Method for controlling service performance of high-temperature and high-pressure bolt steel matched with induction quenching and tempering process

Abstract

The application provides a high-temperature and high-pressure bolt steel service performance control method matched with an induction quenching and tempering process and belongs to the field of steel preparation.The method comprises the following steps: obtaining a casting blank with a set chemical composition;obtaining a heating temperature of the casting blank based on a quantitative relationship between the set chemical composition and a large-size precipitated particle resolubilization temperature of the casting blank;heating the casting blank at the heating temperature, and then performing rolling, cooling and annealing to obtain a bolt steel.Through reasonable design of the chemical composition, the specific content of nitrogen elements and carbon elements are used to cooperate, which is more conducive to the complete analysis of V and Ti, and plays a role in improving the high-temperature performance; the heating temperature of the casting blank is obtained through the quantitative relationship between the set chemical composition and the large-size precipitated particle resolubilization temperature of the casting blank, so that the large-size precipitated particle resolubilization of the casting blank is ensured. The particle precipitation process supporting the high-temperature performance is designed to be moved forward, and the alloy elements are reasonably matched with the high-temperature creep performance, so that the high-temperature service performance of the bolt steel is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of steel production, and in particular to a high-temperature and high-pressure bolt steel service performance control method matched with an induction quenching and tempering process. BACKGROUND

[0002] With the rapid development of the petrochemical industry, large-scale, diversification and complication have become the main trend. In the fields of oil pipelines, steam pipelines and oil extraction platforms, high-temperature, high-pressure, flammable, explosive and toxic corrosive materials are used for storage and transportation. The material is used in an environment with a service temperature higher than 550 DEG C and a service pressure greater than 45 Mpa. As a safety core component, the flange bolt joint plays a significant role in safety support. Therefore, the bolt material strength is required to be greater than 800 Mpa, and the material specification is required to be greater than 65 mm. The performance requirements are harsh. At the same time, the induction quenching and tempering process replaces the traditional heating furnace heat treatment route. The quenching austenitizing and tempering holding time are shortened from 2-3 hours to a few seconds, thereby meeting the requirements of the fastener industry for green and low-carbon development.

[0003] However, after the induction quenching and tempering process is used to replace the traditional quenching and tempering heat treatment process in the prior art, the precipitation conditions of Mo, V and Cr carbide and carbonitride particles supporting high-temperature service performance are not met, thereby causing low high-temperature performance of the bolt material and unstable cross-section performance, and further causing poor long-term high-temperature service performance of the bolt material. SUMMARY

[0004] The application provides a high-temperature and high-pressure bolt steel service performance control method matched with an induction quenching and tempering process, to solve the technical problem of how to improve the long-term high-temperature service performance of the fastener material.

[0005] In a first aspect, the application provides a high-temperature and high-pressure bolt steel service performance control method matched with an induction quenching and tempering process, which comprises the following steps:

[0006] A casting blank with a set chemical composition is obtained. The set chemical composition comprises, in mass fraction, C: 0.36% to 0.47%, N: 0.0045% to 0.0105%, V: 0.25% to 0.35%, and Ti: 0.075% to 0.15%.

[0007] A heating temperature of the casting blank is obtained based on a quantitative relationship between the set chemical composition and a large-size precipitated particle resolubilization temperature of the casting blank.

[0008] The casting blank is heated at the heating temperature, and then is subjected to rolling, cooling and annealing to obtain a bolt steel.

[0009] Optionally, the set chemical composition satisfies the following relationship:

[0010] 2.0≤1-lg[(C 2 +100N) / (V+100Ti)]≤2.4

[0011] In the formula, [C] represents the content of C in the preceding numerical value, [N] represents the content of N in the preceding numerical value, [V] represents the content of V in the preceding numerical value, and [Ti] represents the content of Ti in the preceding numerical value.

[0012] Optionally, the set chemical composition further comprises, in mass fraction, Si: 0.2% to 0.3%, Mn: 0.6% to 0.65%, Cr: 0.8% to 1.2%, Mo: 0.5% to 0.65%, and the balance of Fe and inevitable impurities.

