HIGH-VANADIUM HIGH-SPEED STEEL AND PREPARATION METHOD THEREFOR, AND USE THEREOF

Abstract

The present disclosure provides a high-vanadium high-speed steel and preparation method therefor, and use thereof, which relate to the technical field of high-vanadium high-speed steel. The preparation method includes: smelting raw materials to form a melt; impacting the melt to a cooling platform to form a high-vanadium high-speed steel casting billet; and performing a spheroidizing annealing treatment and a quenching and tempering treatment, so as to obtain a resultant. The spheroidizing annealing treatment includes: heating the high-vanadium high-speed steel casting billet to 820-910 C.; holding for 2-4 h; then cooling down to 450-550 C. at a cooling rate larger than 40 C./h; and then air cooling to a room temperature.

Claims

1. A preparation method of a high-vanadium high-speed steel, comprising: smelting raw materials to form a melt, wherein the raw materials in mass percentage comprise C: 2.0-2.5%, Cr: 4-6%, W: 2.5-6%, Mo: 3-7%, V: 4-10%, Si: 0.3-0.6%, Mn: 0.3-0.8%, and a balance of Fe; impacting the melt to a cooling platform to form a high-vanadium high-speed steel casting billet; carrying out a spheroidizing annealing treatment on the high-vanadium high-speed steel casting billet to obtain an annealed ingot, wherein the spheroidizing annealing treatment comprises heating the high-vanadium high-speed steel casting billet to 820-910 C.; holding for 2-4 h; then cooling down to 450-550 C. at a cooling rate larger than 40 C./h; then air cooling to a room temperature; and performing a quenching and tempering treatment on the annealed ingot, so as to obtain a resultant.

2. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein the cooling rate is 45-75 C./h.

3. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein the high-vanadium high-speed steel casting billet is heated with a furnace in a tube furnace protected by an inert gas.

4. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein the raw materials are smelted by using an intermediate frequency induction furnace at a smelting temperature of 1480-1520 C.; the intermediate frequency induction furnace is vacuumized to 100-400 Pa when smelting; and subsequently the inert gas is filled for protection.

5. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein a pressure difference between an inner chamber of the melt and an outer chamber during the melt impacting is 0.05-0.25 MPa, and a spraying speed is 0.75-1.75 m/s.

6. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein a speed of the cooling platform moving downward is 50-120 mm/s.

7. The preparation method of the high-vanadium high-speed steel according to claim 1, wherein the quenching and tempering treatment comprises: preheating the annealed ingot at 600-750 C. for 5-15 min; then carrying out a quenching and holding a temperature at 1000-1230 C., wherein a holding duration is 10-30 min, and carrying out the quenching in oil to a room temperature; and then tempering 1-4 times at 520-600 C. for 1 h each time, wherein the tempering is carried out each time after air cooling to the room temperature.

8. The preparation method of the high-vanadium high-speed steel according to claim 7, wherein the annealed ingot is preheated in a muffle furnace, and quenched in a tube furnace filled with an inert atmosphere.

9. A high-vanadium high-speed steel, wherein the high-vanadium high-speed steel is prepared by using the preparation method of the high-vanadium high-speed steel according to claim 1.

10. A use of the high-vanadium high-speed steel according to claim 9 in a preparation of a roll, a hammer head, a ball mill liner, or a rotor body.

11. The high-vanadium high-speed steel according to claim 9, wherein an annealing hardness of the high-vanadium high-speed steel is 315-360 HV.

12. The high-vanadium high-speed steel according to claim 9, wherein a tempering hardness of the high-vanadium high-speed steel is 863-980 HV.

13. The high-vanadium high-speed steel according to claim 9, wherein a tempering bending strength of the high-vanadium high-speed steel is 1157-1404 MPa.

14. The high-vanadium high-speed steel according to claim 9, wherein a vanadium content in the high-vanadium high-speed steel is 4-10%.

15. The high-vanadium high-speed steel according to claim 9, wherein after the high-vanadium high-speed steel is annealed, vanadium carbide in the ingot is in a shape of sphere, and is uniformly distributed in a base.

