JP2019137880A - Tool regeneration method - Google Patents

Abstract

To provide a method for repairing a high speed tool steel base material by forming a suitable build-up layer in an arbitrary region and a tool manufactured by the method, and to provide a method for repairing by forming a suitable build-up layer without causing peeling or cracking even for a high speed tool steel base material having a rapidly solidified structure.SOLUTION: The tool regeneration method includes a step for heat-treating a high speed tool steel base material at a temperature higher than 700°C and below 825°C, and a step for forming a repair build-up layer on the surface of the high speed tool steel base material subjected to the heat treatment. The heat treatment temperature is preferably greater than 775°C and less than 825°C. The high speed tool steel base material is preferably a high speed tool steel laser build-up layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for regenerating a tool material by forming a repair build-up layer in an arbitrary region of a high-speed tool steel base material and a tool material manufactured by the manufacturing method.

  2. Description of the Related Art Conventionally, as one of surface treatment techniques, a technique for improving the wear resistance and the like of the outermost surface by building up 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

  For example, if an appropriate build-up layer can be formed only in a region where a crack or chipping of a metal substrate has occurred using the laser cladding method, it can be a very efficient and inexpensive repair method. Furthermore, if a repairing method for the laser cladding layer formed by laser cladding can be established, a new business model including the production of tool materials to the reuse can be constructed. For example, if the material cost can be reduced by forming an appropriate laser cladding layer on the surface of an inexpensive steel material to make a tool material, and only the damaged area of the laser cladding layer can be repaired, this is necessary. Use can be continued only at cost.

  However, high-speed tool steel that is widely used as a tool material has high hardness, excellent wear resistance, and the like, but as a trade-off of the characteristics, the toughness is essentially lowered. As a result, when the metal base material is a high-speed tool steel, it has been a big problem that the reconstructed build-up layer is peeled off from the heat-affected zone of the metal base material. In particular, when the high-speed tool steel base material has a rapidly solidified structure, crystallized carbides segregate at the base material crystal grain boundaries and the toughness decrease becomes more prominent. Was extremely difficult.

  In view of the problems in the prior art as described above, an object of the present invention is to provide a method for repairing by forming an appropriate overlay layer in an arbitrary region of a high-speed tool steel base material, and a tool manufactured by the method. To provide materials. In particular, for the purpose of providing a repair method capable of forming an appropriate repair build-up layer without causing peeling or cracking even for a high-speed tool steel build-up material having a rapidly solidified structure. Yes.

  In order to achieve the above object, the present inventors have conducted extensive research on a method for forming a built-up layer on a high-speed tool steel base material. As a result, the high-speed tool steel base material is subjected to 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 heat treatment step of heat-treating the high-speed tool steel substrate at a temperature higher than 700 ° C. and lower than 825 ° C .;
A repair build-up process for forming a repair build-up layer on the surface of the high-speed tool steel substrate subjected to the heat treatment,
A method of regenerating a tool material characterized by the above.

  The structure and mechanical properties of the high-speed tool steel base material on which the repair build-up layer is formed vary, but by applying heat treatment at over 700 ° C. and less than 825 ° C., toughness that can withstand the repair build-up process is imparted. be able to. More specifically, if the region where the repair build-up layer of the high-speed tool steel base material is formed can be appropriately softened, peeling or cracking in the repair build-up process can be suppressed.

  On the other hand, as a result of intensive studies, the present inventors have found that there is an appropriate heat treatment temperature range in order to efficiently soften the high-speed tool steel substrate, and the temperature range is over 700 ° C. and 825 ° C. It became clear that it was less than. Although the reason why the softening is promoted in the temperature range is not necessarily clear, by setting the heat treatment temperature to be higher than 700 ° C. and lower than 825 ° C., the phase change in the base material is not caused in the base material. Dissolved carbon and alloying elements are precipitated and aggregated as carbides and become a certain size, and the amount of carbon and alloying elements that contributed to solid solution strengthening decreases, so dislocation movement becomes easier. It is thought that the hardness decreases. Further, a more efficient temperature range for softening the high-speed tool steel substrate is more than 775 ° C. and less than 825 ° C.

