A brazed cemented carbide reinforced composite grinding roller and a preparation method thereof

Abstract

The present invention relates to a brazed cemented carbide reinforced composite grinding roller and a preparation method thereof, belonging to the field of grinding roller preparation, and the preparation method comprises the following steps: step one, respectively setting grooves on the bottom surface and the cylindrical surface of the cemented carbide column nail, and filling the grooves with brazing material; step two, placing the cemented carbide column nail processed in step one into a metal cylinder to obtain a cemented carbide preform; step three, after preheating the prepared cemented carbide preform, installing the cemented carbide preform on the inner surface of the casting mold according to the distribution law of the cemented carbide column nails designed on the grinding roller surface; step four, after closing the mold, casting the roller body material melt into the casting mold cavity to obtain a brazed cemented carbide composite reinforced grinding roller. The method can solve the problem of uneven welding area caused by the gravity flow of the brazing material during the casting process, improve the bonding strength between the cemented carbide and the roller body, and the column nails of the prepared composite grinding roller are less likely to fall off during the working process.

Description

Technical Field

[0001] The invention belongs to the field of grinding roller preparation, and in particular relates to a brazed hard alloy reinforced composite grinding roller and a preparation method thereof. Background Art

[0002] High-pressure roller mill is a new type of high-efficiency and energy-saving crushing equipment. At present, high-pressure roller mill has been successfully applied in the crushing of ore, cement raw material and clinker and other materials. The working principle of high-pressure roller mill is that when the material is fed between the two rollers, the moving roller rotates under the strong radial hydraulic pressure to drive the material downward, and the fixed roller is driven to rotate in the opposite direction. The material is continuously pressed into cakes in the adjustable roller gap and the crushing effect is achieved.

[0003] The crushing principle of high pressure roller mill is mainly based on the theory of laminated crushing, which means that a large number of granular materials are gathered together under the spatial constraints of high pressure, and the group crushing is formed by contact and extrusion under the action of strong external force. Laminated crushing is also called material layer crushing. Its main advantages are high pressure during crushing, high fine particle content of the final product after crushing, and cracks are easily generated inside the ore particles, thereby improving the dissociation degree of the ore, reducing the energy consumption of subsequent grinding operations and increasing the output.

[0004] At present, the more advanced wear-resistant roller surface of the high-pressure roller mill is the cemented carbide (tungsten carbide) stud inlaid roller surface. The preparation process of the cemented carbide inlaid roller surface is as follows: first, a roller surface substrate with a certain strength is selected, then blind holes with a certain distribution pattern are processed on the roller surface, and finally the sintered cemented carbide is inlaid into the blind holes on the roller surface. Since the cemented carbide studs have extremely high hardness and wear resistance, the wear on the entire roller surface is very small. However, the wear resistance and compressive strength of the high-pressure roller substrate material are insufficient, which will cause the cemented carbide studs to fall off directly during use, resulting in wear and failure of the roller surface.

[0005] Patent document CN114669362A discloses a method for manufacturing a roller sleeve, which utilizes the superheated heat capacity and solidification heat capacity of molten steel to heat the brazing alloy plate between the column pins and the column pins, melts the brazing alloy, and makes the column pins and the column pins brazed to form the wear-resistant layer of the roller sleeve as a whole. In this method, multiple column pins are placed in a cylinder made of thin-walled steel plates, and are placed layer by layer. Brazing alloy plates are placed between the column pins, and a brazing alloy plate is sandwiched between every two layers of column pins. In this way, although the brazing material is constrained in the cylinder after melting, the brazing material flows downward due to gravity after melting in the cylinder, resulting in uneven actual welding areas between column pins, especially uneven brazing between the upper column pins and the lower column pins and the roller body, so that the column pins are subjected to uneven force during operation and have the risk of falling off. In addition, the brazing material elements are dissolved into the roller matrix, which also affects the performance of the roller matrix. Summary of the invention

[0006] The purpose of the present invention is to provide a brazed cemented carbide reinforced composite grinding roller and a preparation method thereof, which utilizes a cemented carbide preform to solve the problem of uneven welding area caused by the gravity flow of the brazing material during the casting process, improves the bonding strength between the cemented carbide and the roller body, and reduces the shedding of the cemented carbide during use.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing a brazed cemented carbide reinforced composite grinding roller, comprising the following steps:

