High-temperature-resistant, high-strength and high-plasticity micro-nano inoculant reinforced die steel and preparation method thereof

Abstract

The invention provides high-temperature-resistant, high-strength and high-plasticity micro-nano inoculant reinforced die steel and a preparation method. The preparation method of the high-temperature-resistant, high-strength and high-plasticity micro-nano inoculant reinforced die steel comprises the following steps: putting Ti powder, B powder and Al powder into a mixing machine to obtain a mixture; after the mixture is wrapped with aluminum foil, a thermal explosion reaction is carried out, an alloy containing a micrometer-size nucleating agent is obtained, C powder, Ti powder and Fe powder are put into a mixing machine to be mixed, a powder mixture is obtained, and the powder mixture is packaged with the aluminum foil; the method comprises the following steps: heating an alloy containing a micron-sized inoculant and commercial die steel to obtain a melt, adding an aluminum foil packaging powder mixture into the melt until the aluminum foil packaging powder mixture is completely molten, and carrying out impurity removal, vacuum casting, forging and heat treatment to obtain the high-temperature-resistant high-strength plastic micro-nano inoculant reinforced die steel with the yield strength of more than or equal to 970MPa and the tensile strength of more than or equal to 1033MPa at the temperature of more than or equal to 600 DEG C; and the fracture strain is greater than or equal to 13.1%.

Description

Technical Field

[0001] The present invention belongs to the technical field of die steel manufacturing, and particularly relates to a die steel with high temperature resistance, high strength and plasticity, and a micro-nano inoculant reinforced die steel and a preparation method thereof. Background Art

[0002] As a key basic material in modern manufacturing, the high-temperature service performance of die steel directly affects the processing accuracy and product quality of key processes such as precision forming and high-temperature die casting. In high-end manufacturing fields such as automobile manufacturing and aerospace, die steel usually needs to withstand continuous thermal loads exceeding 500 °C. Such a high-temperature environment will cause the toughness, wear resistance of the die to decrease, and then cause the die size to deform, ultimately affecting the product quality. Therefore, developing die steel with excellent high-temperature service performance has become the core research direction to break through the bottleneck of the die service life. The existing technology mainly increases the content of precious metal elements in die steel to introduce MC and M 2 C-type high-temperature strengthening phases, so as to improve the high-temperature performance of die steel. However, adding a large amount of alloying elements will not only increase the brittleness and processing difficulty of die steel, but also significantly increase the cost of die steel. In addition, the existing technology usually adopts quenching-deep cryogenic treatment-multi-stage tempering and other methods to improve the high-temperature performance of die steel, but the above processes will generate residual stress in die steel during application, resulting in deformation or cracking of die steel. In summary: Although the existing technology can improve the high-temperature service performance of die steel, it will lead to an increase in the high-temperature brittleness, cracking, processing difficulty of die steel, and it is difficult to synchronously improve the strength and plasticity, which is not conducive to large-scale industrial production. Therefore, how to reduce the raw material addition cost, simplify the process, synchronously improve the high-temperature service performance and strength and plasticity performance of die steel, and achieve large-scale industrial production while maintaining good toughness and processing performance of die steel is a technical problem to be solved urgently at present. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a die steel with high temperature resistance, high strength and plasticity, and a micro-nano inoculant reinforced die steel, and its preparation method includes the following steps:

[0004] (1) Mix Ti powder, B powder and Al powder in a mixer with a rotation speed of 30-50 r / min according to a mass ratio of 1-3: 2-6: 11-17 for 20-60 min to obtain powder mixture 1; after wrapping powder mixture 1 with aluminum foil, perform a thermal explosion reaction to obtain an alloy containing micron-sized inoculants, and mix C powder, Ti powder and Fe powder in a mixer with a rotation speed of 20-60 r / min according to a mass ratio of 1-2: 1-2: 6-8 for 15-45 min to obtain powder mixture 2; after packaging powder mixture 2 with aluminum foil, obtain mixture 3;