[0013] Optionally, the heating temperature satisfies the following relationship:

[0014] T≥1270×{1.05-lg[([C]+[N]) / ([V]+[Ti])]}

[0015] In the formula, T represents the heating temperature, [C] represents the content of C, [N] represents the content of N, [V] represents the content of V, and [Ti] represents the content of Ti.

[0016] Optionally, the entry temperature of the rolling is 740°C to 820°C.

[0017] Optionally, in the interval of 850°C to 750°C of the cooling, the cooling rate is 0.1°C / s to 0.5°C / s.

[0018] In a second aspect, the application provides a bolt steel prepared by the method of any one of the embodiments of the first aspect, wherein the proportion of the precipitated amount of V to the content of V is ≥68%, and the proportion of VN or VCN precipitated particles with a size ≤10nm is ≥90%.

[0019] Optionally, in the bolt steel, the proportion of V and Ti precipitated particles with a size ≥100nm is ≤3%.

[0020] In a third aspect, the application provides a fastener prepared by an induction quenching and tempering process on the bolt steel of the embodiments of the second aspect.

[0021] Optionally, the fastener satisfies at least one of the following properties: Rp0.2(500°C) is 705Mpa to 728Mpa, Rp0.2(550°C) is 590Mpa to 608Mpa, and the creep limit strength (550°C) is 176Mpa to 185Mpa.

[0022] Compared with the prior art, the above technical solution provided in the embodiments of the application has the following advantages:

[0023] The application provides a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process, comprising the following steps: obtaining a casting blank with a set chemical composition; the set chemical composition comprises, in terms of mass fraction, C: 0.36% to 0.47%, N: 0.0045% to 0.0105%, V: 0.25% to 0.35% and Ti: 0.075% to 0.15%; obtaining a heating temperature of the casting blank based on a quantitative relationship between the set chemical composition and a large-size precipitated particle re-dissolution temperature of the casting blank; and heating the casting blank at the heating temperature, and then performing rolling, cooling and annealing to obtain a bolt steel. By reasonably designing the chemical composition, the nitrogen element and the carbon element with specific contents are used in cooperation, which is more conducive to the precipitation of V and Ti, and plays a role in improving the high-temperature performance; the heating temperature of the casting blank is obtained through the quantitative relationship between the set chemical composition and the large-size precipitated particle re-dissolution temperature of the casting blank, so that the large-size precipitated particle re-dissolution of the casting blank is ensured. The preparation method provided by the application moves the particle precipitation process that supports the high-temperature performance forward, and designs the reasonable matching between the alloy elements and the high-temperature creep performance, so that the high-temperature service performance of the bolt steel is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0026] Figure 1 A flowchart of a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process provided by the embodiments of the present application is shown in the figure;

[0027] Figure 2 A high-temperature performance quantitative curve of the fastener provided by the embodiment 3 and the comparative example 4 in the range of 500-560 DEG C is shown in the figure;

[0028] Figure 3 A high-temperature creep ultimate strength of the fastener provided by the embodiment 3 and the comparative example 4 at 550 DEG C is shown in the figure. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0030] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which applies to any range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) in the indicated range.

[0031] In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but not limited to". In the present application, the relationship terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the cases of A alone, A and B together, and B alone. Wherein A, B can be singular or plural. In the present application, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including single item or any combination of multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, c can be single or multiple.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0033] Figure 1A flowchart of a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process is provided for an embodiment of the present application.

[0034] See Figure 1 The present application provides a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process, which comprises the following steps:

[0035] S1, obtaining a casting blank with a set chemical composition; the set chemical composition includes, in terms of mass fraction, C: 0.36% to 0.47%, N: 0.0045% to 0.0105%, V: 0.25% to 0.35%, and Ti: 0.075% to 0.15%;

[0036] The positive effect of controlling the content of C to be 0.36% to 0.47% is that the carbon element dissolved in the steel improves the hardenability of the steel and increases the strength of the steel matrix; the V and Ti elements added to the steel for strengthening and refining the grains need to be matched with the carbon element to precipitate VC, VCN and TiC particles. If the content of carbon is lower than 0.36%, the strength of the fastener produced will be low, and the added V and Ti elements will not be beneficial to precipitation; if the content of carbon is higher than 0.47%, the toughness and plasticity of the produced fastener cannot meet the requirements. Exemplarily, the content of C can be 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.47%, etc.

