Title of Invention	A PROCESS FOR MANUFACTURING STEEL PLATES / STRIPS RESISTANT TO CORROSION IN MOLASSES
Abstract	The invention provides a process for manufacturing steel plates/strips resistant to corrosion in molasses comprising the following steps in sequence :- (a) preparing molten steel of required chemical composition (by weight %) : C - 0.10 max., Mn - 0.80 max., Si - 0.30 max., S - 0.03 max., P - 0.04 max., Cu - 0.25 to 0.35 and Fe - the balance, from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace by adding medium-carbon ferro-manganese or silico-mangenese and ferro-silicon, ores, and steel scraps in required quantities; (b) tapping the molten steel into a preheated ladle at 1630 Ý 20¯C; (c) adding cathode copper bar in the ladle in required quantity; (d) top-pouring molten steel into the ingot mould(s) of a continuous casting system to cast ingots of rectangular cross section, or slabs directly; (e) soaking and rolling the ingots into slabs in a slabbing mill at 1300 - 1320¯C for 6 hours; (f) re-soaking the slabs at 1200 Ý 20¯C for 3 hours, and rolling the slabs into plates in a plate mill or into hot strips in a strip mill; (g) finish rolling the plates and strips to the reduced thickness upto 32 mm at 850 - 875¯C, and upto 12 mm at 900 - 920¯C respectively; (h) air cooling and normalising the plates; (i) water cooling the strips on a run-out table at a cooling rate of 18 Ý 2¯C per second to allow formation of an equiaxed ferrite-pearlite microstructure in the strips; and (j) coiling the strips at 640 - 660¯C.

Title of Invention

A PROCESS FOR MANUFACTURING STEEL PLATES / STRIPS RESISTANT TO CORROSION IN MOLASSES

Abstract

The invention provides a process for manufacturing steel plates/strips resistant to corrosion in molasses comprising the following steps in sequence :- (a) preparing molten steel of required chemical composition (by weight %) : C - 0.10 max., Mn - 0.80 max., Si - 0.30 max., S - 0.03 max., P - 0.04 max., Cu - 0.25 to 0.35 and Fe - the balance, from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace by adding medium-carbon ferro-manganese or silico-mangenese and ferro-silicon, ores, and steel scraps in required quantities; (b) tapping the molten steel into a preheated ladle at 1630 Ý 20¯C; (c) adding cathode copper bar in the ladle in required quantity; (d) top-pouring molten steel into the ingot mould(s) of a continuous casting system to cast ingots of rectangular cross section, or slabs directly; (e) soaking and rolling the ingots into slabs in a slabbing mill at 1300 - 1320¯C for 6 hours; (f) re-soaking the slabs at 1200 Ý 20¯C for 3 hours, and rolling the slabs into plates in a plate mill or into hot strips in a strip mill; (g) finish rolling the plates and strips to the reduced thickness upto 32 mm at 850 - 875¯C, and upto 12 mm at 900 - 920¯C respectively; (h) air cooling and normalising the plates; (i) water cooling the strips on a run-out table at a cooling rate of 18 Ý 2¯C per second to allow formation of an equiaxed ferrite-pearlite microstructure in the strips; and (j) coiling the strips at 640 - 660¯C.

