CN106636837A - Preparation method of ultra-coarse grain WC-Co hard alloy - Google Patents

Abstract

The invention provides a method for preparing ultra-coarse-grained WC-Co cemented carbide, which belongs to the field of cemented carbide material preparation. The method is as follows: mix ultra-fine WC powder with ultra-coarse WC powder, Co powder, tungsten powder and carbon black, add paraffin, then add absolute alcohol and hard alloy grinding rods, put them into a ball mill for ball milling, and vacuum dry Made into a mixture, then pressed and sintered into ultra-coarse-grained WC-Co cemented carbide. The present invention adds ultra-fine WC powder, tungsten powder and carbon black on the basis of traditional ultra-coarse WC powder and Co powder, which can significantly improve the bending strength of WC-Co cemented carbide, reduce the brittleness of the alloy, and improve its impact resistance force. In the invention, by changing the proportion of the grinding body, the grinding rod and the bar material, and the material-liquid ratio of the mixture and the grinding medium, the breakage of WC crystal grains is effectively reduced, and the cemented carbide with a grain size larger than 6.0 μm is prepared. The ultra-coarse-grained hard alloy prepared by the method of the invention has a uniform microstructure, large average grain size of the WC hard phase, narrow grain distribution, small porosity of the product, and good comprehensive performance.

Description

A kind of preparation method of ultracoarse grain WC-Co cemented carbide

technical field

The invention belongs to the technical field of hard alloy material preparation, in particular to a preparation method of ultra-coarse grain WC-Co hard alloy.

Background technique

According to ISO4499-2, cemented carbide with WC grain size ≧6.0μm is called ultra-coarse grained cemented carbide. Ultra-coarse-grained cemented carbide has excellent thermal conductivity, thermal shock resistance, thermal fatigue resistance and high bending strength. It is an ideal material for mining, engineering and molds, and it is also one of the development directions of cemented carbide. The traditional process of preparing cemented carbide is to use tungsten carbide powder and cobalt powder as the main raw materials, form a mixture through batching, ball milling, drying and granulation, and then prepare a product green body with a certain forming process, and then prepare it through a sintering process. Carbide products.

From the preparation of raw materials, due to the continuity of the microstructure, fine-grained tungsten carbide powder is usually used to prepare fine WC grain cemented carbide, and coarse-grained tungsten carbide powder is used to prepare coarse WC grain cemented carbide. Therefore, the current method of producing ultra-coarse-grained WC-Co cemented carbide mainly uses ultra-coarse tungsten carbide powder and cobalt powder as raw materials, and after batching, ball milling, drying, and granulation, it is pressed and sintered to form a product. However, the ultra-coarse tungsten carbide powder will be broken during the ball milling process, and the particle size will be greatly reduced. During the sintering process, the WC grains cannot grow into ultra-coarse grain WC grains. The grain size is only 3.0-6.0μm; if the sintering temperature is excessively increased or the holding time is prolonged, although the WC grains can be coarsened, it will lead to a widening of the WC grain distribution and a decrease in the performance of the cemented carbide; Strength, although the tungsten carbide powder in the mixture can maintain a large particle size, but the mixture obtained in this way lacks enough active fine powder, and the remaining large particle size tungsten carbide powder does not have enough activity. It cannot be prepared into dense cemented carbide in subsequent sintering. Therefore, it is difficult to prepare ultra-coarse-grained cemented carbide with ultra-coarse tungsten carbide powder.

