CN117165836A - Powder metallurgy corrosion-resistant precipitation hardening high-speed steel - Google Patents
Powder metallurgy corrosion-resistant precipitation hardening high-speed steel Download PDFInfo
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- 238000004881 precipitation hardening Methods 0.000 title claims abstract description 66
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- 238000004663 powder metallurgy Methods 0.000 title claims abstract description 40
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- 239000002245 particle Substances 0.000 claims description 9
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Abstract
The invention provides powder metallurgy corrosion-resistant precipitation hardening high-speed steel, which comprises the following chemical components in percentage by mass: si:0.5% -1.2%; cr:2.0% -15.0%; co:8.0% -16.0%; w:0% -5.0%; mo:18.0% -25.0%; (mo+w/2): 18.0% -27.0%; the balance of iron and impurities, and the steel mainly comprises an iron-based cubic solid solution matrix and a mu phase of intermetallic compound (IMC for short) in the matrix, wherein the mu phase is (Fe, co) 7 (Mo+W/2) 6 Type (2). The invention is thatThe prepared powder metallurgy corrosion-resistant precipitation hardening high-speed steel has fine mu-phase size and uniform distribution, has excellent comprehensive performance, particularly outstanding corrosion resistance and tempering softening resistance, and meets the requirements of different working conditions.
Description
Technical Field
The invention relates to precipitation hardening high-speed steel, in particular to powder metallurgy corrosion-resistant precipitation hardening high-speed steel.
Background
In the fields of aerospace, marine chemical industry and the like, tools or parts are required to be subjected to the corrosion action of moisture, acid or other corrosive media besides the working stress loading and impact, and in order to be suitable for the working conditions and have long service life, the materials must have good strength and toughness matching and corrosion resistance.
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.
However, when the precipitation hardening high-speed steel is prepared by adopting the traditional casting and forging process, the precipitation hardening high-speed steel is limited by the characteristic of slow cooling and solidification of molten steel in the process, alloy components are easy to segregate in the solidification process, the bad structure cannot be effectively solved by a hot processing mode, bad influence is generated on the alloy performance, the high-speed steel performance including strength, toughness, grindability and the like is in a low level, the requirements of high-end processing and manufacturing on the material performance and service life are difficult to meet, and the corrosion resistance of the existing precipitation hardening steel is also difficult to meet the use in the high-end field.
Disclosure of Invention
In view of this, the present invention provides a powder metallurgy precipitation corrosion-resistant hardened high-speed steel having good structure and excellent properties.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
a powder metallurgy corrosion-resistant precipitation hardening high-speed steel, characterized in that the steel comprises the following chemical components in percentage by mass:
Si：0.5％-1.2％；
Cr：2.0％-15.0％；
Co：8.0％-16.0％；
W：0％-5.0％；
Mo：18.0％-25.0％；
(Mo+W/2)：18.0％-27.0％；
the balance of iron and impurities;
and, intermetallic compounds (i.e., IMC phases) in the precipitation hardening high-speed 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 corrosion resistance of the steel.
Specifically, the Co (cobalt) in the precipitation hardening high-speed steel of the present invention acts to be solid-dissolved in the matrix to make the alloy into a martensitic steel, thereby improving the hardness and strength of the ferritic alloy by one step, and the increase in Co content suitably reduces the toughness of the steel, and in the present invention, the Co element content ranges from 8.0% to 16.0%, preferably from 10.0% to 16.0%.
The high melting point of W (tungsten) can increase the strength and tempering stability of steel, the high-temperature creep resistance and the tempering softening resistance of steel, so that the steel has less surface layer temperature rise and hardness reduction in the process of processing and using, and the content of W element in the invention is 0% -5.0%, preferably 0% -3.0%.
Mo (molybdenum) acts on W in the same manner, and can completely replace W, and is lower in price 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 content of the Mo element in the present invention is in the range of 18% to 25.0%, preferably 18.0% to 22.0%.
Cr (chromium) is added into steel to act, firstly, particles can be coarsened, so that red hardness is reduced to some extent, and the machinability is improved; on the other hand, part of Cr is dissolved in the matrix, so that the corrosion resistance and hardenability of the steel can be improved. The Cr element content in the present invention is in the range of 2.0% to 15.0%, preferably 2.0% to 12.0%.
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%, preferably 0.5% to 1.0%. .
As a limitation of the above manner, the powder metallurgy corrosion-resistant precipitation hardening high-speed steel comprises the following chemical components in mass percent:
Si：0.5％-1.0％；
Cr：2.0％-12.0％；
Co：10.0％-16.0％；
W：0％-3.0％；
Mo：18.0％-22.0％；
(Mo+W/2)：18.0％-23.5％；
the balance being iron and impurities.
In order to achieve better comprehensive performance, each chemical component in the powder metallurgy corrosion-resistant 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 6.0 μm.
Further, the volume fraction of the mu phase in the powder metallurgy corrosion-resistant precipitation hardening high-speed steel is 15-27%.
Further, the hardness of the powder metallurgy corrosion-resistant precipitation hardening high-speed steel is more than 63HRC, and the impact toughness value of the non-notch sample is more than 12.0J.
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 corrosion-resistant precipitation hardening high-speed steel, which 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 heat, and 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 meanwhile, the removal of harmful inclusions 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. The tundish is preheated before molten steel enters the tundish, so that the molten steel can be prevented from being partially coagulated when entering 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 precipitated intermetallic compound mu phase is finer and more uniform due to the specific chemical composition and the rapid condensation process of the powder metallurgy, has excellent hardness, corrosion resistance, tempering softening resistance and toughness, obtains the hardness above 63HRC after solution aging treatment, has no notch impact toughness above 12.0J, and is suitable for being used in the working condition with load and corrosive medium at the same time.
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 corrosion resistant tool steel of comparative example A of the present invention;
FIG. 8 is a microstructure of the powder metallurgy high-speed steel prepared in comparative example 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 will be described in detail below with reference to the drawings in connection with embodiments.
The invention relates to a group of powder metallurgy corrosion-resistant precipitation hardening high-speed steel, which comprises the following chemical components in percentage by mass: si:0.5% -1.2%; cr:2.0% -15.0%; co:8.0% -16.0%; w:0% -5.0%; mo:18.0% -25.0%; (mo+w/2): 18.0% -27.0%; 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, corrosion resistance and toughness of the steel.
Secondly, the present invention also relates to a method for preparing the precipitation hardening high-speed steel, wherein the performance is reduced due to the fact that the solidification speed is slow and segregation is easy to occur when the precipitation hardening high-speed steel is prepared 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 powder metallurgy process is adopted 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 hot isostatic pressing sheath at 200-600 ℃ in the vacuumizing process, continuously heating and preserving the heat 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 1100-1180 ℃ 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 certain 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 530 ℃ 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 corrosion-resistant precipitation hardening high-speed steel of the present invention and the preparation thereof will be further described below with specific prepared examples and comparative examples, and corresponding performance tests.
Eight precipitation hardening high-speed steels having different compositions were obtained in total from example 1 and example 8 by the above preparation method, and compared with cast forging tool steels (alloy a) and powder metallurgy tool steels (alloy B), the results were as follows:
table 1: composition of the ingredients
| Alloy | Si | Co | W | Mo | (Mo+W/2) | C | Mn | Cr | V | Fe |
| Example 1 | 0.58 | 15.52 | 0.01 | 22.45 | 22.45 | - | - | 4.93 | - | Allowance of |
| Example 2 | 0.60 | 14.70 | 0.01 | 19.20 | 19.20 | - | - | 4.05 | - | Allowance of |
| Example 3 | 0.58 | 24.96 | 0.02 | 20.3 | 20.31 | - | - | 4.93 | - | Allowance of |
| Example 4 | 0.50 | 8 | 0 | 18.00 | 18.0 | - | - | 2.0 | - | Allowance of |
| Example 5 | 1.20 | 16 | 5.00 | 25.00 | 27.50 | - | - | 15.0 | - | Allowance of |
| Example 6 | 0.50 | 10.0 | 0.0 | 18.0 | 18.0 | - | - | 2.0 | - | Allowance of |
| Example 7 | 1.0 | 16.0 | 3.0 | 22.0 | 23.5 | - | - | 12.0 | - | Allowance of |
| Example 8 | 1.10 | 17.0 | 4.0 | 23.0 | 25.0 | - | - | 13.0 | - | Allowance of |
| Comparative example A | 0.38 | 0.02 | 0.02 | 0.03 | 0.03 | 1.02 | 0.33 | 16.77 | 0.10 | Allowance of |
| Comparative example B | 0.37 | 10.56 | 6.51 | 6.94 | 10.19 | 2.23 | 0.28 | 4.22 | 6.44 | Allowance of |
The "-" in the table indicates that the element is not contained, or the element content is little to no analysis.
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 phases of fig. 1 to 6 are dispersed in the matrix, and that fig. 7 and 8 contain two precipitated phases, one of which is bright white and has a large size, and the other of which is off-white and has a small size. Because the hardening phases in examples 1-7 are distributed in the matrix in a fine dispersion manner, the wear resistance, toughness and service life of the material can be remarkably improved.
The high speed steels prepared in examples 1 to 8 after heat treatment were compared with the content of precipitated phases, particle sizes, and compositions in alloy A, B as shown in table 2.
TABLE 2 content of precipitated phases and chemical composition
The "-" in the table indicates that the element is not contained, or the element content is small and is not analyzed
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 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. In alloy B, VC-type carbide is also present, and the components are mainly C, V, cr and Fe.
The precipitation hardening high-speed steel has the volume fraction of mu phase reaching 15-27%, fine granularity, most mu phase granularity smaller than or equal to 1.5 mu m and maximum size not exceeding 6.0 mu m, and the precipitated phases have fine size and large dispersity, and meanwhile, the mu phase high-temperature aggregation resistance is higher than that of carbide, so that the material has better wear resistance, toughness and service life.
The VC-type carbide in the alloy B prepared by adopting the powder metallurgy process is the finest, most of the VC-type carbide is less than or equal to 1.5 mu m, the largest dimension is less than or equal to 5.0 mu m, the volume fraction is 3.81%, but the (Cr, fe) C-type carbide with a large quantity and a size range of 5-9 mu m also exists in the structure. Coarse carbides have the detrimental effect of splitting the matrix. A alloy produced by adopting an ingot casting process has a small amount of VC-type carbide with small granularity, and most of VC-type carbide is less than or equal to 1.5 mu m, but the same structure also has a large amount of (Cr, fe) C-type carbide with the size range of 5-12 mu m, so that the performance is adversely affected.
(II) Heat treatment hardness and impact toughness analysis
In order to verify the influence of a heat treatment system on the performance of the prepared precipitation hardening high-speed steel, 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 powder metallurgy corrosion-resistant precipitation hardening high-speed steel of the present invention has a hardness of 63HRC or more and an unnotched sample impact toughness value of 12.0J or more, and although the precipitation hardening high-speed steel of the present invention has a relatively low impact toughness, the measured value satisfies the requirement of the application field for toughness, so that the precipitation hardening high-speed steel of the present invention is particularly suitable for use in the case of less impact load operation.
Analysis of Corrosion resistance
Using 5% HNO 3 The +1% hcl solution was dip etched at room temperature for examples 1 to 8 and alloy A, B, and then the etching rate was measured. And then the polarization curve is measured in a 1% NaCl solution, and finally the self-corrosion potential is obtained, the corrosion resistance comparison result is shown in table 4, and the verification parameters are set to reference JB/T7901 and GB/T17899.
TABLE 4 comparison of Corrosion resistance
| Alloy | Quenching tempering/solid solution aging | Corrosion rate mm/y | Self-etching potential E corr |
| Example 1 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.454 |
| Example 2 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.468 |
| Example 3 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.460 |
| Example 4 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.401 |
| Example 5 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.572 |
| Example 6 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.377 |
| Example 7 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.539 |
| Example 8 | 1190 ℃ oil quenching +600 ℃ for 3h | ≤150 | -0.551 |
| Comparative example A | Oil quenching at 1100 ℃ and 200 ℃ for 2h for 2 times | ≤300 | -0.341 |
| Comparative example B | 1170 ℃ oil quenching +550 ℃ for 1h for 3 times | ≤400 | -0.127 |
As can be seen from the comparative data of table 4, the precipitation hardening steel of the present invention exhibits more excellent corrosion resistance. Because the content of C in the precipitation hardening steel is very small, the precipitation hardening steel can not be separated out with Cr in the form of carbide basically, and most of Cr element in the steel is dissolved in a matrix in a solid manner, so that higher corrosion resistance can be obtained. The precipitation hardening high-speed steel can have good toughness matching and corrosion resistance, thereby meeting the requirements of specific working conditions.
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%; mn:0% -0.3%; cr:2.0% -12.0%; co:10.0% -16.0%; w:0% -3.0%; mo:18.0% -22.0%; (mo+w/2): 12.0% -25.0%; the balance being iron and impurities. The precipitation hardening high-speed steel of the present invention, which is composed of the above components, can achieve an ideal structure and excellent properties to meet the demands.
In order to achieve better comprehensive performance, each chemical component in the powder metallurgy corrosion-resistant precipitation hardening high-speed steel is controlled within a required range. Specifically, the size of a mu phase of at least 80% of the volume fraction is less than or equal to 1.5 mu m, and the largest dimension of the mu phase is not more than 6.0 mu m. And the volume fraction of the μ phase is 15-27%.
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; and (3) corrosion-resistant parts.
In conclusion, the powder metallurgy corrosion-resistant precipitation high-speed steel has excellent mechanical properties, in particular good corrosion 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 corrosion-resistant precipitation hardening high-speed steel is characterized by comprising the following chemical components in percentage by mass:
Si：0.5％-1.2％；
Cr：2.0％-15.0％；
Co：8.0％-16.0％；
W：0％-5.0％；
Mo：18.0％-25.0％；
(Mo+W/2)：18.0％-27.0％；
the balance of iron and impurities;
and, intermetallic compound in the powder metallurgy 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 corrosion resistant precipitation hardening high speed steel according to claim 1, wherein the chemical composition thereof comprises in mass percent:
Si：0.5％-1.0％；
Cr：2.0％-12.0％；
Co：10.0％-16.0％；
W：0％-3.0％；
Mo：18.0％-22.0％；
(Mo+W/2)：18.0％-23.5％；
the balance being iron and impurities.
3. The powder metallurgy corrosion resistant precipitation hardening high speed steel according to claim 1 or 2, characterized in that: at least 80% of the volume fraction of the particles of said mu phase have a size of 1.5 mu m or less.
4. The powder metallurgy corrosion resistant 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 6.0 μm.
5. The powder metallurgy corrosion resistant 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 corrosion-resistant precipitation hardening high-speed steel is 15-27%.
6. The powder metallurgy corrosion resistant precipitation hardening high speed steel according to claim 1 or 2, characterized in that: the hardness of the powder metallurgy corrosion-resistant precipitation hardening high-speed steel is more than 63HRC, and the impact toughness value of the non-notch sample is more than 12.0J.
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