CN117165835A - Powder metallurgy precipitation hardening high speed steel - Google Patents
Powder metallurgy precipitation hardening high speed steel Download PDFInfo
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- 229910000997 High-speed steel Inorganic materials 0.000 title claims abstract description 58
- 238000004881 precipitation hardening Methods 0.000 title claims abstract description 58
- 238000004663 powder metallurgy Methods 0.000 title claims abstract description 44
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910052742 iron Inorganic materials 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 13
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910000765 intermetallic Inorganic materials 0.000 claims abstract description 8
- 239000002245 particle Substances 0.000 claims description 8
- 229910000831 Steel Inorganic materials 0.000 abstract description 59
- 239000010959 steel Substances 0.000 abstract description 59
- 238000005496 tempering Methods 0.000 abstract description 11
- 239000011159 matrix material Substances 0.000 abstract description 7
- 230000032683 aging Effects 0.000 abstract description 5
- 239000006104 solid solution Substances 0.000 abstract description 4
- 239000000243 solution Substances 0.000 abstract 1
- 238000009827 uniform distribution Methods 0.000 abstract 1
- 239000000843 powder Substances 0.000 description 37
- 238000000034 method Methods 0.000 description 35
- 230000008569 process Effects 0.000 description 33
- 229910045601 alloy Inorganic materials 0.000 description 22
- 239000000956 alloy Substances 0.000 description 22
- 238000010438 heat treatment Methods 0.000 description 16
- 238000001513 hot isostatic pressing Methods 0.000 description 16
- 239000000203 mixture Substances 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 238000003860 storage Methods 0.000 description 11
- 238000005242 forging Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 238000002360 preparation method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 239000011261 inert gas Substances 0.000 description 8
- 238000001556 precipitation Methods 0.000 description 7
- 238000012216 screening Methods 0.000 description 7
- 238000000889 atomisation Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 239000002893 slag Substances 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 238000013461 design Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
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- 238000005266 casting Methods 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
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- 239000007789 gas Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
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- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910001315 Tool steel Inorganic materials 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
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- 230000005494 condensation Effects 0.000 description 2
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- 229910000734 martensite Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910000521 B alloy Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910000846 In alloy Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 241001085205 Prenanthella exigua Species 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
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- 238000011068 loading method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910000601 superalloy Inorganic materials 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
- 238000010200 validation analysis Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
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Abstract
The invention provides powder metallurgy precipitation hardening high-speed steel, which comprises the following chemical components in percentage by mass: si:0.5% -1.2%; co:16.0% -30.0%; w:0% -5.0%; mo:15.0% -22.0%; (mo+w/2): 15.0% -23.0%; ce:0.01-0.1%, the balance being iron and impurities, and the steel mainly consists of an iron-based cubic solid solution matrix and a mu phase of intermetallic compounds (IMC for short) in the matrix, wherein the mu phase is (Fe, co) 7 (Mo+W/2) 6 Type (2). The powder metallurgy precipitation hardening high-speed steel prepared by the invention has fine mu phase size, uniform distribution and excellent mechanical property, the hardness after solution aging treatment can reach more than 65HRC, the notch-free impact toughness value can reach more than 11.0J, and particularly the tempering softening resistance is outstanding.
Description
Technical Field
The invention relates to novel high-speed steel, in particular to powder metallurgy precipitation hardening high-speed steel.
Background
High-speed steel is widely used in the field of machining and manufacturing as a first-choice material for machining other materials at high speed. Precipitation hardening steel is a carbon-free iron-based martensitic precipitation hardening tool alloy, and due to the low content of C in the composition, no substantial carbide precipitation occurs, and the structure is mainly an intermetallic compound (i.e., IMC) of the iron-based matrix and Fe-Co-Mo-W, the hardening effect being due to IMC particles precipitated during aging. The precipitation hardening high-speed steel has good grindability, tempering softening resistance and dimensional stability.
