JP3441106B2 - Shot material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shot member for shot peening, and more particularly to a shot member for spraying a surface of a metal product or the like to harden the surface. 2. Description of the Related Art In the shot peening method, a number of shot members having a small particle diameter are accelerated by using centrifugal force or are put on compressed air to thereby provide a machine represented by a spring or a screw. This is a method of hardening the surface by spraying it onto the surface of metal products such as parts and tools (hereinafter abbreviated as “workpiece”). Generally, it changes the structure near the surface of the workpiece and reduces the compressive residual stress. As a method for increasing the surface hardness and the fatigue strength by causing such a phenomenon, it has been widely used conventionally. Further, as the above-mentioned shot member, steel, glass, ceramic particles or the like having a hardness equal to or higher than the hardness of the workpiece has been used (JP-A-62-278224, JP-A-62-278224). 61-18397
No. 5). [0004] However, conventional shot members made of glass or ceramics have poor durability due to low impact resistance indicating the degree of breakage when an impact is applied. When a is repeatedly used, abrasion, chipping, or cracking due to collision with a workpiece is generated, and the workability is deteriorated. Therefore, there has been a problem that machining conditions are not stable for a long time. Further, in the case of a shot member made of steel, there has been a problem that when used repeatedly, iron rust is generated, the shot member is easily deteriorated, and rust adheres to the surface of the workpiece. [0005] Furthermore, if the shot member itself has a square shape, or if the shot member has a square shape due to abrasion, chipping, or cracked shape, the surface of the workpiece is damaged. Was. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in view of the fact that when a surface hardening treatment of a workpiece is performed by a shot peening method, the material is sprayed onto a surface. In the shot member, an oxide of a Group 3a element containing Si ₃ N ₄ as a main component, SiO ₂ , Al ₂ O ₃ , Mg
_2. Silicon nitride ceramics containing at least one of O as a sintering aid, and MgO as a stabilizer containing ZrO ₂ as a main component.
A partially stabilized zirconia ceramic containing 0 to 3.8% by weight, a hard layer containing 80 to 99% by weight of a carbonitride of a Group 4a, 5a or 6a element in the periodic table and a TiC containing nickel or cobalt as a binder phase. It is made of any one of TiN-based cermets, has an average crystal grain size of 1 to 30 μm, and has a spherical polycrystalline sintered body having a fracture toughness (K _1C ) of 5.0 MPa な る m or more. The spherical shape according to the present invention is a shape having no edge portion, and has a sphericity of 0.75 (when the radius of the minimum circumscribed circle is 1, the actual minimum radius of the spherical shape is 0.7).
5) The above, preferably a sphericity of 0.9 or more. According to the present invention, the shot member has a fracture toughness (K
_By forming a polycrystalline sintered body having a spherical shape of ₁ MPa) of 3.0 MPa√m or more, it can be used in a state where processing conditions are stabilized for a long time, and the surface of the workpiece is not damaged. Embodiments of the present invention will be described below in detail. In the shot peening method, as shown in the cross-sectional view of FIG. 1, a supply port (not shown) and a compressed air outlet (not shown) of the shot member 1 are connected at a certain distance from the workpiece A. The shot member 1 is jetted from the jet port 2 together with compressed air at an appropriate speed using the nozzle 3 having the jet port 2 and the jet member 2 is caused to collide with the surface of the workpiece A so as to form irregularities. It is performed by processing. Here, the shot member 1 has a fracture toughness (K
_1c ) is a shot member 1 made of a polycrystalline sintered body having a spherical shape of 3.0 MPa√m or more, and the grounds for making them preferable are described below. First, it is better that the fracture toughness (K _1c ) indicates that it is hard to break when subjected to an impact. However, if it is smaller than 3.0 MPa√m, the fracture toughness (K _1c ) of the work A It is preferably at least 3.0 MPa√m, more preferably at least 5.0 MPa√m, because wear, chipping, or cracking due to collision is likely to occur and durability is deteriorated. If the shape is other than spherical, a sharp portion is formed, and the surface of the workpiece A is easily damaged, and cracks or chips are easily generated during a shot. It is preferable to have a spherical shape with a sphericity of at least 75, more preferably at least 0.9. The particle diameter of the shot member 1 is 0.3 m
If it is smaller than m, the impact destructive force on the workpiece A decreases,
Conversely, if it is larger than 1.6 mm, it is difficult to enter a small portion, and the number of pieces in a certain area is reduced, and the efficiency of applying energy to the workpiece A is reduced.
It is preferably 1.6 mm, and from this, it is preferable that the radius of curvature is 0.15 to 0.8 mm. Furthermore, if the sintered body is a single crystal, the mechanical strength is stabilized because the strength is high in one direction and low in the direction perpendicular to the direction of the crystal axis. For this purpose, it is preferably a polycrystalline sintered body. The fracture toughness (K1c) is 5.0 MPa√
Examples of the polycrystalline sintered body of m or more include ceramics such as silicon nitride and zirconia, and cermet. Here, the silicon nitride-based ceramic has Si ₃ N ₄ as a main component, an oxide of a Group 3a element such as Y ₂ O ₃ , SiO ₂ ,
At least one of Al ₂ O ₃ and MgO is used as a sintering aid. Then, zirconia ceramics, a ZrO ₂ as a main component, MgO was contained 3.0 to 3.8 wt% as a stabilizer, using partially stabilized zirconia containing tetragonal. Further, the cermet contains 80 to 99% by weight of a carbonitride composed of an element from Groups 4a, 5a, and 6a of the periodic table, such as titanium, niobium, and molybdenum, as a hard phase, and a metal such as nickel or cobalt as a binder phase. And 70% by weight of the hard phase is TiC, TiN, TiC
A TiC-TiN-based cermet made of N; In the method of manufacturing the shot member 1 made of the above-mentioned material, for example, the raw material particles serving as nuclei are rolled on the raw material powder while being sprayed with a binder or the like so that the raw material powder adheres to the surfaces of the core particles. It is manufactured by rolling and forming by a rolling granulation method for forming a spherical body of a desired size. When such a shot member 1 is used,
Since the impact resistance is large, the durability is improved, the processing conditions are stabilized for a long time, and the deterioration of the shot member 1 due to iron rust and the adhesion of rust to the surface of the workpiece A are also eliminated. Further, since the shape is spherical, the surface of the workpiece A is not damaged. The hardness of the shot member 1 may be equal to or higher than that of the workpiece A, and if the shot member 1 has the following conditions, it is more suitable for use. Can be. (1) The center line average roughness (Ra) of the surface is set to 0.01 to 0.5 μm or less. This is 0.5 μm
If it is larger than this, the characteristics as an abrasive will appear,
This is because the surface of the workpiece is scratched,
If it is smaller than 1 μm, it flows on the surface. (2) The specific gravity is set to 2.0 to 8.0. This is because if it is larger than 8.0, it is difficult to get on the compressed air at the time of injection, and if it is smaller than 2.0, it becomes too light and the efficiency of applying energy to the workpiece A is greatly reduced. is there. (3) The thermal conductivity is set to 4.0 W / m · K or more. This is because if the thermal conductivity is smaller than 4.0 W / m · K, the heat storage of the shot member 1 proceeds to increase the temperature of the workpiece A. (4) The average crystal grain size is 1 to 30 μm, more preferably 1 to 10 μm. This is to maintain high material strength and fracture toughness (K _1c ) as a polycrystalline sintered body. Experimental Example 1 Here, shot peening was actually performed using the shot member 1 according to the present embodiment and a shot member made of glass, chromium molybdenum steel, and alumina ceramics as a comparative example. As the material of the shot member 1, the following comparative examples shown in (1) and the examples shown in (2) to (4) were used. (1) A polycrystalline sintered body having an SiC content of 99% by weight, B ₄ C, and C as sintering aids and an average crystal grain size of 10 μm, and a Vickers hardness of 24 GPa. , Fracture toughness (K _1c ) is 3.4MP
A silicon carbide ceramic having a 質 m, a specific gravity of 3.2 and a thermal conductivity of 62 W / m · K. (2) Silicon nitride ceramics Si ₃ N ₄ content is 92% by weight, Y ₂ O ₃ , Al ₂ O ₃
Is a polycrystalline sintered body having an average crystal grain size of 10 μm, a Vickers hardness of 14.5 GPa, a fracture toughness (K _1c ) of 5.7 MPa√m, and a specific gravity of 3. 2. Silicon nitride ceramics having a thermal conductivity of 21 W / m · K. (3) Partially stabilized zirconia ceramics A polycrystalline sintered body having a MgO content of 3.5% by weight, a balance of ZrO ₂ and an average crystal grain size of 10 μm, a Vickers hardness of 11 GPa and a fracture toughness (K _1c ) Is 6.7 MPa√m, specific gravity is 6.0, and thermal conductivity is 4 W / m · K. (4) 90% by weight of TiN-based cermet hard phase, TiN content of TiC, TiC
N is a polycrystalline sintered body having an average crystal grain size of 5 μm, a Vickers hardness of 15.3 GPa, and a fracture toughness (K
_1c ) is 11 MPa @ m, specific gravity is 7.7, and thermal conductivity is 8 W
/ M · K TiN-based cermet. The glass as a comparative example has a Vickers hardness of 6 GPa and a fracture toughness (K _1c ) of 1.5 MPa√.
m and specific gravity of 2.3 were used. The chromium molybdenum steel used had a Vickers hardness of 3.0 GPa, a fracture toughness (K _1c ) of 3.1 MPa√m, and a specific gravity of 8.1. Further, alumina is a polycrystalline sintered body having an Al ₂ O ₃ content of 87% by weight and an average crystal grain size of 10 μm, a Vickers hardness of 12 GPa, a fracture toughness (K _1c ) of 2.9 MPa√m, Specific gravity is 3.6, thermal conductivity is 17W /
m · K was used. The shot member 1 has a sphericity of 0.92, a particle size of 0.8 mm, and a center line average roughness (Ra).
The workpiece A is made of carbon steel for mechanical structure having a Vickers hardness of 2.5 GPa, the injection port 2 is separated from the workpiece A by 5 cm, and the air pressure is 6 kg. / cm ^2, experiments were conducted on the condition that the injection shot member 1 injection speed 25 m / sec. First, the workpiece A was sprayed for 30 seconds, and the hardness of the workpiece A having an initial Vickers hardness of 2.5 GPa was measured. Next, when the shot member 1 was continuously jetted to the workpiece A, the time until 50% or more of the shot members 1 became unusable due to cracks or the like was measured. The results are as shown in Table 1. [Table 1] According to Table 1, when the shot member 1 of the present invention is used, the Vickers hardness of the processed workpiece A is 2.7.
To 2.8 GPa, and the effect of surface hardening was confirmed. Further, under the same conditions, the effect was larger when a material having a higher specific gravity was used. Next, regarding the usable time, the shot member 1 made of the conventional material can be used only for 50 hours with glass, 150 hours with chromium molybdenum steel, and 250 hours with alumina ceramics, whereas the shot member 1 according to the present invention can be used. Since the shot member 1 according to the example can be used for 450 hours or more, it can be seen that the shot member 1 according to the embodiment of the present invention can be used with more stable processing conditions for a long time. Further, the fracture toughness (K _1c ) is 5.0MP.
When a material of a√m or more is used, it can be used for 500 hours or more, so that the fracture toughness (K _1c ) is 5.
It is more preferable to use a material of 0 MPaＭＰm or more. As a result, the fracture toughness (K _1c ) is 3.0 MPa√.
It can be seen that the shot member 1 made of a polycrystalline ceramic having a spherical shape of not less than m, more preferably not less than 5.0 MPa√m is preferable. EXPERIMENTAL EXAMPLE 2 Next, as an embodiment of the present invention, a shot member 1 made of zirconia ceramics and having a different sphericity was manufactured, and shot peening was performed for 30 seconds under the same conditions as in Experimental Example 1, and then the workpiece was processed. The surface of the object A was observed with a microscope, and the presence or absence of a flaw was examined. In addition, shot peening was performed continuously, and the time until 50% or more of the shot members 1 became unusable due to cracks or the like (usable time) was examined. Here, the sphericity is a ratio of the minimum radius of the actual shot member 1 to the radius of the minimum circumscribed circle of the shot member 1, and the closer the sphericity value is to 1, the closer to a perfect sphere. become. As shown in Table 2, the sphericity was 0.7
If it is smaller than 5, the work A will be damaged,
Not only may the strength of the workpiece A be reduced due to the scratch, but the shot member 1 itself is liable to crack or chip, so that the usable time is as short as 300 hours. On the other hand, when the sphericity was 0.75 or more, the workpiece A was not damaged, and the usable time was as long as 450 hours or more. [Table 2] As described above, according to the shot member according to the present invention, a spherical polycrystalline sintered body having a fracture toughness (K _1c ) of 3.0 or more is formed, and thus the shot member is obtained. It is possible to provide a shot member that prevents chipping and wear of itself, can be used in a stabilized state for a long period of time, and does not damage the surface of a workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a state in which shot peening is performed using a shot member of the present invention. [Description of Signs] 1: Shot member 2: Injection port 3: Nozzle A: Workpiece

Claims (1)

(57) [Claim 1] A shot member for spraying onto a surface when performing a surface treatment of a metal product or the like by a shot peening method, wherein the shot member is mainly composed of Si ₃ N ₄ . Group 3a element
Oxide, SiO ₂ , Al ₂ O ₃ , MgO
Mainly ZrO ₂ , a silicon nitride ceramic used as a sintering aid
3.0-3.8% by weight of MgO as a component and a stabilizer
Containing partially stabilized zirconia ceramics, hard layer and
To form a carbonitride of Group 4a, 5a or 6a
0 to 99% by weight and containing nickel or cobalt as binder phase
Made of any of TiC-TiN-based cermets
It has an average crystal grain size of 1 to 30 μm and a fracture toughness (K _1C )
A shot member comprising a polycrystalline sintered body having a spherical shape of 5.0 MPa√m or more.