CN113770363B

CN113770363B - Preparation method of gradient hard alloy sand mill part

Info

Publication number: CN113770363B
Application number: CN202111073804.0A
Authority: CN
Inventors: 汪建昌; 李佳; 赖家晖
Original assignee: Sichuan Klt Carbide Co ltd
Current assignee: Sichuan Klt Carbide Co ltd
Priority date: 2021-09-14
Filing date: 2021-09-14
Publication date: 2023-06-09
Anticipated expiration: 2041-09-14
Also published as: CN113770363A

Abstract

The invention discloses a preparation method of a gradient hard alloy sand mill part, which comprises the steps of preparing hard alloy raw materials; adding tungsten carbide into a ball mill, adding forming agent paraffin and ethanol, and performing wet ball milling; drying after wet ball milling is completed; placing tungsten carbide in a sand mill part die for compression molding to obtain a molding blank of the sand mill part; processing the formed blank of the sand mill part to form a welding area and a working area on the prepared sand mill part; wherein the welding area is treated by adopting a sintering infiltration method, and the working area is treated by adopting a melt infiltration method. The invention adopts a gradient alloy method, so that the welding area of the rod pin has good toughness, and is matched with an improved welding process, so that cracks are not easy to appear after tungsten carbide and stainless steel are welded and cooled. The working area of the gradient alloy is mainly high in hardness and wear resistance, and can meet the working condition requirements of a sand mill.

Description

Preparation method of gradient hard alloy sand mill part

Technical Field

The invention relates to the technical field of material processing, in particular to a preparation method of a gradient hard alloy sand mill part.

Background

Tungsten carbide is a compound consisting of tungsten and carbon, and has a molecular formula of WC and a molecular weight of 195.85. The alloy is a black hexagonal crystal, has metallic luster, has hardness similar to that of diamond, and is a good conductor of electricity and heat. Tungsten carbide is insoluble in water, hydrochloric acid and sulfuric acid, and is readily soluble in nitric acid-hydrofluoric acid mixed acids. Pure tungsten carbide is brittle, and if a small amount of metals such as titanium and cobalt are incorporated, brittleness can be reduced. Tungsten carbide, which is used as a steel cutting tool, is often added with titanium carbide, tantalum carbide or a mixture thereof to improve antiknock capability. The chemical properties of tungsten carbide are stable. Tungsten carbide powder is applied to hard alloy production materials.

Since 1893, german scientists have made tungsten carbide by heating tungsten trioxide and carbon together in an electric furnace to a high temperature, and have attempted to make wire dies or the like using their high melting point, high hardness or the like, in order to replace diamond materials. However, tungsten carbide has not been industrially used because of its high brittleness, susceptibility to cracking, low toughness, and the like. In the twentieth of the twentieth century, research by the german scientist Karl Schroter has found that pure tungsten carbide cannot adapt to the drastic stress changes formed during drawing, and that a blank can have certain toughness only by adding a low-melting-point metal into WC without reducing the hardness. Schroter in 1923 first proposed a powder metallurgy process in which tungsten carbide is mixed with small amounts of iron group metals (iron, nickel, cobalt) and then compression molded and sintered in hydrogen at temperatures above 1300 c to produce a hardness alloy.

Tungsten carbide and stainless steel are the most common alloy materials, both of which have good metal working performance, but also have certain differences. There are large differences in physical properties between tungsten carbide and stainless steel, mainly in terms of linear expansion coefficient, thermal conductivity, specific heat rate, etc., which cause problems in the welding process of cemented carbide and stainless steel.

For example, the rod pin is one of main parts of the sand mill, and one end of the rod pin is welded with the sand mill, so that the rod pin can rotate under the drive of a rotating device of the sand mill; the other end is used as a working area for polishing and other treatment processes of the workpiece to be processed. The rod pin is generally made of hard alloy, and the main component is tungsten carbide, so that the tungsten carbide has good wear resistance and can meet the requirements of polishing equipment. However, the coefficient of linear expansion of tungsten carbide is only one-fourth to one-half that of stainless steel, and the physical properties are greatly different. The larger the linear expansion coefficient is, the larger the free expansion degree is in the heating process, and the larger the shrinkage degree is after heating and cooling; in the welding process of the tungsten carbide and the stainless steel, the tungsten carbide and the stainless steel are free to expand, natural cooling is carried out after the welding is finished, and the linear expansion coefficient of the tungsten carbide is lower than that of the stainless steel, so that the welding line is in a stressed state, and the surface of the prime alloy is subjected to tensile stress. If the residual stress is greater than the tensile strength of the cemented carbide, cracks may occur on the surface of the cemented carbide; this is one of the most significant causes of cracking in cemented carbide welding.

Therefore, the rod pin of the sander needs to possess two features:

1. can have a linear expansion coefficient equivalent to that of stainless steel, and is convenient for not easily generating cracks after welding.

2. The front end of the bar pin needs to be polished, and thus the wear resistance of the bar pin needs to be improved.

In order to solve the technical problems, the welding process can be improved, the rod pin material can be optimized, and the rod pin processing process can be perfected.

The material properties of the finished tungsten carbide piece are affected in many ways, for example, the difference of the material components of the tungsten carbide material can directly affect the strength, the wear resistance and the like of the product; different phase structures, different grain sizes, uniformity and the like can all influence the tungsten carbide matrix material.

For example, chinese patent 1: CN104439233B discloses a material for cutting tools of hard alloy, which is prepared by mixing spherical nickel powder with granularity of 0.6-1.0 μm, tungsten carbide with granularity of 3-6 μm, spherical nickel powder with granularity of 1.0-2.0 μm and chromium carbide with granularity of 1.0-2.0 μm in a wet mill, adding ethanol for wet milling, sieving, drying and compacting.

The patent firstly directly blends two kinds of tungsten carbide with the grain diameters of 0.6-1.0 mu m and 3-6 mu m, so that the problems of tungsten carbide accumulation, grain growth and coarse clamping are easy to occur, and the chromium carbide is adopted to inhibit the tungsten carbide grain growth so as to overcome the defects of tungsten carbide accumulation, grain growth and coarse clamping, but the chromium carbide can inhibit the coarse tungsten carbide grain growth at the same time, so that the toughness of the coarse tungsten carbide is reduced;

secondly, the patent mixes two kinds of tungsten carbide with different particle sizes and then carries out ball milling, namely, the tungsten carbide with two kinds of different particle sizes is crushed again, and the particle sizes of the coarse tungsten carbide and the fine tungsten carbide after ball milling are equivalent, so that tungsten carbide with uniform particle sizes is obtained, and no coarse particle and fine particle are separated, so that the tungsten carbide with coarse particle and the tungsten carbide with fine particle cannot be simultaneously provided.

For example, document 1: the authors of the' influence of temperature on the wear resistance of tungsten carbide coatings: han Yongmei; the following technical information is disclosed: preparing a WC-10Co-4Cr coating by using a supersonic flame spraying technology (HVOF), performing heat treatment on the coating at 300 ℃ for 1h and 500 ℃ for 1h, detecting changes in the structure, morphology and hardness of the coating before and after the heat treatment by using an X-ray, a scanning electron microscope and a microhardness meter, and performing an abrasive particle abrasion test to analyze the changes in the abrasion resistance of the coating, wherein the results show that: the hardness, morphology and wear resistance of the coating are not obviously changed compared with the spraying state after heat treatment at 300 ℃ for 1 h; the hardness of the coating is reduced by 8 percent after heat treatment at 500 ℃ for 1h, and the abrasion loss is increased by about 20 percent.

For example, patent 2: CN202010780748.3 discloses a method for welding wear-resistant materials, which is used for solving the problem that in the prior art, a wear-resistant layer formed by welding single-component tungsten carbide on the surface of a blade of a steel base metal is easy to fall off from the steel base metal.

The method comprises the steps of firstly, cleaning the surface of a blade;

and secondly, melting the nickel-based wear-resistant alloy on the surface of the blade by using a powder plasma arc cladding process, adding tungsten carbide hard alloy particles for layer-by-layer surfacing, wherein the tungsten carbide hard alloy particles are uniformly embedded in the wear-resistant layer, and the weight ratio of the tungsten carbide hard alloy particles to the nickel-based wear-resistant alloy is 40-60%.

The (WCNi 60) mixed wear-resistant material powder and the plasma arc surfacing process method are suitable for manufacturing paddles and other wear-resistant materials, so that the wear-resistant layer is resistant to impact, and the paddles can especially meet the use requirements of a strong mixer.

The problem in the prior art can be solved to a certain extent in the patent 2, and the method can enable the tungsten carbide material to have certain wear resistance, and the welding end is more stable compared with the common welding process. However, this method is an improvement of the welding method, and it is known that the implementation effect of the welding method is related to the proficiency of the welder, and the product effect of the same welding method is different for different persons, so that the practical effect of the invention is unstable and reliable. Secondly, in the process of melting the nickel-based wear-resistant alloy and adding the tungsten carbide hard alloy particles for layer-by-layer overlaying, the materials are mixed and melted uniformly, so that the deviation of the welding effect is increased.

Therefore, by improving the material itself, compared with a welding method, the welding method has a more stable technical effect and can be more easily implemented.

Disclosure of Invention

The invention aims to provide a preparation method of a gradient hard alloy sand mill part.

The technical problems to be solved by the invention at least comprise the following technical problems:

1. because of the large difference of linear expansion coefficients, the tungsten carbide and the stainless steel base material are easy to crack after being welded, so that parts such as a rod pin and the like are easy to fall off and break when in use.

2. The working area of the parts of the sand mill such as the rod pin and the like can have very good wear resistance.

In order to achieve the above object, in one embodiment of the present invention, a method for manufacturing a component of a gradient cemented carbide sander is provided, comprising the steps of:

step (1): preparing a hard alloy raw material; the hard alloy raw materials comprise tungsten carbide coarse materials and tungsten carbide fine materials;

each part of tungsten carbide coarse material comprises: 84-86 parts of tungsten carbide coarse matrix; 9-12 parts of nickel powder; 1 to 2 parts of tungsten powder; 0.5 to 2.5 parts of tantalum carbide and 0.5 to 2.5 parts of niobium carbide;

wherein the Fisher particle size of the tungsten carbide coarse matrix is 2.8-4.6 mu m;

each part of tungsten carbide fine materials comprises: 88-92 parts of tungsten carbide fine matrix; 6-8 parts of nickel powder; 1 to 2 parts of tungsten powder; 0.3 to 1 part of tantalum carbide and 0.6 to 1.5 parts of niobium carbide; 0.1 to 0.5 part of auxiliary material carbon black;

wherein the Fisher particle size of the tungsten carbide fine matrix is 0.6-0.9 mu m;

step (2) adding the tungsten carbide coarse material into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is completed;

step (3) adding the tungsten carbide fine materials into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is completed;

step (4) placing the tungsten carbide fine materials into a sand mill part die for compression molding to form a working area; then adding the tungsten carbide coarse material into a sand mill part die, filling the residual cavity, and then performing compression molding to form a welding area above the working area; finally, a molding blank of the sand mill part is obtained;

a welding area is arranged above the molding blank, and the nickel content of the welding area is 9% -12%;

a working area is arranged below the forming blank, and the nickel content of the working area is 6% -8%;

step (5) processing the molding blank of the sand mill part so as to form a welding area and a working area on the prepared sand mill part; wherein the welding area is treated by adopting a sintering infiltration method, and the working area is treated by adopting a melt infiltration method;

the sintering infiltration process comprises the following steps: placing the molded blank in a sintering furnace, and placing infiltration materials on the end surface of the welding area; then heating to 1350-1450 ℃, and preserving heat for 10-15 min; then heating to 1450-1620 ℃ and preserving heat for 5-10 min; in the sintering process, the infiltration material is melted and continuously infiltrated and diffused from the end face of the welding area to the inner side;

the process of melt infiltration is as follows: and taking out the molded blank after sintering infiltration treatment, and placing the working area into an infiltration melt formed by melting the infiltration material, wherein the welding area is not contacted with the infiltration melt.

In an optimized scheme of the invention, in the step (1), the tungsten carbide coarse material comprises: 85 parts of tungsten carbide coarse matrix; 10 parts of nickel powder; 1 part of tungsten powder; 2 parts of tantalum carbide and 2 parts of niobium carbide; wherein the coarse matrix of tungsten carbide has a Fisher size of 3.5 μm.

In an optimized scheme of the invention, in the step (1), the tungsten carbide fine material comprises: 92 parts of tungsten carbide fine matrix; 6 parts of nickel powder; 1 part of tungsten powder; 0.3 parts of tantalum carbide and 0.6 parts of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the fine matrix of tungsten carbide has a Fisher size of 0.7 μm.

In the optimized scheme of the invention, the addition amount of the forming agent paraffin in the step (2) is 2% -2.5% of the tungsten carbide coarse material; ball milling time is 36-42 h, and ball-material ratio is 4-5: 1.

in the optimized scheme of the invention, the ball milling rotating speed of the wet ball milling in the step (2) is 120 r/min-180 r/min; the ball milling rotating speed of the wet ball milling in the step (3) is 200 r/min-250 r/min.

