Title of Invention	"A DEVICE FOR REDUCING CURVATURE FORMED IN HOT-ROLLED STEEL PLATES COOLED IN STACKS ON COOLING BEDS IN STEEL PLANTS"
Abstract	A device made in the form of a cover of rectangular cross section of preferred dimensions 12.5 m in length, 4.0 a in width and 1.0 m in depth, with 6.0 mm thick mild steel sheets (1) supported on beams (4, 5, 8) disposed along the length and width of the top horizontal surface and the four vertical sides thereof, and also on angles disposed diagonally one each in the areas supported on adjacent pairs of beams disposed along the length and width of the said horizontal surface and vertical sides, accessories (7) being fitted on said horizontal surface disposed one each at the crossings of said beams for lifting the device by a finger type crane and the imer surface of the device being provided with lining (2) of heat insulation materials.

Title of Invention

"A DEVICE FOR REDUCING CURVATURE FORMED IN HOT-ROLLED STEEL PLATES COOLED IN STACKS ON COOLING BEDS IN STEEL PLANTS"

Abstract

A device made in the form of a cover of rectangular cross section of preferred dimensions 12.5 m in length, 4.0 a in width and 1.0 m in depth, with 6.0 mm thick mild steel sheets (1) supported on beams (4, 5, 8) disposed along the length and width of the top horizontal surface and the four vertical sides thereof, and also on angles disposed diagonally one each in the areas supported on adjacent pairs of beams disposed along the length and width of the said horizontal surface and vertical sides, accessories (7) being fitted on said horizontal surface disposed one each at the crossings of said beams for lifting the device by a finger type crane and the imer surface of the device being provided with lining (2) of heat insulation materials.

Full Text	The present invention relates to a device for reducing curvature formed in hot-rolled steel plates cooled in stacks on cooling beds in steel plants. The invention relates more particularly to a cover made of mild steel plates supported with mild steel angles and beams at intervals, the internal surface of the cover being lined with heat insulating materials and the cover being of dimensions suitable for enclosing the hot steel plates of relatively large dimentions stacked on air cooling beds located neap the roughing stands in steel plants. In the existing practice the hot steel plates at a temperature of 900-950°C are stacked on the cooling beds and are allowed to cool in natural air. In view of the relatively large dimensions and heavy weight i.e. 6-8 tonne of each plate, only 4-5 plates are normally piled in each stack so that the stack is not too heavy to be handled by means of a finger type lift of weight carrying capacity upto 45 tonne. The stacks placed on the cooling beds being exposed to natural air during their cooling, the plates lying at the top of the stacks cool at a faster rate while those lying below the top plate cool at a slower rate. For example, the temperature of the plates lying at the top of the stacks may be lowered within half an hour of cooling from an initial 900-950°C to 650-700°C and that of the plates lying below the top plate drops only marginally during the same period of cooling. Because of the non-uniform rates of cooling of the plates in a stack in the existing method of cooling, the flat surface of the plates lying at the tops of the stacks cumbers readily to take a wavy form of varying amplitude and wavelength leading to their down-grading/rejection or re-flattening by means of capital intensive hydraulic press of adequately large dimensions and pressing capacity. Moreover the mechanical properties of the plates cooled in the existing method may deteriorate and their hydrogen content may increase because of their cooling at a non-uniform rate. The object of the present invention is to provide a device in the form of a cover having an internal lining of heat insulating material of appropriate thickness for enclosing the stacks of hot steel plates during their cooling on the cooling beds and thereby controlling the cooling rate of all the plates in the stacks to be more or less uniform and thus preventing the formation of excessive curvature of the flat surface of the plates lying at the top of the stacks. Another object is to provide a device for retaining the mechanical properties of the cooled hot plates unaffected during cooling. Yet another object is to provide a device for improving the ultrasonic soundness of the cooled plates by reducing the hydrogen content thereof. The invention is described fully and particularly with reference to the accompanying drawings in which - Figure 1 is a view of the horizontal section of the device; and Figure 2 is a sectional end view of the device. The device is made in the form of a cover of rectangular cross section and preferred dimensions 12.5 m in length, 4.0 m in width and 1.0 m in depth, to make the same suitable for enclosing stacks of steel plates of various dimensions produced in the steel plants. The device is made of mild steel sheet (1) of preferred thickness 6.0 mm, supported on tv/o pairs of beams (4, 5) disposed along the length, the separation between the beams of each pair being 1.0 m, and on thirteen beams (8) disposed along the v/idth of horizontal top surface thereof and on horizontally and vertically disposed beams (not shown) on the four vertical sides thereof, the beams being of height 150/200 mm and width 75/100 mm. The areas of the mild steel sheet lying between the adjacent pairs of horizontally and transversely disposed beams on the top horizontal surface and horizontally and vertically disposed beams on the four vertical sides of the device are each further supported by means of a diagonally disposed mild steel angle (not shown) of typical dimensions 75 x 75 x 10 mm. The internal surface of the device is provided with a lining (2) of heat insulation materials like ceramic fibre wool, formed typically in three layers, each 25.0 mm thick, being held in position by means of wire mesh (3) and fittings (not shown) of stainless steel of AISI 304 grade. The accessories (7) fitted on the outside horizontal surface of the device for lifting the device by means of finger type crane, comprise typically eighteen mild steel plates each of dimentions 700 x 425 x 25 mm, disposed in two rows of nine each at the crossings of each pair of longitudinally disposed beams (4, 5) and intermediate nine of the thirteen transversely disposed beams (8), excluding two beams (8) adjacent each side of the device. The upper ends of each row of accessories (7) are supported on beams (6) disposed along the length of the device. Filed trials have been conducted using the invented device for determining the time required for cooling of the steel plates of different thickness and for optimising the thickness of the heat insulating materials used in lining (2) to maintain the cooling time of a stack of steel plates to be in the range of 6 to 10 hours for achieving the desired production rate in a steel plant. Stacks containing 4-5 steel plates of different thickness, width and length have been cooled from an initial temperature of 637-853°C to a finishing temperature 278-377°C. The cooling time required for each stack has been noted. The curvature produced in the cooled plates has been measured in terms of the amplitude in mm and number of waves formed in the cooled plates in a length of 4.0 m thereof and compared against the acceptable values specified in international standards. The test results are presented in Table I. The mechanical properties of the plates cooled with and without using the device have been determined for comparison. The test results are given in Table II. The hydrogen content of the plates cooled v/ith and without using the device has been assessed analytically. It has been found to be 4-5 ppm in plates cooled using the device and 6-7 ppm in plates cooled without using the device. From the test results obtained the following observations are made :- (a) The curvature in plates cooled using the device is well within the acceptable limits according to International standards. (b) The mechanical properties of the plates cooled using the device are more or less similar to those of the plates cooled without using the device. (c) The time for cooling the plates using the device is within the allowable range of 6 to 10 hours. (d) The hydrogen content of the plates cooled using the device is appreciably lower (4-5 ppm) in comparison v/ith the plates cooled without using the device (6-7 ppm), with expected better ultrasonic soundness of the former. Table I. Cooling Time and Curvature (Table Removed) Table II.. (Table Removed) We Claim :- 1. A device for reducing curvature formed in hot-rolled steel plates cooled in stacks on cooling beds in steel plants, characterised in that (a) the device is made in the form of a cover of rectangular cross section, of preferred dimensions 12.5 m in length, 4.0 m in width and 1.0 m in depth, with mild steel sheets (1) of thickness 6.0 mm, which is supported on a plurality of beams (4, 5, 8) disposed along the length and width of the top horizontal surface and the four vertical sides thereof, and also on a plurality of angles disposed diagonally one each in the areas thereof supported on the adjacent pairs of beams disposed along the length and width of the top horizontal surface and four vertical sides of the device; (b) plurality of accessories (7) are fitted on the top horizontal surface of the device disposed one each at the crossings of the beams (4, 5, 8) provided along the length and width thereof, for lifting the device by a finger type crane; and (c) the inner surface of the device is provided with a lining (2) of heat insulation materials, for allowing cooling of the hot-rolled steel plates in stacks in 6 to 10 hours. 2. The device as claimed in claim 1, wherein the horizontal top surface is supported on two pairs of beams (4, 5) along the length disposed at a separation of 1.0 m between the beams of each pair, and on thirteen teams (8) along the width at a separation of 1.0 m between the adjacent ones. 3. The device as claimed in any preceding claim, wherein the accessories (7) used for lifting the device are eighteen in number, disposed along the length of the top horizontal surface thereof in two rows of nine accessories each, the upper ends of each row being supported on a beam (6) disposed along the length of the top horizontal surface of the device. 4. The device as claimed in any preceding claim, wherein the lining (2) of heat insulation materials is made of ceramic fibre wool disposed in three layers, each 25.0 mm thick and held in position by means of wiremesh (3) and fittings of stainless steel of AISI 304 grade.

Full Text

The present invention relates to a device for reducing curvature formed in hot-rolled steel plates cooled in stacks on cooling beds in steel plants.
The invention relates more particularly to a cover made of mild steel plates supported with mild steel angles and beams at intervals, the internal surface of the cover being lined with heat insulating materials and the cover being of dimensions suitable for enclosing the hot steel plates of relatively large dimentions stacked on air cooling beds located neap the roughing stands in steel plants.
In the existing practice the hot steel plates at a temperature of 900-950°C are stacked on the cooling beds and are allowed to cool in natural air. In view of the relatively large dimensions and heavy weight i.e. 6-8 tonne of each plate, only 4-5 plates are normally piled in each stack so that the stack is not too heavy to be handled by means of a finger type lift of weight carrying capacity upto 45 tonne.
The stacks placed on the cooling beds being exposed to natural air during their cooling, the plates lying at the top of the stacks cool at a faster rate while those lying below the top plate cool at a slower rate. For example, the temperature of the plates lying at the top of the stacks may be lowered within half an hour of cooling from an initial 900-950°C to 650-700°C and that of the plates lying below the top plate drops only marginally during the same period of cooling. Because of the non-uniform rates of cooling of the plates in a stack in the existing method of cooling, the flat surface of
the plates lying at the tops of the stacks cumbers readily to take a wavy form of varying amplitude and wavelength leading to their down-grading/rejection or re-flattening by means of capital intensive hydraulic press of adequately large dimensions and pressing capacity.
Moreover the mechanical properties of the plates cooled in the existing method may deteriorate and their hydrogen content may increase because of their cooling at a non-uniform rate.
The object of the present invention is to provide a device in the form of a cover having an internal lining of heat insulating material of appropriate thickness for enclosing the stacks of hot steel plates during their cooling on the cooling beds and thereby controlling the cooling rate of all the plates in the stacks to be more or less uniform and thus preventing the formation of excessive curvature of the flat surface of the plates lying at the top of the stacks.
Another object is to provide a device for retaining the mechanical properties of the cooled hot plates unaffected during cooling.
Yet another object is to provide a device for improving the ultrasonic soundness of the cooled plates by reducing the hydrogen content thereof.
The invention is described fully and particularly with reference to the accompanying drawings in which -
Figure 1 is a view of the horizontal section of the device; and
Figure 2 is a sectional end view of the device.
The device is made in the form of a cover of rectangular cross section and preferred dimensions 12.5 m in length, 4.0 m in width and 1.0 m in depth, to make the same suitable for enclosing stacks of steel plates of various dimensions produced in the steel plants. The device is made of mild steel sheet (1) of preferred thickness 6.0 mm, supported on tv/o pairs of beams (4, 5) disposed along the length, the separation between the beams of each pair being 1.0 m, and on thirteen beams (8) disposed along the v/idth of horizontal top surface thereof and on horizontally and vertically disposed beams (not shown) on the four vertical sides thereof, the beams being of height 150/200 mm and width 75/100 mm. The areas of the mild steel sheet lying between the adjacent pairs of horizontally and transversely disposed beams on the top horizontal surface and horizontally and vertically disposed beams on the four vertical sides of the device are each further supported by means of a diagonally disposed mild steel angle (not shown) of typical dimensions 75 x 75 x 10 mm. The internal surface of the device is provided with a lining (2) of heat insulation materials like ceramic fibre wool, formed typically in three layers, each 25.0 mm thick, being held in position by means of wire mesh (3) and fittings (not shown) of stainless steel of AISI 304 grade. The accessories (7) fitted on the outside horizontal surface of the device for lifting the device by means of finger type crane, comprise typically eighteen mild steel plates each of dimentions 700 x 425 x 25 mm, disposed in two rows of nine each
at the crossings of each pair of longitudinally disposed beams (4, 5) and intermediate nine of the thirteen transversely disposed beams (8), excluding two beams (8) adjacent each side of the device. The upper ends of each row of accessories (7) are supported on beams (6) disposed along the length of the device.
Filed trials have been conducted using the invented device for determining the time required for cooling of the steel plates of different thickness and for optimising the thickness of the heat insulating materials used in lining (2) to maintain the cooling time of a stack of steel plates to be in the range of 6 to 10 hours for achieving the desired production rate in a steel plant.
Stacks containing 4-5 steel plates of different thickness, width and length have been cooled from an initial temperature of 637-853°C to a finishing temperature 278-377°C. The cooling time required for each stack has been noted.
The curvature produced in the cooled plates has been measured in terms of the amplitude in mm and number of waves formed in the cooled plates in a length of 4.0 m thereof and compared against the acceptable values specified in international standards. The test results are presented in Table I.
The mechanical properties of the plates cooled with and without using the device have been determined for comparison. The test results are given in Table II.
The hydrogen content of the plates cooled v/ith and without using the device has been assessed analytically. It
has been found to be 4-5 ppm in plates cooled using the device and 6-7 ppm in plates cooled without using the device. From the test results obtained the following observations are made :-
(a) The curvature in plates cooled using the device is
well within the acceptable limits according to International
standards.
(b) The mechanical properties of the plates cooled using
the device are more or less similar to those of the plates
cooled without using the device.
(c) The time for cooling the plates using the device is
within the allowable range of 6 to 10 hours.
(d) The hydrogen content of the plates cooled using the
device is appreciably lower (4-5 ppm) in comparison v/ith the
plates cooled without using the device (6-7 ppm), with expected
better ultrasonic soundness of the former.
Table I. Cooling Time and Curvature
(Table Removed)
Table II.. (Table Removed)

We Claim :-
1. A device for reducing curvature formed in hot-rolled
steel plates cooled in stacks on cooling beds in steel plants,
characterised in that (a) the device is made in the form of a
cover of rectangular cross section, of preferred dimensions
12.5 m in length, 4.0 m in width and 1.0 m in depth, with mild
steel sheets (1) of thickness 6.0 mm, which is supported on a
plurality of beams (4, 5, 8) disposed along the length and
width of the top horizontal surface and the four vertical sides
thereof, and also on a plurality of angles disposed diagonally
one each in the areas thereof supported on the adjacent pairs
of beams disposed along the length and width of the top
horizontal surface and four vertical sides of the device;
(b) plurality of accessories (7) are fitted on the top horizontal surface of the device disposed one each at the crossings of the beams (4, 5, 8) provided along the length and width thereof, for lifting the device by a finger type crane; and (c) the inner surface of the device is provided with a lining (2) of heat insulation materials, for allowing cooling of the hot-rolled steel plates in stacks in 6 to 10 hours.
2. The device as claimed in claim 1, wherein the
horizontal top surface is supported on two pairs of beams
(4, 5) along the length disposed at a separation of 1.0 m
between the beams of each pair, and on thirteen teams (8)
along the width at a separation of 1.0 m between the adjacent
ones.
3. The device as claimed in any preceding claim, wherein
the accessories (7) used for lifting the device are eighteen
in number, disposed along the length of the top horizontal surface thereof in two rows of nine accessories each, the upper ends of each row being supported on a beam (6) disposed along the length of the top horizontal surface of the device.
4. The device as claimed in any preceding claim, wherein
the lining (2) of heat insulation materials is made of ceramic
fibre wool disposed in three layers, each 25.0 mm thick and
held in position by means of wiremesh (3) and fittings of
stainless steel of AISI 304 grade.

Documents:

326-del-1998-abstract.pdf

326-del-1998-claims.pdf

326-del-1998-correspondence-others.pdf

326-del-1998-correspondence-po.pdf

326-del-1998-description (complete).pdf

326-del-1998-drawings.pdf

326-del-1998-form-1.pdf

326-del-1998-form-19.pdf

326-del-1998-form-2.pdf

326-del-1998-form-4.pdf

326-del-1998-gpa.pdf

abstract.jpg

« Previous Patent

Next Patent »

Patent Number

216102

Indian Patent Application Number

326/DEL/1998

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

07-Mar-2008

Date of Filing

09-Feb-1998

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

ISPAT BHAWAN, LODI ROAD, NEW DELHI-110003.

Inventors:

#	Inventor's Name	Inventor's Address
1	ARJUN PRASAD SINGH	R AND D CENTRE FOR IRON AND STEEL, SAIL, DORANDA, RANCHI-834 002,
2	GANTI MAHAP ATRUNI DAKSHINA	R AND D CENTRE FOR IRON AND STEEL, SAIL, DORANDA, RANCHI-834002
3	SUDHAKAR JHA	R AND D CENTRE FOR IRON AND STEEL, SAIL, DORANDA, RANCHI-834002
4	PRAMOD KUMAR PRUSTY	R AND D CENTRE FOR IRON AND STEEL, SAIL, DORANDA, RANCHI-834002

PCT International Classification Number

B21B 45/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA