CN112210710B - Low-noise steel rail for bridge crane and preparation method thereof - Google Patents

Low-noise steel rail for bridge crane and preparation method thereof Download PDF

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CN112210710B
CN112210710B CN202011058266.3A CN202011058266A CN112210710B CN 112210710 B CN112210710 B CN 112210710B CN 202011058266 A CN202011058266 A CN 202011058266A CN 112210710 B CN112210710 B CN 112210710B
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molten iron
steel rail
graphite
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CN112210710A (en
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孙楠
许旸
郜永福
黄志强
刘保健
张欣昱
王旭
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Jiangsu Hualong Precision Intelligent Manufacturing Co ltd
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Jiangsu Hualong Continuous Cast Iron Co ltd
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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
    • C22C37/04—Cast-iron alloys containing spheroidal graphite
    • 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
    • B22D11/055—Cooling the moulds
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/10—Making spheroidal graphite cast-iron
    • 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
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
    • 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
    • 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
    • C21D5/00—Heat treatments of cast-iron
    • 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
    • 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
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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    • Y02P10/25—Process efficiency

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Abstract

The invention discloses a low-noise steel rail for a bridge crane, which comprises the following components in percentage by mass: 3.4-3.6%, Si 2.4-2.6%, Mn: 0.3% -0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3% -0.5%, Mg: 0.03-0.045%, and the balance of Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the steel rail is more than or equal to 880MPa, the elongation is more than or equal to 8%, and the hardness of the top surface layer is more than or equal to 55 HRC.

Description

Low-noise steel rail for bridge crane and preparation method thereof
Technical Field
The invention belongs to the technical field of ferrous metal materials, and relates to a low-noise steel rail for a bridge crane and a preparation method thereof.
Background
Noise of a bridge crane (commonly called as a travelling crane) running in a large workshop of a mechanical manufacturing enterprise is a main component in a noise spectrum in the workshop, and is gradually paid attention to by people in the process of upgrading and improving the production environment of the enterprise. In the effort of reducing the vibration noise of the bridge crane, the early focus is to increase the rigidity of the crane structure and the natural frequency of the crane structure, so that the crane structure is far away from the vibration frequency excited by the driving motor and the speed reducing mechanism, and the occurrence of resonance is avoided. After years of practice, particularly after a hollow truss structure is widely adopted, the self weight is reduced, the integral rigidity is high, and the structural rigidity design of the hollow truss structure is close to an ideal state, so that although the natural frequency of the crane covers a larger frequency spectrum range due to different hoisting weights and the position change of a hoisting motor, the natural frequency can be ensured to be far lower than the first-order natural resonance frequency, the running speed of the crane is slow, and the rotating speeds of a moving driving motor, the hoisting motor and a speed reducer thereof are lower, so that the resonance phenomenon can not occur. However, the large-span bridge structure and the suspended feature of the free simply-supported beam of the crane still provide convenience for generating vibration noise and bring great difficulty to the suppression of noise pollution. According to the regulations of the relevant national standard (GB/T14405-2011), the noise of the bridge crane cab is qualified as long as the noise is lower than 85 decibels. But the common general knowledge tells us that noise above 70 db is already an acoustic pollution to human hearing, whereas noise above 80 db is undoubtedly a chronic injury to drivers and other staff working in this environment for a long time. Therefore, the reduction of the driving noise is one of the tasks of technical improvement and environmental management of related enterprises.
One important reason why the noise of the bridge crane is difficult to be further reduced after the structural design and manufacture of the bridge crane reach the prior art high platform is that designers often focus on the crane itself, and neglect the "contribution" of the rail material as the supporting system of the crane to the noise, which proves that a ready fact of this is that, except for adopting the rubber sheet for lining between the rail and the concrete beam, there is little discussion on the literature, reports or patents for manufacturing low-noise rails by using high-damping materials, whereas 5 rail materials listed in the ferrous metallurgy standards of China-crane rails (YB/T5055-2014) -U71 Mn, U75V, U78CrV, U77MnCr, U76CrRE, and the materials Q235 and 50Mn and the like required by the standard sectional materials of the light rail and the heavy rail are common steel materials which only have excellent mechanical properties without shock absorption physical properties, there is substantially no damping effect on vibration and noise. As for the rubber pads between the track and the concrete beam, it is possible to absorb part of the vibration energy, but its side effect is that it lowers the first order natural frequency of the crane mechanical system, and when the free simply supported bridge beam exhibits frequency division vibration at certain frequency(s) and the relatively independent substructure in the bridge beam resonates, the elastic support will increase its amplitude, but rather the noise.
The bridge crane is contacted with the guide rail through four steel rollers, a simply supported beam system with two freely supported ends is formed actually, vibration noise of the system is not only from a simply supported beam (bridge crane) body system, but also from a supporting subsystem, and material physical properties of the supporting system also have important influence on noise of the whole system from material and mechanical analysis. These effects are manifested in:
1) the friction and vibration between the four pairs of rollers and the steel rail generate noise. Although the bridge crane and the guide rail have rolling friction and small friction coefficient, the friction system is not lubricated and is in a dry friction state, so that vibration and noise are inevitably caused by unsmooth friction;
2) the noise is propagated. Noise caused by the vibration of the body of the bridge crane is partially directly diffused in the air to form a noise field with the vibration source as the center, and the other part is diffused to a farther position through a solid transmission path, namely is transmitted to the guide rail through the roller and is diffused to a far position by the guide rail. The propagation speed of sound in air is 340 m/s, and the propagation speed in steel is 4000-5000 m/s, so that the noise propagated by the solid accounts for a larger proportion of the total noise. When the main beam of the bridge crane is transformed from an early box-type structure into a hollow truss structure, the resonance of the box body is effectively avoided, and the proportion of noise transmitted by solids is further increased after the vibration frequency spectrum shifts up.
3) Vibration and noise caused by the suspension of a section in a rail lay. Design and constructor often treat as "thick living" to bridge crane rail laying, require to the roughness of cement roof beam when laying roughly, use drift and clamp plate to guarantee orbital upper and lower roughness in the cooperation for the rail is in unsettled state on some or long or short district section, on the gyro wheel traveles these district sections, the track takes place the flexural deformation, drive bridge type roof beam body structure and take place the torsional deformation, frequency division vibration and multiple frequency vibration's probability has been increased, vibration and noise have been increased.
4) Secondary noise in the plant. After the crane in the workshop generates noise, secondary noise is formed through reflection of the workshop and equipment.
The effect of suppressing the change of the track material is not significant when the above-mentioned various vibrations and noises are above 80 db, but when the noise is required to be reduced below 70 db at present, the marginal effect of various measures is not insignificant, and the importance of the material selection problem which has been neglected before is revealed. The common steel material has poor damping capacity and no function of absorbing vibration and noise, but the cast iron material is mostly used as a base for machine tools and large-scale mechanical equipment to realize the shock absorption and noise reduction by utilizing the higher damping capacity of the cast iron material, and the crane steel rail is supposed to be changed into the high damping material to achieve the same effect.
However, unlike the heavy and thick bases of machine tools and large-scale equipment, the cross-sectional area of the guide rail of the bridge crane is small, the load per unit area is heavy in service, and sufficient mechanical properties are required. The mechanical properties of 5 steel rail materials listed in the industry standard, crane steel rail (YB/T5055-2014) are as follows:
number plate Tensile strength Rm/MPa Elongation after break A%
U71Mn ≥880 ≥9
U75V ≥980 ≥9
U78CrV ≥1080 ≥8
U77MnCr ≥980 ≥9
U76CrRE ≥1080 ≥9
Obviously, the common cast iron inherently has better shock absorption and noise reduction functions, but the ordinary cast iron, namely the gray iron, the nodular iron and the vermicular iron, far from reaching the mechanical performance indexes provided by the crane steel rail standard. Therefore, the problem is summarized as: how to combine the mechanical property of common steel and the damping property of cast iron into a whole to prepare a material with both obdurability and damping property, so as to manufacture the bridge crane guide rail capable of absorbing shock and reducing noise.
Disclosure of Invention
One object of the present invention is to provide a low-noise steel rail for a bridge crane, which can suppress vibration and noise transmitted to a truss of the crane while simultaneously achieving toughness and damping.
The invention also aims to provide a preparation method of the low-noise steel rail for the bridge crane.
The first technical scheme adopted by the invention is a low-noise steel rail for a bridge crane, which comprises the following components in percentage by mass: 3.4% -3.6%, Si: 2.4% -2.6%, Mn: 0.3% -0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3% -0.5%, Mg: 0.03-0.045%, and the balance of Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the steel rail is more than or equal to 880MPa, the elongation is more than or equal to 8 percent, and the hardness of the top surface layer is more than or equal to 55 HRC.
The graphite in the surface structure of the steel rail is 100 percent of eutectic graphite, the diameter of graphite nodules is less than or equal to 25 mu m, and the density of the graphite nodules is more than or equal to 400 graphite nodules per mm2And the spheroidization rate is 100 percent.
The second technical scheme adopted by the invention is a preparation method of a low-noise steel rail for a bridge crane, which comprises the following steps:
step 1, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component materials comprise the following components in percentage by mass: 3.4-3.5%, Si 1.55-1.65%, Mn: 0.3% -0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3 to 0.5 percent of Fe and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent;
step 2, carrying out spheroidizing, slagging and inoculation on the molten iron in sequence to ensure that the final silicon content of the molten iron is 2.50 +/-0.1 percent and the content of residual magnesium is 0.03-0.045 percent;
step 3, pouring the molten iron treated in the step 2 into a heat preservation furnace of horizontal continuous casting equipment for horizontal continuous casting, and drawing nodular cast iron I-shaped sections with uniform surface color, wherein the length of each section is 1.4-1.6 meters greater than the fixed length;
step 4, carrying out metallographic observation and electronic scanning detection on the drawn section barWhen 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 is 400 per mm2Step 5 is carried out, otherwise, the nodular cast iron I-shaped section bar is prepared again;
step 5, annealing and straightening the profile in sequence to enable the curvature of the profile to be less than or equal to 1.0 mm/m;
step 6, carrying out induction quenching treatment on the top surface of the section bar to enable the top surface of the steel rail to obtain a hardened layer of 2-3 mm, and carrying out induction heating and spray cooling treatment on other parts of the section bar;
and 7, mechanically calibrating and cutting the section bar processed in the step 6 to enable the section bar to meet the product size requirement specified by the steel rail standard for the bridge crane.
In the step 2, 1.4-1.6% of nodulizer is added when the molten iron is subjected to nodulizing, and 75# ferrosilicon is added into the molten iron to perform inoculation treatment on the molten iron, wherein the inoculation time is 4-7 min.
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 after 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 or the carbon equivalent and silicon carbon ratio in the molten iron at each position of the crystallizer are adjusted to ensure that the color of the surface of the blank is uniform, then the length is counted, and the blank is cut according to the length of 1.4-1.6 meters.
The crystallizer is a combined type abdomen cooling crystallizer and mainly comprises an inner trapezoidal graphite bushing, an outer water-cooling sandwich plate and a clamping clamp, wherein an I-shaped cavity and two through holes are formed in the middle of the graphite bushing, the two through holes are respectively located in the waist portions of two sides of the I-shaped cavity, an abdomen cooling pipe with a sealed end portion is embedded into the through holes, and a water inlet pipe and a water outlet pipe which are communicated with the abdomen cooling pipe are arranged on the water-cooling sandwich plate.
And 5, annealing treatment in the step 5, which comprises the steps of putting the section into an annealing furnace, heating the annealing furnace to 860 +/-10 ℃ in a stepped manner, preserving heat for 2-3 hours, slowly cooling the section to below 300 ℃ along with the furnace, and finally discharging the section from the furnace and cooling the section to room temperature.
And 6, carrying out induction quenching treatment and induction heating and spray cooling treatment on the section by using a medium-frequency induction coil, wherein the inner side of the medium-frequency induction coil corresponding to the top surface of the section is provided with a small hole with the diameter of 1.3-1.6 mm, and the inner sides of the medium-frequency induction coils corresponding to the side surface and the bottom surface of the section are provided with small holes with the diameter of 0.8-1.1 mm.
The power of a medium-frequency power supply of the medium-frequency induction coil is not less than 100KW, and the frequency is 300-800 Hz.
The invention has the beneficial effects that:
(1) firstly, drawing out an I-shaped steel full-section ultrafine grained nodular cast iron profile material by a horizontal continuous casting technology, then carrying out special heat treatment to obtain an ultra-fine austenite structure and spherical graphite, enabling the mechanical property of the material to reach the standard of a crane steel rail, having the unique functions of shock absorption and noise reduction, simultaneously considering obdurability and damping property, inhibiting vibration and noise transmitted by the crane truss, and finally manufacturing the low-noise steel rail for the bridge crane by a corresponding machining process.
(2) In view of the uneven cross section of the steel rail blank, the combined type belly cooling crystallizer is adopted in the horizontal continuous casting process, so that the consistency of the cooling speed of iron water on the section of the steel rail is ensured, uniform and consistent eutectic structures are generated in the steel rail, the diameter of graphite spheres within 15mm of the surface layer of the section is less than or equal to 25 mu m, the spheroidization rate is 100%, and the density of the graphite spheres is 400/mm2The sound absorption and shock absorption capacity and the material fracture toughness of the steel rail are improved, and the crack propagation rate is slowed down;
(3) spheroidizing annealing is carried out on the continuous casting steel rail blank, so that dendrites in the matrix structure can be converted into isometric crystals, and carbon atoms of individual graphite prisms are accelerated to be dissolved into the matrix, and the spheroidization rate is further improved;
(4) the steel rail blank after the spheroidizing annealing is subjected to induction quenching and spray cooling, a hardened layer of 2-3 mm is obtained on the top surface of the steel rail, and the wear resistance is improved; other parts are sprayed and cooled to enable the steel rail to obtain a fine pearlite structure, the steel rail has good toughness, the tensile strength of the steel rail can be guaranteed to be more than 880MPa, the elongation is not less than 8%, and other mechanical performance indexes exceed the specified indexes of the crane industry standard YB/T55O 5-2014.
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 graphite lining 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 drawing of a steel rail post-casting annealing process according to an embodiment of the present invention;
FIG. 6 is a schematic cross-sectional view of an embodiment of the invention showing rail induction hardening plus spray cooling;
fig. 7 is an induction hardening and spray cooling apparatus employed in an embodiment of the present invention.
In the figure, 1, a root flange plate, 2, a clamping card, 3, a right side plate water outlet nozzle, 4, a right side web cold water outlet pipe, 5, an I-shaped cavity, 6, a right side web cold water inlet pipe, 7, a right side plate water inlet nozzle, 8, a bottom plate water inlet nozzle, 9, a trapezoidal pressure plate, 10, a bottom plate water outlet nozzle, 11, a trapezoidal graphite lining, 12, a through hole, 13, a left side web cold water inlet pipe, 14, a left side plate water inlet nozzle, 15, a top plate water outlet nozzle, 16, a top plate water inlet nozzle, 17, a web cold pipe, 18, a top water-cooling interlayer plate, 19, a bottom water-cooling interlayer plate, 20, a right side water-cooling interlayer plate, 21, a crystal guiding head, 22, a crystal guiding steel rail, 23, M16, 24, a steel plate, 25, M22, 33, a steel rail profile, 34, an induction heating coil, 35, a water spraying quenching area, 36, a spraying cooling area, 37, an induction heating transformer, 38, a compression roller, 91 and a support roller, 92. an induction heating water spraying ring 93, a steel wire rope 94 and a rope winding wheel.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The horizontal continuous casting technology on which the present invention relies is well established and has a large amount of patent and literature information, which need not be repeated. However, the horizontal continuous casting technique, which is a well-known technique, does not solve the special problems of the present invention, which are specifically shown below:
1) the low-noise steel rail manufactured by the invention has the advantages that the mechanical property is tough, the tensile strength of the top surface part subjected to friction stress is more than 1080MPa, the tensile strength of the other parts is more than 880MPa, and the elongation of the steel rail is more than 8-9%, so that the cast structure or the heat treatment structure of the common ductile iron is difficult to achieve, even if an ADI structure is obtained by adopting a common horizontal continuous casting and isothermal quenching process, the index is difficult to achieve, because the common horizontal continuous casting structure has thick and thin parts, the existing of the primary thick graphite spheres can not be avoided, 1-5% of the graphite spheres are not round, and the mechanical property of the section is reduced by the factors.
2) The steel rail to be manufactured by the invention has good shock absorption and noise reduction functions, and the function is determined by the diameter and the density of graphite nodules for nodular cast iron. The mechanism of absorption of vibration by graphite in cast iron is that the relative sliding between graphite and matrix structure and the resulting twisting between graphite inner sheet layers consume vibration energy, which is dissipated in the air as heat energy. Thus, the larger the interface area between the graphite and the substrate, the more vibrational energy is absorbed, i.e., the stronger the internal dissipation damping. In general, the interface area between graphite and matrix in nodular iron and vermicular cast iron is smaller than that of gray iron, so that the shock-absorbing capacity is weaker, but if the graphite spheres are fine enough and are distributed in a dispersing way, the specific surface area of the graphite spheres is the same as that of the graphite flakes in the gray iron, the shock-absorbing and noise-reducing functions of the graphite spheres are similar, and the shock-absorbing and noise-reducing functions are remarkably improved and similar to that of the gray iron. Specifically, the graphite nodule diameter of the common nodular iron is 50-120 μm, and the nodule density is 100-160 pieces/mm2The damping capacity is similar to that of steel, and even if the mechanical property is improved through heat treatment, the graphite nodules are difficult to have sufficient shock absorption and noise reduction functions, and the graphite nodules are difficult to change in size and quantity depending on solid phase change in the liquid-solid phase change period, so that the shock absorption and noise reduction damping capacity is enhanced. When the diameter of graphite nodules in the nodular iron is reduced to about 20 mu m, the density of the nodules reaches 400/mm2Above, the interface of graphite and the substrateThe product is equivalent to gray iron, so the damping internal loss capacity is similar to that of the gray iron, but the mechanical property is close to that of steel. The normal horizontal continuous casting can only approach the index on the shallow surface layer of the section bar part, and the cast structure and the performance can not be obtained on the full section.
3) The common continuous casting nodular cast iron is mostly a section with the same curvature (circular section) of the outer edge outline or smaller change (rectangular section with round corners), only a jacket type water-cooling crystallizer with a simple structure is needed, the invention draws a section with an I-shaped section, and requires the fine and compact cast structure of the whole section and the fine and round graphite balls, the required crystallizer can provide a uniform temperature field for the solidification and heat dissipation process of the outer edge of the section, simultaneously needs to add cooling to the vertical ribs of the section at the central part, and can adjust the water flow quantity, namely the cooling speed at each part on line.
4) Considering that the section of the horizontal continuous casting section is not too thin, otherwise drawing cracks can be generated, the size of the cross section of the traditional steel rail needs to be changed slightly, the thickness of the rail web and the rail bottom is increased, the thinnest part of the rail web and the rail bottom is not less than 20mm, and the height of the rail web is correspondingly reduced. The specific gravity of the ductile iron is 90% of that of the common steel rail, and the increase of the cross section area of the section does not increase the total weight.
5) Induction quenching and spray cooling are performed simultaneously. During the last heat treatment, the medium frequency induction coil is used to heat the whole section of the steel rail, but only the top surface of the steel rail is quenched by spraying water to improve the hardness, and other parts are cooled by spraying water to convert the matrix into a fine pearlite structure.
Aiming at the special problems, the invention is improved on the basis of the common horizontal continuous casting in two aspects, on one hand, the periphery of the cross section of the I-shaped steel section bar is uniformly cooled so as to accurately control the drawing speed, and not only is the cooling speed of individual parts prevented from being too slow, but also the cooling speed of other parts is prevented 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 is easy to leak out; whereas if the surface had blackened in some areas, indicating that below 600 c, the brittleness increased and surface cracks occurred. On the special-shaped section with a circular section or a large curvature radius at the edge, the cooling speed is approximately consistent at all the periphery, and the situation is not easy to occur, but the steel rail to be prepared by the invention has severe concave-convex fluctuation of the section shape and large variation of the curvature radius at all the positions, and the steel rail section with uniform and consistent cross section structure and low component segregation can be drawn by arranging a relatively precise temperature field. On the other hand, the surface color of the section is observed on line, and the molten iron composition is adjusted on line so as to be in the range of pseudo-eutectic composition.
In the following, a detailed description is given to how to prepare a new rail having a heavy rail model (QU120) consistent with the mechanical properties of one of 4 steel rails listed in the metallurgical industry standard, i.e., crane rail (YB/T5055-2014), and having both the functions of damping and reducing noise.
Example 1
A low-noise steel rail for a bridge crane is prepared, the steel rail corresponds to a heavy steel rail with a mark QU120 in a metallurgical industry standard (YB/T5055-2014), and the preparation process comprises the following steps:
step 1, preparing a horizontal continuous casting apparatus
Step 1.1, a crystallizer is manufactured, and referring to fig. 1 and fig. 2, the crystallizer to be used in the application is a combined type abdomen cooling crystallizer and comprises a trapezoidal graphite bush 11, four water-cooling sandwich plates are arranged on the outer side surface of the trapezoidal graphite bush 11, the adjacent water-cooling sandwich plates are fixedly connected through a clamping card 2, an I-shaped cavity 5 and two circular through holes 12 are formed in the trapezoidal graphite bush 11, the diameter of each through hole is 1.5 inches, namely 37.5mm, the two through holes 12 are respectively located at the waist parts of two sides of the I-shaped cavity 5, the distance between the inner side of each through hole and a section bar vertical bar is not less than 20mm, a copper thick-wall abdomen cooling pipe 17 with a sealed end part is arranged in each through hole 12, and a water outlet pipe and a water inlet pipe which are communicated with the abdomen cooling pipe 17 are arranged on the water-cooling sandwich plates on two side surfaces of the trapezoidal graphite bush 11. The clamping card 2 consists of two number-matching clamping plates, bolts and nuts, and the two clamping plates are connected and fixed through the bolts and the nuts.
Referring to fig. 3, a top water-cooling interlayer plate 18 is arranged at the top of the trapezoidal graphite lining 11, a water flow channel is arranged inside the top water-cooling interlayer plate 18, and a top plate water outlet nozzle 15 and a top plate water inlet nozzle 16 which are communicated with the water flow channel are arranged outside the top water-cooling interlayer plate 18. The bottom of the trapezoidal graphite lining 11 is provided with a bottom water-cooling sandwich plate 19, a water flow channel is arranged inside the bottom water-cooling sandwich plate 19, and a bottom plate water outlet nozzle 10 and a bottom plate water inlet nozzle 8 which are communicated with the water flow channel are arranged outside the bottom water-cooling sandwich plate 19. The outer left side of 11 left side outsides in trapezoidal graphite bush is provided with left side water-cooling sandwich panel, and left side water-cooling sandwich panel is inside to be provided with rivers passageway, and the outside is provided with left side board intake nozzle 14 and left side board faucet with rivers passageway intercommunication, the cold inlet tube of left side abdomen 13 and the cold outlet pipe of left side abdomen with the cold pipe 17 intercommunication of left abdomen. The outer right side water-cooling sandwich panel 20 that is provided with of 11 right side faces of trapezoidal graphite bush, the inside rivers passageway that is provided with of right side water-cooling sandwich panel 20, the outside is provided with the right side board intake nozzle 7 and the right side board faucet 3 with rivers passageway intercommunication, the cold inlet tube of right side abdomen 6 and the cold outlet pipe 4 of right side abdomen with the cold pipe 17 intercommunication on right side.
Root flange discs 1 are arranged outside the end portions of the liquid inlets of the trapezoidal graphite bushings 11, trapezoidal pressing plates 9 are arranged outside the outlet ends of the profiles, fixing holes are formed in the outer edges of the root flange discs 1 and are connected with the heat preservation furnace in a threaded mode, and the trapezoidal pressing plates 9 are connected with the end portions of the four water-cooling sandwich plates through screws. Through holes which can enable the left abdominal cooling water inlet pipe 13, the left abdominal cooling water outlet pipe, the right abdominal cooling water inlet pipe 6 and the right abdominal cooling water outlet pipe 4 to penetrate through are formed in the side faces, close to the two ends of the through hole 12, of the trapezoidal graphite bushing. The size of the I-shaped cavity in the middle of the graphite lining is 0.5 percent larger than that of the steel rail to be prepared, so that the size which is the same as the cross section of the steel rail is obtained after molten iron is solidified and cooled to room temperature (except for machining allowance on the upper surface and the lower surface).
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 thick steel plate wire, 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 when pouring is started 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 steel 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 or equal to the distance between the crystallizer and 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 5mm 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 1 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. In the experimental stage, one crystallizer is used, 3-4 steel rail profiles can be simultaneously drawn during formal production, and at the moment, 3-4 crystallizers are required to be assembled and installed in rows. 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 ℃.
And 2, melting the hypoeutectic component material into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component material comprises the following components in percentage by mass: c: 3.45%, Si 1.60%, Mn: 0.4%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.4 percent of Fe and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent. Stopping flaming preheating, starting the tractor, inserting the seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer.
And 3, performing spheroidization, slagging and inoculation on the molten iron in sequence, namely pouring 600Kg 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 later is 1430 ℃. Adding nodulizer with the weight about 1.5 percent of the total weight of the molten iron into the bottom of the ladle in advance, adding 4.8Kg of 75# ferrosilicon after nodulizing and slagging-off, and inoculating for 5min, so that the final silicon content of the molten iron after inoculation and nodulizing 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 1420-1430 ℃. 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.
And 4, 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. And after 15-20 seconds, part of molten iron is solidified with the screw at the end part of the seeding rod into a whole, and the solidified molten iron is also solidified into a guide rail blank shape. And then starting a traction machine, pulling a crystal guiding rod, and carrying out step-by-step drawing, wherein the length of each step is 40-50 mm, the interval is about 3 seconds, and the drawing speed is based on the principle that the surface of the drawn blank is 800-950 ℃. After the blank is pulled out for 3-5 m, 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, so that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, and the length is counted. Then, the cut is cut out by a subsequent online cutting machine according to the length of more than 1.4m, and a cut is cut out every 13.4 m and is pressed and broken by a press machine.
Step 5, 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 400/mm2If all the indexes do not meet the detection standard,then the section bar needs to be prepared again;
step 6, 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 to 860 ℃ in a stepped manner, preserving the heat for 2 hours, slowly cooling the section to below 300 ℃ along with the furnace, and finally discharging the section from the furnace and cooling the section to room temperature in an air cooling manner; 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 allowances of the top surface and the bottom surface of the guide rail section on a milling machine, wherein the machining allowances are respectively 3mm and 6 mm.
Step 7, carrying out induction quenching and spray cooling treatment on the milled guide rail on a special device, and firstly manufacturing a medium-frequency induction quenching and spray coil according to the specific shape and size of the guide rail; the coil is made of a copper tube with a section size of 20mm square, the inner edge surface of the shape of the coil is 10mm away from the outer edge surface of the steel rail, and small water spraying holes with different diameters are drilled in different sections: drilling small holes with the diameter of 1.4mm at the inner side of the coil part corresponding to the top surface of the steel rail, wherein the hole spacing is 2.5 mm; and small holes with the diameter of 1.0mm are drilled at other parts, the hole interval is 10mm, and the water spraying direction and the axial direction of the steel rail form an included angle of 45 degrees. Fig. 6 is a schematic cross-sectional view of steel rail induction quenching and spray cooling, an induction heating transformer 37 and a water inlet 38 are connected to an end of an induction heating coil 34, the induction heating coil 34 is sleeved on a steel rail section 33, a water spray quenching area 35 is a gap between the top surface of the steel rail section 33 and the induction heating coil, and a spray cooling area 36 is a gap between the side surface and the bottom surface of the steel rail section and the induction heating coil.
The induction quenching and spray cooling device comprises an upper press roll 39, a lower support roll 91 and an induction heating water spray ring 92, wherein the top surface of the guide rail is placed on the row of support rolls 91 downwards, the upper press roll 39 presses the bottom surface of the guide rail tightly, and the induction heating water spray ring 92 is sleeved on the outer side of the steel rail and is pulled to advance by a steel wire rope 93. The rotation speed of the rope winding wheel 94 is electrically controlled and matched with parameters such as power of the induction heating device, distance between the induction coil and the surface of the guide rail and the like, so that the effects of top surface quenching and spray cooling of other parts are achieved. The induction heating water spraying coil is a medium-frequency induction coil, the power of a medium-frequency power supply is not less than 100KW, and the frequency is 500 Hz.
Step 8, mechanically calibrating the quenched section by using a special precision straightening machine to ensure that the section reaches the bending degree specified by the national standard in the vertical and horizontal directions; and then cutting off the lengthening allowance required by straightening the two ends to obtain a finished steel rail with a standard fixed length and size.
The mechanical property of the prepared steel rail finished product is measured, the tensile strength is 920MPa, the elongation is 13%, and the hardness of the top surface layer is 67 HRC. Observing the microstructure of the prepared steel rail finished product, wherein the graphite within 15mm of the surface layer is 100% eutectic graphite, the diameter of graphite nodules is about 22 mu m, and the density of the graphite nodules is about 430 per mm2。
Example 2
The preparation method of the low-noise steel rail for the bridge crane comprises the following steps:
step 1, preparing horizontal continuous casting equipment, wherein the specific process is the same as that of the example 1;
and 2, melting the hypoeutectic component material into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component material comprises the following components in percentage by mass: c: 3.4%, Si: 1.55%, Mn: 0.3%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3 percent of Fe and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent. Stopping flaming preheating, starting the tractor, inserting the seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer.
And 3, performing spheroidization, slagging and inoculation on the molten iron in sequence, namely pouring 600Kg 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 later is 1430 ℃. Adding nodulizer with the weight about 1.5 percent of the total weight of the molten iron into the bottom of the ladle in advance, adding 4.8Kg of 75# ferrosilicon after nodulizing and slagging-off, and inoculating for 5min, so that the final silicon content of the molten iron after inoculation and nodulizing 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.
And 4, 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 15 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. And then starting a traction machine, pulling a crystal guide 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 800-950 ℃. After the blank is pulled out for 3-5 m, 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, so that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, and the length is counted. Then, the cut is cut out by a subsequent online cutting machine according to the length of more than 1.5m, and a cut is cut out every 13.5 m and is pressed and broken by a press machine.
Step 5, 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 400/mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
step 6, 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, heating the annealing furnace to 850 ℃ in a stepped manner, preserving the heat for 2 hours, slowly cooling the section to below 300 ℃ along with the furnace, and finally discharging the section from the furnace and air cooling the section 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 allowances of the top surface and the bottom surface of the guide rail section on a milling machine, wherein the machining allowances are respectively 3mm and 6 mm.
Step 7, carrying out induction quenching and spray cooling treatment on the milled guide rail on a special device, and firstly manufacturing a medium-frequency induction quenching and spray coil according to the specific shape and size of the guide rail; the coil is made of a red copper pipe with the cross section size of 23mm square, the inner edge surface of the shape of the coil is 12mm away from the outer edge surface of the steel rail, and small water spraying holes with different diameters are drilled in different sections: drilling small holes with the diameter of phi 1.3mm at the inner side of the coil part corresponding to the top surface of the steel rail, wherein the hole spacing is 2.5 mm; and small holes with the diameter of 0.8mm are drilled at other parts, the hole interval is 10mm, and the water spraying direction and the axial direction of the steel rail form an included angle of 45 degrees. Fig. 6 is a schematic cross-sectional view of steel rail induction quenching and spray cooling, an induction heating transformer 7 and a water inlet 8 are connected to the end of an induction heating coil 4, the induction heating coil 4 is sleeved on a steel rail section 3, a water spray quenching area 5 is a gap between the top surface of the steel rail section 3 and the induction heating coil, and a spray cooling area 6 is a gap between the side surface and the bottom surface of the steel rail section and the induction heating coil.
The induction quenching and spray cooling device comprises an upper press roll 9, a lower support roll 91 and an induction heating water spray ring 92, wherein the top surface of the guide rail is placed on the row of support rolls 91 downwards, the upper press roll 9 compresses the bottom surface of the guide rail, and the induction heating water spray ring 92 is sleeved on the outer side of the steel rail and is pulled to advance by a steel wire rope 93. The rotation speed of the rope winding wheel 94 is electrically controlled and matched with parameters such as power of the induction heating device, distance between the induction coil and the surface of the guide rail and the like, so that the effects of top surface quenching and spray cooling of other parts are achieved. The induction heating water spraying coil is a medium-frequency induction coil, the power of a medium-frequency power supply is not less than 100KW, and the frequency is 300 Hz.
Step 8, mechanically calibrating the quenched section by using a special precision straightening machine to ensure that the section reaches the bending degree specified by the national standard in the vertical and horizontal directions; and then cutting off the lengthening allowance required by straightening the two ends to obtain a finished steel rail with a standard fixed length and size.
The prepared steel rail finished product is subjected to mechanical property measurement, the tensile strength is 890MPa, the elongation is 9%, and the hardness of the top surface layer is 70 HRC. Observing the microstructure of the prepared steel rail finished product, wherein the graphite within 15mm of the surface layer is 100% eutectic graphite, the diameter of graphite nodules is about 23 mu m, and the density of the graphite nodules is about 410 graphite nodules per mm2。
Example 3
The preparation method of the low-noise steel rail for the bridge crane comprises the following steps:
step 1, preparing horizontal continuous casting equipment, wherein the specific process is the same as that of the example 1;
and 2, melting the hypoeutectic component material into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component material comprises the following components in percentage by mass: c: 3.48%, Si: 1.63%, Mn: 0.45%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.45 percent and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent. Stopping flaming preheating, starting the tractor, inserting the seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer.
And 3, performing spheroidization, slagging and inoculation on the molten iron in sequence, namely pouring 600Kg 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 later is 1430 ℃. Adding nodulizer with the weight about 1.5 percent of the total weight of the molten iron into the bottom of the ladle in advance, adding 4.8Kg of 75# ferrosilicon after nodulizing and slagging-off, and inoculating for 5min, so that the final silicon content of the molten iron after inoculation and nodulizing 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.
And 4, 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 15 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. And then starting a traction machine, pulling a crystal guide 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 800-950 ℃. After the blank is pulled out for 3-5 m, 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, so that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, and the length is counted. Then, the cut is cut out by a subsequent online cutting machine according to the length of more than 1.4m, and a cut is cut out every 13.4 m and is pressed and broken by a press machine.
Step 5, 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 400/mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
step 6, 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, heating the annealing furnace to 865 ℃ in a stepped manner, preserving the heat for 2.5 hours, slowly cooling the section to below 300 ℃ along with the furnace, and finally discharging the section from the furnace and air cooling the section 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 allowances of the top surface and the bottom surface of the guide rail section on a milling machine, wherein the machining allowances are respectively 3mm and 6 mm.
Step 7, carrying out induction quenching and spray cooling treatment on the milled guide rail on a special device, and firstly manufacturing a medium-frequency induction quenching and spray coil according to the specific shape and size of the guide rail; the coil is made of a red copper pipe with the cross section size of 24mm square, the inner edge surface of the shape of the coil is 14mm away from the outer edge surface of the steel rail, and small water spraying holes with different diameters are drilled in different sections: drilling small holes with the diameter of 1.5mm at the inner side of the coil part corresponding to the top surface of the steel rail, wherein the hole spacing is 2.5 mm; and small holes with the diameter of 0.9mm are drilled at other parts, the hole interval is 10mm, and the water spraying direction and the axial direction of the steel rail form an included angle of 45 degrees. The end part of the induction heating coil 4 is connected with an induction heating transformer 7 and a water inlet 8, the induction heating coil 4 is sleeved on the steel rail section bar 3, a water spray quenching area 5 is arranged between the top surface of the steel rail section bar 3 and the induction heating coil, and a spray cooling area 6 is arranged between the side surface and the bottom surface of the steel rail section bar and the induction heating coil.
The induction heating quenching and spray cooling device comprises a press roll 9 above, a supporting roll 91 below and an induction heating water spray ring 92, wherein the top surface of the guide rail is placed on the supporting roll 91 in a row downwards, the press roll 9 above compresses the bottom surface of the guide rail, and the induction heating water spray ring 92 is sleeved outside the steel rail and is pulled by a steel wire rope 93 to advance. The rotation speed of the rope winding wheel 94 is electrically controlled and matched with parameters such as power of the induction heating device, distance between the induction coil and the surface of the guide rail and the like, so that the effects of top surface quenching and spray cooling of other parts are achieved. The induction heating water spraying coil is a medium-frequency induction coil, the power of a medium-frequency power supply is not less than 100KW, and the frequency is 650 Hz.
Step 8, mechanically calibrating the quenched section by using a special precision straightening machine to ensure that the section reaches the bending degree specified by the national standard in the vertical and horizontal directions; and then cutting off the lengthening allowance required by straightening the two ends to obtain a finished steel rail with a standard fixed length and size.
The mechanical property of the prepared steel rail finished product is measured, the tensile strength is 900MPa, the elongation is 10%, and the hardness of the top surface layer is 75 HRC. Observing the microstructure of the prepared steel rail finished product, wherein the graphite within 15mm of the surface layer is 100% eutectic graphite, the diameter of graphite nodules is about 22 mu m, and the density of the graphite nodules is about 410 graphite nodules per mm2。
Example 4
The preparation method of the low-noise steel rail for the bridge crane comprises the following steps:
step 1, preparing horizontal continuous casting equipment, wherein the specific process is the same as that of the example 1;
and 2, melting the hypoeutectic component material into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component material comprises the following components in percentage by mass: c: 3.5%, Si 1.65%, Mn: 0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.5 percent and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent. Stopping flaming preheating, starting the tractor, inserting the seeding rod into the crystallizer, and enabling the end part of the seeding rod to reach the middle part of the crystallizer.
And 3, performing spheroidization, slagging and inoculation on the molten iron in sequence, namely pouring 600Kg 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 later is 1430 ℃. Adding nodulizer with the weight about 1.5 percent of the total weight of the molten iron into the bottom of the ladle in advance, adding 4.8Kg of 75# ferrosilicon after nodulizing and slagging-off, and inoculating for 5min, so that the final silicon content of the molten iron after inoculation and nodulizing 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.
And 4, 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 15 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. And then starting a traction machine, pulling a crystal guide 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 800-950 ℃. After the blank is pulled out for 3-5 m, 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, so that the surface color of the drawn nodular cast iron I-shaped section is uniform and consistent, and the length is counted. Then, the cut is cut out by a subsequent online cutting machine according to the length of more than 1.6m, and a cut is cut out every 13.6 m and is pressed and broken by a press machine.
Step 5, 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 400/mm2If all indexes do not meet the detection standard, the section bar needs to be prepared again;
step 6, 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, heating the annealing furnace to 870 ℃ in a stepped manner, preserving the heat for 3 hours, slowly cooling the section to below 300 ℃ along with the furnace, and finally discharging the section from the furnace and air cooling the section 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 allowances of the top surface and the bottom surface of the guide rail section on a milling machine, wherein the machining allowances are respectively 3mm and 6 mm.
Step 7, carrying out induction quenching and spray cooling treatment on the milled guide rail on a special device, and firstly manufacturing a medium-frequency induction quenching and spray coil according to the specific shape and size of the guide rail; the coil is made of a copper tube with the cross section size of 25mm square, the inner edge surface of the shape of the coil is 15mm away from the outer edge surface of the steel rail, and small water spraying holes with different diameters are drilled in different sections: drilling small holes with the diameter of 1.6mm at the inner side of the coil part corresponding to the top surface of the steel rail, wherein the hole spacing is 2.5 mm; and small holes with the diameter of 1.1mm are drilled at other parts, the hole interval is 10mm, and the water spraying direction and the axial direction of the steel rail form an included angle of 45 degrees. The end part of the induction heating coil 4 is connected with an induction heating transformer 7 and a water inlet 8, the induction heating coil 4 is sleeved on the steel rail section bar 3, a water spray quenching area 5 is arranged between the top surface of the steel rail section bar 3 and the induction heating coil, and a spray cooling area 6 is arranged between the side surface and the bottom surface of the steel rail section bar and the induction heating coil.
The induction heating quenching and spray cooling device comprises a press roll 9 above, a supporting roll 91 below and an induction heating water spray ring 92, wherein the top surface of the guide rail is placed on the supporting roll 91 in a row downwards, the press roll 9 above compresses the bottom surface of the guide rail, and the induction heating water spray ring 92 is sleeved outside the steel rail and is pulled by a steel wire rope 93 to advance. The rotation speed of the rope winding wheel 94 is electrically controlled and matched with parameters such as power of the induction heating device, distance between the induction coil and the surface of the guide rail and the like, so that the effects of top surface quenching and spray cooling of other parts are achieved. The induction heating water spraying coil is a medium-frequency induction coil, the power of a medium-frequency power supply is not less than 100KW, and the frequency is 800 Hz.
Step 8, mechanically calibrating the quenched section by using a special precision straightening machine to ensure that the section reaches the bending degree specified by the national standard in the vertical and horizontal directions; and then cutting off the lengthening allowance required by straightening the two ends to obtain a finished steel rail with a standard fixed length and size.
The mechanical property of the prepared steel rail finished product is measured, the tensile strength is 910MPa, the elongation is 11%, and the hardness of the top surface layer is 72 HRC. Observing the microstructure of the prepared steel rail finished product, wherein the graphite within 15mm of the surface layer is 100% eutectic graphite, the diameter of graphite nodules is about 22 mu m, and the density of the graphite nodules is about 415 pieces/mm2。

Claims (4)

1. The low-noise steel rail for the bridge crane is characterized by comprising the following components in percentage by mass: 3.4-3.6%, Si 2.4-2.6%, Mn: 0.3% -0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3% -0.5%, Mg: 0.03-0.045%, and the balance of Fe, wherein the sum of the mass percentages of the components is 100%; the tensile strength of the steel rail is not less than 880MPa, the elongation is not less than 8%, the top surface layer hardness is not less than 55HRC, the graphite in the surface layer structure of the steel rail is 100% of eutectic graphite, the diameter of graphite nodules is not more than 25 mu m, and the density of the graphite nodules is not less than 400/mm2And the spheroidization rate is 100 percent.
2. A preparation method of a low-noise steel rail for a bridge crane is characterized by comprising the following steps:
step 1, melting hypoeutectic component materials into molten iron in a medium-frequency induction furnace, wherein the hypoeutectic component materials comprise the following components in percentage by mass: 3.4-3.5%, Si 1.55-1.65%, Mn: 0.3% -0.5%, P: less than or equal to 0.02 percent, S: less than or equal to 0.02 percent, Cr: less than or equal to 0.3 percent, Cu: 0.3 to 0.5 percent of Fe and the balance of Fe, wherein the sum of the mass percent of the components is 100 percent;
step 2, carrying out spheroidizing, slagging and inoculation on the molten iron in sequence to ensure that the final silicon content of the molten iron is 2.50 +/-0.1 percent and the content of residual magnesium is 0.03-0.045 percent; adding nodulizer into molten iron for nodulizing, wherein the nodulizer accounts for 1.4-1.6% of the total weight of the molten iron, and adding No. 75 ferrosilicon into the molten iron for inoculation for 4-7 min;
step 3, pouring the molten iron treated in the step 2 into horizontal continuous casting equipment for horizontal continuous casting, and drawing into nodular cast iron I-shaped section bars with uniform surface color;
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 after 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 or the carbon equivalent and silicon carbon ratio in 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 the blank according to the length of more than 1.4 m-1.6 m; the crystallizer is a combined type abdomen cooling crystallizer and mainly comprises an inner trapezoidal graphite bushing, an outer water-cooling sandwich plate and a clamping card, wherein an I-shaped cavity and two through holes are formed in the middle of the graphite bushing, the two through holes are respectively positioned at the waist parts of two sides of the I-shaped cavity, an abdomen cooling pipe with a closed end part is embedded in each through hole, and a water inlet pipe and a water outlet pipe which are communicated with the abdomen cooling pipe are arranged on the water-cooling sandwich 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 400 per mm2Step 5 is carried out, otherwise, the nodular cast iron I-shaped section bar is prepared again;
step 5, annealing and straightening the profile in sequence to enable the curvature of the profile to be less than or equal to 1.0 mm/m;
step 6, carrying out induction quenching treatment on the top surface of the section bar, and carrying out induction heating and spray cooling treatment on other parts of the section bar;
and 7, mechanically calibrating and cutting the section bar processed in the step 6 to enable the section bar to meet the product size requirement specified by the steel rail standard for the bridge crane.
3. The method for preparing a low-noise steel rail for a bridge crane according to claim 2, wherein the annealing treatment in the step 5 comprises placing the section into an annealing furnace, heating the annealing furnace to 860 +/-10 ℃ in a stepwise manner, keeping the temperature for 2-3 hours, slowly cooling the section to 300 ℃ along with the annealing furnace, and finally discharging the section from the annealing furnace and air cooling the section to room temperature.
4. The method for preparing a low-noise steel rail for a bridge crane according to claim 2, wherein in the step 6, the intermediate frequency induction coil is used for carrying out induction quenching treatment and induction heating and spray cooling treatment on the section, the inner side of the intermediate frequency induction coil corresponding to the top surface of the section is provided with small holes with the diameter of 1.3mm to 1.6mm, and the inner sides of the intermediate frequency induction coils corresponding to the side surface and the bottom surface of the section are provided with small holes with the diameter of 0.8mm to 1.1 mm.
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JP2001181779A (en) * 1999-12-22 2001-07-03 Hyundai Motor Co Ltd Method for producing cv graphite cast iron
CN106947912A (en) * 2017-04-26 2017-07-14 含山县朝霞铸造有限公司 A kind of austempering ductile iron and its casting method
CN109750218A (en) * 2019-02-22 2019-05-14 西安理工大学 A kind of eutectic graphite steel and preparation method thereof of self-lubricating abrasion-resistant damage
CN109877550A (en) * 2019-02-22 2019-06-14 西安理工大学 A kind of low-noise, self-lubricated medium and small modulus cylindrical gear and preparation method
CN110565007A (en) * 2019-09-16 2019-12-13 西安理工大学 Threaded lead screw of lead screw pair based on structure energized material and manufacturing method
CN110592465A (en) * 2019-09-16 2019-12-20 西安理工大学 Sliding bearing based on structure enabling material and preparation method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001181779A (en) * 1999-12-22 2001-07-03 Hyundai Motor Co Ltd Method for producing cv graphite cast iron
CN106947912A (en) * 2017-04-26 2017-07-14 含山县朝霞铸造有限公司 A kind of austempering ductile iron and its casting method
CN109750218A (en) * 2019-02-22 2019-05-14 西安理工大学 A kind of eutectic graphite steel and preparation method thereof of self-lubricating abrasion-resistant damage
CN109877550A (en) * 2019-02-22 2019-06-14 西安理工大学 A kind of low-noise, self-lubricated medium and small modulus cylindrical gear and preparation method
CN110565007A (en) * 2019-09-16 2019-12-13 西安理工大学 Threaded lead screw of lead screw pair based on structure energized material and manufacturing method
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