CN113770363A - Preparation method of gradient hard alloy sand mill parts - Google Patents
Preparation method of gradient hard alloy sand mill parts Download PDFInfo
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- CN113770363A CN113770363A CN202111073804.0A CN202111073804A CN113770363A CN 113770363 A CN113770363 A CN 113770363A CN 202111073804 A CN202111073804 A CN 202111073804A CN 113770363 A CN113770363 A CN 113770363A
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- B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
- B22F7/06—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools
- B22F7/062—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools involving the connection or repairing of preformed parts
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- B22F9/00—Making metallic powder or suspensions thereof
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- C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
- C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
- C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
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- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
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Abstract
The invention discloses a preparation method of a gradient hard alloy sand mill part, which comprises the steps of preparing a hard alloy raw material; adding tungsten carbide into a ball mill, and adding forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished; placing tungsten carbide in a sand mill part mould 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 a sintering infiltration method, and the working area is treated by a melt infiltration method. The method adopts a gradient alloy method, so that the welding area of the bar pin has good toughness, and after the tungsten carbide and the stainless steel are welded, cracks are not easy to appear after welding and cooling by matching with an improved welding process. The working area of the gradient alloy is mainly high-hardness wear-resistant performance, and can meet the working condition requirement of the sand mill.
Description
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, having the molecular formula WC and a molecular weight of 195.85. Is black hexagonal crystal with metallic luster and 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 easily soluble in mixed acid of nitric acid and hydrofluoric acid. Pure tungsten carbide is brittle and can be reduced by incorporating small amounts of metals such as titanium, cobalt, etc. Tungsten carbide, often added with titanium carbide, tantalum carbide or mixtures thereof, is used as a steel cutting tool to improve blast resistance. Tungsten carbide is chemically stable. The tungsten carbide powder is applied to hard alloy production materials.
Since 1893, german scientists have taken tungsten carbide by heating tungsten trioxide and carbon together in an electric furnace to high temperatures and have attempted to make wire-drawing dies, etc., to replace diamond materials, taking advantage of its high melting point, high hardness, etc. However, tungsten carbide has not been industrially used for reasons such as high brittleness, easy cracking, and low toughness. In the twentieth century, the research of Karl Schroter, a German scientist, found that pure tungsten carbide can not adapt to the drastic stress change formed in the drawing process, and only by adding a low-melting metal into WC, the blank can have certain toughness without reducing the hardness. Schroter first proposed in 1923 a powder metallurgy method of mixing tungsten carbide with small amounts of an iron group metal (iron, nickel, cobalt), followed by press forming and sintering in hydrogen at temperatures above 1300 ℃ to produce a hard alloy.
Tungsten carbide and stainless steel are the most common alloy materials, both of which have good metal working performance, but also have some differences. The physical properties of tungsten carbide and stainless steel are greatly different and mainly reflected in linear expansion coefficient, thermal conductivity, specific heat rate and the like, and the physical properties cause problems in the welding process of the hard alloy and the stainless steel.
For example, the pin is one of the main parts of the sand mill, and one end of the pin is welded with the sand mill, so that the pin can be driven by a rotating device of the sand mill to rotate; the other end is used as a working area for the processing technologies such as polishing of the workpiece to be processed and the like. The rod pin is generally made of hard alloy, and the main component of the rod pin is tungsten carbide, because the tungsten carbide has good wear resistance, the requirements of polishing equipment can be met. However, the linear expansion coefficient of tungsten carbide is only one-fourth to one-half of that of stainless steel, and the physical properties are greatly different. The larger the linear expansion coefficient is, the larger the free expansion degree in the heating process is, and the larger the shrinkage degree of cooling after heating is; in the welding process of the tungsten carbide and the stainless steel, the tungsten carbide and the stainless steel both expand freely, and are naturally cooled after welding, and as the linear expansion coefficient of the tungsten carbide is lower than that of the stainless steel, the welding seam is in a pressure state, and the surface of the mass alloy bears tensile stress. If the residual stress is greater than the tensile strength of the cemented carbide, cracks may develop on the surface of the cemented carbide; this is one of the most important causes of cracks in cemented carbide welding.
Thus, the pin of the sander needs to have two features:
1. the welding material has a linear expansion coefficient equivalent to that of stainless steel, and is convenient for generating cracks after welding.
2. The front end of the pin needs to be ground, and thus, the wear resistance of the pin needs to be improved.
In order to solve the technical problems, the welding process can be improved, the material of the bar pin can be optimized, and the bar pin processing process can be perfected.
The material properties of the tungsten carbide finished product are affected in many ways, for example, the difference of the material components of the tungsten carbide material will directly affect the strength, wear resistance and the like of the product; different phase structures, different grain sizes, different degrees of uniformity and the like all affect the tungsten carbide matrix material.
For example, chinese patent 1: CN104439233B discloses a material for a hard alloy slitting cutter, which is prepared by putting tungsten carbide with the particle size of 0.6-1.0 mu m and 3-6 mu m, spherical nickel powder with the particle size of 1.0-2.0 mu m and chromium carbide with the particle size of 1.0-2.0 mu m into a wet grinder for mixing, adding ethanol for wet grinding, sieving, drying and pressing for forming.
The method is characterized in that firstly, two tungsten carbides with the grain diameters of 0.6-1.0 mu m and 3-6 mu m are directly mixed, so that the problems of tungsten carbide accumulation, grain growth and coarse clamping are easy to occur;
secondly, the tungsten carbide of two kinds of different particle diameters is mixed and ball-milled, and the tungsten carbide of two kinds of different particle diameters is actually crushed again, and the particle diameters of the coarse tungsten carbide particles and the fine tungsten carbide particles are equivalent after ball-milling, so that the tungsten carbide with uniform particle size is formed, and the tungsten carbide does not have the difference between the coarse particles and the fine particles, so that the tungsten carbide cannot have the performances of both the coarse tungsten carbide particles and the fine tungsten carbide particles.
For example, document 1: the authors of the "influence of temperature on the wear resistance of tungsten carbide coatings": korean Yongmei; the following technical information is disclosed: the WC-10Co-4Cr coating is prepared by using a supersonic flame spraying technology (HVOF), heat treatment is carried out on the coating at 300 ℃ for 1h and at 500 ℃ for 1h, changes of the structure, the appearance and the hardness of the coating before and after the heat treatment are detected by using an X ray, a scanning electron microscope and a microhardness instrument, and an abrasive wear test is carried out to analyze the changes of the wear resistance of the coating, wherein the results show that: the hardness, appearance and wear resistance of the coating after heat treatment at 300 ℃ for 1h are not obviously changed compared with those of a spraying state; after heat treatment at 500 ℃ for 1h, the hardness of the coating is reduced by 8%, and the abrasion loss mass is increased by about 20%.
For example, patent 2: CN202010780748.3 discloses a method for welding wear-resistant materials, which is used to solve the problem in the prior art that a wear-resistant layer formed by welding tungsten carbide with a single component on the surface of a blade of a steel base material is easy to fall off from the steel base material.
The method comprises the steps of firstly, cleaning the surface of the 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 to carry out build-up welding layer by layer, 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 material is 40-60%.
According to the invention, the (WCNi60) mixed wear-resistant material powder and the plasma arc surfacing process method are suitable for manufacturing the paddle and other wear-resistant materials, so that the wear-resistant layer is resistant to impact, and the paddle can particularly meet the use requirement of a strong mixer.
The problem in the prior art can be solved to a certain extent in patent 2, and the method can enable the tungsten carbide material to have certain wear resistance, and the welding end is more stable than a common welding process. However, the method is an improvement on the welding method, and as is known, the implementation effect of the welding method is related to the proficiency of welding workers, and the product effects of different persons adopting the same welding method are different, so that the actual 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 to carry out build-up welding layer by layer, the materials are not uniformly mixed and melted, so that the deviation of the welding effect is increased.
Therefore, compared with a welding method, the improved material has more stable technical effect and can be implemented more easily.
Disclosure of Invention
The invention aims to provide a preparation method of a gradient hard alloy sand mill component.
The technical problems to be solved by the invention at least comprise the following technical problems:
1. because of the large difference of the linear expansion coefficients, cracks are easy to appear after the tungsten carbide and the stainless steel base material are welded, so that parts such as a bar pin and the like are easy to fall off and break when in use.
2. The working area of the sand mill parts such as the rod pin can have very good wear resistance.
In order to achieve the above object, one embodiment of the present invention provides a method for manufacturing a component of a gradient cemented carbide sand mill, comprising the following steps:
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 a tungsten carbide coarse matrix; 9-12 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.5-2.5 weight portions and niobium carbide 0.5-2.5 weight portions;
wherein the Fisher size of the tungsten carbide coarse matrix is 2.8-4.6 mu m;
each part of tungsten carbide fine material comprises: 88-92 parts of tungsten carbide fine matrix; 6-8 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.3-1 part, niobium carbide 0.6-1.5 parts; 0.1 to 0.5 portion of auxiliary material carbon black;
wherein the Fisher-size particle size of the tungsten carbide fine matrix is 0.6-0.9 μm;
adding the tungsten carbide coarse material into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
adding tungsten carbide fine materials into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
step (4), placing the tungsten carbide fine material in a sand mill part mould to be pressed and formed to form a working area; then adding the tungsten carbide coarse material into a sand mill part mould, filling the rest cavity, and then performing compression molding to form a welding area above the working area; finally obtaining a molding blank of the sand mill part;
a welding area is arranged above the formed blank, and the nickel content of the welding area is 9-12 percent;
a working area is arranged below the formed blank, and the nickel content of the working area is 6-8 percent;
step (5) 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 a sintering infiltration method, and the working area is treated by a melt infiltration method;
wherein the sintering infiltration process comprises the following steps: placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1350-1450 ℃, and preserving the heat for 10-15 min; then heating to 1450-1620 ℃, and preserving the heat for 5-10 min; melting the infiltration material in the sintering process, and continuously infiltrating and diffusing the infiltration material inwards from the end surface of the welding area;
wherein the process of melt infiltration comprises the following steps: taking out the formed blank after sintering infiltration treatment, and then placing the working area in an infiltration melt formed by melting the infiltration material, wherein the welding area is not contacted with the infiltration melt.
In the 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 Fisher size of the tungsten carbide coarse matrix is 3.5 mu m.
In the optimized scheme of the invention, in the step (1), the tungsten carbide fine material comprises the following components: 92 parts of tungsten carbide fine matrix; 6 parts of nickel powder; 1 part of tungsten powder; 0.3 part of tantalum carbide and 0.6 part of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the Fisher size of the tungsten carbide fine matrix is 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; the ball milling time is 36-42 h, and the ball-material ratio is 4-5: 1.
in the optimized scheme of the invention, the ball milling speed of the wet ball milling in the step (2) is 120 r/min-180 r/min; the ball milling speed of the wet ball milling in the step (3) is 200r/min to 250 r/min.
In the optimized scheme of the invention, in the step (5), the heat preservation time for melt infiltration is 25-40 min.
In the optimized scheme of the invention, the sintered and infiltrated infiltration material 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.
In the optimized scheme of the invention, the infiltration material infiltrated by the melt 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. according to the invention, a gradient alloy method is adopted, so that the welding area of the bar pin has good toughness, and the difference of linear expansion coefficients of the tungsten carbide and the stainless steel is reduced after the tungsten carbide and the stainless steel are welded by matching with an improved welding process, and cracks are not easy to appear after welding and cooling. The working area at the other end of the gradient alloy is mainly high-hardness wear-resistant performance, and can meet the working condition requirement of the sand mill.
2. The welding zone needs to have good welding performance and toughness, and the work area is located the excellent nail top, compares the welding function district, and the operating mode condition is harsher, and the linear velocity is higher, scour strength is bigger, consequently needs good hardness and wear resistance.
According to the invention, the welding area and the working area of the tungsten carbide are respectively treated by adopting a sintering infiltration-melt infiltration method, so that good welding force can be formed after the welding area is welded with the stainless steel, the toughness of a welding material is improved, welding cracks are eliminated, and meanwhile, 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 low-cost raw materials without silver and the like are used as the materials of a welding area and a working area, so that the aim of reducing the cost is fulfilled.
4. According to the invention, an infiltration material is placed on the top of a prefabricated part by a sintering-infiltration method, and the infiltration material is melted at high temperature and gradually infiltrated into pores of the prefabricated part, so that a composite material is formed; the invention adopts the liquid metal infiltration technology to be convenient to control, can obtain good product effect and has good stability.
Drawings
FIG. 1 is a schematic illustration of infiltration of a pin rod according to one embodiment of the present invention;
FIG. 2 is a metallographic representation of the cemented carbide material of comparative examples 1-1 in accordance with an embodiment of the present invention;
fig. 3 is a gold phase diagram of a cemented carbide material according to example 1 of the present invention.
Wherein; 1. a working area; 2. a welding zone; 3. and (4) infiltrating the material.
Detailed Description
The invention provides a preparation method of a gradient hard alloy sand mill part, which comprises the following steps:
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 a tungsten carbide coarse matrix; 9-12 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.5-2.5 weight portions and niobium carbide 0.5-2.5 weight portions;
wherein the Fisher size of the tungsten carbide coarse matrix is 2.8-4.6 mu m;
each part of tungsten carbide fine material comprises: 88-92 parts of tungsten carbide fine matrix; 6-8 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.3-1 part, niobium carbide 0.6-1.5 parts; 0.1 to 0.5 portion of auxiliary material carbon black;
wherein the Fisher-size particle size of the tungsten carbide fine matrix is 0.6-0.9 μm;
adding the tungsten carbide coarse material into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
adding tungsten carbide fine materials into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
step (4), placing the tungsten carbide fine material in a sand mill part mould to be pressed and formed to form a working area; then adding the tungsten carbide coarse material into a sand mill part mould, filling the rest cavity, and then performing compression molding to form a welding area above the working area; finally obtaining a molding blank of the sand mill part;
a welding area is arranged above the formed blank, and the nickel content of the welding area is 9-12 percent;
a working area is arranged below the formed blank, and the nickel content of the working area is 6-8 percent;
step (5) 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 a sintering infiltration method, and the working area is treated by a melt infiltration method;
wherein the sintering infiltration process comprises the following steps: placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1350-1450 ℃, and preserving the heat for 10-15 min; then heating to 1450-1620 ℃, and preserving the heat for 5-10 min; melting the infiltration material in the sintering process, and continuously infiltrating and diffusing the infiltration material inwards from the end surface of the welding area;
wherein the process of melt infiltration comprises the following steps: taking out the formed blank after sintering infiltration treatment, and then placing the working area in an infiltration melt formed by melting the infiltration material, wherein the welding area is not contacted with the infiltration melt.
Example 1: preparing hard alloy 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 Fisher size of the tungsten carbide coarse matrix is 3.5 mu m.
The tungsten carbide fines include: 92 parts of tungsten carbide fine matrix; 6 parts of nickel powder; 1 part of tungsten powder; 0.3 part of tantalum carbide and 0.6 part of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the Fisher size of the tungsten carbide fine matrix is 0.7 μm.
Example 2: method for producing a shaped blank
Example 2-1: the method for producing the shaped blank of the present invention
Adding the tungsten carbide coarse material into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished; the addition of the paraffin is 2 percent of the tungsten carbide coarse material; the ball milling time is 40h, and the ball milling rotating speed of the wet ball milling is 150 r/min; ball material ratio 4: 1.
adding tungsten carbide fine materials into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished; the addition of the paraffin is 2 percent of the tungsten carbide fine material; the ball milling time is 40 h. The ball milling speed of the wet ball milling is 220 r/min.
Placing tungsten carbide fine materials in a sand mill part mould to be pressed and formed to form a working area; then adding the tungsten carbide coarse material into a sand mill part mould, filling the rest cavity, and then performing compression molding to form a welding area above the working area; finally obtaining a molding blank of the sand mill part;
a welding area is arranged above the formed blank, and the nickel content of the welding area is 9-12 percent;
the lower part of the formed blank is a working area, and the nickel content of the working area is 6-8%.
Example 2-2: method for preparing conventional formed blank
Adding tungsten carbide and all auxiliary materials into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished; the addition of the paraffin is 2 percent of the tungsten carbide coarse material; the ball milling time is 40h, and the ball milling rotating speed of the wet ball milling is 150 r/min; ball material ratio 4: 1.
and after the ball milling is finished, placing the tungsten carbide mixture in a sand mill part mould for compression molding to obtain a molding blank of the sand mill part.
Example 3: sintering of shaped blanks
Example 3-1: the sintering method of the present 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 a sintering infiltration method, and the working area is treated by a melt infiltration method.
The sintering infiltration process comprises the following steps: placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1400 ℃, and preserving heat for 15 min; then heating to 1550 ℃ and preserving heat for 8 min; the infiltration material is melted during the sintering process and infiltrated and diffused from the end face of the welding zone to the inner side.
The sintered and infiltrated infiltration material comprises the following components in parts by weight:
18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; 2.3 parts of titanium.
The process of melt infiltration is as follows: taking out the formed blank after sintering infiltration treatment, then placing the working area in an infiltration melt formed by melting the infiltration material, and preserving heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The infiltration material infiltrated by the melt comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.
The first experimental example: influence on fracture toughness of the Pin of the invention
Purpose of the experiment: the change conditions of the fracture toughness and the linear expansion coefficient of the bar pin are verified when different sintering methods are adopted.
The experimental method comprises the following steps:
1. the raw material of the tungsten carbide hard alloy is 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 processing method of the comparative example:
comparative example 1-1 the following procedure was employed:
A. placing the formed blank in a sintering furnace, heating to 1400 ℃, and preserving heat for 15 min; then the temperature is raised to 1550 ℃ and the temperature is kept for 8 min.
B. Taking out the formed blank after sintering infiltration treatment, then placing the working area in an infiltration melt formed by melting the infiltration material, and preserving heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The infiltration material infiltrated by the melt comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.
Comparative examples 1 to 2 the following methods were employed:
A. placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1400 ℃, and preserving heat for 15 min; then heating to 1550 ℃ and preserving heat for 8 min; the infiltration material is melted during the sintering process and infiltrated and diffused from the end face of the welding zone to the inner side.
The sintered and infiltrated infiltration material comprises the following components in parts by weight: 18 parts of cobalt; and 15 parts of nickel. Taking out the formed blank after sintering infiltration treatment, then placing the working area in an infiltration melt formed by melting the infiltration material, and preserving heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The infiltration material infiltrated by the melt comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.
Comparative examples 1 to 3 were carried out by the following methods:
A. placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1400 ℃, and preserving heat for 15 min; then heating to 1550 ℃ and preserving heat for 8 min; the infiltration material is melted during the sintering process and infiltrated and diffused from the end face of the welding zone to the inner side.
The sintered and infiltrated infiltration material comprises the following components in parts by weight: 18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; taking out the formed blank after sintering infiltration treatment, then placing the working area in an infiltration melt formed by melting the infiltration material, and preserving heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The infiltration material infiltrated by the melt comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.
Comparative examples 1 to 4 were carried out by the following methods:
A. placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1400 ℃, and preserving heat for 15 min; then heating to 1550 ℃ and preserving heat for 8 min; the infiltration material is melted during the sintering process and infiltrated and diffused from the end face of the welding zone to the inner side.
The sintered and infiltrated infiltration material comprises the following components in parts by weight: 18 parts of cobalt; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; taking out the formed blank after sintering infiltration treatment, then placing the working area in an infiltration melt formed by melting the infiltration material, and preserving heat for 30min, wherein the welding area is not contacted with the infiltration melt in the heat preservation process. The infiltration material infiltrated by the melt comprises the following components in parts by weight: 15 parts of zirconium; 3.2 parts of manganese.
In comparative example 1-1, no treatment was performed with an infiltration material during sintering.
Comparative example 1-2 the infiltration material equivalent to melt infiltration was increased in cobalt by 18 parts, relative to comparative example 1-1; and 15 parts of nickel.
Comparative examples 1 to 3 the infiltration material equivalent to the melt infiltration had increased cobalt by 18 parts, as compared with comparative example 1 to 1; 15 parts of nickel; and 4 parts of zinc.
Comparative examples 1 to 4 the infiltration material equivalent to the melt infiltration had an increased amount of cobalt of 18 parts relative to comparative example 1 to 1; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum.
Experimental example 1 the infiltration material equivalent to the melt infiltration was increased by 18 parts of cobalt with respect to comparative example 1-1; 15 parts of nickel; 4 parts of zinc; 3 parts of lanthanum; 2.3 parts of titanium.
The detection method comprises the following steps:
the sand mill parts are mainly sand mill pin, and the main problem of the sand mill pin is welding, so that the fracture toughness and the linear expansion coefficient of the alloy material are mainly detected, and the quality effect of the hard alloy material after welding can be reflected by the detection elements; the risk of weld breakage is likely to occur.
(1) The detection method of the fracture toughness is used for detecting through an indentation method; the units are MPa.
(2) The linear expansion coefficient is the coefficient of linear expansion, which refers to the ratio of the change in length of a solid mass in one direction when the temperature is changed by 1 degree celsius to its length at 20 ℃ (i.e., standard laboratory environment). The linear expansion coefficient can be detected by a dial indicator method, an optical mechanical method, an electromagnetic induction thermomechanical method and a TMA static thermomechanical analysis method, wherein the TMA static thermomechanical analysis method is used for testing most accurately.
5. The result of the detection
| 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 to 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 |
As can be seen from the above test results, example 1 of the present invention has the best fracture toughness and the largest expansion coefficient, which shows that the fracture toughness and the expansion coefficient of the weld zone of the infiltrated portion can be significantly improved by performing infiltration treatment during sintering process, compared to the control group 1-1, i.e., compared to the prior art, and thus, the present invention can facilitate welding and form a good weld zone.
Experimental example II hardness test of working area of the present invention
Abrasion resistance refers to the ability of a material to resist mechanical wear. Under the condition of a certain load of grinding speed, the abrasion of a unit area in unit time. Hardness is in direct proportion 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 feedstock
The components of each group in experimental example two are as follows:
2. the hardness test results of the groups 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 groups 2-4 | 85 |
| Example 1 working area | 95 |
It follows that in the same case, the hardness will decrease as the nickel content increases. The hardness of the working area in example 1 of the present invention is the highest, which shows that when two components, that is, hard alloy materials with different particle sizes are respectively ball-milled to form a welding area and a working area, a product obtained by impregnating the working area can have very high hardness, and is very suitable for the working area, and is used for processing and polishing a preform.
While the present invention has been described in detail with reference to the illustrated embodiments, it should not be construed as limited to the scope of the present patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.
Claims (8)
1. A preparation method of a gradient hard alloy sand mill part comprises the following steps:
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 a tungsten carbide coarse matrix; 9-12 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.5-2.5 weight portions and niobium carbide 0.5-2.5 weight portions;
wherein the Fisher size of the tungsten carbide coarse matrix is 2.8-4.6 mu m;
each part of tungsten carbide fine material comprises: 88-92 parts of tungsten carbide fine matrix; 6-8 parts of nickel powder; 1-2 parts of tungsten powder; tantalum carbide 0.3-1 part, niobium carbide 0.6-1.5 parts; 0.1 to 0.5 portion of auxiliary material carbon black;
wherein the Fisher-size particle size of the tungsten carbide fine matrix is 0.6-0.9 μm;
adding the tungsten carbide coarse material into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
adding tungsten carbide fine materials into a ball mill, and adding a forming agent paraffin and ethanol for wet ball milling; drying after wet ball milling is finished;
step (4), placing the tungsten carbide fine material in a sand mill part mould to be pressed and formed to form a working area; then adding the tungsten carbide coarse material into a sand mill part mould, filling the rest cavity, and then performing compression molding to form a welding area above the working area; finally obtaining a molding blank of the sand mill part;
a welding area is arranged above the formed blank, and the nickel content of the welding area is 9-12 percent;
a working area is arranged below the formed blank, and the nickel content of the working area is 6-8 percent;
step (5) 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 a sintering infiltration method, and the working area is treated by a melt infiltration method;
wherein the sintering infiltration process comprises the following steps: placing the formed blank in a sintering furnace, and placing infiltration materials on the end surface of a welding area; then heating to 1350-1450 ℃, and preserving the heat for 10-15 min; then heating to 1450-1620 ℃, and preserving the heat for 5-10 min; melting the infiltration material in the sintering process, and continuously infiltrating and diffusing the infiltration material inwards from the end surface of the welding area;
wherein the process of melt infiltration comprises the following steps: taking out the formed blank after sintering infiltration treatment, and then placing the working area in an infiltration melt formed by melting the infiltration material, wherein the welding area is not contacted with the infiltration melt.
2. The method of 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 Fisher size of the tungsten carbide coarse matrix is 3.5 mu m.
3. The method of 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 part of tantalum carbide and 0.6 part of niobium carbide; 0.1 part of auxiliary material carbon black; wherein the Fisher size of the tungsten carbide fine matrix is 0.7 μm.
4. The method of claim 1, wherein: the addition amount of the forming agent paraffin in the step (2) is 2 to 2.5 percent of the tungsten carbide coarse material; the ball milling time is 36-42 h, and the ball-material ratio is 4-5: 1.
5. the method of claim 1, wherein: the ball milling speed of the wet ball milling in the step (2) is 120 r/min-180 r/min; the ball milling speed of the wet ball milling in the step (3) is 200r/min to 250 r/min.
6. The method of claim 1, wherein: in the step (5), the heat preservation time for the melt infiltration is 25 min-40 min.
7. The method of claim 1, wherein: the sintering infiltration material 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.
8. The method of claim 1, wherein: the infiltration material infiltrated by the melt comprises the following components in parts by weight: 10-20 parts of zirconium; 2-5 parts of manganese.
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