Preparation method of food-grade diamond roller

Abstract

The invention discloses a preparation method of a food-grade diamond roller, and belongs to the technical field of roller manufacturing, and the preparation method comprises the following steps: S1, selecting a tubular roller base material; s2, roller base material heat treatment and machining forming; s3, pretreating the surface of the roller body; s4, preparing a deposition material, wherein the deposition material comprises diamond micro-powder; s5, preparing a solution; s6, uniformly dispersing the deposition material in the solution; and S7, the roller body is suspended in a solution, the deposition material is migrated and deposited on the surface of the roller body through a physical method under the action of an external electric field, and the food-grade diamond roller is prepared. By optimizing a base material and a processing technology, combining with ultrahigh heat conductivity and hardness of diamond, and adopting a unique physical deposition technology to perform diamond composite treatment on the surface of the roller body, the roller has the characteristics of high heat conductivity, superhardness, wear resistance, no wire drawing, no running-in and the like, does not contain harmful heavy metals such as cobalt, nickel and the like, and completely meets the national food safety standard; the method is low in cost, simple in process, environment-friendly and energy-saving.

Description

Technical Field

[0001] The invention belongs to the technical field of roller manufacturing, and particularly relates to a method for preparing a food-grade diamond roller. Background Art

[0002] Different types of rollers are suitable for different working environments and material processing requirements. For example, cast iron rollers are widely used in rolling iron, steel and other metal materials due to their good casting performance, wear resistance and low cost, but they may have problems such as cracks, thermal cracks and uneven surface hardness; high-speed steel and carbide rollers are suitable for high-precision, high-speed and high-strength rolling requirements due to their excellent wear resistance and hardness, but the cost is relatively high; bimetallic composite rollers combine the advantages of different metals. The outer layer uses alloy steel with good wear resistance and the inner layer uses cheap carbon steel. This design can provide good intrinsic toughness while ensuring surface hardness, but it also has backward processing technology, high energy consumption, high pollution and high overall cost.

[0003] In addition, the high temperature generated during the operation of the existing rollers needs to be cooled by external water cooling or air cooling, which is a complicated process. In addition, the common surface coating technology often contains harmful heavy metals such as cobalt and nickel, which cannot be used in the food processing field.

[0004] Specifically, the existing rollers and their preparation have the following deficiencies: 1. The production process of the roll base is complicated. The ingredients, mixing, mold adjustment, smelting and casting before machining are time-consuming, labor-intensive and expensive. The production is difficult, the production safety risk is high, the carbon emissions are high, the production cost is high, the labor cost is high, the factory occupies a large area, and the land resources are wasted. The reasons for the problem are: first, the production process is backward, second, the surface coating technology is limited, and third, the material of the working layer on the surface of the roll is limited.

[0005] 2. The current metallurgical casting roller technology consumes at least 1,000 kWh of electricity to melt each ton of steel, resulting in high carbon emissions and high power consumption.

[0006] 3. After repeated wire drawing for about 10 times, the rollers will be scrapped and then transported to the smelter for melting. Due to the short service life of the rollers, frequent shutdowns and disassembly, high production costs, high expenses and low efficiency.

[0007] 4. The alloy layer accounts for more than 80% of the entire roll cost, and the alloy material does not have the wear resistance and heat dissipation properties of diamond and cubic boron nitride.

[0008] 5. At present, some companies use supersonic spraying technology to coat the wear-resistant material tungsten carbide alloy on the surface of the roller to improve the wear resistance of the roller. However, due to the food safety standards for food machinery, it is prohibited to contain heavy metals such as cobalt and nickel, which poses a food safety problem.

[0009] 6. When the rollers used in food machinery such as flour mills run at high speed, the surface temperature of the rollers will reach over 100 degrees, which will seriously destroy the protein, vitamins and enzymes of materials such as wheat, damage starch particles, and cause the quality of flour to decline. Summary of the invention

[0010] The object of the present invention is to provide a method for preparing a food-grade diamond roller in order to solve at least one technical problem in the above-mentioned prior art.

[0011] To achieve the above object, the present invention provides the following technical solution: a method for preparing a food-grade diamond roller, comprising the following steps: S1. Select a tubular roller substrate; S2, heat treatment and machining of roller substrate; S3, roller surface pretreatment; S4, preparing a deposition material, wherein the deposition material includes diamond powder; S5, preparing solution; S6, uniformly dispersing the sediment material in the solution; S7. Suspending the roller in the solution, and allowing the deposited material to migrate and deposit on the roller surface by physical means under the action of an external electric field to form a composite layer on the roller surface, thereby obtaining a food-grade diamond roller.

[0012] Furthermore, the base material of the rolling roller in S1 is carbon steel or 40 chrome or stainless steel.

[0013] Furthermore, S2 includes the following steps, and heat treatment is performed before each of the following steps: S201, obtaining a roller shaft head by forging or directly using round steel, and pressing the roller shaft head into a roller base material; S202, cutting of roller base material and roller shaft head; S203, grinding the part where the bearing is installed; S204, the surface of the roller substrate is subjected to wire drawing treatment.

[0014] Furthermore, S3 includes the following steps: S301, cleaning to remove pollutants and impurities on the surface of the roller; S302, roughening treatment, through sand blasting or shot blasting to control the roller surface roughness Ra < 0.4um; S303, drying treatment, through natural air drying or oven drying to make the roller surface free of moisture residue.

[0015] Furthermore, the deposition material in S4 includes the following raw materials in parts by weight: 40-85 parts of diamond powder; 1-10 parts of cubic boron nitride; 1-5 parts of titanium powder; 1-5 parts of molybdenum powder; and 1-5 parts of chromium powder.

[0016] Furthermore, the solution in S5 comprises the following raw materials in parts by weight: 60-80 parts of main salt; 20-40 parts of conductive salt; 5-10 parts of buffer; 1-5 parts of brightener; 1-5 parts of wetting agent; and the balance is water.

[0017] Furthermore, the main salt is either or both of nitrate and copper sulfate; the conductive salt is either or both of sodium sulfate and ammonium chloride; the buffer is boric acid; the brightener is sodium saccharin, and the wetting agent is sodium dodecyl sulfate.

[0018] Furthermore, the current range of the external electric field in S7 is 500-5000A.

[0019] Furthermore, in S7, the temperature is controlled at 50-76° C., and the deposition time is 4-10 hours.

[0020] Furthermore, after the food-grade diamond roller is prepared in S7, the surface is ground.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention aims to provide a method for preparing a rolling mill roll which is low in cost, simple in process, environmentally friendly, energy-saving and casting-free. By optimizing the substrate material and processing technology, combined with the ultra-high thermal conductivity and hardness of diamond, a unique physical deposition technology is used to perform diamond composite treatment on the surface of the roller body, so that the roller has the characteristics of high thermal conductivity, super-hardness and wear resistance, no wire drawing, no running-in, etc., and does not contain harmful heavy metals such as cobalt and nickel, and fully meets the national food safety standards. DETAILED DESCRIPTION

[0022] This embodiment provides a method for preparing a food-grade diamond roller, comprising the following steps: S1. Select a tubular roller substrate; S2. Heat treat and machine the roller substrate; S3. Pretreat the roller surface; S4. Prepare a deposition material, which includes diamond powder; S5. Prepare a solution; S6. Evenly disperse the deposition material in the solution; S7. Suspend the roller in the solution, and under the action of an external electric field, allow the deposition material to migrate and deposit on the roller surface by physical means to form a composite layer on the roller surface, thereby obtaining a food-grade diamond roller.

[0023] In the tubular roll base material selected by S1, the roll base material is selected from carbon steel or 40 chrome or stainless steel with relatively low cost and certain strength and toughness; these materials can be purchased directly, eliminating the casting process.

[0024] S2 includes the following steps, and heat treatment is performed before each of the following steps: S201. Obtain the roller shaft head by forging or directly using round steel, and press the roller shaft head into the roller base material to ensure a firm connection; S202. Cut the roller base material and the roller shaft head according to the size requirements of the drawing; S203. Accurately grind the part of the roller shaft head where the bearing is installed; S204. Perform wire drawing on the surface of the roller base material according to the technical parameters required by the product.

[0025] The roller surface of the roller substrate is quenched / annealed by plasma or laser processes. In order to reduce costs and simplify processes, the present invention selects carbon steel, 40 chromium and stainless steel profiles with low cost and certain strength and toughness as the roller substrate. However, compared with the high-speed steel, cemented carbide and bimetallic composite alloy layer used in the current rollers, the strength, toughness and corrosion resistance of these profiles cannot meet the requirements of the roller production process. Therefore, the roller body needs to be heat treated during the manufacturing process. The roller substrate with certain strength and toughness is replaced by bimetallic centrifugal casting cold hard alloy cast iron through quenching / annealing processes to achieve the purpose of saving costs, simplifying processes, reducing energy consumption and pollution.

[0026] For example, during the wire drawing process, due to the sufficient toughness of carbon steel but insufficient strength, wire deviation and wire breakage may occur. At this time, quenching is needed to improve its strength. When the strength of carbon steel is sufficient but the toughness is insufficient, the grinding teeth are prone to cracking and breaking. At this time, annealing is needed to improve its toughness and reduce its brittleness. Normalizing or annealing treatment is performed before cutting. By combining quenching with tempering at different temperatures, the strength, toughness and fatigue strength of the metal can be greatly improved, and the combination of these properties (comprehensive mechanical properties) can be obtained to meet different usage requirements.

[0027] The S3 roller surface pretreatment includes the following steps: S301, cleaning, remove pollutants and impurities on the roller surface; use ultrasonic cleaning or other physical and chemical methods to remove pollutants and impurities on the substrate surface. Clean the substrate, that is, mechanically or chemically clean to remove any dirt, debris or other contaminants on the substrate surface. This is important because any impurities on the substrate surface will affect the quality of the coating; S302, roughening treatment, controlling the roller surface roughness to Ra < 0.4um by sandblasting or shot peening; forming a rough surface on the substrate through relevant processes to make the composite layer easier to adhere; S303, drying treatment, by natural air drying or oven drying to make the roller surface free of moisture residue.

[0028] In the S4 preparation of the deposition material, the deposition material includes the following raw materials in parts by weight: 40-85 parts of diamond micropowder; 1-10 parts of cubic boron nitride; 1-5 parts of titanium powder; 1-5 parts of molybdenum powder; and 1-5 parts of chromium powder.

[0029] In S5, a solution is prepared; the solution includes the following raw materials in weight: 60-80 parts of main salt; 20-40 parts of conductive salt; 5-10 parts of buffer; 1-5 parts of brightener; 1-5 parts of wetting agent; the balance is water. In some embodiments, the weight of the brightener is 3-4 parts. In some embodiments, the proportion of all salts in the solution is 0.2-1%.

[0030] The main salt is either one or both of nitrate and copper sulfate. When the two are used, any ratio is used, and the nitrate that can provide metal ions is selected. During the composite process, nitrate and copper sulfate are reduced and deposited at the cathode (the composite workpiece, including the matrix of the diamond abrasive tool, etc., in this embodiment, the roller body) to form a composite layer. These main salts can provide sufficient metal ions to ensure that the composite process proceeds smoothly.

[0031] The conductive salt is either one or both of sodium sulfate and ammonium chloride; any ratio is used when both are used; sodium sulfate and ammonium chloride mainly increase the conductivity of the liquid, making the current distribution more uniform, which is conducive to better movement of metal ions to the cathode surface for deposition under the action of the electric field.

[0032] The buffer is boric acid; its function is to stabilize the pH value of the composite liquid. During the composite process, hydrogen ions will discharge at the cathode, causing the pH value of the liquid to change. Boric acid can slow down this change and maintain the pH value of the composite liquid within a suitable range, specifically around 7, to ensure the composite quality.

[0033] The brightener is sodium saccharin, which can make the surface of the composite layer brighter and smoother.

[0034] The wetting agent is sodium dodecyl sulfate, which can reduce the surface tension of the composite layer and prevent defects such as pinholes from occurring on the workpiece surface.

[0035] In S7, the roller body is suspended in the solution, and the deposited material is physically migrated and deposited on the surface of the roller body under the action of an external electric field, and a composite layer is formed on the surface of the roller body to obtain a food-grade diamond roller. This embodiment is used for roller preparation, and the length of the tank cavity containing the solution is ≥800mm. In some other embodiments, the method of this embodiment can be adjusted to tool preparation, brake disc preparation, roller preparation, grinding disc preparation, heat sink preparation, chip packaging preparation, etc. During the deposition process, the process parameters are strictly controlled, such as temperature control at 50-76°C; deposition time 4-10h. The rated current of the rectifier is ≥500A, and the specific current range of the external electric field is 500-5000A. A large amount of gas will be generated during the deposition process and discharged from the solution in the form of bubbles. The gas flow rate is controlled at 300-500l / min, which is specifically adjusted according to the total amount of solution material in the tank cavity. During the deposition process, titanium powder, molybdenum powder and chromium powder can carry diamond powder and deposit on the workpiece surface. Titanium powder, molybdenum powder and chromium powder can increase the holding force of diamond powder and cubic boron nitride on the workpiece surface, making the composite layer more stable.

[0036] The differences between the preparation method of the food-grade diamond roller in this embodiment and the existing related technology are as follows: The physical vapor deposition PVD technology, which is similar in principle to the present embodiment, places the workpiece in a vacuum, while the present embodiment places the workpiece in a liquid; The existing physical vapor deposition (PVD) technology is to gasify the surface of the material source into atoms and molecules, and deposit functional materials on the surface of the substrate through low-pressure gas or plasma processes to change the surface properties of the workpiece. This embodiment directly suspends the functional material powder in a liquid medium, and deposits it on the surface of the workpiece through electrodeposition and coating to change the surface properties of the workpiece, without the need to gasify, atomize, moleculeize, or ionize the material source; The existing physical vapor deposition (PVD) technology is to gasify the surface of the material source, and then the atoms and molecules are deposited on the surface of the workpiece under the vacuum low-pressure environment and gravity. The material source powder of the technology of this embodiment migrates and deposits on the surface of the workpiece under the action of an external electric field. The existing electroplating technology is to use the material source and the workpiece as the cathode and anode respectively. With the participation of the electrolyte medium, the metal cations migrate and deposit on the workpiece surface through electrochemical reaction under the action of the electric field. Strictly speaking, electroplating is a chemical liquid phase deposition technology. In this embodiment, the material source (deposition material) powder is migrated and deposited on the workpiece surface by physical methods under the action of an external electric field; In the existing electroplating technology, the metal on the workpiece surface is bonded to the workpiece by chemical bonds, which are covalent bonds. In this embodiment, the material source and the workpiece are bonded by holding force and entrainment force; Existing electroplating technology generally uses metal nickel as the base, and then deposits metal or non-metal particles. This technology does not require metal nickel as the base; In summary, whether from the gas phase medium or liquid phase medium, the method of particle generation, the type of power for particle migration and deposition, the way the material source particles are combined with the workpiece, and many other aspects, the technical features of this embodiment have relatively obvious differences and distinctions from the existing electroplating technology and physical vapor deposition (PVD) technology.

[0037] After S7 makes food-grade diamond rollers, it grinds the surface; uses precision grinding heads to finely grind the composite layer surface to improve surface finish and wear resistance. Using the super hardness and excellent thermal conductivity of diamond, physical deposition technology is used to form a diamond composite layer on the roller surface (the roller body after quenching / annealing still cannot meet the wear resistance requirements) to enhance the wear resistance and heat dissipation of the roller, so that the roller has super hardness and wear resistance, super long life, high thermal conductivity, low operating temperature and other characteristics, and no wire drawing and running-in are required, which improves production efficiency. The diamond composite layer does not contain harmful heavy metals such as cobalt and nickel, and fully meets national food safety standards.

[0038] About the performance of the prepared food grade diamond roller: Roller surface hardness: The Rockwell hardness of the existing roller surface alloy is HRA78-90, the Mohs hardness of diamond is 10, and the microhardness is 10000kg / mm. The main material of the roller surface prepared in this embodiment is diamond, and the hardness is determined by the performance of the ultimate material diamond; Roller surface thermal conductivity: The existing roller is made of gray iron smelting and casting. The thermal conductivity of gray iron is 40-55W / (Mk) at room temperature, and the thermal conductivity of diamond can reach 2000W / (Mk) at room temperature. The low temperature characteristics of the roller prepared in this embodiment are determined by the material; Food safety: At present, the rollers sprayed with tungsten carbide are cobalt-based tungsten carbide or nickel-based tungsten carbide, which contain heavy metals such as cobalt and nickel. The roller working layer prepared in this embodiment does not contain cobalt and nickel, but is a molybdenum, titanium, and copper-based diamond coating; The above parameters are determined by the physical properties of diamond. Compared with the existing rolling rollers, the rolling roller prepared in this embodiment has superior wear resistance, thermal conductivity and safety.

[0039] The roll preparation process and cost in this embodiment are already the best or even the most optimal solution in the current industry, and are irreplaceable by surface treatment processes such as thermal spraying, electroplating, brazing, surfacing, laser cladding, chemical deposition, and physical vapor deposition. The wear resistance and heat dissipation of diamond and cubic boron nitride are irreplaceable and incomparable to currently known materials including alloy materials.

[0040] Specifically, the method for preparing the food-grade diamond roller of this embodiment has the following technical advantages over the physical vapor deposition technology, including but not limited to: The existing physical PVD technology has a too small workpiece cavity space, which is suitable for small workpieces and cannot process large workpieces (such as medium and large rolls). In this embodiment, the cavity is larger, which can process large workpieces, and two rolls can be prepared in the experimental tank cavity at the same time. The existing physical PVD technology has complex material source particle migration conditions, requires the installation of auxiliary equipment, and requires vacuum operation. The particle migration amount is small and cannot meet the needs of large workpieces. The material source of this embodiment is a formed metal and non-metallic powder product, which can provide saturated supply for large workpieces and does not require the installation of auxiliary equipment; Compared with the traditional electroplating process, the existing physical PVD technology generates a certain amount of liquid waste. The method of this embodiment does not generate liquid waste, and only requires subsequent replenishment of material sources and adjustment of liquid pH index, and subsequent addition of brightener, wetting agent and buffer. The existing physical PVD technology has expensive vapor deposition process equipment; the liquid deposition process equipment is polluting and sacrifices the anode material. The method of this embodiment does not lose the anode material, does not pollute, can greatly reduce the equipment cost, and can process large workpieces; In summary, the method of this embodiment has four characteristics: first, it is an innovative breakthrough in the roller substrate; second, it is a technological breakthrough in PVD process technology and equipment; third, it is an innovative breakthrough in materials, in which diamond is coated on the working layer on the surface of the workpiece, with the content reaching 85%; fourth, it does not use cobalt-based and nickel-based materials, does not contain heavy metals such as cobalt and nickel, and meets national food safety standards.

[0041] The technical solutions disclosed in the present invention and the technical details disclosed in the embodiments are merely illustrative of the concept of the present invention and do not constitute a limitation of the present invention. Any non-creative changes made to the technical details disclosed in the present invention have the same inventive spirit as the present invention and are within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a food-grade diamond roller, characterized in that: The following steps are involved: S1. Select a tubular roller substrate; S2, heat treatment and machining of roller substrate; S3, roller surface pretreatment; S4, preparing a deposition material, wherein the deposition material includes diamond powder; S5, preparing solution; S6, uniformly dispersing the sediment material in the solution; S7. Suspending the roller in the solution, and allowing the deposited material to migrate and deposit on the roller surface by physical means under the action of an external electric field to form a composite layer on the roller surface, thereby obtaining a food-grade diamond roller.

2. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: The base material of the roller in S1 is carbon steel or 40 chrome or stainless steel.

3. The method for preparing the food-grade diamond roller according to claim 1, characterized in that: The S2 includes the following steps, and heat treatment is performed before each of the following steps: S201, obtaining a roller shaft head by forging or directly using round steel, and pressing the roller shaft head into a roller base material; S202, cutting of roller base material and roller shaft head; S203, grinding the part where the bearing is installed; S204, the surface of the roller substrate is subjected to wire drawing treatment.

4. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: The S3 includes the following steps: S301, cleaning to remove pollutants and impurities on the surface of the roller; S302, roughening treatment, through sand blasting or shot blasting to control the roller surface roughness Ra < 0.4um; S303, drying treatment, through natural air drying or oven drying to make the roller surface free of moisture residue.

5. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: The deposition material in S4 includes the following raw materials in parts by weight: 40-85 parts of diamond powder; 1-10 parts of cubic boron nitride; 1-5 parts of titanium powder; 1-5 parts of molybdenum powder; and 1-5 parts of chromium powder.

6. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: The solution in S5 comprises the following raw materials in parts by weight: 60-80 parts of main salt; 20-40 parts of conductive salt; 5-10 parts of buffer; 1-5 parts of brightener; 1-5 parts of wetting agent; and the balance is water.

7. The method for preparing a food-grade diamond roller according to claim 6, characterized in that: The main salt is either or both of nitrate and copper sulfate; the conductive salt is either or both of sodium sulfate and ammonium chloride; the buffer is boric acid; the brightener is sodium saccharin, and the wetting agent is sodium dodecyl sulfate.

8. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: The current range of the external electric field in S7 is 500-5000A.

9. The method for preparing a food-grade diamond roller according to claim 1 or 8, characterized in that: In the step S7, the temperature is controlled at 50-76° C. and the deposition time is 4-10 hours.

10. The method for preparing a food-grade diamond roller according to claim 1, characterized in that: After the food-grade diamond roller is prepared in S7, the surface is ground.