16. The high-vanadium high-speed steel according to claim 9, wherein after the high-vanadium high-speed steel is tempered, vanadium carbide in the ingot is in a shape of sphere and block, and is distributed dispersedly, wherein vanadium carbide with a coarse size and an irregular shape does not appear.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the examples of the present disclosure, the drawings to be used in the examples will be briefly introduced below. It should be understood that the following drawings only show certain examples of the present disclosure, and therefore should not be regarded as a limitation of the scope. Other relevant drawings can be obtained from these drawings by a person of ordinary skill in the art without inventive efforts.

[0030] FIG. 1 shows a metallographic microstructure of preparing a high-vanadium high-speed steel casting billet by a melt impact method provided by Example 4 of the present disclosure;

[0031] FIG. 2 shows a schematic diagram of a rapid spheroidizing annealing process of preparing a high-vanadium high-speed steel by a melt impact method provided by Example 4 of the present disclosure;

[0032] FIG. 3 shows a metallographic microstructure of a high-vanadium high-speed steel casting billet after a rapid spheroidizing annealing provided by Example 4 of the present disclosure; and

[0033] FIG. 4 shows a metallographic microstructure of a high-vanadium high-speed steel casting billet after quenching-tempering provided by Example 4 of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0034] In order to make the purpose, technical solutions and advantages of the examples of the present disclosure clearer, the technical solutions in the examples of the present disclosure will be described clearly and completely in the following. Where specific conditions are not indicated in the examples, they shall be performed based on the usual conditions or those recommended by manufacturers. The reagents or instruments used without indication of the manufacturers are conventional products that can be purchased commercially.

[0035] The present disclosure provides a preparation method of a high-vanadium high-speed steel, including the following steps.

S1, Smelting.

[0036] The raw materials is smelted to form a melt.

[0037] In the present disclosure, the raw materials are prepared according to the chemical element composition of vanadium, and are smelted to obtain the melt of the high-vanadium high-speed steel, wherein the raw materials in mass percentage include C: 2.0-2.5%, Cr: 4-6%, W: 2.5-6%, Mo: 3-7%, V: 4-10%, Si: 0.3-0.6%, Mn: 0.3-0.8%, and a balance of Fe.

[0038] The raw material is smelted by using an intermediate frequency induction furnace at a smelting temperature of 1480-1520 C.; the intermediate frequency induction furnace is vacuumized to 100-400 Pa when smelting; and subsequently the inert gas is filled for protection.

S2, Melt Impacting.

[0039] The melt is impacted to a cooling platform to form a high-vanadium high-speed steel casting billet.

[0040] Specifically, when the smelting reaches a preset temperature (1480-1520 C.), the melt is deposited on a pre-cooled cooling platform (such as a water-cooled copper mold) at a spraying speed of 0.75-1.75 m/s by the inert gas, at which time the melt is rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet.

[0041] The impacting temperature of the high-vanadium high-speed steel of the above composition melt is controlled to be 1480-1520 C., wherein the superheat should not be too high, otherwise the grain of solidification microstructure will be coarse; and the fluidity is poor when it is lower than this temperature, which is not easy to realize the rapid impacting and easy to block the nozzle.

[0042] A pressure difference between an inner chamber of the melt and an outer chamber during the melt impacting is 0.05-0.25 MPa, wherein the pressure difference refers to a pressure difference between the chamber of the melt in the crucible and the outer chamber. The specific realizing step can be described as: vacuumizing the chamber formed by the intermediate frequency induction furnace, and filling the inert atmosphere subsequently, at which time there is still a certain pressure difference with the outside; and filling the inert gas flow into the melt when the melt reaches the holding temperature, so as to promote the rapid spraying of the melt. The structure is mainly controlled by means of airflow, which is easy to realize and operate.

[0043] The cooling platform can move up and down under the driving of the movement mechanism, so as to control a distance between the cooling platform and the nozzle of the intermediate frequency induction furnace, so as to perform the melt impacting better, wherein the speed of the downward movement of the cooling platform is 50-120 mm/s. The present disclosure found by research that when lower than 50 mm/s, it will have the problem of the lower quality of metallurgical bonding between layers, which is easy to cause a large amount of porosity defects; and when higher than 120 mm/s, the melt of the next layer has arrived before the melt of the last layer forms a valid solidification thickness, which cannot play a crushing effect on the dendritic crystal.

