JP3111857B2 - Shape control method for hot-dip coated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the shape of a hot-dip coated steel sheet in a gas drawn portion of a continuous hot-dip coated steel sheet.

[0002]

2. Description of the Related Art After passing through a continuous annealing furnace, a hot-dip coated steel sheet is circulated around a sink roll in a bath in which a molten metal such as zinc or aluminum is melted to form a support roll disposed outside the sheet. It is manufactured by being raised while being supported, controlled to a predetermined amount by the molten metal wiping force of the gas discharged from the gas throttle nozzle installed above the bath surface, and passed through an alloying furnace as necessary. .

However, when the plate shape at the gas restricting portion is warped in the width direction and is not flat, the distance between the gas restricting nozzle and the plate changes in the width direction, so that the molten metal wiping force of the gas restricting gas differs. The amount of adhesion changes in the width direction of the plate. As a result, the weldability, paint adhesion, quality, etc., change in the width direction, causing problems.

As a countermeasure, a method of controlling the plate shape by controlling the position of a roll in a bath such as a sink roll or a support roll so as to flatten the plate shape at the gas throttle portion has been widely used. For example, JP-A-6-101008
Japanese Patent Application Laid-Open Publication No. H11-163,086 discloses a method of controlling the initial position of a roll in a bath with a plate deformation amount based on a conventionally known theory of thin film deformation in a tension leveler. JP-A-6-145934 and JP-A-6-192806 show relational expressions such as the amount of sheet warpage, the material of the sheet and the amount of pressing of the support roll, and the roll position is initially set based on the amount of warpage. A method for determining the amount is disclosed. Further, Japanese Patent Application Laid-Open No. 5-1551 proposes a method of controlling the position of a roll in a bath from a signal of a non-contact position detector and controlling the shape of a plate in a gas throttle section.

[0005]

However, the method disclosed in Japanese Unexamined Patent Publication No. Hei 6-101008 is not suitable for determining an initial setting position online in terms of calculation load. Further, the sheet after passing through the continuous annealing furnace is deformed under various conditions before entering the sink roll.
Even if the rolls in the bath are preset so that the amount of warpage becomes zero by the methods disclosed in Japanese Patent Application Laid-Open No. 145934 and JP-A-6-192806, the plate deformation at the gas throttle nozzle is not necessarily zero.

In order to reduce the deformation of the plate at the gas throttle nozzle to zero, a method of correcting the roll position with a signal from a contacted detector, such as the method disclosed in JP-A-5-125516, is effective. However, there is no indication as to how much correction can be made to quickly reduce the amount of warpage to the plate, and in order to flatten the shape of the plate, an appropriate roll is required based on the results of several roll position changes. The position must be determined, which is not a quick control method.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for controlling the shape of a hot-dip coated steel sheet that can easily determine the initial roll position online. Further, it is an object of the present invention to provide a method for controlling the shape of a hot-dip coated steel sheet which can quickly correct the roll position so that the sheet warpage amount becomes substantially zero when the sheet warpage amount does not become zero in the initial setting. Aim.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention firstly supports a steel sheet to be plated which rises around a sink roll installed in a hot-dip plating bath. In controlling the shape of a hot-dip coated steel sheet using an apparatus that corrects the sheet shape by moving a support roll disposed on the side of the steel sheet, a relational expression expressed by the following equation (1) is used. An object of the present invention is to provide a method for controlling the shape of a hot-dip coated steel sheet, in which a preset amount is calculated by calculating a movement amount of a support roll.

[0009] ^{_{IM 0 = α · t a1 ·}} σ y a2 · E a3 · E T a4 ............ (1) However, IM ₀ is the initial setting pushed-in position of the support roll (mm), t is the thickness (mm ), Σ _y is the yield stress (kg /
mm ^2), a longitudinal elastic coefficient ^{E (kg / mm 2),} E T is the tangent modulus _{(kg / mm 2), α} , a1, a2, a3, a4
Is a constant determined by the shape and arrangement of the rolls installed in the bath.

Secondly, when the plate shape cannot be flattened only by the preset (initial setting) in the first aspect of the present invention, the position of the support roll during the passing of the support roll is changed to:
An object of the present invention is to provide a method for controlling the shape of a hot-dip coated steel sheet, wherein the method is modified from a relational expression represented by the following expression (2) based on a deformation amount measured by a non-contact shape detector.

[0011] ^{ΔIM = β · t b1 · σ} y b2 · E b3 · E T b4 · W -2 · C m ......... (2) However, the correction amount of .DELTA.IM support roll position (m
m), C _m is the detected sheet warpage (mm), W is the sheet width (mm), β, b1, b2, b3, b4 are constants determined by the shape and arrangement of the rolls installed in the bath. It is.

If the shape and arrangement of the in-bath rolls to be used are known in advance, even in the case of producing hot-dip coated steel sheets of different thicknesses and materials, the initial relation is simply expressed by the above equation (1). Since the roll setting position can be determined, it is possible to set the position of the support roll so that the plate shape at the gas throttle unit can be easily flattened online. Further, even when the sheet warpage is not zero, since the initial correction amount can be obtained by a simple relational expression such as the above equation (2), the plate shape can be quickly corrected.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The equipment used here is
As shown in FIG.
Are disposed, and the steel sheet 1 to be passed is a sink roll 3
It is provided so as to go around and rise. On the downstream side of the synchroose 3, a movable support roll 4a and a fixed support roll 4b are arranged so as to support a steel plate. A gas throttle nozzle 5 is disposed above the upstream side of the support rolls 4a and 4b, and the gas discharged from the gas throttle nozzle 5 wipes off the molten metal adhering to the steel plate 1 and controls the amount of the adhering metal to a predetermined amount. A non-contact shape detector 6 is provided directly above the gas throttle nozzle, and the measured deformation amount is output to the arithmetic unit 7. The arithmetic unit 7 performs an arithmetic operation based on the given signal, and outputs the result to the roll position control unit 8. Then, the movement support roll 4a is controlled to an optimum position by the roll position control device 8.

The method of the present invention was carried out using such an apparatus. In the plating apparatus used here, the diameter of the sink roll 3 shown in FIG. 1 is 750 mm, the diameters of the movable and fixed support rolls 4a and 4b are both 250 mm, the distance between the sink roll 3 and the movable support roll 4a is 775 mm, The distance between the fixed support roll 4b and the fixed support roll 4b is 150 mm.

In such a plating apparatus, the coefficients of the above (1) are as follows. α = 10 ^10.46 , a1 =
−1.17, a2 = 3.755, a3 = −3.486,
a4 = 0.382.

[0016] Such a plating apparatus has a thickness of 1.2 m.
m, a hot-dip coated steel sheet 1 having a sheet width of 940 mm was passed. The properties of the steel sheet, which were measured in advance at the temperature of the galvanizing bath 2, were as follows: yield stress σ _y = 12.3 kg / mm ² , modulus of longitudinal elasticity E = 18400 kg / mm ² , tangent coefficient E _T = 24
When 0 kg / mm ₂ is substituted into the above equation (1) to obtain the initial support roll setting position IM ₀ , IM ₀ = 4.8 m
m, the moving support roll 4a was moved to this value.

In this state, the steel plate 1 was passed, but it is considered that the plate had already been deformed by the time it reached the sink roll 3, and the non-contact shape detector 6 installed immediately above the gas throttle nozzle 5 was used. Then, the amount of warp Cm in the plate width direction is -3.4 _m .
m was detected.

The position correction amount ΔIM of the moving support roll 4a is calculated using the arithmetic unit 7 based on the above equation (2).
Was calculated. Here, the respective coefficients of the above-mentioned equation (2) in this plating apparatus are β = 10 ^11.41 , b1 = −0.5
90, b2 = 1.789, b3 = -1.908, b4 =
Since it was 0.203, ΔIM = −2.0 was determined. Therefore, the moving support roll 4a was pulled back by the roll position control device 8 by this value while passing the sheet. Warp amount C _m detected by the state was -0.9Mm. The correction amount at this time was determined based on the following expression (3), assuming that the support roll pushing amount and the C warpage (warpage in the plate width direction) had a linear relationship.

This time ΔMI = current C warpage amount × previous support roll movement amount / (difference between previous C warpage amount and current C warpage amount) (3) That is, current ΔIM = − 0.9 × (−2.0) /
｛−3.4 − (− 0.9) = − 0.72.

Therefore, the present movement support roll 4
The movement amount of “a” was −0.72 mm, and the correction was performed by this value. As a result, the detected C warpage amount was −0.05.

As described above, it has been confirmed that by correcting the position of the movable support roll 4a several times using the non-contact shape detector 6, the amount of C warpage of the steel sheet can be extremely reduced. Further, it was confirmed that by correcting the position of the support roll based on the expression (3), the warpage of the steel sheet could be corrected with high accuracy. FIG. 2 shows the amount of C warpage of the steel sheet due to the preset and correction of the movement support roll as described above.

With respect to the steel sheet in which the C warpage was corrected in this manner, the zinc adhesion amount distribution in the width direction was determined. The results are shown in FIG. 3 in comparison with the zinc deposition amount distribution before warpage correction.
In FIG. 3, white circles indicate the amount of adhesion after the correction, and black circles indicate the amount of adhesion before the correction. As is clear from FIG. 3, it was confirmed that in the steel sheet in which the warpage of the steel sheet was corrected according to the present invention, the uniformity of the zinc adhesion distribution was significantly higher than in the case where the correction was not performed.

[0023]

As described above, according to the present invention, when controlling the shape of a hot-dip coated steel sheet, the initial roll position can be easily determined online, and the amount of sheet warpage is zero in the initial setting. If not, the amount of warpage can be quickly reduced to substantially zero. Therefore, a hot-dip coated steel sheet having a uniform amount of adhesion in the sheet width direction can be manufactured, and quality defects due to shape defects can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a hot-dip plating apparatus used to carry out the present invention.

FIG. 2 is a view showing the effect of correcting the position of a support roll on correcting the warpage of a plated steel sheet.

FIG. 3 is a view showing a difference in distribution of a surface adhesion amount of a hot-dip galvanized steel sheet depending on whether or not warpage is corrected.

[Explanation of symbols]

1 ... steel plate, 2 ... plating bath, 3 ... sink roll, 4
a: moving support roll, 4b: fixed support roll, 5: gas throttle nozzle, 6: non-contact shape detector,
7 arithmetic unit, 8 roll position control unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (2)

(57) [Claims] 1. A plate shape correction is performed by moving a support roll disposed on a side of a steel plate so as to support a steel plate to be plated, which rises around a sink roll provided in a hot-dip plating bath. In controlling the shape of hot-dip coated steel sheet using the equipment, the following (1)
A method of controlling the shape of a hot-dip coated steel sheet, comprising calculating a support roll movement amount from a relational expression represented by an equation and performing presetting. ^{_{IM 0 = α · t a1 ·}} σ y a2 · E a3 · E T a4 ............ (1) However, IM ₀ is the initial setting pushed-in position of the support roll (mm), t is the thickness (mm), σ _y is the yield stress (kg /
mm ^2), a longitudinal elastic coefficient ^{E (kg / mm 2),} E T is the tangent modulus _{(kg / mm 2), α} , a1, a2, a3, a4
Is a constant determined by the shape and arrangement of the rolls installed in the bath. 2. The position of the support roll in the threading of the support roll according to claim 1 based on a relational expression represented by the following expression (2) based on the deformation amount measured by the contacted shape detector. A method for controlling the shape of a hot-dip coated steel sheet, wherein the method is modified. ^{ΔIM = β · t b1 · σ} y b2 · E b3 · E T b4 · W -2 · C m ......... (2) However, the correction amount of .DELTA.IM support roll position (m
m), C _m is the detected sheet warpage (mm), W is the sheet width (mm), β, b1, b2, b3, b4 are constants determined by the shape and arrangement of the rolls installed in the bath. It is.