A cemented carbide sintering process

Abstract

The present application relates to the technical field of hard alloy, aiming at the problems of low applicability of batch industrial production, high process difficulty and high production cost of the technical means for solving the problem of hard alloy sintering adhesion, a hard alloy sintering process is disclosed, comprising the following steps: taking hard alloy compact, sequentially performing first sintering, cooling, second sintering and forming treatment to obtain hard alloy product; wherein in the cooling process, the temperature is controlled to be reduced by 90-1370 DEG C based on the first sintering temperature. The hard alloy sintering process can make the product shrink, reduce the expansion and adhesion of hard alloy caused by high temperature sintering, effectively avoid the product sintering adhesion phenomenon and improve the production efficiency and yield of the product by only adjusting the temperature of the sintering process without changing other sintering devices and means.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hard alloy, in particular to a hard alloy sintering process. BACKGROUND

[0002] Hard alloy is an alloy material made of refractory metal hard compound and binder metal through powder metallurgy process, which has the characteristics of high hardness, good wear resistance and good red hardness at high temperature, and is widely used in cutting, mining, infrastructure and other national economic fields, as well as military, nuclear energy, aerospace and other national defense and military fields.

[0003] In the process of preparing hard alloy, sintering is an important link of powder metallurgy process, and the sintering effect directly determines the quality of hard alloy products. In order to reduce production cost and save sintering resources, the gap between product compacts in the loading process of sintering process will be as small as possible to improve the sintering efficiency. However, such loading method will cause the products to contact each other due to expansion at high temperature sintering stage, resulting in product sticking phenomenon, which affects the appearance quality and qualified rate of products. In order to solve the sticking problem of hard alloy in sintering process, at present, the methods of increasing product gap, improving boat structure or adding isolation material are mainly used to reduce the mutual contact between products, so as to reduce the product sticking phenomenon.

[0004] For example, the patent with publication number CN208165518U discloses a conveying and isolating structure of sintering tray, which places the small precision samples in the positioning groove in the tray, and clamps the small precision samples in the positioning groove by rotating the bolt sleeve, so as to avoid the contact and sticking of the small precision samples with the adjacent small precision samples.

[0005] For example, the patent with publication number CN106116595A discloses a sticking preventing powder and a method for batch sintering of sheet-shaped ceramics by using the powder, which scatters the sticking preventing powder between the ceramics to avoid the sticking of sheet-shaped ceramic blanks. However, the above-mentioned sticking preventing powder will affect the furnace atmosphere and product quality to some extent during sintering, and increase the production cost, which is not suitable for actual industrial production, and has low practicability and poor popularization.

[0006] Based on the current hard alloy sintering process, there is an urgent need for a hard alloy sintering process which has wider applicability, stronger practicability and better solves the sticking problem in the sintering process of hard alloy. SUMMARY

[0007] The technical problem to be solved by the present application is:

[0008] In the production process of cemented carbide, expansion and adhesion between adjacent products are prone to occur due to high-temperature sintering. At present, the main treatment methods to solve the above-mentioned cemented carbide product adhesion problem are to increase the placement gap when loading the product green body into the boat, to improve the boat structure or to add isolation materials, etc. However, the above-mentioned methods will bring the problems of small loading amount in batch production, large process difficulty and high production cost, that is, the cemented carbide product adhesion problem cannot be solved without other negative effects.

[0009] The technical scheme adopted by the present application is:

[0010] The application provides a cemented carbide sintering process, which comprises the following steps:

[0011] Taking a cemented carbide green body, the following steps are sequentially performed: primary sintering, cooling, secondary sintering and forming treatment, so that a cemented carbide product is obtained.

[0012] In the cooling process, the temperature is controlled to be reduced by 90-1370 DEG C based on the sintering temperature.

[0013] Preferably, the primary sintering comprises the following two sintering processes:

[0014] (1) first heating to 1230-1250 DEG C and keeping for 20-120 min;

[0015] (2) then continuously heating to 1350-1390 DEG C and keeping for 10-60 min.

[0016] Preferably, in step (1), the heating rate is 2-5 DEG C / min.

[0017] Preferably, in step (2), the heating rate is 1-3 DEG C / min, and in this process, the temperature should be controlled to be slightly higher than the temperature near the liquid phase appearance temperature of the cemented carbide.

[0018] Preferably, in the secondary sintering, the temperature is increased to 1400-1460 DEG C and kept for 20-60 min.

[0019] Preferably, in the secondary sintering, the heating rate is 1-2 DEG C / min.

[0020] Preferably, in the cooling process, Ar is filled to rapidly cool to the required temperature, or the furnace is cooled to the required temperature.

[0021] Preferably, in the forming treatment, the pressure is 1-10 MPa, the pressure keeping time is 5-40 min, and then the pressure is released to ≤4 MPa.

[0022] Preferably, the cemented carbide green body comprises one or more of WC-Co, WC-Co and WC-Ni, Ti(C, N) and Co and / or Ni, and Ti(C, N)-WC-Co / Ni.

[0023] Preferably, the cemented carbide raw material powder comprises ≥ 10 vol.% of binder.

[0024] The technical mechanism and beneficial effects adopted by the present application are:

[0025] During the sintering process of cemented carbide, due to the high temperature, expansion deformation occurs, that is, contact between adjacent cemented carbide products occurs, so that the cemented carbide reacts during the high-temperature liquid-phase sintering process, thereby causing the phenomenon of sticking. In the present application, a cooling treatment step is added in the high-temperature sintering stage, so that the alloy can shrink as much as possible during the solid-phase sintering stage and / or the initial stage of liquid-phase sintering, so as to increase the gap between the products, which can effectively avoid the expansion and sticking of cemented carbide during the sintering process, and at the same time improve the sintering quality and production efficiency of the cemented carbide, and also increase the loading amount, improve the use efficiency of the equipment, and reduce the cost of the equipment.

[0026] Compared with the existing technical means for overcoming the sintering sticking problem of cemented carbide, the cemented carbide sintering process of the present application can effectively avoid the phenomenon of product sintering sticking, improve the production efficiency and yield, and the process is simple and easy to implement, and can be applied to different specifications of cemented carbide products, and is suitable for large-scale industrial production, and has strong popularization. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the sintering temperature and pressure curve diagram in Example 1;

[0028] Figure 2 is the product schematic diagram of ZYT15 cemented carbide in Example 1;

[0029] Figure 3 is the sintering temperature and pressure curve diagram in Comparative Example 1;

[0030] Figure 4 is the product schematic diagram of ZYT15 cemented carbide in Comparative Example 1. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0032] The present application provides a cemented carbide sintering process, which takes cemented carbide raw material powder, and after conventional treatment such as selection, grinding and pressing, a cemented carbide compact is obtained, and the following sintering process treatment is carried out:

[0033] The sintering temperature of S1 is 1230-1250 DEG C, the holding time is 20-120 min, and the heating rate is 3-5 DEG C / min;

[0034] After the holding of S2, the temperature is increased to 1350-1390 DEG C for sintering for 10-60 min, the heating rate is 1-3 DEG C / min, and the temperature should be controlled to be slightly higher than the liquid phase appearance temperature of the hard alloy;

[0035] After the holding of S3, the temperature is decreased to 20-1260 DEG C, which can be rapidly cooled to the required temperature by filling Ar, or the furnace cooling mode is adopted to naturally cool to the required temperature;

[0036] S4 continues to increase the temperature to 1400-1460 DEG C for sintering, the holding time is 20-60 min, and the heating rate is 1-2 DEG C / min;

[0037] After the holding of S5, the pressure is 1-10 MPa, the pressure holding time is 5-40 min, and then the pressure is released to ≤4 MPa.

[0038] The hard alloy compact can be selected from one or more of WC-Co, WC-Co and WC-Ni, Ti(C,N) and Co and / or Ni, and Ti(C,N)-WC-Co / Ni, and is especially suitable for the production sintering of the hard alloy product with the binder content ≥10 vol.%.

[0039] In the present application, in the process of high-temperature and high-pressure sintering of the hard alloy, the shrinkage of the alloy is increased as much as possible in the solid phase sintering stage and the initial stage of the liquid phase sintering stage by the multi-stage sintering theory and the synergistic effect of the multi-stage sintering, so that the gap between the alloys is increased, and the adhesion phenomenon is avoided.

[0040] <EMBODIMENT>

[0041] Embodiment 1

[0042] (1) Preparation of ZYT15 (TiCN-WC-10 vol.% Ni) hard alloy:

[0043] The components are composed of 47% Ti(C,N), 27% TiC, 10.4% WC, 7% Ni, 6% Co, 2.2% Mo and 0.4% NbC by volume fraction; wherein the Feeding particle size of the Ti(C,N) powder is 1.5 μm, the Feeding particle size of the TiC powder is 1.5 μm, the Feeding particle size of the WC powder is 0.6 μm, the Feeding particle size of the Ni powder is 1.0 μm, and the Feeding particle size of the Co powder is 1.0 μm.

[0044] The total 100 kg of raw material powder was weighed according to the above volume fraction, loaded into a 150 L ball mill tank, and 1.5 kg of paraffin, 40 L of hexane and 24 g of isomycin were added for rolling ball milling for 72 h. Among them, the grinding body is Φ6 alloy ball, the ball to material ratio is 4.5:1, and the rotating speed is 46 r / min. After ball milling, the slurry is dried for 5 h using a dryer and then uniformly treated with a 40 mesh sieve to obtain a mixture. The mixture is loaded into the cavity of the S-20A imitation Doster press mold to press into a ZYT15 cemented carbide blank.

[0045] (2) The ZYT15 cemented carbide blank was subjected to the following sintering process:

[0046] S1 sintering temperature is 1240℃, heating rate is 2.7℃ / h, and holding time is 30 min;

[0047] S2 After holding ends in step S1, the temperature is raised to 1360℃ at a rate of 2℃ / min, and sintering is performed for 30 min;

[0048] S3 After holding ends in step S2, sufficient Ar gas is introduced to rapidly cool to 660℃;

[0049] S4 The temperature is raised to 1460℃ for sintering at a rate of 1.7℃ / min, and the holding time is 30 min;

[0050] S5 After holding ends, the pressure is 9 MPa, the pressure holding time is 40 min, then Ar gas is introduced to rapidly cool to 65℃, and the pressure is released to 4 MPa.

[0051] As shown in Figure 2 , the ZYT15 cemented carbide prepared by the above sintering process does not appear to be adhered.

[0052] Example 2

[0053] (1) Preparation of YG12 (WC-20vol%Co) cemented carbide:

[0054] According to the volume fraction, it is composed of 79% WC, 20% Co, 0.009% Cr2C3, and 0.001% VC.

[0055] Among them, the Fei's particle size of the WC powder is 1.0 μm, the Fei's particle size of the Co powder is 1.0 μm, the Fei's particle size of the Cr2C3 powder is 1.2 μm, and the Fei's particle size of the VC powder is 1.6 μm.

[0056] The total 100 kg of raw material powder is weighed according to the above volume fraction, loaded into a 150 L ball mill tank, and 2 kg of paraffin, 45 L of hexane and 50 g of isomycin are added for rolling ball milling for 48 h. Among them, the grinding body is Φ6 alloy ball, the ball to material ratio is 4.5:1, and the rotating speed is 46 r / min. After ball milling, the slurry is dried for 5 h using a dryer and then uniformly treated with a 40 mesh sieve to obtain a mixture. The mixture is loaded into the cavity of the S-20A imitation Doster press mold to press into a YG12 hard alloy blank.

[0057] (2) The YG12 hard alloy blank is subjected to the following sintering process treatment:

[0058] S1 The sintering temperature is 1240℃, the heating rate is 3℃ / min, and the holding time is 30 min;

[0059] S2 After the holding of step S1 is completed, the temperature is raised to 1380℃ at a rate of 2℃ / min, and sintering is performed for 30 min;

[0060] S3 After the holding of step S2 is completed, sufficient Ar gas is introduced to rapidly cool to 1260℃;

[0061] S4 The temperature is raised to 1455℃ for sintering at a rate of 2℃ / min, and the holding time is 30 min;

[0062] S5 After the holding is completed, the pressure is increased to 6 MPa, the pressure holding time is 30 min, then Ar gas is introduced to rapidly cool to 65℃, and the pressure is released to 1 MPa.

[0063] The YG12 hard alloy prepared by the above sintering process does not appear to be adhered.

[0064] Example 3

[0065] (1) Preparation of YG16 (WC-25vol.%) hard alloy:

[0066] According to the volume fraction, it is composed of 74% WC, 25% Co, 0.009% Cr2C3, and 0.001% VC;

[0067] Among them, the Fei's particle size of the WC powder is 1.0 μm, the Fei's particle size of the Co powder is 1.0 μm, the Fei's particle size of the Cr2C3 powder is 1.2 μm, and the Fei's particle size of the VC powder is 1.6 μm.

[0068] The total 100 kg of raw material powder is weighed according to the above volume fraction, loaded into a 150 L ball mill tank, and 2 kg of paraffin, 45 L of hexane and 60 g of isopar M are added for rolling ball milling for 48 h. Among them, the grinding body is Φ6 alloy ball, the ball to material ratio is 4.5:1, and the rotating speed is 46 r / min. After ball milling, the slurry is dried for 5 h using a dryer and then uniformly treated with a 40 mesh sieve to obtain a mixture. The mixture is loaded into the cavity of the S-20A imitation Doster press mold to press into a YG16 hard alloy blank.

[0069] (2) The YG16 hard alloy blank is subjected to the following sintering process:

[0070] S1 sintering temperature is 1240℃, heating rate is 3℃ / min, and holding time is 30 min;

[0071] S2 After holding ends in step S1, the temperature is raised to 1350℃ at a rate of 2℃ / min, and sintering is performed for 30 min;

[0072] S3 After holding ends in step S2, sufficient Ar gas is introduced to rapidly cool to 350℃;

[0073] S4 The temperature is raised to 1450℃ for sintering at a rate of 2℃ / min, and the holding time is 30 min;

[0074] S5 After holding ends, the pressure is increased to 9 MPa, the pressure holding time is 30 min, then sufficient Ar gas is introduced to rapidly cool to 65℃, and the pressure is released to normal pressure.

[0075] The YG16 hard alloy prepared by the above sintering process has almost no sticking phenomenon.

[0076] <Comparative Example>

[0077] Comparative Example 1

[0078] ZYT15 hard alloy is prepared in the same way as in Example 1, and the ZYT15 hard alloy is subjected to the following sintering process:

[0079] S1 sintering temperature is 1240℃, heating rate is 2.7℃ / h, and holding time is 30 min;

[0080] S2 After holding ends in step S1, the temperature is raised to 1360℃ at a rate of 2℃ / min, and sintering is performed for 30 min;

[0081] S3 The temperature is raised to 1460℃ for sintering at a rate of 1.7℃ / min, and the holding time is 30 min;

[0082] After the end of S4, the pressure was increased to 9 MPa, the pressure holding time was 40 min, then Ar gas was introduced to rapidly cool to 65℃, and the pressure was released to 4 MPa.

[0083] The main difference between the present comparative example and Example 1 is that after the end of step S2, no temperature reduction treatment is performed, but the temperature is directly increased to continue sintering.

[0084] As shown in Figure 4 The ZYT15 cemented carbide prepared by the above sintering process in the present comparative example is severely adhered between each small product, and the adhered product sample accounts for about 92% of the total product amount.

[0085] Comparative Example 2

[0086] YG12 cemented carbide was prepared in the same manner as Example 2, and the following sintering process was performed on the YG12 cemented carbide:

[0087] S1, the sintering temperature was 1240℃, the heating rate was 3℃ / min, and the holding time was 30 min;

[0088] S2, after the end of S1, the temperature was increased to 1380℃ at a rate of 2℃ / min, and sintering was performed for 30 min;

[0089] S3, the temperature was increased to 1455℃ at a rate of 2℃ / min, and sintering was performed for 30 min;

[0090] S4, after the end of the holding, the pressure was increased to 6 MPa, the pressure holding time was 30 min, then Ar gas was introduced to rapidly cool to 65℃, and the pressure was released to 1 MPa.

[0091] The main difference between the present comparative example and Example 2 is that after the end of step S2, no temperature reduction treatment is performed, but the temperature is directly increased to continue sintering.

[0092] The YG12 cemented carbide prepared by the above sintering process in the present comparative example is severely adhered between each small product, and the adhered product sample accounts for about 96% of the total product amount.

[0093] Comparative Example 3

[0094] YG16 cemented carbide was prepared in the same manner as Example 3, and the following sintering process was performed on the YG16 cemented carbide:

[0095] S1, the sintering temperature was 1240℃, the heating rate was 3℃ / min, and the holding time was 30 min;

[0096] S2, after the end of S1, the temperature was increased to 1350℃ at a rate of 2℃ / min, and sintering was performed for 30 min;

[0097] S3, sintering at 1450℃ with a heating rate of 2℃ / min and a holding time of 30min;

[0098] S4, after the holding time, pressurizing at 9MPa for 30min, then cooling to 65℃ with Ar gas and releasing the pressure to normal pressure.

[0099] The main difference between the present comparative example and example 3 is that, after step S2, no cooling treatment is performed, but directly heating to continue sintering.

[0100] The YG16 hard alloy prepared by the above sintering process of the present comparative example has a serious adhesion between the small products, and the adhesion product accounts for about 98% of the total product.

[0101] <Experimental Example>

[0102] Samples: examples 1-3 and comparative examples 1-3

[0103] The sintering process of examples 1-3 and comparative examples 1-3 is used to prepare the hard alloy product, and the adhesion rate of the product is measured and calculated, and the results are shown in Table 1 below:

[0104] Table 1: Adhesion rate of samples

[0105] Sample Product blocking rate Example 1 0 Example 2 0 Example 3 2％ Comparative Example 1 92％ Comparative Example 2 96％ Comparative Example 3 98％

[0106] According to the results in Table 1 above, the hard alloy products obtained in examples 1-3 have almost no adhesion phenomenon, and even in the way of densely packed boat, the adhesion problem of the product can be effectively avoided; while the adhesion rate of the products obtained in comparative examples 1-3 is very high, which indicates that the sintering process of the hard alloy provided by the present application can truly and efficiently avoid the adhesion problem of the hard alloy in large-scale batch industrial production.

[0107] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A cemented carbide sintering process, characterized in that, Includes the following steps: Take a cemented carbide billet and perform a first sintering, cooling and temperature reduction, a second sintering, and forming process in sequence to obtain a cemented carbide product. One sintering process includes the following two sintering stages: (1) First, raise the temperature to 1230~1250℃, the heating rate is 2~5℃ / min, and hold for 20~120min; (2) Continue to raise the temperature to 1350~1390℃, with a heating rate of 1~3℃ / min, and hold for 10~60min; During the cooling process, the temperature is controlled to be reduced by 90~1370℃ from the primary sintering temperature. In the secondary sintering, the temperature is raised to 1400~1460℃ at a rate of 1~2℃ / min, and held for 20~60min. The cemented carbide blank comprises one or more of WC-Co, WC-Co and WC-Ni, Ti(C,N) and Co and / or Ni, and Ti(C,N)-WC-Co / Ni, and the cemented carbide raw material powder comprises ≥10 vol.% binder.

2. The cemented carbide sintering process according to claim 1, characterized in that, During the cooling process, Ar is introduced to rapidly cool the furnace to the required temperature, or the furnace is cooled to the required temperature along with the Ar.

3. The cemented carbide sintering process according to claim 1, characterized in that, During the molding process, apply pressure of 1~10MPa, hold pressure for 5~40min, and then release pressure to ≤4MPa.

Images