JPH02277724A - Method for continuously annealing cold-rolled stainless steel strip - Google Patents

Abstract

PURPOSE:To reduce the development of defect ratio in connecting part of a strip by arranging a degreasing device and an oil coating device at inlet side of a continuous annealing furnace for cold-rolled stainless steel strip and changing oil coating thickness on the steel strip according to changing ratio of strip thicknesses at the time of changing the thickness of the steel strip. CONSTITUTION:At the time of annealing the stainless steel strip 5 in the continuous annealing furnace 1 after cold-rolling, the degreasing device 7 and the oil coating device 8 for executing pre-treatment are arranged at the inlet side of the annealing furnace 1. At first, stuck rolling oil and roll worn powder on the steel strip 5 are removed with the degreasing device 7 to make clean surface of the steel strip and immediately the oil is uniformly applied on the surface with the oil coating device 8. Then, at the time of changing the thickness of the steel strip 5, the oil coating thickness on the steel strip 5 is changed to zero or the prescribed thickness according to the changing ratio of the strip thickness so as to make heating temp. constant. By this method, the development of pattern caused by uneven luster on the connecting part of the strip is prevented and the yield is improved.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides a method for continuous annealing of cold-rolled stainless steel strips.
The present invention relates to a continuous annealing method for cold-rolled stainless steel strips for reducing the defect rate at plate joints.

[Conventional technology]

In general, cold-rolled products of stainless steel strips have a high gloss and smooth surface (and a certain level of strength).

In order to guarantee properties such as elongation, it is necessary to heat the clay at a certain annealing temperature, but in the normal manufacturing process, the cold-rolled stainless steel strip is annealed by continuous annealing as shown in Figure 5. I do. In the figure, stainless steel strip 5
are an inlet roller 2 and an outlet roller 3 installed in an annealing furnace l,
While traveling in the furnace supported by the furnace support rollers 4a, 4b, etc., it is heated to a predetermined annealing temperature by the burner 6 provided on the side wall of the furnace.

By the way, rolling oil, rolling wear particles, etc. adhere unevenly to the surface of a stainless steel strip that has been cold rolled.
If annealing was continued in this state, the surface oxidation reaction proceeded non-uniformly depending on the state of these deposits, resulting in patterns such as uneven gloss on the surface of the copper strip. Therefore, in order to prevent this, there are methods to degrease the stainless steel band on the entrance side of the annealing furnace to clean the surface, and methods to clean the surface after cold rolling, as proposed in Japanese Patent Application Laid-Open No. 62-17138. There is a method of uniformly applying oil to the surface of a stainless steel strip to which rolling oil and rolling wear particles are unevenly adhered, thereby uniformly dispersing the rolling oil and rolling wear particles that were originally attached to the surface. be.

[Problem to be solved by the invention]

However, in the above method, although patterns such as uneven gloss on the surface of the steel strip after annealing are generally resolved,
As shown in Figure 6, when the plate joints between coils of different plate thickness pass through the furnace, the rate of temperature rise is different for thick and thin plates, so thick stainless steel plates are heated to a specified temperature. If you try to do this, the temperature of the thin steel sheet will rise too much, which not only makes it impossible to guarantee the strength and elongation properties of the steel sheet, but also causes quality defects at each joining point of the sheet, such as deterioration of pickling properties in the post-process. There was a problem that this caused deterioration of product yield.

This invention has been made in view of these conventional problems, and aims to solve the above problems by, for example, changing the thickness of the oil coating depending on the thickness of the plate.

[Means to solve the problem]

This invention provides a degreasing device and an oil applicator for performing pretreatment on the entrance side of a continuous annealing furnace when continuously annealing a stainless steel strip after cold rolling, and also provides an oil coating device when changing the plate thickness of the stainless steel strip. This is a continuous annealing method for a cold rolled stainless steel strip in which the thickness of oil applied to the stainless steel strip by a coating device is changed to zero or a predetermined thickness according to the change ratio of the thickness of the steel sheet. .

[Effect]

This invention has the above-mentioned structure, and before the stainless steel strip is annealed, rolling oil and rolling wear particles unevenly attached to the surface of the stainless steel strip are first removed in a degreasing device to make the surface clean. Become. Next, oil is uniformly applied to the surface of the steel strip in an oil applicator. However, when steel strips of different thicknesses are connected and threaded, the thickness of the oil applied to the copper strip by the oil applicator should be adjusted based on the knowledge (experimental values) that has already been obtained, depending on the change ratio of the strip thickness. By changing the temperature and annealing, it is possible to make the firing temperature the same.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment, and the annealing furnace 1 is the same as that of the conventional example shown in FIG.

However, a degreasing device 7 and an oil coating device 8 are disposed close to the entrance side of the annealing furnace 1.

In the continuous annealing furnace configured in this way, the stainless steel strip 5 is first subjected to a degreasing device 7 in which rolling oil that has non-uniformly adhered to the surface is removed, and rolling abrasion powder that has also adhered to the surface is removed. Foreign matter adhering in the previous process is also removed, leaving a clean surface.

Next, the stainless steel strip 5 is immediately placed in an oil applicator 8.
The oil is evenly applied to the surface. However, the method for applying the oil may be any known method such as spraying or roll coating, but it is important to apply the oil uniformly to the surface. Here, based on FIG. 4, a method of applying oil to a plate joint according to the present invention will be described.

Figure 4 shows the relationship between the plate thickness change ratio at the plate joint and the corresponding amount of oil applied. The amount of oil applied at the joint part was determined as a result of various experiments so that the firing temperature of the thick steel plate and the thin steel plate would be constant by changing the amount of oil applied at the joint.

For example, if the plate thickness is not changed at all, the oil will be approximately 3.0g.
However, when steel strips of 2 mm and 1.5 mm thickness are connected and passed through the furnace, 2 mm
The thickness change ratio is (2,0-1,5)/2.0=25%, so for the 1.5mm steel strip, it is approximately 0.3g/%. % oil means that the baking temperature will be the same, and 2.0m and 1.0m
When the plate is welded and passes through the furnace, the plate thickness change ratio is 50%, which means that the amount of oil applied to the plate of 1.0 shell should be zero.

As shown in FIG. 2, the amount of oil applied only needs to be changed when the welded part 12 is in the furnace (that is, the amount of oil applied is changed by the length of the furnace). When going out of the furnace 1 in the direction of the arrow, the amount of oil applied to the part M following the thin material 12 is different from that of the thick material, so the predetermined amount (
In Figure 2, it is necessary to return it to 3°Og/bo).

FIG. 3 shows the next embodiment. This shows a heat curve when a stainless steel plate is annealed in an annealing furnace with a furnace length of 50 m. The white circles in the diagram indicate the plate thickness from 2ml1 to 1
The heat curve of the thick material (2M) when changed to mm, and the black circle in the figure shows the heat curve of the thin material (1 mm). As mentioned above, the amount of oil applied to thick materials is 3.0g/
B. Since the plate thickness change ratio is 50%, the amount of oil applied to the thin material was annealed without applying any oil at all. From this figure,
It can be seen that thin objects can be annealed with only about 10°C of overheating compared to thick objects. Additionally, from the above results, as shown in Figure 7, there was a failure in baking at the temporary joint.

The incidence of defects such as poor pickling was reduced to approximately 1,150.

〔Effect of the invention〕

As explained above, according to the present invention, the time in the furnace is reduced.

In addition to preventing the occurrence of uneven gloss, the defect rate at temporary joints was significantly reduced, improving product yield.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a continuous annealing furnace in which the present invention is implemented, Fig. 2 is an explanatory diagram of a method of applying oil to a plate joint, and Fig. 3 is a heating curve of a toning belt according to an embodiment of the present invention. Graph, Figure 4 is a graph showing the relationship between plate thickness change ratio and oil application amount, Figure 5 is a schematic cross-sectional view of a continuous annealing furnace in a conventional example, and Figure 6 is a heating curve of a plate joint in a conventional example. The graph shown in FIG. 7 is a graph showing the ratio of defective joint portions of the present invention and the conventional example. ■... Continuous annealing furnace, 5... Stainless steel strip, 7... Degreasing device, 8... Oil coating device.

Claims (1)

[Claims] (1) During continuous annealing of stainless steel strip after cold rolling,
A degreasing device and an oil coating device are installed on the entrance side of the continuous annealing furnace for pre-treatment, and when changing the thickness of the stainless steel strip, the thickness of oil applied to the stainless steel strip by the oil coating device is controlled. A continuous annealing method for a cold rolled stainless steel strip, characterized in that the thickness is changed to zero or to a predetermined thickness according to the change ratio of the sheet thickness.