KR101832289B1 - Copper-based alloy having excellent forgeability, stress corrosion cracking resistance and dezincification corrosion resistance - Google Patents

Abstract

The steel sheet according to any one of claims 1 to 3, wherein the Cu content is 61.0 to 63.0%, Pb is 1.3 to 2.0%, Sn is 1.8 to 2.8%, Sb is 0.05 to 0.25%, P is 0.04 to 0.15, It is an object of the present invention to provide a copper base alloy having satisfactory machinability and strength and having excellent mono-composition, stress corrosion cracking resistance and anti-slag corrosion resistance.

Description

TECHNICAL FIELD [0001] The present invention relates to a copper base alloy having excellent corrosion resistance, corrosion resistance, corrosion resistance and anti-corrosion resistance,

The present invention relates to a copper base alloy which is excellent in monoaxiality, stress corrosion cracking resistance and anti-slip zinc corrosion resistance, and more particularly to a copper base alloy having excellent monotonicity and high stress corrosion cracking resistance and anti- It is suitable for manufacturing.

As a copper base alloy for forgings having excellent stress corrosion cracking resistance and anti-slag corrosion resistance, Patent Document 1 discloses a copper base alloy containing 0.1 to 0.8% of Sn, 0.01 to 0.5% of Si, and Pb of 0.3 to 3.5% But the mono-composition was still insufficient.

Japanese Patent Application Laid-Open No. 2003-247035

BACKGROUND ART In recent years, products having a hollow portion such as a joint and a valve have been produced by hollow forging in many cases. However, in order to cope with this, a material having a small thermal deformation resistance and excellent monoaxiality than conventional ones is required.

In addition, it is indispensable that such a product is excellent in stress corrosion cracking resistance and anti-slag corrosion resistance.

The present invention has been made to cope with such tendency and demand, and it is an object of the present invention to provide a copper alloy having excellent machinability and strength that can be satisfactorily industrially satisfactory and having excellent mono-composition, stress corrosion cracking resistance and anti- Base alloy.

In order to achieve the above object, the present invention provides, as a first aspect, a copper base alloy which comprises, as a first component, a composition containing 61.0 to 63.0% of Cu, 1.3 to 2.0% of Pb, 1.8 to 2.8% of Sn, 0.25%, P: 0.04 to 0.15, and the remainder is composed of Zn and impurities, and is characterized by excellent mono-composition, stress corrosion cracking resistance and anti-slag corrosion resistance.

The second aspect of the present invention is to provide a copper base alloy which comprises 61.0 to 63.0% of Cu, 1.3 to 2.0% of Pb, 1.8 to 2.8% of Sn, 0.05 to 0.25% of Sb, 0.04 to 0.15 of P, , Te: 0.01 to 0.45%, and Se: 0.02 to 0.45%, and the balance of Zn and impurities, and is excellent in mono-composition, stress corrosion cracking resistance and anti-slip zinc corrosion resistance .

The present invention improves the mono-composition and improves the stress corrosion cracking resistance and the anti-slag corrosion resistance by adjusting the mixing ratio of the Sn component as compared with the copper base alloy described in Patent Document 1, and adjusting other components.

The copper base alloy according to the present invention can be manufactured without causing cracks even in a hot forging product which is difficult to be molded unless the upset ratio is high, such as hot forging or the like, and the stress corrosion cracking resistance and the internal zinc corrosion resistance great.

Further, the copper base alloy according to the present invention is different from the invention of Patent Document 1, and it is not necessary to add Si, Ni or the like.

Fig. 1 shows a composition table of a copper base alloy used for evaluation.
Fig. 2 shows evaluation results of test piece monotonization, stress corrosion cracking resistance, internal zinc corrosion resistance and mechanical properties.
Figure 3 shows the alloy composition used to evaluate the effect of addition of Sb.
Fig. 4 shows the results of analysis of the amounts of components in the? -Phase and the? -Phase.
Figure 5 shows a micrograph after dezincification test.
6 shows a test method for mono-composition.
Fig. 7 shows the sample shape and the torque added male thread used in the stress corrosion cracking test.
Figure 8 shows a sample contained in a desiccator.
Fig. 9 shows a photograph example of a test result of mono-composition.

