A high-wear-resistance high-toughness long-service-life steel for a shield machine cutter and a heat treatment process of the shield machine cutter

Abstract

The application provides a high-wear-resistance high-toughness long-service-life steel for a shield machine cutter and a heat treatment process of the shield machine cutter, the composition of the steel comprises Cr, Mo, V, Ni, C, Si, Mn, Al, Ti, P, S, N, O, and the rest is Fe and other inevitable impurities; the composition satisfies M=60*%C+10*%Mn+12*%Si+20*%Cr+25*%Mo+32*%V>=220; Q=50*(N%-2.1*Al%-3.4*Ti%) / 14>=0.015; X=(63*%Ni+25*%V+22*%Mo)+(3.6*%V+6.5*%Mo)*120*%N>=140. The steel has a hardness of greater than or equal to 65HRC, a room-temperature impact energy KV2 of greater than or equal to 40J, and the service life of the cutter is increased by 30-40%, and the steel can be used in extremely harsh and complex hard rock stratum environments.

Description

Technical Field

[0001] This invention belongs to the field of alloy steel and relates to a high wear-resistant, high toughness, and long-life shield tunneling machine cutter steel and a heat treatment process for shield tunneling machine cutters, which is applicable to the preparation of shield tunneling machine cutter rings. Background Technology

[0002] Tunnel boring machines (TBMs), as underground engineering and tunnel excavation machinery, are widely used in major projects such as subways, highways and railways, energy transmission, and underground passages. The cutterhead is the key component of the TBM for rock breaking. Its working conditions are harsh and the stresses are complex, resulting in extremely high wear and tear. Its performance and lifespan directly affect the construction effect and efficiency of underground engineering projects. During excavation, the cutterhead ring suffers from poor wear resistance or is prone to breakage. Excavating hard rock and layers with soft upper rock and hard lower rock requires the cutterhead ring to have good toughness to resist rock impact and to maximize the hardness of the material itself to extend its service life.

[0003] Chinese patent CN 113278893 A, published on August 20, 2021, discloses the composition and preparation of steel for tunnel boring machine cutters under complex conditions in spring water areas. The composition is as follows: C: 0.41%-0.47%, Si: 0.9%-1.2%, Mn: 0.34%-0.38%, P: 0.015%-0.017%, S: 0.04%-0.06%, Mg: 0.0001%-0.0002%, Cr: 4.8%-5.0%, Ni: 0.23%-0.26%, Mo: 1.4%-1.7%, Cu: 0.07%-0.09%, Al: 0.2%-0.4%, Ti: 0.018%-0.02%, V: 0.8%-1 The steel composition is as follows: 0.0%, Nb: 0.01%-0.03%, W: 0.03%-0.06%, B: 0.0015%-0.002%, Ce: 0.016%-0.02%, La: 0.001%-0.003%, with the balance being iron and unavoidable impurities. The tool steel of this patent is obtained through powder metallurgy and requires the addition of rare earth metals Ce and La, which makes production difficult and costly.

[0004] Chinese patent CN 108277431A, published on July 13, 2018, discloses a round steel for tunnel boring machine cutters and its manufacturing method. The steel composition is: C: 0.65-0.75%, Si: 0.90-1.10%, Mn: 0.40-0.50%, Cr: 3.00-4.00%, Mo: 1.10-1.40%, V: 1.20-1.50%, N: 0.02-0.03%, S≤0.005%, P≤0.020%, with the remainder being Fe and unavoidable impurities. A high-wear-resistant and high-toughness cutter steel is obtained through smelting and casting + electroslag remelting + forging. However, its performance data are laboratory results and have not been verified through practical application. The hardness reaches 60-61 HRC, and the steel measures 10×10×55mm. 3 The impact energy of the V-notch specimens is 34-38 J, which is low and cannot meet the application requirements. The high carbon content (0.65-0.75%) of this patent results in limited toughness (impact energy of only 34-38 J), and the lack of Ni element makes it impossible to improve toughness through solid solution treatment. The electroslag remelting process of this patent is complex and costly, and it does not solve the problem of uniform microstructure in large-size blade rings.

