AU2019232893B2 - Manufacturing method of rails for heavy-haul railways - Google Patents
Manufacturing method of rails for heavy-haul railways Download PDFInfo
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- AU2019232893B2 AU2019232893B2 AU2019232893A AU2019232893A AU2019232893B2 AU 2019232893 B2 AU2019232893 B2 AU 2019232893B2 AU 2019232893 A AU2019232893 A AU 2019232893A AU 2019232893 A AU2019232893 A AU 2019232893A AU 2019232893 B2 AU2019232893 B2 AU 2019232893B2
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- Australia
- Prior art keywords
- rail
- heat treatment
- rails
- treatment unit
- early stage
- Prior art date
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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
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
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
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
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,
improve the rail strength and continuously improve the toughness of rails.
There is provided herein a manufacturing method of rails for 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, 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
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.
Optionally, an ingot blank is slowly cooled in a burial pit the early stage of rail casting.
According to an aspect of the invention, there is provided a manufacturing method of rails for
heavy-haul railways, the method comprising the steps of:
1) allowing a rail to be subjected to a primary heat treatment in a heat treatment unit by
using waste heat of rolling, wherein the rail is heated to650 C - 900 C using the waste heat of
rolling, and wherein the primary heat treatment step also includes the steps of: accelerated
cooling of the rail in the heat treatment unit at 1 - 5 °C/s to reduce the temperature of the rail to
400 C - 550 C, and withdrawing the rail from the heat treatment unit to end the primary heat
treatment,
2) re- heating the rail to 650 C - 700 C using a heating device, wherein the heating device
is an induction heating device,
3) and then applying the rail to the heat treatment unit again for secondary heat
treatment, wherein accelerated cooling occurs at 2 - 50 °C/s; and when the cooled rail drops
to 400 C - 550 C, the rail is withdrawn from the heat treatment unit to end the secondary
heat treatment,
wherein the rail is cast in the early stage using molten iron with low S content, and the
refining slag possesses high basicity, and the carburant used in the early stage of rail casting
includes anthracite and a low Nitrogen (N) alloy, and a foaming agent is used in the ladle
furnace (LF) heating process to prevent the rail from being exposed to air and inhaling
excessive Nitrogen (N) in the early stage of rail casting, and an ingot blank from which the
rail is produced is cooled in a burial pit in the early stage of rail casting.
3a
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
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/2 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
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
accuracy.
In order to ensure the accuracy of the primary heat treatment, the rail is 650 °C - 900 °C when 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 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 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 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
Chemical compositions/% Item No. C Si+Mn+P+S+Cr+V
Example 1# 0.85 1.80
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
Cooling rate . Cooling rate Primary heat Induction Item No. Inlet of primary treatment heating of secondary temperature heat heat temperature temperature treatment 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 765 2 500 - example
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
1# 10 8
2# 10 9
Example 3# 11 9 4# 12 7
5# 13 6
Comparative 6# 7 10 example 7# 7 14
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
Fracture toughness Item No. Tensile strength Elongation at -20 °C
1# 1395 15 41
2# 1391 17 39
Example 3# 1380 15 38
4# 1390 16 40
5# 1410 17 42
Comparative 6# 1330 11 32 example 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
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
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
the stated features, integers, steps or components, but not precluding the presence of one or more
other features, integers, steps or components.
Claims (3)
1. A manufacturing method of rails for heavy-haul railways, the method comprising the steps
of:
1) allowing a rail to be subjected to a primary heat treatment in a heat treatment unit by
using waste heat of rolling, wherein the rail is heated to650 °C - 900 °C using the waste heat of
rolling, and wherein the primary heat treatment step also includes the steps of: accelerated
cooling of the rail in the heat treatment unit at 1 - 5 °C/s to reduce the temperature of the rail to
400 °C - 550 °C, and withdrawing the rail from the heat treatment unit to end the primary heat
treatment,
2) re-heating the rail to 650 °C - 700 °C using a heating device, wherein the heating device is
an induction heating device,
3) and then applying the rail to the heat treatment unit again for secondary heat treatment,
wherein accelerated cooling occurs at 2 - 50 °C/s; and when the cooled rail drops to 400 °C - 550
°C, the rail is withdrawn from the heat treatment unit to end the secondary heat treatment,
wherein the rail is cast in the early stage using molten iron with low S content, and the
refining slag possesses high basicity, and the carburant used in the early stage of rail casting
includes anthracite and a low Nitrogen (N) alloy, and a foaming agent is used in the ladle furnace
(LF) heating process to prevent the rail from being exposed to air and inhaling excessive
Nitrogen (N) in the early stage of rail casting, and an ingot blank from which the rail is produced
is cooled in a burial pit in the early stage of rail casting.
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 AU2019232893A1 (en) | 2020-05-14 |
| AU2019232893B2 true AU2019232893B2 (en) | 2021-07-22 |
Family
ID=64998159
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2019232893A Active AU2019232893B2 (en) | 2018-10-30 | 2019-09-20 | Manufacturing method of rails for heavy-haul railways |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN109207691A (en) |
| AU (1) | AU2019232893B2 (en) |
Citations (8)
| 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 |
| US4714500A (en) * | 1984-12-21 | 1987-12-22 | Krupp Stahl Ag | Method for thermal treatment of pearlitic rail steels |
| JPH04202626A (en) * | 1990-11-30 | 1992-07-23 | Nippon Steel Corp | Production of steel rail excellent in drop weight resisting characteristic |
| US20080060726A1 (en) * | 2006-09-12 | 2008-03-13 | Panzhihua Iron And Steel (Group) Corporation | Method and apparatus for heat treatment of steel rail |
| 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 |
| CN105063267A (en) * | 2015-08-24 | 2015-11-18 | 武汉钢铁(集团)公司 | Production method for high-strength alloy R320Cr steel rails |
| US20160083820A1 (en) * | 2013-03-27 | 2016-03-24 | Jfe Steel Corporation | Pearlitic rail and method for manufacturing pearlitic rail |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| 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 |
| 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 |
-
2018
- 2018-10-30 CN CN201811280755.6A patent/CN109207691A/en active Pending
-
2019
- 2019-09-20 AU AU2019232893A patent/AU2019232893B2/en active Active
Patent Citations (8)
| 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 |
| US4714500A (en) * | 1984-12-21 | 1987-12-22 | Krupp Stahl Ag | Method for thermal treatment of pearlitic rail steels |
| JPH04202626A (en) * | 1990-11-30 | 1992-07-23 | Nippon Steel Corp | Production of steel rail excellent in drop weight resisting characteristic |
| US20080060726A1 (en) * | 2006-09-12 | 2008-03-13 | Panzhihua Iron And Steel (Group) Corporation | Method and apparatus for heat treatment of steel rail |
| 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 |
| US20160083820A1 (en) * | 2013-03-27 | 2016-03-24 | Jfe Steel Corporation | Pearlitic rail and method for manufacturing pearlitic rail |
| CN105063267A (en) * | 2015-08-24 | 2015-11-18 | 武汉钢铁(集团)公司 | Production method for high-strength alloy R320Cr steel rails |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109207691A (en) | 2019-01-15 |
| AU2019232893A1 (en) | 2020-05-14 |
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