A wear plate having a graphite-tin bronze sintered layer and a method of making the same

Abstract

This invention relates to a friction-reducing plate with a graphite-tin bronze sintered layer and its preparation method. The friction-reducing plate is obtained by the following steps: First, a substrate is selected and its surface is pretreated. Then, tin bronze powder is spread and sintered once. Afterward, it is vacuum-immersed in an oil-based graphite lubricant containing PAO, flake graphite powder, silica sol, alumina sol, phosphate ester, and oil-soluble polyester modified silicone oil. After a first drying, it is vacuum-immersed in an acidic curing initiator solution, dried a second time, and sintered a second time to anchor the graphite particles in the pores. Finally, it is cooled to room temperature to obtain the finished friction-reducing plate. In this technical solution, the graphite particles in the pores on the surface of the tin bronze sintered layer of the friction-reducing plate are uniformly penetrated and have a strong bonding force with the tin bronze sintered layer. This provides excellent and long-lasting self-lubricating properties while avoiding weakening the strength of the tin bronze sintered layer.

Description

Technical Field

[0001] This invention relates to the field of tire mold technology, and more specifically to a friction-reducing plate with a graphite-tin bronze sintered layer and its preparation method. Background Technology

[0002] The tire mold friction reducing plate is a composite structure consisting of a low-carbon alloy steel substrate and a tin bronze sintered layer on the surface. The tin bronze sintered layer is formed by heating tin bronze powder so that its particles are bonded together into a solid layer at high temperature. In this process, a micro-pore structure is formed. These pores are used to store lubricating particles, thereby enhancing the wear resistance of the friction reducing plate during use and providing lubrication, effectively reducing friction loss and extending the service life of the mold.

[0003] The production process of friction-reducing plates generally relies on immersing the pre-made substrate with a tin-bronze sintered layer completely in an aqueous graphite lubricant. The graphite particles are then allowed to penetrate into the pores by capillary action. Subsequently, the graphite is fixed inside the pores through drying and sintering, thereby giving the friction-reducing plate its self-lubricating properties.

[0004] Water-based graphite lubricant is a lubricating material that provides lubrication and reduces wear by dispersing graphite particles in an aqueous matrix. However, due to the inherently high surface tension of the aqueous medium, graphite particles cannot fully penetrate into the pores of the tin bronze sintered layer during the impregnation of the friction-reducing plate. They tend to agglomerate and clog at the pore inlet, resulting in insufficient pore filling rate. Even if they penetrate into the pores with the help of external force, after drying, the graphite particles can only form physical contact with the bronze pore walls and lack effective adhesion. They are prone to falling off during subsequent assembly or friction, thus causing lubrication failure and reduced wear resistance.

[0005] To address the issue of poor permeability caused by excessive surface tension in water-based graphite lubricants, oil-based graphite lubricants are currently commonly used as an alternative. The oil phase medium, with its lower surface tension, can more effectively wet and penetrate into the pores of the tin bronze sintered layer, thereby improving the uniformity and depth of graphite particle filling. However, this approach still falls under the category of simple physical impregnation and fails to solve the defects of weak bonding between graphite particles and the tin bronze sintered layer, and easy detachment during friction.

[0006] Furthermore, if graphite powder and tin bronze powder are directly mixed and sintered, uneven graphite distribution and agglomeration are likely to occur, which not only damages the structural integrity of the tin bronze sintered layer, but also affects the service life of the friction-reducing plate due to the weak bonding force between graphite and bronze.

[0007] Therefore, existing friction-reducing plates have poor lubrication continuity and wear resistance under medium and high load conditions, which limits their application in mechanical transmission, engineering machinery and other fields. Summary of the Invention

[0008] In view of the above, in order to overcome the problems of insufficient penetration and weak bonding force when using graphite lubricant to impregnate tire mold friction-reducing plates in the prior art, as well as the uneven distribution, agglomeration, and weakening of the strength of tin bronze sintered layer caused by directly mixing and sintering graphite powder and metal powder, the purpose of this invention is to provide a friction-reducing plate and its preparation method that has uniform graphite particle penetration and strong bonding force with tin bronze sintered layer, which provides excellent and long-lasting self-lubricating properties while avoiding weakening the strength of tin bronze sintered layer.

[0009] To achieve the above objectives, the technical solution of the present invention is: A method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer, comprising the following steps: Substrate pretreatment: Remove oil film and oxide film from the substrate surface, and rinse and dry; Powder spreading: Tin bronze powder is selected and spread onto the substrate surface; One-time sintering: The substrate is transferred to a sintering furnace for sintering, and then naturally cooled to room temperature, forming a tin bronze sintered layer on the substrate surface; Vacuum immersion: The substrate is transferred to a vacuum impregnation tank, and an oil-based graphite lubricant is injected into the tank. The substrate is then vacuum-immersed until the liquid surface is stable and no visible bubbles escape. The oil-based graphite lubricant comprises, by weight, 40-60 parts of PAO, 25-35 parts of flake graphite powder, 12-18 parts of silica sol, 3-5 parts of alumina sol, 0.5-1.5 parts of phosphate ester, and 0.2-1 parts of oil-soluble polyester modified silicone oil. First drying: Remove the substrate and transfer it to an oven for drying; Secondary vacuum immersion: The substrate is transferred to a vacuum immersion tank and an acidic curing initiator solution is injected into the tank. The substrate is then vacuum-immersed until the liquid surface is stable and no visible bubbles escape. The acidic curing initiator solution includes, by mass, 3-7 parts of dilute nitric acid, 0.3-1 parts of ethanolamine, and the remainder is a mixture of deionized water and isopropanol. Secondary drying: Remove the substrate and transfer it to an oven for drying; Secondary sintering: The substrate is removed and transferred to the sintering furnace again for sintering, so that the tin bronze skeleton is partially remelted and softened, and held at a certain temperature for a period of time. At the end of the holding period, pressure is applied to the substrate and held at that pressure for a period of time, so that the tin bronze skeleton is plastically deformed and the pores shrink, anchoring the graphite particles in the pores. Then it is cooled to room temperature to obtain the finished friction-reducing plate.

[0010] Preferably, the matrix is ​​Q235B carbon structural steel or DC01 cold-rolled low-carbon steel, with a thickness of 3 to 10 mm and a surface roughness of Ra3.2 to Ra6.3 μm.

[0011] Preferably, if the substrate surface is free of oxide scale, the substrate pretreatment step involves grinding the substrate surface, then immersing it in a 5% sodium hydroxide alkaline cleaning agent for 10-15 minutes, and after cleaning, placing it in a vacuum drying oven at a drying temperature of 100-120°C for 2-3 hours to achieve a surface roughness of Ra3.2-Ra6.3μm.

[0012] Preferably, if there is oxide scale on the substrate surface, the substrate pretreatment step involves grinding the substrate surface, immersing it in a 5% sodium hydroxide alkaline cleaning agent for 10-15 minutes, rinsing it with clean water, then immersing it in a 10% hydrochloric acid and corrosion inhibitor mixture for 5-8 minutes, followed by a second cleaning, and then immersing it in a 1-3% sodium carbonate solution to neutralize the residual acid on the surface. After the final cleaning, it is placed in a vacuum drying oven and dried at 100-120°C for 2-3 hours to achieve a surface roughness of Ra3.2-Ra6.3μm.

[0013] Preferably, the tin bronze powder comprises, by weight parts: 85.3 to 91.3 parts copper, 8 to 12 parts tin, 0.5 to 2 parts zinc, and 0.2 to 0.7 parts phosphorus.

[0014] Preferably, the tin bronze powder comprises, by weight, 89.1 parts copper, 10 parts tin, 1 part zinc, and 0.4 parts phosphorus.

[0015] Preferably, the oil-based graphite lubricant comprises, by weight parts: 50 parts PAO, 30 parts flake graphite powder, 15 parts silica sol, 4 parts alumina sol, 1 part phosphate ester, and 0.5 parts oil-soluble polyester modified silicone oil. The acid curing initiator comprises, by mass, 95 parts of a mixture of deionized water and isopropanol, 5 parts of dilute nitric acid, and 0.5 parts of ethanolamine.

[0016] Preferably, in the powder spreading step, tin bronze powder with a particle size of 60-200 mesh is selected and spread on the substrate surface with a spreading thickness of 0.8-2.5 mm. In one sintering step, under the protection of an inert atmosphere, the temperature inside the sintering furnace is raised to 620-680°C at a heating rate of 3-5°C / min, held for 30-90 minutes, and then naturally cooled to room temperature.

[0017] Preferably, in one vacuum immersion step, the pressure inside the vacuum immersion tank is evacuated to -0.099 to -0.095 MPa, and the immersion time is maintained at 30 to 60 minutes; In one drying step, the substrate is dried in an oven for 4 hours; In the secondary vacuum soaking step, the pressure inside the vacuum impregnation tank is evacuated to -0.095 to -0.08 MPa, and the soaking time is maintained at 10 to 20 minutes. In the secondary drying step, the substrate is dried in an oven for 1.5 to 2.5 hours; In the secondary sintering step, under the protection of an inert atmosphere, the temperature inside the sintering furnace is raised to 730-780℃ at a heating rate of 5-10℃ / min, and held for 20-40 minutes. At the end of the holding period, a pressure of 5-25MPa is applied and maintained for 2-10 minutes. Then, the temperature is cooled to room temperature at a cooling rate of 3-5℃ / min to obtain the finished abrasion-reducing plate.

[0018] A friction-reducing plate is prepared using the above-described preparation method.

[0019] Compared with the prior art, the advantages of the present invention are as follows: The friction-reducing plate provided by this invention includes a substrate and a tin bronze sintered layer bonded to its surface. The tin bronze sintered layer is sequentially impregnated with an oil-based graphite lubricant and an acidic curing initiator, and then subjected to subsequent curing and sintering treatments. This process forms an in-situ "carbon-inorganic ceramic composite" network skeleton within its pores. This network skeleton, together with the pores that shrink during the sintering densification process, constrains the graphite particles that are uniformly distributed within the pores, thereby firmly anchoring the graphite particles within the pores of the tin bronze sintered layer. While maintaining the structural strength of the tin bronze sintered layer, a stable and durable lubrication interface is formed on its surface. Ultimately, this results in the friction-reducing plate having an extremely low coefficient of friction, excellent wear resistance, and a long service life under dry friction conditions. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application and how they solve the aforementioned technical problems will be clearly and completely described below with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] The terms “first,” “second,” “third,” “fourth,” etc. (if present) used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein.

[0023] In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0024] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this application can be achieved, and this is not limited herein.

[0025] As described in the background section, tire mold friction-reducing plates are composite structures consisting of a low-carbon alloy steel matrix and a sintered tin bronze layer. The surface of the sintered tin bronze layer is densely covered with micropores. The friction-reducing plate is immersed in an aqueous graphite lubricant using an impregnation process, allowing graphite particles to penetrate into the pores and form a solid lubricating layer at the friction interface, thereby improving friction reduction and wear resistance. However, due to differences in crystal structure, coefficient of thermal expansion, and compatibility, it is difficult to achieve a strong and sufficient metallurgical bond between the two at the interface. At the same time, the aqueous graphite lubricant has a high surface tension, making it difficult for graphite particles to fully penetrate into the depths of the pores during the impregnation process. Even if they penetrate with external force, they are prone to falling off during subsequent assembly or friction due to the lack of effective adhesion. If a process of directly mixing and sintering graphite powder and tin bronze powder is used, it is easy to cause uneven distribution and agglomeration of graphite, which not only damages the structural integrity of the tin bronze skeleton but also affects the overall service life of the friction-reducing plate due to insufficient bonding between graphite and the matrix. All of the above factors result in poor lubrication continuity and wear resistance durability of existing friction-reducing plates under medium and high load conditions.

[0026] Based on this, this application provides a friction-reducing plate with a graphite-tin bronze sintered layer and its preparation method. The friction-reducing plate is prepared by the following steps: Substrate pretreatment: Remove the oil film and oxide film on the substrate surface, and rinse and dry to give the substrate a suitable surface condition.

[0027] Powder spreading: Select tin bronze powder and spread it relatively evenly on the substrate surface to form a powder layer of a certain thickness. After spreading, use a scraper or leveling tool to smooth the powder layer in the same direction to ensure that the powder layer is of uniform thickness and flat.

[0028] One-time sintering: The substrate coated with tin bronze powder is sent into a sintering furnace and sintered under the set sintering process conditions. Then it is allowed to cool naturally to room temperature, thereby forming a tin bronze sintered layer with a certain porosity on the surface of the substrate.

[0029] One-time vacuum immersion: The substrate is transferred to a vacuum impregnation tank, and the pressure inside the tank is evacuated to a vacuum. Under the condition of maintaining the vacuum, an oil-based graphite lubricant is injected into the tank to immerse the substrate in vacuum, ensuring that the oil-based graphite lubricant completely submerges the substrate. After the oil-based graphite lubricant is injected, under the liquid pressure and capillary action, the lubricant fully penetrates into the pores of the tin bronze sintered layer until the liquid surface is stable and no visible bubbles escape. The oil-based graphite lubricant disperses graphite particles with high-temperature resistant lubricating oil and has reactive inorganic precursors and reaction promoters. The oil-based graphite lubricant includes, by mass parts: 40-60 parts PAO, 25-35 parts flake graphite powder, 12-18 parts silica sol, 3-5 parts alumina sol, 0.5-1.5 parts phosphate ester, and 0.2-1 parts oil-soluble polyester modified silicone oil.

[0030] PAO, or polyalphaolefin, has high thermal stability and good oxidation stability. As the base oil for oil-based graphite lubricants, flake graphite powder is a solid lubricant with a particle size of 1–10 μm. Silica sol and alumina sol are both ceramic precursors. Phosphate ester is an oil-soluble reactant with extreme pressure anti-wear capabilities. Silica sol is stable at high temperatures and can be well adsorbed on the surface of the tin bronze sintered layer, forming a grid that constrains graphite particles. Alumina sol not only plays a role in reinforcing the gel network in the system, but the aluminum ions it releases also react with the phosphate ions in the phosphate ester to generate aluminum phosphate compounds with excellent heat resistance, thereby significantly improving the hardness, density, and high-temperature stability of the grid after curing. Oil-soluble polyester modified silicone oil acts as a dispersant to ensure that graphite particles and sol are uniformly and stably dispersed in the oil phase, avoiding sedimentation.

[0031] First drying: The substrate is removed from the vacuum impregnation tank and transferred to an oven for drying. During the drying process, PAO forms a semi-solid oil film in the pores of the tin bronze sintered layer, which acts as a temporary binder for graphite particles, initially confining the graphite particles in the pores. At the same time, as the water evaporates, the silica sol and alumina sol undergo a preliminary condensation reaction. The silanol (Si-OH) and aluminaol (Al-OH) in the silica sol begin to dehydrate and condense, forming Si-O-Si bonds and Al-O-Al bonds, respectively. Furthermore, heterogeneous condensation occurs between the aluminaol and silanol to form Si-O-Al bonds, ultimately resulting in a silica-alumina hybrid gel network, realizing the transformation from sol to wet gel. The gel network and the oil film together constrain and encapsulate the graphite particles, enabling them to temporarily position themselves in the pores and preventing them from being lost in subsequent steps.

[0032] Secondary vacuum immersion: The substrate is transferred to the vacuum impregnation tank again, and the pressure inside the tank is evacuated to the set high vacuum level and maintained. Under the condition of maintaining the vacuum, acid curing initiator is injected into the tank, and the substrate is vacuum-immersed again to ensure that the acid curing initiator completely submerges the substrate. After the acid curing initiator is injected, under the liquid pressure and capillary action, the acid curing initiator fully penetrates into the pores of the tin bronze sintering layer until the liquid surface is stable and no visible bubbles escape. The acid curing initiator, by mass parts, includes: 3-7 parts dilute nitric acid, 0.3-1 parts ethanolamine, and the balance is a mixture of deionized water and isopropanol.

[0033] Dilute nitric acid acts as a catalyst, accelerating the condensation reaction between ethanolamine and the gel network, and providing an acidic environment to allow the reaction to proceed in a stepwise polymerization manner. This reduces stress during gel network formation, thus preventing cracking due to excessively rapid reaction. Simultaneously, it inhibits the reactivity of ethanolamine, which acts as a crosslinking agent to bridge and solidify the gel network. The mixture of deionized water and isopropanol acts as a polar solvent and participates in reaction control. More specifically, when the matrix is ​​immersed in the acidic curing initiator, the deionized water and isopropanol mixture significantly reduces the surface tension of the acidic curing initiator, allowing it to penetrate deeply into the pores of the tin bronze sintered layer and into the gel network. The hydroxyl groups at the end of ethanolamine undergo a condensation reaction with unreacted silanol and aluminol groups to form covalent bonds, thereby bridging and solidifying the gel network and achieving partial densification. The condensation reaction is accelerated by dilute nitric acid, which reduces the internal stress during the formation of the gel network and prevents cracking caused by excessively rapid reaction. The boiling point of the mixture of deionized water and isopropanol is lower than that of water. During the subsequent drying and curing of the gel mesh, isopropanol preferentially and slowly evaporates at a lower temperature. At the same time, through the azeotropic effect formed with deionized water, it uniformly removes residual moisture, thereby controlling the evaporation rate, reducing the stress generated by evaporation, and further inhibiting the cracking of the gel mesh during the curing process.

[0034] It is worth mentioning that during the secondary vacuum impregnation process, the substrate needs to be statically impregnated to ensure that the acid curing initiator liquid smoothly replaces the gas in the pores and penetrates to a deep depth under vacuum. After impregnation, the substrate should be slowly lifted until it is removed from the vacuum impregnation tank. This reduces the impact of sudden changes in liquid pressure when the liquid level recedes, avoids impacting the still relatively fragile mesh skeleton in the pores, and ensures effective encapsulation of graphite particles.

[0035] Secondary drying: The matrix is ​​removed from the vacuum impregnation tank and transferred to an oven for drying. Under the drive of heat, the condensation reaction between the amino and hydroxyl groups of ethanolamine and the residual silanol and aluminol hydroxyl groups in the gel network is greatly accelerated, generating covalent bonds and releasing water molecules. The continuous heat accelerates the evaporation of water produced by the reaction and residual solvents such as isopropanol and deionized water, making the reaction irreversible. As the solvent and reaction water are discharged, the gel network shrinks and gradually becomes denser. The pre-dispersed PAO and graphite particles play a buffering role, inhibiting cracking that may be caused by shrinkage stress.

[0036] Secondary sintering: The gel-cured substrate is removed from the oven and transferred to a high-temperature sintering furnace for sintering, where it is held at that temperature for a period of time. During the secondary sintering process, the high temperature causes local remelting and softening of the tin bronze sintered layer, resulting in narrowing and deformation of its surface pores, thus densifying it. Meanwhile, under thermal drive, the organic components such as ethanolamine within the pre-formed gel mesh decompose, transforming into heat-resistant residual carbon firmly attached to the inorganic framework. The inorganic components further condense and densify, transforming into a "carbon-inorganic ceramic composite" network framework (hereinafter referred to as the mesh framework). The softened tin bronze matrix and the shrinkage-hardened composite mesh are interlocked and interpenetrated, so that the mesh skeleton and graphite particles are firmly anchored in the pores of the tin bronze sintered layer. At the end of the heat preservation period, pressure is applied to the matrix and held for a period of time, so that the tin bronze skeleton plastically deforms and improves its density. At this time, the pores on the surface of the tin bronze sintered layer shrink, and the softened flowing alloy liquid phase and the shrinkage-hardened mesh skeleton work together to form a firm wrapping and anchoring of the graphite particles, and improve the metallurgical bonding strength between the tin bronze sintered layer and the matrix. Then, it is cooled to room temperature to obtain the finished friction-reducing plate.

[0037] Furthermore, the substrate is either Q235B carbon structural steel or DC01 cold-rolled low-carbon steel. The friction-reducing plate made of Q235B carbon structural steel is suitable for high-load conditions, while DC01 cold-rolled low-carbon steel is suitable for situations with stringent requirements for forming processes, thus meeting diverse application needs. The substrate thickness is 3-10mm, thereby avoiding material redundancy while maintaining rigidity requirements. The surface roughness of the substrate is Ra3.2-Ra6.3μm, which improves the adhesion of the tin bronze sintered layer while avoiding uneven tin bronze powder coverage due to excessive roughness, thereby improving the appearance quality and corrosion resistance of the tin bronze sintered layer.

[0038] Furthermore, if the substrate surface has no oxide scale, the substrate pretreatment step involves first using a wire brush and grinding wheel to polish the substrate surface to remove thick rust and loose material. The polished substrate is then immersed in a 5% sodium hydroxide alkaline cleaning agent for 10–15 minutes to remove the grinding debris and embedded grease remaining on the surface. After cleaning, the substrate is placed in a vacuum drying oven and dried at 100–120°C for 2–3 hours to achieve a surface roughness of Ra3.2–Ra6.3 μm.