In terms of technology, the preparation of ultra-coarse-grained cemented carbide mainly involves prolonging the ball milling time of the mixture, complex pretreatment of the mixture powder, complex WC particle size control process, increasing the sintering temperature and extending the holding time. Among them, prolonging the ball milling time of the mixture will easily lead to severe breakage of WC grains, and it is difficult to prepare ultra-coarse-grained cemented carbide with large grain size. Although increasing the sintering temperature or prolonging the holding time can make the WC grains thicker, it is easy to induce WC grains. The widening of the grain distribution leads to a decrease in the mechanical properties of the cemented carbide. However, the above-mentioned other methods for preparing ultra-coarse-grained cemented carbide have complex processes, long production cycles, and high production costs, making it difficult to achieve mass production.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the existing technology of preparing ultra-coarse-grained hard alloy ball-milling, such as long ball milling time and serious broken WC grains, and provide a method for preparing ultra-coarse-grained WC-Co hard alloy. By adding pretreated ultra-fine WC powder, tungsten powder and carbon black to the raw materials, and improving the ball milling and pressing process, it is possible to prepare cemented carbide with an average grain size of 5.7-6.5 μm and excellent performance. . The ultra-coarse-grained hard alloy prepared by using the raw material and the method of the invention has a uniform microstructure, large average grain size of the WC hard phase, narrow grain distribution, small porosity, good density and good mechanical properties. The object of the invention is achieved through the following technical solutions:

A preparation method of ultra-coarse-grained WC-Co cemented carbide, comprising the following steps:

1) Mix pre-ground ultra-fine WC powder with ultra-coarse WC powder, Co powder, tungsten powder and carbon black to obtain mixture I, and add paraffin to obtain mixture II, the mass percentage of paraffin wax and mixture I is 1% ~2.5%;

2) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.2mL/Kg～0.3mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time , the rod-to-material ratio of the cemented carbide grinding rod to the mixture II is 1.2:1～1.8:1;

3) Mill the material prepared in step 2) in a ball mill for 7 to 13 hours, then vacuum dry for 3 to 6 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III is 5.7 μm to 6.5 μm;

4) The mixture III is pressed and sintered to form an ultra-coarse-grained WC-Co cemented carbide.

Compared with the existing raw materials of WC-Co cemented carbide, the present invention adds superfine WC powder, tungsten powder and carbon black on the basis of traditional ultracoarse WC powder and Co powder. The tungsten powder is separated out by high-temperature melting and adheres to the original ultra-coarse WC powder to further increase the grain size of the alloy. At the same time, it can also change the cobalt phase in the alloy, enhance the strength of the cemented carbide and balance the carbon content in the alloy. the goal of. The addition of carbon black can enhance the strength of cemented carbide, improve its impact resistance, and at the same time optimize the amount of carbon in the alloy to reduce the brittleness of cemented carbide. The present invention adds ultra-fine WC powder to the raw material and pre-grinds it for a certain period of time. The purpose is to increase its activity so that it can melt and separate out during high-temperature sintering, and adhere to the ultra-coarse WC to make the crystal grains of cemented carbide meet the design requirements.

As a preferred method for preparing the ultra-coarse-grained WC-Co cemented carbide of the present invention, the mass ratio of the ultra-fine WC powder, ultra-coarse WC powder, Co powder, tungsten powder and carbon black is 5-10:75-91 : 6-15: 0-1: 0-1.5 parts.

As a further preference for the preparation method of the ultra-coarse-grained WC-Co cemented carbide of the present invention, the Fischer particle size of the ultra-fine WC powder is 0.2 μm to 0.6 μm, and the Fischer particle size of the ultra-coarse WC powder is 15 μm to 26 μm, The Fisherman's particle size of the Co powder is 1 μm-3 μm, the Fisherman's particle size of the tungsten powder is 0.45-0.8 μm, and the Fisherman's particle size of the carbon black is 1-1.3 μm.

As a further preferred method for preparing the ultra-coarse-grained WC-Co cemented carbide of the present invention, the ultra-fine WC powder needs to be pre-grinded separately for 40-50 hours before being added, and then precipitated for use. The superfine WC powder of the present invention is the same as pre-grinding and mass-grinding, using a roller ball mill with a ball-to-material ratio of 1:5 and anhydrous alcohol as a grinding medium for pre-grinding. The realization of this pre-grinding technology is conventional to those skilled in the art, and there is no special limit to the particle size of the ultrafine WC after grinding, as long as the pre-grinding is carried out according to the conventional method defined by the present invention, the superfine WC pre-grinding of the present invention can be realized. Any purpose is acceptable.

