CN109219671B

CN109219671B - Method for manufacturing powder roller

Info

Publication number: CN109219671B
Application number: CN201780033569.XA
Authority: CN
Inventors: 水津龙夫; 神野晃宏; 安尾典之; 横田忠树
Original assignee: Donghualong Corp
Current assignee: Donghualong Corp
Priority date: 2016-06-03
Filing date: 2017-05-26
Publication date: 2020-08-21
Anticipated expiration: 2037-05-26
Also published as: JP6556349B2; CN109219671A; US20190119802A1; WO2017208998A1; JPWO2017208998A1

Abstract

The invention provides a manufacturing method of a pulverizing roller, which comprises the following steps: a surface roughening step of performing a spray treatment on the surface (2a) of a roll base material (2) constituting a smooth roll (1); and a coating step of spraying a spray material on the surface (2a) of the roughened roll base material (2) to form a spray coating film (3) having pores (5) for retaining water. By the manufacturing method of the powder roller, the smooth roller (1) with the surface layer having the water retention function can be formed. By preventing the drying of the grains in the milling step and maintaining an appropriate moisture content, good grain powder can be obtained.

Description

Method for manufacturing powder roller

Technical Field

The present invention relates to a method for manufacturing a milling roller used in a milling process of grains such as wheat.

Background

After the grains such as wheat are subjected to a selection step, a conditioning step, and the like, a milling step is performed. Currently, milling of grains such as wheat is mainly performed by roll milling. This method is said to be developed in the second half of the 19 th century, and is expected to contribute to the industrialization of the flour making industry because productivity and quality are greatly improved as compared with the stone milling method.

In the milling process of the roll milling method, first, grains are roughly milled by a breaker roll (breaker roll) to remove the skin, and then the milling and classification operation by a smoothing roll (smooth roll) are repeated to finally complete the product. In general, in the case of a crushing roller, grooves with a pitch of about 10mm are formed on the surface by filing, and in the case of a smooth roller, a pearskin-like uneven surface is formed by inserting an intermediate (medium) between two rotating rollers and applying a matting process to the surface. Patent documents 1 and 2 describe a matte treatment of a smooth roll.

These powder rolls use hardened steel having a surface hardness of about 600 in terms of vickers hardness HV. When the hardened steel milling roll is used for a long period of time, the surface irregularities are worn away, and grains cannot be ground into an appropriate size and shape, and thus a high-quality powder cannot be obtained. In order to restore the surface roughness of the pulverizing roll, it is necessary to repair and process the surface, but in the conventional method, it takes a lot of time and labor to polish the surface first and then repair and process the surface. Therefore, the roller itself is often replaced, resulting in an increase in cost.

Patent document 3 describes a roller for food processing which can improve the biting property (biting property) of a raw material, efficiently treat the raw material, and maintain a good biting property for a long time. In this document, a plurality of grooves are formed on the surface of a roller by laser processing, or a plurality of recesses are formed on the surface of a roller by laser processing after a build-up layer is formed on the surface of the roller. The shape for biting food is a groove or a recess recessed from the smooth outer peripheral surface of the roller, and the biting property of food can be maintained even if the roller is worn due to long-term use.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. H10-131948

Patent document 2: japanese laid-open patent publication No. H11-28621

Patent document 3: re-published Japanese patent application No. WO2013/179356

Disclosure of Invention

Problems to be solved by the invention

In the milling process of grains, there are special problems in addition to the abrasion of the surface unevenness of the milling roll. For example, since dried wheat is hard and scatters during grinding, and a powder having a desired shape and size cannot be obtained, a certain amount of moisture needs to be contained during grinding of wheat. When the smooth rolls described in patent documents 1 and 2 or the food processing roll described in patent document 3 are used in the wheat milling step, the rolls are gradually heated by friction between the rolls and wheat. If heat is stored in the roller, moisture in the wheat is evaporated due to the influence of the temperature thereof, and an appropriate amount of moisture cannot be maintained in the wheat, so that good powder of a desired shape and size cannot be obtained.

In view of the problems of the prior art, an object of the present invention is to provide a method for manufacturing a milling roll capable of obtaining a good grain powder by preventing drying of the grain in the milling step and maintaining an appropriate moisture content.

