JPH05302183A - Treating method for preventing discoloration of copper and copper alloy - Google Patents

Abstract

PURPOSE:To provide a method to suppress discoloration caused by the ununiformity of treatment in a treating process for preventing the discoloration of copper and copper alloy. CONSTITUTION:Copper and copper alloy bar stock 2 are degreased by passing through a degreasing vessel 3 and a washing vessel 6, are treated for preventing discoloration in a discoloration preventing treating vessel 8 and are cleaned by a shower 13 of a cleansing solution. The solution is previously preheated to >=40 deg.C by passing through a heat exchanger 10 in a recycle vessel 9 of a discoloration preventing treating solution previously kept at 60-80 deg.C. Thus, a metal bar stock is discoloration preventing treated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a discoloration preventing treatment method using an aqueous solution of an inhibitor for copper and copper alloy strips, which does not impair the discoloration preventing treatment effect by the inhibitor and is less likely to cause discoloration due to poor drainage. ..

[0002]

2. Description of the Related Art Copper alloys such as copper, brass and phosphor bronze are metallic materials having relatively high corrosion resistance, but when their surface is exposed to the atmosphere, an oxide film grows and discolors, which reduces the commercial value. I have something to do. In order to prevent this discoloration, it is usually immersed in an aqueous solution containing a benzotriazole-based compound as an inhibitor to perform discoloration prevention treatment.

Although various heat treatments and rolling processes are carried out in the manufacturing process of strip products, discoloration preventing processes are appropriately performed as temporary rust prevention during the process. For example, discoloration prevention treatment may be performed by appropriately adding an inhibitor such as benzotriazole to the final hot water washing tank in an air annealing line, or discoloration prevention treatment may be performed in a step of degreasing rolling oil after rolling.

However, when discoloration prevention treatment is carried out with an aqueous solution of an inhibitor, it is customary to pull up the strip from the treatment liquid, cut the liquid film on the strip surface as much as possible with a roll or an air knife, and then dry. However, if the drainage and the drying are not uniform, discoloration due to the unevenness may be recognized as a patch of appearance. Even if this discoloration is not visually observed immediately after the treatment, it may become clear after a few days and become a defective product.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a method for suppressing discoloration due to nonuniform treatment in the discoloration preventing treatment step of copper and copper alloy strips.

[0006]

Means for Solving the Problems The method of the present invention for solving the above-mentioned problems, in the discoloration preventing treatment of copper and copper alloy, when the metal discharged from the discoloration preventing treatment liquid is washed with a shower of a washing liquid, Copper which is preheated to 40 ° C. or higher by passing the washing solution through a discoloration-preventing treatment solution which is previously held at 60 to 80 ° C., and the metal discharged from the discoloration-preventing treatment solution is washed with the washing solution preheated to 40 ° C. or higher; This is a method for preventing discoloration of a copper alloy.

The continuous discoloration preventing treatment for copper and copper alloys is performed by degreasing, pickling, etc., followed by washing with water, that is, after the metal surface is made as clean as possible, it is immersed in a discoloration preventing treatment solution. It is customary to However, various impurities brought in from the previous step are present in the washing liquid and are brought into the discoloration preventing treatment liquid. Further, it is difficult to completely activate the metal surface, and the metal surface is covered with a surface oxide or a trace amount of organic matter. Surface coatings of these metals will contaminate the tarnish preventative treatment. If such a contaminant of the discoloration preventing treatment liquid is unevenly drained after the discoloration preventing treatment, it remains unevenly on the surface and causes discoloration. In the case of a liquid-draining roll, the wear of the roll surface is uneven due to the metal, and in extreme cases, it may be damaged. The unevenness on the surface of the liquid draining roll causes liquid draining failure, but it is difficult to completely manage this. Even when an air knife is used, it is difficult to always cut the liquid uniformly over the entire width of the metal material (strip). Therefore, even if any known draining method is used, if the operation is continued for a long time, the uniformity of draining will be deteriorated.
Therefore, if the strip surface is washed again with pure water after the discoloration prevention treatment, the discoloration due to the drainage failure can be almost eliminated.

However, the protective film formed by the inhibitor is
In particular, if water is excessively washed immediately after the discoloration preventing treatment, the protective property is lowered. In particular, if the washing temperature is high, the protective property of the inhibitor film is lowered, so it is important to strictly control the temperature of the washing solution to an appropriate value. The discoloration-preventing treatment of copper and copper alloys is a reaction to form a complex compound of an inhibitor. Therefore, the higher the temperature of the aqueous solution is, the more efficient it is, and it is usually performed at 60 to 80 ° C in consideration of operability. In this case, the washing temperature is preferably the same as that of the inhibitor aqueous solution. The temperature of the washing liquid is lower than the temperature of the discoloration-preventing treatment liquid, and 40 ° C. or higher is more suitable than the temperature of the discoloration-preventing treatment liquid. If it is higher than this, the protective property of the protective film is lowered, and if it is lower than this, the cleaning effect is lowered and, further, it impedes continuous drying. Since the strips are preheated to 60 to 80 ° C in the discoloration prevention treatment tank, even if the temperature of washing with water after the discoloration prevention treatment is somewhat low, it is easy to dry because the washing time is short, but still 40 ° C or less. In this case, discoloration due to uneven drying is likely to occur.

Therefore, the washing liquid is very efficient when it is subjected to cleaning after the discoloration prevention treatment after the pipes are passed through the discoloration prevention treatment liquid to exchange heat with the same temperature as the discoloration prevention treatment liquid. Target. The liquid temperature control method of the present invention is extremely effective for stabilizing the discoloration preventing treatment effect and preventing discoloration due to defective drainage. Further, as compared with the case where a temperature control device dedicated to washing water is provided, the operation management can be performed easily and stably.

As a method of washing with water, a method such as a spraying method after pulling up the strip from the discoloration-preventing treatment liquid until the drainage, or a short-time immersion treatment of about 1 second can be considered. , There are no particular restrictions.

When an inhibitor is added to the cleaning solution, the surface of the strip can be cleaned without lowering the protective property of the discoloration preventing film. There are no impurities in the cleaning liquid, and a small amount of cleaning liquid can effectively solve the discoloration problem due to poor drainage.

The present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram of a line process for carrying out the present invention.

First, the metal strip 2 is unwound from the unwinding roll 1 and sent to the degreasing tank 3. Inside the degreasing tank 3, a brush roll 5 and a backup roll 4 are opposed to each other, and the metal strip 2 removes the oil adhering thereto with, for example, an alkaline cleaning liquid while passing between them.

Next, after entering the washing tank equipped with several sets of washing sprays to wash away the washing solution, it enters the discoloration preventing treatment tank 8 and sprays 12 the discoloration preventing solution containing the inhibitor.
Is jetted from. The discoloration preventing solution containing the inhibitor is treated by the discoloration preventing solution circulating pipe 17 to prevent the discoloration preventing treatment tank 8
And the circulation tank 9 are circulated. In the circulation tank 9, the discoloration preventing liquid is maintained at a predetermined temperature by a heat source such as steam.

The metal strip 2 which has been subjected to the discoloration prevention treatment is washed with a washing spray 13. The washing liquid is sent from the washing liquid supply pipe 11 and is installed in the circulation tank 9 in the heat exchanger 1.
After being preheated by 0, it is sprayed from the water spray 13 onto the metal strip 2.

After washing with water, the metal strip 2 is drained by the draining roll 14, passed through the dryer 15, and then wound up by the winding roll 16.

The present invention will be specifically described below with reference to examples and comparative examples.

[0018]

[Example] A rolled material of phosphor bronze strip (Cu-8% Sn-0.1% P) having a plate thickness of 0.2 mm and a width of 600 mm to which rolling oil is adhered is subjected to alkali immersion degreasing, water washing, discoloration prevention treatment, and drying. Degreasing and discoloration prevention treatment were performed by a continuous degreasing line. Table 1 shows the results of testing discoloration resistance after treating under various conditions.

The strip running test conditions are shown below. After the liquid was drained, it was dried and wound into a coil, and then sampled to evaluate the effect of preventing discoloration due to hydrogen sulfide gas, and the occurrence of discoloration due to poor liquid draining.

Degreasing and discoloration prevention treatment 1) Degreasing liquid composition Sodium carbonate 20 g / L Tertiary sodium phosphate 35 g / L Sodium tripolyphosphate 5 g / L Sodium metasilicate 30 g / L Surfactant 10 g / L Temperature 50 ° C. Time 10 seconds 2) Washing with water Spray washing time 3 seconds 3) Discoloration prevention treatment Composition benzotriazole 100 ppm Temperature 70 ° C time 3 seconds 4) Cleaning As shown in Fig. 1, after being pulled out from the discoloration prevention treatment tank 8, a ringer roll (drainage roll) ) 14, a washing spray 13 was provided before the liquid was drained, and pure water was sprinkled on it.

The washing time, that is, the time from spraying to draining the liquid by the draining roll 14 was kept constant at 1 second.

Liquid supply amount by spray is 600 m of material
The flow rate was 6 L / min with respect to the m width. The temperature of the cleaning liquid was 70 ° C.

5) Temperature Control of Cleaning Solution Pure water for cleaning was heated through a heat exchanger arranged in a circulation tank for the discoloration preventing treatment solution. Further, in order to see the effect of the washing temperature on the discoloration prevention treatment, under some conditions, the pure water for washing passed through the heat exchanger was further heated.

6) Draining Draining was performed by using a neoprene rubber roll having a diameter of 200 mmφ from both sides of the strip. For the purpose of seeing the effect of poor drainage, the rubber roll surface has a depth of 0.5 mm and a length of 20 mm.
A scratch with 0 mm was used.

Discoloration resistance evaluation method A phosphor bronze strip was cut into a strip-shaped test piece and 3 ppmH
_The test piece was exposed to a hydrogen sulfide atmosphere of ₂ S, 40 ° C. and 50% RH for 20 minutes, and the degree of sulfurization discoloration of the test piece was visually evaluated.

Evaluation of occurrence of discoloration due to poor drainage 1 for each strip width (600 mm) of phosphor bronze strip for each strip condition
The sample was cut out to a length of m and exposed to a room for 1 week, and the presence or absence of discoloration due to poor drainage was visually observed.

[0027]

[Table 1]

[0028]

As described above, according to the present invention, in the discoloration preventing treatment step of copper and copper alloy strips, discoloration due to drainage failure is prevented without lowering the discoloration preventing treatment effect by the inhibitor. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a specific example of the present invention.

[Explanation of symbols]

 1 Unwinding roll 2 Article 3 Degreasing tank 4 Backup roll 5 Brush roll 6 Washing tank 7 Washing spray 8 Discoloration prevention treatment tank 9 Circulation tank 10 Heat exchanger 11 Washing liquid supply pipe 12 Spray 13 Washing spray 14 Draining roll 15 Drying Container 16 Winding roll 17 Discoloration prevention liquid circulation pipe

Claims (1)

[Claims] 1. In the discoloration-preventing treatment of copper and copper alloy strips, when the metal strip having discharged the discoloration-preventing treatment solution is washed with a shower of a washing solution, the washing solution is preheated to 60 to 80 ° C.
Characterized in that it is preheated to 40 ° C. or higher by passing it through the discoloration prevention treatment liquid held in the above step, and the metal strip discharged from the discoloration prevention treatment liquid is washed with this washing water preheated to 40 ° C. or higher. Discoloration prevention treatment method.