JPS6017032B2 - Salt wiping method and device in salt bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for wiping a metal strip in a salt bath for descaling or heat treatment by immersing the metal strip in molten salt.

When removing surface oxidized scale in the manufacturing process of stainless steel strips, silicon steel strips, etc., a method of soaking the strip in molten salt and then pickling is generally used.

This dipping treatment in molten salt (hereinafter referred to as salt treatment) is a treatment to change the delicate and stable oxide scale, which is difficult to remove by pickling alone, to make it easier to remove by pickling.
This is usually done using a salt bath as shown in Figure 1. That is, the strip plate 1 advances in the direction of the arrow, enters the salt bath 2, is immersed in the molten salt 3 between the inlet sink roll 4 and the outlet sink roll 5, is bent by the deflector roll 6, and then leaves the salt bath. I go outside. In FIG. 1, 7 and 8 are wipers for preventing the molten salt from adhering to the strip plate and coming out of the salt bath 2, and 9 is a wiper for preventing the molten salt from adhering to the strip plate and being discharged outside the salt bath 2;
10 is a cover. Conventionally, a non-contact steam wiper has been used to prevent surface scratches from forming on the strip. Conventionally used steam wipers for salt baths are installed on the outlet side of the strip in the salt bath, as shown in Figure 1, for example, and spray heated steam on the front and back surfaces. There is a problem.

○｝The steam injected from the edge of the strip hits the molten salt liquid surface, and the salt droplets adhere to the inner surface of the salt bath cover and solidify, falling onto the strip surface and causing mud on the strip surface. . {2' The steam injection slit nozzle of the wiper is thermally deformed, causing nozzle clogging and uneven injection.

{3' The wiping effect in the width direction of the strip is not uniform, and the reaction due to the adhering salt after the strip leaves the salt bath is uneven in the width direction, resulting in uneven gloss after descaling.

The present invention is intended to solve these conventional problems in salt baths, and it reduces the amount of molten salt to the necessary minimum, eliminates uneven salt adhesion to the strips, and improves the internal and external parts of the salt bath. The purpose of the present invention is to provide a salt wiping method and apparatus that do not cause problems such as generation of surface roughness of strips and environmental deterioration due to scattering of molten salt.

The salt wiping method of the present invention is characterized by wiping the molten salt from the surface of the strip by rotatably pressing a metal roll whose surface is coated with molten salt against the strip. The feature of the ping device is that the metal roll that wipes the top surface of the strip is placed between the outlet sink roll and the deflector roll in the salt bath, and the metal roll that wipes the bottom surface of the strip slope is placed in the salt bath behind the deflector roll. The metal rolls are provided in pressure contact with the strip plate, and the roll diameter is small so that the surface of each of the metal rolls is coated with molten salt, and a cold air intrusion prevention wall is provided at the salt bath outlet.

The salt wiping method of the present invention will be explained in detail below.

A metal roll is rotatably pressed against a strip that is continuously drawn out from a molten salt tank to remove excess molten salt adhering to the surface of the strip, and at the same time remove any remaining molten salt on the surface of the strip. Eliminate unevenness. The salt used is N
Since various salts are added to aOH' and melted by heating to 400 to 500 qo, metal rolls are used. The surface of the metal roll must be coated with molten salt. This is because when the molten salt that comes into contact with the strip and adheres to the roll surface solidifies, the surface of the strip becomes rough due to the solidified salt. In order for the surface of a metal roll to be coated with molten salt, there is a method of heating the roll by an appropriate means so that the entire surface temperature of the roll is always maintained at a temperature higher than the freezing point of the molten salt, or a method of heating the roll by an appropriate means so that the temperature of the entire surface of the roll is always maintained at a temperature higher than the freezing point of the molten salt, or A method is used in which the diameter of the roll is reduced so that the retained heat keeps the roll at a temperature above the freezing point of the molten salt. In the latter case, if the roll diameter is made too small, the roll will be deformed during the rolling reduction adjustment described later, so it is necessary to set the roll diameter to an appropriate value.

Reducing the roll diameter does not require special heating means.
Furthermore, since the contact with the strip approaches a line contact, the wiping effect of the molten salt increases. When determining the roll diameter, consider factors such as the temperature of the molten salt, viscosity, roll atmosphere temperature, roll rotation speed, rolling force, roll length, and thermal conductivity of the strip, so that the entire surface of the roll is coated with the molten salt. to be done. Further, the roll is pressed against the strip with an appropriate force in order to remove excess molten salt adhering to the strip and eliminate uneven adhesion of molten salt remaining on the strip. If the rolling force is insufficient, excess molten salt will adhere to the strip and be pushed out of the salt bath, while if the rolling force is too large, the rotation of the rolls will be inhibited and slipping will occur on the strip. Next, the salt wiping device of the present invention will be explained in detail based on the drawings.

FIG. 2 shows a part of a side view of a salt bath showing a preferred example of the apparatus of the present invention.

A small diameter metal roll 11 for wiping the top surface of the molten salt adhering to the top surface of the strip plate 1 is provided between the outlet side sink roll 5 and the deflector heel 6, and a small diameter metal roll 11 for wiping the molten salt adhering to the top surface of the strip plate 1 is installed in the salt bath behind the deflector roll 6. A small-diameter metal roll 12 for wiping the adhered molten salt is provided, and the rolls 11 and 12 are attached to the roll adjustment handle 1 so as to be rotatably pressed against the strip plate 1.
The pressure is adjusted by steps 3 and 14. Moreover, cold air intrusion prevention walls 15 and 16 are provided at the salt bath outlet. Second
The figure shows two small metal rolls 11 for upper surface wiping (11-1 and 11-2), which are preferred examples for the following reasons.

In other words, foreign substances such as iron oxide are often floating in the molten salt in the salt bath, and these foreign substances adhere to the top surface of the strip along with the molten salt, and solids may fall onto the strip. However, the upper surface wiping metal roll 11 may be damaged. If the roll is damaged, the roll marks will be printed on the strip, damaging the surface quality of the strip. Therefore, two metal rolls 11 for wiping the upper surface are provided, one of which is pressed against the strip plate, and if the roll becomes bent, the other roll is used. In the example of FIG. 2, the upper surface wiping metal rolls 11-2 are pressed against the strip, and the rolls 11-1 are floating from the strip. The metal rolls for wiping, both for the upper and lower surfaces, are set to the maximum length as shown in FIG. If the roll is held inside the salt bath, heat is absorbed by the holding mechanism and the molten salt on the roll surface solidifies, potentially damaging the strip surface and causing problems such as bearing oil in the holding mechanism flowing out. So I don't like it. Cold air prevention wall 15 at the salt bath outlet
, 16, cold air from a jet cooler or the like for cooling the strip after salt treatment enters the salt bath, cools the wiping metal roll, solidifies the molten salt on the surface of the roll, and cools the strip. installed to prevent damage to the

As mentioned above, the diameter of the small metal roll for wiping is as follows:
It is necessary to set an appropriate value depending on the salt used and operating conditions, but when processing a stainless steel strip with a maximum width of about 120 m² at a maximum speed of about 36 m²/min, molten salt of about 48 mm x 0.0 m is passed through it. It is preferable to have 4 to 10 enemies.

Although the above description of the present invention has been mainly concerned with salt treatment for descaling strips, the same configuration can also be used for heat treatment to bring about similar effects.

By using the method of the present invention or bag straightening, the amount of salt consumed in the salt bath is significantly reduced, the amount of curls in the treated strips is reduced, and the working environment near the salt bath is also improved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the structure of a subordinate salt bath, Fig. 2 is a partial detailed view showing an embodiment of the salt wiping device according to the present invention, and Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. be. 1...Strip plate, 2...Salt bath, 3.
...Melting salt, 4,5"""Thin roll, 6
""" Deflector roll, 7, 8...Wiper, 10
...Force bar, 11, 12...Small diameter metal roll,
13, 14... Lower adjustment handle, 15, 16...
...Cold air prevention wall. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. Salt wiping in a salt bath, characterized in that a metal roll whose surface is coated with the molten salt is rotatably pressed against a metal strip continuously drawn from the molten salt. Method. 2. A small-diameter metal roll rotatably pressed against the upper surface of the metal strip to be treated is provided between the outlet sink roll and the deflector roll in the salt bath, and the lower surface of the strip is placed in the salt bath behind the deflector roll. 1. A salt wiping device for a salt bath, characterized in that a small-diameter metal roll is rotatably pressed against the salt bath, and a cold air intrusion prevention wall is provided at the salt bath outlet.