[0005] The particle size range of the described B powder is 60 - 120 μm, the particle size range of the Ti powder is 25 - 90 μm, the particle size range of the Al powder is 15 - 130 μm, the particle size range of the C powder is 40 - 150 μm, and the particle size range of the Fe powder is 10 - 80 μm;

[0006] The described thermal explosion reaction is as follows: under argon protection, the pressure is 0.1 - 0.5 MPa and the temperature is 800 - 1300 °C;

[0007] (2) The alloy containing the micron-sized inoculant obtained in step (1) and commercial die steel are held at 1750 - 1950 °C for 0.5 - 1.5 h according to a mass ratio of 0.01% - 0.03%:1 to obtain a melt. Then, the mixture 3 obtained in step (1) is added to the melt at 0.01% - 0.03% of the mass of the commercial die steel until it is completely melted. After impurity removal, vacuum casting, forging, and heat treatment, a high-temperature resistant, high-strength, and high-plasticity die steel strengthened by micro-nano inoculants is obtained;

[0008] The chemical composition of the described commercial die steel by mass percentage is as follows: Cr: 9.0 - 14.0 wt.%, C: 0.25 - 0.5 wt.%, Si: 0.50 - 1.00 wt.%, Mn: 0.25 - 1.50 wt.%, Mo: 0.15 - 3.00 wt.%, V: 0.10 - 1.00 wt.%, P: 0.025 - 0.045 wt.%, S: 0.025 - 0.045 wt.%, and Fe: the balance;

[0009] The described forging treatment: the forging temperature is 850 - 1150 °C and the forging ratio is 7 - 10:1;

[0010] The described heat treatment is as follows: after holding at 1020 - 1060 °C for 20 - 40 min, oil quenching is carried out, and then it is held at 540 - 600 °C for 4 - 6 hours;

[0011] When the described high-temperature resistant, high-strength, and high-plasticity die steel strengthened by micro-nano inoculants is used at ≥600 °C, its yield strength ≥970 MPa, tensile strength ≥1033 MPa, and fracture strain ≥13.1%; the high-temperature resistant, high-strength, and high-plasticity die steel strengthened by micro-nano inoculants contains 0.01 - 0.03 wt.% of micron-sized and 0.01 - 0.03 wt.% of nano-sized inoculants, and the two are uniformly dispersed inside the die steel.

[0012] Furthermore, in step (1), the particle size range of the described B powder is 80 - 110 μm, the particle size range of the Ti powder is 30 - 80 μm, the particle size range of the Al powder is 30 - 100 μm, the particle size range of the C powder is 50 - 130 μm, and the particle size range of the Fe powder is 40 - 70 μm.

[0013] Further, the thermal explosion reaction in step (1) is as follows: under argon protection, the pressure is 0.2 - 0.3 MPa, and the temperature is 900 - 1100 °C.

[0014] Further, the chemical composition of the commercial die steel in step (2) is as follows by mass percentage: Cr: 9.5 - 11.5 wt.%, C: 0.30 - 0.40 wt.%, Si: 0.70 - 0.90 wt.%, Mn: 0.30 - 0.50 wt.%, Mo: 0.50 - 2.00 wt.%, V: 0.50 - 0.80 wt.%, P: 0.03 - 0.04 wt.%, S: 0.03 - 0.04 wt.%, and the balance is Fe. Description of the Drawings

[0015] Figure 1 This is the high-temperature tensile curve of the high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant strengthened die steel 1 at 600 °C in Example 1 of the present invention;

[0016] Figure 2 This is the high-temperature tensile curve of the high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant strengthened die steel 2 at 620 °C in Example 2 of the present invention;

[0017] Figure 3 This is the high-temperature tensile curve of the high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant strengthened die steel 3 at 630 °C in Example 3 of the present invention;

[0018] Figure 4 This is the high-temperature tensile curve of the commercial die steel at 600 °C in step 2 of Examples 1 - 3 of the present invention. Detailed Embodiments

[0019] Example 1

[0020] The high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant strengthened die steel 1, and its preparation method includes the following steps:

[0021] (1) Mix Ti powder, B powder and Al powder in a mixer with a rotation speed of 40 r / min according to a mass ratio of 1:2:7 for 40 min to obtain powder mixture 1; after wrapping powder mixture 1 with aluminum foil, carry out a thermal explosion reaction to obtain alloy 1 containing micron-sized inoculants, mix C powder, Ti powder and Fe powder in a mixer with a rotation speed of 60 r / min according to a mass ratio of 3:3:14 for 20 min to obtain powder mixture 2; after packaging powder mixture 2 with aluminum foil, obtain mixture 3;

[0022] The particle size range of the B powder is 60 - 120 μm, the particle size range of the Ti powder is 25 - 90 μm, the particle size range of the Al powder is 15 - 130 μm, the particle size range of the C powder is 40 - 150 μm, and the particle size range of the Fe powder is 10 - 80 μm;

[0023] The thermal explosion reaction is as follows: under argon protection, pressure: 0.3 MPa, temperature: 900 °C.

[0024] (2) Alloy 1 containing micron-sized inoculant obtained in step (1) and commercial die steel are melted at 1850 °C for 1 h according to a mass ratio of 0.01%:1. Then, the mixture 3 obtained in step (1) is added to the melt at 0.01% of the mass of the commercial die steel until completely melted. After impurity removal, vacuum casting, forging, and heat treatment, a high-temperature resistant, high-strength, and high-plasticity die steel 1 strengthened by micro-nano inoculants is obtained;

[0025] The chemical composition of the commercial die steel is as follows by mass percentage: Cr: 9.95 wt.%, C: 0.32 wt.%, Si: 0.82 wt.%, Mn: 0.31 wt.%, Mo: 1.88 wt.%, V: 0.72 wt.%, P: 0.03 wt.%, S: 0.03 wt.%, and the balance is Fe.

[0026] The forging treatment: the forging temperature is 1000 °C, and the forging ratio is 9:1.

[0027] The heat treatment is as follows: after holding at 1040 °C for 30 min, oil quenching is carried out, and then it is held at 580 °C for 5 hours.

[0028] The high-temperature resistant, high-strength, and high-plasticity die steel 1 strengthened by micro-nano inoculants contains 0.01 wt.% of micron-level and 0.01 wt.% of nano-level inoculants, and the two are uniformly dispersed inside the die steel.

[0029] The high-temperature tensile curve of the high-temperature resistant, high-strength, and high-plasticity die steel 1 prepared in this example at 600 °C is as Figure 1 shown: its yield strength is 970 MPa, tensile strength is 1033 MPa, and fracture strain is 16.4%. The high-temperature tensile curve of the commercial die steel at 600 °C in step (2) is as Figure 4 shown: its yield strength, tensile strength, and fracture strain are 861 MPa, 965 MPa, and 11.1% respectively. Compared with the commercial die steel, the yield strength, tensile strength, and fracture strain of the high-temperature resistant, high-strength, and high-plasticity die steel 1 prepared in this example are increased by 12.6%, 7.1%, and 47.1% respectively. In addition, the high-temperature resistant, high-strength, and high-plasticity die steel 1 obtained in the present invention simultaneously improves the strength and plasticity at high temperatures, and at the same time avoids problems such as brittleness, cracking, and increased processing difficulty, and is suitable for industrial production.

[0030] Example 2

[0031] High-temperature resistant, high-strength and high-plasticity, micro-nano inoculant-reinforced die steel 2, and its preparation method includes the following steps:

[0032] (1) Mix Ti powder, B powder and Al powder in a mixer with a rotation speed of 30 r / min according to a mass ratio of 1:2:17 for 60 min to obtain powder mixture 1; after wrapping powder mixture 1 with aluminum foil, carry out a thermal explosion reaction to obtain alloy 2 containing micron-sized inoculants, and mix C powder, Ti powder and Fe powder in a mixer with a rotation speed of 40 r / min according to a mass ratio of 1:1:8 for 35 min to obtain powder mixture 2; after packaging powder mixture 2 with aluminum foil, obtain mixture 3;

[0033] The particle size range of the B powder is 60 - 120 μm, the particle size range of the Ti powder is 25 - 90 μm, the particle size range of the Al powder is 15 - 130 μm, the particle size range of the C powder is 40 - 150 μm, and the particle size range of the Fe powder is 10 - 80 μm;

[0034] The thermal explosion reaction is as follows: under argon protection, the pressure is 0.2 MPa and the temperature is 1000 °C.

[0035] (2) According to a mass ratio of 0.02%:1, mix alloy 2 containing micron-sized inoculants obtained in step (1) with commercial die steel and keep it at 1750 °C for 1.5 h to obtain a melt, then add mixture 3 obtained in step (1) to the melt according to 0.02% of the mass of the commercial die steel until it is completely melted, and after impurity removal, vacuum casting, forging and heat treatment, obtain high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant-reinforced die steel 2;

[0036] The chemical composition of the commercial die steel is calculated by mass percentage: Cr: 9.95 wt.%, C: 0.32 wt.%, Si: 0.82 wt.%, Mn: 0.31 wt.%, Mo: 1.88 wt.%, V: 0.72 wt.%, P: 0.03 wt.%, S: 0.03 wt.%, Fe: the balance.

[0037] The forging treatment: the forging temperature is 850 °C and the forging ratio is 10:1.

[0038] The heat treatment is as follows: keep it at 1020 °C for 40 min, then carry out oil quenching, and then keep it at 540 °C for 6 hours.

[0039] The high-temperature resistant, high-strength and high-plasticity, micro-nano inoculant-reinforced die steel 2 contains 0.02 wt.% of micron-level and 0.02 wt.% of nano-level inoculants, and the two are uniformly dispersed inside the die steel.

[0040] In this embodiment, the prepared high-temperature resistant, high-strength and high-plasticity die steel 2 strengthened by micro-nano inoculants has a high-temperature tensile curve at 620 °C as follows: Figure 2 As shown: its yield strength is 971 MPa, its tensile strength is 1053 MPa, and its fracture strain is 15.5%. When compared with commercial die steel used at 600 °C, the yield strength, tensile strength, and fracture strain of the high-temperature resistant, high-strength and high-plasticity die steel 2 strengthened by micro-nano inoculants prepared in this embodiment are increased by 12.6%, 9.1%, and 39.6% respectively. In addition, the high-temperature resistant, high-strength and high-plasticity die steel 2 obtained in the present invention simultaneously improves the strength and plasticity at higher temperatures, and at the same time avoids problems such as easy brittleness, cracking, and increased processing difficulty, and is suitable for industrial production.

[0041] Example 3

[0042] The preparation method of the high-temperature resistant, high-strength and high-plasticity die steel 3 strengthened by micro-nano inoculants includes the following steps:

[0043] (1) Mix Ti powder, B powder and Al powder in a mixer with a rotation speed of 50 r / min according to a mass ratio of 3:6:11 for 20 min to obtain powder mixture 1; after wrapping powder mixture 1 with aluminum foil, carry out a thermal explosion reaction to obtain alloy 3 containing micro-sized inoculants. Mix C powder, Ti powder and Fe powder in a mixer with a rotation speed of 30 r / min according to a mass ratio of 1:1:3 for 45 min to obtain powder mixture 2; after packaging powder mixture 2 with aluminum foil, obtain mixture 3;

[0044] The particle size range of the B powder: 60 - 120 μm, the particle size range of the Ti powder: 25 - 90 μm, the particle size range of the Al powder: 15 - 130 μm, the particle size range of the C powder: 40 - 150 μm, the particle size range of the Fe powder: 10 - 80 μm;

[0045] The thermal explosion reaction is: under argon protection, pressure: 0.1 MPa, temperature: 1100 °C.

[0046] (2) According to a mass ratio of 0.03%:1, add the alloy 3 containing micro-sized inoculants obtained in step (1) and commercial die steel and keep it warm at 1950 °C for 0.5 h to obtain a melt, then add the mixture 3 obtained in step (1) to the melt according to 0.03% of the mass of the commercial die steel until it is completely melted. After impurity removal, vacuum casting, forging and heat treatment, the high-temperature resistant, high-strength and high-plasticity die steel 3 strengthened by micro-nano inoculants is obtained;

[0047] The chemical composition of the commercial die steel is as follows by mass percentage: Cr: 9.95 wt.%, C: 0.32 wt.%, Si: 0.82 wt.%, Mn: 0.31 wt.%, Mo: 1.88 wt.%, V: 0.72 wt.%, P: 0.03 wt.%, S: 0.03 wt.%, and the balance is Fe.

[0048] The forging treatment is as follows: the forging temperature is 1150 °C, and the forging ratio is 7:1.

[0049] The heat treatment is as follows: after holding at 1060 °C for 20 min, oil quenching is carried out, and then it is held at 600 °C for 4 hours.

[0050] The high-temperature high-strength and high-plasticity, micro-nano inoculant-strengthened die steel 3 contains 0.03 wt.% of micron-sized and 0.03 wt.% of nano-sized inoculants, and the two are uniformly dispersed inside the die steel.

[0051] The high-temperature high-strength and high-plasticity, micro-nano inoculant-strengthened die steel 3 prepared in this example has a high-temperature tensile curve at 630 °C as Figure 3 shown: its yield strength is 1061 MPa, its tensile strength is 1157 MPa, and its fracture strain is 13.1%. Compared with the commercial die steel when used at 600 °C, the yield strength, tensile strength, and fracture strain of the high-temperature high-strength and high-plasticity, micro-nano inoculant-strengthened die steel 3 prepared in this example are increased by 23.2%, 19.8%, and 18% respectively. In addition, the high-temperature high-strength and high-plasticity, micro-nano inoculant-strengthened die steel 3 obtained in the present invention simultaneously improves the strength and plasticity at higher temperatures, and at the same time avoids problems such as easy brittleness, cracking, and increased processing difficulty, and is suitable for industrial production.

[0052] In summary: Compared with commercial die steels, the die steel obtained in the present invention, when used at the same temperature or a higher temperature, while improving the strength and plasticity, avoids problems such as brittleness, cracking, and increased processing difficulty, and is suitable for industrial production; in addition, compared with the prior art, the present invention controls the inoculant content to be ≤0.06 wt%, saving costs and simplifying the process, simultaneously improving the strength and plasticity of the die steel and avoiding problems such as brittleness, cracking, and increased processing difficulty, and is suitable for industrial production. The components, ratios, and process parameters used in Examples 1-3 of the present invention are all different. Among them, the die steel obtained in Example 3 has the best strength, and the die steel obtained in Example 1 has the best plasticity. However, the particle content ratios and process parameters added in Examples 1 and 3 are different. This shows that the best performance of the die steel obtained in the present invention is not determined by a certain component, ratio, or process parameter, but is achieved through the synergistic regulation of the interaction between components, component ratios, processes, and process parameters. In addition, compared with commercial die steels, when used at the same temperature or a higher temperature, the die steels obtained in all examples of the present invention have better performance than commercial die steels, simultaneously improving the strength and plasticity of the die steel and avoiding problems such as brittleness, cracking, and increased processing difficulty. Therefore, compared with the prior art, the present invention has achieved a significant improvement in technical effects, and only within the scope of the claims of the present invention can the simultaneous improvement of the high-temperature strength and plasticity of the die steel and the avoidance of problems such as brittleness, cracking, and increased processing difficulty be achieved; in addition, the micron-sized and nano-sized inoculants obtained in the present invention are uniformly dispersed in the die steel matrix without agglomeration, and the inoculant content is controlled to be ≤0.06 wt%, with a low raw material addition cost and a simplified process. Therefore, the present invention simplifies the process and reduces the production cost, simultaneously improving the high-temperature strength and plasticity of the die steel, and is suitable for industrial production.

Claims

1. High temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel, characterized by: Its preparation method comprises the following steps: (1) Ti powder, B powder and Al powder are mixed in a mixer at a speed of 30-50 r / min for 20-60 min in a mass ratio of 1-3:2-6:11-17 to obtain powder mixture 1; powder mixture 1 is wrapped with aluminum foil and subjected to thermal explosion reaction to obtain an alloy containing a micron-sized inoculant; C powder, Ti powder and Fe powder are mixed in a mixer at a mass ratio of 1-2:1-2:6-8 for 15-45 min at 20-60 r / min to obtain powder mixture 2; powder mixture 2 is wrapped with aluminum foil to obtain mixture 3; The particle size range of the B powder is 60-120 μm, the particle size range of the Ti powder is 25-90 μm, the particle size range of the Al powder is 15-130 μm, the particle size range of the C powder is 40-150 μm, and the particle size range of the Fe powder is 10-80 μm; The thermal explosion reaction is: under argon protection, pressure: 0.1-0.5MPa, temperature: 800-1300°C; (2) the alloy containing the micron-sized inoculant obtained in step (1) and commercial die steel are kept at 1750-1950° C. for 0.5-1.5 h in a mass ratio of 0.01%-0.03%:1 to obtain a melt, and then the mixture 3 obtained in step (1) is added to the melt in a mass ratio of 0.01%-0.03% of the mass of the commercial die steel until it is completely melted, and after impurity removal, vacuum casting, forging and heat treatment, a high-temperature resistant, high-strength and plastic micro-nano inoculant-reinforced die steel is obtained; The chemical composition of the commercial mold steel is calculated by mass percentage: Cr: 9.0-14.0wt.%, C: 0.25-0.5wt.%, Si: 0.50-1.00wt.%, Mn: 0.25-1.50wt.%, Mo: 0.15-3.00wt.%, V: 0.10-1.00wt.%, P: 0.025-0.045wt.%, S: 0.025-0.045wt.%, Fe: balance; The forging process: the forging temperature is 850-1150°C, and the forging ratio is 7-10:1; The heat treatment is as follows: after keeping the temperature at 1020-1060°C for 20-40 minutes, oil quenching is performed, and then keeping the temperature at 540-600°C for 4-6 hours; When the high temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel is used at ≥600°C, its yield strength is ≥970MPa, its tensile strength is ≥1033MPa, and its fracture strain is ≥13.1%; the high temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel contains 0.01-0.03wt.% of micron-level and 0.01-0.03wt.% of nano-level inoculants, which are uniformly dispersed inside the mold steel.

2. The high temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel according to claim 1, characterized in that: The particle size range of the B powder in step (1) is 80-110 μm, the particle size range of the Ti powder is 30-80 μm, the particle size range of the Al powder is 30-100 μm, the particle size range of the C powder is 50-130 μm, and the particle size range of the Fe powder is 40-70 μm.

3. The high temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel according to claim 1, characterized in that: The thermal explosion reaction in step (1) is carried out under the protection of argon gas at a pressure of 0.2-0.3 MPa and a temperature of 900-1100°C.

4. The high temperature resistant, high strength and plasticity, micro-nano inoculant reinforced mold steel according to claim 1, characterized in that: The chemical composition of the commercial mold steel described in step (2) is calculated by mass percentage: Cr: 9.5-11.5wt.%, C: 0.30-0.40wt.%, Si: 0.70-0.90wt.%, Mn: 0.30-0.50wt.%, Mo: 0.50-2.00wt.%, V: 0.50-0.80wt.%, P: 0.03-0.04wt.%, S: 0.03-0.04wt.%, Fe: balance.

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