阅读说明：本技术 一种4Cr5MoSiV1合金钢力学性能调控方法 (Method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel ) 是由 董世运 闫世兴 赵轩 吕耀辉 刘晓亭 夏丹 于 2020-12-29 设计创作，主要内容包括：本发明提供了一种4Cr5MoSiV1合金钢力学性能调控方法,包括如下步骤：(1)对4Cr5MoSiV1合金钢粉末进行预处理；(2)对基板材料进行预处理；(3)采用激光立体成型工艺,制备4Cr5MoSiV1合金钢成型件；(4)对第(3)步获得的4Cr5MoSiV1合金钢成型件进行热处理。本发明的4Cr5MoSiV1合金钢力学性能调控方法,可在保证成型件具有优良拉伸性能和延展性能的前提下,明显降低热处理过程中的加热温度和加热时间,进而实现短周期、低能耗以及高性能4Cr5MoSiV1合金钢的制备。(The invention provides a method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel, which comprises the following steps: (1) pretreating 4Cr5MoSiV1 alloy steel powder; (2) pre-treating a substrate material; (3) preparing a 4Cr5MoSiV1 alloy steel molding piece by adopting a laser three-dimensional molding process; (4) and (4) carrying out heat treatment on the 4Cr5MoSiV1 alloy steel formed piece obtained in the step (3). The method for regulating and controlling the mechanical properties of the 4Cr5MoSiV1 alloy steel can obviously reduce the heating temperature and the heating time in the heat treatment process on the premise of ensuring that a formed part has excellent tensile property and ductility, thereby realizing the preparation of the 4Cr5MoSiV1 alloy steel with short period, low energy consumption and high performance.)

1. A method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel is characterized by comprising the following steps: the method comprises the following steps:

(1) pretreating 4Cr5MoSiV1 alloy steel powder;

(2) pre-treating a substrate material;

(3) preparing a 4Cr5MoSiV1 alloy steel molding piece by adopting a laser three-dimensional molding process;

(4) and (4) carrying out heat treatment on the 4Cr5MoSiV1 alloy steel formed piece obtained in the step (3).

2. The method of claim 1, wherein: in the step (1), the 4Cr5MoSiV1 alloy steel powder comprises the following components in percentage by mass: c: 0.35 wt%, V: 1 wt%, Cr: 5.05 wt%, Mn: 0.32 wt%, Mo: 1.35 wt%, Si: 0.95 wt% and the balance Fe.

3. The method according to claim 1 or 2, characterized in that: in the step (1), 4Cr5MoSiV1 alloy steel powder is placed in a vacuum drying oven, heat preservation is carried out for 4 hours at the temperature of 110 ℃, and then cooling is carried out to the room temperature in the vacuum drying oven.

4. A method according to any one of claims 1 to 3, characterized in that: in the step (2), a rolled and annealed Q235 alloy steel plate is selected as a substrate material, the surface of the substrate is polished by using No. 200 abrasive paper, the surface of the substrate is cleaned by using absolute ethyl alcohol after the metallic luster is exposed on the surface of the substrate, and the substrate is reserved after the surface of the substrate is air-dried.

5. The method according to any one of claims 1 to 4, characterized in that: step by stepIn the step (3), 4Cr5MoSiV1 alloy steel powder is molten and deposited layer by adopting a synchronous powder feeding method; the powder feeding device is in two-way, four-way, six-way, eight-way or annular shape; the laser is selected from semiconductor laser, fiber laser, and CO₂YAG laser and Nd.

6. The method of claim 5, wherein: four paths of coaxially-fed 4Cr5MoSiV1 alloy steel powder are melted and deposited on a Q235 alloy steel substrate by adopting laser emitted by a YSL-4000 fiber laser.

7. The method according to any one of claims 1 to 6, wherein: the specific parameters of the laser three-dimensional forming process in the step (3) are set as follows: laser power 2500w, incident energy 125J/mm²The lapping rate is 50%, the powder feeding rate is 11.6g/min, the scanning speed is 5mm/s, the Z-axis lifting amount of adjacent deposition layers is 1mm, the diameter of a laser spot is 4mm, high-purity argon is used as powder feeding gas and protective gas, the purity of the argon is 99.999%, and a reciprocating type scanning path is adopted by a laser cladding head.

8. The method according to any one of claims 1 to 7, wherein: the heat treatment in the step (4) is specifically as follows: heating the formed part in a heating furnace from 25 ℃ to 650 ℃ at a heating rate of 8 ℃/min, preserving heat at 650 ℃ for 50min, closing a heating device after heat preservation is finished, cooling the formed part to 450 ℃ in the heating furnace, taking out the formed part, and cooling the taken out formed part to about 25 ℃ in air.

9. The method according to any one of claims 1 to 8, wherein: and (4) carrying out heat treatment in a muffle furnace, wherein the atmosphere in the heat treatment process is air.

10. A4 Cr5MoSiV1 alloy steel is characterized in that: prepared with the method according to any one of claims 1 to 9, wherein the 4Cr5MoSiV1 alloy steel has a tensile strength greater than 1500MPa and a yield strength greater than 1300 MPa; the elongation is greater than 12%, more preferably greater than 13%.

Technical Field

The invention relates to a method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel. More particularly, the invention relates to a method for regulating and controlling the mechanical properties of 4Cr5MoSiV1 alloy steel through a laser three-dimensional forming process and a heat treatment process. The invention belongs to the technical field of laser additive manufacturing.

Background

The comprehensive performance of the domestic autonomously produced 4Cr5MoSiV1 hot work die steel can meet the use requirements of conventional working conditions. However, in the aspect of preparing hot-work die steel with ultra-high die life or serving under extremely severe working conditions, the domestic large-scale, complex, precise and long-life high-end 4Cr5MoSiV1 hot-work die steel has obvious gap from the countries of America, Germany, Japan and the like in the aspects of technology, process, product level and the like. At present, the domestic high-end 4Cr5MoSiV1 die steel market is monopolized by foreign manufacturers such as the great identity, Hitachi, Wudhoum (one hundred victory), Bailu, Shanyang and the like. Among them, the problems of cleanliness and carbide segregation of high-end 4Cr5MoSiV1 die steel materials become one of the most important problems restricting the development of high-end die steel in China.

The high-end 4Cr5MoSiV1 die steel material prepared by the laser three-dimensional forming technology has the following advantages: (1) because a molten pool with small turbulence can be formed in the laser forming process, alloy steel powder can be fully melted, gas is not easy to be involved in the molten pool, and a nearly compact formed part can be obtained after the molten pool is solidified; (2) the laser three-dimensional forming technology is not limited by the size of the die steel member, and the large-size complex die steel member can be prepared by a layer-by-layer accumulation method.

However, the heat treatment process of the traditional processing method is still adopted for the deposited 4Cr5MoSiV1 alloy steel at present, and comprises stress relief annealing (heat preservation at 650 ℃ for 8 hours), austenitizing treatment (heat preservation at 1020 ℃ for 70-75 minutes), quenching and twice quenching and tempering treatment (heat preservation at 585 ℃ for 2.25-3 hours), the heat treatment process is not simplified according to the process characteristics of laser additive manufacturing of 4Cr5MoSiV1 alloy steel components, the heating temperature of the heat treatment process is high, the heat preservation time is long, and therefore the energy consumption and the processing period are larger. In addition, the mechanical property of the existing deposited and heat treated 4Cr5MoSiV1 alloy steel member is low, and the elongation can only reach about 6.5 percent, which is far lower than that of the 4Cr5MoSiV1 alloy steel member prepared by the traditional processing method.

Disclosure of Invention

In order to solve the technical problems, the invention provides a novel method for regulating and controlling the mechanical properties of 4Cr5MoSiV1 alloy steel, and 4Cr5MoSiV1 alloy steel with high tensile strength and high elongation is prepared by redesigning the laser three-dimensional forming process of 4Cr5MoSiV1 alloy steel and the heat treatment process matched with the laser three-dimensional forming process.

In a first aspect, the invention relates to a method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel, which comprises the following steps:

(1) pretreating 4Cr5MoSiV1 alloy steel powder;

(2) pre-treating a substrate material;

(3) preparing a 4Cr5MoSiV1 alloy steel molding piece by adopting a laser three-dimensional molding process;

(4) and (4) carrying out heat treatment on the 4Cr5MoSiV1 alloy steel formed piece obtained in the step (3).

In a preferred embodiment, in the step (1), the 4Cr5MoSiV1 alloy steel powder consists of the following components in percentage by mass: c: 0.35 wt%, V: 1 wt%, Cr: 5.05 wt%, Mn: 0.32 wt%, Mo: 1.35 wt%, Si: 0.95 wt% and the balance Fe.

In a preferred embodiment, in the step (1), 4Cr5MoSiV1 alloy steel powder is placed in a vacuum drying oven, kept at 110 ℃ for 4 hours and cooled to room temperature in the vacuum drying oven to remove moisture in the powder.

In a preferred embodiment, in the step (2), the substrate material is a rolled and annealed Q235 alloy steel plate, the surface of the substrate is polished by using # 200 sand paper, the surface of the substrate is cleaned by using absolute ethyl alcohol after the metallic luster is exposed on the surface of the substrate, and the substrate is prepared for standby after the surface of the substrate is air-dried.

In a preferred embodiment, in the step (3), 4Cr5MoSiV1 alloy steel powder is subjected to layer-by-layer fusion deposition by adopting a synchronous powder feeding method; the powder feeding device is in two-way, four-way, six-way, eight-way or annular shape; the laser is selected from semiconductor laser, fiber laser, and CO₂YAG laser and Nd.

In a more preferred embodiment, four-pass co-axial powdered 4Cr5MoSiV1 alloy steel powder was melt deposited on a Q235 alloy steel substrate using a laser emitted from a YSL-4000 fiber laser.

In a preferred embodiment, the specific parameters of the laser stereolithography process in step (3) are set as follows: laser power 2500w, incident energy 125J/mm²The lapping rate is 50%, the powder feeding rate is 11.6g/min, the scanning speed is 5mm/s, the Z-axis lifting amount of adjacent deposition layers is 1mm, the diameter of a laser spot is 4mm, high-purity argon is used as powder feeding gas and protective gas, the purity of the argon is 99.999%, and a reciprocating type scanning path is adopted by a laser cladding head. The method for calculating the laser incident energy comprises the following steps:in the formula P_LIs the laser power (W), V is the scanning speed, d_LLaser spot diameter.

In a preferred embodiment, the heat treatment of step (4) is specifically as follows: heating the formed part to 650 ℃ from 25 ℃ at a heating rate of 8 ℃/min in a heating furnace, gradually raising the temperature while keeping the temperature fields inside and outside the substrate and the deposited layer uniformly distributed, keeping the temperature at 650 ℃ for 50min (under the conditions of the heating temperature and the holding time, the 4Cr5MoSiV1 alloy steel can be recrystallized to a certain degree, and abnormal growth of recrystallized grains is avoided), closing a heating device after the temperature keeping is finished, cooling the formed part to 450 ℃ in the heating furnace, taking out the formed part (taking out the formed part from the heating furnace at the temperature so as to avoid first-class temper brittleness inside the formed part during heat treatment), and cooling the taken-out formed part to 25 ℃ in the air.

In a more preferred embodiment, the heat treatment of step (4) is performed in a muffle furnace, and the atmosphere during the heat treatment is air.

In a second aspect, the invention relates to a 4Cr5MoSiV1 alloy steel obtained with the method as described above, the 4Cr5MoSiV1 alloy steel having a tensile strength of more than 1500MPa and a yield strength of more than 1300 MPa; the elongation is greater than 12%, more preferably greater than 13%.

According to the invention, the high-tensile-strength 4Cr5MoSiV1 alloy steel formed part is prepared by optimizing laser three-dimensional forming process parameters, and then the deposited 4Cr5MoSiV1 alloy steel releases residual stress and is recrystallized to a certain degree in the deposited 4Cr5MoSiV1 alloy steel by adopting a heat treatment process matched with the laser three-dimensional forming process, so that the elongation of the 4Cr5MoSiV1 alloy steel is obviously improved. Compared with the existing heat treatment process, the mechanical property regulating method for laser forming of the 4Cr5MoSiV1 alloy steel can obviously reduce the heating temperature and the heating time in the heat treatment process on the premise of ensuring that a formed part has excellent tensile property and ductility, and further realizes the preparation of the 4Cr5MoSiV1 alloy steel with short period, low energy consumption and high performance.

Drawings

FIG. 1 is a temperature-time curve of a heat treatment process in the method of the present invention.

FIG. 2 shows Electron Back Scattering Diffraction (EBSD) results of as-deposited 4Cr5MoSiV1 alloy steel before and after the heat treatment process in the method of the present invention. (a) The alloy steel is deposited 4Cr5MoSiV1 alloy steel; (b) the alloy steel is 4Cr5MoSiV1 alloy steel in a deposition and heat treatment state.

FIG. 3 is a graph of the dimensions of a tensile test piece in the method of the present invention.

FIG. 4 is a graph of engineering stress-strain curves of as-deposited 4Cr5MoSiV1 alloy steel before and after a heat treatment process in accordance with the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Example 1: method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel

The method for regulating and controlling the mechanical property of 4Cr5MoSiV1 alloy steel is described by way of example with reference to the accompanying drawings, and comprises the following steps:

(1) the 4Cr5MoSiV1 alloy steel powder is pretreated. The 4Cr5MoSiV1 alloy steel powder comprises the following components in percentage by mass: c: 0.35 wt%, V: 1 wt%, Cr: 5.05 wt%, Mn: 0.32 wt%, Mo: 1.35 wt%, Si: 0.95 wt% and the balance Fe. And (3) putting the powder into a vacuum drying oven, preserving the heat for 4 hours at the temperature of 110 ℃, and cooling the powder to room temperature along with the oven so as to remove the moisture in the powder.

(2) The substrate material is pre-treated. The substrate material is a rolled and annealed Q235 alloy steel plate, and the specific size is 210mm multiplied by 190mm multiplied by 15 mm. And (3) polishing the surface of the substrate by using No. 200 abrasive paper, cleaning the surface of the substrate by using absolute ethyl alcohol after the metal luster is exposed on the surface of the substrate, and airing the surface of the substrate for later use.

(3) And preparing a 4Cr5MoSiV1 alloy steel molded part by using a laser three-dimensional forming process. Fusing and depositing four paths of coaxially-fed 4Cr5MoSiV1 alloy steel powder on the Q235 alloy steel substrate treated in the step (2) by adopting laser emitted by a YSL-4000 fiber laser, wherein the specific process parameters are set as follows: laser power 2500w, incident energy 125J/mm²The lapping rate is 50%, the powder feeding rate is 11.6g/min, the scanning speed is 5mm/s, the Z-axis lifting amount of adjacent deposition layers is 1mm, the diameter of a laser spot is 4mm, and high-purity argon is used as the argon gasThe purity of argon gas is 99.999% for powder feeding gas and protective gas, and the laser cladding head adopts a reciprocating scanning path. The laser stereolithography of 4Cr5MoSiV1 alloy steel has dimensions of 72mm x 28mm x10 mm and a number of 2, one of the moulded parts being used for heat treatment.

(4) Raising the temperature from 25 ℃ to 650 ℃ in a muffle furnace at the heating rate of 8 ℃/min, preserving the heat for 50min at 650 ℃, closing a heating device after the heat preservation is finished, cooling the formed part to 450 ℃ in the muffle furnace, taking out the formed part, and cooling the formed part taken out to about 25 ℃ in the air.

Example 2: microstructural analysis

The alloy steel in the deposition state 4Cr5MoSiV1 and the alloy steel in the deposition state and the heat treatment state 4Cr5MoSiV1 are finely ground until the surfaces of the alloy steel are free of scratches, and then electrolytic polishing is carried out. The electrolytic polishing electrolyte composition was a mixed solution of 8% perchloric acid, 80% ethanol and 12% water, so that the grain structure of the molded article can be studied using Electron Back Scattering Diffraction (EBSD). As shown in fig. 2(a), the grain morphology of the as-deposited 4Cr5MoSiV1 alloy steel is multi-lamellar martensite. As shown in FIG. 2(b), after heat treatment, a plurality of equiaxed grains appear in the heat-treated 4Cr5MoSiV1 alloy steel, the morphological characteristics of flaky martensite are obviously weakened, and the increase of equiaxed fine grains is beneficial to improving the ductility of the deposited 4Cr5MoSiV1 alloy steel.

Example 3: analysis of tensile Properties at Room temperature

Test tensile properties of the shaped articles were determined by means of an AG-X100kN testing machine, the tensile rate during the test being referred to GB/T228.1-2010. The dimensions of these tensile specimens (cf. ISO 6892-1: 2016) are shown in FIG. 3. The tensile curve of the formed part is shown in FIG. 4, and the tensile strength of the as-deposited 4Cr5MoSiV1 alloy steel is 1981 + -30 MPa, the yield strength is 1358 + -14 MPa, and the elongation is 8 + -0.7%. The tensile strength of the 4Cr5MoSiV1 alloy steel in the deposition and heat treatment state is 1575 +/-38 MPa, the yield strength is 1349 +/-25 MPa, and the elongation is 13 +/-0.9%. Therefore, the simplified heat treatment process designed by the invention can obviously improve the elongation of the deposited 4Cr5MoSiV1 alloy steel under the condition of realizing high tensile strength, thereby realizing the regulation and control of the mechanical properties of the deposited 4Cr5MoSiV1 alloy steel.

Although the present invention has been described in terms of the preferred embodiment, it is not intended that the invention be limited to the embodiment. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also belong to the protection scope of the present invention. The scope of the invention should therefore be determined with reference to the appended claims.