Asphalt milling tooth hard alloy and preparation method and application thereof

Abstract

The invention discloses an asphalt milling tooth hard alloy and a preparation method and application thereof, and is characterized in that the main chemical components are WC and Co, the content of WC is greater than that of Co, the average grain size of WC is 1.0-3.9 [mu] m, the proportion of WC grains with the grain size less than 1.0 [mu] m is 10-50%, the proportion of WC grains with the grain size more than 3 times of the average grain size is 15-55%, and the balance is Fe. And the particle size distribution curve of the WC crystal grains is in a coarse grain trailing shape. The asphalt milling tooth hard alloy disclosed by the invention has the characteristics of better obdurability and wear resistance, low tooth breaking rate of cutting tooth alloy and long service life under the asphalt milling working conditions of expressways, primary roads and secondary roads.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbides, and in particular relates to an asphalt milling tooth cemented carbide and a preparation method and application thereof. Background Art

[0002] The composition of asphalt pavement structure can be subdivided from multiple levels, including surface layer, base layer, subbase layer and cushion layer. The asphalt structure layer of asphalt pavement is essentially a flexible pavement, but the composition of its base layer is more diverse. In addition to flexible materials, rigid cement concrete or semi-rigid hydraulic materials can also be used.

[0003] During asphalt milling, the construction team first needs to determine the milling location and mark the required width and depth. Before the operation begins, two technicians usually operate the milling machine and adjust the depth of the cutter according to the construction requirements. Once the width and depth are set, the milling operation can be started. During the milling process, a dedicated person should guide the loading vehicle forward to avoid the milling machine's discharge conveyor belt colliding with the rear compartment of the loading vehicle. At the same time, it is also necessary to pay attention to whether the material in the loading compartment is full. If it is full, the milling machine must be ordered to stop discharging and the next loading vehicle must be instructed to prepare to receive the material to ensure smooth receipt of the milled material.

[0004] During the milling process, if the road surface is found to be uneven or deep grooves, the operation should be stopped immediately, and the milling drum and cutter head should be checked for damage such as broken teeth, and replaced in time to ensure the quality of the milling operation. In addition, since water is needed for cooling and spraying during the milling process, a water truck should be on standby at all times on site to replenish the water in the milling machine's water tank. After the milling operation is completed, the road surface will be cleaned by a road sweeper.

[0005] The working mechanism of asphalt milling teeth involves the rotation of the milling drum of the road milling machine and the horizontal movement of the machine, which work together to complete the milling operation of the asphalt pavement. When the cutter head starts to cut the pavement, its back blade contacts the pavement, causing impact and extrusion, forming elastic deformation cracks. As the milling drum further rotates and descends, the cutter head continues to cut into the ground, and its rotational motion will be applied to the asphalt pavement material, causing shear cracks and elastic cracks to expand. When the cutting force of the cutter head on the asphalt pavement increases to exceed the elastic deformation limit of the pavement material, the pavement material will be sheared, crushed and collapsed, completing the milling operation.

[0006] Existing asphalt pavement milling teeth are usually made of YG6C cemented carbide material with a grain size of 2-3μm (according to ISO4499 intercept method). However, in the asphalt milling conditions of expressways and first and second-class highways, the milling teeth of this material are prone to cracking and insufficient wear resistance. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a hard alloy asphalt milling tooth.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned asphalt milling tooth cemented carbide.

[0009] Another object of the present invention is to provide an application of the above-mentioned asphalt milling tooth cemented carbide.

[0010] The technical solution of the present invention is as follows:

[0011] An asphalt milling tooth cemented carbide, the main chemical components of which are WC and Co, the content of WC is greater than that of Co, the average grain size of WC is 1.0μm-3.9μm, the proportion of WC grains below 1.0μm is 10%-50%, the proportion of WC grains above 3 times the average grain size is 15-55%, and the grain size distribution curve of the WC grains presents a coarse-grained tailing morphology.

[0012] In a preferred embodiment of the present invention, the chemical composition includes the following components: WC 91.5wt.%-94.9wt.%, Co 6wt.%-10wt.% and other components 0.1wt.%-0.5wt.%, and other components include TaC, NbC and ZrC.

[0013] The technical principle of the method for preparing the asphalt milling tooth cemented carbide of the present invention is as follows:

[0014] Existing cemented carbide picks for asphalt milling teeth usually use tungsten carbide (WC) powder of a single particle size as raw material, and are prepared by post-processing of ultra-coarse powder and optimization of the wet grinding process. In the cemented carbide obtained by this preparation method, the WC grain size presents a normal distribution. However, in hard rock, dry holes and complex rotary drilling conditions, the alloy with a normal particle size distribution cannot effectively isolate and wrap the WC grains due to the uneven distribution of the bonding phase. In particular, at the WC / WC interface, there is an extremely thin bonding phase, and it is this extremely thin bonding phase that determines the strength and toughness of the alloy. At the same time, the bonding phase area around the WC grains has poor wear resistance and is easily worn during operation. Therefore, the existing cemented carbide picks for asphalt milling teeth are prone to broken teeth and poor wear resistance under asphalt milling conditions on highways and primary and secondary roads.

[0015] To solve this problem, the present invention uses continuously distributed ultra-coarse WC powder and uses it in combination with medium-coarse WC powder. Figure 1 As shown in the figure, the medium-coarse WC powder is dispersed in the gaps of the ultra-coarse WC powder, thereby refining the grains of the cobalt (Co) binder phase. In addition, the continuously distributed ultra-coarse WC grains further increase the thickness of the cobalt layer at the WC / WC junction, thereby significantly improving the strength and toughness of the alloy.

[0016] The preparation method of the above-mentioned asphalt milling tooth cemented carbide specifically comprises the following steps:

[0017] (1) According to the ratio of the alloy, WC powder, Co powder and forming agent powder are premixed to obtain a premixed powder; wherein the WC powder is composed of medium-coarse WC powder and ultra-coarse WC powder prepared by high-temperature reduction and high-temperature carbonization process in a weight ratio of 64:36-65:35, the medium-coarse WC powder has a supplied particle size of 2.1 μm-2.3 μm, and a ground particle size of 1.4 μm-1.7 μm, and the ultra-coarse WC powder has a supplied particle size of 17 μm-19 μm and a ground particle size of 6.8 μm-7.0 μm;

[0018] (2) ball-milling the premixed powder obtained in step (1) to obtain a mixed material;

[0019] (3) The mixture obtained in step (2) is spray-dried and granulated and low-pressure sintered in sequence to obtain the asphalt milling tooth cemented carbide.

[0020] In a preferred embodiment of the present invention, in the ball milling of step (2): baseball is added at a ball-to-material ratio of 2:1-3:1, alcohol is added at a liquid-to-solid ratio of 0.10L / kg-0.13L / kg, and the ball milling time is 20h-30h.

[0021] In a preferred embodiment of the present invention, the temperature of the low-pressure sintering in step (3) is 1440-1460°C.

[0022] In a preferred embodiment of the present invention, in the ball milling of step (2): baseball is added at a ball-to-material ratio of 2:1-3:1, alcohol is added at a liquid-to-solid ratio of 0.10-0.13 L / kg, and the ball milling time is 20h-30h; the temperature of the low-pressure sintering in step (3) is 1440-1460°C.

[0023] The application of the above-mentioned asphalt milling tooth cemented carbide in the preparation of milling teeth.

[0024] A milling tooth, the raw material of which comprises the above-mentioned asphalt milling tooth hard alloy.

[0025] A milling cutter head comprises the above-mentioned milling teeth.

[0026] An asphalt pavement milling device comprises the above-mentioned milling cutter head. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the asphalt milling tooth carbide of the present invention.

[0028] Figure 2Schematic diagram of the particle size distribution of the asphalt milling tooth cemented carbide of the present invention. In which: a is the WC grain size distribution of the asphalt milling tooth cemented carbide prepared in Example 1 of the present invention, and b is the WC grain size distribution of conventional YG6C cemented carbide.

[0029] Figure 3 This is a working condition photo of Example 2 of the present invention.

[0030] Figure 4 This is a working condition photo of Example 3 of the present invention.

[0031] Figure 5 The following are comparative photos of the milling teeth after operation of Example 3 of the present invention. The left picture is of the present invention, and the right picture is of the comparative example.

[0032] Figure 6 The metallographic photographs of the asphalt milling tooth cemented carbide prepared in Example 1 of the present invention. Among them: a is the metallographic photograph of the asphalt milling tooth cemented carbide of Example 1 of the present invention, and b is the metallographic photograph of the conventional YG6C cemented carbide for comparison. It can be seen that in the metallographic photograph of the asphalt milling tooth cemented carbide prepared in Example 1, the fine WC particles are evenly dispersed and filled in the gaps between the coarse WC particles. In contrast, the WC particle size distribution of the conventional YG6C alloy is more concentrated, the number of fine WC particles is small, and the distribution is irregular. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further illustrated and described below through specific implementation modes in combination with the accompanying drawings.

[0034] Example 1

[0035] (1) According to the composition ratio of YG6C alloy, Co accounts for 6wt.%, and the content of other carbides (TaC, NbC and ZrC) is less than 0.03wt.%, and the rest is WC. WC powder, Co powder and paraffin molding agent powder are simultaneously charged into a double cone mixer for premixing for at least 3 hours to obtain a premixed powder; wherein the WC powder is composed of medium-coarse WC powder and ultra-coarse WC powder prepared by high-temperature reduction and high-temperature carbonization process in a weight ratio of 65:35, the medium-coarse WC powder has a supplied particle size of 2.2μm and a ground particle size of 1.6μm, and the ultra-coarse WC powder has a supplied particle size of 18μm and a ground particle size of 6.8μm;

[0036] (2) adding the premixed powder obtained in step (1) into a ball mill for ball milling to obtain a mixed material, wherein in the ball milling of this step: baseball is added at a ball-to-material ratio of 3:1, anhydrous ethanol is added at a liquid-to-solid ratio of 0.12 L / kg, and the ball milling time is 25 h;

[0037] (3) After the mixed material obtained in step (2) is discharged, spray drying and granulation and low-pressure sintering at 1450° C. are performed in sequence to obtain Figure 6The asphalt milling tooth cemented carbide shown in a has an average grain size of WC of 2.5 μm, WC grains below 1.0 μm account for 25%, and WC grains above 3 times the average grain size account for 20%. Figure 2 As shown in a, the particle size distribution curve of the WC grains presents a coarse-grained tailing morphology, and there is no obvious double-peak structure on the particle size frequency distribution curve of WC. Double peaks refer to two peaks on the particle size distribution curve, indicating that there are two particle sizes with a high proportion in the particle size distribution.

[0038] Example 2

[0039] This example mainly tests the asphalt milling tooth cemented carbide prepared in Example 1 and the existing YG6C (obtained through commercial channels, with a grain size distribution as shown in FIG. Figure 2 As shown in b, the metallographic Figure 6 b) is tested on the surface of the asphalt pavement for comparison. The test site is located at Chengmian Expressway, Fucheng District, Mianyang City. Figure 3 As shown, the model of the milling machine is Wirtgen 195. The working condition of the road surface is relatively bad, and the surface aggregate is mixed with hard pebbles and other large stones. The test method is to install two types of cutter heads on the left and right sides of the milling drum for testing, and make different marks on the bottom of the steel body of the cutter head to distinguish them. The test is carried out under the same road conditions, and the wear and broken teeth of the cutter heads are observed during the milling process; the milling speed is 12-15m / min, the depth is 10cm, and the milling length is 800m. The broken teeth of all cutter heads are observed, and the wear of the two cutter heads is measured at the same symmetrical position on the left and right sides of the milling drum. The results are shown in Table 1.

[0040] Table 1 Application effect

[0041] Segment Amount of broken teeth Remaining blade length Example 1 0 82.56mm Existing YG6C 15 80.02mm

[0042] Example 3

[0043] This example mainly tests the asphalt milling tooth carbide prepared in Example 1 and the existing YG6C (obtained through commercial channels) on the surface layer and water-stable layer of high-speed asphalt pavement for comparison. The test location is the expressway in Pidu District, Chengdu City. The model of the on-site milling machine is Wirtgen 195. The test parameters are: milling speed 10-12m / min, asphalt layer milling depth 16-18cm, water-stable layer milling depth 25cm, and a total of 9,000 square meters are milled, including 4,000 square meters of asphalt layer and 5,000 square meters of water-stable layer. The test results of this example are as follows: Figure 4 , Figure 5 And as shown in Table 2.

[0044] Table 2

[0045] Segment Amount of broken teeth Remaining blade length Example 1 0 85.50mm Existing YG6C 5 81.05mm

[0046] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. An asphalt milling tooth carbide, characterized in that: The main chemical components are WC and Co, the content of WC is greater than that of Co, the average grain size of WC is 1.0μm-3.9μm, the proportion of WC grains with a grain size below 1.0μm is 10%-50%, the proportion of WC grains above 3 times the average grain size is 15-55%, and the particle size distribution curve of WC grains presents a coarse-grained tailing morphology.

2. The asphalt milling tooth cemented carbide according to claim 1, characterized in that: Its chemical composition includes the following components: WC 91.5wt.%-94.9wt.%, Co 5wt.%-8wt.% and other components 0.1wt.%-0.5wt.%, and other components include TaC, NbC and ZrC.

3. The method for preparing the asphalt milling tooth cemented carbide according to claim 1 or 2, characterized in that: The steps include: (1) According to the ratio of the alloy, WC powder, Co powder and forming agent powder are premixed to obtain a premixed powder; wherein the WC powder is composed of medium-coarse WC powder and ultra-coarse WC powder prepared by high-temperature reduction and high-temperature carbonization process in a weight ratio of 64:36-65:35, the medium-coarse WC powder has a supplied particle size of 2.1 μm-2.3 μm, and a ground particle size of 1.4 μm-1.7 μm, and the ultra-coarse WC powder has a supplied particle size of 17 μm-19 μm and a ground particle size of 6.8 μm-7.0 μm; (2) ball milling the premixed powder obtained in step (1) to obtain a mixed material; (3) The mixture obtained in step (2) is spray-dried and granulated and low-pressure sintered in sequence to obtain the asphalt milling tooth cemented carbide.

4. The preparation method according to claim 3, characterized in that: In the ball milling of step (2), baseball is added at a ball-to-material ratio of 2:1-3:1, alcohol is added at a liquid-to-solid ratio of 0.10 L / kg-0.13 L / kg, and the ball milling time is 20 h-30 h.

5. The preparation method according to claim 3, characterized in that: The temperature of the low-pressure sintering in step (3) is 1440-1460°C.

6. The preparation method according to claim 3, characterized in that: In the ball milling of step (2), baseball is added at a ball-to-material ratio of 2:1-3:1, alcohol is added at a liquid-to-solid ratio of 0.10-0.13 L / kg, and the ball milling time is 20h-30h; the low-pressure sintering temperature of step (3) is 1440-1460°C.

7. Use of the asphalt milling tooth cemented carbide according to claim 1 or 2 in the preparation of milling teeth.

8. A milling tooth, characterized in that: The raw material thereof comprises the asphalt milling tooth hard alloy as claimed in claim 1 or 2.

9. A milling cutter head, characterized in that: A milling tooth according to claim 8.

10. An asphalt pavement milling device, characterized in that: A milling cutter head according to claim 9.

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