A construction process for mining anchor bolts

Abstract

This invention discloses a construction process for mining anchor bolts, relating to the field of mining anchor bolt construction technology, including the following steps: raw material preparation and pretreatment; preparation of functionalized rolling penetrant; heating and roughing / intermediate rolling; online reactive finishing rolling; cooling and shaping; and post-treatment. This invention constructs a gradient composite modified layer on the anchor bolt surface through online reactive rolling, achieving interfacial chemical bonding and grain boundary indentation of nano-functional units. This not only reduces installation frictional resistance but also enhances the material's corrosion resistance and hydrogen embrittlement resistance through a dense shielding network and self-healing mechanism, ensuring the reliability of support in complex environments.

Description

Technical Field

[0001] This invention relates to the field of mining anchor bolt construction technology, and specifically to a mining anchor bolt construction process. Background Technology

[0002] In deep mining operations, underground tunnels often face high ground stress and complex corrosive environments. Currently, mining anchor bolts, as the core component of the support system, frequently exhibit insufficient durability in practical applications. Existing anchor bolts are prone to rapid oxidation and erosion after contact with damp or acidic moisture underground, causing the support strength to continuously decrease with the extension of service time.

[0003] Furthermore, in actual construction and installation, the significant frictional resistance between the anchor bolt surface and the borehole wall, as well as the support material, often leads to difficulties in the screwing-in process, increasing energy consumption and wear on construction equipment. More seriously, existing anchor bolts are highly susceptible to brittle fracture under the combined effects of harsh mechanical and chemical media. This environmentally induced performance degradation makes the reliability of the tunnel support system unpredictable, increasing uncertainties and risks in safe production. Current technologies cannot effectively mitigate the impact of these negative phenomena on support quality. Summary of the Invention

[0004] The purpose of this invention is to provide a construction process for mining anchor bolts, which solves the problems existing in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides a construction process for mining anchor bolts, comprising the following steps:

[0006] S1. Raw material preparation and pretreatment: Select high-strength alloy steel continuous casting billet as the base material, and perform shot blasting on the surface of the billet to remove oxide scale and surface oil, thereby exposing the metal matrix.

[0007] S2. Preparation of functionalized rolling penetrant: A modified fluid for high-temperature rolling environment is prepared. This step includes four sub-steps: carrier activation, functional loading, surface grafting and dispersion compounding. Graphene oxide nanocomposite loaded with rare earth elements and corrosion inhibitors and containing phosphate ester bonding groups on the surface is obtained by chemical grafting and dispersed in high-temperature resistant base oil.

[0008] S3, Heating and Roughing and Intermediate Rolling: The steel billet after S1 treatment is sent into a heating furnace, heated to the austenitizing temperature range and held at that temperature, and then subjected to multiple passes of roughing and intermediate rolling to process the steel billet into intermediate billets with a certain cross-sectional size.

[0009] S4. Online reactive finishing rolling: In the pass before the intermediate billet enters the finishing mill to form the anchor bolt thread shape, the functionalized rolling penetrant prepared in S2 is uniformly sprayed onto the surface of the red-hot intermediate billet using a high-pressure spraying system; under the rolling contact pressure of the finishing mill pass and the residual heat of the billet itself, the active groups in the functionalized rolling penetrant undergo an in-situ chemical reaction with the steel matrix to generate a chemically bonded interface layer, and press the nano-functional units into the grain boundaries of the anchor bolt surface layer;

[0010] S5. Cooling, Shaping and Post-processing: After rolling, the anchor rods enter the controlled cooling section to control the cooling rate to fix the surface modified structure. Then, they are cut to length, straightened and packaged.

[0011] Preferably, in step S2, the preparation of the functionalized rolling penetrant specifically includes the following sub-steps:

[0012] (1) Activation of the carrier: Graphene oxide powder is dispersed in an aqueous ethanol solution and ultrasonically dispersed at 300-500W for 30-60 minutes to form a uniform suspension; then silane coupling agent is added dropwise under stirring, the temperature is raised to 60-80℃ and refluxed for 4-8 hours. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol and vacuum dried at 60-80℃ to obtain aminated graphene oxide.

[0013] (2) Functional loading: The aminated graphene oxide obtained in step (1) is redispersed in deionized water, and the corrosion inhibitor benzotriazole and rare earth cerium salt are added in sequence. The pH value is adjusted to 4-6, and the reaction is carried out for 12-24 hours under constant temperature water bath and magnetic stirring at 25-40℃. The reaction product is separated by centrifugation and dried to obtain graphene oxide composite loaded with cerium-benzotriazole.

