A method for controlling the sintering deformation of circular ring cemented carbide

Abstract

This invention belongs to the field of cemented carbide technology, specifically relating to a method for controlling the sintering deformation of circular cemented carbide. The method involves biaxially pressing a circular alloy compact, inserting a graphite column in the center, and sintering it once on a treated graphite boat. Then, calcined alumina particles are used to fill the compact for a second sintering, correcting the product shape and improving the amount of deformation. This invention offers high pressing efficiency, uniform compact density, no material waste, minimal deformation of the sintered product, high dimensional accuracy, and eliminates the need for subsequent micro-machining or grinding. It is highly adaptable to various sizes of circular alloy products and various cobalt-content tungsten-cobalt alloys, exhibiting good product performance stability and minimizing decarburization issues, thus facilitating large-scale industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide technology, specifically a method for controlling the sintering deformation of a ring-shaped cemented carbide. Background Technology

[0002] During the sintering process, ring-shaped cemented carbide products are affected by various factors (such as uneven compact density, binder dissolution and flow, their own gravity, and frictional resistance of the boat surface), leading to varying degrees of deformation such as ellipticity and unevenness after sintering, especially for relatively thin, tall, and high-cobalt-content products. Traditional pressing methods result in significant density differences between the two ends of the compact, leading to substantial dimensional discrepancies after sintering. Cold isostatic pressing of solid cylinders followed by machining into rings is time-consuming and wasteful of materials. During sintering, the liquefied flow of the binder, the product's own gravity, and the frictional force of the boat cause the boat-side end to be relatively larger after sintering, resulting in unevenness. Large products formed using traditional sintering methods exhibit significant dimensional fluctuations, requiring subsequent grinding to meet high precision requirements. Summary of the Invention

[0003] To address the problems existing in the prior art, the main objective of this invention is to propose a method for controlling the sintering deformation of circular ring cemented carbide, thereby improving the sintering deformation of circular ring cemented carbide products.

[0004] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A method for controlling the sintering deformation of a circular ring-shaped cemented carbide includes the following steps:

[0006] S1. Bidirectional pressing yields a circular pressed blank;

[0007] S2. Alumina particles that have been calcined at high temperature are spread on a graphite boat to obtain a treated graphite boat. A circular ring compact is placed on the treated graphite boat, and a graphite column is inserted into the middle of the circular ring compact. The compact is then sintered in a sintering furnace to obtain a primary sintered cemented carbide.

[0008] S3. A high-temperature calcined alumina particles are laid flat at the bottom of the graphite box to obtain a treated graphite box; a primary sintered cemented carbide is placed in the treated graphite box, and sintered alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered; the treated graphite box containing the primary sintered cemented carbide is then sintered in a sintering furnace for a second time and then taken out to obtain a ring-shaped cemented carbide.

[0009] In a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in steps S2 and S3, the alumina particles have a particle size of 60-80 mesh.

[0010] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in steps S2 and S3, the temperature of the alumina particles for high-temperature calcination is 1410-1430℃ and the time is 90-110 min.

[0011] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S2, the process of obtaining the treated graphite boat by spreading alumina particles calcined at high temperature on the graphite boat is as follows: after brushing a layer of glue on the graphite boat, 1 to 2 layers of alumina particles are spread on it.

[0012] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S2, the height of the graphite column is consistent with that of the ring-shaped cemented carbide, and the outer diameter of the graphite column is equal to or slightly larger than the inner diameter of the ring-shaped cemented carbide.

[0013] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S2, 2 to 4 layers of coating are applied to the surface of the graphite column. The components of the coating include alumina, ultrapure carbon black, wear-resistant carbon black, PEG, Tween 80, alcohol, and distilled water. The above components are mixed and ball-milled for 10 to 30 hours to obtain the coating.

[0014] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S2, the temperature of the first sintering is 1330~1360℃ and the time is 30~40min.

[0015] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S3, the process of obtaining the graphite box after high-temperature calcination of alumina particles by spreading them on the bottom of the graphite box is as follows: after brushing a layer of glue on the bottom of the graphite box, 1 to 2 layers of alumina particles are spread on it.

[0016] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S3, the temperature of the secondary sintering is 1390~1410℃ and the time is 80~110min.

[0017] As a preferred embodiment of the method for controlling the sintering deformation of a ring-shaped cemented carbide according to the present invention, in step S3, after secondary sintering, the ring-shaped cemented carbide is taken out and subjected to comprehensive sandblasting treatment to obtain the ring-shaped cemented carbide.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention proposes a method for controlling the sintering deformation of circular cemented carbide. A circular alloy compact, formed by biaxial pressing, is inserted with a graphite column and sintered once on a treated graphite boat. Then, calcined alumina particles are used to fill the compact for a second sintering, correcting the product shape and reducing deformation. This invention offers high pressing efficiency, uniform compact density, no material waste, minimal deformation, high dimensional accuracy, and eliminates the need for subsequent micro-machining or grinding. It is highly adaptable to various sizes of circular alloy products and tungsten-cobalt alloys with varying cobalt contents. The products exhibit good performance stability, are less prone to decarburization, and are suitable for large-scale industrial applications. Detailed Implementation

[0020] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention proposes a method for controlling the sintering deformation of circular ring cemented carbide, which is used to improve the sintering deformation of circular ring cemented carbide products.

[0022] According to one aspect of the present invention, the present invention provides the following technical solution:

[0023] A method for controlling the sintering deformation of a circular ring-shaped cemented carbide includes the following steps:

[0024] S1. Bidirectional pressing yields a circular pressed blank;

[0025] S2. Alumina particles that have been calcined at high temperature are spread on a graphite boat to obtain a treated graphite boat. A circular ring compact is placed on the treated graphite boat, and a graphite column is inserted into the middle of the circular ring compact. The compact is then sintered in a sintering furnace to obtain a primary sintered cemented carbide.

[0026] S3. A high-temperature calcined alumina particles are laid flat at the bottom of the graphite box to obtain a treated graphite box; a primary sintered cemented carbide is placed in the treated graphite box, and sintered alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered; the treated graphite box containing the primary sintered cemented carbide is then sintered in a sintering furnace for a second time and then taken out to obtain a ring-shaped cemented carbide.

[0027] Preferably, in step S1, the bidirectional pressing can be performed using a pressing process commonly used in the prior art. For example, after unidirectional pressing, the bidirectional pressing of the annular blank is achieved by displacing the mold cavity downward by 1 to 5% of the blank height.

[0028] Preferably, in steps S2 and S3, the alumina particles have a particle size of 60-80 mesh, and the high-temperature calcination temperature of the alumina particles is 1410-1430℃, with a time of 90-110 min. This solves the problems of impurities affecting the alumina particles and decarburization caused by excessive oxygen content. Specifically, the high-temperature calcination temperature of the alumina particles can be, for example, but not limited to, any one or any two of 1410℃, 1415℃, 1420℃, 1425℃, and 1430℃; the high-temperature calcination time of the alumina particles can be, for example, but not limited to, any one or any two of 90 min, 95 min, 100 min, 105 min, and 110 min.

[0029] Preferably, in step S2, the process of obtaining the treated graphite boat by spreading high-temperature calcined alumina particles on the graphite boat is as follows: after brushing a layer of adhesive onto the graphite boat, 1-2 layers of alumina particles are spread on it; the height of the graphite pillars is consistent with that of the ring-shaped cemented carbide, and the outer diameter of the graphite pillars is equal to or slightly larger than the inner diameter of the ring-shaped cemented carbide; 2-4 layers of coating are applied to the surface of the graphite pillars, the components of which include alumina, ultra-pure carbon black, wear-resistant carbon black, PEG, Tween 80, alcohol, and distilled water, and the above components are mixed and ball-milled for 10-30 hours to obtain the coating. Compared with traditional coated boats and sprayed boats, the treated boat of this invention has the advantages of low friction, strong isolation, and non-stick properties.

[0030] Preferably, in step S2, the temperature of the first sintering is 1330–1360°C, and the time is 30–40 min. The first sintering mainly completes the shrinkage during the dewaxing stage and the product curing, greatly facilitating subsequent adjustments to the product's size and shape. Specifically, the temperature of the first sintering can be, for example, but not limited to, any one or any two of 1330°C, 1335°C, 1340°C, 1345°C, 1350°C, 1355°C, and 1360°C; the time of the first sintering can be, for example, but not limited to, any one or any two of 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, and 40 min.

[0031] Preferably, in step S3, the process of obtaining the graphite box after high-temperature calcination of alumina particles by spreading them flat at the bottom of the graphite box is as follows: after brushing a layer of adhesive on the bottom of the graphite box, 1-2 layers of alumina particles are spread flat. The sintered alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered; the filler plays a good role in horizontal restraint, causing the ring-shaped cemented carbide to shrink uniformly towards the center; the secondary sintering has a larger product shrinkage adjustment space, improving product dimensional deformation. Preferably, in step S3, the secondary sintering temperature is 1390-1410℃, and the time is 80-110 minutes. Preferably, in step S3, after secondary sintering, the product is removed and subjected to full sandblasting treatment to obtain the ring-shaped cemented carbide. Specifically, the temperature of the secondary sintering can be, for example, but not limited to, any one or a range between any two of 1390℃, 1395℃, 1400℃, 1405℃, and 1410℃; the time of the secondary sintering can be, for example, but not limited to, any one or a range between any two of 80min, 85min, 90min, 95min, 100min, 105min, and 110min.

