Method for determining quenching medium concentration of seamless steel pressure vessel

Abstract

The application provides a steel seamless pressure vessel quenching medium concentration determination method, comprising the following steps: S1, processing multiple end-quenching samples; S2, configuring multiple groups of water-based quenching agent solutions; S3, heating and heat-insulating the end-quenching samples, and contacting the test end face of the end-quenching samples with the water-based quenching agent solutions; S4, processing a detection face on the end-quenching samples, and measuring the hardness; S5, drawing a relationship curve between the distance from the test end face and the hardness value at the corresponding position, and obtaining the distance L of the hardness detection point corresponding to the hardness inflection point from the test end face; S6, drawing a relationship diagram of L and the water-based quenching agent solution concentration; and S7, based on the relationship diagram of S6, determining the water-based quenching agent concentration K during heat treatment quenching cooling of the pressure vessel with a nominal wall thickness H. The application solves the problems of multiple large furnace test times and inapplicability to different nominal wall thicknesses in the prior art, can quickly and effectively determine the quenching medium concentration, and effectively improves the safety and reliability of the pressure vessel use.

Description

Technical Field

[0001] This invention relates to the field of pressure vessels, and in particular to a method for determining the concentration of quenching medium in seamless steel pressure vessels. Background Technology

[0002] Seamless steel pressure vessels are mainly used for storing and transporting various high-pressure compressed gases and liquefied gases. To ensure the safety and reliability of the stored and transported gases, the pressure-bearing capacity of the pressure vessel must meet the requirements. Therefore, it is necessary to ensure that the performance of the vessel material meets the design requirements.

[0003] In the manufacturing process of seamless steel pressure vessels, quenching followed by high-temperature tempering is often used to adjust the material properties of the vessel body to ensure that its performance meets design requirements. Water-based quenching solutions are typically used for quenching and cooling of seamless steel pressure vessels, primarily for the following reasons: ① Seamless steel pressure vessels have a hollow structure, and both ends are closed during quenching and cooling. Using water as the quenching medium results in rapid cooling, which can easily lead to cracking and product scrap. Water-based quenching solutions can reduce the cooling rate by adjusting the concentration, thus preventing cracking; ② Water quenching results in high structural stress, which can easily lead to severe product deformation and affect subsequent processing. Water-based quenching media result in lower structural stress and reduced product deformation tendency. Therefore, water-based quenching solutions are widely used as quenching media in the manufacturing of seamless steel pressure vessels.

[0004] Currently, seamless steel pressure vessels of different pressure ratings have different material grades and nominal wall thicknesses. Therefore, during quenching and cooling, it is often necessary to adjust the concentration of water-based quenching agent according to the material grade and nominal wall thickness to ensure thorough quenching while avoiding excessively rapid cooling that could cause cracking. However, because seamless steel pressure vessels are sealed at both ends during quenching and cooling, the vessel is in a single-sided quenching and cooling state. Conventional small-scale process tests involve double-sided quenching and cooling, which is completely different from the single-sided quenching and cooling state of the vessel. Conventional small-scale process tests cannot effectively replace the heat treatment state of pressure vessels.

[0005] Existing technologies typically employ a large furnace with a sealed test ring for quenching and cooling tests, determining the optimal water-based quenching agent concentration based on magnetic particle testing and post-heat treatment mechanical property testing results. However, this method requires multiple large furnace tests, is time-consuming and costly, and the quenching medium concentration determined by this method is not applicable to seamless steel pressure vessels of other nominal wall thicknesses under the same material grade. If it is necessary to determine the quenching medium concentration for seamless steel pressure vessels of the same grade but different nominal wall thicknesses, the relevant tests need to be repeated, resulting in excessive large furnace heat treatment cycles, cumbersome testing operations, and low testing efficiency. Summary of the Invention

