JPS60133927A - Control method of breakdown mill - Google Patents

Abstract

PURPOSE:To execute a continuous operation when changing a plate thickness, and to improve a yield by adjusting most suitably a rolling reduction of a breakdown stand in accordance with a variation of the plate thickness. CONSTITUTION:A plate thickness of a steel band is measured by a plate thickness meter 12 installed at the entry of a breakdown stand, and in accordance with a difference of a measured value and a measured value of an initializing time, a controller 11 operates a correcting quantity of an inter-roll gap of each breakdown stand. A result of said operation is outputted as a control signal to a rolling reduction device having rolling-reduction motors 14a-14d... for adjusting the inter-roll gap, and the rolling reduction reduction motors 14a-14d... are controlled. A controlled variable of each stand is detected by detectors 15a-15d... of a selsyn counter etc., and its information is fed back to an operator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a breakdown mill, and more particularly to a method for controlling the reduction of a roll forming type forming stand in an electric resistance welded tube manufacturing line.

In an electric resistance welding pipe production line, copper strips are generally bent into a circular shape using a breakdown stand and a fin pass stand, which are made up of multiple sets each consisting of two upper and lower rolls, and then both edges of the copper strip are Pipes are made by resistance welding.

Breakdown stand and Finpass stand are
The molding method is different. In other words, the name of the song is that a copper strip is sandwiched between the upper and lower rolls, and the cross-sectional shape of the copper strip is the same as that of a roll caliper, whereas the latter involves wrapping a copper strip that has already been formed into a circular shape to some extent with a hole-shaped roll. Shaped by

Due to this difference in forming method, changes in plate thickness have a greater effect on the Breaktown stand than on the Finpass stand.

In order to form the copper strip with precision using a breakdown stand, one thing is that both the forming roll and the breakdown roll must have a caliber shape commensurate with the thickness of the plate, and the other is that the gap between the upper and lower rolls must match the thickness of the plate. There are two necessary conditions: complete matching.

However, the thickness of the copper strips used in ERW pipes varies within the same coil due to skid marks, for example, and between different coils, so it is necessary to properly set the gap between the rolls at the start of pipe production. Even if it is set, it is not always possible to maintain an appropriate inter-roll gap that matches the thickness of the copper strip in the pipe making center. In addition, when manufacturing pipes with the same outer diameter but different wall thickness, the pipes are manufactured continuously without stopping the mill to improve productivity.
Immediately after the plate thickness is changed, the cap between the upper and lower rolls of the breakdown stand becomes inappropriate.

If the gap between the upper and lower rolls of the breakdown stand is inappropriate for the plate thickness, the following problems will occur.

(1) If the inter-roll gap is small relative to the plate thickness, the first
As shown in Figures (a) and (b), the thickness of the steel strip 3 is rolled, and the tube wall thickness 7 may become uneven like the plate thickness 8 due to over-reduction, or roll flaws 6 may occur due to heavy reduction. may occur. Furthermore, if the inter-roll gap is small relative to the plate thickness, an overload phenomenon of the drive motor will occur.

(2) If the roll cap is larger than the plate thickness, there will be a gap between the steel strip 3 and the roll 2, as shown in FIG. 2, resulting in insufficient forming of the steel strip 3. In particular, if the edge portion 4 of the steel strip 3 is insufficiently formed, the welding condition may become unstable, or the edge portion 4 may cause deterioration of the roundness of the product as shown in Fig. 3. . In this case, the driving force of the lower roll 1.2 may not be sufficiently transmitted to the steel strip 3, resulting in poor sheet feeding and meandering of the sheet.

FIG. 4 is Char 1 illustrating variations in the thickness of the copper strip. When coils No. 1-No. 4 are continuously measured, there is a variation a in the plate thickness within the same coil, and a variation b in plate thickness between different coils. These fluctuations cause the above-mentioned defects.

For the reasons mentioned above, there has been a desire for a technology that can always maintain an appropriate gap between the upper and lower rolls of a breaktown stand in response to changes in plate thickness.

An object of the present invention is to provide a control method that satisfies such requirements.

FIG. 5 is a block diagram of an embodiment of the present invention.

Breakdown stand 16 (16a, 16b, 1
6C, 16d,...) are installed on the entrance side, and the plate thickness T and plate threading speed V are continuously measured and the information is input to the computer 11. .

The computing device 11 calculates the distance between the sheet threading speed meter 13 and each breakdown stand 16a, 16b, 16c, 16d-. The delay time is calculated from the speed V, and a reduction change command is sent to the reduction device of each stand in accordance with the difference between the measured plate thickness and the initial setting plate thickness.

Adjust the inter-roll cap of each breakdown stand according to this command. This adjustment is to match the plate thickness measurement value with the inter-roll gap of each breakdown stand when the plate thickness measuring section is broken down at each breakdown stand. This control is performed continuously.

The calculation in the computer 11 is performed as follows.

V double plate speed standing n Nibreak Town Mill Distance between nth stand and plate thickness gauge Gn (t): Gap between rolls of breakdown nth stand at time t (t: l: plate at time t Thickness measurement value k(T): correction term (for example, backlash during rolling, roll slack, etc.), then the inter-roll gap correction amount ΔG is given by the following equation.

ΔG=Gn (t)-Gn (0) Sentence n T (Of o (1/v) di))・・・・・・(
1) In other words, the plate thickness of the copper strip is measured using the plate thickness meter 12 installed on the entrance side of the breakdown stand, and the controller 1
1 is a rolling motor 14a which calculates the correction ΔG of the inter-roll gap of each break-down stand using the above equation (1), and adjusts the inter-roll gap of each breakdown stand by using the result of the calculation as a control value; 14b, 1
4c, 14d, . . . and output to the lower device, each breakdown stand 16a, 16b.

16c, 16d, . . . lowering motor 14a,
14b, 14c, 14d, . . . At this time, the distance between the plate thickness meter 12 and each breakdown stand is determined by calculating the delay time using the formula (1) in accordance with the plate passing speed. The controller of each stand is a detector 15a, 15b, 15c such as a cell syn counter.

15j,..., and the information is sent to the computer 11.
Give feedback.

By using the method of the present invention and optimally adjusting the reduction of the breakdown stand in accordance with changes in plate thickness, the following effects could be obtained.

(Continuous operation when changing the Tl standard (plate thickness) became possible, and the yield improved. The improvement due to this was 0.28%.

・Can deal with deviations in plate thickness due to skid marks.

(The formability of multi-edge steel pipes has improved. The bead cutting failure rate due to poor formability was previously 0.13%, but it was 0.03%.
%Became.

It is highly effective in preventing 4-no-roll defects.

Poison breakdown stand drive motor overload prevention,
Prevents poor copper band feeding.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the breakdown overpressure condition.
FIG. 2 is an explanatory diagram showing the relationship between the gap and the cross section of the copper strip, FIG. 2 is an explanatory diagram showing insufficient plate edge forming due to insufficient breakdown reduction, and FIG. The figure is a cross-sectional view of a tube showing poor roundness due to insufficient edge forming, Figure 4 is a chart 1 showing an example of variation in plate thickness, and Figure 5 is a system diagram of an embodiment of the present invention. ■...Top roll 2...Bottom roll 3...Copper strip 4...Edge of copper strip 5...Over-pressure area 6...Roll flaw occurrence location 7...Original Plate thickness 8... Plate thickness decreased due to overpressure 11... Computing machine 12... Plate thickness meter 13... Plate threading speed meter 14 (14a, 14b, 14c, 14d) - Reduction motor 15 ( 15a, 15b, 15c, 15'd) --- Cellsyn counter 16 (16a, 16b, 16C, 1, 6d) --- Breakdown stand Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Yoshi Kosugi, male patent attorney Kazunori Saito Figure 1 (C1) Figure 2

Claims (1)

[Claims] 1. Measure the plate thickness and plate threading speed at the entrance side of the breakdown mill of the electric resistance welded pipe production line, calculate a control signal from the measured values, output the calculated value to the rolling down device of each breakdown stand, and A method for controlling a breakdown mill, comprising matching a measured value of plate thickness with a cap between rolls of each of the breakdown stands during breakdown.