RU2093285C1 - Backup rolling roll operation method (its variants) - Google Patents

Abstract

FIELD: rolling equipment. SUBSTANCE: backup roll of wide strip hot rolling mill begins to operate in finish group of rolling stands until wear of active layer of said roll by 40-60%. Then slopes with length no more than 370 mm and depth no more than 2 mm are made and said backup roll operates in rough group of stands until its complete wear. In second variant of invention backup roll in finish group of stands operates until crumbling out edge of its barrel. Then slopes of above mentioned size are made on end portions of roll barrel and said roll operates in rough group of stands. EFFECT: lowered crumbling out of backup rolling rolls, enhanced quality of rolled stock due to elimination of thickness difference of rolled sheet. 2 cl, 1 dwg

Description

 The invention relates to the field of rolling and can be used in the production of strips and sheets on broadband hot rolling mills.

 There is a method of operating a support roll of a hot rolling mill, in which the support roll is subjected to turning to a depth of 8-10 mm to remove the softened layer after a certain number of resurfacing [1] The disadvantage of this method is the low resistance of the backup roll due to the formation of chips in its surface, especially as the diameter of the roll decreases.

 A known method of operating a backup roll, including periodic machining of the roll barrel to give a predetermined profile and removing the defective riveted layer, and the regulated operating routes of the rolls in finishing stands [2] A disadvantage of the known technical solution is the low resistance of the backup rolls due to the formation of spalling on the side parts roll barrels, as the roll is operated only in finishing stands and, after wear, the regulated thickness of the active layer is not transferred to roughing stands, and bevels are not produced at the edges of the roll barrel.

The closest in technical essence and the achieved result is a method of operating a backup roll, including periodic machining of the roll barrel and the production of bevels on the edges of the barrel for a length of 75-250 mm and a depth of 1-5 mm [3]
A disadvantage of the known technical solution is the low quality of the rolled metal due to its thickness variation when using a roll with bevels in the finishing group of stands, as well as its low resistance due to the increase in linear pressure in the middle of the barrel during rolling of a wide strip.

 The purpose of the invention is to increase the resistance of the support rolls by reducing chipping and improving the quality of the rolling by eliminating the thickness of the sheet.

 This goal is achieved in that the support roll of the stands of the quarto broadband hot rolling mill is started to be operated in the finishing group of the stands until the active layer is worn by 40-60%, then bevels are made with a length of not more than 370 mm and a depth of not more than 2 mm and operate the roll in rough group of stands until its complete failure. According to the second option, operation is carried out in the finishing group of stands before the formation of a crumb from the edges of the barrel (regardless of the degree of wear of the active layer), they make bevels from the edges of the barrel of the roll of the same size as in the first version, and operate the roll in the roughing group of stands its failure.

 The drawing shows a diagram of the backup roll, where 1 neck, 2 roll barrel, D barrel diameter, L barrel length, l bevel length, h bevel depth.

 The support roll is introduced into the work of the finishing group of stands without bevels due to the fact that in this group of stands the strip has a maximum width close to the length of the roll barrel. So, for example, the length of the roll barrel NShS 2000 of NLMK JSC has 2000 mm, and the maximum strip width is 1850 mm. Thus, the execution of bevels along the edges of the roll barrel leads to a decrease in the length of the roll contact, which is equivalent to shortening the length of the roll of the backup roll, and, consequently, to its overload and chipping. The lack of contact at the edges of the barrels of the support and work rolls leads to a bend of the latter and the thickness difference of the rolled strip. It is known that during the operation of the backup roll fatigue phenomena accumulate in its active layer, especially along the edges of the barrel, which is associated with the wear of the middle part of the work roll and the redistribution of inter-roll pressure on the edges of the barrel. In this case, fatigue phenomena accumulate and spalling becomes more frequent as the diameter of the roll decreases. For this reason, the operation of a new back-up roll is started in the stands of the finishing group and is operated up to wear of the active layer thickness by 40-60 since up to 40 wear of the active layer of spalling is practically not observed, and with more than 60, the spalls have a greater depth and they cannot be removed by turning. Due to the fact that when the active layer is consumed by 40-60%, fatigue phenomena accumulate in the lateral parts of the barrel and there is a high probability of spalling in these parts, the roll is transferred to work in the roughing group of stands, having previously produced on it along the edges of the bevel no more than 370 mi and a depth of not more than 2 mm. The lateral bevels of the above-regulated value remove the riveted danger zone of the back-up roll from contact with the worker, thereby preventing chipping. Moreover, the implementation of bevels up to 370 mm long does not affect the redistribution of inter-roll pressure, because the strip in the rough stands has a small width. And with a bevel length of more than 370 mm and a depth of more than 2 mm, the real length of the roll barrel is reduced (by reducing the length of the roll contact), which leads to increased wear of the roll and chipping of the active layer.

 If spalling occurred on the lateral parts of the roll with a distance from the edge of the roll barrel to the far edge of the crumb no more than 300 mm, then instead of turning the entire roll barrel to remove the crumb (which leads to the rapid consumption of the active layer), it is advisable to make side bevels on a regulated value and transfer the roll for further operation in the roughing group of stands. This preserves the active layer and the crumbled area is removed from the contact.

 Examples of the method.

 Example 1. Mill 2000 of NLMK JSC has 12 stands, of which 1-5 stands are draft, 6-12 are finishing. The support rolls are made of 9HF steel, the barrel length is 2000 mm, the maximum diameter is 1600 mm, and the minimum is 1480 mm. A new roll is put into operation in the 12th stand with a further transfer of the roll to other stands of the finishing group in the direction of rolling direction. The roll is taken out of work in the 6th mill with a diameter of 1540 mm (which corresponds to 50% wear of the active layer). On the sides of the roll barrel, bevels are made with a length of 300 mm and a depth of 1.5 mm from the edge of the roll barrel. The roll is put into operation in the 5th stand and operated in the direction of rolling and taken out of operation in the first stand with complete wear of the roll barrel. There was no chipping on the roll barrel; it failed as a result of complete wear of the active layer of the roll barrel and rolled 2 million tons.

 Example 2. The back-up roll is operated similarly to examples 1, and with a diameter of 1564 mm (which corresponds to a 30% wear of the active layer) a crumb was formed at a distance of 150 mm from the edge of the roll barrel. The roll is taken out of operation, bevels are produced at the edges of the roll barrel with a length of 320 mm and a depth of 1.5 mm, and subsequently operated in the roughing group of stands. The roll failed due to complete wear of the active layer and rolled 1.8 million tons of metal.

 The technical and economic advantages of the claimed method of operating the backup rolls are to increase the roll resistance, improve the quality of the rolled metal, increase the productivity of the mill by reducing unplanned downtime to replace crumbling rolls, and reduce the loading of machine equipment necessary for turning rolls with crumbs.

Used Books
1. Polukhin P.I. Zheleznov Yu.D. Polukhin V.P. Sheet rolling and roll service. M. Metallurgy, 1967.S. 281.

 2. Borovik L.I. Dobronravov A.I. The technology of preparation and operation of rolls of sheet mills. M. Metallurgy, 1984.P. 22, 90.

 3. Profiling rolls of sheet mills / A.A. Budakova, Yu.V. Konovalov, K.N. Tkalich et al. K. Tekhnika, 1986.P. 135-137, 152-165.

Claims (2)

 1. A method of operating a support roll by stands of a quarto broadband hot rolling mill, comprising periodically machining the roll barrel between campaigns and making bevels at the edges of the barrel, characterized in that the roll is operated first in the finishing group of the stands until the active layer is worn 40-60% after what do bevels do with a length of not more than 370 mm and a depth of not more than 2 mm and operate the roll in the roughing group of stands before its complete failure.  2. A method of operating a support roll of stands of a quarto broadband hot rolling mill, comprising periodically machining the roll barrel between campaigns and making bevels at the edges of the barrel, characterized in that the roll is operated first in the finishing group of the stands until a crumb from the edges of the barrel is formed, and then made bevels with a length of not more than 370 mm and a depth of not more than 2 mm and are operated in the roughing group of stands before its complete failure.