[0037] The positive effect of controlling the content of N to be 0.0045% to 0.0105% is that the nitrogen element is generally a harmful element in steel, which aggravates the work hardening effect of the steel and reduces the toughness and plasticity of the material. A certain content of nitrogen element cooperates with the carbon element, which is more beneficial to the precipitation of V and Ti elements and improves the high-temperature performance. If the content of nitrogen is lower than 0.0055%, the added V and Ti cannot be fully precipitated, which cannot achieve the best performance; if the content is higher than 0.0105%, the toughness and plasticity of the steel and the processing performance are poor, which cannot meet the performance requirements. Exemplarily, the content of N can be 0.0045%, 0.0055%, 0.0060%, 0.0070%, 0.0080%, 0.0090%, 0.010%, 0.0105%, etc.

[0038] The positive effect of controlling the content of V to be 0.25% to 0.35%: the vanadium element combines with carbon and nitrogen to precipitate VC, VN and VCN particles to play a role of high temperature strengthening, the precipitation temperature interval is closely related to the content of vanadium, carbon and nitrogen, which is beneficial to the optimization design of element content to realize the industrial production control. If the content of vanadium is lower than 0.25%, the high temperature creep performance of the material will be low; if the content of vanadium is higher than 0.35%, the high temperature thermal plasticity of the material will be greatly reduced, which will lead to serious cracks of the casting blank, in addition, the material is not economical. Exemplarily, the content of V can be 0.25%, 0.27%, 0.29%, 0.30%, 0.32%, 0.34%, 0.35% and the like.

[0039] The positive effect of controlling the content of Ti to be 0.075% to 0.15%: the titanium element combines with C, N and other elements to form TiN, TiC and TiCN precipitates, which plays a role of strengthening, wear resistance and improving high temperature creep performance. Titanium is relatively cheap, but it is difficult to control in industrial production. The content of titanium cooperates with the vanadium element in the steel to match the induction heat treatment process, so as to realize the high high temperature performance of the material. If the content is lower than 0.075%, the high temperature creep performance cannot be supported; if the content is higher than 0.15%, large size TiN particles of inclusion level (micron level) will be precipitated, which will greatly reduce the toughness and plasticity of the material, affecting the forming of the material. Exemplarily, the content of Ti can be 0.075%, 0.08%, 0.09%, 0.10%, 0.11%, 0.13%, 0.15% and the like.

[0040] In some embodiments, the set chemical composition satisfies the following relationship:

[0041] 2.0≤1-lg[(C 2 +100N) / (V+100Ti)]≤2.4

[0042] In the formula, [C] represents the content of C in front of the numerical value, [N] represents the content of N in front of the numerical value, [V] represents the content of V in front of the numerical value, and [Ti] represents the content of Ti in front of the numerical value.

[0043] In the production process, the content of C, N, V and Ti in the steel is accurately controlled to satisfy the relationship, which is beneficial to the precipitation of nano-sized small size V and Ti particles, and at the same time avoids high solid solution proportion of V and Ti particles. Exemplarily, the value of 1-ln[([C] 2 +[N] 2 ) / ([V]+[Ti])] can be 2.0, 2.1, 2.2, 2.3, 2.4 and the like.

[0044] In some embodiments, the set chemical composition further comprises, in mass fraction, Si: 0.2%-0.3%, Mn: 0.6%-0.65%, Cr: 0.8%-1.2%, Mo: 0.5%-0.65%, and the balance being Fe and inevitable impurities.

[0045] S2, obtaining a heating temperature of the casting blank based on the set chemical composition and a quantitative relationship between the casting blank large-size precipitated particle solution temperature;

[0046] In some embodiments, the heating temperature satisfies the following relationship:

[0047] T≥1270×{1.05-lg[([C]+[N]) / ([V]+[Ti])]}

[0048] In the formula, T represents the heating temperature, [C] represents the content of C, [N] represents the content of N, [V] represents the content of V, and [Ti] represents the content of Ti.

