Claims:CLAIMS:
1. A modified heat shield for use in Vacuum Arc Refining comprising of :-
a material addition / pouring hole in the shape of cylindrical base and conical top;
a bend plate fixed at the boundary of the heat shield near to the circumference of the said hole; and
the top surface of the heat shield is made tapered towards the circumference of the hole.

2. A modified heat shield for use in Vacuum Arc Refining as claimed in claim 1, wherein the plate is of 2.5 feet long & 100 mm height.

3. A modified heat shield for use in Vacuum Arc Refining as claimed in claim 1, wherein the top surface of the heat shield is configured to minimize the spill of ferro-alloy and top jam of the ladle and further minimizes the damage to the metallic addition chute.
4. A modified heat shield for use in Vacuum Arc Refining as claimed in claim 1, wherein the pouring hole dimensions are as:
Bottom cylindrical dia – 32 cm
Conical Top dia – 56 cm
Total height of the modified addition hole – 46 cm

5. A modified heat shield for use in Vacuum Arc Refining as claimed in claim 1, wherein the dimension of the taper of the conical Performa is equal to 600 from the base of the heat shield.
Dated: this day of August, 2016
(N. K. Gupta)
Patent Agent,
Of NICHE,
To, For SAIL
The Controller of Patents,
The Patent Office, Kolkata.
, Description:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(Section 10 and rule 13)

TITLE

MODIFIED HEAT SHIELD FOR USE IN VACUUM ARC REFINING

APPLICANT
STEEL AUTHORITY OF INDIA LIMITED,
A GOVT. OF INDIA ENTERPRISE,
ROURKELA STEEL PLANT,
ROURKELA – 769011,
ORISSA, INDIA

The following specification particularly describes the nature of the
invention and the manner in which it is to be performed

MODIFIED HEAT SHIELD FOR USE IN VACUUM ARC REFINING

FIELD OF THE INVENTION
The present invention relates to modified heat shield for minimization of Spillage of Ferro alloys & Damage of Addition chute in Vacuum Arc Refining. More particularly, the present invention relates to modified heat shield is designed, having cylindrical bottom with conical top configured to prevent the spillage of Ferro alloys during casting.

BACKGROUND OF THE INVENTION

It is known to utilize furnaces for casting metal wherein a mold is placed within the furnace and molten metal is poured into the mold. After a specified heating time at specific temperatures, the mold is then moved from the heating zone of the furnace into a zone wherein the metal within the mold is cooled and solidified. The precise heating temperatures in conjunction with heating rates and cooling rates enable the casting of a metal, such as a super alloy, having a specific oriented metallic structure.

French Pat. No. A 2,604,378 describes a heat shield in conjunction with such a furnace wherein the heat shield is mounted between the heating and cooling zones of the furnace to prevent the heat exchange there between. The heat shield in this invention performs the heat insulation function, but at the same time allows the mold to pass between the heating zone and the cooling zone.

U.S. Pat. No. 3,714,977 to Terkelsen illustrates a casting furnace having a heat shield wherein a mold is moved between a heating zone and a cooling zone. The heat shield in Terkelsen is attached to the mold mounting device such that it surrounds the mold.
The known devices do not provide any protection in regard with spill of valuable ferro-alloys between the heating and cooling zones in those instances wherein the geometry of mold is complex. Since inception of VAR unit Ferro alloy addition hole in VAR heat shield was in cylindrical shape, with outwards slope. This hole is just under the metallic addition chute. When ladle top is perfectly clean, it was not a problem for addition of Ferro alloy in the ladle during processing of heats. With due passage, of time lot of modifications were done by increasing the ladle height to accommodate the increased volume of production. After installation of CCM-I, all the heats are to be processed through secondary steel and all special quality steel are to be processed through VAR. So it is not possible to maintain ladle top clean all the time. With slight ladle top jam, VAR heat shield not sitting in perfect horizontal position. So there is a mismatch of metallic addition chute with VAR heat shield hole. Due to this mismatch, various problems often encountered are as furnished point wise:
1. Addition chute bend was frequent.
2. Ferro alloy spillage inside the tank. (About 2.50Ton of Si-Mn, 2.0Ton of Fe-Si & 1.5Ton of Al along with Lime & CP Coke per month)
3. For spillage of Ferro alloy, slag and ladle jam inside the tank, cleaning was done at least once in a week.
4. Sometimes the addition chute gets damaged while in operation.
5. For chute repair, VAR is taken shut down by mechanical section for avg. 6 hrs at least 6-7 times in a month.
6. Heat processing time increases due to chute jamming.
7. Chute jam causes interruption in smooth processing of heat & heat matching.
8. Chute jam creates more operational problems like sequence mismatching, improper chemistry & low temperature heat finish.
9. It was also unsafe to poke the chute jammed material by a bend pipe during heat processing.
10. Due to damaged addition chute & spilled ferro-alloys, extra manpower required for tank cleaning.
11. During frequent tank cleaning, the refractory lining of the tank gets damaged, thus increasing refractory consumption.
12. Tank cleaning for spilled Ferro-alloys creates lot of dust causing enormous environmental pollution.

SUMMARY OF INVENTION

The invention relates to provide a better cost-efficient means of minimization of Spillage of Ferro alloys & Damage of Addition chute in Vacuum Arc Refining. Studies, shows that the heat shield having cylindrical hole was main cause for damage of addition chute as well as spillage of costly Ferro-alloys. To avoid these problems, an innovative heat shield is designed, having cylindrical bottom with conical top. A long bend plate welded to frame and then the heat shield castable material is casted, slopping towards inner side of material addition hole. This adjusted the top jam of the ladle to large extent & minimized the damage to the metallic addition chute and solved the spillage of Ferro alloy.

Therefore such as herein described, there is provided a modified heat shield for use in Vacuum Arc Refining comprising of a material addition/pouring hole in the shape of cylindrical base and conical top; a bend plate fixed at the boundary of the heat shield near to the circumference of the said hole; and the top surface of the heat shield is made tapered towards the circumference of the hole.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 illustrates a pictorial representation of the old cylindrical shape chute as prior art;
Fig. 2 illustrates schematic line diagram of old cylindrical shape chute as prior art;
Fig. 3 illustrates a pictorial representation of first modification to the cast in accordance with the present invention;
Fig. 4 illustrates a pictorial representation of second modification to the cast in accordance with the present invention;
Fig. 5 illustrates schematic line diagram of modified cylindrical shape chute in accordance with the present invention.

DETAILED DESCRIPTION

In order to minimize the spillage Minimization of Spillage of Ferro alloys & Damage of Addition chute in Vacuum Arc Refining, the prior known heat shield is modified and re-designed. The heat shield having cylindrical hole was main cause for damage of addition chute as well as spillage of costly ferro-alloys. The prior known cylindrical material-addition/pouring hole is replaced / modified by a hole with cylindrical bottom and conical top. In addition a long bend plate is welded to frame and then the heat shield castable material is casted, slopping towards inner side of material addition hole. The modification in design has adjusted the top jam of the ladle to large extent & minimized the damage to the metallic addition chute and solved the spillage of Ferro alloy. Moreover, the discussed modification has also led to Manpower reduction for tank cleaning by avoiding spillage. The shut down time is reduced from 8 to 7 times per month to 1 to 2 times per month, thus avoiding the unsafe conditions to poke the chute jam material by bend pipe and also avoiding any spillage. Environment and safety has also enhanced.

The modified hole with cylindrical bottom with conical top as described herein is guarded from the near side of the heat shield with 100 mm height with 2.5 ft long bend plate, which is welded to frame and then the heat shield castable material is casted, slopping towards inner side of material addition hole. This adjusted the top jam of the ladle to large extent & minimized the damage to the metallic addition chute and solved the spillage of Ferro alloy.

Proposed modifications Implemented: -
Modification No.1: To overcome the prior art problem, first modification done on VAR heat shield. “A Conical Performa with Cylindrical Base “has been made & installed instead of previously existing cylindrical Performa during casting of heat shield as shown in Figure no. 1.
Modification No.2: Due to this modification spillage of Ferro alloy as well as damage of metallic addition chute reduced significantly. The second modification of cylindrical bottom, conical top with more slope towards outer side and extra 2.5 feet long & 100 mm height –a bend plate welded to the frame of heats shield and then the heat shield castable material casted, tapered towards the circumference of the hole i.e. inner side of material addition hole as shown in 2nd modification Fig. 4.
As an exemplary embodiment and example, the dimensions of the modified heat shield are:-
Hole Dimension & Taper dimension:-
Bottom cylindrical dia – 32 cm
Conical Top dia – 56 cm
Total height of the modified addition hole – 46 cm
Taper of the conical Performa – 600 from the base of the heat shield.

Elimination the ferroalloy spillage:

Ferro-Alloys Quantity(T)

Silico-Manganese 3.5

Ferro-Silicon 2.5

Aluminium 1.5

Cost Analysis:
Ferro-Alloys Quantity(T) Rate(Rs/T) Saving

Silico-Manganese 3.5 63,750 26,77,500
Ferro-Silicon 2.5 80, 300 27,21,600

Aluminium 1.5 57, 040 36,96,000

Elimination of contract labor cost:-
Average contract labours required for tank cleaning per week 4

One contract labor charge Rs 353/-

Average frequency tank cleaning in a week 1

Before modification frequency tank cleaning in a year 52

After modification frequency tank cleaning in a year 12

No of weeks saved in a year 52-12= 40

Cost of saving incurred 40X4X353 = Rs 56,480 /-.

Reduction in refractory lining consumption
No of bricks required on an average required for lining 150
Cost of one brick Rs 6
So the cost incurred 150X6X40 =Rs 36,000/-
TOTAL SAVINGS
ITEMS SAVINGS
Saving due to Silico-Manganese Rs 26,77,500/-.

Saving due to Ferro-Silicon Rs 27,21,600/-.

Saving due to Aluminium Rs 36,96,000/-.

Saving due to contract labor Rs 56,480 /-.

Saving due to refractory lining Rs 36,000/-

Total Savings Rs 91, 87,580.00/-

Intangible Benefits:-
• Manpower reduced for tank cleaning by avoiding spillage.
• Shut down time reduced from8 to 7 times per month to 1 to 2 times per month.
• Avoiding the unsafe conditions to poke the chute jam material by bend pipe.
• Avoiding the spillage, the house keeping become has significantly improved.
• Environment and safety enhanced.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.