Nb-containing steel with high wear resistance, high toughness and long service life for shield tunneling machine cutter and production method of shield tunneling machine cutter

Abstract

The invention provides Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield tunneling machine cutter and a production method of the shield tunneling machine cutter, the Nb-containing high-wear-resistance high-toughness long-service-life steel comprises C, Si, Mn, Cr, Mo, V, Nb, Ni, Fe and the like, M = (60 *% C + 10 *% Mn + 12 *% Si + 20 *% Cr + 25 *% Mo + 32 *% V) * (1 + 1.4 *% Nb) > = 225, Q = 50 * (N%-2.1 * Al%-3.4 * Ti%) / 14 > = 0.015, and X = (63 *% Ni + 25 *% V + 22 *% Mo) + (3.6 *% V + 6.5 *% Mo) * (1 + 8.3 *% Nb) * 120 *% N > = Through component design optimization, cutter key manufacturing parameter control and heat treatment matching, the tunneling life of the cutter is prolonged by 35-50%, and the cutter can be used in an extremely severe and complex hard rock stratum environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of alloy steel, and particularly relates to a Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter and a production method of the shield machine cutter. BACKGROUND

[0002] The shield machine is a tunneling construction machine for underground projects, and is widely used in major projects such as subways, highways and railway transportation, energy transmission and underground passages. The shield cutter is a key part for rock breaking of the shield machine, and has a poor working condition and a relatively complex stress, so the wear is great, and the performance and service life of the shield cutter directly affect the construction effect and efficiency of the underground project. The cutter ring has the problems of poor wear resistance or easy breakage in tunneling. The cutter ring is required to have good toughness to resist the impact of rocks and to improve the hardness of the material itself as much as possible to prolong the service life when tunneling hard rocks and soft and hard rock layers.

[0003] A Chinese patent with the publication number CN 112048668A disclosed on December 8, 2020 discloses a high-hardness steel for a shield cutter and a manufacturing method thereof, and the components and the weight percentage thereof are as follows: C: 0.40-0.60%, Si: 0.80-1.20%, Mn: 0.20-0.60%, Cr: 4.00-6.00%, Mo: 1.10-1.30%, V: 0.45-1.00%, Ni: 0.30%, Ti: 0.10-0.60%, S≤0.005%, P≤0.020%, and the balance is Fe and inevitable impurities. The steel uses quenching plus partitioning heat treatment process or a complex structure of martensite and residual austenite, the hardness can reach more than 55HRC, the room temperature impact energy is more than 28J, and the toughness is improved by introducing residual austenite through the partitioning heat treatment process, but the hardness is low.

[0004] A Chinese patent with the publication number CN 108486499A disclosed on September 4, 2018 discloses a steel for a shield machine cutter and a manufacturing method thereof, and the components and the mass percentage of the steel for the shield machine cutter are as follows: C: 0.70%-0.75%, Si: 0.15%-0.25%, Mn: 0.45%-0.55%, Cr: 5.00%-5.20%, Mo: 2.30%-2.40%, V: 0.50%-0.60%, P<0.020%, S<0.005%, and the balance is Fe and inevitable impurities. The steel is obtained through smelting casting+electroslag remelting+forging, has good wear resistance, high hardness and good toughness, but the process is complex, the flow is long, the energy consumption is high, the efficiency is low and the process is not environmentally friendly.

[0005] Therefore, it is necessary to provide a steel for a shield machine cutter which has a simple process flow, low energy consumption, excellent performance and high hardness. SUMMARY

[0006] The application aims to provide a Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter and a production method of the shield machine cutter.

[0007] The specific technical scheme of the application is as follows:

[0008] A Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter comprises the following components in percentage by mass:

[0009] Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Nb 0.015%-0.030%, Ni 0.50%-0.80%, C 0.36%-0.42%, Si 1.20%-1.50%, Mn 0.50%-0.80%, Al ≤0.0080%, Ti ≤0.0050%, P ≤0.012%, S ≤0.005%, N 0.015%-0.030%, O ≤0.0012%, and the balance being Fe and inevitable impurities.

[0010] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0011] The wear-resistance factor M is greater than or equal to 225, and M=(60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V)×(1+1.4×%Nb).

[0012] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0013] The precipitation coefficient Q is greater than or equal to 0.015, and Q=50×(N%-2.1×Al%-3.4×Ti%) / 14.

