WO2017208998A1

WO2017208998A1 - Method for manufacturing of flour milling roll

Info

Publication number: WO2017208998A1
Application number: PCT/JP2017/019721
Authority: WO
Inventors: 水津　竜夫; 晃宏神野; 典之安尾; 忠樹横田
Original assignee: トーカロ株式会社
Priority date: 2016-06-03
Filing date: 2017-05-26
Publication date: 2017-12-07
Also published as: JP6556349B2; CN109219671B; US20190119802A1; JPWO2017208998A1; CN109219671A

Abstract

A smooth roll 1 having a moisture-retaining function at a superficial layer thereof is obtained by a manufacturing method comprising: a roughening step for applying a blast treatment to the surface 2a of a roll base material 2 forming the smooth roll 1; and a coating step for spraying a thermal spray material over the roughened surface 2a of the roll base material 2 so as to form a thermal spray coating 3 having pores 5 that hold moisture. This configuration prevents grain from drying during a milling process, and enables maintaining of an adequate amount of moisture, thereby making it possible to produce quality grain powder.

Description

Manufacturing method of milling roll

The present invention relates to a method for producing a milling roll used in a milling process for grains such as wheat.

Cereals such as wheat are subjected to a milling process after a fine selection process and a tempering process. Currently, milling of grains such as wheat is mainly performed by a roll crushing method. This method is said to have been developed in the latter half of the 19th century, and has greatly improved productivity and quality compared to the stone mill method, contributing to the industrialization of the milling industry.

In the milling process using the roll crushing method, first, the grain is largely broken with a brake roll to remove the skin, and then the process of grinding and classifying with a smooth roll is repeated to complete the final product. In general, the surface of a brake roll is sharpened to form a groove having a pitch of about 10 mm, and the surface of a smooth roll is matted by inserting media between two rotating rolls. As a result, a satin-like uneven surface is formed. The mat processing for the smooth roll is described in Patent Documents 1 and 2.

For these milling rolls, chilled steel having a surface hardness of about 600 Vickers hardness HV is used. If a milling roll made of chilled steel is used for a long period of time, the unevenness present on the surface will be worn, and the grains cannot be pulverized into an appropriate size and shape, so that a high quality powder cannot be obtained. In order to restore the surface roughness of the milling roll, it is necessary to repair and process the surface. However, in the current method, polishing is performed first, and then repair and processing are performed. Therefore, it tends to be a case where the roll itself is replaced, and the cost increases.

Patent Document 3 describes a food processing roll that improves the biting property of raw materials, can efficiently process the raw materials, and can maintain good biting properties for a long time. In this document, a plurality of grooves are formed on the roll surface by laser processing, or a build-up weld layer is formed on the roll surface, and a plurality of concave portions are formed on the surface by laser processing. The shape for biting the food is a groove or a recess recessed from the smooth outer peripheral surface of the roll, so that the biting property of the food can be maintained even if the roll is worn due to long-term use.

JP-A-10-131948 Japanese Patent Laid-Open No. 11-28621 Republished Patent Publication WO2013 / 179356

In the grain milling process, there are specific problems other than the wear on the surface irregularities of the milling roll. For example, dried wheat is hard and scatters when pulverized, and a powder of the desired shape and size cannot be obtained. Therefore, when pulverizing wheat, a certain amount of moisture is included. When the smooth roll described in Patent Documents 1 and 2 and the food processing roll described in Patent Document 3 are used in the flour milling process, friction between the rolls through wheat and friction between the rolls and wheat The roll gradually gets hot. When the heat is stored in the roll, the moisture of the wheat will evaporate due to the effect of the temperature, the wheat can not hold an appropriate amount of moisture, and obtain the desired shape and size of the powder I can't.

Therefore, in view of the problems of the prior art, the present invention provides a method for producing a milling roll capable of preventing grain drying in a milling process and obtaining a good grain powder by maintaining an appropriate amount of moisture. Objective.

