WO1993024664A1

WO1993024664A1 - Equipment for continuously annealing steel strips

Info

Publication number: WO1993024664A1
Application number: PCT/JP1993/000633
Authority: WO
Inventors: Hiroshi Ikegami
Original assignee: Nippon Steel Corporation
Priority date: 1992-05-25
Filing date: 1993-05-13
Publication date: 1993-12-09
Also published as: JP3203581B2; CN1028880C; DE69329272T2; KR960006583B1; EP0613958A1; CN1080661A; KR940701456A; DE69329272D1; EP0613958A4; EP0613958B1

Abstract

To provide equipment for continuously annealing a steel strip which has been cold-rolled, intended to stably operate an annealing furnace by preventing the slip of bridle rolls and hearth rolls. The diameter D of bridle rolls (2) is set so that a surface pressure p^_ expressed by the equation p=h(σ1+σ2)/D becomes not lower than 10 kPa (kilopascal); wherein σ1 is unit tension of the portion of a steel strip (1) which is on the upstream side of bridle rolls (2) and hearth rolls (3) in a furnace; σ2 unit tension of the portion of the steel strip (1) which is on the downstream side of the rolls (2, 3); h^_ the thickness of the steel strip; and D the diameter of the bridle rolls (2).

Description

Specification

Title of invention

Continuous annealing equipment for steel strip

The present invention relates to a continuous annealing facility for a steel strip after cold rolling.

Here, the steel strip refers to a steel strip that is subjected to tin plating, zinc plating, etc. as necessary after continuous annealing, and is finally supplied to the production of cans, steel furniture, automobiles, and the like. Background art

(Conventional technology)

In general, the tension of the steel strip in the furnace of the continuous annealing equipment is preferably as large as possible for the purpose of preventing walk and flash ringing, while the tension is preferably as small as possible for the purpose of preventing heat backlash.

Due to these conflicting demands, the tension of the steel strip is reduced in a heating furnace or soaking furnace where the temperature of the steel strip is high in normal operation, and in a cooling furnace where the temperature of the steel strip is relatively low, in an overageing furnace, The tension is being increased.

Such a tension distribution can be obtained by finely adjusting the Z-control of the speed of the hearth roll, but if it is desired to change the tension abruptly at a certain point in the furnace, a bridle roll is placed in the furnace. It is common to provide one.

Fig. 1 is a drawing showing an example of this. The hearth provided in each furnace is designed to guide the steel strip 1 supplied into each furnace from the inlet side to the outlet side. A roll group consisting of rolls 3, a heating furnace 4, and a bridle roll 2 are provided just before the steel strip 1 that has passed through the soaking furnace 5 enters a quench furnace 6 exposed to a high-speed gas jet. The tension of the steel strip 1 becomes large after passing through the bridle opening 2 and passes through the subsequent quenching furnace 6, overaging furnace 7, and final cooling furnace 8.

(Problem to be solved)

By the way, the bridle opening 2 and the hearth roll 3 provided for such a purpose, of course, must surely restrain the steel strip 1 and cause no slip. Absent. However, in reality, it has been found that the bridle opening 2 and the hearth roll 3 often slip, especially when the steel strip becomes thin, and do not perform their original functions.

The present invention solves such a problem, and provides a continuous annealing facility for a steel strip in which the functions of a bridle roll and a heart roll are sufficiently exhibited to stably operate an annealing furnace. Disclosure of the invention

In order to solve the above problems, the present invention employs the equipment described in the following (1) to (5).

(1) In a continuous annealing facility for steel strip having a group of rolls arranged in the furnace so as to guide the steel strip supplied into the furnace from the inlet side to the outlet side, a small number of rolls in the group of rolls are used. When the unit tension of the steel strip on the roll entry side of one roll is 1, the unit tension on the output side is σ 2, the thickness of the steel strip is h, and the diameter of the roll is D, the following formula is used. A roll with a diameter D such that the surface pressure P expressed by (I) is 10 kPa (kilopascal) or more Continuous annealing equipment for steel strip with p = h (σ1 + σ2) D (I) (2) The facility according to the above (1), wherein at least one roll in the roll group is a bridle roll.

(3) The facility according to the above (1), wherein at least one roll in the roll group is a hearth roll.

(4) In a continuous annealing facility for steel strip having a group of rolls arranged in the furnace so as to guide the steel strip supplied into the furnace from the inlet side to the outlet side, the bridle rolls in the group of rolls When the unit tension of the steel strip on the inlet side is 1, the unit tension on the outlet side is 2, the thickness of the steel strip is h, and the diameter of the bridle roll is D, the surface expressed by the following formula (I) Continuous annealing equipment for steel strip equipped with bridle rolls of diameter D such that the pressure p is 10 kPa or more. p = h (a l + a 2) / D (I)

(5) In a continuous annealing facility for steel strip having a group of rolls arranged in the furnace so as to guide the steel strip supplied into the furnace from the inlet side to the outlet side, When the unit tension of the steel strip on the entrance side of the hearth roll is σ 1, the unit tension on the exit side is σ 2, the thickness of the steel strip is h, and the diameter of the hearth roll is D, it is expressed by the following formula (I). Continuous annealing equipment for steel strip with a hearth roll of diameter D such that the surface pressure p is 10 kPa or more. p = h (^ l + 2) / D (I) (action)

Engineeringly, as shown in Fig. 2, the entrance tension of the bridle roll 2 is T1, the exit tension is T2, and the winding angle of the steel roll 1 on the bridle rolls 2a, 2b, and 2c is 0. (= 0 1 + 0 2 + 0 3), and letting the friction coefficient be 〃, the maximum tension T 2 that does not cause slip is expressed by the following equation (I).

T 2 = T 1 · exp ((I) In other words, the tension magnification T 2 / T 1 is uniquely determined by the parameter 〃 0 and is not related to the absolute value of the tension. In the inner bridle roll, even if the tension ratio is the same, the slip tends to occur when the absolute value of the tension becomes small, that is, the friction coefficient is considered to be affected by the tension.

There is no limitation on the number of bridle rolls, and the number of bridle rolls may be one.

In an actual continuous annealing furnace, the friction coefficient at the limit of slip occurrence was measured for hearth rolls and bridle rolls with different diameters.As shown in Fig. 3, the friction coefficient was D for the bridle roll diameter. When W is the width of the steel strip, it was found that it was a function of the surface pressure p shown in the following equation (II). P = (T 1 + T 2) / (DW) (Π) As an important fact, as is clear from Fig. 3, there is a transition point of the friction coefficient near the contact pressure p = 10 kPa. (Hereafter, the contact pressure at this transition point is referred to as the critical contact pressure PC)

In the region where the surface pressure is equal to or higher than pc, the bridle roll and the hoop roll are in a state where the steel strip is normally restrained. In order for the bridle roll and hearth roll to function properly, their diameter must be determined so that this surface pressure is equal to or greater than pc.

The purpose of the hearth roll is to transport the steel strip without changing its tension. However, as can be seen from FIG. 3, the present inventor has found that at a surface pressure of 10 kPa or less, a kinetic friction state occurs and slippage occurs due to a slight difference in tension between around Haas π-rule. At first glance, the phenomenon of slipping with little difference in tension is strange, but since the control device of the motor that drives the hearth roll has no means for knowing the true speed of the steel strip, the roll speed must be reduced. This phenomenon occurs because control is performed to the command value (same as the bridle roll peripheral speed). In addition, the roll peripheral speed does not follow the command because the diameter of the hearth roll that has thermally expanded in a high-temperature furnace is not known accurately, which contributes to this phenomenon. The presence of such slippage causes flaws in the steel strip, or permanent slipping, which causes the building door to adhere to the surface of the hearth roll (iron warp-like fixation, which also causes flaws in the steel strip). Above the critical surface pressure This problem can be solved by selecting an appropriate roll diameter so that

Now, normal operation is performed so that the unit tension of the steel strip is constant, so if the equation (H) is rewritten using the relationship of tension T = CT hW, the equation (W) is obtained . p = h (<7 l + and 2) ZD (IV) Brief description of the drawing

FIG. 1 is a schematic side view showing an example of the arrangement of the in-furnace bridle rolls and hearth holes to which the present invention is applied.

Figure 2 is a drawing that generally describes the relationship between the winding angle of the steel strip around the bridle roll and the tension.

FIG. 3 is a drawing showing actually measured values obtained by determining the relationship between the surface pressure of a bridle roll and a hearth roll, which are basic data of the present invention, and the friction coefficient. BEST MODE FOR CARRYING OUT THE INVENTION

Examples will be described below.

Example 1

An example of a bridle roll design based on the above findings is shown below.

Unit tension of steel strip at inlet side of bridle roll σ 1 2 0.7 kg / mm ² , Unit tension of outlet side σ 2 = 1.2 kg / mm ² , Steel strip thickness h = 0.25 mm, roll Number = 3, each roll The winding angle = 180 degrees, the tension magnification of each roll is constant (= σ 2 / σ 1 = 1.2), and the limiting surface pressure pc = 10 kPa is substituted into the equation (IV), and the diameter of each roll is calculated. When D l, D 2, and D 3 are obtained, D l = 390 mm, D 2 = 46 O mm, and D 3 = 550 mm.

Actually, each roll has a different diameter, which is troublesome in both production and maintenance. Therefore, all roll diameters should be less than 390 mm in view of the safe side.

The data shown in Fig. 3 are for steel rolls with smooth finishes and hearth rolls, and were obtained at line speeds of 350 to 60 Ompm. Example 2

An example of a hearth roll design based on the above findings is shown below. The tension before and after the hearth roll is generally the same (and 1 = σ 2), but the condition (IV) can be applied to the slip roll prevention condition, similarly to the bridle roll.

σ 1 = σ 2 = 0.7 kg / mm ² , thickness of steel strip h = 0.25 mm Roll diameter D = 350 mm or less.

If the surface finish roughness or line speed of the bridle roll or hearth roll is significantly different, the critical surface pressure pc determined from Fig. 3 may change, but the bridle roll diameter or the hearth roll diameter is limited. The basic idea of setting the pressure to be higher than the pressure remains unchanged.

Note that the idea of selecting the unit diameter so that the surface pressure P is at a limit value that does not cause slip is based on the bridging roll as described above. Not only can it be applied to all hearth rolls. If the diameter of the hearth opening cannot be reduced due to dimensional restrictions on the equipment, such as a heating furnace equipped with a radial tube, excessive driving force exceeding the torque required to transport the steel strip to the hearth roll. Consider the design and adjustment of the control system of the hearth roll so as not to add the noise. For example, limit the speed command that is common to the furnace so that the speed error does not exceed a certain value (several mpm). Also, giving proper drooping characteristics is an important technical finding suggested by the present invention. Industrial applicability

As described above, by applying the technology of the present invention, the bridging roll and the hearth roll provided in the continuous annealing furnace can surely exert the function of amplifying the tension of the steel strip, which is its original function. It is possible to achieve a high level of stable operation of the continuous annealing furnace for steel strip. Also, serious defects such as flaws caused by slip between the steel strip and the roll can be prevented.

Claims

The scope of the claims

(1) In a continuous annealing facility for steel strip having a group of rolls arranged in the furnace so as to guide the steel strip supplied into the furnace from the inlet side to the outlet side, a small number of rolls in the group of rolls are used. When the roll entrance side of one roll is σ 1 for the unit tension of the steel strip, the unit tension of the exit side is σ 2, and the thickness of the steel strip is h, the diameter of the roll is D, the following formula (I) Continuous annealing equipment for steel strips equipped with rolls of diameter D such that the surface pressure P expressed by と is 10 kpa (kilopascal) or more. p = h (a l + a 2) / D (I)

(2) The facility according to (1), wherein at least one roll in the roll group is a bridle roll.

(3) The equipment according to (1), wherein at least one roll in the roll group is a hearth roll.

(4) In a continuous steel strip annealing facility having a group of rolls arranged in the furnace so as to guide the steel band supplied into the furnace from the inlet side to the outlet side, the bridle rolls in the group of rolls When the unit tension of the steel strip on the inlet side is 1, the unit tension on the outlet side is 2, the thickness of the 鐧 band is h, and the diameter of the bridle roll is D, the surface expressed by the following formula (I) Continuous annealing equipment for steel strip equipped with bridle rolls of diameter D such that the pressure p is 10 kPa or more. p = h (al + a 2) / D (I) (5) In continuous annealing equipment for steel strips having a group of rolls arranged in the furnace so as to guide the steel strip supplied into the furnace from the inlet side to the outlet side, hearth rolls in the group of rolls When the unit tension of the steel strip on the inlet side is 1 and the unit tension on the outlet side is 2, the thickness of the steel strip is h, and the diameter of the hearth roll is D, the surface pressure expressed by the following formula (I) Continuous annealing equipment for steel strips with hearth rolls of diameter D such that p is 10 kPa or more.

P = h (CT l + a 2) / D (I)