[0006] In view of this, the present invention aims to propose a method for determining the concentration of quenching medium for seamless steel pressure vessels, in order to solve the problems of existing technologies in determining the optimal concentration of water-based quenching agent for pressure vessels, such as the large number of furnace heat treatments, cumbersome experimental operations, and low experimental efficiency.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A method for determining the concentration of quenching medium in a seamless steel pressure vessel includes: S1, taking steel of any material grade and processing multiple end-quenched samples; S2, preparing multiple sets of water-based quenching agent solutions, wherein each end-quenched sample corresponds to a water-based quenching agent solution; S3, heating and holding the end-quenched samples at a certain temperature, then contacting the test end face of the end-quenched sample with the corresponding water-based quenching agent solution to perform an end-face quenching and cooling test; S4, machining a test surface on the end-quenched sample after the end-face quenching and cooling test, and measuring the hardness on the test surface; S5, according to the steps... Based on the hardness measurement results in step S4, plot the relationship curve between the distance from the test end face and the hardness value at the corresponding position, and obtain the distance L from the test end face of the hardness test point corresponding to the hardness value inflection point; S6, based on the L of each end-quenched sample obtained in step S5, and the concentration of the water-based quenching agent solution corresponding to each end-quenched sample, plot the relationship graph between L and the concentration of the water-based quenching agent solution; S7, based on the relationship graph obtained in step S6, determine the concentration K of the water-based quenching agent during heat treatment quenching and cooling for any pressure vessel with a nominal wall thickness H.

[0009] Furthermore, the main body of the end-quenched specimen is a cylinder, the central axis of the end-quenched specimen is denoted as the axis, and one end face of the end-quenched specimen is the test end face, which is used to contact the water-based quenching agent solution.

[0010] Furthermore, the test end face is circular, and the detection surface is obtained by cutting along a direction parallel to the axis of the end-quenched sample using any chord of the test end face.

[0011] Furthermore, in step S2, the concentrations of any two groups of water-based quenching agent solutions are different, and the number of groups of water-based quenching agent solutions is equal to the number of end-quenching samples in step S1.

[0012] Furthermore, the distance L obtained in step S5 is equal to the nominal wall thickness.

[0013] Further, step S7 includes: S71, based on the relationship diagram obtained in step S6, determining the concentration K of the water-based quenching agent during heat treatment quenching and cooling for any pressure vessel with a nominal wall thickness H; S72, taking a sample with a nominal wall thickness H for heat treatment, conducting a test ring furnace heat treatment test based on the concentration K of the water-based quenching agent, performing surface magnetic particle testing and mechanical property testing after heat treatment, and determining whether the sample meets the qualification conditions. If yes, then K is used to perform furnace heat treatment on the pressure vessel product with a nominal wall thickness H; if not, then the concentration of the water-based quenching agent is adjusted.

[0014] Furthermore, the qualified condition is that the sample is thoroughly quenched and does not crack.

[0015] Compared with existing technologies, the method for determining the quenching medium concentration of seamless steel pressure vessels described in this invention has the following advantages:

[0016] The present invention discloses a method for determining the concentration of quenching medium for seamless steel pressure vessels. It determines the distance L corresponding to the material hardness inflection point under different water-based quenching agent concentrations; this distance L is the nominal wall thickness of the material. Based on this, a relationship diagram between the water-based quenching agent concentration and the nominal wall thickness of the material is established. This diagram effectively guides the selection of water-based quenching medium concentration for heat treatment quenching and cooling of materials with different nominal wall thicknesses and grades. This solves the problems of numerous large-furnace tests and lack of applicability to different nominal wall thicknesses in existing technologies. It can quickly and effectively determine the quenching medium concentration for pressure vessels of different material grades and nominal wall thicknesses, guiding the heat treatment of seamless steel pressure vessels and effectively improving the safety and reliability of seamless steel pressure vessels.

[0017] Compared with existing technologies, the method of this application requires fewer tests and is simple and convenient to operate, which is conducive to improving test efficiency. At the same time, this application has good applicability to the same grade of material and can effectively guide the heat treatment problem of seamless steel containers with different nominal wall thicknesses, ensuring that the material is thoroughly quenched and does not crack after quenching and cooling, so that the heat-treated seamless steel pressure vessel has good strength and toughness matching, thereby ensuring the mechanical properties of the seamless steel pressure vessel after heat treatment and the safety and reliability of the product. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 This is a schematic diagram of the end-quenching sample in a method for determining the concentration of quenching medium in a seamless steel pressure vessel according to an embodiment of the present invention.

[0020] Figure 2This is an isometric view of the end-quenching sample in a method for determining the quenching medium concentration of a seamless steel pressure vessel according to an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure after the detection surface is cut out in the method for determining the concentration of quenching medium in a seamless steel pressure vessel according to an embodiment of the present invention.

