Safety wheel for rubber wheel metro vehicle bogie and preparation method of safety wheel

Abstract

The invention discloses a safety wheel for a rubber wheel metro vehicle bogie and a preparation method of the safety wheel. The wheel comprises the following chemical components in percentage by mass: 0.52%-0.60% of C, 0.30%-0.40% of Si, 0.70%-0.80% of Mn, less than or equal to 0.015% of P, less than 0.010% of S, 0.20%-0.30% of Cr, 0.05%-0.23% of Ni, 0.04%-0.06% of V, (60-80) * 10 <-4%) of N, less than or equal to 0.012% of Al, less than or equal to 0.005% of Ti and the balance of Fe and inevitable impurities. The composition proportion of N and Al is controlled by adjusting C and adding V, so that the volume fraction of the tread ferrite reaches 5-12%, and the volume fraction of the rim reaches 10-16%; meanwhile, the metallurgical quality is controlled, the proportion of plastic inclusions is larger than or equal to 90%, the proportion of the size below 10 micrometers is larger than 85%, and the wrapping rate is larger than or equal to 80%. And finally, the average value of the fracture toughness of the wheel is larger than or equal to 85 MPam1 / 2, the unit value is larger than or equal to 80 MPam1 / 2, the rolling contact fatigue resistance is remarkably improved, and the cracking risk of large-size inclusions is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of railway wheel preparation, and in particular, the present application relates to a safety wheel for a bogie of a rubber-tyred metro vehicle and a preparation method thereof. BACKGROUND

[0002] Urban rail transit is an important way for citizens to travel. With the acceleration of urbanization and the rapid development of urban rail transit, the running smoothness, riding comfort and running safety of vehicles are also increasingly demanding. The wheel is a key running component of the rail vehicle, and the repeated action of wheel-rail contact stress and vibration impact during service can easily lead to surface use damage such as wheel non-circularization, affecting the running safety of the vehicle and the riding experience.

[0003] In the face of the increasingly scarce urban land space resources, some large cities have to consider small curve radii when building new metro lines or in mountainous countries and regions. In this situation, in order to meet the needs of citizens for metro and riding comfort, rubber-tyred metro vehicles are becoming more and more popular. Rubber-tyred metro vehicles, i.e. using rubber wheels as running wheels, while traditional steel wheels are used as "spare tires", i.e. so-called "safety wheels": during vehicle travel, when the rubber wheel encounters a flat tire or a blowout, the safety wheel can play a supporting, running and guiding role, fully ensuring the safe operation of the vehicle.

[0004] Due to the special shape of the safety wheel and its very important role, many vehicle manufacturers have put forward more stringent requirements for safety wheels, such as higher toughness matching, differentiated strength requirements for the wheel flange / tread, etc. Therefore, for the special design of the bogie safety wheel of the rail vehicle, the differentiated performance requirements and higher mechanical performance indicators make the research and development of the product face greater risks and challenges.

[0005] A Chinese patent with publication number CN115558765A discloses a wheel with reduced hardness near the surface of the tread and a production method thereof. The invention adopts an intermittent quenching method for the tread, and through "weak-stop-strong" intermittent heat treatment cooling, first uses flow L1 to spray the wheel tread, after the flow L1 spraying is completed, the wheel is placed at the natural environment temperature for 5-15s, and then switches to flow L2 to spray the wheel tread. The flow L1 is 1 / 6-1 / 5 of the flow L2. The continuous quenching time t1 of L1 follows the formula: t1=227.6xC+74.5xSi+11.5x(1.2xCr+1.8xMo+Ni)+54.6xV-82.3. This method can reduce the hardness near the surface of the wheel tread, and basically does not reduce the internal hardness of the tread subsurface and the rim. However, this patent still has the problem of optimizing the quenching process parameters, and needs to further adjust the matching relationship of flow L1 and L2, the setting of quenching time t1 and t2, the rotational angular velocity of the wheel during quenching, etc. to improve the performance and quality of the wheel.

[0006] A Chinese patent with publication number CN115558745A discloses a city rail vehicle wheel with a narrow hardness range and a production method thereof. The invention adopts appropriate high temperature tempering, so that C in the cementite is "heat activated", and with the passage of time, C diffusion causes the cementite to "twist→deform→break→gather→grow", the lamellar pearlite will crack and spheroidize, and the adjacent ferrite will be squeezed together under the action of thermal expansion, accelerating the cracking and spheroidizing of the cementite, and finally forming granular pearlite, resulting in a decrease in hardness. However, this patent still has the problem of precise control of tempering temperature and holding time, and needs to precisely control the tempering temperature and holding time through experiments and actual operation experience to obtain better wheel performance and service life. SUMMARY

[0007] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a safety wheel for a bogie of a rubber-tyred metro vehicle, which aims to realize differential control of the organization and performance of the tread and the rim part of the wheel, so as to make the wheel obtain excellent tough matching performance and effectively improve the wear resistance and service life of the wheel.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a safety wheel for a bogie of a rubber-tyred metro vehicle, comprising the following mass percentage components: C: 0.52-0.60%, Si: 0.30-0.40%, Mn: 0.70-0.80%, P≤0.015%, S<0.010%, Cr: 0.20-0.30%, Ni: 0.05-0.23%, V: 0.04-0.06%, N: (60-80) x 10 -4%, Al: ≤0.012%, Ti: ≤0.005%, the balance being Fe and unavoidable impurity elements.

[0009] The composition of the safe wheel also satisfies: 0.5 ≤ Fn1= w (N) / w (Al) < 1.0.

[0010] The functions of the key elements in the wheel steel of the application are as follows: C element: C is one of the elements that contribute most to the hardness of the wheel, and increasing the C content in the wheel steel can significantly improve the hardness of the wheel, thereby improving the wear resistance, but too high content of C will reduce the plasticity and toughness of the wheel. A safe wheel for a bogie of a rubber-tyred metro vehicle needs to consider both wear resistance and plasticity and toughness, and therefore a medium C content design should be adopted, and therefore the range of C content is determined to be 0.52-0.60%.

[0011] Si element: adding Si element can improve the strength and hardness of the wheel through solid solution strengthening, and at the same time, the phase transition point Ac3 of the wheel steel is improved, which helps to improve the thermal damage resistance of the wheel, but too high Si will increase the hot working sensitivity and brittleness of the wheel steel, and therefore the range of Si content is determined to be 0.30-0.40%.

[0012] Mn element: Mn can be dissolved in the matrix structure to improve the stability of austenite structure, thereby improving the strength and hardness of ferrite and pearlite, but excessive Mn will destroy the hot plasticity of the steel during hot rolling, and at the same time, it will also reduce the room temperature plasticity of the steel, and therefore the range of Mn content is determined to be 0.70-0.80%.

