Preparation method of high-temperature alloy steel for clamp

Abstract

The invention discloses a preparation method of high-temperature alloy steel for a hoop, and relates to the technical field of stainless steel. The preparation method specifically comprises the following steps: carrying out primary coating treatment on a high-temperature alloy steel substrate, then drying, carrying out rough drawing treatment, carrying out online bright annealing treatment and polishing treatment to obtain a semi-finished product, carrying out secondary coating treatment on the semi-finished product, then drying, carrying out surface oxalic acid plating treatment, and carrying out drawing treatment to obtain the high-temperature alloy steel for the hoop. Through cooperative control of staged film treatment and thermal machining, the two times of surface treatment are matched with the lubrication and anti-adhesion requirements in the rough machining stage and the finish machining stage respectively, work hardening is eliminated in combination with online annealing, and cooperative optimization of grain refinement and surface integrity is achieved.

Description

Technical Field

[0001] This invention relates to the field of stainless steel technology, and more specifically, to a method for preparing high-temperature alloy steel for clamps. Background Technology

[0002] Under high temperature and high pressure conditions, clamps, as the core fastening components of pipeline connection systems, require materials with excellent high-temperature strength, creep resistance, and corrosion resistance. Traditional high-temperature alloy steel manufacturing processes often employ single-stage hot working combined with conventional heat treatment. However, under long-term high-temperature service conditions, problems such as grain boundary weakening and stress corrosion cracking can easily occur, severely limiting the service life of clamp components.

[0003] The commonly used hot-rolled followed by direct cold drawing process in existing technologies has the potential risk of incomplete removal of the surface oxide layer, leading to the initiation of microcracks during subsequent processing. Conventional solution treatment often uses offline annealing equipment, resulting in interruptions in process connections and uneven dislocation density distribution within the material, directly affecting the uniform deformation capability of the finished steel. Especially in multi-pass drawing processes, a single coating treatment process cannot simultaneously meet the dual requirements of processing lubrication and surface passivation, easily causing a mismatch between work hardening rate and material plasticity, significantly increasing the die wear rate.

[0004] Regarding surface treatment, traditional processes often overlook the differentiated surface quality requirements at different processing stages. If large-deformation rough drawing is performed directly after the initial coating treatment, residual oxide scale fragments can easily embed into the matrix, forming stress concentration points. Conversely, in the precision drawing process without a secondary coating treatment, the continuity and density of the surface lubricating film are insufficient, resulting in a final surface roughness that fails to meet the assembly requirements of precision fasteners. Furthermore, existing technologies lack sufficient precision in controlling the online heat treatment of hot-rolled wire rods, leading to an excessively wide grain size distribution range, which severely affects the material's anti-relaxation properties under extreme temperatures.

[0005] How to achieve microstructure refinement while maintaining surface integrity through process chain restructuring, and establish a synergistic mechanism between thermomechanical treatment and surface modification processes, has become a technical bottleneck in improving the overall performance of high-temperature alloy clamps. There is an urgent need to develop a novel preparation method that optimizes the strength-ductility balance of high-temperature alloy steel through dynamic matching of multi-stage surface treatment and work hardening, thereby meeting the stringent material performance requirements of clamp components under complex working conditions. Summary of the Invention

[0006] This invention achieves synergistic optimization of grain refinement and surface integrity by using a phased film treatment and thermomechanical processing in synergistic control. The two surface treatments are respectively matched to the lubrication and anti-adhesion requirements of the roughing and finishing stages. Combined with online annealing to eliminate work hardening, the invention also achieves synergistic optimization of grain refinement and surface integrity.

[0007] This invention provides a method for preparing high-temperature alloy steel for clamps, the method specifically including the following steps: S1. The high-temperature alloy steel substrate is dried after undergoing a single coating treatment. S2. The high-temperature alloy steel substrate that has undergone one coating treatment and drying in step S1 is subjected to rough drawing treatment in sequence. S3. Online bright annealing treatment; S4. Polishing process yields a semi-finished product; S5. The semi-finished product obtained in step S4 is subjected to a second coating treatment and then dried. S6, Surface oxalic acid plating treatment; S7. Finally, after drawing, high-temperature alloy steel for clamps is obtained.

[0008] Compared with existing technologies, this invention utilizes a phased coating process and thermomechanical processing in synergistic control. Building upon the grain refinement achieved through solution heat treatment, the initial coating process combined with rough drawing and online annealing effectively eliminates work hardening while maintaining dislocation strengthening. The secondary coating process and the final drawing process synergistically optimize surface density. This process enables the material to possess high strength, high elongation, and uniform hardness distribution at high temperatures, overcoming the inverse relationship between strength and plasticity in traditional processes. This significantly improves the creep resistance and service life of clamps under extreme operating conditions.

[0009] In one possible implementation, in step S1, the raw material of the high-temperature alloy steel for the clamp is composed of the following components by mass percentage: C: ≤0.08%, Si: ≤1.00%, Mn: ≤2.00%, P: ≤0.03%, S: ≤0.02%, Cr: 13.50-16.00%, Ni: 24.00-27.00%, Mo: 1.00-1.50%, Ti: 1.90-2.35%, Al: ≤0.35%, V: 0.10-0.50%, B: 0.001-0.01%, with the balance being Fe and unavoidable impurities.

[0010] Compared with existing technologies, this invention achieves multiphase strengthening synergy through precise control of alloy element ratios. The high-proportion composite addition of Cr, Ni, and Mo constructs a high-temperature oxidation corrosion barrier and stabilizes the austenite matrix. The synergistic precipitation strengthening of Ti and V effectively suppresses grain boundary slip and dislocation climb, significantly improving creep resistance. The trace introduction of B strengthens grain boundary bonding, and combined with low C and ultra-low P and S content control, it reduces the risk of intergranular segregation while maintaining the material's high-temperature toughness. The limited constraint of Al and Si elements avoids the formation of large inclusions while retaining solid solution strengthening potential. This compositional system enables the alloy to form a dense passivation film and a nanoscale precipitate composite structure at extreme temperatures, achieving a balance of high strength, excellent ductility, and hardness stability.

[0011] In one possible implementation, the specific steps of the first coating treatment in step S1 are as follows: first, immerse the high-temperature alloy steel substrate in a coating solution with a temperature of 25°C and a concentration of 1.08-1.18 mol / L for 2-6 minutes, and then dry it in an oven with a temperature of 125-155°C for 20-40 minutes.

[0012] In one possible implementation, the parameters for the coarse extraction process in step S2 are as follows: the area reduction rate is 10-15%.

[0013] In one possible implementation, in step S3, the online bright annealing process is carried out under a protective atmosphere, and the parameters are as follows: annealing temperature is 1050℃, and annealing speed is 3-9m / min.

[0014] Compared with existing technologies, this invention constructs a deformation-recrystallization synergistic control mechanism by dynamically matching the roughing reduction rate (10-15%) with online annealing parameters: Appropriate reduction in surface area induces dislocation entanglement to form a substructure strengthening framework, simultaneously triggering dynamic recovery to release local stress concentration; the annealing temperature of 1050℃ under a protective atmosphere precisely matches the alloy's recrystallization critical point, combined with a linear velocity control of 3-9 m / min to achieve a rate balance between dislocation rearrangement and grain boundary migration, promoting incomplete recrystallization in the work-hardened zone, forming a gradient structure with high dislocation density grains and nano-precipitates. This process eliminates the internal stress of roughing while retaining the deformation strengthening effect, and the surface oxide layer is simultaneously reduced during annealing, providing a high-cleanliness, low-residual-stress semi-finished matrix for subsequent finishing, significantly improving the material's strength-ductility product and work-hardening potential.

[0015] In one possible implementation, the protective atmosphere is a mixture of N2 and H2 gases, with a flow rate of 1.2 ± 0.5 m³ / h and a volume ratio of 1:3.

[0016] Compared with existing technologies, this invention constructs an adaptive reducing protection system using a N2-H2 mixed gas (1:3 volume ratio) and dynamic flow control (1.2±0.5 m³ / h). H2 preferentially reduces residual oxides on the surface after rough drawing, simultaneously suppressing the high-temperature volatilization of alloying elements. The N2 matrix atmosphere reduces oxygen partial pressure through dynamic displacement, blocking the tendency for grain boundary oxidation embrittlement. The two-phase gas forms a gradient concentration interface during turbulent transport, enabling the material surface to simultaneously undergo oxide stripping and atomic hydrogen permeation passivation during annealing. This eliminates bright spot defects caused by free carbon segregation on the surface and promotes dislocation rearrangement efficiency through hydrogen-induced vacancy migration, ultimately obtaining a bright surface without oxide scale and with pure grain boundaries. This provides a low-friction coefficient active interface for subsequent precision drawing and enhances the material's resistance to hydrogen-induced cracking.

[0017] In one possible implementation, the specific steps of drying after secondary film treatment in step S5 are as follows: first, immerse the semi-finished product in a film solution with a temperature of 25°C and a concentration of 1.08-1.18 mol / L for 2-6 minutes, and then dry it in an oven with a temperature of 125-155°C for 20-40 minutes.

[0018] In one possible implementation, the parameters for the drawing process in step S7 are as follows: the reduction rate is 2-5%.

[0019] Compared with existing technologies, this invention sets an extremely low area reduction rate of 2% in the final drawing stage, forming a deformation-lubrication synergistic control mechanism with secondary film treatment: the area reduction precisely matches the load-bearing limit of the surface composite coating, while controlling the dislocation slip path at the nanoscale, it forces the grains to extend directionally along the tensile stress direction, forming a highly oriented submicron-level fibrous structure, so that the clamp surface forms a dense textured reinforcement layer, achieving a cross-scale synergistic improvement in stress relaxation resistance and fatigue life while maintaining ultra-precise dimensional tolerances. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0021] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0023] Example 1 This embodiment provides a high-temperature alloy steel for clamps, which is prepared by the following method: S1. The raw material of the high-temperature alloy steel for clamps is composed of the following components by mass percentage: C: 0.03%, Si: 0.65%, Mn: 1.25%, P: 0.01%, S: 0.01%, Cr: 13.50%, Ni: 24.00%, Mo: 1.00%, Ti: 1.90%, Al: 0.35%, V: 0.10%, B: 0.001%, with the balance being Fe and unavoidable impurities; S2. First, immerse the high-temperature alloy steel substrate obtained in step S2 in a film solution with a temperature of 25°C and a concentration of 1.08 mol / L for 2 minutes, and then dry it in an oven with a temperature of 125°C for 20 minutes. S3. The high-temperature alloy steel that has undergone one coating treatment and drying in step S2 is subjected to rough drawing and online bright annealing, followed by polishing to obtain a semi-finished product. The parameters for rough drawing are as follows: surface area reduction rate 10-15%; the online bright annealing is carried out under a protective atmosphere with the following parameters: annealing temperature 1050℃, annealing speed 3m / min; the protective atmosphere is a mixture of N2 and H2 gas, and the flow rate is 1.2±0.5m³ / min. 3 / h, and the volume ratio is 1:3; S4. The semi-finished product obtained in step S3 is first immersed in a film solution with a temperature of 25℃ and a concentration of 1.08mol / L for 2 minutes, and then dried in an oven with a temperature of 125℃ for 20 minutes. S5. Perform oxalic acid plating on the surface; S6. Finally, after drawing, high-temperature alloy steel for clamps is obtained. The drawing parameters are as follows: the area reduction rate is 2-5%.

[0024] Example 2 This embodiment provides a high-temperature alloy steel for clamps, which is prepared by the following method: S1. The raw material of high-temperature alloy steel for clamps is composed of the following components by mass percentage: C: 0.02%, Si: 0.65%, Mn: 1.12%, P: 0.01%, S: 0.01%, Cr: 14.5%, Ni: 25%, Mo: 1.1%, Ti: 1.95%, Al: 0.21%, V: 0.2%, B: 0.002%, with the balance being Fe and unavoidable impurities.

[0025] S2. First, immerse the high-temperature alloy steel substrate obtained in step S1 in a film solution at a temperature of 25°C and a concentration of 1.1 mol / L for 3 minutes, and then dry it in an oven at a temperature of 130°C for 25 minutes. S3. The high-temperature alloy steel that has undergone a single coating treatment and drying in step S2 is subjected to rough drawing and online bright annealing treatment in sequence, and then polished to obtain a semi-finished product. The parameters of the rough drawing treatment are as follows: the surface area reduction rate is 12%; the online bright annealing treatment is carried out under a protective atmosphere, and the parameters are as follows: the annealing temperature is 1050℃, the annealing speed is 4m / min; the protective atmosphere is a mixture of N2 and H2 gas, the flow rate is 1.2±0.5m / h, and the volume ratio is 1:3. S4. The semi-finished product obtained in step S3 is first immersed in a film solution with a temperature of 25℃ and a concentration of 1.1mol / L for 3 minutes, and then dried in an oven with a temperature of 130℃ for 25 minutes. S5. Perform oxalic acid plating on the surface; S6. Finally, after drawing, high-temperature alloy steel for clamps is obtained. The drawing parameters are as follows: the area reduction rate is 2-5%.

[0026] Example 3 This embodiment provides a high-temperature alloy steel for clamps, which is prepared by the following method: S1. The raw material of high-temperature alloy steel for clamps is composed of the following components by mass percentage: C: 0.06%, Si: 0.95%, Mn: 1.9%, P: 0.03%, S: 0.02%, Cr: 15%, Ni: 25%, Mo: 1.1%, Ti: 2.2%, Al: 0.35%, V: 0.3%, B: 0.004%, with the balance being Fe and unavoidable impurities; S2. First, immerse the high-temperature alloy steel substrate obtained in step S1 in a film solution at a temperature of 25°C and a concentration of 1.13 mol / L for 4 min, and then dry it in an oven at a temperature of 135°C for 30 min. S3. The high-temperature alloy steel that has undergone one film treatment and drying in step S2 is subjected to rough drawing and online bright annealing treatment in sequence, and then polished to obtain a semi-finished product. The parameters of the rough drawing treatment are as follows: the surface reduction rate is 13%; the online bright annealing treatment is carried out in a protective atmosphere, and the parameters are as follows: the annealing temperature is 1050℃, the annealing speed is 6m / min; the protective atmosphere is a mixture of N2 and H2 gas, the flow rate is 1.2±0.5m / h, and the volume ratio is 1:3. S4. The semi-finished product obtained in step S3 is first immersed in a film solution with a temperature of 25℃ and a concentration of 1.13mol / L for 4 minutes, and then dried in an oven with a temperature of 135℃ for 30 minutes. S5, Surface oxalic acid plating treatment; S6. Finally, after drawing, high-temperature alloy steel for clamps is obtained. The drawing parameters are as follows: the area reduction rate is 2-5%.

[0027] Example 4 This embodiment provides a high-temperature alloy steel for clamps, which is prepared by the following method: S1. The raw material of high-temperature alloy steel for clamps is composed of the following components by mass percentage: C: 0.08%, Si: 0.95%, Mn: 1.5%, P: 0.02%, S: 0.02%, Cr: 15.5%, Ni: 26.5%, Mo: 1.40%, Ti: 2.25%, Al: 0.25%, V: 0.10%, B: 0.008%, with the balance being Fe and unavoidable impurities. S2. First, immerse the high-temperature alloy steel substrate obtained in step S1 in a film solution with a temperature of 25°C and a concentration of 1.15L for 5 minutes, and then dry it in an oven with a temperature of 145°C for 35 minutes. S3. The high-temperature alloy steel substrate that has undergone one film treatment and drying in step S2 is subjected to rough drawing and online bright annealing treatment in sequence, and then polished to obtain a semi-finished product. The parameters of the rough drawing treatment are as follows: the surface area reduction rate is 14%; the online bright annealing treatment is carried out in a protective atmosphere, and the parameters are as follows: the annealing temperature is 1050℃, the annealing speed is 8m / min; the protective atmosphere is a mixture of N2 and H2 gas, the flow rate is 1.2±0.5m / h, and the volume ratio is 1:3. S4. The semi-finished product obtained in step S3 is first immersed in a film solution with a temperature of 25℃ and a concentration of 1.13mol / L for 5 minutes, and then dried in an oven with a temperature of 145℃ for 35 minutes. S5. Perform oxalic acid plating on the surface; S6. Finally, after drawing, high-temperature alloy steel for clamps is obtained. The drawing parameters are as follows: the area reduction rate is 2-5%.

[0028] Example 5 This embodiment provides a high-temperature alloy steel for clamps, which is prepared by the following method: S1. The raw material of high-temperature alloy steel for clamps consists of the following components by mass percentage: C: 0.08%, Si: 0.65%, Mn: 1.50%, P: 0.03%, S: 0.02%, Cr: 16.00%, Ni: 27.00%, Mo: 1.50%, Ti: 2.35%, Al: 0.25%, V: 0.35%, B: 0.008%, with the balance being Fe and unavoidable impurities. S2. First, immerse the high-temperature alloy steel substrate obtained in step S1 in a film solution at a temperature of 25°C and a concentration of 1.18 mol / L for 6 minutes, and then dry it in an oven at a temperature of 125-155°C for 40 minutes. S3. The high-temperature alloy steel that has undergone a single coating treatment and drying in step S2 is subjected to rough drawing and online bright annealing treatment in sequence, and then polished to obtain a semi-finished product. The parameters of the rough drawing treatment are as follows: the surface area reduction rate is 15%; the online bright annealing treatment is carried out under a protective atmosphere, and the parameters are as follows: the annealing temperature is 1050℃, the annealing speed is 9m / min; the protective atmosphere is a mixture of N2 and H2 gas, the flow rate is 1.2±0.5m / h, and the volume ratio is 1:3. S4. The semi-finished product obtained in step S3 is first immersed in a film solution with a temperature of 25℃ and a concentration of 1.18mol / L for 6 minutes, and then dried in an oven with a temperature of 155℃ for 40 minutes.

[0029] S5, Surface treated with oxalic acid.

[0030] S6. Finally, after drawing, high-temperature alloy steel for clamps is obtained. The drawing parameters are as follows: the area reduction rate is 2-5%.

[0031] The inventors conducted performance tests on the high-temperature alloy steel for clamps prepared in Examples 1-5, and the test results are as follows: The tensile strength of the high-temperature alloy steel used for the clamp in Example 1 is 555 / mm². 2 It has an elongation of 40% and a glossy surface, free from defects such as black or yellow lines, scratches, cracks, folds, and peeling.

[0032] The tensile strength of the high-temperature alloy steel used for the clamps in Example 2 is 550 mm². 2 It has an elongation of 40% and a glossy surface, free from defects such as black or yellow lines, scratches, cracks, folds, and peeling.

[0033] The tensile strength of the high-temperature alloy steel used for the clamp in Example 3 is 600 mm². 2 It has an elongation of 38% and a glossy surface, free from defects such as black or yellow lines, scratches, cracks, folds, and peeling.

[0034] The tensile strength of the high-temperature alloy steel used for the clamps in Example 4 is 578 mm. 2 It has an elongation of 42% and a glossy surface, free from defects such as black or yellow lines, scratches, cracks, folds, and peeling.

[0035] The tensile strength of the high-temperature alloy steel used for the clamps in Example 5 is 582 / mm². 2 It has an elongation of 40% and a glossy surface, free from defects such as black or yellow lines, scratches, cracks, folds, and peeling.

[0036] Comparative Example 1 This comparative example provides a high-temperature alloy steel for clamps. The only difference from Example 1 is that step S2 is not performed in the preparation process of this comparative example. Everything else is the same as in Example 1, and will not be repeated here.

[0037] Testing revealed that the tensile strength of this comparative example is 387 / mm². 2 It has an elongation of 50% and a glossy surface, but slight cracks are present.

[0038] Comparative Example 2 This comparative example provides a high-temperature alloy steel for clamps. The only difference from Example 1 is that the secondary coating treatment is not performed in step S4 of this comparative example. The rest is the same as in Example 1, and will not be repeated here.

[0039] Testing revealed that the tensile strength of this comparative example is 344 / mm². 2 The elongation rate is 48%, the surface is relatively glossy, and fine cracks appear.

[0040] The inventors analyzed that the performance advantage of Example 1 stems from the deep synergy between staged film treatment and thermomechanical processing: the primary film treatment removes the oxide layer through oxalic acid etching and embeds a molybdenum disulfide lubricating layer, forming a uniform dislocation substructure during rough drawing, combined with online annealing to eliminate stress and retain deformation strengthening; the secondary film treatment repairs annealed grain boundary defects and constructs a nano-lubricating texture, guiding the orderly slip of dislocations during final drawing and activating twinning strengthening. In contrast, the comparative examples, due to the lack of staged surface modification, resulted in microcracks caused by oxide layer embedding during rough drawing (Comparative Example 1), or insufficient lubrication during final drawing induced grain boundary slip and stress concentration (Comparative Example 2).

[0041] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for preparing high-temperature alloy steel for clamps, characterized in that, The preparation method specifically includes the following steps: S1. The high-temperature alloy steel substrate is dried after undergoing a single coating treatment. S2. The high-temperature alloy steel substrate that has undergone one coating treatment and drying in step S1 is subjected to rough drawing treatment in sequence. S3. Online bright annealing treatment; S4. Polishing process yields a semi-finished product; S5. The semi-finished product obtained in step S4 is subjected to a second coating treatment and then dried. S6, Surface oxalic acid plating treatment; S7. Finally, after drawing, high-temperature alloy steel for clamps is obtained.

2. The preparation method according to claim 1, characterized in that, In step S1, the raw material of the high-temperature alloy steel for the clamp is composed of the following components by mass percentage: C: ≤0.08%, Si: ≤1.00%, Mn: ≤2.00%, P: ≤0.03%, S: ≤0.02%, Cr: 13.50-16.00%, Ni: 24.00-27.00%, Mo: 1.00-1.50%, Ti: 1.90-2.35%, Al: ≤0.35%, V: 0.10-0.50%, B: 0.001-0.01%, with the balance being Fe and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that, In step S1, the specific steps of the first coating treatment are as follows: first, immerse the high-temperature alloy steel substrate in a coating solution with a temperature of 25°C and a concentration of 1.08-1.18 mol / L for 2-6 minutes, and then dry it in an oven with a temperature of 125-155°C for 20-40 minutes.

4. The preparation method according to claim 1, characterized in that, In step S2, the parameters for the coarse extraction process are as follows: the area reduction rate is 10-15%.

5. The preparation method according to claim 1, characterized in that, In step S3, the online bright annealing process is carried out under a protective atmosphere, and the parameters are as follows: annealing temperature is 1050℃, and annealing speed is 3-9m / min.

6. The preparation method according to claim 5, characterized in that, The protective atmosphere is a mixture of N2 and H2 gases, with a flow rate of 1.2 ± 0.5 m³ / h and a volume ratio of 1:

3.

7. The preparation method according to claim 1, characterized in that, In step S5, the specific steps for drying after secondary film treatment are as follows: First, immerse the semi-finished product in a film solution with a temperature of 25℃ and a concentration of 1.08-1.18mol / L for 2-6 minutes, and then dry it in an oven with a temperature of 125-155℃ for 20-40 minutes.

8. The preparation method according to claim 1, characterized in that, In step S7, the parameters for the drawing process are as follows: the area reduction rate is 2-5%.