Hot-press molding grinding wheel based on liquid phenolic resin and preparation method of hot-press molding grinding wheel

Abstract

The invention discloses a hot-press molding grinding wheel based on liquid phenolic resin and a preparation method of the hot-press molding grinding wheel, and belongs to the technical field of grinding tool manufacturing. The preparation method comprises the steps of raw material preparation, mixing and blank making, hot-pressing curing, post-curing treatment, processing and checking. Resol type liquid thermosetting phenolic resin is adopted as a binding agent in the raw materials, and is matched with a grinding material with a specific particle size, a functional filler and a curing accelerator, and the problems that a traditional powdery resin grinding wheel is poor in mixing uniformity and insufficient in resin infiltration are solved through step-by-step feeding and mixing, step-by-step heating and pressurizing hot-pressing curing and step-by-step heating post-curing treatment. The hardness uniformity deviation of the prepared grinding wheel is within + / -2HRY, the grinding material is fully infiltrated and combined by liquid phenolic resin, and the grinding wheel has high bonding strength, excellent grinding performance and long service life, can be made into various types such as cutting discs and cymbal-shaped grinding wheels, and is suitable for processing materials such as metal and ceramic.

Description

Technical Field

[0001] This invention relates to the field of abrasive manufacturing technology, and in particular to a grinding wheel based on hot pressing of liquid phenolic resin and its preparation method. Background Technology

[0002] Grinding wheels are key tools in industry for grinding, polishing, and cutting, and are widely used in the processing of various materials such as metals, ceramics, glass, and stone. The core performance of a grinding wheel is determined by three main factors: abrasive, bonding agent, and porosity. Among them, the core role of the bonding agent is to firmly hold the high-hardness abrasive particles together, forming a grinding wheel structure with specific strength and shape, which directly affects the service life and processing accuracy of the grinding wheel.

[0003] In existing grinding wheel manufacturing technologies, binders are mainly classified into three categories: ceramic binders, metal binders, and resin binders. Among them, resin-bonded grinding wheels, especially those using phenolic resin as a binder, occupy an important market position in metal processing, building material cutting, and other fields due to their excellent elasticity, self-sharpening properties, polishing effect, and high bonding strength. Currently, mainstream phenolic resin grinding wheels on the market are generally produced using powdered phenolic resin as a raw material.

[0004] However, the use of powdered phenolic resin to prepare grinding wheels has significant technical drawbacks: First, the uniformity of mixing is difficult to control. During the dry mixing process, the powdered resin is prone to segregation due to differences in particle density and size, resulting in uneven distribution of hardness and strength in the finished grinding wheel and affecting processing stability. Second, the powdered resin has poor fluidity, making it difficult to fully wet the surface of the abrasive during hot pressing, resulting in insufficient coating of the abrasive and reducing the binding force of the binder on the abrasive grains, which can easily lead to premature detachment of the abrasive grains. Third, the powdered resin is prone to generating dust during transportation and mixing, which not only pollutes the production environment but also poses potential health hazards to operators, failing to meet the requirements of modern green production.

[0005] Liquid phenolic resin (Resol type) has the characteristics of low viscosity, excellent flowability, and good surface wettability, which can quickly and fully coat the surface of abrasive and filler particles. If applied to grinding wheel manufacturing, it is expected to fundamentally solve the aforementioned defects of powdered resin, significantly improving the mixing uniformity and bonding strength of the grinding wheel. However, the introduction of liquid resin also brings new technical challenges: liquid resin makes the mixture viscous, increasing the difficulty of spreading and pre-pressing; at the same time, the curing shrinkage characteristics of liquid resin differ from those of powdered resin, making existing hot pressing process parameters unsuitable, easily leading to problems such as grinding wheel deformation and internal stress concentration. Therefore, this invention proposes a grinding wheel based on liquid phenolic resin hot pressing molding and its preparation method to achieve stable production of high-performance grinding wheels. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor mixing uniformity and insufficient resin wetting in existing powdered resin grinding wheel manufacturing processes, and to provide a method for preparing grinding wheels based on hot pressing molding of liquid phenolic resin. This method utilizes the excellent wettability of liquid resin, and through a specific formulation and hot pressing curing process, produces grinding wheel products with uniform abrasive distribution, high bonding strength, good wear resistance, and long service life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a grinding wheel based on hot pressing of liquid phenolic resin includes the following steps:

[0009] a. Raw material preparation: Provide abrasives, liquid thermosetting phenolic resin, functional fillers, and curing accelerators;

[0010] b. Mixing and blanking: Mix the above raw materials evenly to obtain a wet mixture, and pre-press it into a blank;

[0011] c. Hot pressing curing: The blank is placed in a hot pressing mold and cured by step-by-step heating and pressurization, including a low-temperature preheating stage and a high-temperature curing stage;

[0012] d. Post-curing treatment: The hot-pressed grinding wheel blank is subjected to a stepped heating heat treatment;

[0013] e. Processing and inspection: Machining and performance testing of the post-cured grinding wheel.

[0014] Further, in step a, the liquid thermosetting phenolic resin is a Resol type phenolic resin with a solid content of 75%-85% and a viscosity of 800-2500 mPa·s (25℃), and its usage accounts for 15%-25% of the total mass of the raw materials.

[0015] Further, in step a, the abrasive is one or more of brown fused alumina, white fused alumina, silicon carbide, and superhard abrasive, with a particle size range of F30-F220, and the amount used accounts for 50%-70% of the total mass of the raw materials.

[0016] Further, in step a, the functional filler includes toughening filler and pore-forming agent, the total amount of which accounts for 8%-20% of the total mass of the raw materials; the curing accelerator is hexamethylenetetramine, the amount of which is added is 1%-5% of the weight of the liquid phenolic resin.

[0017] Furthermore, in step b, the mixing adopts a stepwise feeding method, first mixing the abrasive, filler and part of the liquid resin, and then adding the remaining resin and curing accelerator for mixing.

[0018] Further, in step c, the pressure of the low-temperature preheating stage is 5-10 MPa, the temperature is 125-140℃, and the time is 2-4 minutes; the pressure of the high-temperature curing stage is 15-25 MPa, the temperature is 160-180℃, and the time is 15-30 minutes.

[0019] Furthermore, in step d, the post-curing treatment adopts a stepped heating program, with the final temperature stage being 140-150℃, and is held at this temperature for 2-4 hours.

[0020] A grinding wheel, prepared by the above method, wherein the abrasive is fully impregnated and bonded by liquid phenolic resin.

[0021] Furthermore, the uniformity deviation of the hardness of the grinding wheel is within ±2HRY.

[0022] Furthermore, the grinding wheel is a cutting disc, a cymbal-shaped grinding wheel, a flat grinding wheel, or a superhard abrasive grinding wheel.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. Significantly improved mixing uniformity: Liquid phenolic resin has excellent fluidity and wettability, which can fully coat each abrasive and filler particle like "glue", completely solving the segregation problem in the dry mixing process of powdered resin, making the composition of the grinding wheel uniform, with high consistency in hardness and strength, and good processing stability.

[0025] 2. Significantly improved bonding strength: The contact area between liquid resin and the abrasive surface is much larger than that of powdered resin, forming stronger mechanical meshing and chemical bonding forces, effectively preventing premature abrasive grain detachment and extending the service life of the grinding wheel.

[0026] 3. High performance adjustability: By adjusting the solid content and viscosity of the liquid resin, as well as the type and amount of functional fillers, the hardness, porosity and toughness of the grinding wheel can be precisely controlled to meet different processing requirements from rough grinding to fine grinding. It is suitable for a variety of workpiece materials and has a wide range of applications.

