A 3d printing additive manufacturing method of die casting die steel metal powder

Abstract

This invention relates to a 3D printing additive manufacturing method for die-casting mold steel metal powder. The metal powder has the following mass percentage content: carbon: 0.20-0.28%, silicon: <0.1%, manganese: 0.20-0.5%, molybdenum: 1.30-1.80%, chromium: 1.50-2.50%, vanadium: 0.10-0.50%, tungsten: 0.3-0.6%, nickel: 2.00-3.00%, copper: 0.80-1.00%, sulfur: ≤0.02%, phosphorus ≤0.025%, oxygen ≤0.025%, with the remainder being Fe and unavoidable impurities. The additive manufacturing method employs selective laser melting, with a laser power of 200W-320W, a laser scanning speed of 800-1100mm / s, a scanning spacing ≤0.1mm, and a laser energy density of 68.17-127.08J / mm². 3 The powder layer thickness is ≤0.03mm, the scanning strategy is 65~70°, and the substrate preheating temperature is 120~150℃ to obtain the alloy. Its beneficial effects are: through alloy composition design and selective laser melting, the prepared alloy exhibits low crack sensitivity and high thermal conductivity, achieving a dual improvement in strength and toughness. It ensures the formation of high-toughness, low-expansion lath martensite, providing excellent toughness while possessing extremely good weldability and being less prone to cracking.

Description

Technical Field

[0001] This invention relates to the field of 3D printing additive manufacturing, and in particular to a 3D printing additive manufacturing method for die-casting mold steel powder. Background Technology

[0002] A mold is a tool made of metal used to repeatedly produce the same product through methods such as stamping, forging, and casting. Large, complex, integrated structural components with high integration are playing an increasingly important role in the manufacturing of new energy vehicles, and molds, as the "mother of industry," are crucial to the manufacture of these complex components.

[0003] In recent years, integrated die-casting molds for new energy vehicles have been widely used. High-quality fabrication technology for large integrated die-casting mold steel modules has become a research hotspot. Additive manufacturing die-casting molds construct mold structures by layer-by-layer material deposition, breaking through the limitations of traditional manufacturing processes in complex structural design. This allows for the integrated molding of complex internal flow channels and other structures, and can produce molds with internal flow channel curvature radii as small as millimeters.

[0004] Currently, alloy powders used for additive manufacturing of die-casting molds are mainly H13 hot-work die steel and 18Ni300 martensitic age-hardening steel, but they have significant drawbacks: H13 is a medium-carbon steel with high crack sensitivity, easily forming microcracks during 3D printing, resulting in poor formability. Directly formed parts reach a hardness of around 55 HRC, and crack propagation is poor. During the use of inlaid molds, crack propagation leads to waterline rupture, posing a significant safety hazard. 18Ni300 steel relies on high Ni (18-19%) and high Co (8.5-9.5%) to achieve age hardening. The high Ni content stabilizes the austenitic structure, forming a single martensitic matrix during rapid cooling after solution treatment, thus improving the fracture toughness of the martensitic age-hardening steel. Co can delay the recovery process of the martensitic matrix during high-temperature treatment, maintaining the stability of the matrix structure and ensuring that the material retains high strength and high dimensional accuracy after aging. However, the raw material cost of 18Ni300 steel is extremely high, and its thermal conductivity is less than 2 / 3 of that of H13. It has poor resistance to thermal fatigue and cannot meet the requirements of high-load molds, thus limiting its application.

[0005] Therefore, the motivation for this invention is to design a new component ratio and develop a low-cost 3D printing additive manufacturing method for die-casting mold steel powder. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a novel 3D printing additive manufacturing method for die-casting mold steel powder. The alloy prepared using this method exhibits low crack sensitivity and high thermal conductivity, achieving a dual improvement in strength and toughness. It ensures the formation of high-toughness, low-expansion lath martensite, providing excellent toughness while also possessing extremely good weldability, making printing less prone to cracking.

[0007] This invention provides a 3D printing additive manufacturing method for die-casting mold steel powder, the technical solution of which is as follows:

[0008] A 3D printing additive manufacturing method for die-casting mold steel metal powder, wherein the mass percentage content of the metal powder is: carbon: 0.20-0.28%, silicon: <0.1%, manganese: 0.20-0.5%, molybdenum: 1.30-1.80%, chromium: 1.50-2.50%, vanadium: 0.10-0.50%, tungsten: 0.3-0.6%, nickel: 2.00-3.00%, copper: 0.80-1.00%, sulfur: ≤0.02%, phosphorus ≤0.025%, oxygen ≤0.025%, with the remainder being Fe and unavoidable impurities; a selective laser melting additive manufacturing method is employed, with a laser power of 200W-320W, a laser scanning speed of 800-1100mm / s, a scanning spacing ≤0.1mm, and a laser energy density of 68.17-127.08J / mm². 3 The powder layer thickness is ≤0.03mm, the scanning strategy is 65~70°, and the substrate preheating temperature is 120~150℃ to obtain the alloy.

[0009] Furthermore, the metal powder is obtained using annular gas jet cold atomization technology, and the particle size range of the metal powder is 15–53 μm.

[0010] Furthermore, to reduce thermal stress and minimize the risk of deformation and cracking, the prepared alloy samples underwent stress-relief annealing. The process was as follows: the furnace was loaded when the furnace temperature was below 200℃, heated to 870±10℃ at a heating rate of 50℃ / h to 80℃ / h, held for 2 to 2.5 hours, cooled to 750±10℃, held for 4 to 5 hours, and then cooled to below 550℃ before being removed from the furnace and air-cooled.

[0011] Furthermore, the stress-relief annealed die-casting mold steel billet undergoes a quenching and tempering toughening treatment. The quenching and tempering toughening treatment process is as follows:

[0012] Two-stage preheating is adopted. The furnace temperature of the mold steel billet is ≤150℃. The first stage of preheating is 550±10℃ and held for 1 hour. The second stage of preheating is 850±10℃ and held for 1 hour.

[0013] The quenching process is as follows: heat to 1020±5℃ at a heating rate of 50℃ / h~80℃ / h, hold for 0.5h after the thermocouple reaches the temperature, quench in vacuum to 200℃, and then air cool after removal from the furnace.

[0014] The tempering process after quenching is as follows: a two-time tempering process at 500-600℃ is adopted, and after holding at the temperature for 2-2.5 hours, the mold steel billet is air-cooled to room temperature.

[0015] The implementation of this invention has the following technical effects:

[0016] The 3D printing additive manufacturing method for die-casting mold steel powder of the present invention, through alloy composition design, selective laser melting, stress-relief annealing, and tempering processes, enables the alloy to possess excellent comprehensive mechanical properties. The prepared alloy exhibits low crack sensitivity and high thermal conductivity, achieving a dual improvement in strength and toughness. It ensures the formation of high-toughness, low-expansion lath martensite, providing excellent toughness while possessing extremely good weldability, making printing less prone to cracking. The substrate preheating temperature is reduced from over 200℃ for traditional H13 steel to 120℃~150℃. The reduced substrate preheating temperature not only avoids cracking but also extends equipment life, shortens production cycles, and effectively reduces the maintenance costs of 3D printing equipment. Attached Figure Description

[0017] Figure 1 The tensile curve of the alloy prepared by the 3D printing additive manufacturing method of die-casting mold steel powder according to an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0019] Example 1

[0020] This embodiment describes a 3D printing additive manufacturing method for die-casting mold steel metal powder: the mass percentage content of the metal powder is as follows: carbon: 0.27%, silicon: <0.09%, manganese: 0.46%, molybdenum: 1.48%, chromium: 2.21%, vanadium: 0.36%, tungsten: 0.43%, nickel: 2.94%, copper: 0.88%, sulfur: ≤0.0026%, phosphorus ≤0.011%, oxygen ≤0.021%, with the remainder being Fe and unavoidable impurities; the metal powder can be obtained using annular gas jet cold atomization technology, and the preferred particle size range of the metal powder is 15-53 μm.

[0021] Selective laser melting (SLM) additive manufacturing was employed, with the laser power controlled at 230W, laser scanning speed at 800mm / s, scanning spacing at 0.1mm, and laser energy density at 96J / mm².3 The powder layer thickness was 0.03 mm, the scanning strategy was 67°, and the substrate preheating temperature was 150° to obtain the alloy sample.

[0022] To reduce thermal stress and minimize the risk of deformation and cracking, the prepared alloy samples underwent stress-relief annealing. The stress-relief annealing process was as follows: the furnace was loaded when the furnace temperature was below 200℃, heated to 870℃ at a heating rate of 50℃ / h, held for 2 hours, cooled to 750℃, held for 4 hours, cooled to below 550℃, and then removed from the furnace and air-cooled.

[0023] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile, and impact testing methods: hardness was 42 HRC, impact toughness was Aku 72 J, and strength and plasticity reached Rm: 1436 MPa, R... p0.2 950MPa, A: 55%, Z: 12%, tensile curve as follows Figure 1 As shown. The mold obtained in this embodiment has suitable strength and toughness, is simple to operate, has a short manufacturing cycle, and exhibits minimal mold deformation.

[0024] Example 2

[0025] The difference between this embodiment and Embodiment 1 is that the stress-relief annealed die-casting mold billet undergoes tempering and toughening treatment. The other steps are the same as in Embodiment 1, and will not be repeated here.

[0026] The stress-relief annealed die-casting mold steel billet is subjected to quenching and tempering toughening treatment. The quenching and tempering toughening treatment process is as follows: a two-stage preheating process is adopted, with the furnace temperature of the mold steel billet ≤150℃. The first stage preheating temperature is 550℃, held for 1 hour, and the second stage preheating temperature is 850℃, held for 1 hour. The quenching process is to heat up to 1020℃ at a rate of 50℃ / h~80℃ / h, hold for 0.5 hours, and then air quench to 200℃ before air cooling. A two-stage high-temperature tempering process is adopted, with the tempering temperature at 500℃, held for 2 hours, and then air cooled to room temperature.

[0027] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile, and impact testing methods: hardness 43.9 HRC, impact toughness Aku 67 J, strength and plasticity reached Rm: 1513 MPa, Rp0.2: 1110 MPa, A: 63%, Z: 16.5%, and the tensile curve is shown below. Figure 1 As shown. The mold steel prepared in this embodiment has improved strength and toughness while reducing the content of retained austenite, but the mold manufacturing cycle and cost increase, and there is a risk of deformation after mold post-processing.

[0028] Example 3

[0029] The difference between this embodiment and Embodiment 2 is the final tempering temperature in the tempering and toughening process. In this embodiment, a two-stage high-temperature tempering process is used, with a tempering temperature of 550°C. Everything else is the same as in Embodiment 2, and will not be repeated here.

[0030] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile, and impact testing methods: hardness 43.6 HRC, impact toughness Aku 99 J, strength and plasticity reached Rm: 1138 MPa, Rp0.2: 1530 MPa, A: 68%, Z: 17%. The tensile curve is shown below. Figure 1 As shown.

[0031] Example 4

[0032] The difference between this embodiment and Embodiment 2 is the final tempering temperature in the tempering and toughening process. In this embodiment, a two-stage high-temperature tempering process is used, with a tempering temperature of 580°C. Everything else is the same as in Embodiment 2, and will not be repeated here.

[0033] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile, and impact testing methods: hardness 44.4 HRC, impact toughness Aku 101 J, strength and plasticity reached Rm: 1502 MPa, Rp0.2: 1304 MPa, A: 68%, Z: 15.5%. The tensile curve is shown below. Figure 1 As shown.

[0034] Example 5

[0035] The difference between this embodiment and Embodiment 2 is the final tempering temperature in the tempering and toughening process. In this embodiment, a two-stage high-temperature tempering process is used, with a tempering temperature of 600°C. Everything else is the same as in Embodiment 2, and will not be repeated here.

[0036] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile, and impact testing methods: hardness 42.4 HRC, impact toughness Aku 75 J, strength and plasticity reached Rm: 1421 MPa, Rp0.2: 1267 MPa, A: 65%, Z: 17%, and the tensile curve is shown below. Figure 1 As shown.

[0037] Table 1 Mechanical property test table for Examples 1 to 5

[0038]

[0039]

[0040] Example 6

[0041] This embodiment describes a 3D printing additive manufacturing method for die-casting mold steel metal powder: the mass percentage content of the metal powder is as follows: carbon: 0.25%, silicon: <0.095%, manganese: 0.33%, molybdenum: 1.32%, chromium: 2.50%, vanadium: 0.12%, tungsten: 0.60%, nickel: 2.00%, copper: 0.98%, sulfur: ≤0.0023%, phosphorus ≤0.011%, oxygen ≤0.020%, with the remainder being Fe and unavoidable impurities; the metal powder can be obtained using annular gas jet cold atomization technology, and the preferred particle size range of the metal powder is 15-53 μm.

[0042] Selective laser melting additive manufacturing was employed, with the laser power controlled at 320W, laser scanning speed at 930mm / s, scanning spacing at 0.1mm, and laser energy density at 70J / mm². 3 The powder layer thickness was 0.03 mm, the scanning strategy was 65°, and the substrate preheating temperature was 140° to obtain the alloy sample.

[0043] To reduce thermal stress and minimize the risk of deformation and cracking, the prepared alloy samples underwent stress-relief annealing. The stress-relief annealing process was as follows: the furnace was loaded when the furnace temperature was below 200°C, heated to 870°C at a heating rate of 80°C / h, held for 2 hours, cooled to 750°C, held for 4 hours, cooled to below 550°C, and then air-cooled after being removed from the furnace.

[0044] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile and impact testing methods, and the results were similar to those of Example 1.

[0045] Example 7

[0046] This embodiment describes a 3D printing additive manufacturing method for die-casting mold steel metal powder: the mass percentage content of the metal powder is as follows: carbon: 0.20%, silicon: <0.092%, manganese: 0.21%, molybdenum: 1.79%, chromium: 1.53%, vanadium: 0.48%, tungsten: 0.30%, nickel: 2.49%, copper: 0.81%, sulfur: ≤0.0025%, phosphorus ≤0.010%, oxygen ≤0.019%, with the remainder being Fe and unavoidable impurities; the metal powder can be obtained using annular gas jet cold atomization technology, and the preferred particle size range of the metal powder is 15-53 μm.

[0047] Selective laser melting additive manufacturing was employed, with the laser power controlled at 200W, laser scanning speed at 1100mm / s, scanning spacing at 0.1mm, and laser energy density at 127J / mm². 3 The powder layer thickness was 0.03 mm, the scanning strategy was 70°, and the substrate preheating temperature was 120°C to obtain the alloy sample.

[0048] To reduce thermal stress and minimize the risk of deformation and cracking, the prepared alloy samples underwent stress-relief annealing. The stress-relief annealing process was as follows: the furnace was loaded when the furnace temperature was below 200℃, heated to 870℃ at a heating rate of 60℃ / h, held for 2 hours, cooled to 750℃, held for 4 hours, cooled to below 550℃, and then removed from the furnace and air-cooled.

[0049] The mechanical properties of the sample prepared in this embodiment were tested using conventional hardness, tensile and impact testing methods, and the results were similar to those of Example 1.

[0050] The steel composition of this invention reduces the carbon content to a medium-low carbon level, thereby reducing the brittleness and residual stress of high-carbon martensite, suppressing solidification cracks, and lowering the upper limit of the substrate preheating temperature. Reducing the carbon content also improves the weldability of the material; thermal conductivity is improved by reducing the Si and Cr content. The addition of Ni-Cu composites expands the γ-phase region, improves austenite stability, delays martensite transformation, reduces phase transformation stress, thus avoiding cold cracking and improving toughness. Due to the reduced Si content, a small amount of Cu is added to assist precipitation strengthening during tempering or aging, replacing Co to achieve low-cost age hardening while simultaneously improving thermal conductivity (Cu thermal conductivity ≈ 400 W / m·K, much higher than Co's 100 W / m·K). Adding Cu alone easily forms CuS inclusions with S, leading to a deterioration of the steel's transverse properties; however, the addition of Ni can form a solid solution with Cu, reducing the hot brittleness tendency of Cu and also reducing sulfide hazards. Reducing carbon and Cr content significantly impacts the strength of hot-work die steel, especially its high-temperature strength. Therefore, optimizing the ratio of strong carbide-forming elements Mo and V avoids strength reduction after lowering carbon content. Through the combined effects of these factors, a low-crack-sensitivity, high-thermal-conductivity metal powder chemical composition for additive manufacturing of die-casting molds is obtained.

[0051] The 3D printing additive manufacturing method for die-casting mold steel powder of the present invention, through alloy composition design, selective laser melting, stress-relief annealing, and tempering, enables the alloy to possess excellent comprehensive mechanical properties. The prepared alloy exhibits low crack sensitivity and high thermal conductivity, achieving a dual improvement in strength and toughness. It ensures the formation of high-toughness, low-expansion lath martensite, providing excellent toughness while possessing extremely good weldability, making it less prone to cracking during printing.

[0052] The preheating temperature limit of the die-casting mold steel metal powder 3D printing substrate of this invention is reduced from the traditional 200℃~250℃ of H13 steel to 120℃~150℃, reducing preheating waiting time, accelerating cooling and disassembly speed, shortening the printing cycle, improving printing efficiency, and improving operational safety, reducing the risk of equipment overheating, and effectively reducing the maintenance cost of 3D printing equipment. The alloy design reduces the brittleness of high-carbon martensite and residual stress, inhibiting solidification cracks and effectively reducing the 3D printing crack sensitivity; the material's thermal conductivity is improved by approximately 21% and 2 times compared to H13 steel and 18Ni300, respectively; after stress-relief annealing, the hardness reaches 42HRC, the impact toughness Aku reaches 72J, and the strength and plasticity Rm: 1436MPa, R... p0.2 : 950MPa, A: 12%, Z: 55%, further improved through tempering process to hardness to 42.4-44.4HRC, impact toughness Aku to 67-101J, strength and plasticity to Rm: 1421-1530MPa, R p0.2 : 1110~1304MPa, A: 15.5~17%, Z: 63-68%.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A 3D printing additive manufacturing method of a die casting die steel metal powder, characterized in that: The mass percentage content of the metal powder is as follows: carbon: 0.20-0.28%, silicon: <0.1%, manganese: 0.20-0.5%, molybdenum: 1.30-1.80%, chromium: 1.50-2.50%, vanadium: 0.10-0.50%, tungsten: 0.3-0.6%, nickel: 2.00-3.00%, copper: 0.80-1.00%, sulfur: ≤0.02%, phosphorus: ≤0.025%, oxygen: ≤0.025%, with the remainder being Fe and unavoidable impurities; The metal powder was obtained using annular gas jet cold atomization technology, with a particle size range of 15~53μm. Selective laser melting additive manufacturing was employed, with a laser power of 200W~320W, a laser scanning speed of 800~1100mm / s, a scanning spacing ≤0.1mm, and a laser energy density of 68.17~127.08J / mm². 3 The powder layer thickness is ≤0.03mm, the scanning strategy is 65~70°, and the substrate preheating temperature is 120~150℃ to obtain the die casting mold steel alloy. The stress-relief annealed die-casting mold steel alloy is then subjected to a quenching and tempering toughening treatment. The process for this treatment is as follows: Two-stage preheating is adopted. The furnace temperature of the die-casting mold steel alloy is ≤150℃. The first stage of preheating is 550±10℃ and held for 1 hour. The second stage of preheating is 850±10℃ and held for 1 hour. The quenching process is as follows: heat to 1020±5℃ at a heating rate of 50℃ / h~80℃ / h, hold for 0.5h after the thermocouple reaches the temperature, quench in vacuum to 200℃, and then air cool after removal from the furnace. The tempering process after quenching is as follows: a two-time tempering process at 500~600℃ is adopted, and after holding at the temperature for 2~2.5h, the die-casting mold steel alloy is air-cooled to room temperature.

2. A 3D printing additive manufacturing method of a die casting die steel metal powder according to claim 1, characterized in that: To reduce thermal stress and minimize the risk of deformation and cracking, the prepared die-casting mold steel alloy undergoes stress-relief annealing. The process is as follows: the furnace is installed when the furnace temperature is below 200℃, and heated to 870±10℃ at a heating rate of 50℃ / h~80℃ / h. After holding at this temperature for 2~2.5h, the furnace is cooled to 750±10℃, held at this temperature for 4~5h, and then cooled to below 550℃ before being removed from the furnace and air-cooled.

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