JPH0320417A - Method for continuously annealing steel strip - Google Patents

Abstract

PURPOSE:To prevent cooling buckle and meandering of a strip by continuously measuring temps. at edge part and center part of a helper roll, locally heating the roll edge part to approach the temp. at the edge part to the temp. at the center part. CONSTITUTION:The helper roll 1 in cooling zone of a continuous annealing furnace is separated from furnace atmosphere with a parting wall. In the separated roll chamber, wall heater 4, tube heater 5 and edge heater 3 are arranged. A furnace thermometer 6 is arranged and also temp. sensors 7 are arranged to measure temp. distribution of the roll 1. When the temp. at the center part in the roll 1 raises higher than the temp. of the edge part, by working the edge heater, the edge part in the roll is locally heated so that the temp. difference between the center part and edge parts becomes within about + or -30 deg.C to control the temp. distribution in the roll.

Description

[Detailed Description of the Invention] <Industrial Icheon Prefecture> The present invention eliminates the temperature difference between the center part and edge part of a helper roll used for cooling 11 of a continuous annealing furnace, and improves the cooling buckle and meandering of the belt. This article relates to a continuous annealing method that prevents this. Previously, the cooling zone of a continuous annealing furnace, especially the helper roll in the first quenching zone, was directly affected by the low-temperature atmosphere. In this case, the temperature difference between the roll edge portion and the center portion, which is approximately the temperature of the steel strip, is 300 to 500°C.
Reach. Therefore, the roll has a convex crown,
A cooling buckle had occurred. Therefore, in Japanese Patent Publication No. 54-41009, the second
As shown in the figure, the helper roll is placed in a roll chamber isolated from a low-temperature atmosphere, and a heat source is installed in this roll chamber, thereby reducing the temperature of the roll surface to a temperature close to that of the strip passing through the roll surface. A method of heating and holding it has been proposed. However, in this case, although heating reduces the temperature difference between the center and edge of the roll, the power consumption and efficiency of the heater is low, and it is difficult to follow changes in line speed, etc. However, it was not possible to sufficiently prevent the cooling buckle of the copper band described above.

Problems to be Solved by the Invention> An object of the present invention is to prevent cooling buckles and meandering in a helper roll for cooling 1y of a continuous annealing furnace.
This paper proposes a continuous annealing method for strips. Another purpose is to propose a continuous annealing method that can prevent cooling buckles and meandering even when the operating conditions of the furnace are drastically changed. Another objective is to propose a continuous annealing method that consumes less power for roll heating than conventional methods. Means for Solving the Problems> In order to solve the above problems, the present invention solves the problems described above by arranging the helper roll of the cooling IF of a continuous annealing furnace for copper strips in a roll chamber isolated from a low-temperature atmosphere. To prevent cooling buckles, the temperature is controlled by locally heating the roll edge using a heating device such as an electric heater so that the temperature of the helper roll edge approaches the temperature of the roll center. At this time, a temperature sensor such as a thermocouple is attached to the helper roll to continuously measure the temperature of the roll edge and center, and the temperature of the roll edge is controlled so that it approaches the temperature of the roll center. This is a continuous annealing method that prevents cooling buckles and meandering of the copper strip.

Function> FIG. 1(a) is an overall view showing one embodiment of the present invention. Figure 1 (b) is a view taken along the AA arrow in (a), and (C) is (c).
This is a view taken along the BB arrow. A helper roll 1 in the cooling zone of a continuous annealing furnace is placed in an isolated roll chamber 2, and while continuously measuring the temperature distribution of the helper roll 1 with a temperature sensor 7 such as a thermocouple,
The roll edge portion is efficiently heated using a heating device such as an electric heater, and the roll temperature distribution is controlled so that the temperature difference between the edge portion and center portion of the helper roll is within ±30°C. This eliminates the temperature difference between the center and edge of the helper roll, and changes in the thermal crown due to changes in the operating conditions of the helper roll.
A large convex crown does not occur, the initial crown is maintained almost as it is, and the cooling buckle of fR 4fF does not occur. Needless to say, it also prevents meandering caused by the occurrence of concave crowns. In addition, the heater arrangement in the roll chamber takes into consideration heater power consumption and efficiency, and in addition to the conventional wall heater and chave heater, a roll edge heater that locally heats only the roll edge is installed, and the wall heater and tube heater When used together, it is possible to efficiently respond to any changes in operating conditions. In addition, a temperature sensor such as a thermocouple provides accurate feedback to the roll temperature distribution control of the roll, thereby improving controllability. The device shown in FIG. 1 includes a wall heater 4, a tube heater 5, and an edge heater 3 for locally heating the roll edge portion as heating devices in a roll chamber 2 in which a helper roll l in a cooling zone is partitioned by a partition wall. In addition to providing a furnace temperature gauge 6,
A temperature sensor 7 is provided to measure the roll temperature distribution of the helper roll 1. This temperature sensor 7 measures the temperature of the center part and the edge part of the helper roll 1, and when the temperature of the center part of the roll 1 rises higher than the temperature of the edge part, the edge heat 3, which is a heating device, is activated. The roll edge portion is locally heated to control the roll temperature distribution so that the temperature difference between the center portion and the edge portion of the helper roll 1 is within ±30°C.

Incidentally, it is empirically known that buckling occurs in Steel 41F when the temperature of the center part is 30°C or higher than the edge part, and conversely, meandering occurs in Steel 41F when the temperature of the edge part is 30°C or higher than the center part. known to.

As a specific temperature control method, for example, during line operation, the roll edge heater 3 is used to heat the center of the roll edge portion. Also, when the line is stopped or when the temperature rises, the wall heater 4. By using the tube heater 5 and edge heater 3 together, local heating of the roll is prevented. In addition, by efficiently controlling the roll temperature distribution of the helper roll mainly through the edge heater in this way, it is possible not only to improve controllability but also to significantly reduce heater power consumption.

FIG. 3 shows an example of the relationship between roll edge temperature and heater power consumption when an edge heater and a wall heater are used. When edge heaters were used, power consumption could be reduced by approximately 100ks/roll compared to wall heaters. Effects of the Invention> In contrast to the conventional control system which only has a heating device such as a tube heater that heats the entire roll in a roll chamber in which a helper roll is placed isolated from the cooling zone, the roll edge part is heated locally. When the method of the present invention using an edge heater was carried out, there was no temperature difference between the roll center part and the edge part, and cooling buckling and meandering of the steel strip did not occur. In addition, the temperature sensor provides excellent followability, making it possible to prevent cooling buckles and meandering even when operating conditions such as line speed change dramatically. We were also able to reduce the power consumption of the roll heater.

[Brief explanation of the drawing]

Claims (1)

[Claims] The helper roll in the cooling zone of a continuous steel strip annealing furnace is separated from the furnace atmosphere by a partition wall, and the roll surface is heated by a heating device so that the temperature of the helper roll edge approaches the temperature of the roll center. In order to prevent cooling buckling and meandering of the belt, the temperature of the helper roll edge part and the roll center part is continuously measured, and the temperature of the roll edge part is adjusted so that the temperature of the roll edge part approaches the temperature of the center part. A continuous annealing method for steel strip characterized by locally heating the steel strip.