S3, Spheroidizing Annealing Treatment.

[0044] The spheroidizing annealing treatment is carried out on the high-vanadium high-speed steel casting billet to obtain an annealed ingot, wherein the spheroidizing annealing treatment includes heating the high-vanadium high-speed steel casting billet to 820-910 C.; holding for 2-4 h; then cooling down to 450-550 C. at a cooling rate larger than 40 C./h; then air cooling to a room temperature.

[0045] In the present disclosure, the high-vanadium high-speed steel casting billet is prepared by the melt impact method based on step S2 first, wherein the microstructure of the formed high-vanadium high-speed steel casting billet is uniform, and the size of the carbide is small. It needs to develop a new annealing process, which can meet the cutting condition, and at the same time prevent the aggregation and growth of the fine carbides. Therefore, the present disclosure adopts the above spheroidizing annealing treatment, which rapidly reduces the temperature to 450-550 C. by a high-speed cooling method. It not only can shorten the duration of the annealing process (the duration of this process is only - of the duration of the conventional annealing process), which is energy saving and high-efficient, but also can realize that the vanadium carbide in the high-vanadium high-speed steel casting billet is in a shape of sphere; is uniformly distributed; has suitable hardness; and is convenient for the subsequent machining.

[0046] The cooling rate can be, for example, 45-75 C./h. In other embodiments of the present disclosure, the cooling rate can be, for example, any one of 45 C./h, 50 C./h, 55 C./h, 60 C./h, 65 C./h, 70 C./h, 75 C./h, or a range value between any two.

[0047] The high-vanadium high-speed steel casting billet is heated with a furnace in the tube furnace protected by the inert gas, and is protected by the inert gas, which can avoid the reaction between the chemical elements in the raw material and the oxygen, and at the same time the heating with the furnace can be better controlled.

S4, Quenching and Tempering Treatment.

[0048] The quenching and tempering treatment is performed on the annealed ingot, so as to obtain a resultant.

[0049] The quenching and tempering treatment includes: preheating the annealed ingot at 600-750 C. for 5-15 min; then carrying out a quenching when holding a temperature at 1000-1230 C., wherein a holding duration is 10-30 min, and carrying out the quenching in oil to a room temperature; and then tempering 1-4 times at 520-600 C. for 1 h each time, wherein the tempering is carried out each time after air cooling to the room temperature. The annealed ingot is preheated in a muffle furnace, and quenched in the tube furnace filled with the inert atmosphere.

[0050] Since the high-vanadium high-speed steel contains a large amount of high-melting-point brittle carbides, in the quenching and tempering treatment of the present disclosure, the annealed ingot is fully preheated in 600-750 C. first, which can prevent the annealed ingot from directly cracking during the heat preservation at 1000-1230 C. The large amounts of carbides can be fully dissolved by quenching in the heat preservation at 1000-1230 C.; and the carbides were sphered and isolated due to the high temperature diffusion dissolution and the driving from the interfacial tension, which is beneficial to improving the morphology of the carbide and to improving its toughness. Additionally, the dissolved alloying element is dissolved in the austenite to increase the hardenability of the alloy, and at the next quenching and cooling process, the base transforms to the strong martensite base. During the tempering at 520-600 C., the stress can be eliminated, so as to promote the dispersion and the precipitation of the secondary carbides, which improves the strength and hardness of the base. The multiple tempering process allows the incomplete residual austenite to transform completely, so as to improve the strength and the hardness of the base. The performance of the high-vanadium high-speed steel is improved by multiple quenching and tempering treatments, so that it has a high hardness, and the good strength and toughness.

[0051] The high-vanadium high-speed steel prepared by using the above preparation method of the high-vanadium high-speed steel has the excellent mechanical property, wherein the annealing hardness of the high-vanadium high-speed steel is 315-360 HV; the tempering hardness of the high-vanadium high-speed steel is 863-980 HV; and the tempering bending strength of the high-vanadium high-speed steel is 1157-1404 MPa. Meanwhile, the vanadium content in the high-vanadium high-speed steel is 4-10%. After the high-vanadium high-speed steel is annealed, the vanadium carbide in the ingot is in a shape of sphere, and is uniformly distributed in the base. After the high-vanadium high-speed steel is tempered, the vanadium carbide in the ingot is mainly in a shape of sphere and block, and is distributed dispersedly, wherein the vanadium carbide with a coarse size and an irregular shape does not appear.

[0052] In the present disclosure, the grain and the primary carbide are crushed by using the impacting effect of the melt, which in turn can improve the strength, toughness, and wear resistance of the high carbon alloy steel, so as to improve the service life. Compared with the prior spray molding method, the biggest difference is that the formed ingot microstructure is dense and uniform, and the carbide is fine. The ingot prepared by the prior spray molding technique has inherent voids. For casting the high-vanadium high-speed steel, the ingot porosity still exists after the heat treatment since the forging process is not included in subsequence, so that the service life is greatly reduced. The preparation method of the high-vanadium high-speed steel provided by the present disclosure prepares the high-vanadium high-speed steel casting billet by using the melt impact method. It refines the grains and carbides, and greatly reduces the generation of porosity. The utilization rate of the melt is higher, and there is no waste of the alloy melt. The solidified ingot microstructure is uniform and dense. Additionally, the high-vanadium high-speed steel casting billet prepared by the melt impact method has fine and uniform carbide particles. In order to prevent the aggregation and growth of the carbide, it adopts the rapid spheroidizing annealing process, which is time-saving and high-efficient, and compared with the conventional annealing process, it greatly shortens the duration. Next, the quenching and tempering treatment is carried out, which can comprehensively improve the mechanical property of the high-vanadium high-speed steel. The high-vanadium high-speed steel obtained can be widely used to prepare the roll, hammer head, ball mill liner, or rotor body.

[0053] The features and performance of the present disclosure are described in further detail below in connection with the examples.

Example 1

[0054] The example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0055] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using an intermediate frequency induction furnace at a smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that a melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0056] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on a pre-cooled water-cooled copper mold at a spraying speed of 1.25 m/s under a pressure difference of 0.15 MPa, wherein a movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0057] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at a rate of 50 C./h; and then it was air cooled. [0058] (4) It was held at a temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered twice at 560 C. for 1 h each time.

Example 2

[0059] The Example is basically the same as Example 1, and the only difference is that the parameters of step (3) and step (4) are different.

[0060] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0061] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using an intermediate frequency induction furnace at a smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0062] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0063] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 880 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. [0064] (4) It was held at the temperature of 1150 C. for 15 min, and quenched in oil to the room temperature; and it was tempered twice at 560 C. for 1 h each time.

Example 3

[0065] The Example is basically the same as Example 1, and the only difference is that the parameters of step (3) and step (4) are different.

[0066] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0067] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using an intermediate frequency induction furnace at a smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0068] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0069] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 910 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. [0070] (4) It was held at the temperature of 1200 C. for 15 min, and quenched in oil to the room temperature; and it was tempered twice at 560 C. for 1 h each time.

Example 4

[0071] The Example is basically the same as Example 1, and the only difference is that the parameters of step (3) and step (4) are different.

[0072] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0073] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0074] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. Referring to FIG. 1, it can be seen from FIG. 1 that the microstructure of the high-vanadium high-speed steel casting billet is fine and distributed uniformly. [0075] (3) Referring to FIG. 2, the rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. Referring to FIG. 3, it can be seen from FIG. 3 that the microstructure of the high-vanadium high-speed steel casting billet after the rapid spheroidizing annealing is fine and distributed uniformly. [0076] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time. Referring to FIG. 4, it can be seen from FIG. 4 that the microstructure of the high-vanadium high-speed steel casting billet after the spheroidizing temper is fine and distributed uniformly.

Example 5

[0077] The Example is basically the same as Example 1, and the only difference is that the parameters of step (3) and step (4) are different.

[0078] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0079] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0080] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0081] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 880 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. [0082] (4) It was held at the temperature of 1150 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Example 6

[0083] The Example is basically the same as Example 1, and the only difference is that the parameters of step (3) and step (4) are different.

[0084] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0085] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0086] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0087] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 910 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. [0088] (4) It was held at the temperature of 1200 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Example 7

[0089] This Example is essentially the same as Example 1, and differs only in that the parameters of steps (1) and (2) are different.

[0090] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0091] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1500 C. During smelting, the intermediate frequency induction furnace was vacuumized to 100 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2% C, 4% Cr, 2.5% W, 5.0% Mo, 4% V, 0.3% Si, 0.5% Mn, and a balance of Fe. [0092] (2) When the smelting reaches 1500 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 0.75 m/s under the pressure difference of 0.05 MPa, wherein the movement speed of the water-cooled copper mold was 50 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0093] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at a rate of 50 C./h; and then it was air cooled. [0094] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered twice at 560 C. for 1 h each time.

Example 8

[0095] This Example is essentially the same as Example 1, and differs only in that the parameters of steps (1) and (2) are different.

[0096] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0097] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1520 C. During smelting, the intermediate frequency induction furnace was vacuumized to 400 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.3% C, 6.0% Cr, 6% W, 7.0% Mo, 10% V, 0.6% Si, 0.8% Mn, and a balance of Fe. [0098] (2) When the smelting reaches 1520 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.75 m/s under the pressure difference of 0.25 MPa, wherein the movement speed of the water-cooled copper mold was 120 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0099] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at a rate of 50 C./h; and then it was air cooled. [0100] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered twice at 560 C. for 1 h each time.

Comparative Example 1

[0101] The Comparative Example is basically the same as Example 4, wherein the only difference is that step (3) adopts the conventional annealing process. The specific steps were as follows. [0102] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0103] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0104] (3) The conventional annealing process was carried out on the ingot obtained by this process, i.e., a temperature of 860 C. was held for 40 h and then it was cooled with the furnace. [0105] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Comparative Example 2

[0106] The Comparative Example is basically the same as Example 4, wherein the only difference is that step (2) adopts the ingot prepared by the spray molding technology. The specific steps were as follows. [0107] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0108] (2) When the smelting reached 1480 C., the high-temperature melt was atomized by the spray molding technology, wherein the melt formed a morphology mixed with solidity, semi-solidity, and liquid under a high-speed gas flow; it was mixed and deposited on the cooling base to form the high-vanadium high-speed steel casting billet; and then it was cooled to the room temperature. [0109] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at the rate of 50 C./h; and then it was air cooled. [0110] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Comparative Example 3

[0111] The Comparative Example is basically the same as Example 4, wherein the only differences are that step (2) adopts the ingot prepared by the spray molding technology, and step (3) adopts the conventional annealing process. The specific steps were as follows. [0112] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0113] (2) When the smelting reached 1480 C., the high-temperature melt was atomized by the spray molding technology, wherein the melt formed a morphology mixed with solidity, semi-solidity, and liquid under a high-speed gas flow; it was mixed and deposited on the cooling base to form the high-vanadium high-speed steel casting billet; and then it was cooled to the room temperature. [0114] (3) The conventional annealing process was carried out on the ingot obtained by this process, i.e., a temperature of 860 C. was held for 40 h and then it was cooled with the furnace. [0115] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Comparative Example 4

[0116] The Comparative Example is basically the same as Example 1, wherein the only difference is that the cooling rate in step (3) is different.

[0117] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0118] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0119] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0120] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at the rate of 30 C./h; and then it was air cooled. [0121] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Comparative Example 5

[0122] The Comparative Example is basically the same as Example 1, wherein the only difference is that the cooling rate in step (3) is different.

[0123] Specifically, the example provided a preparation method of the high-vanadium high-speed steel, including the following steps. [0124] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0125] (2) When the smelting reached 1480 C., the melt was deposited by the inert gas on the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature. [0126] (3) The rapid spheroidizing annealing process was carried out on the ingot obtained by this process; a temperature of 850 C. was held for 2 h; it was cooled to 500 C. at the rate of 100 C./h; and then it was air cooled. [0127] (4) It was held at the temperature of 1100 C. for 15 min, and quenched in oil to the room temperature; and it was tempered three times at 560 C. for 1 h each time.

Comparative Example 6

[0128] The Comparative Example is basically the same as Example 4, wherein the only difference is that no heat treatment was performed in the Comparative Example. The specific steps were as follows. [0129] (1) The raw material was prepared according to the chemical element composition of vanadium, and was smelted by using the intermediate frequency induction furnace at the smelting temperature of 1480 C. During smelting, the intermediate frequency induction furnace was vacuumized to 250 Pa and subsequently the inert gas was filled for protection, so that the melt of the high-vanadium high-speed steel was obtained, wherein the raw material in mass percentage included 2.5% C, 5.0% Cr, 4% W, 3.0% Mo, 8% V, 0.5% Si, 0.3% Mn, and a balance of Fe. [0130] (2) When the smelting reached 1480 C., the pre-cooled water-cooled copper mold at the spraying speed of 1.25 m/s under the pressure difference of 0.15 MPa, wherein the movement speed of the water-cooled copper mold was 100 mm/s, at which time the melt was rapidly solidified and molded, so as to form the high-vanadium high-speed steel casting billet, and then it was cooled to the room temperature without any heat treatment.

Experimental Example

[0131] The microstructures of the high-vanadium high-speed steels provided by the above Examples 1-8 and Comparative Examples 1-6 were statistically analyzed. The carbide agglomeration condition was evaluated according to the standard of the national standard GB-T 14979-1994 method for evaluating non-uniformity of eutectic carbide of steel, wherein the uniform distribution could be defined as 1-2 levels, and the more uniform distribution was defined as 3-4 levels. The porosity was evaluated according to the national standard GB 12823-91 grade and content of defect of steel casting, wherein the critical porosity of the steel casting was a smallest porosity under the casting process condition, wherein it was usually 3%5%, and should not exceed 5%. The low porosity in the example could be defined as smaller than 3%, and the high porosity was defined as 3%5%. The service life of the high-speed steel was evaluated according to the national standard GB-T16461-1996 life test of single edge turning tool.

[0132] The high-vanadium high-speed steels provided by Examples 1-8 and Comparative Examples 1-6 above were used to carry out the mechanical property test, wherein the test method of the annealing hardness was characterized by the Vickers indentation technique; the test method of the tempering hardness was characterized by the Vickers indentation technique; and the test method of the tempering bending strength was tested by three-point bending experiment. When without carrying out the heat treatment, it only needed to test the hardness and the bending strength, wherein the test method of the hardness was characterized by the Vickers indentation technique; and the test method of the bending strength was characterized by the three-point bending experiment. The test result refers to Table 1 and Table 2.

TABLE-US-00001 TABLE 1 Statistical table of microstructures of high-vanadium high-speed steels provided by different examples Carbide size Carbide (spherical agglomeration Service Material particle) condition Porosity life Example 4 2.26 m uniform distribution low long Comparative 3.72 m relatively uniform low relatively Example 1 distribution long Comparative 2.07 m uniform distribution relatively short Example 2 high Comparative 3.68 m relatively uniform relatively short Example 3 distribution high Comparative 3.25 m uniform distribution low relatively Example 4 long Comparative 2.66 m uniform distribution low relatively Example 5 long Comparative 2.21 m uniform distribution low short Example 6

TABLE-US-00002 TABLE 2 Statistical table of mechanical properties of high-vanadium high-speed steels provided by different examples Tempering Annealing Tempering bending Bending hardness hardness strength Hardness strength Material (HV) (HV) (MPa) (HV) (MPa) Example 1 360 863 1271 / / Example 2 345 864 1199 / / Example 3 315 954 1404 / / Example 4 360 894 1192 / / Example 5 345 891 1157 / / Example 6 315 980 1258 / / Example 7 311 775 1391 Example 8 350 929 1170 Comparative 356 810 1014 / / Example 1 Comparative 363 786 567 / / Example 2 Comparative 349 792 550 / / Example 3 Comparative 354 853 1173 / / Example 4 Comparative 368 860 1155 / / Example 5 Comparative / / / 834 891 Example 6

[0133] As can be seen from the above table, the microstructure of the high-vanadium high-speed steel ingot prepared by the melt impact method is fine and dense, and it has both high tempering hardness and high bending strength. The Comparative Example 1 adopts the conventional annealing process, which results in a significant increase in the carbide size, and it is up to 3.72 m. The Comparative Example 2 adopts the spray molding process to prepare the high-vanadium high-speed steel ingot, wherein the ingot has a higher porosity and the mechanical property is significantly lower than that of Example 4. In Comparative Example 3, the step (2) adopts the ingot prepared by the spray molding technology, and at the same time the step (3) adopts the conventional annealing process, which results in a significant increase in the carbide size and a significant decrease in the mechanical property. The Comparative Example 4 and the Comparative Example 5 adopt different cooling rates, wherein the cooling rate of the Comparative Example 4 is lower than the range value of the present disclosure, which results in a significant increase in the carbide size; and in Comparative Example 5, the cooling rate is too large; the spheroidizing annealing process is not sufficient; the microstructure softening is not sufficient; and it has the highest annealing hardness, which is not beneficial for cutting processing; and it cannot further reduce the carbide size, but the carbide size increases slightly; and the secondary solid solution effect is poor, which results in a certain reduction of the mechanical property. Since the heat treatment is not carried out in Comparative Example 6, the secondary hardening and strengthening could not be realized, so that its mechanical property is significantly reduced. In the present disclosure, the selection of a rapid spheroidizing annealing process for preparing the high-vanadium high-speed steel ingot by the melt impact method follows principles of time saving and high efficiency, so as to obtain the annealing hardness similar to that of the conventional annealing process under a long cycle and a high energy consumption, and the proper rapid spheroidizing annealing process avoids the aggregation and roughening of fine carbides. In the subsequent quenching-tempering treatment, the high-vanadium high-speed steel ingot prepared by the melt impact method has the satisfactory mechanical property.

[0134] In summary, the preparation method of the high-vanadium high-speed steel provided by the present disclosure prepares the high-vanadium high-speed steel casting billet by adopting the melt impact method first, which can play the role of crushing grains and crushing primary carbides when performing the melt impacting, so as to improve the strength, the toughness, and the wear resistance of the high-vanadium high-speed steel, so as to improve the service life. Compared with the prior spray molding method, the biggest difference is that the formed ingot microstructure is dense and uniform, and the carbide is fine. The ingot prepared by the prior spray molding technology has inherent porosity. For casting the high-vanadium high-speed steel, the ingot porosity still exists after the heat treatment since the forging process is not included in subsequence, so that the service life is greatly reduced. The method of the present disclosure refines the grains and carbides, and greatly reduces the generation of porosity. The utilization rate of the melt is higher, and there is no waste of the alloy melt. The solidified ingot microstructure is uniform and dense. Additionally, the high-vanadium high-speed steel casting billet prepared by the melt impact method has fine and uniform carbide particles. In order to prevent the aggregation and growth of the carbide, it adopts the rapid spheroidizing annealing process, wherein after it is heated to 820-910 C. with the furnace and held for 2-4 h, it is cooled down to 450-550 C. at a cooling rate larger than 40 C./h; and then it is air cooled to a room temperature, wherein the temperature cooling speed is fast, so as to realize the rapid annealing, so that the tungsten carbide in the high-vanadium high-speed steel is not easily agglomerated, and is uniformly distributed in conglobate shape. The rapid spheroidizing annealing process is time-saving and high-efficient, wherein compared with the conventional annealing process, it greatly shortens the duration. Next, the quenching and the tempering are carried out, which comprehensively improve the mechanical property of the high-vanadium high-speed steel.

[0135] The foregoing is merely preferred embodiments of the present disclosure and is not intended to limit the present disclosure, and the present disclosure has various modification changes for those skilled in the art. Any modifications, equivalent substitutions, and improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.