CN112301268B - Shock-absorbing noise-reducing high-speed railway track and manufacturing method thereof - Google Patents

Shock-absorbing noise-reducing high-speed railway track and manufacturing method thereof Download PDF

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CN112301268B
CN112301268B CN202011063516.2A CN202011063516A CN112301268B CN 112301268 B CN112301268 B CN 112301268B CN 202011063516 A CN202011063516 A CN 202011063516A CN 112301268 B CN112301268 B CN 112301268B
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molten iron
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CN112301268A (en
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许旸
董彦录
高凡
刘保建
张欣昱
王旭
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/10—Cast-iron alloys containing aluminium or silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/009—Continuous casting of metals, i.e. casting in indefinite lengths of work of special cross-section, e.g. I-beams, U-profiles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/045—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds for horizontal casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/055—Cooling the moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/04—Flash butt welding
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/20—Isothermal quenching, e.g. bainitic hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/08—Making cast-iron alloys
    • C22C33/10—Making cast-iron alloys including procedures for adding magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/06—Cast-iron alloys containing chromium
    • C22C37/08—Cast-iron alloys containing chromium with nickel
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/006—Graphite

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Abstract

The invention discloses a shock-absorbing noise-reducing high-speed railway track which is formed by welding a plurality of I-shaped sections, wherein the I-shaped sections comprise the following components in percentage by mass: 3.3-3.6%, Si: 2.3-2.7%, Mn: 0.3-0.5%, Ni: 0.6-1.0%, Cu: 0.4-0.7%, Mg: 0.03-0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the I-shaped section is more than or equal to 880MPa, the elongation is more than or equal to 8 percent, the metallographic structure of the I-shaped section is a complex phase structure consisting of an austenite body and graphite nodules, the austenite body consists of high-carbon austenite and needle-shaped high-silicon ferrite, the diameter of the graphite nodules in the surface layer of the I-shaped section within 12 mm-18 mm is less than or equal to 25 micrometers, and the density of the graphite nodules is more than or equal to 300/mm2. The invention also discloses a manufacturing method of the shock-absorbing noise-reducing high-speed railway track, and the manufactured track has good tensile strength and shock-absorbing noise-reducing performance.

Description

Shock-absorbing noise-reducing high-speed railway track and manufacturing method thereof
Technical Field
The invention belongs to the technical field of high-speed rail equipment manufacturing, and relates to a shock-absorbing noise-reducing high-speed railway track and a manufacturing method thereof.
Background
When a train runs on a track, vibration occurs due to various factors, and noise is generated. This vibration and noise comes from four aspects: noise generated between the wheels and the track, air resistance noise, locomotive power collection system (or current collection system) noise, and secondary noise reflected by the building. They all increase with increasing train speed, but at different rates. When the train speed exceeds 200km/h and then reaches 360km/h, namely on the current motor train and high-speed railway, vibration and noise mainly come from air resistance and between wheel rails. The noise of air resistance is higher than the noise between wheel tracks in decibel, but the frequency of the former is low, so that the auditory discomfort caused by people is small, and the vibration and noise frequency between high-speed rails is wide in distribution range, wherein the noise with the frequency between 500 Hz and 4000Hz gives strong auditory disturbance to people, so that the treatment urgency is stronger.
The wheel-rail noise can be subdivided into three parts, namely, the wheel-rail rolling noise which is the noise excited by roughness ripples on the surfaces of wheels and rails; second, the wheel rail impact noise caused by the defects such as the surface scar of the track; and thirdly, axial friction between the wheel rim and the side surface of the track when the train turns, and creeping noise between the wheels and the track, wherein the two noises are all squealing noise.
With the gradual increase of the vehicle speed, the network density of the high-speed rail is rapidly increased, and the high-speed rail noise becomes one of the environmental pollutions on the soil in China. The frequency of the high iron noise, as tested, extends from tens of hertz to 4000 hertz. Mainly caused by the wheel track, in the frequency domain of about 1000 hertz, the noise radiation sound power level is up to more than 100dB, which far exceeds the tolerance limit of human hearing to frequency and intensity, and is one of the environmental hazards generated when high-speed rails bring convenience to human travelling.
In the conventional exploration for controlling the noise of the high-speed rail, a damping layer with the thickness of 4mm is adhered to the side surface of the rail and the lower flange, and a thicker damping layer with a groove expanding layer is manufactured. The damping effect of the two methods is that the noise is reduced by less than 5 dB in the frequency domain below 1000Hz, and is reduced by less than 10 dB in the frequency domain above 1000 Hz. The transmission speed of sound in the air is 340 m/s, the speed in steel is more than 4000 m/s, and the whole surface of the track cannot be wrapped by a damping layer, so the pasting measure can only realize partial absorption and obstruction of track noise, belongs to a temporary and permanent noise reduction method, and is difficult to radically control the transmission and scattering of noise. In fact, such damping layers have not been practically used to date due to noise reduction effects, production costs and operational limitations of railway construction operations.
The exploration that a high-damping alloy material is used for manufacturing the track is always carried out, but besides the large damping and low cost of the cast iron (particularly the grey cast iron) with complex-phase damping characteristic, the cost of other high-damping alloys is not so high, and the popularization is difficult. However, the mechanical properties of gray iron are too poor to be used for rail manufacturing.
The existing rail materials of high-speed rails in China mainly comprise hot-rolled steel and pearlite steel U71MnG and U75VG, and in recent years, in order to adapt to the requirements of railway speed increase and increasingly severe use environments and improve the rolling contact fatigue strength of rails, bainite steel rails, PD3 and BNbRe steel rails are tested and tried, so that the vision and the knowledge are widened. However, the mechanical properties of the material are changed, and the damping coefficient of the material is the same as that of pearlite type and hot rolled section steel in physical properties, so that the material has no inhibition effect on vibration noise. The practice of high-speed rail development shows that only a high-speed rail track which has excellent mechanical properties, can greatly reduce vibration and noise and accords with the actual situation of railway construction work can effectively improve the noise pollution on a high-speed rail.
Disclosure of Invention
The invention aims to provide a shock-absorbing and noise-reducing high-speed railway track, which solves the problem that the existing high-speed railway track has larger vibration noise.
Another object of the present invention is to provide a method of manufacturing a shock absorbing and noise reducing high speed railway track.
The first technical scheme adopted by the invention is that the shock-absorbing and noise-reducing high-speed railway track is formed by welding a plurality of I-shaped sections, wherein the I-shaped sections comprise the following components in percentage by mass: 3.3-3.6%, Si: 2.3-2.7%, Mn: 0.3-0.5%, Ni: 0.6-1.0%, Cu: 0.4-0.7%, Mg: 0.03-0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the I-shaped section is more than or equal to 880MPa, and the elongation is more than or equal to 8%.
The present invention is also technically characterized in that,
the metallographic structure of the I-shaped section is a complex phase structure consisting of an austenite body and graphite nodules, wherein the austenite body consists of high-carbon austenite and needle-shaped high-silicon ferrite.
The diameter of graphite nodules within 12-18 mm of the surface layer of the I-shaped section is less than or equal to 25 microns, and the density of the graphite nodules is more than or equal to 300 graphite nodules per mm2And the roundness is 100%.
The second technical scheme adopted by the invention is a preparation method of a shock-absorbing noise-reducing high-speed railway track, which comprises the following steps:
step 1, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace;
and 2, carrying out spheroidizing, slagging and inoculation on the molten iron in sequence, wherein the components and the mass percentages of the treated molten iron are respectively C: 3.3-3.6%, Si: 2.3-2.7%, Mn: 0.3-0.5%, Ni: 0.6-1.0%, Cu: 0.4-0.7%, Mg: 0.03-0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%;
step 3, pouring the molten iron treated in the step 2 into horizontal continuous casting equipment for horizontal continuous casting, and drawing into a nodular cast iron I-shaped section with uniform surface color, wherein the thickness of the bottom of the I-shaped section is increased by 5-7 mm compared with that of a standard track, the thickness of the top of the I-shaped section is increased by 2-4 mm compared with that of the standard track, and the thickness of the abdominal stud is increased by 6-8 mm compared with that of the standard track;
step 4, carrying out metallographic observation and electronic scanning detection on the drawn section, wherein if the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 microns, the spheroidization rate is 100 percent,and the density of graphite nodules is 300/mm2Step 5 is carried out, otherwise, the nodular cast iron I-shaped section bar is prepared again;
step 5, spheroidizing annealing and straightening the profile in sequence to enable the curvature of the profile to be less than or equal to 1.0mm/m, and milling redundant materials at the bottom and the top of the profile according to the size of a standard track;
step 6, carrying out isothermal quenching treatment on the section, heating the section to 930 +/-10 ℃, preserving heat for 1-2 hours, spraying nitrate liquid on the section to rapidly cool the section, immersing the section in a nitrate tank, preserving heat for a period of time, and then cooling the section to room temperature by air;
step 7, mechanically calibrating and cutting the section bar processed in the step 6 into a length of 100 meters, and welding a plurality of section bars together end to end in sequence by flash welding to enable the section bars to accord with the length specified by the high-speed railway track standard;
and 8, normalizing the welding seam section, grinding the machining allowance of the surface of the rail, and removing the exposed graphite on the surface of the rail to obtain the shock-absorbing and noise-reducing high-speed railway rail.
In step 3, the horizontal continuous casting comprises the steps of pouring molten iron treated in the step 2 into a continuous casting heat-preserving furnace from a pouring gate, adjusting the water flow of the crystallizer when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace, starting a tractor when the molten iron is solidified into a guide rail blank shape, pulling a crystal guiding rod, observing whether the surface color of the blank is uniform or not when a temperature field in the crystallizer is stable, and continuing to pull if all the parts are uniform; if the surface of the blank is uneven in brightness, the water flow, the carbon equivalent and the silicon-carbon ratio in the molten iron in the crystallizer are adjusted to enable the surface color of the blank to be uniform, then the length is counted, and the blank is cut according to the fixed length.
The crystallizer is a combined type abdominal cooling crystallizer and mainly comprises an inner trapezoidal graphite bushing, an outer water-cooling interlayer plate and a clamping card, wherein an I-shaped cavity and two strip-shaped through holes are formed in the middle of the graphite bushing, the two through holes are respectively positioned in the waist parts of two sides of the cavity, a water-cooling thick-wall pipe with two closed ends is inserted into the through holes, and a water inlet pipe and a water outlet pipe which are communicated with the water-cooling thick-wall pipe are arranged on the water-cooling interlayer plate.
And 5, spheroidizing annealing treatment in the step 5, which comprises the steps of putting the section into an annealing furnace, heating the annealing furnace to 880 +/-10 ℃ in a stepped manner, preserving heat for 2-3 h, cooling to 700 +/-10 ℃ along with the furnace, preserving heat for 1-3 h, cooling to below 300 ℃ along with the furnace, discharging and air cooling to room temperature.
And 6, carrying out isothermal quenching treatment on the section by using a through induction heating furnace and a nitrate tank, wherein an induction heating and spraying coil is additionally arranged in a partition wall of the through induction heating furnace and the nitrate tank, nitrate liquid is introduced into a hollow tube of the coil, inclined through holes are densely distributed on the coil, and the nitrate liquid is sprayed to the section from the inclined through holes, so that the section is rapidly cooled to 300 +/-5 ℃, then is immersed in the nitrate tank for heat preservation for 1-2 h, and finally is air-cooled to room temperature to finish the quenching treatment.
And 8, normalizing the welding seam section, namely raising the temperature to 800 +/-10 ℃, preserving the temperature for 0.3-1 h, and then cooling to room temperature in air.
The invention has the beneficial effects that:
(1) firstly, drawing out H-shaped section bar of nodular cast iron with uniform surface color by horizontal continuous casting, and then carrying out spheroidizing annealing and isothermal quenching treatment on the section bar to ensure that the section bar structure is a complex phase structure consisting of austenite (the austenite consists of high-carbon austenite and needle-shaped high-silicon ferrite) and graphite nodules, wherein the diameter of the graphite nodules on the surface layer of the section bar is less than or equal to 25 microns, and the density of the graphite nodules is more than or equal to 300/mm2The roundness is 100%, the tensile strength of the track is more than or equal to 880MPa, the elongation is more than or equal to 8%, and the track has good shock absorption and noise reduction performance due to the large interfacial area between the fine graphite spheres and the matrix;
(2) the combined type abdominal cooling crystallizer is adopted, so that the consistency of iron water cooling on the section of the steel rail is ensured, and uniform and consistent eutectic structures are generated inside the steel rail;
(3) compared with a standard rail, the bottom and the top of the profile are thickened, so that cracks at two ends of the bottom of the profile due to too high cooling speed are avoided, and the thickened profile also becomes the machining allowance of tooth marks pressed on the profile by a traction roller cone; the abdomen vertical rib of the section bar is thickened, so that the cooling speed of the abdomen vertical rib is close to that of the upper part and the lower part, and the transverse vibration and the noise of the vertical rib in service are further reduced;
(4) the rail blank after the spheroidizing annealing is subjected to isothermal quenching treatment, in the austenitizing process, the isometric crystal and the spheroidization rate of the material are improved again, in the austenitizing process, a matrix structure is converted into high-carbon austenite and high-silicon acicular ferrite, namely an austenite body, so that the high-carbon austenite has excellent toughness and compatibility, when the stress is greater than the yield strength of the high-carbon austenite, the high-carbon austenite is immediately converted into a martensite structure on the surface layer, the hardness is increased to about HV550, and the wear resistance is greatly increased;
(5) a plurality of sectional materials are welded together by adopting flash welding, the carbon content in the sectional materials reaches 3.3-3.6%, and the sectional materials can react with oxygen atoms in the air in the gap during the flash welding process to generate CO \ CO2The gas escapes, and the rest part is extruded out together with molten iron during the final upsetting extrusion, so that the residual oxides at the joint are extremely small, the gray spot tissue is effectively reduced, and the excellent mechanical property of the welding position is ensured. In addition, the eutectic graphite steel has high heat conductivity, and a heat affected zone of a joint can be widened by adopting preheating type flash welding, so that the gradient distribution of residual stress is smooth, and the reduction of mechanical properties is further restrained.
Drawings
FIG. 1 is a schematic structural view of a combined-type abdominal cooling crystallizer of the present invention;
FIG. 2 is a schematic view of the internal structure of the combined type abdominal cooling crystallizer of the present invention;
FIG. 3 is a schematic structural view of a trapezoidal graphite bushing in the combined-type abdominal cooling crystallizer of the present invention;
FIG. 4 is a schematic structural diagram of a seed-guiding rod used in an embodiment of the present invention;
FIG. 5 is a graph illustrating an annealing process for a rail profile according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating an isothermal quenching process for rail sections according to an embodiment of the present invention;
FIG. 7 is a normalizing process curve for a weld in a rail in an embodiment of the invention.
In the figure, 1, a root flange plate, 2, a clamping clamp, 3, a right side plate water outlet nozzle, 4, a right side abdomen cold water outlet pipe, 5, a right side abdomen cold water inlet pipe, 6, a cavity, 7, a right side plate water inlet nozzle, 8, a bottom plate water inlet nozzle, 9, a bottom plate water outlet nozzle, 10, an outer end flange plate, 11, a left side plate water inlet nozzle, 12, a left side abdomen cold water inlet pipe, 13, a through hole, 14, a trapezoidal graphite bushing, 15, a top plate water outlet nozzle, 16, a top plate water inlet nozzle, 21, a crystal guiding head, 22, a crystal guiding steel rail, 23, M16 screws, 24, a steel plate and 25, M22 screws.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention relates to a shock-absorbing noise-reducing high-speed railway track which is cast by adopting a horizontal continuous casting technology, wherein a water-cooled crystallizer is horizontally connected to one side of the lower part of a vertical heat-preserving furnace, so that an L-shaped molten iron channel is formed. At first, a crystal leading head of a crystal leading rod is stretched into the inner cavity of the crystallizer by half depth to block molten iron to flow in. And pouring the molten iron which is melted, inoculated and spheroidized into a holding furnace which is preheated by flame spraying, so that the molten iron flows into a crystallizer. The molten iron entering the crystallizer is solidified from the inner wall of the graphite sleeve to the center of the liquid core and is embedded with the screw at the end of the crystal guiding rod. And after about 20-30 seconds, starting a traction machine, and drawing outwards step by step to obtain the section with the same shape as the inner sleeve cavity of the crystallizer. And molten iron is poured into the heat preservation furnace continuously or periodically during drawing, so that the drawing process is continuous. And cutting the drawn section according to the customized length.
One of the difficulties with the horizontal continuous casting technique in the production of profiles with non-circular cross-section is to obtain a uniform cooling of the profile cross-section over its periphery in order to precisely control the drawing speed, both to prevent the cooling of individual portions from being too slow and to prevent the cooling of other portions from being too fast. After the section is pulled out of the crystallizer, if the temperature of some parts is too high, a solidified layer is too thin, and molten iron in the core part is easy to leak out; whereas if the surface had blackened in some areas, indicating that below 600 c, the brittleness increased and the drawing caused surface cracks. The cooling speed is roughly consistent at each position of the periphery on the section with a circular section or a rectangular section but with a large radius of curvature at the edges, which is not easy to happen, but the invention needs to draw the ductile iron section with the cross section in the shape of a track, the shape of the cross section has severe concave-convex fluctuation, the radius of curvature at each position is greatly changed, and the track section with uniform cross section temperature and low component segregation can be drawn by relatively precise temperature field arrangement. In order to ensure the uniform temperature of the cross section of the rail section, the combined type abdomen cooling crystallizer is adopted in the invention to enhance the cooling speed of the waist part of the rail, and the cooling speed is specifically shown in the following embodiment.
Example 1
The method for preparing the shock-absorbing and noise-reducing high-speed railway track specifically comprises the following steps:
step 1, finishing preparation work before horizontal continuous casting
Step 1.1, manufacturing a crystallizer, and referring to fig. 1 and fig. 2, the crystallizer comprises a trapezoidal graphite lining 14, wherein an I-shaped cavity 6 and two strip-shaped through holes 13 are formed in the middle of the trapezoidal graphite lining 14, the two strip-shaped through holes 13 are respectively located in the waist portions of two sides of the cavity 6, the upper portion and the lower portion of each through hole 13 are semicircular, the straight edges of the through holes 13 are identical to the distance between adjacent graphite cavities, copper water-cooling thick-wall pipes with two closed ends are installed in the through holes 13, a root flange plate 1 is arranged on the inner end face of the trapezoidal graphite lining 14, an outer end flange plate 10 and a pressing plate are arranged on the outer end face of the trapezoidal graphite lining 14, and the outer end flange plate 10 and the pressing plate are connected through screws. The top of the trapezoidal graphite liner 14, the water-cooled sandwich plate is characterized in that water-cooled sandwich plates are arranged at the bottom and the left and right sides, adjacent water-cooled sandwich plates are fixedly connected through clamping cards 2, a water flow channel is arranged inside each water-cooled sandwich plate, a top plate water inlet nozzle 16 and a top plate water outlet nozzle 15 which are communicated with the water flow channels are arranged on the top water-cooled sandwich plate, a bottom plate water inlet nozzle 8 and a bottom plate water outlet nozzle 9 which are communicated with the water flow channels are arranged on the bottom water-cooled sandwich plate, a left side plate water inlet nozzle 11 and a left side plate water outlet nozzle which are communicated with the water flow channels are arranged on the left side water-cooled sandwich plate, a left side abdominal cooling water inlet pipe 12 and a left side abdominal cooling water outlet pipe which are communicated with adjacent copper water-cooled thick-wall pipes are also arranged on the bottom water-cooled sandwich plate, a right side plate water inlet nozzle 7 and a right side plate water outlet nozzle 3 which are communicated with the water flow channels are arranged on the right side water-cooled sandwich plate, and a right side abdominal cooling water inlet pipe 5 and a right side abdominal cooling water outlet pipe 4 (see fig. 3) which are communicated with the adjacent copper water-cooled thick-wall pipes.
The shape size of the I-shaped cavity in the middle of the graphite lining is 0.5 percent larger than the size of the steel rail to be prepared. And the bottom height of the cavity is 6mm greater than the bottom height of the steel rail to be prepared, the top height is 3mm greater than the top height of the steel rail to be prepared, the middle width is 7mm greater than the thickness of the steel rail stud, and the 3mm, 6mm and 7mm are used as machining allowance. In addition, the thickness of the two wings of the rail bottom is increased, and the thickness of the end part is 19mm, so that drawing micro-cracks on the surface of the I-shaped section are avoided.
Step 1.2, manufacturing a crystal leading rod, and referring to fig. 4, wherein the crystal leading rod consists of a crystal leading head 21 and a crystal leading steel rail 22 (a standard steel rail), the crystal leading head 21 is formed by cutting a steel plate wire with the thickness of 200mm, the outline dimension is 0.5mm smaller than the size of a cavity in a graphite lining, and the purpose is to block molten iron at the beginning of pouring so as not to leak outwards. Two M16 screw holes are drilled on the end face of the inner end of the crystal guiding head 21, and an M16 screw 23 is screwed on, and the screw is embedded with the cooled molten iron to bear the drawing force, so that the rail parison is drawn out of the crystallizer until reaching a tractor. A threaded hole phi 22 is drilled in the middle of the rail web at the position of 40mm at one end outside the seeding head. The end part of the crystal leading head is polished into a slope by a hand-held grinder, so that the crystal leading head can be smoothly inserted into the inner cavity of the crystallizer.
The seeding rail 22 is made of a long rail, and the length is greater than the distance from the crystallizer to the second pair of rollers of the tractor. The top surface of the crystal-leading rod is welded with a steel band with the thickness of 3mm, and the two ends of the bottom of the crystal-leading rod are welded with 2 steel bands with the thickness of 6mm and the width of 20mm, so that the total height of the steel rail is consistent with the height of the crystal-leading head. The seeding steel rail is also drilled with a phi 22 hole in the middle of the rail web at the end connected with the seeding head, and the seeding steel rail and the seeding head are connected by a steel plate 24 and two M22 screws 25. And straightening the seeding rod to enable the bending degree of the seeding rod to be less than 3 mm/m.
Step 1.3, installing a crystallizer
And (3) mounting the crystallizer manufactured in the step (1.1) on a continuous casting heat-preserving furnace, adjusting the level to ensure that the error does not exceed +/-2 degrees, and introducing a small amount of cooling water. One end of a crystal guiding rod is inserted into an inner cavity of the crystallizer, the other end of the crystal guiding rod is placed on a lower traction roller of a tractor, and the horizontal condition of the crystal guiding rod is measured by a horizontal ruler so as to adjust the height of a lower roller of the tractor, so that the height of the upper plane of the crystal guiding rod is consistent with the height of a lower plane of a graphite cavity in the crystallizer, and the error is within 5 mm. And the other supporting rollers are adjusted to be close to the height of the crystal guiding rod. Then starting a hydraulic cylinder of the tractor, pressing the crystal guiding rod downwards, starting the traction motor, drawing the crystal guiding rod out of the crystallizer, and standing by at a position about one meter away from the crystallizer.
And step 1.4, preheating a hearth of the heat preservation furnace by using a flame spraying device, so that the temperature of the inner wall of the bottom of the hearth reaches over 600 ℃.
Step 2, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace;
stopping flame spraying and preheating, starting a tractor, inserting a seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer;
the method comprises the following steps of carrying out spheroidization, slagging-off and inoculation on molten iron in sequence, and specifically comprises the steps of pouring 400Kg of molten iron into a ladle after ladle ironing, wherein the tapping temperature of the molten iron in a first ladle is 1480 ℃, the tapping temperature of the molten iron in a second ladle is 1450 ℃, and the tapping temperature of the molten iron in a third ladle and the tapping temperature after the third ladle are 1430 ℃. Adding nodulizer with weight about 1.5% of the total weight of molten iron into the bottom of the ladle in advance, adding 75 Kg of 3.2Kg of slag after nodulizing and slagging-off#And (3) inoculating the ferrosilicon for 5min so that the final silicon content of the molten iron after inoculation and spheroidization is 2.50 +/-0.05 percent, and the content of residual magnesium is 0.03-0.045 percent. The temperature of the first ladle molten iron after inoculation and spheroidization is 1420 ℃. If the multi-flow drawing is adopted, the weight of each ladle of molten iron is properly increased, and the pouring interval time is ensured not to exceed 10 minutes.
The processed molten iron comprises the following components in percentage by mass: 3.5%, Si: 2.5%, Mn: 0.4%, Ni: 0.8%, Cu: 0.5%, Mg: 0.04 percent, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, less than or equal to 0.3 percent of Cr, less than or equal to 0.5 percent of Mo, less than or equal to 0.5 percent of V, and the balance of Fe, wherein the sum of the mass percentages of the components is 100 percent;
and 3, pouring the inoculated and spheroidized molten iron into a continuous casting heat-preserving furnace from a pouring gate, wherein the temperature of the molten iron is about 1400 ℃, and the water flow of the crystallizer is increased when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace. After 20 seconds, part of molten iron and the screw at the end of the seeding rod are solidified into a whole, and the molten iron is also solidified into the shape of the guide rail blank. Then starting a tractor, pulling a crystal guiding rod, and carrying out step-by-step drawing, wherein the length of each step is 40mm, the interval is about 3 seconds, and the drawing speed is based on the principle that the surface of the drawn blank is 900 ℃. After several meters of drawing, the temperature field in the crystallizer is stabilized, and whether the color of the surface of the blank is uniform or not can be observed. If all the parts are uniform, continuously drawing; if the brightness is uneven, adjusting the water amount at each position of the crystallizer; if the color can not be normal by adjusting the water amount, the carbon equivalent and the silicon-carbon ratio of the molten iron are required to be adjusted to ensure that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, the length is counted, and the section is fused by an oxygen lance at intervals of 104 meters.
Due to the consideration of avoiding drawing cracks and indentation of the profile by a traction roller, the thickness of the bottom of the I-shaped profile is increased by 6mm compared with that of a standard track, and the thickness of the top of the I-shaped profile is increased by 3mm compared with that of the standard track; and because the cooling speed of the cross section of the rail and the uniformity of the as-cast structure need to be improved, the thickness of the stud at the belly of the rail is increased by 7mm compared with that of a standard rail.
Step 4, carrying out metallographic observation and electronic scanning detection on the drawn section, and detecting whether the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 microns, the spheroidization rate is 100 percent, and whether the density of the graphite spheres reaches 300 per mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
the diameter of graphite spheres within 15mm of the surface layer of the section bar is less than or equal to 25 mu m, the spheroidization rate is 100 percent, and the density of the graphite spheres reaches 300 per mm2The principle of the method lies in that flaky graphite in the gray iron cuts off continuity of matrix tissues, so that the elongation and toughness are avoided, and when the graphite is agglomerated into a spherical shape, the toughness is generated, and the elongation can reach over 10 percent. The wear resistance and fatigue life of nodular cast iron with different spherical diameters (corresponding to different graphite nodule densities) are different. The larger the number of graphite balls, the higher the wear resistance and the probability of fatigue life. Compared with steel, the damping capacity of the cast iron material is greater than that of steel, and the absorption capacity of the cast iron material on vibration and noise is strong. But the shock absorption and noise reduction capability of the gray iron is highIn the case of ductile iron, the interface area between the graphite flakes and the matrix structure is large, and vibration waves and sound waves can be absorbed more. Therefore, when graphite nodules in the nodular iron are distributed in a fine and dispersed mode, the interface area of graphite/matrix is increased to be equivalent to that of the gray iron, and the shock absorption and noise reduction capabilities of the nodular iron and the gray iron are equivalent. The fine, round and dispersed graphite nodules avoid stress concentration on the wall of the graphite hole after the material is stressed, and improve the fracture toughness and crack propagation rate of the material of the manufactured part.
Tests have shown that (xu 26104, geling, et al.. the thermal coupling effect of ultra-fine ADI in service and the observation of graphite nodule coatings [ J ] casting technology, 2019, (3): 849-54.) graphite nodules in continuous cast ductile iron shapes have a diameter of about 20 microns, and at this size, the graphite nodules accumulate the most latent heat of crystallization at the periphery during crystallization and form a coating layer during subsequent rapid cooling. The coating layer collects impurity elements and compounds in molten iron, so that impurities are reduced on a grain boundary of a matrix structure, the grain boundary is purified, and the fatigue strength and the fatigue life of the material are improved. On the other hand, when the part is subjected to small elastic deformation after being stressed, the frictional heat in the graphite sphere coating layer generates a thermal coupling effect, so that the matrix tissue close to the coating layer is annealed and softened, and fatigue cracks can never be generated.
And 5, after the metallographic phase and the electron microscope scanning detection are qualified, putting the section into a specially-made long furnace for spheroidizing annealing treatment, referring to fig. 5, heating the annealing furnace in a stepped manner, firstly heating to 300 ℃, preserving heat for 1h, then heating to 600 ℃, preserving heat for 1h, then heating to 750 ℃, preserving heat for 1h, finally heating to 880 ℃, preserving heat for 3h, then slowly cooling to 700 ℃ along with the furnace, preserving heat for 2h, then cooling to below 300 ℃ along with the furnace, taking out of the furnace, and air cooling to room temperature. The spheroidizing annealing is carried out on the continuous casting rail blank, so that the dendrite in the matrix structure can be converted into isometric crystal, and simultaneously, the carbon atoms of the angular graphite are accelerated to be dissolved into the matrix, and the spheroidizing rate is further improved.
Straightening the annealed profile to ensure that the bending degree is less than or equal to 1.0 mm/m; and then, milling the machining allowance of the top surface and the rail bottom of the guide rail profile on a milling machine, wherein the machining allowance of the top of the profile is 3mm, and the machining allowance of the bottom of the profile is 6 mm.
Step 6, carrying out isothermal quenching treatment on the section by adopting a through type induction heating furnace and a nitrate tank
An induction heating and spraying coil is additionally arranged in a partition wall between the through type induction heating furnace and the nitrate tank, nitrate liquid is introduced into a hollow tube of the coil, inclined through holes are densely distributed on the coil, and an included angle between each inclined through hole and a central shaft is 45 degrees. A mechanical rail conveying device is arranged in front of the through type induction heating furnace and clamps the section to move slowly, the length of a furnace body heating area is matched with the moving speed, and the heat preservation of the rail blank material of each unit length is ensured for more than 1 hour; at the entrance of the furnace body, acetylene flame is used for preheating the surface of the track, and the acetylene flame also serves as a fire curtain to prevent air from entering the hearth. CO gas is introduced into the hearth to prevent high-temperature oxidation. The material of the support rail in the through-type furnace is a sintered hexagonal boron nitride block. Hexagonal boron nitride, also known as white graphite, has high-temperature strength and a coefficient of friction of only 0.2 or less.
Referring to fig. 6, a through-type induction heating furnace is adopted to heat the section bar to 930 ℃ and preserve heat for 1h, and then nitrate liquid is sprayed to the section bar through a coil, so that the section bar is cooled rapidly; spraying nitrate liquid to the section bar from the oblique through hole, rapidly cooling the section bar to 300 ℃, immersing the section bar into a nitrate groove, preserving heat for 1h to obtain an austenite structure, finally air-cooling to room temperature, completing quenching treatment, and washing away the salt stain by hot water.
The nitrate liquid used for spraying is from an ultra-long nitrate tank and is executed by a stainless steel pipeline pump. The sprayed salt bath flows into a groove at the bottom and is pumped into a nitrate groove by another stainless steel pipeline. A heating and cooling device is arranged in the ultralong nitrate tank close to the induction coil, so that the salt bath is always kept in the temperature range required by the quenching process. The preliminarily quenched rail section is inserted into the side wall at the initial end of the nitrate tank, the opening of the side wall is the same as the section of the rail section, and the gap is squeezed by asbestos to prevent salt bath leakage. The length of the ultra-long nitrate salt bath is the same as that of the heating furnace, so that the salt bath quenching time is ensured to be more than 1 hour. Stainless steel supporting rollers are arranged in the groove, so that the slow advancing action of the section bar is flexible and smooth.
When the rail blank after the spheroidizing annealing is subjected to isothermal quenching, the isometric crystal and the spheroidization rate of the material are improved again in the austenitizing process. In the subsequent austempering, the matrix structure is transformed into high-carbon austenite and high-silicon acicular ferrite, which is a structure called "ausferrite" having excellent toughness and toughness. The rail material can ensure that the tensile strength is not less than 900MPa and the elongation is not less than 12% when the hardness is 300-330 HB, and other mechanical performance indexes exceed the specified indexes of high-speed railway steel rail TB/T3276-2011 in the railway industry standard. The high-carbon austenite in the ausferrite structure is thermodynamically stable and can exist stably at room temperature. When the stress is larger than the yield strength, the steel is immediately transformed into a martensite structure on the surface layer, the hardness is increased to about HV550, and the wear resistance is greatly increased.
Step 7, mechanically calibrating the section processed in the step 6 to enable the upper and lower directions and the left and right directions of the section to reach the bending degree specified by the national standard; cutting off the lengthening allowance required by straightening the two ends to obtain a semi-finished product with the length of 100m, and then welding the 5 sectional materials together end to end in sequence by flash welding;
step 8, normalizing the welding seam section, referring to fig. 7, firstly heating to 800 ℃, preserving heat for 0.5h, then air-cooling to room temperature, and finishing the normalizing treatment; and then grinding off the machining allowance on the surface of the rail, and removing residual graphite on the surface of the rail by using a special mobile ultrasonic cleaning machine so as to eliminate the self-lubricating capacity of the rail and shorten the sliding distance of the train during braking, thereby finally preparing the shock-absorbing and noise-reducing high-speed railway rail.
After milling processing is carried out on the railhead tread, graphite spheres are exposed, and the area of the graphite spheres accounts for 13-15% of the total area. These graphites need to be removed or become solid lubricants. Although the graphite film can reduce the friction between the rail and the wheel and prolong the service life of the wheel rail, the side effect is that the braking distance of the train is prolonged by several times, which is not beneficial to the driving safety. The graphite nodules have a diameter of about 20 microns, so that the graphite nodules can be cleaned only by an ultrasonic cleaning method.
The performance of the prepared high-speed railway track is detected, the tensile strength is 913MPa, the elongation is 11%, and the mechanical performance requirements of the standard high-speed railway track are met.
Example 2
The method for preparing the shock-absorbing and noise-reducing high-speed railway track specifically comprises the following steps:
step 1, the preliminary work before the horizontal continuous casting was completed, and the concrete procedure was the same as that of example 1
Step 2, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace
Stopping flame spraying and preheating, starting a tractor, inserting a seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer;
the method comprises the following steps of carrying out spheroidization, slagging-off and inoculation on molten iron in sequence, and specifically comprises the steps of pouring 400Kg of molten iron into a ladle after ladle ironing, wherein the tapping temperature of the molten iron in a first ladle is 1480 ℃, the tapping temperature of the molten iron in a second ladle is 1450 ℃, and the tapping temperature of the molten iron in a third ladle and the tapping temperature after the third ladle are 1430 ℃. Adding nodulizer with weight about 1.5% of the total weight of molten iron into the bottom of the ladle in advance, adding 75 Kg of 3.2Kg of slag after nodulizing and slagging-off#And (3) inoculating the ferrosilicon for 5min so that the final silicon content of the molten iron after inoculation and spheroidization is 2.50 +/-0.05 percent, and the content of residual magnesium is 0.03-0.045 percent. The temperature of the first ladle iron after inoculation and spheroidization is 1425 ℃. If the multi-flow drawing is adopted, the weight of each ladle of molten iron is properly increased, and the pouring interval time is ensured not to exceed 10 minutes.
The processed molten iron comprises the following components in percentage by mass: 3.3%, Si: 2.7%, Mn: 0.4%, Ni: 0.6%, Cu: 0.7%, Mg: 0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%;
and 3, pouring the inoculated and spheroidized molten iron into a continuous casting heat-preserving furnace from a pouring gate, wherein the temperature of the molten iron is about 1400 ℃, and the water flow of the crystallizer is increased when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace. After 25 seconds, part of molten iron and the screw at the end of the seeding rod are solidified into a whole, and the molten iron is also solidified into the shape of the guide rail blank. Then starting a tractor, pulling a crystal guiding rod, and carrying out step-by-step drawing, wherein the length of each step is 40mm, the interval is about 3 seconds, and the drawing speed is based on the principle that the surface of the drawn blank is 900 ℃. After several meters of drawing, the temperature field in the crystallizer is stabilized, and whether the color of the surface of the blank is uniform or not can be observed. If all the parts are uniform, continuously drawing; if the brightness is uneven, adjusting the water amount at each position of the crystallizer; if the color can not be normal by adjusting the water amount, the carbon equivalent and the silicon-carbon ratio of the molten iron are required to be adjusted to ensure that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, the length is counted, and the section is fused by an oxygen lance at intervals of 104 meters.
Due to the consideration of avoiding drawing cracks and indentation of the profile by the traction roller, the bottom thickness of the I-shaped profile is increased by 5mm compared with the standard track, and the top thickness is increased by 2.5mm compared with the standard track; and because the cooling speed of the cross section of the rail and the uniformity of the as-cast structure need to be improved, the thickness of the stud at the belly of the rail is increased by 6mm compared with that of a standard rail.
Step 4, carrying out metallographic observation and electronic scanning detection on the drawn section, and detecting whether the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 microns, the spheroidization rate is 100 percent, and whether the density of the graphite spheres reaches 300 per mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
and 5, after the metallographic phase and electron microscope scanning detection are qualified, putting the section into a specially-made long furnace for spheroidizing annealing treatment, heating the annealing furnace in a stepped manner, firstly heating to 300 ℃ and preserving heat for 1h, then heating to 600 ℃ and preserving heat for 1h, then heating to 750 ℃ and preserving heat for 1h, finally heating to 870 ℃ and preserving heat for 2h, then slowly cooling to 690 ℃ along with the furnace and preserving heat for 2h, then cooling to below 300 ℃ along with the furnace, and taking out of the furnace and air cooling to room temperature.
Straightening the annealed profile to ensure that the bending degree is less than or equal to 1.0 mm/m; and then milling the machining allowance of the top surface and the bottom surface of the guide rail profile on a milling machine.
Step 6, carrying out isothermal quenching treatment on the section by adopting a through type induction heating furnace and a nitrate tank
Firstly, heating the section to 920 ℃ by using a through type induction heating furnace, preserving heat for 1.5h, and then spraying nitrate liquid to the section through a coil to rapidly cool the section; spraying nitrate liquid to the section bar from the oblique through hole, rapidly cooling the section bar to 300 ℃, immersing the section bar into a nitrate groove, preserving heat for 1h to obtain an austenite structure, finally air-cooling to room temperature, completing quenching treatment, and washing away the salt stain by hot water.
Step 7, mechanically calibrating the section processed in the step 6 to enable the upper and lower directions and the left and right directions of the section to reach the bending degree specified by the national standard; cutting off the lengthening allowance required by straightening the two ends to obtain a semi-finished product with the length of 100m, and then welding the 5 sectional materials together end to end in sequence by flash welding;
step 8, normalizing the welding seam section, namely heating the temperature to 790 ℃, preserving the temperature for 0.7h, then cooling the welding seam section to room temperature in air, and finishing the normalizing treatment; and then grinding off the machining allowance on the surface of the rail, and removing residual graphite on the surface of the rail by using a special mobile ultrasonic cleaning machine so as to eliminate the self-lubricating capacity of the rail and shorten the sliding distance of the train during braking, thereby finally preparing the shock-absorbing and noise-reducing high-speed railway rail.
The prepared high-speed railway track is subjected to performance detection, the tensile strength is 887MPa, the elongation is 9%, and the mechanical performance requirements of the standard high-speed railway track are met.
Example 3
The method for preparing the shock-absorbing and noise-reducing high-speed railway track specifically comprises the following steps:
step 1, the preliminary work before the horizontal continuous casting was completed, and the concrete procedure was the same as that of example 1
Step 2, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace
Stopping flame spraying and preheating, starting a tractor, inserting a seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer;
the method comprises the following steps of carrying out spheroidization, slagging-off and inoculation on molten iron in sequence, and specifically comprises the steps of pouring 400Kg of molten iron into a ladle after ladle ironing, wherein the tapping temperature of the molten iron in a first ladle is 1480 ℃, the tapping temperature of the molten iron in a second ladle is 1450 ℃, and the tapping temperature of the molten iron in a third ladle and the tapping temperature after the third ladle are 1430 ℃. Adding nodulizer with weight about 1.5% of the total weight of molten iron into the bottom of the ladle in advance, adding 75 Kg of 3.2Kg of slag after nodulizing and slagging-off#Inoculating ferrosilicon for 5min to make molten iron be pregnantThe final silicon content after the breeding and spheroidizing is 2.50 +/-0.05 percent, and the content of residual magnesium is 0.03 to 0.045 percent. The temperature of the first ladle iron after inoculation and spheroidization is 1425 ℃. If the multi-flow drawing is adopted, the weight of each ladle of molten iron is properly increased, and the pouring interval time is ensured not to exceed 10 minutes.
The processed molten iron comprises the following components in percentage by mass: 3.4%, Si: 2.6%, Mn: 0.4%, Ni: 0.8%, Cu: 0.6%, Mg: 0.03 percent, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, less than or equal to 0.3 percent of Cr, less than or equal to 0.5 percent of Mo, less than or equal to 0.5 percent of V, and the balance of Fe, wherein the sum of the mass percentages of the components is 100 percent;
and 3, pouring the inoculated and spheroidized molten iron into a continuous casting heat-preserving furnace from a pouring gate, wherein the temperature of the molten iron is about 1400 ℃, and the water flow of the crystallizer is increased when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace. After 23 seconds, part of molten iron and the screw at the end of the seeding rod are solidified into a whole, and the molten iron is also solidified into the shape of the guide rail blank. Then starting a tractor, pulling a crystal guiding rod, and carrying out step-by-step drawing, wherein the length of each step is 40mm, the interval is about 3 seconds, and the drawing speed is based on the principle that the surface of the drawn blank is 900 ℃. After several meters of drawing, the temperature field in the crystallizer is stabilized, and whether the color of the surface of the blank is uniform or not can be observed. If all the parts are uniform, continuously drawing; if the brightness is uneven, adjusting the water amount at each position of the crystallizer; if the color can not be normal by adjusting the water amount, the carbon equivalent and the silicon-carbon ratio of the molten iron are required to be adjusted to ensure that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, the length is counted, and the section is fused by an oxygen lance at intervals of 104 meters.
Due to the consideration of avoiding drawing cracks and indentation of the profile by a traction roller, the thickness of the bottom of the I-shaped profile is increased by 6mm compared with that of a standard track, and the thickness of the top of the I-shaped profile is increased by 3mm compared with that of the standard track; and because the cooling speed of the cross section of the rail and the uniformity of the as-cast structure need to be improved, the thickness of the stud at the belly of the rail is increased by 7mm compared with that of a standard rail.
Step 4, carrying out metallographic observation and electronic scanning detection on the drawn section, detecting whether the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 mu m or not and the spheroidization rate is 100% or not, andwhether the density of graphite nodules reaches 300 pieces/mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
and 5, after the metallographic phase and electron microscope scanning detection are qualified, putting the section into a specially-made long furnace for spheroidizing annealing treatment, heating the annealing furnace in a stepped manner, heating to 310 ℃ for heat preservation for 1h, heating to 610 ℃ for heat preservation for 1h, heating to 760 ℃ for heat preservation for 1h, heating to 880 ℃ for heat preservation for 2.5h, then slowly cooling to 700 ℃ along with the furnace for heat preservation for 3h, cooling to below 300 ℃ along with the furnace, taking out of the furnace, and air cooling to room temperature.
Straightening the annealed profile to ensure that the bending degree is less than or equal to 1.0 mm/m; and then milling the machining allowance of the top surface and the bottom surface of the guide rail profile on a milling machine.
Step 6, carrying out isothermal quenching treatment on the section by adopting a through type induction heating furnace and a nitrate tank
Firstly, heating the section to 925 ℃ by using a through type induction heating furnace, preserving heat for 1.5h, and then spraying nitrate liquid to the section through a coil to rapidly cool the section; spraying nitrate liquid to the section bar from the oblique through hole, rapidly cooling the section bar to 305 ℃, immersing the section bar into a nitrate groove, preserving heat for 2h to obtain an austenite structure, finally air-cooling to room temperature, completing quenching treatment, and washing away the salt stain by hot water.
Step 7, mechanically calibrating the section processed in the step 6 to enable the upper and lower directions and the left and right directions of the section to reach the bending degree specified by the national standard; cutting off the lengthening allowance required by straightening the two ends to obtain a semi-finished product with the length of 100m, and then welding the 5 sectional materials together end to end in sequence by flash welding;
step 8, normalizing the welding seam section, namely heating the temperature to 800 ℃, preserving the temperature for 0.5h, then cooling the welding seam section to room temperature in air, and finishing the normalizing treatment; and then grinding off the machining allowance on the surface of the rail, and removing residual graphite on the surface of the rail by using a special mobile ultrasonic cleaning machine so as to eliminate the self-lubricating capacity of the rail and shorten the sliding distance of the train during braking, thereby finally preparing the shock-absorbing and noise-reducing high-speed railway rail.
The prepared high-speed railway track is subjected to performance detection, the tensile strength is 893MPa, the elongation is 9.5%, and the mechanical property requirement of the standard high-speed railway track is met.
Example 4
The method for preparing the shock-absorbing and noise-reducing high-speed railway track specifically comprises the following steps:
step 1, the preliminary work before the horizontal continuous casting was completed, and the concrete procedure was the same as that of example 1
Step 2, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace
Stopping flame spraying and preheating, starting a tractor, inserting a seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer;
the method comprises the following steps of carrying out spheroidization, slagging-off and inoculation on molten iron in sequence, and specifically comprises the steps of pouring 400Kg of molten iron into a ladle after ladle ironing, wherein the tapping temperature of the molten iron in a first ladle is 1480 ℃, the tapping temperature of the molten iron in a second ladle is 1450 ℃, and the tapping temperature of the molten iron in a third ladle and the tapping temperature after the third ladle are 1430 ℃. Adding nodulizer with weight about 1.5% of the total weight of molten iron into the bottom of the ladle in advance, adding 75 Kg of 3.2Kg of slag after nodulizing and slagging-off#And (3) inoculating the ferrosilicon for 5min so that the final silicon content of the molten iron after inoculation and spheroidization is 2.50 +/-0.05 percent, and the content of residual magnesium is 0.03-0.045 percent. The temperature of the first ladle iron after inoculation and spheroidization is 1425 ℃. If the multi-flow drawing is adopted, the weight of each ladle of molten iron is properly increased, and the pouring interval time is ensured not to exceed 10 minutes.
The processed molten iron comprises the following components in percentage by mass: 3.6%, Si: 2.3%, Mn: 0.3%, Ni: 0.6%, Cu: 0.4%, Mg: 0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%;
and 3, pouring the inoculated and spheroidized molten iron into a continuous casting heat-preserving furnace from a pouring gate, wherein the temperature of the molten iron is about 1400 ℃, and the water flow of the crystallizer is increased when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace. After 23 seconds, part of molten iron and the screw at the end of the seeding rod are solidified into a whole, and the molten iron is also solidified into the shape of the guide rail blank. Then starting a tractor, pulling a crystal guiding rod, and carrying out step-by-step drawing, wherein the length of each step is 40mm, the interval is about 3 seconds, and the drawing speed is based on the principle that the surface of the drawn blank is 900 ℃. After several meters of drawing, the temperature field in the crystallizer is stabilized, and whether the color of the surface of the blank is uniform or not can be observed. If all the parts are uniform, continuously drawing; if the brightness is uneven, adjusting the water amount at each position of the crystallizer; if the color can not be normal by adjusting the water amount, the carbon equivalent and the silicon-carbon ratio of the molten iron are required to be adjusted to ensure that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, the length is counted, and the section is fused by an oxygen lance at intervals of 104 meters.
Due to the consideration of avoiding drawing cracks and indentation of the profile by a traction roller, the thickness of the bottom of the I-shaped profile is increased by 7mm compared with that of a standard track, and the thickness of the top of the I-shaped profile is increased by 4mm compared with that of the standard track; and because the cooling speed of the cross section of the rail and the uniformity of the as-cast structure need to be improved, the thickness of the stud at the belly of the rail is increased by 8mm compared with that of a standard rail.
Step 4, carrying out metallographic observation and electronic scanning detection on the drawn section, and detecting whether the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 microns, the spheroidization rate is 100 percent, and whether the density of the graphite spheres reaches 300 per mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
and 5, after the metallographic phase and electron microscope scanning detection are qualified, putting the section into a specially-made long furnace for spheroidizing annealing treatment, heating the annealing furnace in a stepped manner, firstly heating to 290 ℃ and preserving heat for 1h, then heating to 600 ℃ and preserving heat for 1h, then heating to 750 ℃ and preserving heat for 1h, finally heating to 890 ℃ and preserving heat for 3h, then slowly cooling to 710 ℃ along with the furnace and preserving heat for 3h, then cooling to below 300 ℃ along with the furnace, and taking out of the furnace and air cooling to room temperature.
Straightening the annealed profile to ensure that the bending degree is less than or equal to 1.0 mm/m; and then milling the machining allowance of the top surface and the bottom surface of the guide rail profile on a milling machine.
Step 6, carrying out isothermal quenching treatment on the section by adopting a through type induction heating furnace and a nitrate tank
Firstly, heating the section to 940 ℃ by using a through type induction heating furnace, preserving heat for 2 hours, and spraying nitrate liquid to the section by using a coil to quickly cool the section; spraying nitrate liquid to the section bar from the oblique through hole, rapidly cooling the section bar to 300 ℃, immersing the section bar into a nitrate groove, preserving heat for 2h to obtain an austenite structure, finally air-cooling to room temperature, completing quenching treatment, and washing away the salt stain by hot water.
Step 7, mechanically calibrating the section processed in the step 6 to enable the upper and lower directions and the left and right directions of the section to reach the bending degree specified by the national standard; cutting off the lengthening allowance required by straightening the two ends to obtain a semi-finished product with the length of 100m, and then welding the 5 sectional materials together end to end in sequence by flash welding;
step 8, normalizing the welding seam section, namely raising the temperature to 810 ℃, preserving the temperature for 1h, then cooling the welding seam section to room temperature in air, and finishing the normalizing treatment; and then grinding off the machining allowance on the surface of the rail, and removing residual graphite on the surface of the rail by using a special mobile ultrasonic cleaning machine so as to eliminate the self-lubricating capacity of the rail and shorten the sliding distance of the train during braking, thereby finally preparing the shock-absorbing and noise-reducing high-speed railway rail.
The prepared high-speed railway track is subjected to performance detection, the tensile strength is 900MPa, the elongation is 9.5%, and the mechanical performance requirements of the standard high-speed railway track are met.

Claims (4)

1. A preparation method of a shock-absorbing noise-reducing high-speed railway track is characterized by comprising the following steps:
step 1, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace;
and 2, carrying out spheroidizing, slagging and inoculation on the molten iron in sequence, wherein the components and the mass percentages of the treated molten iron are respectively C: 3.3-3.6%, Si: 2.3-2.7%, Mn: 0.3-0.5%, Ni: 0.6-1.0%, Cu: 0.4-0.7%, Mg: 0.03-0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%;
step 3, pouring the molten iron treated in the step 2 into horizontal continuous casting equipment for horizontal continuous casting, and drawing into a nodular cast iron I-shaped section with uniform surface color, wherein the thickness of the bottom of the I-shaped section is increased by 5-7 mm compared with that of a standard track, the thickness of the top of the I-shaped section is increased by 2-4 mm compared with that of the standard track, and the thickness of the abdominal stud is increased by 6-8 mm compared with that of the standard track;
in the step 3, the horizontal continuous casting comprises the steps of pouring molten iron treated in the step 2 into a continuous casting heat-preserving furnace from a pouring gate, adjusting the water flow of the crystallizer when the molten iron enters a graphite cavity of the crystallizer from the continuous casting heat-preserving furnace, starting a tractor when the molten iron is solidified into a guide rail blank shape, pulling a crystal guiding rod, observing whether the surface color of the blank is uniform or not when a temperature field in the crystallizer is stable, and continuing to pull if all the parts are uniform; if the surface of the blank is uneven in brightness, adjusting the water flow, the carbon equivalent and the silicon-carbon ratio in the molten iron at each position of the crystallizer to enable the color of the surface of the blank to be uniform, then starting to count the length, and intercepting according to a fixed length; the crystallizer is a combined type abdominal cooling crystallizer and mainly comprises an inner trapezoidal graphite bushing (14), an outer water-cooling interlayer plate and a clamping card (2), wherein an I-shaped cavity (17) and two strip-shaped through holes (13) are formed in the middle of the graphite bushing (14), the two through holes (13) are respectively located in the waist parts of two sides of the cavity (17), a water-cooling thick-wall pipe with two closed ends is inserted into each through hole (13), and a water inlet pipe and a water outlet pipe communicated with the water-cooling thick-wall pipe are arranged on the water-cooling interlayer plate;
and 4, carrying out metallographic observation and electronic scanning detection on the drawn section, wherein if the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 micrometers, the spheroidization rate is 100%, and the density of the graphite spheres is 300 per mm2Step 5 is carried out, otherwise, the nodular cast iron I-shaped section bar is prepared again;
step 5, spheroidizing annealing and straightening the profile in sequence to enable the curvature of the profile to be less than or equal to 1.0mm/m, and milling redundant materials at the bottom and the top of the profile according to the size of a standard track;
step 6, carrying out isothermal quenching treatment on the section, heating the section to 930 DEG first
Figure 134594DEST_PATH_IMAGE001
Keeping the temperature at 10 ℃ for 1-2 h, spraying nitrate liquid to the section bar to quickly cool the section bar, then immersing the section bar in a nitrate tank for keeping the temperature for a period of time, and then cooling the section bar to room temperature by air;
in the step 6, a through-type induction heating furnace and a nitrate tank are adopted to carry out isothermal quenching treatment on the section bar, an induction heating and spraying coil is additionally arranged in a partition wall of the through-type induction heating furnace and the nitrate tank, nitrate liquid is introduced into a hollow tube of the coil, inclined through holes are densely distributed on the coil, and the nitrate liquid is sprayed to the section bar from the inclined through holes, so that the section bar is rapidly cooled to 300 +/-5 ℃, then is immersed into the nitrate tank for heat preservation for 1 h-2 h, and finally is air-cooled to room temperature to finish quenching treatment;
step 7, mechanically calibrating and cutting the section bars processed in the step 6, and welding a plurality of section bars together end to end in sequence by flash welding to enable the section bars to conform to the length specified by the high-speed railway track standard;
and 8, normalizing the welding seam section, grinding the machining allowance of the surface of the rail, and removing the exposed graphite on the surface of the rail to obtain the shock-absorbing and noise-reducing high-speed railway rail.
2. The method for preparing a shock-absorbing and noise-reducing high-speed railway track according to claim 1, wherein the spheroidizing annealing treatment in the step 5 comprises the steps of putting the section into an annealing furnace, heating the annealing furnace to 880 +/-10 ℃ in a stepped manner, preserving heat for 2h-3h, cooling the section to 700 +/-10 ℃ along with the furnace, preserving heat for 2h-3h, cooling the section to below 300 ℃ along with the furnace, discharging the section out of the furnace, and cooling the section to room temperature.
3. The method for preparing a shock-absorbing noise-reducing high-speed railway track according to claim 1, wherein in the step 8, the normalizing treatment is carried out on the welding seam section, and comprises the steps of firstly increasing the temperature to 800 +/-10 ℃, preserving the temperature for 0.3-1 h, and then air cooling to room temperature.
4. The vibration and noise reduction high-speed railway track prepared by the preparation method of the vibration and noise reduction high-speed railway track according to any one of claims 1 to 3, which is characterized by being formed by welding a plurality of I-shaped sections, wherein the I-shaped sections comprise the following components in percentage by mass, and C: 3.3-3.6%, Si: 2.3-2.7%, Mn: 0.3-0.5%, Ni: 0.6-1.0%, Cu: 0.4-0.7%, Mg: 0.03-0.045%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, Cr is less than or equal to 0.3%, Mo is less than or equal to 0.5%, V is less than or equal to 0.5%, and the balance is Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the I-shaped section is more than or equal to 880MPa, and the elongation is more than or equal to 8 percent;
the metallographic structure of the I-shaped section is a complex phase structure consisting of an austenite body and graphite nodules, the austenite body consists of high-carbon austenite and needle-shaped high-silicon ferrite, the diameter of the graphite nodules within 12-18 mm of the surface layer of the I-shaped section is less than or equal to 25 microns, and the density of the graphite nodules is more than or equal to 300/mm2。
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