[0022] Figure 4 This is a graph showing the relationship between the location of the hardness inflection point (distance between the hardness test point and the test end face) and the concentration of the quenching medium in Embodiment 1 (4130X steel) of the present invention.

[0023] Figure 5 This is a graph showing the relationship between the location of the hardness inflection point (distance between the hardness test point and the test end face) and the concentration of the quenching medium in Embodiment 2 (4142 steel) of the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Test end face; 2. Axis; 3. Detection surface. Detailed Implementation

[0026] The inventive concepts of this disclosure will be described below using terminology commonly used by those skilled in the art to communicate the essence of their work to others skilled in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this invention can be combined with each other. The concentration percentages in this application are mass concentration percentages.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] In existing technologies, determining the optimal water-based quenching agent concentration for a pressure vessel typically involves conducting quenching and cooling tests using a large furnace with a test ring seal. The optimal concentration is then determined based on magnetic particle testing and post-heat treatment mechanical property testing results. However, this method requires multiple large furnace tests, which is time-consuming and costly. Furthermore, the quenching medium concentration determined by this method is not applicable to seamless steel pressure vessels of the same material grade but with different nominal wall thicknesses. If it is necessary to determine the quenching medium concentration for seamless steel pressure vessels of the same grade but different nominal wall thicknesses, the relevant tests need to be repeated, resulting in excessive furnace heat treatment cycles, cumbersome testing operations, and low testing efficiency.

[0030] To address the problems of numerous furnace heat treatment cycles, cumbersome experimental operations, and low experimental efficiency in determining the optimal water-based quenching agent concentration for pressure vessels using existing technologies, this embodiment proposes a method for determining the quenching medium concentration for seamless steel pressure vessels, including:

[0031] S1. Take any grade of steel and process multiple end-quenched samples;

[0032] It should be noted that this application can be used for testing steel of any material grade, but for testing a certain material grade of steel, multiple end-quenched specimens of the same specification are processed using that material grade of steel.

[0033] As attached Figure 1-2 As shown, the main body of the end-quenched specimen is cylindrical. Geometrically, the end-quenched specimen has a central axis, denoted as axis 2. One end face of the end-quenched specimen is the test end face 1, which is used to contact the water-based quenching agent solution for testing. The outer edge of the other end is provided with a flange. The diameter of the end with the flange is larger than the diameter of the test end face 1, so as to facilitate the fixing or clamping of the end-quenched specimen.

[0034] S2. Prepare multiple sets of water-based quenching agent solutions, with each end-quenched sample corresponding to a water-based quenching agent solution;

[0035] In step S2, preferably, the concentrations of any two groups of water-based quenching agent solutions are different, and the number of groups of water-based quenching agent solutions is equal to the number of end-quenching samples in step S1; thus, one end-quenching sample corresponds to one group of water-based quenching agent solutions, and there is no situation where the concentration of water-based quenching agent solutions is repeated, avoiding unnecessary repeated tests and unnecessary waste of materials.

[0036] S3. Heat and keep the end-quenched sample at a certain temperature, and then bring the test end face 1 of the end-quenched sample into contact with the corresponding water-based quenching agent solution to carry out the end-face quenching and cooling test.

[0037] In step S3, since the "corresponding water-based quenching agent solution" also has a corresponding concentration, it can be understood that the end-quenched sample comes into contact with a solution of the corresponding water-based quenching agent concentration. Furthermore, step S3 is not limited to testing only one end-quenched sample; it can involve testing multiple end-quenched samples individually, or even testing all end-quenched samples from step S1 individually, depending on the experimental requirements. For different grades of steel, the heating temperature and holding conditions during heat treatment vary; relevant operating conditions in existing technologies can be referenced, and this application does not impose specific limitations.

[0038] S4. For the end-quenched specimen after the end-face quenching and cooling test, a test surface 3 parallel to the axis 2 of the end-quenched specimen is machined on the outer side wall of the end-quenched specimen near the test end face 1, and the hardness is measured on the test surface 3.

[0039] As attached Figure 3 As shown, any chord of the test end face 1 (circular) can be used to make a cut along a direction parallel to the axis 2 of the end-quenched sample. The cut surface that is parallel to the axis 2 of the end-quenched sample is the test surface 3.

[0040] S5. Based on the hardness measurement results in step S4, plot the relationship curve between the distance from the test end face 1 and the hardness value at the corresponding position, and obtain the distance L from the test end face 1 to the hardness test point corresponding to the hardness value inflection point.

[0041] Wherein, distance L is the nominal wall thickness. To avoid ambiguity, in this application, "distance" refers to the minimum distance from any hardness measurement point to the test end face 1, which is a conventional understanding in geometry.

[0042] Similarly, steps S4 and S5 can both be understood as the process of testing each of the multiple end-quenched specimens.

[0043] S6. Based on the L of each end-quenched sample obtained in step S5, and the concentration of the water-based quenching agent solution corresponding to each end-quenched sample, draw a graph showing the relationship between L and the concentration of the water-based quenching agent solution.

[0044] Thus, step S6 yields the nominal wall thickness that the material can be hardened through in water-based quenching agent solutions of different concentrations. The concentration of the water-based quenching agent during heat treatment quenching and cooling can then be determined based on the nominal wall thickness. The heat treatment process in this application includes quenching and high-temperature tempering.

[0045] Correspondingly, as shown in the appendix Figure 4 , 5 As shown in the diagram, the quenching medium concentration is the vertical axis and the "distance from the hardness inflection point to the end face" is the horizontal axis. The "distance from the hardness inflection point to the end face" can be specifically understood as the minimum distance from the hardness test point corresponding to the hardness value inflection point to the test end face 1. This distance is the nominal wall thickness.

[0046] S7. Based on the relationship diagram obtained in step S6, determine the concentration K of the water-based quenching agent during heat treatment quenching and cooling for any pressure vessel with a nominal wall thickness H.

[0047] Therefore, the method for determining the quenching medium concentration of seamless steel pressure vessels proposed in this application determines the distance L corresponding to the material hardness inflection point under different water-based quenching agent concentrations. This distance L is the nominal wall thickness of the material. Based on this, a relationship diagram between the water-based quenching agent concentration and the nominal wall thickness of the material is established. This relationship diagram can effectively guide the concentration of water-based quenching medium for heat treatment quenching and cooling of materials of different grades and nominal wall thicknesses. It solves the problems of the existing technology, such as the large number of furnace tests and the lack of applicability to different nominal wall thicknesses. It can quickly and effectively determine the quenching medium concentration of pressure vessels of different material grades and nominal wall thicknesses, guide the heat treatment of seamless steel pressure vessels, and effectively improve the safety and reliability of seamless steel pressure vessels.

[0048] Compared with existing technologies, the method of this application requires fewer tests and is simple and convenient to operate, which is conducive to improving test efficiency. At the same time, this application has good applicability to the same grade of material and can effectively guide the heat treatment problem of seamless steel containers with different nominal wall thicknesses, ensuring that the material is thoroughly quenched and does not crack after quenching and cooling, so that the heat-treated seamless steel pressure vessel has good strength and toughness matching, thereby ensuring the mechanical properties of the seamless steel pressure vessel after heat treatment and the safety and reliability of the product.

[0049] Furthermore, to ensure the accuracy of the obtained concentration values, step S7 of this application includes:

[0050] S71. Based on the relationship diagram obtained in step S6, determine the concentration K of the water-based quenching agent during heat treatment quenching and cooling for any pressure vessel with a nominal wall thickness H.

[0051] S72. Take a sample with nominal wall thickness H and perform heat treatment. Based on the concentration K of water-based quenching agent, conduct a test ring furnace heat treatment test. After the test, perform surface magnetic particle testing and mechanical property testing after heat treatment to determine whether the sample meets the qualification conditions. If yes, then use K to perform furnace heat treatment on the pressure vessel product with nominal wall thickness H. If not, then adjust the concentration of water-based quenching agent.

[0052] The qualified condition is that the sample is thoroughly quenched and does not crack. The operation and sample selection for the test ring furnace heat treatment test can directly adopt existing technology and will not be elaborated further.

[0053] Therefore, after determining the relationship between the nominal wall thickness H and the concentration K of the water-based quenching agent (i.e., the relationship diagram obtained in step S6), this application continues to use conventional test ring furnace heat treatment tests to further verify the results of the relationship diagram. After confirming the correctness of the concentration values, it is then applied to the furnace heat treatment of pressure vessel products. On the one hand, this ensures the correctness of the test results and provides further assurance for the pass rate of pressure vessel products. On the other hand, it helps to promptly identify any errors or mistakes that may exist in the experimental process and to adjust and correct the corresponding problems in a timely manner.