[0005] Therefore, it is essential to provide a steel for tunnel boring machine cutters that is low in cost, easy to smelt, and has excellent hardness and impact performance. Summary of the Invention

[0006] The purpose of this invention is to provide a high-wear-resistant, high-toughness, and long-life shield tunneling machine (TBM) cutterhead steel and a heat treatment process for the TBM cutters. Through optimized composition design and heat treatment processes, high-quality steel is obtained, suitable for the preparation of TBM cutterhead rings. The produced TBM cutters have a surface hardness ≥65HRC, a room temperature impact energy KV2 ≥40J, and a cutterhead tunneling life increased by 30-40%. This meets the requirements for use in extremely harsh and complex hard rock formation environments.

[0007] The specific technical solution of this invention is as follows:

[0008] A high-wear-resistant, high-toughness, long-life steel for tunnel boring machine cutters comprises the following components by weight percentage:

[0009] Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Ni 0.50%-0.80%, C 0.40%-0.45%, Si 0.50%-0.80%, Mn 1.20%-1.50%, Al ≤0.0080%, Ti ≤0.0050%, P≤0.012%, S≤0.005%, N 0.015%-0.030%, O≤0.0012%; the remainder is Fe and other unavoidable impurities.

[0010] After heat treatment, the tool has a tempered bainite content of 20-30% and a tempered martensite content of 70-80% at 1 / 2 distance from the core of the tool ring. The tool has a hardness of ≥65HRC and an impact energy of KV2 ≥40J.

[0011] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0012] Wear resistance factor M≥220; M=60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V.

[0013] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0014] The precipitation coefficient Q ≥ 0.015, Q = 50 × (N% - 2.1 × Al% - 3.4 × Ti%) / 14.

[0015] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0016] Toughness factor X≥140, X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5%×Mo)×120×%N.

[0017] The symbols for each element above represent the mass percentage of each element, expressed as a percentage (%). When calculating, simply substitute the value before the percentage into the formula.

[0018] This invention provides a heat treatment process for tunnel boring machine (TBM) cutters, which are manufactured using the aforementioned high-wear-resistant, high-toughness, and long-life TBM cutter steel. The quenching holding time is related to the cutter ring diameter D and the quenching heating temperature, and the quenching is performed in stages with controlled cooling. The tempering holding time is also related to the cutter ring diameter D and the tempering heating temperature.

[0019] The heat treatment process includes quenching and tempering. Combining the size of the cutting tool ring and the final microstructure design, this invention studies and selects appropriate austenitizing temperature and time to ensure the full dissolution of some carbonitrides while controlling the nucleation and growth of the microstructure. During the cooling process, a staged quenching method is used to control the cooling rate to ensure the microstructure ratio of the cutting tool ring. Furthermore, this invention studies and selects appropriate tempering temperature and time to ensure the proportion, morphology and distribution of tempered martensite and tempered bainite, to ensure that dispersed carbonitrides precipitate in appropriate positions and control their growth, and ultimately to ensure the finished product performance and service life of the cutting tool ring.

[0020] The quenching holding time t1 is determined by the diameter of the blade ring D and the quenching heating temperature T1, specifically: 360+D / 5-T1 / 4≤t1≤380+D / 5-T1 / 4;

[0021] In the formula, D is the diameter of the blade ring in mm; t1 is the quenching holding time in min; and T1 is the quenching heating temperature in °C.

[0022] Preferably, the quenching process specifically involves heating the blade ring at a rate of 10-30℃ / min to a quenching heating temperature T1890-940℃, holding it at that temperature for a time t1, and then cooling it using a staged quenching method. The cooling rate is controlled at 10-13℃ / s above 500℃ and at 16-19℃ / s below 500℃.

[0023] The tempering holding time t2 is determined by the blade ring diameter D and the tempering heating temperature T2, specifically: 600+D / 3-T2 / 2≤t2≤620+D / 3-T2 / 2.

[0024] In the formula, D is the diameter of the blade ring, in mm; t2 is the tempering holding time, in min; and T2 is the tempering heating temperature, in °C.

