JPS5825747B2 - Continuous coloring method for stainless steel products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously coloring stainless steel products.

In recent years, chromic acid has been used as a method for coloring stainless steel.
A method of chemically coloring stainless steel products by immersing them in a sulfuric acid mixed acid aqueous solution has been developed and put into practical use.

The colored film obtained by this coloring method is an extremely thin oxide film of 1 micron or less formed on the surface of the material to be colored, and is an interference color that appears colored due to the interference effect of light depending on the thickness of the oxide film. Therefore, in the coloring process, it is necessary to control the color tone with good reproducibility.

As one of the coloring control methods, a method is known in which the potential difference between the surface of the material to be colored and a reference electrode is determined (see Japanese Patent Publication No. 52-25817).

This method uses a platinum electrode as a counter electrode (reference electrode) to measure the electric double layer charge generated by an oxidation reaction on the surface of the material to be colored using a precision potentiometer. Very good control results are obtained when the material to be colored is immersed in the coloring liquid without stirring and colored without moving. Since the double layer is destroyed, there is a problem in that the color tone cannot be controlled electrically.

Therefore, this control method was considered unsuitable for continuous processing of rolled copper strips or continuous processing of small molded parts by moving them on hangers.

The present invention is intended to solve the above-mentioned conventional problems, and provides a method that can reliably control coloring and can continuously color molded parts and long strip products.

In the continuous coloring method of the present invention, when a stainless steel material to be colored is immersed in a chromic acid-sulfuric acid mixed acid coloring liquid bath, the coloring liquid is adjusted in accordance with the moving direction and speed of the colored material in the bath. It is characterized by moving.

In the present invention, by moving the coloring liquid together with the material to be colored as described above, the electric double layer formed on the surface of the material to be colored is maintained for a predetermined time without being destroyed. A colored film can be formed.

In the present invention, the coloring liquid is not particularly limited.
Conventional compositions can be used as is.

The coloring control method utilizes the conventionally known principles as they are.

The invention also relates to a coloring device capable of moving a coloring liquid without destroying the electric double layer.

Hereinafter, the present invention will be explained according to the drawings.

FIG. 1 is an explanation showing the potential difference coloring control method in mixed acid coloring treatment, and shows a state in which an electric double layer A is formed on the surface of the material 1 to be colored by immersing the material 1 in the coloring liquid 2. .

In the figure, 3 is a platinum electrode, and 4 is a potentiometer for measuring the potential difference.

A platinum plate is usually used as the platinum electrode. It is said that the potential difference between the material to be colored 1 and the platinum electrode 3 is caused by an electric double layer in contact with an oxide film formed on the surface of the material to be colored 1.

This electric double layer is extremely thin and unstable because, for example, when anions are selectively adsorbed onto the surface of the material to be treated, the remaining cation layers are attracted electrostatically and are formed opposite each other. It is.

Therefore, when the material to be colored is rapidly moved in the coloring liquid, the electric double layer disappears from the surface of the material to be colored.

FIG. 2 is a sectional view showing one embodiment of the present invention, and shows an example in which a stainless steel strip is continuously colored.

In the figure, reference numeral 1' denotes a stainless steel strip as a material to be colored, which is supplied from the left side of the figure, passes through the coloring tank 5, and is wound up to the right side.

Liquid storage tanks 6 and 7 are provided at the left and right ends of the coloring tank 5, and a coloring liquid circulation pipe 8 is provided along the lower side of the coloring tank 5 to connect the liquid storage tanks 6 and 7. ing.

For coloring, the copper strip 1' is immersed in the coloring tank 5 by means of an acid-resistant guide roller 9 provided in the coloring tank 5, and is gently moved.

The copper strip 1' is colored by the oxidation reaction during this movement, but if the steel strip 1' is simply moved, the electric double layer formed on the surface of the steel strip 1' as described above will become colored. Since the platinum electrode 3 does not move together with the electrode 1, the platinum electrode 3 always measures an insufficient potential difference, making it impossible to control the desired coloring.

Therefore, in the present invention, the colored liquid is moved from the left to the right in the figure in accordance with the moving speed of the steel strip 1'.

