JPS59116331A - Vertical type continuous annealing furnace for extra low carbon steel - Google Patents

Abstract

PURPOSE:To prevent snaking and heat buckling of a steel strip by decreasing the taper or crown of upper hearth rolls with respect to lower hearth rolls in the high temp. zone in a vertical type continuous annealing furnace. CONSTITUTION:The taper index R of a hearth roll (a) is first selected at about 3.0 and the taper index R of a hearth roll (b) at about 1.2 at which an extra low carbon steel plate P is passed in the stage of passing said plate P in a heating zone 10 of an annealing furnace. The taper index R of an upper hearth roll (c) is selected at about 0.9 and the taper index R of a lower hearth roll (d) at about 1.8 and the steel plate P on the outlet side of the zone 10 is heated roughly to a soaking temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vertical continuous annealing furnace for ultra-low carbon steel that can prevent heat buckling.

There is a vertical continuous annealing furnace that continuously anneals copper strips.

Such an annealing furnace has multiple berths in the upper and lower parts of the furnace.
In this process, the copper strips are successively suspended on the hearth rolls, and the copper strips are heated as necessary during this process. Usually, in order to pass the copper strip straight through the furnace, the hearth roll is provided with a taper as shown in FIGS. 1 and 2 or a round as shown in FIG. 3.

However, due to the taper provided on the throttle, etc., in each case, the centering force exceeds the buckling load in the width direction of the copper strip, causing heat buckling (the copper strip in the width direction at high temperatures). (buckling phenomenon).

(1) If the mechanical strength of the copper strip decreases due to high-temperature annealing, (2) If the centering force becomes excessive with a wide material, (3) If the taper or crown amount of the roll is excessive,
(4) The tension on the copper strip is too strong.

For example, when the upper roll and lower roll are each made with a taper of 3.0, and a 0.8 x 1350 m ultra-low carbon copper strip is passed through a furnace with a height of 17 m, even if the tension at the lower roll position is 10 KF, the tension at the upper roll position is The tension depends on the weight of the copper strip.l) 164
Ky/c4. In such a case, the tension on the upper roll is too high, and due to the effect of (4) mentioned above, the tension is concentrated on the upper roll, causing heat buckles.The 5-pole low carbon steel strip has a low carbon content ( 1-2000 ppm
), so the material is usually softer than Cold Ting Dongtei. Therefore, the upper nozzle of the high temperature furnace zone of the vertical continuous annealing furnace has a weight of 200 K9/n? due to the weight of the steel strip. The taper or crown of the no-throttle roll, which is applied with a certain amount of tension and is intended to prevent the strip from meandering in the furnace, is a cause of heat buckling. It is necessary to reduce the force, reduce the centering force generated there, and prevent heat buckling.

On the other hand, as for the lower roll, the tension becomes extremely small, so unless an appropriately large tapered brush is attached, the centering force will become too small, causing the problem of meandering of the copper strip.

An object of the present invention is to provide a vertical continuous annealing furnace for ultra-low carbon steel that prevents the occurrence of heat buckling and meandering.

The present invention achieves the above object by changing the roll shapes of the upper roll and the first roll to optimize the centering force generated at each position (if).

Figure 4 shows rolls with various top and bottom identical tapers or crowns made of ultra-low carbon steel (for example, 0,7
1320 fin) and found the dangerous range of the heat buckle. This figure shows the effects of roll taper and steel plate tension on heat buckles, and it can be seen that the larger the roll taper, the smaller the tension tends to cause heat buckles. Note that the taper in each roll should be adjusted with your finger & 9. R is as follows.

Normal taper roll: R-r T/lrX 1000
For crown roll: I also = 2 r t /L T
For X 1000 double taper roll: 1j=r,/
1Txlo00 As is clear from Figure 4, the taper must be selected so that it does not fall into the heat hack danger range.
Furnace temperature &820℃, in case of tapered hearth roll,
When an ultra-low carbon steel strip with a plate thickness of 0.7 mm and between 11 plates and 1320 plates is annealed, the taper index of the upper and lower rolls is the result of the inventor's implementation (= according to upper). The copper strip tension in the throttle is 200 Kp/+! In order to reduce the meandering of the tip of the lower throttle, it is desirable that the index of the upper throttle is less than 1.2. It was found that a value of 1.2 or more is highly desirable. Hiko, at this time...
-The steel strip tension in the thrall is equal to the copper strip's own weight/J'l
It is about 90Kf. An example of this is shown in Figure 5 (-).

Figure 5 shows the tension in the high-temperature furnace zone (at the beginning of the heating zone 10 where heat nockles are likely to occur). In the figure, 1-roll a mait = 3.0 is selected, and the rolling base plate is not straightened in the 3-cedar shape, so the emphasis is on preventing meandering.
Notsuta - Thrall b is selected to be above = 1.2. No--
The throttles C and d are according to the present invention, and the no-throttle C (upper hearth roll) is It = 0.9 and no\-
Thrall d (lower) - throttle) is H. = 1.8 +
The steel plate P in the Karotropics output 111+1 was selected as follows.
is heated at a soaking temperature of 1. Incidentally, in the conventional technique, R = 1 for both upper and lower hearth rolls.
．． It's 8.

Note that the present invention is applicable to determining the roll shapes of rolls that differ in the height direction in a continuous line.

As is clear from the above, according to the present invention, by changing the shapes of the upper roll and lower roll of the vertical furnace, it is possible to prevent excessive centering force on the upper roll, and to prevent heat buckling and meandering. It can be prevented.

[Brief explanation of the drawing]

ε+< 11Mi, Figures 2 and 3 are front views of the normal taper roll, two-stage taper roll, and crown roll used in the continuous annealing furnace (Fig. 4 shows the heat buckling limit characteristics of ultra-low carbon steel) Fig. 5 is a front view showing an embodiment of the present invention. 10...Heating zone, a, b, C9d.../-Throll. Fig. 1 Fig. 4 +2345 0-Ruteha 0 (R) □

Claims (1)

[Claims] (1) A plurality of hearth rolls are installed at the upper and lower parts of the furnace at a predetermined height at a predetermined interval, and an rBs-order ultra-low carbon steel strip is passed through each of these hearth rolls for annealing. In a vertical continuous annealing furnace, the taper or crown of the lower hearth roll installed in the high temperature furnace zone has been made smaller! [! Vertical continuous annealing furnace for ultra-low carbon steel.