[0025] Preferably, the tempering process involves heating the blade ring at a rate of 10-30℃ / min to a tempering heating temperature T2 of 570-620℃, holding it at that temperature for t2 time, and then water-cooling or air-cooling it.

[0026] When calculating the above formulas, simply substitute the numerical value before the unit into the formula.

[0027] To achieve high strength, toughness, and wear resistance, the blade ring designed in this invention has a microstructure area of ​​20-30% tempered bainite and 70-80% tempered martensite (M) at the halfway point from the core. The heat treatment process used in this invention is a staged quenching followed by tempering.

[0028] The produced tunnel boring machine cutters have a hardness ≥65HRC, a room temperature impact energy KV2 ≥40J, and a cutter tunneling life increased by 30-40%.

[0029] This invention features ultra-low impurity control: Al ≤0.008%, Ti ≤0.005%, O ≤0.0012%, P ≤0.012%, S ≤0.005%, and nitrogen enhancement: N = 0.015-0.030% (promoting V / N composite precipitates) to maximize vanadium nitride (VN) precipitation, refine grains, and improve toughness (see the formula Q≥0.015). This invention utilizes the synergistic effect of nitrogen, innovatively establishing Q and X value formulas to quantitatively correlate nitrogen content with the V / Mo composite precipitation effect, achieving a balance between hardness and toughness.

[0030] In this invention, the carbon design (0.40-0.45%) avoids high carbon brittleness, while the hardness is compensated by multi-element composite reinforcement (Cr / Mo / V). The addition of Ni (0.50-0.80%) significantly improves the toughness of the matrix (see the highest Ni coefficient in the X value).

[0031] In terms of process control, a dynamic calculation formula for quenching / tempering time and the diameter (D) and temperature (T1 / T2) of the cutting tool ring is proposed for the first time. Through two-stage cooling rate control, martensitic transformation stress cracks are avoided, while carbide coarsening is suppressed (comparative example 1 shows a sharp drop in performance due to uncontrolled cooling rate), solving the problem of uniformity control of the core structure of large-size cutting tool rings (such as 480mm).

[0032] Compared with existing technologies, this invention addresses the special application requirements of a cutter ring that is hard on the outside and tough on the inside. At the same time, it is difficult to obtain uniform microstructure and properties for large-sized cutter rings. This invention achieves a hardness ≥65HRC and a room temperature impact energy KV2 ≥40J through optimized composition design and matching heat treatment, which far exceeds the comparison document (hardness ≤61HRC, room temperature impact energy KV2 ≤38J). The tool's tunneling life is increased by 30-40%, thus meeting the requirements for use in extremely harsh and complex hard rock formation environments. Attached Figure Description

[0033] Figure 1 This is a diagram showing the morphological structure of the cutterhead ring of the tunnel boring machine in Embodiment 1 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0035] This invention provides a high-wear-resistant, high-toughness, long-life steel for tunnel boring machine cutters, comprising the following components by mass percentage:

[0036] Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Ni 0.50%-0.80%, C 0.40%-0.45%, Si 0.50%-0.80%, Mn 1.20%-1.50%, Al ≤0.0080%, Ti ≤0.0050%, P≤0.012%, S≤0.005%, N 0.015%-0.030%, O≤0.0012%, with the remainder being Fe and other unavoidable impurities.

[0037] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0038] Wear resistance factor M≥220; M=60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V.

[0039] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0040] The precipitation coefficient Q ≥ 0.015, Q = 50 × (N% - 2.1 × Al% - 3.4 × Ti%) / 14.

[0041] The composition of the steel used for high wear resistance, high toughness, and long service life tunnel boring machine cutters also meets the following requirements:

[0042] Toughness factor X≥140, X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5%×Mo)×120×%N.

[0043] Carbon is the most effective element for improving the hardness and strength of steel. It also affects the segregation and uniformity of the steel's structure. Furthermore, it strengthens the matrix and improves wear resistance by precipitating various carbides during tempering, in conjunction with elements such as chromium, molybdenum, and vanadium. However, excessive carbon can lead to segregation during solidification, affecting the uniformity of hardness and impact toughness of the steel. Therefore, this invention controls the carbon content to 0.40%-0.45%.

[0044] Mn: An appropriate amount of Mn can effectively improve the strength of steel, eliminate the hot brittleness of steel caused by sulfur and oxygen, improve the hot working performance of steel, and improve the cold brittleness tendency of steel. However, excessive Mn content makes steel brittle. Therefore, in order to ensure that the structure does not coarsen and segregation is light, the present invention controls Mn to be 1.20%-1.50%.

[0045] Si: Si is an effective solid solution strengthening element in steel, which improves the strength and hardness of steel. However, Si tends to segregate at austenite grain boundaries, which reduces the grain boundary bonding force and causes brittleness. Therefore, this invention is designed with a low Si composition, with a control range of 0.50%-0.80%.

[0046] Cr: Cr is a carbide-forming element that can improve the hardenability and strength of steel and greatly ensure wear resistance. However, because its carbides are prone to coarsening, they have a certain detrimental effect on toughness. Therefore, the content of chromium in this invention is appropriately controlled to be 4.60%-5.20%.

[0047] Mo: Mo dissolved in the matrix enables the steel microstructure to maintain high stability during tempering and effectively reduces the segregation of impurity elements such as P, S, and As at grain boundaries, thereby improving the toughness of the steel and reducing temper brittleness. Mo reduces the stability of M7C3; when the Mo content is high, acicular Mo2C will form, leading to a reduction in the Mo content in the matrix. Mo can improve the strength of steel through the combined effects of solid solution strengthening and precipitation strengthening, and can also change the toughness of steel by altering the precipitation of carbides. Therefore, the Mo content in this invention is controlled at 1.30%-1.70%.

[0048] Vanadium (V) primarily functions to refine grain size, reduce overheating sensitivity, and increase tempering stability and wear resistance, thereby extending service life. Furthermore, due to its strong affinity for nitrogen, vanadium can fix nitrogen in steel, forming VN and promoting the formation of fine eutectic carbides. This invention controls the V content to be 1.20%-1.40%.

[0049] Ni: Ni can refine ferrite grains, improve the ductility and toughness of steel, and enhance the hardening properties of steel. In this invention, the range of Ni is controlled to be 0.50%-0.80%.

[0050] [N]: Nitrogen can form compounds with V, B, Ti, and Al, refining the grain size. Simultaneously, trace amounts of nitrogen can promote the precipitation of V(C,N), increasing the quantity and stability of undissolved carbides in quenched steel. As a nucleation core, it reduces the size of eutectic carbides such as Cr23C6, thereby enhancing the overall performance of the steel through increased grain refinement and precipitation strengthening, and improving the material's hardness and toughness. This invention controls [N] to be 150-300 ppm.

[0051] To ensure the hardness and wear resistance of the cutter ring material during use, this invention incorporates beneficial alloying elements in specific proportions. In this compositional system, carbon (C) is the most effective element for improving the hardness and strength of steel, with a contribution coefficient of 60. Mn, Si, Cr, Mo, and V can all effectively improve the hardness of steel, and their coefficients are defined as 10, 12, 20, 25, and 32 respectively, based on their contribution. To ensure the wear resistance of the cutter ring material during tunneling, the wear resistance factor of the steel is defined as M, which should be ≥220.

[0052] Wear resistance factor M≥220; M=60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V.

[0053] This invention, by adding nitrogen element, can promote the precipitation of V(C,N), increase the quantity and stability of undissolved quenched carbides in steel, and reduce the size of eutectic carbides such as Cr23C6 as nucleation cores, thereby further improving the wear resistance and toughness of steel. To ensure sufficient precipitation effect, the precipitation coefficient Q≥0.015.

[0054] The precipitation coefficient Q ≥ 0.015, Q = 50 × (N% - 2.1 × Al% - 3.4 × Ti%) / 14.

[0055] In this invention, Ni effectively improves the impact toughness of the material, V effectively refines the grains and improves toughness, and Mo greatly improves tempering stability, thus ensuring toughness. Based on their respective contributions to the system's toughness, their influence coefficients are defined as 63, 25, and 22, respectively. Simultaneously, the elements in the system also interact, affecting performance. V, Mo, and other elements combine with C to form extremely fine (V, Mo) N-type carbides of approximately 2 nm, greatly improving the bulk toughness, with an influence coefficient of 120. The contributions of the remaining individual elements are also cumulative. To ensure the material's usability and toughness, the toughness factor X ≥ 140.

[0056] Toughness factor X≥140, X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5%×Mo)×120×%N.

[0057] This invention also provides a method for producing this steel. The steel has high hardness and toughness, which greatly improves the service life of the cutter ring during tunnel boring machine excavation, with a cutter excavation life ≥20mm.

[0058] The present invention provides a method for producing tunnel boring machine (TBM) cutters, utilizing the aforementioned high wear-resistant, high-toughness, and long-life TBM cutter steel.

[0059] The method for producing the tunnel boring machine cutters includes the following process flow:

[0060] Electric arc furnace smelting → LF furnace refining → RH vacuum degassing → continuous casting → heating → four-way forging → punching and forging → machining → heat treatment → finishing → packaging and warehousing.

[0061] Electric arc furnace smelting: oxygen is determined before tapping, and slag discharge is strictly controlled during the tapping process;

[0062] LF furnace refining: C, Si, Mn, Cr, Mo, Ni, V and other elements are adjusted to target values;

[0063] RH vacuum degassing: pure degassing time ≥ 20 minutes, ensuring that the [H] content after vacuum treatment is ≤ 1.5 ppm;

[0064] Continuous casting: The target temperature of molten steel in the ladle is controlled at 20-40℃ above the liquidus temperature, for continuous casting of round billets / square billets.

[0065] The cutter head production process includes: heating → four-way forging → punching and forging → machining → heat treatment → finishing → packaging and warehousing.

[0066] Heat treatment includes quenching and tempering.

[0067] The quenching holding time t1 is determined by the diameter of the blade ring D and the quenching heating temperature T1, specifically: 360+D / 5-T1 / 4≤t1≤380+D / 5-T1 / 4;

[0068] In the formula, D is the diameter of the blade ring in mm; t1 is the quenching holding time in min; and T1 is the quenching heating temperature in °C.

[0069] Preferably, the quenching process specifically involves heating the blade ring at a rate of 10-30℃ / min to a quenching heating temperature T1890-940℃, holding it at that temperature for a time t1, and then cooling it using a staged quenching method. The cooling rate is controlled at 10-13℃ / s above 500℃ and at 16-19℃ / s below 500℃.

[0070] The tempering holding time t2 is determined by the blade ring diameter D and the tempering heating temperature T2, specifically: 600+D / 3-T2 / 2≤t2≤620+D / 3-T2 / 2.

[0071] In the formula, D is the diameter of the blade ring, in mm; t2 is the tempering holding time, in min; and T2 is the tempering heating temperature, in °C.

[0072] The tempering process involves heating the blade ring at a rate of 10-30℃ / min to the tempering heating temperature T2 570-620℃, holding it at that temperature for t2 time, and then water-cooling or air-cooling it.

[0073] When calculating the above formulas, simply substitute the numerical value before the unit into the formula.

[0074] To achieve high strength, toughness, and wear resistance, the microstructure of the blade ring is designed to consist of 20-30% tempered bainite (B) and 70-80% tempered martensite (M) at the halfway point from the core. The heat treatment process used in this invention is a staged quenching followed by tempering.

[0075] Specific technical embodiments and comparative examples of the present invention are as follows:

[0076] Examples 1-3

[0077] A high wear-resistant, high toughness, and long-life shield tunneling machine cutter steel comprises the following composition by mass percentage as shown in Table 1. The balance not shown in Table 1 is Fe and unavoidable impurities.

[0078] Comparative Examples 1-4

[0079] A type of steel for tunnel boring machine cutters comprises the following composition by mass percentage as shown in Table 1, where the balance not shown in Table 1 is Fe and unavoidable impurities.

[0080] Table 1 Chemical composition (wt%) of embodiments of the present invention

[0081]

[0082] The method for producing the tunnel boring machine cutters includes the following process flow:

[0083] Electric arc furnace smelting → LF furnace refining → RH vacuum degassing → continuous casting → heating → four-way forging → punching and forging → machining → heat treatment → finishing → packaging and warehousing.

[0084] Electric arc furnace smelting: oxygen is determined before tapping, and slag discharge is strictly controlled during the tapping process;

[0085] LF furnace refining: C, Si, Mn, Cr, Mo, Ni, V and other elements are adjusted to target values;

[0086] RH vacuum degassing: pure degassing time ≥ 20 minutes, ensuring that the [H] content after vacuum treatment is ≤ 1.5 ppm;

[0087] Continuous casting: The target temperature of molten steel in the ladle is controlled at 20-40℃ above the liquidus temperature, for continuous casting of round billets / square billets.

[0088] The cutter head production process includes: heating → four-way forging → punching and forging → machining → heat treatment → finishing → packaging and warehousing.

[0089] Among them, heat treatment includes quenching and tempering.

[0090] The quenching holding time t1 is determined by the diameter of the blade ring D and the quenching heating temperature T1, specifically: 360+D / 5-T1 / 4≤t1≤380+D / 5-T1 / 4;

[0091] In the formula, D is the diameter of the blade ring in mm; t1 is the quenching holding time in min; and T1 is the quenching heating temperature in °C.

[0092] Preferably, the quenching process specifically involves heating the blade ring at a rate of 10-30℃ / min to a quenching heating temperature T1890-940℃, holding it at that temperature for a time t1, and then cooling it using a staged quenching method. The cooling rate is controlled at 10-13℃ / s above 500℃ and at 16-19℃ / s below 500℃.

[0093] The tempering holding time t2 is determined by the blade ring diameter D and the tempering heating temperature T2, specifically: 600+D / 3-T2 / 2≤t2≤620+D / 3-T2 / 2.

[0094] In the formula, D is the diameter of the blade ring, in mm; t2 is the tempering holding time, in min; and T2 is the tempering heating temperature, in °C.

[0095] The tempering process involves heating the blade ring at a rate of 10-30℃ / min to the tempering heating temperature T2 570-620℃, holding it at that temperature for t2 time, and then water-cooling or air-cooling it.

[0096] When calculating the above formulas, simply substitute the numerical value before the unit into the formula.

[0097] To achieve high strength, toughness, and wear resistance, the microstructure of the blade ring is designed to consist of 20-30% tempered bainite (B) and 70-80% tempered martensite (M) at the halfway point from the core. The heat treatment process used in this invention is a staged quenching followed by tempering.

[0098] The specific heat treatment parameters for each embodiment and comparative example are shown in Table 2.

[0099] Table 2. Heat treatment processes of embodiments and comparative examples of the present invention.

[0100]

[0101] The performance testing methods are as follows:

[0102] Performance: Samples were taken from the finished product after heat treatment of the cutter head, and mechanical property tests were conducted according to GB / T 230.1 and GB / T 229. The mechanical properties are shown in Table 3.

[0103] Table 3 Performance of each embodiment and comparative example product

[0104]

[0105] Figure 1 The diagram shows the microstructure of the cutterhead ring in Embodiment 1 of the present invention. As can be seen from the diagram, the microstructure of the cutterhead ring in Embodiment 1 is tempered martensite (78%) + tempered bainite (22%) in a quenched and tempered state. The microstructure is uniform and dense, indicating that the cutterhead ring designed by the composition heat treatment of the present invention has good performance.

[0106] The chemical composition and heat treatment process of the steels in Examples 1-3 were appropriately controlled, resulting in good hardness, toughness, and service life. Comparative Example 1 had a reasonable composition design, but the heating and holding time during heat treatment was too short, the cooling rate in the high-temperature section during graded cooling was too low, leading to insufficient hardening and quenching of the cutting ring. The cooling rate in the low-temperature section was too fast, resulting in high internal stress, causing the material microstructure to fail to meet design requirements, insufficient hardness and toughness, and a short service life. Comparative Examples 2 and 3 had low wear resistance factors and low effective precipitation coefficients, indicating unsuitable chemistry. After heat treatment, the cutting rings had low hardness, insufficient toughness, and a short service life. Comparative Example 4 had a low toughness factor, unsatisfactory chemical composition, insufficient heat treatment holding time, incomplete microstructure transformation, poor strength-toughness matching in the cutting ring microstructure, unsatisfactory performance, and a low service life.

[0107] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high wear resistant high toughness long life steel for a shield machine cutter, characterized by, The high wear resistance high toughness long service life shield machine cutter steel comprises the following mass percentage components: Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Ni 0.50%-0.80%, C 0.40%-0.45%, Si 0.50%-0.80%, Mn 1.20%-1.50%, Al ≤0.0080%, Ti ≤0.0050%, P ≤0.012%, S ≤0.005%, N 0.015%-0.030%, O ≤0.0012%, and the rest is Fe and other inevitable impurities; after heat treatment, the high wear resistance high toughness long service life shield machine cutter steel produces a shield machine cutter, the tempering bainite content at 1 / 2 of the core of the shield machine cutter is 20-30%, the tempering martensite content is 70-80%, the hardness of the shield machine cutter is ≥65HRC, and the impact energy KV2 is ≥40J.

2. The high abrasion resistant high toughness long life steel for tunneling machine cutter as claimed in claim 1, wherein, The components of the high wear resistance high toughness long service life shield machine cutter steel also satisfy: The wear resistance factor M is ≥220; M = 60 × %C + 10 × %Mn + 12 × %Si + 20 × %Cr + 25 × %Mo + 32 × %V.

3. The high abrasion resistant high toughness long life steel for tunneling machine cutter as claimed in claim 1 wherein, The components of the high wear resistance high toughness long service life shield machine cutter steel also satisfy: The precipitation coefficient Q is ≥0.015; Q = 50 × (N%-2.1 × Al%-3.4 × Ti%) / 14.

4. The high abrasion resistant high toughness long life steel for tunneling tools according to claim 1, characterized in that, The components of the high wear resistance high toughness long service life shield machine cutter steel also satisfy: The toughness factor X is ≥140; X = (63 × %Ni + 25 × %V + 22 × %Mo) + (3.6 × %V + 6.5% × Mo) × 120 × %N.

5. A heat treatment process for a shield machine cutter, characterized by, The high wear resistance high toughness long service life shield machine cutter steel is produced by using the high wear resistance high toughness long service life shield machine cutter steel in any one of claims 1-4, a heat treatment process comprises quenching and tempering, the quenching holding time is related to the cutter ring diameter D and the quenching heating temperature, and the quenching is graded controlled cooling; and the tempering holding time is related to the cutter ring diameter D and the tempering heating temperature.

6. The heat treatment process of claim 5, wherein, The quenching holding time t1 is determined by the cutter ring diameter D and the quenching heating temperature T1, and specifically, 360+D / 5-T1 / 4 ≤t1 ≤380+D / 5-T1 / 4. In the formula, D is the cutter ring diameter, unit: mm; t1 is the quenching holding time, unit: min; and T1 is the quenching heating temperature, unit: ℃.

7. The heat treatment process of claim 6, wherein, The quenching specifically comprises the following steps: the cutter ring is heated to the quenching heating temperature T1 890-940 ℃ at a speed of 10-30 ℃ / min, and held for t1 time; and in the cooling process, the cutter ring is cooled in the form of graded quenching, the cooling speed is controlled to be 10-13 ℃ / s above 500 ℃, and the cooling speed is controlled to be 16-19 ℃ / s below 500 ℃.

8. The heat treatment process of claim 5, wherein, The tempering holding time t2 is determined by the cutter ring diameter D and the tempering heating temperature T2, and specifically, 600+D / 3-T2 / 2 ≤t2 ≤620+D / 3-T2 / 2; in the formula, D is the cutter ring diameter, unit: mm; t2 is the tempering holding time, unit: min; and T2 is the tempering heating temperature, unit: ℃.

9. The heat treatment process of claim 8, wherein, The tempering: the knife ring is heated to a tempering heating temperature T2 of 570-620 ℃ at a speed of 10-30 ℃ / min, kept for a t2 time, and then water-cooled or air-cooled.

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