Cemented carbide reburning device and cemented carbide reburning method

Abstract

The present invention discloses a cemented carbide reburning device and a cemented carbide reburning method. The cemented carbide reburning device comprises: a graphite box for containing the cemented carbide to be reburned; a filler layer, the filler layer is filled in the gap between the surrounding of the cemented carbide to be reburned and the graphite box shell; wherein the filler layer is formed by mixing Al2O3 powder and TiO2 powder, the mass fraction of the Al2O3 powder is 20-95%, and the remainder is TiO2 powder. It has been verified that the carburization degree of the cemented carbide treated by the cemented carbide reburning device and the cemented carbide reburning method of the present invention is significantly reduced, the magnetic saturation is significantly reduced, and the bending strength is significantly improved. It can be seen that the present invention has a simple structure, is easy to use, has a good decarburization effect, and has strong practicality.

Description

Technical Field

[0001] The invention relates to the technical field of cemented carbide, in particular to the technical field of eliminating free carbon structures in cemented carbide, and specifically to a cemented carbide burning-back device and a cemented carbide burning-back method. Background Art

[0002] As an alloy material made by powder metallurgy, cemented carbide has a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, corrosion resistance, etc., so it is widely used in tool materials. Cemented carbide can be used to cut cast iron, non-ferrous metals, plastics, chemical fibers, graphite, glass, stone and ordinary steel, and can also be used to cut heat-resistant steel, stainless steel, high manganese steel, tool steel and other difficult-to-process materials.

[0003] In the process of cemented carbide production, the control requirements of alloy carbon content are extremely high, especially for the matching of carbon matching and sintering process. The alloy carbon content has always been the core of quality control of cemented carbide production enterprises and is the most difficult to stabilize. Frequently, due to fluctuations in raw materials, abnormal sintering furnaces, and process mismatches, cemented carbide products will have different degrees of free carbon structure (i.e. carburization) after sintering, which will cause the performance of cemented carbide to drop sharply and basically have no use value, and then produce batches of unqualified products, causing huge economic losses. For this reason, it is very necessary to take measures to eliminate the free carbon structure (i.e. decarburization) in cemented carbide to turn waste into treasure.

[0004] There are mainly two existing decarburization methods: The first decarburization method is the re-sintering method, which is to put the cemented carbide with excessive free carbon structure into alumina, and use the hydrogen decarburization effect to heat it in a hydrogen furnace for repeated sintering. This decarburization method only has a certain decarburization effect on slightly carburized cemented carbide, but cannot completely decarburize severely carburized cemented carbide. Another decarburization method is to heat the cemented carbide with excessive free carbon structure in a vacuum furnace and then quickly cool it with inert gas. This method has a good decarburization effect, but it is more expensive and difficult to commercialize on a large scale. Summary of the invention

[0005] The main purpose of the present invention is to provide a cemented carbide reburning device and a cemented carbide reburning method to solve the technical problem of poor decarburization effect in the decarburization method in the prior art.

[0006] In order to achieve the above object, according to a first aspect of the present invention, a cemented carbide burn-back device is provided, and the technical solution is as follows:

[0007] The invention discloses a cemented carbide reburning device, comprising: a graphite box for containing the cemented carbide to be reburned; a filler layer, the filler layer being filled in the gap between the periphery of the cemented carbide to be reburned and a graphite box shell; wherein the filler layer is formed by mixing Al2O3 powder and TiO2 powder, the mass fraction of the Al2O3 powder is 20-95%, and the remainder is TiO2 powder.

[0008] As a further improvement of the first aspect of the present invention, the particle size of the Al2O3 powder is 20 to 100 μm; the particle size of the TiO2 powder is 10 to 80 μm.

[0009] As a further improvement of the first aspect of the present invention, the particle size of the Al2O3 powder is 50 to 80 μm; the particle size of the TiO2 powder is 30 to 60 μm.

[0010] As a further improvement of the first aspect of the present invention, the thickness of the filler layer is ≥2 mm.

[0011] As a further improvement of the first aspect of the present invention, the cemented carbide to be reburned is cylindrical or flat; when the diameter or thickness of the cemented carbide to be reburned is ≥4mm and <10mm, the thickness of the packing layer is ≥4mm; when the diameter or thickness of the cemented carbide to be reburned is ≥10mm and <30mm, the thickness of the packing layer is ≥6mm; when the diameter or thickness of the cemented carbide to be reburned is ≥30mm, the thickness of the packing layer is ≥8mm.

[0012] As a further improvement of the first aspect of the present invention, the mass fraction of the Al2O3 powder is 20-95%, and the remainder is TiO2 powder.

[0013] As a further improvement of the first aspect of the present invention, it also includes a graphite cover plate adapted to the graphite box.

[0014] In order to achieve the above object, according to a second aspect of the present invention, a cemented carbide burn-back method is also provided, and the technical scheme is as follows:

[0015] The cemented carbide reburning method comprises the following steps:

[0016] (1) Obtaining a graphite box that is suitable for the size of the hard alloy to be reburned;

[0017] (2) Spread the mixed powder on the bottom of the graphite box and then compact it;

[0018] (3) Place the hard alloy to be re-sintered;

[0019] (4) Continue to lay the mixed powder so that the surrounding and upper parts of the hard alloy to be re-fired are filled with the mixed powder, and then compact it;

[0020] (5) placing the graphite box in a sintering furnace for sintering;

[0021] The mixed powder is formed by mixing Al2O3 powder and TiO2 powder, the mass fraction of Al2O3 powder is 20-95%, and the balance is TiO2 powder.

[0022] As a further improvement of the second aspect of the present invention, the compaction pressure used is 4 to 8 kg / m 3 .

[0023] As a further improvement of the second aspect of the present invention, the graphite box is sintered using a sintering process for preparing the hard alloy to be re-fired.

[0024] The present invention has the following advantages:

[0025] First, the filler layer is composed of metal oxide powder. Therefore, the metal oxide absorbs a certain amount of oxygen on the one hand, and on the other hand, it can react with carbon to undergo redox reaction when combined with oxygen at high temperature. Therefore, by covering the surface of the cemented carbide with free carbon structure with a metal oxide filler layer, during the high-temperature sintering process, the oxygen provided by the filler layer eliminates the free carbon through diffusion and redox reaction, thereby achieving the effect of eliminating the free carbon structure.

[0026] Secondly, the purpose of decarburization is to remove the free carbon structure in the hard alloy, but there is also bound carbon useful to its performance in the hard alloy, and when bound carbon is more, the toughness strength of the hard alloy can improve.Compared with Al2O3 powder, the diffusion of oxygen in the TiO2 powder and the redox reaction with the free carbon are more intense, and for the product with slight free carbon degree, the TiO2 powder easily causes the excessive backburning and then makes the bound carbon of the hard alloy be excessively removed, and then affects the toughness strength of the hard alloy.Therefore, the filler layer of the present invention is composed of Al2O3 powder and TiO2 powder of a certain ratio, and by Al2O3 powder and TiO2 powder cooperate with each other, can ensure the decarburization effect of free carbon, can prevent bound carbon from being removed again, finally reach suitable decarburization degree, thereby ensure the performance of hard alloy.

[0027] In addition, the graphite box made of graphite can not only maintain a high strength at high temperature to support the cemented carbide to be re-fired, but also absorb free carbon, which is conducive to the decarburization reaction of the cemented carbide at high temperature.

[0028] Furthermore, by applying appropriate compaction treatment to the metal oxide, the metal oxide can be fully and closely contacted with the hard alloy to be sintered, and the air permeability can be ensured during the high-temperature sintering process, so as to facilitate the decarburization reaction to eliminate free carbon. At the same time, by compaction treatment and shielding with a graphite cover plate, it is possible to prevent the metal oxide powder from escaping due to vacuuming during the sintering process, thereby affecting the decarburization effect and causing pollution to the sintering equipment.

[0029] It has been verified that the carburization degree of the cemented carbide treated by the cemented carbide reburning device and the cemented carbide reburning method of the present invention is significantly reduced, the magnetic saturation is significantly reduced, and the bending strength is significantly improved. It can be seen that the present invention has a simple structure, is easy to use, has a good decarburization effect, and is extremely practical.

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of the present invention are used to assist in understanding the present invention. The contents provided in the drawings and their related descriptions in the present invention can be used to explain the present invention, but do not constitute improper limitations on the present invention. In the drawings:

[0032] Figure 1 It is a structural schematic diagram of a specific implementation mode of the cemented carbide burn-back device of the present invention.

[0033] The relevant marks in the above drawings are:

[0034] 100-hard alloy to be re-fired, 200-graphite box, 300-filling layer, 400-graphite cover plate. DETAILED DESCRIPTION

[0035] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0036] The technical solutions and technical features provided in each part of the present invention, including the following description, may be combined with each other if there is no conflict.

[0037] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] About the terms and units in the present invention: The terms "include", "have" and any variations thereof in the description and claims of the present invention and related parts are intended to cover non-exclusive inclusions.

[0039] Figure 1It is a structural schematic diagram of a specific implementation mode of the cemented carbide burn-back device of the present invention.

[0040] like Figure 1 As shown, the specific embodiment of the cemented carbide reburning device of the present invention includes a graphite box 200, a packing layer 300 and a graphite cover plate 400. The graphite box 200 is used to contain the cemented carbide 100 to be reburned. The packing layer 300 is filled in the gap between the surrounding of the cemented carbide 100 to be reburned and the shell of the graphite box 200. The packing layer 300 is filled with Al2O3 powder and TiO2 powder after mixing. The mass fraction of the Al2O3 powder is 20-95%, preferably 20-83%, and the remainder is TiO2 powder. The graphite cover plate 400 is adapted to the graphite box 200.

[0041] The particle size of the Al2O3 powder is 20-100 μm, preferably 50-80 μm; the particle size of the TiO2 powder is 10-80 μm, preferably 30-60 μm. When the particle size is higher than the above numerical range, it is easy to cause uneven contact between the filler layer 300 and the hard alloy 100 to be reburned. When the particle size is lower than the above numerical range, it is not only expensive, but also easy to cause poor permeability due to dense stacking. Therefore, too high and too low particle size will affect the decarburization effect. When the particle size of the Al2O3 powder is 50-80 μm and the particle size of the TiO2 powder is 30-60 μm, the best decarburization effect can be achieved, and the material cost is low.

[0042] The thickness of the filler layer 300 is ≥ 2 mm, so that the metal oxide in the filler layer 300 can provide enough oxygen to carry out redox reaction with the free carbon in the hard alloy 100 to be sintered, thereby ensuring the decarburization effect.

[0043] The hard alloy to be reburned is cylindrical or flat; when the diameter or thickness of the hard alloy to be reburned is ≥4mm and <10mm, the thickness of the packing layer is ≥4mm; when the diameter or thickness of the hard alloy to be reburned is ≥10mm and <30mm, the thickness of the packing layer is ≥6mm; when the diameter or thickness of the hard alloy to be reburned is ≥30mm, the thickness of the packing layer is ≥8mm.

[0044] The specific implementation of the cemented carbide burning-back method of the present invention is to use the above-mentioned cemented carbide burning-back device, which specifically includes the following steps:

[0045] (1) Obtain a graphite box 200 that is suitable for the size of the cemented carbide 100 to be reburned;

[0046] (2) Spreading the mixed powder on the bottom of the graphite box 200 and then compacting it;

[0047] (3) Place 100 hard alloys to be re-sintered;

[0048] (4) Continue to lay the mixed powder so that the surroundings and the upper part of the cemented carbide 100 to be re-fired are filled with the mixed powder, and then compact and cover with a graphite cover plate 400;

[0049] (5) placing the graphite box 200 into a sintering furnace for sintering;

[0050] The compaction pressure is preferably 4 to 8 kg / m 3 When the pressing force is higher than 8kg / m 3 When the pressing force is lower than 4kg / m 3 On the one hand, the metal oxide mixed powder is easy to escape under the vacuum effect, so that the metal oxide mixed powder cannot evenly and completely cover the surroundings of the hard alloy 100 to be reburned. On the other hand, the hard alloy 100 to be reburned is easy to contact with the graphite box 200 under the action of its own weight, thereby aggravating the carburization hazard.

[0051] The graphite box 200 is sintered by using the sintering process for preparing the hard alloy 100 to be re-fired, which can avoid the hardness and grain size of the hard alloy 100 to be re-fired from deteriorating due to re-fire, and can be sintered together with the product without the need for separate furnace sintering.

[0052] The beneficial effects of the present invention are described below through specific embodiments.

[0053] Table 1

[0054]

[0055] The raw material ratios of the filler layers and the thickness of the filler layers of Examples 1-10 are shown in Table 1. The pressing force in Examples 1-10 is the same, and the sintering processes used are all the sintering processes of the corresponding hard alloys to be sintered.

[0056] The difference between Examples 1-3 is only in the particle size of Al2O3 and TiO2. From the performance data, it can be seen that both too large and too small particle sizes are not conducive to re-sintering modification.

[0057] The difference between Example 1 and Example 4 is only the proportion of TiO2 in the filler layer. It can be seen from the performance data that appropriately increasing the proportion of TiO2 can improve the re-firing effect.

[0058] Compared with Example 1 and Example 4, the carburization degree in Example 5-6 is improved, and the proportion of TiO2 is increased accordingly, achieving a better burning-back effect. It can be seen that for different degrees of carburization, it is necessary to match the corresponding filler ratio. When the carburization degree is high, the proportion of TiO2 can be increased.

[0059] The difference between Example 7 and Example 8 is the thickness of the filler layer. By comparison, it can be seen that the magnetic saturation decrease and the bending strength increase of Example 8 are both smaller, and the free carbon is not completely eliminated, which means that when the diameter of the cemented carbide to be re-sintered is large and the thickness of the filler layer is too thin, it is very unfavorable for re-sintering.

[0060] By comparing Example 7, Example 9 and Example 10, it can be seen that the decarburization effect of the filler layer composed solely of Al2O3 is poor, while the filler layer composed solely of TiO2 will result in the adsorption of combined carbon that is beneficial to the material properties while eliminating free carbon, which is not conducive to the improvement of properties such as strength, and instead fails to achieve the desired anti-burning effect.

[0061] As can be seen from Table 1, the hard alloy treated by the burn-back device and the burn-back method of the present invention has reduced magnetic saturation, significantly improved flexural strength, relatively stable coercive force and hardness (indicating that the performance has not deteriorated), and significantly reduced carburization degree. It can be seen that the device and method of the present invention have excellent decarburization effect, especially when the particle size of Al2O3 powder is 50-80μm, the particle size of TiO2 powder is 30-60μm, and the mass fraction of Al2O3 powder is 20-83%, a filler layer of a certain thickness can achieve the best decarburization effect.

[0062] The test method for "magnetic saturation" is "GB / T 23369-2009 Standard Test Method for Determination of Magnetic Saturation (MS) of Cemented Carbide".

[0063] The test method for "coercive force" is "GB / T 3848-2017 Determination Method of Coercive (Magnetic) Force of Cemented Carbide".

[0064] The test method for “hardness” is “GB / T 7997-2014 Test method for Vickers hardness of cemented carbide”.

[0065] The test method for "bending strength" is "GB / T 3851-2015 Test method for transverse fracture strength of cemented carbide".

[0066] The test method for the “degree of carburization” is “GB_T 3489-2015 Metallographic Determination of Porosity and Uncombined Carbon in Cemented Carbide”.

[0067] The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of the present invention, all other embodiments obtained by a person skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. Cemented carbide burning-back device, characterized by: include: Graphite box, used to hold the hard alloy to be reburned; A packing layer, wherein the packing layer is filled in the gap between the periphery of the hard alloy to be re-sintered and the graphite box housing; The filler layer is formed by mixing Al2O3 powder and TiO2 powder and then compacting and filling them. The mass fraction of the Al2O3 powder is 20-95%, and the remainder is TiO2 powder.

2. The cemented carbide burn-back device according to claim 1, characterized in that: The particle size of the Al2O3 powder is 20 to 100 μm; the particle size of the TiO2 powder is 10 to 80 μm.

3. The cemented carbide burn-back device according to claim 2, characterized in that: The particle size of the Al2O3 powder is 50-80 μm; the particle size of the TiO2 powder is 30-60 μm.

4. The cemented carbide burn-back device according to claim 1, characterized in that: The thickness of the packing layer is ≥2mm.

5. The cemented carbide burning-back device according to claim 4, characterized in that: The hard alloy to be reburned is cylindrical or flat; when the diameter or thickness of the hard alloy to be reburned is ≥4mm and <10mm, the thickness of the packing layer is ≥4mm; when the diameter or thickness of the hard alloy to be reburned is ≥10mm and <30mm, the thickness of the packing layer is ≥6mm; when the diameter or thickness of the hard alloy to be reburned is ≥30mm, the thickness of the packing layer is ≥8mm.

6. The cemented carbide burn-back device according to claim 1, characterized in that: Also included is a graphite cover plate adapted to the graphite box.

7. A method for re-burning cemented carbide, comprising the following steps: (1) Obtaining a graphite box that is suitable for the size of the cemented carbide to be reburned; (2) Spread the mixed powder on the bottom of the graphite box and compact it; (3) Place the hard alloy to be re-burned; (4) Continue to lay the mixed powder so that the surrounding and upper parts of the cemented carbide to be refired are filled with the mixed powder, and then compact it; (5) placing the graphite box in a sintering furnace, and sintering the graphite box using the sintering process for preparing the hard alloy to be sintered; The mixed powder is prepared by mixing Al2O3 powder and TiO2 powder, wherein the mass fraction of the Al2O3 powder is 20-95% and the remainder is TiO2 powder.

8. The cemented carbide reburning method according to claim 7, characterized in that: The compaction force used is 4-8 kg / m 3 .

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