CN110629095A

CN110629095A - Gradient hard alloy composite bar and preparation method thereof

Info

Publication number: CN110629095A
Application number: CN201910735318.7A
Authority: CN
Inventors: 杨康宁; 陈曼可
Original assignee: Zhuzhou Meet-You Carbide Co Ltd
Current assignee: Zhuzhou Meet-You Carbide Co Ltd
Priority date: 2019-08-09
Filing date: 2019-08-09
Publication date: 2019-12-31

Abstract

The invention discloses a gradient hard alloy composite bar which comprises, by mass, 81.5 parts of ~ 87.5.5 parts of WC powder, 6 parts of Co powder, ~ 10 parts of carbon powder, 5.5 parts of carbon powder, ~ 6.5.5 parts of paraffin wax, 1 part of ~ 2 parts of paraffin wax, and also provides a preparation method of the gradient hard alloy composite bar.

Description

Gradient hard alloy composite bar and preparation method thereof

Technical Field

The invention relates to the technical field of hard alloy, in particular to a gradient hard alloy composite bar and a preparation method thereof.

Background

The hard alloy is a common industrial material, is formed by bonding and interlacing uniformly distributed carbide ceramic phase frameworks and metals, has the performances of high hardness, high strength, high elastic modulus, wear resistance, corrosion resistance and the like, and is widely used for manufacturing various cutting tools, mining tools and wear-resistant and corrosion-resistant parts.

However, because the conventional cemented carbide has a uniform structure formed by bonding and interleaving a carbide ceramic phase skeleton and a metal, the change of the wear resistance and the change of the fracture toughness of the cemented carbide have a negative correlation, that is, the hardness and the toughness of the cemented carbide are difficult to be synchronously improved, thereby limiting the application of the cemented carbide material in the cutting processing of high-hardness and difficult-to-process materials.

Disclosure of Invention

Therefore, it is necessary to provide a gradient cemented carbide composite bar and a preparation method thereof for solving the technical problem that the hardness and toughness of cemented carbide are not high.

A gradient hard alloy composite bar comprises, by mass, 81.5 parts of WC powder ~ 87.5.5 parts, 6 parts of Co powder ~ 10 parts, 5.5 parts of carbon powder ~ 6.5.5 parts and 1 part of paraffin ~ 2 parts.

In one embodiment, the mean grain size of the WC powder is between 2.5 μm and 10.6 μm.

The invention also provides a preparation method of the gradient hard alloy composite bar, which comprises the following steps:

grinding: the WC powder was ground in a ball mill.

And (3) drying: the milled WC powder was dried.

And (3) mixing and grinding, namely adding 81.5 parts by mass of ~ 87.5.5 parts by mass of dry WC powder, 6 parts by mass of ~ 10 parts by mass of Co powder, 5.5 parts by mass of ~ 6.5.5 parts by mass of carbon powder and 1 part by mass of ~ 2 parts by mass of paraffin into a ball mill for mixing and grinding.

Secondary drying: and drying the ground mixed powder.

Screening: and sieving the mixed powder after the secondary drying through a screen.

Blank preparation: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Pre-sintering: and (4) placing the blank sample into a vacuum tube furnace for heating, and pre-sintering the blank sample to obtain a sample.

High-temperature carburization: and putting the pre-sintered sample into a high-pressure atmosphere furnace, carbonizing the sample in a hydrogen-methane gas mixture, and carbonizing the sample to obtain the gradient hard alloy composite bar.

In one embodiment, 95% alcohol is added to the ball mill during the milling operation.

In one embodiment, the mulling operation lasts 0.8h ~ 1.2.2 h.

In one embodiment, hexane is added to the ball mill at a concentration of 99% during the mixing operation.

In one embodiment, the mixed powder is dried in a rotary evaporation dish.

In one embodiment, the oversize from the screening operation is ground in a mortar, and the ground powder is screened again through a screen until the oversize completely passes through the screen.

In one embodiment, the presintering temperature of the vacuum tube furnace is between 700 DEG^oC to 900^oAnd C.

In one embodiment, the high temperature carburization operation lasts 0.8h ~ 1.2.2 h.

