GB2118579A - Heat treatment of rails - Google Patents
Heat treatment of rails Download PDFInfo
- Publication number
- GB2118579A GB2118579A GB08202558A GB8202558A GB2118579A GB 2118579 A GB2118579 A GB 2118579A GB 08202558 A GB08202558 A GB 08202558A GB 8202558 A GB8202558 A GB 8202558A GB 2118579 A GB2118579 A GB 2118579A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rail
- head
- steel rail
- transformation
- pearlite
- 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.)
- Withdrawn
Links
- 238000010438 heat treatment Methods 0.000 title description 4
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims abstract description 15
- 230000009466 transformation Effects 0.000 claims abstract description 15
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 14
- 239000010959 steel Substances 0.000 claims abstract description 14
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 9
- 238000005098 hot rolling Methods 0.000 claims abstract description 3
- 239000011651 chromium Substances 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 11
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 230000007704 transition Effects 0.000 claims description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 2
- 239000003595 mist Substances 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 239000011733 molybdenum Substances 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 230000008569 process Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
This invention provides a method of heat treating a length of steel rail having a head, a web and a flange portion, in which, following hot rolling, the rail is discharged to a cooling bank for the web and flange portions to cool naturally to transform to pearlite, the rail then being force cooled upon the incidence of transformation of the head to pearlite to restrict the level of the consequential temperature rise during this transformation whereby to promote a very fine pearlitic structure in the surface of the head.
Description
SPECIFICATION
Steel rails
This invention relates to steel rails, and more particularly relates to a method of heat treating rails so as to provide better properties than hitherto. Typical improved properties are in respect of resistance to abrasive wear and plastic deformation in the rail head, a greater level of hardness in the surface of the head coupled with a more uniform hardness throughout the remainder of the rail section in the sense of a smoother transition in these levels between the surface and the interior of the head and the avoidance of very high hardness levels in the web and flange tips.
From one aspect the present invention provides a method of heat treating a length of steel rail having a head, a web and a flange portion, in which following hot rolling the rail is discharged to a cooling bank for the web and flange portions to cool naturally to transform to pearlite, the rail then being force cooled upon the incidence of transformation of the head to pearlite to restrict the level of the consequential temperature rise during this transformation whereby to promote a very fine pearlitic structure in the surface of the head.
Typically the pearlitic lamellae in the head surface may be of the order of 800-1 1 00A. The rail may be of a standard carbon composition (0.7C-0.8C) giving rise to typical head surface hardness values of the order of 280 BHN or it may additionally incorporate about 1% chromium giving rise to surface hardness values of the order of 360 BHN.
The force cooling medium is preferably air, but a water mist could alternatively be employed.
In order that the invention may be fully understood one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings in which:
Figure 1 is a section through a 1% chromium rail treated in accordance with this invention showing typical Brinell hardness levels obtained;
Figure 2 is a section through AREA (American Railway Engineering Association) carbon rail treated in accordance with this invention showing typical Brinell hardness levels obtained; and
Figure 3 is a graph of 0.2% Proof Stress/Ultimate Tensile Strength showing the enhanced values obtained in accordance with this invention and the results from a comparable "standard" rail for both 1% chromium rail and AREA carbon rail.
In accordance with this invention the properties of rail steel are enhanced by interfering with the natural cooling and transformation of the rail in such a way that much finer than usual peralite is produced.
The process itself comprises the following. Initially, a bloom which is substantially free from segregation is 'soaked' in a furnace to give a constant temperature along its whole length, and it is then rolled in a regular manner to give a preferred austenite grain size of ASTM 4. The long length is then cut into the shorter lengths required and these are not allowed to contact one another again until well through the treatment process in order that natural air cooling will remove heat in a similar pattern from each rail. The rails travel down the racks separately and are likewise spaced on to the cooling surfaces separately, lying on their sides.
Thus far, the process is in accord with standard practice. Now when the rails have cooled to a critical temperature, transformation would begin and they would heat up considerably due to the exothermic reaction, only when transformation is almost complete do the rails resume cooling.
Because of the different section thickness different parts of the rail reach these transformation temperatures at different points in time. The result is that the rail contorts itself during transformation and eventually finishes up with a different structure and properties in different parts of the rail section.
In accordance with this invention however, we interfere with the natural cooling at that part of the process where the head is giving out heat of transformation. More particularly, when the head of the rail to be treated is about to begin transformation this event is anticipated and the natural rate of heat extraction is increased by fan coo!ing. This accelerated cooling step is typically equivalent to doubling the cooling rate from say 0.8"C per second to 1 .6 C per second, however, as the rail is actually increasing in temperature at the time the effect is shown as a decrease in heating rate.This increased rate of heat removal allows faster transformation at a lower average temperature than normal, thus reducing the resultant interlamellar spacing of the ferrite and cementite laths in the pearlite from around 1 500 Angstrom to below 1000
Angstrom, even as low as 800.
After only 4 minutes fan cooling the rail temperature is approximately 600"C and the critical stage of transformation is completed. The treated rails are then rafted together to retard cooling and reduce stresses in the rail. Indeed, the rails can stay rafted together until cool or can be placed in cooling pits for hydrogen removal as required. Finally, the rails are then straightened and finished in the regular manner.
The improvement obtained depends upon the hardenability of the steel being known and the appropriate rate of heat removal being applied. In the instance quoted the rate of heat removal happens to be fixed at twice the natural cooling rate and the hardenability of the steel must be matched to this fact. Hence the rails must be within certain chemical limits in order that the part of hardenability governed by chemistry is known and controlled. Grain size and time at temperature also affect hardenability and the heating and rolling process must be made consistent enough for this to be held constant.
Table 1 below shows two sets of results obtained, standard AREA and 1% chromium being compared with the enhanced results obtained with these steels when subjected to the process according to this invention.
TABLE 1.
Chemical Composition Tensile Elong- Hardness Quality ation Brinell C Si Mn P S Cr N/mm T/ins Kg/mm % AREA Spec. .70/.82 .10/.35 .75/1.05 .035x .040x 860 57 87 - 248 121 .
lbs/yd Typi & over cal. .73/.76 .20/.30 .80/.90 .03 x .035x 928 61 90 11 245/260 1% Spec. .70/.82 .50x. .80/1.05 .03 x .04 x .90/1.15 1040 70 100 8 Chrom- Typjum jcal .73/.80 .30/.35 .85/1.05 .025x .02/.025 .90/1.15 1098 73 110 10 320/340 U.T.S. 0.2% Proof Elong- Hardness Quality Chemical Composition N/mm lbs/ins N/mm lbs/ins ation % Brinell Enhanced As AREA Min 920 134,000 480 69,500 8 270 AREA Typical 945 137,000 560 81,500 12 280 Enhanced As 1% Cr Min 1120 163,500 690 100,000 8 340 Chromium Typical 1165 170,000 730 107,000 10 360 Referring to Figs. 1 and 2 there are shown profiles fot two particular specimens of enhanced chromium and enhanced AREA rails, respectively included in the table above from which specific hardness levels throughout the rail section can be seen.Typically, the chromium steel provides hardness levels of about 360 Brinell in the rail head wear zone and 340 Brinell in the rail head centre with corresponding values of 280 BHN and 275 BHN with carbon steel. There is a gradual smooth transition from the wear zone to the centre and there is no soft heat affected zone below the wear zone as experienced with some head hardened rails. Further, there are no unduly high hardness levels in the web and flanges; indeed the only part of the rail to have its structure regulated is the head where a much smaller interlamellar spacing of the pearlite structure is achieved by the enhanced cooling. Whilst other structures such as bainite, tempered martensite and martensite may be very wear resistant, all have a lower limiting level than pearlite in respect of plastic flow.
As regards strength levels, Fig. 3 graphically depicts test results of both standard and enhanced 1% chromium and AREA carbon steels showing the much improved breaking (or ultimate tensile) strength values v 0.2% Proof Stress for the enhanced rails treated in accordance with this invention. There is a substantial increase in strength without any loss in ductility.
As regards welding properties the enhanced rails are more readily weldable than their 'standard' counterparts utilising flash butt or Thermit welding; although post heat treatment is still required for the alloy grade the heat affected zone is greatly reduced.
Although the invention has been described with reference to the particular embodiments illustrated, it is to be understood that various modifications may readily be made without departing from the scope of the invention. For example, more selected alloying may be undertaken to further improve the properties realised such as by the use of vanadium, chromium and molybdenum. The chromium and manganese content may be reducedompatible with achieving the enchanced hardness values-to improve weldability towards the optimum where the rails can be joined by normal flash butt welding procedures and where the hardness of the weld will match that of the rail head.
Claims (9)
1. A method of heat treating a length of steel rail having a head, a web and a flange portion, in which following hot rolling the rail is discharged to a cooling bank for the web and flange portions to cool naturally to transform to pearlite, the rail then being force cooled upon the incidence of transformation of the head to pearlite to restrict the level of the consequential temperature rise during this transformation whereby to promote a very fine pearlitic structure in the surface of the head.
2. A method according to Claim 1, in which the rail is force cooled by air or by a water mist.
3. A method according to Claim 1 or Claim 2 in which the steel rail has a carbon value of between about 0.7% and 0.8%.
4. A method according to Claim 3, in which the steel rail incorporates chromium at a value of about 1%
5. A method according to claim 3 or Claim 4, in which the steel rail incorporates molybdenum and/or vanadium.
6. A method according to any one of claims 1 to 5 in which the hardness of the head surface is not less than about 280 BHN.
7. A method according to any one of Claims 1 to 6, in which the head exhibits a substantially uniform hardness profile throughout its cross-section, save for a gradual transition from the surface wear zone to a lower hardness value in the centre.
8. A method of heat treating a length of steel rail substantially as hereindescribed with reference to the accompanying drawings.
9. A steel rail treated in accordance with the method according to any one of Claims 1 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08202558A GB2118579A (en) | 1982-01-29 | 1982-01-29 | Heat treatment of rails |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08202558A GB2118579A (en) | 1982-01-29 | 1982-01-29 | Heat treatment of rails |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2118579A true GB2118579A (en) | 1983-11-02 |
Family
ID=10527965
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08202558A Withdrawn GB2118579A (en) | 1982-01-29 | 1982-01-29 | Heat treatment of rails |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2118579A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0358362A1 (en) * | 1988-08-19 | 1990-03-14 | The Algoma Steel Corporation, Limited | Method for the manufacture of alloy railway rails |
| EP0469560A1 (en) * | 1990-07-30 | 1992-02-05 | Burlington Northern Railroad Company | High-strength, damage-resistant rail |
| US5209792A (en) * | 1990-07-30 | 1993-05-11 | Nkk Corporation | High-strength, damage-resistant rail |
| US5658400A (en) * | 1993-12-20 | 1997-08-19 | Nippon Steel Corporation | Rails of pearlitic steel with high wear resistance and toughness and their manufacturing methods |
| US20110297752A1 (en) * | 2010-06-04 | 2011-12-08 | Csx Transportation | Process and apparatus for rail restoration and rail manufacture using welding |
| CN110760761A (en) * | 2019-07-31 | 2020-02-07 | 攀钢集团攀枝花钢铁研究院有限公司 | A Method for Controlling Martensite Structure of R260 Rail Flash Welded Joints |
| CN110777245A (en) * | 2019-11-05 | 2020-02-11 | 中国铁建重工集团股份有限公司道岔分公司 | Rod heating method, heating device and computer readable storage medium |
| CN112276030A (en) * | 2020-10-13 | 2021-01-29 | 攀钢集团攀枝花钢铁研究院有限公司 | A kind of high-strength anti-delayed fracture hot-rolled steel rail and preparation method thereof |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB217916A (en) * | 1923-02-13 | 1925-03-06 | Cie Des Forges De Chatillon Co | Process for the thermic treatment of steel and alloys susceptible of tempering |
| GB228490A (en) * | 1924-02-01 | 1925-08-12 | Compagnie Des Forges De Chatillon Commentry Et Neuves-Maisons | |
| GB512879A (en) * | 1937-11-29 | 1939-09-28 | Percy Rayner Smith | Improvements in the manufacture of hardened rails |
| GB515251A (en) * | 1938-04-12 | 1939-11-30 | Christer Peter Sandberg | Improved process and apparatus for the heat treatment of steel rails |
| GB978312A (en) * | 1960-04-07 | 1964-12-23 | Margot Von Linsingen | Quenching device for the heat treatment of sectional steel |
| GB1370144A (en) * | 1970-10-02 | 1974-10-09 | Wendel Sidelor | Process for heat treating rails having a high wear resistance and the rails treated by said process |
| GB1457061A (en) * | 1973-05-02 | 1976-12-01 | Bethlehem Steel Corp | Method of heat treating steel rail |
-
1982
- 1982-01-29 GB GB08202558A patent/GB2118579A/en not_active Withdrawn
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB217916A (en) * | 1923-02-13 | 1925-03-06 | Cie Des Forges De Chatillon Co | Process for the thermic treatment of steel and alloys susceptible of tempering |
| GB228490A (en) * | 1924-02-01 | 1925-08-12 | Compagnie Des Forges De Chatillon Commentry Et Neuves-Maisons | |
| GB512879A (en) * | 1937-11-29 | 1939-09-28 | Percy Rayner Smith | Improvements in the manufacture of hardened rails |
| GB515251A (en) * | 1938-04-12 | 1939-11-30 | Christer Peter Sandberg | Improved process and apparatus for the heat treatment of steel rails |
| GB978312A (en) * | 1960-04-07 | 1964-12-23 | Margot Von Linsingen | Quenching device for the heat treatment of sectional steel |
| GB1370144A (en) * | 1970-10-02 | 1974-10-09 | Wendel Sidelor | Process for heat treating rails having a high wear resistance and the rails treated by said process |
| GB1457061A (en) * | 1973-05-02 | 1976-12-01 | Bethlehem Steel Corp | Method of heat treating steel rail |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0358362A1 (en) * | 1988-08-19 | 1990-03-14 | The Algoma Steel Corporation, Limited | Method for the manufacture of alloy railway rails |
| EP0469560A1 (en) * | 1990-07-30 | 1992-02-05 | Burlington Northern Railroad Company | High-strength, damage-resistant rail |
| US5209792A (en) * | 1990-07-30 | 1993-05-11 | Nkk Corporation | High-strength, damage-resistant rail |
| US5658400A (en) * | 1993-12-20 | 1997-08-19 | Nippon Steel Corporation | Rails of pearlitic steel with high wear resistance and toughness and their manufacturing methods |
| US20110297752A1 (en) * | 2010-06-04 | 2011-12-08 | Csx Transportation | Process and apparatus for rail restoration and rail manufacture using welding |
| US8367960B2 (en) * | 2010-06-04 | 2013-02-05 | Csx Transportation | Process for rail restoration and rail manufacture using welding |
| CN110760761A (en) * | 2019-07-31 | 2020-02-07 | 攀钢集团攀枝花钢铁研究院有限公司 | A Method for Controlling Martensite Structure of R260 Rail Flash Welded Joints |
| CN110777245A (en) * | 2019-11-05 | 2020-02-11 | 中国铁建重工集团股份有限公司道岔分公司 | Rod heating method, heating device and computer readable storage medium |
| CN110777245B (en) * | 2019-11-05 | 2021-08-20 | 中国铁建重工集团股份有限公司道岔分公司 | Rod heating method, heating device and computer readable storage medium |
| CN112276030A (en) * | 2020-10-13 | 2021-01-29 | 攀钢集团攀枝花钢铁研究院有限公司 | A kind of high-strength anti-delayed fracture hot-rolled steel rail and preparation method thereof |
| CN112276030B (en) * | 2020-10-13 | 2021-11-19 | 攀钢集团攀枝花钢铁研究院有限公司 | High-strength delayed fracture-resistant hot-rolled steel rail and preparation method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |