Uniform roll shaft with high hardness and high wear resistance as well as preparation and application methods

Abstract

The invention provides a high-hardness high-wear-resistance uniform roll shaft as well as a preparation method and an application method thereof, belongs to the technical field of mechanical manufacturing, and solves at least one of the technical problems of insufficient wear resistance, hardness, adaptability and the like of a roll shaft for producing a dry-method battery pole piece at present. The high-hardness high-wear-resistance uniform roll shaft is made of alloy steel, and the surface hardness of a roll shaft base body is 62-67 HRC; the surface of a roll shaft base body is plated with a coating, the hardness of the coating is 10 GPa or above, the plastic deformation quantity is 20% or above, the binding force of the coating and the base body is 20 N or above, and the abrasion rate is 5 * 10 <-15 > m < 3 > / (N.m) or below. The roll shaft operates in a range from room temperature to 400 DEG C. The roll shaft disclosed by the invention can be suitable for production of dry-method battery pole pieces, the equipment level of all-solid-state battery production is improved, and the core difficulty of large-scale industrialization of all-solid-state batteries in China is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical manufacturing, and relates to a roller shaft with uniform high hardness and high wear resistance and a preparation and application method. BACKGROUND

[0002] With the rapid development of the new energy industry, the requirements for battery energy density, cycle life and safety in the fields of power batteries and energy storage batteries continue to improve. Dry method for preparing battery pole pieces has gradually become a research hotspot and development trend in the field of battery manufacturing due to its significant advantages such as no need for solvents, environmental protection, high efficiency and low energy loss. In the preparation process of dry battery pole pieces, the roller shaft, as a core key component, is widely used in key processes such as calendering, forming and conveying of the pole pieces. The performance of the roller shaft directly determines the thickness uniformity, surface flatness, density and mechanical stability of the pole pieces, and further affects the overall electrochemical performance and service life of the battery.

[0003] At present, the roller shaft for dry battery pole piece production is mainly manufactured by using traditional metal rollers and surface spraying WC. However, there are many technical defects in its actual application. Firstly, the wear resistance is insufficient. In the preparation of dry pole pieces, powder materials such as active materials, conductive agents and binders are often involved in extrusion and friction. During long-term operation, the roller shaft is prone to defects such as roundness error and coaxiality deviation due to wear and thermal deformation, which cannot maintain high precision, thereby causing large fluctuations in the thickness of the pole pieces, affecting the consistency of the battery, shortening the single cycle time on the machine and increasing the maintenance cost. Secondly, the hardness is insufficient. Under high-temperature working conditions such as dry pole piece hot pressing and continuous conveying, the roller shaft is prone to thermal softening, resulting in a significant decrease in hardness. Not only does this increase the wear rate, but it also increases the elastic deformation of the roller shaft surface, further damaging the thickness uniformity and surface flatness of the pole pieces. Thirdly, the adaptability is insufficient. The material system (such as silicon-based negative electrode and high-nickel positive electrode) and the preparation process (such as cold pressing, hot pressing and continuous forming) of dry pole pieces are diversifying. The hardness, surface roughness and thermal stability of the existing roller shaft cannot meet the needs of different processes and materials at the same time, especially under high-temperature working conditions. The problems of hardness decay and insufficient thermal stability are more prominent, which easily leads to problems such as pole piece sticking, layering and cracking.

[0004] Therefore, it is of great significance to develop a roller shaft for dry battery pole piece production with excellent wear resistance, good hardness retention under high-temperature working conditions and good performance consistency and stability, in order to improve the production quality and efficiency of dry battery pole pieces, reduce production costs and promote the sustainable development of the new energy battery industry. SUMMARY

[0005] In view of the above analysis, the present application provides a roller shaft with uniform high hardness and high wear resistance and a preparation and application method to solve at least one of the technical problems of insufficient wear resistance, hardness and adaptability of the current roller shaft for producing dry battery pole pieces.

[0006] It is mainly achieved through the following technical solutions:

[0007] On one hand, this invention provides a roller with high hardness and uniform wear resistance. The roller is made of alloy steel, and the surface hardness of the roller substrate is 62-67 HRC. The roller substrate surface is coated with a coating with a hardness of 10 GPa or higher, a plastic deformation of 20% or higher, a bonding force between the coating and the substrate of 20 N or higher, and a wear rate of 5 × 10⁻⁶. -15 m 3 / (N·m) or less; the roller operates in the range of room temperature to 400°C.

[0008] Furthermore, the chemical composition of the alloy steel, by mass percentage, is: C: 0.90–1.15%, Si ≤ 0.70%, Mn ≤ 0.45%, P ≤ 0.015%, S ≤ 0.015%, Co: 4.0–8.0%, Mo: 3.0–10.0%, V: 0.5–1.5%, Cr: 4.0–6.0%, Nb: 0.1–0.5%, Ni+Cu ≤ 0.5%, N ≥ 200 ppm, with the balance being Fe and unavoidable impurities.

[0009] Furthermore, the surface hardness uniformity of the roller substrate is within ±0.3HRC, the hardened layer depth is above 20mm, the coating thickness is above 5μm, and the coating material is TiAlN or TiN.

[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned roller shaft, comprising the following steps:

[0011] Step 1: Form the roller blank using hot isostatic pressing;

[0012] Step 2: Heat treat the blank;

[0013] Step 3: Roughly machine the heat-treated blank to obtain the primary roller product;

[0014] Step 4: Perform induction heat treatment on the primary product;

[0015] Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft;

[0016] Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

[0017] Furthermore, step 1 includes the following sub-steps:

[0018] Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying.

[0019] Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling.

[0020] Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1180-1220℃ and simultaneously pressurized to 130-170MPa. After holding the heat and pressure for 3-4 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

[0021] Furthermore, after step 1 and before step 2, there is step 1', in which the hot isostatically pressed blank is placed in a gas furnace and heated to 1100-1150℃, held for 2-4 hours, and then extruded. The extrusion ratio is ≥2.25 and the extrusion rate is 3-8 mm / s.

[0022] Furthermore, in step 2, the heat treatment is as follows: the blank at 950-1000℃ is placed in a circulating oil bath at 30-60℃ and cooled to room temperature, followed by electric furnace tempering at 550-650℃, held for 10-15 hours, and then air-cooled to room temperature.

[0023] Furthermore, step 4 includes the following sub-steps:

[0024] Step 4.1: Preheat the rough-processed primary roller product to 350-400℃ and keep it at that temperature for 1.5-2 hours.

[0025] Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode method, and then water quench it. After the heating temperature reaches 1170~1230℃ and is held for ≥20min, quickly perform overall water spray quenching. The cooling time is 15~30 minutes, cooling it to below 80℃.

[0026] Step 4.3: Place the quenched primary roller into a resistance furnace with a protective atmosphere for tempering. The first tempering temperature is 535-550℃, and the holding time is more than 20 hours. After tempering, remove the roller from the furnace and air cool to room temperature. The second tempering temperature is 520-530℃, and the holding time is more than 20 hours. After tempering, remove the roller from the furnace and air cool to room temperature. The third tempering temperature is 500-515℃, and the holding time is more than 20 hours.

[0027] Furthermore, step 6 involves processing the intermediate grade product using physical vapor deposition (PVD), which includes the following sub-steps:

[0028] Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning;

[0029] Step 6.2, Coating Deposition: Deposit TiN or TiAlN coating using magnetron sputtering technology, with a coating thickness of 5-8 μm.

[0030] Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller.

[0031] Finally, the present invention also provides a method for applying the above-mentioned roller shaft, or the roller shaft prepared by the above method, to the rolling, forming and conveying production of dry-process battery electrode sheets.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. This invention improves the red hardness of the roller substrate by designing the steel composition and applies a TiAlN or TiN surface coating to the roller substrate, which further improves the hardness of the working surface. This results in high hardness and good hardness uniformity of the roller surface, which can adapt to the working environment requirements from room temperature to 400℃. Moreover, it has high thermal conductivity, and the temperature field of the roller surface can be guaranteed to be sufficiently uniform when heated, with the axial and circumferential temperature difference not exceeding 1℃.

[0034] 2. The method of the present invention uses hot isostatic pressing to form the blank, which ensures sufficient compositional uniformity and high density, or further uses extrusion molding process to improve the density of the blank, thereby ultimately improving the thermal conductivity and uniformity of the material.

[0035] 3. The tempering temperature during the heat treatment of the blank and the induction heat treatment of the primary product in the method of the present invention is above 500℃, and the induction heat treatment is tempered multiple times, which can ensure that the hardness does not decrease when used in working conditions below 500℃; in addition, the primary product adopts the overall induction heat treatment method, which can ensure that the hardness and thermal conductivity properties are fully uniform.

[0036] 4. The roller of the present invention can be applied to the production of dry-process battery electrodes, improves the equipment level of all-solid-state battery production, and solves the core difficulties of large-scale industrialization of all-solid-state batteries in China. Detailed Implementation

[0037] The following detailed description, in conjunction with specific embodiments, provides a roller shaft with high hardness and uniform wear resistance, as well as its preparation and application methods. These embodiments are for illustrative purposes only, and the present invention is not limited to these embodiments.

[0038] Because dry-process electrode preparation often involves the extrusion and friction of powder materials, such as active substances, conductive agents, and binders, especially battery cathode materials which have higher hardness, greater brittleness, and higher activity, and whose material complexity, electrochemical stringency, and structural and functional requirements have reached their peak, the process control window for electrode roll forming is narrower. Therefore, the rollers are required to have excellent wear resistance, good hardness retention under high-temperature conditions, and especially good performance consistency and stability. The inventors discovered through research that a roller with a working surface hardness of over 10 GPa and a substrate hardness of over 62 HRC, capable of adapting to working environments from room temperature to 400°C, and maintaining a certain degree of performance consistency at different points on the roller, can meet the current production requirements of dry-process battery electrodes, especially the production of cathode electrodes.

[0039] In view of this, the present invention proposes a roller with high hardness, high wear resistance and uniform performance. The roller is made of alloy steel, with a diameter of 150-350 mm and a length of 400-1000 mm. The surface hardness of the roller substrate is 62-67 HRC, with a hardness uniformity within ±0.3 HRC, and a hardened layer depth of 20 mm or more, such as 20-25 mm. The roller substrate surface is coated with a coating with a thickness of 5 μm or more, such as 5-8 μm. The coating material is either TiAlN or TiN, with a hardness of 10 GPa or more, such as 10-20 GPa, a plastic deformation of 20% or more, such as 20-30%, a bonding force between the coating and the substrate of 20 N or more, such as 20-30 N, and a wear rate of 5 × 10⁻⁶. -15 For rollers with a capacity of m3 / (N·m) or less, the roller can operate in the range of room temperature to 400℃, and the axial and circumferential temperature difference ΔT of the roller surface is not greater than 1℃, such as 0.2~0.8℃. Room temperature refers to 10~25℃.

[0040] Specifically, the hardness testing of the hardened layer shall be performed in accordance with GB / T 13313-2008; the depth of the hardened layer shall be determined by destructive testing at the machining allowance, through metallographic observation or hardness gradient testing. The coating thickness shall be measured using a scanning electron microscope (SEM); the coating hardness shall be determined using a nanoindenter; the plastic deformation shall be determined using a micropillar compression test; the adhesion between the coating and the substrate shall be measured using a scratch tester; and the wear rate shall be measured using a tribometer.

[0041] Furthermore, the chemical composition of the roller, by mass percentage, is: C: 0.90–1.15%, Si ≤ 0.70%, Mn ≤ 0.45%, P ≤ 0.015%, S ≤ 0.015%, Co: 4.0–8.0%, Mo: 3.0–10.0%, V: 0.5–1.5%, Cr: 4.0–6.0%, Nb: 0.1–0.5%, Ni+Cu ≤ 0.5%, N ≥ 200 ppm, with the balance being Fe and unavoidable impurities.

[0042] C: It forms various types of carbides with alloying elements such as Cr, Mo, V, and W. It has high hardness and strong stability, and is the core of improving the high-temperature hardness of rollers. In particular, after quenching, carbon can be dissolved in the martensitic matrix to ensure the hardness of the matrix. However, considering factors such as toughness, the carbon content is controlled within the range of 0.9% to 1.15%.

[0043] Si: Not a major strengthening element, but a basic element in steel, its content is controlled to be ≤0.70%;

[0044] Mn: Not a major strengthening element, but a basic element in steel, its content is controlled at ≤0.45%;

[0045] P and S are both harmful elements in steel, but they are unavoidable in general steel. The content should be controlled to ≤0.015% and kept as low as possible.

[0046] Co: It does not form carbides, but mainly dissolves in the matrix, significantly improving the bonding strength between carbides and the matrix and enhancing the resistance of carbides to peeling off. At the same time, Co can improve the red hardness and thermal conductivity of steel, making the rollers less prone to softening at high temperatures, and ensuring uniform heat dissipation, thus reducing thermal deformation. Considering cost, the content is controlled between 4.0% and 8.0%.

[0047] Mo: A typical alloying element that improves the resistance of steel to temper brittleness. It can be dissolved in the martensitic matrix to improve the steel's resistance to temper brittleness and high-temperature tempering stability, such as maintaining high strength at 500℃ and above. In particular, it easily forms M2C type carbides with C, which have strong high-temperature hardness retention. Considering economic factors, the content is controlled at 3.0-10.0%.