According to the gradient hard alloy composite bar, carbon powder is added into a mixture of WC powder and Co powder, so that carbon elements are provided for WC-Co-based hard alloy generated by pre-sintering operation, the carbon content in the hard alloy is favorably adjusted, and a surface layer which is poor in CO and has no eta phase, a transition layer which is rich in CO and has no eta phase and a core part which contains eta phase and has gradient distribution are formed at equal levels, so that the hardness difference and the toughness difference of each layer are adjusted, the hardness and the toughness of the gradient hard alloy composite bar are synchronously improved, and the purpose of improving the cutting performance of the gradient hard alloy composite bar is achieved; according to the preparation method of the gradient hard alloy composite bar, the WC recrystallization degree of the gradient hard alloy round bar and the carbon content in the near surface layer and the core part of the gradient hard alloy round bar are regulated and controlled through a selective carburizing method and liquid phase sintering, the gradient hard alloy round bar containing neither eta phase nor grain growth inhibitor is prepared, the prepared gradient hard alloy round bar is high in hardness and good in fracture toughness, the problem that the hardness and the toughness of the hard alloy round bar cannot be considered at the same time in subsequent processing can be effectively solved, and therefore the application range of hard alloy materials is expanded.

Drawings

Fig. 1 is a process flow diagram of a method for preparing a gradient cemented carbide composite rod in example 1;

FIG. 2 is a graph of Co content versus hardness for various levels of a WC — Co-based cemented carbide according to one embodiment;

FIG. 3 is a process flow diagram of a method for preparing a gradient cemented carbide composite rod according to example 2;

FIG. 4 is a process flow diagram of a method for preparing a gradient cemented carbide composite rod of example 3;

FIG. 5 is a process flow diagram of a method of making a gradient cemented carbide composite rod of example 4;

FIG. 6 is a process flow diagram of a method of making a gradient cemented carbide composite rod of example 5;

FIG. 7 is a graph illustrating the variation of grain sizes at different locations on a gradient cemented carbide composite rod according to an embodiment;

FIG. 8 is a graph illustrating the variation of Co content at different locations on a gradient cemented carbide composite rod according to an embodiment;

FIG. 9 is a graph illustrating the trend of hardness changes at different locations on a gradient cemented carbide composite rod according to an embodiment;

FIG. 10 is a graph illustrating the hardness and toughness of a gradient cemented carbide composite rod versus a conventional cemented carbide according to one embodiment;

in fig. 2: x-axis represents the distance from the inside of the WC — Co-based cemented carbide to its surface, X1: skin layer, X2: intermediate layer, X3 denotes core; the Y1 axis represents Co content values and the Y2 axis represents hardness values;

in fig. 7: the X-axis represents the surface distance and the Y-axis represents the grain size value;

in fig. 8: the X-axis represents the surface distance and the Y-axis represents the Co content value;

in fig. 9: the X-axis represents surface distance and the Y-axis represents hardness value;

in fig. 10: the X-axis represents hardness values and the Y-axis represents toughness values.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example 1

The invention provides a gradient hard alloy composite bar which comprises the following components in parts by mass: 81.5 parts of WC powder, 10 parts of Co powder, 6.5 parts of carbon powder and 2 parts of paraffin.

According to the gradient hard alloy composite bar, carbon powder is added into a mixture of WC powder and Co powder, so that carbon elements are provided for WC-Co-based hard alloy generated by pre-sintering operation, the carbon content in the hard alloy is favorably adjusted, a surface layer which is poor in CO and has no eta phase, a transition layer which is rich in CO and has no eta phase and a core part which contains eta phase and has gradient distribution are formed, the hardness difference and the toughness difference of each layer are adjusted, the hardness and the toughness of the gradient hard alloy composite bar are synchronously improved, and the purpose of improving the cutting performance of the gradient hard alloy composite bar is achieved.

Referring to fig. 1, the method 10 for manufacturing the gradient cemented carbide composite bar includes the following steps:

step S101: the WC powder was ground in a ball mill.

Specifically, ultra-coarse grain WC powder with the average grain size of 10.6 microns is taken, the ultra-coarse grain WC powder and 95% alcohol are added into a ball mill for grinding, and the ultra-coarse grain WC powder is continuously ground for 120 hours under the condition that the ball-to-material ratio is 6:1, so that the fine grain WC powder is obtained. By grinding the ultra-coarse grain WC powder into the fine grain WC powder, the specific surface area of the WC powder is increased, in other words, the contact area and the action area of the WC powder and the Co powder are increased, so that the WC powder is more easily combined with the Co powder to generate WC-Co-based hard alloy in the pre-sintering operation, namely, the amount of the WC-Co-based hard alloy generated by combining the WC powder and the Co powder is increased, the amount of the WC-Co-based hard alloy participating in the high-temperature carburization operation is synchronously increased, and the conversion rate of preparing the gradient hard alloy by using the WC powder and the Co powder is obviously increased. It should be noted that, in this embodiment, the alcohol provides lubrication for the grinding of the ultra-coarse grain WC powder, that is, the ultra-coarse grain WC powder is ground by a wet method, so that heat generated by grinding the ultra-coarse grain WC powder and the ball material is transferred to the alcohol solution, thereby preventing the ultra-coarse grain WC powder from being heated rapidly during the grinding process, and further preventing the problem of explosion of the ball mill caused by the rapid heating, and improving the safety of the grinding operation of the ultra-coarse grain WC powder.

Step S102: the milled WC powder was dried.

Specifically, a large amount of alcohol and water remain on the surface of the WC powder after grinding, that is, the product of the grinding operation is WC slurry, and if the WC slurry is directly added into a ball mill to be mixed and ground with Co powder, carbon powder and paraffin, the content of alcohol and water adhered to the WC powder is not easily determined, which causes a large mass error of the WC powder actually added in the mixing and grinding operation, thereby affecting the effective performance of the pre-sintering operation and the high-temperature carburizing operation.

In one embodiment, the wet-milled WC slurry is placed in a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 65 degrees^oC, rotating the rotary evaporating dish at the rotating speed of 80rpin and continuously drying the WC slurry for 0.8 h. By mixingThe WC slurry is placed in the rotary evaporation dish to be dried, the rotary evaporation dish uniformly heats up in the rotating process of the rotary evaporation dish, and the WC slurry placed on the rotary evaporation dish is uniformly heated, so that the WC slurry on the rotary evaporation dish synchronously heats up, the drying degree of the WC slurry tends to be consistent, and the drying effect of the WC slurry is ensured.

Step S103: 81.5 parts by mass of dry WC powder, 10 parts by mass of Co powder, 6.5 parts by mass of carbon powder, and 2 parts by mass of paraffin were added to a ball mill and mixed and ground.

Specifically, after the WC powder is dried, the dry WC powder, the Co powder, the carbon powder and the paraffin wax are accurately weighed according to the corresponding parts by mass, the powder is added into a ball mill, and the mixed powder is continuously ground for 0.8h under the condition that the ball-to-material ratio is 3: 1. By mixing and grinding the powder, the mixed powder generates relative motion while being ground to be uniformly mixed, so that the contact area of each component in the mixed powder is increased, and the mixed powder is combined and reacted in the subsequent pre-sintering operation conveniently. It should be noted that, in this embodiment, the carbon powder provides a carbon element for the generation of the WC — Co based cemented carbide, and it can also be understood that the carbon element is supplemented by the high-temperature carburization operation of the carbon powder for the WC — Co based cemented carbide, so as to facilitate the adjustment of the carbon content in the gradient cemented carbide, thereby achieving the adjustment of the hardness of the gradient cemented carbide. Paraffin wax has a strong adhesive property, and in this example, paraffin wax is used as a binder. Specifically, the paraffin is fully mixed with WC powder, Co powder and carbon powder in the ball milling process, and the WC powder, the Co powder and the carbon powder are firmly adhered together by the paraffin in the blank making process, so that a blank sample prepared in the blank making process is not easy to disperse and crack, and the blank sample is favorably presintered in a vacuum tube furnace.

In addition, during the operation of mixing and grinding the mixed powder, hexane having a concentration of 99% was added as a lubricant to the mixed powder, and since the specific heat capacity of hexane was greater than that of WC powder, Co powder and carbon powder, after hexane was added to the ball mill, the mixed powder and hexane formed a mixed slurry, and the amount of mixed powder particles floating in the ball mill was small, and the mixed powder was generated during the grinding processThe heat is transferred into the hexane solution, the temperature rise of the mixed powder is less, so that the problem of explosion of the ball mill caused by the temperature rise of the mixed powder can be prevented, and the operation safety is improved. Specifically, the hexane with the concentration of 99 percent is heated to 70 ℃ outside a ball mill^oAfter C, the paraffin to be added was dissolved in the hexane solution to form a mixed solution, and then the mixed solution was added to a ball mill to be mixed and ground with the WC powder, Co powder and carbon powder. The paraffin is added into the high-temperature hexane solution, so that the paraffin dissolution can be accelerated, the paraffin enters the ball mill in a molecular form, the combination of the paraffin, the WC powder, the Co powder and the carbon powder is facilitated, the combination of the WC powder, the Co powder and the carbon powder is firmer, and the stability of a blank sample in subsequent operation is improved.

Step S104: and carrying out secondary drying on the ground mixed powder.

Specifically, after mixing and grinding, the hexane content in the mixed slurry is difficult to determine, and therefore, the slurry formed by the mixed powder needs to be dried to eliminate the interference of hexane on the carbon content in the subsequently produced WC — Co-based cemented carbide. Specifically, the mixed slurry in the ball mill is poured into a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 70 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 0.8h to obtain dry mixed powder.

Step S105: and sieving the mixed powder after the secondary drying through a screen.