  The overlaying method in the repair overlaying process is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known overlaying methods can be used. For example, laser cladding or plasma arc welding can be used, but it is preferable to use laser cladding. By using laser cladding, it is possible to accurately form a build-up layer only in a desired region. Moreover, in addition to being able to suppress the heat input with respect to a high-speed tool steel base material by using laser cladding, the dilution between a build-up layer and a high-speed tool steel base material can be suppressed.

  Moreover, in the reproduction | regenerating method of the tool material of this invention, it is preferable that the said high speed tool steel base material is a high speed tool steel laser cladding layer. Since the high-speed tool steel laser cladding layer is rapidly cooled in the formation process, the crystallized carbide becomes a typical rapidly solidified structure that segregates at the grain boundary of the base material, but the method for manufacturing the tool material of the present invention should be used. Thus, a good repair build-up layer can be formed also on the surface of the high-speed tool steel laser build-up layer. Further, by repairing the high-speed tool steel laser overlay layer, the tool material in which the use of expensive and rare raw materials is minimized can be reused.

  The metal structure of the high-speed tool steel laser overlay formed by the laser cladding method becomes a rapidly solidified structure, and crystallized carbides such as tungsten carbide, chromium carbide, vanadium carbide, and molybdenum carbide are network-like at the base crystal grain boundary. Segregate. The segregation of the crystallized carbide reduces the bending stress, toughness, impact resistance, etc. of the build-up layer. In particular, the crystallized carbide becomes spherical by performing heat treatment in a temperature range of more than 775 ° C. and less than 825 ° C. And the mesh-like distribution is divided.

  When the cladding layer formed by the laser cladding method is regenerated and repaired, if the cladding layer is subjected to laser cladding, peeling from the heat-affected zone occurs. On the other hand, in the method for regenerating the tool material of the present invention, in addition to the improvement of segregation of crystallized carbide in the build-up layer by the heat treatment process, the hardness is moderately reduced, so the purpose is to repair repair Even if it is a case where an overlaying layer is formed, peeling can be suppressed effectively.

  Moreover, in the regeneration method of the tool material of this invention, it is preferable that the holding time of the said heat processing shall be 30 minutes or more. By setting the heat treatment holding time to 30 minutes or more, it is possible to sufficiently advance the separation of crystallized carbides segregated in a network, and to reduce the hardness of the high-speed tool steel substrate to 500 HV or less. . As a result, the toughness and impact resistance of the high-speed tool steel base material can be improved, and peeling at the time of regeneration repair can be suppressed. In addition, the more preferable hardness of a high-speed tool steel base material is 400 HV or less, a more preferable holding time is 1 hour or more, and the most preferable holding time is 3 hours or more.

  In the method for regenerating a tool material of the present invention, it is preferable to perform the heat treatment by laser irradiation. By using laser irradiation for heat treatment, it is not necessary to separately prepare equipment such as a heat treatment furnace, and 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 laser irradiation position can be easily controlled, and heat treatment can be easily performed on large members such as rolling rolls.

  Furthermore, in the method for regenerating a tool material according to the present invention, it is preferable that the composition of the high-speed tool steel substrate and the repair overlay layer is substantially the same. By making the compositions of the high-speed tool steel base material and the repair overlay layer formed on the surface of the high-speed tool steel base material substantially the same, it is possible to suppress a decrease in material characteristics due to dilution. In addition, when the high-speed tool steel base material is a high-speed tool steel laser overlay layer, basically, the conditions used during the overlaying can be applied as they are to the repair overlay conditions. There is no need to perform work associated with powder exchange.

The present invention also provides:
A repair overlay is formed on at least a portion of the high-speed tool steel substrate,
In the vicinity of the joint interface between the repair build-up layer and the high-speed tool steel substrate, the crystallized carbide of the high-speed tool steel substrate is substantially spherical, and is not segregated at the base material crystal grain boundary,
A tool material characterized by the above is also provided.