[0027] 4. Green and environmentally friendly with high production efficiency: The use of liquid resin completely eliminates dust pollution caused by powdered resin, improves the production environment, and protects the health of operators; at the same time, the mixing process of liquid resin is simple and efficient, eliminating the need for complex dry mixing equipment, shortening the production cycle, and reducing production costs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Example 1: Preparation of a high-performance cutting disc

[0032] 1. Raw material ratio (by weight): 65 parts of F46 brown corundum abrasive, 20 parts of liquid phenolic resin (Resol type, solid content 80%, viscosity 1500mPa·s at 25℃), 10 parts of fine alumina powder (toughening filler), 4 parts of refined naphthalene particles (pore-forming agent), and 0.6 parts of hexamethylenetetramine (curing accelerator) (3% of the weight of liquid resin).

[0033] 2. Mixing and Preparing: Add brown corundum abrasive and fine alumina powder to a double planetary mixer and stir for 1.5 minutes until evenly dispersed; add 10 parts of liquid phenolic resin and continue stirring for 4 minutes to initially wet the surface of the solid particles; then add the remaining 10 parts of liquid phenolic resin and 0.6 parts of hexamethylenetetramine and stir for 7 minutes to obtain a uniform wet mixture; add the wet mixture quantitatively to a circular pre-pressing mold and maintain a pressure of 6 MPa for 2.5 minutes to pre-press into a blank with a diameter of 100 mm and a thickness of 3 mm.

[0034] 3. Drying pretreatment: Place the pre-pressed blank in an 80℃ forced-air oven and keep it at that temperature for 30 minutes to evaporate some of the volatile solvents and prevent bubbles from forming during the hot pressing process.

[0035] 4. Hot pressing and curing: Place the dried blank into a hot press mold preheated to 110℃. After closing the mold, perform the following procedures: ① Low temperature preheating: Pressurize to 8MPa, raise the temperature to 135℃, and maintain the temperature and pressure for 3 minutes; ② High temperature curing: Pressurize to 20MPa, raise the temperature to 175℃, and maintain the temperature and pressure for 20 minutes; ③ Cooling and depressurization: Maintain a pressure of 20MPa, lower the temperature to 55℃ through the mold cooling water jacket, depressurize and open the mold, and take out the grinding wheel blank.

[0036] 5. Post-curing treatment: Place the grinding wheel blank in a forced-air drying oven and perform post-curing according to the following procedure: room temperature → 100℃ (heating rate 8℃ / min, holding for 1h) → 120℃ (heating rate 8℃ / min, holding for 1h) → 150℃ (heating rate 8℃ / min, holding for 3h), and then cool naturally to room temperature.

[0037] 6. Machining and Inspection: The post-cured grinding wheel blank is machined and finished to ensure that the outer diameter, thickness and end face flatness meet the design requirements; after balance correction, its performance is tested: Rockwell hardness (HRY) is 80, hardness uniformity deviation is ±1.2HRY, rotational strength test (according to GB / T 2493-2017 standard) is qualified, grinding efficiency is high and durability is good.

[0038] Example 2: Preparation of heavy-duty flat grinding wheel

[0039] 1. Raw material ratio (by weight): 50 parts of F30 size white corundum abrasive, 20 parts of F30 size silicon carbide abrasive (70 parts of mixed abrasive), 18 parts of liquid phenolic resin (Resol type, solid content 85%, viscosity 2000 mPa·s at 25℃), 5 parts of rubber powder (toughening filler), 5 parts of iron oxide powder (grinding aid filler), and 0.5 parts of hexamethylenetetramine (curing accelerator) (accounting for 2.8% of the weight of liquid resin).

[0040] 2. Mixing and Preforming: Add white corundum, silicon carbide, rubber powder and iron oxide powder to a plow-type mixer and stir for 2 minutes until uniform; add 12 parts of liquid phenolic resin and stir for 5 minutes until initially wetted; then add the remaining 6 parts of liquid phenolic resin and 0.5 parts of hexamethylenetetramine and stir for 8 minutes to obtain a wet mixture; add the wet mixture to a flat pre-pressing mold and maintain a pressure of 8MPa for 3 minutes to pre-press into a blank with a diameter of 300mm and a thickness of 50mm.

[0041] 3. Hot pressing and curing: Place the blank into a hot press mold preheated to 120℃. After closing the mold, perform the following: ① Low temperature preheating: pressurize to 10MPa, heat to 140℃, and hold for 4 minutes; ② High temperature curing: pressurize to 25MPa, heat to 180℃, and hold for 25 minutes; ③ Cooling and depressurizing: maintain a pressure of 25MPa, cool to 50℃, depressurize, and remove the blank.

[0042] 4. Post-curing treatment: The post-curing procedure is as follows: room temperature → 100℃ (hold for 1 hour) → 120℃ (hold for 1 hour) → 145℃ (hold for 4 hours), with a heating rate of 10℃ / min.

[0043] 5. Machining and Inspection: The blank is subjected to external turning, end face finishing and balance correction; performance test results: Rockwell hardness (HRY) is 85, and the hardness uniformity deviation is ±1.5HRY; the grinding wheel has high strength and good toughness, and is suitable for heavy-duty grinding.

[0044] Comparative experiment (compared to powdered resin grinding wheels)

[0045] To verify the superiority of the method of the present invention, a comparative sample was prepared using the cutting disc formulation of Example 1 as a benchmark, with the same raw materials (only the liquid phenolic resin was replaced with an equal mass of powdered phenolic resin, with a softening point of 105°C), following a traditional dry-mixing process. The test results are as follows:

[0046] Table 1 Performance Test Results

[0047]

[0048]

[0049] The comparative results show that the liquid phenolic resin and supporting process used in this invention are significantly superior to the traditional powdered resin process in terms of grinding wheel performance and environmental friendliness, thus verifying the technical value of this invention.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a grinding wheel based on hot pressing of liquid phenolic resin, characterized in that, Includes the following steps: a. Raw material preparation: Provide abrasives, liquid thermosetting phenolic resin, functional fillers, and curing accelerators; b. Mixing and preforming: Mix the above raw materials evenly to obtain a wet mixture, and pre-press it into a preform; c. Hot pressing curing: The blank is placed in a hot pressing mold and cured by step-by-step heating and pressurization, including a low-temperature preheating stage and a high-temperature curing stage; d. Post-curing treatment: The hot-pressed grinding wheel blank is subjected to stepped heating heat treatment; e. Processing and inspection: Machining and performance testing of the post-cured grinding wheel.

2. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step a, the liquid thermosetting phenolic resin is a Resol type phenolic resin with a solid content of 75%-85% and a viscosity of 800-2500 mPa·s (25℃), and its usage accounts for 15%-25% of the total mass of the raw materials.

3. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step a, the abrasive is one or more of brown fused alumina, white fused alumina, silicon carbide, and superhard abrasive, with a particle size range of F30-F220, and the amount used accounts for 50%-70% of the total mass of the raw materials.

4. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step a, the functional filler includes toughening filler and pore-forming agent, the total amount of which accounts for 8%-20% of the total mass of the raw materials; the curing accelerator is hexamethylenetetramine, the amount of which is added is 1%-5% of the weight of the liquid phenolic resin.

5. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step b, the mixing adopts a stepwise feeding method. First, the abrasive, filler and part of the liquid resin are mixed, and then the remaining resin and curing accelerator are added and mixed.

6. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step c, the pressure of the low-temperature preheating stage is 5-10 MPa, the temperature is 125-140℃, and the time is 2-4 minutes; the pressure of the high-temperature curing stage is 15-25 MPa, the temperature is 160-180℃, and the time is 15-30 minutes.

7. The method for preparing a grinding wheel based on hot pressing of liquid phenolic resin according to claim 1, characterized in that: In step d, the post-curing treatment adopts a stepped heating program, with the final temperature stage being 140-150℃, and is held at this temperature for 2-4 hours.

8. A grinding wheel, characterized in that: The abrasive is prepared by the method described in any one of claims 1-7, wherein the abrasive is fully impregnated and bonded with liquid phenolic resin.

9. The grinding wheel according to claim 8, characterized in that: The uniformity of the hardness of the grinding wheel is within ±2HRY.

10. The grinding wheel according to claim 8 or 9, characterized in that: The grinding wheel is a cutting disc, a cymbal-shaped grinding wheel, a flat grinding wheel, or a superhard abrasive grinding wheel.

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