[0008] Step 1: grooves are respectively provided on the bottom surface and the cylindrical surface of the cemented carbide stud, and solder is filled after a paste solder is applied in the groove, wherein a part of the solder located on the bottom surface is located in the groove of the bottom surface, and the other part covers the bottom surface outside the groove;

[0009] Step 2, the carbide stud processed in step 1 is placed in a metal cylinder, the inner diameter of the metal cylinder is equal to the diameter of the carbide stud, and the metal cylinder covers the groove and the solder, and the top surface and a part of the cylindrical surface of the carbide stud are exposed from the metal cylinder, so as to obtain a carbide preform; the melting point of the metal cylinder is higher than the melting point of the solder and lower than the temperature of the roller material melt;

[0010] Step 3: After the prepared hard alloy preform is preheated, the hard alloy preform is installed on the inner surface of the mold according to the distribution pattern of the hard alloy studs designed on the surface of the grinding roller. During the installation, the part of the hard alloy preform exposed from the metal cylinder is fixed on the inner surface of the mold;

[0011] Step 4: After closing the mold, the roller material melt is cast into the casting cavity to obtain a brazed cemented carbide composite reinforced grinding roller.

[0012] The groove on the bottom surface of the hard alloy column nail is located at the center of the bottom surface.

[0013] The groove on the cylindrical surface of the hard alloy column nail is an annular groove, and one or more annular grooves are provided.

[0014] The cemented carbide stud has a plurality of grooves on the cylindrical surface, which are distributed on the cylindrical surface at intervals.

[0015] In step 1, the size of the cemented carbide column nail is 10-30mm in diameter and 10-40mm in height.

[0016] In step 1, the wall thickness of the metal tube is 1-4 mm, and the internal depth is 5-10 mm less than the height of the carbide stud.

[0017] In step 1, the metal cylinder is a steel cylinder.

[0018] In step three, the preheating temperature is 300-500°C.

[0019] The present invention also proposes a brazed cemented carbide reinforced composite grinding roller, comprising a roller body and a cemented carbide stud array distributed on the surface of the roller body, wherein the cemented carbide stud array comprises a plurality of cemented carbide studs, and the cemented carbide studs are fixed on the roller body using the above-mentioned preparation method.

[0020] Furthermore, the cemented carbide stud array is formed by staggered arrangement of the plurality of cemented carbide studs in the axial and circumferential directions of the roller body.

[0021] The technical principle of the present invention is that the present invention grooves the column surface and the bottom surface of the cemented carbide column nail and fills the solder, instead of filling the solder in the gap between the cemented carbide column nail and the metal tube, in order to prevent the solder from flowing due to gravity after melting and causing uneven brazing. When the solder is filled in the corresponding groove, the solder can only flow in the groove after melting; and the part of the cemented carbide column nail where the solder is arranged is wrapped by the metal tube. The melting point of the solder is generally 700-1000°C, while the melting point of the steel tube is about 1500°C. Therefore, the solder can be prevented from being lost under the wrapping of the metal tube, so the problem of uneven brazing caused by the flow of the solder can be solved.

[0022] The beneficial effects of the present invention are as follows: when the method of the present invention is adopted, it is possible to prevent the brazing material from flowing downward under the influence of gravity after melting, resulting in uneven brazing; after the cemented carbide column nails are wrapped with a metal cylinder, on the one hand, it can prevent the loss of the brazing material, and on the other hand, the steel cylinder can be used as an intermediate layer to relieve stress and reduce the falling off of the cemented carbide column nails; after casting, the cemented carbide column nails can form a metallurgical bond with the roller body, and the column nails are less likely to fall off during the operation of the high-pressure roller mill.

[0023] During operation, the greatest load borne by the cemented carbide studs is the impact load from the top of the studs downwards. The solder at the bottom is stepped, and a buffer pad can be formed at the weld after casting, which plays a buffering role and reduces the proportion of studs falling off due to impact.

[0024] The overall solution of the present invention is simpler and more convenient than processes such as infiltration casting and negative pressure casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a flow chart of the method for preparing the brazed cemented carbide reinforced composite grinding roller described in Example 1 of the present invention;

[0027] Figure 2 A cross-sectional view of the cemented carbide preform in Example 1 of the present invention installed on a casting mold;

[0028] Figure 3 It is a schematic diagram of the structure of the cemented carbide stud described in Example 1 of the present invention;

[0029] Figure 4 It is a schematic structural diagram of a cemented carbide preform in Example 1 of the present invention;

[0030] Figure 5 It is a partial view of the brazed cemented carbide reinforced composite grinding roller described in Example 1 of the present invention;

[0031] Figure 6 This is a schematic diagram of the structure of the brazed cemented carbide reinforced composite grinding roller described in Example 2 of the present invention;

[0032] Figure 7 for Figure 6 A partial view of the joint between the middle roller and the column pin;

[0033] Figure 8 is a partial cross-sectional view of a cemented carbide preform in Example 3 of the present invention;

[0034] Fig. 9 It is a schematic diagram of the structure of the cemented carbide stud described in Example 4 of the present invention;

[0035] Markings in the figure: 1, casting mold, 2, cemented carbide preform, 3, casting mold cavity, 4, cemented carbide column nail, 5, metal cylinder, 6, ring groove, 7, solder, 8, bottom groove, 9, roller body, 10, trapezoidal groove, 11, pointed bottom groove, 12, arched groove, 13, cylindrical groove. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the invention in any way.

[0037] Example 1: Figure 1-5 As shown, a method for preparing a brazed cemented carbide reinforced composite grinding roller comprises the following steps:

[0038] Step 1: groove the cylindrical surface and bottom surface of the cemented carbide stud 4, including forming an annular groove 6 extending in the circumferential direction on the cylindrical surface, forming a cylindrical bottom surface groove 8 at the center of the bottom surface, brushing a paste brazing agent in the annular groove 6 and the bottom surface groove 8, and then filling the brazing material 7;

[0039] The solder 7 in the annular groove 6 is distributed in an annular shape, and the solder 7 at the bottom surface groove 8 is stepped, having two cylindrical sections of different diameters, the cylindrical section with a smaller diameter is filled in the bottom surface groove 8, and the cylindrical section with a larger diameter covers the bottom surface of the cemented carbide stud 4; the paste solder used in this embodiment is QJ308 solder paste, and the solder 7 used is BCu84MnNi;

[0040] Step 2: Put the carbide stud 4 filled with solder 7 into a metal tube 5 with one end open. The inner diameter of the metal tube 5 is the same as the diameter of the carbide stud 4. The inner depth of the metal tube 5 is lower than the height of the carbide stud 4, so that the end of the carbide stud 4 can be exposed from the metal tube 5. Figure 4 The hard alloy preform 2 shown;

[0041] Step 3: After the hard alloy preform 2 is preheated to 300-500°C, the exposed hard alloy studs 4 on the hard alloy preform 2 are fixed to the inner surface of the mold 1 according to the hard alloy stud distribution pattern designed on the surface of the grinding roller, so as to form a multi-layer array of hard alloy preforms 2 with each layer uniformly distributed in the circumferential direction, and the cross section thereof is as follows: Figure 2 As shown;

[0042] Step 4: After the mold is closed, the roller material melt is cast into the casting cavity 3. During the casting process, the metal cylinder 5 of the cemented carbide preform 2 and the filled brazing material 7 are melted by the roller material melt. After cooling, a cemented carbide composite reinforced grinding roller is obtained, the surface of which is evenly distributed with cemented carbide studs 4, and the cemented carbide studs 4 are metallurgically bonded to the roller body. The local structure of the obtained cemented carbide composite reinforced grinding roller is as follows: Figure 5 shown.

[0043] Specifically, Figure 3 , 4 As shown, the carbide stud 4 is a cylinder with a diameter of 10-30mm and a height of 10-40mm. A ring groove 6 extending circumferentially is provided on the cylindrical surface, and a bottom groove 8 is provided at the center of the bottom surface; the metal cylinder 5 is a thin-walled steel cylinder with a wall thickness of 1-4mm and an internal depth of 5-10mm less than the height of the carbide stud 4. The material of the metal cylinder 5 is selected from spring steel with good elasticity such as 65Mn.

[0044] The brazing filler metal 7 is made of commonly used hard alloy brazing filler metals such as silver-based, copper-based, and nickel-based, and the roller body material is made of medium-low alloy steel with good toughness.

[0045] In a specific implementation, the metal cylinder 5 may also be made of other materials having a higher melting point than the solder 7 and capable of being melted by the roller body material melt.

[0046] Example 2: Figure 6 , 7As shown, a brazed cemented carbide reinforced composite grinding roller comprises a roller body 9 and a plurality of cemented carbide studs 4 distributed on the surface of the roller body 9, wherein the cemented carbide studs 4 are fixed on the roller body 9 by the preparation method described in Example 1, and a welding area is formed by the flow of the brazing material at the position where the brazing material is filled on the cemented carbide studs 4, the cemented carbide studs 4 are brazed evenly with the roller body 9, and the cemented carbide studs 4 and the roller body 9 form a metallurgical bond, and during the operation of the high pressure roller mill, the cemented carbide studs 4 are less likely to fall off.

