An anti engine burn fracture and high-toughness steel rail and preparation method thereof

Abstract

A scratch-resistant and high-strength and -toughness steel rail, comprising the following chemical components and ratios: in percentage by mass: C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, and Ti, wherein V accounts for 0.02-0.15%, Ti accounts for 0.001-0.030%, and Nb accounts for 0.01-0.08%, and the balance of Fe and inevitable impurities. In addition, the present invention further relates to a method for preparing the scratch-resistant, high-strength and high-toughness steel rail by using the chemical components and the ratios. According to the present invention, the contradiction between the mechanical property and the scratch resistance of the steel rail is solved, and good matching of the strength, the toughness, and the scratch resistance of the steel rail is realized.

Description

An anti engine burn fracture and high-toughness steel rail and preparation method thereof Technical Field The present invention relates to the field of steel rail manufacturing, and in particular to an anti engine burn fracture and high-toughness steel rail and preparation method thereof. Background Steel rails are one of the most critical components in wheel-rail system of rail transit. With the construction of new rail transit projects and ultimate pursuit of safety, comfort, efficiency, and longevity in the rail transit, the performance and quality of the prior steel rail is facing new challenges. With the development of the steel rails towards longevity, in addition to excellent wear resistance and fatigue resistance, the steel rails should also have excellent scratch resistance performance. Scratch for the steel rail is one of the main forms of rail damage in high-speed and heavy-haul railways at home and abroad, and it has been found in almost all major railway lines. Scratch for the steel rail affect the smoothness of the track seriously, and may cause stripping, chipping, and fatigue cracks on the surface of the steel rail. If scratch for the steel rail is not treated in time, it will increase the cost of rail maintenance and repair, and it may also increase the risk of rail breakage. Scratch for the steel rail is usually occurred during starting or braking for locomotive. Due to abnormal sliding between the wheel and the track, a large amount of frictional heat is generated, and a deep white layer structure is usually formed on the surface of the steel rail. The process of scratch for rail involves rapid heat exchange, where a pearlite is first heated to transform into an austenite, and then the austenite is rapidly cooled to transform into a white layer martensite (i.e., white layer structure). The formation process of the white layer structure caused by scratches is essentially the process of quenching the steel rail base material to form martensite structure. Therefore, the anti engine burn fracture performance of the steel rail can generally be evaluated by their ability to form martensite structure and their resistance to contact fatigue damage caused by the white layer structure formed on surface of the rail. The greater the critical cooling rate of steel for the steel rail, the better its anti engine burn fracture performance; the higher the austenitizing temperature of rail steel, the less likely the formation of a white layer structure during the friction process between the rail and the wheel; at the same time, the thinner the thickness of the white layer structure, the better its anti engine burn fracture performance. For the rails which have the same compositions, the higher the hardness of the rail base material, the smaller the hardness difference and gradient between the white layer martensite and the rail base material, and the higher the resistance to peeling of the white layer structure, the stronger the rail's resistance to fatigue fracture. The patent document CN 112226697 A discloses an anti engine burn fracture steel rail and its production method. The patent achieves a high resistance to martensite formation by reducing the carbon content of the rail steel and using a long-term heating method to make the depth of the decarburized layer of the rail greater than 0.5mm and further reducing the carbon content on the surface of the rail, thereby obtaining high resistance to martensite formation while maintaining high strength inside the rail. Although the method described in this patent improves the scratch resistance of the rail surface, due to severe decarburization, the strength and hardness of the rail has decreased and the wear and contact fatigue resistance of the rail will be greatly reduced, rapid surface peeling and chipping damage will occur, the service life of the rail will be reduced. At the same time, this method only improves the scratch resistance of the very shallow surface layer of the rail, and after the surface layer wears out, the scratch resistance of the rail will be decreased. Therefore, it is desirable to provide an anti engine burn fracture and high-toughness steel rail and preparation method thereof, to address the aforementioned issues. Summary In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is that the prior design for compositions and production process of the steel rail cannot simultaneously improve the strength and anti engine burn fracture of the steel rail, the term “anti engine burn fracture” is sometimes also referred to as scratch-resistant. Therefore, the present invention provides a scratch-resistant and high-toughness steel rail and preparation method thereof. In order to achieve the above object, the technical solutions provided by the present invention are as follows. According to an aspect of the present invention, there is provided an anti engine burn fracture and high-toughness steel rail, the steel rail has a composition comprising, by mass percentage, 0.50-0.65% of C, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% ofV, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance ofFe and inevitable impurities. In an example of the present invention, the content of of Si and Cr in terms of mass percentage meets the following conditions: 1.20%^ Si + Cr^1.65%. In an example of the present invention, the content of Mn in terms of mass percentage is 0.40 - 0.70%. In an example of the present invention, the content of Cu and Ni in terms of mass percentage meets the following conditions: 0.30% ^ Cu + Ni ^ 0.50%. According to an aspect of the present invention, there is also provided a method for preparing an anti engine burn fracture and high-toughness steel rail, comprising the steps of: step 1), controlling a molten steel to have a composition comprising: by mass percentage, 0.50-0.65% ofC, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% ofV, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance of Fe and inevitable impurities; step 2), arranging the molten steel in a tundish for continuous casting, and using multi-stage electromagnetic stirring, low superheat and high casting speed processes to treat the molten steel to obtain a low segregation steel billet; step 3),arranging the low segregation steel billet in a walking beam furnace for heating, and rolling it into a steel rail through universal rolling; and step 4), performing accelerated cooling on the steel rail from an austenite region by using compressed air with an accelerated cooling rate of 5.0 C / s to 6.5C / s, and then performing natural cooling on the steel rail after cooling to 540 C to 570C. In an example of the present invention, in step 2), the low segregation steel billet is prepared from blast furnace molten iron by converter smelting, LF refining, electric heating and continuous casting; the low segregation steel billet has a narrow facewith a C segregation degree of 0.96 to 1.04, a Mn segregation degree of 0.97 to 1.03, and a Cr segregation degree of 0.97 to 1.03 in its 50-150mm area. In an example of the present invention, the continuous casting process of the low segregation steel billet uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone; the superheat during the continuous casting process is 12 C to 20 C and the casting speed of the billet is 0.82 m / min to 0.95m / min. In an example of the present invention, in step 3), the heating process of the steel billet comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 750 C to 950 C and a heating time of 50 min to 70min; the second stage has a heating furnace chamber temperature of 1100C to 1280C and a heating time of 70 min to 100min; the third stage has a heating furnace chamber temperature of 1200 C to 1230C and a heating time of50 min to 90min; and the time for the heating furnace chamber temperature to be greater than 1200C during the heating process of the steel billet is controlled to be no less than 90 minutes. In an example of the present invention, in step 3), the universal rolling includes universal rough rolling, universal medium rolling, and universal finish rolling. In an example of the present invention, in step 4), the accelerated cooling rate is 4.5 C / s to 6.0C / s, and the natural cooling is performed after cooling to 430 C to 470C. Compared with the prior art, the present invention has the following advantages by adopting the above technical solution: The present invention improves the austenitizing temperature of pearlite structure during the heating process of the steel rail scratching through specific chemical compositions design for the steel rail, increases the threshold of the possibility of scratch, and reduces the thickness of white layer structure caused by the scratch. In the present invention, the multi-stage electromagnetic stirring, the low superheat and the high casting speed processes is used to obtain the low segregation steel billet, which broadens the heat treatment process window of the steel rail, allowing for online heat treatment with large cooling rates. The synergistic effect of alloying elements and heat treatment processes is fully utilized to improve the performance of the steel rail, which is result in strong mechanical properties and improve the scratch resistance. The contradiction between the mechanical property and the scratch resistance of the steel rail is solved, and the strength, the toughness and the scratch resistance of the steel rail are well matched. Detailed Description It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments have been described in detail in the present invention, those skilled in the art can easily appreciate that various modifications are feasible without substantially departing from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the spirit of the present invention, other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, parameters, and the like of the following exemplary embodiments. The present invention provides an anti engine burn fracture and high-toughness steel rail. The steel rail has a composition comprising, by mass percentage, 0.50-0.65% of C, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% of V, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance of Fe and inevitable impurities. The present invention improves the austenitizing temperature of pearlite structure during the heating process of the steel rail scratching through specific chemical compositions design for the steel rail, increases the threshold of the possibility of scratch, and reduces the thickness of white layer structure caused by the scratch. In the above steel rail, the content of Si and Cr in terms of mass percentage meets the following conditions: 1.20%<Si + Cr^1.65%; the content of Mn in terms of mass percentage is 0.40-0.70%; the content of Cu and Ni in terms of mass percentage meets the following conditions: 0.30% ^ Cu + Ni < 0.50%. In addition, the present invention also provides a method for preparing an anti engine burn fracture and high-toughness steel rail, comprising the steps of: step 1), controlling a molten steel to have a composition comprising: by mass percentage,0.50-0.65% ofC, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% ofV, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance of Fe and inevitable impurities; step 2), arranging the molten steel in a tundish for continuous casting, and using multi-stage electromagnetic stirring, low superheat and high casting speed processes to treat the molten steel to obtain a low segregation steel billet; step 3),arranging the low segregation steel billet in a walking beam furnace for heating, and then rolling it into a steel rail through universal rolling; and step 4), performing accelerated cooling on the steel rail from an austenite region by using compressed air with an accelerated cooling rate of 5.0°C / s to 6.5 °C / s, and then performing natural cooling on the steel rail after cooling to 540 C to 570C. The present invention improves the austenitizing temperature of pearlite structure during the heating process of the steel rail scratching through specific chemical compositions design for the steel rail, increases the threshold of the possibility of scratch, and reduces the thickness of white layer structure caused by the scratch. In the present invention, the multi-stage electromagnetic stirring, the low superheat and the high casting speed processes is used to obtain the low segregation steel billet, which broadens the heat treatment process window of the steel rail, allowing for online heat treatment with large cooling rates. The synergistic effect of alloying elements and heat treatment processes is fully utilized to improve the performance of the steel rail, which is result in strong mechanical properties and improve the scratch resistance. The contradiction between the mechanical property and the scratch resistance of the steel rail is solved, and the strength, the toughness and the scratch resistance of the steel rail are well matched. In the above method, in step 2), the low segregation steel billet is prepared from blast furnace molten iron by converter smelting, LF refining, electric heating and continuous casting; the low segregation steel billet has a narrow face with a C segregation degree of 0.96 to 1.04, a Mn segregation degree of 0.97 to 1.03, and a Cr segregation degree of 0.97 to 1.03 in its 50-150mm area. In the above method, the continuous casting process of the low segregation steel billet uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone; the superheat during the continuous casting process is 12 C to 20 C and the casting speed of the billet is 0.82 m / min to 0.95m / min. In the above method, in step 3), the heating process of the steel billet comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 750C to 950 C and a heating time of 50 min to 70min; the second stage has a heating furnace chamber temperature of 1100 C to 1280 C and a heating time of 70 min to 100min; the third stage has a heating furnace chamber temperature of 1200 C to 1230 C and a heating time of 50 min to 90min; and the time for the heating furnace chamber temperature to be greater than 1200C during the heating process of the steel billet is controlled to be no less than 90 minutes. In the above method, in step 3), the universal rolling includes universal rough rolling, universal medium rolling, and universal finish rolling. In the above method, in step 4), the accelerated cooling rate is 4.5 C / s to 6.0 C / s, and the natural cooling is performed after cooling to 430C to 470C. The above technical solutions of the present invention are described in detail through specific embodiments. The main methods for improving the strength of steel in the steel rail are alloying, heat treatment, and combination of alloying and heat treatment, wherein combination of alloying and heat treatment is the most commonly used and an effective method for improving the strength of steel of the steel rail. For most alloying elements, after adding them to the steel of the steel rail, the cooling C curve of the steel of the steel rail shifts to right direction, and the critical cooling rate for martensitic transformation decreases, which improves the ability of the steel rail to form white layer structures caused by scratching, and reduces the anti engine burn fracture performance of the steel rail. Under the existing composition system and production process, if the strength of the steel rail is further improved, the anti engine burn fracture performance of the steel rail will inevitably be reduced. Therefore, in the present invention, through specific chemical compositions design and smelting and heating processes, the segregation of cast billet and the steel rail can be reduced, the critical cooling rate for martensitic transformation is greatly improved, and the process window for heat treatment of the steel rail is widened, so that large cooling rate online heat treatment can be implemented. The synergistic cooperation between alloy elements and heat treatment processes is fully utilized to improve the performance of the steel rail. In addition, through specific alloy composition design of the present invention, the A1 and A3 temperature of the steel rail is increased, and the anti engine burn fracture performance of the steel rail is further improved. The method of the present invention improves the performance of the steel rail while maintains the overall alloy content level of the steel rail comparable to that of the prior art, or the method of the present invention reduces the overall alloy content level of the steel rail and improves the anti engine burn fracture performance of the steel rail while maintains the existing performance. The present invention provides an anti engine burn fracture and high-toughness steel rail. The body of the steel rail has a composition comprising, by mass percentage, 0.50-0.65% of C, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% of V, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance of Fe and inevitable impurities. Preferably, in the above steel rail, the content of Si and Cr in terms of mass percentage meets the following conditions: 1.20% ^ Si + Cr ^ 1.65%; the content ofMn in terms of mass percentage is 0.40-0.70%; the content ofCu and Ni in terms of mass percentage meets the following conditions: 0.30% ^ Cu + Ni < 0.50%. The present invention provides an anti engine burn fracture and high-toughness steel rail with a eutectoid transformation temperature A1 above 780 C and A3 above 810C; a critical cooling rate for martensitic transformation greater than 6.0C / s, a scratch white layer / rail base material hardness ratio after wheel rail scratch test less than 1.80. The present invention also provides a method for preparing an anti engine burn fracture and high-toughness steel rail comprising the following steps. Step 1, preparation ofa molten steel The molten steel is prepared from blast furnace molten iron by converter smelting, LF refining, and vacuum degassing. The molten steel has a composition comprising, by mass percentage,0.50-0.65% ofC, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% ofV, 0.001-0.030% of Ti, 0.01-0.08% of Nb, and the balance ofFe and inevitable impurities. Step 2, preparation of a low segregation steel billet or low segregation casting blank The molten steel having the above composition is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone. The continuous casting process has a casting superheat of 12C to 20 C and a casting speed of 0.82 m / min to 0.95m / min. The low segregation casting blank has a narrow face with a C segregation degree of 0.96 to 1.04, a Mn segregation degree of 0.97 to 1.03, and a Cr segregation degree of 0.97 to 1.03 in its 50-150mm area. Step 3, heating process of casting blank The casting blank having the above composition is arranged in a walking beam furnace for heating. The heating process of the casting blank comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 750 C to 950°C and a heating time of 50 min to 70min; the second stage has a heating furnace chamber temperature of 1100C to 1280C and a heating time of 70 min to 100min; the third stage has a heating furnace chamber temperature of 1200C to 1230C and a heating time of 50 min to 90min. And the time for the heating furnace chamber temperature to be greater than 1200C during the heating process of the casting blank is controlled to be no less than 90 minutes. The purpose of prolonged high-temperature heating is to fully diffuse the segregated elements in the casting blank, improve the uniformity of the composition of the casting blank, and prevent the formation of spot-like martensitic structures due to the use of large cooling rates during the subsequent accelerated cooling heat treatment processes. To prevent severe decarburization of the surface of the casting blank caused by prolonged high-temperature heating, a high-temperature protective coating is applied to the surface of the casting blank before loading into the furnace. Step 4, rolling for the steel rail After heating, the casting blank is rolled into the steel rail through cogging rolling and universal rolling with an initial rolling temperature of 1150 C to 1220C, and a final rolling temperature of 880C to 930C. Step 5, online heat treatment after rolling After rolling, the steel rail is subjected to heat treatment using residual heat from rolling. The temperature of top surface for the steel rail is decreased from 790°C-820°C to 430 C-470C at an accelerated cooling rate of 4.5-6.0°C / s before natural cooling. In the present invention, the steel billet in the following examples and comparative examples is prepared by the method known to those skilled in the art from blast furnace molten iron by converter smelting, LF refining, electric heating and continuous casting. Example 1 The body of the steel rail in this example has a composition comprising, by mass percentage, 0.53 percent of C, 0.63 percent of Si, 0.68 percent of Mn, 0.76 percent of Cr, 0.30 percent of Cu, 0.17 percent of Ni, 0.09 percent ofV, and the balance of Fe and inevitable impurities. In this example, the chemical composition of the steel billet is consistent with that of the body of the steel rail. The molten steel having the above composition is prepared from blast furnace molten iron by converter smelting, LF refining, and vacuum degassing. The molten steel is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone. The continuous casting process has a casting superheat of 13 C to 17 C and an average casting speed of 0.86 m / min. After cooling and cleaning, the casting blank is sprayed with anti-decarburization coating, and then loaded into a walking beam furnace for heating. The heating process comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 836C and a heating time of 67min; the second stage has a heating furnace chamber temperature of 1250C and a heating time of 86min; and the third stage has a heating furnace chamber temperature of 1214C and a heating time of 81min. The casting blank is rolled into the steel rail through cogging rolling, universal rough rolling, universal medium rolling, and universal finish rolling. The temperature of the steel rail after rolling is 904C. When the center temperature of the top surface of the steel rail is 826C, the steel rail enters an online heat treatment unit. The steel rail is cooled to 447C at an average accelerated cooling rate of 5.7C / s, and then returns to a cooling bed for natural cooling to room temperature. Example 2 The body of the steel rail in this example has a composition comprising, by mass percentage, 0.59 percent of C, 0.78 percent of Si, 0.57 percent of Mn, 0.52 percent of Cr, 0.24 percent of Cu, 0.15 percent of Ni, 0.07 percent ofV, and the balance of Fe and inevitable impurities. In this example, the chemical composition of the steel billet is consistent with that of the body of the steel rail. The molten steel having the above composition is prepared from blast furnace molten iron by converter smelting, LF refining, and vacuum degassing. The molten steel is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone.. The continuous casting process has a casting superheat of 14C to 17 °C and an average casting speed of 0.85 m / min. After cooling and cleaning, the casting blank is sprayed with anti-decarburization coating, and then loaded into a walking beam furnace for heating. The heating process comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 847 C and a heating time of 71min; the second stage has a heating furnace chamber temperature of 1243C and a heating time of 91min; and the third stage has a heating furnace chamber temperature of 1207C and a heating time of 66min. The casting blank is rolled into the steel rail through cogging rolling, universal rough rolling, universal medium rolling, and universal finish rolling. The temperature of the steel rail after rolling is 893C. When the center temperature of the top surface of the steel rail is 821C, the steel rail enters an online heat treatment unit. The steel rail is cooled to 442C at an average accelerated cooling rate of 5.3C / s, and then returns to a cooling bed for natural cooling to room temperature. Example 3 The body of the steel rail in this example has a composition comprising, by mass percentage, 0.63 percent of C, 0.76 percent of Si, 0.41 percent of Mn, 0.61 percent of Cr, 0.22 percent of Cu, 0.16 percent of Ni, 0.05 percent ofV, and the balance ofFe and inevitable impurities. In this example, the chemical composition of the steel billet is consistent with that of the body of the steel rail. The molten steel having the above composition is prepared from blast furnace molten iron by converter smelting, LF refining, and vacuum degassing. The molten steel is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone. The continuous casting process has a casting superheat of 15 C to 18 C and an average casting speed of 0.84 m / min. After cooling and cleaning, the casting blank is sprayed with anti-decarburization coating, and then loaded into a walking beam furnace for heating. The heating process comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 876 C and a heating time of 61min; the second stage has a heating furnace chamber temperature of 1262C and a heating time of 85min; and the third stage has a heating furnace chamber temperature of 1224C and a heating time of 92min. The casting blank is rolled into the steel rail through cogging rolling, universal rough rolling, universal medium rolling, and universal finish rolling. The temperature of the steel rail after rolling is 907C. When the center temperature of the top surface of the steel rail is 817C, the steel rail enters an online heat treatment unit. The steel rail is cooled to 453C at an average accelerated cooling rate of 5.0C / s, and then returns to a cooling bed for natural cooling to room temperature. Example 4 The body of the steel rail in this example has a composition comprising, by mass percentage, 0.58 percent of C, 0.95 percent of Si, 0.58 percent of Mn, 0.43 percent of Cr, 0.21 percent of Cu, 0.16 percent of Ni, 0.08 percent of V, and the balance of Fe and inevitable impurities. In this example, the chemical composition of the steel billet is consistent with that of the body of the steel rail. The molten steel having the above composition is prepared from blast furnace molten iron by converter smelting, LF refining, and vacuum degassing. The molten steel is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone. The continuous casting process has a casting superheat of 12 °C to 15 °C and an average casting speed of 0.86 m / min. After cooling and cleaning, the casting blank is sprayed with anti-decarburization coating, and then loaded into a walking beam furnace for heating. The heating process comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 836C and a heating time of 65min; the second stage has a heating furnace chamber temperature of 1256C and a heating time of 89min; and the third stage has a heating furnace chamber temperature of 1215C and a heating time of 85min. The casting blank is rolled into the steel rail through cogging rolling, universal rough rolling, universal medium rolling, and universal finish rolling. The temperature of the steel rail after rolling is 886C. When the center temperature of the top surface of the steel rail is 820C, the steel rail enters an online heat treatment unit. The steel rail is cooled to 543C at an average accelerated cooling rate of 5.5C / s, and then returns to a cooling bed for natural cooling to room temperature. Comparative Example 1 The body of the steel rail in this comparative example has a composition comprising, by mass percentage, 0.73 percent of C, 0.35 percent of Si, 1.13 percent of Mn, 0.12 percent of Cr and the balance of Fe and inevitable impurities. The steel rail in Comparative Example 1 was prepared using prior methods. The continuous casting process has a casting superheat of 26 C to 35 C and a casting speed of 0.71 m / min. The casting blank is rolled through universal rolling with a universal final rolling temperature of 931 °C. After rolling, the steel rail is subjected to online heat treatment using residual heat from rolling. The steel rail is cooled to 548C at an accelerated cooling rate of 2.1°C / s, and then naturally cooled to room temperature in air. Comparative Example 2 The body of the steel rail in this comparative example has a composition comprising, by mass percentage, 0.77 percent of C, 0.61 percent of Si, 0.87 percent of Mn, 0.02 percent of Cr, 0.05 percent ofV, and the balance ofFe and inevitable impurities. The steel rail in Comparative Example 2 was prepared using prior methods. The continuous casting process has a casting superheat of 28C to 36C and a casting speed of 0.71 m / min. The casting blank is rolled through universal rolling with a universal final rolling temperature of 927C. After rolling, the steel rail is subjected to online heat treatment using residual heat from rolling. The steel rail is cooled to 523C at an accelerated cooling rate of 2.6°C / s, and then naturally cooled to room temperature in air. Comparative Example 3 The body of the steel rail in this comparative example has a composition comprising, by mass percentage, 0.59 percent of C, 0.78 percent of Si, 0.64 percent of Mn, 0.53 percent of Cr, 0.24 percent of Cu, 0.15 percent of Ni, 0.06 percent of V, and the balance of Fe and inevitable impurities. The steel rail in Comparative Example 3 was prepared using prior methods. The continuous casting process has a casting superheat of 27 C to 35 C and a casting speed of 0.71 m / min. The casting blank is rolled through universal rolling with a universal final rolling temperature of 926 C. After rolling, the steel rail is subjected to online heat treatment using residual heat from rolling. The steel rail is cooled to 527C at an accelerated cooling rate of 2.6°C / s, and then naturally cooled to room temperature in air. Comparative Example 4 The body of the steel rail in this comparative example has a composition comprising, by mass percentage, 0.71 percent of C, 0.36 percent of Si, 1.04 percent of Mn, 0.09 percent of Cr and the balance of Fe and inevitable impurities. In this comparative example, the chemical composition of the steel billet is consistent with that of the body of the steel rail. The molten steel having the above composition is prepared from blast furnace molten iron by converter smelting, LF refining and vacuum treatment. The molten steel is arranged in a tundish for continuous casting. The continuous casting process uses a multi-stage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone. The continuous casting process has a casting superheat of 14 C to 19C and an average casting speed of 0.84 m / min. After cooling and cleaning, the casting blank is sprayed with anti-decarburization coating, and then loaded into a walking beam furnace for heating. The heating process comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 877 C and a heating time of 65min; the second stage has a heating furnace chamber temperature of 1250 C and a heating time of 76min; and the third stage has a heating furnace chamber temperature of 1219 C and a heating time of 88min. The casting blank is rolled into the steel rail through cogging rolling, universal rough rolling, universal medium rolling, and universal finish rolling. The temperature of the steel rail after rolling is 902C. When the center temperature of the top surface of the steel rail is 811C, the steel rail enters an online heat treatment unit. The steel rail is cooled to 463C at an accelerated cooling rate of 3.2C / s, and then returns to a cooling bed for natural cooling to room temperature. The yield strength, tensile strength and elongation of the steel rail prepared in the above Examples 1-4 and Comparative Examples 1-4 were tested according to GB / T 228.1 standard, and the Brinell hardness of the steel rail prepared in the above Examples 1-4 and Comparative Examples 1-4 was tested according to GB / T 231.1 standard. The contact fatigue life test was conducted on the TIME 8123 rolling contact fatigue tester with a test contact stress of 1200MPa and a slip of 1.0%. The specific microstructure and conventional mechanical properties of the relevant tests are shown in Table 1-2 below. Table 1 Microstructure and conventional mechanical properties of examples and comparative examples No. Microstructure Rm / MPa A / % Tread hardness / HB A1 temperature / C A3 temperature / C Critical cooling rate / C / s Example 1 2.0% ferrite+ pearlite 1159 16.5 349 783 819 6.5 Example 1 1.0% ferrite+ pearlite 1161 15.5 350 777 814 6.5 Example 3 0.5% ferrite+ pearlite 1178 15.0 357 776 812 6.25 Example 4 0.5% ferrite+ pearlite 1165 15.5 351 779 814 7.0 Comparative Example 1 <0.5% ferrite+ pearlite 1139 12.5 341 726 743 3.0 Comparative Example 2 pearlite 1187 11.5 361 733 749 3.5 Comparative Example 3 <0.5% ferrite+ pearlite 1148 13.5 341 778 816 6.5 Comparative Example 4 1.0% ferrite+ pearlite 1163 14.0 353 727 743 3.5 As shown in Table 1, the steel rail prepared using the components and process of the present invention has high strength and hardness, while maintain a high post-fracture elongation rate. The A1 temperature of the steel rail of the present invention reaches above 775 C and the A3 temperature of the steel rail of the present invention reaches above 819 C, and the critical cooling rate for martensitic transformation of the steel rail of the present invention reaches above 6.0C / s. Comparative Example 1 is an U71Mn heat-treated steel rail produced using prior conventional processes, and the strength, hardness, and post-fracture elongation rate of Comparative Example 1 are lower than those of the steel rail prepared according to the present invention. The A1 temperature of Comparative Example 1 is 726 C and the A3 temperature of Comparative Example 1 is 743C, and the critical cooling rate for martensitic transformation of Comparative Example 1 is 3.0 C / s. Comparative Example 2 is a U75V heat-treated rail produced using prior conventional processes, and although the strength and hardness of the U75V heat-treated rail are slightly higher than those of the steel rail prepared using the present invention, the post-fracture elongation rate of the rail of Comparative Example 2 is significantly lower than that of the rail prepared according to the present invention. The A1 temperature of the steel rail of Comparative Example 2 is 726C and the A3 temperature of the steel rail of Comparative Example 2 is 743 C, and the critical cooling rate for martensitic transformation of the steel rail of Comparative Example 2 is 3.5 C / s. Comparative Example 3 is a rail produced using the components of the present invention and using prior processes. Although the strength and hardness of the rail of Comparative Example 3 have been improved, the post-fracture elongation rate is low, making it impossible to achieve a strong and tough match. Comparative Example 4 is a modified rail based on the U71Mn rail and uses the process of the present invention. The strength and plasticity of the rail of Comparative Example 4 are slightly improved compared to those of the U71Mn rail produced using conventional processes, but the A1 temperature of the rail of Comparative Example 4 is 726 C and the A3 temperature of the rail of Comparative Example 4 is 743C, and the critical cooling rate for martensitic transformation of the rail of Comparative Example 4 is 3.0 C / s. Therefore, the steel rail produced using the method of the present invention has good strength and toughness properties, and the A1 temperature, the A3 temperature, and the critical cooling rates for martensitic transformation are significantly improved compared to those of conventional components and processes. Table 2 Microstructure and conventional mechanical properties for examples and comparative examples No. Hardness for rail base material / HV0.1 Hardness for white layer structure / HV0.1 white layer structure to base material hardness ratio Thickness for white layer structure / pm Rolling contact fatigue cycles / million time Example 1 356 624 1.75 48 41.8 Example 2 358 619 1.73 53 33.6 Example 3 363 628 1.73 54 37.2 Example 4 357 621 1.74 56 36.4 Comparative example 1 346 746 2.16 102 19.8 Comparative example 2 370 739 2.00 95 25.5 Comparative example 3 359 672 1.87 57 34.1 Comparative example 4 347 737 2.12 99 21.2 As shown in Table 2, the rail base material of the steel rail prepared using the components and process of the present invention has high hardness, and the white layer structure formed by scratching has low hardness, therefore the steel rail has a white layer structure to base material hardness ratio (below 1.80), that is, the difference in hardness between the white layer structure and the rail base material is low, in other words, the gradient in hardness between the white layer structure and the rail base material is small. At the same time, the thickness for the white layer structure formed by scratching is also low, therefore the rolling contact fatigue cycles is high. However, in Comparative Examples 1-4, whether it is a rail produced using existing conventional components and processes, a rail produced using optimized components and conventional processes, or a rail produced using existing components and improved processes, it cannot simultaneously improve both toughness and scratch resistance. It can be seen from Examples 1-4 and Comparative Examples 1-4 that the steel rail prepared using the present invention has good scratch resistance and good toughness matching. The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. Any modifications or equivalent substitutions to the present invention without departing from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an anti engine burn fracture and high-toughness steel rail, characterized by comprising the steps of:step 1), controlling a molten steel to have a composition comprising: by mass percentage, 0.50-0.65% of C, 0.45-0.95% of Si, 0.35-0.85% of Mn, 0.30-0.80% of Cr, 0.20-0.55% of Cu, 0.10-0.30% of Ni, at least one of 0.02-0.15% of V, 0.0010.030% of Ti, 0.01-0.08% of Nb, and the balance of Fe and inevitable impurities, wherein the content of Si and Cr in terms of mass percentage meets the following conditions: 1.20%< Si+Cr <1.65%;step 2), arranging the molten steel in a tundish for continuous casting, and using multi-stage electromagnetic stirring, low superheat and high casting speed processes to treat the molten steel to obtain a low segregation steel billet, wherein the continuous casting process of the low segregation steel billet uses a multistage composite electromagnetic stirring method that combines electromagnetic stirring in crystallizer, electromagnetic stirring in secondary cooling zone, and electromagnetic stirring in final solidifying zone; the superheat during the continuous casting process is 12 C to 20 C and the casting speed of the billet is 0.82 m / min to 0.95m / min;step 3), arranging the low segregation steel billet in a walking beam furnace for heating, and then rolling it into a steel rail through universal rolling, wherein the heating process of the steel billet comprises a first stage, a second stage, and a third stage, wherein the first stage has a heating furnace chamber temperature of 750°C to 950 C and a heating time of 50 min to 70min; the second stage has a heating furnace chamber temperature of 1100 C to 1280 C and a heating time of 70 min to 100min; the third stage has a heating furnace chamber temperature of 1200C to 1230C and a heating time of 50 min to 90min; and the time for the2024211006   04 Aug 2026heating furnace chamber temperature to be greater than 1200 C during the heating process of the steel billet is controlled to be no less than 90 minutes; andstep 4), performing accelerated cooling on the steel rail from an austenite region by using compressed air with an accelerated cooling rate of 5.0 C / s to 6.5C / s, and then performing natural cooling on the steel rail after cooling to 540C to 570C.

2. The method according to claim 1, characterized in that in step 2), the low segregation steel billet is prepared from blast furnace molten iron by converter smelting, LF refining, electric heating and continuous casting; and the low segregation steel billet has a narrow face with a C segregation degree of 0.96 to 1.04, a Mn segregation degree of 0.97 to 1.03, and a Cr segregation degree of 0.97 to 1.03 in its 50-150mm area.

3. The method according to claim 1 or claim 2, characterized in that in step 3), the universal rolling includes universal rough rolling, universal medium rolling, and universal finish rolling.

4. The method according to any one of claims 1-3, characterized in that in step 4), the accelerated cooling rate is 4.5 C / s to 6.0 °C / s, and the natural cooling is performed after cooling to 430C to 470C.

5. The method according to any one of claims 1-4, characterized in that the content of Mn in terms of mass percentage is 0.40-0.70%.

6. The method according to any one of claims 1-5, characterized in that the content of Cu and Ni in terms of mass percentage meets the following conditions: 0.30% < Cu+Ni < 0.50%.