3D printing additive manufacturing method for die-casting die steel metal powder

Abstract

The invention relates to a 3D printing additive manufacturing method for die-casting die steel metal powder. The metal powder comprises, by mass, 0.20%-0.28% of carbon, 1t of silicon, 0.20%-0.30% of carbon and the balance iron. The steel comprises the following components in percentage by weight: 0.1% of Fe, 0.20-0.5% of Mn, 1.30-1.80% of Mo, 1.50-2.50% of Cr, 0.10-0.50% of V, 0.3-0.6% of W, 2.00-3.00% of Ni, 0.80-1.00% of Cu, less than or equal to 0.02% of S, less than or equal to 0.025% of P, less than or equal to 0.025% of O and the balance of Fe and inevitable impurities. A selective laser melting additive manufacturing method is adopted, the laser power ranges from 200 W to 320 W, the laser scanning speed ranges from 800 mm / s to 1100 mm / s, the scanning distance is smaller than or equal to 0.1 mm, the laser energy density ranges from 68.17 J / mm < 3 > to 127.08 J / mm < 3 >, the powder laying layer thickness is smaller than or equal to 0.03 mm, the scanning strategy ranges from 65 DEG C to 70 DEG C, the substrate preheating temperature ranges from 120 DEG C to 150 DEG C, and the alloy is prepared. The preparation method has the beneficial effects that through alloy component design and a selective laser melting method, the prepared alloy has low crack sensitivity and high thermal conductivity, the obdurability is improved, the formation of high-toughness and low-expansion lath martensite is ensured, excellent toughness is provided, meanwhile, excellent weldability is achieved, and cracking is not prone to occurring.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of 3D printing additive manufacturing, in particular to a 3D printing additive manufacturing method of die casting die steel metal powder. BACKGROUND

[0002] A die is a mold made of metal, which is a tool for repeatedly producing the same product through stamping, forging, casting and other methods. Large-scale integrated complex structural parts with high integration degree play an increasingly important role in new energy vehicle manufacturing, and as the "mother of industry", die is crucial to the manufacturing of these complex structural parts.

[0003] In recent years, integrated die casting dies have been widely used in new energy vehicles. The high-quality preparation technology of large-scale integrated die casting die steel modules has become a research hotspot. Additive manufacturing of die casting dies builds die structures by layer-by-layer accumulation of materials, breaking through the limitations of traditional manufacturing processes in complex structure design, enabling integrated forming of complex internal flow channels and other structures, and enabling the manufacture of dies with internal flow channel curvature radii as small as millimeters.

[0004] Currently, alloy powders used for additive manufacturing of die casting dies are mainly H13 hot work die steel and 18Ni300 maraging steel, but there are significant defects: H13 is a medium carbon steel with high crack sensitivity, which is prone to micro-cracks during 3D printing, has poor formability, and the hardness of the directly formed part reaches about 55HRC, with poor crack ductility. During the use of the inlaid die, the crack propagation water line breaks, which poses a great safety hazard. 18Ni300 steel relies on high Ni(18-19%) and high Co(8.5-9.5%) to achieve age hardening, and the high Ni content stabilizes the austenite structure, forming a single martensite matrix after solid solution treatment and rapid cooling, which improves the fracture toughness of the maraging steel; Co can delay the recovery process of the martensite matrix at high temperature, maintain the stability of the matrix structure, and ensure that the material still maintains high strength and high dimensional accuracy after aging. However, the raw material cost of 18Ni300 steel is extremely high, and the thermal conductivity is only 2 / 3 of that of H13, with poor thermal fatigue resistance, making it difficult to meet the demand for high-load dies, and there is a bottleneck in application.

[0005] Therefore, the design of a new component ratio and the development of a low-cost 3D printing additive manufacturing method of die casting die steel metal powder are the research motivation of the present application. SUMMARY

[0006] The application aims to overcome the deficiencies of the prior art and provide a novel 3D printing additive manufacturing method of die casting die steel metal powder.

[0007] The application provides a 3D printing additive manufacturing method of die casting die steel metal powder.

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

[0009] Further, the metal powder is obtained by using the ring-hole air spray air cold atomization technology, and the particle size range of the metal powder is 15-53 μm.

[0010] Further, in order to reduce thermal stress, reduce deformation and cracking risk, the prepared alloy sample is subjected to stress relief annealing, and the process is as follows: the furnace temperature is lower than 200℃, the furnace is loaded at a heating speed of 50-80℃ / h, the furnace is heated to 870±10℃, the furnace is cooled to 750±10℃ after being kept for 2-2.5 h, the furnace is cooled to a furnace temperature lower than 550℃ after being kept for 4-5 h, and the furnace is discharged and air cooled.

[0011] Further, the die casting die steel blank after stress relief annealing is subjected to quenching and toughening treatment, and the process of quenching and toughening treatment is as follows:

[0012] Two-stage preheating is adopted, the die steel blank is put into the furnace at a furnace temperature of ≤150℃, the first-stage preheating is at 550±10℃ for 1 h, and the second-stage preheating is at 850±10℃ for 1 h.

[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 for die-casting mold steel powder, characterized in that: The metal powder contains the following mass percentages: 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 800–1100 mm / s, a scanning interval ≤0.1 mm, and a laser energy density of 68.17–127.08 J / 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.

2. The 3D printing additive manufacturing method for die-casting mold steel powder according to claim 1, characterized in that: The metal powder was obtained using annular gas jet cold atomization technology, and the particle size range of the metal powder was 15–53 μm.

3. The 3D printing additive manufacturing method for die-casting mold steel powder according to claim 1, characterized in that: 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.

4. The 3D printing additive manufacturing method for die-casting mold steel powder according to claim 1, characterized in that: The stress-relief annealed die-casting mold steel billet 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 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. 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 2-2.5 hours, the mold steel billet is air-cooled to room temperature.

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