A steel rail with excellent corrosion resistance and contact fatigue resistance and preparation method thereof

Abstract

The present invention relates to a steel rail with excellent corrosion resistance and contact fatigue resistance, and its chemical composition and proportion are as follows: by mass percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest are Fe and unavoidable impurities. In addition, the present invention also relates to a method for preparing the above-mentioned steel rail. Through the present invention, the present invention achieves a synergistic improvement in performance and realizes that the steel rail has both corrosion resistance, fatigue resistance and excellent weldability.

Description

Technical Field

[0001] The invention relates to the technical field of rail manufacturing, and in particular to a rail with excellent corrosion resistance and contact fatigue resistance for plateau mountain railways and a preparation method thereof. Background Art

[0002] Rails are one of the core components of the rail transit wheel-rail system. With the construction of new rail transit projects and the ultimate pursuit of safety, comfort, efficiency and longevity in rail transit, the performance and quality of existing rails are facing new challenges. Under the combined effects of extreme natural environments such as plateaus, low temperatures, large temperature differences, wind and sand, and humidity, and harsh operating conditions such as super-long ramps, small radius curves, high speeds, heavy loads, and frequent starting and braking, rails are prone to a series of problems such as abrasions, abnormal wear, thermal damage failure, fatigue failure, and wheel-rail interface adhesion during service. At the same time, they also face engineering problems such as welding, use, maintenance, and replacement. Rails are required to have not only excellent wear resistance and contact fatigue performance, but also good low-temperature toughness and plasticity, abrasion resistance, corrosion resistance, and excellent weldability.

[0003] In terms of improving the wear resistance and contact fatigue resistance of rails, alloying and heat treatment technologies have become relatively mature; in terms of improving toughness and plasticity, some breakthroughs have been made in improving the toughness and plasticity of rails by obtaining bainite structure through alloying; however, due to the limitations of basic research and process equipment, most of the current research and products focus on improving performance in one aspect, and fail to fully consider the overall improvement of comprehensive performance such as rail wear, contact fatigue, low-temperature toughness and plasticity, and weldability. Under the existing rail material design theory and manufacturing process, wear, contact fatigue, (low-temperature) toughness and plasticity, and anti-scratch properties theoretically restrict each other and are difficult to improve simultaneously. Although bainitic rails have potential application prospects due to their excellent strength and toughness combination, the bainite microstructure is complex and the service performance is unstable, which limits their application in harsh service conditions such as the Sichuan-Tibet Railway and high-speed freight railways.

[0004] Patent document CN10192950A discloses a hypoeutectoid rail for high-speed and quasi-high-speed railways, wherein the weight percentage of alloying elements in the basic alloy system is: C: 0.40%-0.64%, Si: 0.10%-1.00%, Mn: 0.30%-1.50%, P: ≤0.025%, S: ≤0.025%, rare earth ≤0.005%, at least one of V, Cr and Ti with a content of 0-0.020%, and the balance is Fe and unavoidable impurities. The patent reduces the carbon content and uses accelerated cooling to compensate for the strength reduction caused by the reduction in carbon content, so that the rail maintains the strength of the high-speed railway rail while improving the yield strength and toughness, thereby improving fatigue resistance. However, the reduction in carbon content and more than 15% proeutectoid ferrite will reduce the wear resistance and contact fatigue resistance of the rail. At the same time, this plan is mainly aimed at lines with light axle weight and small traffic volume. It does not propose a solution to the problems of rail wear resistance, corrosion resistance and toughness for lines with heavy axle weight and corrosive environment.

[0005] Patent document CN113981332A discloses a wear-resistant and corrosion-resistant hypoeutectoid rail and a production method thereof, wherein the chemical composition weight percentage is: carbon: 0.50-0.70%, copper: 0.10-0.80%, nickel: 0.01-0.50%, chromium 0.10-0.70%, vanadium: 0.03-0.12%, phosphorus: 0.010-0.025%, sulfur: 0.001-0.009%, silicon and manganese: 0.8-2.0%, and the balance is iron and unavoidable impurities. The invention uses low carbon content to obtain hypoeutectoid structure, adds copper, nickel, chromium, vanadium, silicon, manganese, phosphorus, sulfur, or adds one or more of niobium, molybdenum, boron and rare earth elements to improve the performance of the rail. Hypoeutectoid structures have various forms, and their microstructures have an important influence on the strength, contact fatigue resistance and toughness of rails. Differences in microstructure will lead to huge changes in rail performance. Adding copper, nickel and chromium elements can improve the corrosion resistance of rails, but it significantly affects the toughness and weldability of rails. The patent does not involve how to resolve the contradiction between corrosion resistance and toughness, weldability, and the optimal ratio of alloy elements.

[0006] Patent document CN 107227429 A discloses a heat treatment method for removing ferrite network structure in rails. By performing segmented accelerated cooling during the heat treatment of rails, the rails with hypoeutectoid components are controlled to first eutectoid ferrite to avoid the appearance of network ferrite structure. The typical composition of rail steel is: C: 0.60-0.72%; Si: 0.25-0.60%; Mn: 0.85-1.05%; Cr: 0.05-0.30%; V: 0.01-0.09%; P≤0.025%; S≤0.025%, N≤0.0080%; the rest is Fe and unavoidable impurities. Although this method uses the method of heat treatment designed by hypoeutectoid carbon content composition to improve the strength and toughness of the rails, it fails to achieve a comprehensive improvement in the wear resistance, corrosion resistance, and contact fatigue resistance of the rails, and is not adaptable enough under complex line conditions.

[0007] Therefore, in view of the above problems, it is desirable to provide a steel rail having excellent corrosion resistance and contact fatigue resistance. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a structural control scheme, a component design scheme and a preparation method for a steel rail that has excellent wear resistance, corrosion resistance, contact fatigue resistance, abrasion resistance and welding performance, thereby solving the problem that the steel rails cannot be improved synergistically under current composition and manufacturing conditions.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] According to one aspect of the present invention, a steel rail with excellent corrosion resistance and contact fatigue resistance is provided, and the chemical composition and proportion of the steel rail are as follows: by mass percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest is Fe and unavoidable impurities.

[0011] In one embodiment of the present invention, the ratio of the chemical components satisfies the following relationship:

[0012] 6.93[C]+1.15[Si]+1.26[Mn]+1.46[Cr]+6.2[V]+0.63[Cu]+0.86[Ni]≥7.0%; and

[0013] 0.71[Si]+1.04[Cr]+1.67[Cu]+1.35[Ni]+2.1[Nb]≥1.7%.

[0014] In one embodiment of the present invention, the carbon equivalent CE satisfies the following relationship:

[0015] [C]+[Mn] / 6+[Cr] / 5+[V] / 5+[Cu] / 15+[Ni] / 15≤0.95%.

[0016] In one embodiment of the present invention, the ratio of the chemical components also satisfies the following relationship:

[0017] [Cr]+[Cu]+[Ni]≥0.60%.

[0018] According to another aspect of the present invention, a method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance is provided, comprising the following steps:

[0019] 1) The chemical composition and proportion of the rail matrix are controlled as follows: by weight percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest is Fe and unavoidable impurities;

[0020] 2) The rail matrix is ​​subjected to combined electromagnetic stirring of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring, and cast at low superheat and high casting speed to obtain a highly homogeneous steel billet;

[0021] 3) The steel billet is placed in a heating furnace for heating and rolled into a rail by a universal rolling method;

[0022] 4) Accelerate the cooling of the rails, cool them to below 500°C, then cool them naturally to room temperature, and straighten them with a small deformation.

[0023] In one embodiment of the present invention, in step 2), the magnetic field intensity of the electromagnetic stirring of the continuous casting crystallizer is 40×10 -4 -50×10 -4 T, the magnetic field intensity of the secondary cooling electromagnetic stirring is 40×10 -4 -50×10 -4 T, superheat is 12-20℃, and the billet drawing speed is 0.82-0.95m / min.

[0024] In one embodiment of the present invention, in step 3), the heating process of the steel billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, and the heating time is 50-70min; in the second stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 45-65min; in the third stage, the furnace temperature of the heating furnace is 1180-1230°C, and the heating time is 35-50min.

[0025] In one embodiment of the present invention, in step 3), the universal rolling method includes universal rough rolling, intermediate rolling and finish rolling.

[0026] In one embodiment of the present invention, the initial rolling temperature is 1150-1200°C, the intermediate rolling temperature is 900-930°C, the elongation coefficient is greater than 1.3, and the final rolling temperature is 850-880°C.

[0027] In one embodiment of the present invention, in step 4), the accelerated cooling of the rail is carried out in stages: in the first stage, the top surface temperature of the rail is accelerated cooled from 790-820°C at a rate of 4.0-5.5°C / s for 42-52s; in the second stage, after the first stage, it is cooled to below 500°C at a rate of 1.0-2.0°C / s.

[0028] In one embodiment of the present invention, in step 4), small deformation straightening is performed by a horizontal straightening machine, wherein the total pressing amount of the movable upper roller of the horizontal straightening machine is 30-40 mm.

[0029] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] The method of the present invention obtains a wider heat treatment window for rails by adopting precise chemical composition design and low-segregation and high-homogeneity smelting process, which provides good conditions for high-cooling-rate heat treatment, and can implement high-cooling-rate heat treatment for rails to obtain extremely fine lamellar pearlite structure, while improving the strength and toughness of the rails; the present invention reasonably controls the content of proeutectoid ferrite and utilizes trace proeutectoid ferrite to improve the toughness of the rails on the one hand, while the precipitation of proeutectoid ferrite also refines the original austenite grains, thereby further improving the toughness of the rails; in terms of coordinated regulation of corrosion resistance and mechanical properties, the present invention achieves coordinated performance improvement by matching the strengthening coefficient, carbon equivalent and corrosion resistance, and realizes that the rails have both corrosion resistance, fatigue resistance and excellent weldability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The microstructure diagram of the steel rail with excellent corrosion resistance and contact fatigue resistance prepared in Example 1 of the present invention is shown;

[0032] Figure 2The microstructure diagram of the steel rail with excellent corrosion resistance and contact fatigue resistance prepared in Example 2 of the present invention is shown. DETAILED DESCRIPTION

[0033] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments are described in detail in the present invention, it is easy for those skilled in the art to appreciate that multiple modifications are feasible without actually departing from the teaching 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 gist of the present invention, other replacements, modifications, changes and deletions may be made to the design, operating conditions and parameters of the following exemplary embodiments.

[0034] The invention provides a steel rail with excellent corrosion resistance and contact fatigue resistance. The chemical composition and proportion of the steel rail are as follows: by mass percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest is Fe and inevitable impurities.

[0035] In the above rails, the chemical composition ratio satisfies the following relationship:

[0036] 6.93[C]+1.15[Si]+1.26[Mn]+1.46[Cr]+6.2[V]+0.63[Cu]+0.86[Ni]≥7.0%; and

[0037] 0.71[Si]+1.04[Cr]+1.67[Cu]+1.35[Ni]+2.1[Nb]≥1.7%;

[0038] [Cr]+[Cu]+[Ni]≥0.60%;

[0039] The carbon equivalent CE satisfies the following relationship:

[0040] [C]+[Mn] / 6+[Cr] / 5+[V] / 5+[Cu] / 15+[Ni] / 15≤0.95%.

[0041] In addition, the present invention also provides a method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0042] 1) The chemical composition and proportion of the rail matrix are controlled as follows: by weight percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest is Fe and unavoidable impurities;

[0043] 2) The rail matrix is ​​subjected to combined electromagnetic stirring of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring, and cast at low superheat and high casting speed to obtain a highly homogeneous steel billet;

[0044] 3) The steel billet is placed in a heating furnace for heating and rolled into a rail by a universal rolling method;

[0045] 4) Accelerate the cooling of the rails, cool them to below 500°C, then cool them naturally to room temperature, and straighten them with a small deformation.

[0046] In the above preparation method, in step 2), the magnetic field intensity of the electromagnetic stirring of the continuous casting crystallizer is 40×10 -4 -50×10 -4 T, the magnetic field intensity of the secondary cooling electromagnetic stirring is 40×10 -4 -50×10 -4 T, superheat is 12-20℃, and the billet drawing speed is 0.82-0.95m / min.

[0047] In the above preparation method, in step 3), the heating process of the steel billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, and the heating time is 50-70min; in the second stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 45-65min; in the third stage, the furnace temperature of the heating furnace is 1180-1230°C, and the heating time is 35-50min.

[0048] In the above preparation method, in step 3), the universal rolling method includes universal rough rolling, intermediate rolling and finish rolling.

[0049] In the above preparation method, the initial rolling temperature is 1150-1200°C, the intermediate rolling temperature is 900-930°C, the elongation coefficient is greater than 1.3, and the final rolling temperature is 850-880°C.

[0050] In the above preparation method, in step 4), the accelerated cooling of the rail is carried out in stages: in the first stage, the top surface temperature of the rail is accelerated cooled from 790-820°C at a rate of 4.0-5.5°C / s for 42-52s; in the second stage, after the first stage, it is cooled to below 500°C at a rate of 1.0-2.0°C / s.

[0051] In the above preparation method, in step 4), small deformation straightening is performed by a horizontal straightening machine, wherein the total pressing amount of the movable upper roller of the horizontal straightening machine is 30-40 mm.

[0052] The above technical solution of the present invention is described in detail below through specific embodiments.

[0053] The special line conditions of plateau mountain railways, such as low temperature, large temperature difference, super long ramps, long tunnels, and plateau uninhabited areas, as well as the operating characteristics of high speed and mixed passenger and freight transportation, put forward higher requirements on the low temperature toughness and plasticity, contact fatigue performance, abrasion resistance, organizational performance stability, weldability, etc. of rails. The present invention innovates the composition design of rails and the entire process of smelting, rolling, and heat treatment, gives full play to the synergy and interaction between alloy elements and the upper and lower processes of the production process, and provides a rail with good comprehensive performance and a preparation method thereof.

[0054] The invention provides a steel rail having excellent wear resistance, corrosion resistance, contact fatigue resistance, abrasion resistance and welding performance.

[0055] The microstructure of the rail head provided by the present invention is 0.5%-3.0% proeutectoid ferrite + very fine lamellar pearlite, wherein the average spacing of pearlite lamellae at 1mm below the top surface of the rail head is 70-80 nanometers, and the average size of austenite grains is 5-15 micrometers; the average spacing of pearlite lamellae at 10mm below the top surface of the rail head is 75-85 nanometers, and the average size of austenite grains is 8-20 micrometers; the pearlite lamellae at 25mm below the top surface of the rail head are 70-80 nanometers, and the average size of austenite grains is 5-15 micrometers; the average spacing of pearlite lamellae at 10mm below the top surface of the rail head is 75-85 nanometers, and the average size of austenite grains is 8-20 micrometer The average spacing is 90-100 nanometers, and the average size of austenite grains is 12-25 microns; the rail has fine original austenite grains (above level 9) and extremely thin pearlite lamellar spacing (below 100 nanometers), and at the same time, with the strengthening effect of nano-precipitation phase, it has good strength and toughness: rail tensile strength Rm ≥ 1100MPa, elongation after fracture A ≥ 14%, yield strength Rp0.2 ≥ 730MPa, low temperature fracture toughness -40℃K IC ≥40MPa·m 0.5 ; In its chemical composition, corrosion-resistant elements such as Cr, Cu, and Ni not only improve the strength of the rail, but also improve the corrosion resistance of the rail. The corrosion resistance is ≥150% relative to U71Mn.

[0056] In the present invention, in order to achieve extremely thin pearlite lamellar spacing, the rail head is cooled at a high cooling rate to undergo pearlite phase transformation at a phase transformation undercooling degree above 200°C.

[0057] In an embodiment of the present invention, the chemical composition and proportion of the steel rail provided by the present invention are as follows: C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70%, and also include at least one of V, Nb, and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, and the rest is Fe and unavoidable impurities.

[0058] In order to achieve the purpose of the present invention, preferably, the content of each element should satisfy the following relationship:

[0059] 6.93[C]+1.15[Si]+1.26[Mn]+1.46[Cr]+3.6[Mo]+6.2[V]+0.63[Cu]+0.86[Ni]≥7.0%;

[0060] 0.71[Si]+1.04[Cr]+1.35[Mo]+1.67[Cu]+1.35[Ni]+3.6[RE]+2.1[Nb]≥1.7%;

[0061] [Cr]+[Mo]+[Cu]+[Ni]+[RE]≥0.60; and

[0062] The carbon equivalent CE should satisfy the following relationship:

[0063] [C]+[Mn] / 6+[Cr] / 5+[Mo] / 5+[V] / 5+[Cu] / 15+[Ni] / 15≤0.95,

[0064] In a specific embodiment of the present invention, the rail of the present invention does not contain Mo and RE elements, so [Mo] = 0, [RE] = 0, that is, the above equation can be:

[0065] 6.93[C]+1.15[Si]+1.26[Mn]+1.46[Cr]+6.2[V]+0.63[Cu]+0.86[Ni]≥7.0%;

[0066] 0.71[Si]+1.04[Cr]+1.67[Cu]+1.35[Ni]+2.1[Nb]≥1.7%;

[0067] [Cr]+[Cu]+[Ni]≥0.60; and

[0068] Carbon equivalent CE should satisfy the following relationship:

[0069] [C]+[Mn] / 6+[Cr] / 5+[V] / 5+[Cu] / 15+[Ni] / 15≤0.95.

[0070] The principle of selecting each alloy element and the corresponding content in the present invention is as follows:

[0071] Carbon (C): Carbon is the most economical and effective alloying element for improving strength, and has a great influence on structure and performance. For every 0.1% increase in C content, the tensile strength Rm increases by about 90MPa, and the yield strength Rel increases by about 40-50MPa. The effect of carbon on improving steel strength is very obvious. Carbon in steel is very unfavorable for corrosion resistance, especially with the increase of carbon content, the resistance to intergranular corrosion is significantly reduced. Although the situation will improve after adding a certain amount of alloy to the steel, the most thorough measure is to reduce the carbon content as much as possible. Therefore, in order to improve the corrosion resistance of corrosion-resistant rails, the carbon content should be reduced, but in order to ensure its performance, the carbon content cannot be too low.

[0072] Silicon (Si): Silicon increases the critical transition temperature of steel during heating and cooling, and increases thermal hysteresis. Silicon can significantly increase the elastic limit, yield strength and yield strength ratio of steel. Studies on wheel steel have shown that increasing the Si content is beneficial to the wheel's anti-peeling and anti-scratch properties. A certain amount of silicon has a significant effect on the corrosion resistance of steel, mainly because when corrosion begins, a dense SiO2 film is formed on the steel surface, which hinders further inward erosion of the corrosive medium. In addition, for steel with a silicon content of more than 0.30%, silicon enrichment occurs between the surface iron oxide scale and the steel matrix, making the iron oxide scale more dense and enhancing the bonding force between the iron oxide scale and the matrix, thereby improving the corrosion resistance of the surface iron oxide scale. Silicon used in combination with other elements such as Cu, Cr, P, and Ca can also improve the weather resistance of steel, especially enhancing resistance to local corrosion.

[0073] Manganese (Mn): Manganese and iron form a solid solution, which increases the hardness and strength of ferrite and austenite in steel. It is also a carbide-forming element. Manganese in steel refines pearlite by lowering the critical transition temperature, and indirectly increases the strength of pearlite steel. Manganese can increase the stability of supercooled austenite and strongly increase the hardenability of steel. Adding Mn to steel can increase the tensile strength and yield limit of steel, but it does not deteriorate the deformation ability of steel; manganese can reduce the tough-to-brittle transition temperature of steel. When manganese increases the yield strength by 15MPa, the tough-to-brittle transition temperature can be reduced by about 5°C.

[0074] Phosphorus (P): Phosphorus is the element that improves the strength of ferrite the most. It exists in both ferrite and cementite in pearlite steel. A certain phosphorus content can improve the mechanical properties of low-carbon steel, but this favorable factor disappears as the carbon content of the steel increases. The higher the carbon content, the greater the brittleness caused by phosphorus. Phosphorus is also very detrimental to the weldability of steel, and it can increase the crack sensitivity of the weld. Phosphorus is the most effective element in improving the corrosion resistance of weathering steel, and plays an important role in the corrosion resistance of weathering steel. Due to the important role of phosphorus in corrosion resistance, but in view of its segregation and brittleness in steel, the phosphorus content of rails needs to be carefully controlled.

[0075] Sulfur (S): MnS inclusions, especially long and chain MnS inclusions, are one of the important factors for pitting and stress corrosion of steel. In view of the requirements of Class A inclusion level control, welding performance and corrosion resistance, the S content is required to be as low as possible.

[0076] Copper (Cu): Copper is an element that expands the γ phase region, but its solubility in iron is not large, and it cannot form a continuous solid solution with iron. The solubility of copper in α iron drops sharply as the temperature decreases. The influence of copper on the mechanical properties of steel can be roughly summarized into two aspects: 1) solid solution strengthening, in which it is only weaker than phosphorus and slightly stronger than silicon; 2) when the content exceeds about 0.75%, after solid solution and aging treatment, ε-Cu precipitation strengthening effect is produced. The addition of copper can improve the corrosion resistance of steel. The reason why copper can improve the corrosion resistance of steel is mainly that during the corrosion process of steel, due to the selective corrosion of different elements, copper enrichment occurs on the surface of copper-containing steel; a thin and tight copper oxide intermediate layer is formed between the corrosion layer and the copper enrichment layer, which can slow down or prevent the continued inward erosion of the corrosive medium. In areas with industrial atmosphere and humid atmosphere, corrosion resistance increases with the increase of copper content. The best effect is achieved when the copper content is 0.30%-0.35%. If the copper content is increased, the increase in effect is not obvious.

[0077] Chromium (Cr): Chromium forms a continuous solid solution with iron and forms a variety of carbides with carbon, which has a significant effect on the properties of steel, especially the wear resistance of steel. Chromium can significantly improve the hardenability of steel. Chromium also reduces the concentration of carbon in pearlite and the limit solubility of carbon in austenite. Chromium is an element with a passivation tendency, so a certain amount of chromium is added to steel to make the steel corrosion-resistant and anti-oxidation. When chromium-containing steel is corroded by a certain medium, an oxide film is formed on the surface of the steel. This film is called a passivation film. Under favorable conditions, the passivation film is dense and insoluble, and when it is damaged, it can recover by itself.

[0078] Nickel (Ni): Nickel can improve the stability of steel. Adding nickel will increase the self-corrosion potential of steel. At the same time, the rich nickel in the rust layer can effectively inhibit Cl -Domestic researchers believe that nickel is an effective element for atmospheric corrosion resistance, but only when the nickel content is high (3.5%), the effect is greater (resistant to various atmospheric corrosion), while when the content is low (about 1%), especially when copper is contained in the steel, the effect of improving corrosion resistance is not obvious. A certain amount of nickel is added to weathering steel (Ni:Cu=1:3-1:2) mainly to prevent copper brittle defects.

[0079] Niobium (Nb): Niobium in high carbon steel still has a certain solid solubility at high temperature, and can be dissolved in about 0.02% at 1200℃. In order to be economical and give full play to the role of niobium, the addition of niobium in rail steel should not exceed 0.02%. Niobium in rail steel mainly plays the role of refining austenite grains, improving plasticity, toughness and fatigue strength, and has no obvious effect on the strength of rail steel. As a common element for refining grains in steel, niobium is also used in research on improving the corrosion resistance of steel.

[0080] In addition, the present invention also provides a method for preparing a steel rail having the above alloy element content, which includes molten iron pretreatment, converter smelting, refining, vacuum treatment, continuous casting, rolling, and online heat treatment processes, and each process is controlled as follows:

[0081] The steel billet containing the above rail matrix components is heated until the steel billet is easy to deform, and is made into a rail by rough rolling, intermediate rolling and finish rolling on a universal rolling mill. The intermediate rolling and rough rolling are carried out by low temperature and large reduction rolling. The rail head is accelerated cooled by a large cooling rate at a phase transformation supercooling degree of more than 200°C to perform pearlite phase transformation, and then cooled to less than 500°C and then naturally cooled to room temperature, and straightened by a small deformation.

[0082] The above-mentioned steel billet is prepared from blast furnace molten iron through converter smelting, LF refining, electric heating and continuous casting; a combined electromagnetic stirring process of continuous casting crystallizer electromagnetic stirring and secondary cooling electromagnetic stirring is adopted, combined with low superheat and high pulling speed casting process to obtain highly homogeneous ingots.

[0083] In the embodiment of the present invention, preferably, the electromagnetic stirring magnetic field intensity of the continuous casting crystallizer should be 40×10 -4 -50×10 -4 T, the magnetic field strength of the secondary cooling electromagnetic stirring is 40×10 -4 -50×10 -4 T.

[0084] In the embodiment of the present invention, preferably, the superheat degree of continuous casting billet casting should be 12-20°C.

[0085] In the embodiment of the present invention, preferably, the casting strand drawing speed should be 0.82-0.95 m / min.

[0086] In an embodiment of the present invention, preferably, the billet heating process is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, and the heating time is 50-70min; in the second stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 45-65min; in the third stage, the furnace temperature of the heating furnace is 1180-1230°C, and the heating time is 35-50min.

[0087] In the embodiment of the present invention, preferably, in the universal rolling, the start rolling temperature is 1150-1200°C, the universal intermediate rolling temperature is 900-930°C, the elongation coefficient is greater than 1.3, and the universal final rolling temperature is 850°C-880°C.

[0088] In the embodiment of the present invention, preferably, the accelerated cooling process is divided into two stages. In the first stage, the rail top surface temperature is accelerated cooled from 790°C to 820°C at a rate of 4.0°C / s to 5.5°C / s for 42-52s to 540-570°C; in the second stage, the rail is cooled to 450-480°C at a rate of 1.0-2.0°C / s and then cooled naturally. The rail starts to be accelerated cooled at 790°C to 820°C. Accelerated cooling using compressed air can increase the austenite transformation undercooling and reduce the transformation temperature from austenite to pearlite, thereby reducing the pearlite lamellar spacing. Generally speaking, the faster the cooling rate, the smaller the pearlite lamella spacing, and the higher the strength of the steel. When the cooling rate is greater than 5.5℃ / s, segregation is inevitable inside the rail. The local area where the C and Mn elements are segregated is prone to produce abnormal structures such as martensite and bainite due to the excessive cooling rate, which leads to the scrapping of the rail. When the cooling rate is less than 4.0℃ / s, the heat treatment cannot fully play its role in improving the strength of the rail. For the present invention, by reducing the content of segregation-prone elements, the heat treatment process window is widened. Within the cooling rate range of 4.0-5.5℃ / s, the strength of the rail can reach more than 1100MPa, and the structure of the rail is pearlite and a small amount of ferrite, without abnormal structures such as martensite and bainite.

[0089] In an embodiment of the present invention, preferably, a horizontal straightening machine is provided for small deformation straightening, wherein the depression of the second roller of the horizontal straightening machine is 13-17 mm, and the total depression of the four movable upper rollers in the horizontal straightening machine is 35-43 mm.

[0090] Therefore, the present invention obtains a wider heat treatment window for rails by adopting precise chemical composition design and low-segregation and high-homogeneity smelting process, which provides good conditions for high-cooling-rate heat treatment of rails, and can implement high-cooling-rate heat treatment of rails to obtain extremely fine lamellar pearlite structure, while improving the strength and toughness of the rails; the present invention reasonably controls the content of proeutectoid ferrite and utilizes trace proeutectoid ferrite to improve the toughness of the rails on the one hand, while the precipitation of proeutectoid ferrite also refines the original austenite grains, thereby further improving the toughness of the rails; in terms of coordinated regulation of corrosion resistance and mechanical properties, the present invention achieves coordinated performance improvement through matching of strengthening coefficient, carbon equivalent and corrosion resistance, and realizes that the rails have comprehensive properties such as excellent corrosion resistance, contact fatigue resistance, low-temperature toughness and weldability.

[0091] The specific preparation processes of the following specific examples 1-6 and comparative examples 1-4 are as follows.

[0092] The chemical compositions and proportions used in Examples 1-6 and Comparative Examples 1-4 are shown in Table 1 below:

[0093] Table 1 Chemical composition and ratio relationship of Examples 1-6 and Comparative Examples 1-4

[0094]

[0095]

[0096] Example 1

[0097] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0098] Constructing a rail matrix according to the chemical composition and proportion shown in numbered embodiment 1;

[0099] The rail substrate is subjected to a magnetic field with a strength of 40×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 40×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 13-16℃, the billet pulling speed is 0.84m / min, and the billet is obtained;

[0100] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 750°C and the heating time is 50 minutes. In the second stage, the furnace temperature of the heating furnace is 1100°C and the heating time is 45 minutes. In the third stage, the furnace temperature of the heating furnace is 1180°C and the heating time is 35 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1150°C, the universal intermediate rolling temperature is 925°C, the elongation coefficient is 1.32, and the final rolling temperature is 850°C.

[0101] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 790℃, it is accelerated cooled at a rate of 4.8℃ / s for 46s, then cooled to 469℃ at a rate of 1.2℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0102] Example 2

[0103] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0104] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered embodiment 2;

[0105] The rail substrate is subjected to a magnetic field with a strength of 45×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 45×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 13-16℃, the billet pulling speed is 0.82m / min, and the billet is obtained;

[0106] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 800°C and the heating time is 60 minutes. In the second stage, the furnace temperature of the heating furnace is 1200°C and the heating time is 50 minutes. In the third stage, the furnace temperature of the heating furnace is 1210°C and the heating time is 40 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1200°C, the universal intermediate rolling temperature is 928°C, the elongation coefficient is 1.32, and the final rolling temperature is 860°C.

[0107] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 800℃, it is accelerated cooled at a rate of 5.30℃ / s for 42s, then cooled to 486℃ at a rate of 1.3℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0108] Example 3

[0109] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0110] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered embodiment 3;

[0111] The rail substrate is subjected to a magnetic field with a strength of 50×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 50×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 12-15℃, the billet pulling speed is 0.86m / min, and the billet is obtained;

[0112] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 950°C and the heating time is 70 minutes. In the second stage, the furnace temperature of the heating furnace is 1200°C and the heating time is 60 minutes. In the third stage, the furnace temperature of the heating furnace is 1230°C and the heating time is 50 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1180°C, the universal intermediate rolling temperature is 918°C, the elongation coefficient is 1.32, and the final rolling temperature is 850°C.

[0113] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 790℃, it is cooled at a rate of 4.50℃ / s for 46s, then cooled to 479℃ at a rate of 1.25℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0114] Example 4

[0115] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0116] Construct a rail matrix according to the chemical composition and proportion shown in numbered embodiment 4;

[0117] The rail substrate is subjected to a magnetic field with a strength of 45×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 50×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 11-15℃, the billet pulling speed is 0.89m / min, and the billet is obtained;

[0118] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 820°C and the heating time is 55 minutes. In the second stage, the furnace temperature of the heating furnace is 1180°C and the heating time is 60 minutes. In the third stage, the furnace temperature of the heating furnace is 1280°C and the heating time is 35 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1150°C, the universal intermediate rolling temperature is 914°C, the elongation coefficient is 1.32, and the final rolling temperature is 880°C.

[0119] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 820℃, it is accelerated cooled at a rate of 4.80℃ / s for 46s, then cooled to 492℃ at a rate of 1.12℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0120] Example 5

[0121] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0122] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered embodiment 5;

[0123] The rail substrate is subjected to a magnetic field with a strength of 50×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 45×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 12-16℃, the billet pulling speed is 0.85m / min, and the billet is obtained;

[0124] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 900°C and the heating time is 55 minutes. In the second stage, the furnace temperature of the heating furnace is 1200°C and the heating time is 60 minutes. In the third stage, the furnace temperature of the heating furnace is 1200°C and the heating time is 35 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1180°C, the universal intermediate rolling temperature is 917°C, the elongation coefficient is 1.32, and the final rolling temperature is 860°C.

[0125] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 800℃, it is cooled at a rate of 5.20℃ / s for 42s, then cooled to 497℃ at a rate of 1.08℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0126] Example 6

[0127] A method for preparing a steel rail with excellent corrosion resistance and contact fatigue resistance, comprising the following steps:

[0128] Construct a rail matrix according to the chemical composition and proportion shown in numbered embodiment 6;

[0129] The rail substrate is subjected to a magnetic field with a strength of 48×10 -4 The electromagnetic stirring and magnetic field strength of the T continuous casting mold are 48×10 -4 The combined electromagnetic stirring process of secondary cooling and electromagnetic stirring of T, the continuous casting superheat is 13-17℃, the billet pulling speed is 0.83m / min, and the steel billet is obtained;

[0130] The steel billet is placed in a heating furnace for heating. In the first stage, the furnace temperature of the heating furnace is 820°C and the heating time is 58 minutes. In the second stage, the furnace temperature of the heating furnace is 1100°C and the heating time is 65 minutes. In the third stage, the furnace temperature of the heating furnace is 1220°C and the heating time is 45 minutes. Then, the steel billet is subjected to universal rough rolling, intermediate rolling and finish rolling to form a rail. In the universal rolling method, the starting rolling temperature is 1150°C, the universal intermediate rolling temperature is 923°C, the elongation coefficient is 1.32, and the final rolling temperature is 880°C.

[0131] After rolling, the residual heat of rolling is used for online heat treatment. When the top surface temperature of the rail is 820℃, it is cooled at a rate of 4.50℃ / s for 50s, then cooled to 462℃ at a rate of 1.13℃ / s, and then naturally cooled to room temperature in the air, and straightened with a small deformation.

[0132] Comparative Example 1

[0133] A method for preparing a rail, comprising the following steps:

[0134] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered comparative example 1;

[0135] The pearlite rail is prepared by the existing method, wherein the continuous casting overheat is 24-35°C, the billet drawing speed is 0.71m / min, the universal rolling method is used for rolling, the universal rolling temperature is 967°C, and the elongation coefficient is 1.19;

[0136] After rolling, the steel was subjected to online heat treatment using the residual heat from rolling, and was accelerated cooled at a rate of 2.1°C / s for 110s to 548°C, and then naturally cooled to room temperature in air.

[0137] Comparative Example 2

[0138] A method for preparing a rail, comprising the following steps:

[0139] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered comparative example 2;

[0140] The pearlite rail is prepared by the existing method, wherein the continuous casting overheat is 19-32°C, the billet drawing speed is 0.69m / min, the universal rolling method is used, the universal rolling temperature is 975°C, and the elongation coefficient is 1.19;

[0141] After rolling, the steel was subjected to online heat treatment using the residual heat from rolling, and was accelerated cooled at a rate of 2.1°C / s for 110s to 562°C, and then naturally cooled to room temperature in air.

[0142] Comparative Example 3

[0143] A method for preparing a rail, comprising the following steps:

[0144] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered comparative example 3;

[0145] Pearlite rails are prepared by the existing method, wherein the continuous casting overheat is 26-35°C, the billet drawing speed is 0.70m / min, the universal rolling method is used, the universal rolling temperature is 952°C, and the elongation coefficient is 1.19;

[0146] After rolling, the steel was subjected to online heat treatment using the residual heat from rolling, and was accelerated cooled at a rate of 2.1°C / s for 110s to 552°C, and then naturally cooled to room temperature in air.

[0147] Comparative Example 4

[0148] A method for preparing a rail, comprising the following steps:

[0149] The rail substrate is constructed according to the chemical composition and proportion shown in the numbered comparative example 4;

[0150] The combined electromagnetic stirring process of continuous casting crystallizer electromagnetic stirring and secondary cooling electromagnetic stirring is adopted, the continuous casting overheat is 12-16°C, the billet drawing speed is 0.83m / min, the universal rolling method is used, the universal intermediate rolling temperature is 921°C, and the elongation coefficient is 1.32;

[0151] After rolling, the residual heat of rolling was used for online heat treatment, with accelerated cooling at a rate of 4.80°C / s for 45s, and then cooled to 472°C at 1.20°C / s, and then naturally cooled to room temperature in air.

[0152] The microstructure diagram of the rails obtained in the above-mentioned embodiments 1 and 2 of the present invention is as follows: Figure 1 , Figure 2 As shown. Figure 1 and 2 It can be seen that the pearlite lamellar structure of the obtained rail is evenly distributed, and no abnormal structures such as martensite and bainite appear.

[0153] In addition, in order to illustrate the relevant properties of the steel rails prepared by the above embodiments of the present invention, the mechanical properties of the steel rails of Examples 1-6 and Comparative Examples 1-4 are tested below, wherein the room temperature metallographic structure is tested according to GB / T 13298 standard, the yield strength, tensile strength and elongation are tested according to GB / T 228.1 standard, and the Brinell hardness is tested according to GB / T 231.1 standard. Specific data are shown in Table 2. The room temperature impact energy is tested according to GB / T 229 standard, the fracture toughness KIC of the rail is tested according to TB / T 2344.1 and GB / T 4161, and the relative corrosion resistance of the rail is tested according to TB / T 2375-1993; the wear volume is tested on an MM-200 wear tester, the wear mode is dry grinding, the rotation speed is 200r / min, the total number of grinding revolutions is 100,000 revolutions, the test load is 980N, and the slip is 10%; the contact fatigue life test is carried out on a TIME 8123 rolling contact fatigue tester, with a test contact stress of 1200MPa and a slip of 1.0%.

[0154] Table 2 Microstructure and general mechanical properties of Examples 1-6 and Comparative Examples 1-4

[0155]

[0156] As can be seen from Table 2 above, the rails prepared by the composition and process of the present invention have smaller austenite grain size and pearlite interlamellar spacing, so they have high strength and hardness while maintaining high elongation after fracture. Comparative Example 1 is a U71Mn carbon rail produced by the current conventional process, and its strength, hardness and elongation after fracture are all lower than those of the rails prepared by the present invention; Comparative Example 2 is a rail produced by conventional process based on U71Mn after alloying and improvement of the composition, although the strength and hardness are improved, the elongation after fracture is low, and it is impossible to achieve strong-toughness matching; Comparative Example 3 is a rail produced by conventional process with the composition of the present invention, and its strength and plasticity are slightly improved compared with U71Mn rails, but compared with Examples 1-6, the yield strength and elongation after fracture are quite different; Comparative Example 4 is a rail with medium carbon content alloying composition produced by the process of the present invention, and obtains finer austenite grain size and pearlite interlamellar spacing, and has good plasticity, but the excessive proeutectoid ferrite content leads to low strength and hardness.

[0157] Table 3 Impact, fracture mechanics, wear, corrosion, and contact fatigue properties of Examples 1-6 and Comparative Examples 1-4

[0158]

[0159] It can be seen from Table 3 that the rails prepared by the composition and process of the present invention have good room temperature and low temperature impact performance and fracture toughness. At the same time, the wear test wear is lower than that of the U71Mn rail in Comparative Example 1, the relative corrosion resistance is ≥143%, and the contact fatigue life reaches more than 550,000 times. Comparative Example 1 is a U71Mn carbon rail produced by the current conventional process, and its room temperature and low temperature impact performance, fracture toughness and contact fatigue life are both low; Comparative Example 2 is a rail produced by conventional process with improved composition alloying on the basis of U71Mn, although the wear amount and contact fatigue life are high, but its room temperature and low temperature impact performance and fracture toughness are low; Comparative Example 3 is a rail produced by the composition of the present invention but by conventional process, although the wear amount and contact fatigue life are high, but its room temperature and low temperature impact performance and fracture toughness are low; Comparative Example 4 is a rail produced by the process of the present invention with medium carbon content alloying composition, although it has good room temperature and low temperature impact performance, fracture toughness and high corrosion resistance, but the wear amount is larger and the contact fatigue life is lower.

[0160] In summary, the method of the present invention obtains a wider heat treatment window for rails by adopting precise chemical composition design and low-segregation and high-homogeneity smelting process, which provides good conditions for high-cooling-rate heat treatment, and can implement high-cooling-rate heat treatment for rails to obtain extremely fine lamellar pearlite structure, while improving the strength and toughness of the rails; the present invention reasonably controls the content of proeutectoid ferrite and utilizes trace proeutectoid ferrite to improve the toughness of the rails on the one hand, while the precipitation of proeutectoid ferrite also refines the original austenite grains, thereby further improving the toughness of the rails; in terms of coordinated regulation of corrosion resistance and mechanical properties, the present invention achieves coordinated performance improvement through matching of strengthening coefficient, carbon equivalent and corrosion resistance, and realizes that the rails have both corrosion resistance, fatigue resistance and excellent weldability.

[0161] 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. If the present invention is modified or replaced by equivalents without departing from the spirit and scope of the present invention, it should be included in the protection scope of the claims of the present invention.

Claims

1. A steel rail with excellent corrosion resistance and contact fatigue resistance, characterized in that: The chemical composition and proportion of the rail are as follows: by mass percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, the rest is Fe and unavoidable impurities, The microstructure of the rail head is 0.5%-3.0% proeutectoid ferrite + extremely fine lamellar pearlite, among which, the average spacing between pearlite lamellae 1mm below the top surface of the rail head is 70-80 nanometers, and the average size of austenite grains is 5-15 microns; the average spacing between pearlite lamellae 10mm below the top surface of the rail head is 75-85 nanometers, and the average size of austenite grains is 8-20 microns; the average spacing between pearlite lamellae 25mm below the top surface of the rail head is 90-100 nanometers, and the average size of austenite grains is 12-25 microns.

2. The steel rail with excellent corrosion resistance and contact fatigue resistance according to claim 1, characterized in that: The ratio of the chemical components satisfies the following relationship: 6.93[C]+1.15[Si]+1.26[Mn]+1.46[Cr]+6.2[V]+0.63[Cu]+0.86[Ni]≥7.0%; and 0.71[Si]+1.04[Cr]+1.67[Cu]+1.35[Ni] +2.1[Nb]≥1.7%.

3. The steel rail with excellent corrosion resistance and contact fatigue resistance according to claim 2, characterized in that: The carbon equivalent CE satisfies the following relationship: [C]+[Mn] / 6+[Cr] / 5+ [V] / 5+[Cu] / 15+[Ni] / 15≤0.95%.

4. A method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance, characterized in that: The following steps are involved: 1) The chemical composition and proportion of the rail matrix are controlled as follows: by weight percentage, C: 0.55-0.70%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.25-0.55%, Ni: 0.15-0.35%, Mn+Cr: 1.15-1.60%, Cu+Ni: 0.40-0.70% and at least one of V, Nb and Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.001-0.08%, the rest are Fe and unavoidable impurities, the rail head microstructure is 0.5%-3.0% proeutectoid ferrite + very fine lamellar pearlite, among which, the average spacing of pearlite lamellae 1mm below the top surface of the rail head is 70-80 nanometers, and the average size of austenite grains is 5-15 microns; the average spacing of pearlite lamellae 10mm below the top surface of the rail head is 75-85 nanometers, and the average size of austenite grains is 8-20 microns; the average spacing of pearlite lamellae 25mm below the top surface of the rail head is 90-100 nanometers, and the average size of austenite grains is 12-25 microns; 2) The rail matrix is ​​subjected to combined electromagnetic stirring of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring, and cast at low superheat and high drawing speed to obtain a high homogeneity steel billet; 3) placing the steel billet in a heating furnace for heating, and rolling it into a steel rail by a universal rolling method; 4) Accelerate the cooling of the rails, cool them to below 500°C, then cool them naturally to room temperature, and straighten them with a small deformation; In step 4), the accelerated cooling of the rail is carried out in stages: in the first stage, the top surface temperature of the rail starts from 790-820°C and is accelerated to cool at a rate of 4.0-5.5°C / s for 42-52s; in the second stage, after the first stage, the rail is cooled at a rate of 1.0-2.0°C / s to below 500°C; The rail head is cooled at a high cooling rate to undergo pearlite transformation at a phase transformation undercooling degree above 200°C.

5. The method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance according to claim 4, characterized in that: In step 2), the magnetic field intensity of the electromagnetic stirring of the continuous casting crystallizer is 40×10 -4 -50×10 -4 T, the magnetic field intensity of the secondary cooling electromagnetic stirring is 40×10 -4 -50×10 -4 T, superheat is 12-20℃, and the billet drawing speed is 0.82-0.95m / min.

6. The method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance according to claim 4, characterized in that: In the step 3), the heating process of the steel billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, and the heating time is 50-70min; in the second stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 45-65min; in the third stage, the furnace temperature of the heating furnace is 1180-1230°C, and the heating time is 35-50min.

7. The method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance according to claim 4, characterized in that: In the step 3), the universal rolling method includes universal rough rolling, intermediate rolling and finish rolling.

8. The method for preparing a steel rail having excellent corrosion resistance and contact fatigue resistance according to claim 7, characterized in that: The starting rolling temperature is 1150-1200℃, the intermediate rolling temperature is 900-930℃, the elongation coefficient is greater than 1.3, and the final rolling temperature is 850-880℃.

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