JPS60128222A - Annealing method capable of preventing development of temper color - Google Patents

Abstract

PURPOSE:To prevent the development of temper color without exerting any unfavorable influence on an annealing effect when a steel sheet or a thin steel strip is annealed in a tight annealing equipment, by covering the edges of the material with thin plates before annealing. CONSTITUTION:When a coil 1 of a steel sheet or a thin steel strip is annealed in a tight annealing equipment, the edges of the coil 1 are covered with coil edge caps 2 made of a thin plate, and the caps 2 are fixed with a packing band 3. The coil 1 is then annealed. Since parts of the coil 1 close to the edges are not excessively exposed to atmospheric gas for annealing, the formation of oxide films is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to annealing technology in a reducing atmosphere gas in tight annealing equipment, and particularly relates to an annealing method for preventing the occurrence of temper color on tin plate blanks. For annealing, tight annealing equipment is used. Normally, the cold-rolled and cleaned coils are tightly wound and stacked in 8 to 5 layers on a mallet base. An inner cover is placed on top of the coils to block outside air, and the inside of the inner cover is The furnace body (
The coil is then heated until it reaches a certain temperature, held at that temperature for a certain period of time (soaking), and then the bell is removed and cooled.

However, this method has a problem in that a milky white temper color occurs at the coil edge portion of the tin plate, which significantly impairs the aesthetic appearance of the tin plate.

An object of the present invention is to provide an annealing method that can effectively prevent the occurrence of temper color on the product during annealing using tight annealing equipment.

In order to achieve this objective, the inventors of the present invention have conducted extensive research and found that silicon and manganese that have become concentrated or attached to the surface of the coil due to excessive exposure of the edge of the coil to atmospheric gas during annealing. It was discovered that the oxide becomes a milky white temper color when oxidized, and based on this knowledge, various experiments were conducted, and as a result, the present invention was completed.

The gist of the present invention is that when a thin steel plate or copper strip is annealed in tight annealing equipment, the end face is covered with a thin steel plate or the like in advance to prevent the vicinity of the end face from being excessively exposed to the annealing atmosphere gas. The present invention provides an annealing method capable of preventing thermal annealing, which is characterized by preventing the formation of an oxide film.

The present invention will be explained in detail below.

The cold-rolled and cleaned coil is tightly wound and then heated in a tight annealing furnace as shown in Figure 1.
The coils G are stacked in 8 to 5 stages on the base B, a center spacer E is arranged between the coils to promote heat transfer, and a top plate (F) for flow rate adjustment is placed on the top stage. and,
Cover with inner cover D to shut off outside air, replace the inside of this inner cover with weakly reducing atmospheric gas, cover with bell A and perform annealing. The flow of atmospheric gas is as shown by arrow H in the figure. There is.

Because the atmospheric gas flows in this way, the edge part of the coil G comes into contact with the atmospheric gas in a particularly large amount, and as a result, the silicon and manganese on the coil surface are exposed to oxygen or H in the atmospheric gas.
It is oxidized by 0, and an oxide film is easily formed.

That is, l' within the annealing temperature range of 500 to 700°C
Comparing the oxygen potentials of e, Mn, and Si redox reactions, the order is Fe>In>Si, and for example, at 800°C, each -92KO
al, -146KOal, -162Kcal,
The partial pressure ratio of H8, H, and O in the equilibrium state is each 2.6.0X
IO', 8.5X10? This is thought to be because it becomes easier to form an oxide film in the order of Si and MnxFe.

The cause of the formation of oxide film on the edges of the coil/17G is thought to be as follows.0 Figure 2 shows the situation between the ends of the coil, which is tightly wound after cold rolling and cleaning. The strip gap A is usually about 0.6 μm, and oxygen in the atmosphere exists in this gap, causing the formation of an oxide film.

Another reason is that the atmospheric gas flowing during annealing tends to enter the strip gap A from the edge portion, and the atmospheric gas contains about 10 pI)m of oxygen, H, and O.

Incidentally, if we assume that a coil with an inner diameter of 15'00 mm can bring in air from the edge to a 100H width area, the amount of oxygen existing between them is calculated to be 1.
5. '7118. On the other hand, regarding the presence of oxygen due to the intrusion of atmospheric gas into the gap, the oxygen concentration is 10 ppm.
If it is included, the amount of oxygen that passes through this part until the completion of annealing is estimated to be approximately 20011188 by the same calculation.〇This amount of oxygen, H80, is particularly concentrated at the edge of the coil one after another. It is easy to imagine that the silicon, manganese, etc. on the surface of the coil will be oxidized and form oxides.

Therefore, in the present invention, the temper color can be removed by taking measures to block the presence and invasion of the atmospheric gas that occupies most of the amount of oxygen existing at the edge portion of the coil or entering from the edge portion. In order to prevent this, for example, as shown in Fig. 8, the end face of the coil is covered with a coil edge cap 2 made of a thin steel plate, fixed with a packing band 8, etc., and annealed in this state. In order to confirm the effectiveness of the present invention in preventing the occurrence of temper color, a coil of tin plate was tightly wound, the end face of the coil was covered with the aforementioned coil end cap, and the coil was packed, and then annealed in a tight annealing furnace. . The results are shown in the table below. In addition, the same table also shows the test results for the conventional method of annealing without using an end face covering as in the present invention.

From the same table, in the case of the method of the present invention, the occurrence of temper color can be significantly reduced, the amount of edge defects removed is significantly reduced, and the yield is also improved by about 20 inches. According to 11 simple measures, it is possible to effectively prevent the occurrence of temper color without adversely affecting the annealing effect, so it is possible to provide beautiful coils with a high yield.

[Brief explanation of drawings]

Fig. 1 is a side view schematically showing the tight annealing equipment, Fig. 2 is a diagram illustrating the state of the end face of the coil accommodated in the tight annealing equipment of Fig. 1, and Fig. 3 is a side view schematically showing the tight annealing equipment. FIG. 3 is an explanatory diagram showing a state in which the end face of the coil is covered with a coil edge cap.・1... Coil 2... Coil edge cap 8... Packing hand A... Bell B... Base D... Inner cover F... Top plate G... Coil a... Strip stomach·
・Strip gap ・Atmospheric gas flow

Claims (1)

[Claims] L When annealing a thin steel plate or copper strip in tight annealing equipment, cover the end face with a thin steel plate in advance to prevent the vicinity of the end face from being excessively exposed to the annealing atmosphere gas and prevent the formation of an oxide film. An annealing method capable of preventing temper color.