FIELD OF INVENTION:
The present invention is directed to a high strength alloy steel Rail sections providing an
UTS value > 1000 MPa and exhibiting fairly high resistance to corrosion and abrasive wear.
The invention is basically directed to development of selective composition for casting into
ingots of 25 kg weight and hot rolling in experimental rolling mill giving different passes
successively following selective process parameters and finishing temperatures, to obtain
said desired high strength and corrosion/wear resistive properties in the resulting Rail Steel
sections having favorable microstructure providing selective fine inter lameller spacing of
pearlitic microstructure ensuring desired strength and corrosion resistive properties. The
same grade is capable for production on commercial scale through the BOF-LF-RH-CC and
ingot route. The process and the composition is providing very reasonable/ economic cost of
production for such grade of rail steel and thus having worldwide application in railway
industries.
BACKGROUND ART:
It is well known in the use of various rail sections made of different grades of steel that are
used for railway transportation, particularly in the transportation of freight traffic of high
intensity at high axle load, that the life of rail tracks are largely influenced by traffic
intensity, wheel/axle load, and curvature on track etc. The speed of the rail traffic is also a
significant factor to influence the wear and tear of the rail tracks. The conventional 880 MPa
Pearlitic Rails having strength of 950 MPa are subjected to abrasive wear and corrosion
under the operating conditions as stated above causing the material of the top layer of rails
to flow plastically resulting in deformity of the railhead, head cracks on gauge corner and
corrugations. Whereas High train speed and wheel load which causes head shelling or dark
spots. This defects originate on the running surface as a small crack owing to rolling contact
fatigue, in which slip contact between rail surface and wheels plays an important role, and
then propagates vertically transverse to the traffic direction under the running contact
surface and at last results in horizontal split or transverse brittle failure. Fine pearlitic
structure is desirable for both wear resistance and fatigue crack prevention. Strength,
toughness and wear resistance of rail steels can be obtained by means of alloying, heat
treatment or both. Technical literature in the relevant field indicates that the enhancement
of strength and corrosion resistivity can be achieved by addition of alloying elements in
2

selective proportion of one or more of Cr, Mo, V, Nb and Cu depending on the specific
requirement. Chromium changes the equilibrium transformation point of the pearlitic steel
and eventually contribute to higher strength by making the pearlite structure fine. At the
same time it improves the wear resistance by refining the cementite phase resulting uniform
and finer pearlitic microstructure.
It is well known in the art of manufacturing rail steel sections, that the basic chemistry of
these steels contain C, Mn & Si. Sometimes the higher Silicon content helps in achieving
higher strength without any adverse effect on ductility when added up to o.60% in rail
steels. Carbon is a strong strengthening element. Silicon is a solid solution strengthener and
decreases eutectoid content of carbon in steels. Steels used by Federal Railroad
Transportation of USA conducted in-track studies of rail behaviour for a number of rail steel
including head-hardened and fully heat treated rails at Facility for Accelerated Service
Testing (FAST) and concluded that Cr-Mo pearlitic rail steel has significantly higher
resistance to wear, metal flow, fracture and shelling among the compositions studied . Also
1 Cr rail has been wearing least in 5% curvature and 2% gradient. Schetky, Lemay and
Dilewijns reported a medium carbon Cr-V-Ni-Cu rail steel composition which combines with
the good performance of Cr-V rail steels with the additional strengthening and corrosion
resistance afforded by addition of copper. The superior properties are related to a carbide
precipitation hardening in a very fine pearlite matrix, which exhibits very little free ferrite.
In recent times, due to extremities of operating conditions and ever increasing demand for
railway transportation as an economic mode particularly for bulk freight transport, there has
been always a need to increase the service life of rails. This necessitates the development of
a new and highly durable rail as per the need and demand of Indian Railways, for
renovation/expansion of railway tracks to be laid in different geographical
locations/situations, ambient/climatic conditions and the required frequencies, all over the
country. Due to such varied and complex nature of use, railways face different problems at
different locations. Moreover, near costal areas and remote areas, adjacent to nomadic
human habitats, rail tracks are often subjected to severe corrosion attacks due to
animal/human excreta deposited on tracks. However, in order to achieve both corrosion
resistance as well as high strength requirements and to bring down the cost of production,
there had been a persistent need to develop a new grade of rail steel to over come the
limitations as described in the related prior art - knowledge and technology.
3

OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to obtaining a variety of steel
for use in Railway tracks such as to provide the properties of high strength (UTS>1000 MPa)
and improved corrosion resistance in such steel in order to achieve longer life span under all
variable operating conditions in railway transportation.
A further object of the present invention is to obtain said rail steel having high strength and
improved corrosion resistance in experimental laboratory heats using induction furnace with
225 kVA power supply, having 100kg capacity to obtain the rail steel of the present
invention in cast ingots of 25 kg each in mould, followed by hot rolling with selective
parameters to obtain plate section exhibiting the enhanced strength and corrosion
resistance properties.
A further object of the present invention is to use the same process for production in
commercial scale through BOF-LF-RH-CC route such as to obtain blooms exhibiting same
properties following selective process steps like maintaining the specified superheat
temperature of melt, casting speed, soaking temperature, hot rolled to R-60 rail profile and
maintaining a preferred finishing temperature and cutting the hot rails to selective lengths
and normal air cooled and straightened.
A still further object of the manufacture of the rail steel having high strength and high
corrosion resistance, obtained by following selective process steps producing steel of
selective composition comprising preferred wt. percent in the range of C: 0.06-0.8, Si:0.3-
0.8, P:0.025 max, S:0.025 max, Mn:0.4-1.3, Cr:0.3-1.4 and Cu:0.02-0.4;
A still further object of the present invention is to manufacture the rail steel having high
strength and high corrosion resistance, by following selective process steps and also the
selective rolling parameters such as to obtain the rail steel conforming to IRS-T-12-96
exhibiting the properties comprising UTS exceeding 1000 MPa and CRI of 2-2.5 in case of
salt spray corrosion test and CRI of 1.5-2 in case of electro-chemical corrosion test,
following the standard testing procedure as compared to the conventional corrosion value of
CRI:1 achievable in 880 MPa pearlitic rails having a strength of about 950 MPa.
4

A still further object of the present invention is to manufacture the rail steel having high
strength and high corrosion resistance directed to obtaining said grade of steel providing
desired enhanced properties by ensuring by means of the selective process steps resulting
in preferred microstructure by selectively adding Cr in the range of 0.7 to 1.2, leading to
pearlitic microstructure with fine inter lamellar spacing providing the enhanced strength and
corrosion resistance for said rail steel, without sacrificing ductility by maintaining Si at
relatively higher wt. percent in the range of 0.3 to 0.8.
A still further object of the present invention is to manufacture the rail steel having high
strength and high corrosion resistance, said R-60 rail sections obtained after hot rolling and
hot saw cutting to lengths of 13 meters, 26 meters or 65 meters are hot stamped, air
cooled, straightened and then tested with eddy-current testing and Ultrasonic testing and
end cutting such as to obtain free of any defect and ready to be laid condition.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is therefore directed to Corrosion resistant
and high strength (UTS > 1000 MPa) rail comprising :
C in an amount of 0.06 to 0.8 wt.%;
Si in an amount of 0.30 to 0.80 wt.%;
S in an amount of upto 0.025 wt % (max.);
P in an amount of upto 0.025 wt % (max.);
Mn. in an amount of 0.40 to 1.30 wt %;
Cr. in an amount of 0.30 to 1.4 wt. % ;and
Cu. in an amount of 0.02 to 0.40 wt%.
A further aspect of the present invention directed to said corrosion resistant and high
strength (UTS > 1000MPa) rail comprising pearlitic structure and fine inter lamellar
spacing preferably in the range of 0.17 to 0.35µm.
A still further aspect of the present invention directed to said corrosion resistant and
high strength (UTS > 1000MPa) rail, comprising mechanical properties such as :
5

YS (MPa): 470-650 ;
UTS(MPa):900-1100;
YS/UTS: 0.52-0.62;
Elongation (%): 10-16 ;
R.A.(%): 15-25;
Hardness (BHN): 280-330.
A still further aspect of the present invention directed to said corrosion resistant and
high strength (UTS > 1000MPa) rail comprising impact & fracture toughness such as:
Impact Charpy (Joule): 5-8 at RT(Room Temp.); and 5-7 at 0°C; and
Fracture Toughness (MPa Öm) 35-45 at RT.
A still further aspect of the present invention directed to a method of manufacture of a
corrosion resistant and high strength (UTS > 1000MPa) rail comprising:
providing a selective charge and synthetic slag ;
casting ingots and cooling followed by hot rolling in rolling mill; and
obtaining the plate such as to have a product composition comprising
C in an amount of 0.06 to 0.80 wt.%;Si in an amount of 0.30 to 0.80 wt.%;
S in an amount of upto 0.025 wt % (max.);P in an amount of upto 0.025 wt %
(max.);Mn. in an amount of 0.40 to 1.30 wt %;Cr. in an amount of 0.30 to 1.40 wt.
% ;and Cu. in an amount of 0.02 to 0.40wt%.
According to another preferred aspect of said method of manufacture of a corrosion
resistant and high strength (UTS > 1000MPa) rail wherein the said synthetic slag comprise
60% lime, 25% Al shots and 15% CaF2 .
6

An yet further aspect of the method of manufacture of said corrosion resistant and high
strength (UTS > 1000MPa) rail comprising of:
Drafting schedule comprising 5 to 9 passes;
Soaking temperature in the range of 1150°C to 1280°C;
and soaking time of 2 to 3 hrs;
Finishing temperature in the range of 850°C to 950°C;
Air cooling of plates produced.
The present invention and its objectives and advantages are described in further details with
reference to the accompanying illustrative examples and figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: SEM microphotograph etched sample revealing the inter lamellar spacing of the
conventional as rolled 880 Grade rail with sp=0.38µm of pearlitic structure.
Figure 2: SEM microphotograph showing the inter lamellar spacing of the Cr Rail of the
present invention with sp=0.20 µm of the pearlitic microstructure.
Figure 3: Shows the flow chart for the production of high strength rail with selective
chemistry improved corrosion resistance achieved through selective process steps providing
selective fine pearlitic micro-structure, ensuring such enhanced properties.
DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
The present invention is directed to obtaining a variety of steel, as described earlier, for use
in Railway tracks such as to provide the properties of high strength (UTS>1000 MPa) as well
as improved corrosion resistance in such steel in order to achieve longer life span under all
variable operating conditions in railway transportation avoiding deformity, wear or crack of
the railhead, at less cost of production.
7

In order to produce such grade of steel, laboratory heats were made to study the influence
of C, Mn, Si, Cr and Cu on the strength and corrosion resistance of the steel. Different
microstructures and inter lamellar spacing were developed and their mechanical behaviour
were studied with respect to enhancement of the desired properties. The manner of
implementation of the manufacturing of the rail steel according to the present invention is
amply illustrated in the following accompanying Examples.
Example-1 :
Experimental laboratory heats were made in 100 kg capacity medium frequency air
induction furnaces with frequency 3000 cycles. Power supply to the induction furnace was of
the rating of 225 KVA. The starting material for the steel making process was taken as low
Carbon Steel Scrap and rail steel scrap as initial charge and a synthetic slag comprising
60% lime, 25% Al shots and 15% CaF2 was selectively used to carry out appropriate
chemical reactions to obtain the desired Chemical composition of the alloy steel for the rail
section according to the invention, to exhibit required properties of strength and corrosion
resistance. It was observed that the pearlitic microstructures with fine inter lamellar spacing
resulted in high strength and improved corrosion resistance, exceeding fairly the
corresponding property values for the conventional 880 MPa pearlitic rail steels. The
chemistry of the product obtained was as follows:
Chemical Composition (Wt. %):
C: 0.06-0.80, Si:0.3-0.8, P:0.025 max, S:0.025 max, Mn:0.40-1.30, Cr:0.30-1.40 and
Cu:0.02-0.40;
The rail steel thus produced were cast into 25 kg moulds and cooled into the mould itself for
24 hours. Hot rolling of ingot was carried out in experimental rolling mill. The details of the
rolling parameters followed for obtaining the R-60 rail section conforming to IRS: T-12-96
standard were as follows:
Drafting schedule :Total no. of passes used was 5 to 9;
Soaking temperature :1150°C -1280°C;
Soaking time :2to3hrs.;
Finishing temperature:850°C -950°C;
Initial size of Ingot :100mmxl00mm;
8

Final size of plate :25mm thick;
Cooling instruction :Air cooling of plates;
Final size/thickness of the plates obtained after rolling was 25mm thick.
Test procedure for the rail steel produced experimentally:
The DC supply based electrochemical corrosion measurements were conducted using round,
metallographically-polished disc specimens of 15mm diameter and 3mm thickness; A
Potentiostat/Galvanostat Model 273A, make- EG & G Prince ton Applied Research Centre,
was used for the purpose; Anodic Polarisation Scans were recorded ±250mV of equilibrium
corrosion potential(Ecorr) at a scan rate of lmV/sec using a Saturated Calomel reference
Electrode(SCE) and graphite counter electrodes in 3.5% Sodium Chloride(NaCI). The testing
was conducted at room temperature in a standard electrochemical corrosion-testing cell.
The equilibrium corrosion current density(Icorr) and the corrosion rate in mils per year (mpy)
were determined by TAFEL extrapolation technique.
Example 2:
The same process steps were also applied experimentally for commercial scale in BOF
furnace of llOton capacity in each heat, following BOF-LF-RH-CC route. Blooms were cast
maintaining the superheat of 30°C and with the casting speed of about 0.85 meter/minute.
The blooms were soaked at 1280°C and hot rolled to obtain rail profile section of R-60, the
finishing temperature was maintained at 870±15°C. Hot rails after rolling were cut to 13
meter, 26 meter and 65 meters lengths and natural air cooled. After cooling at room
temperature the rails were straightened in horizontal and vertical straightening machine.
The straightened rails were passed through Eddy-current and Ultrasonic testing machines.
Finally the straightened and tested rails were inspected for any visual defects, dimensions
and straightness before dispatch to stock/user. The properties obtained for the rail steel
following the process of the present invention ensuring desired pearlitic microstructure with
fine inter lamellar spacing, which conforms to IRS:T-12-96, shows the comparative
enhancement of mechanical properties as represented in the accompanying Table 1 and
Table 2. Accompanying Table 3 shows the improved corrosion resistance properties of the
product obtained according to the invention, compared to the conventional rail steel already
in use.
9

Attention is now invited to accompanying figure 1 and figure 2 wherein the desired
pearlitic microstructure with favoured fine inter lamellar spacing (sp) according to the
invention are illustrated in Optical and SEM micro-photographs, in comparison to those for
the conventional 880MPa rail steel. It has been seen that the as rolled 880 Grade rail having
a value of sp of about 0.38µm whereas the Cr rail steel of the present invention exhibiting a
value of sp of about 0.20µm on the average. The accompanying Figure 3 shows the flow
chart of the process steps followed for obtaining said rails with high strength and improved
corrosion resistance.

It is thus possible by way of the present invention to obtain a grade of rail steel having
selective composition and following selective process parameters and steps such as to
obtain said rail sections of steel that exhibit higher strength and improved corrosion
resistance values capable for use for railway track subjected to adversities of extreme
climatic or operational variabilities including heavy axle load, high traffic intensity, higher
curvature of track etc and still providing longer life between replacements due to enhanced
properties as compared to the conventional grades of steel for similar use for rail tracks, in
a economic way.
10

We Claim:
1. Corrosion resistant and high strength (UTS > 1000MPa) rail comprising :
C in an amount of 0.06 to 0.80 wt.%;
Si in an amount of 0.30 to 0.80 wt.%;
S in an amount of upto 0.025 wt % (max.);
P in an amount of upto 0.025 wt % (max.);
Mn. in an amount of 0.40 to 1.30 wt %;
Cr. in an amount of 0.30 to 1.40 wt. % ;and
Cu. in an amount of 0.02 to 0.40wt%.
2. Corrosion resistant and high strength (UTS > 1000MPa) rail as claimed in claim 1
comprising pearlitic structure and fine inter lamellar spacing in the range of 0.17 to
0.25 µm.
3. Corrosion resistant and high strength (UTS > 1000MPa) rail as claimed in anyone of
claims 1 or 2 comprising mechanical properties comprising :
YS (MPa): 470-650;
UTS(MPa):900-1100;
YS/UTS: 0.52-0.62;
Elongation (%): 10-16;
R.A.(%): 15-25;
Hardness (BHN): 280-330.
4. Corrosion resistant andhigh strength (UTS > 1000MPa) rail as claimed in anyone of
claims 1 to 3 comprising impact & fracture toughness comprising:
Impact Charpy (Joule): 5-8 at RT(Room Temp.); and 5-7 at 0°C; and
Fracture Toughness (Mpa Öm) :35-45 at RT.
5. A method of manufacture of a corrosion resistant and high strength (UTS >
1000MPa) rail as claimed in anyone of claims 1 to 3 comprising:
providing a selective charge and synthetic slag ;
11

casting ingots and cooling followed by hot rolling in rolling mill; and
obtaining the plate such as to have a product composition comprising
C in an amount of 0.06 to 0.80 wt.%;Si in an amount of 0.30 to 0.80 wt.%;
S in an amount of upto 0.025 wt % (max.);P in an amount of upto 0.025 wt %
(max.);Mn. in an amount of 0.40 to 1.30 wt %;Cr. in an amount of 0.30 to
1.40wt.% ;and Cu. in an amount of 0.02 to 0.40wt%.
6. A method of manufacture of a corrosion resistant and high strength (UTS >
1000MPa) rail as claimed in claim 5 wherein the said synthetic slag comprise 60%
lime,25% Al shots and 15% CaF2 .
7. A method of manufacture of a corrosion resistant and high strength (UTS >
1000MPa) rail as claimed in anyone of claims 5 or 6 comprising of:
Drafting schedule comprising 5 to 9 passes;
Soaking temperature in the range of 1150°C to 1280°C and
soaking time of 2 to 3 hrs.;
Finishing temperature in the range of 850°C to 950°C;
Air cooling of plates produced.
8. Corrosion resistant and high strength (UTS > 1000MPa) rail and its method of
manufacture substantially as hereindescribed and illustrated with reference to the
accompanying figures.
Dated this 16th day of July,2007.

The present invention is directed to a high strength alloy steel Rail sections providing a UTS 1000 MPa and high corrosion resistance. The invention involves development of selective
composition for casting into 25 kg ingots and hot rolling in selective successive roll passes
following selective process parameters and finishing temperatures, to obtain said desired
high strength and corrosion/wear resistive properties in the resulting Rail Steel sections
having favorable microstructure providing selective fine inter lamellar spacing of pearlitic
microstructure ensuring desired strength and corrosion resistive properties. The same grade
is capable for production on commercial scale as well through the BOF-LF-RH-CC and ingot
route. The process and the composition is providing very reasonable/ economic cost of
production for such grade of rail steel and thus having prospects of worldwide application in
railways industries and the like.