JP2019136799A - Method for manufacturing tool material and tool material - Google Patents

Abstract

To provide a method for efficiently improving other mechanical properties (flexural stress, toughness, impact resistance, and the like) without largely impairing abrasion resistance, high temperature softening resistance and the like of a build-up layer formed by a laser cladding method, and to provide a tool material in which a build-up layer of a high speed tool steel having excellent flexural stress, toughness, impact resistance, abrasion resistance, and the like is formed on the outermost surface of a comparatively inexpensive metal base material.SOLUTION: A method for manufacturing a tool material includes: a laser cladding step of irradiating a surface of a metal base material with a laser beam while supplying high-speed tool steel powder to the surface of the metal base material to form a build-up layer; a spheroidizing step of heating the build-up layer at 750-880°C; a quenching step of quenching the build-up layer subjected to the spheroidizing step; and a tempering step of tempering the build-up layer subjected to the quenching step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tool material manufacturing method and a tool material manufactured by the manufacturing method by forming a built-up layer of high-speed tool steel on the surface of a metal substrate using a laser cladding method.

  Conventionally, as one of the surface treatment techniques, a technique for improving the wear resistance and the like of the outermost surface by embedding a high hardness material different from the metal base material on the surface of the metal base material is known. . When the technique is used, the base material can retain its original shape even if the surface build-up layer formed using a high-hardness material is worn. Therefore, it can be used repeatedly. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-176778) discloses a laser cladding method for forming a high-hardness build-up layer on the surface of a metal substrate using a laser as a technique for performing the build-up. Yes.

  Here, as a typical high-hardness material used for build-up, high-speed tool steel used for high-speed cutting of a metal member can be exemplified. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-155155) discloses a technique in which a high-speed tool steel is built up on the surface of a metal substrate using a laser cladding method. The build-up layer has a hardness and wear resistance equal to or higher than those of a HIP (hot isostatic pressing method) material.

JP 2013-176778 A JP 2006-155155 A

  However, in the conventional overlay using the laser cladding method, the build-up layer becomes a rapidly solidified structure, and crystallized carbides segregate at the crystal grain boundaries of the base material, resulting in a decrease in bending stress. It was. In addition, since the toughness is reduced as a trade-off for high hardness, it has been difficult to adapt to applications that require impact resistance.

  In view of the problems in the prior art as described above, the object of the present invention is to provide other mechanical properties without significantly degrading the wear resistance or high temperature softening resistance of the overlay layer formed by the laser cladding method ( It is to provide a method for efficiently improving bending stress, toughness, impact resistance and the like. In addition, the present invention provides a tool in which a built-up layer of high-speed tool steel having excellent bending stress, toughness, impact resistance, wear resistance, etc. is formed on the outermost surface of a relatively inexpensive metal base material. It also aims to provide materials.

  In order to achieve the above object, the present inventors conducted extensive research on the structure control method of the high-speed tool steel overlay formed by the laser cladding method, and as a result, performed heat treatment in an appropriate temperature range. This has been found to be extremely effective, and the present invention has been achieved.

That is, the present invention
A laser cladding step of forming a built-up layer by irradiating a laser beam while supplying high-speed tool steel powder to the surface of the metal substrate;
A spheroidizing annealing step of heat-treating the overlay layer at 750 to 880 ° C .;
A quenching step of quenching the overlay layer subjected to the spheroidizing annealing step;
A tempering step of tempering the overlay layer subjected to the quenching step,
A tool material manufacturing method characterized by the above.

  The metallographic structure of the built-up layer formed by the laser cladding method is a rapidly solidified structure. When high-speed tool steel powder is used as a raw material, crystallized carbides such as tungsten carbide, chromium carbide, vanadium carbide and molybdenum carbide are used as the base material. It segregates in a network form at the grain boundaries. While segregation of the crystallized carbide reduces the bending stress, toughness, impact resistance, etc. of the build-up layer, the crystallized carbide is spheroidized by heat treatment in a temperature range of 750 to 880 ° C. A mesh-like distribution can be divided.

  Moreover, in the manufacturing method of the tool material of this invention, after hold | maintaining the said buildup layer at 820-880 degreeC in the said spheroidizing annealing process, it cools to about 750 degreeC with the cooling rate of 10-50 degreeC / hour. Then, it is preferable to cool at a cooling rate of 50 to 150 ° C./hour. In the spheroidizing annealing step, it is preferable that the temperature of the build-up layer is 775 to 825 ° C. from the viewpoint of promoting the spheroidization of the crystallized carbide and the division of the network distribution.

  Moreover, after hold | maintaining an overlaying layer at 820-880 degreeC, a base structure can be made into a full pearlite structure | tissue by gradually cooling to about 750 degreeC with the cooling rate of 50-150 degreeC / hour. Here, it is preferable to hold at 750 ° C. for about 1 hour. When the heat treatment temperature is controlled by the furnace temperature, it is assumed that the material temperature (the temperature of the built-up layer) cannot follow even if the furnace temperature shows 750 ° C. However, by maintaining the temperature at 750 ° C. for about 1 hour, The temperature of the built-up layer can be reliably set to 750 ° C. In addition, although it cools finally with the cooling rate of 50-150 degreeC / hour, the said cooling rate is easily realizable by furnace cooling, for example.

  Moreover, in the manufacturing method of the tool material of this invention, it is preferable that the quenching temperature of the said quenching process shall be 1120-1190 degreeC. By setting the quenching temperature in the temperature range, it is possible to ensure toughness while imparting sufficient hardness to the high-speed tool steel laser cladding layer.

  Moreover, in the manufacturing method of the tool material of this invention, it is preferable that the tempering temperature of the said tempering process shall be 540-570 degreeC, and it is more preferable to set it as about 560 degreeC. If the tempering temperature is set lower than the temperature (peak temperature) at which the tempering hardness of the built-up layer is the highest, the resulting structure will be unstable, but tempering is performed at a temperature higher than the peak temperature. By doing so, a stable tissue can be obtained. Moreover, a stable structure can be obtained more reliably by repeating the tempering step three times or more.

  Furthermore, in the method for manufacturing a tool material according to the present invention, in the laser cladding step, two or more layers of the build-up layer are formed in the thickness direction, and end portions of the adjacent lower build-up layer and upper build-up layer are formed. It is preferable not to be in the same position. By forming two or more overlay layers in the thickness direction, the total thickness of the overlay layer can be arbitrarily set, and the end portions of the adjacent lower overlay layer and the upper overlay layer are at the same position. By avoiding this, peeling of the overlay layer can be suppressed.

The present invention also provides:
Two or more laser build-up layers of high-speed tool steel are formed in the thickness direction on the surface of the metal substrate,
The crystallized carbide of the laser build-up layer is substantially spherical and not segregated at the base material crystal grain boundary,
A tool material characterized by the above is also provided.

  In the tool material of the present invention, the outermost surface is a high-speed tool steel laser cladding layer having excellent high-temperature softening resistance and wear resistance, and the crystallized carbide of the laser cladding layer is substantially spherical, Since it is not segregated at the material crystal grain boundaries, it has high bending stress and impact resistance. That is, the tool material of the present invention can be used for various tools, wear-resistant members, and the like, and since the laser cladding layer can be formed in a wide area, it can also be suitably used as a large member. In addition, the material cost of the tool material can be reduced by making the metal base material an inexpensive material. For example, the entire tool material can be obtained by using a metal base material having toughness superior to the laser cladding layer. It is also possible to improve the reliability and the like.

  Here, “crystallized carbide is almost spherical” means that spheroidization progresses compared to crystallized carbide that segregates at the grain boundaries of a general high-speed tool steel cladding layer having a rapidly solidified structure. It means that In addition, “crystallized carbide is not segregated at the crystal grain boundary of the base metal” means that crystallized carbide segregated at the crystal grain boundary in a general rapidly solidified structure is not only in the crystal grain boundary but also in the crystal grain. It means that the crystallized carbides are separated from each other. As a result, the propagation of cracks along the crystallized carbide can be suppressed.

  The metal substrate is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal substrates can be used, but the adhesion to the high-speed tool steel laser cladding layer formed on the surface is not limited. From the viewpoints of suppression of dilution, mechanical properties, and the like, it is preferable to use a steel material. For example, tool steel or bearing steel can be suitably used.

  The thickness of the high-speed tool steel laser cladding layer and the thickness of the high-speed tool steel laser cladding layer are not particularly limited, and the high-speed tool having a thickness suitable only for the necessary region of the metal substrate surface. The steel laser overlaying layer should just be formed.

  Moreover, in the tool material of this invention, it is preferable in the said laser cladding layer that the edge part of an adjacent lower laser cladding layer and an upper laser cladding layer is a different position. Since the positions of the end portions of the lower laser build-up layer and the upper laser build-up layer are different, peeling of the build-up layer due to application of various stresses or thermal shock can be suppressed.