[0047] The middle part of the roller body 9 is the working section of the grinding roller, and the carbide studs 4 are distributed on the working section. The multiple carbide studs 4 arranged along the axial direction of the roller body 9 are defined as stud rows, and the multiple carbide studs 4 arranged along the circumferential direction of the roller body 9 are defined as stud columns. The multiple carbide studs 4 of adjacent stud rows are staggered in the circumferential direction of the roller body 9, that is, two adjacent carbide studs 4 located in adjacent rows are not on the same circumference; the multiple carbide studs 4 of adjacent stud columns are staggered in the axial direction of the roller body 9, that is, two adjacent carbide studs 4 located in adjacent columns are not on the same axis. The staggered arrangement of the carbide studs 4 in the axial and circumferential directions of the roller body 9 allows more carbide studs 4 to be arranged in the working section of the roller body 9 of the same area.

[0048] Embodiment 3: In Embodiment 1, a rectangular annular groove 6 is provided on the cylindrical surface of the cemented carbide stud 4 and filled with solder 7, and a bottom surface groove 8 is provided at the center of the bottom surface of the cemented carbide stud 4. Compared with Embodiment 1, the present embodiment is different in that a plurality of annular grooves 6 are provided on the cylindrical surface of the cemented carbide stud 4 and filled with solder, and the cross-sectional shape of the annular groove 6 is an arc, an arch, a trapezoid or a pointed bottom groove, wherein the pointed bottom groove is obtained by setting the groove bottom into two intersecting inclined surfaces based on the rectangular cross-section of the annular groove in Embodiment 1, and the shapes of the pointed bottom groove 11, the arched groove 12 and the trapezoidal groove 10 are as follows: Figure 8 In addition, the bottom surface of the cemented carbide stud 4 in this embodiment can also be provided with a plurality of bottom surface grooves 8, and the shape of the bottom surface grooves 8 can be adjusted according to needs and processing conditions.

[0049] Embodiment 4: In the above embodiment, the cylindrical surface of the cemented carbide stud 4 is provided with an annular groove 6, i.e., an annular groove extending along the circumference of the cylindrical surface. In this embodiment, a plurality of cylindrical grooves 13 may be distributed along the circumference on the cylindrical surface of the cemented carbide stud 4 according to actual conditions. The cross-sectional shape of each cylindrical groove 13 may refer to the several types listed in Embodiment 3, for example, Fig. 9 As shown, two cylindrical grooves 13 are arranged on the same circumference.

[0050] After the brazed carbide reinforced composite grinding roller in the above-mentioned embodiments 1-4 is used in the high-pressure roller mill, the brazing material is more evenly distributed during the casting process, and the brazing material forms a metallurgical bond with the roller body. At the same time, the brazing material on the bottom of the carbide stud 4 is a step-shaped material, which can form a buffer pad after casting, which plays a buffering role on the impact load of the carbide stud 4 during the operation of the grinding roller, thereby reducing the shedding rate of the carbide stud 4 and extending the service life of the grinding roller. According to the test, the carbide stud 4 did not fall off after the grinding roller worked for 2700 hours.

[0051] Comparative Example 1: A grinding roller of a high pressure roller mill, the roller surface of which is processed with blind holes having a certain distribution pattern, and then cemented carbide studs are embedded in the blind holes on the roller surface.

[0052] This comparative example does not adopt the method described in Example 1. Although the cemented carbide studs have extremely high hardness and wear resistance, the wear resistance and compressive strength of the high-pressure roller base material are insufficient. The grinding roller base gradually wears during use, and more and more cemented carbide studs are exposed. The bonding force between the embedded cemented carbide studs and the base is insufficient, causing the cemented carbide studs to begin to fall off after about 1500 hours of use.

[0053] Comparative Example 2: The difference from Example 1 is that there is no solder on the bottom surface of the cemented carbide column nail 4, and only the column surface grooves are filled with solder.

[0054] During the operation of the grinding roller, the maximum load on the carbide studs is the impact load from the top of the studs downward. Although the preparation method of comparative example 2 also uses a metal cylinder, which can make the brazing material on the stud surface evenly distributed, there is no brazing material on the bottom surface of the carbide studs 4 to form brazing, and the buffer pad described in the present invention cannot be formed, and the impact load cannot be buffered, making the bonding force between the carbide studs 4 and the roller body weaker than that of the present invention. After testing, the grinding roller prepared in comparative example 2 began to fall off after working for about 2000 hours.

