy.

[0138] In addition, warm spinning of the blank can prevent the end cap from cracking due to temperature drop during spinning, effectively correct geometric errors generated during hot stamping, and eliminate residual stress, thereby improving the forming accuracy and surface quality of the end cap, further preventing cracking and springback problems in LNG storage tank end caps, and improving the accuracy of end cap dimensional control.

[0139] Example

[0140] The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0141] Example 1:

[0142] The high-manganese steel sheet has a Mn content of 22.986%, a yield strength of 525 MPa, a tensile strength of 894 MPa, an elongation of 46%, an average impact energy of 198.4 J at -196℃, and a thickness of 12.0 mm.

[0143] The high-manganese steel sheet is a circular sheet with a diameter of 4400mm. There is a weld seam in the center of the circular sheet. The target head to be manufactured has a diameter of 3600mm.

[0144] S1: Entering the first stamping stage, the sheet material is fed into the heating furnace at room temperature. The first heating rate is 85℃ / h, and the second heating rate is 200℃ / h. After the furnace temperature reaches 920℃, the sheet material undergoes the first heat treatment. After heat treatment for 30 minutes, the sheet material is removed from the furnace and stamped. The stamping deformation is 8%, the stamping height is 140mm, and the diameter of the stamped sheet is 3400mm. The stamped sheet material is then returned to the heating furnace at 920℃ for 15 minutes.

[0145] S2: Enter the second stamping stage. The sheet material that has been held for 15 minutes in the S2 heating furnace is taken out of the furnace and stamped. The stamping deformation is 6%, the stamping height is 130mm, and the diameter of the sheet material after stamping is 3650mm. Then the stamped sheet material is put back into the heating furnace at a furnace temperature of 920℃ and a holding time of 15 minutes.

[0146] S3: Entering the third stamping pass, the sheet material that has been held for 15 minutes in the S2 heating furnace is stamped. The stamping deformation is 5%, the stamping height is 120mm, and the diameter of the stamped sheet is 3650mm. Then, the stamped sheet is put back into the heating furnace at a furnace temperature of 920℃ for a holding time of 15 minutes.

[0147] S4: Entering the fourth stamping pass, the sheet material that has been held for 15 minutes in the S3 heating furnace is stamped. The stamping deformation is 5%, the stamping height is 120mm, and the diameter of the stamped sheet is 3650mm. Then, the stamped sheet is put back into the heating furnace at a furnace temperature of 930℃ for a holding time of 10 minutes.

[0148] S5: Entering the fifth and final stamping pass, the sheet that has been kept warm for 10 minutes in the S4 heating furnace is taken out of the furnace and stamped. The stamping deformation is 5%, the stamping height is 120mm, the diameter of the sheet after stamping is 3600mm, and a straight edge is produced to obtain the blank.

[0149] S6: Trim the ends of the blank and perform surface shot blasting.

[0150] S7: Put the blank back into the furnace and heat it to 400℃, then hold it for 20 minutes.

[0151] S8: After the blank is taken out of the furnace, it is subjected to warm spinning treatment. During warm spinning, the spinning temperature is controlled to be ≥250℃ using the flame gun blowing mode until the finished head size is reached.

[0152] S9: The surface of the finished end cap is partially ground, and the ends of the finished end cap are trimmed to obtain the end cap for LNG storage tanks.

[0153] The dimensions of the LNG storage tank end cap obtained in this embodiment meet the requirements of the drawings, and no cracking occurred in the weld during the stamping process, nor did any micro-cracks appear on the surface of the end cap.

[0154] Example 2:

[0155] The high-manganese steel sheet has a Mn content of 23.793%, a yield strength of 517 MPa, a tensile strength of 905 MPa, an elongation of 48%, an average impact energy of 202.6 J at -196℃, and a thickness of 12.0 mm.

[0156] The high-manganese steel sheet is a circular sheet with a diameter of 3500mm. There are two weld seams in the center of the circular sheet. The target head to be manufactured has a diameter of 2800mm.

[0157] S1: Entering the first stamping stage, the sheet material is fed into the heating furnace at room temperature. The first heating rate is 80℃ / h, and the second heating rate is 200℃ / h. After the furnace temperature reaches 880℃, the sheet material undergoes the first heat preservation treatment. After heat preservation for 30 minutes, the sheet material is removed from the furnace and stamped. The stamping deformation is 7%, the stamping height is 120mm, and the diameter of the stamped sheet is 2500mm. The stamped sheet material is then returned to the heating furnace at 920℃ for 15 minutes.

[0158] S2: Enter the second stamping stage. The sheet material that has been held for 15 minutes in the S2 heating furnace is taken out of the furnace and stamped. The stamping deformation is 5%, the stamping height is 120mm, and the diameter of the sheet material after stamping is 2650mm. Then the stamped sheet material is put back into the heating furnace at a furnace temperature of 920℃ and a holding time of 15 minutes.

[0159] S3: Entering the third stamping pass, the sheet material that has been held for 15 minutes in the S2 heating furnace is stamped. The stamping deformation is 5%, the stamping height is 120mm, and the diameter of the stamped sheet is 2850mm. Then, the stamped sheet is put back into the heating furnace at a furnace temperature of 920℃ for a holding time of 10 minutes.

[0160] S4: Enter the fourth stamping pass, the sheet that has been kept warm for 10 minutes in the S3 heating furnace is taken out of the furnace and stamped. The stamping deformation is 4%, the stamping height is 130mm, the diameter of the sheet after stamping is 2850mm, and a straight edge is produced to obtain the blank.

[0161] S5: Trim the ends of the blank and perform surface shot blasting.

[0162] S6: Put the blank back into the furnace and heat it to 350℃, then hold it for 25 minutes.

[0163] S7: After the blank is taken out of the furnace, it is subjected to warm spinning treatment. During warm spinning, the spinning temperature is controlled to be ≥250℃ using the flame gun blowing mode until the finished head size is reached.

[0164] S8: The surface of the finished end cap is partially ground, and the ends of the finished end cap are trimmed to obtain the end cap for LNG storage tanks.

[0165] The dimensions of the LNG storage tank end cap obtained in this embodiment meet the requirements of the drawings, and no cracking occurred in the weld during the stamping process, nor did any micro-cracks appear on the surface of the end cap.

[0166] Comparative Example 1:

[0167] The high-manganese steel sheet has a Mn content of 22.5%, a yield strength of 438 MPa, a tensile strength of 847 MPa, an elongation of 45%, an average impact energy of 184 J at -196℃, and a thickness of 10.0 mm.

[0168] At room temperature, high manganese steel sheets are cold stamped using a stamping press, and a bowl-shaped blank is obtained by two stamping passes.

[0169] Under the condition that the processing temperature is controlled at 300℃, the bowl-shaped blank is subjected to warm spinning to the finished diameter size to obtain the end cap for LNG storage tank.

[0170] The dimensions of the LNG storage tank head obtained in this comparative example do not meet the design requirements of the drawings, and cracks have appeared at the weld joints.

[0171] Comparative Example 2:

[0172] The high-manganese steel sheet has a Mn content of 23.78%, a yield strength of 468 MPa, a tensile strength of 927 MPa, an elongation of 47%, an average impact energy of 178 J at -196℃, and a thickness of 12.0 mm.

[0173] At room temperature, high manganese steel sheets are cold stamped using a stamping press, and a bowl-shaped blank is obtained by three stamping passes.

[0174] Under the condition that the processing temperature is controlled at 200℃, the bowl-shaped blank is subjected to warm spinning to the finished diameter size to obtain the end cap for LNG storage tank.

[0175] The dimensions of the LNG storage tank head obtained in this comparative example do not meet the design requirements of the drawings, and microcracks visible to the naked eye appear on the surface of the vertical end.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for processing a head for an LNG storage tank, characterized in that, The method includes: Based on the target diameter of the LNG storage tank end cap, the number of stamping passes N for the LNG storage tank end cap is determined, where N is positively correlated with the target diameter of the end cap, N≥2, and the stamping deformation amount of each stamping pass is X, where 5%≤X≤10%. The high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank. The blank is subjected to warm spinning to obtain the LNG storage tank head. Based on the target diameter of the LNG storage tank head, the number of stamping passes N for the LNG storage tank head is determined, including: When the target end cap diameter for the LNG storage tank is >3000mm, 4≤N≤6; When the target end cap diameter for the LNG storage tank is ≤3000mm, and 2≤N≤4, the high-manganese steel sheet is hot-stamped according to the number of stamping passes to obtain a blank, including: In the first stamping pass, the high manganese steel sheet is hot stamped using a heating-stamping-heating method. In any stamping pass other than the first stamping pass and the Nth stamping pass, the high manganese steel sheet is hot stamped by stamping first and then heating. In the Nth stamping pass, the high-manganese steel sheet obtained in the (N-1)th stamping pass is subjected to a stamping and edge straightening process to obtain the blank. The high-manganese steel sheet is subjected to hot stamping treatment using a heating-stamping-heating method, including: The high-manganese steel sheet is fed into a heating furnace; The furnace is preheated using a first heating rate, and after the furnace reaches the preheating target temperature, it is heated using a second heating rate, wherein the second heating rate is greater than the first heating rate. After the temperature in the heating furnace reaches the first preset temperature range, the heating furnace is subjected to a first heat preservation treatment. The high-manganese steel sheet is sent out of the heating furnace for stamping. The high-manganese steel sheet, after being stamped, is fed into the heating furnace, and the furnace undergoes a second heat preservation treatment, wherein the time of the second heat preservation treatment is shorter than the time of the first heat preservation treatment. The high-manganese steel sheet is subjected to hot stamping treatment using a method of first stamping and then heating, including: The high-manganese steel sheet is sent out of the heating furnace for stamping. The high-manganese steel sheet after stamping is fed into a heating furnace, and the furnace temperature is controlled within a second preset temperature range. The heating furnace is subjected to the second heat preservation treatment. And the method satisfies one or more of the following conditions: (1) The first heating rate is 50℃ / h-100℃ / h; (2) The target preheating temperature is 200℃; (3) The second heating rate is 180℃ / h-220℃ / h; (4) The first preset temperature range is 880℃-950℃; (5) The first heat preservation treatment time is 25 min-35 min; (6) The second preset temperature range is 900℃-940℃; (7) The second heat preservation treatment time is 10 min-15 min.

2. The processing method for LNG storage tank end caps according to claim 1, characterized in that, The blank is subjected to warm spinning treatment to obtain the end cap for the LNG storage tank, comprising: The blank is placed in a heating furnace, and the furnace temperature is controlled within a third preset temperature range. The heating furnace is subjected to a third heat preservation treatment; The blank is sent out of the heating furnace for warm spinning treatment to obtain the end cap for the LNG storage tank, wherein the processing temperature of the warm spinning treatment is controlled within a fourth preset temperature range.

3. The processing method for LNG storage tank end caps according to claim 2, characterized in that, The method satisfies one or more of the following conditions: (1) The third preset temperature range is 300℃-400℃; (2) The duration of the third heat preservation treatment is 20 min to 30 min; (3) The fourth preset temperature range is 250℃-350℃.

4. The processing method for LNG storage tank end caps according to claim 1, characterized in that, Before hot stamping the high-manganese steel sheet according to the number of stamping passes, the method further includes: The high-manganese steel sheet is subjected to an anti-oxidation treatment.

5. The processing method for LNG storage tank end caps according to claim 1, characterized in that, The high-manganese steel sheet meets one or more of the following conditions: (1) The Mn content of the high-manganese steel sheet is 22.5%-25.5%; (2) The tensile strength of the high manganese steel sheet is 800MPa-950MPa; (3) The Charpy impact energy KV of the high manganese steel sheet at -196℃ is 60J-300J.

Images