The reason for determining the components of the copper base alloy in the present invention will be described below.

In the brass for forging, in order to ensure ductility at the time of hot working, the appearance of β phase is indispensable. However, if β phases are mixed in the metal phase after the forging, dezinc corrosion occurs from the β phase easy.

Further, when a hard and soft γ phase appears in the metal structure, the elongation of the mechanical properties is lowered, and when the segregation is increased in the crystal grain boundaries, stress corrosion cracks are likely to appear.

Further, the? Phase is more susceptible to dezinc corrosion than the? Phase.

When the content of the Cu component exceeds 63% (all parts by mass%), the deformation resistance during hot working becomes too large. When the Cu content is lower than 61% (lower), the corrosion resistance of the internal zinc decreases.

Pb is an additive element for improving machinability. In order to secure machinability in the present invention, Pb component is added in an amount of not less than 1.3%, and when it exceeds 1.8%, there is concern that the composition may decrease. According to the experiment, it was found that the Pb component can be added up to 2.0%.

When the Sn content is added in the range of 1.8 to 2.8%, the hot-phase composition is improved and the stress corrosion cracking resistance, which was not obtained by Sn alone, is improved in combination with Sb.

When the content of Sn in the component system is less than 1.8%, the mono-composition is deteriorated.

The Fe component is an impurity in the present invention, the P-Fe compound increases, P is consumed, and the effective additive amount of P is insufficient and the internal zinc corrosion resistance is lowered.

Therefore, the Fe component is 0.1% or less, preferably 0.05% or less, and more preferably 0.02% or less.

Further, in the present invention, Ni and Si components are also impurities.

The Ni content is preferably 0.02% or less, and the Si content is preferably 0.01% or less.

The Sb component improves the corrosion resistance of the internal zinc and improves the stress corrosion cracking resistance, and is particularly effective in combination with Sn.

At least 0.05% addition is required to work effectively.

However, since Sb makes the copper alloy very rough, it was estimated that 0.10% was the limit, but the upper limit was found to be 0.25% by further experiments.

When the copper base alloy according to the present invention is naturally cooled to room temperature after forging, a γ phase is precipitated in addition to the α phase, and the metal phase has a β phase of about 5% or less remaining.

Details will be described later. However, a dezinc corrosion test was conducted in accordance with the ISO method. As shown in Fig. 5, it was found that the γ phase was dezincified as shown in the example of the metal structure photograph.

Therefore, the EPMA analysis of the localized concentrations of the added components in the α-phase and the γ-phase of the copper alloy reveals that Sb exists more in the γ phase than in the α phase. Increasing the amount of Sb increases the concentration of Sb in the γ phase And it was confirmed that the effect of suppressing the de-zinc corrosion on the γ phase was confirmed.

From this, it has been found that the Sb component is preferably in the range of 0.05 to 0.25%.

The Sb component is preferably 0.06% or more, more preferably 0.09% or more and 0.25% or less.

It is mentioned that there is a? Phase segregation as one of the causes of dezinc corrosion. Conventionally, studies for dispersing? Phase in small amount have been proposed, but there is no way to increase the Sb concentration in the? Phase as in the present invention.

The P component has a function of improving the internal zinc corrosion resistance. P also suppresses the migration of Pb into the grain boundary, thereby improving hot workability.

The appropriate amount of P is 0.04 to 0.15%.

The Te component improves the machinability. The Te component has an effect at 0.01% or more, an effect corresponding to the additive amount, and an economical efficiency of 0.45%.

The Se component improves the cutting performance, but since the unit cost is high, it is preferable to suppress the Se.

In addition, since the hot workability deteriorates, it is preferably 0.45% or less.

Therefore, in the case of adding the Se component, the range of 0.02 to 0.45% is preferable.