As a preferred method for preparing the ultra-coarse-grained WC-Co cemented carbide of the present invention, after the preparation of the mixture III and before pressing, it also includes passing the mixture III through a 200-500 mesh sieve and putting it into the preparation after sieving. Roll in the granulator for 12 to 18 minutes to granulate, and the granulation adopts repeated granulation to make suitable granules loosely packed to form compressible performance granules. This design can solve the technical problems of poor fluidity and feeding difficulties of ultra-coarse-grained mixtures to a certain extent.

As a preferred method for preparing ultra-coarse-grained WC-Co cemented carbide of the present invention, the size of the cemented carbide grinding rod is In addition, the cemented carbide grinding rod adopts ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 20 μm-26 μm. In the ball milling process of WC-Co cemented carbide, the present invention uses cemented carbide grinding rods instead of traditional cemented carbide balls, which can significantly reduce the ball milling time from 20 to 28 hours to 7 to 13 hours , while improving the ball milling effect, it can effectively reduce the breakage of WC grains; and the present invention sets the Fischer grain size of ultra-coarse cemented carbide WC for the preparation of cemented carbide grinding rods to 20 μm to 26 μm, which helps to reduce the ball milling time and improve Milling efficiency.

In the present invention, the rod-to-material ratio of the cemented carbide grinding rod to the mixture II is set at 1.2:1 to 1.8:1, and the material-to-liquid ratio of the mixture II to anhydrous alcohol is set to 0.2mL/Kg to 0.3mL/Kg , can reduce the viscosity of the mixture and effectively reduce the grinding time.

As a preferred method for preparing the ultra-coarse-grained WC-Co cemented carbide of the present invention, the pressing pressure is 60-95 MPa; the sintering step is to sinter the pressed compact under vacuum conditions, and the sintering temperature is controlled at 1400 ℃～1500℃, the holding time is controlled at 90～100min, and the pressure in the sintering furnace is 3～7MPa.

Further, the pressing adopts three or more times of repeated vibration feeding; the pressing abrasive adopts an alloy abrasive, and the shrinkage coefficient of the abrasive is 1.23-1.26; the press used in the pressing adopts two-way pressurization . The present invention adopts more than three times or multiple times of repeated vibration feeding, which effectively solves the technical problems of poor fluidity of the ultra-coarse-grained mixture and difficult feeding; The shrinkage coefficient is set at 1.23-1.26, which effectively solves the problems of poor fluidity and molding difficulties of ultra-coarse-grained mixtures. Ensure that the product blank is not delaminated, cracked, and unpressed; the press adopts two-way pressurization and moderate pressure retention, which makes the product more dense and reduces the phenomenon of delamination and cracks in semi-finished products .

As a specific embodiment of a method for preparing ultra-coarse-grained WC-Co cemented carbide of the present invention, the preparation method includes the following steps:

1) Take 5 parts of superfine WC powder with a Fischer particle size of 0.4 μm and pre-grind it separately for 45 hours before settling for use;

2) Combine pre-ground ultra-fine WC powder with 77 parts of ultra-coarse WC powder with a Fischer particle size of 20 μm, 12 parts of Co powder with a Fischer particle size of 2 μm, 0.5 parts of tungsten powder with a Fischer particle size of 0.45 μm and 1 part Carbon black with a Fischer particle size of 1.3 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 1.5%;

3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.2mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, the cemented carbide grinding The rod to material ratio of the mixture II is 1.5:1, the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 24 μm;

4) The material prepared in step 3) was ball milled in a ball mill for 10 hours, and then vacuum-dried for 4 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.0 μm;

5) Put the mixture III through a 200-mesh sieve and put it into a granulator to roll for 15 minutes to granulate, then press it under a pressure of 80MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1400° C., the holding time is 100 minutes, and the pressure in the sintering furnace is 5 MPa.

As a specific embodiment of a method for preparing ultra-coarse-grained WC-Co cemented carbide of the present invention, the preparation method includes the following steps:

1) Take 8 parts of ultra-fine WC powder with a Fibonacci particle size of 0.2 μm and pre-grind for 40 hours, and then precipitate for use;

2) Combine the pre-ground ultra-fine WC powder with 90 parts of ultra-coarse WC powder with a Fischer particle size of 15 μm, 10 parts of Co powder with a Fischer particle size of 3 μm, 1 part of tungsten powder with a Fischer particle size of 0.8 μm and 1.2 parts Carbon black with a Fischer particle size of 1 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 2.0%;

3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.3mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, and the cemented carbide grinding The rod to material ratio of the mixture II is 1.7:1, the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 24 μm;

4) Mill the material prepared in step 3) in a ball mill for 11 hours, then vacuum-dry for 5 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III is 6.5 μm;

5) Put the mixture III through a 400-mesh sieve and put it into a granulator to roll for 12 minutes to granulate, then press it under a pressure of 60MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1500° C., the holding time is 95 minutes, and the pressure in the sintering furnace is 7 MPa.

Beneficial effects of the present invention:

1. Compared with the existing raw materials of WC-Co cemented carbide, the present invention adds ultra-fine WC powder, tungsten powder and carbon black on the basis of traditional ultra-coarse WC powder and Co powder. Under the premise of meeting the requirements of ultra-coarse grain size, the bending strength of WC-Co cemented carbide can be significantly improved, the carbon content in the alloy can be balanced and optimized, the brittleness of the alloy can be reduced, and its impact resistance can be improved.

2. Compared with the existing preparation process of the present invention, the present invention adjusts the material-liquid ratio of the mixture and the grinding medium (alcohol) by changing the ratio of the grinding body and the mixture grinding rod, thereby effectively reducing the breakage of the WC crystal grains and preparing crystal grains. Cemented carbide with a particle size greater than 6.0 μm.

3. The ultra-coarse-grained hard alloy prepared by the method of the invention has a uniform structure, the average grain size of the WC hard phase is large, the grain distribution is narrow, the porosity of the product is small, the density is good, and the comprehensive performance is good; the present invention is Improvement and optimization are carried out on the basis of the original ball milling process, and the existing production equipment is not changed. The process is simple, the production cost is low, and it is suitable for industrial production.

Description of drawings

Fig. 1 is the WC-Co cemented carbide particle size distribution figure prepared by embodiment 1;

Fig. 2 is the scanning electron micrograph of the cemented carbide crystal phase with an average WC-Co particle size of 6.0 μm prepared in Example 1

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1

The preparation method of the ultra-coarse-grained WC-Co cemented carbide in this embodiment is as follows:

1) Take 5 parts of superfine WC powder with a Fischer particle size of 0.4 μm and pre-grind it separately for 45 hours before settling for use;

2) Combine pre-ground ultra-fine WC powder with 77 parts of ultra-coarse WC powder with a Fischer particle size of 20 μm, 12 parts of Co powder with a Fischer particle size of 2 μm, 0.5 parts of tungsten powder with a Fischer particle size of 0.45 μm and 1 part Carbon black with a Fischer particle size of 1.3 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 1.5%;

3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.2mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, the cemented carbide grinding The rod to material ratio of the mixture II is 1.5:1, the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 24 μm;

4) The material prepared in step 3) was ball milled in a ball mill for 10 hours, and then vacuum-dried for 4 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.0 μm;

5) Put the mixture III through a 200-mesh sieve and put it into a granulator to roll for 15 minutes to granulate, then press it under a pressure of 80MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1400° C., the holding time is 100 minutes, and the pressure in the sintering furnace is 5 MPa.

