CN115181901B - High-strength and high-toughness hard low-temperature bainite hot work die steel and preparation method thereof - Google Patents

High-strength and high-toughness hard low-temperature bainite hot work die steel and preparation method thereof Download PDF

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CN115181901B
CN115181901B CN202210357469.5A CN202210357469A CN115181901B CN 115181901 B CN115181901 B CN 115181901B CN 202210357469 A CN202210357469 A CN 202210357469A CN 115181901 B CN115181901 B CN 115181901B
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die steel
work die
hot work
steel
hot
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CN115181901A (en
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王天生
孙晓文
王岳峰
冯熠婷
荣盛伟
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Yanshan University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention discloses high-strength and high-toughness hard low-temperature bainite hot work die steel which is characterized by comprising the following chemical components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities. In addition, the invention also discloses a preparation method of the high-strength and high-toughness hard low-temperature bainite hot work die steel. The secondary tempering structure of the hot work die steel still maintains the shape of low-temperature bainite, and carbide is separated out from the structure, so that the hot work die steel has good thermal stability; the preparation process flow is simple and feasible, is beneficial to industrial production, and has high preparation efficiency.

Description

High-strength and high-toughness hard low-temperature bainite hot work die steel and preparation method thereof
Technical Field
The invention relates to the technical field of die steel, in particular to high-strength and high-toughness hard low-temperature bainite hot working die steel and a preparation method thereof, wherein the low-temperature bainite hot working die steel has the tensile strength of not lower than 1900 MPa, the hardness of not lower than 53 HRC and the unnotched impact energy of not lower than 500J, and is particularly suitable for the fields of thermoforming, machining and the like.
Background
The production and manufacturing level of the mould industry in the modern industry has attracted a great deal of attention to the manufacturing industry, and the industrial level has become one of important marks for measuring the national manufacturing level. With the global economic industry structure adjustment, the world market determines that China will develop into a large die manufacturing country. In the world die production values, the manufacturing proportion of the Chinese die is obviously improved, and the use amount of die steel is also obviously increased.
The hot working die steel is most widely applied in the die industry, wherein the main steel types in the hot working die steel are H13, 3Cr2W8V and 5CrMnMo steel, and the hot working die steel has higher toughness, thermal fatigue resistance, high hardenability and better wear resistance. However, the domestic traditional hot-work die steel is compared with the imported hot-work die steel, and the domestic material has the defects of band segregation, along-grain carbide and the like, so that the problems of poor isotropic performance, shorter service time and the like are caused, and the service life of the die is influenced.
In order to meet the actual production requirement, a plurality of research and development units also carry out a plurality of improvements and research and development works of hot work die steel, and the following description is made: the publication No. CN101240400B proposes a low-cost hot work die steel comprising the following components: 0.38-0.42%, si:0.9 to 1.1%, mn: 0.3-0.5%, W:0.9 to 1.2%, cr: 4.8-5.8%, mo: 0.45-0.55%, V: 0.25-0.45%, and final heat treatment adopts a quenching and tempering process, wherein the hardness after tempering at 570 ℃ is not more than 52 HRC, and the tensile strength is not more than 1800 MPa. The invention patent with the publication number of CN11748733A 'an H13 hot work die steel and a preparation method thereof' comprises the following components in percentage by mass: 0.36-0.42%, si: 0.18-0.23%, mn:0.39 to 0.46%, ni: 0.06-0.12%, cr: 4.5-5.00%, mo: 2.20-2.70%, V: 0.5-0.8%, after quenching and secondary tempering treatment, the tempered hardness is not more than 40 HRC, and the tensile strength is not more than 1400 MPa. The patent document with the publication number of CN110484812A proposes a high-performance hot stamping die steel and a manufacturing process thereof, wherein the components (mass percent) of the steel C:0.78%, si:1.00%, mn:0.40%, cr:5.50%, mo:1.60%, V:0.45 percent, and the room temperature impact energy of the hot stamping die steel after twice tempering at 580 ℃ is more than or equal to 260J.