Full Text	The present invention relates to a process for manufacturing steel plates/strips resistant to acidic corrosion. The invention relates more particularly to a process for producing steel plates/sprips, the chemical composition and grain structure of which has been optimised for making the same adequately resistant to corrosion in contact with molasses. The conventional mild steel plates/strips at present used for making containers such as tanks for storing molasses are not found to possess adequate resistance to corrosion in contact with molasses which have an acidic pH of 5.0. As a result molasses stored in such containers for a prolonged duration of several months are liable to be contaminated with corroded steel particles released from the containers and also the containers filled in with molasses are liable to be damaged through corrosion in contact with molasses with reduction in their service life. The object of the present invention is to provide a process for manufacturing steel plates/strips having adequately high resistance to corrosion in contact with molasses for preventing contamination of molasses by corroded steel particles released from the containers fabricated therefrom and also for prolonging the service life of the said container. Thus the invention provides a process for manufacturing steel plates/strips resistant to acidic corrosion, characterised in that the process comprises the following steps in sequence :- - 2 - (a) preparing molten steel of chemical composition (by weight %) : C - 0.05 - 0.10, Mn - 0.30 - 0.80, Si - 0.15 - 0.30, S - 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max., and Fe - the balance, from blast furnace pig Iron in a Basic Oxygen/Open Hearth furnace; (b) tapping the molten steel into a ladle preheated at 1630 ± 20°C containing cathode copper bar, ferro-manganese and ferro-silicon in required quantity; (c) pouring molten steel into the ingot mould(s) or in the tundish of a continuous casting machine to cast ingots of rectangular cross section, or slabs respectively; (d) soaking the ingots at 1280 - 1300°C for 4 to 6 hours, and rolling into slabs in a slabbing mill; (e) re-soaking the slabs at 1230 ± 20°C for 2.5 to 3 hours, and rolling the slabs into plates in a plate, mill or into hot strips in a strip mill; (f) finish rolling the plates and strips at 875 - 920°C; (g) controlled cooling the strips on a run-out table at a cooling rate of 10 to 20°C per second; and (h) coiling the strips at 640 - 66o°C. The invention is described fully and particularly without restricting its scope in any manner with reference to the accompanying drawings in which Figure 1 is a flow chart showing the main processing steps followed in sequence in the invented process; and - 3 - Figure 2 shows the increase in weight loss with time of (A) conventional mild steel and (B) steel produced in the invented process through corrosion in molasses. At present tanks for storing molasses are fabricated from conventional semi-killed mild steel plates/strips with high carbon content of around 0.20% by weight, which are found to corrode in contact with molasses at a relatively fast rate. With reference to Fig. 1 the invented process for manufacturing steel plates/strips of increased resistance to corrosion in contact with molasses comprises the following steps in sequence :- - 4 - (a) preparing molten steel of required chemical composition from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace by adding medium-carbon ferro-manganese or silico- manganese and ferro-silicon. Ores, and steel scraps in required quantities; (b) tapping the molten steel into a preheated ladle at a temperature of 1630 ± 20°C; (c) adding cathode copper bar in the ladle in required quantity; (d) top-pouring molten steel into the ingot mould (s) of a continuous casting system to cast ingots of rectangular cross section each weighing 12 T or slabs directly; (e) soaking the ingots at a temperature of 1300 - 1320°C for about 6 hours, and rolling the soaked ingots into slabs in a slabbing mill; (f ) re-soaking the slabs in a reheating furnace at a temperature of 1200 ± 20°C for a period upto 3 hours; (g) rolling the slabs into plates in a plate mill or into hot strips in a strip mill; (h) finish rolling the plates to a reduced thickness upto 32 mm at a temperature of 850 - 875°C or finish rolling the hot strips to a reduced thickness upto 12 mm at a temperature of 900-920°C; (i) air cooling the plates and normalising the same in the known method; (j) water cooling the hot strips on a run-out table at a cooling rate of 18 + 2 C per second to allow formation of an equlaxed ferrite-pearlite microstructure in the strips; and - 5 - (k) coiling the strips at a temperature of 640-660°C. The chemical composition of the steel plates/strips produced is optimised to be (by weight %): C - 0.05 -. 0-10, Mn - 0,30 - 0.80, Si - 0.15 - 0.30, S - 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max. and Fe - the balance. The micrographic study of the plates/strips reveals the presence of equiaxed ferrite-pearlite grains in the microstructure of the steel produced. The mechanical properties of the steel produced are found to be as given in Table I. Table I Mechanical properties of the steel produced in the invented process. Mechanical Properties Values Yield stress 250 MPa min. Tensile stress 380 MPs min. Elongation % at break 25.0 min. Impact toughness at 20°C 30 Joule min. Bend 3-t max. A quantity of around 1000 T of steel plates/strips has been produced in the invented process, a substantial quantity of which is fabricated into tanks for storing molasses. Field trials conducted on the tanks by filling the same with molasses have shown satisfactory performance of the tanks with reduced corrosion in contact with molasses. - 6 - The results of study of the loss in weight with time of (A) conventional mild steel and (B) steel produced in the invented process through corrosion in contact with molasses as shown in Fig. 2 reveals that the steel produced in the invented process is more resistant to corrosion in molasses compared with the conventional mild steel, the difference being more pronounced for longer period (around 90 days) of contact with molasses. - 7 - We Claim :- 1. A process for manufacturing steel plates/strips resistant to acidic corrosion, characterised in that the process comprisesthe following steps in sequence :- (a) preparing molten steel of chemical composition (by weight %) : C - 0.05 - 0.10, Mn - 0.30 - 0.80, Si - 0.15 - 0,30, S * 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max., and Fe - the balance, from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace; (b) tapping the molten steel into a ladle preheated at 1630 ± 20°C containing cathode copper bar, ferro-manganese and ferro-silicon/required quantity; (c) pouring molten steel into the ingot mould(s) or in the tendish of a continuous casting machine to cast ingots of rectangular cross section, or slabs respectively; (d) soaking the ingots at 1280 - 1300°C for 4 to 6 hours and rolling into slabs in a slabbing mill; (e) re-soaking the slabs at 1230 ± 20°C for 2.5 to 3 hours, and rolling the slabs into plates in a plate mill or into hot strips in a strip mill; (f) finish rolling the plates and strips at 875 - 920°C; (g) controlled cooling the strips on a run-out table at a cooling rate of 10 to 20°C per second; and (h) coiling the strips at 640 - 660°C. - 8 - 2. A process for manufacturing steel plates/strips resistant to acidio corrosion, substantially as herein described. - 9 - Dated this 24th day of June 1998. The invention provides a process for manufacturing steel plates/strips resistant to corrosion in molasses comprising the following steps in sequence :- (a) preparing molten steel of required chemical composition (by weight %) : C - 0.10 max., Mn - 0.80 max., Si - 0.30 max., S - 0.03 max., P - 0.04 max., Cu - 0.25 to 0.35 and Fe - the balance, from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace by adding medium-carbon ferro-manganese or silico-mangenese and ferro-silicon, ores, and steel scraps in required quantities; (b) tapping the molten steel into a preheated ladle at 1630 Ý 20¯C; (c) adding cathode copper bar in the ladle in required quantity; (d) top-pouring molten steel into the ingot mould(s) of a continuous casting system to cast ingots of rectangular cross section, or slabs directly; (e) soaking and rolling the ingots into slabs in a slabbing mill at 1300 - 1320¯C for 6 hours; (f) re-soaking the slabs at 1200 Ý 20¯C for 3 hours, and rolling the slabs into plates in a plate mill or into hot strips in a strip mill; (g) finish rolling the plates and strips to the reduced thickness upto 32 mm at 850 - 875¯C, and upto 12 mm at 900 - 920¯C respectively; (h) air cooling and normalising the plates; (i) water cooling the strips on a run-out table at a cooling rate of 18 Ý 2¯C per second to allow formation of an equiaxed ferrite-pearlite microstructure in the strips; and (j) coiling the strips at 640 - 660¯C.

