High-strength iron-based die steel powder for laser powder bed melting and production method of high-strength iron-based die steel powder

Abstract

The invention discloses high-strength iron-based die steel powder for laser powder bed melting additive manufacturing and a production method of the high-strength iron-based die steel powder. The high-strength iron-based die steel powder has the characteristics of being high in process controllability, excellent in powder performance, wide in application prospect and the like. The method can be widely applied to manufacturing of high-performance molds in the fields of automobiles, aerospace, electronic packaging and the like, and has good industrial popularization value.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal material preparation, in particular to a high-strength iron-based die steel powder for a laser powder bed fusion (LPBF) additive manufacturing process and a production method thereof. BACKGROUND

[0002] With the wide application of additive manufacturing technology (especially metal 3D printing) in the industrial field, the performance requirements of metal powder materials are increasingly improved.

[0003] The bottleneck of the prior art is that the traditional die steel is prone to cracks, pores and other defects in the LPBF process, mainly because the component design is not optimized (for example, the C equivalent is generally greater than or equal to 0.3%); the oxygen content is not well controlled in the ordinary atomization process (usually greater than 300 ppm), which affects the mechanical properties of the formed part; the powder has poor sphericity, uneven particle size distribution and other problems, which are prone to poor flowability, uneven powder laying and poor fusion in the laser powder bed fusion process, thereby limiting its application in high-performance die manufacturing; the vacuum control is insufficient in the smelting process, resulting in high impurity content; the atomization process parameters are not accurate, which affects the powder particle size distribution; the heat treatment is insufficient, which affects the comprehensive mechanical properties of the material; and the component design is unreasonable, which is difficult to meet the dual requirements of high strength and thermal fatigue performance. SUMMARY

[0004] In view of the above problems, the application provides a high-strength iron-based die steel powder for laser powder bed fusion and a production method thereof, and specifically relates to a high-performance die steel powder with high sphericity, low oxygen content and uniform particle size distribution, which is prepared by a vacuum induction smelting combined with a high-pressure argon gas atomization process, and has the advantages of high sphericity, low oxygen content, concentrated particle size distribution and good flowability, and simultaneously provides a production method with good repeatability and strong process controllability.

[0005] To solve the above technical problems, the technical scheme adopted by the application is as follows: a high-strength iron-based die steel powder for laser powder bed fusion, the iron-based die steel powder comprises the following components in percentage by mass: C: 0.18%-0.25%, Cr: 7.0%-9.0%, Mo: 1.8%-2.5%, Ni: 2.0%-2.5%, V: 1.2%-2.0%, Mn: 0.5%-1.0%, Si: 0.2%-1.0%, Nb: 0.15-0.20%, Al: 0.03-0.05%, Ti: 0.20-0.30%, Ce+La: 0.05%, and the balance is Fe and inevitable impurities.

[0006] Further, the production method of the high-strength iron-based die steel powder for laser powder bed fusion comprises the following steps: Step 1: Raw material preparation and vacuum melting: Mix the raw materials of the above ingredients in proportion and load them into a vacuum induction melting furnace; wherein: Vacuumize to 1 Pa before melting to ensure a highly clean environment in the furnace; Set the initial intermediate frequency power to 50 kW for 20 minutes to preliminarily melt the raw materials; Subsequently, increase the intermediate frequency power to 80 kW and continue heating, maintaining the vacuum degree in the melting chamber ≤ 20 Pa during the process. If the value exceeds this, start the vacuum pump to assist air extraction; Continue to increase the power to 100 kW and maintain for 20 minutes to ensure that the alloy is fully melted; Subsequently, gradually increase to 150 kW, 220 kW, until the raw materials in the furnace are completely melted; After melting, adjust the power to 180 kW for 30 minutes of heat preservation to achieve uniformity of the alloy composition; During heat preservation, still maintain the vacuum degree ≤ 20 Pa to prevent oxidation and impurities from being mixed in; Step 2: Argon gas atomization, wherein: After 30 minutes of heat preservation, increase the power to 200 kW and maintain for 5 minutes; Subsequently, fill high-purity argon into the furnace to a pressure of 0.08 MPa; Start high-pressure argon atomization with an atomization pressure of 5 MPa and continue for 25 minutes.