Means for solving the problems

The present inventors have studied a method for preventing drying of grains in a milling step, and as a result, have succeeded in maintaining a proper moisture content in grains by forming a spray coating film having pores for retaining moisture by performing thermal spraying treatment on the surface of a milling roller, thereby solving the problem.

That is, the method for manufacturing a pulverizing roller according to the present invention includes: a surface roughening step of performing a blasting treatment (blasting treatment) on the surface of the base material; and a coating step of spraying a spray material on the roughened surface of the substrate to form a spray coating film having pores for retaining water.

According to the present invention, since the spray coating film is formed on the surface of the base material, the unevenness of the surface layer can be maintained even when the pulverizing roll is used for a long time, and the pulverizing performance is not impaired. Further, according to thermal spraying, the size and the existence ratio of pores in the produced film can be controlled by adjusting the thermal spraying conditions. The spray coating film formed according to the present invention has pores for holding water, so that heat is hard to be transferred to grains, and the water retentivity of the surface layer of the milling roll is improved, so that the cooling property for grains can be obtained. Further, since the spray coating film is formed on the substrate having a large surface area and surface roughness by performing the spray treatment, the spray coating film can be prevented from peeling off. Therefore, the problems such as abrasion of the surface layer of the milling roll and peeling of the sprayed coating can be solved, and the proper moisture content of the grain can be maintained, so that good grain powder can be obtained.

The value of the surface roughness Ra of the milling roll suitable for milling grains varies depending on the purpose of use. When a powder roller is used as the smooth roller, the surface roughness Ra after the coating step is preferably 5 to 15 μm. On the other hand, in the case of using a pulverizing roll as the crushing roll, since the crushing can be performed by using grooves engraved on the base material, the roughness does not need to be as smooth as the roll, and the surface roughness Ra after the coating step is preferably 2 to 8 μm in view of durability.

Generally, ceramics and cermets have lower thermal conductivity than metals, and therefore, a pulverizing roll made of ceramics or cermets as a material by thermal spraying a coating on the surface of a base material of a metallic material has a tendency to store frictional heat generated during pulverization. Therefore, the thickness of the spray coating formed by thermal spraying is preferably not too large. On the other hand, however, it is necessary to have unevenness with a surface roughness of a certain degree or more in order to crush wheat or the like, and it is necessary to have a film thickness of a certain degree or more in order to realize such unevenness by spraying a coating film. In order to solve this problem, the surface roughness of the base material may be reflected on the surface roughness of the powder coating roll. That is, the surface roughness Ra of the base material is preferably adjusted to be in the range of-2 to +8 μm with respect to the surface roughness Ra of the pulverizing roll after the coating step. This makes it possible to provide the powder roller with the necessary surface roughness while minimizing the thickness of the spray coating.

Preferably, the vickers hardness HV of the surface of the pulverizing roll after the coating step is greater than 1000. Therefore, the wear resistance of the pulverizing roller is greatly improved.

The above spray material is not limited, but carbide cermet is particularly preferable. By using carbide cermet as the spray material, high surface hardness of the powder roller (specifically, a value of more than 1000 in terms of vickers hardness HV) can be easily obtained, so that good wear resistance can be obtained.

Preferably, the average thickness of the spray coating is 10 to 150 μm. If the average thickness of the spray coating film is less than 10 μm, the durability in the case of long-term use is concerned, while if it exceeds 150 μm, the problem of frictional heat accumulation is concerned.

The manufacturing method of the pulverizing roller can further comprise the following steps: and an adjustment step A of smoothing fine irregularities in the undulations (irregularities) on the surface of the spray coating by performing shot blasting as a post-treatment after the coating step. This can prevent the crushed grains from adhering to and clogging in the undulations of the surface of the sprayed coating.

In the method for manufacturing the pulverizing roller, the method may further include: and an adjustment step B of performing peak clipping (peak treatment) as post-treatment after the coating step to flatten the tips of the projections on the surface of the spray coating. Thus, the contact part between the surface of the spray coating film and grain point can be reduced, and the wear resistance can be improved.

ADVANTAGEOUS EFFECTS OF INVENTION

The milling roller manufactured according to the present invention can obtain the cooling performance for grains by the spray coating film having the water retention function existing on the surface layer. The spray coating film is formed on a substrate having a large surface area and surface roughness by performing a spray treatment, and peeling of the spray coating film can be prevented. The high cooling property of the spray coating film prevents the grains from being heated in the milling process, and inhibits the grains from being dried. This enables the grain to retain an appropriate moisture content, and a good grain powder can be obtained.

