JPH0569018A - Plate rolling method for determining plate thickness - Google Patents

Abstract

PURPOSE:To reduce the incomformity of thickness by requiring and correcting the transformation of the aimed crown through a specified expression when the weight of a slab is measured before the start of rolling and the weight of the measured slab is lighter than the weight of the target slab. CONSTITUTION:After the weight of the slab 3 is measured by a weight measuring instrument 7, it is compared with an estimated slab weight, a new amount of the aimed crown is decided, then, a rough rolling is carried out, the aimed crown is secured by a finish rolling mill 2 to make a rolled article 4. The measured value T2 of the slab weight before rolling is compared with the estimated weight T1 and when T1 is smaller, rolling is carried out according to schedule. When the measured weight value T2 is smaller, the aimed crown is changed. When the article length L1, the article width W1, the density rho are given, the transformation DELTACr of the aimed crown is required by DELTACn =F (T1, T2,5, L2, W1) and corrected in advance. In this way, after the slab weight is measured, the aimed crown is changed and a thick plate is rolled, consequently, the inconformity of thickness can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling a thick plate using a rolling machine capable of controlling a crown, which is characterized in that after the slab weight is measured, the target crown is changed online to perform the thick plate rolling.

[0002]

2. Description of the Related Art When a slab weight is found to be lighter than a planned weight after measurement, a rolling mill having no crown control function directly changes the target thickness for rolling. That is, in order to prevent length mismatch and width mismatch, the target thickness is reduced and rolling is performed.

[0003]

Conventionally, since the crown could not be controlled, the aimed thickness was directly changed to prevent the occurrence of length mismatch and width mismatch. However, recently, it is not possible to take measures to prevent inconsistencies when the slab weight is light because the target thickness cannot be reduced for important security properties. Also, because the target thickness was changed, there is a risk that a new thickness mismatch will occur, so the effect was not as expected.

[0004]

Means for Solving the Problems The present invention is for solving the above-mentioned problems, and in a thick plate rolling line having a finish rolling machine capable of crown control, the weight of the slab is measured before the start of rolling. If the actual measured slab weight is lighter than the target slab weight, the target crown change amount ΔCr is ΔCr = F (T ₁ , T ₁ when product length L ₁ , product width W ₁ and density ρ are satisfied. T ₂ , ρ, L ₁ , W ₁ ) and is corrected beforehand.

[0005]

According to the present invention, the weight of the slab is measured before the start of rolling in a thick plate rolling line having a finish rolling machine capable of controlling the crown, and the weight is larger than the slab weight planned at the material design stage. If it is light, the target crown is reduced in advance and rolling is performed to suppress the occurrence of length mismatch and width mismatch. In this case, the target thickness has not been changed, so it can be applied to important security properties, etc., and there is no risk of a new thickness mismatch.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining an embodiment of the present invention. 1 is a rough rolling mill, 2 is a finish rolling mill, 5 is a hot straightening machine, which is a facility for straightening a defective rolling shape after rolling, 6
Is a forced cooler, which is a facility for making material by forcibly cooling the steel sheet after rolling with water. Reference numeral 7 is a slab weight measuring device, which is a measuring device for weighing the slab 3 to be rolled in advance. The slab weight measuring device may be provided before the rough rolling mill and before the heating furnace. The slab 3 is compared with the planned slab weight after the weight measurement with the weight measuring device 7, the target crown amount is newly determined, then rough rolling is performed, and the finish rolling is performed by the finishing rolling mill 2 to secure the target crown. Then, the rolled product 4 is produced.

FIG. 2 is a view comparing the conventional method and the method of the present invention with respect to the method for changing the target plate thickness and crown depending on the slab weight.

(A) is the conventional method, and (b) is the method of the present invention. 1, 1'in the figure is the target thickness distribution in the material claim stage, 2,
2'represents the target thickness distribution after measuring the material weight. In the conventional method, since the crown control could not be performed, the target thickness was directly changed as shown in the method (a).
Therefore, it was necessary to make the control board thickness of 3 thinner than the initial target value, and it was impossible to implement it in important safety properties. Moreover, since the target thickness is reduced, there is a possibility that a new thickness mismatch may occur. Therefore, if you have a rolling mill that can control the crown, you can secure the metal by changing the target crown without changing the target thickness as shown in method (b), and prevent length mismatch and width mismatch. To do.

FIG. 3 is a flow chart showing the flow of the target dimension change according to the present invention.

