A composite modification process for high-toughness wear-resistant cutter ring of a tunneling shield machine

Abstract

The application discloses a composite modification process of a high-toughness wear-resistant cutter ring for a shield tunneling machine, and comprises the following steps: step one, a medium-carbon alloy steel material is used as a cutter ring base body, and a blank is prepared by using a hot forging process; step two, the blank obtained in the step one is subjected to carburizing quenching treatment, and then is subjected to oil cooling; step three, the cutter ring after the oil cooling in the step two is subjected to high-temperature tempering treatment, so that unstable martensite after quenching is completely converted into tempered martensite; step four, the cutter ring after the high-temperature tempering in the step three is subjected to surface induction quenching; step five, the cutter ring after the induction quenching in the step four is subjected to low-temperature tempering treatment; and step six, the cutter ring after the low-temperature tempering in the step five is subjected to surface layer ultrasonic impact modification, so as to obtain a composite modified cutter ring. The application uses heat treatment processes such as carburizing and nitriding and ultrasonic impact modification, and constructs a gradient structure cutter ring, so that the cutter ring has high wear resistance, buffer resistance and impact toughness.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and in particular to a composite modification process for high-toughness and wear-resistant cutterheads used in tunnel boring machines. Background Technology

[0002] As specialized equipment for tunnel excavation, tunnel boring machines (TBMs) subject their cutterheads to immense impact, friction, and high-pressure stress during the excavation process, leading to failures such as chipping, wear, and edge curling. Currently, a major problem with TBM cutterheads is the difficulty in achieving a good balance between hardness and impact toughness. Most processes utilize heat treatment to increase the hardness of the cutterheads, thereby enhancing their wear resistance. However, this also reduces their impact resistance, making them unable to withstand high impact loads. Ultimately, insufficient cutter toughness leads to chipping and cutterhead breakage. The cutterhead is a critical component of the TBM, with the highest maintenance costs. Therefore, developing high-performance, long-life TBM cutterheads is of paramount importance for reducing TBM construction costs and improving construction efficiency.

[0003] Chinese patent application CN201710903630.3 describes a method that combines overall tempering and partial tempering of the quenched blade ring body to give it wear resistance, buffering ability, and impact toughness, thereby improving its rock-breaking ability.

[0004] Chinese patent applications CN202010897638.5 and CN202210963344.7 involve adding wear-resistant particles to molten alloy steel matrix during casting, followed by centrifugal casting, high-temperature forging, and annealing to obtain a hob cutter ring blank. Subsequent machining of the blank yields a composite hob cutter ring, achieving a gradient distribution of wear-resistant particles within the ring, thus combining both hardness and toughness. While these methods retain the inherent impact toughness of the hob, the uneven material distribution within the cutter ring results in minimal improvement in wear resistance and does not effectively extend the hob's lifespan.

[0005] Chinese patent application CN201710020201.1 describes a process that involves plasma nitriding the outer edge of a tool ring to form a nitrided layer, thereby giving it excellent cutting performance, wear resistance, and high impact toughness, thus improving the tool's service life.

[0006] Chinese patent application CN201710195596.9 employs laser alloying technology to perform surface strengthening and subsequent heat treatment on the cutter ring of a shield tunnel boring machine, in order to meet the performance requirements of the cutter ring to withstand strong extrusion, high torque, strong impact, and high wear under harsh service environments.

[0007] Chinese patent application CN201911098806.8 describes the use of robotic additive manufacturing technology to clad an alloy layer on the surface of a hob cutter ring. This improves the surface hardness, toughness, and wear resistance of the hob cutter ring, effectively reduces wear, enhances impact resistance, and extends the service life of the hob cutter ring.

[0008] Chinese patent application CN201811130116.1 describes a method using laser spraying to coat diamond powder onto the outer circumferential surface of the cutter ring substrate. This gives the substrate extremely high toughness, and the diamond wear-resistant layer exhibits high compressive strength, hardness, and wear resistance, thus extending its lifespan. While these methods improve the cutter ring's performance, the surface reinforcement layer is thin and brittle. Furthermore, they primarily focus on the surface hardness of the cutter ring, neglecting its overall impact resistance and failing to improve its ability to break hard rock.

[0009] In view of the problem that the surface hardened layer of the cutterhead in tunnel boring machines is thin, making it difficult to simultaneously achieve both hardness and impact toughness, resulting in insufficient impact toughness and wear resistance of the cutterhead ring, this invention provides a high-toughness and wear-resistant cutterhead ring for tunnel boring machine excavation and its high-energy composite modification process to overcome the above problems. Summary of the Invention

[0010] The purpose of this invention is to provide a composite modification process for a high-toughness and wear-resistant cutterhead ring used in tunnel boring machine excavation, which constructs a gradient structure cutterhead ring, so that the cutterhead ring has high wear resistance, buffering capacity and impact toughness.

[0011] To achieve the above objectives, the solution of the present invention is: a composite modification process for high-toughness and wear-resistant cutterhead rings used in tunnel boring machines, comprising the following steps:

[0012] Step 1: The hobbing cutter ring base is made of medium carbon alloy steel and the blank is prepared by hot forging process;

[0013] Step 2: Carburize and quench the blank obtained in Step 1, and then oil cool it.

[0014] Step 3: Perform high-temperature tempering on the cutter ring after oil cooling in Step 2 to completely transform the unstable martensite after quenching into tempered martensite.

[0015] Step 4: Perform surface induction hardening on the cutting tool ring after high-temperature tempering in Step 3;

[0016] Step 5: Perform low-temperature tempering on the induction hardened blade ring from Step 4;

[0017] Step Six: Perform surface ultrasonic impact modification on the cutter ring after low-temperature tempering in Step Five to obtain a composite modified cutter ring.

[0018] Furthermore, in step two, only the blank obtained in step one is quenched; between steps five and six, the blade ring after low-temperature tempering is nitrided.

[0019] Furthermore, the material of the composite modified blade ring is 4Cr5MoSiV1, 40CrNiMo, 47Cr5MoSiV1 or 7Cr7Mo2V2Si.

[0020] Furthermore, the composite modified blade ring is divided into four regions, A, B, C, and D, from the blade surface to the base. Region A is a high-energy modified layer, region B is a phase change layer, region C is a transition layer, and region D is the base layer.

[0021] Furthermore, in step two, the temperature of the blank carburizing and quenching stage is 920-1000℃, the carburizing time is 6h, and the thickness of the resulting blade ring phase transformation layer B is greater than 3mm.

[0022] Furthermore, in step three, the high-temperature tempering temperature is 550-650℃.

[0023] Furthermore, in step four, induction hardening yields a blade edge surface hardening depth greater than 5mm and a maximum hardness greater than 800HV.

[0024] Furthermore, in step five, the low-temperature tempering temperature shall not be less than 300℃.

[0025] Furthermore, in step six, the ultrasonic impact modification frequency is 20-25kHz, the load is 900-1500N, the feed rate is 0.1mm / r, and the rotation speed is 200rpm. The resulting blade ring composite modification layer A has a hardness greater than 1050HV, and at the same time, the surface blade edge has ultra-high residual compressive stress and ultra-fine effective grain field.

[0026] After adopting the above solution, the beneficial effects of the present invention are as follows:

[0027] This invention constructs a gradient structure hobbing cutter ring through a high-energy composite modification process, resulting in a composite modified cutter ring that simultaneously possesses both hardness and impact toughness.

[0028] This process utilizes heat treatment processes such as carburizing and nitriding, along with ultrasonic impact modification, to obtain a high-hardness cutting edge and a high-toughness cutting head, namely a cutting ring with high surface hardness and high core toughness. The overall structure forms a gradient structure, which gives the hobbing cutter ring high wear resistance, buffering capacity, and impact toughness. At the same time, the cutting edge has ultra-high residual compressive stress and ultra-fine effective grain field, which gives the hobbing cutter ring a longer service life. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a composite modified blade ring structure according to an embodiment of the present invention;

[0030] Figure 2 yes Figure 1 Schematic diagram of the composite modified blade ring partition structure at point Q. Detailed Implementation

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This invention provides a composite modification process for high-toughness and wear-resistant cutterheads used in tunnel boring machines, comprising the following steps:

[0033] Step 1: The base of the hobbing cutter ring 1 is made of medium carbon alloy steel and the blank is prepared by hot forging process;

[0034] Step 2: The blank obtained in Step 1 is subjected to carburizing and quenching treatment, and then oil cooling; the temperature of the blank during the carburizing and quenching stage is 920-1000℃, the carburizing time is 6h, and the thickness of the phase transformation layer B of the obtained blade ring is greater than 3mm.

[0035] After heating, the blade ring becomes austenitic, and then cooled to obtain a martensitic or bainitic structure, which gives the blade ring surface a high hardness and improves its wear resistance.

[0036] Step 3: Perform high-temperature tempering on the cutter ring after oil cooling in Step 2 to completely transform the unstable martensite after quenching into tempered martensite. The high-temperature tempering temperature is 550-650℃.

[0037] High-temperature tempering yields a mixture of ferrite and fine-grained cementite, known as tempered sorbite, which gives the steel blade ring excellent comprehensive mechanical properties.

[0038] Step 4: Perform surface induction hardening on the blade ring after high-temperature tempering in Step 3. The induction hardening results in a blade edge surface hardening depth greater than 5mm and a maximum hardness greater than 800HV.

[0039] Step 5: Perform low-temperature tempering on the induction hardened tool ring from Step 4; the low-temperature tempering temperature should not be less than 300℃. Low-temperature tempering can eliminate quenching stress and obtain tempered martensite structure.

[0040] Step Six: Perform surface ultrasonic impact modification on the hot knife ring after the low temperature recovery in Step Six to obtain a composite modified knife ring.

[0041] The ultrasonic impact modification frequency is 20-25kHz, the load is 900-1500N, the feed rate is 0.1mm / r, and the rotation speed is 200rpm. The resulting blade ring composite modification layer A has a hardness greater than 1050HV, and the surface blade edge has ultra-high residual compressive stress and ultra-fine effective grain field.

[0042] Depending on the working conditions or the material itself, the present invention may choose to use either the carburizing treatment in step two or the nitriding treatment between steps five and six, or both, to obtain a blade ring with wear resistance, buffering capacity, and impact toughness.

[0043] The material of the blade ring is 4Cr5MoSiV1, 40CrNiMo, 47Cr5MoSiV1 or 7Cr7Mo2V2Si.

[0044] The blade ring 1 is divided into four regions, A, B, C and D, from the blade surface to the base. Region A is a high-energy modified layer, region B is a phase change layer, region C is a transition layer and region D is the base layer.

[0045] Example 1:

[0046] This embodiment provides a high-energy composite modification process for high-toughness and wear-resistant cutterheads used in tunnel boring machines, including the following steps:

[0047] 1) Preparation of blank

[0048] like Figure 1 and 2 As shown, the cutting edge ring 1 is divided into four regions, A, B, C, and D, from the cutting edge surface to the base. Region A is the high-energy modified layer, region B is the phase transition layer, region C is the transition layer, and region D is the base layer. The material of cutting edge ring 1 is 4Cr5MoSiV1, with the following mass percentages of elements: C 0.41%, Si 1.03%, Mn 0.4%, Cr 5.05%, Mo 1.27%, V 0.89%, impurity P ≤ 0.022%, and impurity S ≤ 0.002%. The blank is rough-machined and then finished to obtain the original cutting edge ring 1.

[0049] 2) Carburizing and quenching

[0050] The original blade ring was carburized and quenched using a vacuum carburizing furnace: first, strong carburizing was carried out at a carbon potential of 1.2% and a temperature of 950℃ for 3 hours; then diffusion carburizing was carried out at a carbon potential of 0.8% for 3 hours; then the temperature was raised to 1020℃ and held for 0.5 hours before oil cooling. The resulting blade ring phase transformation layer B thickness was greater than 3 mm.

[0051] 3) High-temperature tempering

[0052] The blade ring is placed in a tempering furnace for high-temperature tempering treatment. It is first heated to 620℃, then held for 4 hours, and tempered twice to completely transform the unstable martensite after quenching into tempered martensite.

[0053] 4) Surface induction hardening

[0054] The cutting edge of the hobbing cutter ring is subjected to induction hardening at industrial frequency. After heating to 1050℃, it is oil cooled to obtain a surface hardening depth of more than 5mm and a maximum hardness of more than 800HV.

[0055] 5) Low-temperature tempering

[0056] The blade ring is placed in a tempering furnace for tempering treatment. It is first heated to 300℃, then held at that temperature for 4 hours, and tempered 3 times.

[0057] 6) Surface ultrasonic shock modification

[0058] The cutting edge of the cutter ring was subjected to ultrasonic impact strengthening at a frequency of 23kHz, a load of 1200N, an axial feed of 0.1mm / r, a spindle speed of 200rpm, and 3 rotations. The resulting composite modified layer A of the cutter ring had a hardness greater than 1050HV, and the surface cutting edge had ultra-high residual compressive stress and an ultra-fine effective grain field.

[0059] Example 2:

[0060] This embodiment provides a high-energy composite modification process for high-toughness and wear-resistant cutterheads used in tunnel boring machines.

[0061] The difference between this embodiment and the previous embodiment is that in step two, only the blank obtained in step one is quenched; and between steps five and six, a nitriding treatment is added to the blade ring after low-temperature tempering, specifically including the following steps:

[0062] 1) Preparation of blank

[0063] like Figure 1 and 2 As shown, the cutting edge ring is divided into four regions: A, B, C, and D, from the cutting edge surface to the base. Region A is the high-energy modified layer, region B is the phase transition layer, region C is the transition layer, and region D is the base layer. The cutting edge ring material is 4Cr5MoSiV1, with the following mass percentages of elements: C 0.41%, Si 1.03%, Mn 0.4%, Cr 5.05%, Mo 1.27%, V 0.89%, impurity P ≤ 0.022%, and impurity S ≤ 0.002%. The blank is rough-machined and then finished to obtain the original cutting edge ring.

[0064] 2) Carburizing and quenching

[0065] The original blade ring was quenched using a vacuum tempering furnace: the temperature was raised to 1020℃ and held for 0.5 hours before being oil cooled.

[0066] 3) High-temperature tempering

[0067] The blade ring is placed in a tempering furnace for high-temperature tempering treatment. It is first heated to 620℃, then held for 4 hours, and tempered twice to completely transform the unstable martensite after quenching into tempered martensite.

[0068] 4) Surface induction hardening

[0069] The cutting edge of the hobbing cutter ring is subjected to induction hardening at industrial frequency. After heating to 1050℃, it is oil cooled to obtain a surface hardening depth of more than 5mm and a maximum hardness of more than 800HV.

[0070] 5) Low-temperature tempering

[0071] The blade ring is placed in a tempering furnace for tempering treatment. It is first heated to 300℃, then held at that temperature for 4 hours, and tempered 3 times.

[0072] 6) Nitriding heat treatment

[0073] The tempered sample was subjected to nitriding treatment: under a gas atmosphere of N2:H2 = 450 ml / min: 150 ml / min, a gas pressure of 300 Pa, a temperature of 480℃, and a holding time of 8 h, the sample was finally cooled with the furnace. The resulting blade ring phase change layer B had a thickness greater than 0.2 mm.

[0074] 7) Surface ultrasonic impact modification

[0075] The cutting edge of the cutter ring was subjected to ultrasonic impact strengthening at a frequency of 23kHz, a load of 1200N, an axial feed of 0.1mm / r, a spindle speed of 200rpm, and 3 rotations. The resulting composite modified layer A of the cutter ring had a hardness greater than 1050HV, and the surface cutting edge had ultra-high residual compressive stress and an ultra-fine effective grain field.

[0076] Comparative Example 1:

[0077] This embodiment provides a commonly used modification process for the cutterhead of a tunnel boring machine, including the following steps:

[0078] 1) Preparation of blank

[0079] The hobbing cutter ring base is made of medium carbon alloy steel. The blank is prepared by hot forging process, and the blank is roughed and finished to obtain the original cutter ring.

[0080] 2) Quenching

[0081] The original blade ring was quenched using a vacuum tempering furnace: the temperature was raised to 1000-1150℃ and held for 0.5 hours before being oil cooled.

[0082] 3) High-temperature tempering

[0083] The blade ring is placed in a tempering furnace for high-temperature tempering treatment. It is first heated to 550℃, then held for 4 hours, and tempered twice to completely transform the unstable martensite after quenching into tempered martensite, thus obtaining the modified blade ring.

[0084] The hobbing cutter rings prepared in Examples 1 and 2 and Comparative Example 1 were tested, and the parameters of each product are as follows:

[0085] Example 1 Example 2 Comparative Example 1 hardness <![CDATA[1017.5HV 0.2 ]]> <![CDATA[1128.1HV 0.2 ]]> <![CDATA[660HV 0.2 ]]> Impact toughness <![CDATA[15.6J / cm 2 ]]> <![CDATA[10.8J / cm 2 ]]> <![CDATA[10.7J / cm 2 ]]>

[0086] As shown in the table above, the hardness of the cutter rings treated in Examples 1 and 2 is greater than 1000 HV. 0.2 Impact toughness greater than 10 J / cm 2 Meanwhile, compared with the commonly used process Example 3, the hardness of Example 1-2 is higher, which helps to improve the wear resistance of the blade ring. In addition, the effective depth of the phase change layer B in Example 1 is greater than 5mm, forming a relatively smooth gradient structure. At the same time, the surface blade edge has ultra-high residual compressive stress and ultra-fine effective grain field.

[0087] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0088] Furthermore, the directions such as front, back, left, and right mentioned in this embodiment are only for reference and do not represent the actual directions in use. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. All equivalent changes made based on the key design features of this case shall fall within the protection scope of this case.

Claims

1. A composite modification process for high toughness wear resistant cutter rings for use in tunnel boring machines, characterized by: The method comprises the following steps: Step one: the base body of the hob ring is made of medium carbon alloy steel material, and a blank is prepared by using a hot forging process; The hob ring is divided into four regions A, B, C and D from the blade surface layer to the base, region A is a high-energy modified layer, region B is a phase change layer, region C is a transition layer, and region D is a base layer; Step two: the blank obtained in step one is subjected to carburizing quenching treatment, and then oil cooling is performed; In step two, the blank is subjected to carburizing quenching at a temperature of 920-1000℃, first subjected to strong carburizing for 3h at a carbon potential of 1.2%, then subjected to diffusion carburizing for 3h at a carbon potential of 0.8%, and then subjected to oil cooling after the temperature is raised to 1020℃ and maintained for 0.5h, so that the thickness of the phase change layer B of the obtained hob ring is greater than 3mm; Step three: the hob ring subjected to oil cooling in step two is subjected to high-temperature tempering treatment, the high-temperature tempering temperature is 550-650℃, so that the unstable martensite after quenching is completely converted into tempered sorbite; Step four: the hob ring subjected to high-temperature tempering in step three is subjected to surface induction quenching, and oil cooling is performed after the heating temperature is raised to 1050℃, so that the hardening depth of the blade surface layer of the hob ring is greater than 5mm, and the maximum hardness is greater than 800HV; Step five: the hob ring subjected to induction quenching in step four is subjected to low-temperature tempering treatment; Step six: the hob ring subjected to low-temperature tempering in step five is subjected to surface layer ultrasonic impact modification, so that a composite modified hob ring is obtained, the hardness of the composite modified layer A of the obtained hob ring is greater than 1050HV, and the surface layer blade has ultrahigh residual compressive stress and an ultrathin effective grain field.

2. A composite modification process for high toughness wear resistant cutter rings for use in tunnel boring machines as claimed in claim 1, characterized in that: In step two, only the blank obtained in step one is subjected to quenching treatment; and the hob ring subjected to low-temperature tempering is subjected to nitriding treatment between step five and step six.

3. A composite modification process for high toughness wear resistant cutter rings for use in tunnel boring machines as claimed in claim 1, characterized in that: The material of the hob ring is 4Cr5MoSiV1, 40CrNiMo, 47Cr5MoSiVl or 7Cr7Mo2V2Si.

4. A composite modification process for high toughness wear resistant cutter rings for use in tunnel boring machines as claimed in claim 1, characterized in that: In step five, the low-temperature tempering temperature is not less than 300℃.

5. A composite modification process for high toughness wear resistant cutter rings for use in tunnel boring machines as claimed in claim 1, characterized in that: In step six, the ultrasonic impact modification frequency is 20-25kHz, the load is 900-1500N, the feed amount is 0.1mm / r, and the rotation speed is 200rpm.

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