Specifically, in order to control the size of the crystal grains in the mixed powder to facilitate the pre-sintering operation, the mixed powder needs to be sieved to remove the crystal grains with larger grain sizes. Specifically, the mixed powder after secondary drying passes through a stainless steel mesh screen of 100 meshes, undersize products are collected, oversize products of the mesh screen are collected into a mortar for grinding, the ground powder is sieved again by using the mesh screen until the mixed powder completely passes through the mesh screen, and the mixed powder with qualified granularity is obtained.

Step S106: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Specifically, after the mixed powder is screened, placing the undersize product of the screening operation in an automatic press with a specific mold blank, starting the automatic press, and enabling the automatic press to extrude and mold the mixed powder at 6 tons of pressure so as to press and obtain a blank sample of the gradient hard alloy round bar.

Step S107: and (4) placing the blank sample into a vacuum tube furnace for heating, and pre-sintering the blank sample to obtain a sample.

Specifically, after the blank sample of the gradient hard alloy round rod is pressed, the blank sample of the gradient hard alloy round rod needs to be pre-sintered to prepare the WC-Co-based hard alloy containing eta phase, so that the initial shaping of the gradient hard alloy round rod is realized, the cracking or the notch of the gradient hard alloy round rod caused by the over-speed of temperature rise when the blank sample is directly subjected to high-temperature carburization is prevented, and the condition is provided for combining WC powder and Co powder to generate the gradient hard alloy round rod with reliable quality. Specifically, the sample is placed in 900^oC, sintering in a vacuum tube furnace, wherein during the sintering process, paraffin in the blank sample is heated and decomposed into CO₂The gas overflows, the blank sample gradually hardens and the volume of the blank sample gradually shrinks, so that the WC-Co-based hard alloy sample containing eta phase with certain strength is obtained, and the subsequent high-temperature carburization operation is effectively carried out. It should be noted that the term "η -phase-containing WC-Co-based cemented carbide" as used herein refers to a cemented carbide in which three phase regions of WC, Co and C exist, i.e., a combination of WC, Co and C exists, including Co₆W₆C、Co₃W₃C and Co₄W₂Since the presence of C increases the hardness of the alloy and limits the toughness thereof, it is necessary to further perform high-temperature carburization of a WC — Co-based cemented carbide sample containing an η phase.

Step S108: placing the pre-sintered sample into a high-pressure atmosphere furnace at 900 DEG^oAnd C, continuously carbonizing the hydrogen-methane gas mixture for 0.8h to obtain the gradient hard alloy composite bar.

Specifically, after the blank sample is pre-sintered, the prepared sample needs to be placed in a high-temperature atmosphere furnace for further carbonization so as to adjust the carbon content in the gradient hard alloy composite bar, and further adjust the hardness and toughness of the gradient hard alloy composite bar.

The carbonization mechanism of the WC-Co-based hard alloy is as follows: in the presintering operation process of a blank sample, Co exists in a liquid phase form, when WC-Co-based hard alloy is subjected to high-temperature carburization treatment, carbon atoms firstly react with eta phase of an alloy surface layer, so that the eta phase of the surface layer is decomposed, WC and Co are further generated, and thus a WC-Co two-phase region gradually appears on the alloy surface layer, the content of liquid phase Co in the two-phase region is higher than that of liquid phase Co in a WC-Co-C three-phase region in the alloy, and a larger liquid phase Co gradient appears. With the further advance of the carburizing operation, the concentration of the C atoms in the liquid phase Co can be in a gradient distribution from the surface to the inside, and the eta phase of the inner layer can further undergo decomposition reaction under the action of the C atoms:

Co₆W₆C→6Co+WC+5W；

Co₃W₃C→3Co+WC+2W；

Co₄W₂C→4Co+WC+W。

due to the gradient distribution of the concentration of the C atoms, the decomposed W atoms are driven to migrate to the outer surface layer, and the decomposed W atoms react with the C atoms in the liquid phase Co to generate WC and a combination of the W and the WC, and are separated out on the surface of the original WC crystal grains, so that the WC crystal grains on the outer surface layer become coarse and the content of the WC crystal grains is increased. Meanwhile, when Co is diffused due to the difference of the chemical potential gradient of Co, the volume defect caused by outward migration of W atoms drives the liquid-phase Co in the outer surface layer to migrate to the inner layer so as to fill the defect, and thus a transition layer with high Co content is formed. Thus, the eta-phase-containing WC-Co-based hard alloy sample is carbonized at high temperature to form three different hierarchical regions, namely a CO-poor eta-phase-free surface layer, a CO-rich eta-phase-free transition layer and a eta-phase-containing core part. Referring to fig. 2, the structure of the surface layer is a mixture of WC and Co, and the Co content is lower than the nominal Co content of the alloy, so that the surface layer has high hardness; the structure of the transition layer is a mixture consisting of WC and Co, but the Co content is higher than the nominal Co content of the alloy, so that the hardness is low and the toughness is high; the structure of the core is a mixture of WC, eta phase and Co, and the Co content and the hardness of the core are the nominal Co content and the nominal hardness of the alloy. That is, the hardness and toughness of each layer of the WC-Co based hard alloy are distributed in different rules, so that the hardness and toughness of the gradient hard alloy generated after the WC-Co based hard alloy is carbonized at high temperature can be synchronously improved through the mutual cooperation and combined action of the layers, and the purpose of improving the cutting performance of the hard alloy is achieved.