[0054] Example 1

[0055] Taking a seamless steel pressure vessel with grade 4130X as an example, this embodiment briefly introduces the process of determining the concentration of its water-based quenching agent.

[0056] 1) Select 4130X material to process end-quenched test specimens, and the number of test specimens is initially determined to be 6;

[0057] 2) The concentration range of the water-based quenching agent solution is adjusted to 1% to 10%. Initially, six groups of water-based quenching agent solutions with concentrations of 1%, 3%, 5%, 6%, 7%, and 10% are used so that one end-quenching sample corresponds to one concentration for subsequent tests. Accordingly, this embodiment only uses six groups as an example, but more groups can also be set.

[0058] 3) After heating the end-quenched sample to 900℃ and holding it at that temperature for 35 minutes, place it on the spraying device and contact the test end face 1 of the end-quenched sample with the corresponding concentration of water-based quenching agent solution to carry out the end-face quenching and cooling test.

[0059] 4) A test surface 3 parallel to the axis 2 of the end-quenched sample is machined on the end-quenched sample, and hardness measurement is performed on the test surface 3.

[0060] 5) Based on the hardness measurement results, plot the relationship curve between the distance from the test end face 1 and the hardness value at the corresponding position, and obtain the distance L corresponding to the inflection point of the hardness value. This distance L is the nominal wall thickness.

[0061] 6) The relationship between the hardness inflection point (i.e., each distance L) and the water-based quenching agent concentration for the end-quenched samples of 4130X material under six groups of water-based quenching agent solutions is shown in the attached figure. Figure 4 As shown, the nominal wall thickness that can be hardened through in a 1%–10% concentration water-based quenching agent solution of 4130X material can be obtained. Observe the attached... Figure 4 The corresponding relationship line shows that the concentration of water-based quenching agent is 7% when quenching and cooling 4130X material with a nominal wall thickness of 10mm, and 1% when quenching and cooling 4130X material with a nominal wall thickness of 30mm.

[0062] 7) A 4130X test ring with a nominal wall thickness of 10mm was subjected to furnace heat treatment using a quenching fluid concentration of 7%. The test ring was then subjected to furnace heat treatment. After the test, surface magnetic particle testing and mechanical property testing were performed. The results showed that the ring was fully quenched and did not crack. Therefore, when quenching and cooling seamless pressure vessels of this specification made of 4130X material, a quenching fluid with a concentration of 7% should be used for furnace heat treatment.

[0063] 8) A 4130X test ring with a nominal wall thickness of 30mm was subjected to furnace heat treatment using a quenching fluid concentration of 1%. The test ring was then subjected to furnace heat treatment. After the test, surface magnetic particle testing and mechanical property testing were performed. The results showed that the ring was fully quenched and did not crack. Therefore, when quenching and cooling seamless pressure vessels of this specification made of 4130X material, a quenching fluid concentration of 1% should be used for furnace heat treatment.

[0064] Example 2

[0065] Taking a seamless steel pressure vessel of grade 4142 as an example, this embodiment briefly introduces the process of determining the concentration of its water-based quenching agent.

[0066] 1) Use 4142 material to process end-quenched test specimens, and the number of test specimens is initially determined to be 8;

[0067] 2) The concentration range of the water-based quenching agent solution is adjusted to 1% to 10%. Initially, eight groups of water-based quenching agent solutions with concentrations of 1%, 2%, 4%, 5%, 6%, 7%, 8%, and 10% are used so that one end-quenching sample corresponds to one concentration for subsequent tests. Accordingly, this embodiment only uses eight groups as an example, but more groups can also be set.

[0068] 3) After heating the end-quenched sample to 860℃ and holding it at that temperature for 30 minutes, place it on the spraying device and contact the test end face 1 of the end-quenched sample with the corresponding concentration of water-based quenching agent solution to carry out the end-face quenching and cooling test.

[0069] 4) A test surface 3 parallel to the axis 2 of the end-quenched sample is machined on the end-quenched sample, and hardness measurement is performed on the test surface 3.

[0070] 5) Based on the hardness measurement results, plot the relationship curve between the distance from the test end face 1 and the hardness value at the corresponding position, and obtain the distance L corresponding to the inflection point of the hardness value. This distance L is the nominal wall thickness.

