JPH06932B2 - Continuous annealing method for cold rolled stainless steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to continuous annealing of a cold rolled stainless steel strip,
The present invention relates to a continuous annealing method for cold-rolled stainless steel strips for reducing the occurrence of a defective rate in a plate connecting portion.

[Conventional technology]

Generally, cold-rolled products of stainless steel strips need to be baked at a constant annealing temperature in order to guarantee properties such as high gloss and no surface defects, and predetermined strength and elongation. In the manufacturing process of 1, the cold rolled stainless steel strip is annealed as it is by continuous annealing as shown in FIG. In the figure, the stainless steel strip 5 is provided on the side wall of the furnace while being supported by the inlet roller 2, the outlet roller 3, the in-furnace supporting rollers 4a and 4b installed in the annealing furnace 1, and traveling in the furnace. It is heated to a predetermined annealing temperature by the burner 6.

By the way, on the surface of the cold rolled stainless steel strip, rolling oil, rolling wear powder, etc. are unevenly attached,
When annealed as it was, the surface oxidation reaction proceeded non-uniformly corresponding to these adhered states, and a pattern such as uneven gloss was generated on the surface of the steel strip. Therefore, in order to prevent this, a method of degreasing the stainless steel strip on the inlet side of the annealing furnace to clean the surface, and a method after cold rolling as proposed in JP-A-62-171318. A method is to evenly apply oil to the surface of the stainless steel strip where rolling oil and rolling wear powder are unevenly attached, and to evenly disperse the rolling oil and rolling wear powder that were originally attached to the surface. is there.

[Problems to be Solved by the Invention]

However, in the method as described above, although the pattern such as uneven gloss on the surface of the steel strip after annealing is almost solved,
As shown in FIG. 6, when a plate joint between coils having different plate thicknesses passes through the furnace, the heating rate of the thick stainless steel sheet is different from that of the thin steel sheet, so that the thick stainless steel sheet is heated to a predetermined temperature. If this is attempted, the temperature of the thin steel sheet will rise too high, and not only the properties such as strength and elongation of the steel sheet cannot be guaranteed, but also quality defects such as deterioration of post-process pickling properties will occur at each joining point of the sheets. Therefore, there is a problem that the product yield is deteriorated.

The present invention has been made in view of such conventional problems, and an object thereof is to solve the above-mentioned problems by changing the oil application thickness according to the plate thickness.

[Means for Solving the Problems]

This invention, in the continuous annealing of the stainless steel strip after cold rolling, while providing a degreasing device for performing pretreatment on the inlet side of the continuous annealing furnace, an oil coating device, when changing the plate thickness of the stainless steel strip, Continuous casting of cold-rolled stainless steel strip in which the oil application thickness of the stainless steel strip by the oil application device is changed according to the change ratio of the plate thickness of the steel strip so that the baking temperature of the steel strip becomes equal. It is a blunt method.

[Action]

According to the present invention, the stainless steel strip has a clean surface before the steel is blunted by first removing rolling oil, rolling abrasion powder, etc. that are unevenly adhered to the surface in the degreasing device. become. Next, the oil is uniformly applied to the surface of the steel strip in the oil applying device. However, when steel strips with different strip thicknesses are connected and threaded, the oil coating thickness of the steel strip by the oil coating device is based on the already obtained knowledge (experimental value) according to the change ratio of the strip thickness. The annealing temperature can be made equal by changing the temperature and annealing.

〔Example〕

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of the embodiment, and the annealing furnace 1 is the same as that of the conventional example already shown in FIG. However, this annealing furnace 1
A degreasing device 7 and an oil applying device 8 are disposed in the vicinity of the inlet side of.

In the continuous annealing furnace configured as described above, the stainless steel strip 5 is first subjected to degreasing device 7 to remove rolling oil that is nonuniformly attached to the surface, and also to be subjected to rolling abrasion powder that is also attached to the surface, Foreign substances and the like attached in the previous step are also removed to form a clean surface.

Next, the stainless steel strip 5 is immediately put in the oil applying device 8,
The oil is evenly applied to the surface. However, the oil may be applied by a known method such as spraying or roll coating, but it is important to apply it uniformly on the surface. Here, a method for applying oil in the plate joint portion of the present invention will be described with reference to FIG.

This FIG. 4 shows the relationship between the plate thickness change ratio in the continuation part and the oil application amount corresponding to it, which is obtained by the inventors using an actual A annealing furnace. The result of various experiments was to obtain the amount of oil applied such that the baking temperature of the thick steel plate and the thin steel plate became constant by changing the oil application amount in the section.

For example, if the plate thickness is not changed at all, oil will be about 3.0 g /
m ² is applied to the strip passing, if the strip of 2mm and thickness of 1.5mm passes are connected furnace, the steel strip 2mm 3.0 g
For steel strips of / m ² and 1.5 mm, the thickness change ratio is (2.0-1.
5) /2.0=25%, which means that if about 0.3 g / m ² of oil is applied, the baking temperature will be the same, and the plate of 2.0 mm and 1.0 mm When the welded steel is welded and passes through the furnace, the plate thickness change ratio is 50%, so it is indicated that the oil application amount of the 1.0 mm plate should be zero.

As shown in FIG. 2, the oil application amount may be changed only when the welded portion 12 is in the furnace (that is, the oil application amount is changed only for the furnace length L), and the thick steel plate 11 is When it goes out of the furnace 1 in the direction of the arrow, the amount of oil applied to the portion M following the thin product 12 differs from that of the thick product because the heat treatment conditions are different, so a predetermined amount (3.0 g / m ^{2 in} Fig. ² ) Need to return to.

FIG. 3 shows the next embodiment. This shows a heat curve when a stainless steel plate is annealed in an annealing furnace having a furnace length of 50 m. The white circles in the figure show the heat curve of a thick material (2mm) when the plate thickness is changed from 2mm to 1mm, and the black circles in the figure show the heat curve of a thin material (1mm). As described above, the amount of oil applied to a thick material was 3.0 g / m ² , and the amount of oil applied to a thin material was a plate thickness change ratio of 50%. From this figure, about 1 for thick materials
It can be seen that the thin material can be annealed only by overheating at 0 ° C. Further, as a result of the above, as shown in FIG. 7, the occurrence rate of defects such as baking defects and pickling defects at the plate joints was reduced to about 1/50.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the generation of defects in the furnace and the unevenness of gloss, and to significantly reduce the occurrence of the defective rate at the plate joint portion, thereby improving the product yield.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a continuous annealing furnace in which the present invention is implemented, FIG. 2 is an explanatory diagram of an oil application method for a plate joint portion, and FIG. 3 is a heating curve of a steel strip which is an embodiment of the present invention. A graph, FIG. 4 is a graph showing a relationship between a plate thickness change ratio and an oil coating amount, FIG. 5 is a schematic sectional view of a continuous annealing furnace in a conventional example, and FIG. 6 is a heating curve of a plate joint in the conventional example. The graph shown in FIG. 7 is a graph showing the ratio of occurrence of defective plate joints in the present invention and the conventional example. 1 ... Continuous annealing furnace, 5 ... Stainless steel strip, 7 ... Degreasing device, 8 ... Oil coating device.

Front page continuation (72) Inventor Harumasa Muramoto 1 Kawasaki-cho, Chiba-shi, Chiba Inside the Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Hiroshi Yaginuma 1 Kawasaki-cho, Chiba-shi Chiba Prefecture Inside the Chiba Steel Co., Ltd.

Claims (1)

[Claims] 1. When continuously annealing a stainless steel strip after cold rolling, a degreasing device and an oil coating device are provided for pretreatment on the inlet side of the continuous annealing furnace, and when the thickness of the stainless steel strip is changed. , Cold rolling, characterized in that the oil application thickness of the stainless steel strip by the oil application device is changed according to the change ratio of the plate thickness of the steel strip so that the baking temperature of the steel strip becomes equal Continuous annealing method for stainless steel strip.