However, under the condition of high-temperature tempering, carbide is easy to precipitate and easily gather and grow up in hot-work die steel with higher Cr element content, so that the service life of the hot-work die steel is reduced. In addition, the proper addition of the alloy elements such as Ni, V and the like is likely to be beneficial to improving the toughness of the hot work die steel.
Moreover, the hot-work die steel belongs to martensitic steel, and the toughness and the thermal stability of the low-temperature bainite are higher than those of martensite, so that the low-temperature bainite can show performance advantages when being used for the hot-work die steel, and is one of the development directions for improving the tempering performance of the die steel. Therefore, it is necessary to develop a high-strength and high-toughness hard low-temperature bainite hot work die steel with excellent comprehensive mechanical properties so as to accelerate the large-scale development and popularization and application of the hot work die steel in China.
Disclosure of Invention
In order to solve the problem that the prior art can not meet the use requirements of high toughness, strength and thermal stability of die materials, the invention provides high-strength and high-toughness hard low-temperature bainite hot work die steel and a preparation method thereof, and the comprehensive mechanical properties of the hot work die steel are improved through component design and a heat treatment process.
In order to solve the technical problems, the invention adopts the following technical scheme:
the high-strength and high-toughness hard low-temperature bainite hot work die steel comprises the following chemical components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities.
The chemical composition ratio satisfies: n is more than or equal to 0.16 and less than or equal to 0.26, ts is more than or equal to 266 and less than or equal to 330, tr is more than or equal to 405 and less than or equal to 525,
wherein n= (2.5 ni—cr+mo)/(2si+mn+1.1v)
Ts=560-306[C]-30[Mn]-12[Si] -20[Ni]-22[Cr]-12[V]+12[Mo]，
Tr=830-110[C]-50[Mn]+41.6[Si]-35[Ni]-60[Cr]-40[V]-20[Mo]。
In addition, the invention also provides a preparation method of the high-strength and high-toughness hard low-temperature bainite hot work die steel, which comprises the following steps: A. smelting: feeding according to the design requirement of the composition components of steel, smelting in a vacuum induction furnace and casting into steel ingots, wherein the composition components of the steel comprise the following components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities; B. hot rolling and annealing: hot rolling the steel ingot, annealing the hot rolled sample, and finally air-cooling to room temperature; C. spheroidizing annealing: heating the sample subjected to the heat treatment in the step B to 830-870 ℃ for heat preservation for 1-1.5 h, cooling to 740-770 ℃ along with a furnace for heat preservation for 2-2.5 h, and finally cooling to 500 ℃ along with the furnace, discharging and air cooling; D. isothermal quenching treatment: heating the sample subjected to the heat treatment in the step C to 990-1050 ℃, preserving heat for 20-30 min, then rapidly placing the sample into a salt bath furnace with the temperature of 280-350 ℃ for isothermal quenching of 1-3 h, and then air-cooling to room temperature; E. tempering: and D, heating the sample subjected to the heat treatment in the step D to 555-565 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling, and then heating to 575-585 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling.
The technical scheme of the invention realizes the aim through the following principle and mode.
(1) On the basis of accurately understanding the principle of controlling the content of the multi-element alloying elements of the high-strength hot working die steel C, si, mn, cr, ni and V, mo, each chemical component (in percentage by weight below) of the low-temperature bainite hot working die steel is reasonably designed and controlled.
C: the C element has stronger solid solution strengthening effect, and part of the C element is dissolved into a matrix in hot work die steel through a heat treatment process to improve the hardness and strength of the matrix, and the other part of the C element is combined with alloy elements to form alloy carbide to enhance wear resistance. The preferable content range is 0.45-0.55.
Mn: mn element has solid solution strengthening effect, and can improve strength, hardness and hardenability of ferrite and austenite. Has stronger affinity with S element, avoids FeS from forming at the grain boundary, and eliminates the harmful effect of S element. The preferable content range is 0.20 to 0.50.
