A low-defect hob ring, a preparation method thereof and a heading machine

Abstract

The application provides a low-defect hob ring, a preparation method thereof and a tunneling machine, wherein, in terms of the total weight of the low-defect hob ring, the low-defect hob ring contains C: 0.8-0.9%, Si: 1-1.3%, Mn: 0.25-0.45%, Cr: 7.5-8.0%, Mo: 1.4-1.7%, V: 2.2-2.6%, Ti: 0.04-0.1%, Nb: 0.02-0.05%, P: ≤0.01%, S: ≤0.005% and Fe balance; and the low-defect hob ring contains Ti-Nb micro-alloying composite phases. In the case that the hardness of the hob ring is basically unchanged, the hardness distribution uniformity of the low-defect hob ring is effectively improved, the volume content of shrinkage and porosity of the low-defect hob ring is reduced, and the impact toughness of the low-defect hob ring is greatly improved.

Description

Technical Field

[0001] This invention relates to a low-defect cutter ring, its manufacturing method, and a tunneling machine, belonging to the technical field of tunneling machine cutter rings. Background Technology

[0002] The geological conditions during tunneling are difficult to predict, so TBMs (Tunnel Boring Machines) are prone to encountering hard strata during excavation. This can apply significant stress to the cutterheads, causing them to fracture. For example, in the Zhongtianshan Tunnel, frequent impacts with boulders during cutterhead rotation resulted in the fracture of nearly 300 front and side cutters, severely impacting construction progress. The fracture of the cutterheads is due to internal defects such as porosity, shrinkage cavities, or cracks, leading to low plasticity and toughness. Under high pressure and instantaneous impact loads, these internal defects initiate cracks, which continue to propagate and eventually lead to fracture. Currently used cutterhead materials are mainly divided into two categories: medium-carbon hot-work die steel and high-carbon cold-work die steel. Cold-work die steel, however, has an impact toughness of only 5-6 J / cm². 2 It cannot meet the requirements of tunneling under increasingly high-intensity and high-impact conditions.

[0003] CN115522138A discloses a manufacturing process for a high-strength tunnel boring machine cutterhead ring, which incorporates pre-stretching and cryogenic treatment steps. This process only improves the strength of the cutterhead ring, with limited improvement on the plasticity and toughness of the cutterhead.

[0004] CN112080705A discloses a hobbing cutter ring and its preparation method, which achieves an impact toughness of 20 J / cm by generating VC. 2 However, it still obtains the blank cutter ring through traditional upsetting and forging processes, which cannot avoid defects such as porosity and shrinkage cavities inside the cutter ring. Moreover, the material of the cutter ring studied is hot work die steel.

[0005] Therefore, in view of the problems of defects and insufficient toughness in the existing hobbing cutter rings, providing a new type of high-quality cold-work die hobbing cutter ring with low internal defects, its preparation method and tunneling machine have become technical problems that urgently need to be solved in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide a low-defect hobbing cutter ring.

[0007] Another object of the present invention is to provide a method for preparing the low-defect hobbing cutter ring described above.

[0008] Another object of the present invention is to provide a tunneling machine comprising the low-defect cutter ring described above.

[0009] To achieve the above objectives, on the one hand, the present invention provides a low-defect hobbing cutter ring, wherein, based on the total weight of the low-defect hobbing cutter ring as 100%, it comprises C: 0.8-0.9%, Si: 1-1.3%, Mn: 0.25-0.45%, Cr: 7.5-8.0%, Mo: 1.4-1.7%, V: 2.2-2.6%, Ti: 0.04-0.1%, Nb: 0.02-0.05%, P: ≤0.01%, S: ≤0.005%, and the balance Fe; and the low-defect hobbing cutter ring comprises a Ti-Nb microalloyed composite phase.

[0010] As a specific embodiment of the low-defect hobbing cutter ring described above in this invention, the low-defect hobbing cutter ring has a hardness of HRC>60, distributed within ±0.5HRC, a volume content of shrinkage cavities and / or porosity of <0.1%, and an impact toughness of 10-12 J / cm. 2 .

[0011] Compared to traditional hobbing cutter rings, this invention appropriately reduces the carbon (C) content in low-defect hobbing cutter rings, improving their toughness while maintaining wear resistance. Excessive chromium (Cr) content in hobbing cutter rings can form various carbides, reducing toughness; therefore, this invention appropriately reduces the Cr content in low-defect hobbing cutter rings to improve their toughness. The low-defect hobbing cutter rings provided by this invention have a high titanium content, which effectively inhibits grain growth and has a strong precipitation strengthening effect, enabling the low-defect hobbing cutter rings to possess high strength. While offering excellent wear resistance and performance, high Ti content can reduce the toughness of the hob ring, making it prone to breakage during subsequent processing. To address this, the present invention adds Nb to the medium-defect hob ring. Nb and Ti can form a Ti-Nb microalloyed composite phase. This Ti-Nb microalloyed composite phase can refine the grains, resulting in fine grain strengthening and promoting the precipitation of carbides, leading to dispersion strengthening. At the same time, the precipitated phase can effectively pin dislocations, thereby accumulating more deformation energy during subsequent die forging and improving the impact toughness of the hob ring.

[0012] On the other hand, the present invention also provides a method for preparing the low-defect hobbing cutter ring described above, wherein the preparation method includes:

[0013] Step (1), raw material purification: Select appropriate raw materials according to the chemical composition of the low-defect hobbing cutter ring and perform smelting, LF refining and VD vacuum degassing on the raw materials;

[0014] Step (2), Inert casting: Circular casting or disc casting is carried out under an inert gas protective atmosphere to form a circular cast steel ingot (also called a circular casting blank) or a disc cast steel ingot.

[0015] Step (3), steel ingot cutting: the circular cast steel ingot is cut to obtain a cut steel ingot; or the disc cast steel ingot is cut and then subjected to upsetting and punching to obtain a punched steel ingot;

[0016] Step (4), hot isostatic pressing: hot isostatic pressing is performed on the cut steel ingot or punched steel ingot and then cooled;

[0017] Step (5), die forging of the blade ring: the hot isostatically pressed steel ingot is forged, and then the forged steel ingot is die forged to obtain a die-forged blade ring;

[0018] Step (6), heat treatment: First, heat the die-forged cutter ring and then perform air-cooled spheroidizing annealing treatment. Then, heat the resulting annealed cutter ring and perform oil-cooled quenching treatment. Finally, heat the resulting quenched cutter ring and perform air-cooled tempering treatment to obtain the low-defect hobbing cutter ring.

[0019] As a specific embodiment of the preparation method described above in this invention, in step (1), LF refining is carried out by uninterrupted diffusion deoxidation, the LF refining time is ≥40min, the white slag holding time is ≥30min, and the sulfur content before leaving the station is ≤0.005wt% and the phosphorus content is ≤0.01wt%.

[0020] As a specific embodiment of the preparation method described above in this invention, in step (1), the VD vacuum degassing is maintained at a pressure of 68-70MPa for more than 20 minutes and the soft blowing time is >10 minutes.

[0021] In step (1) of the preparation method described above in this invention, both LF (ladle furnace) refining and VD vacuum degassing are ladle refining processes. That is, in step (1), refining is carried out in another container on the basis of smelting to remove sulfur, oxygen, and phosphorus, thereby achieving the purpose of removing relevant impurities. In addition, in step (1), LF refining is carried out by continuous diffusion deoxidation to maintain the reducibility of the slag. Furthermore, this invention uses LF refining and VD vacuum degassing to purify the raw materials. At the same time, by extending the duration / holding time of white slag, non-metallic inclusions are controlled to float sufficiently, reducing the content of P, S, etc., and by appropriately extending the vacuum degassing time, the gas content in the parent material is reduced, thereby reducing segregation caused by gas accumulation.

[0022] This invention does not impose specific requirements on the raw materials used, and can be reasonably selected according to the actual operation needs, as long as the raw materials used and their proportions can ultimately obtain a low-defect hobbing cutter ring with the above chemical composition.

[0023] As a specific embodiment of the preparation method described above in this invention, in step (2), the inner diameter d of the annular cast steel ingot is... 锭内 =d内 +(1-5)L, outer diameter d 锭外 =d 外 -(3-10)L, where d 内 d is the inner diameter of the low-defect hob cutter ring. 外 The outer diameter of the low-defect hobbing cutter ring is L, which is 1-5 mm. The difference between the inner diameter of the annular cast steel ingot and the inner diameter of the low-defect hobbing cutter ring is (1-5)L smaller than the difference between the outer diameter of the annular cast steel ingot and the outer diameter of the low-defect hobbing cutter ring. Wherein, d is calculated... 锭内 and d 锭外 The L value used can be the same or different.

[0024] The present invention does not impose specific requirements on the inert gas used in step (2) of the preparation method described above, and it can be reasonably selected according to the actual needs of on-site operations. For example, in some embodiments of the present invention, the inert gas includes argon, etc.

[0025] In step (2) of the preparation method described above, the circular ingot is directly cast in an inert environment. Considering the material loss during the die forging process, the size of the circular cast steel ingot is customized according to the size of the finished low-defect hob cutter ring, which can ensure the filling performance of the steel ingot in the subsequent die forging. In addition, the circular ingot significantly reduces the time required for punching and expanding the cylindrical steel billet (solid) used in conventional hob cutter rings, thereby improving production efficiency.

