INTRODUCTION TO THE FIELD OF THE INVENTION.
This invention relates to Improvements in or Relating to Porous Plug.
PRIOR ART AND DRAWBACK.
Porous plugs are used in Steel Plants for purging inert gases like Argon and Nitrogen. Purging is required for the following:-
Uniform temperature in the melt. Uniform mixing of alloy addition. Presently , many Plants are using random porosity porous plugs.
The life obtained is 400-700 minutes of purging. In order to get life of + 1000 minutes of purging, a special type of product was developed.
It is very important to achieve uniform temperature in the melt as well as uniform mixing of the components, when alloying elements are added to a melt to achieve the critical properties. It is thus imperative that proper and effective distribution of the alloying elements are ensured in the melt so that the end product exhibits the required standard properties.
It is also important to have a gas distribution plug which would not only ensure such an effective distribution of the gases (which ensures proper mixing) but also lasts for a longer time to make the process economical.

OBJECTS OF THE INVENTION
It is an object of this invention to propose a Porous Plug, which will effect improved purging of gas into the melt.
It is another object of this invention to propose such an improved plug, which will last for a longer time and can be used effectively
It is further object of this invention to propose such an improved plug, which will be unique in construction
It is a still further object of this invention to propose such an improved plug, which can be easily used
These and other object of the invention are briefly stated herein below
BRIEF DETAILS OF MANUFACTURE.
In preparing the new plug we have designed the core unit of the plug in two parts These are
surrounded by an overlapping outer unit The upper part of the core unit is again made of a plurality of independent sub units, which are assembled together to form the upper inner core unit. Each such sub-unit is provided with a longitudinal slot sufficient enough to distribute the purging gas from the hollow interior It can be of convenient length and shape
The lower sub-unit is made as usual of porous plug. There is gas continuity passage from the lower unit to the upper unit
The inner core unit is accommodated with an outer unit of steel material of conical shape
According to this invention there is provided an improved Porous Plug having directional porosity comprising (1) a first part made predominantly of high grade alumina refractory having 85 to 95% by weight of AI2O3, the balance being made of additive Oxides like SiO2, Cr2O3, Fe2O3, (2) a second part made predominantly of high grade Magnesia having 90% to 98% by weight of MgO, the balancve being made of additive Oxides like SiO2, FE2O3 & AI2O3 the first and the second
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parts being assembled within a metallic plug cover, the said first pat forming the top of the assembly and arranged in co-axial manner over the bottom second part the top part having a plurality of gas purging slots while the bottom part has a gas flow means and is in flow communication with the slots in the top part
The top part is made of a number of similar units each having a slot provision so that when these plurality of parts are assembled together these from then plurality of slots and the second part forming the bottom part is a porous body and the metalling casing is a steel hollow body having a gas inlet tube at the bottom
The range of AI2O3 is preferably 8 to 92 of by Wt Part-1 and the amount of Fe2O3 in part -1 is 0,2 to 1 0 1 Cr2O3 is 2 to 10% and SiO2 is 2 to 10% based on the weight of part -1.
The grain size of AI2O3 is 1-2 mm that of SiO2 and Cr2O3 ts 2-10 mm
The range of Mgo is preferably 95-97 of part 2 and the amount of AI2O3 is 0 2 to 1 0% by wt And those of SiO2 and Fe2O3 are 0 05 to 1 0% each by wt. of part 2
The grain size of MgO 0 09 mm that of AI2O3 is 1-2 mm that of SiO2 is 0 5 to 1 mm and that of Fe2O3 is 2 to 0 5 mm
There is also provided a method for the manufacture of a porous plug as claimed in claims 1 to 10 wherein the major component is mixed with a conventional binder and water thoroughly to prepare a mix of necessary consistency whereafter required amount of additives are added mixed thoroughly, followed by subjecting the blend to a pressure of 1000-1600 Kg/cm thereafter drying the pressed compact at temperature upto 150 c and firing at higher temperature.
The part 1 component is prepared by pressing the wet mixture from the top while the part 2 is prepared by pressing both from the top and bottom of the mould and is prepared by filing at temperature of 1500-1600 C
The part 2 is prepared by firing at temperature of 1500-1750 C.
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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
In an experimental design we prepared an improved porous plug as shown in the accompanying drawings of the Provisional Specification, wherein Figure 1 shows a partly open section of the improved plug.
DETAILED DESCRIPTON OF THE DRAWINGS
The plug 1 has an outer unit 2 housing within its hollow region, a two component inner unit made of an upper inner unit 3 and a lower inner unit 4.
We prepared the upper inner unit from a plurality of independent parts. For the sake of experimental evaluation we prepared four independent parts 3a, 3b, 3c and 3d each having an opening of sufficient mm width and length rectangular openings. The four parts are surrounded by a high grade castable refractory unit 2.
The lower unit is the random porosity with circular dimension having a length for the withdrawal of
the plug from use.
Both the upper part and the lower part are assembled together to form a porous plug
The plug was designed to have two parts The one having a length, which is considered for use and the bottom, one as safety device which when exposed is taken out from use.
For evaluation purposes we made the upper part using high grade Alumina refractories (88-92% AI2O3), while the lower part was made using grade Magnesia (95-97 MgO) refractories forming the major component while silica was the minor component. Sufficient quantities were used to achieve the necessary Apparent porosity percentage (AP) and Bending Density (BD).
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The properties of the plug is given below

Part-1 Part-2
88-92 -
- 95-97
2-4 0 1-0.5
20-22 22-30
2.90-3 00 2 60-2 70
AI2O3 (%)
MgO (%)
SiO2 (%)
A P (%)
B D (gm/cc)
Gas flow rate of assembled
Plug at 0.4 Kg/cm2. = 40-80 Ltrs./min.
The following are important to note -
1. The assembled plug is of two parts core unit and a single outer steel casing.
2. The slotted units are pressed separately These independent units are essential inside
the casing unit
3 Slots are there in one side of the individual units When four units are assembled to form one body, the slotted channels are formed
4. The purging gas is introduced to the plug through the steel pipe provided at the bottom of the steel casing.
5 The slots are because of combination of 4 (four) slits and are in vertical plane.
6 Process of manufacture
Part - 1 Batching/Mixing - Pressing - Drying -Firing - Testing - Assembling 4 slots by Motor to make Part - 1
Part - 2: Batching/Mixing - Pressing - Drying -Firing - Testing.

Then fixing part 1 & 2 inside the steel casting, welded with the bottom portion with steel pipe
7 It will not be possible to visualize anything by seeing the assembled plug. Therefore, we are not sending any sample. However, we feel, from the details stated above will clarify the requirements.
ADDITIONAL DETAILS OF MANUFACTURE.
Part-1 Part - II
1. Amount of starting material 50Kgs Batch 300 Kgs. Batch
2. Composition
AI2O3 % 85-95 02-1 0
SiO2% 2-10 0.05-1.5
Cr2O3 % 2-10 -
Fe2O3 % 0 2-1 0 0.05 -1 0
MoO% 90-98
3. Grain Size (mm) (1 -2), (0.5-1) (1 -2), (0.5-1)
(0 2-0.5), 0 09 (0.2-0 5), 0.09
4 Mixing details: Coarse (> 0 2 mm) same as Part 1
+ Binder + water
Mixing (5-10) mnts.
Additives
Mixing (20-30) mnts
5. Pressing pressure 1000 - 1600 Kg/cm2 1000 -1600 Kg/cm2
6. Mode of pressing From top both top & bottom 'pressing
7. Temperature of drying 70 -150°C 70 -150°C
8 Firing Temperature 1500-1600°C 1600-1750°C
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We Claim
1 An improved Porous Plug having directional porosity comprising (1) a first part made predominantly of high grade alumina refractory having 85 to 95% by weight of AI2O3, the balance being made of additive oxides like SiO2, Cr2O3, Fe2O3, (2) a second part made predominantly of high grade Magnesia having 90 to 98% by wt of MgO, the balance being made of additive oxides like SiO2, Fe2O3 & AI2O3 the first and the second parts being assembled within a metallic plug cover, the said first part forming the top of the assembly and arranged in co-axial manner over the bottom second part the top part having a plurality of gas purging slots while the bottom part has a gas flow means and is in flow communication with the slots in the top part
2. An improved porous plug as claimed in Claim 1 wherein the top part is made of a number
of similar units each having a slot provision so that when these plurality of parts are
assembled together these form then plurality of slots.
3. An improved porous plug as claimed in claims 1 and 2 wherein the second part, forming
the bottom part is a porous body.

4 An improved porous plug as claimed in claims 1 to 3 wherein the metalling casing is a
steel hollow body having a gas inlet tube at the bottom.
5 An improved porous plug as Claimed in Claim 1 wherein the range of AI2O3 is preferably
88 to 92 of by wt. part -1.
6. An improved porous plug as claimed in Claim 5 wherein the amount of Fe2O3 in part 1 is 0 2 to 1.0.1 Cr2O3 is 2 to 10% and SiO2 is 2 to 10% based on the weight of part - 1
7 An improved porous plug as claimed in Claim 6 wherein the grain size of AI2O3 is 1-2 mm that of SiO2 and Cr2O3 is 2-10 mm
8. An improved porous plug as claimed in Claim 1 wherein the range of MgO is preferably 95-97 of part 2.
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9 An improved porous plug as claimed in Claim 8 wherein the amount of AI2O3 is 0 2 to 1.0% by wt And those of SiO2 and Fe2O3 are 0 05 to 1.0% each by wt of part 2.
10. An improved porous plug as claimed in claims 8 and 9 wherein the grain size of MgO
0 09 mm that of AI2O3 is 1-2 mm that of SiO2 is 0 5 to 1 mm and that of Fe2O3 is 0 2 to
0.5 mm
11. A method for the manufacture of a porous plug as claimed in claims 1 to 10 wherein the
major component is mixed with a conventional binder and water thoroughly to prepare a
mix of necessary consistency, whereafter required amount of additives are added mixed
thoroughly, followed by subjecting the blend to a pressure of 1000-1600 Kg/cm thereafter
drying the pressed compact at temperature upto 150 °C and firing at higher temperature
12. A method as claimed in Claim 11 wherein the part 1 component is prepared by pressing
the wet mixture from the top while the part 2 is prepared by pressing both from the top
and bottom of the mould
13 A method as claimed in claims 11 and 12 wherein part 1 is prepared by filing at
temperature of 1500 -1600 °C
14. A method as claimed in claims 11 and 12 wherein part 2 is prepared by firing at
temperature of 1500 -1750°C.
15. A porous plug substantially as herein described with reference to the accompanying
drawings.
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16 A method of preparing a porous plug substantially as herein described
There is provided an improved Porous Plug having directional porosity comprising (1) a first part made predominantly of high grade alumina refractory having 85 to 95% by weight of AI2O3, the balance being made of additive oxides tike SiO2, Cr2O3, Fe2O3, (2) a second part made predominantly of high grade Magnesia having 90 to 98% by wt. of MgO, the balance being made of additive oxides like SiO2, Fe2O3 & AI2O3 the first and the second parts being assembled within a metallic plug cover, the said first part forming the top of the assembly and arranged in co-axial manner over the bottom second part the top part having a plurality of gas purging slots while the bottom part has a gas flow means and is in flow communication with the slots in the top part.