Superhard cutting tool and brazing method thereof

Abstract

This invention provides a superhard cutting tool and its brazing method, relating to the field of brazing technology. Specifically, the brazing method includes the following steps: immersing a PcBN cutting tip or metal substrate in solder paste, removing it after immersion and pre-sintering to obtain a preform; sequentially assembling and brazing the preform with the PcBN cutting tip or metal substrate to obtain the superhard cutting tool; wherein the solder paste comprises the following components by weight: 8-20 parts of metal brazing powder, 0.2-1 parts of binder, and 8-20 parts of solvent. This invention, by using a specially formulated solder paste and employing an immersion pre-sintering method for solder pre-placement, provides a brazing method for superhard cutting tools with high and stable product quality and higher production efficiency. It offers advantages such as high weld joint strength and long tool life, and can significantly reduce production costs, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, and more specifically, to a superhard cutting tool and its brazing method. Background Technology

[0002] In recent years, with the implementation of the 14th Five-Year Plan and the support of relevant policies, the superhard cutting tool industry is ushering in a historic strategic development opportunity. Polycrystalline cubic boron nitride (PcBN) tools, with their excellent hardness, wear resistance, and chemical stability, have become ideal tool materials. PcBN is also considered a major replacement tool for this century due to these advantages.

[0003] Currently, PcBN cutting tools are mainly classified into two types according to their manufacturing processes: one is integral polycrystalline cutting tools, which are prepared by directly sintering pure superhard material micropowder under ultra-high pressure and high temperature conditions; the other is inlaid polycrystalline cutting tools, which involve brazing the superhard cutting tool onto a cemented carbide substrate. Due to the high cost and stringent process conditions of integral polycrystalline cutting tool manufacturing, inlaid brazing is currently the widely used process for manufacturing polycrystalline cutting tools. Specifically, the brazing method commonly used for welding PcBN cutting tips and cemented carbide substrates is vacuum brazing. Because the solder used is paste-like and has a certain degree of fluidity, the cutting tip is generally assembled manually. This involves applying brazing paste to the connection between the cemented carbide substrate and the PcBN cutting tip, then fixing the entire assembly with a carbon tube, and finally placing it in a vacuum furnace for vacuum brazing. This operation is highly dependent on manual experience and is prone to defects such as low assembly efficiency, excessive or insufficient solder paste, and uneven weld gaps, thus having a significant negative impact on the tool's accuracy, quality stability, and production efficiency.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a brazing method for superhard cutting tools. Existing processes require manual application of solder paste, assembly of the cutting head and substrate, and final attachment of a carbon nanotube, resulting in slow production efficiency (an average assembly time of 30 to 40 seconds per unit). Furthermore, the process is affected by worker skill levels, and training a skilled worker requires significant time and resources. These issues lead to inconsistent quality during manual assembly and a high rate of tool defective products. To address this, this invention employs a specially formulated solder paste and a pre-soaking method for solder preparation, thereby providing a brazing method for superhard cutting tools with high and stable product quality and higher production efficiency.

[0006] The second objective of this invention is to provide a superhard tool obtained by the brazing method of the superhard tool described above.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] The brazing method for the superhard cutting tool includes the following steps:

[0009] The PcBN cutting tip or metal substrate is immersed in solder paste, then removed and pre-sintered to obtain a preform.

[0010] The preform is sequentially assembled and brazed with the PcBN cutting head or metal substrate to obtain a superhard cutting tool;

[0011] The solder paste comprises the following components by weight: 8-20 parts of metal solder powder, 0.2-1 parts of binder, and 8-20 parts of solvent.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] (1) The present invention simplifies the assembly process and increases the assembly efficiency to at least five times that of the current process; at the same time, it facilitates the control of weld size, greatly improves the quality stability and accuracy of the cutting tools, and improves the joint strength of the weld surface.

