A rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures

Abstract

The present invention discloses a rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures, comprising: S1. Slowly adding a pre-prepared molding agent solution to WC powder; S2. Drying the uniformly stirred material in S1, sieving and granulating by rubbing; S3. Pressing 3 green compact samples, measuring the height of the green compact, and taking the average value H; S4. Wet-milling the WC powder in S1 with a binder powder and a molding agent, drying, sieving by rubbing, and then pressing and sintering to detect the sintering shrinkage rate η of the alloy block; S5. Repeating steps S1 to S4 to draw a relationship curve between the green compact height H and the shrinkage rate η at the WC powder particle size; S6. For the WC powder to be measured, after measuring the green compact height H of the WC powder according to steps S1 to S3, obtaining the shrinkage rate η of the mixture according to the relationship curve in step S5. The present invention can perform accurate characterization, has a higher index resolution, is more convenient and efficient in testing, has a short identification period, generally less than 2 h, and can be used to guide the mass production of cemented carbide.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and particularly relates to a rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures. Background Art

[0002] The sintering shrinkage rate of cemented carbide mixtures is a key index affecting the formability of cemented carbide mixtures and the control of the appearance size of alloy sintering. The commonly used characterization methods at present generally require, according to the component requirements of the alloy grade, mixing WC powder, binder phase powder and corresponding forming agents for wet grinding, then drying, sieving and granulating, and then pressing and sintering to detect the sintering shrinkage rate of the alloy block. This method has a high sample preparation cost and a long identification period, generally more than 48 hours. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures. By directly measuring the height of the green compact after WC powder is formed, the sintering shrinkage rate after it is made into a mixture is characterized. This method can accurately characterize, has a higher index resolution, is more convenient and efficient in testing, has a short identification period, generally less than 2 hours, and can be used to guide the batch production of cemented carbide.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures, the detection method comprising the following steps:

[0005] S1. Adding forming agent: Take an appropriate amount of WC powder, and slowly add the pre-dissolved forming agent solution to the WC powder while stirring, and stir evenly;

[0006] S2. Drying and granulating: After drying the uniformly stirred material in S1, sieve and granulate it;

[0007] S3. Pressing and detecting the height of the WC green compact: Using a certain pressing pressure, prepare 3 green compact samples, measure the height of the green compact, and take the average value H;

[0008] S4. Detecting the alloy sintering shrinkage rate of the mixture: According to certain component requirements, mix the WC powder in S1 with binder phase powder and forming agent for wet grinding, then dry, sieve and press and sinter, and detect the sintering shrinkage rate η of the alloy block;

[0009] S5. Drawing a relationship curve: Repeat steps S1 to S4, and draw the relationship curve between the height H of the green compact and the shrinkage rate η at this WC powder particle size for subsequent shrinkage rate detection;

[0010] S6. Detect the WC powder sample: After measuring the compact height H of the WC powder to be tested according to steps S1 to S3, obtain the shrinkage rate η of the mixture according to the relationship curve in step S5.

[0011] Further, in step S1, the weight ratio of the molding agent to the WC powder is 1:40 - 70; the molding agent is paraffin.

[0012] Further, in step S2, take out the solution stirred evenly in step S1 after drying in an oven at 120°C for 5 - 40 min, and screen and granulate it with a 60-mesh sieve.

[0013] Further, in step S3, the pressing pressure is 100 - 200 Mpa, and the single pressing weight of the compact sample is 20 - 100 g.

[0014] The detection principle of the present invention is as follows:

[0015] The calculation formulas for the sintering shrinkage coefficient and shrinkage rate of cemented carbide powder are as follows:

[0016]

[0017]

[0018]

[0019]

[0020] represents the volume shrinkage coefficient; η represents the linear shrinkage rate;

[0021] , respectively represent the volumes of the compact and the alloy after sintering;

[0022] , respectively represent the weights of the compact and the alloy after sintering;

[0023] , respectively represent the densities of the compact and the alloy after sintering;

[0024] a, b, h respectively represent the dimensions of the compact in the three directions of length, width, and height;

[0025] It can be deduced from the above formulas that during the pressing and sintering process, and and When a and b are usually specific values, the shrinkage rate η of the alloy sintered wire is determined by the height h of the green compact of the mixture, and there is a corresponding relationship between the two;

[0026] Since the plasticity of the bonding phase powder is significantly greater than that of the WC powder and the powder sphericity is also higher; during the pressing process, the frictional resistance of the relative movement of the bonding phase powder is much smaller than that of the WC powder. The volume of the green compact after pressing the mixture mainly depends on the size of the skeleton formed by the WC powder. Therefore, under the same cobalt powder, binder and the same mixture formula and production process, the value H of the green compact height of the WC powder and the green compact height h of the mixture are positively correlated, and there is a corresponding relationship between the two. The sintering shrinkage rate η of the mixture for cemented carbide can be characterized by measuring the value H of the green compact height of the raw material WC powder.

[0027] The beneficial effects of the present invention are: compared with the prior art, a rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixture provided by the present invention characterizes the sintering shrinkage rate of the mixture after it is made by directly measuring the height of the green compact after the WC powder is formed. This method can accurately characterize, has a higher index resolution, and is more convenient and efficient for testing; from the comparison of the WC powder identification consumption and identification cycle in Table 1 below, the method of measuring the value of the green compact height of the raw material WC powder also has the advantages of low sample preparation cost and short identification cycle, and can be used to guide the mass production of cemented carbide.

[0028] Table 1

[0029] Identification method WC powder consumption g Identification period h Prepare a small batch of mixed materials to identify the sintering shrinkage rate 500～1000 ＞48 WC detect the compact height 50～100 ＜2 Description of the Drawings

[0030] Figure 1 It is the relationship curve (1.3μm) between the green compact height H and the shrinkage rate η in Example 1.

[0031] Figure 2 It is the relationship curve (0.4μm) between the green compact height H and the shrinkage rate η in Example 2. Detailed Embodiments

[0032] The present invention will be further described below through specific examples. However, these examples are only used to illustrate the present invention and not to limit the scope of the present invention.

[0033] Example 1

[0034] Taking WC powder with a Fisher particle size of 1.3μm as an example.

[0035] 1. Take 150 g of WC powder with a Fisher particle size of 1.3 μm and different shrinkage rates in 12 batches, add the pre-dissolved paraffin solution (the weight of paraffin powder is 3 g), and stir evenly.

[0036] 2. Take out the evenly stirred material in step 1 after drying in an oven at 120 °C for 20 min, and screen and granulate it with a 60-mesh sieve.

[0037] 3. Use a pressing pressure of 160 Mpa, press a single weight of 20 g, press 3 green compact samples for each batch of WC powder, with dimensions of 20 mm * 16 mm * H (green compact height), measure the height of the green compact, and take the average value.

[0038] 4. According to the composition requirements of the alloy grade to be produced (mass ratio: WC:Co:Wax = 95.5:4.5:2), mix the 12 batches of WC powder in step 1 with the binder phase powder and the forming agent, wet grind them, then dry and granulate them, and perform pressing and sintering. Detect the sintering shrinkage rate η of the alloy block, and draw the relationship curve between the green compact height H and the shrinkage rate η, as Figure 1 , which can be used for subsequent shrinkage rate detection of WC powder with a Fisher particle size of about 1.3 μm.

[0039] If the Fisher particle size of the WC powder of the sample to be measured is about 1.3 μm, then the Figure 1 relationship curve between the green compact height H and the shrinkage rate η can be used. Take 150 g of the WC powder to be measured, and according to the above steps 1 to 3, measure its green compact height to be 8.7 mm. According to the Figure 1 curve relationship, the alloy sintering shrinkage rate of the WC powder to be measured after being made into a mixture is 18.02%, which is close to the result of 18.07% identified by the actual batch production of finished products. This shows that the detection method adopted in this example can quickly detect the sintering shrinkage rate of the mixture and be used to guide the mass production of cemented carbide.

[0040] Example 2

[0041] Taking WC powder with a Fisher particle size of 0.4 μm as an example,

[0042] 1. Take 210 g of WC powder with a Fisher particle size of 0.4 μm and different shrinkage rates in 12 batches, add the pre-dissolved paraffin solution (the weight of paraffin powder is 3 g), and stir evenly.

[0043] 2. Take out the evenly stirred solution in step 1 after drying in an oven at 120 °C for 30 min, and screen and granulate it with a 60-mesh sieve.

[0044] 3. Apply a compaction pressure of 150 Mpa, with a single weight of 30 g. Compact 3 green compact samples for each WC powder batch, with dimensions of 20 mm * 16 mm * H (height of the green compact). Measure the height of the green compact and take the average value;

[0045] 4. According to the composition requirements of the alloy grade to be produced (mass ratio: WC:Co:Wax = 88:12:2), mix the 12 batches of WC powder in step 1 with the binder phase powder and the molding agent, wet grind them, then dry and granulate, and perform compaction and sintering. Detect the sintering shrinkage rate η of the alloy block, and plot the relationship curve between the height H of the green compact and the shrinkage rate η, as Figure 2 , which can be used for subsequent shrinkage rate detection of WC powder with an Fsss particle size of about 0.4 μm.

[0046] If the Fsss particle size of the WC powder of the sample to be tested is about 0.4 μm, then Figure 2 the relationship curve between the height H of the green compact and the shrinkage rate η in Figure 2 can be used. Take 210 g of the WC powder to be tested, and according to the above steps 1 to 3, measure the height of its green compact to be 13.35 mm. According to

[0047] the curve relationship, the sintering shrinkage rate of the alloy made from the WC powder to be tested after being made into a mixture is 22.73%, which is close to the result of 22.78% identified in the actual batch production of finished products. This shows that the detection method adopted in this embodiment can quickly detect the sintering shrinkage rate of the mixture and be used to guide the mass production of cemented carbide.

Claims

1. A rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixtures, characterized in that: The detection method includes the following steps: S1. Adding a molding agent: Take an appropriate amount of WC powder, and slowly add the pre-dissolved molding agent solution to the WC powder while stirring until evenly mixed; the weight ratio of the molding agent to the WC powder is 1:40 - 70; S2. Drying and granulating: After drying the evenly stirred material in S1, sieve and granulate it; S3. Pressing and detecting the height of the WC green compact: Using a certain pressing pressure, prepare 3 green compact samples, measure the height of the green compact, and take the average value H; the pressing pressure is 100 - 200 Mpa, and the single pressing weight of the green compact sample is 20 - 100 g; S4. Detecting the alloy sintering shrinkage rate of the mixture: According to certain component requirements, mix and wet-grind the WC powder in S1 with the binder powder and the molding agent, then dry, sieve, and press and sinter it, and detect the sintering shrinkage rate η of the alloy block; S5. Drawing a relationship curve: Repeat steps S1 to S4 to draw the relationship curve between the green compact height H and the shrinkage rate η at the WC powder particle size for subsequent shrinkage rate detection; S6. Detecting the WC powder sample: For the WC powder to be tested, after measuring the green compact height H of the WC powder according to steps S1 to S3, obtain the shrinkage rate η of the mixture according to the relationship curve in step S5.

2. The rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixture according to claim 1, characterized in that: In step S1, the molding agent is paraffin.

3. The rapid detection method for characterizing the sintering shrinkage rate of cemented carbide mixture according to claim 1, characterized in that: In step S2, take out the evenly stirred material in step S1 after drying it in an oven at 120 °C for 5 - 40 min, and sieve and granulate it with a 60-mesh sieve.

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