Example 2

The invention provides a gradient hard alloy composite bar which comprises the following components in parts by mass: 82.02 parts of WC powder, 10 parts of Co powder, 5.98 parts of carbon powder and 2 parts of paraffin.

Referring to fig. 3, the method 20 for manufacturing the gradient cemented carbide composite bar includes the following steps:

step S201: the WC powder was ground in a ball mill.

Specifically, WC powder with the average grain size of 5.6 microns is taken, the WC powder and 95% alcohol are added into a ball mill for grinding, and the WC powder is continuously ground for 120 hours under the condition that the ball-to-material ratio is 6:1, so that the fine-grain WC powder is obtained.

Step S202: the milled WC powder was dried.

Placing the WC slurry after wet grinding into a rotary evaporation dish, and heating the rotary evaporation dish to 65 DEG C^oC, rotating the rotary evaporating dish at the rotating speed of 80rpin and continuously drying the WC slurry for 0.9 h.

Step S203: 82.02 parts by mass of dry WC powder, 10 parts by mass of Co powder, 5.98 parts by mass of carbon powder and 2 parts by mass of paraffin wax were added to a ball mill and mixed and ground.

After the WC powder is dried, accurately weighing the dry WC powder, the Co powder, the carbon powder and the paraffin wax in corresponding parts by mass, adding the powder into a ball mill, and continuously grinding the mixed powder for 1.1h under the condition that the ball-to-material ratio is 1: 2.

Step S204: and carrying out secondary drying on the ground mixed powder.

Specifically, the mixed slurry in the ball mill is poured into a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 70 DEG^oC, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously aligningAnd drying the WC slurry for 0.8h to obtain dry mixed powder.

Step S205: and sieving the mixed powder after the secondary drying through a screen.

Specifically, the mixed powder after secondary drying passes through a stainless steel mesh screen of 100 meshes, undersize products are collected, oversize products of the mesh screen are collected into a mortar for grinding, the ground powder is sieved again by using the mesh screen until the mixed powder completely passes through the mesh screen, and the mixed powder with qualified granularity is obtained.

Step S206: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Specifically, after the mixed powder is screened, placing the undersize product of the screening operation in an automatic press with a specific mold blank, starting the automatic press, and enabling the automatic press to extrude and mold the mixed powder at 6.5 tons of pressure so as to press and obtain a blank sample of the gradient hard alloy round bar.

Step S207: and (4) placing the blank sample into a vacuum tube furnace for heating, and pre-sintering the blank sample to obtain a sample.

Specifically, the blank sample is placed 830^oC, sintering in a vacuum tube furnace, wherein during the sintering process, paraffin in the blank sample is heated and decomposed into CO₂The gas overflows, the blank sample gradually hardens and the volume of the blank sample gradually shrinks, so that the WC-Co-based hard alloy sample containing eta phase with certain strength is obtained, and the subsequent high-temperature carburization operation is effectively carried out.

Step S208: placing the pre-sintered sample into a high-pressure atmosphere furnace at 1000 deg.C^oAnd C, continuously carbonizing the hydrogen-methane gas mixture for 0.9h to obtain the gradient hard alloy composite bar.

According to the preparation method 20 of the gradient hard alloy composite bar, the WC recrystallization degree of the gradient hard alloy round bar and the carbon content in the near surface layer and the core part of the gradient hard alloy round bar are regulated and controlled through a selective carburizing method and liquid phase sintering, the gradient hard alloy round bar containing neither eta phase nor grain growth inhibitor is prepared, the prepared gradient hard alloy round bar is high in hardness and good in fracture toughness, the problem that the hardness and the toughness of the hard alloy round bar cannot be considered simultaneously in subsequent processing can be effectively solved, and therefore the application range of hard alloy materials is expanded.

Example 3

The invention provides a gradient hard alloy composite bar which comprises the following components in parts by mass: 86.98 parts of WC powder, 6 parts of Co powder, 6.02 parts of carbon powder and 1 part of paraffin.

Referring to fig. 4, the method 30 for manufacturing the gradient cemented carbide composite bar includes the following steps:

step S301: the WC powder was ground in a ball mill.

Specifically, WC powder with the average grain size of 2.5 microns is taken, the WC powder and 95% alcohol are added into a ball mill for grinding, and the WC powder is continuously ground for 120 hours under the condition that the ball-to-material ratio is 6:1, so that the fine-grain WC powder is obtained.

Step S302: the milled WC powder was dried.

Specifically, the WC slurry after wet grinding is placed in a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 65 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 1 h. In this example, the initial grain size of the WC powder was smaller when grinding than in example 2, and therefore, the grain size of the fine-grained WC powder was smaller under the same grinding conditions, and thus, the content of alcohol encapsulated between the WC powder particles was higher, so that it was necessary to extend the drying time to completely remove the alcohol from the WC powder, thereby eliminating the influence of the alcohol on the added amount of the WC powder.

Step S303: 86.98 parts by mass of dry WC powder, 6 parts by mass of Co powder, 6.02 parts by mass of carbon powder, and 1 part by mass of paraffin wax were added to a ball mill and mixed and ground.

Specifically, after the WC powder is dried, the dry WC powder, the Co powder, the carbon powder and the paraffin wax are accurately weighed according to the corresponding parts by mass, the powder is added into a ball mill, and the mixed powder is continuously ground for 1 hour under the condition that the ball-to-material ratio is 1: 2.

Step S304: and carrying out secondary drying on the ground mixed powder.

Specifically, the mixed slurry in the ball mill is poured into a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 70 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 1 hour to obtain dry mixed powder.

Step S305: and sieving the mixed powder after the secondary drying through a screen.

Step S306: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Specifically, after the mixed powder is screened, placing the undersize product of the screening operation in an automatic press with a specific mold blank, starting the automatic press, and enabling the automatic press to extrude and mold the mixed powder at 6.8 tons of pressure so as to press and obtain a blank sample of the gradient hard alloy round bar.

Step S307: and (4) placing the blank sample into a vacuum tube furnace for heating, and pre-sintering the blank sample to obtain a sample.

Specifically, the sample is placed at 700^oC, sintering in a vacuum tube furnace, wherein during the sintering process, paraffin in the blank sample is heated and decomposed into CO₂The gas overflows, the blank sample gradually hardens and the volume of the blank sample gradually shrinks, so that the WC-Co-based hard alloy sample containing eta phase with certain strength is obtained, and the subsequent high-temperature carburization operation is effectively carried out.

Step S308: placing the pre-sintered sample into a high-pressure atmosphere furnace at 1100 deg.C^oAnd C, continuously carbonizing the hydrogen-methane gas mixture for 1 hour to obtain the gradient hard alloy composite bar.

According to the preparation method 30 of the gradient hard alloy composite bar, the WC recrystallization degree of the gradient hard alloy round bar and the carbon content in the near surface layer and the core part of the gradient hard alloy round bar are regulated and controlled through a selective carburizing method and liquid phase sintering, the gradient hard alloy round bar containing neither eta phase nor grain growth inhibitor is prepared, the prepared gradient hard alloy round bar is high in hardness and good in fracture toughness, the problem that the hardness and the toughness of the hard alloy round bar cannot be considered simultaneously in subsequent processing can be effectively solved, and therefore the application range of hard alloy materials is expanded.

Example 4

The invention provides a gradient hard alloy composite bar which comprises the following components in parts by mass: 81.89 parts of WC powder, 10 parts of Co powder, 6.11 parts of carbon powder and 2 parts of paraffin.

Referring to fig. 5, the method 40 for manufacturing the gradient cemented carbide composite bar includes the following steps:

step S401: the WC powder was ground in a ball mill.

Specifically, ultra-coarse grain WC powder with the average grain size of 10.6 microns is taken, the ultra-coarse grain WC powder and 95% alcohol are added into a ball mill for grinding, and the ultra-coarse grain WC powder is continuously ground for 120 hours under the condition that the ball-to-material ratio is 6:1, so that the fine grain WC powder is obtained.

Step S402: the milled WC powder was dried.

Specifically, the WC slurry after wet grinding is placed in a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 65 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 1 h.

Step S403: 81.89 parts by mass of dry WC powder, 10 parts by mass of Co powder, 6.11 parts by mass of carbon powder and 2 parts by mass of paraffin were added to a ball mill and mixed and ground.

