A production method for refining the interlamellar spacing of h370 rail

Abstract

The application discloses a production method for refining the interlamellar spacing of H370 steel rail, and the chemical composition of the steel rail in percentage of the rail quality comprises the following components: C 0.80-0.86%; Si 0.50-0.70%; Mn 0.90-1.25%; Cr 0.20-0.30%; P≤0.020%; S≤0.020%, and the rest is Fe and inevitable impurities; after plastic deformation of the steel rail through rolling, the final rolling temperature is 920 DEG C ± 10 DEG C, the steel rail is cooled to 780 DEG C at a cooling rate of 0.5 DEG C / s, then is rapidly air-cooled to 510 DEG C at a cooling rate of 2.5-2.0 DEG C / s, and then is slowly cooled to room temperature; and the pearlite interlamellar spacing is less than or equal to 100 nm. The application aims to provide a production method for refining the interlamellar spacing of H370 steel rail, and adopts the approach of increasing the carbon content, reducing the Cr content and adopting a suitable heat treatment process to refine the pearlite interlamellar spacing.

Description

Technical Field

[0001] This invention belongs to the field of rail production and application technology, and in particular relates to a production method for refining the spacing between H370 rail laminations. Background Technology

[0002] The metallographic structure of rails is pearlite, which is a structure of alternating ferrite and cementite phases precipitated during the eutectoid transformation of austenite. Its morphology is a layered complex of thin layers of ferrite and cementite stacked alternately. Depending on the size of the lamellar spacing, it can be divided into three types: pearlite, sorbite, and troostite.

[0003] Domestic and international railways are developing towards high speed and large capacity, which requires a gradual improvement in the wear resistance, toughness, and safety of rails. Especially in areas with small radius curves, rail wear is severe, and the surface is prone to peeling and other damage, which greatly affects the safety of train operation and reduces the service life of rails. In order to further improve this situation, it is necessary to further enhance the strength and toughness of rails.

[0004] Pearlite lamellar spacing is approximately 100-450 nm, forming at temperatures between Al and 650℃. Pearlite formed within the 500-550℃ temperature range has a smaller lamellar spacing, approximately 80-120 nm. This fine-laminated pearlite structure is called sorbite. Temperature is a major factor affecting the lamellar spacing. As the cooling rate increases, the austenite transformation temperature decreases, and the supercooling increases, the lamellar spacing of the transformed pearlite continuously decreases, gradually improving the strength and toughness of the rail. Therefore, by rationally controlling the cooling rate after rail rolling, a fine-laminated pearlite structure can be obtained, improving the strength and toughness of the rail. Summary of the Invention

[0005] The purpose of this invention is to provide a production method for refining the interlayer spacing of H370 steel rails by increasing carbon content, reducing Cr content, and using a suitable heat treatment process to achieve the refinement of pearlite interlayer spacing.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention discloses a production method for refining the interlayer spacing of H370 steel rails, which adopts the approach of increasing carbon content, reducing Cr content, and using appropriate heat treatment processes to achieve the refinement of pearlite interlayer spacing.

[0008] The chemical composition of the rail by mass percentage includes: C 0.80~0.86%; Si 0.50~0.70%; Mn 0.90~1.25%; Cr 0.20~0.30%; P≤0.020%; S≤0.020%, with the remainder being Fe and unavoidable impurities;

[0009] The billet heating time is ≥3.5 hours and the heating temperature is ≥1250℃; the initial rolling temperature is 1130℃±10℃; after the rail undergoes plastic deformation during rolling, the final rolling temperature is 920℃±10℃, and it is cooled to 780℃ at a rate of 0.5℃ / s, followed by rapid air jet cooling to 510℃ at a cooling rate of 2.5~2.0℃ / s, and then the rail is slowly cooled to room temperature.

[0010] Pearlite lamellar spacing ≤100nm.

[0011] Furthermore, the rails must have a yield strength ≥820MPa, tensile strength ≥1280MPa, elongation ≥10%, and tread hardness ≥370HBW.

[0012] Furthermore, the chemical composition of the rail by mass percentage includes: C: 0.83%; Si: 0.58%; Mn: 1.20%; P: 0.010%; S: 0.006%; Cr: 0.26%, with the remainder being Fe and unavoidable impurities.

[0013] Furthermore, the billet heating time is 3.6 hours.

[0014] Furthermore, the heating temperature is 1280℃; the initial rolling temperature is 1132℃; and after the rail undergoes plastic deformation during rolling, the final rolling temperature is 930℃.

[0015] Furthermore, the rails are slowly cooled to room temperature at a rate of 0.4°C / s.

[0016] Furthermore, after the rail cooled to room temperature, its mechanical properties were tested. The microstructure was a fine lamellar pearlite structure with a lamellar spacing of 98 nm. The rail's yield strength was 830 MPa, tensile strength was 1300 MPa, elongation was 11.5%, and tread hardness was 375 HBW.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0018] Mechanical properties of the rails were tested after cooling to room temperature. The microstructure was fine lamellar pearlite with a lamellar spacing of ≤100nm. The rail yield strength was ≥820MPa, tensile strength was ≥1280MPa, elongation was ≥10%, and tread hardness was ≥370HBW. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 Metallographic photograph of Comparative Example 1;

[0021] Figure 2 The images show the metallographic structure (left) and interlamellar spacing (right) of Example 1. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments, so as to provide a clearer understanding of the present invention.

[0023] Comparative Example 1

[0024] The production method of the present invention is used for pearlitic steel rails with a specific composition range, wherein the chemical composition of such specific steel rails, by mass percentage, includes: C: 0.78%; Si: 0.58%; Mn: 1.20%; P: 0.012%; S: 0.008%; Cr: 0.26%; with the remainder being Fe and unavoidable impurities.

[0025] Specific production steps:

[0026] The billet was heated for 3.6 hours at a temperature of 1280℃. The initial rolling temperature was 1135℃. After plastic deformation during rolling, the final rolling temperature of the rail was 933℃. The rail was cooled to 800℃ at a rate of 0.5℃ / s, followed by rapid air cooling to 520℃ at a rate of 2.2℃ / s. The rail was then slowly cooled to room temperature.

[0027] Mechanical properties of the rails were tested after cooling to room temperature. The microstructure consisted of fine lamellar pearlite with a small amount of ferrite, with a pearlite lamellar spacing of 160 nm. The rails exhibited a yield strength of 830 MPa, a tensile strength of 1300 MPa, an elongation of 11.5%, and a tread hardness of 375 HBW. A photograph of the pearlite microstructure is available below. Figure 1 .

[0028] Example 1

[0029] The production method of the present invention is used for pearlitic steel rails with a specific composition range, wherein the chemical composition of such specific steel rails, by mass percentage, includes: C: 0.83%; Si: 0.58%; Mn: 1.20%; P: 0.010%; S: 0.006%; Cr: 0.26%, with the remainder being Fe and unavoidable impurities.

[0030] Specific production steps:

[0031] The billet was heated for 3.6 hours at a temperature of 1280℃. The initial rolling temperature was 1132℃. After plastic deformation during rolling, the final rolling temperature of the rail was 930℃. The rail was then slowly cooled to room temperature at a rate of 0.4℃ / s.

[0032] Mechanical properties of the rail were tested after cooling to room temperature. The microstructure was fine lamellar pearlite with a lamellar spacing of 98 nm. The rail had a yield strength of 830 MPa, a tensile strength of 1300 MPa, an elongation of 11.5%, and a tread hardness of 375 HBW. See the image for a photograph of the pearlite microstructure. Figure 2 .

[0033] Comparing Comparative Example 1 and Example 1, the rail composition of Comparative Example 1 did not reach the composition range specified in this invention, mainly due to its low carbon content. The rail was manufactured using the post-rolling cooling rate required by the patent, resulting in a microstructure of fine lamellar pearlite and a small amount of ferrite. While the rail's strength and hardness met the requirements, the pearlite lamellar spacing did not meet the target. In Example 1, the rail composition met the range specified in this invention, but the carbon content was increased. The rail was slowly cooled to room temperature after rolling, resulting in a microstructure of coarse lamellar pearlite. Both strength and hardness met the patent requirements. Therefore, as seen from the examples and comparative examples, a combination of rail composition and controlled cooling is necessary to achieve a pearlite rail with fine lamellar spacing. Pearlite rails produced according to the manufacturing method specified in this invention have high strength and good toughness. Refining the pearlite lamellar spacing effectively improves the rail's wear resistance and extends its service life.

[0034] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A production method for refining the interlayer spacing of H370 steel rail plates, characterized in that: The method of refining the interlamellar spacing of pearlite is achieved by increasing the carbon content, reducing the Cr content, and using appropriate heat treatment processes. The chemical composition of the rail by mass percentage includes: C 0.80~0.86%; Si 0.50~0.70%; Mn 0.90~1.25%; Cr 0.20~0.30%; P≤0.020%; S≤0.020%, with the remainder being Fe and unavoidable impurities; The billet heating time is ≥3.5 hours and the heating temperature is ≥1250℃; the initial rolling temperature is 1130℃±10℃; after the rail undergoes plastic deformation during rolling, the final rolling temperature is 920℃±10℃, and it is cooled to 780℃ at a rate of 0.5℃ / s, followed by rapid air jet cooling to 510℃ at a cooling rate of 2.5~2.0℃ / s, and then the rail is slowly cooled to room temperature. Pearlite lamellar spacing ≤100nm.

2. The production method for refining the interlayer spacing of H370 rail plates according to claim 1, characterized in that: The rail has a yield strength ≥820MPa, tensile strength ≥1280MPa, elongation ≥10%, and tread hardness ≥370HBW.

3. The production method for refining the interlayer spacing of H370 rail plates according to claim 1, characterized in that: The chemical composition of the rail by mass percentage Includes: C: 0.83%; Si: 0.58%; Mn: 1.20%; P：0.010%； S: 0.006%; Cr: 0.26%, the remainder being Fe and unavoidable impurities.

4. The production method for refining the interlayer spacing of H370 rail plates according to claim 3, characterized in that: The billet heating time is 3.6 hours.

5. The production method for refining the interlayer spacing of H370 rail plates according to claim 4, characterized in that: The heating temperature is 1280℃; the initial rolling temperature is 1132℃; and the final rolling temperature is 930℃ after the rail undergoes plastic deformation during rolling.

6. The production method for refining the interlayer spacing of H370 rail plates according to claim 5, characterized in that: The rails were cooled to room temperature slowly at a rate of 0.4°C / s.

7. The production method for refining the interlayer spacing of H370 rail plates according to claim 6, characterized in that: Mechanical properties of the rail were tested after it cooled to room temperature. The microstructure was fine lamellar pearlite with a lamellar spacing of 345 nm. The rail had a yield strength of 706 MPa, a tensile strength of 1189 MPa, an elongation of 13.0%, and a tread hardness of 356 HBW.

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