CN116814922A - Method for reducing residual stress of rare earth heat treated steel rail - Google Patents

Method for reducing residual stress of rare earth heat treated steel rail Download PDF

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Publication number
CN116814922A
CN116814922A CN202310414275.9A CN202310414275A CN116814922A CN 116814922 A CN116814922 A CN 116814922A CN 202310414275 A CN202310414275 A CN 202310414275A CN 116814922 A CN116814922 A CN 116814922A
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CN
China
Prior art keywords
steel rail
residual stress
rare earth
heat treated
treated steel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202310414275.9A
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Chinese (zh)
Inventor
苏航
梁正伟
薛虎东
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Baotou Iron and Steel Group Co Ltd
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Baotou Iron and Steel Group Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Baotou Iron and Steel Group Co Ltd filed Critical Baotou Iron and Steel Group Co Ltd
Priority to CN202310414275.9A priority Critical patent/CN116814922A/en
Publication of CN116814922A publication Critical patent/CN116814922A/en
Pending legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B1/00Metal-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
    • B21B1/08Metal-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
    • B21B1/085Rail sections
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/005Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/009Pearlite
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention discloses a method for reducing residual stress of a rare earth heat treated steel rail, which comprises the following production processes: converter smelting, LF ladle refining, VD vacuum degassing, continuous casting, billet heating, rail rolling and rail heat treatment; the heating temperature is 1200 ℃; the tapping temperature is not lower than 1100 ℃; the rolling temperature is 1080-1150 ℃ and the final rolling temperature is 930-950 ℃; the straightening process reduces the rolling reduction of the No. 2 straightening roller to 20mm. The invention aims to provide a method for reducing the residual stress of a rare earth heat treated steel rail, which is used for smelting and rolling a steel rail with good strength and toughness proportion and excellent high strength and high toughness, so that the residual stress of the steel rail is reduced, and the steel rail can be applied to severe regional environments.

Description

Method for reducing residual stress of rare earth heat treated steel rail
Technical Field
The invention relates to the field of metallurgical engineering, in particular to a method for reducing residual stress of a rare earth heat treated steel rail.
Background
Modern railway transportation is moving towards high speed and heavy load mass transport. The existing common steel rail has low strength level, poor wear resistance and short service life, is not suitable for the needs of railway development, and is imperative to develop and upgrade the updated high-strength steel rail.
At present, the abrasion resistance of the steel rail mainly comprising the common heavy-load U75V steel rail is difficult to meet the requirements of heavy load and high strength in railway transportation, and a new generation of heavy-load abrasion-resistant heat treatment steel rail is urgently required to be developed. The main problems faced at present are: the heat-treated steel rail is extremely easy to have abnormal structure due to high strength and high hardness, and has overlarge residual stress and crack expansion rate; the asymmetric section shape characteristic of the steel rail causes the problems of uneven structure-temperature and hardness, inconsistent wear resistance and the like.
Disclosure of Invention
The invention aims to provide a method for reducing the residual stress of a rare earth heat treated steel rail, which is used for smelting and rolling a steel rail with good strength and toughness proportion and excellent high strength and high toughness, so that the residual stress of the steel rail is reduced, and the steel rail can be applied to severe regional environments.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention relates to a method for reducing residual stress of a rare earth heat treated steel rail, which comprises the following production processes: converter smelting, LF ladle refining, VD vacuum degassing, continuous casting, billet heating, rail rolling and rail heat treatment; the method is characterized in that:
the heating temperature is 1200 ℃; the tapping temperature is not lower than 1100 ℃; the rolling temperature is 1080-1150 ℃ and the final rolling temperature is 930-950 ℃;
the straightening process reduces the rolling reduction of the No. 2 straightening roller to 20mm.
Further, the steel rail comprises the following chemical components in percentage by mass: c:0.74 to 0.78 percent; si: 0.61-0.70%; mn:0.84 to 0.91 percent; p is less than or equal to 0.020%; s is less than or equal to 0.020%; cr:0.15 to 0.3 percent; nb:0.01 to 0.05 percent; n i:0.15 to 0.5 percent; ce:0.001%, and the balance of Fe and unavoidable impurities.
Further, the rail structure is pearlite+a small amount of ferrite.
Further, the specific process of the heat treatment is as follows: air-cooling to 780 ℃, and rapidly cooling to 510 ℃ on line; the steel rail returns to 560 ℃ and undergoes isothermal transformation.
Further, the heat treatment time is 100-140s.
Further, the time of the heat treatment was 120s.
Compared with the prior art, the invention has the beneficial technical effects that:
on the premise of the existing process route, a specific heat treatment process is adopted, so that the crack propagation rate performance of the steel rail is improved, and the service life of the steel rail is prolonged; while reducing residual stress.
Detailed Description
A method for reducing residual stress of a rare earth heat treated steel rail comprises the following production processes: converter smelting, LF ladle refining, VD vacuum degassing, continuous casting, billet heating, rail rolling and rail heat treatment; the heating temperature is 1200 ℃; the tapping temperature is not lower than 1100 ℃; the rolling temperature is 1080-1150 ℃ and the final rolling temperature is 930-950 ℃; the straightening process reduces the rolling reduction of the No. 2 straightening roller to 20mm.
The time of on-line heat treatment is 100-140 s; the heat treatment process for rolling 60N U76CrREH steel rail comprises the following specific steps:
the quenching time of the production heat-treated steel rail is 100-120 s, the nozzle distance is 26-32 mm, and the control parameters of the quenching process are shown in the following table.
The steel rail which does not meet the regulation requirement is directly pre-bent; the steel rail meeting the requirements guarantees the inlet temperature of the cooling unit through the induction heater, monitors the stability of the cooling medium in the whole process, and stops rolling in time for processing when abnormality is found. The cooling parameters are finely adjusted according to the temperature change of the cooling medium so as to ensure that the outlet temperature of the cooling unit is controlled within the range specified by the regulations. The method comprises the steps of stopping rolling periodically, checking and confirming the running states of a nozzle, a side guide, a pinch roll and a thermometer in a cooling unit, tracking and confirming the running state of a steel rail in the cooling unit one by one after rolling start, strictly controlling deformation, checking and confirming the surface quality of the steel rail after exiting the cooling unit, and checking and confirming according to the rule requirement frequency during continuous production.
In order to improve the residual stress of the steel rail, the invention optimizes the straightening process and reduces the rolling reduction of the No. 2 straightening roller according to the simulation result of ABAQUS software, and the specific implementation process is shown in the following table:
scheme for the production of a semiconductor device Roll reduction (mm) of straightening roll
Improved pre-straightening process 2#:23 4#:15 6#:10 8#:0
The invention relates to a straightening process 2#:20 4#:15 6#:10 8#:3
Case (B)
The production process comprises the steps of air cooling the steel rail rolled by BD1, BD2 and CCS to 780 ℃, rapidly cooling to 510 ℃ on line, and carrying out on-line heat treatment for 120s; the steel rail is returned to 560 ℃ and subjected to isothermal transformation, and then naturally cooled to obtain the hundred-meter fixed-length online heat-treated steel rail, and the finished steel rail comprises the following chemical components:
TABLE 1 Rail chemical composition%
Rail tensile strength Rm:1370MPa, elongation after break A:12.5%, tread hardness: 391HB, rail head Cross section Hardness (HRC) A l :38.8、B l :38.6、C l :38.8、D l :39.0、E l :39.1; rail head cross section Hardness (HRC) a 4 :39.8、B 5 :39.1、C 5 :39.2、D 3 :39.6、E 3 :39.4, the structure is pearlite+ferrite (less), and the lamellar spacing is as follows: the remaining properties at 69.4nm meet the requirements for U76CrREH in TB/T2344.1-2020.
Wherein residual stress performance is compared to that before improvement as shown in the following table:
TABLE 2 residual stresses on rails
Compared with the residual stress value of the 1# 4 experimental steel before improvement, the residual stress value of the 1# 4 experimental steel is reduced by about 50MPa, the fluctuation range is smaller, the rolling reduction of a 2# straightening roller is reduced by adjusting the straightening process under the same condition of the quenching process, the purpose of reducing the residual stress of the U76CrREH steel rail is realized, and the expected effect of the invention is achieved. The invention can effectively reduce the residual stress of the 1# 4 experimental steel.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.

Claims (6)

1. A method for reducing residual stress of a rare earth heat treated steel rail comprises the following production processes: converter smelting, LF ladle refining, VD vacuum degassing, continuous casting, billet heating, rail rolling and rail heat treatment; the method is characterized in that:
the heating temperature is 1200 ℃; the tapping temperature is not lower than 1100 ℃; the rolling temperature is 1080-1150 ℃ and the final rolling temperature is 930-950 ℃;
the straightening process reduces the rolling reduction of the No. 2 straightening roller to 20mm.
2. The method of reducing residual stress in a rare earth heat treated steel rail according to claim 1, wherein: the steel rail comprises the following chemical components in percentage by mass: c:0.74 to 0.78 percent; si: 0.61-0.70%; mn:0.84 to 0.91 percent; p is less than or equal to 0.020%; s is less than or equal to 0.020%; cr:0.15 to 0.3 percent; nb:0.01 to 0.05 percent; ni:0.15 to 0.5 percent; ce:0.001%, and the balance of Fe and unavoidable impurities.
3. The method of reducing residual stress in a rare earth heat treated steel rail according to claim 1, wherein: the steel rail structure is pearlite and a small amount of ferrite.
4. The method of reducing residual stress in a rare earth heat treated steel rail according to claim 1, wherein: the specific process of the heat treatment is as follows: air-cooling to 780 ℃, and rapidly cooling to 510 ℃ on line; the steel rail returns to 560 ℃ and undergoes isothermal transformation.
5. The method of reducing residual stress in a rare earth heat treated steel rail according to claim 4, wherein: the heat treatment time is 100-140s.
6. The method of reducing residual stress in a rare earth heat treated steel rail according to claim 5, wherein: the time for the heat treatment was 120s.
CN202310414275.9A 2023-04-18 2023-04-18 Method for reducing residual stress of rare earth heat treated steel rail Pending CN116814922A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310414275.9A CN116814922A (en) 2023-04-18 2023-04-18 Method for reducing residual stress of rare earth heat treated steel rail

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310414275.9A CN116814922A (en) 2023-04-18 2023-04-18 Method for reducing residual stress of rare earth heat treated steel rail

Publications (1)

Publication Number Publication Date
CN116814922A true CN116814922A (en) 2023-09-29

Family

ID=88117488

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310414275.9A Pending CN116814922A (en) 2023-04-18 2023-04-18 Method for reducing residual stress of rare earth heat treated steel rail

Country Status (1)

Country Link
CN (1) CN116814922A (en)

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