In the optimized scheme of the invention, in the step (5), the heat preservation time of melt infiltration is 25-40 min.

In the optimized scheme of the invention, the infiltration material for sintering infiltration comprises the following components in parts by weight: 15-25 parts of cobalt; 10-20 parts of nickel; 3-5 parts of zinc; 2-5 parts of lanthanum; 1 to 3 parts of titanium.

In the optimized scheme of the invention, the melt-infiltrated infiltration material comprises the following components in parts by weight: 10-20 parts of zirconium; 2-5 parts of manganese.

In summary, the invention has the following advantages:

1. the invention adopts a gradient alloy method, so that the welding area of the rod pin has good toughness, and the linear expansion coefficient difference between the tungsten carbide and the stainless steel is reduced after the tungsten carbide and the stainless steel are welded together with an improved welding process, so that cracks are not easy to occur after welding and cooling. The other end working area of the gradient alloy is mainly high in hardness and wear resistance, and can meet the working condition requirements of a sand mill.

2. The welding area needs to have good welding performance and toughness, the working area is positioned at the top end of the rod nail, and compared with the welding functional area, the working condition is worse, the linear speed is higher, the scouring strength is higher, and therefore good hardness and wear resistance are needed.

The invention adopts the sintering infiltration-melt infiltration method to treat the welding area and the working area of the tungsten carbide respectively, so that good welding force can be formed after the welding area is welded with stainless steel, the toughness of the welding material is improved, welding cracks are eliminated, and the wear resistance of the working area is improved. The invention adopts a gradient structure to organically combine the two functional materials, so that the rod nail has good welding performance, wear resistance and corrosion resistance.

3. On the premise of ensuring the welding performance and the wear resistance of the tungsten carbide alloy material, the cheap raw materials without silver and the like are used as the materials of the welding area and the working area, thereby achieving the purpose of reducing the cost.

4. The invention adopts a sintering-infiltration method, an infiltration material is placed on the top of a prefabricated member, and the infiltration material is melted at high temperature and gradually infiltrates into the pores of the prefabricated member, so as to form a composite material; the invention adopts the liquid metal infiltration technology, is convenient to control, can obtain good product effect and has good stability.

Drawings

FIG. 1 is a schematic illustration of infiltration of a pin in one embodiment of the present invention;

FIG. 2 is a diagram of the alloy material of control group 1-1 according to one embodiment of the present invention;

fig. 3 is a diagram of the cemented carbide material of example 1 in one embodiment of the invention.

Wherein; 1. a working area; 2. a welding area; 3. infiltration material.

Detailed Description

The invention provides a preparation method of a gradient hard alloy sand mill part, which comprises the following steps:

Example 1: preparation of cemented carbide raw material

The tungsten carbide coarse material comprises: 85 parts of tungsten carbide coarse matrix; 10 parts of nickel powder; 1 part of tungsten powder; 2 parts of tantalum carbide and 2 parts of niobium carbide; wherein the coarse matrix of tungsten carbide has a Fisher size of 3.5 μm.

The tungsten carbide fines include: 92 parts of tungsten carbide fine matrix; 6 parts of nickel powder; 1 part of tungsten powder; 0.3 parts of tantalum carbide and 0.6 parts of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the fine matrix of tungsten carbide has a Fisher size of 0.7 μm.

Example 2: method for producing shaped blanks

Example 2-1: the preparation method of the formed blank

Adding the tungsten carbide coarse material into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is completed; the addition amount of paraffin is 2% of the tungsten carbide coarse material; ball milling time is 40h, and ball milling rotating speed of wet ball milling is 150r/min; ball-to-material ratio 4:1.

adding tungsten carbide fine materials into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is completed; the addition amount of paraffin is 2% of the tungsten carbide fine material; ball milling time is 40h. The ball milling rotating speed of the wet ball milling is 220r/min.

Placing the tungsten carbide fine material into a sand mill part die for compression molding to form a working area; then adding the tungsten carbide coarse material into a sand mill part die, filling the residual cavity, and then performing compression molding to form a welding area above the working area; finally, a molding blank of the sand mill part is obtained;

the working area is arranged below the forming blank, and the nickel content of the working area is 6% -8%.

Example 2-2: method for preparing conventional molding blank

Adding tungsten carbide and all auxiliary materials into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is completed; the addition amount of paraffin is 2% of the tungsten carbide coarse material; ball milling time is 40h, and ball milling rotating speed of wet ball milling is 150r/min; ball-to-material ratio 4:1.

and after ball milling is finished, placing the tungsten carbide mixture into a sand mill part die for compression molding, and obtaining a molding blank of the sand mill part.

Example 3: sintering of shaped blanks

Example 3-1: the sintering method of the invention

Processing the formed blank of the sand mill part to form a welding area and a working area on the prepared sand mill part; wherein the welding area is treated by adopting a sintering infiltration method, and the working area is treated by adopting a melt infiltration method.

The sintering infiltration process comprises the following steps: placing the molded blank in a sintering furnace, and placing infiltration materials on the end surface of the welding area; then heating to 1400 ℃, and preserving heat for 15min; then heating to 1550 ℃, and preserving heat for 8min; the infiltration material is melted in the sintering process and continuously infiltrates and diffuses from the end face of the welding zone to the inner side.

The infiltration material for sintering infiltration comprises the following components in parts by weight:

18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; titanium 2.3 parts.

The process of melt infiltration is as follows: and taking out the molded blank after sintering infiltration treatment, placing the working area into an infiltration melt formed by melting the infiltration material, and preserving the heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The melt-infiltrated infiltration material comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.

Experimental example one: fracture toughness impact study of inventive rod pins

The purpose of the experiment is as follows: the change in fracture toughness and linear expansion coefficient of the pins was verified using different sintering methods.

The experimental method comprises the following steps:

1. the raw materials of the tungsten carbide hard alloy are adopted in the raw material in the embodiment 1;

2. the method for preparing the molding blank of the tungsten carbide hard alloy adopts the method disclosed in the embodiment 2-1;

3. the sintering method of experimental example 1 employed the sintering method disclosed in example 3-1;

4. the treatment method of the comparative example comprises the following steps:

comparative example 1-1 employed the following procedure:

A. placing the formed blank in a sintering furnace, then heating to 1400 ℃, and preserving heat for 15min; then heating to 1550 ℃, and preserving heat for 8min.

B. And taking out the molded blank after sintering infiltration treatment, placing the working area into an infiltration melt formed by melting the infiltration material, and preserving the heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The melt-infiltrated infiltration material comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.

Comparative examples 1-2 used the following method:

A. placing the molded blank in a sintering furnace, and placing infiltration materials on the end surface of the welding area; then heating to 1400 ℃, and preserving heat for 15min; then heating to 1550 ℃, and preserving heat for 8min; the infiltration material is melted in the sintering process and continuously infiltrates and diffuses from the end face of the welding zone to the inner side.

The infiltration material for sintering infiltration comprises the following components in parts by weight: 18 parts of cobalt; 15 parts of nickel. And taking out the molded blank after sintering infiltration treatment, placing the working area into an infiltration melt formed by melting the infiltration material, and preserving the heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The melt-infiltrated infiltration material comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.

The following procedure was used for comparative examples 1-3:

The infiltration material for sintering infiltration comprises the following components in parts by weight: 18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; and taking out the molded blank after sintering infiltration treatment, placing the working area into an infiltration melt formed by melting the infiltration material, and preserving the heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The melt-infiltrated infiltration material comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.

The following procedure was used for comparative examples 1-4:

The infiltration material for sintering infiltration comprises the following components in parts by weight: 18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; and taking out the molded blank after sintering infiltration treatment, placing the working area into an infiltration melt formed by melting the infiltration material, and preserving the heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The melt-infiltrated infiltration material comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.

In comparative example 1-1, no infiltration material was used for treatment during sintering.

Comparative example 1-2 corresponds to an increase of 18 parts of cobalt in the melt-infiltrated material relative to comparative example 1-1; 15 parts of nickel.

Comparative example 1-3 corresponds to an increase of 18 parts of cobalt in the melt-infiltrated material relative to comparative example 1-1; 15 parts of nickel; 4 parts of zinc.

Comparative example 1-4 corresponds to an increase of 18 parts of cobalt in the melt-infiltrated material relative to comparative example 1-1; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum.

Experimental example 1 corresponds to the melt-infiltrated infiltration material increased by 18 parts of cobalt relative to comparative example 1-1; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; titanium 2.3 parts.

The detection method comprises the following steps:

the parts of the sand mill are mainly sand mill rod pins, and the sand mill rod pins mainly have the problem of welding, so that the fracture toughness and the linear expansion coefficient of alloy materials are mainly detected, and the detection element can reflect the quality effect of hard alloy materials after welding; whether or not the risk of weld fracture is likely to occur.

(1) The fracture toughness detection method is used for detecting through an indentation method; unit MPa.

(2) The coefficient of linear expansion is the ratio of the change in length of a solid substance in one direction when the temperature changes by 1 degree celsius to its length at 20 ℃ (i.e., standard laboratory environment). The linear expansion coefficient can be detected by adopting a dial gauge method, an optomechanical method, an electromagnetic induction thermomechanical method and a TMA (thermo mechanical analysis) static thermomechanical analysis method, wherein the TMA static thermomechanical analysis method is used for testing most accurately.

5. Detection result

Group of	Fracture toughness	Coefficient of expansion
			Control group 1-1	9.6	-
Control group 1-2	13.4	5.2×10 ^-6
			Control groups 1-3	16.8	8.6×10 ^-6
Control groups 1-4	16.9	7.6×10 ^-6
			Experimental example 1	19.8	12.3×10 ^-6

From the above results, it can be seen that example 1 of the present invention has the best fracture toughness and the maximum expansion coefficient, which shows that compared with comparative group 1-1, that is, compared with the prior art, the embodiment of the present invention performs the infiltration treatment during the sintering process, so as to significantly improve the fracture toughness and expansion coefficient of the welding area of the infiltration portion, and facilitate the welding, thereby forming a good welding area.

Experimental example two, hardness detection of working area of the invention

Wear resistance refers to the ability of a material to resist mechanical wear. The abrasion per unit area in unit time is carried out under the condition of a constant-load abrasion speed. Hardness is proportional to wear resistance, and the higher the hardness of a material is, the better the wear resistance is, so the hardness value is often taken as one of important indexes for measuring the wear resistance of the material.

1. Hardness comparison of different cemented carbide raw materials

The components of each group in experimental example two are shown in the following table:

2. the hardness test results of each group in the second experimental example are as follows:

group of	Hardness HRC
		Control group 2-1	94
Control group 2-2	93
		Control group 2-3	90
Control group 2-4	85
		Example 1 working area	95

It follows that in the same case, as the nickel content increases, its hardness will decrease. The working area of the embodiment 1 of the invention has the highest hardness, which shows that when two components, namely hard alloy raw materials with different particle diameters are adopted for ball milling respectively, a welding area and a working area are formed, and the product obtained after the working area is impregnated can have very high hardness and is very suitable for the working area and is used for processing and polishing prefabricated parts.

Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, it should not be construed as limiting the scope of protection of the present patent. Various modifications and variations which may be made by those skilled in the art without the creative effort are within the scope of the patent described in the claims.

Claims

1. A preparation method of a gradient hard alloy sand mill part comprises the following steps:

the process of melt infiltration is as follows: taking out the molded blank after sintering infiltration treatment, and then placing the working area into an infiltration melt formed by melting the infiltration material, wherein the welding area is not contacted with the infiltration melt;

the infiltration material for sintering infiltration comprises the following components in parts by weight: 15-25 parts of cobalt; 10-20 parts of nickel; 3-5 parts of zinc; 2-5 parts of lanthanum; 1-3 parts of titanium;

the melt-infiltrated infiltration material comprises the following components in parts by weight: 10-20 parts of zirconium; 2-5 parts of manganese.

2. The method of manufacturing according to claim 1, wherein: in the step (1), the tungsten carbide coarse material comprises: 85 parts of tungsten carbide coarse matrix; 10 parts of nickel powder; 1 part of tungsten powder; 2 parts of tantalum carbide and 2 parts of niobium carbide; wherein the coarse matrix of tungsten carbide has a Fisher size of 3.5 μm.

3. The method of manufacturing according to claim 1, wherein: in the step (1), the tungsten carbide fine material comprises: 92 parts of tungsten carbide fine matrix; 6 parts of nickel powder; 1 part of tungsten powder; 0.3 parts of tantalum carbide and 0.6 parts of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the fine matrix of tungsten carbide has a Fisher size of 0.7 μm.

4. The method of manufacturing according to claim 1, wherein: the addition amount of the forming agent paraffin in the step (2) is 2% -2.5% of the tungsten carbide coarse material; ball milling time is 36-42 h, and ball-material ratio is 4-5: 1.

5. the method of manufacturing according to claim 1, wherein: the ball milling rotating speed of the wet ball milling in the step (2) is 120 r/min-180 r/min; the ball milling rotating speed of the wet ball milling in the step (3) is 200 r/min-250 r/min.

6. The method of manufacturing according to claim 1, wherein: in the step (5), the heat preservation time of melt infiltration is 25-40 min.