JP2001259728A - Method for annealing and pickling copper and copper alloys - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] A large amount of metal is oxidized and worn in an annealing step, and the production yield is reduced. In order to remove a thick oxide film by pickling in a short time, it is necessary to increase the concentrations of sulfuric acid and hydrogen peroxide and increase the amount of use. In particular, there is a problem that hydrogen peroxide is expensive and consumes a large amount. In an annealing pickling treatment of copper and a copper alloy,
An annealing and pickling method for copper and copper alloys in which the thickness of the oxide film after annealing is controlled to 100 nm or less and then immersed in an aqueous sulfuric acid solution for pickling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for annealing and pickling copper and copper alloys in a continuous annealing pickling line using a butane combustion type annealing furnace or the like.

[0002]

2. Description of the Related Art Copper and copper alloy strips are used in various fields such as high-performance springs, connectors, terminals, lead frames, electronic and electrical materials such as printed circuit boards, and the like. Is repeatedly processed to the product thickness. Here, annealing includes (1) softening a material hardened by rolling to restore rolling workability, (2) adjusting crystal grain size and crystal orientation to impart desired properties to a product, and (3) finalizing. The strain relief annealing after rolling is performed for the purpose of improving the resiliency of the product, removing residual stress, and the like.

In general, for annealing copper and copper alloys, a continuous annealing furnace such as a butane combustion type is often used.
When this type of annealing furnace is used, an oxide film having a thickness of 100 to 300 nm is inevitably formed on the surface of the material. Such an oxide film causes poor appearance of the product and also deteriorates the surface characteristics of the product. Therefore, the oxide film is removed by pickling in the next step. In the pickling treatment, an aqueous solution called a mixed acid, in which sulfuric acid and hydrogen peroxide are mixed, has conventionally been used.

[0004]

Heretofore, in the continuous annealing using an annealing furnace such as a butane combustion type, attention has been paid only to the production of product characteristics. That is, in order to obtain desired characteristics, importance is placed on the furnace temperature and the material passing speed, and the atmosphere in the annealing furnace, which has an important effect on the formation of an oxide film, is not considered. Then, a thick oxide film is formed in an annealing furnace, and in the next pickling step, copper and copper alloy strips are removed by a method of removing with a mixed aqueous solution of sulfuric acid and hydrogen peroxide having a strong corrosive power. Had been manufactured.

[0005] In such a conventional mode of annealing and pickling, there are the following problems, which are factors that lower the production efficiency and increase the production cost. (1) The amount of metal that is oxidized and worn in the annealing step is large, and the production yield is reduced. (2) In order to remove a thick oxide film by pickling in a short time, it is necessary to increase the concentrations of sulfuric acid and hydrogen peroxide and increase the amount of use. In particular, hydrogen peroxide is expensive and consumes a large amount, which has been a major factor in increasing costs.

(3) When an aqueous sulfuric acid solution mixed with hydrogen peroxide is used, not only the oxide film but also the base material of copper and copper alloy are dissolved. For this reason, the amount of metal eluted in the pickling solution increases, and the life of the solution is shortened. In addition, the amount of metal in the waste liquid increases, and the processing cost increases. When the metal concentration in the pickling solution increases, a precipitate is formed.
Further, when a copper alloy containing Sn or the like is treated, an oxide precipitate of SnO ₂ is generated. These precipitates cause problems such as clogging of the pickling tank piping.

The crystal structure of the material may appear,
In this case, color unevenness occurs on the surface of the material after the pickling.

The present invention has been made in view of the above circumstances. (1) After controlling the atmosphere in a furnace such as a butane combustion type annealing furnace to suppress the formation of an oxide film, (2)
By optimizing the pickling conditions and removing the oxide film with a sulfuric acid aqueous solution containing no hydrogen peroxide, the above-mentioned problems can be solved and a method that can efficiently and efficiently perform the annealing and pickling of copper and copper alloys at low cost. The purpose is to provide.

[0009]

Means for Solving the Problems The atmosphere in the butane combustion type annealing furnace contains C ₄ H ₁₀ , CO, CO ₂ , O ₂ and H ₂ O. The thickness of the oxide film after annealing is determined by the respective concentrations of CO, CO ₂ and O ₂ , the annealing time, and the temperature. Since the annealing time and temperature are determined depending on the target product characteristics, it is necessary to control the concentrations of CO, CO ₂ and O ₂ to suppress the formation of an oxide film.