The inventors of the present invention have studied the means for preventing grain drying in the milling process. As a result, the surface of the milling roll is subjected to thermal spraying to form a thermal spray coating having pores for retaining moisture. We have succeeded in maintaining the quantity, which has led to solving the problem.

That is, in the method for producing a milling roll of the present invention, the surface of the base material is subjected to a blasting process, and the sprayed material is sprayed onto the roughened surface of the base material to retain moisture. And a coating step of forming a thermal spray coating having pores.

According to the present invention, since the thermal spray coating is formed on the surface of the base material, even if the milling roll is used for a long time, the unevenness of the surface layer can be maintained, and the pulverization performance is not impaired. In addition, according to the thermal spraying, the size and the existence ratio of the pores in the film to be produced can be controlled by adjusting the thermal spraying conditions. Since the thermal spray coating formed according to the present invention has pores for retaining moisture, it can be made difficult to transfer heat to the grain, and the water retention in the surface layer of the milling roll is enhanced, so that the cooling ability to the grain is obtained. Moreover, since it is the base material which increased the surface area and the surface roughness by performing a blasting process, the thermal spray coating can be prevented from peeling off. Therefore, the problem of abrasion on the surface layer of the milling roll and peeling of the sprayed coating can be eliminated, and an appropriate amount of moisture can be maintained in the grain, and a good grain powder can be obtained.

The value of the surface roughness Ra of a milling roll suitable for pulverizing grains varies depending on the purpose of use. When the milling roll is used as a smooth roll, the surface roughness Ra after the coating step is preferably 5 to 15 μm. On the other hand, when the milling roll is used as a brake roll, it is not necessary to be as rough as a smooth roll because it can be pulverized by grooves engraved in the base material. The surface roughness Ra is preferably 2 to 8 μm.

Generally, ceramics and cermets have a lower thermal conductivity than metals. Therefore, milling rolls made by thermal spray coating ceramics or cermets on the surface of metal substrates are made of frictional heat generated during the grinding process. Tend to accumulate. Therefore, it is better not to make the thickness of the thermal spray coating formed by thermal spraying too large. However, on the other hand, pulverization of wheat or the like requires irregularities having a surface roughness of a certain level or more, and in order to realize such irregularities with a sprayed coating, a film thickness of a certain level or more is necessary. This problem can be solved if the surface roughness of the substrate is reflected in the surface roughness of the milling roll. That is, the surface roughness Ra of the base material is preferably adjusted within the range of −2 to +8 μm with respect to the surface roughness Ra of the milling roll after the coating step. Thereby, while keeping the film thickness of a sprayed coating to the minimum, required surface roughness can be provided with respect to a milling roll.

The Vickers hardness HV of the surface of the milling roll after the coating step is preferably larger than 1000. Thereby, the abrasion resistance of the milling roll is significantly improved.

The thermal spray material is not limited, but is preferably a carbide cermet. By using a carbide cermet as the thermal spray material, a high surface hardness of the milling roll (specifically, a Vickers hardness HV value greater than 1000) can be easily obtained, and good wear resistance can be imparted. .

The average thickness of the sprayed coating is preferably 10 to 150 μm. If the average thickness of the thermal spray coating is less than 10 μm, there is a concern about durability when used for a long period of time, while if it is greater than 150 μm, there is a concern about the problem of frictional heat accumulation.

In the method for producing the milling roll, an adjustment step A may be included in which a shot blast treatment is performed as a post-treatment after the coating step to smooth fine irregularities in the undulations on the surface of the sprayed coating. Thereby, it is possible to prevent the pulverized grains from adhering to the undulations on the surface of the sprayed coating and clogging.

The milling roll manufacturing method may include an adjustment step B in which a peak cut treatment is performed as a post-treatment after the coating step to flatten the tip of the convex portion on the surface of the sprayed coating. Thereby, the site | part which becomes a point contact with respect to the grain of the surface of a sprayed coating reduces, and abrasion resistance can be improved.

