A tool holder and a method of manufacturing the same

Abstract

This invention provides a tool holder and its manufacturing method, relating to the technical field of tool holders for tunnel boring machines. The tool holder provided by this invention comprises alloy steel and a piezoelectric ceramic layer disposed on the surface of the alloy steel for contact with the cutter shaft. By welding the piezoelectric ceramic layer to the surface in contact with the cutter shaft, the inherent properties of the piezoelectric ceramic enable the tool holder to absorb the vibration and impact energy generated by the rock-breaking action of the roller cutter during operation, converting it into electrical energy. This reduces the vibration and impact on the tool holder, improves its wear resistance, reduces the risk of crushing and cracking, and extends its service life.

Description

Technical Field

[0001] This invention belongs to the field of tunnel boring machine tool holder technology, specifically relating to a tool holder and its preparation method. Background Technology

[0002] During use, the cutter head surface, which is in contact with the cutter shaft, is frequently subjected to impact and vibration. For example, during the tunnel boring machine (TBM) excavation process, the main tool for rock breaking is the cutter head, which squeezes the rock at the tunnel face to break the rock. Rock breaking is achieved by squeezing the rock with the cutter head, causing the rock to crack. However, the cutter head is constantly subjected to forces of different directions and magnitudes when breaking the rock, which causes the cutter head to generate a large impact and vibration on the cutter head.

[0003] The material of the cutter holder is generally alloy steel. The conventional technology is to improve the surface hardness and wear resistance through surface hardening. However, under the action of huge vibration, as the supporting component of the cutter, the cutter holder will still be subjected to frequent impacts of large loads, which will cause the cutter holder to wear, crush or even fail. Due to the harsh working conditions, the cutter holder needs to be frequently repaired by welding during the TBM tunneling process. This is not only time-consuming and labor-intensive, but may also affect the project schedule.

[0004] A patent published on February 14, 2023, with authorization announcement number CN109522626B, discloses a design method for vibration reduction of TBM cutterheads. This method achieves vibration reduction by replacing some of the hobbing wedge block material with a damping alloy. However, the hobbing wedge block material accounts for a relatively small percentage of the overall mass of the cutterhead, and the damping alloy's vibration reduction effect is limited. Therefore, a cutter holder capable of reducing vibration and impact is still lacking. Summary of the Invention

[0005] The purpose of this invention is to provide a tool holder that solves the problem in the prior art where the surface of the tool holder is easily crushed and cracked when the assembly position of the tool holder and the tool shaft is subjected to impact and vibration.

[0006] The second objective of this invention is to provide a method for preparing a tool holder that solves the problem of low bonding strength between the alloy steel and the piezoelectric ceramic layer in the tool holder.

[0007] To achieve the above objectives, the technical solution of the tool holder of the present invention is as follows:

[0008] A tool holder includes alloy steel and a piezoelectric ceramic layer disposed on the surface of the alloy steel for contact with a tool shaft.

[0009] This invention improves upon existing technology by providing a tool holder. By welding a piezoelectric ceramic layer onto the contact surface with the tool shaft, the piezoelectric ceramic's inherent properties enable the tool holder to absorb the vibration and impact energy generated by the rock-breaking action of the roller cutter during operation, converting it into electrical energy. This reduces the vibration and impact on the tool holder, improves its wear resistance, lowers the risk of crushing and cracking, and extends its lifespan.

[0010] To further improve the absorption of vibration and impact energy by the tool holder, preferably, the piezoelectric coefficient d31 of the piezoelectric ceramic is -100 to -300 pC / N.

[0011] To further improve the impact resistance of the tool holder by combining alloy steel with piezoelectric ceramics, the alloy steel preferably has the following chemical composition by mass fraction: 0.26-0.34% C, 0.17-0.37% Si, 0.5-0.8% Mn, 1.8-2.2% Cr, 1.8-2.2% Ni, 0.3-0.5% Mo, and the balance Fe.

[0012] The technical solution of the tool holder preparation method of the present invention is as follows:

[0013] A method for preparing a tool holder involves welding a piezoelectric ceramic layer onto alloy steel using a vacuum brazing method.

[0014] The tool holder preparation method provided by the present invention uses vacuum brazing to weld piezoelectric ceramics onto alloy steel, which can effectively improve the bonding strength between alloy steel and piezoelectric ceramics, and the preparation method is simple.

[0015] To further improve the strength of the welded joint and the bonding strength between alloy steel and piezoelectric ceramics, preferably, the brazing filler metal used in the vacuum brazing method consists of the following components by mass fraction: 10–18% chromium, 0.1–0.5% iron, 0.1–0.3% silicon, 0.1–0.5% carbon, 7–13.5% boron, 0.5–2.5% graphene, and the balance nickel. Introducing graphene into the brazing filler metal refines the brazed weld microstructure, promotes wetting and spreading between the filler metal and the substrate, reduces the formation of harmful phases at the interface, and significantly improves the joint strength between alloy steel and piezoelectric ceramics.

[0016] To further improve the wetting and spreading of the brazing filler metal, improve the crystal structure of the weld, and enhance the microstructure and properties of the weld, preferably, the vacuum brazing is vacuum high-temperature brazing, which includes two heating and holding processes. The first heating and holding process involves heating to 700-800°C and then holding the temperature, while the second heating and holding process involves heating to 1000-1200°C and then holding the temperature.

[0017] To further improve the microstructure and properties of the weld, preferably, the heating rate during the two-stage heating and holding process is 5–20 °C / min, and the holding time is 10–30 min.

[0018] To further refine the weld grain structure, preferably, the vacuum high-temperature brazing process includes a cooling process, which involves cooling to 200-300°C and then naturally cooling to room temperature, with a cooling rate of 10-20°C / min. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the assembly of the tool holder and the hob provided by the present invention;

[0020] In the attached diagram, 1 is the hob; 2 is the hob shaft; 3 is the piezoelectric ceramic layer; and 4 is the alloy steel. Detailed Implementation

[0021] The tool holder described in this invention is used to assemble a hob. The tool holder and the hob are assembled according to the assembly method of the prior art. For the specific assembly relationship, please refer to the assembly method of the hob in the tool box described in the patent with authorization announcement number CN106285707B.

[0022] A tool holder includes alloy steel and a piezoelectric ceramic layer disposed on the surface of the alloy steel for contact with a tool shaft.

[0023] In a specific embodiment, the piezoelectric ceramic is a PZT piezoelectric ceramic.

[0024] A method for preparing a tool holder involves welding a piezoelectric ceramic layer onto alloy steel using a vacuum brazing method.

[0025] In a specific embodiment, the preparation method of the brazing filler metal includes the following steps: adding nickel powder, chromium powder, iron powder, silicon powder, carbon powder, boron powder and graphene powder into an acetone solution, and immersing all the powders in the acetone, then subjecting them to ultrasonic vibration until the acetone evaporates, and then drying them for 15 to 30 minutes.

[0026] In a specific embodiment, the vacuum brazing is performed in a vacuum brazing device. The specific method is as follows: the brazing filler metal for welding piezoelectric ceramics to the tool holder alloy steel is evenly spread between the alloy steel and the piezoelectric ceramic layer, and the piezoelectric ceramic layer is welded to the alloy steel using vacuum brazing. The thickness of the brazing filler metal is 0.3 to 0.6 mm.

[0027] In a specific embodiment, the vacuum degree of the vacuum brazing is (2~10)x10. -3 Pa.

[0028] In a specific embodiment, the pretreatment step of the material to be brazed before vacuum brazing includes: cleaning the alloy steel with ethanol to remove oil stains from the surface of the alloy steel, and then polishing it with sandpaper to remove oxides and burrs; and ultrasonically cleaning the piezoelectric ceramic in an acetone solution.

[0029] In a specific implementation, after vacuum welding is completed, sandpaper is used to polish the surface of the welded joint to remove debris.

[0030] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, all chemical reagents involved in the following examples are commercially available conventional products. The chemical composition of the PZT piezoelectric ceramic is: 13.2–14.5% Zr, 7.0–7.8% Ti, 14.7–14.8% O, and the balance Pb, with dimensions (length * width * thickness) of 35 mm * 16 mm * 3 mm. The piezoelectric coefficients of the piezoelectric ceramics in the examples were all measured using a quasi-static piezoelectric coefficient measuring instrument.

[0031] I. Specific Embodiments of the Preparation Method of the Tool Holder of the Present Invention

[0032] Example 1

[0033] The method for preparing the tool holder in this embodiment includes the following steps:

[0034] 1) Pretreatment of materials to be brazed: The chemical composition of the alloy steel used in this embodiment is: 0.26-0.34% C, 0.17-0.37% Si, 0.5-0.8% Mn, 1.8-2.2% Cr, 1.8-2.2% Ni, 0.3-0.5% Mo and balance Fe. The alloy steel is cleaned with ethanol to remove oil stains from the surface, and then polished with sandpaper to remove oxides and burrs. The chemical composition of the PZT piezoelectric ceramic is: 13.2% Zr, 7.8% Ti, 14.8% O and balance Pb, with a piezoelectric coefficient d31 of -235 pC / N. The PZT piezoelectric ceramic is ultrasonically cleaned in acetone solution.

[0035] 2) Preparation of brazing filler metal: The brazing filler metal in this embodiment is composed of 81.4% nickel and 10.0% chromium, 0.5% iron, 0.1% silicon, 0.5% carbon, 7.0% boron, and 0.5% graphene by mass. The corresponding mass of nickel powder, chromium powder, iron powder, silicon powder, carbon powder, boron powder, and graphene powder are added to an acetone solution, and all powders are submerged in acetone. Then, ultrasonic vibration is performed until the acetone evaporates, and then the mixture is dried for 20 minutes to obtain the brazing filler metal.

[0036] 3) Brazing: The above-mentioned brazing filler metal is evenly spread between the alloy steel and the PZT piezoelectric ceramic layer, with a thickness of 0.5 mm. The mixture is then placed in a vacuum brazing apparatus for brazing. During brazing, the temperature is first increased to 700℃ at a rate of 5℃ / min and held for 10 minutes to ensure uniform temperature within the furnace. Then, the temperature is further increased to 1200℃ and held for 10 minutes. Afterward, the temperature is lowered to 240℃ at a rate of 10℃ / min, and then the furnace is cooled to room temperature. The vacuum degree during the brazing process is 4 x 10⁻⁶. -3 After brazing, sandpaper is used to remove impurities from the surface of the weldment. The resulting alloy steel and the PZT piezoelectric ceramic welded to the surface of the alloy steel form a tool holder. The assembly diagram of the tool holder and hob obtained in this embodiment is shown below. Figure 1 As shown, the alloy steel 4 and the piezoelectric ceramic layer 3 welded to the contact surface of the alloy steel 4 and the hob shaft 2 form the tool holder of the present invention, and the hob 1 is assembled on the tool holder through the hob shaft 2.

[0037] The tool holder obtained in this embodiment is the tool holder provided by the present invention. The following embodiments are the same and will not be described again.

[0038] Example 2

[0039] The method for preparing the tool holder in this embodiment differs from that in Example 1 in that: the chemical composition of the PZT piezoelectric ceramic used in step 1) is: 14.5% Zr, 7.0% Ti, 14.7% O and the balance Pb, with a piezoelectric coefficient d31 of -100 pC / N; the composition of the brazing filler metal used in step 2) is: 72.9% nickel and 13.0% chromium, 0.1% iron, 0.3% silicon, 0.2% carbon, 11% boron and 2.5% graphene; in step 3), during brazing, the temperature is first raised to 800℃ at a rate of 10℃ / min and held for 20min to ensure uniform temperature in the furnace, then the temperature is raised to 1050℃ and held for 20min, and then cooled down to 200℃ at a rate of 15℃ / min, and then the furnace is cooled to room temperature.

[0040] Example 3

[0041] The method for preparing the tool holder in this embodiment differs from that in Example 1 in that: the chemical composition of the PZT piezoelectric ceramic used in step 1) is: 13.7% Zr, 7.5% Ti, 14.8% O and the balance Pb, with a piezoelectric coefficient d31 of -300 pC / N; the composition of the brazing filler metal used in step 2) is: 66.0% nickel and 18.0% chromium, 0.2% iron, 0.2% silicon, 0.1% carbon, 13.5% boron and 2.0% graphene; in step 3), during brazing, the temperature is first raised to 750℃ at a rate of 20℃ / min and held for 30min to ensure uniform temperature in the furnace, then the temperature is raised to 1000℃ and held for 30min, and then cooled down to 300℃ at a rate of 20℃ / min, and then the furnace is cooled to room temperature.

[0042] The solder composition formula used in the above embodiments is shown in Table 1 below:

[0043] Table 1 shows the composition of the solder used in the embodiments.

[0044] Example 1 Example 2 Example 3 chromium / % 10.0 13.0 18.0 iron / % 0.5 0.1 0.2 silicon / % 0.1 0.3 0.2 carbon / % 0.5 0.2 0.1 boron / % 7.0 11.0 13.5 Graphene / % 0.5 2.5 2.0 nickel / % 81.4 72.9 66.0

[0045] Example 4

[0046] The difference between the preparation method of the tool holder provided in this embodiment and that in embodiment 1 is that BNT piezoelectric ceramic (piezoelectric coefficient d31 is -104pC / N) is used in steps 1) and 3), not PZT piezoelectric ceramic.

[0047] II. Comparative Example

[0048] Comparative Example 1

[0049] The difference between the preparation method of the tool holder provided in this comparative example and that in Example 1 is that: no PZT piezoelectric ceramic layer is welded to the surface of the alloy steel, and the surface of the alloy steel is subjected to surface quenching treatment, with a quenching layer depth of 5mm and a quenching layer hardness of 600HV.

[0050] Comparative Example 2

[0051] The difference between the preparation method of the tool holder provided in this comparative example and that in Example 1 is that the brazing filler metal is composed of 81.9% nickel and 10.0% chromium, 0.5% iron, 0.1% silicon, 0.5% carbon, and 7.0% boron by mass fraction.

[0052] Comparative Example 3

[0053] The difference between the preparation method of the tool holder provided in this comparative example and that in Example 1 is that the ordinary ceramic Al2O3 is used in steps 1) and 3), not piezoelectric ceramic.

[0054] III. Experimental Examples

[0055] Experimental Example 1

[0056] This experimental example tests the impact wear performance of the tool holder through an impact wear test. Samples of the same size were used for the test. The test parameters were: impact energy of 2 J, time of 1 hour, impact frequency of 100 times / min, abrasive material of quartz sand, and the friction pair of the impact wear test was GCr15 bearing steel with a hardness of 62 HRC. After the impact wear test, the wear loss was measured, and the cracking of the ceramic layer was observed. The hardness of the alloy steel substrate and the surface hardness of the tool holder formed after welding the piezoelectric ceramic layer were tested using an HV-1000Z Vickers hardness tester. In Comparative Example 1, the hardness of the alloy steel before quenching is the hardness of the alloy steel substrate, and the hardness after quenching is the surface hardness of the tool holder.

[0057] The impact wear test and hardness test results of the examples and comparative examples are shown in Table 2.

[0058] Table 2. Impact wear performance and hardness test results of the examples and comparative examples.

[0059]

[0060] As shown in Table 2, the test results indicate that the tool holder provided by this invention, by welding piezoelectric ceramics onto the alloy steel surface, significantly improves wear resistance compared to the comparative example's method of quenching the alloy steel surface. Furthermore, under simulated impact conditions, no cracks appear on the tool holder surface, demonstrating that the piezoelectric ceramic layer can absorb vibration and impact energy, reducing the vibration and impact load on the tool holder. Additionally, compared to the comparative example's method of quenching the alloy steel surface, this invention significantly improves the surface hardness of the tool holder through welding the piezoelectric ceramic layer.

[0061] Experimental Example 2

[0062] In this experimental example, the strength of the welded joint of the alloy steel and piezoelectric ceramic in the embodiment was tested using a UTM535X-30T universal testing machine at a loading speed of 0.5 mm / min. The joint strength test results are shown in Table 3.

[0063] Table 3. Test results of welded joint strength

[0064] Welded joint strength, MPa Example 1 33.4 Example 2 41.0 Example 3 38.6 Comparative Example 2 25.5

[0065] As can be seen from the test results in Table 3, the joint strength obtained by welding piezoelectric ceramics with the brazing filler metal provided by the present invention is generally higher than 30 MPa, indicating that the introduction of graphene can greatly improve the welding strength of alloy steel and piezoelectric ceramics.

Claims

1. A tool holder characterized in that, It includes alloy steel and a piezoelectric ceramic layer disposed on the surface of the alloy steel for contact with the cutter shaft; the piezoelectric ceramic layer is welded to the alloy steel by vacuum brazing, wherein the brazing filler metal used in the vacuum brazing method consists of the following components by mass fraction: 10-18% chromium, 0.1-0.5% iron, 0.1-0.3% silicon, 0.1-0.5% carbon, 7-13.5% boron, 0.5-2.5% graphene and the balance nickel.

2. The tool holder of claim 1 wherein, The piezoelectric coefficient d31 of piezoelectric ceramics is -100 to -300 pC / N.

3. A tool holder according to claim 1 or 2, characterised in that The chemical composition of the alloy steel consists of the following mass fractions: 0.26~0.34% C, 0.17~0.37% Si, 0.5~0.8% Mn, 1.8~2.2% Cr, 1.8~2.2% Ni, 0.3~0.5% Mo and the balance Fe.

4. A method of manufacturing a tool holder according to claim 1, characterized in that A piezoelectric ceramic layer is welded onto alloy steel using a vacuum brazing method. The brazing filler metal used in the vacuum brazing method consists of the following components by mass fraction: 10-18% chromium, 0.1-0.5% iron, 0.1-0.3% silicon, 0.1-0.5% carbon, 7-13.5% boron, 0.5-2.5% graphene, and the balance nickel.

5. The method of claim 4, wherein the insert is formed by a process comprising: The piezoelectric ceramic is PZT piezoelectric ceramic.

6. A method of manufacturing a tool holder according to claim 4 or 5, characterized in that, The vacuum brazing is vacuum high-temperature brazing, which includes two stages of heating and holding. The first stage of heating and holding involves heating to 700~800℃ and then holding the temperature, while the second stage of heating and holding involves heating to 1000~1200℃ and then holding the temperature.

7. The method of claim 6, wherein the insert is formed by a process comprising: The heating rate during the two-stage heating and holding process is 5~20℃ / min, and the holding time is 10~30min.

8. The method of claim 6, wherein the insert is formed by a process comprising: The vacuum high-temperature brazing process includes a cooling process, which involves cooling to 200~300℃ and then naturally cooling to room temperature at a cooling rate of 10~20℃ / min.

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