[0014] (2) The present invention has a solder layer on the non-soldering surface, which causes a certain degree of solder waste; however, in general, the cost reduction achieved by the upgrade of process efficiency is far greater than the increase in solder cost compared to the increase in solder cost.

[0015] (3) The pre-firing process of the present invention only requires mixing the workpiece and the brazing paste, scooping them out, and then sintering them in the furnace. No manual supervision is required, and the number of pre-firings at one time can exceed 5,000, which greatly saves labor costs. The overall cost of the increased efficiency is far greater than the energy cost of pre-firing.

[0016] (4) PcBN has high internal stress. The pre-burning process of the present invention can effectively reduce the internal stress of PcBN cutting tools, which helps to improve the rigidity of the cutting tools and avoid cracking on the welding surface, thus helping to increase the strength and life of superhard cutting tool products. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A physical image of the cutter head after pre-sintering in Embodiment 1 of the present invention is provided;

[0019] Figure 2 A physical image of the superhard cutting tool in Embodiment 1 of the present invention is provided. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "a", "b", "1", "2", etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] The present invention is carried out through the following specific embodiments: a brazing method for a superhard cutting tool, comprising the following steps: immersing a PcBN cutting tip or a metal substrate in solder paste, removing it after immersion and pre-sintering it to obtain a preform; sequentially assembling and brazing the preform with the PcBN cutting tip or the metal substrate to obtain a superhard cutting tool; wherein the solder paste comprises the following components by weight: 8-20 parts of metal brazing powder, 0.2-1 parts of binder, and 8-20 parts of solvent.

[0022] One of the PcBN cutting tip and the metal substrate is immersed in the solder paste. In some special embodiments, the PcBN cutting tip and the metal substrate can be immersed in the solder paste simultaneously. As a preferred embodiment, the PcBN cutting tip is immersed in the solder paste for preheating because the metal substrate is usually larger in volume, and the PcBN cutting tip is preferred over the metal substrate for the purpose of saving solder costs.

[0023] Those skilled in the art will understand that when a PcBN cutter head is used for immersion and pre-firing, the resulting preform is then assembled and brazed with an untreated metal substrate; when a metal substrate is used for immersion and pre-firing, the resulting preform is then assembled and brazed with an untreated PcBN cutter head.

[0024] As an optional implementation, the weight parts of the raw material components of the solder paste include, but are not limited to: metal solder powder 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20; binder 0.2, 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, 1; solvent 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20; the above weight parts can be any one of the listed values, or a range of values ​​formed by any two points.

[0025] In one preferred embodiment, the metal solder powder includes copper powder, tin powder, and titanium powder; or, the metal solder powder includes silver powder, copper powder, and titanium powder; other active solder components may also be used, and the above two combinations are only two preferred examples.

[0026] In a more preferred embodiment, the mass ratio of the copper powder, the tin powder, and the titanium powder is (6.5-7.5):(1.5-2.5):(0.5-1.5); or, the mass ratio of the silver powder, the copper powder, and the titanium powder is (6.0-7.5):(2.0-3.5):(0.1-0.7).

[0027] In a preferred embodiment, the metal solder powder comprises CuSnTi alloy powder or AgCuTi alloy powder; in a more preferred embodiment, the CuSnTi alloy powder comprises the following components by weight percentage: Cu 60%–75%, Sn 15%–25%, and Ti 5%–15%, and the AgCuTi alloy powder comprises the following components by weight percentage: Ag 60%–75%, Cu 20%–35%, and Ti 1%–7%.

[0028] In some optional embodiments, the alloy powder includes, but is not limited to, Cu71Sn19Ti10, Ag68.8Cu26.7Ti4.5, Ag69.7Cu27Ti3.3, or Ag70.5Cu27.5Ti2. Those skilled in the art will understand that the brazing powder of the present invention can be obtained by mixing elemental metals, or by using commercially available alloy materials with designated grades; and both types of brazing powder can achieve the brazing method of the present invention and obtain the same technical effects.

[0029] In a preferred embodiment, the particle size range of the metal solder powder is 10μm to 30μm, including but not limited to any one or any two of the following values: 10, 12, 15, 18, 20, 22, 25, 28, and 30 (μm).

[0030] In a preferred embodiment, the adhesive includes at least one of epoxy resin, hydroxypropyl methylcellulose, modified acrylic acid, or polyurethane.

[0031] In a preferred embodiment, the solvent includes water.

[0032] In a preferred embodiment, the method for preparing the solder paste includes the following steps: thoroughly mixing the metal solder powder, the binder, and the solvent to obtain the solder paste. Typically, thorough mixing can be achieved through methods such as shaking, stirring, or ultrasonication. During the immersion of the PcBN cutting tip or metal substrate, shaking, stirring, or ultrasonication can also be maintained, or the solder paste can be periodically dispersed to ensure a more uniform composition.

[0033] In a preferred embodiment, the soaking includes the following steps: immersing a batch of the PcBN cutting heads or the metal substrate into the solder paste, and then retrieving them to obtain a batch of workpieces for pre-sintering; in this invention, the soaking time is not limited. By adjusting the composition of the solder paste, the physical properties such as viscosity, concentration, and water content of the solder paste are kept within a specific fluctuation range. Therefore, even if the workpiece is removed quickly after soaking, the solder paste can still be uniformly and completely adhered to the surface of the workpiece.

[0034] Furthermore, after the pre-sintering, the solder component in the solder paste solidifies on the surface of the PcBN cutter or the metal substrate; in this invention, it is not necessary to perform other surface processing on the pre-sintered surface solder layer, nor is it necessary to detect the thickness of the attached solder after pre-sintering, and it is sufficient to observe the smoothness with the naked eye.

[0035] In a preferred embodiment, the pre-sintering temperature is 830℃~870℃, and the pre-sintering time is 10min~30min.

[0036] As an optional implementation, the pre-sintering temperature includes, but is not limited to, any one or any two of the following numerical ranges: 830, 835, 840, 845, 850, 855, 860, 865, and 870 (°C). The pre-sintering time includes, but is not limited to, any one or any two of the following numerical ranges: 10, 12, 15, 18, 20, 22, 24, 25, 28, and 30 (min).

[0037] In a preferred embodiment, the assembly takes an average of 5 to 10 seconds.

[0038] In a preferred embodiment, the brazing is vacuum brazing; the brazing temperature is 830℃~870℃, and the brazing time is 5min~20min.

[0039] As an optional implementation, the brazing temperature includes, but is not limited to, any one or any two of the following numerical ranges: 830, 835, 840, 845, 850, 855, 860, 865, and 870 (°C). The brazing time includes, but is not limited to, any one or any two of the following numerical ranges: 5, 6, 7, 8, 10, 12, 14, 15, 16, 18, and 20 (min).

[0040] Example 1

[0041] 1) Mix copper powder (-400 mesh), tin powder (-400 mesh), and titanium powder (-400 mesh) in a mass ratio of 7:2:1 to form a metal brazing powder; then mix it with epoxy resin adhesive and water to form a solder paste, with a mass ratio of 10:0.5:10.

[0042] 2) Immerse the PcBN cutting tip in CuSnTi solder paste; heat the immersed tip to 850℃ and hold for 20 minutes for pre-sintering, allowing the solder to solidify and pre-adhere to the surface of the PcBN cutting tip; in this embodiment, the pre-sintered semi-finished cutting tip is as follows: Figure 1 As shown.

[0043] 4) The PcBN cutting tip with pre-sintered solder attached is brazed to the YG8 metal substrate. The vacuum brazing conditions are: heating to 850℃ and holding for 10 minutes; the finished brazed cutting tool in this embodiment is as follows: Figure 2 As shown.

[0044] Example 2

[0045] It is basically the same as Example 1, except that:

[0046] In step 1): tin powder is replaced with silver powder; and the mass ratio of silver powder, copper powder and titanium powder is 6.5:3:0.5.

[0047] Example 3

[0048] It is basically the same as Example 1, except that:

[0049] In step 1): copper powder, tin powder, and titanium powder are combined and replaced with Cu71Sn19Ti10 alloy powder.

[0050] Example 4

[0051] It is basically the same as Example 1, except that:

[0052] In step 1): copper powder, tin powder, and titanium powder are combined and replaced with Ag70.5Cu27.5Ti2 alloy powder.

[0053] Example 5

[0054] It is basically the same as Example 1, except that:

[0055] In step 2): Pre-sintering is performed by holding at 830℃ for 30 minutes.

[0056] Example 6

[0057] It is basically the same as Example 1, except that:

[0058] In step 2): Pre-sintering is performed by holding at 870℃ for 10 minutes.

[0059] Example 7

[0060] It is basically the same as Example 1, except that:

[0061] In step 3): brazing is performed by holding the temperature at 870℃ for 5 minutes.

[0062] Comparative Example 1

[0063] It is basically the same as Example 1, except that:

[0064] In step 1), the mass ratio of brazing filler metal powder, binder and water is 10:0.5:22.

[0065] Comparative Example 2

[0066] It is basically the same as Example 1, except that:

[0067] In step 1): No adhesive is added.

[0068] Comparative Example 3

[0069] It is basically the same as Example 1, except that:

[0070] In step 2): Pre-sintering is performed by holding the temperature at 650℃ for 30 minutes.

[0071] The weld strength of the PCBN tools obtained in the above embodiments and comparative examples was tested, and the results are shown in Table 1 below.

[0072] Table 1

[0073]

[0074]

[0075] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A brazing method for a superhard cutting tool, characterized in that, The brazing method includes the following steps: The PcBN cutting tip or metal substrate is immersed in solder paste, then removed and pre-sintered to obtain a preform. The preform is sequentially assembled and brazed with the PcBN cutting head or metal substrate to obtain a superhard cutting tool; The pre-sintering temperature is 830℃~870℃, and the pre-sintering time is 10min~30min; the brazing is vacuum brazing, the brazing temperature is 830℃~870℃, and the brazing time is 5min~20min. The solder paste comprises the following components by weight: 8-20 parts of metal solder powder, 0.2-1 parts of binder, and 8-20 parts of solvent.

2. The brazing method for superhard cutting tools according to claim 1, characterized in that, The brazing filler metal powder includes copper powder, tin powder, and titanium powder; Alternatively, the metal solder powder may include silver powder, copper powder, and titanium powder.

3. The brazing method for superhard cutting tools according to claim 2, characterized in that, The mass ratio of the copper powder, the tin powder, and the titanium powder is (6.5~7.5):(1.5~2.5):(0.5~1.5). Alternatively, the mass ratio of the silver powder, the copper powder, and the titanium powder is (6.0~7.5):(2.0~3.5):(0.1~0.7).

4. The brazing method for superhard cutting tools according to claim 1, characterized in that, The metal brazing powder includes either CuSnTi alloy powder or AgCuTi alloy powder; The CuSnTi alloy powder includes Cu71Sn19Ti10; The AgCuTi alloy powder comprises Ag68.8Cu26.7Ti4.

5.

5. The brazing method for superhard cutting tools according to claim 1, characterized in that, The particle size range of the brazing filler metal powder is 10μm to 30μm.

6. The brazing method for superhard cutting tools according to claim 1, characterized in that, The adhesive includes at least one of epoxy resin, hydroxypropyl methylcellulose, modified acrylic acid, or polyurethane.

7. The brazing method for superhard cutting tools according to claim 1, characterized in that, The method for preparing the solder paste includes the following steps: thoroughly mixing the metal solder powder, the binder, and the solvent to obtain the solder paste.

8. A superhard tool obtained by the brazing method of any one of claims 1 to 7.

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