Example  One

An ingot (having an outer diameter of 60 mm and a columnar length of 80 mm) having various alloy compositions as shown in Fig. 1 was extruded into a round rod shape having an outer diameter of 22 mm at a hot (600 to 620 캜) (Air-cooled) to obtain a copper base alloy material.

In the table of Fig. 1, the components of the column indicated by the inventive alloy correspond to the examples of the present invention. 21 to 23 and No. 25 and 26 show that at least one of the components of the alloy deviates from the scope of the present invention. 24 are sampled from commercial materials.

≪ Evaluation test >

(1) Forging test

The copper base alloy material obtained above was cut to a length of 22 mm, and the monoaxiality was evaluated by the test method shown in Fig.

In FIG. 6, it is a strict test method that a value of upset ratio (%) = {(22-h) / 22) × 100 is large.

In the present invention, since the product which is difficult to be forged is considered in mind, the mono-composition was evaluated at an upset ratio of 60 to 90%.

The forging temperature was set at 700, 750 and 800 ℃.

The forging machine used 250 tons of mechanical press.

As the evaluation, the product at the temperature of the single most favorable composition among the three kinds of temperatures was selected at the upset ratio of 80%, and those in which cracks did not occur were evaluated as?, Those in which cracks were partially observed? Was evaluated as x.

The photograph shown in Fig. 1 (b) is an example of Comparative Example No. 1; 22, and the upset ratio is 70%, 80%, 90% from the top at a forging temperature of 800 占 폚.

(2) Stress corrosion cracking test

A copper base alloy material having an outer diameter of 22 mm was cut into a length of 78 mm and subjected to hot forging to complete the shape shown in Fig. 7 (a).

The outer diameter of the female thread portion was 25 mm and the inner thread was made of 1/2 inch tapered female thread.

The tapered male thread joint of 1/2 inch wound with a sealing tape as shown in FIG. 7 (b) was twisted with a torque of 60 N · m, and the sample was placed in a desiccator containing ammonia water with an ammonia concentration of 14% And the test was conducted.

The test state is shown in Fig.

After 24 hours had elapsed, each specimen was taken out from the desiccator, washed with dilute acid, and evaluated for the presence or absence of cracks by visual inspection.

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(3) Anti-Zinc corrosion test

According to the ISO method, the test material was immersed in a solution of 12.7 g / l of CuCl ₂ .2H ₂ O at 75 ± 3 ° C for 24 hours, and the dezinc corrosion depth was measured and evaluated according to the following criteria.

When the depth of the zinc depletion is 100 탆 or less, it is determined to be acceptable (∘).

(4) Mechanical properties

An ingot (having an outer diameter of 60 mm and a columnar length of 80 mm) having various alloy compositions as shown in Fig. 1 was extruded into a round rod shape having an outer diameter of 10 mm at a hot (600 to 620 캜) Thereby obtaining a copper base alloy material.

This was subjected to a tensile test by machining such that the diameter of the parallel portion was 7 mm and the gauge length was 25 mm, and the 0.2% proof stress, tensile strength, and elongation at break were measured.

Here, the determination standard was a tensile strength of 370 N / mm ² or more and a breaking elongation of 15% or more.

A case of satisfying all of them, a case of satisfying one item, and a case of not satisfying all of them were evaluated as X, respectively.

The chemical components of FIG. 1 and the evaluation results of FIG. 2 will be examined.

Of the examples according to the present invention, 1 to 10 are in a range of 1.3 to 2.0% of Pb, 1.8 to 2.8% of Sn, 0.05 to 0.25% of Sb and 0.04 to 0.15% of P, respectively, so that the composition, stress corrosion cracking resistance, None of the properties were practically problematic.

Inventive alloy No. 6 ~ No. 10 is an additional trial evaluation.

Alloy No. 6 had a Pb component content of 1.97% and an Sb component content of 0.22%, but all of the mono-composition, stress corrosion cracking resistance, internal zinc corrosion resistance and mechanical properties passed through the standards as shown in the table of FIG.

Alloy No. 7 ~ No. 10 is the order of increasing the amount of Sb.

Alloy No. 10 was somewhat weaker than that in which 0.144% of Sb was added, and the mechanical properties were slightly lowered, but the other characteristics were not changed.

The behavior of Sb in the copper alloy structure will be described later.

On the other hand, 21 had a Sb content of 0.01%, which is smaller than the range of the present invention, 0.05%, so that the stress corrosion cracking resistance was particularly deteriorated.

Comparative Example No. 1 22 contained more than 63.0% of Cu (63.1%) and Pb exceeded 2.0% (2.09%).

Comparative Example No. 1 23, Pb exceeded the range of the present invention and Sn was below the range of the present invention, so that monolithic composition and stress corrosion cracking resistance were particularly deteriorated.

Comparative Example No. 1 24 commercially available materials were deteriorated in all the quality items other than the mechanical properties than the alloy of the present invention.

Comparative Example No. 1 25 had a slightly deteriorated mono-composition because Pb exceeded the range of the present invention.

Comparative Example No. 1 26 exhibited deterioration in monotonicity and stress corrosion cracking resistance because Pb exceeded the range of the present invention and Sn and Sb were within the range of the present invention.

In order to confirm the effect of adding Sb, the following test and evaluation were carried out.

An ingot having an alloy composition of the components shown in the table of Fig. 3 (columnar shape having an outer diameter of 60 mm and a length of 80 mm) was extruded into a round rod shape having an outer diameter of 17 mm at a hot (600 to 630 캜) A copper base alloy material was obtained by air cooling.

The hot condition in the extrusion process is close to forging.

On the other hand, in the metal structure, the precipitate is elongated in the extrusion direction.

Therefore, the extrusion-treated material is inferior to the forged material in terms of dezinc corrosion test conditions.

Therefore, the test piece was immersed in a solution of 12.7 g / L of CuCl ₂ .2H ₂ O at 75 ± 3 ° C for 24 hours, in accordance with the ISO method, with a plane perpendicular to the extrusion direction, And the maximum dezincification depth (unit: 占 퐉) was determined.

As the amount of Sb added increases, the internal zinc corrosion resistance becomes good, but when the Sb content is more than 0.15%, the improvement effect is not observed.

Therefore, the upper limit was set to 0.25% in consideration of the mechanical properties.

In order to investigate the reason why the amount of Sb added is increased to improve the internal zinc corrosion resistance, quantitative analysis of the minute portion by EPMA is carried out, and the results are shown in Fig.

When the addition amount of Sb is increased, the Sb amount in the? -Phase is increased although the Sb amount in the? -Phase is not observed.

From these results, it was found that Sb migrates into the γ phase, thereby suppressing the de-zinc corrosion.

However, if Sb in the γ phase exceeds 0.9%, the effect does not seem to change.

Further, paying attention to the amount of the Sb component in the? Phase, the amount of the Sb component in the? Phase is preferably in the range of 0.6 to 1.3%.

Industrial availability

Since the copper base alloy according to the present invention is excellent in monoaxiality, stress corrosion cracking resistance and anti-slip zinc corrosion resistance, it can be applied not only to piping joints and valves but also to various forging products.

Claims (2)

The balance being composed of Zn and impurities in a mass percentage of 61.0 to 63.0%, Pb of 1.3 to 2.0%, Sn of 1.8 to 2.8%, Sb of 0.05 to 0.25% and P of 0.04 to 0.15, Wherein the copper base alloy is excellent in monoaxiality, stress corrosion cracking resistance and anti-slag corrosion resistance. Wherein the steel sheet comprises at least one of Cu: 61.0 to 63.0%, Pb: 1.3 to 2.0%, Sn: 1.8 to 2.8%, Sb: 0.05 to 0.25%, P: 0.04 to 0.15, 0.02 to 0.45%, and the balance of Zn and impurities, and is excellent in monocomponent, stress corrosion cracking resistance and anti-slag corrosion resistance.

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