Preparation method of squeeze-cast nano VC composite wear-resistant hob cutter ring

Abstract

The invention discloses a preparation method of a squeeze-cast nano VC composite wear-resistant hob cutter ring, and belongs to the technical field of composite hob cutter rings. According to the method, alloy raw materials are weighed according to alloy components and put into an electric frequency induction furnace to be smelted, and then extrusion casting is conducted; the sample obtained after extrusion casting is pretreated, and then the sample is machined into a hob casting; the hob casting is subjected to heat treatment and subzero treatment; the problems that according to a traditional forging method, the number of forging heating times is large, procedures after forming are complicated, and the production efficiency is affected are solved; rapid cooling conditions provided by extrusion casting can inhibit precipitation of primary VC and provide necessary conditions for subsequent precipitation of nano VC; the material structure can be homogenized and refined through cold treatment, nano VC separated out through subsequent tempering can be further refined, the cyclic load can be resisted through the more uniform structure and smaller stress concentration, and therefore the wear resistance of the material is improved.

Description

Technical Field

[0001] This invention belongs to the field of composite hobbing cutter ring technology, and particularly relates to a method for preparing a squeeze-cast nano-VC composite wear-resistant hobbing cutter ring. Background Technology

[0002] A tunnel boring machine (TBM), also known as a shield tunneling machine, is a large-scale engineering machine specifically designed for excavating underground tunnels. It is widely used in the construction of railways, highways, large and medium-sized hydropower stations, urban elevated structures, underground pipelines, subway projects, and river-crossing tunnels, encompassing numerous tunnel construction projects. A TBM is a tunnel boring machine that uses the shield tunneling method, relying on cutterheads to cut through the soil. These cutterheads are subject to impact and wear, and once they reach their maximum wear value, they must be replaced immediately. According to relevant data, 33% to 50% of total energy consumption is due to friction and wear; approximately 80% of machine component failures are caused by wear, and the economic losses caused by cutterhead wear are enormous. To ensure the working performance and tunneling efficiency of a TBM, it is essential to extend the lifespan of the cutterheads.

[0003] Traditional hobbing cutter rings are mostly made of cast steel or forged steel, and their hardness and strength are improved through heat treatment. Although this material has good mechanical properties, it is still prone to cracking and spalling under long-term high-intensity working conditions, leading to cutter ring failure. Carbide-inserted hobs are composite hobs formed by welding carbide onto the hob ring. Carbide-inserted hobs exhibit good wear resistance, significantly improving service life compared to traditional hobs. However, carbide has a certain degree of brittleness; when encountering unevenly hard or boulder formations, the carbide material is susceptible to direct impact from hard rocks, easily leading to chipping, breakage, and tooth breakage in the hob ring. Ceramic-reinforced metal matrix composites, containing a large amount of high-hardness ceramic phase, exhibit high hardness and high wear resistance, and also possess designability, gradually becoming an important development direction for new wear-resistant materials. However, the interface bonding effect of the hob ring prepared by this method is poor, resulting in defects that significantly reduce its performance in practical applications. Furthermore, this method involves a complex production process, long preparation cycle, high preparation difficulty, and difficulty in controlling the production process, increasing production costs and making large-scale production applications difficult.

[0004] Based on the above analysis, the existing technologies have the following problems and defects: the existing hob steel has poor wear resistance and short service life; the cemented carbide insert hob is brittle and prone to chipping, breakage, and tooth breakage of the cutter ring; the ceramic-reinforced metal-based composite hob ring has a relatively complex manufacturing process, long preparation cycle, high manufacturing difficulty, and difficulty in controlling the production process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a nano-VC composite wear-resistant hobbing cutter ring by extrusion casting, specifically including the following steps: (1) Smelting: Weigh the alloy raw materials according to the alloy composition and put them into the electric frequency induction furnace for smelting, and then perform extrusion casting; in order to prevent vanadium oxidation and improve the absorption rate, the molten steel is first pre-deoxidized, and then ferrovanadium is added in the later stage of smelting to reduce the high temperature residence time of the molten steel. Before tapping, 0.1% pure aluminum is added for final deoxidation.

[0006] (2) The sample after squeeze casting is pretreated and then processed into a hobbing casting.

[0007] (3) The hobbing castings are subjected to heat treatment and cryogenic treatment.

[0008] Preferably, the nano-VC composite wear-resistant hobbing cutter ring of the present invention comprises, by mass percentage, C: 0.70–1.20%, Si: 0.80–1.20%, Mn: 0.80–1.20%, Cr: 0.80–1.20%, Mo: 0.80–1.20%, Ti: 0.10–0.30%, N: 0.10–0.30%, Nb: 0.10–0.30%, V: 1.00–5.00%, P≤0.030%, S≤0.030%, and the balance Fe.

[0009] Preferably, in the smelting process described in this invention: the temperature of the molten steel is set at 1500-1600℃, aluminum wire is added to the ladle for deoxidation, the ladle is preheated to 100-200℃, slag is removed from the ladle once, until no impurities are visually observed floating in the molten steel.

[0010] Preferably, the pouring temperature of the extrusion casting according to the present invention is set to 1500-1550℃, the pouring pressure is set to 100-500MPa, the extrusion time is ≤30s, and the holding time is 3-5min.

[0011] Preferably, the specific conditions for the pretreatment described in this invention are as follows: when the hobbing casting is cooled to 200-300℃, it is taken out for annealing. The annealing process involves heating it to 650℃ at 60℃ / h, holding it at that temperature for 0.5h, then heating it to 900℃ at 30℃ / h, holding it at that temperature for 1-3h, and then directly removing it from the furnace and air cooling it.

[0012] Preferably, the specific conditions for the heat treatment described in this invention are as follows: the quenching process heats the material to 650°C at 60°C / h, holds it at that temperature for 0.5h, then heats it to 1050°C at 30°C / h, holds it at that temperature for 2h, and then performs oil quenching.

[0013] Preferably, the cryogenic treatment described in this invention involves immersing the roller cutter ring in liquid nitrogen for 4 hours, removing it, restoring it to room temperature, then heating it to 450°C at a rate of 60°C / h and holding it at that temperature for 2 hours before air cooling.

[0014] The beneficial effects of this invention are: (1) Compared with the traditional forging method, which involves more forging fires and complicated processes after forming, affecting production efficiency, the present invention adopts integrated forming, which only requires rough machining in the later stage, greatly improving production efficiency; the method of the present invention applies a pressure of 100-500MPa, which significantly increases the supercooling of the melt and greatly increases the nucleation rate, thereby refining the matrix grains and precipitates; it can obtain dense and defect-free castings and ensure the performance of the matrix; the method of the present invention can make the composition distribution around the forming VC particles more uniform; it suppresses the initial coarse VC, obtains supersaturated solid solution, creates a "raw material library" for subsequent nanoprecipitation, and at the same time, high pressure refines the grains, laying the foundation for a fine-grained matrix.

[0015] (4) The composite wear-resistant hobbing cutter ring prepared by the method of the present invention contains VC particles generated in situ from the inside of the metal matrix. It has a coherent or semi-coherent interface with the matrix and has a high atomic matching degree, avoiding weak bonding interfaces such as oxide layer and gas adsorption layer introduced by external particles. The nano VC particles have a strong hindrance effect on dislocation movement, improving the comprehensive performance of the material. The nano VC itself is an extremely hard ceramic phase (~2800 HV). The dispersed hard particles can effectively support the load and resist the cutting and plowing of abrasive particles during the wear process. The dense matrix structure prevents large pieces from peeling off during the wear process.

[0016] (5) The present invention also performs deep cryogenic treatment on the hobbing casting. The low temperature greatly reduces the solid solubility of alloying elements such as V and C in the matrix, providing a huge chemical potential gradient for the supersaturated solid solution, forcing atoms to agglomerate and precipitate; it promotes the transformation of residual austenite into martensite. This process generates a large number of crystal defects such as dislocations and twins, providing excellent non-uniform nucleation sites for the precipitation of VC; in addition, atomic diffusion is extremely slow at low temperature, and once the precipitated VC particles are formed, they are difficult to grow, thus ensuring that they maintain the nanoscale and achieve the best precipitation strengthening effect; a more uniform structure and less stress concentration are beneficial to resisting cyclic loads. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention.

[0018] Figure 2 This is a heat treatment route diagram of the present invention.

[0019] Figure 3 This is a schematic cross-sectional view of the hobbing cutter ring described in this invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Example 1 A method for preparing a wear-resistant hob cutter ring by extrusion casting nano-VC composite includes the following steps: (1) Weigh various raw materials according to the alloy composition: C: 0.70%, Si: 0.80%, Mn: 0.80%, Cr: 0.80%, Mo: 0.800%, Ti: 0.10%, N: 0.10%, Nb: 0.10%, V: 1.00%, P≤0.030%, S≤0.030%, with the balance being Fe; the raw materials selected are: pig iron, round steel, ferrovanadium (containing 70% V), high carbon ferrochrome (containing 70% Cr), ferrochrome nitride (containing 2% N), ferrosilicon (containing 75% Si), high carbon ferromanganese (containing 69% Mn), ferromolybdenum (containing 50% Mo), ferroniobium (containing 65% Nb), nickel blocks (containing 99.9999% Ni), and titanium rods (containing 99.9999% Ti).

[0022] (2) Smelting: The required weight of alloy is placed in an electric frequency induction furnace for smelting (ferrovanadium is added in the later stage of smelting). The temperature of the molten steel is set to 1550℃. A certain amount of aluminum wire is added to the ladle for deoxidation. The ladle is preheated to 150℃ in advance. The ladle is slag removed once until no impurities are visible on the surface of the molten steel.

[0023] (3) Extrusion casting: The pouring temperature is set to 1550℃, the pouring pressure is set to 100MPa, the extrusion time is 30s, the holding time is 5min, and the mold is pre-sprayed with release agent.

[0024] (4) Pretreatment: When the hobbing casting is cooled to about 250°C, it is taken out for annealing. The annealing process heats it to 650°C at 60°C / h, holds it for 0.5h, then heats it to 900°C at 30°C / h, holds it for 2h, and then directly takes it out of the furnace and air-cools it.

[0025] (5) Hobbing: The hobbing casting is machined using a machine tool.

[0026] (6) Heat treatment: The quenching process involves heating the material to 650℃ at 60℃ / h, holding it for 0.5h, then heating it to 1050℃ at 30℃ / h, holding it for 2h, and then oil quenching.

[0027] (7) Cryogenic treatment: The roller cutter ring is placed in liquid nitrogen for 4 hours and then removed. After returning to room temperature, the temperature is increased to 450℃ at 60℃ / h and kept for 2 hours before air cooling.

[0028] The nano-VC composite wear-resistant hobbing cutter ring prepared in this embodiment can achieve a hardness of 60 HRC and an impact toughness of 23 J / cm. 2 Its bending strength can reach 2536MPa, and its wear resistance is 1.3 times that of H13 steel.

[0029] Example 2 A method for preparing a wear-resistant hob cutter ring by extrusion casting nano-VC composite includes the following steps: (1) Weigh each raw material according to the alloy composition: C: 0.95%, Si: 1.0%, Mn: 0.80%, Cr: 1.0%, Mo: 1.0%, Ti: 0.20%, N: 0.20%, Nb: 0.20%, V: 3.00%, P≤0.030%, S≤0.030%, with the balance being Fe; the raw materials selected are pig iron and round steel, ferrovanadium (containing 70% V), high carbon ferrochrome (containing 70% Cr), ferrochrome nitride (containing 2% N), ferrosilicon (containing 75% Si), high carbon ferromanganese (containing 69% Mn), ferromolybdenum (containing 50% Mo), ferroniobium (containing 65% Nb), nickel blocks (containing 99.9999% Ni), and titanium rods (containing 99.9999% Ti).

[0030] (2) Smelting: The required weight of alloy is placed in an electric frequency induction furnace for smelting (ferrovanadium is added in the later stage of smelting). The temperature of the molten steel is set to 1500℃. A certain amount of aluminum wire is added to the ladle for deoxidation. The ladle is preheated to 100℃ in advance. The ladle is slag removed once until no impurities are visible on the surface of the molten steel.

[0031] (3) Extrusion casting: The pouring temperature is set to 1500℃, the pouring pressure is set to 500MPa, the extrusion time is 30s, the holding time is 3min, and the mold is pre-sprayed with release agent.

[0032] (4) Pretreatment: When the hobbing casting is cooled to about 200℃, it is taken out for annealing. The annealing process heats it to 650℃ at 60℃ / h, holds it for 0.5h, then heats it to 900℃ at 30℃ / h, holds it for 2h, and then directly takes it out of the furnace and air-cools it.

[0033] (5) Hobbing: The hobbing casting is machined using a machine tool.

[0034] (6) Heat treatment: The quenching process involves heating the material to 650℃ at 60℃ / h, holding it for 0.5h, then heating it to 1050℃ at 30℃ / h, holding it for 2h, and then oil quenching.

[0035] (7) Cryogenic treatment: The roller cutter ring is placed in liquid nitrogen for 4 hours and then removed. After returning to room temperature, the temperature is increased to 500℃ at 60℃ / h and kept for 2 hours before air cooling.

[0036] The nano-VC composite wear-resistant hobbing cutter ring prepared in this embodiment can achieve a hardness of 63 HRC and an impact toughness of 18 J / cm. 2 Its bending strength can reach 2046MPa, and its wear resistance is 1.6 times that of H13 steel.

[0037] Example 3 A method for preparing a wear-resistant hob cutter ring by extrusion casting nano-VC composite includes the following steps: (1) Weigh each raw material according to the alloy composition: C: 1.20%, Si: 1.20%, Mn: 1.20%, Cr: 1.20%, Mo: 1.20%, Ti: 0.30%, N: 0.30%, Nb: 0.30%, V: 5.00%, P≤0.030%, S≤0.030%, with the balance being Fe; the raw materials selected are pig iron and round steel, ferrovanadium (containing 70% V), high carbon ferrochrome (containing 70% Cr), ferrochrome nitride (containing 2% N), ferrosilicon (containing 75% Si), high carbon ferromanganese (containing 69% Mn), ferromolybdenum (containing 50% Mo), ferroniobium (containing 65% Nb), nickel blocks (containing 99.9999% Ni), and titanium rods (containing 99.9999% Ti).

[0038] (2) Smelting: The required weight of alloy is placed in an electric frequency induction furnace for smelting (ferrovanadium is added in the later stage of smelting). The temperature of the molten steel is set to 1600℃. A certain amount of aluminum wire is added to the ladle for deoxidation. The ladle is preheated to 200℃ in advance. The ladle is slag removed once until no impurities are visible on the surface of the molten steel.

[0039] (3) Extrusion casting: The pouring temperature is set to 1550℃, the pouring pressure is set to 150MPa, the extrusion time is 30s, the holding time is 4min, and the mold is pre-sprayed with release agent.

[0040] (4) Pretreatment: When the hobbing casting is cooled to about 300℃, it is taken out for annealing. The annealing process heats it to 650℃ at 60℃ / h, holds it for 0.5h, then heats it to 900℃ at 30℃ / h, holds it for 2h, and then directly takes it out of the furnace and air-cools it.

[0041] (5) Hobbing: The hobbing casting is machined using a machine tool.

[0042] (6) Heat treatment: The quenching process involves heating the material to 650℃ at 60℃ / h, holding it for 0.5h, then heating it to 1050℃ at 30℃ / h, holding it for 2h, and then oil quenching.

[0043] (7) Cryogenic treatment: The roller cutter ring is placed in liquid nitrogen for 4 hours and then removed. After returning to room temperature, the temperature is increased to 550℃ at 60℃ / h and kept for 2 hours before air cooling.

[0044] The nano-VC composite wear-resistant hobbing cutter ring prepared in this embodiment can achieve a hardness of 67 HRC and an impact toughness of 15 J / cm. 2 Its bending strength can reach 1940MPa, and its wear resistance is 1.8 times that of H13 steel.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a nano-VC composite wear-resistant hobbing cutter ring by extrusion casting, characterized in that: Specifically, the following steps are included: (1) Smelting: Weigh the alloy raw materials according to the alloy composition and put them into an electric frequency induction furnace for smelting, and then perform extrusion casting; (2) The sample after squeeze casting is pretreated and then processed into a hob casting; (3) The hobbing castings are subjected to heat treatment and cryogenic treatment.

2. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1, characterized in that: The nano-VC composite wear-resistant hobbing cutter ring, by mass percentage, includes C: 0.70–1.20%, Si: 0.80–1.20%, Mn: 0.80–1.20%, Cr: 0.80–1.20%, Mo: 0.80–1.20%, Ti: 0.10–0.30%, N: 0.10–0.30%, Nb: 0.10–0.30%, V: 1.00–5.00%, P≤0.030%, S≤0.030%, and the balance Fe.

3. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1 or 2, characterized in that: During the smelting process: the temperature of the molten steel is set at 1500-1600℃. Aluminum wire is added to the ladle for deoxidation. The ladle is preheated to 100-200℃. Slag is removed from the ladle once until no impurities are visually observed floating in the molten steel.

4. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1, characterized in that: The pouring temperature for extrusion casting is set at 1500-1550℃, the pouring pressure is set at 100-500MPa, the extrusion time is ≤30s, and the holding time is 3-5min.

5. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1, characterized in that: The specific conditions for pretreatment are as follows: when the hobbing casting is cooled to 200-300℃, it is taken out for annealing. The annealing process involves heating it to 650℃ at 60℃ / h, holding it for 0.5h, then heating it to 900℃ at 30℃ / h, holding it for 1-3h, and then directly removing it from the furnace and air cooling it.

6. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1, characterized in that: The specific conditions for heat treatment are as follows: the quenching process involves heating the material to 650℃ at 60℃ / h, holding it at that temperature for 0.5h, then heating it to 1050℃ at 30℃ / h, holding it at that temperature for 2h, and finally oil quenching.

7. The method for preparing the extrusion-cast nano-VC composite wear-resistant hobbing cutter ring according to claim 1, characterized in that: Cryogenic treatment: The roller cutter ring is immersed in liquid nitrogen for 4 hours and then removed. After returning to room temperature, the temperature is increased to 450℃ at a rate of 60℃ / h and held for 2 hours before being air-cooled.

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