CN116590593A - High-corrosion-resistance and high-wear-resistance pearlitic steel rail and preparation method thereof - Google Patents

Abstract

The invention discloses a pearlitic steel rail with high corrosion resistance and high wear resistance and a preparation method thereof. In the continuous casting process in the method, the molten steel is cast by a low superheating process, and the superheating degree is controlled in the range of 15-30°C. Internal; continuous casting electromagnetic stirring adopts the combination of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring; the online heat treatment process includes: the first stage of cooling: when the temperature of the top surface of the rail after final rolling is between 700 and 850 °C , at a cooling rate of 1.5-6.0°C/s, the top surface of the rail, the fillets on both sides of the rail head, and both sides are accelerated to cool until the temperature of the top surface of the rail is 400-500°C; the second stage of cooling: after the first The stage cooled steel rail is placed on the cooling bed, and the steel rail is air-cooled to room temperature. This method can obtain a pearlitic steel rail with high corrosion resistance and high wear resistance without adding a large amount of alloying elements, its tensile strength is ≥1150MPa, and its elongation after fracture is ≥15%. The hardness is in the range of 320-360HB, and the impact toughness of the rail head at room temperature is ≥35J.

Description

A kind of pearlitic steel rail with high corrosion resistance and high wear resistance and preparation method thereof

technical field

The invention relates to the technical field of rail production, in particular to a pearlite rail with high corrosion resistance and high wear resistance and a preparation method thereof.

Background technique

my country's railways are in a stage of rapid development, and the scope of laying is expanding year by year. The increasingly complex laying environment has put forward higher requirements for the corrosion resistance and wear resistance of the rails. Whether the rails have better resistance to marine environments and industrial acidic atmospheres The wear resistance of the environment and complex environment has become an important basis for judging whether the rail has excellent service performance, safety performance and service life.

At present, in order to improve the wear resistance of rails at home and abroad, online heat treatment is mainly used to increase the strength and hardness of rails. However, the increase in the strength and hardness of rails will lead to a decrease in the toughness of rails, which will affect the fatigue life of rails during use. Service safety; while the improvement of the corrosion resistance of rails currently mainly depends on coating the surface of the rail with a corrosion-resistant coating or adding a large amount of alloying elements such as copper and nickel to the composition of the rail. The complexity of the surface treatment of the rail and the composition system have led to The cost and reliability of corroded rails are prohibitive. Among the related patents on pearlitic steel rails and their preparation methods disclosed in the prior art, although the steel rails disclosed in most of the patents have good strength, hardness, and certain corrosion resistance, corrosion resistance is rarely considered With the comprehensive improvement of wear resistance and wear resistance, the obtained pearlitic steel rail still cannot fully meet the long-life service requirements of my country's railway complex environment, and the production process and composition system of corrosion-resistant and wear-resistant steel rails are complicated, making it difficult to achieve large-scale application. .

Therefore, in the prior art, there is a need for a pearlitic steel rail with high corrosion resistance and high wear resistance and an improved preparation method thereof.

Contents of the invention

In view of this, the purpose of the embodiments of the present invention is to propose a pearlitic steel rail with high corrosion resistance and high wear resistance and a preparation method thereof. The steel rail prepared by this method has high corrosion resistance and wear resistance and meets the requirements of Long-life service requirements in complex railway environments.

Based on the above purpose, the embodiment of the present invention provides a method for preparing a pearlitic steel rail with high corrosion resistance and high wear resistance, which sequentially includes converter smelting, LF furnace refining, RH vacuum treatment, and continuous casting to obtain a billet. Carry out rolling and on-line heat treatment, among which, the continuous casting process includes:

During the continuous casting process, the molten steel is cast with low superheating technology, and the superheating degree is controlled within the range of 15-30°C;

Continuous casting electromagnetic stirring adopts the combination of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring;

The online heat treatment process includes:

The first stage of cooling: when the temperature of the top surface of the rail after final rolling is between 700 and 850°C, the top surface of the rail, the two upper fillets of the rail head and the two sides are accelerated at a cooling rate of 1.5 to 6.0°C/s Cooling treatment until the temperature of the top surface of the rail is 400-500°C;

Second-stage cooling: Place the rail after the first-stage cooling on the cooling bed, and air-cool the rail to room temperature.

In some embodiments, the specific process of electromagnetic stirring in the continuous casting mold is as follows: the installation position is within the range of 4.5-5.5m from the molten steel surface of the mold, the electromagnetic stirring current is 300-450A, and the stirring frequency is 1.5-2.5Hz.

In some embodiments, the specific process of secondary cooling electromagnetic stirring is as follows: the installation location is within the range of 13.0-17.0 m from the molten steel surface of the mold, the electromagnetic stirring current is 250-400A, and the stirring frequency is 5-10 Hz.

In some embodiments, the cooling medium used in the online heat treatment is at least one of water mist, compressed air, and a mixture of compressed air and water mist.

The present invention also provides a pearlitic steel rail with high corrosion resistance and high wear resistance. In terms of weight percentage, the chemical composition of the rail includes: C: 0.50-0.75%, Si: 0.40-0.90%, Mn: 0.40- 1.00%, Cr: 0.25-0.65%, Cu: 0.20-0.50%, Ni: 0.15-0.35%, P: ≤0.020%, S: ≤0.015%, and at least one of V, Nb, Ti, the balance For Fe and unavoidable impurities.

In some embodiments, by weight percentage, the added value of Mn and Cr in the rail is between 1.10% and 1.50%, and the added value of Cu and Ni is between 0.40% and 0.70%.

In some embodiments, the content of at least one of V, Nb, and Ti contained in the rail is V: 0.02-0.15%, Nb: 0.01-0.08%, and Ti: 0.001-0.030%, by weight percentage.

In some embodiments, the tensile strength of the rail is ≥1150 MPa, the elongation after fracture is ≥15%, the hardness of the central surface of the rail head is in the range of 320-360HB, and the impact toughness of the rail head at room temperature is ≥35J.

The present invention has at least the following beneficial technical effects:

The present invention adopts the preparation method of controlling the smelting and continuous casting process, the chemical composition of the steel rail and the on-line heat treatment process, and can obtain the pearlitic steel rail with high corrosion resistance and high wear resistance without adding a large amount of various alloy elements , the tensile strength is ≥1150MPa, the elongation after fracture is ≥15%, the surface hardness of the center of the rail head is in the range of 320-360HB, and the impact toughness of the rail head at room temperature is ≥35J. Therefore, the pearlitic steel rail of the present invention can effectively reduce the corrosion condition of the steel rail in the marine environment and industrial acidic atmospheric environment, and effectively improve the wear resistance and service safety of the steel rail during service. At the same time, the pearlitic rail preparation method provided by this patent is simple and easy to operate, which is beneficial to its large-scale popularization and application in railway lines.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with specific examples.

The terms "comprising" and "having" and any variations thereof in the description and claims of the present invention are intended to cover non-exclusive inclusion; the terms "first" and "second" in the description and claims of the present invention etc. are used to distinguish different objects, not to describe a specific order. "Plurality" means two or more, unless otherwise clearly and specifically defined.

Furthermore, reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The occurrences of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments.

The invention provides a method for preparing a pearlitic steel rail with high corrosion resistance and high wear resistance, which sequentially includes converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain a billet, rolling the billet, and on-line heat treatment, Among them, the continuous casting process includes:

During the continuous casting process, the molten steel is cast with low superheating technology, and the superheating degree is controlled within the range of 15-30°C;

Continuous casting electromagnetic stirring adopts the combination of continuous casting mold electromagnetic stirring and secondary cooling electromagnetic stirring;

The online heat treatment process includes:

The first stage of cooling: when the temperature of the top surface of the rail after final rolling is between 700 and 850°C, the top surface of the rail, the two upper fillets of the rail head and the two sides are accelerated at a cooling rate of 1.5 to 6.0°C/s Cooling treatment until the temperature of the top surface of the rail is 400-500°C;

Second-stage cooling: Place the rail after the first-stage cooling on the cooling bed, and air-cool the rail to room temperature.

Furthermore, the specific process of electromagnetic stirring in the continuous casting mold is as follows: the installation position is within the range of 4.5-5.5m from the molten steel surface of the mold, the electromagnetic stirring current is 300-450A, and the stirring frequency is 1.5-2.5Hz.

Further, the specific process of secondary cooling electromagnetic stirring is as follows: the installation position is within the range of 13.0-17.0 m from the molten steel surface of the crystallizer, the electromagnetic stirring current is 250-400A, and the stirring frequency is 5-10 Hz.

Further, the cooling medium used in the online heat treatment is at least one of water mist, compressed air, and a mixture of compressed air and water mist.

Among them, for the smelting and continuous casting process, tundish casting with a low superheat of 15-30°C can effectively reduce the precipitation time of inclusions in the steel, and can effectively control the size of inclusions in billets and rolled rails. Improve the purity of rail steel to improve the wear resistance of the rail, thereby improving the service safety of the rail.

For continuous casting multi-stage electromagnetic stirring, the combination of 300~450A/1.5~2.5Hz continuous casting mold electromagnetic stirring and 250~400A/5~10Hz secondary cooling electromagnetic stirring can effectively control the continuous casting billet during continuous casting solidification The molten steel in the rolling mill must move, and a billet with higher homogeneity can be obtained, so that the rolled rail has more consistent full-scale performance and better corrosion resistance.

For the on-line heat treatment process, when the rail head tread is at 700-850°C, the rail structure is still in the austenite state. At this time, the rail head of the rail is cooled at a higher cooling rate, so that the formed pearlite structure can be formed as much as possible. Possible refinement, thereby improving the strength, hardness and ductility of the rail, therefore, it is necessary to adopt a large cooling rate of 1.5 ~ 6.0 ℃ / s.

For the second stage of cooling: After the accelerated cooling stage, the internal temperature of the rail head is in the range of 400-500°C. At this time, the rail has completed the pearlite phase transformation process, and it is meaningless to continue the accelerated cooling. The rail can be air-cooled to Room temperature for subsequent processing.

The complete production process of the preparation method of the pearlitic steel rail with high corrosion resistance and high wear resistance described in the present invention can be: adopt low-sulfur molten steel, smelt through converter or electric furnace, undergo LF refining, RH or VD vacuum treatment , Bloom protection continuous casting, billet heating furnace heating, high pressure water descaling before billet rolling, universal rolling mill rolling, rail on-line heat treatment, step-by-step cooling bed air cooling, horizontal and vertical compound straightening, rail specification and quality inspection, processing Line processing, surface inspection and storage.

The present invention also provides a pearlitic steel rail with high corrosion resistance and high wear resistance prepared based on the above method. In terms of weight percentage, the chemical composition of the steel rail includes: C: 0.50-0.75%, Si: 0.40-0.90% , Mn: 0.40-1.00%, Cr: 0.25-0.65%, Cu: 0.20-0.50%, Ni: 0.15-0.35%, P: ≤0.020%, S: ≤0.015%, and at least V, Nb, Ti One, the balance being Fe and unavoidable impurities.

Further, in terms of weight percentage, the added value of Mn element and Cr element content in the steel rail is between 1.10% and 1.50%, and the added value of Cu element and Ni element content is between 0.40% and 0.70%.

Further, in terms of weight percentage, the content of at least one of V, Nb and Ti contained in the rail is V: 0.02-0.15%, Nb: 0.01-0.08%, and Ti: 0.001-0.030%.

Further, the tensile strength of the rail is ≥1150MPa, the elongation after fracture is ≥15%, the hardness of the central surface of the rail head is in the range of 320-360HB, and the impact toughness of the rail head at room temperature is ≥35J.

The reason for limiting the content of the main chemical elements of the rail in the present invention will be described in detail below.

C is the most important and cheapest element in pearlitic steel rails to obtain good comprehensive mechanical properties and promote pearlite transformation. When the C content is less than 0.50%, under the production process of the present invention, it is impossible to ensure that the steel rail has suitable strength and wear resistance; when the C content is > 0.75%, under the production process of the present invention, the steel rail’s If the proportion of carbides is too high, the strength and hardness of the rail will be too high, which will adversely affect the wear resistance of the rail; therefore, the carbon content in the present invention is limited to 0.50-0.75%.

The main function of Si in steel is to inhibit the formation of cementite and act as a solid solution strengthening element to increase the hardness of ferrite matrix and improve the strength and hardness of steel. When the Si content is less than 0.40%, the solid solution content is too low and the strengthening effect is not obvious; when the Si content is more than 0.90%, it is easy to produce local segregation, which will reduce the toughness, plasticity and weldability of the steel, and has a negative effect on the safe use of the rail. Influence. Therefore, the Si content in the present invention is limited to 0.15 to 0.60%.

Mn is essential to increase the strength of ferrite and austenite in steel. When the Mn content is less than 0.40%, it is difficult to achieve the effect of increasing the carbide hardness and thereby increasing the strength and hardness of the steel; when the Mn content is greater than 1.00%, it will coarsen the grain size and affect the microstructure change of the rail steel during heat treatment. Significantly reduce the toughness and plasticity of steel; at the same time, Mn has a significant effect on the diffusion of C in steel, and abnormal structures such as bainite or martensite may be formed in the Mn segregation area, and at the same time affect the welding performance of the rail. Therefore, the Mn content in the present invention is limited to 0.40 to 1.00%.

As a carbide forming element, Cr can form a variety of carbides with carbon in the steel; at the same time, Cr can evenly distribute the carbides in the steel, reduce the size of the carbides, and improve the wear resistance of the rail. When the Cr content is less than 0.25%, the hardness and proportion of the formed carbides are low, the hardenability of the rail is low, and it is difficult to obtain high internal performance of the rail head; when the Cr content is greater than 0.65%, the hardenability of the rail is too high, It is easy to make the rail produce harmful bainite and martensite structures. While reducing the mechanical properties of the rail, it is impossible to ensure that the rail is a full pearlite structure. Therefore, the Cr content in the present invention is limited to 0.25 to 0.65%.

Cu is the most important element in steel to improve corrosion resistance, and its enrichment at the corrosion interface of rail steel can effectively inhibit the progress of corrosion reaction. When the Cu content is less than 0.20%, its corrosion resistance effect is not obvious, and it is difficult to achieve the corrosion resistance effect required by the present invention; when the Cu content is greater than 0.50%, its selective oxidation in the smelting and rolling process will easily lead to Cracks are generated on the surface, and the welding performance of the rail is seriously reduced at the same time. Therefore, the Cu content in the present invention is limited to 0.20 to 0.50%.

In Cu-containing steel, Ni can increase the solubility of Cu in austenite and reduce the occurrence of copper embrittlement. When the Ni content is less than 0.15%, its strengthening effect on the Cu element in the steel is not obvious; when the Ni content is more than 0.35%, it has exceeded the upper limit of its content for improving corrosion resistance and preventing copper embrittlement, and the Ni element is excessive. Therefore, the Ni content in the present invention is limited to 0.15 to 0.35%.

V precipitates in the form of vanadium carbonitride in the steel, inhibits the growth of austenite grains, and can refine the grain size in the steel. When the V content is less than 0.02%, the precipitation of carbonitrides is less, and the strengthening effect is not obvious; when the V content is more than 0.15%, coarse carbonitrides are easily formed in the steel, which reduces the toughness and plasticity of the steel. Therefore, the V content in the present invention is limited to 0.02 to 0.15%.

The role of Nb in steel is similar to that of vanadium, through the precipitation of niobium carbonitride to refine austenite grains, and at the same time improve the hardness and ductility of steel. When the Nb content is less than 0.01%, the carbonitride precipitation is less, and the strengthening effect is not obvious; when the Nb content is more than 0.08%, coarse carbonitrides are easily formed in the steel, which reduces the toughness and plasticity of the steel. Therefore, the Nb content in the present invention is limited to 0.01 to 0.08%.

Ti mainly plays the role of refining austenite grains in steel, which can improve the toughness and plasticity of steel. When the Ti content is less than 0.001%, the number of carbides formed in the steel is extremely low, and no effective strengthening can be formed; when the Ti content is more than 0.030%, titanium nitride and titanium carbide are easy to be enriched, resulting in the impact load of the steel. Easy to break down. Therefore, the Ti content in the present invention is limited to 0.001 to 0.030%.

Both P and S are impurity elements that cannot be completely removed from the rail. P will segregate at the grain boundary of the rail structure, seriously reducing the toughness of the rail; S is easy to form MnS inclusions in the steel, which is harmful to the wear resistance and contact fatigue resistance of the rail. Therefore, the P content in the present invention needs to be controlled below 0.020%; the S content needs to be controlled below 0.015%.

The present invention will be described in detail through examples below, but the scope of the present invention is not limited thereto.

The examples and comparative examples correspond to the steel rails with the following numbers 1-3 chemical compositions, and the specific chemical compositions are shown in Table 1.

Table 1

serial number C Si mn Cr Cu Ni V Nb Ti P S 1# 0.67 0.49 0.85 0.39 0.45 0.22 0.12 / / 0.017 0.006 2# 0.72 0.53 0.97 0.48 0.32 0.27 / 0.08 / 0.012 0.008 3# 0.53 0.66 0.90 0.30 0.28 0.30 / / 0.012 0.010 0.005

The balance is Fe and unavoidable impurities.

The heat treatment process parameters of the smelting and continuous casting machines of Examples 1-6 and Comparative Examples 1-6 are shown in Table 2, and the differences between the other processes of Examples and Comparative Examples are negligible.

Table 2

In the present invention:

① Test the tensile strength and elongation of the rail in accordance with GB/T 228.1 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method";

② According to GB/T 231.1 "Brinell Hardness Test of Metallic Materials Part 1: Test Method", test the surface hardness of the rail top surface of the rail;

③ According to GB/T 229.1 "Charpy Pendulum Impact Test Method for Metal Materials", test the room temperature impact toughness of the rail;

④ Test the corrosion resistance of rails according to TB/T 2375 "Test Method for Periodic Infiltration Corrosion of Weathering Steel for Railways". The specific conditions are: temperature: 45±2℃, humidity: 70±5%RH, cycle period: 60±3min( Immersion time 12±1.5min), test time: 300h, sample size 120mm×60mm×3mm, test solution: 2% NaCl solution (marine atmospheric environment)/0.02mol/L NaHSO ₃ solution (acidic atmospheric environment).

⑤ Wear resistance test Test method: Testing machine: M-200 wear testing machine, sample size: thickness 10mm×diameter 36mm circular sample, test load: 150kg, slip: 5%, material of the sample under grinding: Surface hardness 280~310HB, environment: air dry friction, rotation rate: 200 rpm, test cycle: 200,000 times.

Table 3 shows the test data of tensile strength, elongation after fracture, surface hardness, impact toughness, corrosion resistance and wear resistance of Examples 1-6 and Comparative Examples 1-6.

table 3

By comparing the examples and the comparative examples, it can be seen that the examples of the present invention have better tensile properties, surface hardness, impact toughness, corrosion resistance and wear resistance than the comparative examples; and the comparative examples The tensile strength, elongation after fracture, surface hardness or impact toughness of the middle rail do not meet the requirements. At the same time, its corrosion resistance and wear resistance are poorer in marine atmospheric environment and industrial acidic atmospheric environment. .

The above are the exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications can be made without departing from the scope of the disclosed embodiments of the present invention defined in the claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in an individual form, they may also be understood as a plurality unless explicitly limited to a singular number.

It should be understood that as used herein, the singular form "a" and "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items.

The serial numbers of the embodiments disclosed in the above-mentioned embodiments of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.

Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is exemplary only, and is not intended to imply that the disclosed scope (including claims) of the embodiments of the present invention is limited to these examples; under the idea of the embodiments of the present invention , the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in details for the sake of brevity. Therefore, within the spirit and principle of the embodiments of the present invention, any omissions, modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the embodiments of the present invention.

Claims (8)

1. The preparation method of the pearlitic steel rail with high corrosion resistance and high wear resistance sequentially comprises the steps of converter smelting, LF furnace refining, RH vacuum treatment and continuous casting to obtain a steel billet, and rolling and online heat treatment are carried out on the steel billet, and the preparation method is characterized in that the continuous casting process comprises the following steps:

casting molten steel in a ladle in a continuous casting process by adopting a low superheat degree process, wherein the superheat degree is controlled within the range of 15-30 ℃;

the continuous casting electromagnetic stirring adopts a mode of combining electromagnetic stirring of a continuous casting crystallizer with secondary cooling electromagnetic stirring;

the on-line heat treatment process comprises the following steps:

first stage cooling: when the temperature of the rail top surface of the steel rail is 700-850 ℃ after finish rolling, carrying out accelerated cooling treatment on the rail top surface of the steel rail, two upper round corners of the rail head and two side surfaces of the rail head at a cooling speed of 1.5-6.0 ℃/s until the temperature of the rail top surface is 400-500 ℃;

and (3) cooling in a second stage: and placing the steel rail cooled in the first stage on a cooling bed, and air-cooling the steel rail to room temperature.

2. The method for preparing the pearlitic steel rail with high corrosion resistance and high wear resistance according to claim 1, wherein the continuous casting crystallizer electromagnetic stirring specific process is as follows: the installation position is within the interval range of 4.5-5.5 m from the steel liquid level of the crystallizer, the electromagnetic stirring current is 300-450A, and the stirring frequency is 1.5-2.5 Hz.

3. The method for preparing the pearlitic steel rail with high corrosion resistance and high wear resistance according to claim 1, wherein the specific process of the secondary cooling electromagnetic stirring is as follows: the installation position is within the interval range of 13.0-17.0 m from the molten steel surface of the crystallizer, the electromagnetic stirring current is 250-400A, and the stirring frequency is 5-10 Hz.

4. The method for producing a high corrosion and wear resistant pearlite rail according to claim 1, wherein said cooling medium used for said on-line heat treatment is at least one of water mist, compressed air, a mixture of compressed air and water mist.

5. A high corrosion and wear resistant pearlitic rail, wherein the rail comprises the following chemical components in weight percent: c:0.50 to 0.75 percent of Si:0.40 to 0.90 percent of Mn: 0.40-1.00%, cr:0.25 to 0.65 percent of Cu:0.20 to 0.50 percent of Ni:0.15 to 0.35 percent, P: less than or equal to 0.020 percent, S: less than or equal to 0.015 percent, at least one of V, nb and Ti, and the balance of Fe and unavoidable impurities.

6. The high corrosion and wear resistant pearlite rail as set forth in claim 5 wherein said rail has a combined Mn and Cr content of between 1.10 and 1.50% and a combined Cu and Ni content of between 0.40 and 0.70% by weight.

7. The high corrosion and wear resistant pearlite rail according to claim 5, wherein said rail contains at least one of V, nb, ti in a weight percentage of V:0.02 to 0.15 percent of Nb:0.01 to 0.08 percent of Ti:0.001 to 0.030 percent.

8. The high corrosion and wear resistant pearlitic rail of claim 5 wherein the tensile strength of the rail is equal to or greater than 1150MPa, elongation after break is equal to or greater than 15%, the hardness of the central surface of the head is in the range of 320 to 360HB, and the room temperature impact toughness of the head is equal to or greater than 35J.