  Moreover, in the tool material of this invention, it is preferable that the bending stress of the said laser cladding layer is 2500 Mpa or more. The high-speed tool steel laser cladding layer, which is essentially excellent in high-temperature softening resistance and wear resistance, has a bending stress of 2500 MPa or more, so that the tool material of the present invention can be used even in applications where large stress is applied to the cladding layer. It can be suitably used.

  Furthermore, in the tool material of this invention, it is preferable that the said metal base material is a column shape. By making the outermost surface of a cylindrical metal base material into a high-speed tool steel laser cladding layer, for example, the tool material of the present invention can be used as a rolling roll.

  Moreover, in the tool material of this invention, it is preferable that the hardness of the said build-up layer is 850 HV or more. When the build-up layer has a hardness of 850 HV or higher, the tool material can be used for various cutting tools, wear-resistant members, and the like.

  In addition, the tool material of this invention can be suitably manufactured using the manufacturing method of the tool material of this invention.

  According to the present invention, other mechanical properties (bending stress, toughness, impact resistance, etc.) can be efficiently achieved without significantly degrading the wear resistance and high-temperature softening resistance of the cladding layer formed by the laser cladding method. Can be provided. In addition, the present invention provides a tool material in which a built-up layer of high-speed tool steel having excellent bending stress, toughness, impact resistance, wear resistance, etc. is formed on the outermost surface of a relatively inexpensive metal substrate. Can be provided.

It is process drawing of the manufacturing method of the tool material of this invention. It is a schematic diagram of the metal structure of the built-up layer before the heat treatment process. It is a schematic diagram of the metal structure of the built-up layer after the heat treatment process. It is a schematic sectional drawing which shows an example of the tool material of this invention. It is a schematic sectional drawing of the tool material (roll for hot rolling) of this invention. It is a schematic sectional drawing of the tool material (roll for steel bars and wire rods) of the present invention. It is a schematic sectional drawing of the tool material (roll for a lump and a steel piece) of this invention. It is a cross-sectional macro photograph of an implementation tool material. It is a graph which shows the Vickers hardness of the build-up layer and sintered compact which were obtained by the Example and the comparative example. It is a structure | tissue photograph of the built-up layer before heat processing of the implementation tool material. It is a structure | tissue photograph of the built-up layer after the heat processing of the implementation tool material. It is a graph which shows the bending stress (bending strength) of an overlaying layer and a sintered compact. It is a graph which shows the abrasion resistance of a building-up layer and a sintered compact.

  Hereinafter, with reference to FIGS. 1-4, the manufacturing method of the tool material of this invention and the typical embodiment in a tool material are demonstrated in detail. However, the present invention is not limited to what is shown in the drawings, and each drawing is for conceptual description of the present invention, and therefore, ratios and numbers are exaggerated or simplified as necessary for easy understanding. In some cases, it is expressed in a form. Further, in the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted.

1. Tool Material Manufacturing Method FIG. 1 is a process diagram of a tool material manufacturing method of the present invention. The manufacturing method of the tool material of the present invention includes a laser cladding step (S01), a spheroidizing annealing step (S02), a quenching step (S03), and a tempering step (S04) as essential steps. ing.

(1) Laser cladding process (S01)
The laser cladding step (S01) is a step for forming a built-up layer by irradiating a laser beam while supplying high-speed tool steel powder to the surface of the metal substrate. There are a plurality of types of high-speed tool steel powders having different compositions, but these may be appropriately selected according to required characteristics such as wear resistance and toughness.

  The laser cladding used in the method for producing a tool material of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known laser cladding methods can be used. The laser cladding method is a surface treatment method in which a fine metal powder with a uniform particle size is supplied to the surface of a metal substrate to a laser irradiation region, and a built-up layer is integrally formed on the metal substrate. However, it is also used for the production of tool materials that are intermediates in the production stage, such as cutting tools and rolling tools.

  In the laser cladding method, the laser beam emitted from the laser light source is condensed and the metal powder is melted by performing local heat input, so that the overlay layer is formed by rapid melting and rapid solidification. Moreover, it is possible to reduce the thermal strain with respect to a base material and a heat affected zone, and to reduce the dilution rate in a base material and the built-up layer formed. Furthermore, the laser beam and the torch that injects the metal powder can be controlled by a robot, and the formation location and shape of the build-up layer can be controlled relatively accurately. It can also be suitably used for repairs.

  In laser cladding, a high-speed tool steel powder having an appropriate composition and particle size distribution is used as a raw material, and the process conditions may be optimized as appropriate depending on the size and characteristics of the built-up layer to be formed. It is preferable to use a high-speed tool steel powder of ˜150 μm. Further, the metal substrate is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal substrates can be used, but the adhesion to the high-speed tool steel overlay layer formed on the surface is also possible. In view of suppression of dilution, mechanical properties, and the like, it is preferable to use a steel material, and tool steel, bearing steel, and the like can be suitably used. More specifically, for example, medium carbon steel (S45C or the like), chrome molybdenum steel, alloy tool steel, high carbon chrome bearing steel, or the like can be used.

  Here, in the laser cladding step (S01), it is fundamental to form a substantially planar multi-layered layer by linearly moving the laser beam and moving it parallel at a predetermined interval, and further reciprocating the whole multiple times. However, the present invention is not limited to this. For example, only the linear movement may be repeated a predetermined number of times to form the build-up portion, or the linear movement or the curve movement may be combined, and this may be repeated a predetermined number of times.

  Furthermore, in the laser cladding step (S01), two or more overlay layers are formed in the thickness direction so that the end portions of the adjacent lower overlay layer and the upper overlay layer are not in the same position. preferable. By forming two or more overlay layers in the thickness direction, the total thickness of the overlay layer can be arbitrarily set, and the end portions of the adjacent lower overlay layer and the upper overlay layer are at the same position. By avoiding this, peeling of the overlay layer can be suppressed.

(2) Spheroidizing annealing process (S02)
The spheroidizing annealing step (S02) is a step of performing a heat treatment for spheroidizing and uniformly dispersing the crystallized carbide on the build-up layer formed in the laser cladding step (S01).

  The metallographic structure of the built-up layer formed by the laser cladding step (S01) becomes a rapidly solidified structure. When high-speed tool steel powder is used as a raw material, crystallized carbides such as tungsten carbide, chromium carbide, vanadium carbide and molybdenum carbide Will segregate in the form of meshes at the base crystal grain boundaries. Segregation of the crystallized carbide reduces the bending stress, toughness, impact resistance, etc. of the build-up layer, but by performing a heat treatment in the temperature range of 750 to 880 ° C., the crystallized carbide becomes spheroidized, The mesh-like distribution is divided.

  Moreover, in the manufacturing method of the tool material of this invention, after hold | maintaining the said buildup layer at 820-880 degreeC in the said spheroidizing annealing process, it cools to about 750 degreeC with the cooling rate of 10-50 degreeC / hour. Then, it is preferable to cool at a cooling rate of 50 to 150 ° C./hour. In the spheroidizing annealing step, it is preferable that the temperature of the build-up layer is 775 to 825 ° C. from the viewpoint of promoting the spheroidization of the crystallized carbide and the division of the network distribution.

  In FIG.2 and FIG.3, the schematic diagram of the metal structure of the overlaying layer before and behind a spheroidizing annealing process (S02) is shown. Prior to the spheroidizing annealing step (S02), the build-up layer is in a state where the crystallized carbide 4 is segregated in a network shape at the grain boundaries of the base material crystal grains 2. Many crystallized carbides 4 have a flat shape. On the other hand, by performing the spheroidizing annealing step (S02), the crystallized carbide 4 is dispersed in the base material crystal grains 2 and the clear network structure disappears. In addition, the crystallized carbide 4 is spheroidized by heat treatment.

  The distribution state and shape change of the crystallized carbide 4 are efficiently obtained by heat treatment in the temperature range of 775 to 825 ° C., and are particularly remarkable in the heat treatment at about 800 ° C. By making the temperature of the heat treatment more than 775 ° C. and less than 825 ° C., the crystallized carbides segregated in a network form at the base crystal grain boundaries are spheroidized with respect to the metal structure of the high-speed tool steel base material that is a rapidly solidified structure. And the mesh distribution can be divided. The change in the crystallized carbide can improve toughness and impact resistance. In addition, the present inventors discovered the said temperature range, as a result of examining in detail the heat processing conditions with respect to the high-speed tool steel laser cladding layer which has a rapidly solidified structure.

  The heat treatment time in the spheroidizing annealing step (S02) is preferably 30 minutes or more. By setting the heat treatment holding time to 30 minutes or longer, the separation of the crystallized carbide 4 segregated in a network can be sufficiently advanced. As a result, the bending stress, toughness, impact resistance, etc. of the high-speed tool steel laser cladding layer can be improved. In addition, a more preferable holding time is 1 hour or more, and the most preferable holding time is 3 hours or more.

  Moreover, after hold | maintaining a high-speed tool steel laser build-up layer at 820-880 degreeC, it cools with the cooling rate of 10-50 degreeC / hour to about 750 degreeC, and then with the cooling rate of 50-150 degreeC / hour. It is preferable to cool. In the spheroidizing annealing step, it is preferable that the temperature of the build-up layer is 775 to 825 ° C. from the viewpoint of promoting the spheroidization of the crystallized carbide 4 and the division of the network distribution.

  Moreover, after hold | maintaining an overlaying layer at 820-880 degreeC, a base structure can be made into a full pearlite structure | tissue by gradually cooling to about 750 degreeC with the cooling rate of 50-150 degreeC / hour. Here, it is preferable to hold at 750 ° C. for about 1 hour. When the heat treatment temperature is controlled by the furnace temperature, it is assumed that the material temperature (the temperature of the built-up layer) cannot follow even if the furnace temperature shows 750 ° C. However, by maintaining the temperature at 750 ° C. for about 1 hour, The temperature of the built-up layer can be reliably set to 750 ° C. In addition, although it cools finally with the cooling rate of 50-150 degreeC / hour, the said cooling rate is simply realizable by furnace-cooling.

  As a heating means for the heat treatment, a heat treatment furnace, a heat treatment tank, or the like can be used, but from the viewpoint of preventing oxidation, it is preferably performed in an inert gas atmosphere or under reduced pressure / vacuum. Further, it is not always necessary to perform heat treatment for the purpose of spheroidizing annealing on the entire high-speed tool steel laser cladding layer. For example, in the case of performing partial heat treatment, laser irradiation or high-frequency heating may be used. it can. By heating by these methods, it is not necessary to separately prepare a large facility such as a heat treatment furnace, and in the case of laser irradiation, a laser irradiation apparatus for laser cladding can be used. In addition, heat treatment can be performed only on a desired region, and energy consumption necessary for the heat treatment can be reduced. In addition, the position of laser irradiation and high-frequency heating can be easily controlled, and heat treatment can be easily performed on large members such as rolling rolls.

  As a specific method of heat treatment using laser irradiation, parameters such as laser output and focus are optimized so that the region to be heat-treated of the built-up layer can maintain the predetermined temperature, and the laser is applied to the target region for a predetermined time. Heating is performed by irradiation.

  If the target area is large and the laser irradiation cannot be performed on the entire surface even if the focus setting with the widest irradiation range is used, the laser irradiation range is moved after the laser scanning speed is optimized. Alternatively, the entire region of interest is scanned by repeating the movement. In this case, there is a difference in heat input between the laser irradiation region and the non-laser irradiation region, but the heat treatment conditions must be satisfied by using the scanning speed and focus setting that can maintain the predetermined temperature throughout the target region. Can do.

(3) Quenching process (S03)
The quenching step (S03) is a step of quenching the high-speed tool steel laser cladding layer in which the shape and dispersion state of the crystallized carbide 4 are improved by the spheroidizing annealing step (S02).

  The quenching temperature is not particularly limited as long as the effects of the present invention are not impaired, and a conventionally known appropriate temperature can be used for the high-speed tool steel, but it is preferably 1120 to 1190 ° C. By setting the quenching temperature in the temperature range, the hardness of the high-speed tool steel laser overlay layer can be sufficiently increased, and toughness can be ensured.

(4) Tempering step (S04)
The tempering step (S04) is a step for stabilizing the structure in addition to adjusting the hardness of the high-speed tool steel laser cladding layer subjected to the quenching step (S03).

  Here, the tempering temperature is not particularly limited as long as the effect of the present invention is not impaired, and a conventionally known appropriate temperature can be used for the high-speed tool steel, but it is preferably 540 to 570 ° C. More preferably, the temperature is set to 560 ° C. If the tempering temperature is set lower than the temperature (peak temperature) at which the tempering hardness of the built-up layer is the highest, the resulting structure will be unstable, but tempering is performed at a temperature higher than the peak temperature. By doing so, a stable tissue can be obtained. Moreover, a stable structure can be obtained more reliably by repeating the tempering step three times or more.

2. Tool Material FIG. 4 shows a schematic cross-sectional view of the tool material of the present invention. In the tool material 10 of the present invention, a high-speed tool steel laser build-up layer 14 is formed on the surface of a metal substrate 12, and the crystallized carbide 4 of the high-speed tool steel laser build-up layer 14 is substantially spherical and has a base crystal. 2 is not segregated at the grain boundaries.

  The metal structure of the high-speed tool steel laser build-up layer 14 is as described with reference to FIG. 3, and the crystallized carbide 4 is dispersed in the base crystal grain 2, and the crystallized carbide 4 has a clear network shape. The network structure is lost. In addition, the crystallized carbide 4 is spheroidized and contains a substantially spherical crystallized carbide 4.

  When the crystallized carbide 4 segregates at the grain boundaries of the base crystal grains 2, the bending stress decreases and the bonding strength of the adjacent base crystal grains decreases, so that when cracks occur, cracks are generated along the base crystal grain boundaries. Although it progresses, since the bonding strength of the adjacent base crystal grains 2 is improved by the dispersion of the crystallized carbide 4, it is possible to suppress the progress of cracks and peeling.

  Moreover, it is preferable that the bending stress of the high-speed tool steel laser cladding layer 14 is 2500 MPa or more. The tool material of the present invention is used even in applications in which a large stress is applied to the build-up layer because the high-speed tool steel laser build-up layer 14 having essentially high temperature softening resistance and wear resistance has a bending stress of 2500 MPa or more. Can be suitably used.

  The hardness of the high-speed tool steel laser cladding layer 14 is preferably 850 HV or higher. When the build-up layer has a hardness of 850 HV or higher, the tool material can be used for various cutting tools, wear-resistant members, and the like.

  Moreover, it is preferable that the high-speed tool steel laser cladding layer 14 is a multilayer cladding layer. The multi-layered overlay layer can be formed by using, for example, a laser cladding method, and can be obtained by continuously forming a build-up layer formed by one-pass laser cladding in the horizontal direction and / or the vertical direction. . By making the high-speed tool steel laser cladding layer 14 into a multilayer cladding layer, the area and thickness to be formed can be easily controlled.

  Moreover, in the tool material of this invention, it is preferable in the said laser cladding layer that the edge part of an adjacent lower laser cladding layer and an upper laser cladding layer is a different position. Since the positions of the end portions of the lower laser build-up layer and the upper laser build-up layer are different, peeling of the build-up layer due to application of various stresses or thermal shock can be suppressed.

  Furthermore, the metal substrate 12 is preferably cylindrical. Since the high-speed tool steel laser cladding layer 14 is formed on the surface of the cylindrical metal substrate 12, the tool material 10 can be suitably used as a rolling roll. Further, when the high-speed tool steel laser build-up layer 14 is damaged or the like, it can be repaired by laser cladding.

  High-speed tool steel powder is used as a raw material for the high-speed tool steel laser cladding layer 14. The high-speed tool steel powder includes a plurality of types having different compositions, and may be appropriately selected according to required characteristics such as wear resistance and toughness. The metal base 12 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal bases can be used. However, the high-speed tool steel laser cladding layer 14 formed on the surface and the metal base 12 can be used. From the viewpoints of adhesion, suppression of dilution, mechanical properties, etc., steel materials are preferably used, and tool steel, bearing steel, and the like can be suitably used. More specifically, for example, medium carbon steel (S45C or the like), chrome molybdenum steel, alloy tool steel, high carbon chrome bearing steel, or the like can be used.

  The tool material of the present invention can be applied to uses that are too large in size or economically unappropriate with conventional HIP (hot isostatic pressing). In addition, for example, an extremely economical business model can be constructed by applying a cylindrical tool material having the high-speed tool steel laser cladding layer 14 to a large rolling roll or the like.

  Sectional drawing of the typical roll using the tool material 10 is shown in FIGS. FIG. 5 shows a hot-rolling roll, FIG. 6 shows a steel bar / wire roll, and FIG. 7 shows a shard / steel roll. In each roll, a high-speed tool steel laser cladding layer 14 is formed on the surface of the metal base 12 with which the work material comes into contact, and sufficient bending stress, toughness, impact resistance and wear resistance are ensured. ing.

  These rolls are not only relatively inexpensive because the high-speed tool steel laser build-up layer 14 is formed only in the required area of the surface, but they are damaged and worn by use. Is a high-speed tool steel laser cladding layer 14 that can be reused by repairing the high-speed tool steel laser cladding layer 14 in a damaged or worn region. As a result, significant energy saving, resource saving, and low environmental load can be achieved as compared with the case of using a roll manufactured by casting.

  Here, in the tool material of the present invention, since the high-speed tool steel laser cladding layer 14 is formed in an arbitrary region, the high-speed tool steel is selected by selecting the raw material powder of the high-speed tool steel laser cladding layer. The hardness and hardness distribution of the steel laser cladding layer 14 can be adjusted as appropriate. For example, the hardness of the high-speed tool steel laser overlay layer 14 of the steel bar / wire roll shown in FIG. 6 can be adjusted for each region depending on the degree of wear due to interaction with the workpiece. Generally, since the wear of the boundary region between the bottom surface and the side surface becomes remarkable, it is preferable that the region has a higher hardness.

  Further, for example, in the roll for a lump / steel piece shown in FIG. 7, different raw material powders are used for each high-speed tool steel laser cladding layer 14, and mechanical properties suitable for each high-speed tool steel laser cladding layer are used. Can also be given. Specifically, for example, the hardness of the high-speed tool steel laser cladding layer 14 can be increased or decreased sequentially with respect to the traveling direction of the roll axis.

  Hereinafter, although the manufacturing method and tool material of the tool material of this invention are further demonstrated in an Example, this invention is not limited to these Examples at all.

<Example 1>
Using a high-speed tool steel (JIS-SKH40) powder having a particle size of 50 to 150 μm, laser cladding is applied to the SCM440 base material to form a built-up layer, and then the built-up layer is heat treated (spheroidized) Annealing, quenching and tempering). A disk laser was used as the laser, and the laser cladding conditions were a laser output of 2 kW, a laser spot diameter (focus diameter) of 4.3 mm, and a laser moving speed of 0.01 m / s.

  The spheroidizing heat treatment was performed in a vacuum furnace (vacuum), and the spheroidizing heat treatment was held at 860 ° C. for 3 hours, then cooled to 750 ° C. at a cooling rate of 20 ° C./hour, held at 750 ° C. for 1 hour, and then cooled in the furnace . Next, the inside of the vacuum furnace was set to a nitrogen atmosphere of 130 Pa, and after holding at 1130 ° C. for 20 minutes, quenching was performed by cooling the fan while further introducing nitrogen. Thereafter, the vacuum furnace was evacuated, held at 560 ° C. for 2 hours, and then tempering by introducing nitrogen and cooling the fan was repeated three times to obtain an implement tool material.

  A cross-sectional macro photograph of the obtained tool material is shown in FIG. A built-up layer of high-speed tool steel is formed on the surface of the substrate, and defects such as peeling and cracking are not recognized. Moreover, in the cross section shown in FIG. 8, the Vickers hardness of the built-up layer of 1 mm and 2 mm from the surface was measured, and the obtained result is shown in FIG. The hardness measurement was performed at a load of 100 gf and a load loading time of 10 s, and the values shown in FIG. 9 are average values obtained by measuring 50 points horizontally at each depth.

  FIGS. 10 and 11 show structural photographs (optical micrographs) of the built-up layer before and after heat treatment (spheroidizing annealing, quenching, and tempering), respectively. Before the heat treatment, the crystallized carbides segregate in a network form at the base crystal grain boundaries, but after the heat treatment, it is understood that the network structure is divided and the crystallized carbides are distributed relatively uniformly. Further, the crystallized carbide is refined and spheroidization is progressing.

<Comparative Example 1>
A comparative tool material 1 was obtained in the same manner as in Example 1 except that no heat treatment was performed. Further, the Vickers hardness of the overlay layer was measured in the same manner as in Example 1, and the obtained results are shown in FIG.

<Comparative example 2>
Comparative tool material 2 was obtained in the same manner as in Example 1 except that spheroidizing annealing and quenching were not performed. Further, the Vickers hardness of the overlay layer was measured in the same manner as in Example 1, and the obtained results are shown in FIG.

<Comparative Example 3>
Comparative tool material 3 was obtained in the same manner as in Example 1 except that spheroidizing annealing and quenching were not performed and the tempering temperature was set to 520 ° C. Further, the Vickers hardness of the overlay layer was measured in the same manner as in Example 1, and the obtained results are shown in FIG.

<Comparative Example 4>
Comparative tool material 4 was obtained in the same manner as in Example 1 except that spheroidizing annealing and quenching were not performed and the tempering temperature was 600 ° C. Further, the Vickers hardness of the overlay layer was measured in the same manner as in Example 1, and the obtained results are shown in FIG.

<Comparative Example 5>
A high-speed tool steel (JIS-SKH40) powder having a particle size of 250 μm was sintered with HIP (hot isostatic pressing) to obtain a comparative tool material 5. The sintering conditions were held at 1240 ° C. and 1000 kgf / cm ² for 3 hours to obtain a cylindrical sintered body. Further, the Vickers hardness of the sintered body was measured in the same manner as in Example 1, and the obtained results are shown in FIG.

  From the Vickers hardness shown in FIG. 9, the implement tool material has a sufficiently high hardness of 850 HV or higher, which is comparable to that of the HIP sintered body (comparative tool material 5), and can be applied to various tools and wear-resistant members. I understand that.

  About the build-up layer of the implementation tool material and the comparative tool materials 1 to 4, and the comparative tool material 5, the bending stress (bending strength) was measured by a four-point bending test. The obtained result is shown in FIG. The build-up layer of the execution tool material has higher bending stress than the build-up layer of the comparative tool materials 1 to 4 that have not been subjected to spheroidizing annealing, and is at the same level as the HIP sintered body (comparative tool material 5). It can be seen that the bending stress is as follows. The results show that by using the method for manufacturing a tool material of the present invention, a high-speed tool steel overlay layer similar to a HIP sintered material can be formed in any region without being limited by shape and size. Yes.

  About the build-up layer of the implementation tool material and the comparative tool materials 1 to 4, and the comparative tool material 5, the wear resistance was evaluated using a block-on-ring test. Specifically, the SUJ2 ring was brought into contact with the build-up layer or the sintered body with each load of 10N, 20N, and 40N, and the width of the formed wear mark was measured. The evaluation was performed under a non-lubricating condition with the rotation speed of the ring being 1000 rpm and the test time being 600 seconds. The obtained result is shown in FIG.

  From the results shown in FIG. 13, the build-up layer of the working tool material has the same level of wear resistance as the build-up layer of the comparative tool materials 1 to 4 and the HIP sintered body (comparative tool material 5) not subjected to spheroidizing annealing. It turns out that it has sex. The results show that the build-up layer of the working tool material maintains good wear resistance despite improving toughness and the like by controlling the structure and adjusting the hardness.

2 ... Base crystal grains,
4 ... Crystallized carbide,
10 ... Tool material,
12 ... Metal substrate,
14: High-speed tool steel laser overlay.

Claims (10)

A laser cladding step of forming a built-up layer by irradiating a laser beam while supplying high-speed tool steel powder to the surface of the metal substrate;
A spheroidizing annealing step of heat-treating the overlay layer at 750 to 880 ° C .;
A quenching step of quenching the overlay layer subjected to the spheroidizing annealing step;
A tempering step of tempering the overlay layer subjected to the quenching step,
The manufacturing method of the tool material characterized by these. In the spheroidizing annealing step, after the build-up layer is held at 820 to 880 ° C,
After cooling to approximately 750 ° C. at a cooling rate of 10-50 ° C./hour,
Cooling at a cooling rate of 50 to 150 ° C./hour,
The manufacturing method of the tool material of Claim 1 characterized by these. The quenching temperature in the quenching step is 1120 to 1190 ° C.,
The method for manufacturing a tool material according to claim 1 or 2. The tempering temperature in the tempering step is 540 to 570 ° C.,
The manufacturing method of the tool material in any one of Claims 1-3 characterized by these. Repeating the tempering step three or more times;
The manufacturing method of the tool material in any one of Claims 1-4 characterized by these. In the laser cladding step, the overlay layer is formed in two or more layers in the thickness direction so that the end portions of the adjacent lower overlay layer and the upper overlay layer are not in the same position,
The method for manufacturing a tool material according to any one of claims 1 to 5. Two or more laser build-up layers of high-speed tool steel are formed in the thickness direction on the surface of the metal substrate,
The crystallized carbide of the laser build-up layer is substantially spherical and not segregated at the base material crystal grain boundary,
Tool material characterized by In the laser overlay layer, the end portions of the adjacent lower laser overlay layer and the upper laser overlay layer are in different positions,
The tool material according to claim 7. The bending stress of the laser cladding layer is 2500 MPa or more,
The tool material according to claim 7 or 8, characterized in that. The metal substrate is cylindrical,
The tool material according to any one of claims 7 to 9.