Vacuum brazing high-toughness bainite tooth body and preparation method thereof

Abstract

The invention relates to a vacuum brazing high-toughness bainite tooth body and a preparation method thereof, belongs to the technical field of steel for tooth bodies, and is used for solving at least one of the problems that high hardness and high toughness of an existing cutting tooth body cannot be considered under the cold condition of a vacuum brazing furnace, and the preparation method is large in pollution, high in cost and the like. Through reasonable component design and strict control of technological parameters in the preparation process, the prepared tooth body has high strength and high toughness. Mn and Cr elements are combined for use, so that the stability of supercooled austenite can be guaranteed, formation of ferrite is inhibited, bainite transformation is promoted to occur in a low-temperature phase region, and the width of a bainite lath is refined; si and Al elements are combined for use, so that separation of cementite in the bainite transformation process can be inhibited, and the stability of retained austenite is improved; nb and Ti are combined for use, so that grain coarsening in the brazing temperature rising and heat preservation stage can be inhibited, and meanwhile microalloy carbide is dispersed and separated out. The alloy elements are combined for use, so that a high-proportion bainite structure can be obtained, and the strength and the toughness of the vacuum brazing tooth body are improved.

Description

Technical Field

[0001] This invention relates to the field of steel for tooth bodies, and in particular to a vacuum brazed high-strength and high-toughness bainitic tooth body and its preparation method. Background Technology

[0002] As a core rock-breaking tool in engineering machinery and mining, cutting picks endure high-frequency impacts, severe wear, and complex stress loads over long periods, directly affecting the equipment's working efficiency and service life. With the development of large-scale and intelligent mining equipment, the problems of insufficient strength-toughness matching and rapid wear resistance degradation in traditional cutting pick steel have become increasingly prominent. Especially under extreme conditions such as hard rock tunneling, they are prone to fracture, chipping, or premature failure, severely restricting the reliability and safety of the equipment. Therefore, developing new cutting picks that combine ultra-high strength, excellent toughness, and good wear resistance has become an urgent industry need.

[0003] Currently, domestic and international manufacturers of cutting tools generally use induction brazing for production. While this significantly reduces brazing costs, it requires immediate quenching after brazing, leading to insufficient shear strength in the brazed layer and a high risk of alloy head detachment during service. In recent years, vacuum induction brazing technology has matured. By utilizing the pressure difference between the molten solder pool and the external environment, it can rapidly expel gases from the brazing area, effectively improving the weld fill factor and enhancing the shear strength of the brazed layer. However, current mainstream cutting tool bodies still utilize traditional materials such as 42CrMo and 35CrMnSi, which undergo quenching-tempering. These materials cannot form martensite in the furnace-cooling and air-cooling environments following vacuum brazing, resulting in insufficient hardness.

[0004] CN 120591689A discloses a method for preparing high wear-resistant cutting teeth. By rapidly transferring the brazed cutting teeth into a salt bath at 220–260°C and holding them for 0.2–2 hours, the tooth body is strengthened and toughened. However, the salt bath treatment in this method causes significant environmental pollution, and the long holding time for isothermal quenching severely restricts production efficiency, resulting in high production costs. CN 111468797A discloses a vacuum induction brazing device and its usage method, which can balance high vacuum and high heating efficiency. However, the complex mechanical structure makes sample transfer after vacuum brazing relatively difficult, and rapid quenching cannot be completed, resulting in insufficient tooth body strength and toughness. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a vacuum brazed high-strength and high-toughness bainitic tooth body and its preparation method, so as to solve at least one of the problems of existing cutting tooth bodies being unable to simultaneously achieve high hardness and high toughness under the cold conditions of vacuum brazing furnace, and the preparation method being highly polluting and costly.

[0006] In a first aspect, the present invention provides a vacuum brazed high-strength and high-toughness bainitic cutting tooth body, wherein the chemical composition of the cutting tooth body, by mass percentage, is: C 0.28%–0.32%, Si 0.50%–1.20%, Al 0.50%–1.00%, Mn 2.80%–3.50%, Cr 0.15%–1.50%, Mo 0.15%–0.25%, Nb 0.01%–0.03%, Ti 0.01%–0.025%, N≤0.005%, P≤0.02%, S≤0.005%, with the remainder being Fe and unavoidable impurities.

[0007] Furthermore, the chemical composition of the cutting tooth body also satisfies the following conditions: 3.0% ≤ Mn + Cr ≤ 4.5%, 1.0% ≤ Si + Al ≤ 2.0%, and 0.025% ≤ Nb + Ti ≤ 0.055%.

[0008] Furthermore, the microstructure of the cutting tooth body includes bainite, and the volume percentage of the bainite is ≥90%.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned cutting tooth body, comprising the following steps:

[0010] Step 1: Prepare the raw materials according to the composition of the cutting tooth body, and obtain the casting billet through smelting and casting;

[0011] Step 2: Homogenize the cast billet;

[0012] Step 3: After descaling the homogenized billet, roll it to obtain a round bar;

[0013] Step 4: Forge and machine the round bar to obtain the cutting tooth body.

[0014] Furthermore, in step 2, the homogenization treatment temperature is 1180–1250°C, and the holding time is 2–5 hours.

[0015] Furthermore, in step 3, the initial rolling temperature is 1080–1150°C, and the final rolling temperature is 860–930°C.

[0016] Furthermore, in step 4, the holding temperature for forging is 950–1000℃, the final forging temperature is 820–860℃, and the compression ratio is ≥8.

[0017] Thirdly, the present invention provides a cutting tooth, including the tooth body described above.

[0018] Fourthly, the present invention provides a method for preparing the cutting tooth, comprising the following steps: placing the tooth body, cemented carbide head, brazing filler and flux in a vacuum brazing setup, heating to the brazing temperature and holding at that temperature, and furnace cooling to room temperature to obtain the cutting tooth.

[0019] Furthermore, the brazing temperature is 890–970°C, and the holding time is 2–30 minutes.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. This invention, through rational composition design, produces tooth bodies with high strength and high toughness. The combined use of Mn and Cr elements ensures the stability of supercooled austenite, inhibits ferrite formation, and promotes bainite transformation in the low-temperature phase region, thereby refining the bainite lath width. The combined use of Si and Al elements inhibits cementite precipitation during bainite transformation, improving the stability of retained austenite. The combined use of Nb and Ti elements inhibits grain coarsening during the brazing heating and holding stages, while simultaneously dispersing microalloyed carbides. The combined use of these alloying elements helps to obtain a high proportion of bainite microstructure, enhancing the strength and toughness of the vacuum brazed tooth body.

[0022] 2. The high-strength and tough tooth steel alloy composition of the present invention has good compatibility with the vacuum brazing process. 3.0%≤Mn+Cr≤4.5% can ensure the stability of supercooled austenite and avoid the formation of ferrite or pearlite during the cooling process, resulting in a microstructure with a bainite content of over 90%. 1.0%≤Si+Al≤2.0% can suppress the precipitation of cementite, avoid the precipitation of carbides during the slow cooling stage, and improve the carbon atom utilization efficiency. 0.025%≤Nb+Ti≤0.055% can refine the original austenite grains, avoid coarse austenite grains during the brazing heating process, and further improve the hardness and toughness of the cutting teeth.

[0023] 3. The high-strength and tough bainitic tooth body provided by this invention has better overall performance. Compared with traditional tooth bodies, it has better strength and toughness under vacuum brazing conditions, room temperature impact energy AKU2≥40J, hardness≥42HRC, which can improve the service life and reliability of cutting teeth.

[0024] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 The OM diagram of the tooth body prepared in Example 1 of the present invention is shown.

[0027] Figure 2 This is a SEM image of the tooth body prepared in Example 1 of the present invention;

[0028] Figure 3 This is a physical image of the cutting teeth prepared in Example 1 of the present invention. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] A specific embodiment of the present invention discloses a vacuum brazed high-strength and high-toughness bainitic cutting tooth body. The chemical composition of the cutting tooth body, by mass percentage, is as follows: C 0.28%–0.32%, Si 0.50%–1.20%, Al 0.50%–1.00%, Mn 2.80%–3.50%, Cr 0.15%–1.50%, Mo 0.15%–0.25%, Nb 0.01%–0.03%, Ti 0.01%–0.025%, N≤0.005%, P≤0.02%, S≤0.005%, with the remainder being Fe and unavoidable impurities.

[0031] The reasons for limiting the steel composition of the vacuum brazed high-strength and high-toughness bainitic tooth body and its preparation method in this invention will be explained. Hereinafter, only the mass percentage of the composition is expressed as %.

[0032] Carbon (C) is a key solid solution strengthening element in high-strength and high-toughness bainitic steel, directly affecting the hardness, strength, and hardenability of the bainitic phase. Carbon atoms can significantly improve the strength of steel and promote the stabilization of retained austenite during the bainitic transformation, thereby enhancing the toughness and impact resistance of the material. However, excessively high carbon content increases the brittleness of the bainitic structure, reducing impact toughness and weldability. Therefore, considering the requirements for strength, toughness, brazing adaptability, and wear resistance, this invention controls the carbon content to 0.28%–0.32%, for example, 0.28%, 0.29%, 0.30%, 0.31%, and 0.32%.

[0033] Silicon (Si): Exists in steel in solid solution form, effectively inhibiting cementite precipitation during bainite transformation, promoting the formation of fine bainitic ferrite laths, and optimizing the strength-toughness balance of the material. It also enhances the tempering resistance of steel, delays high-temperature softening, and strengthens the stability of cutting teeth under heavy-load impact and friction-wear conditions. Therefore, considering the overall strengthening effect, toughness, and brazing adaptability, this invention sets the Si content to 0.50%–1.20%, for example, 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 1.10%, and 1.20%.

[0034] Aluminum (Al): Exists in steel in solid solution form, which can regulate the bainitic phase transformation kinetics, increase the bainitic transformation rate, optimize production process efficiency, and, together with silicon, inhibit cementite precipitation. Aluminum can form AlN precipitates with nitrogen, improving steel cleanliness and optimizing material toughness. Therefore, considering oxidation resistance, grain refinement effect, and process adaptability, this invention controls the Al content at 0.50%–1.00%.

[0035] Manganese (Mn) is a key hardenability element in high-strength and high-toughness bainitic steel. It is inexpensive and provides excellent hardenability. It significantly improves austenite stability, lowers the bainite transformation temperature, and promotes the formation of fine lath bainite, thereby enhancing the strength and toughness of the steel. It effectively inhibits ferrite precipitation in high-temperature regions, increases the bainite transformation ratio during continuous cooling, and ensures the uniformity of microstructure in large-section workpieces. Therefore, considering hardenability, phase transformation control, and microstructure uniformity, this invention limits the Mn content to 2.80%–3.50%, for example, 2.80%, 2.90%, 3.00%, 3.10%, 3.20%, 3.30%, 3.40%, and 3.50%.

[0036] Chromium (Cr): As an important hardenability element in high-strength and high-toughness bainitic steel, it can significantly improve the hardenability of steel, refine the size of bainite lath bundles, and enhance tempering resistance, thereby improving the high-temperature strength and wear resistance of the steel. Considering the balance between hardenability, microstructure refinement, corrosion resistance, and processing performance, this invention limits the Cr content to 0.15%–1.50%, for example, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 1.0%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, and 1.5%.

[0037] Molybdenum (Mo): As a key microalloying element in bainitic steel, Mo can significantly improve hardenability and delay high-temperature phase transformation; it also refines the bainitic lath structure through the solute dragging effect, enhancing dislocation strengthening. Therefore, considering hardenability control, microstructure refinement, and economy, this invention optimizes the Mo content to 0.15%–0.25%, for example, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, and 0.25%.

[0038] Niobium (Nb) is a microalloying carbonitride forming element. During rolling, it can suppress recrystallization and refine the original austenite grains. Simultaneously, deformation-induced precipitation of nanoscale Nb(C,N) pins dislocations and grain boundaries, increasing the bainite nucleation density and refining the bainite lath bundle size. Therefore, considering grain refinement, precipitation strengthening, and process adaptability, the niobium content in this invention ranges from 0.01% to 0.03%, for example, 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, 0.02%, 0.022%, 0.024%, 0.026%, 0.028%, and 0.3%.

[0039] Titanium (Ti): A microalloying carbonitride forming element. The solid solubility of nitrides formed by Ti combining with N is lower than that of Nb, enabling the formation of titanium nitride at high temperatures. This refines austenite grains. However, excessive titanium content leads to the precipitation and significant coarsening of TiN in the liquid phase, negatively impacting the hot working performance of the gear teeth. Therefore, considering all factors, the titanium content in this invention ranges from 0.01% to 0.025%, for example, 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, 0.020%, 0.022%, 0.024%, and 0.025%.

[0040] Phosphorus (P): It is a harmful element in bainitic steel, and the phosphorus content in this invention does not exceed 0.02%.

[0041] Sulfur (S): It is a harmful element in bainitic steel. The sulfur content in this invention does not exceed 0.005%.

[0042] The high-strength and high-toughness bainitic tooth body of this invention has low cost. It adopts a medium-carbon Mn-Cr-Si / Al main element alloy design, combined with a small amount of Mo element and Nb and Ti composite microalloying, without the need to introduce expensive alloying elements, and the tooth body steel has good economic efficiency.

[0043] Specifically, the chemical composition of the cutting tooth body also satisfies the following conditions: 3.0% ≤ Mn + Cr ≤ 4.5%, for example, Mn + Cr is 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.5%; 1.0% ≤ Si + Al ≤ 2.0%, for example, Si + Al is 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%; and 0.025% ≤ Nb + Ti ≤ 0.055%, for example, Nb + Ti is 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%.

[0044] The high-strength and tough tooth steel alloy composition of this invention has good compatibility with the vacuum brazing process. The 3.0% ≤ Mn + Cr ≤ 4.5% composition can ensure the stability of supercooled austenite and avoid the formation of ferrite or pearlite during cooling, resulting in a microstructure with a bainite content of over 90%. The 1.0% ≤ Si + Al ≤ 2.0% composition can suppress the precipitation of cementite, avoid the precipitation of carbides during the slow cooling stage, and improve the carbon atom utilization efficiency. The 0.025% ≤ Nb + Ti ≤ 0.055% composition can refine the original austenite grains, avoid coarse austenite grains during the brazing heating process, and further improve the hardness and toughness of the cutting teeth.

[0045] This invention, through rational composition design and strict control of process parameters, produces tooth bodies with high strength and high toughness. The combined use of Mn and Cr elements ensures the stability of supercooled austenite, inhibits ferrite formation, and promotes bainite transformation in the low-temperature phase region, thereby refining the bainite lath width. The combined use of Si and Al elements inhibits cementite precipitation during bainite transformation and improves the stability of retained austenite. The combined use of Nb and Ti elements inhibits grain coarsening during the brazing heating and holding stages, while simultaneously dispersing microalloyed carbides. The combined use of these alloying elements helps to obtain a high proportion of bainite microstructure, improving the strength and toughness of the vacuum brazed tooth body.

[0046] Specifically, the microstructure of the cutting tooth body includes bainite, and the volume percentage of bainite is ≥90%.

[0047] Preferably, the microstructure of the tooth body further includes martensite / austenite islands (martensite + retained austenite) and microalloyed carbides, without proeutectoid ferrite.

[0048] Another specific embodiment of the present invention discloses a method for preparing the above-mentioned cutting tooth body, comprising the following steps:

[0049] Step 1: Prepare the raw materials according to the composition of the cutting tooth body, and obtain the casting billet through smelting and casting;

[0050] Step 2: Homogenize the cast billet;

[0051] Step 3: After descaling the homogenized billet, roll it to obtain a round bar;

[0052] Step 4: Forge and machine the round bar to obtain the cutting tooth body.

[0053] Specifically, in step 1, the smelting includes converter smelting, LF refining, RH or VD degassing, electromagnetic stirring treatment, and casting to obtain a billet.

[0054] Specifically, in step 2, the homogenization treatment temperature is 1180-1250℃, for example, 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, and the holding time is 2-5h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0055] It should be noted that in order to reduce elemental segregation in the tooth body and to take into account the grain coarsening caused by the high-temperature melting of titanium nitride particles, the homogenization temperature is controlled at 1180-1250℃. At the same time, the high Si and Al content in the tooth body leads to poor thermal conductivity, which easily causes cracking and incomplete burning. Therefore, the billet should be in the furnace for no less than 2-5 hours before continuous rolling.

[0056] Specifically, in step 3, the initial rolling temperature is 1080–1150℃, for example, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, or 1150℃, and the final rolling temperature is 860–930℃, for example, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, or 930℃.

[0057] It should be noted that if the final rolling temperature is too high, the hot-rolled austenite grains will be coarser, and the refining effect of titanium and niobium precipitates on the austenite grains during the hot rolling stage will be insignificant; if the final rolling temperature is too low, vanadium carbide particles will precipitate and coarsen prematurely, weakening the precipitation strengthening effect.

[0058] Specifically, in step 3, the diameter of the round bar is 28 to 45 mm, for example, 28 mm, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, or 45 mm.

[0059] Specifically, in step 4, the holding temperature for forging is 950-1000℃, for example, 950℃, 960℃, 970℃, 980℃, 990℃, or 1000℃, and the final forging temperature is 820-860℃, for example, 820℃, 830℃, 840℃, 850℃, or 860℃, and the compression ratio is ≥8, for example, 8, 9, 10, 11, 12, 13, or 14.

[0060] It should be noted that excessively high forging holding temperatures can lead to excessive austenite grain growth, while the re-dissolution of titanium and niobium carbonitrides weakens the subsequent precipitation strengthening effect. Conversely, excessively low holding temperatures significantly increase the resistance to hot deformation, making microcracks more likely and resulting in insufficient dynamic recrystallization, thus affecting the uniformity of the microstructure. When the compression ratio is insufficient, dendritic segregation and shrinkage cavities in the steel bar microstructure are difficult to break up completely, affecting the consistency of the steel bar's mechanical properties. However, excessively high compression ratios will significantly increase the equipment load and may lead to excessive core temperature rise, causing abnormal local grain growth.

[0061] Another specific embodiment of the present invention discloses a cutting tooth made from the above-described cutting tooth body.

[0062] Another specific embodiment of the present invention discloses a method for preparing a cutting tooth, comprising the following steps: placing the tooth body, brazing material and flux in a vacuum brazing setup, heating to the brazing temperature and holding at that temperature, and furnace cooling to room temperature to obtain the cutting tooth.

[0063] Specifically, the brazing temperature is 890–970℃, for example, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, and the holding time is 2–30 min, for example, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min.

[0064] It should be noted that excessively high brazing temperatures can lead to coarsening of the tooth grains, excessive spread and loss of the brazing filler metal, and even localized erosion. Conversely, excessively low temperatures result in insufficient fluidity of the brazing filler metal, making it difficult to achieve proper wetting and gap filling, thus reducing joint strength. Insufficient holding time leads to inadequate brazing filler metal diffusion and poor interfacial metallurgical bonding; excessive holding time can easily lead to the formation of brittle intermetallic compounds and increase the risk of grain growth.

[0065] Specifically, the furnace cooling rate is 0.3℃ / s to 3℃ / s above 500℃, for example, 0.3℃ / s, 0.5℃ / s, 0.7℃ / s, 0.9℃ / s, 1.1℃ / s, 1.3℃ / s, 1.5℃ / s, 1.7℃ / s, 1.9℃ / s, 2.1℃ / s, 2.3℃ / s, 2.5℃ / s, 2.7℃ / s, 2.9℃ / s, and 3℃ / s. The cooling rate is 0.01℃ / s to 0.3℃ / s between 500℃ and 200℃, for example, 0.01℃ / s, 0.05℃ / s, 0.10℃ / s, 0.15℃ / s, 0.2℃ / s, 0.25℃ / s, and 0.3℃ / s.

[0066] This invention employs a furnace cooling process that combines rapid cooling above 500°C with slow cooling. Rapid cooling above 500°C ensures efficient production of bainitic gear teeth. Slow cooling between 500°C and 200°C guarantees the full transformation of bainite, resulting in a microstructure with a bainite content exceeding 90%. Simultaneously, it reduces the cooling rate requirements above 500°C, preventing damage to vacuum brazing equipment due to excessive cooling. Below 200°C, the bainite transformation is complete, and there are no restrictions on the cooling rate.

[0067] In step 5, the brazing of the tooth body uses either resistance heating or induction heating. Resistance heating allows for precise temperature control and is suitable for uniform heating of complex-shaped teeth; induction heating has the advantages of rapid heating and a narrow heat-affected zone, making it suitable for localized heating of the tooth tip and helping to reduce the loss of matrix microstructure properties.

[0068] The high-strength and tough bainitic tooth body provided by this invention has superior overall performance. Compared with traditional tooth bodies, it has better strength and toughness under vacuum brazing conditions, room temperature impact energy AKU2≥40J, hardness≥42HRC, which can improve the service life and reliability of cutting teeth.

[0069] The advantages of precise control over the composition and process parameters of the high-strength and high-toughness bainitic tooth profile for vacuum brazing of the present invention are demonstrated below with specific embodiments and comparative examples. The chemical composition of the tooth profiles in the embodiments and comparative examples is shown in Table 1, the specific process parameters are shown in Table 2, and the mechanical properties of the bainitic cutting tooth profiles obtained during the preparation process are shown in Table 3.

[0070] Example

[0071] The raw materials are smelted in a converter, refined by LF refining, degassed by RH, electromagnetically stirred, and continuously cast into 280mm×280mm square billets. These billets are then cut into 8000mm long billets, rolled, and heated to 1180–1250℃, held for 2–5 hours, and descaled. After exiting the furnace, they are hot-rolled into steel bars with a diameter of 28–45mm. The initial rolling temperature is 1080–1150℃, and the final rolling temperature is 860–930℃. After hot rolling, the bars are air-cooled. The prepared round steel bars undergo pretreatment such as pickling to remove surface oxide scale. They are then hot-forged, with a forging holding temperature of 950–1000℃ and a final forging temperature of 820–860℃. The compression ratio is ≥8:1. Finally, the bars are machined to obtain the cutter teeth of the target dimensions.

[0072] Finally, the tooth body, cemented carbide head (YG8 tungsten steel), copper-based brazing filler and borax flux are assembled and placed in a vacuum brazing equipment. The equipment is heated to 890-970℃ for brazing, held for 2-30 minutes, and then furnace cooled to room temperature to obtain a high-strength and tough vacuum brazed cutting tooth. The cooling rate above 500℃ is 0.3℃ / s to 3℃ / s, and the cooling rate between 500-200℃ is 0.01℃ / s to 0.3℃ / s.

[0073] Comparative Example

[0074] The preparation method of the comparative example is similar to that of the example. The specific chemical composition of the tooth body is shown in Table 1. The process parameters in the preparation method are shown in Table 2. The mechanical properties of the cutting teeth prepared in the comparative example and the example are shown in Table 3.

[0075] Table 1. Chemical composition (%) of the steel used for the tooth bodies in the examples and comparative examples, with the balance being iron and unavoidable impurities.

[0076]

[0077]

[0078] Table 2. Process parameters during the preparation of the examples and comparative examples.

[0079]

[0080]

[0081] Table 3 Mechanical properties of the cutting teeth prepared by vacuum brazing in the examples and comparative examples.

[0082]

[0083] According to Table 3, the microstructure of the tooth body prepared by the present invention has a bainite volume fraction of ≥91%, preferably 91-97%, and also includes martensite + retained austenite with a volume fraction of ≤9%, preferably 3-9%, a hardness of ≥42.5HRC, preferably 42.5-45.8HRC, and a room temperature impact energy AKU2 ≥42J, preferably 42-85J.

[0084] The OM diagram of the tooth body prepared in Example 1 of this invention is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2 As shown, according to Figure 1 and Figure 2 It can be seen that the microstructure of the tooth body of the present invention is mainly bainite. A physical image of the cutting tooth prepared in Example 1 is shown below. Figure 3 As shown.

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A vacuum-brazed high-strength and high-toughness bainitic cutting tooth body, characterized in that, The chemical composition of the cutting tooth body, by mass percentage, is as follows: C 0.28%–0.32%, Si 0.50%–1.20%, Al 0.50%–1.00%, Mn 2.80%–3.50%, Cr 0.15%–1.50%, Mo 0.15%–0.25%, Nb 0.01–0.03%, Ti 0.01–0.025%, N≤0.005%, P≤0.02%, S≤0.005%, with the remainder being Fe and unavoidable impurities.

2. The vacuum brazed high-strength and high-toughness bainitic cutting tooth body according to claim 1, characterized in that, The chemical composition of the cutting tooth body also satisfies the following conditions: 3.0% ≤ Mn + Cr ≤ 4.5%, 1.0% ≤ Si + Al ≤ 2.0%, and 0.025% ≤ Nb + Ti ≤ 0.055%.

3. The vacuum brazed high toughness bainite tooth body of claim 1 wherein, The microstructure of the cutting tooth body includes bainite, and the volume percentage of bainite is ≥90%.

4. A method of manufacturing a pick body according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Prepare the raw materials according to the composition of the cutting tooth body, and obtain the casting billet through smelting and casting; Step 2: Homogenize the cast billet; Step 3: After descaling the homogenized billet, roll it to obtain a round bar; Step 4: Forge and machine the round bar to obtain the cutting tooth body.

5. The method of claim 4, wherein the tooth body is formed by, In step 2, the homogenization treatment temperature is 1180–1250℃, and the holding time is 2–5 hours.

6. The method of claim 4, wherein the tooth body is formed by, In step 3, the initial rolling temperature is 1080–1150°C, and the final rolling temperature is 860–930°C.

7. The method of claim 4, wherein the tooth body is formed by, In step 4, the holding temperature for forging is 950-1000℃, the final forging temperature is 820-860℃, and the compression ratio is ≥8.

8. A pick, comprising: Includes the tooth body as described in any one of claims 1-3 or the tooth body prepared by the method of any one of claims 4-7.

9. A method of manufacturing a pick according to claim 8, characterised in that, The process includes the following steps: placing the tooth body, carbide head, brazing filler and flux in a vacuum brazing setup, heating to the brazing temperature and holding at that temperature, then furnace cooling to room temperature to obtain the cutting tooth.

10. The method of claim 9, wherein the tooth is formed by, The brazing temperature is 890–970℃, and the holding time is 2–30 min.

Images