Rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder

Abstract

The present invention relates to the technical field of material preparation, specifically to a rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder, comprising a copper infiltration furnace, the copper infiltration furnace comprising a furnace body, a placement rack, a guide assembly, a control system, a heating system, and a furnace tube, the placement rack runs through the furnace body, the placement rack is provided with a first placement point and a second placement point, the furnace body and the guide assembly are slidably connected, the furnace tube is provided with a first valve, a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, and a seventh valve, the first valve and the second valve are connected to nitrogen and hydrogen respectively, and furnace doors are provided at both ends of the copper infiltration furnace. The purpose of the present invention is to provide a rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder, which can realize uninterrupted preparation of tungsten carbide powder copper infiltration samples, realize rapid sample preparation and detection, and a sample preparation time is controlled within 2 hours, which is 24 hours compared with the previous sample preparation, thereby improving efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of material preparation, in particular to a rapid copper infiltration furnace for preparing tungsten carbide powder metallographic samples. Background Art

[0002] Cemented carbide is a powder metallurgy product made by sintering high-hardness refractory metals such as tungsten carbide (WC) and titanium carbide (TiC) as the main hard matrix and cobalt (Co) or nickel (Ni) as a binder. Cemented carbide has a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, and corrosion resistance. In particular, its high hardness and high wear resistance remain basically unchanged even at a temperature of 500°C, and it still has a high hardness at 1000°C, making it an important tool material for processing various other engineering materials and mining various natural resources, and is known as the "industrial teeth".

[0003] According to different uses, cemented carbide needs to be produced with raw material WC of different particle sizes, because the hardness of cemented carbide mainly depends on the cobalt content and WC grain size. With the increase of cobalt content or the increase of WC grain size, the hardness of cemented carbide decreases, and vice versa. Ultrafine-fine grain WC is used for finishing cutting cemented carbide tools, and medium grain WC is used for rough machining alloy tools; mining tools: if the rock hardness is high and the impact load is large, coarse grain WC is used, and medium grain WC is used as raw material when the rock impact is small and the impact load is small; wear-resistant parts: when emphasizing its wear resistance, compression resistance and surface finish, ultrafine-fine and medium grain WC are used as raw materials, and impact-resistant tools are mainly made of medium and coarse grain WC raw materials. According to ISO 4499 standard, tungsten carbide grain size of 0.2-1.3μm can be called ultrafine-fine grain, 1.3-2.5μm is medium grain, and 2.5μm or more is coarse-ultra-coarse grain.

[0004] A very small amount of coarse grains (coarse grains refer to grains whose diameter is 5 times larger than the average grain diameter of cemented carbide) in ultrafine and fine-grained cemented carbide will greatly reduce the service life of cemented carbide. The content of coarse grains is very small. For example, in ultrafine-grained cemented carbide, there is usually one coarse grain in one million to ten million grains, which will significantly deteriorate the alloy performance and reduce the service life of the alloy. Therefore, WC powder manufacturers do their best to adjust and control the process to avoid the appearance of coarse particles in WC powder; cemented carbide manufacturers strive to detect the WC raw materials used to avoid using WC powder containing coarse particles to produce cemented carbide.

[0005] At present, the main methods for testing powder particle size are: air permeability method, namely Fischer particle size analyzer method (FSSS), specific surface area method (BET), laser particle size analysis method, sieving method, scanning electron microscopy (SEM), sedimentation method, etc. FSSS and BET are used to detect the average particle size of WC powder; laser particle size analysis method, sieving method, SEM, sedimentation method, etc. are currently commonly used methods for detecting powder particle size distribution, but according to the research experience of the patent applicant, the above methods cannot detect a very small amount of coarse particles in the powder. The patent applicant has tried to use SEM to directly observe the coarse particles in the powder sample. In actual operation, it was found that when SEM directly observes the powder sample, because the powder sample is uneven, the large particles are usually buried in a large number of fine powders, and the coarse particles are not obviously compared with the normal fine powder particles. When the content of coarse particles is very small, the workload is extremely large, time-consuming, and not operable.

[0006] To detect the inclusions in tungsten carbide powder, the copper infiltration metallographic method can be used to prepare the sample: the WC powder and copper powder are mixed evenly, pressed and formed, copper is infiltrated at 1080~1200℃, and then polished to make a metallographic sample. This method uses the characteristics of W-Cu and C-Cu being almost insoluble below 2000℃. During the heating copper infiltration process, the WC grains will not grow, and the copper will fill in the pores of the WC powder under the action of capillary force, thereby fixing the WC particles and facilitating metallographic sample preparation; in order to increase the wetting performance of copper, hydrogen protection is usually required. After the sample is polished, it can be observed under a common metallographic microscope to quickly confirm whether there are inclusions in the tungsten carbide powder sample. At present, in the copper infiltration process, the traditional tubular copper infiltration furnace is used, which has obvious shortcomings: the sample copper infiltration and cooling cycle is long, and the heating and cooling sample time exceeds 12 hours; the traditional tubular furnace is batch-based, and only when the furnace is completely cooled down can the sample be taken out, a new sample can be put in, and then reheated, resulting in only one batch of samples in one shift. Summary of the invention

[0007] Technical issues solved

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a rapid copper infiltration furnace for preparing tungsten carbide powder metallographic samples, which can realize uninterrupted preparation of tungsten carbide powder copper infiltration samples and realize rapid sample preparation and detection. The sample preparation time is controlled within 2 hours, which improves efficiency compared with the previous sample preparation time of 24 hours.

[0009] Technical Solution

[0010] To achieve the above purpose, the present invention is implemented by the following technical scheme: a rapid copper infiltration furnace for making tungsten carbide powder metallographic samples, comprising a copper infiltration furnace, the copper infiltration furnace comprising a furnace body, a placement rack, a guide assembly, a control system, a heating system, and a furnace tube, the placement rack runs through the furnace body, the placement rack is provided with a first placement point and a second placement point, the furnace body and the guide assembly are slidably connected, the furnace tube is provided with a first valve, a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, and a seventh valve, the first valve and the second valve are connected to nitrogen and hydrogen respectively, and furnace doors are provided at both ends of the copper infiltration furnace;

[0011] The method for using a rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder includes the following steps:

[0012] 1) Place the green billet at the first placement point and the second placement point in the copper infiltration furnace, and place the pipe plug;

[0013] 2) At the beginning, the furnace body is at the first placement point, the copper infiltration furnace is started, and under the automatic control of the control system, the heating system starts heating, the second valve, the third valve, and the sixth valve are closed, and the first valve, the second valve, the fifth valve, and the fourth valve are opened to introduce nitrogen into the copper infiltration furnace;

[0014] 3) After a certain period of time, the first valve, the seventh valve, the sixth valve, and the third valve are closed, and the second valve, the fifth valve, and the fourth valve are opened, and hydrogen is introduced into the copper infiltration furnace;

[0015] 4) When the temperature reaches 1080-1150℃, exceeding the melting point of copper, the copper sheet or pure copper green body placed on the top of the green body will melt. Under the action of the pore capillary force, the molten copper penetrates into the green body and fills the pores;

[0016] 5) Fix the WC powder, and the copper and WC particles in the sample will be evenly distributed. The temperature reaches 1150℃ and is kept for 10 minutes;

[0017] 6) Under the automatic control of the control system, the furnace body slowly moves along the track to the position of the second placement point, starts to heat the sample placed at the second placement point, and cools the sample at the first placement point;

[0018] 7) The completed copper infiltration sample can be taken out by opening the furnace door.

[0019] The guide assembly is located between the bottom of the placement rack and the furnace body and is connected via rollers.

[0020] In step 2), the heating system temperature rise rate is controlled at 15-20 ℃ / min.

[0021] When the furnace body moves to the second placement point, the cold hydrogen in the furnace tube can not only protect the sample placed at the No. position from being oxidized, but also accelerate the cooling of the sample at the No. position.

[0022] When taking out the sample at the first placement point, the second valve, the seventh valve, the fourth valve and the fifth valve of the control system are closed, and the first valve, the third valve and the sixth valve are opened to introduce nitrogen into the furnace tube to replace the hydrogen in the furnace tube with nitrogen. After minutes, the furnace door can be opened to take out the pipe plug and the copper-infiltrated sample at the first placement point, put in a new sample, and then put the pipe plug back to its original position, close the furnace door, close the first valve, the fifth valve and the fourth valve, and open the second valve, the seventh valve, the third valve and the sixth valve until the copper infiltration of the sample at the position is completed, and the furnace body automatically moves to the first placement position for heating.

[0023] Beneficial Effects

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The purpose of the present invention is to provide a rapid copper infiltration furnace for preparing tungsten carbide powder metallographic samples, which can realize uninterrupted preparation of tungsten carbide powder copper infiltration samples and realize rapid sample preparation and detection. The sample preparation time is controlled within 2 hours, which is 24 hours compared with the previous sample preparation, thereby improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the present invention.

[0027] (1. Furnace body, 2. Placement rack, 3. Guide assembly, 4. First placement point, 5. Second placement point, 6. First valve, 7. Second valve, 8. Third valve, 9. Fourth valve, 10. Fifth valve, 11. Sixth valve, 12. Seventh valve, 13. Furnace door) DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] The present invention provides a technical solution: a rapid copper infiltration furnace for preparing metallographic samples of tungsten carbide powder, comprising: fully mixing ultrafine-fine WC powder to be tested with copper powder using a Turbula three-dimensional mixer for 10 minutes, pressing the mixture into a circular green body with a diameter of about 15 mm, placing the pressed green body at the first placement point 4 and the second placement point 5 in the copper infiltration furnace of the present invention, placing another copper sheet or pure copper green body with a diameter of about 12 mm on top of the green body, at the beginning, the furnace body is at the first placement point 4, the copper infiltration furnace is started, and under the automatic control of the control system, the heating system starts heating and the temperature rise speed is controlled at 15-20 ℃ / min, the second valve 7, the third valve 8, and the sixth valve 11 are closed, the first valve 6, the second valve 7, the fifth valve 10, and the fourth valve 9 are opened to introduce nitrogen into the copper infiltration furnace. After 10 minutes, the first valve 6, the seventh valve 12, the sixth valve 11, and the third valve 8 are closed, the second valve 7, the fifth valve 10, and the fourth valve 9 are opened, and hydrogen is introduced into the copper infiltration furnace. Under the protection of hydrogen, when the temperature reaches 1080-1150℃, which exceeds the melting point of copper, the copper sheet or pure copper green billet placed on the top of the green billet will melt, and under the action of the pore capillary force, the molten copper will penetrate into the green billet, fill the pores, fix the WC powder, and the copper and WC particles in the sample will be evenly distributed. The temperature reaches 1150 ℃, and after being kept warm for 10 minutes, under the automatic control of the control system, the furnace body slowly moves to the position of the second placement point 5 along the track, and starts to heat the sample placed at the second placement point 5 position, and the sample on the first placement point 4 is cooled. The cold hydrogen in the furnace tube can not only protect the sample placed at position No. 4 from being oxidized, but also accelerate the cooling of the sample at position No. 4. After 30 minutes, the sample at position No. 4 can be cooled to below 100 ℃; if it is necessary to take out the sample at position No. 4 at this time, the second valve 7, the seventh valve 12, the fourth valve 9, and the fifth valve 10 of the control system are closed, and the first valve 6, the third valve 8, and the sixth valve 11 are opened to pass nitrogen in the furnace tube, and the hydrogen in the furnace tube is replaced with nitrogen. After 10 minutes, the furnace door 13 can be opened to take out the pipe plug and the copper infiltration sample completed at the first placement point 4 position. Put in a new sample, then put the pipe plug back to its original position, close the furnace door 13, close the first valve 6, the fifth valve 10, and the fourth valve 9, and open the second valve 7, the seventh valve 12, the third valve 8, and the sixth valve 11 until the sample at position 5 is completed copper infiltration. The furnace body automatically moves to the first placement point 4 for heating. Repeat the above process continuously to achieve uninterrupted production of tungsten carbide powder copper infiltration samples and rapid sample preparation and detection. Then, the copper infiltrated sample is embedded in epoxy resin for grinding and polishing. After selective etching with an etchant, the sample is observed under a metallographic microscope with a magnification of 100-200 times. The normal grains are clearly contrasted with the coarse grains. The field of view for one observation is large. The detection of a sample can be completed within 10 minutes, and it can be quickly, accurately and efficiently determined whether there are coarse particles in the ultrafine-fine and medium-crystalline WC powder raw materials.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder, characterized by: The copper infiltration furnace comprises a furnace body, a placement rack, a guide assembly, a control system, a heating system, and a furnace tube. The placement rack runs through the furnace body, and a first placement point and a second placement point are arranged on the placement rack. The furnace body and the guide assembly are slidably connected. A first valve, a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, and a seventh valve are arranged on the furnace tube. The first valve and the second valve are connected to nitrogen and hydrogen respectively. Furnace doors are arranged at both ends of the copper infiltration furnace. The method for using a rapid copper infiltration furnace for making metallographic samples of tungsten carbide powder includes the following steps: 1) Place the green billet at the first placement point and the second placement point in the copper infiltration furnace, and place the pipe plug; 2) At the beginning, the furnace body is at the first placement point, the copper infiltration furnace is started, and under the automatic control of the control system, the heating system starts heating, the second valve, the third valve, and the sixth valve are closed, and the first valve, the second valve, the fifth valve, and the fourth valve are opened to introduce nitrogen into the copper infiltration furnace; 3) After a certain period of time, the first valve, the seventh valve, the sixth valve, and the third valve are closed, and the second valve, the fifth valve, and the fourth valve are opened, and hydrogen is introduced into the copper infiltration furnace; 4) When the temperature reaches 1080-1150℃, which exceeds the melting point of copper, the copper sheet or pure copper green body placed on the top of the green body will melt. Under the action of the pore capillary force, the molten copper penetrates into the green body and fills the pores. 5) Fix the WC powder, and the copper and WC particles in the sample will be evenly distributed, the temperature reaches 1150℃, and keep warm for 10 minutes; 6) Under the automatic control of the control system, the furnace body slowly moves along the track to the position of the second placement point, starts to heat the sample placed at the second placement point, and cools the sample at the first placement point; 7) The copper infiltration sample can be taken out by opening the furnace door; When taking out the sample at the first placement point, the second valve, the seventh valve, the fourth valve and the fifth valve of the control system are closed, and the first valve, the third valve and the sixth valve are opened to introduce nitrogen into the furnace tube to replace the hydrogen in the furnace tube with nitrogen. After minutes, the furnace door can be opened to take out the pipe plug and the completed copper infiltration sample at the first placement point, put in a new sample, and then put the pipe plug back to its original position, close the furnace door, close the first valve, the fifth valve and the fourth valve, and open the second valve, the seventh valve, the third valve and the sixth valve until the sample at the position completes copper infiltration, and the furnace body automatically moves to the first placement point for heating.

2. The rapid copper infiltration furnace for preparing metallographic samples of tungsten carbide powder according to claim 1, characterized in that: The guide assembly is located between the bottom of the placement rack and the furnace body and is connected via rollers.

3. The rapid copper infiltration furnace for preparing metallographic samples of tungsten carbide powder according to claim 1, characterized in that: In step 2), the heating system temperature rise rate is controlled at 15-20°C / min.

4. The rapid copper infiltration furnace for preparing metallographic samples of tungsten carbide powder according to claim 1, characterized in that: When the furnace body moves to the second placement point, the cold hydrogen in the furnace tube can not only protect the sample placed at position No. from being oxidized, but also accelerate the cooling of the sample at position No.

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