The slab weight is measured before the start of rolling. The weight is measured with a slab weighing machine installed in front of the rolling mill. The measured value is taken as T ₂ and compared with the planned weight T ₁ . When T ₁ is smaller, rolling is performed with the initially planned dimensions without changing the target crown. If the actual weight T ₂ is smaller, the target crown is changed. The target crown change amount is determined based on the following grounds.

Average thickness = t ₁ +2 (t ₂ −t ₁ ) / 3 = (2t ₂ + t ₁ ) / 3 product length L ₁ , product width W ₁ , product edge thickness / center thickness t ₁ , t ₂ , When the density is ρ, there is a relationship of L ₁ × W ₁ × (2t ₂ + t ₁ ) 3 × ρ = T ₁ at the time of material design.

Accordingly, (2t ₂ + t) / 3 = T ₁ / (ρ × L ₁ × W ₁ ) Similarly, if the center thickness after the slab weight is determined is t2 ′, then (2t ₂ + t ₁ ) / 3 = T ₂ / (ρ × L ₁ × W ₁ ) −2 (t ₂ ′ −t ₂ ) / 3 = (T ₂ −T ₁ ) / (ρ × L ₁ × W ₁ ) t ₂ ′ −t ₂ = (3 / 2) × (T ₂ −T ₁ ) / (ρ × L ₁ × W ₁ ) Since the edge thickness t ₁ does not change, t ₂ ′ −t _{2 in the} equation becomes the target crown change amount.

Examples will be shown below. First Example-Conventional method Plate width 4000 mm, length 40 M, thickness 20
Since the slab weight measurement was lighter than the planned weight for a thick plate of mm, the thickness of 0.05 mm was aimed thinly. As a result, a metal of 0.05 × 4000 × 400000 = 8 × 10 ⁷ mm ³ was secured, and a length mismatch up to 8 × 10 ⁷ ÷ (4000 × 20) = 1000 mm was repaired.

・ This method: plate width 4000 mm, length 40
Since the slab weight measurement was performed with a thick plate of M and a thickness of 20 mm, the target crown was changed to 0.02 mm because the target weight was 0.15 mm.

A metal of ((0.15-0.02) / 2) × 4000 × 400000 = 10.4 × 10 ⁷ mm ³ is secured, and up to 10.4 × 10 ⁷ ÷ (4000 × 20) = 1300 mm He rescued the length mismatch.

The target thickness change and the crown change are calculated by using a formula based on the slab weight measurement result. Second Example A thick plate having a plate width of 2500 mm, a length of 50 M, and a thickness of 10 mm, which was initially found to have a weight of 10.0 Ton, was found to be only 9.95 Ton by actual measurement. Changed as follows.

T2′-t2 = (3/2) × (10−9.95) / (7.8 × 50 × 2.5) = 1.5 × 10 ⁻⁴ M = 0.15 mm The target crown is initially set. It was 0.15 mm smaller than planned.

FIG. 4 is a graph showing the results of the first and second embodiments.

If the slab weight is less than the planned weight after the actual measurement, the nonconformity rate becomes 100% if nothing is done. If the conventional method is adopted, the length / width mismatch will be reduced to 50%, but the thickness mismatch will newly occur at 10%. Therefore, the reduction amount of disagreement is 40%. On the other hand, in the present method, the effect is greater than in the conventional method, and thus the discontinuity is reduced to 30%. Moreover, since the target thickness is not changed, the thickness mismatch will not occur. Therefore, the reduction amount of incompatibility is 70%, which is a great effect.

[0021]

As described above, according to the present invention,
Since the target crown is changed and the plate is rolled after the slab weight is measured, the thickness mismatch can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram comparing a conventional method and a method of the present invention with respect to a method for changing a target plate thickness and a crown depending on a slab weight.

FIG. 3 is a flowchart showing a flow of changing a target dimension according to the present invention.

FIG. 4 is a graph showing the results of the first and second examples.

[Explanation of symbols]

 1 Rough rolling mill 2 Finish rolling mill 3 Slab 4 Rolled product 5 Hot straightening machine 6 Forced cooling machine 7 Slab weight measuring instrument

Claims (1)

[Claims] 1. The product length is measured when the weight of the slab is measured before the start of rolling in a plate rolling line having a finish rolling machine capable of crown control and the measured slab weight is lighter than the target slab weight. When L _{1 is} the product width, W _{1 is} the density, and ρ is the density, the target crown change amount ΔCr is ΔCr = F (T ₁ , T ₂ , ρ, L ₁ , W ₁ ) and is corrected in advance. Characteristic method for determining the thickness of rolled plate.