Rolling process for improving yield strength of pearlite steel rail

Abstract

The invention discloses a rolling technology for improving the yield strength of a pearlite steel rail. The rolling technology comprises the steps that the temperature of a steel billet heating soaking section ranges from 1230 DEG C to 1280 DEG C; the tapping temperature is not lower than 1030-1080 DEG C; the initial rolling temperature is 1000-1070 DEG C, and the final rolling temperature is less than 900 DEG C; in the cooling process of the steel rails of the cooling bed, the steel rail interval is not smaller than 350 mm, and straightening is conducted after natural cooling to 80 DEG C or below; the steel rail comprises the following chemical components in percentage by mass: 0.75 to 0.85 percent of C; 0.45 to 0.6 percent of Si; 1.0% to 1.2% of Mn; less than or equal to 0.020% of P; less than or equal to 0.020% of S; 0.2-0.3% of Cr, and the balance Fe and inevitable impurities. The rolled steel rail has the following properties: the tensile strength is greater than or equal to 980MPa, the yield strength is greater than or equal to 510MPa, the elongation is greater than or equal to 10%, and the tread hardness of the steel rail is greater than or equal to 310HB after the steel rail is hot-rolled.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a rolling process for improving the yield strength of pearlite rails. Background Art

[0002] Railways have become an important mode of transportation in the world with their advantages of high speed, large operating volume, high punctuality, safe driving, good comfort, small footprint, environmental protection, and low energy consumption. At present, the rail materials used in railway transportation are basically rails in the TB / T2344 standard, and the content of trace elements such as V and Cr is effectively controlled on the basis of the standard. Rails usually produce major failure forms such as wear and peeling cracks during the service of the line. These problems are closely related to the material, track parameter settings, and running speed. Among them, if the rail peeling cracks occur too early, serious damage such as peeling off will occur, affecting the safety of train operation; the way to reduce peeling cracks from the mechanical properties of the material is to increase the yield strength of the material and increase the material's ability to resist deformation. Therefore, based on the chemical composition and production process required by the material standard, designing a reasonable chemical composition and giving full play to the characteristics of the rolling process can maximize the strength and toughness of the rails. It has very important production and economic significance to reduce the occurrence of early peeling cracks in the service of rails. Summary of the invention

[0003] The purpose of the present invention is to provide a rolling process for improving the yield strength of pearlite rails. The rail performance after rolling meets the following requirements: the tensile strength of the rail after hot rolling is ≥980MPa, the yield strength is ≥510MPa, the elongation is ≥10%, and the rail tread hardness is ≥310HB.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The invention discloses a rolling process for improving the yield strength of pearlite steel rails, comprising: the temperature of the steel billet heating and soaking section is 1230-1280°C; the furnace discharge temperature is not lower than 1030-1080°C; the starting rolling temperature is 1000-1070°C, and the final rolling temperature is lower than 900°C; during the cooling process of the steel rails on the cooling bed, the interval between the steel rails is not less than 350mm, and the steel rails are naturally cooled to below 80°C for straightening;

[0006] The chemical composition of the steel rail includes, by mass percentage, C: 0.75-0.85%, Si: 0.45-0.6%, Mn: 1.0-1.2%, P≤0.020%, S≤0.020%, Cr: 0.2-0.3%, and the rest is Fe and unavoidable impurities.

[0007] Furthermore, the mechanical properties of the rail after hot rolling meet the following requirements: tensile strength ≥ 980 MPa, yield strength ≥ 510 MPa, elongation ≥ 10%, and rail tread hardness ≥ 310 HB.

[0008] Furthermore, the chemical composition of the steel rail includes, by mass percentage, C: 0.81%, Si: 0.58%, Mn: 1.18%, P: 0.012%, S: 0.0050%, Cr: 0.23%, and the rest is Fe and unavoidable impurities.

[0009] Furthermore, the chemical composition of the steel rail includes, by mass percentage, C: 0.80%; Si: 0.59%; Mn: 1.19%; P: 0.013%; S: 0.0030%; Cr: 0.237%, and the rest is Fe and unavoidable impurities.

[0010] Furthermore, the chemical composition of the steel rail includes, by mass percentage, C: 0.81%, Si: 0.57%, Mn: 1.18%, P: 0.014%, S: 0.0020%, Cr: 0.232%, and the rest is Fe and unavoidable impurities.

[0011] Compared with the prior art, the beneficial technical effects of the present invention are:

[0012] The performance of the steel rail after rolling by the rolling process of the present invention meets the following requirements: the tensile strength of the steel rail after hot rolling is ≥980MPa, the yield strength is ≥510MPa, the elongation is ≥10%, and the hardness of the steel rail tread is ≥310HB

[0013] The steel rail of the invention has good strength, hardness and mechanical properties. The steel rail produced by the steel rail meets the technical requirements and has improved yield strength, which plays an important role in reducing and minimizing the formation of early peeling cracks. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below with reference to specific embodiments.

[0015] 1) In order to improve the yield strength, the internal control components of smelting are reasonably designed within the standard range, with the focus on controlling the C content at the upper limit of the standard composition and the Si content at the upper limit. The specific composition of the smelting ingot is shown in Table 1.

[0016] Table 1. Composition content of continuous casting products

[0017] Example C / ％ Si / % Mn / % P / ％ S / ％ Cr / ％ Example 1 0.81 0.58 1.18 0.012 0.0050 0.230 Example 2 0.80 0.59 1.19 0.013 0.0030 0.237 Example 3 0.81 0.57 1.18 0.014 0.0020 0.232

[0018] 2) Billet heating: The total heating time is more than 50 minutes, and the heating temperature of each section is shown in Table 2.

[0019] Table 2 Rail heating process

[0020] Preheating section Heating 1 stage Heating 2 stages Heat soaking section temperature ≤800℃ 1150-1280℃ 1180℃～1290℃ 1230℃～1280℃

[0021] 3) Rolling temperature: The casting is rolled into rails by a universal rolling mill. The starting rolling temperature is 1000℃-1070℃. The final rolling temperature is based on the second rolling temperature. The final rolling target temperature of the rail is less than 900℃. The specific processes of each example are shown in Table 3.

[0022] Table 3 Rolling process of each example

[0023] 4)

[0025] After rolling, the rails were tested in detail for various indicators such as conventional tensile properties and tread hardness in accordance with the requirements of AREMA-2019 standard strength carbon rails. The test results show that all conventional and special properties meet the standard requirements. The specific test results are shown in Table 4.

[0026] Table 4 Mechanical properties of each example

[0027]

[0028] As can be seen from Figure 4, each example has good strength, hardness and mechanical properties (low yield strength ratio). The rails produced using them meet the technical requirements, and the yield strength is improved, which plays an important role in reducing and minimizing the formation of early peeling cracks.

[0029] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rolling process for improving the yield strength of pearlite rail, characterized in that: include: The temperature of the steel billet heating and soaking section is 1230℃-1280℃; the furnace temperature is not less than 1030℃-1080℃; the starting rolling temperature is 1000℃-1070℃, and the final rolling temperature is less than 900℃; the rail spacing during the cooling process of the cooling bed rail is not less than 350mm, and it is naturally cooled to below 80℃ for straightening; The chemical composition of the steel rail includes, by mass percentage: C: 0.75-0.85%; Si: 0.45-0.6%; Mn: 1.0-1.2%; P≤0.020%; S≤0.020%; Cr: 0.2-0.3%, and the rest is Fe and unavoidable impurities.

2. The rolling process for improving the yield strength of pearlite rail according to claim 1, characterized in that: The mechanical properties of the rails after hot rolling meet the following requirements: tensile strength ≥980MPa, yield strength ≥510MPa, elongation ≥10%, and rail tread hardness ≥310HB.

3. The rolling process for improving the yield strength of pearlite rail according to claim 1, characterized in that: The chemical composition of the steel rail includes, by mass percentage, C: 0.81%, Si: 0.58%, Mn: 1.18%, P: 0.012%, S: 0.0050%, Cr: 0.23%, and the rest is Fe and unavoidable impurities.

4. The rolling process for improving the yield strength of pearlite rail according to claim 1, characterized in that: The chemical composition of the steel rail includes, by mass percentage, C: 0.80%, Si: 0.59%, Mn: 1.19%, P: 0.013%, S: 0.0030%, Cr: 0.237%, and the rest is Fe and unavoidable impurities.

5. The rolling process for improving the yield strength of pearlite rail according to claim 1, characterized in that: The chemical composition of the steel rail includes, by mass percentage, C: 0.81%, Si: 0.57%, Mn: 1.18%, P: 0.014%, S: 0.0020%, Cr: 0.232%, and the rest is Fe and unavoidable impurities.

Images