When the alloy is prepared by adopting the traditional casting and forging process, the alloy composition is easily segregated in the solidification process due to the limitation of the slow cooling solidification characteristic of molten steel in the process, the bad structure can not be effectively solved by a hot working mode, the bad structure can have bad influence on the alloy performance, the high-speed steel performance including strength, toughness, grindability and the like is in a low level, and the requirements of high-end processing and manufacturing on the material performance and service life are difficult to meet.
Disclosure of Invention
In view of this, the present invention provides a powder metallurgy precipitation hardening high-speed steel having a good structure and excellent mechanical properties.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
a powder metallurgy precipitation hardening high-speed steel, characterized in that it comprises the following chemical components in mass percent:
Si：0.5％-1.2％；
Co：16.0％-30.0％；
W：0％-5.0％；
Mo：15.0％-22.0％；
(Mo+W/2)：15.0％-23.0％；
Ce：0.01％-0.1％；
the balance of iron and impurities;
and, intermetallic compounds (i.e., IMC phases) in the precipitation hardening steel are μ phases, the μ phases being of the type (Fe, co) 7 (Mo+W/2) 6 。
The invention can promote precipitation of mu phase when preparing precipitation hardening high-speed steel by adopting a powder metallurgy process through reasonable design of alloy components and proportions, thereby improving tempering softening resistance and toughness of the steel.
Co (cobalt) is solid-dissolved in the matrix to make the alloy a martensitic steel, thereby improving the hardness and strength of the ferritic alloy by one grade, and the increase of Co content can properly reduce the toughness of the steel, and in the present invention, the Co element content is in the range of 16.0% -30.0%, preferably 18.0% -30.0%.
The W (tungsten) has high melting point, can increase the strength and tempering stability and the high-temperature creep resistance of the steel, and can also increase the tempering softening resistance of the steel, so that the steel has less surface layer temperature rise and less hardness drop in the processing and using processes, and the W element content range is 0% -5.0%, preferably 0% -3.0% in the invention.
Mo (molybdenum) acts in the same way as W, can completely replace W, and is cheaper than W. On the other hand, the higher the Mo content, the higher the initial precipitation temperature of the mu phase, and the larger the granularity of the mu phase, the Mo element content in the present invention is in the range of 15% to 22.0%, preferably 15.0% to 20.0%.
Si (silicon) is not a carbide forming element but is used as a deoxidizer and matrix strengthening element to improve the strength and hardness of steel, but Si is excessive to lower the plasticity and toughness of the matrix, and the Si content of the present invention is controlled to be 0.5% to 1.2%, and preferably 0.5% to 1%.
Ce (cerium) is added in the refining stage, can react with oxygen, sulfur and the like in molten steel to generate compounds, is discharged from the molten steel as impurities, and can play roles in deoxidation, desulfurization and modification.
As a limitation of the above manner, the powder metallurgy precipitation hardening high-speed steel comprises the following chemical components in mass percent:
Si：0.5％-1％；
Co：18.0％-30.0％；
W：0％-3.0％；
Mo：15％-20.0％；
(Mo+W/2)：15.0％-21.5％；
the balance being iron and impurities.
In order to achieve better comprehensive performance, each chemical component in the powder metallurgy precipitation hardening high-speed steel is controlled within a required range.
Further, at least 80% of the volume fraction of the mu phase has a particle size of 1.5 μm or less.
Further, the maximum particle size of the μ phase is not more than 5.5 μm.
Further, the volume fraction of the mu phase in the powder metallurgy precipitation hardening high-speed steel is 12-20%.
Further, the powder metallurgy precipitation hardening high-speed steel has a hardness of 65HRC or more and an unnotched sample impact toughness value of 11.0J or more.
In the invention, precipitation hardening steel is prepared by adopting a powder metallurgy process, the problem of element segregation can be solved, and thus, a uniform tissue structure is obtained, and the main steps of preparing precipitation hardening high-speed steel by adopting the powder metallurgy process comprise: atomizing powder preparation and hot isostatic pressing, the molten steel is rapidly cooled into powder, alloy elements in the molten steel are completely solidified without segregation, and after the powder is solidified into a material, the structure is fine and uniform, so that the performance is greatly improved compared with precipitation hardening high-speed steel produced by the traditional casting or electroslag process.
The invention also provides a preparation method for preparing the powder metallurgy precipitation hardening high-speed steel, which specifically comprises the following steps:
s1. preparing precipitation hardening molten steel according to the chemical composition requirement and transferring to a ladle;
s1.1. maintaining the superheat degree of molten steel by heating covering slag covered on the upper surface of molten steel in a ladle; introducing inert gas into the bottom of the ladle to stir molten steel;
s1.2, flowing molten steel into a preheated tundish through a flow guide pipe at the bottom of a ladle at a stable flow rate, and applying protective slag to the upper surface of the molten steel when the molten steel enters the lower end surface of the flow guide pipe buried in the tundish;
s1.3. continuously compensating and heating the tundish, and maintaining the superheat degree of molten steel;
s1.4, atomizing the molten steel from the tundish into an atomizing chamber, pulverizing by adopting inert gas, settling the obtained metal powder to the bottom of the atomizing chamber, then entering a powder storage tank body with protective atmosphere, screening the metal powder by a protective screening device, and then entering the powder storage tank body for storage;
and s1.5, transferring the metal powder in the powder storage tank body to a hot isostatic pressing sheath under the protection of inert gas, carrying out vacuum degassing treatment on the hot isostatic pressing sheath after the metal powder is filled and compacted in a vibrating mode, carrying out seal welding treatment on the end portion of the hot isostatic pressing sheath, and then carrying out hot isostatic pressing treatment to enable the metal powder to be fully densified and consolidated to finish a powder metallurgy process.
The powder metallurgy process comprises non-vacuum melting atomization pulverizing and hot isostatic pressing links, and the process adopts full-flow protection to control the oxygen content and the form of precipitated phases and optimize the performance of precipitation hardening steel.
The covering slag of the ladle has the functions of isolating air and conducting and heating. Inert gas is introduced into the bottom of the ladle through the air holes, so that the temperature of molten steel at different positions in the ladle is balanced, and the removal of harmful impurities is accelerated. The flow guiding pipe at the bottom of the steel ladle plays a role in guiding the molten steel, so that turbulence is reduced in the molten steel circulation process, slag is prevented from being rolled up, impurities are prevented from entering the next link, and on the other hand, the flow guiding pipe is prevented from exposing the molten steel to the air, and the oxygen content of the molten steel is prevented from rising. Before molten steel enters the tundish, the tundish needs to be preheated to prevent local condensation or early precipitation of a second phase when the molten steel enters the tundish.
The powder storage tank is internally provided with atmosphere protection and forced cooling functions, the powder protection screening device plays a role in protecting the powder screening process and simultaneously prevents powder from flying, the powder storage tank body is in sealing connection with the hot isostatic pressing sheath, the hot isostatic pressing sheath is filled with inert gas before powder filling to discharge air, and the oxygen content in the powder can be prevented from rising.
The precipitation hardening high-speed steel is prepared by adopting a powder metallurgy process, the component design is reasonable, various effective protection means are adopted in the preparation process to prevent molten steel and powder from being polluted, and the specific chemical composition and the rapid condensation process of the powder metallurgy form the components (Fe, co) 7 (Mo+W/2) 6 The intermetallic compound mu phase is finer and more uniform, the hardness of more than 65HRC is obtained after heat treatment, the intermetallic compound mu phase has excellent hardness, tempering softening resistance and toughness matching, and the application requirements of different types can be met.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a microstructure of precipitation hardening high-speed steel prepared in example 1 of the present invention;
FIG. 2 is a microstructure of precipitation hardening high-speed steel prepared in example 2 of the present invention;
FIG. 3 is a microstructure of precipitation hardening high-speed steel prepared in example 4 of the present invention;
FIG. 4 is a microstructure of precipitation hardening high-speed steel prepared in example 5 of the present invention;
FIG. 5 is a microstructure of precipitation hardening high-speed steel prepared in example 6 of the present invention;
FIG. 6 is a microstructure of precipitation hardening high-speed steel prepared in example 7 of the present invention;
FIG. 7 is a microstructure of the powder metallurgy process high-speed steel prepared in comparative example A of the present invention;
FIG. 8 is a microstructure of the high-speed steel for electroslag process prepared in comparative example B according to the present invention.
FIG. 9 is a comparative chart of tempering resistance of examples 1 to 8 and comparative examples A and B of the present invention
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention relates to powder metallurgy precipitation hardening high-speed steel, which comprises the following chemical components in percentage by mass: si:0.5% -1.2%; co:16.0% -30.0%; w:0% -5.0%; mo:15.0% -22.0%; (mo+w/2): 15.0% -23.0%; ce:0.01% -0.1%; the balance of iron and impurities; and, intermetallic compound (i.e., IMC phase) in the powder metallurgy high-speed steel is a μ phase, and the type of μ phase is (Fe, co) 7 (Mo+W/2) 6 。
The invention can promote precipitation of mu phase when preparing precipitation hardening high-speed steel by adopting a powder metallurgy process through reasonable design of alloy components and proportions, thereby improving tempering softening resistance and toughness of the steel.
The invention also relates to a method for preparing the precipitation hardening high-speed steel, which is easy to generate segregation to reduce performance due to slow solidification speed when the preparation is carried out by adopting a traditional ingot casting or electroslag process. Therefore, in order to ensure that the prepared precipitation hardening high-speed steel ingot has uniform composition and structure, tiny mu phase and high purity, the invention adopts a powder metallurgy process to prepare the steel ingot, and the steel ingot is forged to obtain the required bar product.
Specifically, the preparation method of the invention comprises the following steps:
s1. the precipitation hardening steel liquid of the invention is filled into a smelting ladle, and the loading weight of the liquid steel is 1.5-8 tons;
s1.1. electrifying and heating covering slag covered on the upper surface of molten steel in a steel ladle by adopting a graphite electrode, introducing argon or nitrogen into the bottom of the steel ladle to stir the molten steel, and opening a molten steel guide pipe when the superheat degree of the molten steel reaches 100-200 ℃;
s1.2, flowing molten steel into a tundish preheated to 800-1200 ℃ through a flow guide pipe at the bottom of a ladle at the flow rate of 10-50Kg/min, and applying covering slag when the molten steel enters the tundish and is buried at the lower end face of the flow guide pipe;
s1.3. continuously compensating and heating the tundish in the atomizing powder making process, and maintaining the superheat degree of molten steel at 100-200 ℃;
s1.4, enabling molten steel to enter an atomization chamber through the bottom of a tundish, opening an atomization gas injection valve, atomizing by adopting nitrogen as a gas medium to prepare powder, wherein the purity of the nitrogen is more than or equal to 99.999%, the oxygen content is less than or equal to 2ppm, and the pressure of an outlet of a gas nozzle is 1.0-5.0MPa; the molten steel is crushed into liquid drops under the nitrogen spraying effect, and is rapidly cooled into metal powder, flies to the bottom of an atomization chamber, and then enters a powder storage tank body with protective atmosphere; after atomization powder preparation is finished, cooling the metal powder in the powder storage tank body to room temperature, and screening the metal powder by a protection screening device; the inside of the cavity of the protection screening device is filled with positive-pressure inert gas, and the inside of the powder storage tank is provided with positive-pressure inert gas protection atmosphere;
s1.5, filling metal powder in a powder storage tank body into a hot isostatic pressing sheath, firstly introducing inert gas into the hot isostatic pressing sheath to exhaust air, then hermetically connecting the hot isostatic pressing sheath with the powder storage tank body, and implementing vibration operation in the filling process to increase the filling density of the metal powder; and (3) carrying out vacuumizing and degassing treatment on the hot isostatic pressing sheath after the completion, heating and preserving the temperature of the hot isostatic pressing sheath at 200-600 ℃ in the vacuumizing process, continuously heating and preserving the temperature for more than 2 hours after degassing to 0.01Pa, then carrying out seal welding treatment on the end part of the sheath, finally carrying out hot isostatic pressing treatment on the sheath, and after the hot isostatic pressing temperature is 1120-1180 ℃ and the maintaining time is more than or equal to 1 hour under the pressure of more than or equal to 100MPa, completely compacting and solidifying the metal powder, and then cooling along with a furnace to complete the powder metallurgy process.
S2, forging and opening the blank
The precipitation hardening high-speed steel is further forged and deformed according to the requirement to obtain bars or forgings with preset shapes and sizes, and different heat treatment systems are adopted to obtain different performances, and the heat treatment comprises annealing, solid solution and aging.
The annealing treatment is designed to heat the bar or the forging to 870-890 ℃, keep the temperature for more than or equal to 2 hours, then cool the bar or the forging to below 550 ℃ at the speed of less than or equal to 15 ℃/hour, and cool the bar or the forging to below 50 ℃ in a furnace or in a static air cooling way; the solid solution treatment comprises preheating the annealed bar or forging at 810-850 ℃, uniformly placing the bar or forging into 1170-1200 ℃ for heat preservation for 15-40 minutes, and then cooling with oil; aging is then carried out at a temperature in the range 580-650 ℃ for 3-4 hours, followed by air cooling to 50 ℃.
The powder metallurgy process adopted by the invention adopts various effective protection means to prevent the molten steel and powder from being polluted in the preparation process, and the high-purity ingot material provides guarantee for finally obtaining the high-performance alloy ingot material.
The powder metallurgy precipitation hardening high-speed steel of this example and its preparation will be further described below with reference to the accompanying drawings and in specific preparation examples and comparative examples, and corresponding performance tests.
Eight precipitation hardening high-speed steels having different compositions were obtained in total from examples 1 to 8 by the aforementioned production method, and compared with powder metallurgy tool steel (alloy a) and cast forging tool steel (alloy B), the results were as follows:
table 1: chemical composition of various examples of high speed steels
| Alloy | Si | Co | W | Mo | (Mo+W/2) | Ce | C | Mn | Cr | V | Fe |
| Example 1 | 0.58 | 24.96 | 0.01 | 19.91 | 19.91 | 0.05 | - | - | - | - | Allowance of |
| Example 2 | 0.60 | 27.74 | 0.01 | 15.80 | 15.80 | 0.08 | - | - | - | - | Allowance of |
| Example 3 | 0.58 | 24.96 | 0.02 | 20.3 | 20.31 | 0.05 | - | - | - | - | Allowance of |
| Example 4 | 0.50 | 16.00 | 0 | 15.0 | 15.0 | 0.01 | - | - | - | - | Allowance of |
| Example 5 | 1.20 | 30.00 | 5.00 | 22.0 | 24.50 | 0.1 | - | - | - | - | Allowance of |
| Example 6 | 0.50 | 18.0 | 0.0 | 15.0 | 15.0 | 0.01 | - | - | - | - | Allowance of |
| Example 7 | 1.0 | 30.0 | 3.0 | 20.0 | 21.5 | 0.1 | - | - | - | - | Allowance of |
| Example 8 | 1.10 | 17.0 | 4.0 | 21.0 | 23.0 | 0.04 | - | - | - | - | Allowance of |
| Comparative example A | 0.37 | 10.56 | 6.51 | 6.94 | 10.19 | - | 2.23 | 0.28 | 4.22 | 6.44 | Allowance of |
| Comparative example B | 0.33 | 9.78 | 9.52 | 9.83 | 14.59 | - | 1.24 | 0.36 | 4.11 | 3.15 | Allowance of |
The "-" in the table indicates that the element is not contained, or the element content is little to no analysis.
Wherein, examples 1 to 8 are powder metallurgy precipitation hardening high-speed steel of the invention, which is prepared by adopting a powder metallurgy process, firstly adopting an air atomization powder preparation process to prepare powder, then carrying out hot isostatic pressing densification on the powder, then preparing an ingot blank with the diameter phi of 400mm, and further carrying out thermal deformation processing to obtain bars with the diameter phi of 60 mm.
Comparative example a prepared by powder metallurgy process, hot deformed to a bar with diameter phi 57 mm; comparative example B, prepared by the electroslag remelting process, was hot deformed to a diameter phi 61mm bar.
Microstructure analysis
Fig. 1 to 6 are schematic diagrams of microstructures of prepared precipitation hardening steel forgings according to example 1, example 2, example 4, example 5, example 6 and example 7, respectively, fig. 7 is a schematic diagram of a microstructure of alloy a, and fig. 8 is a schematic diagram of a microstructure of alloy B, based on a scanning electron microscope.
It is apparent that the off-white hardened phase of fig. 1-6 is dispersed throughout the matrix, which can significantly improve the wear resistance, toughness and service life of the material. Two precipitated phases are included in fig. 7 and 8, one of which is bright white and has a large size, and the other of which is off-white and has a small size.
Examples 1 to 8 after heat treatment were compared with the content of precipitated phases, the particle size, and the composition of alloy A, B, as shown in table 2.
Table 2: content of precipitated phase and chemical composition
Where "-" indicates that the element is absent or is present in a small amount without analysis.
As can be seen from Table 2, in examples 1 to 8, the detected IMC was mainly a μ phase, of the type (Fe, co) 7 (Mo+W/2) 6 The main component is Fe, co, mo, W and a small amount of alloy elements such as Si. In alloys A and B, the detected strengthening phase is mainly of two major types, one is VC type carbide, the components are mainly C, V, cr and Fe, the other is Cr-rich carbide, the type is (Cr, fe) C type carbide, the components are mainly C, V, cr and Fe, and a small amount of Mo is contained.
The precipitation hardening high-speed steel has the volume fraction of mu phase reaching 12% -20%, fine granularity, most mu phase granularity smaller than or equal to 1.5 mu m, maximum size smaller than 5.5 mu m, fine precipitated phase size and high dispersity, and the mu phase high-temperature aggregation resistance is higher than that of carbide, so that the material has better service life.
In the alloy A prepared by adopting the powder metallurgy process, VC-type carbide is the finest, but (Cr, fe) C-type carbide with a large quantity and a size range of 5-9 mu m also exists in the structure. In the B alloy prepared by adopting the electroslag remelting process, although the size of VC type carbide is similar to the size of mu phase in the precipitation hardening high-speed steel example, a large number of (Cr, fe) C type carbide with the size of 5-9 mu m also exists in a structure.
(II) Heat treatment hardness and impact toughness analysis
In order to verify the influence of a heat treatment system on the performance of the precipitation hardening high-speed steel prepared by the invention, heat treatment processes with different solid solution temperatures and aging temperatures are set for carrying out heat treatment on the prepared bar, and verification parameter setting references GB/T230.1 and GB/T229 are used for reference.
The hardened steels and alloys A, B obtained in examples 1 to 8 were heat treated, and the hardness and impact toughness obtained are shown in Table 3.
Table 3: comparison of mechanical Properties
As can be seen from Table 3, the impact toughness of the precipitation hardened high-speed steel of the present invention is relatively low, but the measured values meet the toughness requirements of the application field, and the precipitation hardened high-speed steel of the present invention is particularly suitable for use in applications with less impact load.
(III) tempering softening resistance analysis
The heat treatment process used for comparison of temper softening resistance of the hardened steels and alloys A, B prepared in examples 1 to 8 is shown in Table 4, the temper softening resistance results are shown in FIG. 9, and reference is made to GB/T230.1, GB/T229 for validation parameter settings.
Table 4: tempering and softening resistant process
As can be seen from fig. 8, the precipitation hardening steel of the present invention exhibits more excellent temper softening resistance.
In addition, the precipitation hardening steel of the present invention is prepared under the above-mentioned implementation conditions due to the limitation of the statistical image analysis software of the number of precipitated phase particles, and the size of the individual μ phase may exist in the structure exceeding the maximum size, but the number thereof is very small, and thus has no substantial influence on the toughness and other mechanical properties of the precipitation hardening steel, and thus may be disregarded. In addition, many smaller mu phases of particles cannot be identified by analysis software, and the statistics of volume fraction and granularity are only used as comparison.
Based on the above description, it can be found that the precipitation hardening high-speed steel of the present invention comprises, as preferable in mass%, the following chemical components: si:0% -0.8%; co:18.0% -30.0%; w:0% -3.0%; mo:15% -20.0%; (mo+w/2): 15.0% -22.0%; the balance being iron and impurities. With the precipitation hardening high-speed steel composed of the above components, a desired structure and excellent properties can be obtained to meet the demand.
In order to achieve better comprehensive performance, each chemical component in the powder metallurgy precipitation hardening high-speed steel is controlled within a required range. Specifically comprising at least 80% by volume of the mu phase having a size of 1.5 μm or less, a maximum size of the mu phase of 5.5 μm or less, and a volume fraction of the mu phase of 12 to 20%.
The invention adopts specific alloy component design and powder metallurgy process to prepare, has high intermetallic compound mu phase content, fine granularity and high dispersity, and has higher high-temperature aggregation resistance than carbide, so that the material has better toughness and longer service life, can meet different application requirements, and can be used for manufacturing (1) cutters for cutting difficult-to-process materials at high speed; (2) high-precision measuring tool; (3) thin and thin blade cutters.
In summary, the powder metallurgy precipitation hardening high-speed steel of the present invention has excellent mechanical properties, particularly excellent temper softening resistance. Because of the alloy composition characteristics, the alloy composition is different from the traditional high-speed steel strengthening mechanism, so that the tempering softening resistance of the alloy composition is superior to that of the traditional high-speed steel and other tool steels.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (6)
1. The powder metallurgy precipitation hardening high-speed steel is characterized by comprising the following chemical components in percentage by mass:
Si：0.5％-1.2％；
Co：16.0％-30.0％；
W：0％-5.0％；
Mo：15.0％-22.0％；
(Mo+W/2)：15.0％-23.0％；
Ce：0.01％-0.1％；
the balance of iron and impurities;
and, intermetallic compound in the powder metallurgy precipitation hardening high-speed steel is a mu phase, and the type of the mu phase is (Fe, co) 7 (Mo+W/2) 6 。
2. The powder metallurgy precipitation hardening high-speed steel according to claim 1, wherein the chemical components thereof comprise, in mass percent:
Si：0.5％-1％；
Co：18.0％-30.0％；
W：0％-3.0％；
Mo：15.0％-20.0％；
(Mo+W/2)：15.0％-21.5％；
Ce：0.01％-0.1％；
the balance being iron and impurities.
3. Powder metallurgy precipitation hardening high speed steel according to claim 1 or 2, characterized in that: at least 80% of the volume fraction of the mu phase has a particle size of 1.5 mu m or less.
4. Powder metallurgy precipitation hardening high speed steel according to claim 1 or 2, characterized in that: the maximum particle size of the μ phase is no more than 5.5 μm.
5. Powder metallurgy precipitation hardening high speed steel according to claim 1 or 2, characterized in that: the volume fraction of the mu phase in the powder metallurgy precipitation hardening high-speed steel is 12-20%.
6. Powder metallurgy precipitation hardening high speed steel according to claim 1 or 2, characterized in that: the hardness of the powder metallurgy precipitation hardening high-speed steel is more than 65HRC, and the impact toughness value of the non-notch sample is more than 11.0J.
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