JP6841280B2 - Surface treatment method for projectiles and hot forged products using the projectiles - Google Patents

Description

The present disclosure relates to a cast iron projecting material used in a step of removing oxide scale adhering to the surface of a metal product manufactured by hot forging or the like, and a surface treatment method using the projecting material.

Conventionally, when a scale made of oxide adheres to the surface of a metal product (for example, processing such as forging), a projecting material made of hard particles is projected onto the surface of the metal product in order to perform a blast treatment for removing the scale. Shot blasting is performed (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-121205

For many metal products, after removing the scale, the dimensions are adjusted as necessary, and then the final product is completed by finishing processing according to the target metal product. For example, when manufacturing a sliding part such as a bearing, a process is performed in which a large number of small dents (dimples) for holding lubricating oil are provided on the surface. Therefore, in the step of removing the scale, if the metal surface can be roughened to form appropriate dimples, it contributes to cost reduction. However, there are no projectiles and blasting methods capable of removing scale and forming suitable dimples on the surface of metal products.

Further, not only in sliding parts, but also in finishing, it is necessary to hold a metal product on a jig. Therefore, the surface of the metal product needs to be roughened to such an extent that the gripping force can be increased. In order to roughen the surface of a metal product, it is necessary to use a projecting material with a relatively large diameter. However, if the size of the projecting material is increased, the coverage (the actual dented area of the projecting material per fixed area) decreases. Therefore, the efficiency of removing the scale is reduced. Further, it is also required to remove defects existing on the surface layer of the metal product, for example, to seal microcracks at the same time as removing the scale.

That is, there is a demand for efficient scale removal and roughening, or removal of defects existing on the surface layer in a single process. However, there are no projection materials and surface treatment methods that make this possible.

Therefore, in the present disclosure, the projection material and the projection material capable of efficiently removing the scale, roughening the surface, or removing the defects existing in the surface layer portion of the metal product on which the scale is formed A surface treatment method using the projection material is provided.

One aspect of the present disclosure is a cast steel projecting material used to remove scale formed on the surface of a metal product by blasting. This projecting material includes a group of projecting materials of a first group and a second group. The first group is a projecting material group in which the particle diameter d1 belongs to the first particle diameter section d1max ≧ d1> d1min, and has the maximum frequency P1 in the first particle diameter section. The second group is a projecting material group in which the particle diameter d2 belongs to the second particle diameter section d2max ≧ d2> d2min, and has the maximum frequency P2 in the second particle diameter section. The first group and the second group satisfy the relationship of d1max = d2min. The particle size frequency distribution of the projection material composed of the first group and the second group is substantially continuous.

The projecting material of the first group mainly contributes to the efficient removal of scale, and the projecting material of the second group removes the scale by blasting and roughens the surface of the metal product, or , Contributes to the removal of defects existing on the surface layer of metal products. In the projection material of the present disclosure, by adjusting the particle size distribution of the projection material so that both the projection material of the first group and the projection material of the second group are present, the advantages of each are maintained and the blast is insufficient. It can complement the processing power. That is, it is possible to efficiently remove the scale from the metal product on which the scale is formed, roughen the surface, and sufficiently remove the defects existing on the surface layer portion of the metal product.

In one embodiment, d1min = 0.710 mm and d2max = 1.700 mm, and d1max may be 1.000 mm or 1.180 mm. In this case, it is possible to effectively roughen the surface of the metal product or remove defects existing in the surface layer portion of the metal product.

In one embodiment, the metal product may be a hot forged product and the projection material may have a Vickers hardness of HV300 to HV600. The projecting material has sufficient hardness for the blasting object at HV300 or higher, and the projecting material has sufficient toughness at HV600 or lower. Therefore, by using a projection material having a Vickers hardness of HV300 to HV600, it is possible to have both sufficient hardness and toughness, and even if the metal product is a hot forged product, sufficient surface treatment can be performed. ..