Drawings

Fig. 1 is a perspective view of a smooth roll manufactured by a method for manufacturing a pulverizing roll according to a first embodiment of the present invention.

Fig. 2 is an enlarged cross-sectional view of the surface layer of the smoothing roll of fig. 1.

Fig. 3 is a graph showing the time until the surface temperature of each test piece reaches a predetermined temperature.

Fig. 4 is a schematic view of the blasting process in the surface roughening process.

Fig. 5(a) is an enlarged cross-sectional view of the surface layer before shot peening, and (b) is an enlarged cross-sectional view of the surface layer after shot peening.

Fig. 6 is a cross-sectional view of the surface layer before and after the peak reduction treatment.

Fig. 7(a) is a partial perspective view of a crushing roller manufactured by the method for manufacturing a pulverizing roller according to the second embodiment of the present invention, and (b) is an enlarged sectional view of a surface portion of the crushing roller.

FIG. 8 is an enlarged cross-sectional view of the surface layer of the circular marking portion of the crushing roller of FIG. 7.

Description of the reference numerals

1: smooth roller

1 a: smoothing the surface of the roll

2: roller base material

2 a: surface of roll base material

3: spray coating leather film

5: pores of

t: thickness of

10: crushing roller

10 a: surface of the crushing roller

11: groove

12: top part

13: roller base material

13 a: surface of roll base material

14: spray coating leather film

15: pores of

20: spray nozzle

21: projection material

Detailed Description

Embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a smooth roll (pulverizing roll) 1 manufactured by a method for manufacturing a pulverizing roll according to a first embodiment of the present invention, and fig. 2 is an enlarged cross-sectional view of a surface layer of the smooth roll 1. In fig. 1, two smoothing rolls 1 are arranged in parallel. The smoothing roll 1 of the present embodiment includes a roll base material 2 (base material) having a circular cross section, and a spray coating film 3 is formed on a surface 2a of the roll base material 2. The pulverizing roll of the present invention is applicable to any type of roll used in the pulverizing process, in addition to the smooth roll and the crushing roll. In an example of an actual milling process, two parallel smooth rolls 1 shown in fig. 1 are rotated in opposite directions to each other, and grains are supplied between the two rolls to perform crushing and classifying operations of the grains.

The smoothing roll 1 of the present embodiment can grind any grain. Specific examples of the grains include wheat, barley, oat, pearl barley, corn, rye, buckwheat, barnyard grass, millet, milo, sorghum, and wild rice. These grains may be used alone or in combination of two or more. Wheat and barley suitable for use in these grains are particularly preferable. Examples of the wheat-derived cereal flour include hard flour, half hard flour, medium hard flour, low hard flour, whole wheat flour, and duran wheat flour.

The size and shape of each portion such as the roll diameter and the length of the smoothing roll 1 are not limited. The material constituting the roll base 2 on which the spray coating film 3 is formed may be applied to a powder roll, and any material may be used as long as it can form various spray coatings. As a material constituting the roller base 2, a metal material is suitably used. Specific examples of the metal material include metals selected from Fe, Cr, Ni, Mo, Co, Cu, Mn, Zn, Ta, W, Al, Ti, and Mg, and alloys such as hardened steel and stainless steel containing one or more of these metals. Such a metal material can be formed by extrusion, cutting, plastic working, forging, or the like.

The spray coating 3 can be formed by depositing various spray materials on the surface 2a of the roll base 2 by high-speed impact in a softened or molten state. The spray material is not limited, but a ceramic or cermet having high hardness is preferable.

Specific examples of the case where ceramics is used as the spray coating material include oxide-based ceramics, nitride-based ceramics, carbide-based ceramics, boride-based ceramics, and mixtures thereof, which contain one or more elements selected from Ni, Cr, Co, Al, Ta, Y, W, Nb, V, Ti, B, Si, Mo, Zr, Fe, Hf, and La.

The oxide-based ceramic may include Al₂O₃、Cr₂O₃、HfO₂、La₂O₃、TiO₂、Y₂O₃、ZrO₂、Al₂O₃·SiO₂、NiO、ZrO₂·SiO₂、SiO₂MgO and CaO. Examples of the nitride-based ceramic include TiN, TaN, AlN, BN, and Si₃N₄、HfN、NbN、YN、ZrN、Mg₃N₂、Ca₃N₂. Examples of the carbide-based ceramic include TiC, WC, TaC and B₄C、SiC、HfC、ZrC、VC、Cr₃C₂. The boride-based ceramic may include TiB₂、ZrB₂、HfB₂、VB₂、TaB₂、NbB₂、W₂B₅、CrB₂、LaB₆。

The cermet material compounded by the metal material and the ceramic material can also be used as a spraying material. Examples of the cermet material include those selected from Cr₃C₂、TaC、WC、NbC、VC、TiC、B₄C、SiC、CrB₂、WB、MoB、ZrB₂、TiB₂、FeB₂、CrN、Cr₂And cermet materials obtained by compounding ceramic materials of N, TaN, NbN, VN, TiN and BN with metal materials selected from Ni, Cr, Co, Al, Ta, Y, W, Nb, V, Ti, B, Si, Mo, Zr, Fe, Hf and La. Among them, carbide cermets are particularly suitable because they can easily form a high-hardness coating film.

The surface of the spray coating 3 is not sealed, and a large number of pores 5 are present inside the spray coating 3. By retaining water in these pores 5, the spray coating 3 has high water retentivity. This can impart water retentivity to the surface layer of the smooth roll 1, prevent the grains from being heated in the milling step, and can cool the grains to suppress the drying of the grains. Further, by pulverizing the grains by the surface irregularities of the smoothing roll 1 while maintaining an appropriate moisture content of the grains, a good grain powder can be obtained.

The average porosity of the sprayed coating 3 may be about 0.5 to 15%, preferably 2.0 to 10%. The adjustment of the average porosity is performed by selecting the thermal spraying method and the thermal spraying conditions. The pores 5 in the spray coating 3 can favorably hold the average porosity of water at 2.0% or more. However, if the average porosity is increased, although the water retention is increased, there is a fear that the abrasion resistance is decreased. Therefore, the average porosity is preferably 10% or less from the viewpoint of maintaining the wear resistance.

The adjustment of porosity in the thermal spraying process is effective by the following method. That is, the particle diameter of the spray material for forming the coating film is selected, the particle velocity at the time of thermal spraying is adjusted, and the thermal spraying distance is adjusted. For example, when the porosity of the spray coating film is reduced to form a dense material, a powder having a fine particle size can be used as the spray coating material, and a powder having a high particle velocity is more preferable. Further, the thermal spraying distance may be selected to be short so that the heat flux is not so large that the coating film is not cracked by the thermal effect. On the other hand, in order to form a porous film with increased porosity, it is effective to form the film by a method reverse to the above method. However, the adjustment is not limited to the change of the film properties to such an extent that the hardness, wear resistance, surface shape retention and the like are not impaired.

In order to verify the heat transfer characteristics based on the water content of the spray coating, the following experiment was performed. In the experiment, first, two samples are prepared for each of the following test materials a to C, and one sample is prepared for the test material D.

Base material: stainless steel

Substrate size: side length of 5cm and thickness of 5mm

Spraying conditions: alumina particles (#60) and a pressure of 0.4MPa

Spraying materials: WC-CrNi

The thermal spraying method comprises the following steps: high velocity flame spraying method (HVOF)

Porosity: 2-4% (cross section was observed at 200 times using SEM; deviation was observed depending on the measurement position; black part inside the skin was regarded as pores from the cross section SEM-BEI image, and the ratio of pores to the whole skin was calculated.)

The thickness of the sprayed film is as follows: 50 μm (test materials A1, A2), 100 μm (test materials B1, B2), 150 μm (test materials C1, C2), no spray coating (test material D)

Tap water was dropped on the surface of each of the test pieces a1, B1, and C1 so that the spray coating film sufficiently contained moisture. Residual water on the surface was gently wiped off with Kim Towel. The test pieces A1 to C1 containing moisture were set on a plate heater (plate heater) maintained at 100 ℃ and the surface temperature of each test piece was measured with a contact thermometer. The time until the surface temperature reached 40 ℃, 60 ℃, 80 ℃ was measured and recorded.

The test materials a2, B2, C2 and D were set on a plate heater maintained at 100 ℃, and the surface temperature of each test material was measured with a contact thermometer. The time until the surface temperature reached 40 ℃, 60 ℃, 80 ℃ was measured and recorded.

From these measurement records, heat transfer characteristics based on the difference in film thickness and the difference in water content were verified. As shown in table 1 and fig. 3, the following results occurred: all samples had little difference in the temperature rise to 40 ℃ regardless of whether moisture was contained, but the spray coating containing moisture at 80 ℃ reached the target temperature for a longer period of time. As is clear from the above, the spray coating film containing moisture can further suppress the temperature increase regardless of the film thickness.

TABLE 1

The average thickness t of the sprayed coating 3 can be set as appropriate, and is preferably 10 to 150 μm, and more preferably 20 to 100 μm. If the average thickness t of the spray coating film 3 is too small, the durability is concerned, and if it is too large, the amount of heat stored in the roller base material 2 due to frictional heat or the like increases, and the grain drying in the milling process is promoted. In particular, ceramics and cermets generally have lower thermal conductivities than metals, and therefore care needs to be taken in the case of thermally spraying ceramics or cermets on metallic materials.

The surface roughness Ra of the roll base material 2 is adjusted to a value of-2 to +8 μm with respect to the final target surface roughness Ra of the smooth roll 1. In other words, the surface roughness Ra of the smoothing roll 1 reflects the surface roughness Ra of the roll base material 2. The spray coating 3 of the present embodiment is formed to have a uniform thickness t so that the surface roughness Ra of the roll base 2 reflects the surface roughness Ra of the smooth roll 1. The term "uniform" as used herein means that the maximum thickness and the minimum thickness of the same coating are within ± 30% of the average thickness.

Further, since the surface 2a of the roll base material 2 is formed with the surface roughness adjusted and the surface area and the surface roughness increased, the spray coating 3 can be prevented from peeling off. An undercoat layer (undercoat layer) may be provided between the roll base material 2 and the spray coating 3 to improve adhesion and the like.

From the viewpoint of grinding and classifying grains, the surface roughness Ra of the smoothing roller 1 is 5 to 15 μm. Thus, a good cereal powder can be obtained. The surface hardness of the surface 1a of the smooth roll 1 is high, and the surface hardness is adjusted to a value of more than 1000 in terms of Vickers hardness HV. This can improve the wear resistance of the smoothing roll 1.

Hereinafter, an example of a method for manufacturing the smooth roll 1 having the spray coating film 3 formed on the surface thereof will be described. A surface roughening step of roughening the surface 2a of the roll base material 2 and a coating step of cleaning the surface 2a of the roll base material 2 to spray a spray material onto the roll base material 2 to form a spray coating film 3 having pores 5 for retaining water are sequentially performed. Depending on the type of the base material and the type of the spray material, other processes such as a preheating process may be included.

In the surface roughening step, as shown in fig. 4, a projection process is performed in which the projection material 21 is caused to strike the surface 2a of the roll base material 2 from a blast nozzle (blast nozzle)20, thereby forming irregularities on the surface 2a of the roll base material 2. Blasting is a method of roughening the surface of a base material by spraying rough-surface particles (grit) on the surface of the base material with compressed air or the like. The roughness of the surface 2a of the roll base material 2 is in the range of-2 to +8 μm with respect to the surface roughness Ra of the pulverizing roll after the coating step of the subsequent step. As the processing conditions, the kind and particle size of the blasting material, the blasting pressure, the blasting treatment time, and the like are appropriately set. In addition, according to the spray treatment, the roll base materials may be treated one by one. Conventionally, a method of interposing an intermediate between two rolls rotating in opposite directions to each other and giving the same surface roughness to each of the pair of rolls has been employed, but in the case of the spray treatment, the surface roughness Ra of each pulverizing roll can be individually specified, and therefore, it is possible to flexibly change the design so that, for example, each of the pair of pulverizing rolls has a different surface roughness Ra depending on the purpose of use.

Examples of the thermal spraying method for obtaining the spray coating 3 in the coating step include an atmospheric plasma spraying method, a low-pressure plasma spraying method, a high-speed flame spraying method, a gas flame spraying method, an arc spraying method, and an explosion spraying method. These thermal spraying methods can be appropriately selected so that the spray coating 3 can retain water, and further thermal spraying conditions such as the type of the spray material, the heat source temperature, the thermal spraying angle, and the thermal spraying distance can be appropriately set according to the thermal spraying method.

In the case of thermal spraying of cermets, high velocity flame spraying (HVOF) is particularly suitable. The thermal spraying method is a thermal spraying method using the combustion energy of combustion gas as a heat source, and is a thermal spraying method which increases the pressure of a combustion chamber to generate a high-speed flame comparable to an explosive combustion flame, supplies a spraying material to the center of the combustion flame jet to accelerate, becomes a molten or semi-molten state, and continuously sprays at a high speed. Since the molten spray particles impact the base material at supersonic velocity, the spray coating 3 having high adhesion force can be formed. Kerosene and H as combustion gas can be used as fuel for the heat source₂Gas, and acetylene, ethylene, propane, etc. containing carbon and hydrogen as main components.

In the case of thermal spraying ceramics, plasma spraying is particularly suitable. The plasma spraying method is a thermal spraying method in which a spray material is heated by plasma to be melted into liquid spray particles, and the spray particles are caused to impact a film surface to be formed of a base material at a high speed by plasma jet. The plasma spraying method using electric energy as a heat source performs film formation using argon, hydrogen, nitrogen, or the like as a plasma source, and can form a film of a high-melting-point material because of a high heat source temperature and a high frame rate (frame rate).

After the spray coating 3 is formed on the surface 2a of the roll base material 2 as described above, an adjustment step for adjusting the surface shape of the spray coating 3 may be performed. Thus, the surface properties according to the use application can be obtained.

Preferably, shot blasting is performed after the spray coating 3 is formed (adjustment step a). Shot blasting is a method of spraying spherical particles onto the surface of a substrate with compressed air or the like to adjust the surface shape of the substrate. Fine irregularities shown in fig. 5(a) exist in the undulations of the surface of the spray coating film 3. By performing the shot blasting, as shown in fig. 5(b), fine irregularities in the undulations of the surface of the spray coating film 3 can be smoothed, and the crushed grains can be prevented from adhering to and clogging in the undulations.

After the spray coating 3 is formed, a peak reduction treatment may be performed as necessary (adjustment step B). Examples of the peak clipping method include buffing (buffering). By performing the peak clipping treatment, as shown in fig. 6, the tips of the convex portions on the surface of the spray coating 3 can be flattened, and the wear resistance can be improved. The peak reduction treatment may be performed after the shot blasting treatment.

Such shot blasting and peak shaving may be performed one by one for the pulverizing rolls. Thus, the surface shape of each pulverizing roller can be adjusted independently, and the design can be flexibly changed according to the use purpose. The value of the surface roughness Ra of the spray coating 3 is changed by the peak clipping treatment, and it is preferable to control the surface roughness Ra of the spray coating 3 within the above numerical range even after the peak clipping treatment in order not to impair the grain grinding performance.

According to the method for manufacturing the powder pulverizing roll of the present embodiment, since the spray coating film 3 is formed on the surface 2a of the roll base material 2 by thermal spraying, the surface layer unevenness can be maintained even if the smooth roll 1 is used for a long time, and the pulverizing performance is not impaired. In addition, according to the thermal spraying, the size and the existence ratio of the pores 5 in the produced film can be controlled by adjusting the thermal spraying conditions.

Since the spray coating film 3 formed by the method for manufacturing a flour milling roll has the pores 5 for holding water, heat is less likely to be transferred to the grain, and the water retentivity of the surface layer of the smooth roll 1 is improved, so that the cooling property for the grain can be obtained. Further, since the spray coating 3 is formed by thermal spraying on the roll base material 2 whose surface area and surface roughness are increased by performing the spray treatment, the spray coating 3 can be prevented from peeling off. Therefore, the problems such as abrasion of the surface layer of the smoothing roll 1 and peeling of the sprayed coating 3 can be solved, and the water retentivity and the cooling property for grains can be improved. By improving the cooling property, the grains can be prevented from being heated in the flour making process, and the drying of the grains can be suppressed. This enables the grain to retain an appropriate moisture content, and a good grain powder to be obtained.

