CN116083696A - Production method of steel for stable incomplete austenite bainite frog - Google Patents

Production method of steel for stable incomplete austenite bainite frog Download PDF

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CN116083696A
CN116083696A CN202211616363.9A CN202211616363A CN116083696A CN 116083696 A CN116083696 A CN 116083696A CN 202211616363 A CN202211616363 A CN 202211616363A CN 116083696 A CN116083696 A CN 116083696A
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frog
steel
percent
rolling
forging
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袁俊
韩振宇
李晓煜
李若曦
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Pangang Group Panzhihua Steel and Vanadium Co Ltd
Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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Pangang Group Panzhihua Steel and Vanadium Co Ltd
Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/085—Rail sections
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/002—Hybrid process, e.g. forging following casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K7/00—Making railway appurtenances; Making vehicle parts
    • B21K7/02—Making railway appurtenances; Making vehicle parts parts for permanent way
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/008—Martensite
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses a production method of steel for a stable incomplete austenite bainite frog, which comprises the following steps: s1, heating a steel billet obtained after smelting and casting; s2, rolling or forging the heated billet; s3, carrying out heat treatment on the steel for the frog obtained after rolling or forging, wherein the cooling temperature of the heat treatment is 700-820 ℃, the cooling rate is 5-15 ℃/S, and the final cooling temperature is 150-250 ℃; s4, when the heat-treated frog steel is cooled to an intercooling temperature, carrying out heat preservation treatment on the full section, wherein the heat preservation treatment time is 240-480 h; and S5, tempering the cooled steel for the frog. The method can obtain fine dispersed and stable retained austenite by controlling the form and quantity of the retained austenite in the heating, rolling or forging and cooling processes of the casting blank, and improves the comprehensive performance of the bainitic frog.

Description

Production method of steel for stable incomplete austenite bainite frog
Technical Field
The invention relates to the technical field of metallurgy, in particular to a production method of steel for a stable residual austenite bainite frog.
Background
Frog is an important component of a railway track structure and is a special device for rolling stock wheels to pass from one track to another, through rail intersections. When the locomotive passes through the frog, the frog is subjected to huge wheel impact load, and the working condition is extremely harsh. The frog is subjected to an impact from the wheel load, and in addition to the increase in dead load, is also the place on the rail where the greatest dynamic load is applied. And the dynamic load on the rail and the turnout is 2-5 times of the static load. Therefore, the frog has extremely strict requirements on the performance of the material.
The existing bainite steel rail is designed with low carbon (carbon content: 0.15-0.25%), and is supplemented with a proper amount of Si, mn, cr, ni, mo and other elements, and carbide-free bainite or B/M complex phase structure and a small amount of residual austenite are obtained under the air cooling condition. Retained austenite refers to austenite that has not yet been transformed after bainite or martensite transformation. Bainitic frog usually contains 5-30% of retained austenite, which affects the performance of the steel: (1) the hardness of the residual austenite is far lower than that of the bainite or martensite, so that the bainite frog is reduced along with the increase of the residual austenite, and the performance index of the bainite frog is obviously influenced; (2) the residual austenite has thermal stability and mechanical stability, and can be converted into a martensitic structure in the tempering or line service wheel-rail contact process, thereby having profound effects on the bainitic frog tempering process and line service; (3) the increase in residual austenite content, after transformation to martensite, generally forms hard particles, which cause a nuclear fracture inside the product. The surface of the frog can be peeled off or cracked in a large area, and the fatigue performance and the line service performance of the bainitic frog are seriously affected; (4) the increase of residual austenite improves the toughness of the bainite frog to a certain extent and improves the impact resistance of the bainite frog.
Therefore, how to control the form and the quantity of the retained austenite becomes a technical problem to be solved in the production process of the steel for the bainitic frog.
Disclosure of Invention
The invention mainly aims to provide a production method of steel for a stable residual austenite frog, which is used for obtaining fine dispersed and stable residual austenite and improving the comprehensive performance of the bainite frog by controlling the form and quantity of the residual austenite in the processes of heating, rolling or forging and cooling a casting blank.
In order to solve at least one of the technical problems, the invention adopts the following technical scheme:
according to the invention, there is provided a method for producing a steel for stable residual austenite bainitic frog, comprising the steps of: s1, heating a steel billet obtained after smelting and casting; s2, rolling or forging the heated billet; s3, carrying out heat treatment on the steel for the frog obtained after rolling or forging, wherein the cooling temperature of the heat treatment is 700-820 ℃, the cooling rate is 5-15 ℃/S, and the final cooling temperature is 150-250 ℃; s4, when the heat-treated frog steel is cooled to the final cooling temperature, carrying out heat preservation treatment on the full section, wherein the heat preservation treatment time is 240-480 h; and S5, tempering the cooled steel for the frog.
According to one embodiment of the invention, the steel for the frog comprises the following components in percentage by mass: 0.24 to 0.35 percent of C,1.20 to 1.8 percent of Si,1.50 to 2.50 percent of Mn,0.002 to 0.020 percent of P,0.002 to 0.020 percent of S,0.30 to 1.70 percent of Cr,0.10 to 0.60 percent of Mo,0.002 to 0.70 percent of Ni,0.01 to 0.15 percent of V,0.001 to 0.004 percent of Al, and the balance of Fe and unavoidable impurity elements.
According to one embodiment of the present invention, in step S1, the soaking temperature of the steel billet is 1050-1150 ℃ and the holding time is 200-350 min.
According to one embodiment of the invention, in the step S2, the final cooling temperature of rolling or forging is 950-1000 ℃, and the rolling compression ratio or forging ratio is more than or equal to 5.
According to an embodiment of the present invention, in step S4, the guide rail is used to constrain the rail web during the heat preservation process.
According to one embodiment of the present invention, in step S4, the heat-insulated steel for frog is naturally cooled.
According to one embodiment of the present invention, in step S5, the cooled frog steel is tempered at 200-400 ℃ for 5-120 hours.
According to one embodiment of the present invention, in step S5, the tempered steel for frog is naturally cooled.
According to one embodiment of the invention, the spacing between adjacent frog steels during the natural cooling process is 100mm.
According to one embodiment of the invention, the casting is performed through protection casting.
In the production method of the stable residual austenite bainitic frog steel according to the embodiment of the invention, the form and the quantity of the residual austenite in the casting blank heating, rolling or forging and cooling processes are controlled to obtain the fine dispersed and stable residual austenite, so that the comprehensive performance of the bainitic frog is improved. The tensile strength of the bainite frog produced by the method is more than or equal to 1350MPa, the elongation is more than or equal to 12%, and the content of residual austenite is less than or equal to 12%. After 500 ten thousand physical frog fatigue tests, the residual austenite conversion rate is as low as within 10 percent. Compared with the conventional bainitic frog or bainitic rail, the early-service damage rate is reduced by 70-90%, the mechanical and structural stability of the bainitic steel is greatly improved, and the service stability of the bainitic frog is improved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 shows a flow chart of a method of producing a stable stub bainitic frog steel according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
The effect of retained austenite on strength, the reinforcement in steel includes: solid solution strengthening, substructure dislocation strengthening, grain boundary strengthening, precipitation strengthening, fine grain strengthening, and multi-phase microstructure strengthening. The strength of the bainitic frog steel containing the retained austenite mainly comes from a strong-hard phase matrix structure in the steel, and mainly comprises ferrite, bainite and martensite. During the drawing process, the retained austenite in the steel may undergo transformation with an increase in deformation amount to form a hard phase martensitic structure, resulting in an increase in tensile strength.
The retained austenite influences the plasticity, when the volume of the bainite frog is increased under the action of plastic deformation, strain hardening is generated, martensitic transformation is generated, the local hardness is improved, and the deformation is difficult to continue. Meanwhile, with the continuous development of phase change, the material obtains very high plasticity. The retained austenite causes an increase in dislocation density during transformation, and dislocation strengthening occurs, resulting in an improvement in strength.
The influence of the residual austenite on the toughness, along with the increase of deformation, the martensite transformation occurs, the work hardening rate of a necking zone is improved, the necking zone is widened, and the necking zone is made to be gentle, so that the toughness of the steel is improved. The residual austenite is a soft phase, and can relax locally concentrated stress through plastic deformation, delay the germination of microscopic cracks and prevent the development and growth of the microscopic cracks. In the crack propagation, the retained austenite can turn to absorb more energy, and the fracture toughness of the bainitic frog is improved.
Fig. 1 shows a flow chart of a method of producing a steel for stable residual austenite bainitic frog according to an embodiment of the present invention, the method generally comprising the steps of:
s1, heating a steel billet obtained after smelting and casting;
s2, rolling or forging the heated billet;
s3, carrying out heat treatment on the steel for the frog obtained after rolling or forging, wherein the cooling temperature of the heat treatment is 700-820 ℃, the cooling rate is 5-15 ℃/S, and the final cooling temperature is 150-250 ℃;
s4, when the heat-treated frog steel is cooled to the final cooling temperature, carrying out heat preservation treatment on the full section, wherein the heat preservation treatment time is 240-480 h;
and S5, tempering the cooled steel for the frog.
In the method for producing a stable residual austenite bainitic steel for frog according to an embodiment of the present invention, the composition of the steel for frog is preferably, in mass percent: 0.24 to 0.35 percent of C,1.20 to 1.8 percent of Si,1.50 to 2.50 percent of Mn,0.002 to 0.020 percent of P,0.002 to 0.020 percent of S,0.30 to 1.70 percent of Cr,0.10 to 0.60 percent of Mo,0.002 to 0.70 percent of Ni,0.01 to 0.15 percent of V,0.001 to 0.004 percent of Al, and the balance of Fe and unavoidable impurity elements.
Among the above components, the use of 0.24 to 0.35% of C significantly reduces the martensite transformation Ms point, thereby improving the stability of austenite. Mn of 1.50 to 2.50% can not only enlarge the austenite phase region but also lower the martensite start temperature Ms.1.20 to 1.8% of Si and 0.002 to 0.020% of P can similarly reduce the Ms temperature of the martensite start temperature, while 0.001 to 0.004% of Al increases the Ms temperature.
In some embodiments, steps S1 to S2 may employ the following parameters: after smelting and casting, the billet is heated to 1050-1150 ℃ and the heat preservation time is 200-350 min. And (3) carrying out rolling or forging after dephosphorization on the steel billet, wherein the final cooling temperature of the rolling or forging is 950-1000 ℃, and the rolling compression ratio or forging ratio is more than or equal to 5. And (3) obtaining small-size residual austenite through low-temperature heating of casting blanks, rolling with a large compression ratio and heat treatment accelerated cooling in the step S3. The smaller the austenite grains, the lower the Ms temperature. In addition, in the deformation process, the stability of the large-size residual austenite is poor, the martensite transformation can be generated under low strain, the stability of the small-size residual austenite is strong, and the transformation can not be generated under high strain.
When the steel for the frog is cooled to the final cooling temperature through heat treatment, the full section is subjected to heat preservation treatment for a long time in the step S4. The whole section is to heat-insulating the whole steel. The steel for frog is I-shaped and is divided into three parts of rail head, rail web and rail bottom. Conventional processes either heat treat the head or heat treat the head and foot. The material of the invention is a composite structure of bainite, martensite, residual austenite and the like, and the comprehensive performance of the whole product can be improved by adopting full-section heat preservation treatment, the internal stress can be reduced and the like. In some embodiments, guide rails are used to constrain the web during the soak process. The heat-insulating steel for the frog can be naturally cooled to room temperature, namely, the spacing between adjacent steel for the frog is 100mm, and the rapid cooling device does not accelerate cooling.
After the component frog steel is rapidly cooled, a certain amount of residual austenite structure can appear in the austenite structure due to the influence of components and cooling speed. The retained austenite structure at room temperature is unstable, and can be transformed into a hard martensite structure again in the subsequent temperature rise or deformation process. After rapid cooling, the heat preservation treatment for a long time is favorable for transforming the residual austenite from an unsteady state to a steady state structure or transforming the residual austenite structure to a bainite structure with better comprehensive performance.
In the step S4, after straightening processing, tempering is carried out on the cooled steel for the frog at the temperature of 200-400 ℃ for 5-120 hours so as to eliminate residual stress. The tempered steel for frog can be cooled down to room temperature by natural cooling. The tempering time is mainly related to heating medium, furnace temperature, chemical composition of steel, structure, sample size shape, charging mode, charging amount and the like, and the influence of the sample size shape and the structure on the tempering time is most obvious. The thickness of the cross section of the steel for the frog can reach 116mm, and the steel is prepared according to the common empirical formula (1):
T＝a×K×D (1)
wherein, T is heating time min; a, the heating coefficient min/mm is related to the size of the workpiece, the heating medium and the chemical composition of steel; k, charging correction coefficient (1.5-2.0); d-effective thickness of part mm)
The minimum tempering time is 300min, namely 5h.
Meanwhile, in the embodiment of the invention, the shared structure of the steel for the frog is a composite structure of bainite, martensite composite, residual austenite and the like, the contents of martensite and residual austenite in the structure are small, the transformation in the tempering process is influenced by the extrusion of the bainite structure, the transformation rate is extremely low, and the required tempering time is long. Experimental study shows that the tempering time is 120h at maximum, and the maximum time of the international bainite material reaches more than 30 days.
In some embodiments, the casting is performed throughout the casting process to control the nitrogen, hydrogen, oxygen content of the steel for the frog.
The following description is made with reference to specific examples.
The steels for frog of the present invention and the comparative examples were cast through a full process protection, wherein the main chemical compositions of examples 1 to 5 are shown in Table 1, and the comparative examples 1 to 2 are the same as the compositions of examples 1 to 2 in mass percent.
Table 1 chemical composition/%of steel for example and comparative example frog
Figure BDA0004001892370000061
The examples and comparative examples use the same smelting, billet heating, rolling or forging process. The soaking temperature of the casting blank is 1050-1150 ℃ and the heat preservation time is 200-350min; the final cooling temperature of rolling or forging is 950-1000 ℃, and the forging ratio or compression ratio is more than or equal to 5. After the waste heat is utilized or the waste heat is heated again, the cooling temperature is 700-820 ℃, the cooling rate is 5-15 ℃/s, and the final cooling temperature is 150-250 ℃. The heat treatment processes of examples and comparative examples are shown in table 2.
Table 2 example and comparative example heat treatment process
Figure BDA0004001892370000071
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After heat preservation treatment of the bainite frog in the examples and the comparative examples, tempering is carried out at 200-400 ℃ for 5-120h after cooling and straightening processing. Examples and comparative examples tensile samples were taken and tested according to the requirements of TB/T2344 Rail ordering technical conditions 43kg/m to 75 kg/m. Meanwhile, a steel rail physical fatigue testing machine is adopted to carry out 500 ten thousand fatigue tests on the bainitic frog. And taking metallographic samples at the rail head fillet before and after the bainitic frog test, and analyzing the residual austenite change condition before and after the test by adopting XRD contrast inspection. The content of residual austenite is less than or equal to 12 percent. After 500 ten thousand physical frog fatigue tests, the residual austenite conversion rate is as low as within 10 percent. The stretching and metallographic data statistics are shown in table 3.
Table 3 tensile properties of example and comparative rail
Figure BDA0004001892370000072
In combination with tables 1 to 3, the parameters related to the composition design, heating process, rolling process of the comparative example were not within predetermined ranges. As shown in Table 4, the tensile strength of the bainite frog produced by the method is more than or equal to 1350MPa, the elongation is more than or equal to 12%, and the residual austenite content is less than or equal to 12%. After 500 ten thousand physical frog fatigue tests, the residual austenite conversion rate is as low as within 10 percent. Compared with the conventional bainitic frog or bainitic rail, the early-service damage rate is reduced by 70-90%, the mechanical and structural stability of the bainitic steel is greatly improved, and the service stability of the bainitic frog is improved.
Those of ordinary skill in the art will appreciate that: the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosure of embodiments of the invention, including the claims, is limited to such examples; combinations of features of the above embodiments or in different embodiments are also possible within the idea of an embodiment of the invention, and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, and the like, which are made within the spirit and principles of the embodiments of the invention, are included within the scope of the embodiments of the invention.

Claims (10)

1. The production method of the steel for the stable incomplete austenite bainite frog is characterized by comprising the following steps of:
s1, heating a steel billet obtained after smelting and casting;
s2, rolling or forging the heated billet;
s3, carrying out heat treatment on the steel for the frog obtained after rolling or forging, wherein the cooling temperature of the heat treatment is 700-820 ℃, the cooling rate is 5-15 ℃/S, and the final cooling temperature is 150-250 ℃;
s4, when the heat-treated frog steel is cooled to the final cooling temperature, carrying out heat preservation treatment on the full section, wherein the heat preservation treatment time is 240-480 h;
and S5, tempering the cooled steel for the frog.
2. The method of claim 1, wherein the frog steel comprises the following components in mass percent: 0.24 to 0.35 percent of C,1.20 to 1.8 percent of Si,1.50 to 2.50 percent of Mn,0.002 to 0.020 percent of P,0.002 to 0.020 percent of S,0.30 to 1.70 percent of Cr,0.10 to 0.60 percent of Mo,0.002 to 0.70 percent of Ni,0.01 to 0.15 percent of V,0.001 to 0.004 percent of Al, and the balance of Fe and unavoidable impurity elements.
3. The method according to claim 1, wherein in step S1, the soaking temperature of the steel billet is 1050-1150 ℃ and the holding time is 200-350 min.
4. The method according to claim 1, wherein in step S2, the final cooling temperature of rolling or forging is 950 to 1000 ℃, and the rolling compression ratio or forging ratio is not less than 5.
5. The method of claim 1, wherein in step S4, the rail web is constrained by a guide rail during the soak process.
6. The method of claim 5, wherein in step S4, the heat-preserved steel for frog is naturally cooled.
7. The method of claim 1, wherein in step S5, the cooled steel for frog is tempered at 200 to 400 ℃ for 5 to 120 hours.
8. The method of claim 7, wherein in step S5, the tempered steel for frog is naturally cooled.
9. The method of claim 6 or 8, wherein the spacing between adjacent frog steels during natural cooling is 100mm.
10. The method of claim 1, wherein the casting is a protective casting throughout.
CN202211616363.9A 2022-12-15 2022-12-15 Production method of steel for stable incomplete austenite bainite frog Pending CN116083696A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024124795A1 (en) * 2022-12-15 2024-06-20 攀钢集团攀枝花钢铁研究院有限公司 Production method for large-compression-ratio steel for bainite frog

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024124795A1 (en) * 2022-12-15 2024-06-20 攀钢集团攀枝花钢铁研究院有限公司 Production method for large-compression-ratio steel for bainite frog

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