[0014] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0015] The toughness factor X is greater than or equal to 145, and X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5×%Mo)×(1+8.3×%Nb)×120×%N.

[0016] The above element symbols represent the mass percentage of each element in the Nb-containing high-wear-resistance high-toughness long-service-life shield machine cutter steel, and the unit is %.

[0017] The application provides a production method of a shield machine cutter.

[0018] The production method of the shield machine cutter comprises heat treatment, and the heat treatment comprises quenching and tempering.

[0019] The quenching is performed at a quenching holding time t1 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.

[0020] In the formula, D is the cutter ring diameter, the unit is mm, t1 is the quenching holding time, the unit is min, and T1 is the quenching heating temperature, the unit is ℃.

[0021] Preferably, the quenching is performed by heating the cutter ring to the quenching heating temperature T1 950-1000 ℃ at a speed of 10-30 ℃ / min, holding for t1 time, and cooling in the form of step quenching, that is, first cooled to 500 ℃ at a speed of 10-13 ℃ / s, and then cooled to room temperature at a speed of 16-19 ℃ / s.

[0022] The tempering is performed at a tempering holding time t2 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.

[0023] In the formula, D is the cutter ring diameter, the unit is mm, t2 is the tempering holding time, the unit is min, and T2 is the tempering heating temperature, the unit is ℃.

[0024] Preferably, the tempering is performed by heating the cutter ring to the tempering heating temperature T2 570-620 ℃ at a speed of 10-30 ℃ / min, holding for t2 time, and then water cooling or air cooling.

[0025] In the formula, the values before the units are directly brought into the formula calculation.

[0026] Preferably, the application provides a production method of a shield machine cutter, which comprises the following process flow:

[0027] Electric arc furnace or converter smelting→LF furnace refining→RH vacuum degassing→continuous casting billet→heating→four-way forging→punching die forging→heat treatment→finishing→packaging and warehousing.

[0028] The LF refining: 2±0.5 kg of aluminum particles and 0.4±0.1 kg of silicon carbide are added per ton of molten steel for deoxidation, the white slag retention time is greater than or equal to 20 min, and the LF refining cycle is 120±20 min.

[0029] When the RH vacuum degassing process is used, the time is greater than or equal to 25 min, the calcium wire feeding is 35±5 m, and the soft blowing time is 20±5 min.

[0030] When the continuous casting billet process is used, the low superheat is controlled to be 15-35 DEG C, and the crystallizer liquid level fluctuation is controlled to be within ±5 mm.

[0031] The continuous casting billet is discharged according to the size requirement of the cutter disc, two-stage heating of a preheating section and a heating section is used, the preheating section is heated from room temperature to 650±10 DEG C at a rate of not greater than 50 DEG C / h, the holding time is determined by the thickness of the sample to be 20-30 s / mm, then the temperature is increased to 1230±10 DEG C at a rate of not greater than 80 DEG C / h, and the holding time of the soaking section is determined by the thickness of the sample to be 1.5-2 min / mm.

[0032] Then the furnace is discharged for forging, the initial forging temperature is controlled to be greater than or equal to 1150 DEG C, the final forging temperature is greater than or equal to 850 DEG C, and the surface temperature of the billet is controlled to be lower than the core temperature by 100-150 DEG C during forging to ensure the forging quality of the core.

[0033] In order to obtain high strength and toughness and wear resistance, the cutter ring is designed to have a structure area ratio of 20-25% tempered bainite B+ at the position of 1 / 2 of the distance from the cutter ring to the core and a structure area ratio of 75-80% tempered martensite M. The heat treatment process is the above-mentioned step quenching + tempering process. Combined with the size of the cutter ring and the final structure and performance design, appropriate temperature and time are selected to ensure the sufficient dissolution and precipitation of carbonitride and control the nucleation and growth thereof, the step quenching is used to control the cooling rate during the cooling process to ensure the proportion, shape and distribution of the final tempered martensite and tempered bainite of the cutter ring, and finally the performance and service life of the cutter ring are ensured.

[0034] The surface hardness of the produced shield machine cutter is greater than or equal to 65 HRC, the room temperature impact energy KV2 is greater than or equal to 45 J, and the transverse and longitudinal impact energy ratio is greater than or equal to 0.80.