[0013] Cr element: Cr is a relatively inexpensive beneficial element in steel, and appropriate addition can improve the stability of supercooled austenite, reduce the transformation temperature and increase the supercooling degree, and has a significant effect of refining the pearlite interlamellar spacing, but if the Cr content is too high, it will significantly reduce the volume fraction of ferrite, which is not conducive to plasticity and toughness, and therefore the range of Cr content is determined to be 0.20-0.30%.

[0014] Ni element: the main function of Ni is to improve the toughness of the matrix structure and refine the pearlite interlamellar spacing, and it also has a good strengthening effect on ferrite, but if the Ni content exceeds 0.25%, the iron oxide scale of the steel billet is not easy to be removed during heating of the rolled steel, and therefore the range of Ni content is determined to be 0.05-0.23%.

[0015] V element: V is the main precipitated strengthening element in the steel, which combines with the interstitial atoms such as C and N in the steel to form a dispersed V(C, N) second phase particle, which produces strong precipitation strengthening effect. The undissolved V forms a second phase particle at the grain boundary, which has the effect of pinning the grain boundary and refining the grain. In addition, V also acts as a ferrite-forming element, which can promote the precipitation of ferrite during the transformation of undercooled austenite, thereby further improving the plasticity and toughness of the steel. Therefore, considering the strength and toughness matching and the economy of alloy composition, the range of V content is determined to be 0.04-0.06%.

[0016] N element: N dissolved in the steel combines with Ti, Al, V and other elements to form second phase particles with good thermal stability, which are segregated on the grain boundary and play a role in pinning the grain boundary during hot working. In theory, the higher the N content, the greater the driving force for the precipitation of second phase particles, the more the number of precipitated particles, and the more obvious the effect of precipitation strengthening and grain refinement. However, too high N content will form "subcutaneous needle" and other defects on the surface of the slab, therefore, considering the stability of N control process during steelmaking, the range of N content is determined to be (60-80) x 10 -4 %。

[0017] Al element: Al is the main deoxidizer in the steel, which exists in the steel in the form of acid-soluble aluminum and insoluble aluminum. Acid-soluble aluminum is equivalent to alloying elements in the steel, while insoluble aluminum forms alumina inclusions. Acid-soluble aluminum dissolved in the matrix can combine with N to form AlN second phase. For V-containing steel, Al and V form a competitive relationship, both of which compete for N in the steel. Therefore, the presence of Al has an adverse effect on the combination of V and N, thereby affecting the role of V in strength and toughness matching. Therefore, considering the deoxidation effect and "N competition" relationship, the upper limit of Al content is determined to be 0.012%.

[0018] Ti element: Since Ti is a carbon and nitrogen compound forming element, strict control of the Ti content in the steel can avoid the competition with V, ensure the effective combination of V and N, and fully exert the essential advantages of V in strength and toughness matching. In addition, the combination of Ti and N can form TiN cubic phase, which damages the plasticity and toughness of the matrix due to its sharp edges. Therefore, considering the current steelmaking process level, the upper limit of Ti content is limited to 0.005%.

[0019] The safety wheel is composed of a wheel body and a web, and does not contain a hub, wherein the wheel body comprises a rim and a tread, the hardness of the wheel body at a position 6mm below the surface of the tread is greater than or equal to 269HB, the tensile strength Rm of the wheel body at a position 6mm below the surface of the tread is greater than or equal to 900MPa, the elongation A after fracture is greater than 14%, the single value of the impact energy Kv2 at room temperature is greater than or equal to 10J, the hardness of the wheel body at a position 21mm below the surface of the tread is greater than or equal to 262HB, the hardness of the wheel body at a position 30mm below the surface of the top end of the rim is less than or equal to 255HB, the tensile strength Rm of the wheel body at a position 30mm below the surface of the top end of the rim is less than or equal to 860MPa, the elongation A after fracture is greater than 14%, and the single value of the impact energy Kv2 at room temperature is greater than or equal to 10J.

[0020] The outer diameter of the tread of the safety wheel is 880-910mm with the middle part of the tread as a reference; the outer diameter of the rim of the safety wheel is 1020-1030mm with the top end of the rim as a reference; the thickness of the tread part is 20-30mm; and the height difference between the rim and the tread is 55-70mm.

[0021] The tensile strength Rm of the web part of the safety wheel is less than or equal to 880MPa, the elongation A after fracture is greater than 14%, and the single value of the impact energy Kv2 at room temperature is greater than or equal to 10J.

[0022] The web part of the safety wheel is uniformly provided with 10 straight holes with a diameter of φ20-φ25mm and 4 threaded holes with a diameter of M12-M16mm in the circumferential direction, which are used for mounting a brake disc.

[0023] The microstructure of the safety wheel is pearlite + a small amount of ferrite, the proeutectoid ferrite is distributed in a network chain or intermittent network shape on the grain boundary, the actual grain size is 6-8 levels, the volume fraction of ferrite at the tread part is 5-12%, the pearlite interlamellar spacing is 130-160nm, the volume fraction of ferrite at the rim part is 10-16%, and the pearlite interlamellar spacing is 150-190nm.

[0024] The application further provides a preparation method of the safety wheel for a bogie of a rubber-tyred metro vehicle.

[0025] The preparation process of the wheel steel comprises a smelting step, wherein the content of S in the molten steel is controlled to be 0.005%-0.009% and the content of T.O (total oxygen content) in the molten steel is controlled to be less than or equal to 12ppm during smelting, and the molten steel is stirred by using an electromagnetic stirring device.

[0026] The preparation process of the wheel steel further comprises a continuous casting step, wherein a strong cooling process is adopted during continuous casting, and the solidification cooling rate of the molten steel is greater than or equal to 60℃ / min.

[0027] Before the wheel is heat treated, only the tread surface is rough-machined to be profiled, the single-side machining amount is 4-6mm, and the rest of the wheel rim surface is not profiled.

[0028] The heat treatment comprises: firstly, heating the wheel blank as a whole into a heating furnace, sufficiently austenitizing the wheel blank, then transferring the wheel blank out of the heating furnace to a horizontal quenching platform for continuous jet cooling water, after the jet quenching is finished, heating and holding the wheel blank as a whole into the heating furnace, and finally, tempering the wheel blank.

[0029] The austenitizing uniform temperature is 850-880 DEG C, and the total time is 2-2.5 h.

[0030] The horizontal quenching platform is provided with six cooling spray guns in the circumferential direction, and the water flow of each spray gun is 18-21 tons / hour.

[0031] The wheel blank jet quenching duration is 150-180 s.

[0032] The austenitizing uniform temperature is 850-880 DEG C, and the total time is 2-2.5 h.