  The material of the high-speed tool steel base material is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known high-speed tool steel materials can be used. As the high-speed tool steel material, for example, various SKH materials and SKH40 defined in JIS G 4403: 2006 can be used.

  In the tool material of this invention, it is preferable that the said high speed tool steel base material is a high speed tool steel laser cladding layer. The build-up layer of high-speed tool steel having excellent high-temperature softening resistance is formed on the surface of an inexpensive metal base material, and the crystallized carbide of the build-up layer is substantially spherical and does not segregate at the grain boundaries. It can also be suitably used for applications requiring toughness and impact resistance. Here, “the crystallized carbide is substantially spherical” means that spheroidization has progressed as compared to the crystallized carbide segregated at the grain boundaries. Also, “crystallized carbide is not segregated at the base crystal grain boundary” means that the crystallized carbide segregated at the base crystal grain boundary in a general rapidly solidified structure is not only the base crystal grain boundary but the base crystal grain boundary. It also exists in the material crystal grains, which 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 repair build-up layer is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal materials can be used, but adhesion to the high-speed tool steel substrate, suppression of dilution, machine It is preferable to select from the standpoint of physical properties.

  Further, the thickness of the area for forming the repair overlay layer and the thickness of the repair overlay layer are not particularly limited, and the repair overlay layer having an appropriate thickness is formed only in the necessary area on the surface of the high-speed tool steel base material. Just do it.

  Moreover, in the tool material of this invention, it is preferable that the hardness of the said high-speed tool steel base material is 500 HV or less. When the hardness of the high-speed tool steel base material is 500 HV or less, the high-speed tool steel base material is provided with excellent toughness, impact resistance, etc., and when a repair overlay is formed for the purpose of regenerative repair Peeling can be suppressed. In addition, by setting the hardness of the high-speed tool steel base material to 400 HV or less, toughness, impact resistance, and the like can be further improved, and peeling during regeneration repair can be more effectively suppressed. Here, it is not necessary to have the above-mentioned hardness in the entire region of the high-speed tool steel base material, and it is sufficient that the hardness adjustment is achieved in the region where the repair overlay layer is formed.

  In the tool material of the present invention, the high-speed tool steel base material is preferably a high-speed tool steel laser overlay layer, and the high-speed tool steel laser overlay layer is a multilayer overlay layer. More preferred. The multilayer build-up layer can be formed using a laser cladding method, and can be obtained by continuously forming the build-up layer in the horizontal direction and / or the vertical direction. By making the build-up layer into a multi-layer build-up layer, the area and thickness for forming the build-up layer can be easily controlled.

  Furthermore, in the tool material of this invention, it is preferable that the said high speed tool steel base material is a column shape. Moreover, it is more preferable that a high-speed tool steel laser overlay layer is formed on the surface of a cylindrical inexpensive metal substrate. Since the build-up layer of high-speed tool steel is formed on the surface of the cylindrical high-speed tool steel base material, for example, it can be suitably used as a relatively inexpensive rolling roll. Further, when the built-up layer is damaged, it can be easily repaired and repaired.

  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, it is possible to provide a method of repairing by forming an appropriate build-up layer in an arbitrary region of a high-speed tool steel base material, and a tool material manufactured by the method, in particular, rapid solidification. It is possible to provide a repair method capable of forming an appropriate build-up layer without causing peeling or cracking even on a high-speed tool steel base material having a structure.

It is process drawing of the reproduction | regenerating 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. 2 is a cross-sectional macro photograph of a high-speed tool steel base material obtained in Example 1. FIG. It is a graph which shows the Vickers hardness of the built-up layer obtained in the Example. It is a structure | tissue photograph of the overlay layer before the heat processing of Example 1. FIG. It is a structure | tissue photograph of the built-up layer after the heat processing of Example 1. FIG. 2 is an overview photograph of a repair overlay layer formed in Example 1. FIG. It is a graph which shows the Vickers hardness of the built-up layer obtained by the comparative example. 2 is an optical micrograph of a cross-section of a built-up layer obtained in Comparative Example 1. 4 is an optical micrograph of a cross-section of a built-up layer obtained in Comparative Example 3. 6 is an optical micrograph of a cross-section of a built-up layer obtained in Comparative Example 4. 6 is an overview photograph of a repair overlay layer formed in Comparative Example 5. FIG.

  Hereinafter, with reference to FIGS. 1 to 4, representative embodiments of the method for regenerating a tool material and the tool material of the present invention will be described 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 Regeneration Method FIG. 1 shows a process diagram of the tool material regeneration method of the present invention. The regeneration method of the tool material of the present invention includes, as essential steps, a heat treatment step (S01) and a repair build-up step (S02) for forming a repair build-up layer on the high-speed tool steel base material subjected to the heat treatment step (S01). ) And.

(1) Heat treatment step (S01)
The heat treatment step (S01) is a step of performing a heat treatment on the high-speed tool steel base material on which the repair overlay layer is formed.

  The structure and mechanical properties of the high-speed tool steel base material on which the repair build-up layer is formed vary, but by applying heat treatment at over 700 ° C. and less than 825 ° C., toughness that can withstand the repair build-up process is imparted. be able to. More specifically, if the region where the repair build-up layer of the high-speed tool steel base material is formed can be appropriately softened, peeling and cracking in the repair build-up process (S02) can be suppressed.

  In particular, by setting the temperature of the heat treatment to more than 775 ° C. and less than 825 ° C., the crystallized carbide segregated in a network form at the base crystal grain boundary with respect to the metal structure of the high-speed tool steel base material that is a rapidly solidified structure. While being able to spheroidize, a mesh-like distribution can be divided. The change in the crystallized carbide can improve toughness and impact resistance.

  In FIG.2 and FIG.3, the schematic diagram of the metal structure of the high speed tool steel base material before and behind heat processing process (S01) is shown. For example, when the high-speed tool steel base material is a high-speed tool steel laser overlay layer, before the heat treatment step (S01), the overlay layer has a network of crystallized carbides 4 at the grain boundaries of the base crystal grains 2. Segregated. Many crystallized carbides 4 have a flat shape or a plate shape. On the other hand, by performing the heat treatment step (S01), the crystallized carbides 4 are dispersed in the base crystal grains 2 and the clear network structure disappears. In addition, the crystallized carbide 4 is spheroidized by heat treatment.

  Changes in the distribution and shape of the crystallized carbide 4 proceed efficiently by heat treatment in a temperature range of more than 775 ° C. and less than 825 ° C., and are particularly noticeable in heat treatment at about 800 ° C. In addition, as a result of detailed examination of heat treatment conditions for the high-speed tool steel overlay layer having a rapidly solidified structure, the present inventors have found the temperature range, and the heat treatment at different temperatures sufficiently obtains the effect. I can't.

  The heat treatment time in the heat treatment step (S01) is preferably 30 minutes or more. By setting the heat treatment holding time to 30 minutes or more, the separation of the crystallized carbide 4 segregated in a network can be sufficiently advanced, and the hardness of the high-speed tool steel overlay layer is reduced to 500 HV or less. Can do. As a result, it is possible to improve the bending stress, toughness, impact resistance and the like of the high-speed tool steel overlay layer, and to suppress peeling during regenerative repair. In addition, the hardness of the more preferable high-speed tool steel overlay is 400 HV or less, the more preferable holding time is 1 hour or more, and the most preferable holding time is 3 hours or more.

  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. Moreover, it is preferable to heat-process by laser irradiation. By using laser irradiation for heat treatment, it is not necessary to separately prepare equipment such as a heat treatment furnace, and 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 laser irradiation position 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 on the high-speed tool steel base can maintain the above-mentioned temperature, and the target region is laser Is heated for a predetermined time.

  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.

(2) Repair build-up process (S02)
In the method for regenerating a tool material of the present invention, even if the high-speed tool steel base material has a rapidly solidified structure, the crystallized carbide 4 segregates in a network form at the base material crystal grain boundary by the heat treatment step (S01). Is spheroidized and the mesh-like distribution is divided. In addition, since the high-speed tool steel base material is moderately softened, it can be easily repaired using laser cladding.

  When the high-speed tool steel laser build-up layer formed by the laser cladding method is regenerated and repaired, if the laser cladding is applied to the build-up layer, peeling from the heat-affected zone occurs. On the other hand, in addition to the improvement of segregation of the crystallized carbide 4 in the build-up layer by the heat treatment step (S01), the hardness is moderately lowered, so that the repair build-up layer is formed. Even if it exists, peeling can be suppressed effectively.

  Laser cladding can be achieved, for example, by irradiating the high-speed tool steel powder with a laser beam while supplying the 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 method of laser cladding 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 laser cladding, it is fundamental to form a substantially planar multi-layer built-up layer by linearly moving the laser beam and moving it parallel at a predetermined interval, and further reciprocating the whole multiple times. It is not limited, for example, only the linear movement may be repeated a predetermined number of times to form the build-up part, or the linear movement or the curve movement may be combined according to the shape of the repaired part, and this may be repeated a predetermined number of times. .

  In addition, it is preferable that the composition of the repair built-up layer formed by repair with a high-speed tool steel base material is made substantially the same. By making the composition of the high-speed tool steel base material and the repair overlay layer substantially the same, it is possible to suppress a decrease in material properties due to dilution. When the high-speed tool steel base material is a high-speed tool steel laser cladding layer, the composition of the high-speed tool steel laser cladding layer and the repair cladding layer is substantially the same, so that the raw material powder can be replaced. The work involved can be omitted.

2. Tool Material FIG. 4 shows a schematic cross-sectional view of the tool material of the present invention. Here, a mode in which a high-speed tool steel laser overlay layer is formed on the surface of the metal substrate, and a repair overlay layer is formed on a part of the high-speed tool steel laser overlay layer will be described. 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. No segregation at the grain boundaries. A repair overlay layer 16 is formed on a part of the high-speed tool steel laser overlay layer 14.

  The metal structure of the high-speed tool steel laser cladding layer 14 in the vicinity of the joint interface with the repair cladding layer 16 is as described with reference to FIG. 3, and the crystallized carbide 4 is dispersed in the base material crystal grains 2. The clear network structure of the crystallized carbide 4 has disappeared. In addition, the crystallized carbide 4 is spheroidized and contains a substantially spherical crystallized carbide 4. Here, “the vicinity of the bonding interface” varies depending on the material, thickness, cladding conditions, and the like of the high-speed tool steel laser cladding layer 14 and the repair cladding layer 16, but for example, a range of about 2 mm from the interface to be bonded corresponds. .

  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.

  The hardness of the high-speed tool steel laser build-up layer 14 in the vicinity of the joint interface with the repair build-up layer 16 is preferably 500 HV or less, and more preferably 400 HV or less. Adjusting the hardness of the high-speed tool steel laser cladding layer 14 within the above range can sufficiently improve the bending stress and toughness, so that the impact resistance is improved and it occurs during regenerative repair using laser cladding. Even when shrinkage during solidification is applied to the high-speed tool steel laser cladding layer 14, generation of cracks and peeling can be suppressed.

  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.

  Furthermore, the metal substrate 12 is preferably cylindrical. By forming the high-speed tool steel laser build-up layer 14 of the high-speed tool steel on the surface of the cylindrical metal substrate 12, the tool material 10 can be suitably used as a rolling roll. In addition, when the high-speed tool steel laser build-up layer 14 is damaged, it can be easily reproduced and repaired.

  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 composition of the high-speed tool steel powder is C: 1.3% by mass or more, Cr: 3% by mass or more, Mo: 4% by mass or more, W: 4% by mass or more, and V: 2% by mass or more. Is preferred.

  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, as the metal substrate 12, for example, medium carbon steel (S45C or the like), chromium molybdenum steel, alloy tool steel, high carbon chromium bearing steel, or the like can be used.

  Further, the material of the repair overlay layer 16 is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known metal materials can be used, but the composition of the high-speed tool steel laser overlay layer 14 and It is preferable to use substantially the same high-speed tool steel. By making the material of the repair build-up layer 16 a high-speed tool steel material that is substantially the same as the composition of the high-speed tool steel laser build-up layer 14, the tool material 10 having the uniform outermost surface can be obtained.

  Further, the tool material of the present invention can be applied to uses that are too large in size or economically unappropriate in 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 reproduction | regenerating 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, a cladding layer was formed by applying laser cladding on a substrate of SCM440, and then the cladding layer was heat-treated. . 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. In addition, the heat treatment was performed using high frequency heating in a vacuum and held at 800 ° C. for 3 hours.

  A cross-sectional macro photograph of the obtained high-speed tool steel substrate is shown in FIG. A built-up layer of high-speed tool steel is formed on the surface of the SCM440 base material, 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.

  Structure photographs (scanning electron micrographs) of the built-up layer before and after heat treatment are shown in FIGS. 10 and 11, respectively. Before heat treatment, crystallized carbide is segregated in the form of a network at the base material crystal grain boundaries, but after the heat treatment, the network structure is divided and the crystallized carbide is also distributed in the base material crystal grains. I understand. In addition, the crystallized carbide has a spherical shape, and in particular, the crystallized carbide in the base crystal grain is substantially spherical.

  The outermost surface of the built-up layer of the obtained high-speed tool steel base was subjected to surface grinding, and laser cladding was applied using the conditions for forming the built-up layer to form a repair built-up layer. An overview photograph of the repair overlay layer is shown in FIG. Peeling of the repair overlay layer at the heat affected zone was not observed, and it was confirmed that a good repair overlay layer was obtained.

<Example 2>
A high-speed tool steel base material was obtained in the same manner as in Example 1 except that the heat treatment was held for 30 minutes. 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. In addition, when the repair buildup layer was formed like Example 1, the peeling of the said repair buildup layer was not recognized.

<Example 3>
A high-speed tool steel base material was obtained in the same manner as in Example 1 except that the heat treatment was held for 1 hour. 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. In addition, when the repair buildup layer was formed like Example 1, the peeling of the said repair buildup layer was not recognized.

<Example 4>
A high-speed tool steel substrate was obtained in the same manner as in the example except that the heat treatment temperature was 750 ° C. Further, the Vickers hardness of the build-up layer was measured in the same manner as in Example 1, and the obtained results are shown in FIG. 13 (FIG. 13 also shows the hardness of the working tool material 1). In addition, when the repair buildup layer was formed like Example 1, the peeling of the said repair buildup layer was not recognized.

<Example 5>
A high-speed tool steel substrate was obtained in the same manner as in Example 1 except that the heat treatment temperature was 775 ° 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. In addition, when the repair buildup layer was formed like Example 1, the peeling of the said repair buildup layer was not recognized.

<Comparative Example 1>
A high-speed tool steel base material was obtained in the same manner as in Example 1 except that the heat treatment temperature was 700 ° 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.

  FIG. 14 shows an optical micrograph of the cross section of the built-up layer of the obtained high-speed tool steel substrate. The network pattern is clearly observed, and it can be seen that the crystallized carbide is segregated at the base material crystal grain boundary. In addition, when the repair built-up layer was formed like Example 1, peeling of the said repair built-up layer in the heat affected zone was recognized.

<Comparative example 2>
A high-speed tool steel base material was obtained in the same manner as in Example 1 except that the heat treatment temperature was 825 ° 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. In addition, when the repair built-up layer was formed like Example 1, peeling of the said repair built-up layer in the heat affected zone was recognized.

<Comparative Example 3>
A high-speed tool steel base material was obtained in the same manner as in Example 1 except that the heat treatment temperature was 850 ° 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.

  An optical micrograph of the cross-section of the resulting high-speed tool steel base material is shown in FIG. The network pattern is clearly observed, and it can be seen that the crystallized carbide is segregated at the base material crystal grain boundary. In addition, when the repair built-up layer was formed like Example 1, peeling of the said repair built-up layer in the heat affected zone was recognized.

<Comparative Example 4>
A high-speed tool steel substrate was obtained in the same manner as in Example 1 except that the heat treatment temperature was 900 ° 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.

  An optical micrograph of the cross-section of the resulting high-speed tool steel substrate is shown in FIG. The network pattern is clearly observed, and it can be seen that the crystallized carbide is segregated at the base material crystal grain boundary. In addition, when the repair built-up layer was formed like Example 1, peeling of the said repair built-up layer in the heat affected zone was recognized.

<Comparative Example 5>
A build-up layer was formed on the surface of the SCM440 substrate in the same manner as in Example 1 except that the heat treatment was not performed. The outermost surface of the built-up layer thus obtained was subjected to surface grinding, and laser cladding was applied under the conditions for forming the built-up layer, thereby forming a repair built-up layer. An overview photograph of the repair overlay layer is shown in FIG. The repair overlay layer was peeled off at the heat-affected zone, and it was confirmed that a good repair overlay layer could not be obtained unless appropriate heat treatment was performed.

  From the Vickers hardness shown in FIG. 9, the build-up layer has a hardness lower than 500 HV by applying heat treatment at 800 ° C. for 30 minutes, and lower than 400 HV by applying for 3 hours.

  From the Vickers hardness shown in FIG. 13, when the heat treatment temperature is 700 ° C. or lower and 825 ° C. or higher, the decrease in the hardness of the built-up layer is small, and the hardness is 500 HV or higher. On the other hand, when the heat treatment temperature is more than 700 ° C. and less than 825, the Vickers hardness is 500 HV or less, and in particular, it can be seen that the hardness is most effectively lowered when the heat treatment temperature is about 800 ° C. In addition, it is thought that the hardness fall in 800 degreeC respond | corresponds to the above-mentioned structure change. That is, the result shows that the hardness can be easily adjusted by heat treatment at 800 ° C., and an ideal structure can be obtained.

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

Claims (12)

A heat treatment step of heat-treating the high-speed tool steel substrate at a temperature higher than 700 ° C. and lower than 825 ° C .;
A repair build-up process for forming a repair build-up layer on the surface of the high-speed tool steel substrate subjected to the heat treatment,
The manufacturing method of the tool material characterized by these. The temperature of the heat treatment is more than 775 ° C. and less than 825 ° C.,
The manufacturing method of the tool steel of Claim 1 characterized by these. The high-speed tool steel substrate is a high-speed tool steel laser overlay,
The method for producing a tool steel according to claim 1 or 2, wherein: The holding time of the heat treatment is 30 minutes or more,
The manufacturing method of the tool material in any one of Claims 1-3 characterized by these. The hardness of the high-speed tool steel base material is 500 HV or less by the heat treatment,
The manufacturing method of the tool material in any one of Claims 1-4 characterized by these. Applying the heat treatment by laser irradiation,
The method for manufacturing a tool material according to any one of claims 1 to 5. The composition of the high-speed tool steel substrate and the repair overlay is substantially the same,
The method for manufacturing a tool material according to any one of claims 1 to 6. A repair overlay is formed on at least a portion of the high-speed tool steel substrate,
In the vicinity of the joint interface between the repair build-up layer and the high-speed tool steel substrate, the crystallized carbide of the high-speed tool steel substrate is substantially spherical, and is not segregated at the base material crystal grain boundary,
Tool material characterized by The high-speed tool steel substrate is a high-speed tool steel laser overlay,
The tool material according to claim 8. The high-speed tool steel base in the vicinity of the joining interface has a hardness of 500 HV or less,
The tool material according to claim 8 or 9, wherein: The high-speed tool steel laser overlay is a multilayer overlay,
The tool material according to claim 9 or 10, wherein: The high speed tool steel substrate is cylindrical,
The tool material according to any one of claims 8 to 11, wherein: