JPS5935635A - Method for box-annealing coil of thin plate - Google Patents

Abstract

PURPOSE:To prevent the production of a strain in a coil even when the plate of the coil is thin by uncoiling a coil of a relatively thin plate and a coil of a relatively thick plate, coiling them so as to position the former coil at the inside and the latter coil at the outside, and annealing the resulting coil. CONSTITUTION:A coil 2A of a relatively thin plate and a coil 2B of a relatively thick plate are uncoiled and coiled again so as to position the coil 2A at the inside and the coil 2B at the outside. The weight of the coil 2B is made >=1/3 time the total weight of the coils 2A, 2B. The resulting coil 20 is mounted on a coil support 10 in an inner cover 8 so that the direction of the coil shaft coincides with the longitudinal direction of the cover 8, and a hot atmospheric gas is fed upward from a central feeding pipe 12 to anneal the coil 20.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a box annealing method for thin plate coils, and in particular, to a box annealing method for a thin plate coil, and in particular to a box that can minimize distortion occurring at the coil side edge in contact with a coil pedestal and distortion occurring at the center in the width direction of the coil. Regarding an annealing method.

The cold-rolled thin steel sheet is wound into a coil and subjected to high-temperature annealing in order to remove strain caused by cold rolling, adjust the composition of the steel sheet such as decarburization, denitrification, deflow, etc., or adjust recrystallization.

In conventional annealing in a patch type annealing furnace, as shown in FIG. The pipe 12 is placed with its winding axis vertically.
The material is annealed by high-temperature atmospheric gas supplied from below.

In other words, the thin plate coil 2 wound with strong winding tension is
The coil is placed on a pedestal 10 and annealed through various thermal cycles. The thin plate coil 2 and the coil pedestal 10 expand and contract in response to temperature changes during heat treatment, and in this case, both expansion and contraction are normal.

It doesn't match completely. Therefore, the surface of the lower surface of the coil 2 that is in contact with the coil holder 10 receives a vertical compressive load due to the weight of the thin plate coil 2 and a horizontal force due to friction, which causes distortion in the end portion 14 of the lower surface of the coil 2. These distortions are generally referred to as ``droppy ears,'' (1).

In addition, the temperature difference in the sheet width direction during cooling during box annealing of thin sheet coils in a batch annealing furnace also has a negative effect on the shape of the steel sheet after annealing, and the temperature difference in the sheet width direction at the outermost periphery has a particularly negative effect. The central part in the width direction expands and becomes swollen, resulting in a defect generally referred to as single stretch 1 when unwinding.

The degree of occurrence of these strains increases as the plate thickness becomes thinner, and becomes noticeable in special KO, 27m thin steel plates, etc. Such distortion at the ends or center of an annealed coil lowers the commercial value of the product and significantly reduces the yield of non-defective products, so preventing or reducing the occurrence of such distortion is an extremely important issue. There is.

1. Thin Plate Coil/7) Various proposals have been disclosed to prevent these distortions occurring during box annealing. For example, one of them is to provide a taper A on the upper surface of the coil holder 10 as shown in FIG.
This reduces the contact area with 0 and alleviates interference due to mutual thermal expansion.

Moreover, as shown in FIG. 2, Utility Model Application No. 55-21062 places a steel plate spacer 16 having the same coefficient of thermal expansion as the thin plate coil 2 to be annealed on the coil pedestal 10, and places the thin plate coil 2 on top of it.
The purpose is to prevent distortion from occurring at the ends of the thin plate coil 2.

By inserting a spacer or cushioning material made of the same material as the coil between the coil 2 and the coil holder 10, the strain can be reduced to some extent, but the plate thickness may become extremely thin. Alternatively, if the plate width of the coil increases, the strength of the material in the coiled state changes, working in a disadvantageous direction in terms of strain generation during box annealing, and the above-mentioned conventional techniques cannot be expected to produce sufficient effects.

SUMMARY OF THE INVENTION An object of the present invention is to provide an effective box annealing method for a thin plate coil, which solves the problems of the prior art described above and can significantly reduce strain generated in the coil, especially when the plate thickness is thin.

The gist of the present invention is as follows.

In other words, in the box annealing method for thin plate coils, in which the thin plate coil is placed on a coil holder inside the inner cover with the winding axis perpendicular and annealed by supplying high-temperature atmospheric gas from below the center, This is a box annealing method for a thin plate coil, which is characterized in that a wound coil is created by placing the coil on the inside and a thick coil on the outside, and then annealing is performed.

The present invention will be explained with reference to FIG. FIG. 3 is a cross-sectional view of the wound coil 2° during box annealing according to the present invention. That is, in the present invention, the coil is unwound before the annealing process, and the two relatively thin coils are placed on the inside, and the thick coil 2B is placed on the outside. The composite wound coil 20 with different plate thicknesses in which a person is wound in the thick coil 2B may be annealed in a normal thermal cycle. For example, in the case of a combination of two relatively thin coils and a thick coil 2B, for example, in the case of a thin coil or an ultra-thin steel plate with a thickness of 2A or 027 or less, the thickness of the relatively thick coil 2B should be as thick as possible. It is better to choose a 9-il with a relatively large difference in plate thickness, for example, 0.35 knots or more, and the weight of the thick coil 2B wound on the outside should be at least 1/3 of the total weight of the electric switch. desirable. This is because the effect of the present invention is extremely small if it is less than 1/3. With this method, the vertical compressive load due to its own weight that was generated at the end 14 in contact with the coil pedestal 10, which occurred in the case of ultra-thin coils or large plate widths, was reduced by conventional methods when the plate thickness was the same. The relatively thin coil 2A is supported by the strong compressive load of the thick coil 2B wound on the outside and the horizontal force due to friction.
The compressive load and horizontal force of one body are reduced, and the coils of extremely high quality can be annealed without almost any ear droop or belly stretch due to distortion that conventionally occurs at the end portion 14. It became so.

Example An embodiment of the present invention will be described with reference to FIG.

A coil 2A with a board thickness of 0.20 m x a board width of 1000 and a cod weight of 4 tons was placed inside, and a coil 2B with a board thickness of 0.35 mm x a board width of 1000 and a weight of 8 tons was placed outside, and a total of 12 pieces were made using the winding method.
Three composite coils 20 of No. 1 were created and box annealed at a temperature of 1150° C. or higher.

On the other hand, for comparison with the north, the conventional method was used to measure plate thickness 0.20 x plate width 10.
One coil of 00tNIIit12t and plate thickness 0.35
Two coils with a width of 1.000 m and a weight of 12 tons were made and box annealed using the same method at a temperature of 1150°C or higher, and the incidence of ear droop and belly elongation was determined for each 10 pieces of sample material. A comparative study was conducted.

The results are shown in Table 1.

Table 1 As is clear from Table 1, although it shows the case using the method of the present invention, the relatively thin inner coil 2A showed no ear droop or belly stretching, and compared to the conventional method with a single plate thickness. Overall, the method of the present invention was able to reduce ear droop by half compared to the conventional method, and also reduce belly elongation to 2/3 of the conventional method.

As is clear from the above examples, all conventional box annealing methods for thin plate coils have only dealt with coils of a single plate thickness, but in the method of the present invention, coils with relatively thin plate thickness are , create composite coils with different plate thicknesses using the winding method so that the thicker coils are positioned on the outside,
Since we adopted a method of box annealing this using a normal heat cycle, we were able to achieve the following effects.

(a) The occurrence of distortion in box annealing of ultra-thin steel coils with a plate thickness of 0.27 mm or less, which could not be avoided in the past, was completely eliminated, as were the two major distortion defects of ear droop and belly elongation.

(b) The method of the present invention does not require the installation or modification of an annealing equipment as in the conventional method, and is a simple method of creating a composite coil by combining inner and outer coils with different plate thicknesses and winding them together, thus reducing costs. Although the increase was only slight, a dramatic improvement in the yield of good products was achieved, making it possible to significantly reduce costs overall.

[Brief explanation of the drawing]

FIGS. 1 and 2 show a conventional box annealing method for a thin coil. FIG. 1 shows a method of creating a taper on the top surface of a coil pedestal, and FIG. 2 shows a method of creating a taper on the top surface of a coil pedestal, and FIG. FIG. 3 is a cross-sectional view showing the box annealing method according to the present invention. 2°°゛Thin plate coil, 8... Inner cover 10
... Coil pedestal, 12 ... High-temperature atmosphere gas supply pipe 2 people ... Relatively thin coil 2B ... Relatively thick coil 20 ... Winding coil (composite Coil) Agent Takeo Nakaji 211- Figure 2 Figure 3

Claims (2)

[Claims] (1) In the box annealing method for thin plate coils, the thin plate coil is placed on a coil holder inside the inner cover with the winding axis perpendicular and annealed by supplying high-temperature atmospheric gas from below the center. A box annealing method for a thin plate coil, which is characterized in that a wound coil is created by placing a thin coil on the inside and a thick coil on the outside, and then annealing is performed. (2) The box annealing method for a thin plate coil according to claim 1, wherein the weight of the relatively thick coil located on the outside is 1/3 or more of the weight of the gold coil.