Manufacturing method of rare earth steel rail with good coupling of abrasion and rolling contact fatigue

Abstract

The invention discloses a manufacturing method of a rare earth steel rail with good coupling of abrasion and rolling contact fatigue, which is characterized by comprising the steps of molten iron pre-desulfurization, converter treatment, LF (ladle furnace) refining, vacuum degassing, continuous casting, heating, rolling, heat treatment and cooling processing. The steel rail comprises the following chemical components in percentage by mass: 0.85-1.10% of C; 0.60 to 0.85 percent of Si; 0.70 to 0.90 percent of Mn; less than or equal to 0.025% of P; s is less than or equal to 0.025%; 0.20% to 0.50% of Cr; v is 0.04 to 0.10 percent; 0.05 to 0.20 percent of Ni; 0.02 to 0.08 percent of Nb; the content of RE is 0.0010 to 0.030 percent; the total mass fraction of the Fe and the impurity elements is 100%. The invention aims to manufacture the steel rail with good strength and toughness ratio and excellent wear resistance, so that the steel rail can be applied to a heavy-load line service environment.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a method for manufacturing a rare earth rail with good coupling of wear and rolling contact fatigue. Background Art

[0002] Heavy-haul railway transportation has attracted extensive attention from railway departments around the world due to its large transport capacity, high efficiency and low cost. In countries and regions with dense heavy-haul railways such as China, Australia, Brazil and the United States, as the axle weight, speed and annual transportation volume of heavy-haul trucks continue to increase, heavy-haul line rails are facing problems such as large wear and peeling during service. In particular, the annual transportation volume of freight lines such as the Daqin Railway in my country has increased rapidly, and the overall line shows two types of damage: wear and rolling contact fatigue. Since there is a mutually restrictive and competitive relationship between rolling contact fatigue and wear of rail materials, it affects the use and daily maintenance of rails, especially on curved lines of mixed passenger and freight lines, where the wheel-rail force is large, the mutually restrictive and competitive relationship between rolling contact fatigue and wear is more obvious, which has a serious impact on the comprehensive service life of rails and driving safety.

[0003] Patent CN 102220545A provides a high-carbon, high-strength heat-treated rail with excellent wear resistance and plasticity and a production method. The main elements of the material composition are C, Si, Mn, Cr, V, Ti, and the rest are iron and inevitable impurities. The tensile strength of the rail after rolling heat treatment is ≥1330MPa, the elongation is ≥9%, the rail head hardness is ≥380HB, the hardened layer depth is more than 25mm, the organization is fine pearlite, it has excellent wear resistance and plasticity, and can meet the use requirements of heavy-duty railways. CN113930667B discloses a steel rail with good coupling between wear and rolling contact fatigue and a production method thereof. The chemical composition of the steel rail includes, by weight percentage, C: 0.75-0.88%, Si: 0.60-0.80%, Mn: 0.90-1.30%, V: 0.08-0.15%, Cr: 0.15-0.30%, Nb: 0.02-0.08%, B: 0.004-0.008%, P≤0.025%, S≤0.025%, and the remainder is Fe and inevitable impurities. By performing accelerated cooling of the rail head in stages, reasonably allocating the cooling speed and cooling time of each stage, and reasonably controlling the pearlite lamellar spacing of the metallographic structure of the rail head, the development of rail wear and rolling contact fatigue can be well coupled, thereby improving the comprehensive performance and service life of the rail.

[0004] Based on the development of industry technology and the comparative application of rail products in the world industry, it is shown that hypereutectoid rails have high strength, hardness and other properties, and show good comprehensive serviceability in large axle load lines and small radius curves. Therefore, in order to solve the wear and rolling contact fatigue damage problems of heavy-duty railway rails, it is of great significance to give full play to the role of RE in purifying molten steel and micro-alloying, and study a pearlite rail steel that refines the pearlite lamellar spacing and improves the rolling contact fatigue resistance and wear resistance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for manufacturing a rare earth rail with good coupling of wear and rolling contact fatigue, so as to manufacture a rail with good strength and toughness ratio and excellent wear resistance, so that it can be used in a heavy-load line service environment.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for manufacturing a rare earth rail with good coupling of wear and rolling contact fatigue, comprising: molten iron pre-desulfurization → converter → LF refining → vacuum degassing → continuous casting → heating → rolling → heat treatment → cooling processing: wherein:

[0008] The smelting adopts aluminum-free deoxidation alloying, and the whole process is poured in vacuum atmosphere;

[0009] The hot metal desulfurization adopts the magnesium powder spraying desulfurization process;

[0010] The converter smelting adopts the top and bottom combined blowing process, and the tapping temperature is controlled at 1650-1680℃, and the tapping C is ≥0.12%;

[0011] The slag basicity of LF refining is controlled at 2.0-2.8;

[0012] Degassing adopts VD deep vacuum treatment, bottom blowing argon pressure is 0.40-0.55MPa, deep vacuum is below 0.1Kpa; soft blowing time is 13-18min, rare earth alloy is added; let it stand for 3-5min and put it on the big bag;

[0013] The continuous casting process uses a large tank long nozzle and a crystallizer immersion nozzle to protect the pouring, the immersion depth is 60-70mm, and the billet drawing speed is controlled at 0.6-0.65m / min;

[0014] After sawing, the continuous casting billet enters the slow cooling pit at 450℃-600℃ for natural slow cooling for 48 hours;

[0015] The specific rolling heat treatment process is:

[0016] The walking beam / regenerative heating furnace is used for three-stage heating of the ingot, with the preheating temperature ≤800℃, the heating temperature 1200-1280℃, the soaking temperature 1220-1260℃, and the total heating time 3h20min-3h45min;

[0017] After uniform heating and insulation, the billet is rolled out of the heating furnace, the starting rolling temperature is 1100-1150℃, the billet rolling compression ratio is ≥9:1, and the final rolling temperature is 880-930℃;

[0018] The rail head after rolling is subjected to online accelerated cooling. The cooling medium is a mixture of wind / wind and fog. The initial cooling temperature is 750-810℃. The cooling rate of the rail head in the first stage is 2.8-5.0℃ / s, and the surface temperature of the rail head is reduced to 520-560℃; the cooling rate of the rail head in the second stage is 2.0-3.5℃ / s, and the surface temperature of the rail head is reduced to 480-520℃; in the third cooling stage, the cooling rate of the rail head is 0.8-1.7℃ / s, and the surface temperature of the rail head is reduced to 420-440℃; then air-cooled to room temperature;

[0019] The chemical composition of the rail by mass percentage is: C 0.85-1.10%; Si 0.60-0.85%; Mn0.70-0.90%; P≤0.025%; S≤0.025%; Cr 0.20-0.50%; V 0.04-0.10%; Ni0.05-0.20%; Nb0.02-0.08%; RE 0.0010-0.030%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

[0020] Furthermore, the rare earth alloy is a high-purity FeCe alloy or a lanthanum-cerium mixed rare earth.

[0021] Furthermore, the chemical composition of the rail by mass percentage is: C 0.869%; Si 0.776%; Mn 0.869%; P0.010%; S 0.006%; Cr 0.251%; V 0.045%; Ni 0.11%; Nb 0.045%; RE 0.006%; the rest are Fe and impurity elements, and the mass fraction totals 100%.

[0022] Furthermore, the chemical composition of the rail by mass percentage is: C 0.873%; Si 0.769%; Mn 0.858%; P 0.012%; S 0.007%; Cr 0.235%; V 0.043%; Ni 0.10%; Nb 0.048%; RE 0.018%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

[0023] Furthermore, the chemical composition of the rail by mass percentage is: C 0.875%; Si 0.782%; Mn 0.870%; P 0.009%; S 0.007%; Cr 0.256%; V 0.044%; Ni 0.11%; Nb 0.047%; RE 0.024%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

[0024] Furthermore, the rail performance meets the following requirements: tensile strength ≥ 1400 MPa, elongation after fracture ≥ 10%, and tread hardness between 400-411 HBW.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are:

[0026] The main alloying elements added to the material are Si, Mn, Nb, Cr, V, Ni, and RE; the purpose is to improve the strength and toughness of the rail and combine heat treatment production to design a reasonable material phase transformation temperature. The C component design in the steel has a large solid solubility with Fe, has a solid solution strengthening effect, improves the strength and hardness of the steel and improves the contact fatigue resistance of the rail. Mn expands the austenite phase region, increases the stability of the supercooled austenite of the steel, and significantly improves the hardenability of the steel, but the Mn content affects the welding of the rail. Si improves the yield strength of the material and resists problems such as early rail peeling and fish scale cracking, but at the same time, considering the weldability of the rail, the Si content should not be too high, because Si has poor heat conductivity, which is not conducive to rail welding; V, Ni, and Nb alloy elements can refine the material microstructure, precipitate C and N compounds to improve the strength and toughness of the material, especially the Nb element plays an important role in the initial grain refinement of the material, and can replace some of the expensive V alloys. In addition, the added RE element controls the morphology of sulfides during the smelting process, forms rare earth oxysulfides and reduces the formation of other metal sulfur compounds. This new sulfur compound does not deform or is very small during the rolling process, so that the grains in the steel are refined. At the same time, rare earths can improve the oxidation resistance and low-temperature resistance of steel. The presence of an appropriate amount of rare earth in steel materials can reduce the ductile-brittle transition temperature, which is of great technical significance to the service of rails.

[0027] The steel rails manufactured by the present application through reasonable composition design and process optimization have excellent performance, not only excellent strength and toughness but also good wear resistance. DETAILED DESCRIPTION

[0028] The chemical compositions of each example are shown in Table 1.

[0029] Table 1 Composition of each example (mass percentage / %)

[0030]

[0031] As shown in Table 1, the contents of C, Si, Mn, Cr, V, Ni, Nb, P, and S in the components of Examples 1 to 4 are substantially the same. No rare earth Ce element is added to Example 1, 6 ppm rare earth Ce element is contained in Example 2, 18 ppm rare earth Ce element is contained in Example 3, and 24 ppm rare earth Ce element is contained in Example 4.

[0032] The mechanical test results of each example are shown in Table 2.

[0033] Table 2 Mechanical properties of each example

[0034]

[0035] As can be seen from Table 2, each example has good strength, hardness and mechanical properties, and the rails produced therefrom have high strength and toughness. As can be seen from Table 2, the tensile strength of Examples 1 to 4 is ≥1400MPa, the elongation after fracture is ≥10%, and the tread hardness is between 400-411HBW. Compared with Example 1, the elongation after fracture of Examples 2 to 4 is increased, and the maximum can reach 11.5%; the tensile strength is increased, and the maximum tensile strength of Example 4 is 1423MPa, and the tread hardness is ≥400HBW. Compared with Example 1, the strength and hardness of Examples 2 to 4 are increased, and the toughness is also improved accordingly.

[0036] Table 3 Wear test parameters during the example process; Wear tests were performed on Examples 1-5.

[0037] Table 3 Material wear test parameters

[0038]

[0039] Table 4 shows the wear values ​​during the embodiment. It can be seen that the average values ​​of Examples 2-4 are lower than those of Example 1 without rare earth, and the lowest wear average value is 8.32 μg / m. The addition of rare earth relatively improves the wear resistance of the material. The wear amount of Example 2 is 98.17% relative to Example 1 without rare earth, and the wear resistance is improved by 1.86%. The wear amount of Example 4 is 95.08% relative to Example 1, and the relative wear resistance is improved by 5.17%.

[0040] Table 4 Wear rate values ​​of different example materials

[0041]

[0042]

[0043] 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 method for manufacturing a rare earth rail with good coupling of wear and rolling contact fatigue, characterized in that: include: Hot metal pre-desulfurization → converter → LF refining → vacuum degassing → continuous casting → heating → rolling → heat treatment → cooling processing: Among them: The smelting adopts aluminum-free deoxidation alloying, and the whole process is poured in vacuum atmosphere; The hot metal desulfurization adopts the magnesium powder spraying desulfurization process; The converter smelting adopts the top and bottom combined blowing process, and the tapping temperature is controlled at 1650-1680℃, and the tapping C is ≥0.12%; The slag basicity of LF refining is controlled at 2.0-2.8; Degassing adopts VD deep vacuum treatment, bottom blowing argon pressure is 0.40-0.55MPa, deep vacuum is below 0.1Kpa; soft blowing time is 13-18min, rare earth alloy is added; let it stand for 3-5min and put it on the big bag; The continuous casting process uses a large tank long nozzle and a crystallizer immersion nozzle to protect the pouring, the immersion depth is 60-70mm, and the billet drawing speed is controlled at 0.6-0.65m / min; After sawing, the continuous casting billet enters the slow cooling pit at 450℃-600℃ for natural slow cooling for 48 hours; The specific rolling heat treatment process is: The walking beam / regenerative heating furnace is used for three-stage heating of the ingot, with the preheating temperature ≤800℃, the heating temperature 1200-1280℃, the soaking temperature 1220-1260℃, and the total heating time 3h20min-3h45min; After uniform heating and insulation, the billet is rolled out of the heating furnace, the starting rolling temperature is 1100-1150℃, the billet rolling compression ratio is ≥9:1, and the final rolling temperature is 880-930℃; The rail head after rolling is subjected to online accelerated cooling. The cooling medium is a mixture of wind / wind and fog. The initial cooling temperature is 750-810℃. The cooling rate of the rail head in the first stage is 2.8-5.0℃ / s, and the surface temperature of the rail head is reduced to 520-560℃; the cooling rate of the rail head in the second stage is 2.0-3.5℃ / s, and the surface temperature of the rail head is reduced to 480-520℃; in the third cooling stage, the cooling rate of the rail head is 0.8-1.7℃ / s, and the surface temperature of the rail head is reduced to 420-440℃; then air-cooled to room temperature; The chemical composition of the rail by mass percentage is: C 0.85-1.10%; Si 0.60-0.85%; Mn0.70-0.90%; P≤0.025%; S≤0.025%; Cr 0.20-0.50%; V 0.04-0.10%; Ni0.05-0.20%; Nb 0.02-0.08%; RE 0.0010-0.030%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

2. The method for manufacturing a rare earth rail with good coupling between wear and rolling contact fatigue according to claim 1, characterized in that: The rare earth alloy is a high-purity FeCe alloy or a lanthanum-cerium mixed rare earth.

3. The method for manufacturing a rare earth rail with good coupling between wear and rolling contact fatigue according to claim 1, characterized in that: The chemical composition of the rail by mass percentage is: C 0.869%; Si 0.776%; Mn 0.869%; P 0.010%; S 0.006%; Cr 0.251%; V 0.045%; Ni 0.11%; Nb 0.045%; RE 0.006%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

4. The method for manufacturing a rare earth rail with good coupling between wear and rolling contact fatigue according to claim 1, characterized in that: The chemical composition of the rail by mass percentage is: C 0.873%; Si 0.769%; Mn 0.858%; P 0.012%; S 0.007%; Cr 0.235%; V 0.043%; Ni 0.10%; Nb 0.048%; RE 0.018%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

5. The method for manufacturing a rare earth rail with good coupling between wear and rolling contact fatigue according to claim 1, characterized in that: The chemical composition of the rail by mass percentage is: C 0.875%; Si 0.782%; Mn 0.870%; P 0.009%; S 0.007%; Cr 0.256%; V 0.044%; Ni 0.11%; Nb 0.047%; RE 0.024%; the rest are Fe and impurity elements, with a total mass fraction of 100%.

6. The method for manufacturing a rare earth rail with good coupling between wear and rolling contact fatigue according to claim 1, characterized in that: The rail performance meets the following requirements: tensile strength ≥ 1400 MPa, elongation after fracture ≥ 10%, and tread hardness between 400-411 HBW.

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