[0007] From the above description of the structure of the present application, compared with the prior art, the present application has the following advantages: High sphericity and low oxygen content: By strictly controlling the oxygen content during vacuum melting and atomization, the obtained powder has good sphericity and oxygen content below 150 ppm, significantly improving the flowability and forming performance of the powder.

[0008] Uniform particle size distribution: Using high-pressure argon gas atomization process, a powder with particle size concentrated in 15-53 µm is obtained, meeting the particle size requirements of laser powder bed melting equipment for raw materials.

[0009] High composition uniformity: Through multi-stage power regulation and heat preservation process, the alloy elements are fully melted and uniformly distributed, improving the comprehensive mechanical properties of the material.

[0010] High strength and good thermal fatigue performance: The powder prepared has excellent tensile strength, hardness and thermal fatigue life after laser melting, suitable for high-requirement mold manufacturing.

[0011] Strong process repeatability: The melting and atomization parameters are clear and controllable, facilitating industrial production and quality control. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0013] Example One

[0014] The high-strength iron-based die steel powder for laser powder bed fusion, characterized by comprising the following components in percentage by mass: C: 0.2%, Cr: 7.0%, Mo: 1.8%, Ni: 2.0%, V: 1.2%, Mn: 0.5%, Si: 0.2%, Nb: 0.15, Al: 0.03, Ti: 0.20, Ce+La: 0.05%, and the balance of Fe and inevitable impurities. The production method of the high-strength iron-based die steel powder for laser powder bed fusion, comprising the following steps: Step one: raw material preparation and vacuum melting: mix the raw materials of the above components in proportion and load into a vacuum induction melting furnace; wherein: Vacuumize to 1 Pa before melting to ensure a highly clean environment in the furnace; Set the initial medium-frequency power to 50 kW for 20 minutes to preliminarily melt the raw materials; Then increase the medium-frequency power to 80 kW and continue heating, maintaining the vacuum degree in the melting chamber ≤20 Pa during the process, and if the value exceeds the value, start the vacuum pump for auxiliary air extraction; Continue to increase the power to 100 kW and maintain for 20 minutes to ensure the alloy is fully melted; Then gradually increase to 150 kW, 220 kW until the raw materials in the furnace are completely melted; After melting, adjust the power to 180 kW for heat preservation for 30 minutes to realize the homogenization of the alloy components; Still maintain the vacuum degree ≤20 Pa during the heat preservation to prevent oxidation and impurities from being mixed in; Step two: argon gas atomization powder making, wherein: After 30 minutes of heat preservation, increase the power to 200 kW and maintain for 5 minutes; Then fill high-purity argon into the furnace to a pressure of 0.08 MPa; Start high-pressure argon atomization with an atomization pressure of 5 MPa and last for 25 minutes.

[0015] The iron-based die steel powder is cooled and sieved to obtain an iron-based die steel powder with concentrated particle size distribution and high sphericity.

[0016] The particle size of the iron-based die steel powder made by the high-pressure argon atomization process is 15-53 µm.

[0017] By controlling the oxygen content in the vacuum melting and atomization process, the oxygen content is less than 150 ppm, improving the powder flowability and forming performance.

[0018] The iron-based die steel powder prepared according to the above steps and proportions: Melting conditions: vacuum to 1 Pa, power staged to 220 kW, holding for 30 minutes; Atomization conditions: argon pressure 0.08 MPa, atomization pressure 5 MPa, time 25 minutes; The obtained powder particle size: average 32 µm, D50 28 µm, sphericity ≥0.92, oxygen content ≤800 ppm; The Vickers hardness of the sample after laser melting is ≥450 HV.

[0019] The hardness of the iron-based die steel powder: HRC 48; tensile strength Rm: 1650 MPa; yield strength Rp0.2: 1300 MPa; total elongation at break At: 12.5%.

[0020] Example Two

[0021] The proportions of the iron-based die steel powder are as follows: It includes the following components: C: 0.25%, Cr: 9.0%, Mo: 2.5%, Ni: 2.5%, V: 2.0%, Mn: 1.0%, Si: 1.0%, Nb: 0.20%, Al: 0.05%, Ti: 0.30%, Ce+La: 0.05%, and the balance is Fe and unavoidable impurities.

[0022] Example Three

[0023] The proportions of the iron-based die steel powder are as follows: It includes the following components: C: 0.2%, Cr: 8%, Mo: 2%, Ni: 2%, V: 1.5%, Mn: 0.8%, Si: 0.7%, Nb: 0.18%, Al: 0.04%, Ti: 0.25%, Ce+La: 0.05%, and the balance is Fe and unavoidable impurities.

Claims

1. A high strength iron-based die steel powder for laser powder bed fusion, characterized in that: The iron-based die steel powder comprises the following components in percentage by mass: C: 0.18% to 0.25%, Cr: 7.0% to 9.0%, Mo: 1.8% to 2.5%, Ni: 2.0% to 2.5%, V: 1.2% to 2.0%, Mn: 0.5% to 1.0%, Si: 0.2% to 1.0%, Nb: 0.15 to 0.20%, Al: 0.03 to 0.05%, Ti: 0.20 to 0.30%, Ce+La: 0.05%, and the balance of Fe and inevitable impurities.

2. The method of producing a high-strength iron-based die steel powder for laser powder bed fusion according to claim 1, characterized in that: The method comprises the following steps: Step one: raw material preparation and vacuum melting: the raw materials of the above components are mixed in proportion and loaded into a vacuum induction melting furnace; wherein: The vacuum degree is extracted to 1 Pa before melting to ensure that the environment in the furnace is highly clean; The initial medium-frequency power is set to 50 kW, and the raw materials are preliminarily melted for 20 minutes; Then the medium-frequency power is increased to 80 kW, and the melting continues, during which the vacuum degree of the melting chamber is maintained to be less than or equal to 20 Pa, and if the value exceeds the value, the vacuum pump is started to assist air extraction; The power is continuously increased to 100 kW and maintained for 20 minutes to ensure that the alloy is fully melted; Then it is gradually increased to 150 kW and 220 kW until the raw materials in the furnace are completely melted; After melting, the power is adjusted to 180 kW for heat preservation for 30 minutes to realize the homogenization of the alloy components; During the heat preservation, the vacuum degree is still maintained to be less than or equal to 20 Pa to prevent oxidation and impurities from being mixed in; Step two: argon gas atomization powder, wherein: After heat preservation for 30 minutes, the power is increased to 200 kW and maintained for 5 minutes; Then high-purity argon gas is filled into the furnace to a pressure of 0.08 MPa; High-pressure argon gas atomization is started, and the atomization pressure is set to 5 MPa and lasts for 25 minutes.

3. A method of producing a high-strength iron-based die steel powder for laser powder bed fusion according to claim 2, characterized in that: The iron-based die steel powder obtained after cooling and screening has a concentrated particle size distribution and high sphericity.

4. A method of producing a high-strength iron-based die steel powder for a laser powder bed fusion according to claim 2, characterized in that: The particle size of the iron-based die steel powder prepared by the high-pressure argon gas atomization process is 15 to 53 µm.

5. The method of producing a high-strength iron-based die steel powder for a laser powder bed fusion according to claim 2, characterized in that: By controlling the oxygen content in the vacuum melting and atomization process, the oxygen content is less than 150 ppm, which improves the flowability and forming performance of the iron-based die steel powder.

6. A method of producing a high-strength iron-based die steel powder for a laser powder bed fusion according to claim 2, characterized in that: The hardness of the iron-based die steel powder is HRC 48, the tensile strength Rm is 1650 MPa, the yield strength Rp0.2 is 1300 MPa, and the total elongation at break At is 12.5%.