The particle size of the ultra-coarse-grained WC-Co cemented carbide prepared in this embodiment is statistically analyzed by the intercept method, and the results are shown in Figure 1. From Figure 1, it can be seen that the ultra-coarse cemented carbide prepared in this embodiment has a significant impact on WC The particle size is effectively controlled, the particle size distribution is narrow, the particle size of medium and ultra-coarse WC is more, and the fine-grained WC is less. Fig. 2 The scanning electron microscope image of the cemented carbide crystal phase with an average WC grain size of 6.0 μm prepared in this example. It can be seen from Fig. 2 that the ultra-coarse grained WC-Co cemented carbide prepared by the present invention has a uniform microstructure and no abnormalities Coarse grains. In summary, the ultra-coarse-grained cemented carbide prepared in this example has a uniform structure, the average grain size of the WC hard phase is large, the grain distribution is narrow, the product has small porosity and good density.

Example 2

The preparation method of the ultra-coarse-grained WC-Co cemented carbide in this embodiment is as follows:

1) Take 8 parts of ultra-fine WC powder with a Fibonacci particle size of 0.2 μm and pre-grind for 40 hours, and then precipitate for use;

2) Combine the pre-ground ultra-fine WC powder with 90 parts of ultra-coarse WC powder with a Fischer particle size of 15 μm, 10 parts of Co powder with a Fischer particle size of 3 μm, 1 part of tungsten powder with a Fischer particle size of 0.8 μm and 1.2 parts Carbon black with a Fischer particle size of 1 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 2.0%;

3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.3mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, and the cemented carbide grinding The rod to material ratio of the mixture II is 1.7:1, the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 24 μm;

4) Mill the material prepared in step 3) in a ball mill for 11 hours, then vacuum-dry for 5 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III is 6.5 μm;

5) Put the mixture III through a 400-mesh sieve and put it into a granulator to roll for 12 minutes to granulate, then press it under a pressure of 60MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1500° C., the holding time is 95 minutes, and the pressure in the sintering furnace is 7 MPa.

The particle size and crystal phase of the ultra-coarse-grained WC-Co cemented carbide product prepared in this example are analyzed by the same method as in Example 1, and have similar effects, which will not be described here.

Example 3

The preparation method of the ultra-coarse-grained WC-Co cemented carbide in this embodiment is as follows:

1) Take 8 parts of ultra-fine WC powder with a Fibonacci particle size of 0.6 μm and pre-grind for 50 hours separately, then settle for use;

2) Combine pre-ground ultra-fine WC powder with 83 parts of ultra-coarse WC powder with a Fischer particle size of 18 μm, 10 parts of Co powder with a Fischer particle size of 1 μm, 0.8 parts of tungsten powder with a Fischer particle size of 0.6 μm, and 1.2 parts Carbon black with a Fischer particle size of 1.1 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 1.2%;

3) Add absolute alcohol to the above-mentioned mixture II as the grinding medium, the ratio of solid to liquid between the mixture II and the absolute alcohol is 0.25mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, and the cemented carbide grinding The rod-to-material ratio of the rod to the mixture II is 1.8:1, and the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 20 μm;

4) The material prepared in step 3) was ball milled in a ball mill for 7 hours, and then vacuum-dried for 5 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.2 μm;

5) Put the mixture III through a 300-mesh sieve and put it into a granulator to roll for 12 minutes to granulate, then press it under a pressure of 90MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum conditions, the sintering temperature is 1450° C., the holding time is 90 minutes, and the pressure in the sintering furnace is 6 MPa.

The particle size and crystal phase of the ultra-coarse-grained WC-Co cemented carbide product prepared in this example are analyzed by the same method as in Example 1, and have similar effects, which will not be described here.