Specifically, after the WC powder is dried, the dry WC powder, the Co powder, the carbon powder and the paraffin wax are accurately weighed according to the corresponding parts by mass, the powder is added into a ball mill, and the mixed powder is continuously ground for 1.2 hours under the condition that the ball-to-material ratio is 1: 2.

Step S404: and carrying out secondary drying on the ground mixed powder.

Specifically, the mixed slurry in the ball mill is poured into a rotary evaporation pan, and the rotary evaporation pan is filled with the mixed slurryThe temperature is raised to 70 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 1 hour to obtain dry mixed powder.

Step S405: and sieving the mixed powder after the secondary drying through a screen.

Step S406: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Specifically, after the mixed powder is screened, placing the undersize product of the screening operation in an automatic press with a specific mold blank, starting the automatic press, and enabling the automatic press to extrude and mold the mixed powder at a pressure of 7.6 tons so as to press and obtain a blank sample of the gradient hard alloy round bar.

Step S407: and (3) placing the blank sample into a high-pressure atmosphere furnace for heating, and decarburizing the blank sample to obtain a sample.

Specifically, the sample is placed at 700^oC contains H₂Performing decarburization treatment in a high-pressure atmosphere furnace in an atmosphere such that part of the carbon powder in the blank sample is mixed with H₂React to generate CO₂And H₂O, namely, the carbon content in the mixed powder is reduced, so that the influence of the C element on the toughness of the gradient hard alloy composite bar is weakened.

Step S408: and further sintering the decarburized sample to prepare the gradient hard alloy composite bar.

Specifically, the decarburized sample is further heated to 1460^oC, continuously sintering the sample at the temperature for 1h, so that WC and Co in the sample prepared by decarburization treatment are combined to form a WC-Co two-phase region, meanwhile, residual C in the sample is combined with WC and Co to form a C-WC-Co three-phase region, the hardness and toughness distribution laws of the two-phase region and the three-phase region are opposite, so that the two-phase region and the three-phase region can be jointly adjusted and matched to form the alloy materialSo that the hardness and the toughness of the gradient hard alloy composite bar are synchronously improved.

According to the preparation method 40 of the gradient hard alloy composite bar, the WC recrystallization degree of the gradient hard alloy round bar and the carbon content in the near surface layer and the core part of the gradient hard alloy round bar are regulated and controlled through a selective carburizing method and liquid phase sintering, the gradient hard alloy round bar containing neither eta phase nor grain growth inhibitor is prepared, the prepared gradient hard alloy round bar is high in hardness and good in fracture toughness, the problem that the hardness and the toughness of the hard alloy round bar cannot be considered simultaneously in subsequent processing can be effectively solved, and therefore the application range of hard alloy materials is expanded.

Example 5

The invention provides a gradient hard alloy composite bar which comprises the following components in parts by mass: 87.5 parts of WC powder, 6 parts of Co powder, 5.5 parts of carbon powder and 1 part of paraffin.

Referring to fig. 6, the method 50 for manufacturing the gradient cemented carbide composite bar includes the following steps:

step S501: the WC powder was ground in a ball mill.

Specifically, coarse grain WC powder with the average grain size of 7.8 microns is taken, the coarse grain WC powder and 95% alcohol are added into a ball mill for grinding, and the coarse grain WC powder is continuously ground for 120 hours under the condition that the ball-to-material ratio is 6:1, so that fine grain WC powder is obtained.

Step S502: the milled WC powder was dried.

Step S503: 87.5 parts by mass of dry WC powder, 6 parts by mass of Co powder, 5.5 parts by mass of carbon powder and 1 part by mass of paraffin were added to a ball mill and mixed and ground.

After the WC powder is dried, accurately weighing the dry WC powder, the Co powder, the carbon powder and the paraffin wax in corresponding parts by mass, adding the powder into a ball mill, and continuously grinding the mixed powder for 1.2 hours under the condition that the ball-to-material ratio is 1: 2.

Step S504: and carrying out secondary drying on the ground mixed powder.

Specifically, the mixed slurry in the ball mill is poured into a rotary evaporation pan, and the temperature of the rotary evaporation pan is raised to 70 DEG^oAnd C, rotating the rotary evaporation dish at the rotating speed of 80rpin and continuously drying the WC slurry for 1.2h to obtain dry mixed powder.

Step S505: and sieving the mixed powder after the secondary drying through a screen.

Step S506: and feeding the undersize products obtained by the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample.

Specifically, after the mixed powder is screened, placing the undersize product of the screening operation in an automatic press with a specific mold blank, starting the automatic press, and enabling the automatic press to extrude and mold the mixed powder at 8 tons of pressure so as to press and obtain a blank sample of the gradient hard alloy round bar.

Step S507: and (3) placing the blank sample into a high-pressure atmosphere furnace for heating, and decarburizing the blank sample to obtain a sample.

Specifically, the sample is placed 720^oC contains H₂Performing decarburization treatment in a high-pressure atmosphere furnace in an atmosphere such that part of the carbon powder in the blank sample is mixed with H₂React to generate CO₂And H₂O, namely, the carbon content in the mixed powder is reduced, so that the influence of the C element on the toughness of the gradient hard alloy composite bar is weakened.

Step S508: and further sintering the decarburized sample to prepare the gradient hard alloy composite bar.

Specifically, the decarburized sample is further heated to 1460^oC, continuously sintering the sample at the temperature for 1.2h, thusWC and Co in the sample prepared by decarburization treatment are combined to form a WC-Co two-phase region, meanwhile, residual C in the sample is combined with WC and Co to form a C-WC-Co three-phase region, the hardness and toughness distribution rules of the two-phase region and the three-phase region are opposite, and thus, the hardness and toughness of the gradient hard alloy composite bar can be synchronously improved by jointly adjusting and matching the two-phase region and the three-phase region.

According to the preparation method 50 of the gradient hard alloy composite bar, the WC recrystallization degree of the gradient hard alloy round bar and the carbon content in the near surface layer and the core part of the gradient hard alloy round bar are regulated and controlled through a selective carburizing method and liquid phase sintering, the gradient hard alloy round bar containing neither eta phase nor grain growth inhibitor is prepared, the prepared gradient hard alloy round bar is high in hardness and good in fracture toughness, the problem that the hardness and the toughness of the hard alloy round bar cannot be considered simultaneously in subsequent processing can be effectively solved, and therefore the application range of hard alloy materials is expanded.

Referring to fig. 7 to 9, the present invention has been made to examine some properties of the gradient cemented carbide composite rods obtained in examples 1 to 5, and it can be seen from the data shown in the figure that the hardness of the gradient cemented carbide composite rods obtained by the formulation and method of the present invention is uniform, thereby overcoming the technical problems of large hardness change of the conventional cemented carbide and easy occurrence of cracks and fractures during the use, and improving the cutting performance of the gradient cemented carbide composite rods. Referring to fig. 10, three curves are shown in the figure, which are hardness and toughness values corresponding to the conventional cemented carbide with Co content of 6%, 10% and 15%, respectively, and points a and B are hardness and toughness points corresponding to the gradient cemented carbide composite bars processed in examples 2 and 3 of the present invention, respectively.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The gradient hard alloy composite bar is characterized by comprising 81.5 parts by mass of WC powder ~ 87.5.5 parts by mass, 6 parts by mass of Co powder ~ 10 parts by mass, 5.5 parts by mass of carbon powder ~ 6.5.5 parts by mass and 1 part by mass of paraffin ~ 2 parts by mass.

2. The gradient cemented carbide composite rod of claim 1, wherein the WC powder has an average grain size between 2.5 μ ι η and 10.6 μ ι η.

3. A preparation method of a gradient hard alloy composite bar comprises the following steps:

grinding: putting WC powder into a ball mill for grinding;

and (3) drying: drying the grinded WC powder;

mixing and grinding, namely adding 81.5 parts by mass of ~ 87.5.5 parts by mass of dry WC powder, 6 parts by mass of ~ 10 parts by mass of Co powder, 5.5 parts by mass of ~ 6.5.5 parts by mass of carbon powder and 1 part by mass of ~ 2 parts by mass of paraffin into the ball mill for mixing and grinding;

secondary drying: drying the ground mixed powder;

screening: screening the mixed powder after secondary drying through a screen;

blank preparation: feeding the undersize products of the screening operation into a press to be pressed into a gradient hard alloy round bar blank sample;

pre-sintering: placing the blank sample into a vacuum tube furnace for heating, and pre-sintering the blank sample to obtain a sample;

4. The method of claim 3, wherein 95% alcohol is added to the ball mill during the milling operation.

5. The method of claim 3, wherein the mulling operation lasts 0.8h ~ 1.2.2 h.

6. The method of claim 3, wherein hexane is added to the ball mill at a concentration of 99% during the mixing operation.

7. The method of claim 3, wherein the mixed powder is dried in a rotary evaporator pan.

8. The method according to claim 3, wherein the oversize product obtained by the screening operation is ground in a mortar, and the ground powder is screened again by the screen until all the oversize product passes through the screen.

9. The method of claim 3, wherein the pre-sintering temperature of the vacuum tube furnace is between 700 ℃^oC to 900^oAnd C.

10. The method of claim 3, wherein the high temperature carburization operation lasts 0.8h ~ 1.2.2 h.