The method of manufacturing the pulverizing roller of the above embodiment is merely exemplary and not restrictive. In the first embodiment, the method for manufacturing the pulverizing roll was described as being applied to the smoothing roll, but the method can also be applied to the crushing roll. Fig. 7(a) is a partial perspective view of the crushing roller 10 manufactured by the method for manufacturing a pulverizing roller according to the second embodiment of the present invention, and (b) is an enlarged sectional view of a surface portion of the crushing roller 10. On the surface portion of the crushing roller 10, a large number of grooves 11 extending in the axial direction are formed over the entire circumference by machining. Each of the grooves 11 is formed in a V-shape in cross section by two inclined surfaces having different inclination angles, and a top portion 12 serving as an outer peripheral surface is present between the adjacent grooves 11.

Fig. 8 is an enlarged cross-sectional view of the surface layer of the circular mark portion M of the crushing roller 10 in fig. 7 (b). A spray coating 14 is formed on the surface 13a of the roller base 13 of the crushing roller 10. The material constituting the roller base 13, the spray material for forming the spray coating 14, the average porosity of the large number of pores 15 present inside the spray coating 14, the adjustment of the porosity in the thermal spraying process, and the thickness t of the spray coating 14 are appropriately set within the above-described ranges according to the function of the crushing roller.

The surface hardness of the surface 10a of the crushing roller 10 and the surface roughness Ra of the roller base 13 are adjusted to a value in the range of-2 to +8 μm with respect to the finally required value of the surface roughness Ra of the crushing roller 10, and are also set as appropriate within the above-mentioned range. The surface roughness Ra of the crushing roller 10 is 2 to 8 μm in order to remove the grain skin as a pre-step before the step of using the smooth roller.

The method of manufacturing the crushing roller 10 having the spray coating 14 formed on the surface thereof is the same as that of the first embodiment, and the surface roughening step of roughening the surface 13a of the roller base 13 and the coating step of cleaning the surface 13a of the roller base 13 to spray the spray coating material onto the roller base 13 are sequentially performed to form the spray coating 14 having the pores 15 for retaining water. Depending on the type of the base material and the type of the spray material, other processes such as a preheating process may be included. The process of the present embodiment may further include adjustment processes a and B for adjusting the surface shape of the spray coating 14 after the spray coating 14 is formed on the surface 13a of the roll base 13.

The manufacturing method of the milling roller can also comprise other working procedures according to the specification and the process form of the milling roller. The configuration and the steps described in the above embodiments may be changed within a range not to impair the effects of the present invention, and the form of other configurations and steps provided as necessary is not limited. The scope of the invention is defined by the claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. A method for manufacturing a pulverizing roller is characterized in that,

the manufacturing method of the powder manufacturing roller comprises the following steps:

a surface roughening step of performing a spray treatment on the surface of the base material; and

a coating step of spraying a spray material on the roughened surface of the base material to form a spray coating film having pores for retaining water; the average porosity of the spray coating is 2.0% or more.

2. The method of manufacturing a pulverizing roller as claimed in claim 1,

the surface roughness Ra of the powder making roller after the coating process is 2-15 mu m.

3. The method of manufacturing a pulverizing roller as claimed in claim 1,

the surface roughness Ra of the base material after the surface roughening step is in the range of-2 to +8 [ mu ] m relative to the surface roughness Ra of the powder making roller after the coating step.

4. The method of manufacturing a pulverizing roller as claimed in claim 1,

the Vickers hardness HV of the surface of the powder roller after the coating process is more than 1000.

5. The method of manufacturing a pulverizing roller as claimed in claim 1,

the spraying material is carbide cermet.

6. The method of manufacturing a pulverizing roller as claimed in claim 1,

the average thickness of the spray coating is 10-150 mu m.

7. The method of manufacturing a pulverizing roller as claimed in claim 1,

the manufacturing method of the powder manufacturing roller comprises the following steps: and an adjustment step A of smoothing fine irregularities in the undulations of the surface of the spray coating by shot blasting after the coating step.

8. The method of manufacturing a pulverizing roller as claimed in claim 1,

the manufacturing method of the powder manufacturing roller comprises the following steps: and an adjustment step B of flattening the tips of the projections on the surface of the spray coating by performing a peak clipping treatment after the coating step.