In one embodiment, the metal product is a sliding component, the maximum frequency P1 is the particle size section 1.180 mm ≧ d1> 1.000 mm, and the maximum frequency P2 is the particle size section 1.700 mm ≧ d2> 1.400 mm. May be present in.

In one embodiment, d1min = 0.600 mm and d2max = 1.180 mm, and d1max may be 1.000 mm or 1.180 mm. In this case, the metal product may be a hot forged product, and the projection material may have a Vickers hardness of HV300 to HV600. Further, the metal product is a sliding component, and even if the maximum frequency P1 exists in the particle size section 1.000 mm ≧ d1> 0.850 mm and the maximum frequency P2 exists in the particle size section 1.180 mm ≧ d2> 1.000 mm. Good.

In one embodiment, d1min = 0.600 mm and d2max = 1.180 mm, and d1max may be 1.000 mm or 1.180 mm. In this case, the metal product may be a hot forged product, and the projection material may have a Vickers hardness of HV300 to HV600. Further, the metal product is a sliding component, and even if the maximum frequency P1 exists in the particle size section 1.000 mm ≧ d1> 0.850 mm and the maximum frequency P2 exists in the particle size section 1.700 mm ≧ d2> 1.400 mm. Good.

In one embodiment, the projecting material may be entirely formed of a convex curved surface. In this case, for example, dimples having innumerable curved surfaces can be formed on the surface. Further, since the contact area of the projection material is uniform and wide, the plastic deformation of the metal product can be efficiently performed, and the defects existing on the surface layer portion of the metal product can be efficiently removed.

Another aspect of the present disclosure is a method for surface-treating a metal product using the above-mentioned projection material, which is a projection material loading step of loading an unused projection material into the blasting device and a projection material by operating the blasting device. The operating mix forming process of forming an operating mix in which the particle size distribution is stable, and the projection material is projected onto the metal product by a blasting device to remove the scale on the surface of the metal product, and the metal product The present invention includes a surface treatment step of roughening the surface or removing defects existing on the surface layer of the surface of the metal product.

According to this disclosure, in the state where the operating mix is formed in the operating mix forming step by using the above-mentioned projection material, the scale of the surface of the metal product is removed, and the surface of the metal product is roughened or described above. Defects existing on the surface layer of the surface of the metal product can be efficiently removed.

In one embodiment, the particle size distribution of the projectile after the operating mix forming step may be 0.250 mm to 1.700 mm and may have maximum frequencies P1 and P2. In this case, it is possible to achieve both the removal of scale and the roughening of the surface of the particle size distribution group having the maximum frequency P1 or the removal of defects existing in the surface layer portion for a long time.

In one embodiment, the maximum frequencies P1 and P2 may satisfy P2 ≦ P1.

In one embodiment, the particle size distribution of the projecting material after the operating mix forming step does not change the positions of the maximum frequencies P1 and P2 as compared with the unused projecting material, and the frequency V between the maximum frequencies P1 and P2 is the maximum. It may increase relative to the frequencies P1 and P2. With this configuration, the particle size distribution between the maximum frequencies becomes broad while maintaining the effect of the projecting material of the first group and the effect of the projecting material of the second group. Therefore, since the size of the dents formed by the projection material has a continuous distribution, the coverage can be increased and the surface treatment can be efficiently performed. In addition, "the frequency V between the maximum frequencies P1 and P2 increases relatively with respect to the maximum frequencies P1 and P2" means the difference between the maximum frequency P1 and the frequency V, and the maximum frequency P2 and the frequency V. It means that at least one of the differences becomes smaller.

In one embodiment, the metal product is a sliding component molded by hot forging, and the surface treatment step removes the scale on the surface of the sliding component, and JIS-B0601: 2000 (JIS: Japanese Industrial Standards). The ten-point average roughness Rz defined by Standards) may be 50 μm to 60 μm. In this case, in the surface treatment step of the sliding parts, the surface roughness can be adjusted to be suitable for post-processing and the like.