[0055] Comparative Example 3: The difference from Example 1 is that after the annular groove 6 and the bottom groove 8 of the cemented carbide stud 4 are filled with brazing material, they are no longer placed in the metal tube 5. Instead, the cemented carbide stud 4 is directly fixed on the inner surface of the mold 1 for casting according to the distribution pattern of the cemented carbide stud 4 designed on the surface of the grinding roller.

[0056] Because the grinding roller prepared in Comparative Example 3 does not use the metal cylinder 5, during the casting process, after the brazing material 7 melts, a part of the brazing material 7 flows downward due to gravity, and it is difficult to evenly distribute around the carbide studs 4, resulting in uneven actual welding areas of the carbide studs 4, causing uneven force on the carbide studs 4 during operation, and there is a risk of falling off. After testing, the grinding roller prepared in Comparative Example 3 began to experience the carbide studs 4 falling off after working for about 2400 hours.

[0057] The technical effect comparison results of the brazed cemented carbide reinforced composite grinding roller prepared in Example 1 of the present invention and the cemented carbide studded grinding rollers prepared in Comparative Examples 1-3 are shown in Table 1.

[0058] Table 1 Comparison of technical effects of Example 1 and Comparative Examples 1-3

[0059]

[0060] By comparison, the brazed cemented carbide reinforced composite grinding roller prepared by the method of the present invention can effectively improve the service life of the grinding roller in the high pressure roller mill.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation modes of the present invention may be modified or replaced by equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A method for preparing a brazed cemented carbide reinforced composite grinding roller, characterized in that: The steps include: Step 1: grooves are respectively provided on the bottom surface and the cylindrical surface of the cemented carbide stud, and solder is filled after a paste solder is applied in the grooves, wherein the solder located on the bottom surface is in a step-shaped shape, with a part located in the groove on the bottom surface and the other part covering the bottom surface outside the groove; Step 2, the carbide stud processed in step 1 is placed in a metal cylinder with an opening at one end, the inner diameter of the metal cylinder is the same as the diameter of the carbide stud, the groove and the solder are covered by the metal cylinder, and the top surface and a part of the cylindrical surface of the carbide stud are exposed from the metal cylinder, so as to obtain a carbide preform; the melting point of the metal cylinder is higher than the melting point of the solder and lower than the temperature of the roller material melt; Step 3: After the prepared hard alloy preform is preheated, the hard alloy preform is installed on the inner surface of the mold according to the distribution pattern of the hard alloy studs designed on the surface of the grinding roller. During the installation, the part of the hard alloy preform exposed from the metal cylinder is fixed on the inner surface of the mold; Step 4: After the mold is closed, the roller material melt is cast into the casting cavity to obtain a brazed cemented carbide composite reinforced grinding roller in which the cemented carbide studs and the roller body are metallurgically combined.

2. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: The groove on the bottom surface of the hard alloy column nail is located at the center of the bottom surface.

3. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: The groove on the cylindrical surface of the hard alloy column nail is an annular groove, and one or more annular grooves are provided.

4. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: The cemented carbide stud has a plurality of grooves on the cylindrical surface, which are distributed on the cylindrical surface at intervals.

5. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: In step 1, the size of the cemented carbide column nail is 10-30mm in diameter and 10-40mm in height.

6. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 5, characterized in that: In step 1, the wall thickness of the metal tube is 1-4 mm, and the internal depth is 5-10 mm less than the height of the carbide stud.

7. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: In step 1, the metal cylinder is a steel cylinder.

8. The method for preparing the brazed cemented carbide reinforced composite grinding roller according to claim 1, characterized in that: In step three, the preheating temperature is 300-500°C.

9. A brazed cemented carbide reinforced composite grinding roller, comprising a roller body and a cemented carbide stud array distributed on the surface of the roller body, wherein the cemented carbide stud array comprises a plurality of cemented carbide studs, characterized in that: The carbide studs are fixed on the roller body by using the preparation method described in any one of claims 1 to 7.

10. The brazed cemented carbide reinforced composite grinding roller according to claim 9, characterized in that: The hard alloy stud array is formed by staggered arrangement of the plurality of hard alloy studs in the axial direction and the circumferential direction of the roller body.

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