Steel for heavy-load wheel with high heat resistance and method for producing wheel by using steel

Abstract

The invention provides steel for a heavy-load wheel with high heat resistance and a method for producing the wheel. The steel comprises the following components: 0.70 to 0.77 percent of C, 0.20 to 0.40 percent of Si, 0.90 to 1.20 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, 0.30 to 0.40 percent of Cr, 0.10 to 0.20 percent of Ni, 0.05 to 0.15 percent of V, 0.05 to 0.10 percent of Zr, 0.003 to 0.010 percent of Ti, 0.002 to 0.005 percent of B, 0.0070 to 0.0120 percent of N and the balance of Fe and inevitable impurity elements. Compared with the prior art, Zr is added, and the high-temperature performance of the wheel steel is remarkably improved through the grain boundary strengthening effect; and B is added, so that the wheel steel can still keep relatively good strength and hardness in a high-temperature environment. A matched heat treatment process is designed, so that the toughness and the plasticity are kept at a relatively high level while the heat resistance is improved.

Description

Technical Field

[0001] The present invention belongs to the field of wheel production, and particularly relates to a steel for high heat-resistant heavy-duty wheels and a method for producing wheels therefrom. Background Art

[0002] With the rapid development of the economy, the demand for logistics is increasing continuously. The world's railway freight transportation is increasingly developing towards the direction of heavy load and high speed. From the development of the axle load and load of freight cars at home and abroad, the increase of axle load and load is the common trend and direction of the development of freight cars in various countries. Improving the axle load and running speed is an important measure commonly adopted in heavy-haul transportation around the world.

[0003] Railway heavy-haul transportation is used for the transportation of bulk goods, especially iron ore, coal, etc. Most of the heavy-haul transportation lines of these mineral deposits are slopes. At present, heavy-haul freight cars generally use wheel brake shoes for braking. The train braking process is actually an energy conversion process in which the kinetic energy of the train and the gravitational potential energy when going downhill are converted into frictional heat energy through the brake shoes and the wheel tread. Most of the frictional heat generated by braking is directly absorbed by the wheels, resulting in an increase in the temperature of the wheels. The increase of the train axle load, the increase of the running speed and the existence of the slope inevitably cause the overall temperature rise of the wheels to intensify, and the thermal fatigue damage of the wheels deteriorates. The wheel is one of the key load-bearing components of heavy-haul freight cars. The increasing thermal damage such as thermal cracks, spalling, and scuffing on the tread not only increases the cost of wheel turning, but more importantly, the frequent turning of the wheels greatly shortens the service life of the wheels.

[0004] Research at home and abroad shows that under certain working conditions, the overall temperature of the wheel rim may reach about 600 °C. Under extreme braking conditions, the temperature of the tread surface is even higher, and it may reach the phase transformation critical temperature of the material. The ability of wheel steel to resist thermal-mechanical fatigue damage and wear resistance at high temperatures both decrease significantly. It is found that for ordinary high-carbon wheel steel, when the temperature rises to 800 °F (427 °C), its strength is reduced to about 70% of that at room temperature; when it rises to 1000 °F (538 °C), the strength is only 40% of that at room temperature. The relatively low high-temperature strength will inevitably reduce the service life of the wheels running at high temperatures. Therefore, it is extremely important to study the ability of wheel steel to resist plastic deformation and failure under the combined action of high temperature and load, that is, the hot strength of wheel steel.

[0005] In addition, with the increase in train axle load and speed, the tendency of wheel-rail sliding is relatively large, and the service conditions of wheels have changed significantly compared with conventional usage conditions, posing higher requirements for the internal quality and organizational properties of wheels. However, the pearlitic structure of the wheel rim tread obtained during the high-temperature transformation of ordinary carbon steel wheels is insufficient to resist the resulting thermal damage. To meet the service conditions of heavy-haul railway freight car wheels and ensure that the wheels have high heat resistance, improving the ability of wheels to resist thermal fatigue damage has become a difficult point in the development of heavy-haul high-speed wheels. Worldwide, only the AAR D material wheels in the American standard AAR M107 / 208 have put forward high-temperature performance requirements, and the high-temperature performance indicators of wheels have not been mentioned in major system standards such as the European standard, Russian standard, and Chinese railway standard. In the research process of wheel steel, the index of thermal strength has rarely been mentioned. Summary of the Invention

[0006] The purpose of the present invention is to provide a steel for heavy-duty wheels with high heat resistance. By adding a small amount of strong carbide-forming element Zr, the high-temperature performance of the wheel steel is significantly improved through grain boundary strengthening; by adding trace element B, the wheel steel can still maintain good strength and hardness in a high-temperature environment.

[0007] Another purpose of the present invention is to provide a method for producing wheels using the steel for heavy-duty wheels with high heat resistance. According to the composition of the steel for heavy-duty wheels with high heat resistance, a matching heat treatment process system is designed to fully exert the potential of the wheel steel, while maintaining high levels of toughness and plasticity while improving heat resistance.

[0008] The specific technical solution of the present invention is as follows:

[0009] A steel for heavy-duty wheels with high heat resistance, comprising the following components in mass percentage (wt%):

[0010] C 0.70 - 0.77%, Si 0.20 - 0.40%, Mn 0.90 - 1.20%, P ≤ 0.015%, S ≤ 0.015%, Cr 0.30 - 0.40%, Ni 0.10 - 0.20%, V 0.05 - 0.15%, Zr 0.05 - 0.10%, Ti 0.003 - 0.010%, B 0.002 - 0.005%, N 0.0070 - 0.0120%, and the balance is Fe and inevitable impurity elements.

[0011] For the wheels produced from the steel for heavy-duty wheels with high heat resistance, the normal-temperature properties of the wheel rim: normal-temperature R m ≥1300 MPa, normal-temperature R p0.2 ≥920 MPa, elongation A ≥ 13%, reduction of area Z ≥ 35%;

[0012] The wheel produced from the steel for high heat-resistant heavy-duty wheels has the following high-temperature properties at 538°C for the rim: high-temperature R m ≥570 MPa, high-temperature R p0.2 ≥460 MPa, elongation A≥39%, reduction of area Z≥85%;

[0013] For the wheel produced from the steel for high heat-resistant heavy-duty wheels, under the high-temperature condition of 538°C, high-temperature R m is maintained at over 43% of the room-temperature Rm, i.e., high-temperature R m / high-temperature R m ≥0.43; high-temperature Rp 0.2 is maintained at over 49% of the room-temperature Rp 0.2 , i.e., high-temperature Rp 0.2 / high-temperature Rp 0.2 ≥0.49;

[0014] For the wheel produced from the steel for high heat-resistant heavy-duty wheels, the hardness of the rim cross-section at room temperature is ≥360 HB, and the hardness difference at the same depth below the tread is ≤15 HB; the impact energy K u of the rim at room temperature is ≥14.0 J, and the fracture toughness K q ≥43 MPa·m 1 / 2 .

[0015] For the wheel produced from the steel for high heat-resistant heavy-duty wheels, the wheel wear performance: under the conditions of a loading stress of 1200 MPa, a rotational speed of 1000 r·min -1 , and a number of cycles of 5×10 5 , the wear amount is ≤0.68 g; the fatigue crack growth threshold value ΔK th ≥2.50 MPa·m 1 / 2 .

[0016] The microstructure of the wheel produced from the steel for high heat-resistant heavy-duty wheels consists of fine pearlite with a lamellar spacing ≤100 nm and ferrite with a volume fraction ≤3%.

[0017] A method for producing a wheel from the steel for high heat-resistant heavy-duty wheels provided by the present invention includes a heat treatment process.

[0018] The wheel is heated and held as a whole, then cooled to the critical point A C3 ±5°C and held; then the wheel is taken out and air-cooled as a whole until the tread temperature reaches the critical point A c1 ±5°C, and then water-spray cooling is carried out; finally, tempering treatment is performed.

[0019] The heating and holding of the wheel as a whole means heating the wheel to A C3 +150°C, and the holding time is 0.5 - 1.5 h; heating the wheel to A C3The heating rate at +150°C is (10 - 20) °C / min;

[0020] Then cool it down to the critical point A again C3 Insulate at ±5°C for 0.5 - 1 h; the cooling rate is (5 - 10) °C / min;

[0021] Furthermore, the cooling rate of spray cooling is V 冷 , and the cooling time is t 冷 , the cooling rate V 冷 and the cooling time t 冷 respectively satisfy: V 冷

[0022] = 37.67 - 4×C - 0.575×Si - 0.73×Mn 2 - 0.53×Ni - 1.86×Cr - 13.33×V - 4.35×Zr - 17.6×B, and V 冷 is rounded to an integer according to the calculation result.

[0023] t 冷 = 4×rim thickness - 50, so that the inside of the rim is cooled below 600°C.

[0024] In the formula, the content of each element is the content of each element × 100%, the unit of the rim thickness is mm, the unit of the cooling rate V 冷 is °C / s, and the unit of the cooling time t 冷 is s.

[0025] When calculating with the above formula, directly substitute the value before the unit into the formula for calculation.

[0026] The cooling rate affects the phase transformation tissue products and is highly correlated with the chemical element composition of the material. The cooling rate formula is obtained by multivariate non - linear fitting to control the quantitative relationship between the actual cooling rate and the chemical elements of the material, so as to realize the mechanical properties and tissue composition of the wheels of the present invention; the cooling time depends on the rim thickness of the wheel. The greater the rim thickness, the longer the cooling time. Sufficient cooling time can ensure that the pearlite tissue transformation is completed in the entire cross - section of the rim, but too long cooling time will, on the one hand, affect the strong - plasticity matching between the rim and the spoke, and on the other hand, interfere with the production rhythm. The present invention realizes precise control of the cooling time for wheels with different rim thicknesses, taking into account the physical quality of the wheels and the production rhythm, and has strong applicability and safety.

[0027] Finally, the tempering treatment means that after the spray cooling is completed, the wheel enters the tempering heating furnace along the roller path for tempering treatment. The tempering temperature is (500 - 560) °C, and it is insulated for more than 4 hours, and then air - cooled to room temperature after tempering.

[0028] The heat - treated wheels are obtained as finished wheels through subsequent machining and other processes.

[0029] Preferably, the method for producing a wheel using the steel for heavy-duty wheels with high heat resistance includes an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process, continuously casting a round billet with a diameter of φ450mm, an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a wheel diameter of 965mm and a rim thickness of 60 - 75mm.

[0030] The design concept of the present invention is as follows:

[0031] So far, the steel for train wheels at home and abroad is medium and high carbon carbon steel with a ferrite - pearlite structure. Compared with other structures, this structure has the best wear resistance when the hardness level is the same. Therefore, the steel for the wheels of the present invention should have a ferrite - pearlite structure state.

[0032] Element C: C is the most important strengthening element in wheel steel and is the element that enables the steel to obtain the highest hardness. More than 50% of the strength in wheel steel comes from the strengthening of element C. C maintains good strengthening effects below 500°C. Even at 500°C, the strengthening effect can still reach 824 MPa / 1%C. However, once the temperature reaches 600°C, due to the aggregation, growth, and spheroidization of cementite, the strengthening effect decays to about half of that at room temperature. With the increase of C content, the normal temperature strength and hardness indexes of the wheels will be significantly improved, which promotes the improvement of high - temperature performance. Therefore, the C content in the present invention is controlled at a relatively high level of 0.70 - 0.77%.

[0033] Element Si: Si is one of the deoxidizing elements in steel. Si can increase the critical transformation temperature during heating and cooling of the steel, thereby reducing the probability of phase transformation due to braking heat and being beneficial to alleviating the generation of thermal damage defects. By increasing Si, the transformation of pearlite can be accelerated during cooling to prevent or reduce the martensite transformation. If pearlite can be generated rapidly, pearlite will be formed before the austenite reaches the martensite transformation start temperature. And the strengthening effect of Si decreases rapidly under high - temperature conditions. Therefore, the range of Si in the present invention is determined to be between 0.20 - 0.40%.

[0034] Element Mn: Mn is also an important strengthening element, which can play a role in solid - solution strengthening and phase - transformation strengthening, can effectively improve the hardenability of wheel steel, and has a significant effect on improving the hardness, wear resistance, yield strength, and toughness of wheel steel. The high - temperature strengthening effect of Mn element is obvious. It can stabilize the pearlite structure at high temperatures, reduce the thermal sensitivity of the steel, and reduce the thermal damage caused by braking. However, when the Mn content is too high, there is an obvious temper brittleness phenomenon, which promotes grain growth and increases the sensitivity to overheating, having an adverse impact on the comprehensive mechanical properties and processing performance of the wheels. The content requirement of Mn element in the present invention is controlled to be 0.90 - 1.20%.

[0035] P and S are impurity elements, so their contents should be controlled to not exceed 0.015%.

[0036] Element Cr: Cr is a strong carbide-forming element in steel, which can significantly improve the hardenability of steel, refine the lamellar spacing of pearlite, and increase the strength and hardness of wheel steel. In the temperature range of about 400 - 600 °C, the strength of the steel significantly decreases, and the wear resistance and rolling friction fatigue performance also decrease accordingly. Adding Cr element to the steel is beneficial to improving the high-temperature stability of cementite in the steel, making it not easy to spheroidize and grow, thereby improving the high-temperature strength and wear resistance of the steel. Element Cr shows strong high-temperature strengthening ability, but a higher Cr content will increase the brittle transition temperature of the steel and promote the temper brittleness of the steel. Therefore, in the present invention, the content of Cr is controlled at 0.30 - 0.40%.

[0037] Element Ni: Ni can expand the austenite region in steel and increase the hardenability of steel. Ni can dissolve infinitely in iron, playing a role in refining grains, reducing the resistance of dislocation movement, and enabling stress relaxation, which can significantly improve the strength and toughness of steel and enhance the heat resistance of steel. In the present invention, the content of Ni is controlled at 0.10 - 0.20%.

[0038] Element V: V produces a strong precipitation strengthening effect and contributes greatly to the room-temperature strength of wheel steel. The addition of V also has a certain influence on the microstructure of wheel steel. Under the heat treatment condition of normalizing, the induced phase transformation effect of V particles increases and refines the proeutectoid ferrite of wheel steel, making the structure more uniform. Therefore, V can improve the strength of wheel steel while also enhancing the plasticity and toughness of the steel. V is not very helpful for the high-temperature softening resistance of wheel steel. Element V basically does not enter cementite but exists alone in the form of precipitates of VC or V(C,N). In the present invention, the range of V is determined to be between 0.05 - 0.15%.

[0039] Element Zr: Zr is a strong carbide-forming element. It forms fine and dispersed carbides that precipitate at grain boundaries and has a significant grain boundary strengthening effect at high temperatures. Zr can dissolve in austenite and has a significant effect on increasing the hardenability, thereby improving its mechanical properties such as strength, hardness, and toughness. In addition, element Zr can not only deoxidize, strengthen, and refine steel but also improve properties such as corrosion resistance and heat resistance. However, excessive Zr element will lead to the formation of brittle inclusions. In the present invention, the content of Zr is controlled at 0.05 - 0.10%.

[0040] Ti element: As a strong carbide and nitride forming element, Ti preferentially combines with C and N to form high melting point TiC and TiN particles (<0.1 μm), effectively pinning the austenite grain boundaries, inhibiting grain coarsening at high temperatures, improving the grain size of the room temperature structure by 1 - 2 grades, and significantly enhancing the strength and toughness of the steel. In the controlled rolling and controlled cooling process, nano-scale TiC particles produce a precipitation strengthening effect, which can significantly increase the yield strength. In microalloyed steels, Ti is often added in combination with Nb and V to achieve better strengthening and toughening effects through synergistic effects. However, excessive Ti will form a "nitrogen competition" relationship with microalloying elements such as V and B, and there is also a potential risk of forming coarse inclusions, thus damaging the performance. In the present invention, the Ti content is controlled within 0.003 - 0.010%.

[0041] B element: Adding a small amount of B to steel can significantly improve the hardenability of the steel, and can even replace a large number of alloying elements such as Mn, Cr, Mo, etc., thereby reducing production costs. By adding B element, the bonding force of the grain boundaries is increased, high melting point phases are formed at the grain boundaries to strengthen the grain boundaries. B can significantly increase the hardness and tensile strength of the steel, improve its mechanical properties. B can also improve the high-temperature performance of the steel, enabling it to maintain good strength and hardness in high-temperature environments. However, excessive B has an adverse effect on the impact toughness and hot workability of the steel. The unique feature of B is that only a very small amount of addition can produce significant effects, which makes it of great value in the production of steel. Therefore, in the present invention, the B content is controlled within 0.002 - 0.005%.

[0042] N element: N can expand the austenite region and also play a role in solid solution strengthening. Nitrogen, like carbon, can dissolve in iron to form an interstitial solid solution. Nitrogen is a very strong element for forming and stabilizing austenite, and has a strong bonding force with vanadium. Increasing nitrogen in steel can not only promote the precipitation of vanadium, but also significantly refine the ferrite grains, giving full play to the grain refinement strengthening and precipitation strengthening effects of vanadium in steel, improving the strength of the steel while also greatly improving its toughness and plasticity. In the present invention, the range of N is determined to be (70 - 120)×10 -4 %.

[0043] Through appropriate microalloying measures and the use of a multi-stage heat treatment process system, the present invention fully exploits the strengthening and toughening potential of the wheel steel, develops heavy-duty wheels with high heat resistance, high plasticity and toughness, and has high resistance to mechanical damage and thermal damage, enabling the wheels to have excellent service performance.

[0044] The present invention adds a small amount of strong carbide forming element Zr to significantly improve the high-temperature performance of the wheel steel through grain boundary strengthening; adds a trace amount of B element to enable the wheel steel to maintain good strength and hardness in high-temperature environments. Moreover, in the subsequent heat treatment of the wheel, the quenching heating is rapidly heated to the critical temperature A C3Above the transformation point by 150 °C, full austenite transformation is completed at high temperature to prevent grain growth, and then the temperature is slowly decreased as a whole in the furnace to the critical temperature A C3 Nearby, it is insulated for a certain period of time to fully dissolve the carbide. During the subsequent cooling process, combined with the specific composition of the wheel steel, the cooling rate is controlled to achieve precise control of the cooling rate, inhibit the precipitation of cementite, and promote the formation of ferrite. While improving the heat resistance, the toughness and plasticity are maintained at a relatively high level.

[0045] Compared with the prior art, the present invention has obtained the following beneficial effects: Compared with the conventional AAR-C wheels, the strength of the heavy-duty wheels with high heat resistance, high plasticity and toughness developed by the present invention can be increased by 5-10%. Among them, the tensile strength at room temperature can stably reach ≥1300 MPa, the yield strength can stably reach ≥890 MPa, and the ratio of the tensile strength at high temperature to that at room temperature stably reaches ≥0.43, and the ratio of the yield strength at high temperature to that at room temperature stably reaches ≥0.49. In addition, the fracture toughness of the wheel at room temperature is stably ≥43 MPa·m 1 / 2 and has high resistance to mechanical damage and thermal damage, meeting the service performance of heavy-duty high-speed wheels. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the microstructure of the wheel produced in Example 1;

[0047] Figure 2 is the microstructure of the wheel produced in Example 2;

[0048] Figure 3 is the microstructure of the wheel produced in Example 3;

[0049] Figure 4 is the microstructure of the wheel produced in Comparative Example 1;

[0050] Figure 5 is the microstructure of the wheel produced in Comparative Example 2;

[0051] Figure 6 is the microstructure of the wheel produced in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0052] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] Example 1

[0054] A method for manufacturing a wheel using a steel for high heat-resistant heavy-duty wheels, comprising the following processes:

[0055] The molten steel with the chemical composition as in Example 1 in Table 1 is processed through an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (continuous casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 62 mm. The heat treatment process is as follows: First, the wheel is rapidly heated to 908 °C at a rate of 20 °C / min, held for 0.5 hour, then cooled to 760 °C at a rate of 10 °C / min and held for 0.5 hour; the wheel is air-cooled until the tread temperature reaches 725 °C and then water-spray cooled, with the cooling rate V 冷 controlled at 32 °C / s and the cooling time t 冷 198 s, so that the inside of the rim is cooled to below 600 °C. After cooling is completed, the wheel enters a tempering heating furnace along the roller table for tempering treatment. The tempering temperature is 560 °C, held for 4 hours, and then air-cooled to room temperature after tempering. The heat-treated wheel is obtained as a finished wheel through subsequent machining and other processes.

[0056] The mechanical properties of the wheel in Example 1 are shown in Tables 2-4. The wheels of the present invention have higher normal temperature tensile strength, yield strength, and cross-sectional hardness than the wheels of Comparative Example 1 without reducing the plasticity index, and higher high-temperature tensile strength and yield strength than the wheels of Comparative Example 1. At the same time, the fracture toughness and impact toughness are also at a relatively high level; in addition, the wear resistance of the wheels in Example 1 is also better than that of the wheels in Comparative Example 1, and the fatigue crack propagation threshold value ΔK th (i.e., the crack arrest performance) is greater than that of the wheels in Comparative Example 1. Combining the comparison with Figure 1 and Figure 4 it can be seen that the microstructure of Example 1 is uniform and fine, with a pearlite lamellar spacing of 97 nm + a ferrite volume fraction of 2.3%, which is the main factor for its better mechanical properties than the wheels of Comparative Example 1.

[0057] Example 2

[0058] A method for manufacturing a wheel using a steel for high heat-resistant heavy-duty wheels, comprising the following processes:

[0059] The molten steel with the chemical composition as shown in Example 2 of Table 1 is processed through the electric furnace steelmaking process, LF furnace refining process, RH vacuum treatment process, round billet continuous casting process (continuous casting into a round billet with a diameter of φ450 mm), ingot cutting and hot rolling process, heat treatment process, machining, and finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 67 mm. The heat treatment process is as follows: First, the wheel is rapidly heated to 913 °C at a rate of 15 °C / min, held for 0.75 hours, then cooled to 763 °C at a rate of 7 °C / min and held for 0.75 hours; the wheel is air-cooled until the tread temperature reaches 725 °C and then sprayed with water for cooling, and the cooling rate V 冷 is controlled at 31 °C / s, and the cooling time t 冷 is 218 s to cool the inside of the rim to below 600 °C. After cooling is completed, the wheel enters the tempering heating furnace with the roller table for tempering treatment. The tempering temperature is 530 °C, held for 5 hours, and then air-cooled to room temperature after tempering. The heat-treated wheel is obtained as a finished wheel through subsequent machining and other processes.

[0060] The mechanical properties of the wheel in Example 2 are shown in Table 2-4. The wheel in Example 2 has obtained significantly better comprehensive mechanical properties than the wheel in Comparative Example 2. Combining the comparison with Figure 2 and Figure 5 it can be seen that the microstructure of Example 2 is uniform and fine, with pearlite having a lamellar spacing of 95 nm + ferrite with a volume fraction of 2.1%, which is the main factor for its better mechanical properties than the wheel in Comparative Example 2.

[0061] Example 3:

[0062] A method for producing a wheel using a steel for high heat-resistant heavy-duty wheels includes the following processes:

[0063] The molten steel with the chemical composition as shown in Example 3 of Table 1 is processed through the electric furnace steelmaking process, LF furnace refining process, RH vacuum treatment process, round billet continuous casting process (continuous casting into a round billet with a diameter of φ450 mm), ingot cutting and hot rolling process, heat treatment process, machining, and finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 73 mm. The heat treatment process is as follows: First, the wheel is rapidly heated to 918 °C at a rate of 10 °C / min, held for 1 hour, then cooled to 768 °C at a rate of 5 °C / min and held for 1 hour; the wheel is air-cooled until the tread temperature reaches 726 °C and then sprayed with water for cooling. The cooling rate V is controlled at V 冷 30 °C / s, and the cooling time t 冷 is 242 s to cool the inside of the rim to below 600 °C. After cooling is completed, the wheel enters the tempering heating furnace with the roller table for tempering treatment. The tempering temperature is 510 °C, held for 5.5 h, and then air-cooled to room temperature after tempering. The heat-treated wheel is obtained as a finished wheel through subsequent machining and other processes.

[0064] In Example 3, the mechanical properties of the wheel are shown in Table 2-4. The wheel in Example 3 obtained comprehensive mechanical properties significantly superior to those of the wheel in Comparative Example 3. Combining the comparison of Figure 3 and Figure 6 , it can be seen that the microstructure of Example 3 is uniform and fine, with pearlite having a lamellar spacing of 94 nm and ferrite with a volume fraction of 2.0%. This is the main factor for its better mechanical properties than the wheel in Comparative Example 3.

[0065] Comparative Example 1:

[0066] A method for producing a wheel from a steel for wheels includes the following processes:

[0067] Molten steel with the chemical composition as shown in Table 1 for Comparative Example 1 is subjected to an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (continuous casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 63 mm. The heat treatment process is as follows: First, the wheel is heated to 860 ℃ , After heat preservation for 2.0 hours , Spray water to cool the wheel tread, and the cooling rate V 冷 of the tread is 40 °C / s, and the cooling time t 冷 is 270 s , and the inside of the rim is cooled to below 500 °C. After the cooling is completed, the wheel enters a tempering heating furnace with the roller table for tempering treatment, Tempering The temperature is 480 °C, insulated for 4.5 h, and after tempering, it is air-cooled to room temperature. The heat-treated wheel undergoes subsequent machining and other processes to obtain a finished wheel.

[0068] Comparative Example 2:

[0069] A method for producing a wheel from a steel for wheels includes the following processes:

[0070] Molten steel with the chemical composition as shown in Table 1 for Comparative Example 2 is subjected to an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (continuous casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 65 mm. The heat treatment process is as follows: First, heat the wheel to 864 °C. After heat preservation for 2.0 hours, spray water to cool the tread of the wheel. The cooling rate V of the tread is 38 °C / s, and the cooling time is 300 s. The inside of the rim is cooled to below 500 °C. After the cooling is completed, the wheel enters a tempering heating furnace with the roller table for tempering treatment, Tempering temperature is 490 °C, insulated for 4.5 h, and after tempering, it is air-cooled to room temperature. The heat-treated wheel undergoes subsequent machining and other processes to obtain a finished wheel.

[0071] Comparative Example 3:

[0072] A method for producing a wheel from a steel for wheels includes the following processes:

[0073] The molten steel with the chemical composition as shown in Comparative Example 3 of Table 1 is processed through an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 75 mm. The heat treatment process is as follows: First, heat the wheel to 868 °C. After heat preservation for 2.5 hours, spray water to cool the tread of the wheel. The cooling rate V of the tread is 37 °C / s, and the cooling time is 320 s , cool the inside of the rim to below 500 °C. After the cooling is completed, the wheel enters a tempering heating furnace along the roller table for tempering treatment. The tempering temperature is 500 °C, and it is held for 5 h, and then air-cooled to room temperature after tempering. The heat-treated wheel undergoes subsequent machining and other processes to obtain a finished wheel.

[0074] Comparative Example 4:

[0075] The molten steel with the chemical composition as shown in Comparative Example 4 of Table 1 is processed through an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 67 mm. The heat treatment process is as follows: First First, heat the wheel to 862 °C. After heat preservation for 2.0 hours, spray water to cool the tread of the wheel. The cooling rate V of the tread is 39 °C / s, and the cooling time is 300 s. cool the inside of the rim to below 500 °C. After the cooling is completed, the wheel enters a tempering heating furnace along the roller table for tempering treatment, Tempering temperature is 490 °C , hold for 4.5 h, and then air-cooled to room temperature after tempering. The heat-treated wheel undergoes subsequent machining and other processes to obtain a finished wheel.

[0076] Comparative Example 5:

[0077] The molten steel with the chemical composition as shown in Comparative Example 5 of Table 1 is processed through an electric furnace steelmaking process, an LF furnace refining process, an RH vacuum treatment process, a round billet continuous casting process (casting into a round billet with a diameter of φ450 mm), an ingot cutting and hot rolling process, a heat treatment process, machining, and a finished product inspection process to form a wheel with a diameter of 965 mm and a rim thickness of 65 mm. The heat treatment process is as follows: First, the wheel is rapidly heated to 915 °C at a speed of 15 °C / min, held for 0.75 h, then cooled to 765 °C at a speed of 7 °C / min and held for 0.75 h; the wheel is air-cooled until the tread temperature reaches 725 °C and then subjected to spray cooling, Cooling rate V 冷 is controlled at 31 °C / s, and the cooling time t 冷 210s , cool the inside of the rim to below 600 °C. After the cooling is completed, the wheel enters a tempering heating furnace along the roller table for tempering treatment. The tempering temperature is 530 °C, held for 5 h, and then air-cooled to room temperature after tempering. The heat-treated wheel undergoes subsequent machining and other processes to obtain a finished wheel.

[0078] Chemical composition (weight percentage %) and critical point temperature (°C) of wheels in each example and comparative example in Table 1

[0079] Element C Si Mn P S Cr V Ni Ti Zr B N Ac1 Ac3 Example 1 0.71 0.22 0.93 0.012 0.009 0.30 0.06 0.10 0.004 0.06 0.002 0.0075 724 758 Example 2 0.74 0.31 1.05 0.011 0.010 0.34 0.12 0.15 0.007 0.07 0.003 0.0092 725 763 Example 3 0.76 0.40 1.18 0.010 0.008 0.39 0.15 0.19 0.010 0.09 0.005 0.0118 726 768 Comparative Example 1 0.70 0.21 0.92 0.009 0.010 0.32 0.05 0.11 0.003 0 0 <![CDATA 0.0043 > 724 760 Comparative Example 2 0.75 0.33 1.08 0.009 0.011 0.35 0.11 0.16 0.005 <![CDATA 0 > <![CDATA 0 > <![CDATA 0.0031 > 725 764 Comparative Example 3 0.77 0.39 1.19 0.008 0.009 0.40 0.15 0.20 0.005 <![CDATA 0 > <![CDATA 0 > <![CDATA 0.0038 > 726 768 Comparative Example 4 0.74 0.30 1.04 0.011 0.009 0.35 0.11 0.14 0.006 0.05 0.004 0.0095 725 762 Comparative Example 5 0.74 0.32 0.95 0.009 0.012 <![CDATA 0.28 > 0.09 0.16 0.005 <![CDATA 0 > <![CDATA 0 > <![CDATA 0.0031 > 725 765

[0080] Table 2 Tensile Results of Wheels in Each Example and Comparative Example

[0081]

[0082] Table 3 Rim Hardness, Impact Energy and Fracture Toughness of Wheels in Examples and Comparative Examples

[0083]

[0084] Table 4 Wear Resistance Performance and Fatigue Crack Propagation Threshold Value ΔK of Wheels in Examples and Comparative Examples th Comparison

[0085]

[0086]

[0087] The underlined data above do not meet the requirements of the present invention.

[0088] The description of the above embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A steel for heavy-duty wheels with high heat resistance, characterized in that, The steel for high heat-resistant heavy-duty wheels described above comprises the following components by mass percentage: C 0.70 - 0.77%, Si 0.20 - 0.40%, Mn 0.90 - 1.20%, P ≤ 0.015%, S ≤ 0.015%, Cr 0.30 - 0.40%, Ni 0.10 - 0.20%, V 0.05 - 0.15%, Zr 0.05 - 0.10%, Ti 0.003 - 0.010%, B 0.002 - 0.005%, N 0.0070 - 0.0120%, and the balance is Fe and inevitable impurity elements.

2. A method for manufacturing a wheel using the steel for heavy-duty wheels with high heat resistance according to claim 1, characterized in that, The production method includes heat treatment; the heat treatment includes: heating and insulating the whole wheel, and then cooling it to the critical point A C3 ±5°C for heat preservation; then taking out the wheel and air-cooling it as a whole until the tread temperature reaches the critical point A c1 ±5°C, and then performing spray cooling; finally, tempering treatment is carried out.

3. The method according to claim 2, wherein The overall heating and heat preservation of the wheel means heating the wheel to A C3 +150 °C, with a heat preservation time of 0.5 - 1.5 h; the heating rate is (10 - 20) °C / min.

4. The method according to claim 2, characterized in that, Re-cooling to critical point A C3 Insulate at ±5°C for 0.5 - 1 h; the cooling rate is (5 - 10) °C / min.

5. The method according to claim 3, wherein The cooling rate of spray cooling is V 冷 , and the cooling time is t 冷 , the cooling rate V 冷 and the cooling time t 冷 respectively satisfy: V 冷 = 37.67 - 4×C - 0.575×Si - 0.73×Mn 2 - 0.53×Ni - 1.86×Cr - 13.33×V - 4.35×Zr - 17.6×B; V 冷 After rounding according to the calculation result, take the integer value; t 冷 = 4 × rim thickness - 50, cooling the inside of the rim to below 600 °C; In the formula, the content of each element is the content of each element × 100%, the unit of the rim thickness is mm, and the cooling rate V 冷 is in the unit of °C / s, and the cooling time t 冷 is in the unit of s.

6. The method according to claim 3, characterized in that, The tempering treatment mentioned above means that the tempering temperature is 500 - 560°C, the holding time is more than 4 hours, and after tempering, it is air-cooled to room temperature.

7. The method according to any one of claims 2-6, characterized in that The wheels produced by the said method have the following normal temperature properties of the rim: normal temperature R m ≥1300 MPa, normal temperature R p0.2 ≥920 MPa, elongation A≥13%, reduction of area Z≥35%; the hardness of the rim cross-section at normal temperature ≥360 HB, and the hardness difference at the same depth below the tread surface ≤15 HB; the impact energy K of the rim at normal temperature u ≥14.0 J, fracture toughness K q ≥43 MPa·m 1 / 2 .

8. The method according to any one of claims 3-7, characterized in that The wheel produced from the steel for high heat-resistant heavy-duty wheels has the following high-temperature properties at 538°C for the rim: high-temperature R m ≥570 MPa, high-temperature R p0.2 ≥460 MPa, elongation A≥39%, reduction of area Z≥85%.

9. The production method according to any one of claims 3-8, characterized in that, The wheel produced from the steel for heavy-duty wheels with high heat resistance has the following wheel wear resistance performance: under the conditions of a loading stress of 1200 MPa, a rotational speed of 1000 r·min -1 , and a number of cycles of 5×10 5 , the wear amount is ≤ 0.68 g;; the fatigue crack growth threshold value ΔK th ≥ 2.50 MPa·m 1 / 2 .

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