Full Text

The present invention relates to a process for manufacturing steel plates/strips resistant to acidic corrosion.
The invention relates more particularly to a process
for producing steel plates/sprips, the chemical composition and
grain structure of which has been optimised for making the same
adequately resistant to corrosion in contact with molasses.
The conventional mild steel plates/strips at present

used for making containers such as tanks for storing molasses are not found to possess adequate resistance to corrosion in contact with molasses which have an acidic pH of 5.0. As a result molasses stored in such containers for a prolonged duration of several months are liable to be contaminated with corroded steel particles released from the containers and also the containers filled in with molasses are liable to be damaged through corrosion in contact with molasses with reduction in their service life.
The object of the present invention is to provide a process for manufacturing steel plates/strips having adequately high resistance to corrosion in contact with molasses for preventing contamination of molasses by corroded steel particles released from the containers fabricated therefrom and also for prolonging the service life of the said container.
Thus the invention provides a process for manufacturing steel plates/strips resistant to acidic corrosion, characterised in that the process comprises the following steps in sequence :-
- 2 -

(a) preparing molten steel of chemical composition (by
weight %) : C - 0.05 - 0.10, Mn - 0.30 - 0.80, Si - 0.15 - 0.30,
S - 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max.,
and Fe - the balance, from blast furnace pig Iron in a Basic
Oxygen/Open Hearth furnace;
(b) tapping the molten steel into a ladle preheated at
1630 ± 20°C containing cathode copper bar, ferro-manganese and
ferro-silicon in required quantity;
(c) pouring molten steel into the ingot mould(s) or in the
tundish of a continuous casting machine to cast ingots of
rectangular cross section, or slabs respectively;
(d) soaking the ingots at 1280 - 1300°C for 4 to 6 hours,
and rolling into slabs in a slabbing mill;
(e) re-soaking the slabs at 1230 ± 20°C for 2.5 to 3 hours,
and rolling the slabs into plates in a plate, mill or into hot
strips in a strip mill;
(f) finish rolling the plates and strips at 875 - 920°C;
(g) controlled cooling the strips on a run-out table at a
cooling rate of 10 to 20°C per second; and
(h) coiling the strips at 640 - 66o°C.
The invention is described fully and particularly without restricting its scope in any manner with reference to the accompanying drawings in which
Figure 1 is a flow chart showing the main processing steps followed in sequence in the invented process; and
- 3 -

Figure 2 shows the increase in weight loss with time of (A) conventional mild steel and (B) steel produced in the invented process through corrosion in molasses.
At present tanks for storing molasses are fabricated from conventional semi-killed mild steel plates/strips with high carbon content of around 0.20% by weight, which are found to corrode in contact with molasses at a relatively fast rate.
With reference to Fig. 1 the invented process for

manufacturing steel plates/strips of increased resistance to
corrosion in contact with molasses comprises the following steps
in sequence :-
- 4 -

(a) preparing molten steel of required chemical composition
from blast furnace pig iron in a Basic Oxygen/Open Hearth
furnace by adding medium-carbon ferro-manganese or silico-
manganese and ferro-silicon. Ores, and steel scraps in required
quantities;
(b) tapping the molten steel into a preheated ladle at a
temperature of 1630 ± 20°C;
(c) adding cathode copper bar in the ladle in required
quantity;
(d) top-pouring molten steel into the ingot mould (s) of a
continuous casting system to cast ingots of rectangular cross
section each weighing 12 T or slabs directly;
(e) soaking the ingots at a temperature of 1300 - 1320°C for about 6 hours, and rolling the soaked ingots into slabs in a slabbing mill;
(f ) re-soaking the slabs in a reheating furnace at a temperature of 1200 ± 20°C for a period upto 3 hours;
(g) rolling the slabs into plates in a plate mill or into hot strips in a strip mill;
(h) finish rolling the plates to a reduced thickness upto 32 mm at a temperature of 850 - 875°C or finish rolling the hot strips to a reduced thickness upto 12 mm at a temperature of 900-920°C;
(i) air cooling the plates and normalising the same in the known method;
(j) water cooling the hot strips on a run-out table at a cooling rate of 18 + 2 C per second to allow formation of an equlaxed ferrite-pearlite microstructure in the strips; and
- 5 -

(k) coiling the strips at a temperature of 640-660°C.
The chemical composition of the steel plates/strips produced is optimised to be (by weight %): C - 0.05 -. 0-10, Mn - 0,30 - 0.80, Si - 0.15 - 0.30, S - 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max. and Fe - the balance.
The micrographic study of the plates/strips reveals the presence of equiaxed ferrite-pearlite grains in the microstructure of the steel produced.
The mechanical properties of the steel produced are found to be as given in Table I.
Table I
Mechanical properties of the steel produced in the invented process.
Mechanical Properties Values
Yield stress 250 MPa min.
Tensile stress 380 MPs min.
Elongation % at break 25.0 min.
Impact toughness at 20°C 30 Joule min.
Bend 3-t max.
A quantity of around 1000 T of steel plates/strips has been produced in the invented process, a substantial quantity of which is fabricated into tanks for storing molasses. Field trials conducted on the tanks by filling the same with molasses have shown satisfactory performance of the tanks with reduced corrosion in contact with molasses.
- 6 -

The results of study of the loss in weight with time of (A) conventional mild steel and (B) steel produced in the invented process through corrosion in contact with molasses as shown in Fig. 2 reveals that the steel produced in the invented process is more resistant to corrosion in molasses compared with the conventional mild steel, the difference being more pronounced for longer period (around 90 days) of contact with molasses.
- 7 -

We Claim :-
1. A process for manufacturing steel plates/strips resistant to acidic corrosion, characterised in that the process comprisesthe following steps in sequence :-
(a) preparing molten steel of chemical composition (by
weight %) : C - 0.05 - 0.10, Mn - 0.30 - 0.80, Si - 0.15 - 0,30,
S * 0.02 max., P - 0.04 max., Cu - 0.30 - 0.35, Al - 0.025 max.,
and Fe - the balance, from blast furnace pig iron in a Basic
Oxygen/Open Hearth furnace;
(b) tapping the molten steel into a ladle preheated at
1630 ± 20°C containing cathode copper bar, ferro-manganese and
ferro-silicon/required quantity;
(c) pouring molten steel into the ingot mould(s) or in the
tendish of a continuous casting machine to cast ingots of
rectangular cross section, or slabs respectively;
(d) soaking the ingots at 1280 - 1300°C for 4 to 6 hours and
rolling into slabs in a slabbing mill;
(e) re-soaking the slabs at 1230 ± 20°C for 2.5 to 3 hours,
and rolling the slabs into plates in a plate mill or into hot
strips in a strip mill;
(f) finish rolling the plates and strips at 875 - 920°C;
(g) controlled cooling the strips on a run-out table at a
cooling rate of 10 to 20°C per second; and
(h) coiling the strips at 640 - 660°C.
- 8 -

2. A process for manufacturing steel plates/strips resistant to acidio corrosion, substantially as herein described.
- 9 -
Dated this 24th day of June 1998.

The invention provides a process for manufacturing steel plates/strips resistant to corrosion in molasses comprising the following steps in sequence :-
(a) preparing molten steel of required chemical composition
(by weight %) : C - 0.10 max., Mn - 0.80 max., Si - 0.30 max.,
S - 0.03 max., P - 0.04 max., Cu - 0.25 to 0.35 and Fe - the balance, from blast furnace pig iron in a Basic Oxygen/Open Hearth furnace by adding medium-carbon ferro-manganese or silico-mangenese and ferro-silicon, ores, and steel scraps in required quantities;
(b) tapping the molten steel into a preheated ladle at
1630 Ý 20¯C;
(c) adding cathode copper bar in the ladle in required
quantity;
(d) top-pouring molten steel into the ingot mould(s) of a
continuous casting system to cast ingots of rectangular cross
section, or slabs directly;
(e) soaking and rolling the ingots into slabs in a slabbing
mill at 1300 - 1320¯C for 6 hours;
(f) re-soaking the slabs at 1200 Ý 20¯C for 3 hours, and
rolling the slabs into plates in a plate mill or into hot strips
in a strip mill;
(g) finish rolling the plates and strips to the reduced
thickness upto 32 mm at 850 - 875¯C, and upto 12 mm at 900 - 920¯C
respectively;
(h) air cooling and normalising the plates;
(i) water cooling the strips on a run-out table at a cooling rate of 18 Ý 2¯C per second to allow formation of an equiaxed ferrite-pearlite microstructure in the strips; and
(j) coiling the strips at 640 - 660¯C.

Documents:

01108-cal-1998-abstract.pdf

01108-cal-1998-assignment.pdf

01108-cal-1998-claims.pdf

01108-cal-1998-correspondence.pdf

01108-cal-1998-description(complete).pdf

01108-cal-1998-drawings.pdf

01108-cal-1998-form-1.pdf

01108-cal-1998-form-2.pdf

01108-cal-1998-form-3.pdf

01108-cal-1998-form-5.pdf

01108-cal-1998-p.a.pdf

1108-cal-1998-granted-abstract.pdf

1108-cal-1998-granted-assignment.pdf

1108-cal-1998-granted-claims.pdf

1108-cal-1998-granted-correspondence.pdf

1108-cal-1998-granted-description (complete).pdf

1108-cal-1998-granted-drawings.pdf

1108-cal-1998-granted-examination report.pdf

1108-cal-1998-granted-form 1.pdf

1108-cal-1998-granted-form 2.pdf

1108-cal-1998-granted-form 3.pdf

1108-cal-1998-granted-form 6.pdf

1108-cal-1998-granted-letter patent.pdf

1108-cal-1998-granted-pa.pdf

1108-cal-1998-granted-reply to examination report.pdf

1108-cal-1998-granted-specification.pdf

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Patent Number

193756

Indian Patent Application Number

1108/CAL/1998

PG Journal Number

30/2009

Publication Date

24-Jul-2009

Grant Date

24-Jun-1998

Date of Filing

24-Jun-1998

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

REEARCH & DEVELOPMENT CENTRE FOF IRON & STEEL,A GOVT,OF INDIA ENTERPRISE,HAVING ITS REGISTERED OFFICE AT ISPAT BHAWAN,LODHI ROAD,NEW DELHI

Inventors:

#	Inventor's Name	Inventor's Address
1	ATUL SAXENA	RDCIS/SAIL,DORANDA,RANCHI-834002
2	BIMAL KUMAR PANIGRAHI	RDCIS/SAIL,DORANDA,RANCHI-834002
3	AMITABH BHATTACHARYYA	RDCIS/SAIL,DORANDA,RANCHI-834002
4	SANAK MISHRA	RDCIS/SAIL,DORANDA,RANCHI-834002

PCT International Classification Number

C21C 7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA