Title of Invention	PROCESS OF MANUFACTURING TEMPERED PITCH BONDED MAGNESIA CARBON REFRACTORIES WITH ADDITIVE FOR HIGH HOT STRENGTH AND OXIDATION RESISTANCE .
Abstract	The present invention relates to a process of manufacturing high hot strength and oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite, pitch and metal powder) of specified quality are used as Magnesia (MgO :85-99.9%; Bulk density : 3-4 g/ cm3); Graphite (Fixed carbon: 80 to 99%; Ash: 1 to 20 %); Pitch (Softening point: 80 to 130°C; Coking index: 40-55%); Aluminium powder (Al: 95 to 99.8%) and where in the Magnesia of specified grain size distribution is mixed with 2- 15% by weight of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of aluminium powder to obtain a through blend; and a hot mix is prepared from then above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as . required to form magnesia carbon bricks.

Title of Invention

PROCESS OF MANUFACTURING TEMPERED PITCH BONDED MAGNESIA CARBON REFRACTORIES WITH ADDITIVE FOR HIGH HOT STRENGTH AND OXIDATION RESISTANCE .

Abstract

The present invention relates to a process of manufacturing high hot strength and oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite, pitch and metal powder) of specified quality are used as Magnesia (MgO :85-99.9%; Bulk density : 3-4 g/ cm3); Graphite (Fixed carbon: 80 to 99%; Ash: 1 to 20 %); Pitch (Softening point: 80 to 130°C; Coking index: 40-55%); Aluminium powder (Al: 95 to 99.8%) and where in the Magnesia of specified grain size distribution is mixed with 2- 15% by weight of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of aluminium powder to obtain a through blend; and a hot mix is prepared from then above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as . required to form magnesia carbon bricks.