[0049] In the embodiments of the present application, since the sizes of V and Ti precipitated from the casting blank are 100-200 nm or even larger during continuous casting, the V and Ti cannot play a strengthening role; however, if the heating temperature of the casting blank is too high, there are a series of problems such as burning and cracking of the casting blank, oxidation and burning loss, decarburization, and the like, and therefore the heating temperature of the casting blank needs to be accurately designed. In order to ensure the solution of the large-size precipitated particles of the casting blank, the present application obtains a precise quantitative relationship between the contents of V, Ti, N and C in the steel and the heating solution temperature of the casting blank, realizes accurate control of the heating system of the heating temperature of the casting blank, and at the same time ensures that the percentage of the V and Ti precipitated particle size ≥100 in the casting blank is ≤3%. If the percentage of the V and Ti precipitated particle size ≥100-200 nm in the casting blank is >3%, the percentage of the V precipitated in the rolled material is less than 68%, and the percentage of the VN or VCN particle size ≤10 nm is less than 90%.

[0050] S3, heating the casting blank at the heating temperature, and then rolling, cooling and annealing to obtain a bolt steel.

[0051] In some embodiments, the entry finish rolling temperature of the rolling is 740-820°C.

[0052] In the embodiments of the present application, the entry finish rolling temperature of the rolling is controlled to be 740°C, and the exit temperature is 820°C, so as to ensure the deformation-induced VN or VCN particle precipitation. Exemplarily, the entry finish rolling temperature of the rolling is 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, and the like.

[0053] In some embodiments, the cooling rate is 0.1-0.5°C / s in the 850-750°C interval of the cooling.

[0054] In the ferrite region in the range of 850-750℃, the small size nano V-containing particles are controlled to precipitate, and the cooling speed is controlled in the range of 0.1-0.5℃ / s. If the cooling speed is greater than 0.5℃ / s, the percentage of VN or VCN particles with a size of ≤10nm in the material is less than 90%; if the cooling speed is less than 0.1℃ / s, the Fe+Fe2O3 structure in the iron oxide scale FeO layer is precipitated, which affects the mechanical descaling performance of the iron oxide scale. Exemplarily, the cooling speed can be 0.1℃ / s, 0.2℃ / s, 0.3℃ / s, 0.4℃ / s, 0.5℃ / s, etc.

[0055] Based on one general inventive concept, the application provides a bolt steel, in which the proportion of the precipitated amount of V to the V content is ≥68%, and the percentage of VN or VCN precipitated particles with a size of ≤10nm is ≥90%.

[0056] In some embodiments, in the bolt steel, the percentage of V and Ti precipitated particles with a size of ≥100nm is ≤3%.

[0057] By obtaining the precise quantitative relationship between the V, Ti, N and C element contents in the steel and the heating return temperature of the casting blank, the application realizes precise control of the heating system of the casting blank heating temperature, and simultaneously uses ultra-low temperature rolling + limit slow cooling process to effectively control the percentage of VN or VCN particles with a size of ≤10nm in the material to be ≥90%, and the percentage of V and Ti particles with a size of ≥100nm to be γ0≤3%. Exemplarily, the proportion of the precipitated amount of V to the V content can be 68%, 69%, 70%, 72%, 74%, 75%, etc., the percentage of VN or VCN precipitated particles with a size of ≤10nm can be 90%, 91%, 92%, 93%, 94%, 95%, etc., and the percentage of V and Ti precipitated particles with a size of ≥100nm can be 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3%, etc.

[0058] The bolt steel is realized based on the preparation method of the above bolt steel. The specific steps of the preparation method of the bolt steel can refer to the above embodiments. Since the bolt steel uses part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0059] Based on one general inventive concept, the application provides a fastener made of bolt steel by induction quenching and tempering process.

[0060] In some embodiments, the fastener satisfies at least one of the following properties: Rp0.2(500℃) is 705Mpa-728Mpa, Rp0.2(550℃) is 590Mpa-608Mpa, and creep limit strength (550℃) is 176Mpa-185Mpa.

[0061] The high-temperature service performance and creep limit strength of the part product after induction heat treatment are greatly improved. Compared with the traditional process, the Rp0.2(550℃) is increased by an average of 42Mpa, and the creep limit strength at 550℃ is increased by an average of 37Mpa. For example, the Rp0.2(500℃) can be 705Mpa, 710Mpa, 715Mpa, 720Mpa, 725Mpa, 728Mpa, etc., the Rp0.2(550℃) is 590Mpa, 592Mpa, 595Mpa, 600Mpa, 605Mpa, 608Mpa, etc., and the creep limit strength (550℃) is 176Mpa, 178Mpa, 180Mpa, 182Mpa, 185Mpa, etc.

[0062] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. The experimental methods in the following examples are not specified, which are generally determined according to the industry standard. If there is no corresponding industry standard, it is determined according to the general international standard, the conventional condition, or according to the condition suggested by the manufacturer.

[0063] The embodiment of the application provides a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process, and the method comprises the following steps:

[0064] S1, obtaining a casting blank with a set chemical composition; the chemical composition of the bolt steel can be seen from Table 1;

[0065] S2, obtaining a heating temperature of the casting blank based on a quantitative relationship between the set chemical composition and a back-dissolving temperature of large-size precipitated particles of the casting blank;

[0066] S3, heating the casting blank at the heating temperature, and then performing rolling, cooling and annealing to obtain a bolt steel; the process parameters of the preparation method of the bolt steel can be seen from Table 2.

[0067] Table 1 Chemical composition (wt%) of the bolt steel, the rest is Fe and unavoidable impurities

[0068] Group C Si Mn Cr Mo V Ti N 1 - lg[(C 2 + 100N) / (V + 100Ti)]]] Example 1 0.36 0.23 0.61 1.10 0.50 0.25 0.085 0.0065 2.05 Example 2 0.38 0.24 0.60 1.01 0.51 0.33 0.075 0.0045 2.12 Example 3 0.41 0.23 0.62 1.02 0.60 0.35 0.085 0.0065 2.03 Example 4 0.37 0.23 0.61 0.80 0.50 0.28 0.085 0.0055 2.11 Example 5 0.39 0.24 0.64 1.15 0.51 0.27 0.105 0.0045 2.25 Example 6 0.42 0.23 0.60 1.11 0.60 0.30 0.095 0.0065 2.07 Example 7 0.36 0.23 0.61 0.81 0.50 0.31 0.085 0.0055 2.11 Example 8 0.38 0.24 0.60 0.82 0.51 0.25 0.105 0.0065 2.13 Example 9 0.41 0.23 0.62 0.91 0.60 0.26 0.125 0.0055 2.25 Example 10 0.45 0.23 0.61 0.82 0.50 0.28 0.150 0.0045 2.37 Example 11 0.39 0.24 0.64 0.91 0.51 0.25 0.120 0.0065 2.18 Example 12 0.42 0.23 0.60 0.82 0.60 0.30 0.095 0.0045 2.19 Example 13 0.42 0.25 0.65 0.91 0.65 0.32 0.145 0.0065 2.25 Comparative Example 1 0.38 0.23 0.61 0.81 0.65 0.35 0.005 0.0065 1.03 Comparative Example 2 0.39 0.24 0.64 0.82 0.63 0.25 0.025 0.0055 1.59 Comparative Example 3 0.40 0.23 0.60 0.91 0.64 0.32 0.025 0.0055 1.60 Comparative Example 4 0.36 0.25 0.61 0.82 0.63 0.35 0.005 0.0040 1.21 Comparative Example 5 0.38 0.23 0.60 0.91 0.63 0.34 0.015 0.0058 1.40

[0069] Table 2 Process parameters of the preparation method of the bolt steel

[0070]

[0071]

[0072] The bolt steels obtained from the examples and the comparative examples were induction quenched and tempered to obtain fasteners, and the high-temperature service performance of the fasteners was evaluated, and the results are shown in Table 3.

[0073] Table 3 High-temperature yield strength and creep limit strength of the fasteners

[0074]

[0075]

[0076] Compared with the examples 1-13 and the comparative examples 1-5 of the present application, the high-temperature yield strength Rp0.2 and the creep limit performance are greatly improved.

[0077] The detailed description of the fastener provided in the examples 1-13 and the comparative examples 1-5 of the present application is as follows: Figure 2 And 3 The detailed description of the fastener provided in the examples 1-13 and the comparative examples 1-5 of the present application is as follows:

[0078] Figure 2 The high-temperature performance quantification curve of the fastener provided in the examples 3 and the comparative example 4 of the present application in the range of 500-560 DEG C.

[0079] Figure 2 In the examples 1-13 and the comparative examples 1-5 of the present application, the new process is the preparation method of the fastener provided in the example 3, and the traditional process is the preparation method of the fastener provided in the comparative example 4, and the high-temperature yield strength of the fastener provided by the new process is higher, which is beneficial to the improvement of the long-term service performance.

[0080] Figure 3 The high-temperature creep limit strength of the fastener provided in the examples 3 and the comparative example 4 of the present application at 550 DEG C.

[0081] Figure 3 In the examples 1-13 and the comparative examples 1-5 of the present application, the new process is the preparation method of the fastener provided in the example 3, and the traditional process is the preparation method of the fastener provided in the comparative example 4, and the high-temperature yield strength of the fastener provided by the new process is higher, which is beneficial to the improvement of the long-term service performance.

[0082] In addition, one or more technical solutions in the examples of the present application at least have the following technical effects or advantages:

[0083] In the examples of the present application, the high-temperature high-pressure bolt steel has the following characteristics after induction heat treatment: compared with the existing original process, the Rp0.2(550 DEG C) is increased by 30Mpa, the 550 DEG C creep limit strength is in the range of 176-185Mpa, and the average is increased by 37Mpa. The high-temperature stability is greatly improved.

[0084] In the embodiment of the present application, a high-temperature high-pressure bolt steel service performance control method matched with an induction quenching and tempering process is provided, a particle precipitation process supporting high-temperature performance is designed to be moved forward, and alloy elements are designed to be reasonably matched with high-temperature creep performance. The high-temperature service performance of the bolt steel is greatly improved, and the equipment is provided with large-scale, diversification and complexification, and higher safety is provided for fastener materials.

[0085] The above description is merely that of the specific embodiments of the application. Various modifications to these embodiments can be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the service properties of high temperature high pressure bolt steels in a matching induction quenching tempering process, characterized in that The method comprises: obtaining a casting blank with a set chemical composition; the set chemical composition, in terms of mass fraction, is: C: 0.36% to 0.47%, N: 0.0045% to 0.0105%, V: 0.25% to 0.35%, Ti: 0.075% to 0.15%, Si: 0.2% to 0.3%, Mn: 0.6% to 0.65%, Cr: 0.8% to 1.2%, Mo: 0.5% to 0.65%, and the balance being Fe and inevitable impurities; obtaining a heating temperature of the casting blank based on a quantitative relationship between the set chemical composition and a dissolution temperature of large-size precipitated particles of the casting blank; heating the casting blank at the heating temperature, and then rolling, cooling and annealing the casting blank to obtain a bolt steel; wherein the set chemical composition satisfies the following relationship: 2.0 < 1 - lg[(C 2 + 100 N) / (V + 100 Ti)] < 2.4 wherein [C] represents the content of C, [N] represents the content of N, [V] represents the content of V, and [Ti] represents the content of Ti; the heating temperature satisfies the following relationship: T >= 1270 * {1.05-lg[([C]+[N]) / ([V]+[Ti])]} wherein T represents the heating temperature, [C] represents the content of C, [N] represents the content of N, [V] represents the content of V, and [Ti] represents the content of Ti; the entry finishing rolling temperature of the rolling is 740 DEG C to 820 DEG C; the cooling rate is 0.1 DEG C / s to 0.5 DEG C / s in the temperature range of 850 DEG C to 750 DEG C.

2. Bolt steel produced by the method according to any one of claims 1, characterized in that In the bolt steel, the proportion of the precipitated amount of V to the content of V is >= 68%, and the proportion of VN or VCN precipitated particles with a size of <= 10 nm is >= 90%.

3. A bolt steel according to claim 2, characterized in that In the bolt steel, the proportion of V and Ti precipitated particles with a size of >= 100 nm is <= 3%.

4. A fastener, characterized by The fastener is obtained by an induction quenching and tempering process of the bolt steel in claim 2 or 3.

5. The fastener of claim 4, wherein, The fastener satisfies at least one of the following properties: Rp0.2(500 DEG C) is 705 Mpa to 728 Mpa, Rp0.2(550 DEG C) is 590 Mpa to 608 Mpa, and the creep limit strength (550 DEG C) is 176 Mpa to 185 Mpa.

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