[0010] The inventors of the present invention have stated that 1) in the annealing and pickling treatment of copper and copper alloys, the thickness of the oxide film after annealing is controlled to 100 nm or less, and then the pickling treatment is performed by dipping in an aqueous sulfuric acid solution. A method of annealing and pickling copper and copper alloys having excellent surface properties. 2) In the annealing process, the oxygen concentration in the annealing furnace was reduced to 0.01 vol%.
The annealing pickling method as described in 1) above, wherein the P _CO / P _CO2 ratio (Pi is the pressure of i) is adjusted to 0.29 or more and the thickness of the oxide film after annealing is controlled to 100 nm or less.

3) In the pickling treatment, the concentration of sulfuric acid is 2 to 30.
wt%, pH 1 or less, temperature 20 ~ 40 ℃, Cu ²⁺ concentration 0.1 ~ 3 w
The annealing and pickling method according to the above 1) and 2), wherein the pickling treatment is performed by immersing the pickling solution in a pickling solution having a concentration of t%. 4) The annealing and pickling method according to the above 1) and 2), wherein the pickling treatment is performed by dipping in a pickling solution having a total concentration of metal ions other than Cu of 2 wt% or less. Was found.

Hereinafter, the present invention will be described in detail. (1) Thickness of oxide film after annealing In order to stably remove the oxide film with a sulfuric acid aqueous solution containing no hydrogen peroxide, the thickness of the oxide film needs to be 100 nm or less. If the thickness of the oxide film exceeds 100 nm, the sulfuric acid aqueous solution cannot completely remove the oxide film even if the pickling conditions are adjusted as described later. Although the oxide film thickness is preferably as small as possible, it is limited by the annealing atmosphere as described below.

(2) The atmosphere in the annealing furnace has an O ₂ concentration of 0.01 vol% or less and a P _CO / P _{CO 2} ratio of 0.29 (P
When i is equal to or higher than i), the thickness of the oxide film of copper and copper alloy after annealing can be controlled to 100 nm or less. of course,
The lower the O ₂ concentration and the higher the P _CO / P _CO2 ratio, the thinner the oxide film, but the disadvantages include increased annealing costs and increased gas explosion and fire risks. A more preferred range is 0.001 ≦ O ₂ concentration (vol%) ≦ 0.01, 0.29 ≦ P _CO / P _CO2 ≦ 1.0. O ₂ concentration and _PCO / _PCO2 ratio can be controlled by adjusting the ratio of air and fuel gas (air-fuel ratio).

(3) Pickling solution: Use an aqueous sulfuric acid solution containing no hydrogen peroxide to a thickness of 100
In order to stably remove oxide films of nm or less, it is necessary to use a pickling solution in the following conditions.

PH: The stability of the metal oxide is governed by the pH, and the lower the pH of the pickling solution, the easier the removal of the oxide film. Even if the pH is high, it must be adjusted to a range of 1 or less. When the temperature of the pickling solution is lower than 20 ° C., the removal rate of the oxide film decreases. On the other hand, if the temperature is higher than 40 ° C., it becomes difficult to stably maintain the pH. The optimal temperature of the pickling solution is 20-40 ° C.

Cu ²⁺ concentration: When Cu ²⁺ is present in the pickling solution, Cu ²⁺ acts as an oxidizing agent, and the corrosion ability of the pickling solution is improved. Such an effect is recognized when Cu ²⁺ is present at 0.1 wt% or more. On the other hand, when the Cu ²⁺ concentration exceeds 3 wt%,
Rather, the ability of the pickling solution to remove the oxide film decreases. Therefore C
The u ²⁺ concentration is preferably 0.1 to 3 wt%.

Concentration of metal ions other than Cu ²⁺ : If the pickling treatment is continued, the metal concentration in the pickling solution increases, and the ability of the pickling solution to remove an oxide film decreases. When a Sn-containing copper alloy such as phosphor bronze is treated, Sn ²⁺ eluted in the pickling solution becomes Sn ⁴⁺ over time to form a precipitate (SnO ₂ ) in the solution. ， Clogging the pickling tank piping. If the concentration of metal ions other than Cu ²⁺ is 2 wt% or less, no decrease in the oxidizing ability of the pickling solution is observed, and no actual harm is caused by the precipitate.

Sulfuric acid concentration: If the sulfuric acid concentration is 2 wt% or more, the thickness of the pickling solution is adjusted to the above range, the thickness becomes 10%.
The 0 nm copper alloy oxide film can be removed. on the other hand,
If the sulfuric acid concentration exceeds 30 wt%, the cost of preparing the pickling solution and the cost of treating the waste liquid increase. Therefore, the sulfuric acid concentration is 2
It is preferably about 30% by weight.

[0019]

[Example] Tough pitch copper (C1100, Cu-0.01% O), phosphor bronze (C5210, Cu-8% Sn-0.1% P), nickel silver (C7521, 64% Cu)
-18% Ni-18% Zn) and brass (C2689, Cu-35% Zn) thickness
Using a butane combustion type horizontal annealing furnace, a 0.3 mm strip was
Annealing was performed in various furnace atmospheres at 00 ° C., and thereafter, pickling treatment was performed using sulfuric acid aqueous solutions adjusted to various states.

Auger electron spectra of the samples before and after pickling were measured by Auger electron spectroscopy while performing Ar sputtering, and the alloy component and oxygen peak intensity in the depth direction were determined. From this profile, the thickness of the oxide film was measured. The boundary between the oxide film and the base material was set at a position where the peak intensity of oxygen was an intermediate value between the value on the sample surface layer and the value on the base material. The Ar sputtering rate used was the value for the standard sample SiO ₂ . Table 1 shows the annealing conditions and the pickling conditions, and shows the oxide film thickness measured in each case.

[0021]

[Table 1]

In Example Nos. 1 to 4 of the present invention, the oxide film thickness after pickling was as thin as 5 nm or less, and the surface color after pickling was also good. On the other hand, No.1 and No.2 of the comparative example, since the P _CO / P _CO2 ratio and the oxygen concentration of each annealing furnace off-specified range, exceeding the oxide film thickness is 100nm after annealing, even after pickling A thick oxide film exceeding 5 nm remained. In Comparative Examples Nos. 3 to 7, the oxide film thickness after annealing was 100 nm or less.
No. 4 because the temperature of the pickling solution was lower than 20 ° C because H exceeded 1, and No. 5 because the Cu ²⁺ concentration was lower than 0.1 wt%
In No. 6, the Cu ²⁺ concentration exceeded 3 wt%, and in No. 7, the metal concentration other than Cu 2 ⁺ exceeded 2 wt%, so that a thick oxide film exceeding 5 nm remained even after pickling.

In each of the comparative examples, dullness and unevenness were observed in the color tone of the sample surface after pickling.

[0024]

As is apparent from the above description, according to the present invention, when copper and copper alloy are annealed in an annealing furnace, the atmosphere in the furnace is controlled and the formation of an oxide film during the annealing is suppressed to 100 nm or less. If it is possible, preferred annealing pickling can be performed without using hydrogen peroxide as a pickling solution in the next pickling step. Also, sulfuric acid 2 ~ 30wt%, pH 1 or less, temperature 20 ~ 40
Efficient pickling is possible by setting the concentration of Cu ²⁺ to 0.1 to 3 wt% and the total concentration of metal ions other than Cu to 2 wt% or less to obtain copper and copper alloy with excellent surface properties. This can be expected to have the effects of increasing the yield, reducing the cost of building baths and the cost of treating waste liquid.

Claims (4)

[Claims] Claims: 1. In the annealing and pickling treatment of copper and copper alloy,
A method for annealing and pickling copper and copper alloys, comprising controlling the thickness of an oxide film after annealing to 100 nm or less, and then performing an acid pickling treatment by immersing in an aqueous sulfuric acid solution. 2. In the annealing treatment, the oxygen concentration in the annealing furnace is reduced.
0.01 vol% or less, by adjusting P _CO / P _CO2 ratio (Pi is the pressure of i) to 0.29 or higher, and controlling the thickness of the oxide film after annealing below 100 nm, of claim 1 Annealing pickling method. 3. The pickling treatment, wherein the sulfuric acid concentration is 2 to 30 wt.
%, PH 1 or less, temperature 20 ~ 40 ℃, Cu ²⁺ concentration 0.1 ~ 3 wt%
3. An annealing pickling method according to claim 1, wherein the pickling treatment is performed by immersing the pickling liquid in the pickling liquid. 4. The annealing acid according to claim 1, wherein in the pickling treatment, the pickling treatment is performed by dipping in a pickling solution having a total concentration of metal ions other than Cu of 2 wt% or less. Washing method.