[0048] V: Forms fine and dispersed MC-type carbides, exhibiting significant high-temperature stability. During high-temperature quenching, it can effectively hinder grain growth and dislocation movement, making it a key element for improving the high-temperature hardness retention of rollers. Considering economic factors, the content is controlled at 0.5-1.5%.

[0049] Cr: The carbides formed are easily dissolved when heated at high temperatures. They dissolve in austenite and improve the hardenability of steel. In particular, when the Cr content is above 5%, it can significantly improve the oxidation resistance and corrosion resistance of steel. The overall content should be controlled between 4.0% and 6.0%.

[0050] Nb: A typical strong carbide-forming element, it has formed MC-type carbides with significant high-temperature stability; in particular, Nb and V can also interact with C, N, etc., to form complex carbonitrides, which play a role in pinning grain boundaries and refining grains during high-temperature austenitization. Considering all factors, the content is controlled within the range of 0.1% to 0.5%.

[0051] Ni and Cu: These are not the main elements used, and their alloy content is controlled to be below 0.5%.

[0052] N: It readily reacts with C, Nb, V, etc., to form complex carbonitrides, which play a role in pinning grain boundaries and refining grains during high-temperature austenitization. However, considering that it is difficult to add to high-carbon steel, its content must be ensured to be ≥200ppm.

[0053] On the other hand, the present invention also provides a method for preparing the above-mentioned roller with high hardness and uniform wear resistance, comprising the following steps:

[0054] Step 1: Form the roller blank using hot isostatic pressing;

[0055] Step 2: Heat treat the blank;

[0056] Step 3: Roughly machine the heat-treated blank to obtain the primary roller product;

[0057] Step 4: Perform induction heat treatment on the primary product;

[0058] Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft;

[0059] Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

[0060] Specifically, step 1 includes the following sub-steps:

[0061] Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying.

[0062] Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling.

[0063] Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1180-1220℃ and simultaneously pressurized to 130-170MPa. After holding the heat and pressure for 3-4 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

[0064] It should be noted that in step 1.1, the alloy composition is prepared according to the mass percentage of the roller composition: C: 0.90~1.15%, Si≤0.70%, Mn≤0.45%, P≤0.015%, S≤0.015%, Co: 4.0~8.0%, Mo: 3.0~10.0%, V: 0.5~1.5%, Cr: 4.0~6.0%, Nb: 0.1~0.5%, Ni+Cu≤0.5%, N≥200ppm, with the balance being Fe and unavoidable impurities.

[0065] The atomizing medium is nitrogen, the atomization pressure is 8-10 MPa, and the temperature of the molten metal is 1500-1550℃ to obtain spherical powder; the vacuum drying treatment is carried out at a drying temperature of 120-150℃ for 2-3 hours to remove adsorbed water and oil from the powder surface.

[0066] In step 1.2, the sheath thickness is 8–10 mm, and the inner wall of the sheath is sandblasted to a roughness of Ra 3.2–6.3 μm. Then, an anti-stick coating is applied with a thickness of 0.1–0.2 mm. The dried powder raw material is then loaded into the sheath, and compaction is achieved through vibration at a frequency of 50–60 Hz for 15–20 min, resulting in a powder density ≥ 6.0 g / cm³. 3 After powder filling, the package is vacuum sealed with a vacuum degree ≤1.0×10⁻⁶. -2 Pa, the weld at the sealing point has been non-destructively tested to ensure there is no leakage.

[0067] In step 1.3, the heating rate is 5-8℃ / min. During the heat holding and pressure holding period, the temperature and pressure are recorded every 30 minutes to ensure that the fluctuation range is within ±5℃ and ±5MPa. After heat holding and pressure holding, the temperature is reduced to below 500℃ at a cooling rate of 5-10℃ / min, and then cooled to room temperature in the furnace. The purpose is to obtain a dense steel ingot with no pores and uniform structure, such as a density ≥99.8%. Then, the oxide scale and other impurities on the surface of the steel ingot can be removed by mechanical grinding, chemical cleaning or electrolytic polishing.

[0068] It should be noted that if the density does not meet the requirements after hot isostatic pressing in step 1, such as when the density is less than 99.8%, the blank needs to be precision forged by extrusion. That is, there is step 1' after step 1 and before step 2.

[0069] Step 1': Precision forging of the blank using an extrusion method.

[0070] Specifically, in step 1', the hot isostatically pressed blank is placed in a gas furnace and heated to 1100–1150°C, held for 2–4 hours, and then extruded. The extrusion ratio is ≥2.25, and the extrusion rate is 3–8 mm / s. A lubricant, such as graphite powder or glass lubricant, is applied to the extrusion die to reduce the frictional resistance between the blank and the die. The extrusion die is preheated to 300–350°C. The extrusion ratio is the ratio of the cross-sectional area of ​​the blank before extrusion to the cross-sectional area of ​​the blank after extrusion.

[0071] The uniformly heated blank is quickly placed into the preheated cavity of an extrusion die. The equipment, such as a hydraulic extruder or screw press, is started, and axial pressure is applied to the blank through the punch. Under the constraint of the extrusion die, the blank undergoes plastic flow, filling the die cavity and further eliminating internal residual porosity. Extrusion is carried out at the set extrusion rate to ensure that the blank is fully densified and meets the dimensional requirements. After extrusion, the die is opened, and the ejection mechanism removes the extruded blank to prevent the blank from cooling and shrinking inside the die, which could cause it to stick to the die. After extrusion, the blank undergoes surface treatment by manual local grinding to remove lubricant residue and the oxide layer generated during forging, ensuring that the blank surface is free of cracks and defects.

[0072] It should be noted that the diameter of the blank formed by hot isostatic pressing alone or by extrusion after hot isostatic pressing is 25-30 mm larger than the diameter of the finished product, and the length of the blank is 20-30 mm longer than the finished product.

[0073] In step 2, the extruded blank can be directly heat-treated using the residual heat from precision forging. If the blank temperature is below 950°C after precision forging or if precision forging was not performed after hot isostatic pressing, the temperature needs to be raised in a heating furnace to 950–1000°C. Then, the roller blank is placed in a circulating oil bath at 30–60°C to cool to room temperature, followed by electric furnace tempering at 550–650°C for 10–15 hours. After tempering, the roller blank has a hardness of 25–40 HRC.

[0074] In step 3, rough machining is performed according to the design drawings. The diameter of the rough-machined primary roller is 4-6 mm larger than that of the finished product. Grinding is then used to ensure that the surface roughness of the primary roller reaches Ra0.8-1.6 μm.

[0075] Specifically, step 4 includes the following sub-steps:

[0076] Step 4.1: Preheat the rough-machined primary roller product;

[0077] Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode heating principle, and then water quench it.

[0078] Step 4.3: Temper the quenched primary product.

[0079] In step 4.1, the primary product is placed in a box furnace for preheating at a temperature of 350-400℃ and held for 1.5-2 hours to ensure that the temperature difference between the core and surface of the primary product is ≤20℃.

[0080] In step 4.2, the primary product is installed on a dedicated integrated induction hardening machine, ensuring that the coaxiality between the shaft and the induction coil is ≤0.5mm to avoid heating misalignment. The gap between the induction coil and the outer surface of the primary roller is 15-20mm. Heating is performed using a single-electrode heating method with a power frequency of 100-250Hz, an output power of 400-1000kW, and a heating time of ≥20min. During heating, the primary roller rotates at a uniform speed of 8-10 rpm to ensure uniform heating of the shaft surface. The heating temperature reaches 1170-1230℃, and after holding for ≥20min, rapid overall water spray quenching is performed within 2min. The water spray pressure is 0.4-0.8MPa, and the cooling time is 15-30 minutes, cooling to below 80℃ to obtain a martensitic structure.

[0081] In step 4.3, the induction-hardened primary roller product is placed in a resistance furnace with a protective atmosphere, such as nitrogen or argon, for tempering within 10 minutes. To ensure material properties, multiple tempering processes are required to ensure sufficient decomposition of residual austenite in the steel and minimize residual stress in the primary product. Specifically, the first tempering temperature is 535–550℃, with a holding time of at least 20 hours, followed by air cooling to room temperature; the second tempering temperature is 520–530℃, with a holding time of at least 20 hours, followed by air cooling to room temperature; the third tempering temperature is 500–515℃, with a holding time of at least 20 hours. The surface hardness of the primary product can reach 62–67 HRC or higher, the hardened layer can reach more than 20 mm, and it has sufficient high-temperature stability.

[0082] In step 5, a precision grinding machine is used to finish the primary product after induction hardening. The grinding wheel linear speed is usually at a high level of 35-60 m / s. The outer diameter is ground to the finished diameter D ± 0.02 mm, and the shaft length is machined to L ± 0.03 mm. Then, an ultra-precision polishing process is used for finishing. The grinding speed needs to be appropriately reduced, with the grinding wheel linear speed at 15-25 m / s. After grinding, the surface roughness of the roller shaft Ra ≤ 0.02 μm, the straightness ≤ 0.005 mm / m, and the roundness ≤ 0.003 mm.

[0083] Specifically, step 6 involves treating the outer cylindrical surface of the finished roller using physical vapor deposition (PVD), which includes the following sub-steps:

[0084] Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning; specific parameters are: vacuum degree below 5.0×10-2Pa, argon flow rate 150~200sccm, bias voltage -500~-800V, bombardment time 30~40min, to remove surface oxide film and oil stains.

[0085] Step 6.2, Coating Deposition: A TiN or TiAlN coating is deposited using a dedicated magnetron sputtering technique. Specific parameters are: deposition temperature above 350℃, such as 350–450℃, and vacuum degree of 1.0 × 10⁻⁶. -3 ~5.0×10 -3 The parameters are: Pa, argon flow rate of 80-100 sccm, nitrogen flow rate of 20-30 sccm, additional ammonia gas of 5-10 sccm required for TiAlN deposition, target material of Ti or TiAl with a purity of ≥99.9%, arc current of 80-100 A, bias voltage of -80 to -120 V, deposition time of 2-3 h, and coating thickness of 5-8 μm.

[0086] Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller. The coating hardness is above 10 GPa, such as 10-20 GPa; the plastic deformation is above 20%; the adhesion between the coating and the substrate is above 20 N, such as 20-30 N; and the wear rate is 5×10⁻⁶. -15 m 3 / (N·m) or less.

[0087] Specifically, coating thickness was measured using a scanning electron microscope (SEM); coating hardness was determined using a nanoindenter; plastic deformation was determined using a microcolumn compression test; the adhesion between the coating and the substrate was measured using a scratch tester; and wear rate was measured using a tribometer.

[0088] It should be noted that this invention improves the red hardness of the roller substrate through steel composition design; ensures sufficient compositional uniformity of the blank by using hot isostatic pressing; or further improves the density of the blank by using extrusion molding, thereby improving the thermal conductivity and uniformity of the material; the tempering temperature during the heat treatment of the blank and the induction heat treatment of the primary product are both above 500℃, and the induction heat treatment involves multiple tempering processes, which can ensure that the hardness does not decrease when used at temperatures below 500℃; the heat treatment of the primary product adopts an overall induction heat treatment method, which can fully guarantee the uniformity of performance; the intermediate product is treated with a surface coating to further improve the hardness of the working surface; ultimately, not only does the roller surface have high hardness and good hardness uniformity, and can adapt to working from room temperature to 400℃, but it also has high thermal conductivity, and the temperature field of the roller surface can be guaranteed to be sufficiently uniform when heated, with the axial and circumferential temperature difference ΔT not exceeding 1℃.

[0089] Finally, the present invention also provides a method for applying the above-mentioned roller with high hardness and high wear resistance uniformity. Applying the roller to the production processes such as calendering, forming and conveying of dry battery electrode sheets can not only ensure the thickness uniformity, surface flatness, density and mechanical stability of the electrode sheets, but also extend the service life of the roller.

[0090] Example 1

[0091] A roller with high hardness, high wear resistance and uniform properties, the roller is made of alloy steel, the roller diameter is 150mm, and the roller length is 400mm.

[0092] A method for preparing the above-mentioned roller shaft includes the following steps:

[0093] Step 1: Form the roller blank using hot isostatic pressing;

[0094] Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying.

[0095] The alloy composition is formulated according to the mass percentage of the roller components: C: 0.90%, Si: 0.70%, Mn: 0.45%, P: 0.010%, S: 0.015%, Co: 4.0%, Mo: 3.0%, V: 0.5%, Cr: 4.0%, Nb: 0.1%, Ni+Cu: 0.5%, N: 200ppm, with the balance being Fe and unavoidable impurities.

[0096] Nitrogen gas was used as the atomizing medium, the atomization pressure was 8 MPa, and the temperature of the molten metal was 1500℃ to obtain spherical powder. The vacuum drying process was carried out at a drying temperature of 120℃ for 2 hours to remove adsorbed water and oil from the powder surface.

[0097] Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling.

[0098] The sheath thickness is 8mm. Based on the final roller dimensions, the sheath's inner diameter is designed to be 192mm and its length 462mm. The inner wall of the sheath is sandblasted to a roughness of Ra3.2μm, then coated with an anti-stick coating with a thickness of 0.1mm. The dried powder raw material is loaded into the sheath, and compaction is achieved through vibration at a frequency of 50Hz for 15 minutes, resulting in a powder density of 6.0g / cm³. 3 After the powder is filled, the package is vacuum-sealed to a vacuum degree of 1.0 × 10⁻⁶. -2 Pa, the weld at the sealing point has been non-destructively tested to ensure there is no leakage.

[0099] Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1180℃ and simultaneously pressurized to 130MPa. After holding at the temperature and pressure for 3 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

[0100] The heating rate was 5℃ / min, and the temperature and pressure were recorded every 30 minutes during the holding and pressure-holding period to ensure that the fluctuation range was within ±5℃ and ±5MPa. After holding and pressure-holding, the temperature was reduced to below 500℃ at a cooling rate of 5℃ / min, and then cooled to room temperature in the furnace to obtain a dense steel ingot with no pores and a uniform microstructure, with a density of 99.8%. Then, the oxide scale and other impurities on the surface of the steel ingot were removed by mechanical grinding and chemical cleaning. After hot isostatic pressing, the blank diameter was 175mm and the length was 420mm.

[0101] Step 2: Heat treat the blank;

[0102] The blank is heated in a furnace to 950°C, then placed in a 30°C circulating oil bath to cool to room temperature. Subsequently, it undergoes electric furnace tempering at 550°C for 10 hours, followed by air cooling to room temperature. The hardness of the tempered roller blank is 25 HRC.

[0103] Step 3: Roughly machine the heat-treated blank to obtain the primary roller product;

[0104] In step 3, rough machining is performed according to the design drawings, and the surface roughness of the shaft of the primary product is Ra1.6μm by grinding.

[0105] Step 4: Perform induction heat treatment on the primary product;

[0106] Step 4.1: Preheat the rough-machined primary roller product;

[0107] Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode heating principle, and then water quench it.

[0108] Step 4.3: Temper the quenched primary product.

[0109] In step 4.1, the primary product is placed in a box furnace for preheating at 350°C and held for 1.5 hours to ensure that the temperature difference between the core and surface of the primary product is ≤20°C.

[0110] In step 4.2, the primary product is installed on a dedicated integrated induction hardening machine, ensuring that the coaxiality between the shaft and the induction coil is ≤0.5mm to avoid heating misalignment. The gap between the induction coil and the outer surface of the primary roller is 15mm. Heating is performed using the single-electrode method, with a power frequency of 100Hz, an output power of 400kW, and a heating time of 20min. During the heating process, the primary roller rotates at a uniform speed of 8 rpm to ensure uniform heating of the shaft surface. The heating temperature reaches 1170℃. After 20min of holding, rapid overall water spray quenching is performed within 2min, with a water spray pressure of 0.4MPa and a cooling time of 15 minutes, cooling to below 80℃ to obtain a martensitic structure.

[0111] In step 4.3, the induction-hardened primary roller product is placed in a nitrogen-filled resistance furnace for tempering within 10 minutes. Specifically, the first tempering temperature is 535℃, the holding time is 20 hours, and it is then air-cooled to room temperature; the second tempering temperature is 520℃, the holding time is 20 hours, and it is then air-cooled to room temperature; the third tempering temperature is 500℃, the holding time is 20 hours. The primary product has a surface hardness of 62 HRC, a hardened layer of 20 mm, and sufficient high-temperature stability.

[0112] Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft;

[0113] In step 5, a precision grinding machine is used to finish the primary product after induction hardening. The grinding wheel linear speed is usually at a high level of 35m / s. The outer diameter is ground to 150mm and the shaft length is machined to 400mm. Then, an ultra-precision polishing process is used for finishing. The grinding speed needs to be appropriately reduced, with the grinding wheel linear speed at 15m / s. After grinding, the surface roughness of the roller shaft Ra≤0.02μm, straightness≤0.005mm / m, and roundness≤0.003mm.

[0114] Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

[0115] The outer cylindrical surface of the finished roller intermediate product is treated by physical vapor deposition (PVD), including the following steps:

[0116] Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning; the specific parameters are: vacuum degree 5.0×10-2Pa, argon flow rate 150sccm, bias voltage -500V, bombardment time 30min, to remove surface oxide film and oil stains.

[0117] Step 6.2, Coating Deposition: A TiN coating is deposited using a dedicated magnetron sputtering technique; specific parameters are: deposition temperature 350℃, vacuum degree 1.0×10⁻⁶. -3 Pa, argon flow rate 80 sccm, nitrogen flow rate 20 sccm, target material Ti, target purity ≥99.9%, arc current 80A, bias voltage -80V, deposition time 2h, coating thickness 5μm.

[0118] Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller.

[0119] The roller substrate has a surface hardness of 62 HRC, with a hardness uniformity within ±0.3 HRC and a hardened layer depth of 20 mm. The roller substrate surface is coated with a 5 μm thick TiAl coating, with a coating hardness of 10 GPa, a plastic deformation of 20%, a coating-substrate adhesion of 20 N, and a wear rate of 5 × 10⁻⁶. -15 The roller has a density of m³ / (N·m) and can operate within a temperature range of room temperature to 400℃, with the axial and circumferential temperature field difference on the roller surface not exceeding 1℃. The chemical composition of the roller, by mass percentage, is: C: 0.90%, Si: 0.70%, Mn: 0.45%, P: 0.010%, S: 0.015%, Co: 4.0%, Mo: 3.0%, V: 0.5%, Cr: 4.0%, Nb: 0.1%, Ni+Cu: 0.5%, N: 200ppm, with the balance being Fe and unavoidable impurities.

[0120] The hardness of the hardened layer shall be tested in accordance with GB / T 13313-2008; the depth of the hardened layer shall be determined by destructive testing at the machining allowance, and by metallographic observation or hardness gradient testing. The coating thickness shall be measured using scanning electron microscopy (SEM) in accordance with GB / T 31563-2015; the coating hardness shall be determined using a nanoindenter in accordance with GB / T 25898-2010; the plastic deformation shall be determined using a micropillar compression test in accordance with GB / T 44839-2024; the adhesion between the coating and the substrate shall be measured using a scratch tester in accordance with JB / T 8554-1997; and the wear rate shall be measured using a tribometer in accordance with GB / T 45593-2025.

[0121] Example 2

[0122] A roller with high hardness, high wear resistance and uniform properties, the roller is made of alloy steel, the roller diameter is 350mm, and the roller length is 1000mm.

[0123] A method for preparing the above-mentioned roller shaft includes the following steps:

[0124] Step 1: Form the roller blank using hot isostatic pressing;

[0125] Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying.

[0126] The alloy composition is formulated according to the mass percentage of the roller components: C: 1.15%, Si: 0.40%, Mn: 0.25%, P: 0.015%, S: 0.010%, Co: 8.0%, Mo: 10.0%, V: 1.5%, Cr: 6.0%, Nb: 0.5%, N: 300ppm, with the balance being Fe and unavoidable impurities.

[0127] Nitrogen gas was used as the atomizing medium, the atomization pressure was 10 MPa, and the temperature of the molten metal was 1550℃ to obtain spherical powder. The vacuum drying process was carried out at a drying temperature of 150℃ for 3 hours to remove adsorbed water and oil from the powder surface.

[0128] Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling.

[0129] The sheath thickness is 10mm. Based on the final roller dimensions, the sheath's inner diameter is designed to be 616mm and its length 500mm. The inner wall of the sheath is sandblasted to a roughness of Ra 6.3μm, then coated with an anti-stick coating of 0.2mm thickness. The dried powder raw material is loaded into the sheath, and compaction is achieved through vibration at a frequency of 60Hz for 20 minutes, resulting in a powder density of 6.2g / cm³. 3 After the powder is filled, the package is vacuum-sealed to a vacuum degree of 5×10⁻⁶. -3 Pa, the weld at the sealing point has been non-destructively tested to ensure there is no leakage.

[0130] Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1220℃ and simultaneously pressurized to 170MPa. After holding the temperature and pressure for 4 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

[0131] The heating rate is 8℃ / min. During the heat preservation and pressure holding period, the temperature and pressure are recorded every 30 minutes to ensure that the fluctuation range is within ±5℃ and ±5MPa. After heat preservation and pressure holding, the temperature is reduced to below 500℃ at a cooling rate of 10℃ / min, and then cooled to room temperature in the furnace. Then, the oxide scale and other impurities on the surface of the steel ingot are removed by mechanical grinding and electrolytic polishing, and the density is 99%.

[0132] Step 1': Precision forging of the blank using an extrusion method;

[0133] The hot isostatically pressed blank was placed in a gas furnace and heated to 1100℃, held for 2 hours, and then extruded at an extrusion ratio of 2.25 and an extrusion rate of 3 mm / s. Glass lubricant was applied to the extrusion die to reduce frictional resistance between the blank and the die. The extrusion die was preheated to 300℃. After extrusion, the blank underwent surface treatment by manual localized grinding to remove lubricant residue and the oxide layer generated during forging. The extruded blank had a diameter of 380 mm and a length of 1030 mm.

[0134] Step 2: Heat treat the blank;

[0135] The residual heat of the precision forged roller blank is used for direct heat treatment. The blank temperature is 900℃. It is then returned to the furnace for reheating until it reaches 1000℃. The roller blank is then placed in a 60℃ circulating oil bath to cool to room temperature. Subsequently, it undergoes electric furnace tempering treatment at a tempering temperature of 650℃ for 15 hours. After air cooling to room temperature, the hardness of the tempered roller blank is 40HRC.

[0136] Step 3: Roughly machine the heat-treated blank to obtain the primary roller product;

[0137] In step 3, rough machining is performed according to the design drawings, and the roughness of the shaft of the primary product is Ra0.8μm by grinding.

[0138] Step 4: Perform induction heat treatment on the primary product;

[0139] Step 4.1: Preheat the rough-machined primary roller product;

[0140] Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode heating principle, and then water quench it.

[0141] Step 4.3: Temper the quenched primary product.

[0142] In step 4.1, the primary product is placed in a box furnace for preheating at 400℃ and held for 2 hours to ensure that the temperature difference between the core and the surface of the primary product is ≤20℃.

[0143] In step 4.2, the primary product is installed on a dedicated integrated induction hardening machine, ensuring that the coaxiality between the shaft and the induction coil is ≤0.5mm to avoid heating misalignment. The gap between the induction coil and the outer surface of the primary roller is 30mm. Heating is performed using a single-electrode method with a power frequency of 250Hz, an output power of 1000kW, and a heating time of 30 minutes. During heating, the primary roller rotates at a uniform speed of 10 rpm to ensure uniform heating of the shaft surface. The heating temperature reaches 1230℃, and after holding at this temperature for more than 30 minutes, rapid overall water spray quenching is performed within 2 minutes at a water spray pressure of 0.8MPa. The cooling time is 30 minutes, cooling to below 80℃ to obtain a martensitic structure.

[0144] In step 4.3, the induction-hardened primary roller product is placed in an argon-filled resistance furnace for tempering within 10 minutes. The first tempering temperature is 550℃, and the holding time is 30 hours, after which it is removed from the furnace and air-cooled to room temperature. The second tempering temperature is 530℃, and the holding time is 30 hours, after which it is removed from the furnace and air-cooled to room temperature. The third tempering temperature is 515℃, and the holding time is 30 hours. The surface hardness of the primary product is 67 HRC, the hardened layer is 30 mm, and it has sufficient high-temperature stability.

[0145] Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft;

[0146] In step 5, a precision grinding machine is used to finish the primary product after induction hardening. The grinding wheel linear speed is usually at a high level of 60m / s. The outer diameter is ground to 350mm and the shaft length is machined to 1000mm. Then, an ultra-precision polishing process is used for finishing. The grinding speed needs to be appropriately reduced, with the grinding wheel linear speed at 25m / s. After grinding, the surface roughness of the roller shaft Ra≤0.02μm, straightness≤0.005mm / m, and roundness≤0.003mm.

[0147] Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

[0148] The outer cylindrical surface of the finished roller intermediate product is treated by physical vapor deposition (PVD), including the following steps:

[0149] Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning; the specific parameters are: vacuum degree 4.0×10-2Pa, argon flow rate 200sccm, bias voltage -800V, bombardment time 40min, to remove surface oxide film and oil stains.

[0150] Step 6.2, Coating Deposition: A TiAlN coating is deposited using a dedicated magnetron sputtering technique; specific parameters are: deposition temperature 450℃, vacuum degree 5.0×10⁻⁶. -3 Pa, argon flow rate 100 sccm, nitrogen flow rate 30 sccm, ammonia 5 sccm, target material TiAl, target purity ≥99.9%, arc current 100A, bias voltage -120V, deposition time 3h, coating thickness 8μm.

[0151] Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller.

[0152] The roller substrate has a surface hardness of 67 HRC, with a hardness uniformity within ±0.3 HRC and a hardened layer depth of 25 mm. The roller substrate surface is coated with an 8 μm thick TiAlN coating. The coating hardness is 20 GPa, the plastic deformation is 30%, the adhesion between the coating and the substrate is 30 N, and the wear rate is 4.5 × 10⁻⁶. -15 m 3The roller has a density of / (N·m) and can operate in the range of room temperature to 400℃, with the temperature difference between the axial and circumferential directions of the roller surface not exceeding 1℃. The chemical composition of the roller, by mass percentage, is: C: 1.15%, Si: 0.40%, Mn: 0.25%, P: 0.015%, S: 0.010%, Co: 8.0%, Mo: 10.0%, V: 1.5%, Cr: 6.0%, Nb: 0.5%, N: 300ppm, with the balance being Fe and unavoidable impurities.

[0153] The hardness of the roller hardened layer, as well as the coating thickness and various performance indicators, are tested using the same methods as in Example 1; the depth of the hardened layer is determined by a destructive test at the machining allowance and by a hardness gradient test.

[0154] Example 3

[0155] A roller with high hardness, high wear resistance and uniform properties, the roller is made of alloy steel, the roller diameter is 250mm, and the roller length is 700mm.

[0156] A method for preparing the above-mentioned roller shaft includes the following steps:

[0157] Step 1: Form the roller blank using hot isostatic pressing;

[0158] Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying.

[0159] The alloy composition is formulated according to the mass percentage of the roller components: C: 1.0%, Si: 0.55%, Mn: 0.35%, P: 0.012%, S: 0.012%, Co: 6.0%, Mo: 6.5%, V: 1.0%, Cr: 5.0%, Nb: 0.3%, Ni+Cu: 0.25%, N: 250ppm, with the balance being Fe and unavoidable impurities.

[0160] Nitrogen gas was used as the atomizing medium, the atomization pressure was 9 MPa, and the temperature of the molten metal was 1525℃ to obtain spherical powder. The vacuum drying process was carried out at a drying temperature of 135℃ for 2.5 hours to remove adsorbed water and oil from the powder surface.

[0161] Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling.

[0162] The sheath thickness is 9mm. Based on the final roller dimensions, the sheath's inner diameter is designed to be 601mm and its length 200mm. The inner wall of the sheath is sandblasted to a roughness of Ra4.8μm, then coated with an anti-stick coating with a thickness of 0.15mm. The dried powder raw material is loaded into the sheath, and compaction is achieved through vibration at a frequency of 55Hz for 17 minutes, resulting in a powder density of 6.1g / cm³. 3 After the powder is filled, the package is vacuum-sealed to a vacuum degree of 7.5 × 10⁻⁶. -3 Pa, the weld at the sealing point has been non-destructively tested to ensure there is no leakage.

[0163] Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1200℃ and simultaneously pressurized to 150MPa. After holding at the temperature and pressure for 3.5 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

[0164] The heating rate was 7℃ / min. During the heat preservation and pressure holding period, the temperature and pressure were recorded every 30 minutes to ensure that the fluctuation range was within ±5℃ and ±5MPa. After heat preservation and pressure holding, the temperature was reduced to below 500℃ at a cooling rate of 8℃ / min, and then cooled to room temperature in the furnace. Then, the oxide scale and other impurities on the surface of the steel ingot were removed by mechanical grinding and chemical cleaning, and the density was 99.5%.

[0165] Step 1': Precision forging of the blank using an extrusion method;

[0166] The hot isostatically pressed blank was placed in a gas furnace and heated to 1125℃, held for 3 hours, and then extruded at an extrusion ratio of 4 and an extrusion rate of 6 mm / s. The extrusion die was coated with graphite powder lubricant to reduce friction between the blank and the die; the extrusion die was preheated to 325℃. After extrusion, the blank underwent surface treatment by manual localized grinding to remove lubricant residue and the oxide layer generated during forging. The diameter of the extruded blank was 277 mm and the length was 725 mm.

[0167] Step 2: Heat treat the blank;

[0168] The residual heat of the precision forged roller blank is used for direct heat treatment at a temperature of 970℃. Then, the roller blank is placed in a circulating oil bath at 45℃ to cool to room temperature. Subsequently, it is subjected to electric furnace tempering at a temperature of 600℃ for 12.5 hours and air-cooled to room temperature. The hardness of the tempered roller blank is 32HRC.

[0169] Step 3: Roughly machine the heat-treated blank to obtain the primary roller product;

[0170] In step 3, rough machining is performed according to the design drawings, and the surface roughness of the primary shaft is Ra1.2μm by grinding.

[0171] Step 4: Perform induction heat treatment on the primary product;

[0172] Step 4.1: Preheat the rough-machined primary roller product;

[0173] Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode heating principle, and then water quench it.

[0174] Step 4.3: Temper the quenched primary product.

[0175] In step 4.1, the primary product is placed in a box furnace for preheating at 375°C and held for 1.8 hours to ensure that the temperature difference between the core and surface of the primary product is ≤20°C.

[0176] In step 4.2, the primary product is installed on a dedicated integrated induction hardening machine, ensuring that the coaxiality between the shaft and the induction coil is ≤0.5mm to avoid heating misalignment. The gap between the induction coil and the outer surface of the primary roller is 17mm. Heating is performed using the single-electrode method, with a power frequency of 175Hz, an output power of 700kW, and a heating time of 25min. During the heating process, the primary roller rotates at a uniform speed of 9 rpm to ensure uniform heating of the shaft surface. The heating temperature reaches 1200℃, and after 25min of holding, rapid overall water spray quenching is performed within 2min at a water spray pressure of 0.6MPa. The cooling time is 20 minutes, cooling to below 80℃ to obtain a martensitic structure.

[0177] In step 4.3, the induction-hardened primary roller product is placed in a nitrogen-filled resistance furnace for tempering within 10 minutes. The first tempering temperature is 543℃, and the holding time is 25 hours, after which it is removed from the furnace and air-cooled to room temperature. The second tempering temperature is 525℃, and the holding time is 25 hours, after which it is removed from the furnace and air-cooled to room temperature. The third tempering temperature is 508℃, and the holding time is 25 hours. The surface hardness of the primary product is 65 HRC, the hardened layer is 22.5 mm, and it has sufficient high-temperature stability.

[0178] Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft;

[0179] In step 5, a precision grinding machine is used to finish the primary product after induction hardening. The grinding wheel linear speed is usually at a high level of 47m / s. The outer diameter is ground to 250mm and the shaft length is machined to 700mm. Then, an ultra-precision polishing process is used for finishing. The grinding speed needs to be appropriately reduced, with the grinding wheel linear speed at 20m / s. After grinding, the surface roughness of the roller shaft Ra≤0.02μm, straightness≤0.005mm / m, and roundness≤0.003mm.

[0180] Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

[0181] The outer cylindrical surface of the finished roller intermediate product is treated by physical vapor deposition (PVD), including the following steps:

[0182] Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning; the specific parameters are: vacuum degree 4.5×10-2Pa, argon flow rate 175sccm, bias voltage -650V, bombardment time 35min, to remove surface oxide film and oil stains.

[0183] Step 6.2, Coating Deposition: A TiAlN coating is deposited using a dedicated magnetron sputtering technique; specific parameters are: deposition temperature 400℃, vacuum degree 3.0×10⁻⁶. -3 Pa, argon flow rate 90 sccm, nitrogen flow rate 25 sccm, ammonia 5 sccm, target material TiAl, target purity ≥99.9%, arc current 90A, bias voltage -100V, deposition time 2.5h, coating thickness 6.5μm.

[0184] Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller.

[0185] The roller substrate has a surface hardness of 65 HRC, with a hardness uniformity within ±0.3 HRC and a hardened layer depth of 22.5 mm. The roller substrate surface is coated with a 6.5 μm thick TiAlN coating, with a coating hardness of 15 GPa, a plastic deformation of 25%, a coating-substrate adhesion of 25 N, and a wear rate of 4 × 10⁻¹⁵ m². 3 The roller has a density of / (N·m) and can operate in the range of room temperature to 400℃, with the temperature difference between the axial and circumferential directions of the roller surface not exceeding 1℃. The chemical composition of the roller, by mass percentage, is: C: 1.0%, Si: 0.55%, Mn: 0.35%, P: 0.012%, S: 0.012%, Co: 6.0%, Mo: 6.5%, V: 1.0%, Cr: 5.0%, Nb: 0.3%, Ni+Cu: 0.25%, N: 250ppm, with the balance being Fe and unavoidable impurities.

[0186] The testing methods for the hardness, depth, coating thickness, and various performance indicators of the roller hardened layer are the same as in Example 1.

[0187] The above description of the present invention represents only some embodiments, but the present invention is not limited to the specific implementations described above. The specific implementations described above are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A roller shaft with high hardness and uniform wear resistance, characterized in that, The roller shaft is made of alloy steel, and the surface hardness of the roller shaft substrate is 62-67 HRC. The roller shaft substrate surface is coated with a coating with a hardness of over 10 GPa, a plastic deformation of over 20%, a bonding force between the coating and the substrate of over 20 N, and a wear rate of 5 × 10⁻⁶. -15 m 3 / (N·m) or less; the roller operates in the range of room temperature to 400°C.

2. The roller shaft according to claim 1, characterized in that, The alloy steel, by mass percentage, has the following chemical composition: C: 0.90–1.15%, Si ≤ 0.70%, Mn ≤ 0.45%, P ≤ 0.015%, S ≤ 0.015%, Co: 4.0–8.0%, Mo: 3.0–10.0%, V: 0.5–1.5%, Cr: 4.0–6.0%, Nb: 0.1–0.5%, Ni+Cu ≤ 0.5%, N ≥ 200 ppm, with the balance being Fe and unavoidable impurities.

3. The roller shaft according to claim 1, characterized in that, The surface hardness uniformity of the roller substrate is within ±0.3HRC, and the hardened layer depth is greater than 20mm; the coating thickness is greater than 5μm, and the coating material is TiAlN or TiN.

4. A method for preparing a roller as described in any one of claims 1-3, characterized in that, The method includes the following steps: Step 1: Form the roller blank using hot isostatic pressing; Step 2: Heat treat the blank; Step 3: Roughly machine the heat-treated blank to obtain the primary roller product; Step 4: Perform induction heat treatment on the primary product; Step 5: Refine the primary product after induction heat treatment to obtain the intermediate product of the roller shaft; Step 6: Apply a surface coating to the intermediate-grade product to obtain the finished roller.

5. The method according to claim 4, characterized in that, Step 1 includes the following sub-steps: Step 1.1, Powder preparation and sieving: Alloy powder was prepared by gas atomization, and powder with a particle size range of 50-150 μm was selected and subjected to vacuum drying. Step 1.2, Packaging preparation and powder filling: The packaging is made of low carbon steel. The dried powder raw material is filled into the packaging, and the packaging is vacuum sealed after filling. Step 1.3, Hot Isostatic Pressing: The sealed sleeve is sent into a hot isostatic press, heated to 1180-1220℃ and simultaneously pressurized to 130-170MPa. After holding the heat and pressure for 3-4 hours, it is cooled and removed. After surface treatment, the forming roller blank is obtained.

6. The method according to claim 4, characterized in that, The process described is followed by step 1' after step 1 and before step 2, where the hot isostatically pressed blank is placed in a gas furnace and heated to 1100-1150°C, held for 2-4 hours, and then extruded. The extrusion ratio is ≥2.25 and the extrusion rate is 3-8 mm / s.

7. The method according to claim 4, characterized in that, In step 2, the heat treatment is as follows: the blank at 950-1000℃ is placed in a circulating oil bath at 30-60℃ and cooled to room temperature, and then tempered in an electric furnace at 550-650℃ for 10-15 hours, and then air-cooled to room temperature.

8. The method according to claim 4, characterized in that, Step 4 includes the following sub-steps: Step 4.1: Preheat the rough-processed primary roller product to 350-400℃ and keep it at that temperature for 1.5-2 hours. Step 4.2: Install the preheated primary product on an integrated induction hardening machine tool, heat it using the single-electrode method, and then water quench it. After the heating temperature reaches 1170~1230℃ and is held for ≥20min, quickly perform overall water spray quenching. The cooling time is 15~30 minutes, cooling it to below 80℃. Step 4.3: Place the quenched primary roller into a resistance furnace with a protective atmosphere for tempering. The first tempering temperature is 535-550℃, and the holding time is more than 20 hours. After tempering, remove the roller from the furnace and air cool to room temperature. The second tempering temperature is 520-530℃, and the holding time is more than 20 hours. After tempering, remove the roller from the furnace and air cool to room temperature. The third tempering temperature is 500-515℃, and the holding time is more than 20 hours.

9. The method according to claim 4, characterized in that, Step 6 involves processing the intermediate-grade product using physical vapor deposition (PVD), and includes the following sub-steps: Step 6.1, Pretreatment: Place the intermediate roller into the PVD vacuum chamber for argon ion bombardment cleaning; Step 6.2, Coating Deposition: Deposit TiN or TiAlN coating using magnetron sputtering technology, with a coating thickness of 5-8 μm. Step 6.3, Post-processing: After deposition, the roller is cooled to below 150°C in the vacuum chamber and then cooled to room temperature to obtain the finished roller.

10. A method of applying the roller as described in any one of claims 1-3, or the roller prepared by the method as described in any one of claims 4-9, to the production of dry-process battery electrode sheets by calendering, forming and conveying.