[0071] 6) The relationship between the hardness inflection point (i.e., each distance L) and the concentration of the water-based quenching agent for the end-quenched samples of 4142 material under 8 groups of water-based quenching agent solutions is shown in the attached figure. Figure 5 As shown, the nominal wall thickness that can be hardened through in a 1%–10% concentration water-based quenching agent solution can be obtained. Observe the attached... Figure 5 The corresponding relationship line shows that the concentration of water-based quenching agent is 8% when quenching and cooling 4142 material with a nominal wall thickness of 10mm, and 4% when quenching and cooling 4142 material with a nominal wall thickness of 30mm.

[0072] 7) A 4142 test ring with a nominal wall thickness of 10mm was subjected to furnace heat treatment using a quenching fluid concentration of 8%. The test was conducted on the 4142 material test ring. After the test, surface magnetic particle testing and mechanical property testing were performed. The results showed that it was thoroughly quenched and did not crack. Therefore, when quenching and cooling seamless pressure vessels of this specification made of 4142 material, an 8% concentration quenching fluid should be used for furnace heat treatment of the product.

[0073] 8) A 4142 test ring with a nominal wall thickness of 30mm was subjected to furnace heat treatment using a quenching fluid concentration of 4%. The test ring was then subjected to furnace heat treatment. After the test, surface magnetic particle testing and mechanical property testing were performed. The results showed that the ring was fully quenched and did not crack. Therefore, when quenching and cooling seamless pressure vessels of this specification made of 4142 steel, a quenching fluid concentration of 4% should be used for furnace heat treatment.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the concentration of quenching medium in a seamless steel pressure vessel, characterized in that, The method includes: S1. Take any grade of steel and process multiple end-quenched samples of the same specifications. S2. Prepare multiple sets of water-based quenching agent solutions, with each end-quenched sample corresponding to a water-based quenching agent solution; S3. Heat and keep the end-quenched sample at a certain temperature, and then bring the test end face (1) of the end-quenched sample into contact with the corresponding water-based quenching agent solution to carry out the end-face quenching and cooling test. S4. After the end-face quenching and cooling test, the test surface (3) is machined on the end-quenched sample, and the hardness is measured on the test surface (3). S5. Based on the hardness measurement results of step S4, plot the relationship curve between the distance from the test end face (1) and the hardness value at the corresponding position, and obtain the distance L from the test end face (1) of the hardness detection point corresponding to the hardness value inflection point. The distance L is equal to the nominal wall thickness H. S6. Based on the L of each end-quenched sample obtained in step S5, and the concentration of the water-based quenching agent solution corresponding to each end-quenched sample, draw a graph showing the relationship between L and the concentration of the water-based quenching agent solution. S7. Based on the relationship diagram obtained in step S6, determine the concentration K of the water-based quenching agent during heat treatment quenching and cooling for any pressure vessel with a nominal wall thickness H; take a sample with a nominal wall thickness H for heat treatment, and conduct a test ring furnace heat treatment test based on the concentration K of the water-based quenching agent. After the test, perform surface magnetic particle testing and mechanical property testing after heat treatment to determine whether the sample meets the qualification conditions. If yes, then use K to perform furnace heat treatment on the pressure vessel product with a nominal wall thickness H; otherwise, adjust the concentration of the water-based quenching agent. In step S2, the concentrations of any two groups of water-based quenching agent solutions are different, and the number of groups of water-based quenching agent solutions is equal to the number of end-quenching samples in step S1.

2. The method for determining the quenching medium concentration of a seamless steel pressure vessel according to claim 1, characterized in that, The main body of the end-quenched sample is a cylinder, the central axis of the end-quenched sample is denoted as the axis (2), and one end face of the end-quenched sample is the test end face (1), which is used to contact the water-based quenching agent solution.

3. The method for determining the quenching medium concentration of a seamless steel pressure vessel according to claim 2, characterized in that, The test end face (1) is circular, and the detection surface (3) is obtained by cutting along any chord of the test end face (1) in a direction parallel to the axis (2) of the end-quenched sample.

4. The method for determining the quenching medium concentration of a seamless steel pressure vessel according to claim 1, characterized in that, The qualified condition is that the sample is thoroughly quenched and does not crack.

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