[0033] The safety wheel for a bogie of a rubber-tyred metro vehicle and the preparation method have the following beneficial effects: 1) By rationally matching the chemical composition of ''adjusting C, controlling N and Al'', the precipitation of pro-eutectoid ferrite is fully promoted, the volume fraction of ferrite in the tread part is 5-12%, and the volume fraction of ferrite in the rim part is 10-16%; in addition, the metallurgical quality control of plastic inclusions wrapping brittle inclusions further improves the toughness of the wheel steel matrix from the physical metallurgical mechanics, the proportion of plastic inclusions is ≥90%, the proportion of sizes below 10 mu m is > 85%, the wrapping rate of plastic inclusions is ≥80%, the average value of fracture toughness is ≥85 MPa.m1 / 2, and the single value is ≥80 MPa.m1 / 2, so that the rolling contact fatigue resistance of the wheel in the service process is significantly improved, and the risk of cracking caused by large-size inclusions is reduced.

[0034] 2) By using a differential jet quenching process control, the rim and tread parts obtain completely different structures and properties, the hardness of the position 6 mm below the surface of the tread part is ≥269 HB, while the tensile strength Rm of the position is ≥900 MPa, the hardness of the position 21 mm below the surface of the tread part is ≥262 HB, while the hardness of the position 30 mm below the surface of the rim part is ≤255 HB, while the tensile strength Rm of the position is ≤860 MPa, not only the user's customized use requirements are met, but also the differential performance regulation of the wheel is realized, a good strength and toughness match is obtained, and the train operation safety is improved.

[0035] 3) The prepared safety wheel for a bogie of a rubber-tyred metro vehicle can adapt to the terrain conditions of small curve radius, when the rubber tire meets deflation or tire burst, the safety wheel can play a supporting, running and guiding role, and fully guarantees the safe operation of the vehicle. Attached Figure Description

[0036] This manual includes the following figures, which illustrate the following: Figure 1 This is a schematic diagram of ductile MnS inclusions encapsulating brittle Al2O3 inclusions in the safety wheel steel of Example 1. Figure 2 A schematic diagram of the blank outline, finished product outline, and processing path of a safety wheel; Figure 3 A schematic diagram showing the location of test points for the cross-sectional hardness of a safety wheel. Figure 4 A schematic diagram showing the sampling locations for impact and tensile tests on different parts of the safety wheel; Figure 5 A schematic diagram of the sampling location for fracture toughness testing of the wheel tread area for safety purposes; Figure 6 For example, the safety wheel of Example 1 (corresponding to) Figure 4 Microscopic tissue diagram of the area marked b in the middle; Figure 7 For Example 2, the safety wheel (corresponding) Figure 4 Microscopic tissue diagram of the area marked b in the middle; Figure 8 For Example 3, the safety wheel (corresponding) Figure 4 Microscopic tissue diagram of the area marked b in the middle; Figure 9 For Example 3, the safety wheel (corresponding) Figure 4 Microscopic tissue diagram (marked at M in the middle); Figure 10 Chemical composition (wt%) of the wheels used in the examples and comparative examples; Figure 11 The cross-sectional hardness and tensile mechanical properties of the wheels used in the examples and comparative examples are shown. Figure 12 The room temperature impact energy and fracture toughness of the wheels used in the examples and comparative examples; The diagram is marked as follows: 1. Tread surface; 2. Wheel blank; 3. Finished wheel; 4. Wheel flange; 5. Tread surface rough machining and profiling. Detailed Implementation

[0037] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0038] In a first aspect, the embodiments of the present application provide a safety wheel for a bogie of a rubber-tyred metro vehicle, comprising a wheel body and a web, and not containing a wheel hub. The wheel body is in a circular ring structure, the web is located at the center of the wheel body and is fixedly connected with the inner circular surface of the wheel body, the wheel body comprises a rim and a tread, the rim is connected with the tread, and the rim is located outside the tread.

[0039] Specifically, to adapt to the terrain conditions of small curve radius and meet the differentiated control of the mechanical properties of the rim and the tread, the embodiments of the present application provide a safety wheel for a bogie of a rubber-tyred metro vehicle and a preparation method thereof.

[0040] In the embodiments of the present application, the safety wheel comprises the following components in percentage by mass: C: 0.52-0.60%, Si: 0.30-0.40%, Mn: 0.70-0.80%, P≤0.015%, S<0.010%, Cr: 0.20-0.30%, Ni: 0.05-0.23%, V: 0.04-0.06%, N: (60-80)×10 -4 %, Al: ≤0.012%, Ti: ≤0.005%, and the balance is Fe and inevitable impurity elements.

[0041] In the embodiments of the present application, the components of the safety wheel also satisfy: 0.5≤Fn1<1.0, Fn1=w(N) / w(Al). The limitation of Fn1=w(N) / w(Al) is a key supplement to the chemical component control strategy of "controlling N by adding V and controlling Al": when Fn1 is in the interval of 0.5-1.0, a double control effect can be achieved: if the content of N is relatively high compared with Al (Fn1≥1.0), excessive N will preferentially combine with V to form coarse VN particles, which will weaken the dispersion strengthening effect; if the content of Al is relatively high compared with N (Fn1<0.5), the combination of V and N will be hindered, and relatively large AlN particles and a large number of brittle aluminum oxide inclusions will be preferentially generated in the steel, resulting in a decrease in the toughness of the wheel. The ratio of 0.5≤Fn1<1.0 can not only ensure the deoxidation effect of Al, but also form fine Al2O3 inclusions (as the core of MnS) in the steel and reserve space for the combination of V and N to form fine VN strengthening phase, thereby fully ensuring the precipitation driving force of the VN strengthening phase.

[0042] In the embodiments of the present application, the outer diameter of the tread is 880-910 mm based on the middle part of the tread; the outer diameter of the rim is 1020-1030 mm based on the tip point of the rim; the thickness of the tread part is 20-30 mm; and the height difference between the rim and the tread is 55-70 mm.

[0043] In the embodiments of the present application, the roughness value of all machined surfaces of the safety wheel is better than Ra 1.6.

[0044] In the embodiment of the present application, the static unbalance value of the safety wheel is ≤25g·m.

[0045] In the embodiment of the present application, in terms of mechanical strength, the hardness of the tread position of the wheel body at 6mm below the surface is ≥269HB, the tensile strength Rm of the tread position of the wheel body at 6mm below the surface is ≥900MPa, the elongation after fracture A is >14%, the impact energy Kv2 at room temperature is ≥10J, the hardness of the tread position at 21mm below the surface is ≥262HB, the hardness of the rim position of the wheel body at 30mm below the surface is ≤255HB, the tensile strength Rm of the rim position of the wheel body at 30mm below the surface is ≤860MPa, the elongation after fracture A is >14%, and the impact energy Kv2 at room temperature is ≥10J.

[0046] In the embodiment of the present application, the tensile strength Rm of the spoke position of the safety wheel is ≤880MPa, the elongation after fracture A is >14%, and the impact energy Kv2 at room temperature is ≥10J.

[0047] In the embodiment of the present application, 10 straight holes with a diameter of φ20-φ25mm and 4 threaded holes with a diameter of M12-M16mm are uniformly arranged in the circumferential direction of the spoke of the safety wheel, and are used for mounting the brake disc.

[0048] In the embodiment of the present application, in terms of fracture mechanics performance, the tread position has a higher fracture toughness, and the average value of the fracture toughness of the 6 CT25 samples uniformly distributed along the circumferential direction of the wheel is ≥85MPa·m1 / 2, and the single value is ≥80MPa·m1 / 2.

[0049] In the embodiment of the present application, the microstructure of the safety wheel is pearlite + a small amount of ferrite, the pro-eutectoid ferrite is distributed in a network chain or intermittent network on the grain boundary, the actual grain size is 6-8 levels, the volume fraction of ferrite in the tread position is 5-12%, and the pearlite interlamellar spacing is 130-160nm, the volume fraction of ferrite in the rim position is 10-16%, and the pearlite interlamellar spacing is 150-190nm.

[0050] The functions of the key elements in the wheel steel of the present application are as follows: C element: C is one of the elements that contribute most to the hardness of the wheel, increasing the C content in the wheel steel can significantly improve the hardness of the wheel, thereby improving the wear resistance, but too high content will reduce the plasticity and toughness of the wheel. A safety wheel for a rubber-tyred metro vehicle bogie needs to consider both wear resistance and plasticity and toughness, and therefore a medium C content design should be adopted, and therefore the range of C content is determined to be 0.52-0.60%.

[0051] Si element: adding Si element can improve the strength of the wheel by solid solution strengthening, and increase the phase transition point Ac3 of the wheel steel, which helps to improve the thermal damage resistance of the wheel, but too high Si will increase the hot working sensitivity and brittleness of the wheel steel, therefore, the range of Si content is determined as 0.30-0.40%.

[0052] Mn element: Mn can be dissolved in the matrix structure to improve the stability of austenite structure, thereby improving the strength of ferrite and pearlite, but excessive Mn will destroy the hot plasticity of the steel during hot rolling, and also reduce the room temperature plasticity of the steel, therefore, the range of Mn content is determined as 0.70-0.80%.

[0053] Cr element: Cr is a relatively inexpensive beneficial element in steel, and appropriate addition can improve the stability of undercooled austenite, reduce the transformation temperature and increase the undercooling degree, and has a significant effect on refining the pearlite interlamellar spacing, but if the Cr content is too high, it will significantly reduce the volume fraction of ferrite, which is not conducive to plasticity and toughness, therefore, the range of Cr content is determined as 0.20-0.30%.

[0054] Ni element: the main role of Ni is to improve the toughness of the matrix structure and refine the pearlite interlamellar spacing, and it also has a good strengthening effect on ferrite, but if the Ni content exceeds 0.25%, the iron oxide scale of the steel billet during heating is not easy to be removed, therefore, the range of Ni content is determined as 0.05-0.23%.

[0055] V element: V is the main precipitation strengthening element in steel, which combines with C, N and other interstitial atoms in steel to form dispersed V(C, N) second phase particles, producing strong precipitation strengthening effect, and the undissolved V forms second phase particles at the grain boundary, which can pin the grain boundary and refine the grain, and V also acts as a ferrite forming element to promote the precipitation of ferrite during the transformation of undercooled austenite, thereby further improving the plasticity and toughness of the steel, therefore, considering the matching of strength and toughness and the economy of alloy composition, the range of V content is determined as 0.04-0.06%.

[0056] N element: N dissolved in steel effectively combines with Ti, Al, V and other elements to form second phase particles with good thermal stability, which are segregated on the grain boundary and play a role in pinning the grain boundary during hot working. In theory, the higher the N content, the greater the driving force for the precipitation of second phase particles, the more the number of precipitated particles, and the more obvious the effect of precipitation strengthening and grain refinement, but too high N content will form "subcutaneous needle" and other defects on the surface of the billet, therefore, considering the stability of N control process during steelmaking, the range of N content is determined as (60-80) x 10 -4 %.

[0057] Al element: Al is the main deoxidizer in steel, which exists in steel in the form of acid-soluble aluminum and insoluble aluminum, the acid-soluble aluminum is equivalent to the alloying element in steel, and the insoluble aluminum forms alumina inclusions. The acid-soluble aluminum dissolved in the matrix can combine with N to form AlN second phase. For V-containing steel, Al and V constitute a competitive relationship, and jointly capture N in the steel, so the existence of Al adversely affects the combination of V and N, thereby affecting the role of V in the strength and toughness matching, therefore, considering the deoxidation effect and the "N competition" relationship, the upper limit of the content of Al is determined as 0.012%.

[0058] Ti element: because Ti is a carbon and nitride forming element, strictly controlling the content of Ti in steel can avoid the competitive relationship with V, ensure the effective combination of V and N, and fully exert the essential advantage of V in the strength and toughness matching. In addition, the combination of Ti and N can form TiN cubic phase, which damages the plasticity and toughness of the matrix due to its sharp edges and corners, therefore, in combination with the current steelmaking process level, the upper limit of the content of Ti is limited to 0.005%.

[0059] In a second aspect, the embodiment of the present application also provides a preparation method of a safety wheel for a bogie of a rubber-tyred metro vehicle, comprising: wheel steel preparation, integral forging, rolling, slow cooling treatment, heat treatment and machining.

[0060] In the embodiment of the present application, the preparation process of the wheel steel includes a smelting step. When smelting, the content of S in the molten steel is controlled to be 0.005%-0.009%, and the content of T.O (total oxygen content) in the molten steel is controlled to be ≤12ppm. An electromagnetic stirring device is used to stir the molten steel, so as to fully refine and disperse Al2O3.

[0061] In the embodiment of the present application, the preparation process of the wheel steel also includes a continuous casting step. When continuous casting, a strong cooling process is adopted, and the solidification cooling rate of the molten steel is ≥60℃ / min. During solidification, fine Al2O3 inclusions are used as non-homogeneous nucleation points to promote the precipitation of granular MnS plastic inclusions in a uniform dispersed state between secondary dendrites, thereby reducing the size of the MnS plastic inclusions. At the same time, the plastic MnS inclusions also achieve effective wrapping of the brittle Al2O3 inclusions. The wrapped Al2O3 inclusions can significantly reduce the "inlaid stress" of the brittle inclusions on the matrix, further improve the toughness of the wheel steel matrix from the perspective of physical metallurgical mechanics, thereby improving the rolling contact fatigue resistance of the wheel during service and reducing the risk of rim cracking.

[0062] In the embodiment of the present application, the reason for controlling the content of S in the molten steel is that when the content of S in the steel is ≥0.010%, it is easy to cause the number and size of sulfide inclusions in the steel to exceed the standard, and when the content of S in the steel is <0.005%, the number is insufficient to ensure the wrapping rate.

[0063] In the embodiment of the present application, before the heat treatment of the wheel, only the tread surface is roughed and profiled, and the remaining wheel rim surface is not profiled, with a single-side machining amount of 4-6mm.

[0064] In the embodiment of the present application, the heat treatment comprises: firstly, heating the wheel blank as a whole in a heating furnace, fully austenitizing the wheel blank, then transferring the wheel blank out of the heating furnace to a horizontal quenching platform for continuous water spray cooling, after the water spray quenching, heating and holding the wheel blank as a whole in the heating furnace, and finally, tempering the wheel blank.

[0065] In the embodiment of the present application, the austenitizing uniform temperature is 850-880℃, and the total time is 2-2.5h.

[0066] In the embodiment of the present application, during the water spray quenching of the wheel blank, the water flow is controlled to only spray the tread surface, so as to ensure that the rim portion is not affected by the cooling water, i.e. to ensure that the rim portion is always in the "red steel" state during the entire water spray quenching process.

[0067] In the embodiment of the present application, the horizontal quenching platform is provided with six cooling spray guns distributed in the circumferential direction, and the water flow of each spray gun is 18-21 tons / hour.

[0068] In the embodiment of the present application, the water spray quenching duration of the wheel blank is 150-180s.

[0069] In the embodiment of the present application, the uniform temperature during the tempering of the wheel blank is 490-520℃, and the total heating time is 4-6h.

[0070] Through the above technical solution, the differential control of the structure and performance of the wheel tread and the rim portion is realized, at the same time, through the chemical composition regulation of "adjusting C, adding V and controlling N, Al", and through the selection of the quenching heating temperature to control the dissolution ratio of V in the steel, the precipitation of proeutectoid ferrite is promoted, so that the wheel has excellent strength and toughness matching performance, and the wear resistance and service life of the wheel are effectively improved.

[0071] Embodiment 1-Embodiment 3 A safety wheel for a bogie of a rubber-tyred metro vehicle, comprising the following mass percentage components: as shown in Figure 10 , Figure 10 The remaining amount not shown is Fe and inevitable impurities.

[0072] Comparative Example 1-Comparative Example 6 A safety wheel for a bogie of a rubber-tyred metro vehicle, comprising the following mass percentage components: as shown in Figure 10 , Figure 10 The remaining amount not shown is Fe and inevitable impurities. Embodiment 1

[0073] In Example 1, the chemical composition of the safety wheel is shown below. Figure 10 During the smelting of safety wheel steel, the sulfur content in the molten steel is precisely controlled to 0.005%, and the total oxygen (TO) content is controlled to 9 ppm. Strong electromagnetic stirring is used to fully refine and disperse Al2O3. A strong cooling process is employed during continuous casting, with the solidification cooling rate of the molten steel at 60℃ / min. During solidification, fine Al2O3 inclusions act as heterogeneous nucleation sites, promoting the uniform dispersion of granular MnS plastic inclusions between secondary dendrites. The average size of the MnS plastic inclusions is 8.6 μm, and they account for 91% of the total inclusions. Simultaneously, ... Figure 1 As shown, the ductile MnS inclusions also effectively encapsulate the brittle Al2O3 inclusions, with an Al2O3 inclusion encapsulation rate of 83%. The encapsulated Al2O3 inclusions can significantly reduce the "embedding stress" of the brittle inclusions on the matrix, further improving the toughness of the wheel steel matrix from the perspective of physical metallurgy and mechanics, thereby improving the wheel's resistance to rolling contact fatigue during service and reducing the risk of rim cracking.

[0074] In Example 1, the safety wheel is manufactured using processes such as integral forging and rolling, slow cooling, heat treatment, and machining. Before the heat treatment of the wheel, such as... Figure 2 As shown, only the tread surface is rough-machined and contoured, with a single-sided machining amount of 4mm, while the rest of the rim surface is not contoured. During heat treatment, the austenitizing temperature of the safety wheel was controlled at 880℃, and the total time was 2 hours. Based on the solid solubility product relationship of CV and NV in the steel, i.e., lg([V]·[C])γ=6.72-9500 / T, lg([V]·[N])γ=3.63-8700 / T (where the unit of temperature T is K; compared with the C content, since the N content is lower, the combination of dissolved V and C is considered here in order to calculate the proportion of dissolved V), it can be ensured that all V in the steel is dissolved. During the spray quenching process, the water flow is controlled to spray only on the tread surface of the safety wheel to ensure that the rim is not affected by the cooling water, that is, to ensure that the rim is always in the "red steel" state throughout the spray quenching process. Six cooling spray guns are evenly distributed around the circumference of the horizontal quenching table, with a water flow rate of 21 tons / hour for each spray gun and a spray quenching duration of 150 seconds. The tempering temperature of the safety wheel is 520℃, and the total heating time is 4 hours.

[0075] After heat treatment, according to Figure 2The following machining path is used to obtain a finished safety wheel: including a wheel body and spokes, excluding the hub. The wheel body includes a rim and a tread. The outer diameter of the finished safety wheel tread is 880mm, the outer diameter of the rim is 1020mm, the thickness of the tread is 20mm, and the height difference between the rim and the tread is 55mm. The spokes are uniformly provided with 10 φ20mm straight holes and 4 M12mm threaded holes around their circumference for mounting brake discs. The surface roughness of all machined surfaces is better than Ra 1.6; the static imbalance value is 15g•m.

[0076] The present invention achieves differentiated control over the microstructure and properties of the wheel tread and rim. Simultaneously, by adjusting the chemical composition through "adjusting C and adding V to control N and Al", and by controlling the dissolution ratio of V in the steel (controlled between 50% and 100%) through the selection of quenching heating temperature, the precipitation of proeutectoid ferrite is synergistically promoted, enabling the wheel to obtain excellent strength and toughness matching performance, effectively improving the wear resistance and service life of the wheel.

[0077] Comparative Example 1: The chemical composition of the safety wheel in Comparative Example 1 is shown in [reference needed]. Figure 10 Compared to Example 1, the main reinforcing elements such as C, Si, Mn, and Cr in the wheel composition of Comparative Example 1 are lower, but the contents of S and TO are higher. w (N) / w The (Al) value is basically the same as in Example 1, and the steelmaking process involving plastic inclusions is also employed. The heat treatment and subsequent processing are completely consistent with those in Example 1.

[0078] like Figures 3-4 As shown, section hardness and tensile mechanical properties tests were conducted on the wheels of Example 1 and Comparative Example 1. The results are shown in [the table / document / etc.]. Figure 11 It can be seen that, compared with the wheel of Example 1, the hardness and strength of the wheel of Comparative Example 1 are relatively low. It does not meet the strength design requirements of a hardness ≥269HB at 6mm below the surface of the tread, a tensile strength Rm ≥900MPa at this location, and a hardness ≥262HB at 21mm below the surface of the tread.

[0079] like Figures 4-5 As shown, room temperature impact and fracture toughness tests were conducted on the wheels of Example 1 and Comparative Example 1. The results are shown in [the table / document / etc.]. Figure 12 It can be seen that the impact performance and fracture toughness level of the wheel of Example 1 are basically the same as those of Comparative Example 1.

[0080] Example 1: Wheel (corresponding) Figure 4 The microstructure at point b) is as follows Figure 6As shown, the microstructure of the wheel is pearlite with a small amount of ferrite. The proeutectoid ferrite is distributed in a network pattern on the grain boundaries, with an actual grain size of 6.5. The ferrite volume fraction in the tread area is 11±0.5%, and the pearlite lamellar spacing is 153±4 nm. Example 2

[0081] Example 2: Chemical composition of the safety wheel (see below) Figure 10 During the smelting of safety wheel steel, the sulfur content in the molten steel is precisely controlled to be 0.009%, and the total oxygen (TO) content is controlled to be 11 ppm. Strong electromagnetic stirring is used to fully refine and disperse Al2O3. During continuous casting, a strong cooling process is used, with the solidification cooling rate of the molten steel being 63℃ / min. During solidification, the fine Al2O3 inclusions serve as heterogeneous nucleation particles, promoting the uniform dispersion precipitation of granular MnS plastic inclusions between secondary dendrites. The average size of the MnS plastic inclusions is 8.9 μm, accounting for 93% of the total inclusions, while the Al2O3 inclusion coverage rate is 82%.

[0082] Example 2: The safety wheel is manufactured using processes such as integral forging and rolling, slow cooling, heat treatment, and machining. Before the wheel's heat treatment, such as... Figure 2 As shown, only the tread surface is rough-machined and contoured, with a single-sided machining allowance of 6mm; the remaining rim surfaces are not contoured. During heat treatment, the austenitizing homogenization temperature of the safety wheel is controlled at 850℃, with a total time of 2.5h. According to the formula calculation, this ensures that more than 50% of the V solid solution matrix is ​​maintained. During the quenching process, the water flow is controlled to spray only onto the tread surface of the safety wheel, ensuring that the rim is not affected by the cooling water, thus ensuring that the rim remains in a "red steel" state throughout the quenching process. Six cooling spray guns are evenly distributed circumferentially on the horizontal quenching table, with a water flow rate of 18 tons / hour for each gun and a quenching duration of 180s. The tempering homogenization temperature of the safety wheel is 490℃, with a total heating time of 6h.

[0083] After heat treatment, according to Figure 2 The following machining path is used to obtain a finished safety wheel: including a wheel body and spokes, excluding the hub. The wheel body includes a rim and a tread. The outer diameter of the finished safety wheel tread is 910mm, the outer diameter of the rim is 1030mm, the thickness of the tread is 30mm, and the height difference between the rim and the tread is 75mm. The spokes are evenly provided with 10 φ25mm straight holes and 4 M16mm threaded holes for mounting brake discs. The surface roughness of all machined surfaces is better than Ra 1.6; the static imbalance value is 20g•m.

[0084] Comparative Example 2: The chemical composition of the safety wheel in Comparative Example 2 is shown in [reference needed]. Figure 10Compared with Example 2, the main strengthening elements such as C, Si, Mn, Cr, V in the wheel component of Comparative Example 2 are higher, but the contents of S and T.O are lower, and the contents of P and S are lower w (N) / w The (Al) value is basically the same as that of Example 2, and the plastic inclusion wrapping steelmaking process is also adopted. The process is completely consistent with that of Example 2 in terms of heat treatment and subsequent processing.

[0085] As shown in Figures 3-4 , the cross-section hardness and tensile mechanical property tests are carried out on the wheels of Example 2 and Comparative Example 2, and the results are shown in Figure 11 . It can be seen that, compared with the wheel of Example 2, the hardness and strength of the wheel of Comparative Example 2 are higher, which does not meet the design requirements of hardness ≤255HB at a position 30mm below the surface of the rim and tensile strength Rm≤860MPa at the same position.

[0086] As shown in Figures 4-5 , the normal temperature impact and fracture toughness tests are carried out on the wheels of Example 2 and Comparative Example 2, and the results are shown in Figure 12 . It can be seen that, compared with the wheel of Example 2, the impact performance and fracture toughness of the wheel of Comparative Example 2 are significantly reduced, and do not meet the toughness design requirements of average fracture toughness ≥85MPa·m1 / 2 and single value ≥80MPa·m1 / 2.

[0087] The microstructure of the wheel of Example 2 (corresponding to the position marked b in Figure 4 ) is shown in Figure 7 . It can be seen that the microstructure of the wheel is pearlite + a small amount of ferrite, and the proeutectoid ferrite is discontinuously distributed in the form of a network on the grain boundary. The actual grain size is 7.5 levels, the volume fraction of ferrite at the tread position is 5.3±0.2%, and the pearlite interlamellar spacing is 134±3nm. Example 3

[0088] The chemical composition of the safety wheel of Example 3 is shown in Figure 10 . During smelting, the S content in the molten steel is accurately controlled to be 0.007%, the T.O content in the steel is controlled to be 9ppm, the Al2O3 is fully refined and dispersed by strong electromagnetic stirring, the strong cold process is adopted during continuous casting, the solidification cooling rate of the molten steel is 65℃ / min, the fine Al2O3 inclusions are used as heterogeneous nucleation sites during solidification, which promotes the uniform dispersion of granular MnS plastic inclusions between the secondary dendrites, the average size of the MnS plastic inclusions is 8.5μm, the proportion of the MnS plastic inclusions in the total inclusions is 92%, and the wrapping rate of the Al2O3 inclusions is 85%.

[0089] The safety wheel of Example 3 is manufactured by the processes of whole forging + rolling forming, slow cooling treatment, heat treatment, machining, etc.: before the heat treatment of the wheel, the wheel is subjected to the processes of Figure 2As shown, only the tread surface is roughed and profiled first, with a single-side machining amount of 5 mm, and the rest of the rim surface is not profiled. When heating for heat treatment, the austenitizing uniform temperature of the safety wheel is controlled to be 860°C, and the total time is 2.5 h; according to the formula calculation, it can be ensured that more than 77% of V is dissolved in the matrix; in the spray quenching process, the water flow is controlled to only spray the tread surface of the safety wheel, ensuring that the rim part is not affected by the cooling water, i.e. ensuring that the rim part is always in the "red steel" state during the entire spray quenching process, and the horizontal quenching table is evenly distributed in the circumferential direction with 6 cooling spray guns, the water flow of each spray gun is 20 tons / hour, and the spray quenching duration is 180 s; the tempering uniform temperature of the safety wheel is 500°C, and the total heating time is 5 h.

[0090] After heat treatment, the safety wheel is machined according to the path shown to obtain the finished product safety wheel: including the wheel body, the web plate, and not containing the hub, wherein the wheel body includes the rim and the tread, the outer diameter of the tread of the finished product safety wheel is 898 mm, the outer diameter of the rim is 1024 mm, the thickness of the tread part is 25 mm, and the height difference between the rim and the tread is 62 mm; the web plate is evenly provided with 10 straight holes of φ23 mm and 4 threaded holes of M14 mm in the circumferential direction for mounting the brake disc; the roughness value of all machined surfaces is better than Ra 1.6; and the static unbalance value is 17 g·m. Figure 2

[0091] Comparative Example 3: The chemical composition of the safety wheel of Comparative Example 3 is shown in Table 2. Figure 10 The main strengthening elements C, Si, Mn, Cr, V, and the contents of S and T.O in the wheel composition of Comparative Example 3 are basically the same as those of Example 3. In terms of heat treatment and subsequent processing, the process is completely consistent with Example 3. The difference lies in that: the contents of N and Al in the wheel of Comparative Example 3 are not controlled, and the plastic inclusion wrapping steelmaking process is not used. w (N) / w (Al) value is not controlled, and the plastic inclusion wrapping steelmaking process is not used.

[0092] As shown in Table 3, the cross-section hardness and tensile mechanical property tests are performed on the wheels of Example 3 and Comparative Example 3, and the results are shown in Table 4. Figures 3-4 As shown in Table 3, the cross-section hardness and tensile mechanical property tests are performed on the wheels of Example 3 and Comparative Example 3, and the results are shown in Table 4. Figure 11 As can be seen, the hardness and strength levels of the wheels of Example 3 and Comparative Example 3 are basically the same.

[0093] As shown in Table 3, the cross-section hardness and tensile mechanical property tests are performed on the wheels of Example 3 and Comparative Example 3, and the results are shown in Table 4. Figures 4-5 As shown in Table 3, the cross-section hardness and tensile mechanical property tests are performed on the wheels of Example 3 and Comparative Example 3, and the results are shown in Table 4. Figure 12 As can be seen, compared with the wheel of Example 3, the impact performance and fracture toughness level of the wheel of Comparative Example 3 are obviously reduced, the scattering difference is obviously increased, and the toughness design requirements of fracture toughness average ≥ 85 MPa·m1 / 2 and single value ≥ 80 MPa·m1 / 2 are not met.

[0094] ​Example 3: Wheel (corresponding) Figure 4 The microstructure at point b) is as follows Figure 8 As shown, the microstructure of the wheel is pearlite with a small amount of ferrite. The proeutectoid ferrite is distributed in a discontinuous network on the grain boundaries, with an actual grain size of 7.0. The ferrite volume fraction in the tread area is 8.5±0.2%, and the pearlite lamellar spacing is 144±5 nm.

[0095] Example 3: Wheel (corresponding) Figure 4 Microstructure at point M (marked in the middle) such as Figure 9 As shown, the microstructure of the wheel is pearlite with a small amount of ferrite. The proeutectoid ferrite is distributed in a network pattern on the grain boundaries, with an actual grain size of 7.0. The volume fraction of ferrite in the rim is 14.4±0.2%, and the interlamellar spacing of pearlite is 169±3 nm.

[0096] Comparative Example 4: The chemical composition of the safety wheel in Comparative Example 4 is shown in [reference needed]. Figure 10 Its chemical composition is basically the same as that of Example 3, and the content of S and TO in the steel is also the same. w (N) / w The (Al) value is basically the same as in Example 3, and the steelmaking process involving plastic inclusions is also used. The subsequent processing is completely consistent with Example 3. The difference lies in the fact that the austenitizing homogenization temperature of the safety wheel is controlled at 840°C during heat treatment; all other process control parameters are completely consistent with Example 3.

[0097] like Figures 3-4 As shown, section hardness and tensile mechanical properties tests were conducted on the wheel of Comparative Example 4. The results are shown in [the table / document / etc.]. Figure 11 It can be seen that, compared with the wheel of Example 3, the wheel of Comparative Example 4 has lower hardness and strength, and does not meet the strength design requirements of hardness ≥269HB at 6mm below the tread surface, tensile strength Rm ≥900MPa at this location, and hardness ≥262HB at 21mm below the tread surface.

[0098] like Figures 4-5 As shown, room temperature impact and fracture toughness tests were conducted on the wheel of Comparative Example 4, and the results are shown in [Figure Number]. Figure 12 It can be seen that the impact performance and fracture toughness level of the wheel in Comparative Example 4 are basically the same as those in Example 3.

[0099] Comparative Example 5: The chemical composition of the safety wheel in Comparative Example 5 is shown in [reference needed]. Figure 10 Its chemical composition is basically the same as that of Example 3, and the content of S and TO in the steel is also the same. w (N) / wThe (Al) value is basically the same as that of Example 3, and the plastic inclusion wrapping steelmaking process is also adopted. In terms of subsequent processing, the process is completely consistent with that of Example 3. The difference lies in that, when the heat treatment heating is carried out, the austenitizing uniform temperature of the control safety wheel is controlled to be 890°C, and the rest of the process control parameters are completely consistent with those of Example 3.

[0100] As shown in Figures 3-4 , the cross-section hardness and tensile mechanical property tests are carried out on the wheel of Comparative Example 5, and the results are shown in Figure 11 . It can be seen that, compared with the wheel of Example 3, the hardness and strength of the wheel of Comparative Example 5 are higher, which does not meet the strength design requirements of the hardness ≤255HB at the position 30mm below the surface of the rim part and the tensile strength Rm≤860MPa at the position.

[0101] As shown in Figures 4-5 , the normal temperature impact and fracture toughness tests are carried out on the wheel of Comparative Example 5, and the results are shown in Figure 12 . It can be seen that, compared with the wheel of Example 3, the impact performance and fracture toughness level of the wheel of Comparative Example 5 are obviously reduced, and do not meet the toughness design requirements of the average value of fracture toughness ≥85MPa·m1 / 2 and the single value ≥80MPa·m1 / 2.

[0102] Comparative Example 6: The chemical composition of the safety wheel of Comparative Example 6 is shown in Figure 10 . The chemical composition is basically the same as that of Example 3, and the contents of S and T.O in the steel and the (Al) value are basically the same as those of Example 3. w (N) / w The (Al) value is basically the same as that of Example 3, and the plastic inclusion wrapping steelmaking process is also adopted. In terms of subsequent processing, the process is completely consistent with that of Example 3. The difference lies in that, when the heat treatment heating is carried out, the austenitizing uniform temperature of the control safety wheel is controlled to be 890°C, and the rest of the process control parameters are completely consistent with those of Example 3.

[0103] As shown in Figures 3-4 , the cross-section hardness and tensile mechanical property tests are carried out on the wheel of Comparative Example 6, and the results are shown in Figure 11 . It can be seen that the hardness and strength levels of the tread part of the wheel of Comparative Example 6 and the strength level of the web part are basically the same as those of Example 3, but the hardness and strength of the rim part of the wheel of Comparative Example 6 are obviously higher, which does not meet the strength design requirements of the hardness ≤255HB at the position 30mm below the surface of the rim part and the tensile strength Rm≤860MPa at the position.

[0104] As shown in Figures 4-5The normal temperature impact and fracture toughness tests were conducted on the wheel of Comparative Example 6, and the results are shown in Table 2. Figure 12 It can be seen that the impact performance, fracture toughness level of the tread portion and the impact performance level of the web portion of the wheel of Comparative Example 6 are basically equivalent to those of Example 3, but the impact performance level of the rim portion of the wheel of Comparative Example 6 is obviously reduced.

[0105] The above detailed description of the safety wheel for a bogie of a rubber-tyred metro vehicle and the preparation method thereof according to the reference examples is illustrative rather than restrictive, and several examples can be listed within the limited range, and thus the changes and modifications without departing from the general concept of the present application shall fall within the protection scope of the present application.

Claims

1. A safety wheel for a bogie of a rubber-tyred metro vehicle, characterized in that, The safe wheel comprises the following mass percentage components: C: 0.52-0.60%, Si: 0.30-0.40%, Mn: 0.70-0.80%, P≤0.015%, S<0.010%, Cr: 0.20-0.30%, Ni: 0.05-0.23%, V: 0.04-0.06%, N: (60-80) x 10 -4 %, Al: ≤0.012%, Ti: ≤0.005%, the balance being Fe and unavoidable impurity elements.

2. The safety wheel for a bogie of a rubber-tyred metro vehicle according to claim 1, characterized in that, The components of the safe wheel also satisfy: 0.5 ≤ Fn1 w (N) / w (Al) < 1.

0.

3. The safety wheel for a bogie of a rubber-tyred metro vehicle according to claim 1, characterized in that, The safe wheel is composed of a wheel body and a web, wherein the wheel body comprises a rim and a tread, the hardness of the tread part of the wheel body at 6mm below the surface is ≥269HB, the tensile strength Rm of the tread part of the wheel body at 6mm below the surface is ≥900MPa, the elongation after fracture A is >14%, the single value of the impact energy Kv2 at room temperature is ≥10J, the hardness of the tread part at 21mm below the surface is ≥262HB, the hardness of the rim part of the wheel body at 30mm below the surface is ≤255HB, the tensile strength Rm of the rim part of the wheel body at 30mm below the surface is ≤860MPa, the elongation after fracture A is >14%, and the single value of the impact energy Kv2 at room temperature is ≥10J.

4. The safety wheel for a bogie of a rubber-tyred metro vehicle according to claim 3, characterized in that, The outer diameter of the tread is 880-910mm with the middle part of the tread as the reference; the outer diameter of the rim is 1020-1030mm with the tip of the rim as the reference; the thickness of the tread part is 20-30mm; and the height difference between the rim and the tread is 55-70mm.

5. The safety wheel for a bogie of a rubber-tyred metro vehicle according to any one of claims 1 to 4, characterized in that, The tensile strength Rm of the web part of the safe wheel is ≤880MPa, the elongation after fracture A is >14%, and the single value of the impact energy Kv2 at room temperature is ≥10J.

6. The safety wheel for a bogie of a rubber-tyred metro vehicle according to any one of claims 1 to 4, characterized in that, The web part of the safe wheel is uniformly provided with 10 straight holes with a diameter of φ20-φ25mm and 4 threaded holes with a diameter of M12-M16mm in the circumferential direction for mounting a brake disc.

7. The safety wheel for a bogie of a rubber-tyred metro vehicle according to any one of claims 1 to 4, characterized in that, The microstructure of the safe wheel is pearlite + a small amount of ferrite, the proeutectoid ferrite is distributed in a network chain or intermittent network on the grain boundary, the actual grain size is 6-8 levels, the volume fraction of ferrite in the tread part is 5-12%, the pearlite interlamellar spacing is 130-160nm, the volume fraction of ferrite in the rim part is 10-16%, and the pearlite interlamellar spacing is 150-190nm.

8. A method of manufacturing the safety wheel for a bogie of a rubber-tyred underground vehicle according to any one of claims 1 to 7, characterized in that, The preparation method comprises the following steps: wheel steel preparation, integral forging, rolling, slow cooling treatment, heat treatment, and machining.

9. The method of claim 8, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: The preparation process of the wheel steel comprises a smelting step, wherein the S content in the molten steel is controlled to be 0.005%-0.009% and the T.O content in the molten steel is controlled to be ≤12ppm during smelting, and the molten steel is stirred by using an electromagnetic stirring device; ​ The preparation process of the wheel steel further comprises a continuous casting step, wherein a strong cooling process is adopted during continuous casting, and the solidification cooling rate of the molten steel is ≥60℃ / min.

10. The method of claim 8, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: Before the heat treatment of the wheel, only the tread surface is rough-machined to be profiled, the single-side machining amount is 4-6mm, and the remaining wheel rim surface is not profiled. ​ 11. The method for manufacturing a safety wheel for a rubber-tired subway car bogie according to any one of claims 8 to 10, characterized in that, The heat treatment comprises the following steps: firstly, the wheel blank is heated in an integral manner, the wheel blank is fully austenitized, the wheel blank is transported out of the heating furnace, the wheel blank is continuously sprayed with cooling water on a horizontal quenching table, the wheel blank is heated and kept in the heating furnace after the end of the water spraying and quenching, and finally, the wheel blank is tempered.

12. The method of claim 11, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: The austenitizing uniform temperature is 850-880℃, and the total time is 2-2.5h.

13. The method of claim 11, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: The horizontal quenching table is uniformly provided with 6 cooling spray guns in the circumferential direction, and the water flow rate of each spray gun is 18-21 tons / hour. ​ 14. The method of claim 11, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: The wheel blank is sprayed and quenched for 150-180s. ​ 15. The method of claim 11, wherein the safety wheel for a bogie of a rubber-tyred metro vehicle is prepared by the steps of: The uniform temperature during the tempering treatment of the wheel blank is 490-520℃, and the total heating time is 4-6h. ​

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