Surface treatment method for micro-powder reinforced mold

Abstract

The invention provides a micro-powder reinforced mold surface treatment method, which comprises the following steps of: performing a stress relieving procedure on a mold, performing a sand blasting operation procedure on the mold subjected to the stress relieving procedure by using a sand body, performing a micro-powder reinforcing procedure on the mold subjected to the sand blasting operation procedure, and performing a micro-powder reinforcing procedure on the mold subjected to the micro-powder reinforcing procedure. According to the micro-powder strengthening procedure, continuous alloy steel micro-powder impacts the surface of the mold at a high speed, the particle size of the alloy steel micro-powder is 0.01-0.1 mm, a compact and compressed structural strengthening area is formed on the surface of the mold through the micro-powder strengthening procedure, the strength of the surface of the mold is improved, the flatness of the surface of the mold is improved, effective treatment can be carried out at the deep hole of the mold, and the service life of the mold is prolonged. And meanwhile, the situation that a sharp corner is changed into an R corner in the treatment process can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to a surface treatment method, and in particular to a micro-powder reinforced mold surface treatment method which utilizes a new impact medium to enhance the mold surface structure performance. Background Art

[0002] After a period of processing or production, the mold often has defects or residual tensile stress on the mold surface, which often causes wear or cracks on the mold, further becoming the starting point for mold rupture, and greatly reducing the service life of the mold. In order to improve the surface defects of the mold and reduce the cracking phenomenon caused by fatigue on the mold surface, the applicant has actively conducted research on the mold surface strengthening treatment technology and developed a mold surface strengthening treatment method of Taiwan Announcement Patent No. 568815. The patent discloses the use of stress relief operation of the mold, and then sandblasting operation procedures with ceramic sand. After the sandblasting operation procedure, the mold is subsequently subjected to shot peening treatment, which uses continuous metal or glass near-spherical small particles to hit the mold surface at high speed, thereby making the mold surface harder and effectively increasing its compressive stress to reduce cracking and other defects, and thereby increase the fatigue resistance of the mold.

[0003] However, the above-mentioned mold surface strengthening treatment method uses bead peening to strengthen the mold surface, but the coverage and uniformity are poor, especially the deep holes of the mold cannot be effectively treated, and during the bead peening process, the mold surface structure is prone to change from sharp corners to R corners, resulting in large errors in dimensional accuracy. Therefore, process optimization is necessary. Summary of the invention

[0004] In view of this, the main purpose of the present invention is to provide a micro-powder reinforced mold surface treatment method, which adopts a micro-powder reinforcement procedure to replace the traditional shot peening method to improve the coverage and uniformity of the mold surface reinforcement, further enhance the strength of the mold surface, improve the mold surface flatness, and break through the original technical usage limitations. It can also effectively treat the deep holes of the mold, and also improve the situation where the sharp corners are easily turned into R corners when the medium collides with the mold.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for treating the surface of a micro-powder-reinforced mold, which comprises the following steps:

[0006] Subject the mold to a stress relief procedure;

[0007] The mold after the stress relief process is subjected to sand blasting operation; and

[0008] The mold after the sandblasting operation procedure is subjected to a micro-powder strengthening procedure. The micro-powder strengthening procedure is to use continuous alloy steel micro-powder to hit the mold surface at high speed. The particle size of the alloy steel micro-powder is 0.01 to 0.1 millimeters (mm). Through the micro-powder strengthening procedure, a compact and compressed structural strengthening area is formed on the mold surface.

[0009] According to an embodiment of the present invention, the material of the mold is high-speed steel, mold steel or stainless steel.

[0010] According to an embodiment of the present invention, the hardness of the mold is 45 to 68 HRC.

[0011] According to an embodiment of the present invention, the hardness of the alloy steel powder is 1000-1200 Hv.

[0012] According to an embodiment of the present invention, the micro-powder strengthening procedure is to use a spray gun to impact the pressurized alloy steel micro-powder onto the mold surface, the pressurized pressure is 2 to 6 bar, the incident angle of the spray gun is 90 degrees, and the operation is performed at room temperature.

[0013] According to an embodiment of the present invention, the depth of the structural reinforcement region is 20 to 50 μm.

[0014] According to an embodiment of the present invention, the mold is cleaned and hardness confirmed before the stress relief process.

[0015] According to an embodiment of the present invention, the stress relief procedure is a tempering treatment.

[0016] According to an embodiment of the present invention, the sand body used in the sandblasting operation procedure is ceramic sand or glass sand.

[0017] According to the micro-powder reinforced mold surface treatment method provided by the present invention, a micro-powder reinforcement procedure is used to replace the traditional shot peening method, that is, a special alloy steel micro-powder medium is used to impact the mold surface at high speed, so that the mold surface undergoes the extrusion effect of physical phenomena, and part of the kinetic energy of the medium is converted into the energy required for the deformation of the mold material, and a compact and compressed structure is formed on the mold surface. Compared with the prior art, the present invention can process a wider range of workpiece hardness, has less impact on the mold surface morphology, and causes greater compressive stress on the mold surface, which can effectively prevent cracking caused by fatigue, thereby extending the service life of the mold.

[0018] The above description can only be used to illustrate the problems to be solved by the present invention, the technical means for solving the problems and the effects produced, etc. The specific details of the present invention will be introduced in detail in the following implementation methods and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] Figure 1 This is a flow chart of the micropowder reinforced mold surface treatment method provided in an embodiment of the present invention.

[0021] Figure 2 and Figure 3 They are appearance pictures of alloy steel powder and traditional medium according to an embodiment of the present invention respectively.

[0022] Figure 4 and Figure 5 The microscopic morphology of the workpiece surface after being processed by the micro-powder strengthening procedure of an embodiment of the present invention and the traditional shot peening method are shown respectively.

[0023] Figure 6 and Figure 7 Schematic diagrams of the compressive stress distribution of the cross section of a workpiece after being processed by the micro-powder strengthening procedure of an embodiment of the present invention and by the traditional shot peening method.

[0024] Reference numerals:

[0025] S10: Steps

[0026] S20: Steps

[0027] S30: Steps

[0028] S31: Steps

[0029] S40: Steps

[0030] S50: Steps DETAILED DESCRIPTION

[0031] Please refer to Figure 1 , which is a flow chart of the micropowder reinforced mold surface treatment method provided by an embodiment of the present invention. The method comprises the following steps:

[0032] First, see step S10, the mold (finished mold product) is cleaned, see step S20, and then the hardness is confirmed; the hardness range of the mold applicable to the present invention is about 45 to 68HRC, for example, the type of the mold can be hot working mold steel, cold working mold steel or plastic mold steel, and for example, the material of the mold can be high-speed steel, mold steel and stainless steel, wherein the hardness of high-speed steel is about 63 to 68HRC, the hardness of mold steel is about 50 to 62HRC, and the hardness of stainless steel is about 48 to 56HRC. Then, see step S30, the mold is subjected to a stress relief procedure, which is mainly to perform the tempering treatment of step S31 to release the stress accumulated by the mold due to the thermal expansion and contraction effect during the production process, and at the same time increase the toughness of the mold surface.

[0033] Afterwards, see step S40, the mold after the stress elimination process of step S30 is subjected to a sandblasting operation procedure to clean the metal or release agent residues remaining on the mold surface, and ceramic sand is mainly used as the sandblasting material. The sandblasting material may also include glass sand, metal sand, etc. The ceramic sand can not only clean the mold surface, but also remove the discharge white layer remaining on the mold surface due to electrical discharge machining (EDM) to avoid cracking of the mold surface due to the residual electrical discharge machining white layer.

[0034] Finally, see step S50, after the mold is subjected to the sandblasting operation procedure of step S40, it enters the micro-powder strengthening procedure. The micro-powder strengthening procedure is to continuously impact the mold surface with alloy steel micro-powder at high speed. The particle size of the alloy steel micro-powder is 0.01-0.1 mm, and the hardness of the alloy steel micro-powder is 1000-1200 Hv. This impact process causes the mold surface to undergo a physical phenomenon of extrusion, converting part of the kinetic energy of the alloy steel micro-powder into the energy required for the deformation of the mold material, and forming a tight and compressed structure on the mold surface, thereby increasing the hardness of the mold surface, which is referred to as a structural strengthening zone. The depth range of this structural strengthening zone is about 20-50 μm. In addition to having a higher hardness, compressive stress is generated during the impact process, which offsets the tensile stress caused by the original mold processing, thereby avoiding the mold surface erosion and cracking caused by the molten high-temperature metal liquid (or the stretching effect of the tensile stress).

[0035] In step S50 of the present invention, the material of the alloy steel powder used in the sandblasting operation procedure can be alloy steel, which is composed of iron, carbon and other alloy elements, including nickel, chromium, silicon, boron, vanadium, molybdenum, etc. Specifically, the machine of the sandblasting operation procedure generally includes a dust collector, a spray gun fixing frame, a dust filter, a pressurized barrel tank and a pressurized spray gun system, and its operation process includes: first, fix the spray gun on the spray gun fixing frame, and fix the spray gun to be about 5 to 15 cm away from the mold surface. Then, close the chamber door, start the dust collector and start the spray gun, adjust the spray gun pressure to be fixed at 2 to 6 bar, and place the mold on the work platform. After that, the spray gun can operate the mold in the XYZ axis direction. In this embodiment, the incident angle of the spray gun is as much as possible 90 degrees, and at room temperature, the spray gun sprays the pressurized alloy steel powder to the mold surface for processing. According to the actual use requirements, the corresponding time and path processing are performed.

[0036] Regarding the operating conditions of the sandblasting operation procedure, the particle size of the alloy steel powder is limited to 0.01 to 0.1 mm, which is the optimal range. If the particle size of the alloy steel powder is greater than 0.1 mm, the mold surface morphology will be poor, the number of impact media at a single time will be low, and the surface strengthening effect will be poor. If the particle size of the alloy steel powder is less than 0.01 mm, the machine equipment has poor control energy for small-particle powder, and there will be too much loss during recycling, which is not economical. In addition, the hardness of the alloy steel powder is limited to 1000 to 1200 Hv. In practical applications, as long as the medium hardness is higher than the mold hardness, a surface strengthening effect can be produced. Generally, alloy steel powder with a hardness of 1000 to 1200 Hv can be used for most mold materials. Compared with traditional shot peening materials that were originally only suitable for hot-working die steel, the present invention uses alloy steel powder as an impact medium to adapt to pressure changes and is not easy to be knocked and broken. The scope of application is also expanded to cold-working die steel, plastic mold steel, etc.

[0037] The following is a comparative description of the micro-powder strengthening process of the embodiment of the present invention and the traditional bead peening method. Figure 2 and Figure 3 , which are the appearance diagrams of the alloy steel powder and the traditional medium of the embodiment of the present invention. The material of the traditional medium used for comparison is carbon steel, its particle size is about 0.2-0.3mm, and the medium shape is round. The alloy steel powder used in this embodiment includes alloy elements such as iron, carbon, nickel, chromium, silicon, boron, vanadium and molybdenum, its particle size is 0.01-0.1mm, and the medium shape is round.

[0038] Next, please refer to Figure 4 and Figure 5 , which are the microscopic morphology of the workpiece surface after being processed by the micro-powder strengthening procedure of the embodiment of the present invention and the traditional shot peening method. Figure 4 As shown in the figure, the hardness of the conventional medium used for comparison is about 45-50HRC, and the surface roughness of the workpiece changes from the original Ra of 0.58 to the Ra of 0.42 after shot peening. Figure 5 As shown in the figure, the hardness of the alloy steel powder used in this embodiment is about 1000-1200Hv, and the surface roughness of the workpiece is reduced from the original Ra of 0.58 to Ra of 0.33 after bead peening. In contrast, when the hardness of the workpiece is too high, the traditional bead peening method has no obvious effect on the surface treatment, while the alloy steel powder used in the present invention has a higher hardness, which can result in a lower surface roughness and has a wider range of applications.

[0039] In addition, please refer to Figure 6 and Figure 7 , which are schematic diagrams of the compressive stress distribution of the workpiece cross section after being processed by the micro-powder strengthening process of the embodiment of the present invention and the traditional shot peening method. Figure 6As shown in the figure, the compressive stress depth of the workpiece after the conventional shot peening treatment is about 10 to 30 μm, and the R angle of the workpiece surface is 53.42 μm. Figure 7 As shown in FIG. 1 , the compressive stress depth of the workpiece after the micro-powder strengthening process used in this embodiment is about 20 to 50 μm, and the R angle of the workpiece surface is 10.81 μm. Figure 6 and Figure 7 It can be found that the R angle of the same workpiece specimen using the traditional bead peening method is 53.42, while when the micro-powder strengthening procedure is used, the R angle is only 10.81. Therefore, the micro-powder strengthening procedure of the present invention can effectively avoid the phenomenon of sharp corners becoming R angles during the processing process, that is, it can reduce the degree of change in the dimensional accuracy of the mold surface.

[0040] In summary, according to the micro-powder reinforced mold surface treatment method disclosed in the present invention, the micro-powder reinforcement procedure is used to replace the traditional bead peening method to improve the coverage and uniformity of the mold surface reinforcement, further improve the strength of the mold surface, improve the mold surface flatness, and break through the original technical usage limitations. It can also effectively treat the deep holes of the mold, and also improve the situation where the sharp corners are easily turned into R corners when the medium collides with the mold. Compared with the prior art, the present invention can process a wider range of workpiece hardness, has less impact on the mold surface morphology, and causes greater compressive stress on the mold surface, which can effectively prevent cracking caused by fatigue, thereby extending the service life of the mold.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any changes or modifications made according to the features and spirit described in the application scope of the present invention should be included in the application scope of the present invention.

Claims

1. A method for surface treatment of a micro powder reinforced mold, characterized in that: The method comprises the following steps: Subjecting a mold to a stress relief process; Performing a sandblasting operation procedure on the mold after the stress relief procedure with a sand body; as well as The mold after the sandblasting operation is subjected to a micro-powder strengthening process, in which continuous alloy steel micro-powder is used to impact the mold surface at high speed. The particle size of the alloy steel micro-powder is 0.01 to 0.1 mm, and a compact and compressed structural strengthening area is formed on the mold surface.

2. The micro-powder reinforced mold surface treatment method according to claim 1, characterized in that: The material of the mold is high speed steel, mold steel or stainless steel.

3. The micro powder reinforced mold surface treatment method according to claim 2, characterized in that: The hardness of the mold is 45 to 68 HRC.

4. The micro powder reinforced mold surface treatment method according to claim 1, characterized in that: The hardness of the alloy steel powder is 1000-1200 Hv.

5. The micro powder reinforced mold surface treatment method according to claim 1, characterized in that: The micro powder strengthening procedure is to use a spray gun to impact the pressurized alloy steel micro powder onto the mold surface, the pressurized pressure is 2 to 6 bar, the incident angle of the spray gun is 90 degrees, and the operation is performed at room temperature.

6. The micro powder reinforced mold surface treatment method according to claim 1, characterized in that: The depth of the structural reinforcement area is 20 to 50 microns.

7. The micro powder reinforced mold surface treatment method according to claim 1, characterized in that: The stress relief process is preceded by cleaning and hardness confirmation of the mold.

8. The micro powder reinforced mold surface treatment method according to claim 1, characterized in that: The stress relief procedure is tempering.

9. The micro-powder reinforced mold surface treatment method according to claim 1, characterized in that: The sand body used in the sandblasting operation procedure is ceramic sand or glass sand.

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