[0014] (3) Surface grafting: The product of step (2) is dispersed in an organic solvent, and long-chain alkyl acid phosphate and p-toluenesulfonic acid catalyst are added. The temperature is raised to 90-110℃ under a nitrogen protective atmosphere and the grafting reaction is carried out for 3-6 hours. The reaction product is filtered, washed and freeze-dried to obtain modified powder with phosphate groups grafted on the surface.

[0015] (4) Dispersion and compounding: Weigh high-temperature resistant modified polyester oil as base oil, add the modified powder and hexagonal boron nitride nanosheets prepared in step (3) according to the mass ratio, place the mixture in a high-shear emulsifier, mix at a speed of 3000-5000 rpm for 15-30 minutes under high shear, and then let it stand in a vacuum environment to degas, thus obtaining the functionalized rolled penetrant.

[0016] Preferably, in step (1), the silane coupling agent is 3-aminopropyltriethoxysilane, and the amount added is 50%-100% of the mass of graphene oxide; the volume ratio of ethanol to water in the ethanol aqueous solution is (3:1)-(5:1).

[0017] Preferably, in step (2), the rare earth cerium salt is cerium nitrate (III) or cerium chloride (III), and the molar ratio of the corrosion inhibitor benzotriazole to the rare earth cerium salt is (1:1)-(2:1); the temperature of the coordination adsorption reaction is controlled at 25-40℃.

[0018] Preferably, in step (4), the component mass percentage of the functionalized rolling penetrant is: 0.5%-2.0% modified powder, 1.0%-3.0% hexagonal boron nitride nanosheets, and the remainder is high-temperature resistant modified polyester oil; the average diameter of the hexagonal boron nitride nanosheets is 100-500 nm.

[0019] Preferably, in step S3, the austenitizing temperature range is 1100-1200℃, and the holding time is 1.5-2.5 hours to ensure the uniformity of the internal structure of the billet; the total elongation coefficient of the rough rolling and intermediate rolling is controlled between 6 and 10.

[0020] Preferably, in step S4, the specific process parameters are as follows:

[0021] (1) Spraying conditions: The functionalized rolling penetrant is sprayed out through the annular nozzle group, the spraying pressure is 5-15MPa, and the nozzle is 100-200mm away from the surface of the billet;

[0022] (2) Reaction temperature: The surface temperature of the intermediate billet is controlled at 800-950℃ during spraying;

[0023] (3) Rolling deformation: The single-pass reduction rate of the finishing mill is 15%-25%. Under the rolling contact pressure and high temperature environment, the phosphate ester group reacts with the iron matrix to generate iron phosphate ceramic phase and reduces graphene oxide.

[0024] Preferably, in step S5, the cooling is controlled by air mist cooling, the cooling rate is controlled at 5-15℃ / s, the final cooling temperature is 400-500℃, and then the cooling is carried out on a cooling bed to room temperature, so as to obtain a ferrite plus pearlite structure in the core of the anchor rod and a fine grain strengthening layer on the surface.

[0025] Preferably, under the high temperature and high pressure of step S4, the functionalized rolling penetrant forms a gradient composite modified layer with a thickness of 10-50 μm on the surface of the anchor rod. The modified layer consists of a lubricating layer rich in hexagonal boron nitride nanosheets, a dense barrier layer containing graphene and ceramic phase, and a diffusion layer that is metallurgically bonded to the matrix from the outside to the inside.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] By introducing a specific functionalized modified layer during the rolling process, the anchor bolt is endowed with excellent interfacial bonding performance. As the modified material achieves tight integration with the matrix during processing, the protective layer can resist high-intensity mechanical friction and shearing during construction. This not only improves the smoothness of the anchor bolt during installation and reduces construction resistance, but also ensures that the protective unit can maintain structural integrity under harsh physical environments, thereby ensuring that the protective layer continues to function throughout the entire service life.

[0028] By constructing a dense gradient structure on the surface, the material's ability to shield against environmental media is effectively improved. The self-healing mechanism inside the modified layer can dynamically compensate for microscopic defects, effectively cutting off the contact path between corrosive media and the substrate. This allows the material to maintain the structural stability of the matrix even when it is in a humid or acidic environment for a long time, effectively reducing the performance loss induced by environmental factors and enhancing the reliability of the support components under complex working conditions.

[0029] By optimizing the microstructure of the material surface, the service performance of the component under complex stress environments was improved. The gradient distribution of functional units can disperse internal stress concentration and play a strengthening role at grain boundaries, thereby enhancing the material's resistance to environmentally sensitive fractures. By refining the surface grains and constructing a multi-layer barrier system, not only was the load-bearing capacity of the threaded section improved, but also the anchor bolts were ensured to have better dimensional stability when subjected to high preload, providing a guarantee for the long-term safe support of deep mines. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a trend analysis diagram showing the correlation between corrosion resistance and wear resistance of the present invention. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Pre-mechanism and model building

[0034] Before conducting formal verification of the mining anchor bolt construction process, this invention pre-established a dynamic correlation model between the tribochemical reaction efficiency and rolling thermodynamic parameters to determine the optimal spraying and rolling window in step S4. Specifically, the model was established on a simulated hot rolling mill using an infrared thermal imager and a rapid-response force sensor to monitor in real-time the wetting and spreading behavior and chemical bonding conversion rate of the functionalized rolling penetrant on the steel surface under different temperatures (700-1100℃) and contact pressures (5-25MPa). Regression analysis data showed that the bonding reaction rate constant between the phosphate groups in the functionalized rolling penetrant and the iron matrix... With temperature and contact pressure Following the modified Arrhenius equation model:

[0035]

[0036] Pre-exponential factors;

[0037] The pressure sensitivity index is fitted to 0.35 in this model;

[0038] It is the activation energy of the reaction;

[0039] It is the gas constant;

[0040] However, at temperatures above 1000°C, the graphene oxide support undergoes premature thermal decomposition and carbonization, leading to functional load failure. At temperatures below 750°C, the activation energy of the reaction is insufficient, and the interfacial bonding strength decreases significantly. Based on the above correlation model, this invention sets the surface temperature of the intermediate billet at 800-950°C as the effective process window for online reactive finishing rolling. Within this range, the contact pressure-induced tribochemical reaction and the thermally activated diffusion process reach the optimal synergistic state, ensuring both the formation of interfacial chemical bonds and the effective indentation of nanofunctional units into grain boundaries.

[0041] Example 1

[0042] This embodiment provides a preferred implementation of a mining anchor bolt construction process, aiming to solve the technical problems of stress corrosion cracking and hydrogen embrittlement of anchor bolts in deep mines under high ground stress and corrosive environments. In step S1, raw material preparation and pretreatment, high-strength alloy steel continuous casting billets are selected as the substrate. The surface of the billets is shot-blasted to remove oxide scale and surface oil, exposing a highly active metal matrix and providing a clean reactive interface for subsequent chemical bonding. In step S2, the preparation parameters of the functionalized rolling penetrant are strictly controlled: in the carrier activation stage, graphene oxide powder is dispersed in an ethanol-water volume ratio of 3: In an ethanol-water solution, the mixture was sonicated at 300W for 30 minutes, and 50% (w / w) of 3-aminopropyltriethoxysilane was added. The mixture was then refluxed at 60°C for 4 hours to obtain aminated graphene oxide. In the functional loading stage, the pH was adjusted to 4, and benzotriazole and cerium(III) nitrate (molar ratio 1:1) were loaded onto a support under magnetic stirring at 25°C. After reacting for 12 hours, the mixture was filtered, washed three times with deionized water, and dried to constant weight in a vacuum drying oven at 60°C. In the surface grafting stage, phosphate groups were grafted under nitrogen protection at 90°C, specifically monododecyl phosphate, to ensure the grafted segments had suitable... The product was subjected to a flexible, constant-temperature reaction for 4 hours, followed by centrifugation to disperse it in a base oil. In the dispersion and compounding stage, 0.5% modified powder and 1.0% hexagonal boron nitride nanosheets (average diameter 100 nm) were dispersed in the base oil, specifically ISO VG32 grade trimethylpropane saturated ester. In step S3, the heating temperature was controlled at 1100℃ and held for 1.5 hours, resulting in a total elongation coefficient of 6 during roughing and intermediate rolling. In the crucial step S4, online reactive finishing rolling, a 5 MPa pressure spray system was used to spray the functionalized rolling penetrant onto the surface of the billet at 800℃, followed by a 15... The single-pass reduction rate is % for finishing rolling; during this process, the phosphate groups in the functionalized rolling penetrant undergo in-situ chemical reaction with the iron matrix under rolling contact pressure and thermal excitation, constructing a chemically bonded interface layer, and forcibly pressing the nano-functional units into the surface grain boundaries to achieve grain boundary strengthening; finally, in step S5, air mist cooling is used at a speed of 5℃ / s, and the final cooling temperature is 400℃; although the modified layer of the anchor prepared in this embodiment is relatively thin (about 10μm), the interfacial bonding force is initially manifested due to chemical bonding. Compared with ordinary anchors, its initial corrosion time in a humid environment is significantly delayed, verifying the feasibility of the process route.

[0043] Example 2

[0044] This embodiment is a further refinement and optimization of the core component preparation steps in Example 1, aiming to improve macroscopic performance by adjusting the microscopic chemical structure; in the preparation of the functionalized rolling penetrant in step S2, the parameters are set as follows:

[0045] First, in the (1) carrier activation step, an ethanol to water volume ratio of 4:1 was used, and the mixture was sonicated at 400W for 45 minutes. In particular, regarding the amount of silane coupling agent added, it is preferred to add 75% by mass of 3-aminopropyltriethoxysilane and react at 70°C for 6 hours. The reason for choosing 75% as the preferred constant is that, according to experimental comparison, if the amount added is only 50%, the degree of amylation on the surface of graphene oxide is insufficient and there are fewer active sites. If the amount added reaches 100%, the excess silane is prone to self-condensation in the system, resulting in the carrier agglomeration and difficulty in dispersion. The amount added at 75% can balance the grafting rate and dispersibility. X-ray photoelectron spectroscopy analysis shows that the N element content reaches the peak at this ratio and there is no obvious Si-O-Si aggregation peak, which confirms that sufficient and uniformly distributed highly active amino sites are introduced on the surface of graphene oxide through silanization treatment.

[0046] Secondly, in the (2) functional loading stage, benzotriazole and cerium(III) chloride were mixed at a molar ratio of 1.5:1, the pH was adjusted to 5, and the mixture was reacted at 30°C for 18 hours. The molar ratio of 1.5:1 was selected to optimize the corrosion inhibition synergistic effect: at this ratio, rare earth cerium ions can form the most stable coordination structure with benzotriazole, which avoids the problem of insufficient coverage of corrosion inhibitor at a 1:1 ratio and also prevents the unstable loading caused by excessive steric hindrance at a 2:1 ratio. Thus, the corrosion inhibitor is firmly anchored by the coordination effect of rare earth ions, and an efficient self-healing reservoir is constructed.

[0047] Furthermore, in the (3) surface grafting stage, a long-chain phosphate ester is introduced at 100°C for 4.5 hours, specifically bis(2-ethylhexyl) phosphate ester, to enhance its solubility in non-polar oil, and to impart dispersion stability of the particles in the oil phase and high-temperature reactivity with the steel matrix; the product obtained here is uniformly referred to as modified powder in subsequent steps.

[0048] Finally, in the dispersion and compounding stage (4), high-temperature resistant modified polyester oil was selected as the base oil, specifically pentaerythritol ester with a kinematic viscosity of 46 mm² / s and a flash point >280℃. Within the specified ratio range, in this embodiment, 1.2% modified powder and 2.0% hexagonal boron nitride nanosheets (average sheet diameter of 300 nm) were mixed at 4000 rpm for 20 minutes. The modified powder addition of 1.2% was selected because a continuous chemical bonded interface layer could not be formed when it was less than 0.5%, while a value higher than 2.0% would significantly increase the fluid viscosity and affect the spray atomization effect. The 2.0% hexagonal boron nitride nanosheets ensured lubricity while avoiding agglomeration and sedimentation caused by excessive solid particles.

[0049] In subsequent processes, the heating temperature is 1150℃, the finishing rolling spray pressure is 10MPa, the billet surface temperature is 875℃, and the single-pass reduction rate is 20%. Under these optimized parameters, the functionalized rolling penetrant penetrates deeper into the microscopic defects of the steel matrix surface, the phosphate ester groups react more fully with the iron matrix, and the generated iron phosphate ceramic phase significantly increases the surface hardness. In this embodiment, a gradient composite modified layer with a thickness of about 30μm is finally formed. The lubricating layer rich in hexagonal boron nitride nanosheets reduces the screwing resistance during anchor installation, and the dense barrier layer containing graphene and ceramic phase effectively blocks the penetration of corrosive media, exhibiting excellent comprehensive performance. It is the preferred solution that balances cost and performance.

[0050] Example 3

[0051] This embodiment aims to explore the performance of the process under the upper limit parameters, especially for the extreme working conditions of highly corrosive mining environments. In step S2, a functionalized rolling penetrant is prepared using the upper limit parameters: 100% of 3-aminopropyltriethoxysilane is added, the molar ratio of benzotriazole to rare earth cerium salt is 2:1, the amount of modified powder is 2.0%, and the amount of hexagonal boron nitride nanosheets is 3.0% (average sheet diameter is 500 nm). In step S3, the heating temperature is increased to 1200℃ and held for 2.5 hours, and the total elongation reaches 10 to ensure complete austenitization and uniformity of the matrix structure. In the critical step S4, the process parameters are pushed to the limit: the injection pressure is set to 15 MPa. With a nozzle distance of 200 mm, the surface temperature of the intermediate billet is controlled at 950 °C, and the single-pass reduction rate of the finishing mill is 25%. Under these extreme high-temperature and high-pressure conditions, the graphene oxide in the functionalized rolling permeating agent undergoes a high degree of in-situ reduction, repairing the conjugated structure and forming a robust shielding network together with the large amount of generated iron phosphate ceramic phase. The anchor bolt prepared in this embodiment has a surface gradient composite modified layer thickness of approximately 50 μm. The high content of rare earth elements and corrosion inhibitors endows the modified layer with extremely strong self-healing ability, while the nano-functional units pressed into the grain boundaries under high pressure significantly refine the surface grains. This allows the anchor bolt to maintain high strength while exhibiting excellent resistance to hydrogen embrittlement, making it suitable for deep well support in extremely harsh geological conditions.

[0052] Example 4

[0053] This embodiment adjusts the matching relationship between the formulation and process, focusing on achieving surface strengthening through high concentrations of modifiers at lower rolling temperatures, and emphasizing the impact of cooling processes on the microstructure. In the preparation stage, the modified powder mass percentage is set to a high limit of 2.0%, and the hexagonal boron nitride nanosheets to a low limit of 1.0%. The heating temperature is reduced to 1120℃ and held for 1.8 hours. During the finishing rolling stage, the spraying pressure is 8 MPa, the intermediate billet surface temperature is 820℃, and the single-pass reduction rate is 18%. Despite the low rolling temperature, sufficient reaction coverage is still ensured due to the high concentration of active components in the functionalized rolling penetrant. In S5, strictly controlled cooling is implemented, with the cooling rate set at 8℃ / s and the final cooling temperature at 420℃. This cooling strategy aims to avoid the formation of hard and brittle phases such as bainite or martensite through moderate cooling rate, ensuring that the core obtains a ferrite plus pearlite structure with good toughness. At the same time, a fine-grained strengthening layer is formed on the surface due to the pinning effect of nanoparticles. Although the amount of ceramic phase generated in the anchor bolt produced in this embodiment is slightly less than that in Example 3, the physical barrier performance of its surface is still excellent due to the high concentration of modified powder filling. The lower temperature reduces the oxidation of the matrix, making the interface bonding layer purer, which is suitable for rockburst mines with high toughness requirements.

[0054] Example 5

[0055] This embodiment focuses on strengthening the surface through physical and mechanical actions, reducing the amount of chemical additives, and verifying the functionality of the gradient structure. In the preparation, the amount of modified powder is reduced to 0.5%, while the amount of hexagonal boron nitride nanosheets is increased to 3.0%. The heating temperature is 1180℃, and the holding time is 2.2 hours. In the finishing rolling stage, a high-pressure injection of 14MPa is used, the surface temperature of the intermediate billet is 930℃, and the single-pass reduction rate is 24%. Using high temperature and high reduction rate, the functionalized rolling penetrant rich in hexagonal boron nitride nanosheets is forcefully pressed into the matrix. In step S5, the cooling rate is 12℃. / s, final cooling 480℃; the anchor bolt obtained in this embodiment has a clear gradient structure on its surface: the outermost layer is enriched with hexagonal boron nitride nanosheets, which gives it an extremely low coefficient of friction; the middle layer is a barrier layer composed of graphene and ceramic phases; the inner layer is a metallurgically bonded diffusion layer; this structure greatly reduces the installation torque during construction, and the surface hardness is significantly improved due to fine grain reinforcement; this embodiment shows that by adjusting the proportion of lubricating components in the formula and the rolling parameters, the functional emphasis of the modified layer can be directionally controlled to adapt to roadway scenarios that require rapid installation and construction;

[0056] The construction and application method of mine anchor bolts includes: drilling anchor bolt holes in the surrounding rock of the mine roadway; pushing the resin cartridge into the bottom of the hole; using an anchor bolt drilling machine to clamp the tail of the mine anchor bolt, rotating and stirring the resin cartridge and pushing it to the bottom of the hole; after the resin has cured, installing the tray and nut and applying pre-tightening force.

[0057] This embodiment demonstrates the application process of the mining anchor bolt prepared by the above-described process in actual construction. First, standard anchor bolt holes are drilled in the surrounding rock of the mine roadway, and resin cartridges are pushed into the bottom of the holes. Then, the tail of the mining anchor bolt prepared by this invention is clamped by an anchor bolt drilling rig and rotated and stirred for propulsion. During this process, the lubricating layer on the surface of the anchor bolt, rich in hexagonal boron nitride nanosheets, plays a key role, significantly reducing the frictional resistance between the anchor bolt, the resin cartridge, and the hole wall, making the stirring process smoother and reducing the torque consumption of the drilling rig. At the same time, the dense barrier layer composed of graphene and ceramic phases maintains the structural integrity during intense stirring and friction, without peeling off, effectively preventing the exposure of the base steel. After the resin cures, the tray and nut are installed and a preload is applied. The fine-grained reinforcing layer on the surface of the anchor bolt ensures that the threaded section does not yield under high preload, achieving a reliable support effect.

[0058] Comparative Example 1

[0059] This comparative example provides a traditional mining anchor bolt construction process; the difference from Example 2 is that: in step S2, no functionalized rolling penetrant is prepared, but ordinary industrial rolling oil is used; in step S4, only conventional cooling water spraying and finishing rolling are performed, without involving in-situ chemical reactions of active groups; the remaining heating, rolling and cooling parameters are consistent with those of Example 2; this comparative example serves as a blank control to evaluate the basic performance improvement brought about by the functionalized rolling penetrant and reactive finishing rolling process.

[0060] Comparative Example 2

[0061] This comparative example provides a modified construction process for mining anchor bolts; the difference from Example 2 is that in the preparation process of step S2, the sub-step (3) surface grafting is omitted, that is, the graphene oxide composite is not grafted with phosphate groups and is directly mixed with base oil and hexagonal boron nitride nanosheets; this means that in step S4, the key mechanism of phosphate groups forming a chemically bonded interface layer with the iron matrix is ​​missing, and only physical adsorption and mechanical interlocking are relied upon; this comparative example aims to verify the necessity of the chemically bonded interface layer for the film bonding force and wear resistance.

[0062] Comparative Example 3

[0063] This comparative example provides a modified construction process for mining anchor bolts; the difference from Example 2 is that the functional loading of step (2) is omitted in the preparation process of step S2, that is, the corrosion inhibitor benzotriazole and rare earth cerium salt are not loaded on the graphene oxide; this results in the lack of chemical corrosion inhibition and self-healing units in the final modified layer; this comparative example is used to reveal the contribution of rare earth and corrosion inhibitor components to long-term corrosion resistance.

[0064] Comparative Example 4

[0065] This comparative example provides a surface treatment process for mining anchor bolts. The difference from Example 2 is that the application of the functionalized rolling penetrant is moved from step S4 to after step S5. That is, after the anchor bolt is rolled, cooled, and restored to room temperature, the functionalized rolling penetrant is sprayed onto the surface of the anchor bolt by electrostatic spraying, followed by low-temperature drying. At this time, due to the lack of a high-temperature and high-pressure environment, in-situ chemical reaction and grain boundary indentation effect cannot occur. This comparative example is used to demonstrate the irreplaceable nature of the specific process step of online reactive finishing rolling compared to traditional cold coating technology.

[0066] Verification test

[0067] To verify the technical effect of the mining anchor bolt construction process of the present invention, performance tests were conducted on the anchor bolts prepared in Examples 1-5 and Comparative Examples 1-4 above;

[0068] Test Standards

[0069] Resistance to neutral salt spray corrosion: Following the GB / T10125 standard "Artificial Atmosphere Corrosion Test - Salt Spray Test", continuous spraying was performed at 35℃, and the time it took for red rust to appear on the sample surface was recorded.

[0070] Slow strain rate tensile (SSRT) reduction of area loss: Following GB / T15970.7 standard, tensile tests were conducted in simulated acidic mine water at pH=3 (preparation method: add 3.5wt% NaCl to deionized water and adjust the pH to 3.0±0.1 by adding sulfuric acid dropwise). By comparing the cross-sectional reduction rate with that in air, the loss rate is calculated;

[0071] Surface film adhesion: In accordance with GB / T9286 "Cross-cut test of paint and varnish film", the cross-cut test is adopted. Grade 0 means that the cut edge is completely smooth and there is no peeling.

[0072] Simulated wear rate during installation: The process of drilling the anchor rod into the rock hole and stirring the resin was simulated. A sandstone specimen with a uniaxial compressive strength of 60MPa was selected, the hole diameter was 28mm, and CK2350 fast-curing resin cartridges were used. The anchor rod was connected to a drilling machine with a torque of 400N·m, and the resin was drilled in and stirred for 30 seconds at a speed of 450r / min. The weight loss ratio of the surface modified layer before and after the test was measured, and the test was repeated 3 times and the average value was taken.

[0073] Specific testing process

[0074] All test samples were taken from anchor bolts of the same specifications (Φ20mm×2000mm) produced in the corresponding examples and comparative examples; each experiment was repeated 5 times, and the average value of the data was taken to eliminate random errors; in the SSRT test, the samples were processed into standard tensile specimens and pre-immersed in the corrosive medium for 24 hours; in addition, for the microstructure and chemical bonding mentioned in the examples, the cross-sectional morphology and elemental distribution were observed using a scanning electron microscope with energy dispersive spectroscopy to confirm the existence of gradient structure; the binding energy shift at the interface was analyzed by X-ray photoelectron spectroscopy to characterize the formation of Fe-OP chemical bonds.

[0075] Data table

[0076] Group Resistance to neutral salt spray corrosion (h) SSRT section reduction of area loss (%) Surface film adhesion strength (level) Simulated wear rate (%) Example 1 1250 12.5 0 2.1 Example 2 1860 6.8 0 1.2 Example 3 2100 4.5 0 0.8 Example 4 1650 8.2 0 1.5 Example 5 1480 9.1 0 0.9 Comparative Example 1 72 45.6 - - Comparative Example 2 650 22.4 2 15.6 Comparative Example 3 920 18.5 0 1.3 Comparative Example 4 480 28.3 3 42.5

[0077] Results Analysis Composition

[0078] As can be seen from the data in the table above and the comparative analysis, the process proposed in this invention has significant advantages in improving the overall performance of anchor bolts;

[0079] Compared with Comparative Example 1, the resistance time to neutral salt spray corrosion in Example 2 increased dramatically from 72 hours to 1860 hours. This is attributed to the dense barrier layer constructed in situ by the functionalized rolling penetrant at high temperature, which effectively cuts off the contact channel between the corrosive medium and the substrate. Compared with Comparative Example 3, the corrosion resistance time of the sample lacking rare earth and corrosion inhibitor loading decreased by nearly half. This mechanistically confirms that rare earth cerium salt and benzotriazole construct an effective chemical passivation and self-repair mechanism inside the modified layer. When microcracks are generated, the active substances can quickly migrate to the defect to form a precipitation film, which is the key to achieving long-term corrosion protection.

[0080] Compared with Comparative Example 2, if the grafting of phosphate groups is omitted, the film bonding strength deteriorates to level 2, and the installation wear rate is as high as 15.6%. This shows that simple physical adsorption cannot resist the strong shear force during construction, while the high-temperature rolling in step S4 induces the phosphate groups to undergo an in-situ chemical reaction with the iron matrix, generating a strong metallurgical bonding interface layer (Fe-OP bond), achieving atomic-level anchoring. Compared with Comparative Example 4, the wear rate of Comparative Example 4 is as high as 42.5%, further confirming the necessity of the online high-temperature pressing process. Only under high temperature and high contact pressure with severe lattice thermal vibration can the nano-functional units truly embed into the grain boundaries, rather than merely floating on the surface.

[0081] Example 3 exhibits the lowest SSRT (Sectional Slope Reduction) loss under limiting parameters, mainly due to the deep gradient structure and grain refinement effect formed under high temperature and high pressure. The dense ceramic phase barrier layer effectively blocks the penetration of hydrogen atoms, while the nanoparticles pressed into the grain boundaries act as hydrogen traps, dispersing hydrogen aggregation and thus significantly reducing hydrogen embrittlement sensitivity in acidic environments. In summary, this invention solves the industry pain points of easy peeling and poor corrosion resistance of traditional coated anchor bolts through deep coupling of chemical formulation and rolling physical field.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A process for the construction of mine bolts, characterized in that, Includes the following steps: S1. Raw material preparation and pretreatment: Select high-strength alloy steel continuous casting billet as the base material, and perform shot blasting on the surface of the billet to remove oxide scale and surface oil, thereby exposing the metal matrix. S2. Preparation of functionalized rolling penetrant: A modified fluid for high-temperature rolling environment is prepared. This step includes four sub-steps: carrier activation, functional loading, surface grafting and dispersion compounding. Graphene oxide nanocomposite loaded with rare earth elements and corrosion inhibitors and containing phosphate ester bonding groups on the surface is obtained by chemical grafting and dispersed in high-temperature resistant base oil. S3, Heating and Roughing and Intermediate Rolling: The steel billet after S1 treatment is sent into a heating furnace, heated to the austenitizing temperature range and held at that temperature, and then subjected to multiple passes of roughing and intermediate rolling to process the steel billet into intermediate billets with a certain cross-sectional size. S4. Online reactive finishing rolling: In the pass before the intermediate billet enters the finishing mill to form the anchor bolt thread shape, the functionalized rolling penetrant prepared in S2 is uniformly sprayed onto the surface of the red-hot intermediate billet using a high-pressure spraying system; under the rolling contact pressure of the finishing mill pass and the residual heat of the billet itself, the active groups in the functionalized rolling penetrant undergo an in-situ chemical reaction with the steel matrix to generate a chemically bonded interface layer, and press the nano-functional units into the grain boundaries of the anchor bolt surface layer; S5. Cooling, Shaping and Post-processing: After rolling, the anchor rods enter the controlled cooling section to control the cooling rate to fix the surface modified structure. Then, they are cut to length, straightened and packaged. In step S2, the preparation of the functionalized rolling penetrant specifically includes the following sub-steps: (1) Carrier activation: Graphene oxide powder is dispersed in an ethanol aqueous solution and ultrasonically dispersed at 300-500W for 30-60 minutes to form a uniform suspension; Subsequently, silane coupling agent was added dropwise under stirring, the temperature was raised to 60-80℃ and refluxed for 4-8 hours. After the reaction was completed, the mixture was separated by centrifugation, washed with anhydrous ethanol and dried under vacuum at 60-80℃ to obtain aminated graphene oxide. (2) Functional loading: The aminated graphene oxide obtained in step (1) is redispersed in deionized water, and the corrosion inhibitor benzotriazole and rare earth cerium salt are added in sequence. The pH value is adjusted to 4-6, and the reaction is carried out for 12-24 hours under constant temperature water bath and magnetic stirring at 25-40℃. The reaction product is separated by centrifugation and dried to obtain graphene oxide composite loaded with cerium-benzotriazole. (3) Surface grafting: The product of step (2) is dispersed in an organic solvent, and long-chain alkyl acid phosphate and p-toluenesulfonic acid catalyst are added. The temperature is raised to 90-110℃ under a nitrogen protective atmosphere and the grafting reaction is carried out for 3-6 hours. The reaction product is filtered, washed and freeze-dried to obtain modified powder with phosphate groups grafted on the surface. (4) Dispersion and compounding: Weigh high-temperature resistant modified polyester oil as base oil, add the modified powder and hexagonal boron nitride nanosheets prepared in step (3) according to the mass ratio, place the mixture in a high-shear emulsifier, mix at a high-shear speed of 3000-5000 rpm for 15-30 minutes, and then let it stand in a vacuum environment to degas, and obtain the functionalized rolled penetrant. In step (2), the rare earth cerium salt is cerium nitrate (III) or cerium chloride (III), and the molar ratio of the corrosion inhibitor benzotriazole to the rare earth cerium salt is (1:1)-(2:1); the temperature of the coordination adsorption reaction is controlled at 25-40℃. In step (4), the component mass percentage of the functionalized rolling penetrant is: 0.5%-2.0% modified powder, 1.0%-3.0% hexagonal boron nitride nanosheets, and the remainder is high-temperature resistant modified polyester oil; the average diameter of the hexagonal boron nitride nanosheets is 100-500 nm.

2. A mine rock bolt construction process according to claim 1, characterised in that, In step (1), the silane coupling agent is 3-aminopropyltriethoxysilane, and the amount added is 50%-100% of the mass of graphene oxide; the volume ratio of ethanol to water in the ethanol aqueous solution is (3:1)-(5:1).

3. A mine rock bolt construction process according to claim 1, characterised in that, In step S3, the austenitizing temperature range is 1100-1200℃, and the holding time is 1.5-2.5 hours to ensure the uniformity of the internal structure of the billet; the total elongation coefficient of rough rolling and intermediate rolling is controlled between 6-10.

4. A mine rock bolt construction process according to claim 1, characterised in that, In step S4, the specific process parameters are as follows: (1) Spraying conditions: The functionalized rolling penetrant is sprayed out through the annular nozzle group, the spraying pressure is 5-15MPa, and the nozzle is 100-200mm away from the surface of the billet; (2) Reaction temperature: The surface temperature of the intermediate billet is controlled at 800-950℃ during spraying; (3) Rolling deformation: The single-pass reduction rate of the finishing mill is 15%-25%. Under the rolling contact pressure and high temperature environment, the phosphate ester group reacts with the iron matrix to generate iron phosphate ceramic phase and reduces graphene oxide.

5. A mine rock bolt construction process according to claim 1, characterised in that, In step S5, the cooling is controlled by air mist cooling, with the cooling rate controlled at 5-15℃ / s and the final cooling temperature at 400-500℃. Then, it is air-cooled to room temperature on a cooling bed to obtain a ferrite plus pearlite structure in the anchor core and a fine-grained strengthening layer on the surface.

6. A mine rock bolt construction process according to claim 1, characterised in that, Under the high temperature and high pressure of step S4, the functionalized rolling penetrant forms a gradient composite modified layer with a thickness of 10-50 μm on the surface of the anchor rod. The modified layer consists of a lubricating layer rich in hexagonal boron nitride nanosheets, a dense barrier layer containing graphene and ceramic phase, and a diffusion layer that is metallurgically bonded to the matrix from the outside to the inside.

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