[0035] Compared with the prior art, the Nb-containing high wear resistance and high toughness long service life shield machine cutter steel is suitable for the preparation of the cutter ring of the shield machine cutter, has high hardness and toughness, and greatly improves the service life of the cutter ring in the tunneling of the shield machine. Through the optimization of the component design and the optimization control of the key manufacturing technical parameters, the surface hardness is greater than or equal to 65 HRC, the room temperature impact energy KV2 is greater than or equal to 45 J, the structure grain size is greater than or equal to 9.5 levels, the transverse and longitudinal impact energy ratio is greater than or equal to 0.80, the cutter tunneling service life is greater than or equal to 25 m, and the cutter tunneling service life is improved by 35-50%. Thus, the extremely harsh and complex hard rock stratum environment is met. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The figure of the organization of the finished tool in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0038] The present application provides a Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter, comprising the following components in mass percentage:

[0039] Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Nb 0.015%-0.030%, Ni 0.50%-0.80%, C 0.36%-0.42%, Si 1.20%-1.50%, Mn 0.50%-0.80%, Al≤0.0080%, Ti≤0.0050%, P≤0.012%, S≤0.005%, N 0.015%-0.030%, O≤0.0012%, and the balance being Fe and unavoidable impurities.

[0040] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0041] The wear-resistance factor M≥225, M=(60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V)×(1+1.4×%Nb).

[0042] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0043] The precipitation coefficient Q≥0.015, Q=50×(N%-2.1×Al%-3.4×Ti%) / 14.

[0044] The components of the Nb-containing high-wear-resistance high-toughness long-service-life steel for a shield machine cutter satisfy:

[0045] The toughness factor X≥140, X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5×%Mo)×(1+8.3×%Nb)×120×%N.

[0046] The above element symbols represent the mass percentage content of each element in the Nb-containing high-wear-resistance high-toughness long-service-life shield machine cutter steel, and the unit is %. When calculating, the value before % is directly brought into the formula for calculation.

[0047] C: Carbon element is the most effective element for improving the hardness and strength of steel, also affects the composition segregation and microstructure uniformity of steel, and through the precipitation of various carbides with chromium, molybdenum, vanadium and other elements during tempering, the purpose of strengthening the matrix and improving the wear resistance is achieved. However, too high carbon will produce segregation structure during solidification, thereby affecting the hardness uniformity and impact toughness of the steel, therefore, the C content is controlled to be 0.36%-0.42% in the present application.

[0048] Mn: The appropriate amount of Mn can effectively improve the strength of the steel, eliminate the effect of sulfur and oxygen on the thermal embrittlement of the steel, improve the hot working performance of the steel, and improve the cold brittleness tendency of the steel, but too high Mn makes the steel brittle, therefore, the Mn content is controlled to be 0.50%-0.80% in the present application to ensure that the structure is not coarsened and the segregation is light.

[0049] Si: Si is an effective solid solution strengthening element in steel, which improves the strength and hardness of the steel, and can improve the tempering stability to ensure the toughness, but too high Si causes brittleness, therefore, the Si content is controlled to be 1.20%-1.50% in the present application.

[0050] Cr: Cr is a carbide forming element, which can improve the hardenability and strength of the steel, and can greatly ensure the wear resistance, but the carbide is easy to coarsen, which has a certain damage effect on the strength and toughness, therefore, the content of chromium element is appropriately controlled to be 4.60%-5.20% in the present application.

[0051] Mo: Mo solid-solved in the matrix can keep the microstructure of the steel stable during tempering, and can effectively reduce the segregation of impurity elements such as P, S and As at the grain boundary, thereby improving the toughness of the steel and reducing the temper brittleness. Mo reduces the stability of M7C3, and when the Mo content is high, needle-like Mo2C will be formed, which will reduce the Mo content of the matrix. Mo can improve the strength of the steel through the combined action of solid solution strengthening and precipitation strengthening, and can also change the toughness of the steel by changing the precipitation of carbides. Therefore, the Mo content is controlled to be 1.30%-1.70% in the present application.

[0052] V: The main role of vanadium is to refine the grain, reduce the overheating sensitivity, increase the tempering stability and wear resistance, thereby improving the service life. At the same time, since vanadium has a strong affinity with nitrogen, vanadium can fix nitrogen in the steel to form VN and promote the formation of fine eutectic carbides. The V content is controlled to be 1.20%-1.40% in the present application.

[0053] Nb: appropriate amount of Nb, on the one hand, greatly inhibits the growth of austenite grains at high temperature, can refine the size of carbide, improve the strength and toughness of the tool. On the other hand, it can slow down the hardness drop of the material surface softening layer when working at high temperature above 200 DEG C, while its friction coefficient is significantly reduced, the wear rate is reduced, and the service life of the tool is improved. The Nb content of the application is controlled to be 0.015%-0.030%.

[0054] Ni: Ni can refine ferrite grains, improve the plasticity and toughness of steel, and improve the hardening performance of steel. The application controls the range of Ni to be 0.50%-0.80%.

[0055] [N]: nitrogen can form compounds with V, Ti and Al, etc. to refine the grains. At the same time, trace amount of nitrogen can promote V(C,N) precipitation, increase the number and stability of quenched undissolved carbides in steel, reduce the size of Cr23C6 eutectic carbides as nucleation core, improve the comprehensive performance of steel through increasing fine-grain strengthening and precipitation strengthening, and improve the hardness and toughness of the material. The application controls [N] to be 150-300ppm.

[0056] In order to ensure the hardness and wear resistance of the cutter ring material during use, beneficial alloying elements are added and specific proportions are selected. In the application, C is the most effective element for improving the hardness and strength of steel, and its contribution coefficient is 60; Mn, Si, Cr, Mo and V can effectively improve the service hardness of steel, and according to the size of their contribution ability, their coefficients are defined as 10, 12, 20, 25 and 32 respectively. A small amount of Nb is added to enhance wear resistance. In order to ensure the wear resistance of the cutter ring material during tunneling, the wear resistance factor M of the steel is defined as M, and M should be greater than or equal to 225.

[0057] M=(60%C+10%Mn+12%Si+20%Cr+25%Mo+32%V) x (1+1.4%Nb).

[0058] By adding N element, trace amount of nitrogen can promote V(C,N) precipitation, increase the number and stability of quenched undissolved carbides in steel, reduce the size of Cr23C6 eutectic carbides as nucleation core, and further improve the wear resistance and toughness of the steel. In order to ensure sufficient precipitation effect, the precipitation coefficient Q is greater than or equal to 0.015.

[0059] Q=50 x (N%-2.1 x Al%-3.4 x Ti%) / 14.

[0060] Ni can effectively improve the impact toughness of the material, V can effectively refine the grain, improve the toughness, Mo greatly improves the tempering stability to ensure the toughness, according to the respective contribution of the system toughness, the influence coefficient is defined as 63, 25, 22, and the elements in the system also have mutual influence on the performance, trace Nb cooperates with V, Mo and N to form (Nb, V, Mo) N type carbide to greatly improve the toughness of the body, the influence coefficient is 120, and the contribution of the remaining single elements is superimposed. In order to ensure the service toughness of the material, the toughness factor X is greater than or equal to 145.

[0061] X>=145, X=(63*%Ni+25*%V+22*%Mo)+(3.6*%V+6.5*%Mo)*(1+8.3*%Nb)*120*%N.

[0062] The application provides a production method of a shield machine cutter, comprising the following process flows:

[0063] Electric arc furnace or converter smelting→LF furnace refining→RH vacuum degassing→continuous casting billet→heating→four-way forging→punching die forging→heat treatment→finishing→packaging and warehousing.

[0064] The LF refining adopts 2±0.5 kg of aluminum particles and 0.4±0.1 kg of silicon carbide per ton of molten steel for deoxidization, the white slag retention time is greater than or equal to 20 min, and the LF refining cycle is 120±20 min.

[0065] When the RH vacuum degassing process is used, the time is greater than or equal to 25 min, the calcium wire feeding is 35±5 m, and the soft blowing time is 20±5 min.

[0066] The continuous casting billet process is used, and the low superheat control is 15-35 DEG C, and the crystallizer liquid level fluctuation is controlled within ±5 mm.

[0067] The continuous casting billet is cut according to the size requirement of the cutter disc, two-stage heating of the preheating section and the heating section is used, the preheating section is heated from room temperature at a rate of not greater than 50 DEG C / h to 650±10 DEG C, the holding time is determined by the thickness of the sample as 20-30 s / mm, and then heated to 1230±10 DEG C at a rate of not greater than 80 DEG C / h, and the holding time of the soaking section is determined by the thickness of the sample as 1.5-2 min / mm.

[0068] Then, the furnace forging is carried out, the initial forging temperature is controlled to be greater than or equal to 1150 DEG C, the final forging temperature is controlled to be greater than or equal to 850 DEG C, and the surface temperature of the billet is controlled to be lower than the core temperature by 100-150 DEG C during forging to ensure the forging quality of the core.

[0069] The knife ring is obtained high toughness, wear resistance, and the structure is designed to be 20-25% tempered bainite + 75-80% tempered martensite (area ratio) at the position of 1 / 2 of the core of the knife ring. The heat treatment process is above graded quenching + tempering process.

[0070] The quenching holding time t1 is determined by the diameter D of the knife ring and the quenching heating temperature T1, and specifically: 360+D / 5-T1 / 4≤t1≤380+D / 5-T1 / 4.

[0071] In the formula, D is the diameter of the knife ring, mm; t1 is the quenching holding time, min; and T1 is the quenching heating temperature, ℃.

[0072] Preferably, the quenching is: heating the knife ring to the quenching heating temperature T1 950-1000℃ at a speed of 10-30℃ / min, holding for t1 time, and cooling in the form of graded quenching, first cooling to 500℃ at a speed of 10-13℃ / s, and then cooling to room temperature at a speed of 16-19℃ / s.

[0073] The tempering holding time t2 is determined by the diameter D of the knife ring and the tempering heating temperature T2, and specifically: 600+D / 3-T2 / 2≤t2≤620+D / 3-T2 / 2.

[0074] In the formula, D is the diameter of the knife ring, mm; t2 is the tempering holding time, min; and T2 is the tempering heating temperature, ℃.

[0075] The tempering is: heating the knife ring to the tempering heating temperature T2 570-620℃ at a speed of 10-30℃ / min, holding for t2 time, and then water cooling or air cooling.

[0076] When the above formula is calculated, the values before the units are directly brought into the formula calculation.

[0077] The following are several specific embodiments and comparative examples of the application:

[0078] Examples 1-3

[0079] A Nb-containing high-wear-resistance high-toughness long-life shield cutter steel, comprising the following mass percentage components: as shown in Table 1, the balance not shown in Table 1 is Fe and unavoidable impurities.

[0080] Table 1 Chemical composition (wt%) of the inventive examples and comparative examples

[0081]

[0082] Comparative Examples 1-5

[0083] A steel for a shield machine cutter, comprising the following mass percentage components: as shown in Table 1, the balance not shown in Table 1 is Fe and inevitable impurities.

[0084] The above embodiments and the shield machine cutter steel production method of the shield machine cutter include the following process flow:

[0085] Electric arc furnace or converter smelting→LF furnace refining→RH vacuum degassing→continuous casting billet→heating→four-way forging→punching die forging→heat treatment→finishing→packaging into warehouse.

[0086] The LF refining: 200±50kg aluminum particles are used for deoxidation (based on 100t of molten steel) in combination with 40±10kg silicon carbide, the white slag retention time is ≥20min, and the LF refining cycle is 120±20min.

[0087] When the RH vacuum degassing process is used, the time is ≥25min, the calcium wire feeding is 35±5m, and the soft blowing time is 20±5min.

[0088] The continuous casting billet process is used, and the continuous casting uses low superheat control of 15-35℃, and the crystallizer liquid level fluctuation is controlled within ±5mm.

[0089] The continuous casting billet is cut according to the size requirements of the cutter disc, and two-stage heating of the preheating section and the heating section is used, the preheating section is heated from room temperature at a rate of not more than 50℃ / h to 650±10℃, the holding time is determined by the thickness of the sample as 20-30s / mm, and then heated at a rate of not more than 80℃ / h to 1230±10℃, the soaking section holding time is determined by the thickness of the sample as 1.5-2min / mm.

[0090] Then, the furnace is discharged for forging, the initial forging temperature is controlled to be ≥1150℃, the final forging temperature is controlled to be ≥850℃, and the billet surface temperature is controlled to be lower than the core temperature by 100-150℃ during forging to ensure the core forging quality.

[0091] The cutter ring is designed to have 20-30% tempered B+70-80% tempered M at the position 1 / 2 away from the core to obtain high strength and toughness and wear resistance.

[0092] The quenching holding time t1 is determined by the cutter ring diameter D and the quenching heating temperature T1, specifically: 360+D / 5-T1 / 4≤t1≤380+D / 5-T1 / 4.

[0093] In the formula, D is the cutter ring diameter, in mm; t1 is the quenching holding time, in min; T1 is the quenching heating temperature, in ℃.

[0094] Preferably, the quenching is: heating the blade ring to quenching heating temperature T1 950-1000℃ at a rate of 10-30℃ / min, holding for t1 time, and cooling by using the form of step quenching, first cooling to 500℃ at a rate of 10-13℃ / s, and then cooling to room temperature at a rate of 16-19℃ / s.

[0095] The tempering holding time t2 is determined by the diameter D of the blade ring and the tempering heating temperature T2, and is specifically: 600+D / 3-T2 / 2≤t2≤620+D / 3-T2 / 2.

[0096] 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 ℃.

[0097] The tempering is: heating the blade ring to tempering heating temperature T2 570-620℃ at a rate of 10-30℃ / min, holding for t2 time, and then water cooling or air cooling.

[0098] When the above formula is calculated, the values before the units are directly brought into the formula calculation.

[0099] The main parameters of the production process of the specific examples and comparative examples are shown in Tables 2 and 3.

[0100] Table 2 Main control parameters of the production process of the examples and comparative examples of the application

[0101]

[0102] Table 3 Main heat treatment parameters of the examples and comparative examples of the application

[0103]

[0104] The performance detection method is as follows:

[0105] Performance: After the heat treatment of the cutter head, samples are taken on the finished product, and mechanical property tests are carried out according to GB / T 230.1 and GB / T 229. The mechanical properties are shown in Table 4.

[0106] Table 4 Mechanical property detection situation of the examples and comparative examples of the application

[0107]

[0108] From Figure 1It can be seen that the structure of the knife ring in Example 1 is tempered martensite (77%) + tempered bainite (23%) in a quenched and tempered state, the structure is fine and uniform, the grain size reaches 10.5 grade, the segregation is small and the compactness is good, which shows that the knife ring produced by the components of the application has excellent performance. The chemical composition and production method of the steel of Examples 1-3 are properly controlled, the structure of the knife ring is fine and uniform, the hardness and toughness are high, and the service life is long. The component design of Comparative Example 1 is reasonable, but the quenching temperature is too high and the heating time is too long, the grain size of the structure does not meet the requirements, the quenching grading cold speed is not properly controlled, the material structure does not meet the design requirements, the hardness and toughness are insufficient, the tool wears fast and is easy to crack, and the service life is insufficient; the component design of Comparative Examples 2 and 3 is insufficient, the wear resistance factor is low, the precipitation coefficient is small, the hardness of the knife ring is low, the toughness is insufficient, and the service life is short; the toughness factor of the chemical composition of Comparative Example 4 is low and does not meet the requirements, the heating time of the heat treatment is too short, the structure transformation is insufficient, the hardness and toughness are both low, the knife ring is not wear-resistant and has a short service life; the production process parameters of Comparative Example 5 are not properly controlled, the deoxidation is not enough, the oxygen of the steel is high, the superheat is high, the heating forging temperature of the knife ring is not properly controlled, the quenching and tempering temperature is too high, the structure of the knife ring is coarse and uneven, the compactness is poor, the transverse and longitudinal toughnesses are greatly different, the overall performance is poor, and the service life is low.

[0109] The underlined data above does not meet the requirements of the application.

[0110] The above description of the embodiments is to facilitate those skilled in the art to understand and use the application. Those skilled in the art can easily make various modifications to the embodiments and apply the general principles described herein to other embodiments without inventive labor. Therefore, the application is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the application without departing from the scope of the application should be within the protection scope of the application.

Claims

1. A steel for shield tunneling machine cutters containing Nb, characterized in that, The Nb-containing high wear-resistant, high-toughness, and long-life shield tunneling machine cutter steel comprises the following composition by mass percentage: Cr 4.60%-5.20%, Mo 1.30%-1.70%, V 1.20%-1.40%, Nb 0.015%-0.030%, Ni 0.50%-0.80%, C 0.36%-0.42%, Si 1.20%-1.50%, Mn 0.50%-0.80%, Al ≤0.0080%, Ti ≤0.0050%, P ≤0.012%, S ≤0.005%, N 0.015%-0.030%, O ≤0.0012%, with the balance being Fe and unavoidable impurities; After heat treatment, the microstructure of the cutter made from the Nb-containing high wear-resistant, high toughness, and long-life shield tunneling machine cutter steel at the 1 / 2 position from the core is tempered bainite B+ with an area of ​​20-25% and an area of ​​75-80%. The grain size of the microstructure is ≥9.5 grade, the surface hardness of the tool is ≥65HRC, the room temperature impact energy KV2 is ≥45J, and the transverse and longitudinal impact energy ratio is ≥0.

80.

2. The Nb-containing high wear-resistant, high-toughness, long-life shield tunneling machine cutter steel according to claim 1, characterized in that, The composition of the Nb-containing high wear-resistant, high-toughness, long-life shield machine cutter steel meets the following requirements: Wear resistance factor M≥225, M=(60×%C+10×%Mn+12×%Si+20×%Cr+25×%Mo+32×%V)×(1+1.4×%Nb).

3. The Nb-containing high wear-resistant, high-toughness, long-life shield tunneling machine cutter steel according to claim 1 or 2, characterized in that, The composition of the Nb-containing high wear-resistant, high-toughness, long-life shield machine cutter steel meets the following requirements: The precipitation coefficient Q ≥ 0.015, Q = 50 × (N% - 2.1 × Al% - 3.4 × Ti%) / 14.

4. The Nb-containing high wear-resistant, high-toughness, long-life shield tunneling machine cutter steel according to claim 1 or 2, characterized in that, The composition of the Nb-containing high wear-resistant, high-toughness, long-life shield machine cutter steel meets the following requirements: Toughness factor X≥145, X=(63×%Ni+25×%V+22×%Mo)+(3.6×%V+6.5×%Mo)×(1+8.3×%Nb)×120×%N.

5. A method for producing tunnel boring machine cutters, characterized in that, The steel used for shield tunneling machine cutters, containing Nb and known for its high wear resistance, high toughness, and long service life, as described in any one of claims 1-4, is used in the production method, which includes heat treatment, specifically quenching and tempering.

6. The production method according to claim 6, characterized in that, 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; 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.

7. The method for producing tunnel boring machine cutters according to claim 6, characterized in that, The quenching process involves heating the blade ring at a rate of 10-30℃ / min to a quenching temperature T1 of 950-1000℃, holding it at that temperature for a time t1, and then cooling it in stages. First, the blade ring is cooled to 500℃ at a rate of 10-13℃ / s, and then cooled to room temperature at a rate of 16-19℃ / s.

8. The method for producing tunnel boring machine cutters according to claim 6, characterized in that, 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.

9. The method for producing tunnel boring machine cutters according to claim 9, characterized in that, 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.

10. The method for producing tunnel boring machine cutters according to any one of claims 6-9, characterized in that, The production method includes the following process flow: smelting in an electric arc furnace or converter → refining in an LF furnace → RH vacuum degassing → continuous casting billet → heating → four-way forging → punching and forging → heat treatment → finishing → packaging and warehousing.

11. The method for producing tunnel boring machine cutters according to claim 10, characterized in that, The heating process employs a two-stage heating method: a preheating stage and a heating stage. In the preheating stage, the temperature is increased from room temperature to 650±10℃ at a rate not exceeding 50℃ / h and held for 20-30s / mm, depending on the sample thickness. Then, the temperature is increased to 1230±10℃ at a rate not exceeding 80℃ / h and held for 1.5-2min / mm, depending on the sample thickness. Subsequently, the sample is forged, with the initial forging temperature controlled at ≥1150℃ and the final forging temperature at ≥850℃. During forging, the surface temperature of the billet is controlled to be 100-150℃ lower than that of the core.

12. The method for producing tunnel boring machine cutters according to any one of claims 6-11, characterized in that, The surface hardness of the produced tunnel boring machine cutters is ≥65HRC, the room temperature impact energy KV2 is ≥45J, the transverse and longitudinal impact energy ratio is ≥0.80, and the cutter tunneling life is increased by 35-50%.

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