A method of manufacturing a die using a blank and a die

Abstract

The application discloses a blank for manufacturing a die and a manufacturing method of the die, and belongs to the technical field of die materials. ~ 1.2%, Cr: 4.5 ~ 6.5%, Mo: 2.0 ~ 3.5%, W: 1.0 ~ 2.5%, V: 0.8 ~ 1.8%, Co: 0.5 ~ 1.5%, Ni: 0.2 ~ 1.0%, Si≤0.5%, Mn≤0.5%, P≤0.03%, S≤0.03%, the balance being Fe and inevitable impurities. The blank is preferably prepared through a powder metallurgy process. The die manufacturing method comprises the following steps: rough machining, cryogenic treatment, first tempering, second tempering and finish machining. Through the combination of the specific composition and the powder metallurgy process, the blank with uniform structure and isotropy is obtained, and through the synergistic treatment of the cryogenic treatment and the specific second tempering process, the final die has high hardness, high toughness and high wear resistance, and the service life of the die under harsh working conditions is significantly prolonged.

Description

Technical Field

[0001] This invention belongs to the field of metal materials and mold manufacturing technology, specifically relating to a special blank suitable for high-strength, high-wear-resistant, and high-toughness molds, its preparation, and a method for manufacturing the molds. Background Technology

[0002] Molds are crucial equipment in industrial production, giving products their dimensions and shapes, and are widely used in stamping, die casting, injection molding, and other fields. With the increasing demands for product efficiency and quality in modern manufacturing, molds face more severe wear, impact, and thermal fatigue conditions. Currently, while commonly used mold steels (such as Cr12MoV and H13) have excellent properties, their wear resistance, toughness, and service life still fall short of higher requirements under extreme conditions. Especially for large, complex molds or those requiring long-term stable production, early failure (such as chipping, wear, and cracking) can lead to production line downtime and significant economic losses.

[0003] The existing technology has the following main shortcomings: First, there is a bottleneck in material performance. The performance improvement of traditional mold steel has reached its limit, and it is difficult to significantly improve strength, toughness, and wear resistance simultaneously through conventional alloying and heat treatment methods.

[0004] Secondly, the manufacturing process is complex. To improve the local performance of the mold, surface treatments (such as nitriding and chrome plating) or insert structures are often used, which increases the complexity of the process and the manufacturing cost, and also has problems such as insufficient bonding or weak performance transition zones.

[0005] Finally, there is the issue of anisotropy. The billets prepared by traditional casting and forging processes inevitably exhibit compositional segregation and microstructural orientation, leading to anisotropy in the performance of the final mold and affecting its overall reliability. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies by providing a mold-making blank with uniform internal structure, excellent performance, and good isotropy, as well as a method for manufacturing high-performance molds using this blank. This method aims to comprehensively improve the material properties of the mold body, simplify the manufacturing process, and extend the mold's service life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a blank for mold making, the chemical composition of which, by weight percentage, comprises: C: 0.8 ~ 1.2%, Cr: 4.5 ~ 6.5%, Mo: 2.0 ~ 3.5%, W: 1.0 ~ 2.5%, V: 0.8 ~1.8%, Co: 0.5 ~ 1.5%, Ni: 0.2 ~ 1.0%, Si≤0.5%, Mn≤0.5%, P≤0.03%, S≤0.03%, balance is Fe and unavoidable impurities.

[0008] Furthermore, the billet is a dense body prepared by powder metallurgy, with a relative density ≥99.5%. Preferably, the powder metallurgy process includes gas atomization powder preparation and hot isostatic pressing densification steps. The internal structure of the billet consists of nanoscale carbides dispersed on a uniform and fine martensitic matrix.

[0009] A second aspect of the present invention provides a method for manufacturing a mold, comprising the following steps: (1) Using a mold as described above to produce a blank; (2) S1. Blank pretreatment: The blank is rough machined to obtain a rough machined part that is close to the final shape of the mold, and a finishing allowance is reserved. S2. Cryogenic Treatment: The rough-machined part is subjected to cryogenic treatment, cooling to -80℃. ~ -120℃ and kept warm, then returned to room temperature; S3. First tempering: Temper the cryogenically treated workpiece at 520℃. ~ The first tempering treatment was carried out at 580℃, followed by cooling to room temperature; S4. Second tempering: The workpiece after the first tempering is subjected to a second tempering treatment, with the tempering temperature being 20°C lower than the first tempering temperature. ~ Hold at 40℃ and then cool to room temperature; S5. Finishing: The workpiece that has undergone heat treatment is finished to obtain the final mold.

[0010] Preferably, in step S2, 1 ~ Cooling rate of 3℃ / min to -80℃ ~ -120℃, heat preservation 2 ~ 6 hours, then at 0.5 ~ The temperature slowly rises to room temperature at a rate of 2℃ / min.

[0011] Preferably, in step S3, the holding time for the first tempering is 2 hours. ~ 4 hours, air cooling method.

[0012] Preferably, in step S4, the holding time for the second tempering is 2 hours. ~ 4 hours, air cooling method.

[0013] Furthermore, in or after step S5, a surface treatment step such as polishing or physical vapor deposition coating is also included on the working surface of the mold.

[0014] The beneficial effects of this invention are: 1. Excellent billet performance: Through specific alloy composition design, combined with powder metallurgy + hot isostatic pressing process, macroscopic segregation is fundamentally eliminated, resulting in billets with extremely uniform, fine, and isotropic microstructure. Dispersed nano-carbides can simultaneously strengthen the matrix and improve wear resistance, while the addition of Co and Ni optimizes toughness and hot strength.

[0015] 2. Excellent overall performance of the mold: The mold manufactured using this method has good consistency between the core and the surface properties, with a hardness of 58-62 HRC, an impact toughness (KU2) of not less than 25 J, high bending strength, and good high-temperature tempering stability, which significantly improves the mold's resistance to chipping and cracking under complex stress.

[0016] 3. Synergistic effects of processes: Cryogenic treatment promotes the transformation of retained austenite to martensite and further refines the martensitic matrix, increasing the number of substructures and providing more nucleation sites for carbide precipitation during subsequent tempering. The unique secondary tempering process can more fully precipitate secondary hardened carbides and eliminate the internal stress generated by cryogenic treatment and primary tempering, enabling the material to achieve the optimal balance of strength, toughness, and dimensional stability.

[0017] 4. Extended service life: Compared with similar molds made of traditional mold steel, the molds manufactured by this invention are expected to have a service life that is more than 50% longer under the same working conditions, making them particularly suitable for demanding applications such as precision stamping dies, large die-casting dies, and high-strength sheet metal forming dies. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a process flow diagram of the mold manufacturing method of the present invention.

[0020] Figure 2 This is a schematic diagram comparing the metallographic structure of the billet (powder metallurgy) of this invention with that of a comparative example billet (conventional casting and forging). (The diagram shows that the microstructure of this invention is more uniform, and the carbides are finer and more dispersed.) Figure 3 This is a structural diagram of an automobile mold part produced by the method of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings. Preferably, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0024] Example 1: Manufacturing a precision automotive structural component stamping die 1. Billet Preparation: An alloy was smelted according to the following proportions: C: 1.0%, Cr: 5.5%, Mo: 3.0%, W: 1.8%, V: 1.2%, Co: 1.0%, Ni: 0.6%, Si: 0.3%, Mn: 0.3%. The alloy was then atomized to produce a pre-alloyed powder with good sphericity and low oxygen content. The powder was packed into a mild steel liner, vacuum-sealed, and then hot isostatically pressed at 1150℃ and 120MPa pressure for 3 hours to obtain a dense modular billet. The relative density of the billet was measured to be 99.8%.

[0025] 2. Mold manufacturing: S1: Perform 3D scanning and rough milling on the blank, leaving a 0.5mm finishing allowance on one side to obtain the rough-machined part.

[0026] S2: Place the rough-machined parts into a cryogenic equipment for cryogenic treatment: cool down to -100℃ at a rate of 2℃ / min, hold for 4 hours, and then slowly return to room temperature at a rate of 1℃ / min.

[0027] S3: Perform the first tempering: Hold the workpiece at 550℃ for 3 hours, then air cool to room temperature.

[0028] S4: Perform the second tempering: Hold the workpiece at 530℃ for 3 hours, then air cool to room temperature.

[0029] S5: Perform CNC precision machining on the workpiece to the final drawing dimensions, and mirror polish the cutting edge to obtain the final mold.

[0030] Testing revealed that the mold prepared in this embodiment had an average hardness of 60 HRC and an impact toughness (KU2) of 28 J. Its metallographic structure is as follows: Figure 2 The left figure shows nanoscale carbides dispersed on a uniform and fine martensitic matrix.

[0031] Example 2: Manufacturing an aluminum alloy die-casting mold core 1. Billet preparation: The composition was adjusted to C: 0.9%, Cr: 5.0%, Mo: 2.5%, W: 1.5%, V: 1.0%, Co: 0.8%, Ni: 0.4%. The preparation process was the same as in Example 1, resulting in a billet with a density ≥ 99.5%.

[0032] 2. Mold manufacturing: S1: Roughly machine the blank, leaving a 0.8mm allowance on one side.

[0033] S2: Cryogenic treatment: Cool to -110℃ at a rate of 1.5℃ / min, hold for 5 hours, and then restore to room temperature at a rate of 0.8℃ / min.

[0034] S3: First tempering: Hold at 560℃ for 2.5 hours, then air cool.

[0035] S4: Second tempering: Hold at 540℃ for 2.5 hours, then air cool.

[0036] S5: After finishing, a PVD TiAlN coating is applied to the surface of the mold cavity.

[0037] The mold was tested and found to have a hardness of 59 HRC, indicating good resistance to thermal fatigue.

[0038] Comparative Example Using traditional H13 forged steel billets, the same stamping dies were manufactured through the same roughing, 1030℃ oil quenching, two temperings at 580℃, and finish machining. Tests showed a hardness of 52 HRC and an impact toughness of 18 J. Its metallographic structure is as follows... Figure 2 As shown in the right figure, the microstructure is uneven, the grains are relatively coarse, and there are areas of compositional segregation. Under the same production conditions, a lifespan test was conducted, and the mold repair interval lifespan of Example 1 of this invention was 2.1 times that of the comparative mold.

[0039] Detailed description of the attached figures like Figure 1As shown, the process flow of the mold manufacturing method of the present invention is as follows: providing powder metallurgy billet → rough machining of billet → cryogenic treatment → first tempering → second tempering → fine machining and surface treatment, and finally obtaining a high-performance mold.

[0040] like Figure 2 As shown, the left side is a schematic diagram of the metallographic structure of the powder metallurgy billet of the present invention, showing that its structure is uniform, the grains are fine, and the carbides are dispersed; the right side is a schematic diagram of the metallographic structure of the traditional cast and forged billet, showing that its structure is uneven, the grains are coarse, and there are segregation zones.

[0041] like Figure 3 The figure shows a schematic diagram of the structure of an automotive drawing die obtained by the method of the present invention. The key features are marked in the figure, including the cutting edge, bolt holes, internal reinforcing ribs, cooling channels and reference surfaces.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A blank for mold making, characterized in that, Its chemical composition, by weight percentage, includes: C: 0.8 ~ 1.2%, Cr: 4.5 ~ 6.5%, Mo: 2.0 ~ 3.5%, W: 1.0 ~ 2.5%, V: 0.8 ~ 1.8%, Co: 0.5 ~ 1.5%, Ni: 0.2 ~ 1.0%, Si≤0.5%, Mn≤0.5%, P≤0.03%, S≤0.03%, balance is Fe and unavoidable impurities.

2. The blank for mold making according to claim 1, characterized in that, The billet is a dense body prepared by powder metallurgy, with a relative density ≥99.5%.

3. The blank for mold making according to claim 2, characterized in that, The powder metallurgy process includes gas atomization powder preparation and hot isostatic pressing densification steps.

4. The blank for mold making according to any one of claims 1-3, characterized in that, Its internal structure consists of nanoscale carbides dispersed on a uniform and fine martensitic matrix.

5. A method for manufacturing a mold, characterized in that, The blank is made using the mold as described in any one of claims 1-4, and includes the following steps: S1. Blank pretreatment: The blank is rough machined to obtain a rough machined part that is close to the final shape of the mold, and a finishing allowance is reserved. S2. Cryogenic Treatment: The rough-machined part is subjected to cryogenic treatment, cooling to -80℃. ~ -120℃ and kept warm, then returned to room temperature; S3. First tempering: Temper the cryogenically treated workpiece at 520℃. ~ The first tempering treatment was carried out at 580℃, followed by cooling to room temperature; S4. Second tempering: The workpiece after the first tempering is subjected to a second tempering treatment, with the tempering temperature being 20°C lower than the first tempering temperature. ~ Hold at 40℃ and then cool to room temperature; S5. Finishing: The workpiece that has undergone heat treatment is finished to obtain the final mold.

6. The method for manufacturing a mold according to claim 5, characterized in that, In step S2, with 1 ~ Cooling rate of 3℃ / min to -80℃ ~ -120℃, heat preservation 2 ~ 6 hours, then at 0.5 ~ The temperature slowly rises to room temperature at a rate of 2℃ / min.

7. The method for manufacturing a mold according to claim 5, characterized in that, In step S3, the holding time for the first tempering is 2 seconds. ~ 4 hours, air cooling method.

8. The method for manufacturing a mold according to claim 5, characterized in that, In step S4, the holding time for the second tempering is 2 seconds. ~ 4 hours, air cooling method.

9. The method for manufacturing a mold according to claim 5, characterized in that, In or after step S5, a step of surface treatment of the working surface of the mold is also included.

10. The method for manufacturing a mold according to claim 9, characterized in that, The surface treatment is polishing or physical vapor deposition coating treatment.

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