In this method, the liquid is caused to flow out from the front liquid storage tank 6 through the rectifying grid 11 at a constant speed.

When the material to be colored is a steel strip as in this example, the coloring liquid flows on the lower side of the copper strip 1', but the copper strip 1' entering the coloring tank 5 on the upper side obstructs the flow of the liquid. Therefore, an appropriate number of rectifying nets 12 are provided above the steel strip 1' and are moved in accordance with the movement of the steel strip 1/.

The rectifying grid 11 and the rectifying net 12 used here are made of acid-resistant materials such as titanium (Ti) and fluororesin, and have a structure as shown in FIGS. 3 and 4, for example.

That is, the rectifying grid 11 is a grid-like frame with a constant thickness so that the colored liquid flows out from the liquid storage tank 6 as a uniform laminar flow vertically parallel to the top, and the rectifying net 12 is designed to prevent liquid from remaining behind. In addition, the net structure should be such that it does not cause turbulence during movement.

The rectifying net 12 is preferably hung on a conveyor 14 such as a plastic cloth as shown in FIG. 2, but if necessary, the lower end is further hung on a Teflon (product name) chain 15 as shown in FIG. It may be supported.

The pre-liquid storage tank 6 is equipped with a discharge pump 10, an agitator 13, a heater 16, and a thermometer 17 to adjust the temperature of the liquid and supply the liquid to the coloring tank 5.

The liquid sent from the coloring tank 5 to the rear liquid storage tank 7 is sent back to the front liquid storage tank 6 via the circulation pipe 8 by the liquid phase pump 18.

An appropriate number of platinum electrodes 3 for potential difference measurement are fixedly provided at appropriate locations in the coloring tank 5.

The copper strip colored as described above is then washed with water, dried and rolled up.

The case where the material to be colored is a steel strip has been described above as an example, but when coloring a molded part, the molded part may be hung on a hanger and placed between rectifying nets.

Note that the coloring tank may be partitioned into two upper and lower tanks, and the colored liquid may be returned to the front storage tank through the lower tank.

The present invention will be explained in detail below.

Dipping and coloring were performed at a liquid temperature of 80° C. using a coloring liquid having the following composition.

Coloring liquid composition: Chromic anhydride 250 g/11 Sulfuric acid 500 g/l Water Residual material to be colored: Material 5US304, long stainless steel strip with thickness 07 mm x width 500 mm. It was fed into the coloring tank at a speed of 1°0 m7 for coloring.

As a result, a beautiful green stainless steel strip was obtained, which had a good hue similar to that colored by the static coloring method.

The following results were obtained by changing the speed and performing the same process.

The color tones obtained were so good that they were indistinguishable from those colored by the static coloring method.

Note that coloring control using a potentiometer during coloring treatment showed changes in potential difference and transition of coloring state similar to those in conventional static bath treatment.

On the other hand, when only the copper strip is moved in a static bath without moving the colored liquid as in the present invention, or when the moving speed of the colored liquid and the copper strip are not made to match, the distance between the copper strip and the platinum electrode is The potential difference was unstable and accurate color tone control was not possible.

As described above, since the method of the present invention is simple in apparatus and operation, coloring can be easily and reliably controlled at any speed using conventional principles.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the coloring control method, Fig. 2 is a sectional view showing an embodiment of the present invention, Fig. 3 is a perspective view of the rectifying grid, and Fig. 4 shows the state in which the rectifying net is used. FIG. In the figure, 1... Material to be colored, 1'... Steel strip, 2... Coloring liquid, 3... Platinum electrode, 4
... Potentiometer, 5 ... Coloring tank, 8 ...
...Liquid circulation pipe, 10...Discharge pump,
11... Rectifier grid, 12... Rectifier net.

Claims (1)

[Claims] 1 When continuously applying oxidation coloring to stainless steel materials such as steel strips by immersing them in a chromic acid/sulfuric acid mixed acid coloring solution, the coloring is done in the same direction according to the moving speed of the material in the coloring solution. A continuous coloring method for stainless steel products characterized by flowing liquid.