JPS6152904A - Continuous hot rolling method - Google Patents

Abstract

PURPOSE:To join preceding and succeeding rolled materials quickly and surely by simple means in butt welding of preceding and succeeding rolled materials by specifying the depth of penetration and the thickness of rolled materials and making continuous finish rolling after welding. CONSTITUTION:In a continuous manufacturing line of a hot strip, rear end of the preceding rolled material 1a and front end of the succeeding rolled material 1b are butted and arc welded. At this time, the ratio D/t of the depth D of penetration of welding and the thickness (t) of rolled materials is set >=2/3, and when necessary, plural electrodes 2 are used. After welding, continuous rolling is made by a finishing roll mill. By this method, the joint of rolled materials becomes a continuous seam, the area of joint becomes large and the joint strength is heightened. Further, the effects such as short welding time, inexpensive equipment cost etc. are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a continuous hot rolling method in which ends of a rolled material are successively connected on the entry side of a finishing rolling mill to continuously roll the material. be.

(b) Prior art In recent years, hot strip rolling technology has focused on high efficiency and high yield, unlike the conventional method of intermittent rolling in which slabs are rolled one by one. A method has been developed in which a preceding rolled material and a subsequent rolled material are connected at the entry side of the machine to perform continuous rolling. For example, JP-A-58-2
No. 0.2981 discloses a method of spot welding the overlapping portions of leading and trailing rolled materials while rolling while being rolled down by a press head having multiple electrodes. Furthermore, Japanese Patent Application Laid-Open No. 58-151971 discloses a method of butting leading and trailing rolled materials together and running welding them using a seven-lash butt welding machine.

However, the above-mentioned method has various problems and is difficult to put into practical use. In the former method, since the overlapping portions are joined by spot welding, the joint area occupying the entire joint surface is small, resulting in a weak joint strength and a drawback that it is easy to break during subsequent rolling. Moreover, it is extremely difficult to run a large-scale press/spot welding machine in synchronization with the varying running speed of the rolled material with high precision. In addition, in the latter method, since the welding requires a large cross-section of about 300 to 500 cm, the flash time is long and it is not possible to join within the short time required as the cycle time. Furthermore, it requires a large-capacity welding power source and a large-scale upsetting device, which poses a problem in practical use.

P-1 Problems to be Solved by the Invention The problems to be solved by the present invention are to provide a method for connecting rolling materials that quickly and reliably connects leading and trailing rolling materials by a simple means.

B) Means for solving the problem In the continuous hot rolling method of the present invention, the trailing end of the preceding rolled material and the tip of the following rolling material are connected on the entry side of the finishing rolling mill, and the continuous hot rolling method of the present invention In a production line for hot steel/tubs that undergo continuous rolling, the rear end of the preceding rolled material is brought into contact with the tip of the following rolled material, the abutted portion is arc welded, and the welding penetration depth is set to Dl. Thickness of rolled material (ratio to tl (D
/l) to 2/3 or more, and by continuously rolling the rolled material using a finishing mill, the above problems are solved.

(E) Example As shown in FIGS. 1 and 2, in the method of the present invention, the rear end of the preceding rolled material 1cL and the tip of the trailing rolled material 1h are butted together, and the abutted portion is arc welded. do. During this arc welding, the ratio (D/l) between the welding penetration depth CD+ and the thickness (tl) of the rolled material is set to 2/3 or more.If necessary, multiple pieces (in this example By using two electrodes, welding time can be shortened.

This arc welding can be either running welding or stationary welding performed by synchronizing the welding machine with the traveling speed of the rolled material. The fixed welding method, in which a looper is installed on the entry side of the finishing mill and is performed using a fixed welding machine, is more advantageous than the traveling welding method, which requires advanced traveling control technology.

Arc welding uses conventional SAW, MIG, GMA,
Any welding method such as CO□ is possible.

If the ratio (D/l) of the weld penetration depth 1)l and the thickness of the rolled material + 1') is less than 2/3, the joint area occupied by the entire joint surface will be small and it will be easy to break during subsequent rolling. .

FIG. 3 is an experimental example that proves this.

In FIG. 3, white circles (◯) indicate good bonding strength, and black circles (@) indicate poor bonding strength.

Therefore, in the method of the present invention, D/l≧2/3.

Next, an example in which the method of the present invention is applied to a hot rolling line will be explained with reference to FIG. This embodiment is a case of fixed welding in which a looper 4 is provided on the entry side of a finishing rolling mill 3. The front and rear ends of the rolled material are cut by a cutting machine 6 provided on the outlet side of the rough rolling mill 5, and after being wound into a coil rough, the rolled material is led from an uncoiler 8 to a fixed welding machine 9, and the front and rear ends are welded. The connected rolled material is supplied to the finishing mill 3 via the looper 4 and the cutter 10 which is stopped. Finish rolling is continued even during welding, so the rolled material in the looper 4 is supplied to the finishing mill in the solvent. Therefore, the loop length is determined by the welding time and the entry speed of the finishing mill. Cutting machine 10
is for cutting the rolled material appropriately.

(F) Effects According to Hondanmei's method, the joint of rolled materials is a continuous seam, the joint area is large, the joint strength is high, the welding time is short, and the equipment is inexpensive. Effects such as this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the method of the present invention. FIG. 2 is a partial vertical sectional view taken along line nn in FIG. 1. FIG. 3 is a graph showing the relationship between the weld penetration depth to plate thickness ratio (D/l) and the joint strength of rolled materials. FIG. 4 is a schematic diagram of an embodiment in which the method of the present invention is applied to a hot rolling line. 1α: Leading rolled material 1b: Following rolling material 2: Electrode
3: Finish rolling mill 4: Looper 5: Rough rolling mill 6: Cutting machine 7: Line 8: Uncoiler 9: Welding machine 10: Cutting machine

Claims (1)

[Claims] In a hot strip manufacturing line where the rear end of the preceding rolled material is connected to the tip of the trailing rolled material on the entry side of the finishing mill, and the finishing mill continuously rolls the material, the rear end of the leading rolled material and the tip of the trailing rolled material are connected. Abutting the tip of the trailing rolled material, arc welding the abutted portion, and setting the ratio (D/t) of the welding penetration depth (D) to the thickness (t) of the rolled material to 2/3. A continuous hot rolling method comprising the above settings and continuously rolling the rolled material using a finishing mill.