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BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates broadly to a process of making a micro-
alloyed locomotive wheel with higher yield strength (YS) to ultimate tensile
strength (UTS) ratio and, more particularly, to an improved process in which
wheels are manufactured to meet the revised Indian Railways specification
number IRS-34-99 with improved YS / UTS ratio by micro alloying the existing
plain C-Mn wheel steel and establishing new set of heat treatment parameters
to achieve designed properties in wheels.
2. DESCRIPTION OF THE PRIOR ART
The increasing demand of introducing higher operating speeds and higher
axle loads in Indian Railways needs to maintain the highest integrity and
reliability of railroad wheels. This requires the use of superior quality steel
made through modem and economic process route. Considering the present
trend of introducing heavier axle loads, higher vehicle speeds and / or larger
traffic volumes, by Indian Railways, it has become essential to reassess the
basic concept underlying the development programmes conducted to date
and to explore the possibility of developing new grades or wheel materials by
process modification to withstand the stringent service conditions. In wheel
steel, increasing carbon contents lead to higher work hardening rates and
higher ultimate tensile strengths. It results in lower yield ratio (YS/UTS). But
for higher axle load applications, the yield ratio should be higher Existing
wheel chemistry even with accelerated cooling during heat treatment does not
allow grains to refine sufficiency. Yield ratio in wheel material is often
considered an important design parameter.
Low YS/UTS ratios were linked with the presence of mixed size of prior
austenite grains. This is a result of uncontrolled grain growth caused by the
absence of any grain coarsening inhibitors, ultimately transforming into mixed
size of coarse pearlite nodules upon cooling and thus producing extremely
lower value of yield strength.
The improved chemistry will ensure evolution of fairly uniform prior
austenite grain size, which will then transform into uniform pearlite colony size
when subjected to modified heat treatment cycle.
Known prior arts for a micro-alloyed steel includes US Pat. No. 6,682,613
dated 01/27/2004 to Bai et al.
US Pat. No. 6,682,613 describes a process for enhancing precipitation
strengthening in steel and for making high-strength micro-alloy steel, and
steel made from the process. The process includes the step of deforming the
steel containing a suitable precipitate strengthening substance, at a
temperature at which the microstructure of the steel is essentially stable and
at which those precipitation strengthening particles that form are of a

3
desirable particle size for precipitation strengthening. Deforming the steel
introduces dislocations in the crystal structure of the steel, which increases
the kinetics of precipitation by increasing the number of precipitation
nucleation sites and accelerating the rate of diffusion of the precipitate
material. The steel may be deformed by bending or rolling the steel.
Preferably the process also includes the step of cooling the steel at a rapid
rate so as to minimize the formation of precipitate particles of a large-than-
desired size.
After an exhaustive study on both the relevant and related patent
documents and on existing conventional process of making a micro-alloyed
locomotive wheel, it has been found that there is a need for an improved
process of making a micro-alloyed locomotive wheel with higher yield strength
(YS) to ultimate tensile strength (UTS) ratio.
Thus, it would be desirable to devise an improved process in which wheels
are manufactured to meet the revised Indian Railways specification number
IRS-34-99 with improved YS / UTS ratio by micro alloying the existing plain C-
Mn wheel steel and establishing new set of heat treatment parameters to
achieve designed properties in wheels.
SUMMARY AND OBJECTS OF THE INVENTION
Accordingly, the present invention is directed to propose a process of
making a micro-alloyed locomotive wheel with higher yield strength (YS) to
ultimate tensile strength (UTS) ratio.
An object of the present invention is to provide a process of making a
micro-alloyed locomotive wheel with higher YS/UTS ratio of 0.7 or above.
Another object of the present invention is to design the heat treatment
parameters.
Another further object of the present invention is to provide a process in
order to design alloy with addition of Fe-V, Fe-Nb and Fe-Mo.
Yet another further object of the present invention is to provide a process
in which mechanical and metallurgical properties of micro-alloyed locomotive
wheels are improved.
Still another object of the present invention is to provide: a process in which
heat treatment parameters are optimised for micro-alloyed locomotive wheels
Still another further object of the present invention is to provide a process
in which lower wheel cycle cost is achieved.
To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly described, a
process of making, a micro-alloyed locomotive wheel with higher yield strength

4
(YS) to ultimate tensile strength (UTS) ratio, the process comprising a plurality
of stages like steel making, ingot casting, saw cutting, pressing, rolling &
dishing, heat treatment, machining and testing, results in alloy designing with
addition of Fe-V, Fe-Nb and Fe-Mo etc., and the said process micro-alloys
with vanadium, niobium and molybdenum by solution strengthening and
precipitation hardening in order to obtaining the properties of steel in rim-
quenched and tempered condition by improving the materials mechanical
properties like grain size, yield strength etc.; and
the said process designs the heat treatment parameter which includes
thermal regimes of heat treatment furnaces, rim spray and tempering, by
establishing heating and soaking temperatures of dissolution of micro alloying
elements and cooling parameters for subsequent precipitation.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, in steel making
stage of the said process all the heats are routed through BOF-VAD-bottom-
poured igot route, and hydrogen in steel is primarily controlled through deep
degassing at VAD with 2mbar chamber pressure and an operating
temperature around 1570ºC.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during passing
through ingot casting stage of the said process wheels are cast in a suitable
diameter fluted moulds with corresponding matching high internal hot tops in a
rake of a plurality of moulds arranged in a plurality of sets.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during teeming,
anti-piping compound and bottom pouring flux are used for producing sound
ingots.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, the said rakes
are prepared in the special casting bay of SMS-l and said teeming is
performed at teeming stage of SMS-II.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during saw
cutting stage of the said process the bottom portions of the said ingots are
dressed and the said dressed ingots are cut to the required length to obtain at
least two blocks from each ingot maintaining the said block weight
approximately between 770 kg to 780 kg.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during pressing
stage of the said process the said blocks are heated in computer-controlled
rotary hearth furnace maintaining the block soaking temperature
approximately between 1260° C to 1280° C, the said blocks are pressed in a
suitable oil hydraulic press in a plurality of steps: (a) upsetting, (b) forming and
(c) punching maintaining a desired reduction ratio.

5
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during rolling
and dishing stage of the said process the forged wheel blanks are reheated in
a box-type furnace maintaining a temperature of approximately between
1140° C to 1160° C, the said heated blanks are rolled in vertical wheel rolling
mill controlled by computers with arrangement for visual display of rolling
parameters and dimensions, the said rolled wheels are dished in an oil
hydraulic press of suitable capacity, and the said dished wheels are
subsequently stamped in a hydraulically operated marking press on backside
of the rim.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during heat
treatment stage of the said process the said wheels are heated in a rotary
hearth type gas fired furnace and subsequently are rim sprayed in a rim-
quenching machine for pre-set duration and pressure, and the said wheels
are placed with the help of mobile chargers an a guide cone in the centre of a
disc rotating at 16 rpm.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, hardening of
the said wheels is done by means of a stationary spray ring with flat jet
nozzles and the said wheels are subsequently tempered in a tempering
furnace and then air-cooled to ambient temperature.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during the
machining stage of the said process the said heat treated wheels are
machined in CNC machine having semi-automatic wheel handling system.
The process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, wherein, during testing
stage of the said process the said wheels are subjected to testing as per the
R-34-99 specification of the Indian Railways.
The various features of novelty that characterise the invention are pointed
out with particularity in the claims annexed to and forming a part of this
disclosure. For a better understanding of the invention, its operating
advantages and specific objects attained by its uses, reference is made to the
accompanying drawings and descriptive matter in which preferred
embodiments of the invention are illustrated.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following description
taken in conjunction with the accompanying drawings, in which Iike reference
numbers indicate like features, and wherein:

6
Fig, 1(a) shows a process flow chart for production of locomotive wheels
according to the present invention;
Fig. 1(b) shows VAD treatment cycle to be followed during wheel making;
Fig. 2 is a schematic heat treatment cycle of conventional process,
Fig. 3 is the hardness profile of the micro-alloyed wheel, according to the
present invention;
Fig. 4 is a schematic diagram illustrating forging and rolling sequence used in
the present invention; and
Fig. 5 depicts the basic dimensions of wheel used in Indian Railways.
DESCRIPTION OF KNOWN ART
Salient features of Indian Railway specification for carriages and
locomotive wheels are illustrated in Table 1. Basic dimension of wheels used
in Indian Railways are given in Table 2. The process / method of
manufacturing conventional locomotive wheel using IRS-34-99 specification of
Indian Railways comprises the following main steps in sequence:
(a) producing steel (for chemical composition of Table 1) in a 120
tonne basic oxygen furnace in the conventional way by blowing
carbon to the extent of 0.07 — 0.08% by weight of the steel, followed
by partial carburisation thereof, addition of the necessary ferro
alloys and petroleum coke to molten steel in VAD ladle, and casting
the molten steel into ingots of required size and cutting into blocks.
(b) forging and roling the blocks into wheels in the conventional
process followed in a wheel making plant;
(c) subjecting the forged and rolled wheels to the heat treatment
involving rim quenching by heating the wheel to a temperature of
880 -900º C, soaking at 880 -900º C for about 01 hour to attain
temperature homogenisation, quenching the wheel rim by spraying
a water jet of high pressure, i.e., 2-4 bar in about 300 - 330
seconds to a temperature of about 200° C and tempering the hot /
cold charge at 500° C followed by air cooling. The actual cycle
subjected to, are varied based on the chemical composition.
Schematic heat treatment cycle of conventional process is shown in
Fig. 2 and Fig. 5 depicts the basic dimensions of wheel used in
Indian Railways;
(d) heat treated wheel are tested for mechanical properties and finally
machined, inspected and dispatched to customers.

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DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO
THE ACCOMPANYING DRAWINGS
Yield ratio in wheel material is often considered an important design
parameter. Present trend on Railways is to introduce heavier axle loads,
higher vehicle speeds and/or larger traffic volumes for economic
considerations. A material is required which should not yield even at these
higher loads. Therefore, with wheels having higher YS/UTS ratio it is possible
to increase axle load, i.e., more material could be transported per unit wheel.
Lower wheel cycle cost is expected through the present invention.
The present invention passes through some stages like steel making, ingot
casting, saw cutting, pressing, raising & dishing, heat treatment, machining
and finally, testing.
(i) Steel making
All the heats are routed through BOF-VAD-bottom poured ingot route. A
modified process for BOF-VAD route has been designed. Hydrogen in steel is
primarily controlled through deep degassing at VAD with 2mbar chamber
pressure. Operating temperature of VAD is restricted to ~1570ºC. Chemical
compositions of the wheel heats made are shown in Table 3.
(ii) Ingot Casting
Wheels are cast in 400 mm diameter fluted moulds with 250 mm high
internal hot tops in a rake of 64 moulds arranged in 8 sets. During teeming
anti-piping compound and bottom pouring flux are used for producing sound
ingots. The rakes are prepared in the special casting bay of SMS-I and
teeming is performed at teeming stage of SMS-II. After the ingots are stripped
off, only the full size ingots with hot top marks are sent for saw cutting.
(iii) Saw Cutting
The bottom portions of the ingots are dressed with the help of oxy-
acetylene torch. The dressed ingots are cut to the required length to obtain
two blocks from each ingot. The block weight is maintained between 770 kg to
780 kg. The top portion containing the hot top and the bottom portion are
removed.
(iv) Pressing
Blocks are heated in rotary hearth furnace with a capacity of 144 blocks
Block soaking temperature is maintained between 1260º C to 1280° C in the
computer-controlled furnace. The blocks after de-scaling are pressed in 63/12
MN oil hydraulic press. Both the top tool frame and the bottom sliding table
movement are longitudinal. The centering device ensures placement of the
wheel blanks at the centre of the press. Pressing is carried out in 03 steps: (a)
upsetting, (b) forming and (c) punching. Die positions and pressing operation
have been ensured by different pre-fixed programmes. Reduction ratio of 4:1
is maintained.

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(v) Rolling and Dishing
The forged wheel blanks are repeated in a box type furnace having
capacity of heating a plurality of blocks. The temperature is maintained
between 1140° C to 1160° C. Heated blanks are rolled in vertical wheel rolling
mill. The mill has 2 power driven web rolls, 2 friction driven edge rolls and 1
tread roll with automatic charging and discharging arrangement. The rolling
operation is controlled by computers with arrangement for visual display of
rolling parameters and dimensions. The rolled wheels are dished in 20 MN oil
hydraulic press. The dished wheels are subsequently stamped in a
hydraulically operated marking press on backside of the rim. Forging and
rolling sequence used in the present invention is shown in Fig. 4.
(vi) Heat Treatment
The experimental wheels are heated in a rotary hearth type gas fired
furnace. These wheels are then rim sprayed in a rim-quenching machine for
preset duration and pressure. Wheels are placed with the help of mobile
chargers on a guide cone in the centre of a disc rotating at 16 rpm. Hardening
is done by means of a stationary spray ring with flat jet nozzles. Arrangements
of 24 numbers of nozzles and rotation of the wheel provide a uniform spray of
water upon the tread. Wheels are subsequently tempered in a tempering
furnace and then air-cooled to ambient temperature. Heat treatment
parameters followed in the present invention are illustrated in Table 4.
(v) Machining
The wheels after heat treatment are machined in CNC machine. The
machines have semi-automatic wheel handling system. The complete
machining of the wheel has been carried out.
(vi) Testing
Wheels produced are subjected to testing as per the R-34-99 specification
of the Indian Railways. Mechanical properties obtained by the improved
process, according to the present invention, are given in Table 5. Hardness
profile of experimented micro alloyed wheel is shown in Fig. 3. Mechanical
and metallurgical properties of micro alloyed and comparison with R-34-99
grade carbon-manganese locomotive wheels are shown is Table 6.
The improved process, according to the present invention, results in alloy
designing with addition of Fe-V, Fe-Nb and Fe-Mo. In the present invention,
micro-alloying with vanadium, niobium and molybdenum has played the
important role by solution strengthening and precipitation hardening for
obtaining the properties of steel in rim quenched and tempered condition by
improving grain size and yield strength. Designing the heat treatment
parameter, according to the present invention, includes thermal regimes of
heat treatment furnaces, rim spray and tempering. Concept involved during
design of heat treatment parameters basically consist of establishing heating
and soaking temperatures of dissolution of micro alloying elements and
cooling parameters for subsequent precipitation.
While the principles of this invention have been described in connection
with specific embodiment, it should be understood clearly that these

9
descriptions are made only by way of example and are not intended to limit
the scope of the invention.



10



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Table 7: Steel-making process-chart for production of steel wheel through
BOF-VAD-lngot route
Grades: R-34-90
BOF /Converter Tapping
• Reblow in BOF to be restricted to one and of < 20 secs
• Ladel pre-heating temperature: 1000ºC
• Tapping temperature: 1660° C; Tapping duration; 4-6 minutes
• Stop carry over slag to minimum. Use ram tree / gunny bag and DART
• Petroleum Coke addition: Dry Calcined Petroleum Coke Addition as
per specification. Silicon carbide - 50/70 kg additions in tapping
stream.
• Ferro-silicon and silico-manganese addition as per specification and
lime 600 kg.
• No aluminium addition should be done. Target Si% = 0.30.
• Expected ladle temperature: 1605 - 1610º C(at VAD)
Transportation time from tap finish to VAD start should be restricted to 20
minutes.
VAD
• Initial homo genisation purging @ 200 Ipm for 2 min
20 kg shots / cube + Fr-Si fines 15 kg + coke lines 10 kg (by small bags of
5kg distributed over slag)
• Celox oxygen measurement
• Arcing depending on initial temperature. Vacuum level during arcing
should be 400 - 600 mbar. Argon flow rate: 100 lpm.
• Additions during homogenisation start;
Dry calcined petroleum coke: as per ladle analysis C%
Fe-Si and Si-Mn as per specification. Target Si% = 0,30/0.35.
Al bar / cube: 30/20/ 15 kg
• Deep degassing for 15 minutes. Argon flow rate 100 -150 Ipm.
• Expected temperature:1580ºC.
• Trim addition of petroleum coke, ferro-silicon, silico-manganese as
required by specification (from bunker). Care must be taken to restrict
trim addition to a minimum, as these ferro alloys are not pre-heated.
• Arcing depending on final despatch temperature. Vacuum level during
arcing should be 400- 500 mbar. Argon flow rate: 100 lpm
• Deep degassing for 10 minutes at < 5 mbar with Argon flow 200 Ipm.
• Celox oxygen measurement
• Soft rinsing at 50 lpm, max 3 minutes.
Ladle out, DET =1550° C

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We Claim:
1. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, the process comprising
a plurality of stages like steel making, ingot casting, saw cutting, pressing,
rolling & dishing, heat treatment, machining and testing, results in alloy
designing with addition of Fe-V, Fe-Nb and Fe-Mo etc., and the said process
micro-alloys with vanadium, niobium and molybdenum by solution
strengthening and precipitation hardening in order to obtaining the properties
of steel in rim-quenched and tempered condition by improving the material's
mechanical properties like grain size, yield strength etc; and
the said process designs the heat treatment parameter which includes
thermal regimes of heat treatment furnaces, rim spray and tempering, by
establishing heating and soaking temperatures of dissolution of micro alloying
elements and cooling parameters for subsequent precipitation.
2. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, in steel making stage of the said process all the heats are routed
through BOF-VAD-bottom-poured ingot route, and hydrogen in steel is
primarily controlled through deep degassing at VAD with 2mbar chamber
pressure and an operating temperature around 1570°C.
3. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, during passing through ingot casting stage of the said process
wheels are cast in a suitable diameter fluted moulds with corresponding
matching high internal hot tops in a rake of a plurality of moulds arranged in a
plurality of sets.
4. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 3,
wherein, during teeming, anti-piping compound and bottom pouring flux are
used for producing sound ingots.
5. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in any of
claims 3 and 4, wherein, the said rakes are prepared in the special casting
bay of SMS-I and said teeming is performed at teeming stage of SMS-II.
6. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, during saw cutting stage of the said process the bottom portions of
the said ingots are dressed and the said dressed ingots are cut to the required

13
length to obtain at least two blocks from each ingot maintaining the said block
weight approximately between 770 kg to 780 kg
7. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, during pressing stage of the said process the said blocks are heated
in computer-controlled rotary hearth furnace maintaining the block soaking
temperature approximately between 1260° C to 1280º C, the said blocks are
pressed in a suitable oil hydraulic press in a plurality of steps: (a) upsetting.
(b) forming and (c) punching maintaining a desired reduction ratio.
8. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, during rolling and dishing stage of the said process the forged wheel
blanks are reheated in a box-type furnace maintaining a temperature of
approximately between 1140° C to 1160° C, the said heated blanks are rolled
in vertical wheel rolling mill controlled by computers with arrangement for
visual display of rolling parameters and dimensions, the said rolled wheels are
dished in an oil hydraulic press of suitable capacity, and the said dished
wheels are subsequently stamped in a hydraulically operated marking press
on backside of the rim.
9. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1.
wherein, during heat treatment stage of the said process the said wheels are
heated in a rotary hearth type gas fired furnace and subsequently are rim
sprayed in a rim-quenching machine for pre-set duration and pressure, and
the said wheels are placed with the help of mobile chargers on a guide cone
in the centre of a disc rotating at 16 rpm.
10. A process of making a micro-alloyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in any one of
claims 1 and 9, wherein, hardening of the said wheels is done by means of a
stationary spray ring with flat jet nozzles and the said wheels are
subsequently tempered in a tempering furnace and then air-cooled to ambient
temperature.
11. A process of making a micro-alloyed locomotive wheel with higher yield,
strength (YS) to ultimate tensife strength (UTS) ratio, as claimed in claim 1,
wherein, during the machining stage of the said process the said heat treated
wheels are machined in CNC machine having semi-automatic wheel handling
system.

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12. A process of making a micro-alpIoyed locomotive wheel with higher yield
strength (YS) to ultimate tensile strength (UTS) ratio, as claimed in claim 1,
wherein, during testing stage of the said process the said wheels are
subjected to testing as per the R-34-99 specification of the Indian Railways.

To,
The Controller of Patents,
The Patent Office, Kolkata.

The present invention relates to a process of making a micro-alloyed
locomotive wheel with higher yield strength (YS) to ultimate tensile strength
(UTS) ratio. The process of making a micro-alloyed locomotive wheel
provides higher YS/UTS ratio of 0.7 or above. The said process designs the
heat treatment parameters and alloy with addition of Fe-V, Fe-Nb and Fe-Mo.
Heat treatment parameters are optimised for micro-alloyed locomotive
wheels, Mechanical and metallurgical properties of micro-alloyed locomotive
wheels are improved utilising the said process. Lower wheel cycle cost is
achieved by the present invention