[0026] As a specific embodiment of the preparation method described above in this invention, step (3) of cutting the annular cast steel ingot includes: first calculating the cutting height based on the volume of the low-defect hobbing cutter ring, and then determining whether the cutting height satisfies: 60mm≤d h If the diameter is ≤90mm, the circular cast steel ingot is cut directly; if it is not, return to step (2) to redesign the inner and outer diameters of the circular cast steel ingot until the cutting height meets the requirements before cutting the circular cast steel ingot.

[0027] As a specific embodiment of the preparation method described above in this invention, in step (3), the cutting height is calculated according to the volume of the low-defect hobbing cutter ring as follows:

[0028]

[0029] In equation 1), d h V is the cutting height. 成 For the volume of the low-defect hob cutter ring, d 锭内 d is the inner diameter of the annular cast steel ingot. 锭外 The outer diameter of the annular cast steel ingot is l, which ranges from 1.05 to 1.15.

[0030] The cutting height in step (3) of the preparation method described above is closely related to the subsequent die forging process of the blade ring. When the cutting height of the steel ingot is too high, the raw material is prone to folding during the die forging process, resulting in uneven structure. When the cutting height of the steel ingot is too low, incomplete forming is likely to occur.

[0031] As a specific embodiment of the preparation method described above in this invention, in step (2), the diameter of the disc-shaped cast steel ingot... Where d1 is the diameter of the disc-shaped cast steel ingot, V 成 The volume of the low-defect hob cutter ring.

[0032] As a specific embodiment of the preparation method described above in this invention, step (3) of cutting the disc-shaped cast steel ingot includes:

[0033] First, calculate the cutting height according to the diameter and upsetting ratio of the disc-shaped cast steel ingot as shown in Formula 2), and then cut the disc-shaped cast steel ingot according to the cutting height.

[0034] l1=m*d1 (Equation 2);

[0035] In Equation 2), d1 is the diameter of the disc-shaped cast steel ingot, and m is the upsetting ratio, which is the upsetting ratio controlled by the upsetting process in step (3), and the value range is 1.5-2.

[0036] As a specific embodiment of the preparation method described above in this invention, in step (3), the upsetting process includes: heating the cut disc-shaped cast steel ingot to 1150-1200℃ for upsetting.

[0037] As a specific embodiment of the preparation method described above in this invention, in step (3), the inner diameter of the punched steel ingot is larger than the inner diameter of the low-defect hobbing cutter ring, and its outer diameter is smaller than the outer diameter of the low-defect hobbing cutter ring. The difference between the inner diameter of the punched steel ingot and the inner diameter of the low-defect hobbing cutter ring is 10-30 mm smaller than the difference between the outer diameter of the punched steel ingot and the outer diameter of the low-defect hobbing cutter ring. The height of the punched steel ingot is 60-90 mm.

[0038] As a specific embodiment of the preparation method described above in this invention, in step (4), the temperature of the hot isostatic pressing is 1000-1100℃, the pressure is 100-150MPa, and the time is 1-4h. The process parameters used in the hot isostatic pressing process are closely related to the chemical composition of the low-defect hobbing cutter ring.

[0039] As a specific embodiment of the preparation method described above in this invention, in step (4), the cooling includes: after hot isostatic pressing, first cooling to 700-800°C at a cooling rate of 30-60°C / min, and then cooling to room temperature at a cooling rate of 10-30°C / min.

[0040] In step (4) of the preparation method described above, the steel ingot is subjected to hot isostatic pressing. Specifically, the steel ingot to be processed is placed in a completely sealed container, such as a hot isostatic press. Under isothermal conditions, the same pressure is applied to all directions of the workpiece, while high temperature is applied. The temperature is maintained within the plastic deformation range of the hobbing cutter ring. Under the dual action of high temperature and high pressure, the internal material of the steel ingot compacts the internal pores and looseness through creep and deformation. The compacted surface can diffuse and connect, thereby making the metal product denser and more uniform, and improving the reliability indicators such as fracture toughness and fatigue performance of the casting.

[0041] After hot isostatic pressing, the steel ingot is cooled at a faster rate, which effectively avoids the occurrence of precipitates and grain growth during the cooling process after densification. This change in cooling operation shortens the production cycle, and accelerated cooling within a certain range can achieve a greater degree of supercooling, increase the nucleation rate, and thus refine the microstructure, preparing the microstructure for subsequent die forging and heat treatment.

[0042] As a specific embodiment of the preparation method described above in this invention, in step (5), the forging temperature is 1150-1200℃.

[0043] As a specific embodiment of the preparation method described above in this invention, in step (5), the die forging includes placing the forged steel ingot into the lower die and pressing the upper die with a press to forge the steel ingot, wherein the pressing speed is 20-80 mm / s.

[0044] The die forging process used in step (5) of the preparation method described above in this invention can enable the integral metal to undergo precise plastic flow in the mold, overcoming the problem of local non-deformation that exists in the ordinary ring rolling process, which is beneficial to improving the density of the metal structure and giving it better mechanical properties.

[0045] As a specific embodiment of the preparation method described above in this invention, in step (6), the heat treatment includes: first heating the die-forged blade ring to 840-860℃, holding it at that temperature for 2-4 hours, and then air-cooling it for spheroidizing annealing treatment; then heating the resulting annealed blade ring to 1010-1050℃, holding it at that temperature for 1-2 hours, and then oil-cooling it for quenching treatment; finally heating the resulting quenched blade ring to 500-530℃, holding it at that temperature for 1-1.5 hours, and then air-cooling it for tempering treatment, wherein the tempering treatment is performed 3 times.

[0046] In another aspect, the present invention also provides a tunneling machine comprising the low-defect hobbing cutter ring described above.

[0047] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0048] Compared to traditional hobbing cutter rings, this invention reduces the C and Cr content in low-defect hobbing cutter rings and adds a high content of Ti and the corresponding Nb, causing Ti and Nb to form a Ti-Nb microalloyed composite phase. This improves the strength and wear resistance of the hobbing cutter ring while increasing its impact toughness, thereby ensuring the machinability of the material during subsequent machining processes.

[0049] In the process of preparing low-defect hobbing cutter rings, LF refining + VD vacuum degassing is used to purify the raw materials, which can effectively reduce the impurity content of the raw materials, thereby improving the uniformity of the structure and the cleanliness level of the steel.

[0050] In the process of preparing low-defect roller cutter rings, hot isostatic pressing of steel ingots and control of cooling rate are used to obtain cutter ring blanks with high microstructure density, low porosity, and low void defects. The internal microstructure is also highly pure, which effectively improves the impact toughness and wear resistance of the roller cutter rings. This makes the roller cutter rings more suitable for complex alternating strata, thereby reducing the number of cutter replacements and improving tunneling efficiency.

[0051] In the process of preparing low-defect hobbing cutter rings, inert ring ingot injection and die forging of the cutter ring are used instead of traditional punching, hole expansion and ring rolling, which greatly reduces the manufacturing process of hobbing cutter rings. During the die forging process, the hobbing cutter ring undergoes overall deformation, which makes the hobbing cutter ring structure more compact.

[0052] The low-defect hobbing cutter ring provided by this invention has a hardness of HRC>60, distributed within ±0.5HRC, exhibiting excellent consistency in material hardness; the volume content of shrinkage cavities and porosity is <0.1%, indicating that the cutter ring has achieved uniform densification and possesses good metallurgical quality; the impact toughness obtained using Charpy U2 notches reaches 10-12 J / cm. 2 This invention effectively improves the uniformity of hardness distribution, reduces shrinkage cavity and porosity content, and significantly enhances impact toughness of low-defect hobbing cutter rings while maintaining essentially the same hardness. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a microscopic morphology image of the low-defect hobbing cutter ring provided in Embodiment 1 of the present invention.

[0055] Figure 2 Microscopic morphology of the hobbing cutter ring provided for Comparative Example 5. Detailed Implementation

[0056] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0057] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0058] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0059] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0060] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0061] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0062] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0063] Example 1

[0064] This embodiment provides a low-defect hobbing cutter ring, which is prepared by a method including the following specific steps:

[0065] Step (a), Composition Design: Raw materials are selected according to the principle that the finished low-defect hobbing cutter ring contains C: 0.85%, Si: 1.2%, Mn: 0.35%, Cr: 7.8%, Mo: 1.6%, V: 2.4%, Ti: 0.06%, Nb: 0.03%, P: 0.009%, S: 0.003%, and Fe as the balance; wherein, the content of each component is calculated based on the total weight of the low-defect hobbing cutter ring as 100%;

[0066] Step (b), material purification: The raw materials are smelted, LF refined, and VD vacuum degassing. The LF refining is carried out by continuous diffusion deoxidation for 40 min, the white slag holding time is 30 min, and the sulfur content and phosphorus content before leaving the station are 0.003% and 0.009%, respectively. The VD vacuum degassing is carried out at 69 MPa for 25 min, followed by soft blowing for 15 min.

[0067] Step (c), Inert Ingot Casting: Circular ingot casting is performed under an argon protective atmosphere to form a circular cast steel ingot (also known as a circular ingot casting blank); taking an 18-inch low-defect hobbing cutter ring as an example, its inner diameter is 285mm and its outer diameter is 451mm. The inner diameter of the cast steel ingot formed during circular ingot casting is 290mm and its outer diameter is 430mm.

[0068] Step (d), Ingot cutting: The finished product volume of the 18-inch low-defect hobbing cutter ring is 4.4 × 10 6 mm 3 The cutting height is calculated using formula 1) as follows, and the calculated cutting height is 75mm.

[0069]

[0070] In equation 1), d h V is the cutting height. 成 For the volume of the low-defect hob cutter ring, d 锭内 d is the inner diameter of the annular cast steel ingot. 锭外 The outer diameter of the annular cast steel ingot is l, which ranges from 1.05 to 1.15.

[0071] The circular cast steel ingot is cut according to the cutting height calculated above to obtain a cut steel ingot;

[0072] Step (e), hot isostatic pressing: the cut ingots are placed in batches into the hot isostatic press and the holding time is controlled to be 3 hours, the holding temperature is 1050℃ and the pressure is 125MPa. After the hot isostatic pressing is completed, the ingots are first cooled to 750℃ at a cooling rate of 50℃ / min, and then cooled to room temperature at a cooling rate of 20℃ / min.

[0073] Step (f), die forging of the blade ring: The hot isostatically pressed steel ingot is heated to 1170℃ for forging, and then the forged steel ingot is placed into the lower die and the upper die is pressed down by a press for die forging, wherein the pressing speed is 50mm / s, and a die forged blade ring is obtained.

[0074] Step (g), heat treatment: First, heat the die-forged cutter ring to 850°C, hold for 3 hours, and then air-cool for spheroidizing annealing. Then, heat the resulting annealed cutter ring to 1020°C, hold for 1 hour, and then oil-cool for quenching. Finally, heat the resulting quenched cutter ring to 510°C, hold for 1 hour, and then air-cool for tempering. The tempering process is repeated 3 times. After the process, the low-defect hobbing cutter ring is obtained.

[0075] Example 2

[0076] This embodiment provides a low-defect hobbing cutter ring, which is prepared by a method including the following specific steps:

[0077] Step (a), Composition Design: Raw materials are selected according to the principle that the finished low-defect hobbing cutter ring contains C: 0.85%, Si: 1.2%, Mn: 0.35%, Cr: 7.8%, Mo: 1.6%, V: 2.4%, Ti: 0.06%, Nb: 0.03%, P: 0.009%, S: 0.003%, and Fe as the balance; wherein, the content of each component is calculated based on the total weight of the low-defect hobbing cutter ring as 100%;

[0078] Step (b), material purification: The raw materials are smelted, LF refined, and VD vacuum degassing. The LF refining is carried out by continuous diffusion deoxidation for 40 min, the white slag holding time is 30 min, and the sulfur content and phosphorus content before leaving the station are 0.003% and 0.009%, respectively. The VD vacuum degassing is carried out at 69 MPa for 25 min, followed by soft blowing for 15 min.

[0079] Step (c), Inert Ingot Casting: A disc-shaped cast steel ingot is formed under an argon protective atmosphere; the volume of the finished 18-inch low-defect hobbing cutter ring (i.e., V) is determined. 成 The value is 4.4 × 10 6 mm 3 ,by The diameter of the disc-shaped cast steel ingot is calculated by taking n as 0.85, and the calculated value is 140 mm.

[0080] Step (d), steel ingot cutting, upsetting and punching: the disc-shaped cast steel ingot is cut and then upsetting and punching is performed to obtain a punched steel ingot;

[0081] First, the cutting height is calculated according to the diameter and upsetting ratio of the disc-shaped cast steel ingot according to the following formula 2), and then the disc-shaped cast steel ingot is cut according to the cutting height.

[0082] l1 = m * d1 (Equation 2);

[0083] In Equation 2), d1 is the diameter of the disc-shaped cast steel ingot, m is the upsetting ratio, which is taken as 1.5, and the calculated cutting height is 210mm;

[0084] The cut disc-shaped cast steel ingots were then heated to 1170℃ for upsetting.

[0085] Finally, the upsetting steel ingot is punched. The inner diameter of the punched steel ingot is larger than the inner diameter of the finished low-defect hob cutter ring, and the outer diameter of the punched steel ingot is smaller than the outer diameter of the finished low-defect hob cutter ring. The difference between the inner diameter of the punched steel ingot and the inner diameter of the finished low-defect hob cutter ring is 15mm smaller than the difference between the outer diameter of the punched steel ingot and the outer diameter of the finished low-defect hob cutter ring. The height of the punched steel ingot is 75mm.

[0086] Step (e), hot isostatic pressing: The punched ingots are placed in batches into a hot isostatic press, and the holding time is controlled to be 3 hours, the holding temperature is 1050℃ and the pressure is 125MPa. After hot isostatic pressing, the ingots are first cooled to 750℃ at a cooling rate of 50℃ / min, and then cooled to room temperature at a cooling rate of 20℃ / min.

[0087] Step (f), die forging of the blade ring: The hot isostatically pressed steel ingot is heated to 1170℃ for forging, and then the forged steel ingot is placed into the lower die and the upper die is pressed down by a press for die forging, wherein the pressing speed is 50mm / s, and a die forged blade ring is obtained.

[0088] Step (g), heat treatment: First, heat the die-forged cutter ring to 850°C, hold for 3 hours, and then air-cool for spheroidizing annealing. Then, heat the resulting annealed cutter ring to 1020°C, hold for 1 hour, and then oil-cool for quenching. Finally, heat the resulting quenched cutter ring to 510°C, hold for 1 hour, and then air-cool for tempering. The tempering process is repeated 3 times. After the process, the low-defect hobbing cutter ring is obtained.

[0089] Comparative Example 1

[0090] This comparative example provides a hobbing cutter ring, which differs from Example 1 only in that:

[0091] No Nb is added, and the increase in Nb content leads to an increase in Fe content.

[0092] Comparative Example 2

[0093] This comparative example provides a hobbing cutter ring, which differs from Example 1 only in that:

[0094] Step (e) is not performed, i.e., hot isostatic pressing is not performed.

[0095] Comparative Example 3

[0096] This comparative example provides a hobbing cutter ring, which differs from Example 1 only in that:

[0097] In step (e), after hot isostatic pressing, the mixture is cooled to room temperature at a cooling rate of <5°C / min.

[0098] Comparative Example 4

[0099] This comparative example provides a hobbing cutter ring, which differs from Example 1 only in that:

[0100] Step (c), Inert Ingot Casting: Circular ingot casting is performed under an argon protective atmosphere to form a circular cast steel ingot (also known as a circular ingot blank); taking an 18-inch low-defect hobbing cutter ring as an example, its inner diameter is 285mm and its outer diameter is 451mm. The inner diameter of the cast steel ingot formed during circular ingot casting is 300mm and its outer diameter is 400mm.

[0101] Step (d), Ingot cutting: The finished product volume of the 18-inch low-defect hobbing cutter ring is 4.4 × 10 6 mm 3 The cutting height is calculated using formula 1) as follows, and the calculated cutting height is 150mm.

[0102]

[0103] In equation 1), d h V is the cutting height. 成 For the volume of the low-defect hob cutter ring, d 锭内 d is the inner diameter of the annular cast steel ingot. 锭外 The outer diameter of the annular cast steel ingot is l, which ranges from 1.05 to 1.15.

[0104] Comparative Example 5

[0105] This comparative example provides a hobbing cutter ring, which differs from Example 1 only in that:

[0106] The Ti content was reduced to 0.01%, and the reduced Ti content increased the Fe content.

[0107] Test Example 1

[0108] In this test example, a microscope was used to observe and analyze the low-defect hobbing cutter ring provided in Example 1 of the present invention and the hobbing cutter ring provided in Comparative Example 5, respectively. The obtained microscopic morphology images are shown below. Figure 1 and Figure 2 As shown. From Figure 1 As can be seen from the table, the low-defect hobbing cutter ring provided in Example 1 of the present invention contains precipitates. Subsequently, energy dispersive spectroscopy analysis was performed on the precipitates, and the results are shown in Table 1 below. It can be seen from Table 1 that the precipitates are nanoscale Ti-Nb microalloyed composite phases precipitated in the steel matrix, which can effectively hinder dislocation movement; while the hobbing cutter ring provided in Comparative Example 5 does not contain Ti-Nb microalloyed composite phases, and only iron matrix exists.

[0109] Table 1

[0110] 1 28.2％ 22.8％ 27.7％ 21.3％

[0111] Test Example 2

[0112] In this test example, the low-defect hobbing cutter rings provided in Examples 1-2 and Comparative Examples 1-5 of this invention were tested for impact energy / impact toughness (impact toughness was obtained using Charpy U2 notch), hardness, and porosity content using existing conventional testing methods in the art. The test results are shown in Table 2 below.

[0113] Table 2

[0114]

[0115] As can be seen from Table 2 above, the hobbing cutter ring provided in Comparative Example 1, due to the absence of Nb, has lower impact toughness than existing conventional cutter rings (5-6 J / cm). 2 This is because the hobbing cutter ring contains a high amount of Ti, which generates a large amount of Ti-containing hard phases, thus disrupting the continuity of the steel matrix. In Comparative Example 2, the hot isostatic pressing step was omitted during the preparation of the hobbing cutter ring. However, due to the change in the composition and manufacturing process of the hobbing cutter ring, the impact toughness of this hobbing cutter ring is still slightly improved compared to the existing conventional cutter rings. However, the problem of porosity defects in the hobbing cutter blades is not solved, and the porosity volume content of this hobbing cutter ring is as high as 0.6%. In Comparative Example 3, the cooling operation after hot isostatic pressing was changed. The slow cooling operation used resulted in coarse grains and a large amount of precipitates, which could not prepare the microstructure for subsequent processing and heat treatment. Therefore, the impact toughness of this hobbing cutter ring was only slightly improved compared to the existing conventional cutter rings. In Comparative Example 4, the size design of the cast steel ingot formed during the ring casting process was unreasonable, resulting in an excessively high cutting height and causing the billet filling failure. In Comparative Example 5, because only a small amount of Ti alloy was added, the Ti-Nb microalloyed composite phase could not be formed. Specifically, as shown in the figure... Figure 2 As shown, the impact toughness of the hobbing cutter rings produced by this method is insufficient; however, the low-defect hobbing cutter rings provided in Examples 1 and 2 of this invention exhibit excellent performance, with a significant improvement in impact toughness compared to existing conventional cutter rings, reaching 11 J / cm. 2 and 12j / cm 2 The uniformity of its hardness distribution has also been greatly improved. The hardness value remains basically unchanged from that of conventional hob rings, indicating that the low-defect hob ring still has good wear resistance. Furthermore, the loose volume of the low-defect hob ring has been greatly reduced, to only 0.05% and 0.06% respectively.

[0116] In summary, the low-defect hobbing cutter ring provided by the embodiments of the present invention has the characteristics of high impact, high wear resistance, high uniformity of hardness distribution and low porosity, and has excellent comprehensive performance.

[0117] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A low-defect hobbing cutter ring, characterized in that, Based on the total weight of the low-defect hobbing cutter ring (100%), it comprises C: 0.8-0.9%, Si: 1-1.3%, Mn: 0.25-0.45%, Cr: 7.5-8.0%, Mo: 1.4-1.7%, V: 2.2-2.6%, Ti: 0.04-0.1%, Nb: 0.02-0.05%, P: ≤0.01%, S: ≤0.005%, and the balance being Fe; and the low-defect hobbing cutter ring contains a Ti-Nb microalloyed composite phase. The method for preparing the low-defect hobbing cutter ring includes: Step (1), raw material purification: Select appropriate raw materials according to the chemical composition of the low-defect hobbing cutter ring and perform smelting, LF refining and VD vacuum degassing on the raw materials; Step (2), Inert casting: Casting is carried out under an inert gas protective atmosphere to form a ring-shaped or disc-shaped cast steel ingot; Step (3), steel ingot cutting: The circular cast steel ingot is cut, including: first, calculating the cutting height based on the volume of the low-defect hobbing cutter ring, and then determining whether the cutting height meets the requirement of 60mm ≤ d h If the diameter is ≤90mm, the circular cast steel ingot is directly cut to obtain the cut steel ingot; if it is not satisfied, return to step (2) to redesign the inner and outer diameters of the circular cast steel ingot until the cutting height meets the requirements before cutting the circular cast steel ingot to obtain the cut steel ingot. Alternatively, the disc-shaped cast steel ingot can be cut and then subjected to upsetting and punching to obtain a punched steel ingot; Step (4), hot isostatic pressing: hot isostatic pressing is performed on the cut steel ingot or punched steel ingot and then cooled; in step (4), the temperature of hot isostatic pressing is 1000-1100℃, the pressure is 100-150MPa and the time is 1-4h; the cooling includes: after hot isostatic pressing, first cooling to 700-800℃ at a cooling rate of 30-60℃ / min, and then cooling to room temperature at a cooling rate of 10-30℃ / min; Step (5), forging of the blade ring: the hot isostatically pressed steel ingot is forged, and then the forged steel ingot is die-forged to obtain a die-forged blade ring; in step (5), the forging temperature is 1150-1200℃ and the die forging includes placing the forged steel ingot into the lower die and pressing the upper die with a press to forge the steel ingot, wherein the pressing speed is 20-80mm / s; Step (6), heat treatment: First, heat the die-forged cutter ring to 840-860℃, hold for 2-4 hours, and then air-cool for spheroidizing annealing. Then, heat the annealed cutter ring to 1010-1050℃, hold for 1-2 hours, and then oil-cool for quenching. Finally, heat the quenched cutter ring to 500-530℃, hold for 1-1.5 hours, and then air-cool for tempering. The tempering process is repeated 3 times to obtain the low-defect hobbing cutter ring.

2. The low-defect hobbing cutter ring according to claim 1, characterized in that, The low-defect hobbing cutter ring has a hardness of HRC>60, distributed within ±0.5HRC, a volume content of shrinkage cavities and / or porosity of <0.1%, and an impact toughness of 10-12 J / cm. 2 .

3. The method for preparing the low-defect hobbing cutter ring according to claim 1 or 2, characterized in that, The preparation method includes: Step (1), raw material purification: Select appropriate raw materials according to the chemical composition of the low-defect hobbing cutter ring and perform smelting, LF refining and VD vacuum degassing on the raw materials; Step (2), Inert casting: Casting is carried out under an inert gas protective atmosphere to form a ring-shaped or disc-shaped cast steel ingot; Step (3), steel ingot cutting: the circular cast steel ingot is cut to obtain a cut steel ingot; or the disc cast steel ingot is cut and then subjected to upsetting and punching to obtain a punched steel ingot; Step (4), hot isostatic pressing: hot isostatic pressing is performed on the cut steel ingot or punched steel ingot and then cooled; Step (5), forging of the blade ring: the hot isostatically pressed steel ingot is forged, and then the forged steel ingot is die-forged to obtain a die-forged blade ring; Step (6), heat treatment: First, heat the die-forged cutter ring to 840-860℃, hold for 2-4 hours, and then air-cool for spheroidizing annealing. Then, heat the annealed cutter ring to 1010-1050℃, hold for 1-2 hours, and then oil-cool for quenching. Finally, heat the quenched cutter ring to 500-530℃, hold for 1-1.5 hours, and then air-cool for tempering. The tempering process is repeated 3 times to obtain the low-defect hobbing cutter ring.

4. The preparation method according to claim 3, characterized in that, In step (1), LF refining is carried out by uninterrupted diffusion deoxidation. The LF refining time is ≥40 min, the white slag retention time is ≥30 min, and the sulfur content before leaving the station is ≤0.005 wt% and the phosphorus content is ≤0.01 wt%.

5. The preparation method according to claim 3 or 4, characterized in that, In step (1), the VD vacuum degassing is maintained at a pressure of 68-70MPa for more than 20 minutes, and the soft blowing time is >10 minutes.

6. The preparation method according to claim 3, characterized in that, In step (2), the inner diameter of the annular cast steel ingot d 锭内 = d 内 +(1-5)L, outer diameter d 锭外 = d 外 -(3-10)L, where, d 内 The inner diameter of the low-defect hob cutter ring, d 外 The outer diameter of the low-defect hob cutter ring is L, which is 1-5mm. The difference between the inner diameter of the annular cast steel ingot and the inner diameter of the low-defect hob cutter ring is (1-5)L smaller than the difference between the outer diameter of the annular cast steel ingot and the outer diameter of the low-defect hob cutter ring.

7. The preparation method according to claim 1, characterized in that, In step (3), the cutting height is calculated based on the volume of the low-defect hob cutter ring according to the following formula 1): Formula 1); In Equation 1), d h For cutting height, V 成 For the volume of the low-defect hob cutter ring, d 锭内 The inner diameter is the diameter of the annular cast steel ingot. d 锭外 The outer diameter of the ring-shaped cast steel ingot. The value range is 1.05-1.

15.

8. The preparation method according to claim 3, characterized in that, In step (2), the diameter of the disc-shaped cast steel ingot ,in, d 1 The diameter of the disc-shaped cast steel ingot. V 成 The volume of the low-defect hob cutter ring.

9. The preparation method according to claim 3 or 8, characterized in that, In step (3), cutting the disc-shaped cast steel ingot includes: First, calculate the cutting height according to the diameter and upsetting ratio of the disc-shaped cast steel ingot as shown in Formula 2), and then cut the disc-shaped cast steel ingot according to the cutting height. Equation 2); In Equation 2), d 1 The diameter of the disc-shaped cast steel ingot. m The upsetting ratio is 1.5-2.

10. The preparation method according to claim 3 or 8, characterized in that, In step (3), the upsetting process includes heating the cut disc-shaped cast steel ingot to 1150-1200℃ for upsetting.

11. The preparation method according to claim 3 or 8, characterized in that, In step (3), the inner diameter of the punched steel ingot is larger than the inner diameter of the low-defect hobbing cutter ring, and its outer diameter is smaller than the outer diameter of the low-defect hobbing cutter ring. The difference between the inner diameter of the punched steel ingot and the inner diameter of the low-defect hobbing cutter ring is 10-30mm smaller than the difference between the outer diameter of the punched steel ingot and the outer diameter of the low-defect hobbing cutter ring. The height of the punched steel ingot is 60-90mm.

12. A tunneling machine, characterized in that, The tunneling machine includes the low-defect roller cutter ring as described in claim 1 or 2.

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