According to the milling roll produced according to the present invention, the cooling property to the grain can be obtained by the thermal spray coating having the water retaining function existing on the surface layer. The thermal spray coating is formed on a base material whose surface area and surface roughness are increased by performing a blast treatment, and the thermal spray coating can be prevented from peeling off. Due to the high cooling property of the sprayed coating, the grain is prevented from being heated in the milling process, and drying of the grain can be suppressed. Thereby, it becomes possible to hold | maintain the suitable moisture content to a grain, and a favorable grain powder can be obtained.

It is a perspective view of the smooth roll manufactured with the manufacturing method of the milling roll concerning a 1st embodiment of the present invention. It is an expanded sectional view of the surface layer of the smooth roll of FIG. The time until the surface temperature of each specimen reaches a predetermined temperature is graphed. It is the schematic of the blast process in a roughening process. (A) is an expanded sectional view of the surface layer before performing a shot blasting process, (b) is an enlarged sectional view of the surface layer after performing a shot blasting process. It is sectional drawing of the surface layer before and behind performing a peak cut process. (A) is a perspective view of a part of a brake roll manufactured by a method for manufacturing a milling roll according to a second embodiment of the present invention, and (b) is an enlarged sectional view of a surface portion of the brake roll. It is an expanded sectional view of the surface layer of the circle mark part of the brake roll of FIG.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a smooth roll (milling roll) 1 manufactured by the method for manufacturing a milling roll according to the first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the surface layer of the smooth roll 1. In FIG. 1, two smooth rolls 1 are arranged in parallel. A smooth roll 1 according to this embodiment includes a roll base 2 (base) having a circular cross section, and a thermal spray coating 3 is formed on a surface 2 a of the roll base 2. In addition, the milling roll of this invention is applied to the roll of all the aspects used at a milling process other than a smooth roll and a brake roll. In an example of an actual milling process, in the state where two smooth rolls 1 shown in FIG. 1 are installed side by side, grains are fed between rolls rotated in the opposite directions and inward, and the grains are crushed and classified. Do work.

In the smooth roll 1 of this embodiment, all grains can be milled. Specific examples of cereals include wheat, barley, oat, pearl barley, corn, rye, buckwheat, millet, millet, millet, sorghum, sorghum, makomo and the like. One kind of these grains may be used alone, or two or more kinds may be used in combination. Among these grains, application to wheat and barley is particularly preferable. Examples of wheat-derived flour include strong flour, semi-strong flour, medium strength flour, weak flour, whole grain flour, and durum semolina.

The dimensions and shape of each part such as the roll diameter and length of the smooth roll 1 are not limited. The material constituting the roll base 2 on which the thermal spray coating 3 is formed can be applied to a milling roll and may be any material that can form various thermal spray coatings. A metal material is suitably used as the material constituting the roll base 2. Specific examples of the metal material include, for example, a metal selected from Fe, Cr, Ni, Mo, Co, Cu, Mn, Zn, Ta, W, Al, Ti, and Mg, or chilled steel containing one or more of these metals. And alloys such as stainless steel. Such a metal material is formed by extrusion, cutting, plastic working, forging, or the like.

The thermal spray coating 3 is formed by colliding and depositing on the surface 2a of the roll base 2 at high speed in a state where various thermal spray materials are softened or melted. The thermal spray material is not limited, but ceramic or cermet having high hardness is preferable.

Specific examples of using ceramics as the thermal spray material include Ni, Cr, Co, Al, Ta, Y, W, Nb, V, Ti, B, Si, Mo, Zr, Fe, Hf, and La. Examples thereof include oxide ceramics, nitride ceramics, carbide ceramics, boride ceramics, and mixtures thereof containing one or more selected elements.

Examples of oxide ceramics include Al ₂ O ₃ , Cr ₂ O ₃ , HfO ₂ , La ₂ O ₃ , TiO ₂ , Y ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ .SiO ₂ , NiO, and ZrO ₂ .SiO. ₂ , SiO ₂ , MgO, and CaO. Examples of nitride ceramics include TiN, TaN, AlN, BN, Si ₃ N ₄ , HfN, NbN, YN, ZrN, Mg ₃ N ₂ , and Ca ₃ N ₂ . Examples of the carbide ceramics include TiC, WC, TaC, B ₄ C, SiC, HfC, ZrC, VC, and Cr ₃ C ₂ . Examples of the boride-based ceramics include TiB ₂ , ZrB ₂ , HfB ₂ , VB ₂ , TaB ₂ , NbB ₂ , W ₂ B ₅ , CrB ₂ , and LaB ₆ .

A cermet material obtained by combining a metal material and a ceramic material may be used as the thermal spray material. As cermet materials, Cr ₃ C ₂ , TaC, WC, NbC, VC, TiC, B ₄ C, SiC, CrB ₂ , WB, MoB, ZrB ₂ , TiB ₂ , FeB ₂ , CrN, Cr ₂ N, TaN, Ceramic materials selected from the group of NbN, VN, TiN, BN are Ni, Cr, Co, Al, Ta, Y, W, Nb, V, Ti, B, Si, Mo, Zr, Fe, Hf, La And a composite material with a metal material selected from the group. Among them, carbide cermet is particularly preferable because a high-hardness film can be easily obtained.

The surface of the thermal spray coating 3 is not sealed, and a large number of pores 5 exist inside the thermal spray coating 3. By keeping moisture inside these pores 5, the thermal spray coating 3 has high water retention. Thereby, water retention is imparted to the surface layer of the smooth roll 1, and the grain is prevented from being heated in the milling process, and cooling performance for the grain is obtained, so that drying of the grain can be suppressed. And a favorable grain powder can be obtained by grind | pulverizing a grain by the surface unevenness | corrugation of the smooth roll 1 with the appropriate moisture content hold | maintained to a grain.

The average porosity of the thermal spray coating 3 may be about 0.5 to 15%, but is preferably 2.0 to 10%. The average porosity is adjusted by selecting the spraying method and the spraying conditions. The average porosity at which the pores 5 in the thermal spray coating 3 can retain moisture satisfactorily is 2.0% or more. However, if the average porosity is increased, the water retention is increased, but there is a concern about a decrease in wear resistance. Therefore, the average porosity is preferably 10% or less from the viewpoint of maintaining wear resistance.

The following methods are effective for adjusting the porosity in thermal spraying. That is, selection of the particle size of the thermal spray material used for film formation, adjustment of the particle velocity during thermal spraying, and adjustment of the thermal spray distance. For example, when reducing the porosity of the thermal spray coating to make it dense, it is better to use a powder with a fine particle size as the thermal spray material, and it is preferable that the particle velocity is higher. Further, it is possible to select a method in which the spraying distance is set to be short so that the coating has a heat flux that does not break due to the heat effect. On the other hand, in order to increase the porosity and form a porous film, a method of forming a film by a method opposite to the above is effective. However, the above-described adjustment needs to be limited to changes that do not impair other film properties such as hardness, wear resistance, and surface shape maintainability.

In order to verify the heat transfer characteristics based on the moisture content of the thermal spray coating, the following experiment was conducted. In conducting the experiment, first, two samples of the following specimens A to C and one sample of the specimen D were prepared.
Base material: Stainless steel Base material size: 5cm square, thickness 5mm
Blasting conditions: Alumina particles (# 60), pressure 0.4 MPa
Thermal spray material: WC-CrNi
Thermal spraying method: HVOF
Porosity: 2 to 4% (The cross section was observed at 200 times using SEM. There were variations depending on the measurement location. From the cross section SEM-BEI image, the black spots inside the coating were considered as pores, and the ratio of the pores to the entire coating was calculated. .)
Thermal sprayed film thickness: 50 μm (samples A1, A2), 100 μm (samples B1, B2), 150 μm (samples C1, C2), no thermal spray (sample D)

The tap water was dropped on the surface of each of the test materials A1, B1, and C1, and the spray coating was sufficiently moistened. Moisture remaining on the surface was gently wiped with a Kim towel. The test materials A1 to C1 soaked with water were placed on a plate heater maintained at 100 ° C., and the surface temperature of each test material was measured with a contact-type thermometer. The time until the surface temperature reached 40 ° C., 60 ° C., and 80 ° C. was measured and recorded.

Sample materials A2, B2, C2, and D were placed on a plate heater maintained at 100 ° C., and the surface temperature of each sample material was measured with a contact-type thermometer. The time until the surface temperature reached 40 ° C., 60 ° C., and 80 ° C. was measured and recorded.

From these measurement records, heat transfer characteristics based on film thickness difference and moisture content difference were verified. As shown in Table 1 and FIG. 3, in all samples, there was almost no difference when the temperature rose to 40 ° C., regardless of the presence or absence of moisture, but at 80 ° C., the sprayed coating containing moisture reached the target temperature. The result is that the time to reach is longer. From the above, it was found that the thermal spray coating containing water can suppress the temperature rise regardless of the film thickness.

The average thickness t of the thermal spray coating 3 is appropriately set, and is preferably 10 to 150 μm, more preferably 20 to 100 μm. If the average thickness t of the thermal spray coating 3 is too small, there is a concern about durability, but if it is too large, the amount of heat stored in the roll base material 2 due to frictional heat or the like increases, and the grain in the milling process It will accelerate the drying of. In particular, since ceramics and cermets generally have lower thermal conductivity than metals, this point should be noted when ceramics or cermets are thermally sprayed on metal materials.

The surface roughness Ra of the roll base 2 is adjusted to be in the range of −2 to +8 μm with respect to the surface roughness Ra of the smooth roll 1 that is finally aimed. In other words, the surface roughness Ra of the smooth roll 1 reflects the surface roughness Ra of the roll base 2. Moreover, the thermal spray coating 3 of this embodiment is formed so that the thickness t is uniform so that the surface roughness Ra of the roll base 2 reflects the surface roughness Ra of the smooth roll 1. Here, the term “uniform” means that the maximum thickness and the minimum thickness of the same film are each included within ± 30% of the average thickness.

Further, since the sprayed coating 3 is formed on the surface 2a of the roll base 2 with the surface roughness adjusted and the surface area and the surface roughness increased, peeling of the sprayed coating 3 can be prevented. An undercoat layer may be provided between the roll substrate 2 and the thermal spray coating 3 for the purpose of improving adhesion.

From the viewpoint of grain crushing and classification, the surface roughness Ra of the smooth roll 1 is 5 to 15 μm. Thereby, a good grain 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 larger than 1000 in terms of Vickers hardness HV. Thereby, the abrasion resistance of the smooth roll 1 can be improved.

An example of the manufacturing method of the smooth roll 1 which formed the sprayed coating 3 on the surface is given. A surface roughening step for roughening the surface 2a of the roll base material 2, a cleaning treatment for the surface 2a of the roll base material 2, a thermal spray coating having a pore 5 for spraying a spray material onto the roll base material 2 and retaining moisture. 3 is performed in this order. Other processes such as a preheating process may be included depending on the type of base material and the type of thermal spray material.

In the roughening step, the surface 2a of the roll base 2 is subjected to a blasting process for causing the projection material 21 to collide with the surface 2a of the roll base 2 as shown in FIG. To do. Blasting refers to a technique in which particles (grit) having a rough surface are sprayed onto the surface of a substrate with compressed air or the like to roughen the surface of the substrate. The roughness of the surface 2a of the roll base 2 is in the range of −2 to +8 μm with respect to the surface roughness Ra of the milling roll after the coating step, which is a subsequent step. As processing conditions, the type and particle size of the blast material, the injection pressure, the blasting time, and the like are set as appropriate. Moreover, according to a blast process, it can construct one by one with respect to a roll base material. Conventionally, a method has been adopted in which a medium is introduced between two rolls rotating in opposite directions, and a similar surface roughness is imparted to each of a pair of rolls. Since the surface roughness Ra of the roll can be uniquely defined, the design can be flexibly changed according to the purpose of use, for example, the surface roughness Ra is different between a pair of milling rolls, for example. .

Examples of the thermal spraying method for obtaining the thermal spray coating 3 in the coating process 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. In order to allow the thermal spray coating 3 to retain moisture, these thermal spraying methods are appropriately selected, and further, depending on the thermal spraying method, the thermal spraying conditions such as the type of thermal spray material, the heat source temperature, the thermal spray angle, the thermal spray distance, etc. Set as appropriate.

When spraying cermet, high-speed flame spraying (HVOF) is particularly suitable. This thermal spraying method is a thermal spraying method that uses the combustion energy of combustion gas as a heat source. By increasing the pressure in the combustion chamber, a high-speed flame comparable to an explosive combustion flame is generated, and a thermal spray material is formed at the center of this combustion flame jet stream. Is sprayed to be accelerated by supplying a molten or semi-molten state and continuously sprayed at a high speed. Since the molten sprayed particles collide with the substrate at supersonic speed, the sprayed coating 3 having high adhesion can be formed. As the fuel used as a heat source, kerosene, H ₂ gas as a combustion gas, acetylene mainly composed of carbon and hydrogen, ethylene, propane, and the like are used.

When spraying ceramics, the plasma spraying method is particularly suitable. The plasma spraying method is a thermal spraying method in which a thermal spray material is heated with plasma and melted to form liquid thermal spray particles, and the thermal spray particles are collided with a film formation surface of a substrate at a high speed by a plasma jet. The plasma spraying method using electrical energy as a heat source is to form a film using argon, hydrogen, nitrogen, etc. as a plasma generation source. Since the heat source temperature is high and the frame speed is high, a high melting point material is formed. It is possible to membrane.

After forming the thermal spray coating 3 on the surface 2a of the roll base 2 as described above, an adjustment step for adjusting the surface shape of the thermal spray coating 3 may be subsequently performed. Thereby, it becomes possible to obtain the surface property according to the intended use.

After forming the thermal spray coating 3, it is preferable to perform shot blasting (adjustment step A). Shot blasting is a method of adjusting the surface shape of a substrate by spraying spherical particles onto the surface of the substrate with compressed air or the like. Within the undulations on the surface of the thermal spray coating 3, there are fine irregularities as shown in FIG. By performing shot blasting, as shown in FIG. 5 (b), fine irregularities in the undulations on the surface of the sprayed coating 3 can be smoothed, and the crushed grains adhere to and clog the undulations. Can be prevented.

After the thermal spray coating 3 is formed, peak cut processing may be performed as necessary (adjustment step B). Examples of the peak cutting method include buffing. By performing the peak cut treatment, as shown in FIG. 6, the tip of the convex portion on the surface of the thermal spray coating 3 can be flattened, and the wear resistance can be improved. Note that the peak cut process may be performed after the shot blast process.

Such shot blasting and peak cutting can be applied one by one to the milling roll. Thereby, since the surface shape of each milling roll can be adjusted independently, a design can be changed flexibly according to the purpose of use. In addition, although the value of the surface roughness Ra of the thermal spray coating 3 is changed by the peak cut treatment, as described above even after the peak cut treatment so as not to impair the pulverization performance of the grains. It is preferable to be within the numerical range.

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

Since the thermal spray coating 3 formed by this method for producing a milling roll has pores 5 for retaining moisture, heat transfer to the grain can be made difficult, and water retention in the surface layer of the smooth roll 1 is enhanced. The cooling property with respect to is obtained. Moreover, since it is the roll base material 2 which increased the surface area and the surface roughness by performing the blasting process, the thermal spray coating 3 can be prevented from peeling off. Therefore, the problem of abrasion on the surface layer of the smooth roll 1 and peeling of the sprayed coating 3 is eliminated, the water retention is improved, and the cooling performance for the grain is enhanced. This high cooling property prevents the grain from being heated in the milling process and can suppress the drying of the grain. Thereby, it becomes possible to hold | maintain the suitable moisture content to a grain, and a favorable grain powder can be obtained.

The production method of the milling roll of the above embodiment is illustrative and not restrictive. In 1st Embodiment, although the manufacturing method of the milling roll was applied and demonstrated to the smooth roll, you may apply the said manufacturing method to a brake roll. FIG. 7A is a perspective view of a part of the brake roll 10 manufactured by the method for manufacturing a milling roll according to the second embodiment of the present invention, and FIG. 7B is an enlarged sectional view of a surface portion of the brake roll 10. . A large number of grooves 11 extending along the axial direction are formed on the entire surface of the brake roll 10 by machining. Each groove 11 is formed in a V-shaped cross section composed of two inclined surfaces having different inclination angles, and a top portion 12 serving as an outer peripheral surface exists between adjacent grooves 11.

FIG. 8 is an enlarged cross-sectional view of the surface layer of the circled portion M of the brake roll 10 of FIG. A sprayed coating 14 is formed on the surface 13 a of the roll base 13 of the brake roll 10. The material constituting the roll base 13, the thermal spray material for forming the thermal spray coating 14, the average porosity of a large number of pores 15 existing in the thermal spray coating 14, the adjustment of the porosity in the thermal spraying construction, the thickness of the thermal spray coating 14 The length t is appropriately set within the above-described range according to the function of the brake roll.

The surface hardness of the surface 10a of the brake roll 10 and the surface roughness Ra of the roll base material 13 are adjusted so as to be in the range of −2 to +8 μm with respect to the final surface roughness Ra of the brake roll 10. The point is also appropriately set within the above-described range. Note that the surface roughness Ra of the brake roll 10 is set to 2 to 8 μm from the viewpoint of removing the grain skin, which is a pre-process of the process using the smooth roll.

The manufacturing method of the brake roll 10 having the sprayed coating 14 formed on the surface thereof is the same as that of the first embodiment, and a roughening step for roughening the surface 13a of the roll base 13 and the cleaning of the surface 13a of the roll base 13 are performed. The coating process of spraying a thermal spray material on the roll base 13 and forming the thermal spray coating 14 having pores 15 for retaining moisture is performed in this order. Other processes such as a preheating process may be included depending on the type of base material and the type of thermal spray material. Adjustment steps A and B for adjusting the surface shape of the thermal spray coating 14 after the thermal spray coating 14 is formed on the surface 13a of the roll base 13 can also be included in the steps of this embodiment.

Depending on the specifications and construction mode of the milling roll, other steps may be included in the milling roll manufacturing method. The configurations and processes described in the above embodiments can be changed as long as the effects of the present invention are not impaired, and other configurations and processes provided as needed are not limited. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Smooth roll 1a Smooth roll surface 2 Roll base material 2a Roll base material 3 Thermal spray coating 5 Pore t Thickness 10 Brake roll 10a Brake roll surface 11 Groove 12 Top 13 Roll base material 13a Roll base material 14 Thermal spray Film 15 Pore 20 Blast nozzle 21 Projection material

Claims

A roughening step for blasting the surface of the substrate;
A coating step of spraying a thermal spray material on the roughened surface of the base material to form a thermal spray coating having pores for retaining moisture;
The manufacturing method of the milling roll characterized by including.
The method for producing a milling roll according to claim 1, wherein the surface roughness Ra of the milling roll after the coating step is 2 to 15 µm.
2. The surface roughness Ra of the base material after the roughening step is in a range of −2 to +8 μm with respect to the surface roughness Ra of the milling roll after the coating step. The manufacturing method of the milling roll of 2.
The method for producing a milling roll according to any one of claims 1 to 3, wherein the surface of the milling roll after the coating step has a Vickers hardness HV of more than 1000.
The method for producing a milling roll according to any one of claims 1 to 4, wherein the thermal spray material is a carbide cermet.
The method for producing a milling roll according to any one of claims 1 to 5, wherein an average thickness of the sprayed coating is 10 to 150 µm.
The milling roll according to any one of claims 1 to 6, further comprising an adjustment step A that performs shot blasting after the coating step and smoothes fine irregularities in the undulations on the surface of the sprayed coating. Production method.
The method for producing a milling roll according to any one of claims 1 to 7, further comprising an adjustment step B in which a peak cut treatment is performed after the coating step to flatten a tip of a convex portion on a surface of the sprayed coating. .