[0039] Furthermore, if oxide scale is present on the substrate surface, the substrate pretreatment step involves first using a wire brush and grinding wheel to polish the surface and remove thick rust and loose material. Then, the substrate is immersed in a 5% sodium hydroxide alkaline cleaning agent for 10–15 minutes to remove residual grinding debris and embedded grease. After removal, the substrate is rinsed with running water to remove alkaline residue. Next, it is immersed in a 10% hydrochloric acid and corrosion inhibitor mixture for 5–8 minutes to remove oxide scale. A second cleaning is then performed to remove residual acid and metal salts. Finally, the substrate is immersed in a 1–3% sodium carbonate solution to neutralize residual acid. After the final cleaning, the substrate is placed in a vacuum drying oven at 100–120°C for 2–3 hours to achieve a surface roughness of Ra3.2–Ra6.3 μm.

[0040] Furthermore, the tin bronze powder selected in the powder spreading step includes copper, tin, zinc, and phosphorus. In the subsequent first sintering step, copper serves as the matrix, forming the plastic framework of the tin bronze sintered layer. Tin reacts with copper at the sintering temperature to generate a low-melting-point eutectic liquid phase, which fills the pores through capillary action, thereby driving the densification of the sintered layer and significantly improving its strength, hardness, and wear resistance. Zinc mainly improves the wettability of the matrix and plays a deoxidizing role, effectively expelling gases from the pores and further increasing the density of the tin bronze sintered layer. In the subsequent second sintering step, if the sintering temperature exceeds the thermal stability threshold of the mesh framework, the framework will undergo severe oxidation, simultaneously causing… Excessive liquid phase in the alloy matrix can erode or even dissolve the brittle mesh skeleton, causing it to collapse and lose its binding and constraint on the graphite particles. In order to keep the secondary sintering temperature in a range that can both soften the alloy and be far below the skeleton failure temperature, phosphorus in tin bronze powder can form a low-melting-point eutectic phase with copper, which lowers the melting point of the tin bronze sintered layer. In the subsequent secondary sintering process, the tin bronze sintered layer can be remelted and softened at a temperature below the thermal damage threshold of the mesh skeleton, thereby avoiding the destruction of the mesh skeleton. The tin bronze powder, by mass parts, includes: 85.3 to 91.3 parts copper, 8 to 12 parts tin, 0.5 to 2 parts zinc, and 0.2 to 0.7 parts phosphorus.

[0041] Furthermore, in the powder spreading step, tin bronze powder with a particle size of 60-200 mesh is selected and spread on the substrate surface with a thickness of 0.8-2.5 mm. It should be noted that the powder spreading can be completed with the help of a powder spreading mold to ensure the uniformity of the powder spreading thickness. In the first sintering step, under the protection of an inert atmosphere, the temperature in the sintering furnace is raised to 620-680℃ at a heating rate of 5-8℃ / min and held for 30-90 minutes, and then naturally cooled to room temperature. A tin bronze sintered layer is formed on the substrate surface. At this time, the tin bronze sintered layer is actually a "sintered blank" with a certain shape retention ability and a high surface porosity, which ensures that in the subsequent first and second vacuum soaking steps, the oil-based graphite lubricant and acid curing initiator can fully penetrate into the pores through capillary action.

[0042] Furthermore, in a vacuum immersion step, the pressure inside the vacuum immersion tank is evacuated to -0.099 to -0.095 MPa, and the immersion time is maintained at 30 to 60 minutes. The purpose is to forcefully remove the air from the pores of the tin bronze sintered layer and use atmospheric pressure to achieve deep penetration of the oil-based graphite lubricant.

[0043] In one drying step, the substrate is dried in an oven for 4 hours. At this time, a large amount of heat is needed to slowly drive the free solvents such as water in the voids of the tin bronze sintered layer to diffuse and evaporate slowly, so as to avoid the bubbling of the initially formed gel network.

[0044] In the secondary vacuum immersion step, the pressure inside the vacuum immersion tank is evacuated to -0.095 to -0.08 MPa, and the immersion time is maintained at 10 to 20 minutes. The purpose is to gently remove the residual air in the pores of the tin bronze sintered layer, protect the fine mesh skeleton structure, and allow the acid curing initiator to fully penetrate into the pores through capillary action, while also penetrating into the microcracks and unfilled micropores of the mesh skeleton.

[0045] In the secondary drying step, the matrix is ​​dried in an oven for 1.5 to 2.5 hours. The purpose is to remove the residual small amount of solvent and the trace amount of moisture introduced by the secondary impregnation, and to promote the further solidification of the gel network, and finally remove all volatile components. The amount of liquid to be removed in this process is small and the diffusion path is short, so only less heat is required and the drying time is shorter than that of the first drying.

[0046] In the secondary sintering step, under an inert atmosphere, the temperature inside the sintering furnace is raised to 730-780℃ at a heating rate of 5-10℃ / min and held for 20-40 minutes, followed by natural cooling to room temperature. The secondary sintering is mainly to densify the tin bronze sintered layer. Specifically, the high-porosity tin bronze sintered layer formed in the first sintering, known as the "sintered blank," is heated to above its eutectic temperature, causing it to remelt and generate a rich liquid phase. Driven by this liquid phase, the tin bronze sintered layer accelerates densification, and the interconnected large-diameter pores inside are filled or transformed into closed micropores. At the same time, the molten alloy liquid phase can fully wet and penetrate into the gaps between the pre-placed carbon mesh skeleton and graphite particles, and finally, after solidification, it is firmly anchored in the dense tin bronze sintered layer. At the end of the holding period, a pressure of 5-25MPa is applied and maintained for 2-10 minutes, followed by cooling to room temperature at a cooling rate of 3-5℃ / min to obtain the finished friction-reducing plate.