Full Text	FIELD OF THE INVENTION This invention relates to a process of manufacturing tempered pitch bonded magnesia carbon refractories with additive for high hot strength and oxidation resistance. BACKGROUND OF THE EVVENTTON AND PRIOR ART AND DRAWBACKS Pitch bonded magnesia carbon bricks are being manufactured in captive brick plant, and used in converters. But in converter, erosion of bricks do not occur uniformly due to difference in operating conditions in different zones of the vessel. In trunion area, slag attack is the predominant factor for erosion. In charge pad, impact of scrap is an additional factor for higher erosion. In tap hole area, abrasion of liquid steel during tapping is an important factor for erosion of lining. Similarly, conditions are different in bottom and top cone area of the converter. In order to improve lining life and to achieve uniform wear profile, different qualities of bricks are used in converter in advanced countries. OBJECT OF THE INVENTION It is a primary object of the invention to propose a method for the preparation of high hot strength and oxidation resistant magnesia carbon bricks. It is another object to use addition of aluminium metal powder as minor additive. It is further object to propose a method of manufacturing such bricks in which hot strength (HMOR- Hot Modulus of Rupture) and oxidation resistance of the developed aluminium powder containing pitch bonded magnesia carbon bricks are much higher than normal pitch bonded magnesia carbon bricks. These and other objects will be apparent from the following paragraphs. BRIEF DETAILS OF MANUFACTURING According to this invention, there is proposed a process of manufacturing high hot strength and oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite, pitch and metal powder) of specified quality as indicated below are used: Magnesia: MgO : 85-99.9% Bulk density : 3-4 g/ cm3 Graphite: Fixed carbon . 80 to 99% Ash : 1 to 20 % Pitch: Softening point . 80 to 130°C Coking index : 40-5 5% Aluminium powder: Al .95 to 99.8% And where in the following steps are followed. a. Magnesia of specified grain size distribution is mixed with 2-15% by weight of graphite, 2-8% by weight of molten, pitch and 0.5-5% by weight of aluminium powder to obtain a through blend, b. A hot mix is prepared from then above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as required to form magnesia carbon bricks. The process has the following salient features: 1. Coarse fractions of magnesia (5-8mm, 3-5mm, 1.6-3mm, 0.5-1.6mm) are heated to the temperature in the range of 120-250°C and mixed with 1-5% by weight of molten liquid pitch in a hot mixer for a time period up to 20 minutes; 2. then, part of the fine fractions (less than 0.5mm) of magnesia and graphite are charged into the mixer and mixing is done for a time period of up to 30 minutes; 3. then, rest of the fine fractions of magnesia and aluminium powder are charged into the mixer and mixing is done for a time period of up to 30 minutes; 4. then, an amount of 1-5% by weight of molten liquid pitch is added into the mixer and further mixing is done for a time period of up to 20 minutes. The Magnesia carbon bricks thus produced is tempered (heat treated) in a kiln for a time period of (10-72 hrs.) at temperature of (50-350 °C) regime to get tempered in pitch blended magnesia carbon bricks having high hot strength and oxidation resistance. The magnesia has the following characteristics: MgO : 85-99.9% CaO : 0.1-4% SiO2 :0.01-4% A12O3 :0.01-4% Fe2O3 :0.01-5% B2O3 :0-0.1% Bulk density : 3-4g/on3 Crystal size : 50 to C00 micronis The graphite used has the following characteristics: Fixed carbon : 80-99% Ash :lto2(4% Size : 0-1 nun The pitch used has the following characteristics: Softening point : 80 to 130°C Benzene insoluble : 15-30% Quinolene insoluble : 5-20% Coking index : 40-55% The aluminium powder used has the lollowing characteristics: Al : 95 to 99.8% Size : 0-0.5 mm Comparision and Performance. Characteristics and Verification of Properties Comparative properties with and without addition of particular amount of aluminium powder are given below: Advantages of the Invention: Hot strength and oxidation res stance of the developed aluminium powder containing pitch bonded magnesia carbon bricks are much higher than normal pitch bonded magnesia carbon bricks. Average hot strength and oxidation resistance at 1400 °C (30 minutes) is 1.5 to 2 times higher than the normal pitch bonded magnesia carbon bricks. Zonal lining with the developed bricks in charge pad and other qualities in other areas has resulted higher lining life of 1054 heats, as compared to 829 and 809 heats for earlier campaigns in 150T BOF of RSP during testing and trials. WE CLAIM: 1. A process of manufacturing high hot strength and oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite, pitch and metal powder) of specified quality as indicated below are used. Magnesia. MgO : 85-99.9% Bulk density : 3-4 g, cm3 Graphite. Fixed carbon : 80 to 99% Ash : 1 to 20 % Pitch: Softening point : 80 to 130°C Coking index : 40-55% Aluminium powder: Al : 95- 99.8% and where in the following steps are followed: a. Magnesia of specified grain size distribution is mixed with 2-15% by weight of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of aluminium powder to obtain a through blend; b. a hot mix is prepared from then above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as required to form magnesia carbon bricks. 2. A process as claimed in claim 1, wherein, the coarse fractions of magnesia (5- 8mm, 3-5mm, 1.6-3mm, 0.5-1. 5mm) are heated to the temperature in the range of 120-250 °C and mixed with 15% by weight of molten liquid pitch in a hot mixer for a time period up to 20 ninutes, then, part of the fine fractions (less than 0.5mm) of magnesia and graphite are charged into the mixer and mixing is done for a time period of up to 3 ) minutes., then, rest of the fine fractions (less than 0.5mm) of magnesia and aluminium powder are charged into the mixer and mixing is done for a time period of up to 30 minutes; and finally, an amount of 1- 5% by weight of molten liquid pitch is added into the mixer and further mixing is done for a time period of up to 20 minutes. 3. A process as claimed in claim I and 2, wherein, the magnesia carbon bricks thus produced is tempered (heat treated) in a kiln for a time period of (10-72 hrs.) at temperature of (50-350 °C) regime to get tempered in pitch blended magnesia carbon bricks having high hot strength and oxidation resistance. 4. A process as claimed in claim 1, 2 and 3, wherein, the magnesia has the following characteristics: MgO : 85-99.9% CaO :0.1-4% SiO2 :0.0-1-4% Al2O3 :0.01-4% Fe2O3 :0.01-5% B2O3 .0-0.1% Bulk density . 3-4g/cm3 Crystal size : 50 to 600 microns 5. A process as claimed in claim 1to 4, wherein, the graphite used has the following characteristics: Fixed carbon : 80-99% Ash : 1 to 204% Size : 0-1 mm 6. A process as claimed in claim 1to 5, wherein, the pitch used has the following characteristics: Softening point : 80 to 130°C Benzene insoluble : 15-30% Quinolene insoluble : 5-20% Coking index : 40-55% 7. A process as claimed in claim 1, 2 and 3, wherein, the aluminium powder used has the following charactei istics. Al : 95 to 99.8% Size : 0-0.5 mm 8. A process of manufacturing high hot strength and oxidation resistance magnesia carbon substantially as herein described with reference to the examples. The present invention relates to a process of manufacturing high hot strength and oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite, pitch and metal powder) of specified quality are used as Magnesia (MgO :85-99.9%; Bulk density : 3-4 g/ cm3); Graphite (Fixed carbon: 80 to 99%; Ash: 1 to 20 %); Pitch (Softening point: 80 to 130°C; Coking index: 40-55%); Aluminium powder (Al: 95 to 99.8%) and where in the Magnesia of specified grain size distribution is mixed with 2- 15% by weight of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of aluminium powder to obtain a through blend; and a hot mix is prepared from then above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as . required to form magnesia carbon bricks.

Full Text

FIELD OF THE INVENTION
This invention relates to a process of manufacturing tempered pitch bonded
magnesia carbon refractories with additive for high hot strength and oxidation resistance.
BACKGROUND OF THE EVVENTTON AND PRIOR ART AND DRAWBACKS
Pitch bonded magnesia carbon bricks are being manufactured in captive brick
plant, and used in converters.
But in converter, erosion of bricks do not occur uniformly due to difference in
operating conditions in different zones of the vessel. In trunion area, slag attack is the
predominant factor for erosion. In charge pad, impact of scrap is an additional factor for
higher erosion. In tap hole area, abrasion of liquid steel during tapping is an important
factor for erosion of lining. Similarly, conditions are different in bottom and top cone
area of the converter. In order to improve lining life and to achieve uniform wear profile,
different qualities of bricks are used in converter in advanced countries.
OBJECT OF THE INVENTION
It is a primary object of the invention to propose a method for the preparation of
high hot strength and oxidation resistant magnesia carbon bricks.
It is another object to use addition of aluminium metal powder as minor additive.
It is further object to propose a method of manufacturing such bricks in which hot
strength (HMOR- Hot Modulus of Rupture) and oxidation resistance of the developed
aluminium powder containing pitch bonded magnesia carbon bricks are much higher than
normal pitch bonded magnesia carbon bricks.
These and other objects will be apparent from the following paragraphs.
BRIEF DETAILS OF MANUFACTURING
According to this invention, there is proposed a process of manufacturing high hot
strength and oxidation resistance magnesia carbon in which input raw materials
(magnesia, graphite, pitch and metal powder) of specified quality as indicated below are
used:

Magnesia:
MgO : 85-99.9%
Bulk density : 3-4 g/ cm3
Graphite:
Fixed carbon . 80 to 99%
Ash : 1 to 20 %
Pitch:
Softening point . 80 to 130°C
Coking index : 40-5 5%
Aluminium powder:
Al .95 to 99.8%
And where in the following steps are followed.
a. Magnesia of specified grain size distribution is mixed with 2-15% by weight of
graphite, 2-8% by weight of molten, pitch and 0.5-5% by weight of aluminium
powder to obtain a through blend,
b. A hot mix is prepared from then above blend in a mixer at a temperature in the
range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the range
of 50-140 °C and pressed in hydraulic or other type of press at a pressure in the
range of 500-2500 kg/cm2 with de-airing as required to form magnesia carbon
bricks.
The process has the following salient features:
1. Coarse fractions of magnesia (5-8mm, 3-5mm, 1.6-3mm, 0.5-1.6mm) are
heated to the temperature in the range of 120-250°C and mixed with 1-5% by
weight of molten liquid pitch in a hot mixer for a time period up to 20
minutes;

2. then, part of the fine fractions (less than 0.5mm) of magnesia and graphite are
charged into the mixer and mixing is done for a time period of up to 30
minutes;
3. then, rest of the fine fractions of magnesia and aluminium powder are charged
into the mixer and mixing is done for a time period of up to 30 minutes;
4. then, an amount of 1-5% by weight of molten liquid pitch is added into the
mixer and further mixing is done for a time period of up to 20 minutes.
The Magnesia carbon bricks thus produced is tempered (heat treated) in a kiln for a time
period of (10-72 hrs.) at temperature of (50-350 °C) regime to get tempered in pitch
blended magnesia carbon bricks having high hot strength and oxidation resistance.
The magnesia has the following characteristics:
MgO : 85-99.9%
CaO : 0.1-4%
SiO2 :0.01-4%
A12O3 :0.01-4%
Fe2O3 :0.01-5%
B2O3 :0-0.1%
Bulk density : 3-4g/on3
Crystal size : 50 to C00 micronis
The graphite used has the following characteristics:
Fixed carbon : 80-99%
Ash :lto2(4%
Size : 0-1 nun
The pitch used has the following characteristics:
Softening point : 80 to 130°C
Benzene insoluble : 15-30%
Quinolene insoluble : 5-20%
Coking index : 40-55%

The aluminium powder used has the lollowing characteristics:
Al : 95 to 99.8%
Size : 0-0.5 mm
Comparision and Performance. Characteristics and Verification of Properties
Comparative properties with and without addition of particular amount of aluminium
powder are given below:

Advantages of the Invention:
Hot strength and oxidation res stance of the developed aluminium powder containing
pitch bonded magnesia carbon bricks are much higher than normal pitch bonded
magnesia carbon bricks. Average hot strength and oxidation resistance at 1400 °C (30
minutes) is 1.5 to 2 times higher than the normal pitch bonded magnesia carbon bricks.
Zonal lining with the developed bricks in charge pad and other qualities in other areas has
resulted higher lining life of 1054 heats, as compared to 829 and 809 heats for earlier
campaigns in 150T BOF of RSP during testing and trials.

WE CLAIM:
1. A process of manufacturing high hot strength and oxidation resistance magnesia
carbon in which input raw materials (magnesia, graphite, pitch and metal powder)
of specified quality as indicated below are used.
Magnesia.
MgO : 85-99.9%
Bulk density : 3-4 g, cm3
Graphite.
Fixed carbon : 80 to 99%
Ash : 1 to 20 %
Pitch:
Softening point : 80 to 130°C
Coking index : 40-55%
Aluminium powder:
Al : 95- 99.8%
and where in the following steps are followed:
a. Magnesia of specified grain size distribution is mixed with 2-15% by weight
of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of
aluminium powder to obtain a through blend;
b. a hot mix is prepared from then above blend in a mixer at a temperature in the
range of 70-150 °C, thereafter the hot mix is cooled to a temperature in the
range of 50-140 °C and pressed in hydraulic or other type of press at a
pressure in the range of 500-2500 kg/cm2 with de-airing as required to form
magnesia carbon bricks.

2. A process as claimed in claim 1, wherein, the coarse fractions of magnesia (5-
8mm, 3-5mm, 1.6-3mm, 0.5-1. 5mm) are heated to the temperature in the range of
120-250 °C and mixed with 15% by weight of molten liquid pitch in a hot mixer
for a time period up to 20 ninutes, then, part of the fine fractions (less than
0.5mm) of magnesia and graphite are charged into the mixer and mixing is done
for a time period of up to 3 ) minutes., then, rest of the fine fractions (less than
0.5mm) of magnesia and aluminium powder are charged into the mixer and
mixing is done for a time period of up to 30 minutes; and finally, an amount of 1-
5% by weight of molten liquid pitch is added into the mixer and further mixing is
done for a time period of up to 20 minutes.
3. A process as claimed in claim I and 2, wherein, the magnesia carbon bricks thus
produced is tempered (heat treated) in a kiln for a time period of (10-72 hrs.) at
temperature of (50-350 °C) regime to get tempered in pitch blended magnesia
carbon bricks having high hot strength and oxidation resistance.
4. A process as claimed in claim 1, 2 and 3, wherein, the magnesia has the following
characteristics:
MgO : 85-99.9%
CaO :0.1-4%
SiO2 :0.0-1-4%
Al2O3 :0.01-4%
Fe2O3 :0.01-5%
B2O3 .0-0.1%
Bulk density . 3-4g/cm3
Crystal size : 50 to 600 microns
5. A process as claimed in claim 1to 4, wherein, the graphite used has the following
characteristics:
Fixed carbon : 80-99%
Ash : 1 to 204%

Size : 0-1 mm
6. A process as claimed in claim 1to 5, wherein, the pitch used has the following
characteristics:
Softening point : 80 to 130°C
Benzene insoluble : 15-30%
Quinolene insoluble : 5-20%
Coking index : 40-55%
7. A process as claimed in claim 1, 2 and 3, wherein, the aluminium powder used
has the following charactei istics.
Al : 95 to 99.8%
Size : 0-0.5 mm
8. A process of manufacturing high hot strength and oxidation resistance magnesia
carbon substantially as herein described with reference to the examples.

The present invention relates to a process of manufacturing high hot strength and
oxidation resistance magnesia carbon in which input raw materials (magnesia, graphite,
pitch and metal powder) of specified quality are used as Magnesia (MgO :85-99.9%;
Bulk density : 3-4 g/ cm3); Graphite (Fixed carbon: 80 to 99%; Ash: 1 to 20 %); Pitch
(Softening point: 80 to 130°C; Coking index: 40-55%); Aluminium powder (Al: 95 to
99.8%) and where in the Magnesia of specified grain size distribution is mixed with 2-
15% by weight of graphite, 2-8% by weight of molten pitch and 0.5-5% by weight of
aluminium powder to obtain a through blend; and a hot mix is prepared from then
above blend in a mixer at a temperature in the range of 70-150 °C, thereafter the hot
mix is cooled to a temperature in the range of 50-140 °C and pressed in hydraulic or
other type of press at a pressure in the range of 500-2500 kg/cm2 with de-airing as .
required to form magnesia carbon bricks.

Documents:

610-cal-2002-granted-abstract.pdf

610-cal-2002-granted-claims.pdf

610-cal-2002-granted-correspondence.pdf

610-cal-2002-granted-description (complete).pdf

610-cal-2002-granted-examination report.pdf

610-cal-2002-granted-form 1.pdf

610-cal-2002-granted-form 13.pdf

610-cal-2002-granted-form 18.pdf

610-cal-2002-granted-form 2.pdf

610-cal-2002-granted-form 26.pdf

610-cal-2002-granted-form 3.pdf

610-cal-2002-granted-reply to examination report.pdf

610-cal-2002-granted-specification.pdf

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Patent Number

231433

Indian Patent Application Number

610/CAL/2002

PG Journal Number

10/2009

Publication Date

06-Mar-2009

Grant Date

04-Mar-2009

Date of Filing

24-Oct-2002

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA, RANCHI

Inventors:

#	Inventor's Name	Inventor's Address
1	NANDY SANDIP KUMAR	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
2	BARUA PULAK	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
3	CHINTAIAH PURIMETLA	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
4	GARAI SWAPAN KUMAR	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
5	CHAKRABORTI DEBI PRASAD	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
6	GHOSH NIRMAL KANTI	RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002

PCT International Classification Number

C04B 35/01

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA