A process for controlling residual stresses in heat treating of die surfaces

Abstract

The application discloses a kind of process methods for controlling mould surface heat treatment residual stress, it is related to mould processing technical field, comprising the following steps: S1, the three-dimensional model parameters of mould are obtained by three-dimensional scanning to the mould to be processed, and by Deform metal plasticity analysis software to the metal surface with this three-dimensional model parameters Simulation analysis is carried out, and the key area of high tensile stress prone on surface is identified.The process method for controlling mould surface heat treatment residual stress is different from traditional overall heat treatment mode, simulation analysis is carried out to the metal surface by Deform metal plasticity analysis software, and the key area of high tensile stress prone on surface is identified, combined with the heating equipment laid for targeted treatment multiple heating cryogenic and carburizing and multiple composite processing of key area, only energy is applied to key area, and energy consumption is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of mold processing technology, specifically to a process method for controlling residual stress on mold surfaces after heat treatment. Background Technology

[0002] A mold is a set of molds and tools used in industrial production to obtain desired products through methods such as injection molding, blow molding, extrusion, die casting, forging, smelting, and stamping. In short, a mold is a tool used to create shaped objects; this tool is composed of various parts, and different molds are composed of different parts. As a core process equipment in modern manufacturing, molds directly determine the precision, surface quality, and production efficiency of formed parts. In high-end manufacturing fields such as automotive body panels, precision injection molding, and die casting, mold surfaces (such as draw beads, runner surfaces, and parting surfaces) typically have complex geometric features and high dimensional stability requirements. However, during mold manufacturing, the heat treatment process inevitably introduces significant residual stress, becoming one of the main causes of early mold failure (such as cracking, deformation, and fatigue spalling).

[0003] Currently, the industry commonly uses a process of integral quenching and tempering to strengthen mold steel. While this method can improve the hardness and wear resistance of the base material, the complex geometry and large differences in wall thickness of the mold surface lead to uneven thermal expansion and contraction in different areas during heating and cooling. This easily results in high-amplitude tensile residual stress in sharp corners, thin walls, and deep cavities. Such tensile stress not only reduces the fatigue resistance of the mold but also induces uncontrollable deformation under subsequent machining or service loads, seriously affecting product consistency. Therefore, we propose a process method to control the residual stress of the mold surface after heat treatment. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a process method for controlling residual stress in the heat treatment of mold surfaces, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides a process method for controlling residual stress on the surface of a mold after heat treatment, comprising the following steps: S1. Perform a 3D scan of the mold to be processed to obtain the 3D model parameters of the mold, and use the 3D model parameters to perform simulation analysis on the metal surface using Deform metal plasticity analysis software, and identify the key areas on the surface that are prone to high tensile stress. S2. Based on the distribution of key areas on the surface that are prone to high tensile stress as described in step S1 above, arrange heating equipment to heat the surface. S3. After heating the entire mold, quench it and keep it at that temperature. S4. Within 8 hours after quenching in step S3 above, start the heating equipment arranged in step S2 to perform tempering heat treatment on the critical area at a low heating rate, so that the local temperature rises to the tempering temperature range and is held at that temperature, while the temperature rise of the remaining non-critical areas does not exceed 70°C. S5. After the tempering and heat preservation are completed according to the above S4 steps, liquid nitrogen atomized gas flow is sprayed into the tempered area to carry out local deep cryogenic aging treatment. The cooling rate is controlled at 80–150℃ / min, the deep cryogenic endpoint temperature is −80℃ to −120℃, and the heat preservation time is 10–30 minutes. S6. After processing according to step S5 above, perform carburizing surface strengthening treatment, and use pre-cooling direct quenching at a quenching temperature of 800-850℃ to reduce deformation and oxidation decarburization. This is suitable for fine-grained steel tools. S7. Repeat steps S4-S6, processing other key areas in a preset order, until the residual stress distribution of the entire surface tends to be in a uniform compressive stress state, and the maximum tensile stress amplitude is reduced by ≥70%. Furthermore, in step S1, the Deform metal plasticity analysis software is used to accurately simulate the metal forming process, analyze key parameters such as forging load, grain flow, and die filling, and provide die optimization functions, including die filling analysis, wear prediction, and life assessment.

[0006] Furthermore, the heating equipment arranged in step S2 should be fitted to the area where the curvature of the mold surface changes, so as to achieve conformal heating.

[0007] Furthermore, in step S4, the tempering temperature range is 160–300℃, and the heating rate is controlled at 5–10℃ / min to suppress temper brittleness and promote carbide precipitation.

[0008] Furthermore, in step S7, the processing order of each key region is dynamically optimized and determined by the stress release path of the key region analyzed by the Deform metal plasticity analysis software, so as to minimize the overall deformation.

[0009] Furthermore, the mold material is H13, Cr12MoV, or NAK80 series hot and cold work die steel.

[0010] Furthermore, after step S7 is completed, the residual stress on the surface is detected by ultrasonic method. If the absolute value of tensile stress in any region is >150 MPa, the local tempering-deep cryogenic parameters are replanned and compensation processing is performed.

[0011] This invention provides a process for controlling residual stress in mold surfaces after heat treatment, which has the following advantages: This process for controlling residual stress in mold surfaces after heat treatment differs from traditional overall heat treatment methods. It utilizes Deform metal plasticity analysis software to simulate and analyze the metal surface, and identifies key areas on the surface that are prone to high tensile stress. At the same time, it combines the installed heating equipment to target key areas with multiple composite treatments such as multiple heating, deep cooling, and carburizing. Energy is applied only to key areas, significantly reducing energy consumption. Furthermore, it has a compensation feedback mechanism. If the local tensile stress is still found to exceed the standard (>150 MPa), the local tempering-deep cooling parameters are re-planned and compensation treatment is performed. It can also be seamlessly integrated into existing heat treatment production lines, with low modification costs and easy industrial application. Detailed Implementation

[0012] A process for controlling residual stress on mold surfaces after heat treatment includes the following steps: S1. Perform a 3D scan of the mold to be processed to obtain the 3D model parameters of the mold, and use the 3D model parameters to perform simulation analysis on the metal surface using Deform metal plasticity analysis software, and identify the key areas on the surface that are prone to high tensile stress. S2. Based on the distribution of key areas on the surface that are prone to high tensile stress as described in step S1 above, arrange heating equipment to heat the surface. S3. After heating the entire mold, quench it and keep it at that temperature. S4. Within 8 hours after quenching in step S3 above, start the heating equipment arranged in step S2 to perform tempering heat treatment on the critical area at a low heating rate, so that the local temperature rises to the tempering temperature range and is held at that temperature, while the temperature rise of the remaining non-critical areas does not exceed 70°C. S5. After the tempering and heat preservation are completed according to the above S4 steps, liquid nitrogen atomized gas flow is sprayed into the tempered area to carry out local deep cryogenic aging treatment. The cooling rate is controlled at 80–150℃ / min, the deep cryogenic endpoint temperature is −80℃ to −120℃, and the heat preservation time is 10–30 minutes. S6. After processing according to step S5 above, perform carburizing surface strengthening treatment, and use pre-cooling direct quenching at a quenching temperature of 800-850℃ to reduce deformation and oxidation decarburization. This is suitable for fine-grained steel tools. S7. Repeat steps S4-S6, processing other key areas in a preset order, until the residual stress distribution of the entire surface tends to be in a uniform compressive stress state, and the maximum tensile stress amplitude is reduced by ≥70%. Furthermore, in step S1, the Deform metal plasticity analysis software is used to accurately simulate the metal forming process, analyze key parameters such as forging load, grain flow, and die filling, and provide die optimization functions, including die filling analysis, wear prediction, and life assessment.

[0013] Furthermore, the heating equipment arranged in step S2 should be fitted to the area where the curvature of the mold surface changes, so as to achieve conformal heating.

[0014] Furthermore, in step S4, the tempering temperature range is 160–300℃, and the heating rate is controlled at 5–10℃ / min to suppress temper brittleness and promote carbide precipitation.

[0015] Furthermore, in step S7, the processing order of each key region is dynamically optimized and determined by the stress release path of the key region analyzed by the Deform metal plasticity analysis software, so as to minimize the overall deformation.

[0016] Furthermore, the mold material is H13, Cr12MoV, or NAK80 series hot and cold work die steel.

[0017] Furthermore, after step S7 is completed, the residual stress on the surface is detected by ultrasonic method. If the absolute value of tensile stress in any region is >150 MPa, the local tempering-deep cryogenic parameters are replanned and compensation processing is performed.

[0018] In summary, the process method for controlling residual stress on mold surfaces after heat treatment includes the following specific steps: S1. The mold to be processed is 3D scanned to obtain the 3D model parameters of the mold. Using these 3D model parameters, the metal surface is simulated and analyzed by Deform metal plasticity analysis software. The key areas on the surface that are prone to high tensile stress are identified. Deform metal plasticity analysis software is used to accurately simulate the metal forming process, analyze key parameters such as forging load, grain flow, and mold filling, and provide mold optimization functions, including mold filling analysis, wear prediction and life assessment. The mold material is H13, Cr12MoV or NAK80 series hot and cold work die steel. S2. Based on the distribution of key areas on the mold surface that are prone to high tensile stress as described in step S1 above, arrange heating equipment to heat the mold surface. The heating equipment should be placed close to the curvature change of the mold surface to achieve conformal heating. S3. After heating the entire mold, quench it and keep it at that temperature. S4. Within 8 hours after quenching in step S3 above, start the heating equipment arranged in step S2 to perform tempering heat treatment on the critical area at a low heating rate, so that the local temperature rises to the tempering temperature range and is held at that temperature, while the temperature rise of the remaining non-critical areas does not exceed 70°C. The tempering temperature range is 160–300°C, and the heating rate is controlled at 5–10°C / min to suppress tempering brittleness and promote carbide precipitation. S5. After the tempering and heat preservation are completed according to the above S4 steps, liquid nitrogen atomized gas flow is sprayed into the tempered area to carry out local deep cryogenic aging treatment. The cooling rate is controlled at 80–150℃ / min, the deep cryogenic endpoint temperature is −80℃ to −120℃, and the heat preservation time is 10–30 minutes. S6. After processing according to step S5 above, perform carburizing surface strengthening treatment, and use pre-cooling direct quenching at a quenching temperature of 800-850℃ to reduce deformation and oxidation decarburization. This is suitable for fine-grained steel tools. S7. Repeat steps S4-S6 to process other key areas in a preset order, so that the residual stress distribution of the entire surface tends to be uniform compressive stress state and the maximum tensile stress amplitude is reduced by ≥70%. The processing order of each key area is dynamically optimized and determined by the stress release path of the key area analyzed by Deform metal plasticity analysis software to minimize the overall deformation. After step S7 is completed, the residual stress of the surface is detected by ultrasonic method. If the absolute value of tensile stress in any area is >150MPa, the local tempering-deep cooling parameters are replanned and compensation processing is performed.

Claims

1. A process for controlling residual stress on mold surfaces after heat treatment, characterized in that, Includes the following steps: S1. Perform a 3D scan of the mold to be processed to obtain the 3D model parameters of the mold, and use the 3D model parameters to perform simulation analysis on the metal surface using Deform metal plasticity analysis software, and identify the key areas on the surface that are prone to high tensile stress. S2. Based on the distribution of key areas on the surface that are prone to high tensile stress as described in step S1 above, arrange heating equipment to heat the surface. S3. After heating the entire mold, quench it and keep it at that temperature. S4. Within 8 hours after quenching in step S3 above, start the heating equipment arranged in step S2 to perform tempering heat treatment on the critical area at a low heating rate, so that the local temperature rises to the tempering temperature range and is held at that temperature, while the temperature rise of the remaining non-critical areas does not exceed 70°C. S5. After the tempering and heat preservation are completed according to the above S4 steps, liquid nitrogen atomized gas flow is sprayed into the tempered area to carry out local deep cryogenic aging treatment. The cooling rate is controlled at 80–150℃ / min, the deep cryogenic endpoint temperature is −80℃ to −120℃, and the heat preservation time is 10–30 minutes. S6. After processing according to step S5 above, perform carburizing surface strengthening treatment, and use pre-cooling direct quenching at a quenching temperature of 800-850℃ to reduce deformation and oxidation decarburization. This is suitable for fine-grained steel tools. S7. Repeat steps S4-S6 to process other key areas in the preset order, so that the residual stress distribution of the entire surface tends to be uniform compressive stress state and the maximum tensile stress amplitude is reduced by ≥70%.

2. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that, In step S1, the Deform metal plasticity analysis software is used to accurately simulate the metal forming process, analyze key parameters such as forging load, grain flow, and die filling, and provide die optimization functions, including die filling analysis, wear prediction, and life assessment.

3. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that: The heating equipment arranged in step S2 should be fitted to the area where the curvature of the mold surface changes, so as to achieve conformal heating.

4. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that: In step S4, the tempering temperature range is 160–300℃, and the heating rate is controlled at 5–10℃ / min to suppress temper brittleness and promote carbide precipitation.

5. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that: In step S7, the processing order of each key region is dynamically optimized and determined by the stress release path of the key region analyzed by the Deform metal plasticity analysis software, so as to minimize the overall deformation.

6. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that: The mold material is H13, Cr12MoV or NAK80 series hot and cold work mold steel.

7. The process method for controlling residual stress on mold surface after heat treatment according to claim 1, characterized in that: After step S7 is completed, the residual stress on the surface is detected by ultrasonic method. If the absolute value of tensile stress in any region is >150MPa, the local tempering-deep cryogenic parameters are replanned and compensation processing is performed.