Example 4

The preparation method of the ultra-coarse-grained WC-Co cemented carbide in this embodiment is as follows:

1) Take 5 parts of superfine WC powder with a Fischer particle size of 0.3 μm and pre-grind it separately for 42 hours, then precipitate it for use;

2) Combine the pre-ground ultra-fine WC powder with 75 parts of ultra-coarse WC powder with a Fischer particle size of 22 μm, 15 parts of Co powder with a Fischer particle size of 1.5 μm, 0.3 parts of tungsten powder with a Fischer particle size of 0.5 μm and 1.5 A part of carbon black with a Fischer particle size of 1.1 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 2.2%;

3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.30mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, the cemented carbide grinding The rod-to-material ratio of the rod to the mixture II is 1.2:1, and the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 25 μm;

4) The material prepared in step 3) was ball milled in a ball mill for 12 hours, and then vacuum-dried for 5 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.5 μm;

5) Put the mixture III through a 500-mesh sieve and put it into a granulator to roll for 18 minutes to granulate, then press it under a pressure of 90MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum conditions, the sintering temperature is 1450° C., the holding time is 90 minutes, and the pressure in the sintering furnace is 6 MPa.

The particle size and crystal phase of the ultra-coarse-grained WC-Co cemented carbide product prepared in this example are analyzed by the same method as in Example 1, and have similar effects, which will not be described here.

The product performance of the ultra-coarse grain WC-Co cemented carbide prepared by embodiment 1 to 4

The morphology of the ultra-coarse-grained WC-Co cemented carbide prepared in Examples 1 to 4 is observed by metallographic microstructure, and the results are shown in Table 1 below:

Table 1 Crystalline structure and morphology of ultra-coarse-grained WC-Co cemented carbide

Example Class A Class B Pores (25-150um) Class C Average particle size (μm) Cobalt phase distribution (μm) Micrographite or η1 1 A02 B00 none C00 6.4 2 E00 2 A02 B00 none C00 6.0 1 E00 3 A02 B00 none C00 6.2 3 E00 4 A02 B00 none C00 5.7 2 E00

It can be seen from the super-coarse-grained WC-Co cemented carbide crystal phase structure morphology prepared by Examples 1 to 4 in Table 1 that the ultra-coarse-grained WC-Co cemented carbide microstructure prepared by the method of the present invention and raw materials is uniform , The average grain size of WC hard phase is coarse, the grain distribution is narrow, the porosity of the product is small, the density is good, and the average grain size is about 6.0 μm, which meets the grain size requirements of ultra-coarse cemented carbide.

The performance of the ultra-coarse-grained WC-Co cemented carbide prepared in Examples 1 to 4 is tested, and the results are shown in Table 2 below:

Table 2 Performance test results of ultra-coarse-grained WC-Co cemented carbide

As can be seen from the performance test results of the ultra-coarse-grained WC-Co cemented carbide prepared in Examples 1 to 4 of Table 2, the flexural strength of the ultra-coarse-grained WC-Co cemented carbide prepared by the preparation method of the present invention and raw materials is It reaches 2590～2850N/mm ² , the coercive force is 5.2～5.6kA/m, the hardness reaches about 108HRA, and the cobalt magnetism reaches more than 6.1%. On the premise, good performance can also be achieved.

comparative example

In order to study and illustrate the influence of the tungsten powder and carbon black added in the cemented carbide raw material of the present invention on the grain size and performance of the cemented carbide product, adopt the same method as the preparation steps of the present invention to prepare the cemented carbide, except that there is no Add tungsten powder and carbon black to study the effect of adding them as raw materials on the particle size and performance of the product cemented carbide. The particle size and performance of the cemented carbide prepared without adding tungsten powder of the present invention and carbon black are shown in Table 3 below:

Table 3 The particle size and performance test results of ultra-coarse-grained WC-Co cemented carbide prepared by adding tungsten powder and carbon black

It can be seen from the data in Table 3 that the addition of tungsten powder has an impact on the average particle size of cemented carbide. When no tungsten powder is added, the average particle size of the prepared cemented carbide product can only reach 5.4 μm, but the particle size It can reach 6.0μm, which meets the requirements of ultra-coarse grains for particle size, but in terms of finishing, the addition of tungsten powder has little effect on the particle size, while carbon black has almost no effect on the particle size of cemented carbide.

In terms of the performance of cemented carbide products, when tungsten powder and carbon black are not added or only one of tungsten powder or carbon black is added, the maximum bending strength of the prepared cemented carbide can only reach 1890N/mm ² , Obviously, the flexural strength of the cemented carbide prepared by adding tungsten powder and carbon black is much lower than that in Examples 1 to 4, illustrating that the tungsten powder and carbon black added by the present invention can effectively improve the flexural strength of the product and reduce the brittleness of the alloy. Improve its impact resistance. At the same time, when no tungsten powder and carbon black are added or only one of tungsten powder or carbon black is added, the cobalt magnetic data of the cemented carbide prepared by it can only reach about 4.5%, which is obviously lower than that of Examples 1 to 4. The cobalt magnetic data of the cemented carbide prepared by tungsten powder and carbon black show that the tungsten powder and carbon black added in the raw materials of the present invention can play a significant role in balancing the amount of carbon therein and improve the cobalt magnetic properties of the alloy.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. a preparation method of ultra-coarse-grained WC-Co hard alloy, is characterized in that, comprises the following steps: 1) Mix pre-ground ultra-fine WC powder with ultra-coarse WC powder, Co powder, tungsten powder and carbon black to obtain mixture I, and add paraffin to obtain mixture II, the mass percentage of paraffin wax and mixture I is 1% ~2.5%; 2) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.2mL/Kg～0.3mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time , the rod-to-material ratio of the cemented carbide grinding rod to the mixture II is 1.2:1～1.8:1; 3) Mill the material prepared in step 2) in a ball mill for 7 to 13 hours, then vacuum dry for 3 to 6 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III is 5.7 μm to 6.5 μm; 4) The mixture III is pressed and sintered to form an ultra-coarse-grained WC-Co cemented carbide. 2. the preparation method of a kind of ultra-coarse-grained WC-Co cemented carbide as claimed in claim 1 is characterized in that, the mass ratio of described ultra-fine WC powder, ultra-coarse WC powder, Co powder, tungsten powder and carbon black 5-10: 75-91: 6-15: 0-1: 0-1.5 parts. 3. A kind of preparation method of ultra-coarse-grained WC-Co cemented carbide as claimed in claim 2, is characterized in that, the Fischer grain size of described ultra-fine WC powder is 0.2 μm～0.6 μm, and described ultra-coarse WC powder The Fischer particle size of the carbon black is 15 μm-26 μm, the Fischer particle size of the Co powder is 1 μm-3 μm, the Fischer particle size of the tungsten powder is 0.45-0.8 μm, and the Fischer particle size of the carbon black is 1-1.3 μm. 4. A method for preparing an ultra-coarse-grained WC-Co cemented carbide according to any one of claims 1 to 3, wherein the ultra-fine WC powder needs to be pre-grinded separately for 40-50 hours before adding, Then precipitate for use. 5. A method for preparing ultra-coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, after the preparation of the mixture III and before pressing, it also includes passing the mixture III through a 200-500 mesh sieve After being screened and sieved, put it into the granulator and roll it for 12-18 minutes to granulate, and the granulation adopts repeated granulation to make suitable material granules loosely packed, forming compressible performance granules. 6. the preparation method of a kind of ultra-coarse grain WC-Co cemented carbide as claimed in claim 1, is characterized in that, the size of described cemented carbide grinding rod is In addition, the cemented carbide grinding rod adopts ultra-coarse cemented carbide, and the WC Fischer particle size of the ultra-coarse cemented carbide prepared is 20 μm-26 μm. 7. A method for preparing ultra-coarse-grained WC-Co cemented carbide as claimed in claim 1, wherein the pressing pressure is 60-95 MPa; Lower sintering, the sintering temperature is controlled at 1400°C-1500°C, the holding time is controlled at 90-100min, and the pressure in the sintering furnace is 3-7MPa. 8. A method for preparing ultra-coarse-grained WC-Co cemented carbide as claimed in claim 1 or 7, wherein said pressing adopts three or more repeated vibration feeds; said pressing abrasive tool adopts alloy Abrasives, and the shrinkage coefficient of the abrasives is 1.23-1.26; the press used for the pressing adopts bidirectional pressure. 9. A kind of preparation method of ultra-coarse-grained WC-Co cemented carbide as claimed in claim 1, is characterized in that, comprises the following steps: 1) Take 5 parts of superfine WC powder with a Fischer particle size of 0.4 μm and pre-grind it separately for 45 hours before settling for use; 2) Combine the pre-ground ultra-fine WC powder with 77 parts of ultra-coarse WC powder with a Fischer particle size of 20 μm, 12 parts of Co powder with a Fischer particle size of 2 μm, 0.5 parts of tungsten powder with a Fischer particle size of 0.45 μm and 1 part Carbon black with a Fischer particle size of 1.3 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 1.5%; 3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.2mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, the cemented carbide grinding The rod-to-material ratio of the rod to the mixture II is 1.5:1, and the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer grain size of the ultra-coarse cemented carbide prepared is 24 μm; 4) The material prepared in step 3) was ball milled in a ball mill for 10 hours, and then vacuum-dried for 4 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.0 μm; 5) Put the mixture III through a 200-mesh sieve and put it into a granulator to roll for 15 minutes to granulate, then press it under a pressure of 80MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1400° C., the holding time is 100 minutes, and the pressure in the sintering furnace is 5 MPa. 10. A kind of preparation method of ultra-coarse-grained WC-Co cemented carbide as claimed in claim 1, is characterized in that, comprises the following steps: 1) Take 8 parts of ultra-fine WC powder with a Fibonacci particle size of 0.2 μm and pre-grind for 40 hours, and then precipitate for use; 2) Combine the pre-ground ultra-fine WC powder with 90 parts of ultra-coarse WC powder with a Fischer particle size of 15 μm, 10 parts of Co powder with a Fischer particle size of 3 μm, 1 part of tungsten powder with a Fischer particle size of 0.8 μm and 1.2 parts Carbon black with a Fischer particle size of 1 μm is mixed to obtain a mixture I, and paraffin wax is added to obtain a mixture II, and the mass percentage of the paraffin wax and the mixture I is 2.0%; 3) Add absolute alcohol to the above mixture II as the grinding medium, the ratio of solid to liquid between mixture II and absolute alcohol is 0.3mL/Kg, and add cemented carbide grinding rods to the mixture II at the same time, and the cemented carbide grinding The rod-to-material ratio of the rod to the mixture II is 1.7:1, and the cemented carbide grinding rod is made of ultra-coarse cemented carbide, and the WC Fischer grain size of the ultra-coarse cemented carbide prepared is 24 μm; 4) The material prepared in step 3) was ball milled in a ball mill for 11 hours, and then vacuum-dried for 5 hours to prepare a mixture III, and ensure that the average particle size of the ultra-coarse tungsten carbide powder in the mixture III was 6.5 μm; 5) Put the mixture III through a 400-mesh sieve and put it into a granulator to roll for 12 minutes to granulate, then press it under a pressure of 60MPa, and finally sinter it into an ultra-coarse-grained WC-Co cemented carbide, in which the sintered It is carried out under vacuum condition, the sintering temperature is 1500° C., the holding time is 95 minutes, and the pressure in the sintering furnace is 7 MPa.