JPH10217122A - Treatment method for metal mold surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a mechanical property of a metal mold surface by projecting a roughly spherical diametrical projecting material hardness of which is within a specific percentage range of Vickers hardness HV of a metal mold surface after heat treatment and a particulate diameter of which is a specific numerical range against the surface of the heat treated metal mold. SOLUTION: A roughly spherical diametrical projecting material hardness of which is 80-100% of Vickers hardness HV of a metal mold surface after heat treatment and a particulate diameter of which is 30-150μm is projected at speed 20-150m/s against the surfaces of a heat treated metal mold. Consequently, as surface roughness of the metal mold after peening treatment becomes less or equal to Ra 1.0μm, generation of scuffing is delayed. Additionally, when a method to project the roughly spherical diametrical projecting material the particulate diameter of which is 30-150μm at speed 20-150m/s is used, the maximum value of compression residual stress is formed on the metal mold surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for minimizing the surface roughness and maximizing the compressive residual stress on the surface of a heat-treated forging or pressing die when the die is subjected to peening. Processing method.

[0002]

2. Description of the Related Art Generally, quenching and tempering heat treatments and a peening process for projecting a shot material are performed for the purpose of improving the mechanical properties of a mold surface.

[0003]

However, even if these treatments are performed, there are various problems in the conventional general treatments, and particularly in the case of a die used for forging, even if the above treatments are performed. In other words, there is a problem that the so-called galling occurs early and the life of the mold is relatively shortened, or the life of the mold is shortened due to generation of cracks due to the galling. Therefore, as a result of an investigation of the cause of galling by the inventor of the present invention, it was found that the surface roughness of the mold was largely caused by galling. In addition, in the conventional peening method, the maximum value of the compressive residual stress generated on the mold surface is generated at a position slightly inside the mold from the mold surface as shown in FIG. There was a problem that the die surface had to be ground after the peening treatment so that the maximum value was located on the die surface. The present invention has been made in view of the above circumstances, and has as its object a method capable of improving the mechanical properties of the mold surface, that is, a method capable of minimizing the surface roughness of the mold. Another object of the present invention is to provide a method capable of generating a maximum value of compressive residual stress on a mold surface.

[0004]

According to a first aspect of the present invention, there is provided a method for treating a surface of a mold, wherein the surface of the heat-treated mold is subjected to a peening treatment. A method capable of minimizing roughness, wherein the hardness of the heat-treated mold surface is 80 to 160% of the Vickers hardness HV of the heat-treated mold surface.
And a projection material having a particle diameter of 30 to 150 μm and a substantially spherical diameter is projected at a speed of 20 to 150 m / s. The method of treating a mold surface according to the second aspect of the present invention can generate a maximum value of compressive residual stress in the vicinity of the surface of the treated surface when the surface of the heat-treated mold is peened. In this method, a substantially spherical blast material having a specific gravity of 11 to 20 and a particle size of 30 to 150 μm is applied to a surface of a heat-treated mold at a speed of 20.
It is characterized by projecting at ~ 150 m / s. In the method for treating a mold surface according to the third aspect of the present invention, it is possible to generate a maximum value of compressive residual stress near the surface of the treated surface when the surface of the heat-treated mold is peened. The method comprises performing a plurality of peening processes on the surface of the heat-treated mold, and among the plurality of peening processes, the shot material of at least one peening process has a higher specific gravity and a reduced particle diameter. Smaller,
In addition, it is characterized by having a higher hardness.

[0005]

According to the present invention, since the surface roughness of the die after the peening treatment becomes 1.0 μm or less, the occurrence of galling is delayed. Claims 2 and 3
In the described invention, the maximum value of the compressive residual stress is generated on the mold surface.

Here, the mold is a mold made of so-called mold steel, which is used for forging and pressing. Heat treatment refers to performing quenching and tempering under conventional conditions. Further, as a shot material having a specific gravity of 11 to 20, a shot material made of a cemented carbide is used. The shot material has a hardness of 80% of that of the mold surface after the heat treatment.
%, There is no peening effect, and if it exceeds 160%, the surface roughness of the mold becomes coarse, and further, the particle size becomes 30%.
If it is less than μm, the processing effect is small, and if it exceeds 150 μm, the surface roughness of the mold becomes rough. The projection speed of the blast material is a general speed for peening, and if this speed is less than 20 m / s, there is no peening effect, and if it exceeds 150 m / s, the surface roughness of the mold becomes rough. Become.

[0007]

EXAMPLE A mold manufactured by using various mold steels was subjected to a heat treatment of quenching and tempering, and thereafter, using an air nozzle (diameter: 8 mm) and changing the pressure of the compression air in various manners, each was used. Various blasting materials having different particle diameters and specific gravities were respectively projected onto a mold. Subsequently, when forging of an automobile part was performed using the mold subjected to the peening treatment in this manner, so-called galling occurred on the mold surface, and the number of manufactured automobile parts at the time of cracking was indicated as the life. Table 1 shows the results. Table 1
The evaluation values shown in Table 1 indicate the average values of the results of three tests performed under the same conditions. Further, the numerical value related to the position of the maximum value of the compressive residual stress indicates the depth position from the die surface when the compressive residual stress is measured using the CrKα characteristic X-ray of the X-ray diffraction stress measuring device.

Table 1

In Table 1, the comparative example in the summary means that this column shows data when one of the general peening processes is performed. Unprocessed in the summary means that this field is not subjected to peening. Furthermore, the first and second times in the abstract means that peening treatment was performed in two stages on the same mold while changing the specific gravity, particle diameter, and hardness of the shot material (mold). B).

The following can be seen from Table 1. That is, first, when the mold is peened, the life of the mold is extended. However, when the peening treatment is performed under the conditions shown in the present invention, the surface roughness of the surface to be treated becomes extremely small, and the life of the mold is reduced. Extend further. In addition, about the projection material,
By making the specific gravity of the first treatment heavier, making the particle diameter smaller, and making the hardness harder, or making the specific gravity of the first treatment heavier, making the particle diameter smaller, and increasing the hardness, Hardening further extends the life of the mold (see mold B). The specific gravity of a commonly used projection material is 7.8, which is the specific gravity of iron. However, making it heavier than this also extends the life of the mold (see the cases of molds B to E). .

[0011]

As is apparent from the above description, claim 1
The described invention has a hardness of 80 to 16 of the Vickers hardness HV of the heat-treated mold surface with respect to the heat-treated mold surface.
A projecting material having an approximate spherical diameter of 0% and a particle diameter of 30 to 150 μm is projected at a speed of 20 to 150 m / s, and the invention according to claim 2 is applied to the surface of a heat-treated mold. On the other hand, the specific gravity is 11 to 20 and the particle size is 30 to
A projectile having a substantially spherical diameter of 150 μm is applied at a speed of 20 to 15
The projection is performed at 0 m / s, and the invention according to claim 3 performs a plurality of peening processes on the surface of the processed mold, and at least one peening process among the plurality of peening processes. For the shot material, the specific gravity was larger, the particle size was smaller, and the hardness was harder, so that the surface roughness of each mold was Ra 1.0 μm.
m or less, and the maximum value of the compressive residual stress is generated on the mold surface, so that machining after the peening process is not required. That is, according to the present invention, an excellent effect is obtained such that the mechanical properties of the mold surface can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a distribution state of compressive residual stress on a die surface peened by a method of the present invention and a conventional method.

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tohru Takahashi 126, Yawatacho Bell Foundry, Toyokawa City, Aichi Prefecture (72) Inventor Junko Kurosaki 6-16-16 Kurako, Toyokawa City, Aichi Prefecture 7 (72) Inventor Toshiro Ito Aichi 3-123 Suwa, Toyokawa-shi, Aichi Prefecture (72) Inventor Takamichi Togashi 50-1, Wadotsu, Toyokawa-cho, Toyokawa-shi, Aichi

Claims (3)

[Claims] 1. A method capable of minimizing the surface roughness of a heat-treated mold when the surface of the heat-treated mold is subjected to peening treatment, wherein the hardness of the surface of the heat-treated mold is reduced. A shot material having a substantially spherical diameter, which is 80 to 160% of the Vickers hardness HV of the mold surface after the heat treatment and has a particle diameter of 30 to 150 μm,
A method for treating a die surface, wherein the projection is performed at a speed of 20 to 150 m / s. 2. A method capable of generating a maximum value of compressive residual stress in the vicinity of a surface of a heat-treated mold when the surface of the heat-treated mold is peened. On the other hand, specific gravity 11-20, particle diameter 30-1
A projecting material having a substantially spherical diameter of 50 μm is applied at a speed of 20 to 150 m /
A method for treating the surface of a mold, characterized by projecting in s. 3. A method capable of generating a maximum value of compressive residual stress in the vicinity of a surface of a heat-treated mold when the surface of the heat-treated mold is peened. Perform peening multiple times for
A method for treating the surface of a mold, characterized in that the shot material of at least one of the plurality of peening treatments has a higher specific gravity, a smaller particle diameter, and a higher hardness. .