Title of Invention

IMPROVED COOLING SYSTEM FOR HIGH SPEED ROTATING CIRCULAR SAW BLADES USED FOR CUTTING HOT ROLLED STOCKS

Abstract

An improved cooling system for high-speed rotating circular saw blades used for cutting hot rolled stocks, characterised in that the system comprises two water spray blocks each fitted with an array of water spray nozzles (1a) on a water pipe line (1) which are disposed one on each side of the cutting teeth (6) of saw blades (2), lying adjacent to the sawing interface (5) of hot rolled stocks (4), and extending over full length of cutting stroke traversed by the cutting teeth, said components (1, 1a, 2, 4, 5, 6) of the system being arranged to operate co-operatively in an inter-dependent manner.

Full Text

The invention relates to improved cooling system for high-speed rotating circular saw blades used for cutting hot rolled stocks. The existing cooling system for high speed circular hot saws used for cutting finished sections like joists, channels, rails, angles etc. comprises a blade of diameter in the range of 1200-1800mm rotating at a speed of about 1200rpm. There are two types of hot saws, namely, of pendulum and sliding frame type. Sliding frame type hot saws are provided with a saw blade cooling arrangement in which the location of water spray headers is such that the heat picked up by the blade teeth gets sufficient time to be transferred to its body before the cooling starts. As a result the blade teeth do not get cooled to ambient temperature and there is progressive temperature build up on the teeth in each rotation. In pendulum type hot saws, there is provision of cooling the blades during its normal position when the blade returns back after cutting stroke. The conventional system of cooling has two water spray headers provided one on each side of the blade. Water falls on the blade periphery only when the blade returns back to its normal position after completion of a sawing stroke. The temperature of the rolled stock cut by the saw blade is in the range of 750-900°C. In the course of cutting, some amount of the heat from the hot rolled stock is picked up by the blade teeth in contact at the cutting interface. In addition, heat is also generated at the interface due to friction. A pipe line is provided to supply water at a pressure of 2 Kg/cm . - 2 - The temperature of blade teeth tips at the interface rises by 150°C during cutting operation and cools in air by about 1OO°C during the remaining part of each revolution, thus causing temperature build up of 50°C each revolution in the first few cycles. After 10-15 revolutions, the teeth temperature fluctuates between 275-425°C. The increase in temperature leads to softening of the teeth and causes rounding/blunting of the tips thereof. Efficient cooling of the blade can prevent the temperature rise and consequent losses in teeth hardness and wear resistance. The conventional system is not capable of preventing heat build up on the blade teeth and hence the temperature rise thereof. The object of the invention is to provide a cooling system for the blade teeth, which is capable of reducing the heat build up therein and thereby increasing the performance life thereof. The invented cooling system is designed on the basis of heat-transfer and other technical considerations, and comprises two spray blocks each with an array of nozzles fitted underneath an apron plate one on each side of a slot through which the blade rotates. The arrays extend up to the full cutting stroke of the blade. Nozzles of the arrays are designed such that water jets are of diverged 'V' shape and form uniform cooling segment on the blade periphery. The fixing arrangement of spray blocks have been designed using brackets to facilitate easy removal and servicing thereof without dismantling the apron plate. The cooling of blade teeth starts immediately - 3 - after each tooth leaves contact with the cutting interface, thus making the cooling system highly efficient to prevent any appreciable temperature rise in the blade teeth. Thus the invention provides an improved cooling system for high-speed rotating circular saw blades used for cutting hot rolled stocks, characterised in that the system omprises two water spray blocks each fitted with an array of water spray nozzles on a water pipe line which are disposed one on each side of the cutting teeth of saw blades lying adjacent to the sawing interface of hot rolled stocks, and extending over full length of cutting stroke traversed by the cutting teeth, said components are arranged to operate co-operatively in an inter-dependent manner. The invention is described fully and particularly without restricting the scope of the invention in any manner with reference to the accompanying drawings, in which - Figure 1A is a sketch showing the front view of the conventional cooling system; Figure 1B is a sketch showing the side view of the conventional cooling system; Figure 2A is a sketch showing the front view of the invented cooling system; Figure 2B is a sketch showing the side view of the invented cooling system; Figure 3A is a sketch showing the top view of the invented cooling system; Figure 3B is a sectional view of Figure 3A; and - 4 - Figure 4 is a graphical plot showing the comparative performance of saw blades in the conventional and invented systems of cooling. Referring to Figs. 1A and 1B, one water spray header (1) with holes (1a) is mounted on each side of the rotating circular hot saw blade (2) at a position (3) which is at a distance of about one-fifth of the circular path traversed by the teeth (6) of the saw blade on completion of a sawing stroke at interface (5) of the hot rolled stock (4). The water spray headers (1) are connected to a pipe line for supplying water at a pressure of 2 kg/cm through the holes (la) in the form of sprays. Referring to Figs. 2A. and 2B, each of the two water spray blocks comprises an array of water spray nozzles (1a), numbering preferably 16, fitted on a pipe line carrying water at a pressure of 2 kg/cm , and located adjacent to the sawing interface (5) of the hot rolled stocks (4) extending over the full length of cutting stroke traversed by the cutting teeth (6) of the saw blades (2). Referring to Figs. 3A and 3B, pipeline (1) containing two arrays of water spray nozzles (1a) are fitted in brackets (9) underneath apron plate (7). A slot (8) is provided in the apron plate (7) for the passage of the teeth (6) of the saw blades (2) through the apron plate in the path (2a). The comparative performance of the conventional and the invented cooling system has been studied over a period in a steel plant using saw blades of medium carbon-manganese steel. - 5 - The performance of the saw blades has been expressed in terms of tonnage of hot rolled stocks cut. The test results, presented in Fig. 4, show that (a) new saw blades during their first use cooled in the invented system can cut 1800 tons of rolled product but when cooled in the conventional system can cut only 1000 tons of rolled product; (b) by using the saw blades for the second time after grinding, the saw blades cooled in the invented system can cut 3200 tons, but when cooled in the conventional system can cut only 1600 tons; (c) by using the saw blades for the third time after grinding, the saw blades cooled in the invented system can cut 3900 tons, but when cooled in the conventional system can cut only 2200 tons; (d) by using the saw blades for the fourth time after grinding, the saw blades cooled in the invented system can cut 4400 tons, but when cooled in the conventional system, the saw blades are worn out to such extent that these are unsuitable for use beyond the third time. Thus by using the invented system of cooling the performance of saw blades can be increased by about 100% compared with the conventional system of cooling. In addition, a significant reduction in the down-time of the rolling mill required for replacement of worn out saw blades is achieved by using the invented cooling system. . - 6 - We Claim :- 1. An improved cooling system for high-speed rotating circular saw blades used for cutting hot rolled stocks, characterised in that the system comprises two water spray blocks each fitted with an array of water spray nozzles (1a) on a water pipe line (1) which are disposed one on each side of the cutting teeth (6) of saw blades (2), lying adjacent to the sawing interface (5) of hot rolled stocks (4), and extending over full length of cutting stroke traversed by the cutting teeth, said components (1, 1a, 2, 4, 5, 6) of the system being arranged to operate co-operatively in an inter-dependent manner. 2. The system as claimed in claim 1, wherein the array of water spray nozzles in each block comprises sixteen nozzles. 3. The system as claimed in claim 1 or 2, wherein the nozzles are capable of producing water jets diverged in V shape. 4. The system as claimed in any one of the preceding claims, wherein the two arrays of water spray nozzles are fitted in brackets (9) underneath an apron plate (7). 5. The system as claimed in claim 4, wherein the apron plate is provided with a slot (8) for the passage of the teeth of saw blades therethrough. 6. An improved cooling system for high-speed rotating circular saw blades used for cutting hot rolled stocks, - 7 - substantially as herein described and illustrated in Figures 2A, 2B, 3A and 3B of the accompanying drawings. 8 - Dated this 19th day of March 1999.

Documents:

00242-cal-1999 abstract.pdf

00242-cal-1999 assignment.pdf

00242-cal-1999 claims.pdf

00242-cal-1999 correspondence.pdf

00242-cal-1999 description(complete).pdf

00242-cal-1999 drawings.pdf

00242-cal-1999 form-1.pdf

00242-cal-1999 form-2.pdf

00242-cal-1999 form-3.pdf

00242-cal-1999 form-6.pdf

00242-cal-1999 letters patent.pdf

00242-cal-1999 pa.pdf

242-cal-1999-granted-abstract.pdf

242-cal-1999-granted-acceptance publication.pdf

242-cal-1999-granted-assignment.pdf

242-cal-1999-granted-claims.pdf

242-cal-1999-granted-correspondence.pdf

242-cal-1999-granted-description (complete).pdf

242-cal-1999-granted-drawings.pdf

242-cal-1999-granted-examination report.pdf

242-cal-1999-granted-form 1.pdf

242-cal-1999-granted-form 2.pdf

242-cal-1999-granted-form 3.pdf

242-cal-1999-granted-form 6.pdf

242-cal-1999-granted-letter patent.pdf

242-cal-1999-granted-pa.pdf

242-cal-1999-granted-reply to examination report.pdf

242-cal-1999-granted-specification.pdf