Russian standard high-strength heat treatment steel rail and smelting method thereof

Abstract

The invention discloses a Russian-standard high-strength heat-treated steel rail and a smelting method thereof. The Russian-standard high-strength heat-treated steel rail provided by the invention comprises the following chemical components in percentage by mass: 0.72-0.78% of C; 0.50% to 0.60% of Si; 1.05 to 1.25 percent of Mn; 0.10% to 0.20% of Cr; 0.08% to 0.15% of V; less than or equal to 0.025% of P; s is less than or equal to 0.025%, N is 0.0120-0.0155%, and the balance is Fe and inevitable impurities. According to the adopted smelting method, smelting process parameters are controlled, particularly, in the first-stage smelting process, converter end point P is controlled to be smaller than or equal to 120 ppm, end point tapping C is controlled to be larger than or equal to 0.10%, the LF refining time is controlled in the second-stage smelting process, the continuous casting speed is controlled in the third-stage continuous casting process, and the produced steel rail meets the conditions that the brinell hardness is larger than or equal to 352 HB, and the impact toughness at the temperature of-60 DEG C is larger than or equal to 25 J / cm < 2 >.

Description

Technical Field

[0001] The invention belongs to the field of industrial smelting of high-strength heat-treated rails, and specifically relates to a Russian standard high-strength heat-treated rail and a smelting method thereof. Background Art

[0002] Most of Russia's territory is located in the Arctic, and most areas are in severe cold all year round, reaching below -60℃. The rails in these places have been in service for a long time under low temperature conditions. The low temperature further increases the brittleness of the steel and welds of the rails, seriously affecting the safety of railway operation. At present, among the rails at home and abroad, only the Russian standard clearly defines the technical conditions for low-temperature resistant rails. The rails produced are required to have excellent impact toughness at -60℃. Domestic rail manufacturers have not successfully produced low-temperature resistant rails in the ГОСТР51685-2013 standard. As we all know, rail steel is high-carbon steel with a carbon content of more than 0.65%. As the carbon content increases, the toughness and plasticity of the steel decrease. However, the Russian standard has a unique composition design and production process for low-temperature resistant rails, which requires research to meet the Russian standard rail smelting production control.

[0003] Currently, Baosteel is producing P65 section rails, so the Russian standard rail material with excellent industrial smelting quality is of great significance to Baosteel's rail production level and stable market supply. Summary of the invention

[0004] In view of the problems existing in the prior art, one aspect of the present invention provides a Russian standard high-strength heat-treated rail, whose chemical composition, by mass percentage, is as follows: C 0.72-0.78%; Si 0.50-0.60%; Mn 1.05-1.25%; Cr0.10-0.20%; V 0.08-0.15%; P≤0.025%; S≤0.025%, N 0.0120-0.0155%, and the rest is Fe and unavoidable impurities.

[0005] In some embodiments, the chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.72-0.76%; Si 0.52-0.55%; Mn 1.12-1.18%; Cr 0.10-0.19%; V 0.08-0.12%; P≤0.020%; S≤0.005%, N 0.0127-0.0152%, and the rest is Fe and unavoidable impurities.

[0006] In some embodiments, the chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.75%; Si 0.53%; Mn 1.18%; Cr 0.10%; V 0.08%; P 0.010%; S 0.005%, N 0.0127%, and the rest is Fe and unavoidable impurities.

[0007] In some embodiments, the chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.76%; Si 0.52%; Mn 1.15%; Cr 0.14%; V 0.10%; P 0.010%; S 0.003%, N 0.0145%, and the rest is Fe and unavoidable impurities.

[0008] In some embodiments, the chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.72%; Si 0.55%; Mn 1.12%; Cr 0.19%; V 0.12%; P 0.019%; S 0.005%, N 0.0152%, and the rest is Fe and unavoidable impurities.

[0009] In some embodiments, the mechanical properties of the Russian standard high-strength heat-treated rail meet the following requirements: yield strength ≥800MPa, tensile strength ≥1180MPa, elongation ≥8%, surface shrinkage ≥25%, Brinell hardness ≥352HB, -60°C impact toughness ≥25J / cm 2 .

[0010] In some embodiments, the mechanical properties of the Russian standard high-strength heat-treated rail meet the following requirements: yield strength ≥870MPa, tensile strength ≥1230MPa, elongation ≥10%, surface reduction ≥26%, Brinell hardness ≥358HB, -60°C impact toughness ≥26J / cm 2 .

[0011] Another aspect of the present invention provides a method for smelting Russian standard high-strength heat-treated rails, which includes the following processes:

[0012] During the smelting process, the P and S contents in the molten iron are controlled, wherein the C content in the converter steel is increased, the C content in the steel is ≥0.10%, the smelting slag basicity is controlled, the heavy slag basicity is controlled at about 2.5 (for example, 2.4-2.6), the converter endpoint P ≤120ppm, and the refining aluminum-free deoxidation process is used for smelting; desulfurization is carried out according to the composition and temperature of the converter molten steel, the composition is fine-tuned and the temperature is increased; the VD deep vacuum time is ≥18min, the soft blowing time is guaranteed, the continuous casting start superheat is ≤25°C, and the continuous casting is carried out at a constant drawing speed.

[0013] In some embodiments, the smelting method includes a first stage smelting, a second stage smelting and a third stage continuous casting, wherein in the first stage smelting, the converter is charged with iron, the smelting time is 35 to 55 minutes, and the final steel output C is controlled to be ≥0.10%, and the P content is ≤120ppm; in the second stage smelting, the LF refining is controlled for 45 to 65 minutes, ferrovanadium and high carbon ferrochrome metal raw materials are added, and silicon calcium barium aluminum-free deoxidizer is used for deoxidation, the VD deep vacuum time is ≥18min, and the vacuum degree is ≤6kpa; the soft blowing time is guaranteed, and the molten steel is stationary for 3-4 minutes after the steel breaks the vacuum; in the third stage continuous casting, the starting superheat is controlled to be ≤25°C, and the continuous casting speed is 0.61 to 0.63m / min.

[0014] In some embodiments, the continuous casting billet obtained by the above smelting method can be rolled according to the rolling process and heat treatment process disclosed in patent document CN116590609A to obtain the Russian standard high-strength heat-treated rail of the present invention.

[0015] The invention has the advantages that: by optimizing the chemical composition and content of the rail and controlling the smelting process parameters, especially controlling the converter end point P≤120ppm and the end point steel tapping C≥0.10% in the first stage of smelting, controlling the LF refining time (45-65 minutes) in the second stage of smelting, and controlling the continuous casting speed (0.61-0.63m / min) in the third stage of continuous casting, the purity of the material and the quality of the casting billet can be guaranteed to meet the technical requirements, and the mechanical properties of the Russian standard high-strength heat-treated rail obtained by the production meet the following requirements: yield strength≥800MPa, tensile strength≥1180MPa, elongation≥8%, area reduction≥25%, Brinell hardness≥352HB, -60℃ impact toughness≥25J / cm 2 , preferably meet the following requirements: yield strength ≥870MPa, tensile strength ≥1230MPa, elongation ≥10%, surface shrinkage ≥26%, Brinell hardness ≥358HB, -60℃ impact toughness ≥26J / cm 2 The component design and unique production process of the present invention are suitable for large-scale production and have good promotion value. DETAILED DESCRIPTION

[0016] The present invention is described in detail below through specific examples. The examples are intended to help understand the present invention but are not intended to limit the present invention.

[0017] Example 1: Russian standard high-strength heat-treated rail

[0018] This embodiment mainly produces Russian standard high-strength heat-treated rails according to the following process steps: smelting production process (first stage smelting, second stage smelting and third stage continuous casting) and rolling process (continuous casting billet → heating → BD1 rolling → BD2 rolling → CCS universal rolling mill continuous rolling → online heat treatment → cooling → straightening, the specific process can be as disclosed in patent document CN116590609A); ​​wherein the smelting production process specifically includes: in the first stage smelting, the converter is charged with iron, and the smelting time is 35 to 55 minutes minutes, and the final steel tapping C is controlled to be ≥0.10%, P≤120ppm; in the second stage of smelting, LF refining is controlled for 45 to 65 minutes, ferrovanadium and high carbon ferrochrome metal raw materials are added, and silicon calcium barium aluminum-free deoxidizer is used for deoxidation, VD deep vacuum time is ≥18min, and vacuum degree is ≤6kpa; the soft blowing time is ensured, and after the steel breaks the vacuum, the molten steel is stationary for 3-4 minutes; in the third stage of continuous casting, the pouring superheat is controlled to be ≤25°C, and the continuous casting speed is 0.61 to 0.63m / min.

[0019] Specific smelting production process parameters are shown in Table 1 below, and the chemical composition and percentage content of the continuous casting billet obtained by continuous casting production are shown in Table 2 below. The continuous casting billet is produced into a steel rail according to the rolling process disclosed in patent document CN116590609A.

[0020] Examples 2-3 and Comparative Examples 1-2 are all carried out according to the operation of Example 1, and the only difference is the chemical composition content or the smelting production process parameters, as shown in Table 1-2 below. The low-magnification inspection results of the continuous casting billets of Examples 1-3 are shown in Table 3 below.

[0021] The mechanical properties of the rail samples produced in Example 1-3 and Comparative Example 1-2 were tested in accordance with TB / T2344-2012. Specifically, the specifications of the tensile test samples are as follows: diameter d0=10mm, gauge length Lo=5do. The tread hardness was randomly sampled on the rail. The sample length was 250mm. The top surface of the rail head was ground off by 0.5mm. There were 5 test points. The Brinell hardness test was performed and the average value was calculated. The test temperature was 20°C ± 5°C. The above sample sampling method, position and size were in accordance with TB / T2344-2012. The impact sampling was tempered in accordance with the Russian standard and kept warm at 200°C for 6 hours. The sampling was carried out in accordance with GB / T229-2007, with the direction being longitudinal and the size being 10mm×10mm×50mm, which is A KU2 Type notch; the test results are shown in Table 4 below.

[0022] Table 1: Smelting production process parameters

[0023]

[0024] Table 2: Chemical composition and percentage of continuous casting slabs

[0025]

[0026] Table 3: Example 1 - 3. Low-power inspection results of continuous casting slabs

[0027] Example Loose center Shrinkage Center Crack Middle crack Subcutaneous cracks Corner cracks Subcutaneous bubbles Inclusions 1 1.0 0 0.5 1.0 0 0.5 0 0.5 2 1.5 0 1 0.5 0 0 0 1 3 1 0 0.5 0.5 0 0 0 0.5

[0028] Table 4: Mechanical properties of rails of Examples 1-3 and Comparative Examples 1-2

[0029]

[0030] As shown in Table 3 above, the continuous casting billets produced by the smelting of Examples 1-3 of the present invention have extremely high inclusions and good quality, and the rail smelting control meets the target requirements. In the actual steel rolling production, the flaw detection did not alarm. As shown in Table 4 above, the mechanical properties of the rails produced by Examples 1-3 of the present invention all exceed the standards, the hardness reaches more than 352HB, and the -60℃ impact toughness reaches 25J / cm 2 The above-mentioned results meet the standard requirements. However, the rails produced by Comparative Examples 1-2, which do not adopt the method of the present invention, cannot meet the standard requirements.

[0031] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A Russian standard high-strength heat-treated rail, characterized in that: The chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.72-0.78%; Si 0.50-0.60%; Mn 1.05-1.25%; Cr 0.10-0.20%; V0.08-0.15%; P≤0.025%; S≤0.025%, N 0.0120-0.0155%, and the rest is Fe and unavoidable impurities.

2. The Russian standard high-strength heat-treated rail according to claim 1, characterized in that: The chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.72-0.76%; Si 0.52-0.55%; Mn 1.12-1.18%; Cr0.10-0.19%; V 0.08-0.12%; P≤0.020%; S≤0.005%, N 0.0127-0.0152%, and the rest is Fe and unavoidable impurities.

3. The Russian standard high-strength heat-treated rail according to claim 2 is characterized in that: The chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.75%, Si 0.53%, Mn 1.18%, Cr 0.10%, V 0.08%, P 0.010%, S 0.005%, N 0.0127%, and the rest is Fe and unavoidable impurities.

4. The Russian standard high-strength heat-treated rail according to claim 2, characterized in that: The chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.76%, Si 0.52%, Mn 1.15%, Cr 0.14%, V 0.10%, P 0.010%, S 0.003%, N 0.0145%, and the rest is Fe and unavoidable impurities.

5. The Russian standard high-strength heat-treated rail according to claim 2, characterized in that: The chemical composition of the Russian standard high-strength heat-treated rail is calculated by mass percentage as follows: C 0.72%, Si 0.55%, Mn 1.12%, Cr 0.19%, V 0.12%, P 0.019%, S 0.005%, N 0.0152%, and the rest is Fe and unavoidable impurities.

6. The Russian standard high-strength heat-treated rail according to any one of claims 1 to 5, characterized in that: The mechanical properties of the Russian standard high-strength heat-treated rails meet the following requirements: yield strength ≥800MPa, tensile strength ≥1180MPa, elongation ≥8%, area reduction ≥25%, Brinell hardness ≥352HB, -60℃ impact toughness ≥25J / cm 2 .

7. The Russian standard high-strength heat-treated rail according to claim 6, characterized in that: The mechanical properties of the Russian standard high-strength heat-treated rails meet the following requirements: yield strength ≥870MPa, tensile strength ≥1230MPa, elongation ≥10%, area reduction ≥26%, Brinell hardness ≥358HB, -60℃ impact toughness ≥26J / cm 2 .

8. The smelting method of the Russian standard high-strength heat-treated rail according to any one of claims 1 to 7, comprising the following processes: During the smelting process, the P and S contents in the molten iron are controlled, among which the C content in the converter steel is increased, the C content in the steel is ≥0.10%, the smelting slag basicity is controlled, the heavy slag basicity is controlled at about 2.5, the converter end point P ≤120ppm, and the refining aluminum-free deoxidation process is used for smelting; desulfurization is carried out according to the composition and temperature of the converter molten steel, the composition is fine-tuned and the temperature is increased; the VD deep vacuum time is ≥18min, the soft blowing time is guaranteed, the continuous casting start superheat is ≤25℃, and the continuous casting is carried out at a constant pulling speed.

9. The smelting method according to claim 8 comprises a first stage smelting, a second stage smelting and a third stage continuous casting, wherein in the first stage smelting, the converter is charged with iron, the smelting time is 35 to 55 minutes, and the final steel tapping C is controlled to be ≥0.10%, and the P content is ≤120ppm; in the second stage smelting, the LF refining is controlled for 45 to 65 minutes, ferrovanadium and high carbon ferrochrome metal raw materials are added, and silicon calcium barium aluminum-free deoxidizer is used for deoxidation, the VD deep vacuum time is ≥18min, and the vacuum degree is ≤6kpa; the soft blowing time is ensured, and the molten steel is stationary for 3-4 minutes after the steel breaks the vacuum; in the third stage continuous casting, the pouring superheat is controlled to be ≤25°C, and the continuous casting speed is 0.61 to 0.63m / min.

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