[0047] Example 1: The matrix is ​​selected as Q235B carbon structural steel.

[0048] The oil-based graphite lubricant is prepared by means of: 50 parts PAO, 30 parts flake graphite powder, 15 parts silica sol, 4 parts alumina sol, 1 part phosphate ester, and 0.5 parts oil-soluble polyester modified silicone oil.

[0049] The acidic curing initiator solution is prepared by mass fractions of: 5 parts dilute nitric acid, 0.5 parts ethanolamine, and 95 parts a mixture of deionized water and isopropanol.

[0050] Tin bronze powder with a particle size of 60-200 mesh was prepared, comprising, by mass parts: 89.1 parts copper, 10 parts tin, 1 part zinc, and 0.4 parts phosphorus.

[0051] The substrate surface was roughened to Ra3.2–Ra6.3 μm, and tin bronze powder with a thickness of 0.8–2.5 mm was deposited on the substrate surface. The substrate was then transferred to a sintering furnace for primary sintering. Under an inert atmosphere, the furnace temperature was raised to 650 °C at a heating rate of 4 °C / min and held for 60 minutes. Afterward, the substrate was allowed to cool naturally to room temperature. The substrate was then transferred to a vacuum impregnation tank and immersed in an oil-based graphite lubricant at -0.097 MPa for 45 minutes. Finally, the substrate was transferred to an oven. The substrate is dried internally for 4 hours, then transferred to a vacuum impregnation tank and immersed in an acidic curing initiator at -0.09 MPa for 15 minutes. The substrate is then transferred to an oven for drying for 2 hours, and finally transferred to a sintering furnace for secondary sintering. Under an inert atmosphere, the temperature inside the sintering furnace is raised to 760°C at a heating rate of 8°C / min and held for 30 minutes. At the end of the holding period, a pressure of 15 MPa is applied and held for 8 minutes, and then cooled to room temperature at a cooling rate of 4°C / min to obtain the finished abrasion-reducing plate.

[0052] Example 2: Compared to Example 1, the oil-based graphite lubricant prepared in this example comprises, by mass parts: 60 parts PAO, 35 parts flake graphite powder, 18 parts silica sol, 5 parts alumina sol, 1.5 parts phosphate ester, and 1 part oil-soluble polyester modified silicone oil.

[0053] The prepared acidic curing initiator solution comprises, by mass parts: 7 parts dilute nitric acid, 1 part ethanolamine, and 92 parts a mixture of deionized water and isopropanol.

[0054] The prepared tin bronze powder comprises, by mass parts: 91.3 parts copper, 12 parts tin, 2 parts zinc, and 0.7 parts phosphorus.

[0055] Example 3: Compared to Example 1, the oil-based graphite lubricant prepared in this example comprises, by mass parts: 40 parts PAO, 25 parts flake graphite powder, 12 parts silica sol, 3 parts alumina sol, 0.5 parts phosphate ester, and 0.2 parts oil-soluble polyester modified silicone oil.

[0056] The prepared acidic curing initiator solution comprises, by mass parts: 3 parts dilute nitric acid, 0.3 parts ethanolamine, and the balance being a mixture of deionized water and isopropanol.

[0057] The prepared tin bronze powder comprises, by mass parts: 85.3 parts copper, 8 parts tin, 0.5 parts zinc, and 0.2 parts phosphorus.

[0058] Example 4: Compared to Example 1, in this example, during the first sintering, the temperature inside the sintering furnace is raised to 680°C at a heating rate of 5°C / min under an inert atmosphere and held for 90 minutes, followed by natural cooling to room temperature. During the first vacuum soaking, the substrate is immersed in oil-based graphite lubricant at -0.095 MPa for 60 minutes. During the second vacuum soaking, the substrate is immersed in acidic curing initiator at -0.08 MPa for 20 minutes. During the second sintering, the temperature inside the sintering furnace is raised to 780°C at a heating rate of 10°C / min under an inert atmosphere and held for 40 minutes. At the end of the holding period, a pressure of 25 MPa is applied and maintained for 10 minutes, followed by cooling to room temperature at a cooling rate of 5°C / min to obtain the finished friction-reducing plate.

[0059] Example 5: Compared to Example 1, in this example, during the first sintering, the temperature inside the sintering furnace is raised to 620°C at a heating rate of 3°C / min under an inert atmosphere and held for 30 minutes, followed by natural cooling to room temperature. During the first vacuum soaking, the substrate is immersed in oil-based graphite lubricant at -0.099 MPa for 30 minutes. During the second vacuum soaking, the substrate is immersed in acidic curing initiator at -0.095 MPa for 10 minutes. During the second sintering, the temperature inside the sintering furnace is raised to 730°C at a heating rate of 5°C / min under an inert atmosphere and held for 20 minutes. At the end of the holding period, a pressure of 5 MPa is applied and maintained for 2 minutes, followed by cooling to room temperature at a cooling rate of 3°C / min to obtain the finished friction-reducing plate.

[0060] Example 6: The matrix is ​​selected as Q235B carbon structural steel.

[0061] The oil-based graphite lubricant is prepared by means of: 60 parts PAO, 35 parts flake graphite powder, 18 parts silica sol, 5 parts alumina sol, 1.5 parts phosphate ester, and 1 part oil-soluble polyester modified silicone oil.

[0062] The acid curing initiator solution is prepared by mass fractions of: 7 parts dilute nitric acid, 1 part ethanolamine, and 92 parts a mixture of deionized water and isopropanol.

[0063] Tin bronze powder with a particle size of 60-200 mesh was prepared, comprising, by mass parts: 91.3 parts copper, 12 parts tin, 2 parts zinc, and 0.7 parts phosphorus.

[0064] The substrate surface was roughened to Ra3.2–Ra6.3 μm, and tin bronze powder with a thickness of 0.8–2.5 mm was deposited on the substrate surface. The substrate was then transferred to a sintering furnace for primary sintering. Under an inert atmosphere, the furnace temperature was raised to 680 °C at a heating rate of 5 °C / min and held for 90 minutes. Afterward, the substrate was allowed to cool naturally to room temperature. The substrate was then transferred to a vacuum impregnation tank and immersed in an oil-based graphite lubricant at -0.095 MPa for 60 minutes. Finally, the substrate was transferred to an oven. After drying for 4 hours, the substrate is transferred to a vacuum impregnation tank and immersed in an acidic curing initiator at -0.08 MPa for 20 minutes. The substrate is then transferred to an oven for drying for 2 hours and finally transferred to a sintering furnace for secondary sintering. Under an inert atmosphere, the temperature inside the sintering furnace is raised to 780°C at a heating rate of 10°C / min and held for 40 minutes. At the end of the holding period, a pressure of 25 MPa is applied and held for 10 minutes. The substrate is then cooled to room temperature at a cooling rate of 5°C / min to obtain the finished abrasion-reducing plate.

[0065] Example 7: The matrix is ​​selected as Q235B carbon structural steel.

[0066] The oil-based graphite lubricant is prepared by the following components by mass: 40 parts PAO, 25 parts flake graphite powder, 12 parts silica sol, 3 parts alumina sol, 0.5 parts phosphate ester, and 0.2 parts oil-soluble polyester modified silicone oil.

[0067] The acidic curing initiator solution is prepared by mass fractions of: 3 parts dilute nitric acid, 0.3 parts ethanolamine, and the balance being a mixture of deionized water and isopropanol.

[0068] Tin bronze powder with a particle size of 60-200 mesh was prepared, comprising, by mass parts: 85.3 parts copper, 8 parts tin, 0.5 parts zinc, and 0.2 parts phosphorus.

[0069] The substrate surface was roughened to Ra3.2–Ra6.3 μm, and tin bronze powder with a thickness of 0.8–2.5 mm was deposited on the substrate surface. The substrate was then transferred to a sintering furnace for primary sintering. Under an inert atmosphere, the furnace temperature was raised to 620°C at a heating rate of 3°C / min and held for 30 minutes. Afterward, the substrate was allowed to cool naturally to room temperature. The substrate was then transferred to a vacuum impregnation tank and immersed in an oil-based graphite lubricant at -0.099 MPa for 30 minutes. Finally, the substrate was transferred to an oven. The substrate is dried internally for 4 hours, then transferred to a vacuum impregnation tank and immersed in an acidic curing initiator solution at -0.095 MPa for 10 minutes. The substrate is then transferred to an oven for drying for 2 hours, and finally transferred to a sintering furnace for secondary sintering. Under an inert atmosphere, the temperature inside the sintering furnace is raised to 730°C at a heating rate of 5°C / min and held for 20 minutes. At the end of the holding period, a pressure of 5 MPa is applied and held for 2 minutes, and then cooled to room temperature at a cooling rate of 3°C / min to obtain the finished abrasion-reducing plate.

[0070] Comparative Example 1: Compared to Example 1, only the substrate is vacuum-soaked using existing water-based graphite lubricant, without the need for secondary vacuum soaking and secondary drying steps.

[0071] Comparative Example 2: Compared to Example 1, only the existing oil-based graphite lubricant is used for vacuum soaking of the substrate. The composition of the oil-based graphite lubricant is recorded by mass percentage as follows: 5-10 parts graphite powder, 85-90 parts base oil, and 3-5 parts dispersant. There are no secondary vacuum soaking and secondary drying steps.

[0072] Performance testing: Performance tests were conducted by reciprocating the grinding element on the surface of the finished anti-friction plates prepared in Examples 1 to 7, and Comparative Examples 1 and 2. The number of reciprocations was set to 10,000. The test results are shown in Table 1 below.

[0073] Table 1 Performance Test Data As can be seen from the experimental results of the various embodiments and comparative examples in Table 1, the finished friction-reducing plate prepared by the above process has a graphite particle shedding rate in the tin bronze sintered layer that is more than 70% lower than that of the traditional friction-reducing plate. Moreover, under dry friction conditions, its average friction coefficient is stable below 0.25, exhibiting excellent self-lubricating and friction-reducing properties. Furthermore, it can avoid weakening the strength of the tin bronze sintered layer. The improvement in the above comprehensive performance makes the overall service life of the friction-reducing plate more than 1.5 times that of the traditional friction-reducing plate under the same working conditions.

[0074] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this application can be achieved, and this is not limited herein.

[0075] The embodiments and descriptions above are merely illustrative of the principles and preferred embodiments of this application. Various changes and modifications may be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed.

Claims

1. A method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer, characterized in that, The steps are as follows: Substrate pretreatment: Remove oil film and oxide film from the substrate surface, and rinse and dry; Powder application: Tin bronze powder is selected and applied to the surface of the substrate; One-time sintering: The substrate is transferred to a sintering furnace for sintering, and then naturally cooled to room temperature, forming a tin bronze sintered layer on the substrate surface; Vacuum immersion: The substrate is transferred to a vacuum impregnation tank, and an oil-based graphite lubricant is injected into the tank. The substrate is then vacuum-immersed until the liquid surface is stable and no visible bubbles escape. The oil-based graphite lubricant comprises, by weight, 40-60 parts of PAO, 25-35 parts of flake graphite powder, 12-18 parts of silica sol, 3-5 parts of alumina sol, 0.5-1.5 parts of phosphate ester, and 0.2-1 parts of oil-soluble polyester modified silicone oil. First drying: Remove the substrate and transfer it to an oven for drying; Secondary vacuum immersion: The substrate is transferred to a vacuum immersion tank and an acidic curing initiator solution is injected into the tank. The substrate is then vacuum-immersed until the liquid surface is stable and no visible bubbles escape. The acidic curing initiator solution includes, by mass, 3-7 parts of dilute nitric acid, 0.3-1 parts of ethanolamine, and the remainder is a mixture of deionized water and isopropanol. Secondary drying: Remove the substrate and transfer it to an oven for drying; Secondary sintering: The substrate is removed and transferred to the sintering furnace again for sintering, so that the tin bronze skeleton is partially remelted and softened, and held at a certain temperature for a period of time. At the end of the holding period, pressure is applied to the substrate and held at that pressure for a period of time, so that the tin bronze skeleton is plastically deformed and the pores shrink, anchoring the graphite particles in the pores. Then it is cooled to room temperature to obtain the finished friction-reducing plate.

2. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, The base material is Q235B carbon structural steel or DC01 cold-rolled low-carbon steel, with a thickness of 3 to 10 mm and a surface roughness of Ra3.2 to Ra6.3 μm.

3. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, If there is no oxide scale on the substrate surface, in the substrate pretreatment step, the substrate surface is polished, and then immersed in 5% sodium hydroxide alkaline cleaning agent for 10 to 15 minutes. After cleaning, it is placed in a vacuum drying oven and dried at 100 to 120°C for 2 to 3 hours to make its surface roughness reach Ra3.2 to Ra6.3 μm.

4. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, If oxide scale is present on the substrate surface, the substrate pretreatment step involves grinding the substrate surface, then immersing it in a 5% sodium hydroxide alkaline cleaning agent for 10–15 minutes, followed by rinsing with clean water. After that, it is immersed in a 10% hydrochloric acid and corrosion inhibitor mixture for 5–8 minutes, followed by a second cleaning. Then, it is immersed in a 1–3% sodium carbonate solution to neutralize the residual acid on the surface. After the final cleaning, it is placed in a vacuum drying oven and dried at 100–120°C for 2–3 hours to achieve a surface roughness of Ra3.2–Ra6.3 μm.

5. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, Tin bronze powder, by mass parts, includes: 85.3–91.3 parts copper, 8–12 parts tin, 0.5–2 parts zinc, and 0.2–0.7 parts phosphorus.

6. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 5, characterized in that, The tin bronze powder comprises, by weight, 89.1 parts copper, 10 parts tin, 1 part zinc, and 0.4 parts phosphorus.

7. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, The oil-based graphite lubricant comprises, by weight parts: 50 parts PAO, 30 parts flake graphite powder, 15 parts silica sol, 4 parts alumina sol, 1 part phosphate ester, and 0.5 parts oil-soluble polyester modified silicone oil. The acid curing initiator comprises, by mass, 95 parts of a mixture of deionized water and isopropanol, 5 parts of dilute nitric acid, and 0.5 parts of ethanolamine.

8. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, In the powder spreading step, tin bronze powder with a particle size of 60-200 mesh is selected and spread on the substrate surface with a spreading thickness of 0.8-2.5 mm. In one sintering step, under the protection of an inert atmosphere, the temperature inside the sintering furnace is raised to 620-680°C at a heating rate of 3-5°C / min, held for 30-90 minutes, and then naturally cooled to room temperature.

9. The method for preparing a friction-reducing plate with a graphite-tin bronze sintered layer according to claim 1, characterized in that, In one vacuum immersion step, the pressure inside the vacuum immersion tank is evacuated to -0.099 to -0.095 MPa, and the immersion time is maintained at 30 to 60 minutes; In one drying step, the substrate is dried in an oven for 4 hours; In the secondary vacuum soaking step, the pressure inside the vacuum impregnation tank is evacuated to -0.095 to -0.08 MPa, and the soaking time is maintained at 10 to 20 minutes. In the secondary drying step, the substrate is dried in an oven for 1.5 to 2.5 hours; In the secondary sintering step, under the protection of an inert atmosphere, the temperature inside the sintering furnace is raised to 730-780℃ at a heating rate of 5-10℃ / min, and held for 20-40 minutes. At the end of the holding period, a pressure of 5-25MPa is applied and maintained for 2-10 minutes. Then, the temperature is cooled to room temperature at a cooling rate of 3-5℃ / min to obtain the finished abrasion-reducing plate.

10. A friction-reducing plate, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 9.

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