Si: the Si element is an element that promotes ferrite formation and has a solid solution strengthening effect on ferrite. Meanwhile, si is an effective element for improving tempering resistance, reduces the diffusion speed of carbon in ferrite, ensures that carbide precipitated during tempering is not easy to aggregate, and increases tempering stability. The preferable content range is 1.20-1.50.
Mo: mo element has solid solution strengthening effect, and Mo is dissolved in austenite to improve the hardenability of steel. Meanwhile, mo element is combined with C element to precipitate Mo in martensite during tempering 2 C, the main alloying element causing the secondary hardening phenomenon. In addition, mo element can prevent tempering brittleness and improve tempering stability of steelAnd qualitatively, the hot work die steel can be tempered at a higher temperature, and the plasticity is improved. The preferable content range is 1.10-1.80.
V: in hot work die steel, the V element has the function of refining the structure and grains of the steel, and as with the Mo element, the V element forms a VC reinforced secondary hardening effect with the C element during tempering. Meanwhile, due to the thermal stability of VC, the tempering stability of steel can be increased. The preferable content range is 0.70-1.30.
Cr: cr element can increase the hardenability of steel, can improve the hardness and wear resistance of high-carbon steel without embrittling the steel, has good high-temperature oxidation resistance and oxidation resistance medium corrosion resistance, and also increases the heat resistance of the steel. But the Cr with higher content can form M with high chromium with carbon in the quenching and tempering process 23 C 6 The invention adopts the component design for reducing the Cr content, inhibits the formation of Cr carbide, promotes the C to be fully combined with carbide stabilizing element V, mo, and forms MC and M with the advantages of small size, dispersion distribution and good high-temperature stability 2 Type C carbide, thereby improving the heat resistance and thermal fatigue properties of the steel. The preferable content range is 2.90-3.50.
Ni: the Ni element has the functions of solid solution strengthening and improving hardenability, the ferrite grains are thinned, the plasticity and toughness of the hot-work die steel are improved, and the hot strength of the hot-work die steel can be improved by combining the Ni element and the Mo element. The preferable content range is 0.8-1.20.
(2) Besides the reasonable control of the chemical composition range of each element, the following innovative technical requirements must be set, and the relative addition amount of a part of key elements must be accurately regulated so as to exert the key regulation and control effects of the elements on the comprehensive mechanical properties of the steel, such as strength, hardness, impact toughness and the like.
(a) Through regulating the relation of 0.16-0.26, ni, cr, mo, si, mn, V alloy elements are required to be subjected to element content proportioning according to n= (2.5 Ni-Cr+Mo)/(2Si+Mn+1.1V). Ni and Mn are favorable for the impact toughness of the hot-working die steel of the invention, and Mo, V and Si are favorable for the improvement of the tempering hardness of the hot-working die steel of the invention. The reduction of Cr is beneficial to the improvement of comprehensive mechanical properties.
(b) According to the regulation relation 266 < Ts < 330 >, 405 < Tr < 525 > and the requirement C, ni, cr, mo, si, mn, V alloy elements, according to' Ts=560-306 < C > -30 < Mn > -12 < Si > -20 < Ni > -22 < Cr > -12 < V > +12 < Mo >, tr=830-110 < C > -50 < Mn > +41.6 < Si > -35 < Ni > -60 < Cr > -40 < V > -20 < Mo >, the austenite-martensite initial transformation temperature Ts of the high-toughness low-temperature bainite hot working die steel is controlled between 266-330 ℃ and the austenite-bainite initial transformation temperature Tr is controlled between 405-525 ℃, the phase-change temperature interval is controlled in a lower range, which is favorable for inhibiting nucleation of an upper bainite structure, promoting generation of a low-temperature bainite structure, ensuring small size of the low-temperature bainite structure, and further improving the mechanical property of the hot working die steel.
The beneficial effects of the invention are as follows:
1. the structure of the high-strength and high-toughness hard low-temperature bainite hot work die steel is mainly a low-temperature bainite structure, namely bainitic ferrite and film-shaped residual austenite among ferrite laths. Wherein the low temperature bainite structure is not less than 75%.
2. The secondary tempering structure of the high-strength and high-toughness hard low-temperature bainite hot work die steel still maintains the appearance of the low-temperature bainite, and carbide is separated out from the structure, so that the high-strength and high-toughness hard low-temperature bainite hot work die steel has good thermal stability.
3. The unnotched impact energy of the secondary tempering sample of the high-strength and high-toughness hard low-temperature bainite hot working die steel is not lower than 500J, the tensile strength is not lower than 1900 MPa, and the hardness is not lower than 53.0 HRC.
4. The high-strength and high-toughness hard low-temperature bainite hot work die steel alloy system is reasonable in control, the preparation process flow is simple and feasible, industrial production is facilitated, and the preparation efficiency is high.
The present invention will be described in detail with reference to the accompanying drawings.
Drawings
FIG. 1 is a scanning electron microscope photograph of an austempered structure of a high-strength and high-toughness hard low-temperature bainitic hot work die steel prepared in example 1;
FIG. 2 is a scanning electron microscope photograph of an austempered structure of the high-strength and high-toughness hard low-temperature bainitic hot work die steel prepared in example 2;
FIG. 3 is a scanning electron microscope photograph of an austempered structure of the high-strength and high-toughness hard low-temperature bainitic hot work die steel prepared in example 3;
FIG. 4 is a scanning electron microscope photograph of a secondary tempering structure of the high-strength and high-toughness hard low-temperature bainitic hot work die steel prepared in example 4;
FIG. 5 is a scanning electron microscope photograph of a secondary tempering structure of the high-strength and high-toughness hard low-temperature bainitic hot work die steel prepared in example 5;
FIG. 6 is a scanning electron microscope photograph of a secondary tempering structure of the high-strength and high-toughness hard low-temperature bainite hot work die steel prepared in example 6.
Detailed Description
The invention provides high-strength and high-toughness hard low-temperature bainite hot work die steel, which comprises the following chemical components in percentage by mass: 0.45-0.55 part of C, 1.2-1.50 part of Si, 0.20-0.50 part of Mn, 2.90-3.50 parts of Cr, 1.10-1.80 parts of Mo, 0.70-1.30 parts of V, 0.80-1.20 parts of Ni, less than 0.01 part of P, less than 0.005 part of S, and the balance of Fe and unavoidable impurities, wherein the hot work die steel structure is low-temperature bainite.
In addition, the proportion of the chemical components is as follows: n is more than or equal to 0.16 and less than or equal to 0.26, ts is more than or equal to 266 and less than or equal to 330, and Tr is more than or equal to 405 and less than or equal to 525.
Wherein n= (2.5 ni—cr+mo)/(2si+mn+1.1v)
Ts=560-306[C]-30[Mn]-12[Si] -20[Ni]-22[Cr]-12[V]+12[Mo]，
Tr=830-110[C]-50[Mn]+41.6[Si]-35[Ni]-60[Cr]-40[V]-20[Mo]。
The invention also provides a preparation method of the high-strength and high-toughness hard low-temperature bainite hot work die steel, which comprises the following steps.
A. Smelting: feeding according to the design requirements of the composition components of the steel, smelting in a vacuum induction furnace and casting into steel ingots.
The steel comprises the following components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities. In addition, the content of the alloy elements must also satisfy the following weight percentages: n is more than or equal to 0.16 and less than or equal to 0.26, ts is more than or equal to 266 and less than or equal to 330, and Tr is more than or equal to 405 and less than or equal to 525.
B. Hot rolling and annealing: and (3) hot rolling the steel ingot, annealing the hot rolled sample, and finally air-cooling to room temperature.
C. Spheroidizing annealing: and C, heating the sample subjected to the heat treatment in the step B to 830-870 ℃ for heat preservation for 1-1.5 hours, cooling to 740-770 ℃ along with a furnace for heat preservation for 2-2.5 hours, and finally cooling to 500 ℃ along with the furnace, and discharging and air cooling.
D. Isothermal quenching treatment: and C, heating the sample subjected to heat treatment in the step C to 990-1050 ℃, preserving heat for 20-30 min, rapidly placing the sample into a salt bath furnace with the temperature of 280-350 ℃ for isothermal quenching of 1-3 h, and then air-cooling to room temperature.
E. Tempering: and D, heating the sample subjected to the heat treatment in the step D to 555-565 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling, and then heating to 575-585 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling.
The invention will be described in detail with reference to specific examples.
Example 1, see fig. 1, in this example.
A. The mass percentages are as follows: the proportions of C0.45, si 1.20, mn 0.25, cr 2.9, mo 1.20, V0.7, ni 0.9, P0.0075, S0.0041 and the balance of Fe are calculated, the charging proportion is calculated, and the mixture is smelted by a vacuum high-frequency induction furnace and is remelted by electroslag, and then the mixture is poured into a round ingot with the diameter of phi 80 mm.
B. Annealing and hot rolling: and heating the steel ingot to 1150 ℃, preserving heat for 5 h, carrying out homogenizing annealing, and cooling along with the furnace. Hot rolling and cogging the round ingot at 1150 ℃ to obtain a steel plate with the thickness of 25 mm; and finally, carrying out post-rolling annealing treatment on the hot rolled and cogged steel plate, wherein the annealing heating temperature is 880 ℃, and cooling along with a furnace after heat preservation of 1.5 and h.
C. Spheroidizing annealing: and heating the hot-rolled plate blank to 860 ℃ for heat preservation of 1.5 and h, cooling to 760 ℃ along with a furnace for heat preservation of 2.5 and h, and finally cooling to 500 ℃ along with the furnace, discharging and air cooling.
D. Isothermal quenching: the plate subjected to spheroidizing annealing is placed into a furnace with the temperature of 1000 ℃, kept for 20 min, then rapidly placed into a salt bath furnace with the temperature of 350 ℃ and the like for 1.5 h, and then discharged from the furnace for air cooling to the room temperature.
Scanning electron microscope for the plate manufactured by the embodimentSEM) analysis, hardness, impact and tensile test, the results are shown in table 1 and fig. 1. As can be seen from fig. 1: the structure is a low-temperature bainite structure, and the volume fraction of the structure is 76%. The low temperature bainite mold steel was prepared in this example, n=0.16, ts=327 ℃, tr=511 ℃, wherein the low temperature bainite structure hardness was 49.3 HRC, the unnotched impact energy was not less than 500J, the charpy U-notch impact energy (KU 2 ) 24 to J, and the tensile strength is 1820 MPa. See in particular the data in table 1.
Example 2, see fig. 2, in this example.
A. The mass percentages are as follows: the proportions of C0.50, si 1.34, mn 0.32, cr 3.2, mo 1.55, V0.98, ni 1.00, P0.0075, S0.0035 and the balance of Fe are calculated, the charging proportion is calculated, and the mixture is smelted by a vacuum high-frequency induction furnace and is remelted by electroslag, and then the mixture is poured into a round ingot with the diameter of phi 80 mm.
B. Annealing and hot rolling: and heating the steel ingot to 1150 ℃, preserving heat for 5 h, carrying out homogenizing annealing, and cooling along with the furnace. Hot rolling and cogging the round ingot at 1150 ℃ to obtain a steel plate with the thickness of 25 mm; and finally, carrying out post-rolling annealing treatment on the hot rolled and cogged steel plate, wherein the annealing heating temperature is 880 ℃, and cooling along with a furnace after heat preservation of 1.5 and h.
C. Spheroidizing annealing: and heating the hot-rolled slab to 860 ℃ and preserving heat by 1.2. 1.2 h, cooling to 750 ℃ along with a furnace, preserving heat by 2 h, cooling to 500 ℃ along with furnace cooling, and discharging and air cooling.
D. Isothermal quenching: the plate subjected to spheroidizing annealing is placed into a furnace with the temperature of 1020 ℃ for heat preservation for 20 min, then is rapidly placed into a salt bath furnace with the temperature of 320 ℃ for isothermal 2 h, and is discharged from the furnace for air cooling to the room temperature.
The sheet material prepared in this example was subjected to Scanning Electron Microscope (SEM) analysis, hardness, impact and tensile test, and the results are shown in table 1 and fig. 2. As can be seen from fig. 2: the structure is a low-temperature bainite structure, and the volume fraction of the structure is 80%. The low temperature bainite mold steel was prepared in this example, n=0.26, ts=298 ℃, tr=462 ℃, wherein the low temperature bainite structure hardness was 50.2 HRC, the unnotched impact energy was not less than 500J, the charpy U-notch impact energy (KU 2 ) 30J, and the tensile strength is 1845 MPa. See in particular the data in table 1.
Example 3 referring to fig. 3, in this example.
A. The mass percentages are as follows: the mixture ratio of C0.55, si 1.50, mn 0.48, cr 3.5, mo 1.75, V1.30, ni 1.20, P0.0055, S0.0045 and the balance of Fe is calculated, the charging proportion is calculated, and the round ingot with the diameter of phi 80 mm is cast after smelting and electroslag remelting in a vacuum high-frequency induction furnace.
B. Annealing and hot rolling: and heating the steel ingot to 1150 ℃, preserving heat for 5 h, carrying out homogenizing annealing, and cooling along with the furnace. Hot rolling and cogging the round ingot at 1150 ℃ to obtain a steel plate with the thickness of 25 mm; and finally, carrying out post-rolling annealing treatment on the hot rolled and cogged steel plate, wherein the annealing heating temperature is 880 ℃, and cooling along with a furnace after heat preservation of 1.5 and h.
C. Spheroidizing annealing: and heating the hot-rolled plate blank to 840 ℃ and preserving heat for 1.2 h, cooling to 740 ℃ along with the furnace and preserving heat for 2 h, and finally cooling to 500 ℃ along with the furnace and discharging from the furnace for air cooling.
D. Isothermal quenching: the plate subjected to spheroidizing annealing is placed into a furnace with the temperature of 1050 ℃, kept for 20 min, then quickly placed into a salt bath furnace with the temperature of 285 ℃ and the like for 2.5 h, and then discharged from the furnace for air cooling to the room temperature.
The sheet material prepared in this example was subjected to Scanning Electron Microscope (SEM) analysis, hardness, impact and tensile test, and the results are shown in table 1 and fig. 3. As can be seen from fig. 3: the structure is a low-temperature bainite structure, and the volume fraction of the structure is 82%. The low temperature bainite mold steel was prepared in this example, n=0.25, ts=265 ℃, tr=406 ℃, wherein the low temperature bainite structure hardness was 51.2 HRC, the unnotched impact energy was not less than 500J, the charpy U-notch impact energy (KU 2 ) 40J and a tensile strength of 1865 MPa. See in particular the data in table 1.
Example 4, see fig. 4, in this example: the austempered sheet material in example 1 was placed in a 560 ℃ box furnace, tempered 1 h with heat preservation, and cooled to room temperature by air-cooling. Then placing the mixture into a box furnace for the second time, heating to 580 ℃ and tempering to 1 h, discharging and air cooling to room temperature.
The sheet material prepared in this example was subjected to Scanning Electron Microscope (SEM) analysis, hardness, impact and tensile test, and the results are shown in table 1 and fig. 4. From FIG. 4, it can be seen thatAnd (3) out: tempered bainite, precipitated carbides, and spherical undissolved carbide structures were prepared in this example. The hardness of the tissue is 53.5 HRC, the impact energy of the non-notch is not less than 500J, and the impact energy of the Charpy U-notch (KU) 2 ) 20. 20J, and the tensile strength is 1920 MPa. See in particular the data in table 1.
Example 5, see fig. 5, in this example: the austempered sheet material in example 2 was placed in a box furnace at 560 ℃ and tempered 1 h with heat preservation, and then taken out of the furnace and air cooled to room temperature. Then placing the mixture into a box furnace for the second time, heating to 580 ℃ and tempering to 1 h, discharging and air cooling to room temperature.
The sheet material prepared in this example was subjected to Scanning Electron Microscope (SEM) analysis, hardness, impact and tensile test, and the results are shown in table 1 and fig. 5. As can be seen from fig. 5: tempered bainite, precipitated carbides, and spherical undissolved carbide structures were prepared in this example. The hardness of the tissue is 53.5 HRC, the impact energy of the non-notch is not less than 500J, and the impact energy of the Charpy U-notch (KU) 2 ) 28J, and the tensile strength was 1935 MPa. See in particular the data in table 1.
Example 6, see fig. 6, in this example: the austempered sheet material in example 3 was placed in a 560 ℃ box furnace, tempered 1 h with heat preservation, and cooled to room temperature by air-cooling. Then placing the mixture into a box furnace for the second time, heating to 580 ℃ and tempering to 1 h, discharging and air cooling to room temperature.
The sheet material prepared in this example was subjected to Scanning Electron Microscope (SEM) analysis, hardness, impact and tensile test, and the results are shown in table 1 and fig. 6. As can be seen from fig. 6: tempered bainite, precipitated carbides, and spherical undissolved carbide structures were prepared in this example. The hardness of the tissue is 55.2 HRC, the impact energy of the non-notch is not less than 500J, and the impact energy of the Charpy U-notch (KU) 2 ) 30J, and the tensile strength was 1966 MPa. See in particular the data in table 1.
The mechanical properties of the high strength and toughness hard low temperature bainitic hot work die steels of examples 1-6 are shown in Table 1 below
。
In conclusion, the high-strength and high-toughness hard low-temperature bainite hot work die steel obtained by the scheme of the invention has high preparation efficiency and excellent tempering performance.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same; while the invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that: modifications may be made to the specific embodiments of the present invention or equivalents may be substituted for part of the technical features thereof; without departing from the spirit of the invention, it is intended to cover the scope of the invention as claimed.

Claims (7)

1. A high-strength and high-toughness hard low-temperature bainite hot work die steel is characterized by comprising the following chemical components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities;
the chemical components of Si, mn, cr, ni, V and Mo in the low-temperature bainite hot work die steel are as follows in percentage by mass: n is more than or equal to 0.16 and less than or equal to 0.26,
n=(2.5Ni-Cr+Mo)/(2Si+Mn+1.1V)；
the chemical components of C, si, mn, cr, ni, V and Mo in the low-temperature bainite hot work die steel are as follows in percentage by mass: 266-330, 405-525,
Ts=560-306[C]-30[Mn]-12[Si] -20[Ni]-22[Cr]-12[V]+12[Mo]，
Tr=830-110[C]-50[Mn]+41.6[Si]-35[Ni]-60[Cr]-40[V]-20[Mo]；
the preparation of the die steel comprises the following steps:
A. smelting: feeding according to the design requirements of the composition components of the steel, smelting in a vacuum induction furnace and casting into steel ingots;
B. hot rolling and annealing: hot rolling the steel ingot, annealing the hot rolled sample, and finally air-cooling to room temperature;
C. spheroidizing annealing: heating the sample subjected to the heat treatment in the step B to 830-870 ℃ for heat preservation for 1-1.5 h, cooling to 740-770 ℃ along with a furnace for heat preservation for 2-2.5 h, and finally cooling to 500 ℃ along with the furnace, discharging and air cooling;
D. isothermal quenching treatment: heating the sample subjected to the heat treatment in the step C to 990-1050 ℃, preserving heat for 20-30 min, then rapidly placing the sample into a salt bath furnace with the temperature of 280-350 ℃ for isothermal quenching of 1-3 h, and then air-cooling to room temperature;
E. tempering: and D, heating the sample subjected to the heat treatment in the step D to 555-565 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling, and then heating to 575-585 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling.
2. The high strength and toughness hard low temperature bainitic hot work die steel according to claim 1, wherein the structure of the low temperature bainitic hot work die steel is composed of a low temperature bainitic structure and undissolved carbide.
3. The high strength and toughness hard low temperature bainitic hot work die steel according to claim 2, wherein the low temperature bainitic structure comprises bainitic ferrite and thin film retained austenite.
4. The high strength and toughness hard low temperature bainitic hot work die steel according to claim 2, wherein the low temperature bainitic structure content is not less than 75%.
5. The high strength and toughness hard low temperature bainitic hot work die steel according to any one of claims 1 to 4, wherein the tensile strength of the hot work die steel is not lower than 1900 MPa.
6. The high strength and toughness hard low temperature bainitic hot work die steel according to any one of claims 1 to 4, wherein the hot work die steel has a hardness of not less than 53.0 HRC and a notch-free impact energy of not less than 500J.
7. A method for preparing a high strength and toughness hard low temperature bainitic hot work die steel, for preparing the low temperature bainitic hot work die steel according to any one of claims 1 to 6, comprising the steps of:
A. smelting: feeding according to the design requirements of the composition components of the steel, smelting in a vacuum induction furnace and casting into steel ingots,
the steel comprises the following components in percentage by mass: 0.45-0.55% of C, 1.2-1.50% of Si, 0.20-0.50% of Mn, 2.90-3.50% of Cr, 1.10-1.80% of Mo, 0.70-1.30% of V, 0.80-1.20% of Ni, less than 0.01% of P, less than 0.005% of S, and the balance of Fe and unavoidable impurities;
B. hot rolling and annealing: hot rolling the steel ingot, annealing the hot rolled sample, and finally air-cooling to room temperature;
C. spheroidizing annealing: heating the sample subjected to the heat treatment in the step B to 830-870 ℃ for heat preservation for 1-1.5 h, cooling to 740-770 ℃ along with a furnace for heat preservation for 2-2.5 h, and finally cooling to 500 ℃ along with the furnace, discharging and air cooling;
D. isothermal quenching treatment: heating the sample subjected to the heat treatment in the step C to 990-1050 ℃, preserving heat for 20-30 min, then rapidly placing the sample into a salt bath furnace with the temperature of 280-350 ℃ for isothermal quenching of 1-3 h, and then air-cooling to room temperature;
E. tempering: and D, heating the sample subjected to the heat treatment in the step D to 555-565 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling, and then heating to 575-585 ℃ for heat preservation for 1-1.5 hours, discharging and air cooling.
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JP2000202548A (en) * 1999-01-19 2000-07-25 Sanyo Special Steel Co Ltd Clad metallic mold for hot pressing and manufacture thereof
JP2000226635A (en) * 1999-02-05 2000-08-15 Sumitomo Metal Ind Ltd Hot tool steel excellent in high temperature strength and toughness
CN1410586A (en) * 2002-10-18 2003-04-16 东风汽车公司 High performance hot working die steel for medium and small cross profile machine forging mould
CN109266970A (en) * 2018-11-28 2019-01-25 攀钢集团攀枝花钢铁研究院有限公司 High-nitrogen, high-chromium plastic die steel and its smelting and heat treatment method
CN109487166A (en) * 2018-12-21 2019-03-19 北京科技大学 A kind of high strength at high temperature low-carbon heated die steel and preparation method thereof
CN111893391A (en) * 2020-08-12 2020-11-06 燕山大学 Nano bainite hot work die steel and preparation method thereof
CN111893395A (en) * 2020-06-09 2020-11-06 黄石市鑫楚精密模具股份有限公司 High-strength die steel and heat treatment method thereof

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000202548A (en) * 1999-01-19 2000-07-25 Sanyo Special Steel Co Ltd Clad metallic mold for hot pressing and manufacture thereof
JP2000226635A (en) * 1999-02-05 2000-08-15 Sumitomo Metal Ind Ltd Hot tool steel excellent in high temperature strength and toughness
CN1410586A (en) * 2002-10-18 2003-04-16 东风汽车公司 High performance hot working die steel for medium and small cross profile machine forging mould
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