JPS6043436A - Continuous annealing method for thin light-gauge strip - Google Patents

Abstract

PURPOSE:To prevent generation of the unmatched part in a welded juncture by welding and connecting light-gauge strips having <=0.35mm. thickness and reducing the thickness of the weld zone to a prescribed thickness prior to continuous annealing and temper rolling. CONSTITUTION:A light-gauge strip 2 having <=0.35mm. thickness is welded to the succeeding light-gauge strip 2-1 by welding electrodes 11. The weld zone thereof is then reduced in thickness by rolls 12, 13 to <=130% of the strip thickness. The strip 2 subjected to the thickness reduction is heated via a cleaning device 4 in a continuous annealing furnace 6 and is temper-rolled in a temper rolling mill 8. The need for opening the roll gap or decreasing the rolling reduction force of the rolls is eliminated by such method and therefore the generation of the unmatched part in the welded juncture is prevented and the occurrence of flaws on the rolls is prevented as well.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a continuous annealing method for thin strips, such as tin blanks, in a continuous annealing line.

(Prior art) A continuous annealing line equipped with a temper rolling mill is used to manufacture blank original sheets.The continuous annealing line's feature of continuous annealing is fully utilized, and the material is Along with obtaining a homogeneous product.

In terms of operation, it is important to consistently operate under specified operating conditions.

The strip to be continuously annealed is connected to the first stage strip by lap welding to form a continuous strip, which is annealed in a continuous annealing furnace at a predetermined thermal cycle, and then temper-rolled in a temper-rolling mill. administered.

By the way, this welded joint is a cause of flaws in the rolls of the temper rolling mill, so in order to avoid this,
Before the weld passes through a temper rolling mill, the upper and lower rolls are opened in advance to avoid contact between the weld and the rolls, or to reduce the rolling edge of the rolls.

For this reason, the area within several meters before and after the welded joint is different from other parts in terms of material and becomes a non-conforming area, so the advantage of the continuous annealing line is that the work is continuous. ) It has not yet been possible to manufacture a tube whose material is uniform over the entire length.

The problem is that the strip is relatively thick.

In the case of cold-rolled steel sheets used for so-called automobile steel sheets, generally a lubricant is used during temper rolling, so there are no roll defects caused by welds, and rolling can be done under constant rolling conditions over the entire length. In the case of a tin plate having a thin plate thickness, for example, 0.35 mm or less, temper rolling is performed in a dry state, and roll defects are likely to occur.

For this reason, in temper rolling, when the welded joint passes through the temper rolling mill, it is necessary to take measures such as opening the mill (opening the space between the upper and lower rolls). The thin strips cannot be used for about 10 meters before and after the desired product. On the other hand, if mill opening is not done, the roll will be flawed and the roll flaws will be printed on subsequent thin strips, resulting in defects over a very long range.

(Object of the Invention) The present invention has been made as a result of various studies in view of the above circumstances, and proposes a continuous annealing method for thin strips that does not produce mismatched portions at welded joints.

(Structure and operation of the invention) The present invention has a plate thickness of 03511L at the entrance side of a continuous annealing line.
When connecting and continuously processing thin strips with a diameter of less than 500 m, the thickness of the lap welded joint should be within 130% of the thickness of the thin strips, so that heating and The soaking and cooling effects are no different from those of other parts, and even in skin pass rolling, no roll flaws occur, and skin pass rolling is performed in the same way as other parts.

(1) It has been found that a uniform material can be obtained over the entire length of the tube, including the area immediately adjacent to the welded joint.

The present invention has been made based on this knowledge, and will be explained in detail below.

FIG. 1 shows the line along which a thin strip is continuously annealed in one embodiment of the invention.

In the drawing, +1-1 and 1-2 are payoff reels.

A thin strip, for example a tin plate 2, is fed out. 3
1 is a welding device equipped with a welding part thickness reduction mechanism, 4 is a cleaning device, and 5 is an entry side looper.

6 is a continuous annealing furnace with a heating zone, soaking zone, and overaging zone.

A cooling zone is provided. Reference numeral 7 indicates an exit looper, and 8 indicates a temper rolling mill.In this embodiment, two mills are provided in succession. Reference numeral 9 indicates a fine adjustment section: LO-1 and 10-2 indicate tension reels.

Incidentally, when a thin strip is continuously annealed and then temper rolled in a temper rolling mill, the relationship between the occurrence of roll flaws and the plate thickness ratio of the welded joint was investigated.

Note that the welded joint plate thickness ratio is the ratio of the welded part plate thickness to the base metal plate thickness.

This investigation was carried out on thin strips having a thickness of 0.25 to 0.35 mm, and the welded joint thickness ratio was changed by reducing the thickness of the welded joint using a pressure roll or an energized pressure roll. Then, when such thin strips were continuously annealed at 630° C. for 25 seconds and temper rolled at a pressure adjustment ratio of 08 to 1.2%, roll flaws that occurred on the rolls were examined. The second result is
As shown in the figure.

In the figure, a is a rolling blade of 200 tons, and b is a rolling blade of 80 tons.
0 ton, dry temper rolling to a plate thickness of 0.28mm
This is an example. The weld thickness ratio is expressed as weld thickness/base metal thickness.

If welded joints are temper rolled from this.

When the plate thickness ratio of the welded joint is 130% or less.

It was found that the occurrence of roll flaws was suppressed regardless of the rolling blade. It has also been found that in this case, a desired degree of thermal refinement can be obtained from the vicinity of the welded joint, and a uniform material can be obtained.

In view of the above, in the present invention, when thin strips are welded and connected on the entrance side of a continuous annealing furnace, the thickness of the welded joint is set to be 130 inches or less of the thickness of the thin strip. Details of the welding device 3 for making such welded connections will be described with reference to FIG.

The thin strip 2 is welded to the next thin strip 2-1 by the welding electrode 11, and then the thickness of the welded joint is reduced by the first pressure roll 12 and second pressure roll 13 provided at the rear. The method for reducing the thickness of the welded joint is not limited to the above-mentioned method. For example, the first pressure roll 12 may be provided with an energizing mechanism to apply pressure while applying a heating effect.

The welded thin strip 2 is cleaned by a cleaning device 4 and passed through an inlet looper 5.

14 (heated in the subsequent annealing furnace 6 to a predetermined temperature, e.g. 60
The product is soaked at a temperature of 0 to 650°C, then cooled to an overaging temperature of 300 to 500°C if necessary, or subjected to an overaging treatment, or is then exposed to the atmosphere without overaging. It is cooled to a temperature at which oxidation does not occur even if it comes into contact with the material.

(Effect of the invention) In the present invention, the skin pass rolling mill 8 performs skin pass rolling at a predetermined pressure adjustment rate according to the degree of temper rolling, but even when the welded joint is temper rolled, the welded joint Since the thickness of the thin strip 2 is set to 130% or less of the plate thickness of the thin strip 2, the welded joint can be temper-rolled in the same manner as other parts without generating roll flaws.

Therefore, a uniform material can be obtained over the entire length except for the welded joint, and there are no mismatched parts.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a continuous annealing line in which an embodiment of the present invention is carried out, FIG. 2 is a diagram of the plate thickness ratio of the welded joint and roll flaws, and FIG. 3 is an explanatory diagram of the welding apparatus. 3: Welding device 6: Continuous annealing furnace 11: Welding electrode 12: [No.] reduction roll 13, second reduction roll

Claims (1)

[Claims] In a continuous annealing line equipped with a temper rolling mill. Thin plate with a thickness of 0.35+n+++ or less) Connect the IJ knob by welding. In the method of continuous annealing, the thickness of the welded joint of the thin strip is reduced to 130% or less of the thickness of the tongue plate, followed by continuous annealing and temper rolling. Annealing method.