Die machining process based on center console supporting beam

Abstract

The invention belongs to the technical field of die machining, and provides a die machining process based on a center console supporting beam, which comprises the following steps: I, sequentially carrying out first annealing and second annealing on a die steel blank to obtain an annealed blank; iI, performing rough machining on the annealed blank by adopting a numerical control milling machine to obtain a rough machining part; iII, sequentially carrying out stress relief annealing, quenching and gradient tempering on the rough machining part to obtain a tempered workpiece; iV, the tempered workpiece is subjected to finish machining, and a finish machining workpiece is obtained; and V, nitriding treatment is conducted on the finish machining part, and the finished mold is obtained. According to the mold processing technology provided by the invention, through cooperation of multi-stage heat treatment stress regulation and control, rough and finish machining forming and nitriding surface strengthening, the finished mold has high dimensional stability, excellent fatigue resistance and good thermal shock resistance, and the problems of deformation cracking, rapid surface abrasion and the like in a traditional technology are effectively solved; the method is suitable for efficient and precise forming of complex-curved-surface automobile structural parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of mold processing, and relates to a mold processing technology based on a console support beam. Background Art

[0002] With the continuous improvement of the requirements for automotive lightweight and safety performance, as a key load-bearing structural component of the vehicle body, the console support beam needs to have high strength, high precision, and the ability to form complex curved surfaces. Traditional mold processing technologies mostly adopt a combination of single heat treatment and conventional machining, but there are significant bottlenecks in practical applications: on the one hand, during multiple high-temperature forming processes of die steel, deformation or cracking is likely to occur due to the concentration of residual stress, affecting the dimensional stability of the support beam; on the other hand, it is difficult to balance the surface hardness and matrix toughness of the mold by conventional nitriding or quenching processes, resulting in a short mold life and high maintenance costs. Especially during mass production, the yield rate fluctuates greatly. In addition, the existing technology lacks systematic design for surface treatment after finish machining, and uneven layer depth is likely to occur in the subsequent nitriding process, directly affecting the surface finish and fatigue resistance of the formed parts. Aiming at the above industry pain points, it is urgent to develop a mold process that integrates material modification, stress regulation, and precision machining for collaborative optimization to break through the efficiency and quality bottlenecks in the manufacturing of high-complexity automotive structural parts. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a mold processing technology based on a console support beam. The mold processing technology provided by the present invention combines multi-stage heat treatment stress regulation, rough and finish machining forming, and nitriding surface strengthening, enabling the finished mold to have high dimensional stability, excellent fatigue resistance, and good thermal shock resistance, effectively solving problems such as deformation cracking and fast surface wear existing in traditional processes, and being applicable to the high-efficiency and precision forming of complex curved surface automotive structural parts.

[0004] To achieve this purpose, the present invention adopts the following technical solutions: The present invention provides a mold processing technology based on a console support beam, and the mold processing technology based on a console support beam includes: Ⅰ. Successively perform the first annealing and the second annealing on the die steel blank to obtain an annealed blank; Ⅱ. Rough machine the annealed blank using a CNC milling machine to obtain a rough machined part; Ⅲ. Successively perform stress relief annealing, quenching, and gradient tempering on the rough machined part to obtain a tempered workpiece; Ⅳ. Finish machine the tempered workpiece to obtain a finish machined part; Ⅴ. Perform nitriding treatment on the finish machined part to obtain a finished mold.

[0005] The die manufacturing process provided by the present invention combines multi-stage heat treatment stress regulation, rough and finish machining forming, and nitriding surface strengthening, enabling the finished die to have high dimensional stability, excellent fatigue resistance, and good thermal shock resistance. It effectively solves problems such as deformation cracking and rapid surface wear existing in traditional processes and is applicable to the high-efficiency precision forming of complex curved surface automotive structural parts. The two annealing treatments are respectively for stress relief and microstructure homogenization. The first annealing eliminates the forming stress of the blank, and the second annealing promotes the dissolution of carbides and refines the grains, creating a stable matrix for subsequent processing. The quenching process adopts stepped heating and oil cooling control to achieve full austenitization while avoiding thermal stress, obtaining a uniform and fine martensite structure. Gradient tempering is regulated by two temperature decreases. First, high-temperature tempering promotes the dispersion precipitation of carbides and decomposes the retained austenite, and then low-temperature tempering optimizes the carbide distribution and releases micro-stresses, enhancing the impact toughness of the workpiece while maintaining high hardness. Pulse ion nitriding forms a dense nitrided layer of 0.15 - 0.2 mm through nitrogen-hydrogen mixed gas and precise temperature control, optimizing the surface hardness and wear resistance.

[0006] The two annealing treatments achieve material modification through gradient temperature control. The first annealing is carried out in the temperature range of 600 - 650 °C, mainly eliminating the local stress concentration formed during the original forming process of the blank and avoiding the cutting vibration problem caused by uneven matrix structure during subsequent processing. The second annealing uses a high-temperature treatment of 880 - 900 °C to promote the full dissolution and diffusion of alloy carbides, creating uniform austenitization conditions for the subsequent quenching of H13 high-alloy die steel. After the two annealing treatments, a staged cooling process is adopted. First, it is cooled at a controlled rate to 300 °C, and then cooled in the furnace, effectively reducing the temperature gradient inside the large-section blank, ensuring both the cutting efficiency during rough machining and avoiding abnormal tool wear caused by the excessive hardness of the material.

[0007] The present invention uses stress relief annealing, quenching, and gradient tempering for the composite heat treatment of rough-machined workpieces, improving the material properties through stress relief and phase transformation strengthening. The stress relief annealing is carried out at 600 - 650 °C for 2 - 3 hours of heat preservation, specifically eliminating more than about 75% of the mechanical stress generated during rough machining and controlling the workpiece deformation within 0.15 mm / m. The quenching process adopts a stepped heating scheme, first preheating at 500 - 550 °C and then heating to 1000 - 1050 °C, which not only avoids the excessive temperature difference between the surface and the core of H13 high-alloy die steel due to poor thermal conductivity during rapid heating but also ensures full austenitization of the material. Finally, gradient tempering is carried out in two stages of 560 - 580 °C and 540 - 560 °C, enabling the processes of martensite decomposition and carbide precipitation to occur step by step. Compared with the single tempering process, it can significantly improve the impact toughness of the workpiece while maintaining a relatively high working hardness.

[0008] After finish machining, the workpiece is nitrided, which can significantly improve the surface properties of the workpiece. Pulse ion nitriding is carried out at 520 - 540 °C for 10 - 12 h. Compared with the gas nitriding process, the plasma generated by glow discharge makes the penetration of nitrogen ions more uniform, forming a dense compound layer of 0.15 - 0.2 mm on the surface of the workpiece. Through nitriding treatment, the finished die can resist the erosion of aluminum alloy melt during long-term use and is not prone to cracking defects.

[0009] As a preferred technical solution of the present invention, in step I, the die steel blank is H13 high-alloy die steel.

[0010] In some alternative examples, the heating rate of the first annealing is 100 - 150 °C / h. For example, it can be 100 °C / h, 105 °C / h, 110 °C / h, 115 °C / h, 120 °C / h, 125 °C / h, 130 °C / h, 135 °C / h, 140 °C / h, 145 °C / h or 150 °C / h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0011] In some alternative examples, the heating temperature of the first annealing is 600 - 650 °C. For example, it can be 600 °C, 605 °C, 610 °C, 615 °C, 620 °C, 625 °C, 630 °C, 635 °C, 640 °C, 645 °C or 650 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0012] In some alternative examples, the holding time of the first annealing is 1 - 2 h. For example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0013] In some alternative examples, after the first annealing is completed, it is cooled in the furnace to 350 - 400 °C, and then the second annealing is carried out. For example, it can be 350 °C, 355 °C, 360 °C, 365 °C, 370 °C, 375 °C, 380 °C, 385 °C, 390 °C, 395 °C or 400 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] As a preferred technical solution of the present invention, in step I, the heating rate of the second annealing is 150 - 200 °C / h. For example, it can be 150 °C / h, 155 °C / h, 160 °C / h, 165 °C / h, 170 °C / h, 175 °C / h, 180 °C / h, 185 °C / h, 190 °C / h, 195 °C / h or 200 °C / h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] In some alternative examples, the heating temperature of the second annealing is 880 - 900 °C. For example, it can be 880 °C, 882 °C, 884 °C, 886 °C, 888 °C, 890 °C, 892 °C, 894 °C, 896 °C, 898 °C or 900 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] The present invention specifically defines the heating temperature of the second annealing as 880 - 900 °C. This temperature range is within the critical range for complete dissolution of austenitization of H13 high-alloy die steel, which can promote the full dissolution of carbides into the matrix while avoiding excessive grain growth. When the annealing temperature reaches 880 °C, the diffusion rate of alloying elements such as chromium and molybdenum in H13 high-alloy die steel significantly increases, which helps to eliminate the compositional segregation formed during forging. When the annealing temperature reaches 900 °C, the migration of austenite grain boundaries is more active, which can effectively break the original coarse grains and form a uniform and fine initial microstructure. This homogenized microstructure provides a stable base for the phase transformation during subsequent quenching, enabling the final finished die to have both good hardness and toughness, which is beneficial for withstanding the repeated impact loads during the forming of the center console support beam.

[0017] When the second annealing temperature is lower than 880 °C, the dissolution process of carbides is limited, and the undissolved carbide particles will remain in the die steel blank in the form of hard inclusions, forming micro stress concentration sources. During the subsequent rough machining process, these hard points are likely to cause abnormal tool wear, increasing the surface roughness of the machining surface. In addition, during the quenching stage, these undissolved carbide particles will also become the starting points of crack initiation, significantly reducing the fatigue resistance of the workpiece. At the same time, incomplete austenitization will leave some ferrite in the workpiece. Such soft-phase regions cannot achieve sufficient phase transformation strengthening during high-temperature tempering, resulting in a decrease in the strength of the workpiece and making it difficult to meet the requirements of the load-bearing capacity of the finished die for automotive structural parts.

[0018] When the second annealing temperature exceeds 900 °C, the austenite grains will enter the rapid coarsening stage. Coarse austenite grains are more likely to form lamellar pearlite or bainite during cooling. The volume expansion effect of the transformation of such structures into martensite during subsequent quenching is more intense, resulting in an increase in the deformation of the workpiece and seriously affecting the dimensional accuracy after finish machining. At the same time, too high an annealing temperature will exacerbate the segregation of alloying elements to the grain boundaries, especially in the regions enriched with carbide-forming elements such as vanadium and molybdenum, which is likely to form an overly thick compound layer during subsequent nitriding treatment, significantly increasing the brittleness of the workpiece surface and seriously affecting the service life of the finished die.

[0019] In some alternative examples, the holding time of the second annealing is 3 - 4 h. For example, it can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h or 4.0 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0020] In some alternative examples, after the second annealing, it is cooled to 300 °C at a cooling rate of 15 - 20 °C / h, and then cooled in the furnace to room temperature. For example, it can be 15 °C / h, 15.5 °C / h, 16 °C / h, 16.5 °C / h, 17 °C / h, 17.5 °C / h, 18 °C / h, 18.5 °C / h, 19 °C / h, 19.5 °C / h or 20 °C / h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0021] Compared with single annealing treatment, the present invention adopts a two - step annealing process, and realizes the optimization of material properties through staged treatment. The first annealing temperature is in the range of 600 - 650 °C, which is mainly used to eliminate the local stress concentration formed during the original forming process of the blank. This temperature range can effectively soften the die steel blank without causing excessive grain growth, and is particularly suitable for dealing with the problem of non - uniform structure existing in high - alloy materials such as H13 high - alloy die steel after casting or forging. When the die steel blank is cooled to 350 - 400 °C, the carbides inside begin to precipitate in a more stable form, creating a relatively uniform blank for subsequent processing. If only one annealing is carried out, a compromise temperature treatment often needs to be selected, which can neither fully eliminate the original stress nor may cause the problem of increased blank sticking during subsequent rough machining due to too high a temperature.

[0022] The second annealing raises the temperature to 880 - 900 °C. Within this temperature range, the alloying elements in the die steel billet diffuse sufficiently. In particular, the uniform distribution of carbide-forming elements such as molybdenum and vanadium directly determines the phase transformation effect during subsequent quenching treatment. The process route of two-stage annealing avoids the problem of grain coarsening caused by single high-temperature treatment. If single annealing is directly carried out above 880 °C, although carbide dissolution can also be achieved, continuous high temperature will cause the grain size to increase, significantly reducing the toughness of the billet. The stepped cooling process after two-stage annealing (first controlled-rate cooling to 300 °C and then furnace cooling) realizes an artificially intervened phase transformation process, enabling specific tissue transformations to occur within different temperature ranges inside the die steel billet, and significantly reducing the residual stress in the billet.

[0023] The morphology of carbides can be optimized through two-stage annealing. During the first annealing process, the coarse chain-like carbides in the die steel billet begin to break and spheroidize. During the second annealing, the remaining fine carbides dissolve further at a higher temperature, forming a more uniform solid solution. Through staged control of carbide morphology, the final annealed billet can maintain sufficient hardness while also having relatively high toughness. In contrast, for the single annealing process, either the carbide dissolution is insufficient, or excessive dissolution leads to grain boundary weakening, making it difficult to achieve a balance between hardness and toughness.

[0024] As a preferred technical solution of the present invention, in step II, the spindle speed of the CNC milling machine is 400 - 600 rpm. For example, it can be 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm, 560 rpm, 580 rpm or 600 rpm, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0025] In some alternative examples, the feed rate of the milling cutter of the CNC milling machine is 200 - 300 mm / min. For example, it can be 200 mm / min, 210 mm / min, 220 mm / min, 230 mm / min, 240 mm / min, 250 mm / min, 260 mm / min, 270 mm / min, 280 mm / min, 290 mm / min or 300 mm / min, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0026] In some optional examples, the cutting depth of the milling cutter of the CNC milling machine is 2 - 3 mm per time. For example, it can be 2.0 mm per time, 2.1 mm per time, 2.2 mm per time, 2.3 mm per time, 2.4 mm per time, 2.5 mm per time, 2.6 mm per time, 2.7 mm per time, 2.8 mm per time, 2.9 mm per time or 3.0 mm per time. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0027] In some optional examples, the unilateral allowance for rough machining is reserved at 2.5 - 3.5 mm. For example, it can be 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm or 3.5 mm. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0028] As a preferred technical solution of the present invention, in step III, the heating rate of the stress relief annealing is 50 - 100 °C / h. For example, it can be 50 °C / h, 55 °C / h, 60 °C / h, 65 °C / h, 70 °C / h, 75 °C / h, 80 °C / h, 85 °C / h, 90 °C / h, 95 °C / h or 100 °C / h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0029] In some optional examples, the heating temperature of the stress relief annealing is 600 - 650 °C. For example, it can be 600 °C, 605 °C, 610 °C, 615 °C, 620 °C, 625 °C, 630 °C, 635 °C, 640 °C, 645 °C or 650 °C. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0030] In some optional examples, the holding time of the stress relief annealing is 2 - 3 h. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0031] In some optional examples, after the stress relief annealing, it is cooled in the furnace to room temperature.

[0032] As a preferred technical solution of the present invention, in step III, the operating steps of the quenching include: The workpiece after stress-relieving annealing is heated to the preheating temperature at the first heating rate and held for a certain time; after the holding is completed, it is continuously heated to the quenching temperature at the second heating rate and held; after the holding is completed, it is immersed in quenching oil for oil cooling, and gradient tempering is immediately carried out when the surface temperature of the workpiece drops to 150-200 °C. For example, it can be 150 °C / h, 155 °C / h, 160 °C / h, 165 °C / h, 170 °C / h, 175 °C / h, 180 °C / h, 185 °C / h, 190 °C / h, 195 °C / h or 200 °C / h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0033] In some alternative examples, the first heating rate is 200-300 °C / h. For example, it can be 200 °C / h, 210 °C / h, 220 °C / h, 230 °C / h, 240 °C / h, 250 °C / h, 260 °C / h, 270 °C / h, 280 °C / h, 290 °C / h or 300 °C / h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] In some alternative examples, the preheating temperature is 500-550 °C. For example, it can be 500 °C, 505 °C, 510 °C, 515 °C, 520 °C, 525 °C, 530 °C, 535 °C, 540 °C, 545 °C or 550 °C, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] In some alternative examples, the holding time at the preheating temperature is 0.5-1.5 h. For example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] In some alternative examples, the second heating rate is 200-300 °C / h. For example, it can be 200 °C / h, 210 °C / h, 220 °C / h, 230 °C / h, 240 °C / h, 250 °C / h, 260 °C / h, 270 °C / h, 280 °C / h, 290 °C / h or 300 °C / h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In some alternative examples, the quenching temperature is 1000~1050°C. For example, it can be 1000°C, 1005°C, 1010°C, 1015°C, 1020°C, 1025°C, 1030°C, 1035°C, 1040°C, 1045°C or 1050°C, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] The present invention specifically limits the quenching temperature to 1000~1050°C. This temperature range is within the optimal temperature range for austenitization of H13 high-alloy die steel, which can achieve the full dissolution of alloy carbides without causing excessive grain coarsening. When the quenching temperature reaches 1000°C, strong carbide-forming elements such as molybdenum and vanadium in H13 high-alloy die steel start to dissolve into the matrix in large amounts, significantly enhancing the alloying degree of austenite, which provides a basis for the formation of fine lath martensite during subsequent oil quenching. As the temperature rises to 1050°C, the diffusion ability of chromium elements increases, which helps to eliminate compositional fluctuations in the micro-region, improving the microstructure uniformity after quenching. In addition, the fine martensite structure not only endows the workpiece with a high basic hardness but also retains a small amount of retained austenite as a toughness buffer phase, which is particularly important for withstanding complex alternating stresses during the forming of the center console support beam. At the same time, an appropriate austenitization temperature avoids the phenomenon of carbide back-dissolution caused by excessive dissolution of vanadium elements, ensuring the stable precipitation of MC-type carbides with a dispersed distribution during subsequent tempering, which helps to maintain the high-temperature red hardness of the workpiece.

[0039] When the quenching temperature is below 1000°C, the dissolution process of carbides cannot proceed fully, and undissolved M23C6-type carbides remain in the matrix in the form of particles with a size of 0.5~2μm. These hard phases become stress concentration points during quenching cooling, and microcracks are easily formed around the undissolved carbides, which will expand into through-cracks during the thermal cycle of subsequent nitriding treatment. In addition, insufficient dissolution of chromium elements will lead to a decrease in hardenability, and a mixed structure of bainite and pearlite is likely to appear in the core of the workpiece, resulting in a large cross-sectional hardness drop. This non-uniform microstructure causes local collapse of the finished die at an early stage of service, especially indentations are likely to appear on the forming surface of the support beam stiffener.

[0040] If the quenching temperature exceeds 1050°C, the austenite grains will enter the abnormal growth stage. When the coarse original austenite grain boundaries transform into martensite during cooling, the micro-stresses generated due to volume expansion will increase significantly, resulting in an increase in the deformation amount of the workpiece after quenching. This not only increases the cost and difficulty of finishing but also forms a residual tensile stress concentration area at the cavity curved surface. In addition, quenching at too high a temperature will exacerbate the surface decarburization phenomenon. During nitriding treatment, the interaction between the decarburized layer and the nitrided layer will form a compound layer with uneven thickness. This structure is prone to lamellar peeling when subjected to shear stress, directly resulting in orange peel defects on the workpiece surface.

[0041] In some alternative examples, keep the temperature for 1 - 2 h at the quenching temperature. For example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0042] In some alternative examples, the temperature of the quenching oil is 60 - 80 °C. For example, it can be 60 °C, 62 °C, 64 °C, 66 °C, 68 °C, 70 °C, 72 °C, 74 °C, 76 °C, 78 °C or 80 °C, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0043] In some alternative examples, the cooling rate of oil cooling is 80 - 100 °C / s. For example, it can be 80 °C / s, 82 °C / s, 84 °C / s, 86 °C / s, 88 °C / s, 90 °C / s, 92 °C / s, 94 °C / s, 96 °C / s, 98 °C / s or 100 °C / s, but it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0044] As a preferred technical solution of the present invention, in step III, the operation steps of the gradient tempering include: Heat the workpiece quenched and oil - cooled to 150 - 200 °C to the first tempering temperature at the third heating rate and keep the temperature, then air - cool to room temperature; continue to heat to the second tempering temperature at the fourth heating rate and keep the temperature, then air - cool to room temperature.

[0045] The present invention adopts the gradient tempering process to optimize and improve the material properties through staged temperature control. The first tempering temperature is set at 560 - 580 °C. This relatively high temperature range can effectively promote the rapid precipitation of supersaturated carbon in quenched martensite, making the carbides disperse in the matrix in the form of fine particles. Keeping the temperature for 2 - 3 h at this temperature not only provides sufficient time for the diffusion of carbon atoms, but also promotes the full decomposition of retained austenite and releases the macroscopic stress accumulated during quenching. Using a rapid heating rate of 150 - 200 °C / h can avoid the premature coarsening of carbides caused by slow heating and prevent the deformation of the workpiece caused by sudden temperature rise.

[0046] The second tempering temperature is reduced to 540 - 560 °C. This temperature adjustment forms a fine control of the workpiece structure. Since most of the macroscopic stresses have been eliminated during the first tempering, the second low-temperature tempering treatment is mainly used to adjust the distribution state of carbides. With a gentle heating rate of 100 - 150 °C / h, the carbides in the matrix are further homogenized. The originally aggregated carbide particles migrate under the drive of the temperature gradient to form more uniformly sized dispersion strengthening phases. At this time, holding for 1 - 2 h not only ensures the optimized adjustment of the carbide distribution but also avoids the matrix softening caused by long-term high-temperature exposure. Another advantage brought about by the reduced temperature gradient is the suppression of excessive aggregation of carbides, enabling reasonable control of the resistance to dislocation movement while maintaining a high hardness of the workpiece, thus significantly improving the impact toughness of the workpiece.

[0047] The orderly reduction of the two tempering temperatures forms a synergistic effect on performance control. The first high-temperature tempering focuses on optimizing the macroscopic properties of the workpiece, fully eliminating stresses and precipitating carbides at high temperature to lay a foundation for subsequent processing; the second low-temperature tempering finely adjusts the microstructure and improves the toughness of the workpiece while maintaining the necessary hardness. Through the tempering treatment process with gradient cooling, the limitations of performance adjustment during single-temperature tempering are avoided. If only high-temperature tempering is used, although the stresses can be completely eliminated, the hardness will be too low; if only low-temperature tempering is used, the residual austenite cannot be effectively decomposed, resulting in a decrease in the stability of the workpiece. Through two-stage gradient cooling tempering in the present invention, the workpiece finally obtains a uniform and fine tempered sorbite structure, achieving the best balance between the fatigue resistance and dimensional stability required for finished molds.

[0048] In some alternative examples, the third heating rate is 150 - 200 °C / h. For example, it can be 150 °C / h, 155 °C / h, 160 °C / h, 165 °C / h, 170 °C / h, 175 °C / h, 180 °C / h, 185 °C / h, 190 °C / h, 195 °C / h or 200 °C / h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0049] In some alternative examples, the first tempering temperature is 560 - 580 °C. For example, it can be 560 °C, 562 °C, 564 °C, 566 °C, 568 °C, 570 °C, 572 °C, 574 °C, 576 °C, 578 °C or 580 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] The present invention particularly limits the first tempering temperature to 560-580 °C. Within this temperature range, it can effectively promote the precipitation of supersaturated carbon in the martensite matrix of the workpiece, while avoiding excessive aggregation of carbides. When the first tempering temperature reaches 560 °C, fine MC-type carbides begin to precipitate uniformly and dispersedly. The interaction between these nano-scale precipitates and dislocations significantly improves the anti-plastic deformation ability of the workpiece, enabling the surface indentation depth of the final finished die to be controlled within 0.02 mm when facing the shear stress generated by metal flow during the forming process of the support beam. When the first tempering temperature reaches 580 °C, the decomposition rate of retained austenite accelerates, and the process of transforming into tempered martensite releases most of the quenching residual stress. This stress release not only improves the dimensional stability of the workpiece but also reduces the deformation amount during subsequent finishing machining.

[0051] When the first tempering temperature is lower than 560 °C, the precipitation process of carbides is significantly inhibited, and the supersaturated carbon atoms that have not precipitated sufficiently will be solid-solved in the matrix, resulting in the lattice distortion of tempered martensite being unable to be effectively relaxed, leading to a relatively high level of residual micro-stress in the obtained tempered workpiece and prone to micro-crack propagation in the stress concentration area during the thermal cycle of nitriding treatment. In addition, when tempering at a low temperature, the retained austenite decomposes incompletely, and this part of the metastable phase will continue to transform during the second tempering treatment, causing uncontrollable shrinkage of the overall size of the workpiece and directly affecting the dimensional accuracy of the final finished die.

[0052] When the first tempering temperature exceeds 580 °C, the workpiece enters the over-tempering state. At this time, the coarsening rate of carbides increases exponentially, and the originally dispersedly distributed nano-scale precipitates will aggregate to form massive carbides with a size of 1-3 μm. These coarse phases not only cut off the continuity of the matrix but also become crack propagation channels under the action of alternating stress, significantly reducing the impact toughness of the workpiece. In addition, too high a tempering temperature leads to excessive precipitation of chromium elements into the carbides, and the chromium content in the matrix decreases significantly, directly weakening the corrosion resistance of the workpiece; at the same time, during the nitriding treatment stage, it is difficult to form a dense compound layer on the chromium-depleted matrix surface, and the bonding strength between the nitrided layer and the matrix decreases, resulting in easy surface spalling of the final obtained finished die during use.

[0053] In some optional examples, keep it warm for 2-3 h at the first tempering temperature. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0054] In some optional examples, the fourth heating rate is 100-150 °C / h. For example, it can be 100 °C / h, 105 °C / h, 110 °C / h, 115 °C / h, 120 °C / h, 125 °C / h, 130 °C / h, 135 °C / h, 140 °C / h, 145 °C / h or 150 °C / h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0055] In some optional examples, the second tempering temperature is 540-560 °C. For example, it can be 540 °C, 542 °C, 544 °C, 546 °C, 548 °C, 550 °C, 552 °C, 554 °C, 556 °C, 558 °C or 560 °C. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0056] The present invention specifically limits the second tempering temperature to 540-560 °C. Within this temperature range, it can promote the further decomposition of retained austenite while inhibiting the excessive coarsening of carbides. When the second tempering temperature reaches 540 °C, the lath martensite formed by quenching begins to recover, and dislocations are rearranged to release part of the micro stress, so that the impact toughness of the material is significantly improved while maintaining high hardness. When the second tempering temperature reaches 560 °C, the precipitation of fine carbides is more uniform. Such dispersed strengthening phases can hinder the movement of dislocations to maintain strength without significantly cutting the continuity of the matrix, so that the final finished die can not only resist the flow wear of aluminum alloy sheets during the forming process of the support beam, but also maintain dimensional stability in the thermal cycle of frequent start and stop.

[0057] When the second tempering temperature is lower than 540 °C, the stress relief of the workpiece is incomplete, the high-density dislocation structure formed in the quenching stage fails to recover sufficiently, and the residual stress level is relatively high, which will lead to: First, the diffusion path of surface nitrogen atoms is blocked during nitriding treatment, and it is easy to form a nitrided layer with uneven thickness, resulting in local spalling during the subsequent use of the finished die; Second, the micro stress concentration areas existing inside the workpiece will become the paths for crack preferential propagation under the action of alternating loads, significantly shortening the service life of the finished die. In addition, the precipitation amount of carbides is insufficient during low-temperature tempering, and the supersaturated carbon atoms in the matrix will solid-solution strengthen the martensite. Although the hardness is relatively high in the short term, the finished die needs to undergo continuous stamping during use. Under the action of the frictional heat generated by continuous stamping, the finished die will accelerate softening, resulting in a collapse deformation of more than 0.05 mm on the forming surface after multiple stampings.

[0058] When the second tempering temperature exceeds 560 °C, the workpiece enters the over-tempered state. At this time, the coarsening rate of carbides rises sharply, and the originally dispersed nanoscale precipitate phases will aggregate to form massive carbides with a size of 1-2 μm. These coarse phases not only reduce the impact resistance of the workpiece but also become the initiation source of microcracks under cyclic stress. In addition, the excessive tempering temperature causes an excessive amount of chromium to precipitate into the carbides, resulting in a significant reduction in the chromium content in the matrix, seriously affecting the corrosion resistance of the finished die. During the nitriding treatment stage, it is difficult to form a dense nitride layer on the chromium-depleted matrix surface, and the bonding strength between the nitrided layer and the matrix decreases. During subsequent use, surface peeling is likely to occur.

[0059] In some alternative examples, the holding time at the second tempering temperature is 1-2 h. For example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0060] As a preferred technical solution of the present invention, in step IV, the finish machining is carried out in a three-axis high-speed milling machining center.

[0061] In some alternative examples, the spindle speed of the three-axis high-speed milling machining center is 8000-10000 rpm. For example, it can be 8000 rpm, 8200 rpm, 8400 rpm, 8600 rpm, 8800 rpm, 9000 rpm, 9200 rpm, 9400 rpm, 9600 rpm, 9800 rpm or 10000 rpm, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0062] In some alternative examples, the feed rate of the milling cutter of the three-axis high-speed milling machining center is 800-1000 mm / min. For example, it can be 800 mm / min, 820 mm / min, 840 mm / min, 860 mm / min, 880 mm / min, 900 mm / min, 920 mm / min, 940 mm / min, 960 mm / min, 980 mm / min or 1000 mm / min, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0063] In some alternative examples, the cutting depth of the milling cutter of the three-axis high-speed milling and machining center is 0.1 to 0.2 mm per pass. For example, it can be 0.1 mm per pass, 0.11 mm per pass, 0.12 mm per pass, 0.13 mm per pass, 0.14 mm per pass, 0.15 mm per pass, 0.16 mm per pass, 0.17 mm per pass, 0.18 mm per pass, 0.19 mm per pass or 0.2 mm per pass. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0064] As a preferred technical solution of the present invention, in step V, the nitriding treatment includes: Put the finish-machined part into a pulsed ion nitriding furnace, evacuate the furnace, and preheat the finish-machined part; subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace, adjust the furnace pressure, and start a pulsed power supply to generate glow discharge while heating the finish-machined part to perform nitriding treatment.

[0065] The nitriding treatment in the present invention mainly plays a role in optimizing the surface performance of the finished mold. Through the pulsed ion nitriding technology, nitrogen atoms penetrate into the surface layer of the finish-machined part under the action of high-energy plasma to form a dense nitride layer. This process significantly improves the surface hardness of the finished mold, effectively resists the wear caused by metal flow during the stamping process during use, and at the same time maintains the toughness of the base material to avoid brittle cracking caused by excessive hardness. When the nitriding temperature is controlled within the range of 520 to 540 °C, combined with gradient heating and gas ratio regulation, the surface layer tissue uniformity of the finally obtained finished mold is improved, and the problem of too thick white layer prone to occur in traditional nitriding is reduced. After the nitriding treatment, the surface residual compressive stress distribution of the finished mold is more reasonable, which can inhibit the propagation of microcracks under alternating stress and extend the fatigue life of the finished mold. In addition, the nitrided layer also has certain corrosion resistance and can cope with oxidation erosion caused by a humid environment or contact with coolant.

[0066] As a preferred technical solution of the present invention, the heating rate during preheating of the finish-machined part is 10 to 15 °C / min. For example, it can be 10 °C / min, 10.5 °C / min, 11 °C / min, 11.5 °C / min, 12 °C / min, 12.5 °C / min, 13 °C / min, 13.5 °C / min, 14 °C / min, 14.5 °C / min or 15 °C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0067] In some optional examples, the preheating temperature of the finish-machined part is 400 - 450 °C. For example, it can be 400 °C, 405 °C, 410 °C, 415 °C, 420 °C, 425 °C, 430 °C, 435 °C, 440 °C, 445 °C or 450 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0068] In some optional examples, the heat preservation time for preheating the finish-machined part is 0.5 - 1.5 h. For example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0069] In some optional examples, the volume ratio of nitrogen to hydrogen in the mixed gas is 2 - 3:1. For example, it can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0070] The present invention specifically defines that the volume ratio of nitrogen to hydrogen in the mixed gas is 2 - 3:1. When the volume ratio of nitrogen to hydrogen is within this range, it can not only provide sufficient supply of active nitrogen atoms but also maintain a stable plasma environment through the reduction effect of hydrogen. When the volume ratio of nitrogen to hydrogen reaches 2:1, the cleaning effect of hydrogen on the workpiece surface is significant, which can effectively remove the oxide film and activate the metal surface, making it easier for nitrogen atoms to penetrate into the substrate. When the volume ratio of nitrogen to hydrogen reaches 3:1, the enhanced nitrogen potential promotes the formation of a dense nitrided layer with a thickness of about 0.2 mm on the surface layer, and the proportion of ε-Fe2-3N phase increases significantly. This high-hardness phase endows the surface of the finished die with excellent anti-abrasive wear resistance. At the same time, within the volume ratio range of 2 - 3:1, the presence of hydrogen inhibits the supersaturated adsorption of nitrogen atoms, avoiding the formation of a continuous brittle nitride network at the grain boundaries, which helps to improve the impact resistance of the finished die during the bending forming of the support beam.

[0071] When the volume ratio of nitrogen to hydrogen is lower than 2:1, the proportion of hydrogen increases. The excessive dilution effect of hydrogen leads to insufficient nitrogen potential, and the supply rate of active nitrogen atoms is lower than the surface absorption capacity, resulting in a significant decrease in the growth rate of the nitrided layer. In addition, excessive hydrogen will react with the carbon element on the workpiece surface at high temperature, causing decarburization of the workpiece surface and a decrease in hardness. At the same time, excessive enrichment of hydrogen is likely to cause hydrogen embrittlement. Especially in the stress concentration area of the finished die, the aggregation of hydrogen atoms to the dislocation line will form a microcrack source. The expansion speed of such defects accelerates under the action of alternating load, greatly shortening the fatigue life of the finished die.

[0072] When the volume ratio of nitrogen to hydrogen exceeds 3:1, the too high nitrogen potential will cause deterioration of the nitrided layer structure. The rapid accumulation of nitrogen atoms on the workpiece surface leads to abnormal growth of the compound layer thickness and a significant increase in surface brittleness. In addition, too high a proportion of nitrogen will weaken the reduction effect of hydrogen. The residual trace oxygen element reacts with nitrogen at high temperature to form nitrogen oxides. Such inclusions form a weak bonding area at the interface between the nitrided layer and the matrix, resulting in a decrease in the interlayer bonding strength between the nitrided layer and the matrix. When the temperature rises due to repeated stamping during the use of the finished die, this structural defect will cause thermal shock cracking of the nitrided layer, resulting in orange peel-like defects on the surface of the finished die.

[0073] In some alternative examples, the furnace internal pressure is adjusted to 300 - 500 Pa. For example, it can be 300 Pa, 320 Pa, 340 Pa, 360 Pa, 380 Pa, 400 Pa, 420 Pa, 440 Pa, 460 Pa, 480 Pa or 500 Pa, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0074] In some alternative examples, the frequency of the pulse power supply is 800 - 1000 Hz. For example, it can be 800 Hz, 820 Hz, 840 Hz, 860 Hz, 880 Hz, 900 Hz, 920 Hz, 940 Hz, 960 Hz, 980 Hz or 1000 Hz, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0075] In some alternative examples, the duty cycle of the pulse power supply is 40 - 50%. For example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0076] In some optional instances, the heating rate of the nitriding treatment of the finished part is 50~100℃ / h, for example, it can be 50℃ / h, 55℃ / h, 60℃ / h, 65℃ / h, 70℃ / h, 75℃ / h, 80℃ / h, 85℃ / h, 90℃ / h, 95℃ / h or 100℃ / h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0077] In some optional instances, the heating temperature of the nitriding treatment of the finished part is 520~540℃, for example, it can be 520℃, 522℃, 524℃, 526℃, 528℃, 530℃, 532℃, 534℃, 536℃, 538℃ or 540℃, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0078] The present invention specifically limits the nitriding treatment heating temperature of the finished parts to 520~540℃. This temperature range not only ensures that nitrogen has a high diffusion coefficient in ferrite, but also avoids the critical temperature of the workpiece for significant recovery and recrystallization. When the nitriding temperature reaches 520℃, the solid solubility of nitrogen atoms in the γ'-Fe4N phase reaches the optimal balance, which can form a continuous and dense compound layer without causing supersaturated nitrogen segregation. When the temperature rises to 540℃, the diffusion depth of nitrogen increases, so that the nitriding layer and the matrix form a gentle concentration gradient. This structure can effectively disperse stress concentration when subjected to shear stress during the forming of the support beam, and avoid peeling at the interface between the nitriding layer and the matrix.

[0079] When the nitriding temperature is lower than 520℃, the diffusion kinetic energy of nitrogen atoms is insufficient, and nitrogen forms a shallow enrichment of 0.05~0.1mm on the surface, but the penetration depth into the matrix is low. This shallow nitriding structure will lead to the following when the support beam is bent: First, the mechanical properties between the high-hardness surface and the soft matrix suddenly change, and interlayer shear cracks are easily generated under repeated stress; second, the nitriding layer is too thin, resulting in insufficient wear resistance, and obvious wear grooves will appear after repeated continuous stamping. In addition, during low-temperature nitriding, nitrogen atoms tend to concentrate at the grain boundaries to form a continuous brittle nitride network. This type of structure will become a crack extension channel under the action of alternating thermal stress, greatly shortening the fatigue life of the finished mold.

[0080] When the nitriding temperature is higher than 540 °C, the carbides in the matrix are significantly coarsened, and the originally dispersed MC-type carbides aggregate to form massive phases with a size of 1 - 2 μm. These coarse phases will severely weaken the tensile strength of the finished die. Meanwhile, high temperature accelerates the over-diffusion of nitrogen atoms, resulting in an excessively thick ε-phase layer formed on the surface of the finished die, with a significant increase in its brittleness. During subsequent use, flaky spalling is likely to occur at the edge parts of the finished die. In addition, the thermal expansion difference caused by excessive temperature will cause the finished die to warp and deform, requiring an additional polishing process to correct, which not only increases production costs but also may damage the integrity of the nitrided layer.

[0081] In some alternative examples, the nitriding treatment time for the precision-machined part is 10 - 12 h. For example, it can be 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h or 12 h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0082] Compared with the prior art, the beneficial effects of the present invention are as follows: The die manufacturing process provided by the present invention combines multi-stage heat treatment stress regulation, roughing and finishing forming, and nitriding surface strengthening, enabling the finished die to have high dimensional stability, excellent fatigue resistance, and good thermal shock resistance, effectively solving problems such as deformation cracking and rapid surface wear existing in traditional processes, and being applicable to the high-efficiency precision forming of complex-curved automotive structural parts. The two annealing treatments are respectively for stress elimination and microstructure homogenization. The first annealing eliminates the forming stress of the blank, and the second annealing promotes the dissolution of carbides and refines the grains, creating a stable matrix for subsequent processing. The quenching process uses stepped heating and oil cooling control to achieve full austenitization while avoiding thermal stress, obtaining a uniform and fine martensite structure. The gradient tempering is regulated by two temperature decreases. First, high-temperature tempering promotes the dispersion precipitation of carbides and decomposes the retained austenite, and then low-temperature tempering optimizes the carbide distribution and releases micro-stresses, improving the impact toughness of the workpiece while maintaining high hardness. Pulse ion nitriding forms a dense nitrided layer with a thickness of 0.15 - 0.2 mm through nitrogen-hydrogen mixed gas and precise temperature control, optimizing the surface hardness and wear resistance. Description of the Drawings

[0083] Figure 1 It is a flowchart of the die manufacturing process for the console support beam provided by Embodiments 1 - 13 of the present invention. Detailed Embodiments

[0084] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein. Embodiment 1

[0085] This embodiment provides a mold processing technology based on a center console support beam, as Figure 1 shown, which specifically includes the following steps: Ⅰ. Heat the H13 high-alloy die steel blank to 600°C at a heating rate of 100°C / h and hold for 2h to complete the first annealing. After the holding is completed, cool it in the furnace to 350°C; then, heat it to 880°C at a heating rate of 150°C / h and hold for 4h to complete the second annealing; after the second annealing is completed, cool it to 300°C at a cooling rate of 15°C / h, and then cool it in the furnace to room temperature to obtain an annealed blank; Ⅱ. Rough machine the annealed blank with a CNC milling machine. The spindle speed of the CNC milling machine is 400 rpm, the feed speed of the milling cutter is 200 mm / min, the cutting depth is 2 mm / time, and the unilateral allowance for rough machining is reserved at 2.5 mm to obtain a rough machined part; Ⅲ. Heat the rough machined part to 600°C at a heating rate of 50°C / h and hold for 3h to complete stress relief annealing. After the holding is completed, cool it in the furnace to room temperature; Heat the workpiece after stress relief annealing to 500°C at a heating rate of 200°C / h and hold for 1.5h; after the holding is completed, continue to heat it to 1000°C at a heating rate of 200°C / h and hold for 2h; after the holding is completed, immerse it in quenching oil at 60°C for oil cooling. The cooling rate of oil cooling is 100°C / s. When the surface temperature of the workpiece drops to 150°C, perform gradient tempering; Heat the workpiece oil-cooled to 150°C after quenching to 560°C at a heating rate of 150°C / h and hold for 3h, and then air-cool it to room temperature; continue to heat it to 540°C at a heating rate of 100°C / h and hold for 2h, and then air-cool it to room temperature to obtain a tempered workpiece; Ⅳ. Finish machine the tempered workpiece on a three-axis high-speed milling machining center. The spindle speed is 8000 rpm, the feed speed is 800 mm / min, and the cutting depth is 0.1 mm / time to obtain a finish machined part; Ⅴ. Place the precision-machined part into a pulsed ion nitriding furnace, evacuate the furnace to 10 Pa, preheat the precision-machined part to 400 °C at a heating rate of 10 °C / min, and hold for 1.5 h. Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace. The volume ratio of nitrogen to hydrogen in the mixed gas is 2:1. Adjust the furnace pressure to 300 Pa and start the pulsed power supply to generate glow discharge. The frequency of the pulsed power supply is 800 Hz and the duty cycle is 40%. At the same time, heat the precision-machined part to 520 °C at a heating rate of 50 °C / h and hold for 12 h to complete the nitriding treatment and obtain the finished die. Example 2

[0086] This example provides a die processing technology based on the center console support beam, as Figure 1 shown, which specifically includes the following steps: Ⅰ. Heat the H13 high-alloy die steel blank to 610 °C at a heating rate of 110 °C / h and hold for 1.8 h to complete the first annealing. After the holding ends, cool it in the furnace to 360 °C. Subsequently, heat it to 885 °C at a heating rate of 160 °C / h and hold for 3.8 h to complete the second annealing. After the second annealing ends, cool it to 300 °C at a cooling rate of 16 °C / h, and then cool it in the furnace to room temperature to obtain the annealed blank. Ⅱ. Rough-machine the annealed blank using a CNC milling machine. The spindle speed of the CNC milling machine is 450 pm, the feed rate of the milling cutter is 220 mm / min, the cutting depth is 2.2 mm per pass, and a unilateral allowance of 2.8 mm is reserved for rough machining to obtain the rough-machined part. Ⅲ. Heat the rough-machined part to 610 °C at a heating rate of 60 °C / h and hold for 2.8 h to complete stress relief annealing. After the holding ends, cool it in the furnace to room temperature. Heat the workpiece after stress relief annealing to 510 °C at a heating rate of 220 °C / h and hold for 1.2 h. After the holding ends, continue to heat it to 1010 °C at a heating rate of 220 °C / h and hold for 1.8 h. After the holding ends, immerse it in quenching oil at 65 °C for oil cooling. The cooling rate of oil cooling is 95 °C / s. When the surface temperature of the workpiece drops to 160 °C, perform gradient tempering. Heat the workpiece oil-cooled to 160 °C after quenching to 565 °C at a heating rate of 160 °C / h and hold for 2.8 h, and then air-cool it to room temperature. Continue to heat it to 545 °C at a heating rate of 110 °C / h and hold for 1.8 h, and then air-cool it to room temperature to obtain the tempered workpiece. Ⅳ. Finish-machine the tempered workpiece on a three-axis high-speed milling and machining center. The spindle speed is 8500 rpm, the feed rate is 850 mm / min, and the cutting depth is 0.12 mm per pass to obtain the precision-machined part. Ⅴ. Place the precision-machined part into a pulsed ion nitriding furnace, evacuate the furnace to 10 Pa, preheat the precision-machined part to 410 °C at a heating rate of 11 °C / min, and hold for 1.2 h. Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace. The volume ratio of nitrogen to hydrogen in the mixed gas is 2.2:1. Adjust the furnace pressure to 350 Pa, and start the pulsed power supply to generate glow discharge. The frequency of the pulsed power supply is 850 Hz, and the duty cycle is 42%. At the same time, heat the precision-machined part to 525 °C at a heating rate of 60 °C / h and hold for 11.5 h to complete the nitriding treatment and obtain the finished die. Example 3

[0087] This example provides a die processing technology based on the center console support beam. As Figure 1 shown, it specifically includes the following steps: Ⅰ. Heat the H13 high-alloy die steel blank to 620 °C at a heating rate of 120 °C / h and hold for 1.5 h to complete the first annealing. After the holding ends, cool it in the furnace to 370 °C. Subsequently, heat it to 890 °C at a heating rate of 170 °C / h and hold for 3.5 h to complete the second annealing. After the second annealing ends, cool it to 300 °C at a cooling rate of 17 °C / h, and then cool it in the furnace to room temperature to obtain the annealed blank. Ⅱ. Rough-machine the annealed blank using a CNC milling machine. The spindle speed of the CNC milling machine is 500 rpm, the feed rate of the milling cutter is 250 mm / min, the cutting depth is 2.5 mm per pass, and a unilateral allowance of 3 mm is reserved for rough machining to obtain the rough-machined part. Ⅲ. Heat the rough-machined part to 620 °C at a heating rate of 70 °C / h and hold for 2.5 h to complete stress relief annealing. After the holding ends, cool it in the furnace to room temperature. Heat the workpiece after stress relief annealing to 520 °C at a heating rate of 250 °C / h and hold for 1 h. After the holding ends, continue to heat it to 1020 °C at a heating rate of 250 °C / h and hold for 1.5 h. After the holding ends, immerse it in quenching oil at 70 °C for oil cooling. The cooling rate of oil cooling is 90 °C / s. When the surface temperature of the workpiece drops to 170 °C, perform gradient tempering. Heat the workpiece oil-cooled to 170 °C after quenching to 570 °C at a heating rate of 170 °C / h and hold for 2.5 h, and then air-cool it to room temperature. Continue to heat it to 550 °C at a heating rate of 120 °C / h and hold for 1.5 h, and then air-cool it to room temperature to obtain the tempered workpiece. Ⅳ. Finish-machine the tempered workpiece on a three-axis high-speed milling machining center. The spindle speed is 9000 rpm, the feed rate is 900 mm / min, and the cutting depth is 0.15 mm per pass to obtain the precision-machined part. Ⅴ. Place the finish-machined part into a pulsed ion nitriding furnace, evacuate the furnace to 10 Pa, preheat the finish-machined part to 420 °C at a heating rate of 12 °C / min, and hold for 1 h. Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace, with the volume ratio of nitrogen to hydrogen in the mixed gas being 2.5:1. Adjust the furnace pressure to 400 Pa, and start the pulsed power supply to generate glow discharge. The frequency of the pulsed power supply is 900 Hz, and the duty cycle is 45%. At the same time, heat the finish-machined part to 530 °C at a heating rate of 70 °C / h and hold for 11 h to complete the nitriding treatment and obtain the finished die. Example 4

[0088] This example provides a die processing technology based on the center console support beam. As Figure 1 shown, it specifically includes the following steps: Ⅰ. Heat the H13 high-alloy die steel blank to 630 °C at a heating rate of 130 °C / h and hold for 1.2 h to complete the first annealing. After the holding ends, cool it in the furnace to 380 °C. Subsequently, heat it to 895 °C at a heating rate of 180 °C / h and hold for 3.2 h to complete the second annealing. After the second annealing ends, cool it to 300 °C at a cooling rate of 18 °C / h, and then cool it in the furnace to room temperature to obtain the annealed blank. Ⅱ. Rough-machine the annealed blank using a CNC milling machine. The spindle speed of the CNC milling machine is 550 rpm, the feed rate of the milling cutter is 280 mm / min, the cutting depth is 2.8 mm per pass, and a unilateral allowance of 3.2 mm is reserved for rough machining to obtain the rough-machined part. Ⅲ. Heat the rough-machined part to 630 °C at a heating rate of 80 °C / h and hold for 2.2 h to complete stress relief annealing. After the holding ends, cool it in the furnace to room temperature. Heat the workpiece after stress relief annealing to 530 °C at a heating rate of 280 °C / h and hold for 0.8 h. After the holding ends, continue to heat it to 1030 °C at a heating rate of 280 °C / h and hold for 1.2 h. After the holding ends, immerse it in quenching oil at 75 °C for oil cooling. The cooling rate of oil cooling is 82 °C / s. When the surface temperature of the workpiece drops to 180 °C, perform gradient tempering. Heat the workpiece quenched and oil-cooled to 180 °C to 575 °C at a heating rate of 180 °C / h and hold for 2.2 h, and then air-cool it to room temperature. Continue to heat it to 555 °C at a heating rate of 130 °C / h and hold for 1.2 h, and then air-cool it to room temperature to obtain the tempered workpiece. Ⅳ. Finish-machine the tempered workpiece on a three-axis high-speed milling and machining center. The spindle speed is 9500 rpm, the feed rate is 950 mm / min, and the cutting depth is 0.18 mm per pass to obtain the finish-machined part. Ⅴ. Place the finish-machined part into a pulsed ion nitriding furnace, evacuate the furnace to 10 Pa, preheat the finish-machined part to 430 °C at a heating rate of 13 °C / min, and hold for 0.8 h. Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace. The volume ratio of nitrogen to hydrogen in the mixed gas is 2.8:1. Adjust the furnace pressure to 450 Pa, and start the pulsed power supply to generate glow discharge. The frequency of the pulsed power supply is 950 Hz, and the duty cycle is 48%. At the same time, heat the finish-machined part to 535 °C at a heating rate of 80 °C / h and hold for 10.5 h to complete the nitriding treatment and obtain the finished die. Example 5

[0089] This example provides a die manufacturing process based on the center console support beam. As Figure 1 shown, it specifically includes the following steps: Ⅰ. Heat the H13 high-alloy die steel blank to 650 °C at a heating rate of 150 °C / h and hold for 1 h to complete the first annealing. After the holding ends, cool it in the furnace to 400 °C. Subsequently, heat it to 900 °C at a heating rate of 200 °C / h and hold for 3 h to complete the second annealing. After the second annealing ends, cool it to 300 °C at a cooling rate of 20 °C / h, and then cool it in the furnace to room temperature to obtain the annealed blank. Ⅱ. Rough-machine the annealed blank using a CNC milling machine. The spindle speed of the CNC milling machine is 600 rpm, the feed rate of the milling cutter is 300 mm / min, the cutting depth is 3 mm per pass, and a unilateral allowance of 3.5 mm is reserved for rough machining to obtain the rough-machined part. Ⅲ. Heat the rough-machined part to 650 °C at a heating rate of 100 °C / h and hold for 2 h to complete stress relief annealing. After the holding ends, cool it in the furnace to room temperature. Heat the workpiece after stress relief annealing to 550 °C at a heating rate of 300 °C / h and hold for 0.5 h. After the holding ends, continue to heat it to 1050 °C at a heating rate of 300 °C / h and hold for 1 h. After the holding ends, immerse it in quenching oil at 80 °C for oil cooling. The cooling rate of oil cooling is 80 °C / s. When the surface temperature of the workpiece drops to 200 °C, perform gradient tempering. Heat the workpiece oil-cooled to 200 °C after quenching to 580 °C at a heating rate of 200 °C / h and hold for 2 h, and then air-cool to room temperature. Continue to heat it to 560 °C at a heating rate of 150 °C / h and hold for 1 h, and then air-cool to room temperature to obtain the tempered workpiece. Ⅳ. Finish-machine the tempered workpiece on a three-axis high-speed milling and machining center. The spindle speed is 10000 rpm, the feed rate is 1000 mm / min, and the cutting depth is 0.2 mm per pass to obtain the finish-machined part. Ⅴ. Place the finish-machined parts into a pulsed ion nitriding furnace, evacuate the furnace to 10 Pa, preheat the finish-machined parts to 450 °C at a heating rate of 15 °C / min, and hold for 0.5 h. Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace. The volume ratio of nitrogen to hydrogen in the mixed gas is 3:1. Adjust the furnace pressure to 500 Pa and start the pulsed power supply to generate glow discharge. The frequency of the pulsed power supply is 1000 Hz and the duty cycle is 50%. At the same time, heat the finish-machined parts to 540 °C at a heating rate of 100 °C / h and hold for 10 h to complete the nitriding treatment and obtain the finished mold. Example 6

[0090] This example provides a mold processing technology based on the center console support beam. The difference from Example 1 is that in Step Ⅰ, the first annealing is omitted, and the H13 high-alloy die steel blank is directly heated to 880 °C at a heating rate of 150 °C / h and held for 4 h to complete the annealing. Other process parameters and operating steps are exactly the same as those in Example 1. Example 7

[0091] This example provides a mold processing technology based on the center console support beam. The difference from Example 1 is that in Step Ⅲ, the stress relief annealing is omitted. Other process parameters and operating steps are exactly the same as those in Example 1. Example 8

[0092] This example provides a mold processing technology based on the center console support beam. The difference from Example 1 is that in Step Ⅲ, during the quenching stage, the first heating is omitted, and the workpiece after stress relief annealing treatment is directly heated to 1000 °C at a heating rate of 200 °C / h and held for 2 h. Other process parameters and operating steps are exactly the same as those in Example 1. Example 9

[0093] This example provides a mold processing technology based on the center console support beam. The difference from Example 1 is that in Step Ⅲ, during the tempering stage, the workpiece oil-cooled to 150 °C after quenching is heated to 560 °C at a heating rate of 150 °C / h and held for 3 h, and then air-cooled to room temperature to obtain the tempered workpiece. Other process parameters and operating steps are exactly the same as those in Example 1. Example 10

[0094] This example provides a mold processing technology based on the center console support beam. The difference from Example 1 is that in Step Ⅲ, during the tempering stage, the workpiece oil-cooled to 150 °C after quenching is heated to 540 °C at a heating rate of 100 °C / h and held for 2 h, and then air-cooled to room temperature to obtain the tempered workpiece. Other process parameters and operating steps are exactly the same as those in Example 1. Example 11

[0095] This embodiment provides a mold processing technology based on the center console support beam. The difference from Embodiment 1 is that in Step III, during the tempering stage, the workpiece quenched and oil-cooled to 150°C is continuously heated to 540°C at a heating rate of 100°C / h, and held for 2 h. Subsequently, it is heated to 560°C at a heating rate of 150°C / h and held for 3 h. Then it is air-cooled to room temperature to obtain the tempered workpiece. Other process parameters and operation steps are exactly the same as those in Embodiment 1. Embodiment 12

[0096] This embodiment provides a mold processing technology based on the center console support beam. The difference from Embodiment 1 is that the nitriding treatment is omitted. Other process parameters and operation steps are exactly the same as those in Embodiment 1. Embodiment 13

[0097] This embodiment provides a mold processing technology based on the center console support beam. The difference from Embodiment 1 is that in Step V, the glow discharge operation is omitted in the carburizing treatment stage. Other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0098] The surface Vickers hardness, impact absorption energy, and sliding wear rate of the finished molds prepared in Embodiments 1 - 13 are tested. The test steps are as follows: (1) Surface Vickers hardness Refer to the national standard GB / T 4340.1 - 2009 "Metallic materials - Vickers hardness test - Part 1: Test method" to test the surface Vickers hardness of the finished mold. Apply a 1 kgf test force on the nitrided layer of the mold surface using a Vickers hardness tester, with a holding time of 15 s, and take the average value of 5 points.

[0099] (2) Impact absorption energy Refer to the national standard GB / T 229 - 2020 "Metallic materials - Charpy pendulum impact test method" to test the impact toughness of the finished mold. Take a U-notch specimen with dimensions of 10×10×55 mm from the core of the finished mold, with a notch depth of 2 mm and a root radius of 1 mm. Use a pendulum impact testing machine to conduct the test at room temperature. The pre-elevation angle of the pendulum is 150°, the striking center distance is 750 mm ± 2 mm, the support span is 40 mm ± 0.2 mm. Release the pendulum to complete the impact, and record the impact absorption energy (KU2 value, unit: joule / J).

[0100] (3) Sliding wear rate The sliding wear rate of the finished die was tested with reference to the national standard GB / T 12444.1-2022 "Metallic materials - Wear test - Part 1: Ring-on-block sliding wear test". Specimens of 30×7×6 mm (retaining the nitrided layer on the surface) were cut from the die surface. GCr15 bearing steel was used as the ring, the normal load was 200 N, the sliding speed was 1 m / s. The mass of the specimen was weighed before and after the sliding wear test, and the sliding wear mass of the specimen was calculated. According to the density of the specimen, the volumetric wear was calculated. The sliding wear rate was calculated using the following formula:

[0101] where ΔV is the volumetric wear (mm 3 ), F is the normal load (N), and L is the sliding distance (m).

[0102] The test results are shown in Table 1.

[0103] Table 1 Performance test results of the finished dies prepared in Examples 1-13 Surface Vickers hardness (HV) Impact energy absorption (J) <![CDATA[Sliding wear rate (mm 3 / N·m)]]> Example 1 1165 27.5 0.7 Example 2 1180 28.9 0.6 Example 3 1197 29.6 0.5 Example 4 1172 26.8 0.8 Example 5 1133 25.4 0.9 Example 6 965 16.8 3.7 Example 7 890 15.2 3.3 Example 8 972 20.5 1.9 Example 9 1020 18.3 2.1 Example 10 1054 9.8 1.5 Example 11 1103 10.9 5.4 Example 12 837 23.3 4.2 Example 13 956 12.7 4.5 From the test data of Example 1 and Example 6, it can be seen that the surface Vickers hardness and impact energy absorption of the finished die obtained in Example 6 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because in Example 6, the first annealing (600~650 °C) was omitted and direct high-temperature annealing was carried out, resulting in incomplete elimination of the initial stress, uneven structure during subsequent quenching, and a decrease in both hardness and toughness.

[0104] From the test data of Example 1 and Example 7, it can be seen that the surface Vickers hardness and impact energy absorption of the finished die obtained in Example 7 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because in Example 7, the stress-relieving annealing step was omitted, and the mechanical stress generated during rough machining was not eliminated. The superposed thermal stress during quenching induced microcracks, so the sliding wear rate was as high as 3.3 mm³ / N·m. At the same time, the residual stress also reduced the impact toughness.

[0105] From the test data of Example 1 and Example 8, it can be seen that the surface Vickers hardness and impact energy absorption of the finished die obtained in Example 8 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because in Example 8, the preheating stage at 500~550 °C was omitted during the quenching stage, and it was directly heated to 1000 °C. Since H13 steel has poor thermal conductivity, rapid heating led to a large temperature difference between the core and the surface, uneven structure after quenching, and a significant decrease in impact energy absorption and surface Vickers hardness.

[0106] It can be seen from the test data of Example 1, Example 9, Example 10 and Example 11 that the surface Vickers hardness and impact energy absorption of the finished molds obtained in Example 9, Example 10 and Example 11 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because the operating conditions of gradient tempering were adjusted in Example 9, Example 10 and Example 11. Only high-temperature tempering (560 - 580 °C) was used in Example 9, only low-temperature tempering (540 - 560 °C) was used in Example 10, and the tempering sequence was reversed in Example 11, with low-temperature tempering first and then high-temperature tempering. The gradient tempering process in Example 1 can decompose retained austenite first and then optimize the carbide distribution by adopting the operating sequence of high-temperature tempering first and then low-temperature tempering. However, Example 9, Example 10 and Example 11 destroyed this synergistic effect. Especially in Example 11, the sequence of high-temperature tempering and low-temperature tempering was reversed, and the carbides precipitated after low-temperature tempering coarsened during the subsequent high-temperature tempering, resulting in a significant increase in the sliding wear rate.

[0107] It can be seen from the test data of Example 1 and Example 12 that the surface Vickers hardness and impact energy absorption of the finished mold obtained in Example 12 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because the nitriding treatment was omitted in Example 12, resulting in a significant reduction in impact energy absorption and surface Vickers hardness.

[0108] It can be seen from the test data of Example 1 and Example 13 that the surface Vickers hardness and impact energy absorption of the finished mold obtained in Example 13 are lower than those in Example 1, and the sliding wear rate is higher than that in Example 1. This is because glow discharge was omitted in the nitriding stage in Example 13, and ordinary gas nitriding was used instead. The lack of activation of the plasma led to uneven nitrided layers, and the hardness and wear resistance were significantly deteriorated.

[0109] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A mold processing technology based on a console support beam, characterized in that, The mold processing technology based on the center console support beam includes: Ⅰ. Successively perform the first annealing and the second annealing on the mold steel blank to obtain an annealed blank; Ⅱ. Rough machine the annealed blank using a CNC milling machine to obtain a rough machined part; Ⅲ. Successively perform stress relief annealing, quenching, and gradient tempering on the rough machined part to obtain a tempered workpiece; Ⅳ. Finish machine the tempered workpiece to obtain a finish machined part; Ⅴ. Perform nitriding treatment on the finish machined part to obtain a finished mold.

2. The mold processing technology based on the console support beam according to claim 1, wherein, In step Ⅰ, the mold steel blank is H13 high alloy mold steel; The heating rate of the first annealing is 100 - 150 °C / h; The heating temperature of the first annealing is 600 - 650 °C; The holding time of the first annealing is 1 - 2 h; After the first annealing is completed, cool it in the furnace to 350 - 400 °C, and then perform the second annealing.

3. The mold processing technology based on the console support beam according to claim 1, characterized in that, In step Ⅰ, the heating rate of the second annealing is 150 - 200 °C / h; The heating temperature of the second annealing is 880 - 900 °C; The holding time of the second annealing is 3 - 4 h; After the second annealing is completed, cool it at a cooling rate of 15 - 20 °C / h to 300 °C, and then cool it in the furnace to room temperature.

4. The mold processing technology based on the center console support beam according to claim 1, characterized in that, In step Ⅱ, the spindle speed of the CNC milling machine is 400 - 600 rpm; The feed rate of the milling cutter of the CNC milling machine is 200 - 300 mm / min; The cutting depth of the milling cutter of the CNC milling machine is 2 - 3 mm per pass; The unilateral allowance for rough machining is reserved at 2.5 - 3.5 mm.

5. The mold processing technology based on the center console support beam according to claim 1, characterized in that, In step Ⅲ, the heating rate of the stress relief annealing is 50 - 100 °C / h; The heating temperature of the stress relief annealing is 600 - 650 °C; The holding time of the stress relief annealing is 2 - 3 h; After the stress relief annealing is completed, cool it in the furnace to room temperature.

6. The mold processing technology based on the center console support beam according to claim 1, characterized in that, In step Ⅲ, the operation steps of quenching include: Heat the workpiece after stress relief annealing to the preheating temperature at the first heating rate and hold it; after the holding is completed, continue to heat it to the quenching temperature at the second heating rate and hold it; after the holding is completed, immerse it in quenching oil for oil cooling, and immediately perform gradient tempering when the surface temperature of the workpiece drops to 150 - 200 °C; The first heating rate is 200 - 300 °C / h; The preheating temperature is 500 - 550 °C; Hold it at the preheating temperature for 0.5 - 1.5 h; The second heating rate is 200 - 300 °C / h; The quenching temperature is 1000 - 1050 °C; Hold it at the quenching temperature for 1 - 2 h; The temperature of the quenching oil is 60 - 80 °C; The cooling rate of the oil cooling is 80 - 100 °C / s.

7. The mold processing technology based on the console support beam according to claim 1, characterized in that, In step Ⅲ, the operation steps of gradient tempering include: Heat the workpiece quenched and oil cooled to 150 - 200 °C to the first tempering temperature at the third heating rate and hold it, and then air cool it to room temperature; continue to heat it to the second tempering temperature at the fourth heating rate and hold it, and then air cool it to room temperature; The third heating rate is 150 - 200 °C / h; The first tempering temperature is 560 - 580 °C; Hold it at the first tempering temperature for 2 - 3 h; The fourth heating rate is 100 - 150 °C / h; The second tempering temperature is 540 - 560°C; Keep it warm for 1 - 2 h at the second tempering temperature.

8. The mold processing technology based on the center console support beam according to claim 1, characterized in that, In step IV, the finish machining is carried out in a three-axis high-speed milling machining center; The spindle speed of the three-axis high-speed milling machining center is 8000 - 10000 rpm; The feed rate of the milling cutter of the three-axis high-speed milling machining center is 800 - 1000 mm / min; The cutting depth of the milling cutter of the three-axis high-speed milling machining center is 0.1 - 0.2 mm per pass.

9. The mold processing technology based on the center console support beam according to claim 1, characterized in that, In step V, the nitriding treatment includes: Put the finish-machined part into a pulse ion nitriding furnace, evacuate the furnace, and preheat the finish-machined part; Subsequently, introduce a mixed gas of nitrogen and hydrogen into the furnace, adjust the furnace pressure, and start the pulse power supply to generate glow discharge, while heating the finish-machined part to carry out nitriding treatment.

10. The mold processing technology based on the console support beam according to claim 9, characterized in that, The heating rate of the finish-machined part during preheating is 10 - 15°C / min; The preheating temperature of the finish-machined part is 400 - 450°C; The holding time of the preheating of the finish-machined part is 0.5 - 1.5 h; The volume ratio of nitrogen to hydrogen in the mixed gas is 2 - 3:1; The furnace pressure is adjusted to 300 - 500 Pa; The frequency of the pulse power supply is 800 - 1000 Hz; The duty cycle of the pulse power supply is 40 - 50%; The heating rate of the nitriding treatment of the finish-machined part is 50 - 100°C / h; The heating temperature of the nitriding treatment of the finish-machined part is 520 - 540°C; The time of the nitriding treatment of the finish-machined part is 10 - 12 h.

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