For metal products on which scales were formed, a projection material and its projection material that can efficiently remove scales, roughen the surface, or remove defects existing on the surface layer were used. A surface treatment method is provided.

It is explanatory drawing which shows typically the particle size distribution of the projection material of this disclosure. (A) is an explanatory diagram showing the projection density when the coverage reaches 100%. (B) is an explanatory diagram showing the number of projecting materials per 1 kg with respect to the particle size of the projecting material. It is explanatory drawing which shows the relationship between the particle diameter of a projecting material and collision energy. It is explanatory drawing which shows the relationship between the particle diameter of a projecting material and the life value of a projecting material. It is explanatory drawing which shows typically the particle size distribution after the operating mix forming process of the projection material of an Example in comparison with the particle size distribution before the operating mix forming process. It is the particle size distribution before the operating mix forming step of the projection material of an Example. It is a particle size distribution after the operating mix forming step of the projection material of FIG. It is the particle size distribution before the operating mix forming step of the projection material of an Example. It is a particle size distribution after the operating mix forming step of the projection material of FIG.

The projection material according to the present disclosure is a cast iron (cast steel) projection material that can be used to remove scale from the surface of a metal product by blasting. Here, the hardness of the projection material can be appropriately selected according to the metal product to be scale-removed. In this embodiment, a projection material that can be used for surface treatment of metal products manufactured (molded) by hot forging such as gears, cylinders, and sliding parts will be described.

The projection material is a spherical shot made of an iron-based material (cast iron) selected from the range of Vickers hardness HV300 to HV600. Here, as such an iron-based material, for example, in terms of weight%, C: 0.8% to 1.2%, Mn: 0.35% to 1.20%, Si: 0.40% to 1.50. %, P ≤ 0.05%, S ≤ 0.05%, a component system containing the balance Fe and unavoidable impurities, and has a tempered martensite structure and / or a bainite structure, or a hardened martensite structure or the like. Particles having a texture can be adopted. Such particles can be produced by a known method such as a water atomization method. Here, the projecting material has sufficient hardness for the blasting object at HV300 or higher, and the projecting material has sufficient toughness at HV600 or lower. As described above, since the projection material of the present disclosure has sufficient hardness and toughness, it can be used for blasting the surface of a hot forged product. Here, the Vickers hardness HV is based on the Japanese Industrial Standards JIS Z 2244 (2009).

FIG. 1 schematically shows the particle size distribution of the projection material. The horizontal axis is the particle size and the vertical axis is the weight fraction. The projecting material is a group of projecting materials belonging to the first particle size section d1max ≧ d1> d1min (particle size d1) that mainly contributes to the removal of scale, and is the first group having the maximum frequency P1 within the particle size section. In the projecting material group belonging to the second particle size interval d2max ≧ d2> d2min (particle size d2), which mainly contributes to roughening the surface of the metal product or removing defects existing on the surface layer of the metal product. It is provided with a second group having a maximum frequency P2 within the particle size interval. Here, the first group and the second group satisfy the relationship of d1max = d2min. Further, the particle size frequency distribution of the projection material composed of the first group and the second group is substantially continuous. In the following, the frequency between the maximum frequencies P1 and P2 is V (V1, V2, ...).

Here, the “particles having a particle size interval d1max ≧ d> d1min” are passed through a standard sieve having a nominal opening d1max specified in JIS Z8801 (2006) and captured by a standard sieve having a nominal opening d1min (passing). Does not) show particles. For example, "particles having a particle size section of 1.700 mm ≥ d> 1.400 mm" means that JIS Z8801 (2006) has passed a standard sieve having a nominal opening of 1.700 mm and a standard having a nominal opening of 1.400 mm. Indicates particles captured (not passed) by sieving. Further, it is allowed to include a maximum of about 5% of particles having a small diameter equal to or less than the lower limit of the particle diameter section. In each figure, the particle diameter on the horizontal axis shows the lower limit value of the particle diameter section as a representative value. For example, when the particle size is 1.400 mm, it means "particles having a particle size section of 1.700 mm ≥ d> 1.400 mm".

The first group of projectiles needs to increase coverage with a smaller amount of projectile in order to efficiently remove scale. FIG. 2A is a graph showing the relationship between the particle size and the projection density when the coverage reaches 100%. The horizontal axis is the particle diameter and the vertical axis is the projection density. The projection density was evaluated by colliding the projection material with the work 1 and the work 2 against a SUJ2 (high carbon chrome bearing steel material) target having a projection speed of 73 m / s and a hardness of HV200 using an impeller type blasting device. The appearance of the work after projection was photographed with a microscope, and the coverage was evaluated by comparing it with the standard photograph.

The smaller the particle size, the more the coverage tended to reach 100% with a smaller projection density. This is because the smaller the particle size, the larger the number of projecting materials per unit mass, and the more opportunities the projecting materials come into contact with metal products. FIG. 2B is a graph of the number of projecting materials per kg with respect to the particle size of the projecting material. The horizontal axis is the particle diameter, and the vertical axis is the number of projectiles per unit mass. It can be seen that when the particle size of the projecting material is 1.000 mm or less, the number of projecting materials per unit mass increases. Therefore, the particle size can be 1.000 mm or less in order to efficiently remove the scale. Further, the projecting material having a particle size of 0.500 mm or less is easily removed by a separator and a dust collector in the blasting treatment described later, which leads to a decrease in the life of the projecting material. Therefore, the particle size may exceed 0.600 mm.

The second group of projectiles provides sufficient collision energy to remove scale by blasting and mainly to remove roughening of the surface of the metal product or defects existing on the surface layer of the metal product. It is necessary to have. FIG. 3 is a graph showing the relationship between the particle size of a projecting material having a single particle size and the collision energy. The horizontal axis is the particle diameter, and the vertical axis is the collision energy per particle. Here, the collision energy was calculated from 1/2 × M × V2 (M = ρ × 4/3 × πr ^{3) at the projecting material weight M and the velocity V.} In addition, ρ = 7.5 g / cm ³ , V = 70 m / s. At least 0.01 J / piece of collision energy is required to roughen the surface of the hot forged product. Therefore, the particle size can be 1.000 mm or more. Further, for removing defects existing in the surface layer portion of the metal product, for example, for sealing microcracks, the particle size can be 1.200 mm or more.

Next, an appropriate particle size was examined from the life of the projecting material. FIG. 4 is a graph showing the relationship between the particle size of the projecting material and the lifetime value. The horizontal axis is the particle diameter and the vertical axis is the lifetime value. The life test of the projecting material conforms to the 100% Replacement Measurement specified in SAE J445 (SAE: SAE: Society of Automotive Engineers), uses an Irvine life tester, has a projection speed of 60 m / s, and has a target hardness of HRC65 (HRC: Rockwell). ), And the cutoff value was measured by a mesh under one screen. The crushed projectile was removed by sieving every fixed number of collisions, the weight of the residual projectile was measured, and the test was conducted until the residual projectile was 30% or less of the initial amount. The value obtained by integrating the life curve showing the relationship between the number of collisions obtained by this test and the weight ratio of the residual projecting material was taken as the life value.

The larger the particle size of the projecting material, the shorter the life. The life value of the projecting material is often required to be 1000 cycles or more. Therefore, the projection material of the second group can be 1.700 mm or less. Further, when a projection material having a large particle size is used, damage to the blasting device, for example, wear of parts becomes large. Therefore, it is not necessary to increase the particle size more than necessary.

With only the first group of projection materials, coverage can be improved and efficient scale removal can be performed, but the surface of the metal product is roughened or defects existing on the surface layer of the metal product are present. The removal cannot be done sufficiently.

On the other hand, the projection material of the second group alone can sufficiently roughen the surface of the metal product or remove defects existing on the surface layer of the metal product, but the number of particles per unit weight is small. Therefore, it leads to a decrease in coverage (actual dent area of the projection material per fixed area).

In the projection material of the present disclosure, by adjusting the particle size distribution of the projection material so that both the projection material of the first group and the projection material of the second group are present, the advantages of each are maintained and the blast is insufficient. It can complement the processing power. That is, it is possible to efficiently remove the scale from the metal product on which the scale is formed, roughen the surface, and sufficiently remove the defects existing on the surface layer portion of the metal product. Here, the first group and the second group may satisfy the relationship of d1max = d2min. Further, the particle size frequency distribution of the projection material composed of the first group and the second group is substantially continuous. As a result, since the size of the dents due to the surface treatment has a continuous distribution, the coverage can be increased and the surface treatment can be performed efficiently. In order to obtain this effect, d1max = d2min may be set to 1.000 mm or 1.180 mm.

Here, even if the maximum frequencies P1 and P2 satisfy P2 ≦ P1 by adjusting the ratio of the projecting materials of the first group in order to effectively perform roughening or removal of defects existing in the surface layer portion. Good.

When the metal product is a sliding component, the maximum frequency P1 exists in the particle size section 1.000 mm ≧ d1> 0.850 mm, and the maximum frequency P2 exists in the particle size section 1.700 mm ≧ d2> 1.400 mm. A projection material can be used. Alternatively, a projection material may be used such that the maximum frequency P1 exists in the particle size section 1.180 mm ≧ d1> 1.000 mm and the maximum frequency P2 exists in the particle size section 1.700 mm ≧ d2> 1.400 mm. Further, when it is desired to reduce the surface roughness, the maximum frequency P1 exists in the particle size section 1.000 mm ≧ d1> 0.850 mm, and the maximum frequency P2 exists in the particle size section 1.180 mm ≧ d2> 1.000 mm. A projection material can be used.

The particle size distribution of the projecting material can be appropriately changed according to the properties (shape, material, scale state, etc.) of the metal product as the work and the purpose of the surface treatment. For example, d1min = 0.710 mm and d2max = 1.700 mm, and d1max may be 1.000 mm or 1.180 mm. Alternatively, d1min = 0.600 mm and d2max = 1.180 mm may be set, and d1max = d2min may be set to 1.000 mm or 1.180 mm. Alternatively, d1min = 0.600 mm and d2max = 1.700 mm may be set, and d1max = d2min may be set to 1.000 mm or 1.180 mm. In either case, having the maximum frequencies P1 and P2 and having a substantially continuous particle size distribution allows efficient scale removal and scale removal for scaled metal products. The surface can be roughened and defects existing on the surface layer of the metal product can be sufficiently removed.

As the projection material, particles prepared by a known method such as a water atomization method are classified by using a sieve having a sieve specified in JIS Z 8801 (2006), and mixed and adjusted so as to have a desired particle size distribution. Can be made.

Next, a surface treatment method for performing scale removal and roughening or sealing treatment by blasting using the above-mentioned projection material will be described.

In order to perform surface treatment of a metal product using the projection material of the present disclosure, for example, a known centrifugal blasting apparatus as described in Patent Document 1 can be used. The blasting method of the present disclosure is not limited to the method using the blasting device.

The blasting device is equipped with a hopper that stores and quantitatively supplies the projection material, an impeller unit that projects the projection material, a circulation device that circulates the projection material, a separator that separates the projection material from sand and scale, and a dust collector. ..

The projecting material is thrown into the impeller unit from the hopper, and the projecting material thrown into the impeller unit is accelerated in the impeller unit and projected onto a metal product arranged in the projection chamber. As a result, the metal product is blasted.

The projected projectile is collected by the circulation device together with the scale removed from the metal product by the blasting process and sent to the separator.

In the separator, the projecting material is dropped in the shape of an apron, sand, scale and crushed fine projecting material are sorted by the air flow generated by the dust collector, and they are discharged to the outside of the dust collector and the device. The projectile material effective for the blasting process is supplied to the impeller unit again and used for circulation.

Since the amount of projecting material in the device is reduced by the amount discharged to the outside of the device, it is necessary to replenish the amount of projecting material corresponding to the reduced amount (projecting material loading process of loading unused projecting material into the blasting device). .. The decrease in projecting material is detected by the load current value of the impeller unit, and new projecting material is automatically or manually replenished to the hopper.

As a result of a series of operations of repeatedly projecting, discharging fine powder from the device, and replenishing the particles, the particle size distribution of the projecting material in the device is stable with a constant particle size distribution different from the particle size distribution of the unused projecting material ( An operating mix forming step of forming an operating mix in which the particle size distribution of the projecting material is stabilized by operating the blasting device). This state of stable particle size distribution is called an operating mix. After the operating mix forming process, the projecting material is projected onto the metal product by a blasting device to remove the scale on the surface of the metal product, and the surface of the metal product is roughened or defects existing on the surface layer of the surface of the metal product. Is removed (surface treatment step). It is important for the projecting material to manage the particle size distribution of the projecting material in the device after forming the operating mix so that efficient blasting can be performed.

By using the projection material of the present disclosure, the particle size distribution in the blasting device after the operating mix forming step can be broadened (for example, 0.250 mm to 1.700 mm) and maximized without any special device or method. It can have frequencies P1 and P2. Then, as compared with the unused projecting material, the positions (particle size) of the maximum frequencies P1 and P2 do not change, and the frequency V between the maximum frequencies P1 and P2 increases relatively with respect to the maximum frequencies P1 and P2. It can have a characteristic distribution. According to this, the particle size distribution between the maximum frequencies becomes broad while maintaining the effect of the projecting material of the first group and the effect of the projecting material of the second group. Since the size of the dents produced by the projecting material has a continuous distribution, coverage can be increased and surface treatment can be performed efficiently.

Further, in order to effectively perform roughening or removal of defects existing on the surface layer while performing efficient scale removal, the maximum frequency P1 is used in the particle size distribution in the blasting apparatus after the operating mix forming step. And P2 may satisfy P2 ≦ P1.

The projecting material may be entirely formed of a convex curved surface. When the surface treatment step is performed using a projection material that is entirely formed of a convex curved surface, for example, dimples having an infinite number of curved surfaces can be formed on the surface. Therefore, dimples for holding the lubricating oil can be formed on the surface without losing the slidability of the metal product. Further, since the contact area of the projection material is uniform and wide, the plastic deformation of the metal product can be efficiently performed, and the defects existing on the surface layer portion of the metal product can be efficiently removed. In addition, "the whole is formed by a convex curved surface" means a shape having no corners. Not only spherical particles but also particles having a chamfered and rounded corners of, for example, cylindrical particles are included.

(Change example)
The form of the projecting material is not limited to shots, and grit, cut wire, and the like can also be used.

The projection material and the surface treatment method of the present disclosure can be applied to the surface treatment of a material on which a scale is formed and a metal product of a manufacturing method other than a hot forged product made of a steel material. For example, it can be applied to scale removal of rolled steel sheets.

(Effect of embodiment)
According to the projection material of the present disclosure and the surface treatment method using the projection material, the scale is efficiently removed from the metal product on which the scale is formed, and the surface is roughened or the surface layer portion is formed. The existing defects can be removed. In particular, by appropriately setting the hardness and particle size distribution of the projection material, it can be used for surface treatment of hot forged products.

Hereinafter, examples performed for confirming the effect of the present disclosure will be described.

Scale removal was performed using the projection material of the present disclosure, and the surface roughness after surface treatment was evaluated. The work piece used in this test is made of SUJ, the shape is a cylinder (inner ring of tapered roller bearing), and the projection test device used in the test is Shotblast SNTX-I type (Shinto Kogyo Co., Ltd.). , The projection speed was 73 m / s. The projection density was the projection density when 100% coverage was reached. Projection ^density was ^{150kg / m 2 ~300kg / m 2} . The evaluation item was surface roughness, and the ten-point average roughness Rz (μm) specified in JIS-B0601: 2000 was adopted as the measurement method.

The projecting material was a steel shot having a hardness of HV450, and a projecting material in which the particle diameter at the maximum frequencies P1 and P2 and the ratio of the maximum frequency P1 and the maximum frequency P2 were changed was prepared and used for the test. In the test, the projection material was put into the projection test apparatus, continuous operation and replenishment were repeated to form an operating mix, and then the projection test was performed.

The particle size distribution of the projection material used in the test is shown below.
(1) The particle diameter at which the maximum frequency P1 of the first group is 0.710 mm (particle diameter section 0.850 mm ≧ d1> 0.710 mm), 0.850 mm (particle diameter section 1.000 mm ≧ d1> 0.850 mm), Three levels of 1.000 mm (particle size section 1.180 mm ≧ d1> 1.000 mm) (2) The particle size that is the maximum frequency P2 in the second group is 1.400 mm (particle size section 1.700 mm ≧ d2> 1.400 mm) ), 1.180 mm (particle diameter section 1.400 mm ≧ d2> 1.180 mm), 1.000 mm (particle diameter section 1.180 mm ≧ d2> 1.000 mm)

Table 1 shows the surface roughness measurement results under each condition. In this way, the surface roughness can be adjusted by selecting an appropriate particle size corresponding to the maximum frequencies P1 and P2. For example, in the surface treatment step of a sliding part manufactured by hot forging, the surface roughness Rz can be adjusted to about 50 μm to 60 μm, which is suitable for post-processing and the like.

The above particle size distribution is shown in a graph below. FIG. 5 is an explanatory diagram schematically showing the particle size distribution of the projection material of the present disclosure after the operating mix forming step in comparison with the particle size distribution before the operating mix forming step. The first group has a maximum frequency P1 particle diameter of 0.850 mm, and the second group has a maximum frequency P2 particle diameter of 1.400 mm. “Initial” is the particle size distribution before the operating mix forming step, and “operating mix” is the particle size distribution after the operating mix forming step. The difference between the maximum frequencies P1 and P2 and the frequency V1 after the operating mix forming step is smaller than the difference between the initial maximum frequencies P1 and P2 and the frequency V1. Further, the difference between the maximum frequencies P1 and P2 and the frequency V2 after the operating mix forming step is smaller than the difference between the initial maximum frequencies P1 and P2 and the frequency V1. In this way, the positions of the maximum frequencies P1 and P2 do not change, and the frequency V (V1, V2) between the maximum frequencies P1 and P2 increases relatively with respect to the maximum frequencies P1 and P2. It was confirmed that With reference to Table 1, the surface roughness can be adjusted to about 54.13 μm by using this projection material.

FIG. 6 shows the particle size distribution of the projection material of the example before forming the operating mix. The horizontal axis is the particle size and the vertical axis is the weight fraction. The first group has a particle diameter of 1.000 mm, and the second group has a particle diameter of 1.400 mm. n is a test number, and the average is the average value of the test results indicated by the test number. FIG. 7 shows the particle size distribution of the projection material of FIG. 6 after forming the operating mix. In this way, the positions (particle size) of the maximum frequencies P1 and P2 do not change, and the frequency V between the maximum frequencies P1 and P2 increases relatively with respect to the maximum frequencies P1 and P2. It was confirmed that. The average maximum frequency P2 after the formation of the operating mix: the maximum frequency P1 is 18:23, which satisfies P2 ≦ P1.

