High-thermal-conductivity die steel material for aluminum alloy die casting and preparation process of high-thermal-conductivity die steel material

Abstract

The invention relates to the technical field of die steel, in particular to a high-thermal-conductivity die steel material for aluminum alloy die casting and a preparation technology of the high-thermal-conductivity die steel material. The preparation process comprises the following steps: preparing the Al-Sr composite modifier; preparing intermediate alloy particles; preparing a hot rolled steel mold; preparing a high-thermal-conductivity die steel material for aluminum alloy die casting; zrB2 is added into aluminum and compounded with the mixed KBF4-K2TiF6 powder, so that intermediate alloy particles are prepared, and the intermediate alloy particles have the characteristics of high melting point and hardness, so that the intermediate alloy particles can be used as a reinforcing phase for preparing the die steel, and the high-temperature strength and toughness of the die steel are improved; and the high-temperature stability of the die steel can be improved, and the heat conduction capacity of the die is improved, so that the generation probability of thermal fatigue cracks of the die steel is reduced, and the service life of the die is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of die steel, and in particular to a high thermal conductivity die steel material for aluminum alloy die casting and a preparation process thereof. Background Art

[0002] Mold steel is an indispensable basic material in modern manufacturing and is widely used in many fields such as machinery, automobiles, electronics, aerospace, plastic processing, etc. Mold steel used for aluminum alloy die-casting needs to work in a high temperature environment, so it must have good heat resistance to prevent the mold from softening and deforming at high temperatures. In addition, in order to resist the erosion and wear of aluminum alloy liquid, the mold steel also needs to have high hardness and good thermal conductivity, which helps to quickly dissipate heat and reduce the impact of thermal expansion and contraction, thereby extending the service life of the mold.

[0003] Commonly used aluminum alloy die-casting mold steels include H13 steel, 8407 steel and LG mold steel, etc. These mold steels generally have good thermal conductivity and heat resistance. For example, H13 steel can still maintain good hardness and physical strength in a short-term high-temperature environment, which is sufficient to complete aluminum alloy die-casting. However, during long-term work, H13 steel is prone to metal thermal fatigue, thereby generating thermal fatigue cracks on the surface. The long-term accumulation of thermal fatigue cracks will affect the die-cast aluminum alloy parts, resulting in a shortened service life. Therefore, the present invention provides a high thermal conductivity mold steel material for aluminum alloy die-casting and a preparation process thereof, which can extend the service life by improving the thermal stability and wear resistance of the mold steel. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a high thermal conductivity die steel material for aluminum alloy die casting and a preparation process thereof.

[0005] S1: Preparation of Al-Sr composite modifier, S1.1: Heat 10-15 parts by mass of industrial pure aluminum to 750-800°C in a graphite crucible under argon atmosphere, keep warm for 20-25 minutes and remove slag; S1.2: Raise the temperature to 850-880°C and keep it warm for 20-25 minutes, add 7-9 parts by mass of Al-10Sr alloy, melt it and keep it warm for 40-45 minutes, pour it into a steel mold preheated at 260°C, and obtain an Al-Sr composite modifier.

[0006] S2: preparing intermediate alloy particles, S2.1: adding 70-75 parts by mass of aluminum ingots into a crucible to melt, heating to 800-850°C, adding 24-28 parts by mass of ZrB2 powder to fully melt it, continuing to heat to 1000-1050°C, adding 4-6 parts by mass of Ti-C-Al powder, standing for 5-10 minutes, then cooling to 900°C, adding 5-6 parts by mass of mixed KBF4-K2TiF6 powder, and standing for 5-10 minutes; S2.2: Then, the temperature is lowered to 760-800°C, 4-8 parts by mass of Al-Sr composite modifier is added, and the temperature is kept at 5-10 minutes, and then the temperature is lowered to 700-750°C, a degassing refining agent is added, and the temperature is kept at 10-15 minutes to obtain a cast composite material; S2.3: The as-cast composite material is dissolved at 510-530°C, water quenched at 60-80°C for 5-6h, crushed and sieved through a 20-mesh sieve to obtain intermediate alloy particles.

[0007] Furthermore, the mass ratio of KBF4 and K2TiF6 in the mixed KBF4-K2TiF6 powder is (2-3): (0.8-1.8).

[0008] Furthermore, the degassing refining agent is a mixture of one or more of sodium chloride, potassium chloride and hexachloroethane.

[0009] S3: preparing a hot-rolled steel mold, S3.1: consolidating raw material powder by vacuum hot pressing, the raw material powder composition is calculated by mass percentage as follows: 0.35-0.38% C, 1.1-1.3% Si, 0.45-0.48% Mn, 5.1-5.3% Cr, 1.35-1.39% Mo, 0.95-1.05% V, 1.2-1.25% intermediate alloy particles, and the balance is Fe; S3.2: The preheating temperature of the vacuum hot pressing furnace is 1000-1100°C, the heat preservation time is 30-35min, the consolidation temperature is 1100-1150°C, the consolidation pressure is 40MPa, the heat preservation time is 2-2.5h, and then the material is cooled with the furnace to obtain a block material; S3.3: After cutting the block material, remove the surface oxide layer, put it into a box furnace at room temperature, heat it to 600-620℃ for preheating for 30-35min, with a heating rate of 8-10℃ / min, then continue to heat it to 650-750℃, keep it warm for 30-40min, then heat it to 1120℃, keep it warm for 1-2min and then roll it to obtain a hot-rolled steel mold.

[0010] Furthermore, the specific method for removing the surface oxide layer of the bulk material is laser cleaning, and the bulk material is laser cleaned for 3-5 minutes at a laser power of 120W and a pulse frequency of 20kHz to remove the surface oxide layer.

[0011] S4: preparing high thermal conductivity mold steel material for aluminum alloy die casting, S4.1: polishing the surface of the hot-rolled steel mold, removing the oil stains on the surface with alcohol and acetone, washing with water, and drying in a drying oven at 60-80°C for 4-6 hours to obtain a dry mold; S4.2: The dry mold is surface treated by multi-source multi-arc ion plating PVD method. Nitrogen is introduced under vacuum with a flow rate of 3L / min. The furnace pressure of the multi-arc ion plating machine is 40Pa, the coating temperature is 390-450℃, the bias voltage is set to 60V, and the multi-arc current is 150A. A TiAlCrN coating with a total thickness of 8-12μm is formed on the surface of the dry mold to obtain a high thermal conductivity mold steel material for aluminum alloy die-casting.

[0012] Furthermore, the components of the TiAlCrN coating are calculated by mass percentage as follows: 20-25% Ti, 55-60% Al, 15-20% Cr and 5-10% N.

[0013] A high thermal conductivity die steel material for aluminum alloy die casting is prepared by the above-mentioned preparation process of the high thermal conductivity die steel material for aluminum alloy die casting.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The present invention adds ZrB2 to aluminum and compounds it with mixed KBF4-K2TiF6 powder to prepare intermediate alloy particles. Adding ZrB2 to aluminum ingots can assist aluminum to react with Zr and Ti to form a composite structure. The formed composite structure makes the intermediate alloy particles have the characteristics of high melting point and hardness, so that they can be used as a reinforcing phase to prepare mold steel, thereby improving the high-temperature strength and toughness of the mold steel. In addition, ZrB2 can form stable compounds with aluminum and chromium elements in steel at high temperatures, further enhancing the matrix properties of the mold steel. Since aluminum alloys are in a high-temperature and high-pressure environment during die casting, adding aluminum-based alloys mainly composed of aluminum ingots to mold steel can also improve the high-temperature stability of the mold steel, improve the thermal conductivity of the mold, thereby reducing the probability of thermal fatigue cracks in the mold steel and increasing the service life of the mold.

[0015] 2. The intermediate alloy particles prepared by adding Al-Sr composite modifier in the present invention contain ZrB2. The composite modifier prepared by Al-10Sr can combine with Zr in ZrB2 to form Al-Sr-Zr three-phase modifier. Under high temperature environment, the three-phase modifier can refine the crystal phase in the aluminum-based alloy, so that the aluminum-based alloy can be crushed into finer particles without changing the properties and microstructure, so that the bulk material can be prepared by hot pressing in the raw material of the mold steel that is subsequently added, and the B element of ZrB2 can combine with Ti to form TiB2, thereby improving the thermal conductivity and high-temperature stability of the mold steel.

[0016] 3. The present invention coats a layer of TiAlCrN coating on the surface of the mold steel by a multi-source multi-arc ion plating PVD method. In the case of aluminum alloy die-casting, the mold steel with good thermal conductivity needs to withstand high temperature, high pressure and high load at the same time, and wear will occur during demolding. By coating the TiAlCrN coating, compared with the simple TiAl composite coating and the silicon-containing coating, the TiAlCrN coating has better high-temperature oxidation resistance, can form a stable oxide layer in a high temperature environment, and protect the mold steel substrate from oxidation corrosion. This enables the mold to maintain better surface quality and dimensional accuracy in high-load and high-wear application scenarios, and reduce wear and scratches. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present application and, together with the description, further serve to explain the principles of the present application and enable those skilled in the relevant art to make and use the present application.

[0018] Figure 1 This is a process flow chart of preparing a high thermal conductivity die steel material for aluminum alloy die casting adopted in an embodiment of the present invention.

[0019] Figure 2 This is a table showing the change of Rockwell hardness over time in thermal stability experiments of Example 1 of the present invention and Comparative Examples 1-2.

[0020] Figure 3 This is a table showing the change of Rockwell hardness over time in thermal stability experiments of Example 1 of the present invention and Comparative Examples 3-4. DETAILED DESCRIPTION

[0021] The following is a detailed description of a high thermal conductivity die steel material for aluminum alloy die casting and its preparation process provided by the present invention in combination with the accompanying drawings and specific embodiments. At the same time, in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternative methods to implement some known technologies; and the accompanying drawings are only for a more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0022] Embodiment 1: A preparation process of high thermal conductivity die steel material for aluminum alloy die casting, such as Figure 1 As shown, the following steps are included: S1: Preparation of Al-Sr composite modifier, S1.1: 10 parts by mass of industrial pure aluminum were heated to 750°C in a graphite crucible under argon atmosphere, melted, kept at this temperature for 20 min and slag removed; S1.2: The temperature is raised to 850°C and kept at this temperature for 20 minutes, 7 parts by mass of Al-10Sr alloy is added, and after melting, the alloy is kept at this temperature for 40 minutes, and then poured into a steel mold preheated at 260°C to obtain an Al-Sr composite modifier.

[0023] S2: preparing intermediate alloy particles, S2.1: adding 70 parts by mass of aluminum ingots into a crucible for melting, heating to 800°C, adding 24 parts by mass of ZrB2 powder to fully melt it, continuing to heat to 1000°C, adding 4 parts by mass of Ti-C-Al powder, standing for 5 minutes, then cooling to 900°C, adding 5 parts by mass of mixed KBF4-K2TiF6 powder, wherein the mass ratio of KBF4 to K2TiF6 in the mixed KBF4-K2TiF6 powder is 2:0.8, and standing for 5 minutes; S2.2: Then, the temperature is lowered to 760°C, 4 parts by mass of Al-Sr composite modifier is added, and the temperature is kept for 5 minutes, and then the temperature is lowered to 700°C, and hexachloroethane, a degassing refining agent, is added, and the temperature is kept for 10 minutes to obtain a cast composite material; S2.3: The as-cast composite material is dissolved at 510°C, water quenched at 60°C for 5h, crushed and sieved through a 20-mesh sieve to obtain intermediate alloy particles.

[0024] S3: preparing hot-rolled steel molds, S3.1: consolidating raw material powders by vacuum hot pressing, the raw material powders have the following components calculated by mass percentage: 0.35% C, 1.1% Si, 0.45% Mn, 5.1% Cr, 1.35% Mo, 0.95% V, 1.2% intermediate alloy particles, and the balance is Fe; S3.2: The preheating temperature of the vacuum hot pressing furnace is 1000°C, the temperature is kept for 30 minutes, the consolidation temperature is 1100°C, the consolidation pressure is 40MPa, the temperature is kept for 2 hours, and then the furnace is cooled to obtain a block material; S3.3: After cutting the block material, the surface oxide layer is removed by laser cleaning. The block material is laser cleaned for 3 minutes at a laser power of 120W and a pulse frequency of 20kHz to remove the surface oxide layer. The block material is placed in a box furnace at room temperature and preheated to 600°C for 30 minutes at a heating rate of 8°C / min. The block material is then heated to 650°C and kept warm for 30 minutes. The block material is then heated to 1120°C and kept warm for 1 minute before rolling to obtain a hot-rolled steel mold.

[0025] S4: preparing high thermal conductivity die steel material for aluminum alloy die casting, S4.1: polishing the surface of the hot-rolled steel die, removing the oil stains on the surface with alcohol and acetone, washing with water, and drying in a drying oven at 60°C for 4h to obtain a dry die; S4.2: Perform HKS-G surface treatment on the dry mold. The HKS-G process adopts a multi-source multi-arc ion plating PVD method. Nitrogen is introduced under vacuum with a flow rate of 3L / min. The furnace pressure of the multi-arc ion plating machine is 40Pa, the coating temperature is 390℃, the bias voltage is set to 60V, and the multi-arc current is 150A. A TiAlCrN coating with a total thickness of 8μm is formed on the surface of the dry mold. The components of the TiAlCrN coating are calculated by mass percentage as follows: 20% Ti, 55% Al, 15% Cr and 10% N, thereby obtaining a high thermal conductivity mold steel material for aluminum alloy die-casting.

[0026] Embodiment 2: A preparation process of high thermal conductivity die steel material for aluminum alloy die casting, such as Figure 1 As shown, the following steps are included: S1: Preparation of Al-Sr composite modifier, S1.1: 15 parts by mass of industrial pure aluminum were heated to 750°C in a graphite crucible under argon atmosphere, melted, kept at this temperature for 20 min and slag removed; S1.2: The temperature is raised to 850°C and kept at this temperature for 20 minutes, 9 parts by mass of Al-10Sr alloy is added, and after melting, the alloy is kept at this temperature for 40 minutes, and then poured into a steel mold preheated at 260°C to obtain an Al-Sr composite modifier.

[0027] S2: preparing intermediate alloy particles, S2.1: adding 70 parts by mass of aluminum ingots into a crucible for melting, heating to 800°C, adding 28 parts by mass of ZrB2 powder to fully melt it, continuing to heat to 1000°C, adding 6 parts by mass of Ti-C-Al powder, standing for 5 minutes, then cooling to 900°C, adding 5 parts by mass of mixed KBF4-K2TiF6 powder, wherein the mass ratio of KBF4 to K2TiF6 in the mixed KBF4-K2TiF6 powder is 3:1.8, and standing for 5 minutes; S2.2: Then, the temperature is lowered to 760°C, 8 parts by mass of Al-Sr composite modifier is added, and the temperature is kept for 5 minutes, and then the temperature is lowered to 700°C, and hexachloroethane, a degassing refining agent, is added, and the temperature is kept for 10 minutes to obtain a cast composite material; S2.3: The as-cast composite material is dissolved at 510°C, quenched in water at 60°C for 5h, crushed and sieved through a 20-mesh sieve to obtain intermediate alloy particles.

[0028] S3: preparing hot-rolled steel molds, S3.1: consolidating raw material powders by vacuum hot pressing, the raw material powder compositions are calculated by mass percentage as follows: 0.38% C, 1.3% Si, 0.48% Mn, 5.3% Cr, 1.39% Mo, 1.05% V, 1.25% intermediate alloy particles, and the balance is Fe; S3.2: The preheating temperature of the vacuum hot pressing furnace is 1000°C, the temperature is kept for 30 minutes, the consolidation temperature is 1100°C, the consolidation pressure is 40MPa, the temperature is kept for 2 hours, and then the furnace is cooled to obtain a block material; S3.3: After cutting the block material, the surface oxide layer is removed by laser cleaning. The block material is laser cleaned for 3 minutes at a laser power of 120W and a pulse frequency of 20kHz to remove the surface oxide layer. The block material is placed in a box furnace at room temperature and preheated to 600°C for 30 minutes at a heating rate of 8°C / min. The block material is then heated to 650°C and kept warm for 30 minutes. The block material is then heated to 1120°C and kept warm for 1 minute before rolling to obtain a hot-rolled steel mold.

[0029] S4: preparing high thermal conductivity die steel material for aluminum alloy die casting, S4.1: polishing the surface of the hot-rolled steel die, removing the oil stains on the surface with alcohol and acetone, washing with water, and drying in a drying oven at 60°C for 4h to obtain a dry die; S4.2: For the surface treatment of the dry mold, a multi-source multi-arc ion plating PVD method is adopted. Nitrogen is introduced under vacuum with a flow rate of 3L / min. The furnace pressure of the multi-arc ion plating machine is 40Pa, the coating temperature is 390℃, the bias voltage is set to 60V, and the multi-arc current is 150A. A TiAlCrN coating with a total thickness of 8μm is formed on the surface of the dry mold. The components of the TiAlCrN coating are calculated by mass percentage as follows: 22% Ti, 58% Al, 15% Cr and 5% N, thereby obtaining a high thermal conductivity mold steel material for aluminum alloy die-casting.

[0030] Embodiment 3: A preparation process of high thermal conductivity die steel material for aluminum alloy die casting, such as Figure 1 As shown, the following steps are included: S1: Preparation of Al-Sr composite modifier, S1.1: 10 parts by mass of industrial pure aluminum were heated to 750°C in a graphite crucible under argon atmosphere, melted, kept at this temperature for 25 min and slag removed; S1.2: The temperature is raised to 880°C and kept at this temperature for 25 minutes, 7 parts by mass of Al-10Sr alloy is added, and after melting, the alloy is kept at this temperature for 45 minutes, and then poured into a steel mold preheated at 260°C to obtain an Al-Sr composite modifier.

[0031] S2: preparing intermediate alloy particles, S2.1: adding 70 parts by mass of aluminum ingots into a crucible for melting, heating to 850°C, adding 24 parts by mass of ZrB2 powder to fully melt it, continuing to heat to 1050°C, adding 4 parts by mass of Ti-C-Al powder, standing for 10 minutes, then cooling to 900°C, adding 5 parts by mass of mixed KBF4-K2TiF6 powder, wherein the mass ratio of KBF4 to K2TiF6 in the mixed KBF4-K2TiF6 powder is 2:0.8, and standing for 10 minutes; S2.2: Then, the temperature is lowered to 800°C, 4 parts by mass of Al-Sr composite modifier is added, and the temperature is kept for 5 minutes, and then the temperature is lowered to 750°C, and hexachloroethane, a degassing refining agent, is added, and the temperature is kept for 15 minutes to obtain a cast composite material; S2.3: The as-cast composite material is dissolved at 530°C, water quenched at 80°C for 6h, crushed and sieved through a 20-mesh sieve to obtain intermediate alloy particles.

[0032] S3: preparing hot-rolled steel molds, S3.1: consolidating raw material powders by vacuum hot pressing, the raw material powders have the following components calculated by mass percentage: 0.35% C, 1.1% Si, 0.45% Mn, 5.1% Cr, 1.35% Mo, 0.95% V, 1.2% intermediate alloy particles, and the balance is Fe; S3.2: The preheating temperature of the vacuum hot pressing furnace is 1100°C, the temperature is kept for 35 min, the consolidation temperature is 1150°C, the consolidation pressure is 40 MPa, the temperature is kept for 2.5 h, and then the furnace is cooled to obtain a block material; S3.3: After cutting the block material, the surface oxide layer is removed by laser cleaning. The block material is laser cleaned for 3 minutes at a laser power of 120W and a pulse frequency of 20kHz to remove the surface oxide layer. The block material is placed in a box furnace at room temperature and preheated to 620°C for 35 minutes at a heating rate of 10°C / min. The block material is then heated to 750°C and kept warm for 30 minutes. The block material is then heated to 1120°C and kept warm for 2 minutes before rolling to obtain a hot-rolled steel mold.

[0033] S4: preparing high thermal conductivity die steel material for aluminum alloy die casting, S4.1: polishing the surface of the hot-rolled steel die, removing the oil stains on the surface with alcohol and acetone, washing with water, and drying in a drying oven at 80°C for 6 hours to obtain a dry die; S4.2: For the surface treatment of the dry mold, a multi-source multi-arc ion plating PVD method is adopted. Nitrogen is introduced under vacuum with a flow rate of 3L / min. The furnace pressure of the multi-arc ion plating machine is 40Pa, the coating temperature is 390℃, the bias voltage is set to 60V, and the multi-arc current is 150A. A TiAlCrN coating with a total thickness of 8μm is formed on the surface of the dry mold. The components of the TiAlCrN coating are calculated by mass percentage as follows: 20% Ti, 55% Al, 15% Cr and 10% N, thereby obtaining a high thermal conductivity mold steel material for aluminum alloy die-casting.

[0034] Comparative Example 1: Compared with Example 1, Comparative Example 1 is a commercially available aluminum alloy die-casting die steel.

[0035] Comparative Example 2: Compared with Example 1, the difference of Comparative Example 2 is that step S1 is not performed, and no Al-Sr composite modifier is added in step S2.2, specifically "S2.2: then lowering the temperature to 760°C, keeping warm for 5 minutes, and then cooling to 700°C, adding degassing refining agent hexachloroethane, and keeping warm for 10 minutes to obtain a cast composite material", and the remaining steps remain unchanged, and the prepared high thermal conductivity mold steel material for aluminum alloy die-casting is recorded as Comparative Example 2.

[0036] Comparative Example 3: Compared with Example 1, the difference of Comparative Example 3 is that ZrB2 powder is not added in step S2.1, specifically "S2.1: add 70 parts by mass of aluminum ingots into a crucible for melting, heat to 800°C, continue to heat to 1000°C, add 4 parts by mass of Ti-C-Al powder, let stand for 5 minutes, then cool to 900°C, add 5 parts by mass of mixed KBF4-K2TiF6 powder, the mass ratio of KBF4 and K2TiF6 in the mixed KBF4-K2TiF6 powder is 2:0.8, and let stand for 5 minutes", and the other steps remain unchanged, and the prepared high thermal conductivity mold steel material for aluminum alloy die-casting is recorded as Comparative Example 3.

[0037] Comparative Example 4: Compared with Example 1, the difference of Comparative Example 4 is that no mixed KBF4-K2TiF6 powder is added in step S2.1, specifically "S2.1: add 70 parts by mass of aluminum ingots into a crucible for melting, raise the temperature to 800°C, add 24 parts by mass of ZrB2 powder to fully melt it, continue to raise the temperature to 1000°C, add 4 parts by mass of Ti-C-Al powder, let it stand for 5 minutes, then cool to 900°C and let it stand for 5 minutes", and the other steps remain unchanged, and the prepared high thermal conductivity mold steel material for aluminum alloy die-casting is recorded as Comparative Example 4.

[0038] Comparative Example 5: Compared with Example 1, the difference of Comparative Example 5 is that step S4.2 is not performed, the surface of the hot-rolled steel mold is polished, the surface oil is removed with alcohol and acetone, washed with water, and dried in a drying oven at 60°C for 4 hours to obtain a high thermal conductivity mold steel material for aluminum alloy die-casting.

[0039] The thermal stability test of Example 1 and Comparative Examples 1-4 was conducted at 700°C to test their Rockwell hardness. Figure 2 and Figure 3 shown.

[0040] The wear resistance of Examples 1-3 and Comparative Example 5 was tested, and the results are shown in Table 1.

[0041] Table 1: 500℃ wear volume statistics (unit: mm 3 )

[0042] from Figure 2 and Figure 3 It can be seen that in Example 1, the Rockwell hardness is reduced from 51 to 46 under a long-term high temperature environment, and the reduction is small. The Rockwell hardness remains stable during the whole process. It can be seen that the mold steel material prepared by the present application has good thermal stability and is not prone to thermal fatigue. The Rockwell hardness of Comparative Examples 1 to Comparative Examples 4 in a high temperature environment has decreased to varying degrees. It can be seen that compared with commercially available products, the present invention has better thermal stability.

[0043] It can be seen from Table 1 that the wear volumes of Examples 1-3 are lower than those of Examples 1 and 5, indicating that the wear resistance of the present invention is better than that of commercially available products, and that the TiAlCrN coating plated by the present invention has an auxiliary effect on improving the wear resistance.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A preparation process of high thermal conductivity die steel material for aluminum alloy die casting, characterized in that: The steps include: S1: Preparation of Al-Sr composite modifier: melt industrial pure aluminum under argon atmosphere, keep it warm and remove slag, then heat it to 850-880℃ and keep it warm, add Al-10Sr alloy, keep it warm after melting, and pour it into a steel mold to obtain Al-Sr composite modifier; S2: preparing intermediate alloy particles, adding aluminum ingots into a crucible to melt, heating up, adding ZrB2 powder, continuing to heat up, adding Ti-C-Al powder, standing, then cooling down, adding mixed KBF4-K2TiF6 powder, standing, adding Al-Sr composite modifier, keeping the temperature, cooling down again, adding degassing refining agent, keeping the temperature, obtaining a cast composite material, dissolving the cast composite material, quenching with water, crushing and sieving to obtain intermediate alloy particles; S3: preparing a hot-rolled steel mold, using vacuum hot pressing to consolidate raw material powder, the raw material powder composition is calculated by mass percentage as follows: 0.35-0.38% C, 1.1-1.3% Si, 0.45-0.48% Mn, 5.1-5.3% Cr, 1.35-1.39% Mo, 0.95-1.05% V, 1.2-1.25% intermediate alloy particles, and the balance is Fe, to obtain a block material, cut the block material, remove the surface oxide layer, put it in a box furnace at room temperature, heat it, and roll it to obtain a hot-rolled steel mold; S4: Prepare high thermal conductivity mold steel material for aluminum alloy die-casting, polish the surface of the hot-rolled steel mold, use alcohol and acetone to remove surface oil stains, wash with water, and dry to obtain a dry mold, perform surface treatment on the dry mold, and use a multi-source multi-arc ion plating PVD method to form a TiAlCrN coating on the surface of the dry mold to obtain a high thermal conductivity mold steel material for aluminum alloy die-casting.

2. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 1, characterized in that: Step S1: Preparation of Al-Sr composite modifier, comprising the following steps: S1.1: In an argon atmosphere, heat 10-15 parts by mass of industrial pure aluminum to 750-800°C in a graphite crucible, keep warm for 20-25 minutes and remove the slag; S1.2: Raise the temperature to 850-880°C and keep it warm for 20-25 minutes, add 7-9 parts by mass of Al-10Sr alloy, melt it and keep it warm for 40-45 minutes, pour it into a steel mold preheated at 260°C, and obtain an Al-Sr composite modifier.

3. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 2, characterized in that: Step S2 is to prepare intermediate alloy particles, comprising the following steps: S2.1: Add 70-75 parts by mass of aluminum ingot into a crucible for melting, heat to 800-850°C, add 24-28 parts by mass of ZrB2 powder to fully melt it, continue to heat to 1000-1050°C, add 4-6 parts by mass of Ti-C-Al powder, let stand for 5-10 minutes, then cool to 900°C, add 5-6 parts by mass of mixed KBF4-K2TiF6 powder, and let stand for 5-10 minutes; S2.2: Then, the temperature is lowered to 760-800°C, 4-8 parts by mass of Al-Sr composite modifier is added, and the temperature is kept at 5-10 minutes, and then the temperature is lowered to 700-750°C, a degassing refining agent is added, and the temperature is kept at 10-15 minutes to obtain a cast composite material; S2.3: The as-cast composite material is dissolved at 510-530°C, water quenched at 60-80°C for 5-6h, crushed and sieved through a 20-mesh sieve to obtain intermediate alloy particles.

4. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 3, characterized in that: Step S3: preparing a hot-rolled steel mold, comprising the following steps: S3.1: The raw material powder is consolidated by vacuum hot pressing. The raw material powder composition is calculated by mass percentage as follows: 0.35-0.38% C, 1.1-1.3% Si, 0.45-0.48% Mn, 5.1-5.3% Cr, 1.35-1.39% Mo, 0.95-1.05% V, 1.2-1.25% master alloy particles, and the balance is Fe; S3.2: The preheating temperature of the vacuum hot pressing furnace is 1000-1100°C, the heat preservation time is 30-35min, the consolidation temperature is 1100-1150°C, the consolidation pressure is 40MPa, the heat preservation time is 2-2.5h, and then the material is cooled with the furnace to obtain a block material; S3.3: After cutting the block material, remove the surface oxide layer, put it into a box furnace at room temperature, heat it to 600-620℃ for preheating for 30-35min, with a heating rate of 8-10℃ / min, then continue to heat it to 650-750℃, keep it warm for 30-40min, then heat it to 1120℃, keep it warm for 1-2min and then roll it to obtain a hot-rolled steel mold.

5. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 4, characterized in that: Step S4 prepares a high thermal conductivity die steel material for aluminum alloy die casting, comprising the following steps: S4.1: Polish the surface of the hot-rolled steel mold, remove the oil stains on the surface with alcohol and acetone, wash with water, and dry in a drying oven at 60-80°C for 4-6 hours to obtain a dry mold; S4.2: The dry mold is surface treated by multi-source multi-arc ion plating PVD method. Nitrogen is introduced under vacuum with a flow rate of 3L / min. The furnace pressure of the multi-arc ion plating machine is 40Pa, the coating temperature is 390-450℃, the bias voltage is set to 60V, and the multi-arc current is 150A. A TiAlCrN coating with a total thickness of 8-12μm is formed on the surface of the dry mold to obtain a high thermal conductivity mold steel material for aluminum alloy die-casting.

6. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 3, characterized in that: The mass ratio of KBF4 and K2TiF6 in the mixed KBF4-K2TiF6 powder is (2-3):(0.8-1.8).

7. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 3, characterized in that: The degassing refining agent is a mixture of one or more of sodium chloride, potassium chloride and hexachloroethane.

8. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 4, characterized in that: The specific method for removing the surface oxide layer of the bulk material is laser cleaning. The bulk material is laser cleaned for 3-5 minutes at a laser power of 120W and a pulse frequency of 20kHz to remove the surface oxide layer.

9. The process for preparing a high thermal conductivity die steel material for aluminum alloy die casting according to claim 5, characterized in that: The components of the TiAlCrN coating are calculated by mass percentage as follows: 20-25% Ti, 55-60% Al, 15-20% Cr and 5-10% N.

10. A high thermal conductivity die steel material for aluminum alloy die casting, which is prepared by the preparation process of the high thermal conductivity die steel material for aluminum alloy die casting according to any one of claims 1 to 9.

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