AU2019232893A1 - Manufacturing method of rails for heavy-haul railways - Google Patents

Manufacturing method of rails for heavy-haul railways Download PDF

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Publication number
AU2019232893A1
AU2019232893A1 AU2019232893A AU2019232893A AU2019232893A1 AU 2019232893 A1 AU2019232893 A1 AU 2019232893A1 AU 2019232893 A AU2019232893 A AU 2019232893A AU 2019232893 A AU2019232893 A AU 2019232893A AU 2019232893 A1 AU2019232893 A1 AU 2019232893A1
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AU
Australia
Prior art keywords
rail
heat treatment
rails
heavy
manufacturing
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Application number
AU2019232893A
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AU2019232893B2 (en
Inventor
Zhenyu Han
Ruoxi Li
Jun Yuan
Ming Zou
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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Publication of AU2019232893A1 publication Critical patent/AU2019232893A1/en
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Classifications

    • 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
    • C21D1/78—Combined heat-treatments not provided for above
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Abstract

Abstract The invention relates to the field of rail preparation method, in particular to a manufacturing method of rails for heavy-haul railways, which can reduce the austenite grain size, refine the interlaminar spacing of pearlite, improve the rail strength and continuously improve the toughness of rails. It comprises the steps of: allowing a rail to be subjected to the primary heat treatment by using waste heat of rolling, heating the rail to 650 °C - 700 °C by a heating device, returning the rail to a heat treatment unit for secondary heat treatment, and quickly withdrawing the rail from the heat treatment unit. In this invention, since the interlaminar spacing has been refined through the primary heat treatment, the interlaminar spacing of pearlite can be further refined after the secondary heat treatment to improve the strength and toughness of rails. The rails produced by the method can reach the tensile strength of more than 1380MPa, and the fracture toughness of not less than 38MPa-mi/2 at -20 °C, thus providing the excellent wear resistance and contact fatigue resistance. The invention is especially suitable for the production of rails for heavy-haul railways.

Description

Manufacturing Method of Rails for Heavy-Haul Railways
Related Application
This application claims priority from Chinese patent application no. CN 201811280755.6 filed 5 on 30 October 2018, the entire contents of which are incorporated herein by reference.
Technical Field
Embodiments of the invention relate to the field of rail preparation method, in particular to a manufacturing method of rails for heavy-haul railways.
Background
The railway has been gradually developing towards high speed or heavy haul as the development of domestic and foreign railway industry. Heavy-haul rails shall have high strength and toughness to adapt to the increasing demand of railway transportation, and to resist the impact 5 load. Existing rails are mainly pearlite rails with an ultimate tensile strength of 1350 MPa.
However, it is difficult to achieve the ultimate tensile strength of 1350 MPa with the existing pearlite system and heat treatment process.
The on-line heat treatment of rails by waste heat of rolling is a main way of rail manufacturing in 20 the world but cannot improve the heat treatment cooling strength, as constrained by the austenite grain size.
A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.
Summary of the Invention
Embodiments of the invention may provide a manufacturing method of rails for heavy-haul railways, which can reduce the austenite grain size, refine the interlaminar spacing of pearlite, 30 improve the rail strength and continuously improve the toughness of rails.
According to one aspect of the invention, there is provided a manufacturing method of rails for d heavy-haul railways, comprising the steps of: allowing a rail to be subjected to the primary heat treatment by using waste heat of rolling, heating the rail to 650 °C - 700 °C by a heating device, 5 returning the rail to a heat treatment unit for secondary heat treatment, and quickly withdrawing the rail from the heat treatment unit.
Optionally, the heating device is an induction heating device.
Optionally, the rail is 650 °C - 900 °C when treated with the waste heat of rolling.
Optionally, the primary heat treatment comprises the steps of: accelerate cooling the rail at 1 - 5 °C/s, reducing the cooled rail to 400 °C - 550 °C, and quickly withdrawing the heat treatment unit to stop the primary heat treatment.
Optionally, after the primary heat treatment is completed, the rail withdrawn from the heat treatment unit is subjected to induction heating by a heating device for heating the rail to 650 °C - 700 °C, and then quickly placing the rail in the heat treatment unit again.
Optionally, the rail subjected to induction heating is fed into the heat treatment unit for accelerated cooling at 2 - 50 °C/s; when the cooled rail drops to 400 °C - 550 °C, the rail is quickly withdrawn from the heat treatment unit to end the secondary heat treatment.
Optionally, the rail is cast in the early stage by molten iron with low S content, and the refining 25 slag with high basicity according to the overall-protection casting process.
Optionally, the carburant used in the early stage of rail casting includes anthracite and low-N alloy.
Optionally, a foaming agent is used in the LF heating process to prevent the rail from contacting with air and inhaling excessive N in the early stage of rail casting.
d Optionally, an ingot blank is slowly cooled in a burial pit the early stage of rail casting.
Advantageously, in actual operation, austenite grain size may be refined through the primary heat treatment, waste heat treatment, and the secondary online heat treatment. During the secondary heat treatment, the cooling strength may be greatly improved. At the same time, since the interlaminar spacing can be refined through the primary heat treatment, the interlaminar spacing of pearlite may be further refined after the secondary heat treatment to improve the strength and 0 toughness of rails. The rails produced by the method may reach the tensile strength of more than 1380MPa, and the fracture toughness of not less than 38MPa-m at -20 °C, thus providing excellent wear resistance and contact fatigue resistance. Embodiments of the invention may be especially suitable for the production of rails for heavy-haul railways.
Description of Embodiments
The manufacturing method of rails for heavy-haul railways comprises the steps of: allowing a rail to be subjected to the primary heat treatment by using waste heat of rolling, heating the rail to 650 °C - 700 °C by a heating device, returning the rail to a heat treatment unit for secondary heat treatment, and quickly withdrawing the rail from the heat treatment unit.
The existing rails are mainly pearlite rail with the ultimate tensile strength of 1350 MPa.
However, it is difficult to achieve the ultimate tensile strength of 1350 MPa with the existing pearlite system and heat treatment process. For the time being, the on-line heat treatment of rails by waste heat of rolling is a main way of rail manufacturing in the world but cannot improve the 25 heat treatment cooling strength, as restricted by the austenite grain size. Embodiments of the invention creatively designs a twice heat treatment method. After the secondary heat treatment, the cooling strength can be greatly improved, and the interlaminar spacing of pearlite can be further refined to improve the strength and toughness of rails. In actual operation, the heating device is preferably an induction heating device to ensure heating efficiency and heating 30 accuracy.
In order to ensure the accuracy of the primary heat treatment, the rail is 650 °C - 900 °C when d treated with the waste heat of rolling. In particular, the primary heat treatment comprises the steps of: accelerate cooling the rail at 1-5 °C/s, reducing the cooled rail to 400 °C - 550 °C, and 5 quickly withdrawing the heat treatment unit to stop the primary heat treatment. After the primary heat treatment is completed, the rail withdrawn from the heat treatment unit is subjected to induction heating by a heating device for heating the rail to 650 °C - 700 °C, and then quickly placing the rail in the heat treatment unit again. The rail is fed into the heat treatment unit for accelerated cooling at 2 - 50 °C/s after induction heating; when the cooled rail drops to 400 °C 0 550 °C, the rail is quickly withdrawn from the heat treatment unit to end the secondary heat treatment.
As far as the rail casting is concerned, embodiments of the invention are also technically improved to further enhance the overall quality of the product. Among them, the rail is cast in the 5 early stage by molten iron with low S content, and the refining slag with high basicity according to the overall-protection casting process; the carburant used in the early stage of rail casting includes anthracite and low-N alloy; a foaming agent is used in the LF heating process to prevent the rail from exposing to air and inhaling excessive N in the early stage of rail casting; and an ingot blank is slowly cooled in a burial pit in the early stage of rail casting.
Example
The chemical compositions in examples of the invention and corresponding comparative examples are provided below.
Table 1 Chemical compositions of rails in examples
Item No. Chemical compositions/%
C Si+Mn+P+S+Cr+V
Example 1# 0.85 1.80
2019232893 20 Sep 2019
The comparative examples had the same chemical compositions, heating and rolling processes as those in the examples.
The rail was subjected to secondary heat treatment by the method in claims, wherein 1# to 5# represent different heat treatment cooling rate and different heating temperature, 6# and 7# are comparative examples, 6# is only subjected to primary heat treatment, and 7# is hot-rolled.
Table 2 Secondary heat treatment process for rails in examples and comparative examples
Item No. Inlet temperature Cooling rate of primary heat treatment Primary heat treatment temperature Induction heating temperature Cooling rate of secondary heat treatment
Example 1# 765 2 500 650 10
2# 765 2 500 700 10
3# 765 2 500 700 2
4# 765 2 500 700 20
5# 765 2 500 700 50
Comparative example 6# 765 2 500 - -
7# 765 2 - - -
Table 3 Austenite grain size and interlaminar spacing of rails in examples and comparative examples.
Item No. Austenite grain size Interlaminar spacing
Example 1# 10 8
2# 10 9
3# 11 9
4# 12 7
5# 13 6
Comparative example 6# 7 10
7# 7 14
2019232893 20 Sep 2019
Six rail specimens were tested for tensile property and fracture toughness at -20 °C as described in TB/T 2344-2012. The test results are given in Table 4.
Table 4 Strength and toughness of rails in examples and comparative examples
Item No. Tensile strength Elongation Fracture toughness at -20 °C
Example 1# 1395 15 41
2# 1391 17 39
3# 1380 15 38
4# 1390 16 40
5# 1410 17 42
Comparative example 6# 1330 11 32
7# 1100 10 30
The examples compare the rails with the same chemical compositions; and five treatment methods given in examples are all methods according to embodiments of the invention. The 0 comparison results in Tables 1 to 3 reveal that the strength and toughness of rails is further enhanced after the secondary heat treatment.
To sum up, the manufacturing method of rails for wear-resistant heavy-haul railways in the examples of the invention is effective for improving the strength and toughness of rails by 15 reducing austenite grain size and interlaminar spacing, and the products on the basis of the method are suitable for domestic and overseas heavy-haul railways.
Where any or all of the terms comprise, comprises, comprised or comprising are used in this specification (including the claims) they are to be interpreted as specifying the presence of 20 the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

Claims (10)

  1. The claims defining the invention are as follows:
    1. A manufacturing method of rails for heavy-haul railways, the method comprising the steps of: allowing a rail to be subjected to the primary heat treatment by using waste heat of rolling, heating the rail to 650 °C - 700 °C by a heating device, returning the rail to a heat treatment unit for secondary heat treatment, and quickly withdrawing the rail from the heat treatment unit.
  2. 2. The manufacturing method of rails for heavy-haul railways according to claim 1, wherein the heating device is an induction heating device.
  3. 3. The manufacturing method of rails for heavy-haul railways according to claim 1 or 2, wherein the rail is 650 °C - 900 °C when treated with the waste heat of rolling.
  4. 4. The manufacturing method of rails for heavy-haul railways according to claim 3, wherein the primary heat treatment comprises the steps of: accelerate cooling the rail at 1 - 5 °C/s, reducing the cooled rail to 400 °C - 550 °C, and quickly withdrawing the heat treatment unit to end the primary heat treatment.
  5. 5. The manufacturing method of rails for heavy-haul railways according to claim 4, wherein, after the primary heat treatment is completed, the rail withdrawn from the heat treatment unit is subjected to induction heating by a heating device for heating the rail to 650 °C - 700 °C, and then quickly placing the rail in the heat treatment unit again.
  6. 6. The manufacturing method of rails for heavy-haul railways according to claim 5, wherein the rail subjected to induction heating is fed into the heat treatment unit for accelerated cooling at 2-50 °C/s; when the cooled rail drops to 400 °C - 550 °C, the rail is quickly withdrawn from the heat treatment unit to end the secondary heat treatment.
  7. 7. The manufacturing method of rails for heavy-haul railways according to claim 1 or 2, wherein the rail is cast in the early stage by molten iron with low S content, and the refining slag
    2019232893 20 Sep 2019 with high basicity according to the overall-protection casting process.
  8. 8. The manufacturing method of rails for heavy-haul railways according to claim 1 or 2, wherein the carburant used in the early stage of rail casting includes anthracite and low-N alloy.
  9. 9. The manufacturing method of rails for heavy-haul railways according to claim 1 or 2, wherein a foaming agent is used in the LF heating process to prevent the rail from exposing to air and inhaling excessive N in the early stage of rail casting.
  10. 10. The manufacturing method of rails for heavy-haul railways according to claim 1 or 2, wherein an ingot blank is slowly cooled in a burial pit in the early stage of rail casting.
AU2019232893A 2018-10-30 2019-09-20 Manufacturing method of rails for heavy-haul railways Active AU2019232893B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201811280755.6A CN109207691A (en) 2018-10-30 2018-10-30 The production method of heavy haul railway rail
CN201811280755.6 2018-10-30

Publications (2)

Publication Number Publication Date
AU2019232893A1 true AU2019232893A1 (en) 2020-05-14
AU2019232893B2 AU2019232893B2 (en) 2021-07-22

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AU (1) AU2019232893B2 (en)

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3971655A (en) * 1974-08-21 1976-07-27 Nippon Steel Corporation Method for treatment of molten steel in a ladle
DE3446794C1 (en) * 1984-12-21 1986-01-02 BWG Butzbacher Weichenbau GmbH, 6308 Butzbach Process for the heat treatment of pearlitic rail steel
JPH04202626A (en) * 1990-11-30 1992-07-23 Nippon Steel Corp Production of steel rail excellent in drop weight resisting characteristic
JP2005171327A (en) * 2003-12-11 2005-06-30 Nippon Steel Corp Method for manufacturing pearlite-based rail having excellent surface damage-resistance and internal fatigue damage-resistance, and rail
CN100482812C (en) * 2006-09-12 2009-04-29 攀枝花钢铁(集团)公司 Rail heat processing method and rail heat processing unit
CN102080185A (en) * 2010-12-21 2011-06-01 南阳汉冶特钢有限公司 High-tensile quenched and tempered steel plate for large-thickness structures and production method thereof
CN102230050A (en) * 2011-06-02 2011-11-02 内蒙古包钢钢联股份有限公司 Method for controlling nitrogen content in 350 km/h and above heavy-rail steel
CN103160736B (en) * 2011-12-14 2015-09-02 鞍钢股份有限公司 A kind of high strength bainite steel rail and thermal treatment process thereof
WO2014157252A1 (en) * 2013-03-27 2014-10-02 Ｊｆｅスチール株式会社 Pearlite rail and method for manufacturing pearlite rail
CN104480390B (en) * 2015-01-07 2016-10-19 攀钢集团攀枝花钢铁研究院有限公司 The rail of high impact toughness and production method thereof
CN105063267B (en) * 2015-08-24 2017-11-24 武汉钢铁有限公司 The production method of high-strength alloy R320Cr rail

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AU2019232893B2 (en) 2021-07-22

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