FIG. 8 shows the particle size distribution of the projection material of the example before forming the operating mix. The horizontal axis is the particle size and the vertical axis is the weight fraction. The first group has a particle diameter of 0.850 mm, and the second group has a particle diameter of 1.000 mm. n is a test number, and the average is the average value of the test results indicated by the test number. FIG. 9 shows the particle size distribution of the projection material of FIG. 8 after forming the operating mix. In this way, the positions (particle size) of the maximum frequencies P1 and P2 do not change, and the frequency V between the maximum frequencies P1 and P2 increases relatively with respect to the maximum frequencies P1 and P2. It was confirmed that. The average maximum frequency P2 after the formation of the operating mix: the maximum frequency P1 is 23:24, which satisfies P2 ≦ P1.

Claims (6)

It is used to remove the scale formed on the surface of the hot forged product by blasting and to roughen the surface of the hot forged product or to remove defects existing on the surface layer of the hot forged product. In cast steel projectiles
Vickers hardness is HV300-HV600,
The first group in which the particle diameter d1 belongs to the first particle diameter section 1.000 mm ≧ d1> 0.600 mm and has the maximum frequency P1 in the first particle diameter section, and the first group.
A projecting material group in which the particle diameter d2 belongs to the second particle diameter section 1.180 mm ≧ d2> 1.000 mm, and the second group having the maximum frequency P2 in the second particle diameter section is provided.
The particle size frequency distribution of the projection material composed of the first group and the second group is such that the frequency corresponding to the particle size of 1.000 mm is greater than 0. It is used to remove the scale formed on the surface of the hot forged product by blasting and to roughen the surface of the hot forged product or to remove defects existing on the surface layer of the hot forged product. In cast steel projectiles
Vickers hardness is HV300-HV600,
The first group in which the particle diameter d1 belongs to the first particle diameter section 1.000 mm ≧ d1> 0.600 mm and has the maximum frequency P1 in the first particle diameter section, and the first group.
A projecting material group in which the particle diameter d2 belongs to the second particle diameter section 1.700 mm ≧ d2> 1.000 mm, and the second group having the maximum frequency P2 in the second particle diameter section is provided.
The particle size frequency distribution of the projection material composed of the first group and the second group is such that the frequency corresponding to the particle size of 1.000 mm is greater than 0. It is used to remove the scale formed on the surface of the hot forged product by blasting and to roughen the surface of the hot forged product or to remove defects existing on the surface layer of the hot forged product. In cast steel projectiles
Vickers hardness is HV300-HV600,
The first group in which the particle diameter d1 belongs to the first particle diameter section 1.180 mm ≧ d1> 0.600 mm and has the maximum frequency P1 in the first particle diameter section, and the first group.
A projecting material group in which the particle diameter d2 belongs to the second particle diameter section 1.700 mm ≧ d2> 1.180 mm, and the second group having the maximum frequency P2 in the second particle diameter section is provided.
The particle size frequency distribution of the projection material composed of the first group and the second group is such that the frequency corresponding to the particle size of 1.180 mm is greater than 0. The hot forged product is a sliding part and
The projection material according to claim 3, wherein the maximum frequency P1 exists in the particle size section 1.180 mm ≧ d1> 1.000 mm, and the maximum frequency P2 exists in the particle size section 1.700 mm ≧ d2> 1.400 mm. The projection material according to any one of claims 1 to 4, wherein the projection material is entirely formed of a convex curved surface. A method for surface-treating a hot forged product using the projection material according to any one of claims 1 to 5.
The projection material loading process for loading unused projection material into the blasting device, and
An operating mix forming step of forming an operating mix in which the particle size distribution of the projection material is stabilized by the operation of the blasting device.
The projection material is projected onto the hot forged product by the blasting device to remove scale on the surface of the hot forged product, and the surface of the hot forged product is roughened or the hot forged product is roughened. A surface treatment process that removes defects existing on the surface layer of the surface of the
Bei obtain surface treatment method of hot forging a.

Images