JPH08174012A - Method for rolling joined part - Google Patents

Abstract

PURPOSE: To prevent the breaking and catching accident with side guides in the rolling of a joined material from being happened. CONSTITUTION: At the time of executing endless hot rolling, by tracking a joined point, not executing edging by retreating vertical rolls 8 in the neighboring region of the joined part and, in addition, changing the setting of the side guides 12 in this region, breaking and catching accident with the side guides 12 are decreased. The opening degrees of the side guides 12 are widened in accordance with the change in the width of the joined material.

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 rolled material having a joint by means of a rolling mill having vertical rolls, and more particularly to a sheet bar on the upstream side of a finish rolling mill. The present invention relates to a method for rolling a joint, which is suitable for use in a hot strip mill finishing mill equipped with a device for joining the joints.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for joining a sheet bar on the entry side of a finish rolling mill.

For example, a sheet bar end portion shaped by a method such as cutting is heated and abutted against each other to join them. There are various methods for this heating, such as a method using induction and a method using direct energization.

Further, a vertical roll (edger) is installed between the finishing rolling mill entry side or the finishing stand to adjust the width.

[0005]

[Problems to be Solved by the Invention]
When the two heated sheet bar ends are butted against each other and joined, there is a problem that a local joining failure may occur.

This is caused by the local residue of the oxide film, the melted layer being burned down, the local lack of heating, and the like, all of which become crack-like defects (cracks) perpendicular to the rolling direction of the sheet bar. .

This crack easily grows as a harmful defect due to the stress distribution in the width direction generated by the width reduction. That is, when the width reduction is performed, the cross-sectional shape becomes a dog bone shape as shown in FIG. 1 (a), and when horizontal rolling is performed, the dog bone portion has a dog bone portion as shown in FIG. 1 (b). Tensile stress acts on the vicinity of compression and dogbone, which causes cracks to grow as harmful defects in the tensile action region.

Therefore, there has been a problem that when the width reduction is carried out, the occurrence rate of breakage during the finish mill rolling of the joint becomes extremely high.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for rolling a joint portion capable of preventing breakage and catching accidents on side guides.

[0010]

According to the present invention, when a rolled material having a joint portion is rolled by a rolling mill having a vertical roll, the joint portion is tracked and detected, and a reduction by the vertical roll is performed around the joint portion. The above object is achieved by retracting the vertical roll during rolling so as not to weaken or apply the force.

The present invention also achieves the above-mentioned object by expanding the side guide opening in response to the change in the width of the bonding material in the area for retracting the vertical roll.

[0012]

According to the present invention, since the vertical roll is retracted around the joint based on the tracking and detection of the joint, the expansion of the joint defect due to the action of the tensile stress during or before the horizontal rolling is suppressed. Therefore, the probability of breakage of the joint is reduced.

Further, in the area for retracting the vertical roll,
By increasing the width of the side guide, it is possible to avoid the accident of being caught by the side guide due to the wide width of the bonding material.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a rolling apparatus to which the method for rolling a joint portion according to this embodiment is applied. In FIG. 2, 2 is a sheet bar, 4 is a measuring roll, 6 is a pulse generator (PLG) that detects the number of rotations of the measuring roll 4, 8 is a vertical roll (edger), 9 is a finish rolling mill, and 10 is a finish. A horizontal mill of the rolling mill, 12 is a side guide for guiding the rolled material so as to pass through the center of the rolling roll in the width direction, 14 is a joining device for joining the rolled material, and 16 is a vertical roll between stands. Further, 18 is an arithmetic processing device (tracking device) for tracking and detecting the joint portion, 20 is a vertical roll position control device, 22 is a side guide opening control device, and these devices are controlled by a process computer (not shown). It

The operation of this embodiment will be described below.

The sheet bar 2 is joined by a joining device 14 on the entry side of the finish rolling mill 9. The position of the joining point is tracked by the arithmetic processing unit 18 based on the vicinity of the pulse generator 6 that detects the rotation speed of the measuring roll 4 installed between the joining device 14 and the finish rolling mill 9.

When the width of the joint is reduced, the limit position L for preventing the joint from being adversely affected and the distance L between the joints are given as a function of the sheet bar pressure, the width reduction amount, and the reduction amount at the finishing stand. The constant of depends on the steel type.

The distance L is set by a process computer (not shown) on the basis of these pieces of information, and the vertical roll is retracted in the area of the distance L from the joining point.

The determination of the area to be rolled for retracting the vertical roll will be described below.

As shown in FIG. 3, changes in the fracture occurrence rate when the rolled region is L and the width reduction amount is ΔW are shown in FIGS. 4 and 5. FIG. 4 shows the case where the seat bar 2 is width-reduced by the F1 stand-entry vertical roll 8, and FIG. 5 shows the case where the seat bar 2 is width-reduced by the inter-stand vertical roll 16.

As shown here, as the L increases, the fracture rate decreases. However, it can be seen that if it becomes larger than a certain level, there is no further effect of reducing the fracture rate thereafter.

This critical L (let this be L0) and Δ
FIG. 6 shows a summary of the relationship of W obtained.

From this, it is understood that increasing the fracture at the joint can be prevented by securing L which is about 10 times the width reduction amount.

The arithmetic processing unit 18 interfaces the process computer with the numerical value of L, and the joining point reaches the front L of the vertical roll 8 installed on the entry side of the finish rolling mill 9 according to the result of the joining point tracking. At that stage, a command is output to the position control device 20 of the vertical roll 8. Upon receiving this, the position control device 20 of the vertical roll 8 widens the opening degree so as not to perform (or reduce) the reduction of the joint portion.

The restart of the width reduction by changing the opening degree of the vertical roll 8 after passing the joining point is also performed by the same information processing.

Further, the area where the vertical roll 8 is opened is traced to the inside of the finish rolling mill 9, and when this area passes through the side guides 12 between the stands, the wide portion is caught by the side guides 12. The side guide opening is controlled so that it does not exist.

Tracking in the mill is performed according to the feed amount of the entrance side measuring roll 4 based on the pass schedule in the mill.

Although this embodiment is an example of application to the vertical rolls 8 installed on the entry side of the finishing rolling mill 9, the same method can be applied to the vertical rolls 16 provided between the finishing stands. In addition, the vertical roll 16 between the stands and the incoming vertical roll 8
If there is, the effect can be further enhanced by applying this control together.

Although the width of the area is locally widened due to the pressure applied to the edge, the influence thereof is extremely small as will be described below, so that it is not a problem.

That is, when the edge reduction is performed, the width is returned by the subsequent horizontal rolling. The ratio of the width reduction amount to the edge reduction amount is called a width reduction ratio, and this numerical value varies depending on the rolling conditions, but when the width reduction amount is 20 to 30 mm in a region of 20 to 40 mm, it is about 0.8. . Further, the maximum reduction amount is restricted by the buckling limit of the rolled material, and the above numerical value is the limit in the plate thickness region.

Therefore, the lower edge pressed portion is finally 4-6.
mm width will be wide. In addition, this length is the case in which a material with a sheet bar thickness of 30 mm is rolled to a finishing thickness of 2 mm,
The maximum length is about 4.5 m. The product length is about 1000 m (2 mm × 1 m width, example of 15.7 T / coil).

As shown in the shaded portion 30 in FIG. 7, the edge portion of the wide portion cannot be used as a product and is cut off. Therefore, the yield reduction is (4.5 m / 1000 m). × (6 mm / 1000 mm)
= 0.27 × 10 ⁻⁴ (0.0027%), which has an extremely small effect.

[0034]

As described above, according to the present invention,
By not performing the width reduction of the joint, it is possible to reduce the fracture of the joint.

Further, when the side guide opening is widened according to the change of the width of the joining material, the occurrence of a catching accident on the finishing side guide of the wide portion which is caused by not performing the width reduction. Can also be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a dogbone shape at a joint portion.

FIG. 2 is a schematic configuration diagram showing a rolling device to which the method for rolling a joint portion according to the present embodiment is applied.

FIG. 3 is a diagram showing a vertical roll retreat area in the present embodiment.

FIG. 4 is a diagram showing the relationship between the length of the vertical roll retraction area and the fracture rate.

FIG. 5 is a diagram showing the relationship between the length of the vertical roll retract area and the fracture rate.

FIG. 6 is a diagram showing the relationship between the critical value of the length of the vertical roll retraction area and the width reduction amount.

FIG. 7 is an explanatory diagram showing a wide edge portion.

[Explanation of symbols]

 2 ... Sheet bar 4 ... Measuring roll 6 ... Pulse generator (PLG) 8 ... Vertical roll (edger) 9 ... Finishing rolling machine 10 ... Horizontal mill 12 ... Side guide 14 ... Joining device 16 ... Vertical roll between stands 18 ... Calculation processing Device (tracking device) 20 ... Vertical roll position control device 22 ... Side guide opening control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshimitsu Fukui, 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Chiba Works, Kawasaki Steel (72) Toshisada Takechi 1st Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Co., Ltd.Chiba Works

Claims (2)

[Claims] 1. When rolling a rolled material having a joint with a rolling mill having a vertical roll, the joint is tracked and detected, and the rolling force around the joint is weakened or not applied. As described above, the method for rolling a joint part is characterized in that the vertical roll being retracted is retracted. 2. The method of rolling a joint portion according to claim 1, wherein the side guide opening is widened in response to a change in the width of the joint material in the area where the vertical roll is retracted.