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0033] The alumina particles used in the following embodiments are all alumina particles that have undergone high-temperature calcination, with a particle size of 80 mesh. The high-temperature calcination temperature is 1420℃, and the time is 100 min. The graphite column surface is coated with three layers of coating. The coating components include alumina, ultrapure carbon black, abrasion-resistant carbon black, PEG, Tween 80, alcohol, and distilled water. The above components are mixed and ball-milled for 20 h to obtain the coating.

[0034] Example 1

[0035] A method for controlling the sintering deformation of a circular ring-shaped cemented carbide includes the following steps:

[0036] S1. Bidirectional pressing yields a circular pressed blank;

[0037] S2. After brushing a layer of glue onto the graphite boat, two layers of alumina particles are laid flat to obtain the treated graphite boat. The circular ring compact is placed on the treated graphite boat. A graphite column with the same height as the circular ring cemented carbide and an outer diameter equal to the inner diameter of the circular ring cemented carbide is inserted into the middle of the circular ring compact. The compact is then sintered in a sintering furnace to obtain a first-sintered cemented carbide. The first sintering temperature is 1350℃ and the time is 30min.

[0038] S3. After brushing a layer of adhesive onto the bottom of the graphite box, two layers of alumina particles are laid flat to obtain the treated graphite box. The primary sintered cemented carbide is placed in the treated graphite box, and alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered. The treated graphite box containing the primary sintered cemented carbide is then subjected to a second sintering in a sintering furnace (temperature 1390℃, time 80min), and then removed and subjected to comprehensive sandblasting to obtain a ring-shaped cemented carbide. Testing showed that the roundness of the ring-shaped cemented carbide prepared in this embodiment is <0.2%, and the dimensional difference between the upper, middle, and lower parts is <0.5mm.

[0039] Example 2

[0040] A method for controlling the sintering deformation of a circular ring-shaped cemented carbide includes the following steps:

[0041] S1. Bidirectional pressing yields a circular pressed blank;

[0042] S2. After brushing a layer of glue onto the graphite boat, a layer of alumina particles is spread on top to obtain the treated graphite boat. The circular ring compact is placed on the treated graphite boat. A graphite column with the same height as the circular ring cemented carbide and an outer diameter slightly larger than the inner diameter of the circular ring cemented carbide is inserted into the middle of the circular ring compact. The compact is then sintered in a sintering furnace to obtain a first-sintered cemented carbide. The first sintering temperature is 1330℃ and the time is 40min.

[0043] S3. After brushing a layer of adhesive onto the bottom of the graphite box, a layer of alumina particles is laid flat to obtain the treated graphite box. The primary sintered cemented carbide is placed in the treated graphite box, and alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered. The treated graphite box containing the primary sintered cemented carbide is then subjected to a second sintering in a sintering furnace (temperature 1400℃, time 100min), and then removed and subjected to comprehensive sandblasting to obtain a ring-shaped cemented carbide. Testing showed that the roundness of the ring-shaped cemented carbide prepared in this embodiment is <0.2%, and the dimensional difference between the upper, middle, and lower parts is <0.7mm.

[0044] Example 3

[0045] A method for controlling the sintering deformation of a circular ring-shaped cemented carbide includes the following steps:

[0046] S1. Bidirectional pressing yields a circular pressed blank;

[0047] S2. After brushing a layer of glue onto the graphite boat, a layer of alumina particles is laid flat to obtain the treated graphite boat. The circular ring blank is placed on the treated graphite boat. A graphite column with the same height as the circular ring cemented carbide and an outer diameter equal to the inner diameter of the circular ring cemented carbide is inserted into the middle of the circular ring blank. The blank is then sintered in a sintering furnace to obtain a first-sintered cemented carbide. The first sintering temperature is 1360℃ and the time is 30min.

[0048] S3. After brushing a layer of adhesive onto the bottom of the graphite box, a layer of alumina particles is laid flat to obtain the treated graphite box. The primary sintered cemented carbide is placed in the treated graphite box, and alumina particles are poured into the graphite box until the primary sintered cemented carbide is completely filled and covered. The treated graphite box containing the primary sintered cemented carbide is then subjected to secondary sintering in a sintering furnace (temperature 1410℃, time 110min), and then removed and subjected to comprehensive sandblasting to obtain a ring-shaped cemented carbide. Testing showed that the roundness of the ring-shaped cemented carbide prepared in this embodiment is <0.2%, and the dimensional difference between the upper, middle, and lower parts is <0.7mm.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that,

[0051] Step S3 is skipped.

[0052] In step S2, the cemented carbide is sintered in a sintering furnace to obtain a single-sintered cemented carbide, which is then removed and subjected to full sandblasting to obtain a ring-shaped cemented carbide.

[0053] Testing revealed that the overall size of the circular cemented carbide ring prepared in this comparative example was 1–5 mm larger than expected, and the roundness was less than 0.2%.

[0054] Comparative Example 2

[0055] The difference from Example 1 is that,

[0056] S2. Without laying alumina particles, only a graphite column with the same height as the ring cemented carbide and an outer diameter equal to the inner diameter of the ring cemented carbide is inserted into the middle of the ring compact and sintered in a sintering furnace to obtain a primary sintered cemented carbide; the primary sintering temperature is 1360℃ and the time is 30min.

[0057] Testing revealed that the overall size of the circular cemented carbide ring prepared in this comparative example was too large. The end near the boat showed signs of sticking to the boat and carburization, exhibiting a funnel shape, and its size was 3-5 mm larger than that of the middle and upper ends.

[0058] Comparative Example 3

[0059] The difference from Example 1 is that,

[0060] In steps S2 and S3, the alumina particles used are alumina particles that have not undergone high-temperature calcination.

[0061] Testing revealed that the cobalt magnetic flux density of the circular ring cemented carbide prepared in this comparative example was 0.1–0.2 lower, and the product was at risk of decarburization.

[0062] This invention involves bidirectional pressing to form a circular alloy compact, inserting a graphite column in the center, and sintering it once on a treated graphite boat. Then, calcined alumina particles are used to fill the compact for a second sintering, correcting the product shape and reducing deformation. This invention boasts high pressing efficiency, uniform compact density, no material waste, minimal deformation, high dimensional accuracy, and eliminates the need for subsequent micro-machining or grinding. It is highly adaptable to various sizes of circular alloy products and tungsten-cobalt alloys with varying cobalt contents. The products exhibit good performance stability, are less prone to decarburization, and are suitable for large-scale industrial applications.

[0063] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for controlling the sintering deformation of a circular ring-shaped cemented carbide, characterized in that, Includes the following steps: S1. Bidirectional pressing yields a circular pressed blank; S2. After brushing a layer of glue onto a graphite boat, spread 1-2 layers of alumina particles calcined at high temperature to obtain a treated graphite boat. Place a circular ring compact on the treated graphite boat, insert a graphite column into the middle of the circular ring compact, and sinter in a sintering furnace to obtain a primary sintered cemented carbide. The primary sintering temperature is 1330-1345℃, and the time is 30-40 minutes. Coat the surface of the graphite column with 2-4 layers of coating. The coating components include alumina, ultrapure carbon black, wear-resistant carbon black, PEG, Tween 80, alcohol, and distilled water. The above coating components are mixed and ball-milled for 10-30 hours to obtain the coating. S3. After brushing a layer of glue on the bottom of the graphite box, spread 1-2 layers of high-temperature calcined alumina particles to obtain the treated graphite box; place the primary sintered cemented carbide into the treated graphite box, and pour the high-temperature calcined alumina particles into the graphite box until the primary sintered cemented carbide is completely filled and covered; the treated graphite box containing the primary sintered cemented carbide is placed in a sintering furnace for secondary sintering and then taken out to obtain a ring-shaped cemented carbide; the secondary sintering temperature is 1390~1395℃, and the time is 80~110min; the roundness of the ring-shaped cemented carbide is <0.2%, and the dimensional difference between the upper, middle and lower parts is <0.7mm; In steps S2 and S3, the alumina particles have a particle size of 60-80 mesh, and the alumina particles are calcined at a temperature of 1410-1430℃ for 90-110 minutes.

2. The method for controlling the sintering deformation of circular ring cemented carbide according to claim 1, characterized in that, In step S2, the height of the graphite column is the same as that of the ring-shaped cemented carbide, and the outer diameter of the graphite column is equal to or slightly larger than the inner diameter of the ring-shaped cemented carbide.

3. The method for controlling the sintering deformation of circular ring cemented carbide according to claim 1, characterized in that, In step S3, after secondary sintering, the material is removed and subjected to full sandblasting to obtain a ring-shaped cemented carbide.