TW201621057A - Copper-based alloy for casting mold with excellent dezincification corrosiveness resistance - Google Patents

Abstract

The purpose of this invention is to provide a method of preparing a casting material made of copper-based alloy for mold casting without causing condensation and cracks during mold casting. The solution of this invention is to use a copper-based alloy with excellent dezincification resistance and mold casting property and comprising in mass% the following components: Cu: 65.1~69%; Pb: 0.05~0.25%; Al: 0.2~0.7%; Mn: 0.2~0.7%; Si: 0.2~0.7%; Fe: 0.06~0.2%; Sn: 0.1~2.0%; the total of any one or more of Sb, As and P: 0.03~0.2%; and the remainder being Zn and impurities.

Description

Copper-based alloy for mold casting excellent in dezincification resistance

The present invention relates to a copper-based alloy excellent in dezincification corrosion resistance, and more particularly to a copper base alloy and a mold casting material for mold casting which are most suitable for corrosion resistance of a faucet or a valve.

As a copper-based alloy which is excellent in corrosion resistance and suppresses casting cracking by die casting, Japanese Laid-Open Patent No. 3,461,081 discloses an alloy for mold casting, which has a composition of Sn, Sb, As, P, Pb, Al, Fe. Zn and Cu are characterized in that the composition ratio of each composition is 0.05 to 0.2% by weight; and either or more of Sb, As or P is 0.05 to 0.3% by weight; according to Zn = 1, Sn = 2. The zinc equivalent calculated by the Guillet coefficient of Pb=1, Al=6, and Fe=0.9 is 35.7 to 41.0% by weight; the remainder is composed of Cu; the area ratio of the β phase is 15% or less, and solidification The temperature range is below 17 °C.

However, in the copper-based alloy disclosed in this publication, it is clearly described that when Sn is 0.2% by weight or more (the solidification temperature range exceeds 17 ° C) and is cast by a mold, solidification cracking occurs.

However, in the production of a brass material, not only a pure material but also a recycled raw material is used. However, in the recycled raw material of general free-cutting brass, Sn may be contained at most about 0.8%.

Therefore, only a small amount of regenerant can be used in the copper-based alloy disclosed in the publication. The use ratio of the pure material such as electrolytic copper or electrolytic zinc becomes high, and as a result, the cost increases.

Further, since the Sn component also has an effect of improving corrosion resistance and rust resistance, it is desired to develop an alloy for mold casting which can allow a certain degree of Sn to be added.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3461081

An object of the present invention is to provide a method for producing a cast material which is composed of a copper-based alloy for corrosion-resistant mold casting which does not undergo solidification cracking during mold casting.

The copper-based alloy used in the present invention is excellent in dezincification corrosion resistance and mold castability, and is a copper-based alloy having a low Pb.

The present alloy is characterized by using a copper-based alloy containing the following composition in mass %; Cu: 65.1 to 69%; Pb: 0.05 to 0.25%; Al: 0.2 to 0.7%; Mn: 0.2 to 0.7%; 0.2~0.7%; Fe: 0.06~0.2%; Sn: 0.1~2.0%; total of one or more of Sb, As and P: 0.03~0.2%; the remaining part is Zn and impurities.

The present invention is characterized in that in the copper-based alloy (brass), the corrosion resistance is improved by adding the Sn component, and the castability is improved by optimizing the combination of the Fe component and the Si component.

Further, the copper-based alloy for mold casting used in the present invention is characterized by containing Cu: 65.1 to 69% by mass%; Pb: 0.05 to 0.25%; and Al: 0.2 to 0.7%; Mn: 0.2 to 0.7%; Si: 0.2 to 0.7%; Fe: 0.06 to 0.2%; Sn: 0.1 to 2.0%; total of one or more of Sb, As, and P: 0.03 to 0.2%; It contains at least one element of Te: 0.01 to 0.45% or Se: 0.02 to 0.45%; the remainder is Zn and impurities.

Further, the copper-based alloy for mold casting used in the present invention is characterized by containing Cu: 65.1 to 69% by mass; Pb: 0.05 to 0.25%; Al: 0.2 to 0.7%; Mn: 0.2 to 0.7%; Si: 0.2 to 0.5%; Fe: 0.06 to 0.2%; Sn: 0.1 to 2.0%; total of one or more of Sb, As or P: 0.03 to 0.2%; further contains Te: 0.01 to 0.45% Or Se: at least one element of 0.02 to 0.45%, or / at least one element of Mg: 0.001 to 0.2% or Zr: 0.005 to 0.2%; the remainder being Zn and impurities.

In the present invention, it is preferred to further add 3 to 15 ppm of the B component to the above alloy.

In the present invention, after the mold is cast using the alloy, it is held at 450 to 550 ° C for 30 minutes or more and 3 hours or less, and the area ratio of the β phase is 15% or less.

The copper-based alloy of the present invention can suppress casting cracking due to mold casting and is excellent in dezincification resistance.

1‧‧‧Insulation

2‧‧‧ Both ends of the restraint

Fig. 1 shows a composition table of a copper-based alloy used in the evaluation.

Fig. 2 shows the evaluation results of a mold cast material of a copper-based alloy.

Fig. 3 shows the mold structure used in the evaluation of the fracture property.

Fig. 4 shows the results of heat treatment of Sn: 1.5%, 1.0%.

Fig. 5 shows the results of heat treatment of Sn: 0.8%, 0.4%.

Fig. 6 shows the results of heat treatment of Sn: 0.2%, 0.08%.

Figure 7 shows the results of the dezincification test.

Hereinafter, the components of the copper-based alloy used in the present invention will be described.

The Cu component is preferably in the range of 65.1 to 69%.

When the Cu component is less than 65%, the β phase increases and the corrosion resistance decreases.

When the Cu component is increased, the corrosion resistance such as dezincification resistance is increased, but it is expensive, so it is preferably in the range of 65.1 to 69%.

Pb is an additive element for improving machinability. In the present invention, 0.05% or more of Pb is added as needed. However, if it exceeds 0.25%, the elution value of lead becomes high, so it is set to 0.25% or less.

As described above, the Sn component is liable to cause solidification cracking during casting. When a copper-based alloy is used for mold casting, it is generally necessary to set the Sn component to 0.2% or less.

In the present invention, casting cracking can be prevented in the range of Sn: 0.05 to 2.0%.

Further, in order to impart dezincification resistance, Sn must be 0.1% or more.

The Fe component promotes the crystallization of the crystal, suppresses cracking during casting, and improves castability.

The Fe component may be in the range of 0.06 to 0.2%.

When the Fe component is controlled within this range, casting cracking due to the addition of Sn can be suppressed.

Especially in the range of Fe: 0.06 to 0.1%, even if Sn is as much as 2.0%, casting cracking is not caused.

The Al component improves fluidity, but when it is more, it will make it resistant to dezincification. The decrease is in the range of 0.2 to 0.7%, preferably in the range of 0.2 to 0.5%.

The Si component is also advantageous for improving the castability, promoting the crystallization of the crystal, suppressing the solidification cracking during casting, and improving the castability.

In particular, if 0.2% or more of Si is added, the effect is large, and it is apparent that the casting crack can be prevented in the range of Sn: 0.05 to 2.0%.

In particular, in the past, it is generally considered that the addition amount of Sn is preferably 0.20% or less. However, in the present invention, sufficient castability can be ensured even in the range of Sn: 0.21 to 2.0%.

However, when the zinc equivalent is as large as 10, the β phase is increased when the amount of Si is large, and the dezincification resistance is impaired, so the upper limit of Si is set to be 0.7%.

The Mn component is a reinforced mold, but it is bonded to Fe to form a hard intermetallic compound and impairs machinability. Therefore, it is set in the range of 0.2 to 0.7%.

In order to improve corrosion resistance, 0.03% or more of the Sb component may be added, but when it exceeds 0.2%, solidification cracking easily occurs, so it is set to 0.2% or less.

Further, in place of Sb, 0.05 to 0.2% of As or P which exhibits the same action as Sb may be added, and a combination of these may be added.

In the case of adding a combination, the total upper limit is 0.3%.

The Te component improves the machinability, and has an effect of 0.01% or more. From the viewpoint of the effect and economical efficiency of the addition amount, 0.45% is made the upper limit.

The Se component improves the machinability, but the material unit price is expensive, so the content is suppressed as much as possible.

Further, since the hot workability is deteriorated, it is preferably 0.45% or less.

When the Se component is added, it is preferably in the range of 0.02 to 0.45%.

The Mg component has increased strength and fluidity due to crystal fineness Rise, deacidification. Desulfurization effect.

When the molten metal contains 0.001% or more of Mg, the S component in the molten metal is removed as MgS.

Further, when Mg exceeds 0.2%, oxidation occurs, and the viscosity of the molten metal is high, which may cause casting defects such as oxide entrapment.

Therefore, the effect of the Mg component in the range of 0.001 to 0.2% can be confirmed.

The Zr component has a fineness of crystal grains.

Adding 0.005% or more will show an effect.

Further, since Zr has a strong affinity with oxygen, oxidation occurs when it exceeds 0.2%, and the viscosity of the molten metal becomes high, which may cause casting defects such as oxide entrapment.

Next, the heat treatment will be described.

The alloy of the present invention has a two-phase structure of α + β in a cast state, but the β phase is reduced by heat treatment at 450 to 550 ° C, and the corrosion resistance is increased.

Further, when the heat treatment time is less than 30 minutes, the β phase is not easily reduced, so it is necessary to maintain it for 30 minutes or longer.

Further, even if it was more than 3 hours, the heat treatment effect did not change, so it was set to be 30 minutes or more and 3 hours or less.

[Example 1]

As the copper-based alloy, molten metal of various alloy compositions as shown in Fig. 1 was prepared, and an evaluation test as described below was carried out.

The results are shown in the table of Figure 2.

<evaluation test>

(1) Casting fracture experiment

The casting fracture property was evaluated by the restraint test method at both ends.

The shape of the mold used is shown in Fig. 3.

A beryllium copper alloy is used as the mold material.

In Fig. 3, the heat insulator 1 is provided at the center portion, and the cooling of the center portion is slower than the restraint portions 2 at both ends.

The restraint distance L is set to 150 mm, and the length of the heat insulator 1 is 100 mm.

In the test, it was judged that the restraint portion was quenched and restrained at both ends, and the solidification contraction force generated was observed to cause cracking in the central portion of the test piece which became the final solidified portion.

In the evaluation, the rupture in the center portion was ○, and it was confirmed that the portion was broken, but the rupture was Δ, and the rupture at the center was ×.

(2) Dezincification resistance test

After the test piece evaluated in the casting fracture test was heat-treated at 470 to 550 ° C for 3 hours, the test material was immersed in CuCl ₂ at 75 ± 3 ° C based on the ISO method. The depth of dezincification corrosion was measured for 24 hours in a 12.7 g/l solution of 2H ₂ O, and evaluated according to the following criteria.

When the dezincification depth is 100 μm or less, it is acceptable (○), and when the dezincification depth exceeds 100 μm, it is assumed to be unacceptable (×).

<inspection>

For example, alloy No. 2 (Sn: about 0.4%), No. 4 (Sn: about 0.2%), No. 5 (Sn: about 1.5%), No. 6 (Sn: about 1.0%), No. The amount of addition of Sn corresponding to .7 (Sn: about 0.8%) and Sn of Comparative Example No. 21: 0.08%, and the photograph of the structure after heat treatment is shown in FIGS. 4 to 6.

Heat treatment was performed at 470 ° C and 550 ° C for 3 hours, respectively, and as a result, only a large amount of β phase remained in No. 21 .

The β phase of other alloys almost disappeared.

It is known that the β phase is poor in dezincification resistance.

Fig. 7 shows a photograph of the tissue after the dezincification test.

No. 5, No. 6, and No. 7 were subjected to a dezincification test after heat treatment at 470 ° C for 3 hours.

Regarding the dezincification depth, No. 5 (Sn: about 1.5%) is 60 μm, No. 6 (Sn: about 1.0%) is 48 μm, and No. 7 (Sn: about 0.8%) is 36 μm, both of which are 100 μm or less. Excellent in dezincification.

Further, about No. 2 (Sn: about 0.4%), No. 4 (Sn: about 0.2%), and No. 21, after heat treatment at 550 ° C for 3 hours, a dezincification test was performed.

Regarding the dezincification depth, No. 2 was 16 μm, and No. 4 was 12 μm, and both were 100 μm or less. However, Sn: 0.08% of No. 21 was 100 μm or more, and dezincification corrosion was caused as a whole.

Therefore, when Sn is less than 0.1%, the dezincification resistance cannot be maintained even if heat treatment is performed.

In addition, Comparative Example No. 23 caused casting cracking.

In summary, Sn is preferably 0.1% or more and 2% or less. Further, when Sb is at 0.02%, the corrosion resistance is poor, and when it exceeds 0.2%, casting cracking occurs, and the range of Sb is preferably 0.03% or more and 0.2% or less.

Claims (4)

A method for producing a mold cast material composed of a copper-based alloy, characterized in that the following copper-based alloy is used for mold casting, followed by heat treatment at 450 to 550 ° C for 30 minutes or more; Contains Cu: 65.1~69%; Pb: 0.05~0.25%; Al: 0.2~0.7%; Mn: 0.2~0.7%; Si: 0.2~0.7%; Fe: 0.06~0.2%; Sn: 0.1~2.0% ; the sum of any one or two of Sb, As, and P: 0.03 to 0.2%; the remainder is Zn and impurities. A method for producing a mold cast material composed of a copper-based alloy, characterized in that the following copper-based alloy is used for mold casting, followed by heat treatment at 450 to 550 ° C for 30 minutes or more; Contains Cu: 65.1~69%; Pb: 0.05~0.25%; Al: 0.2~0.7%; Mn: 0.2~0.7%; Si: 0.2~0.7%; Fe: 0.06~0.2%; Sn: 0.1~2.0% ; a total of one or more of Sb, As, and P: 0.03 to 0.2%; further containing at least one of Te: 0.01 to 0.45%, Se: 0.02 to 0.45%; the remainder being Zn and impurities. A method for producing a mold cast material composed of a copper-based alloy, characterized in that the following copper-based alloy is used for mold casting, followed by heat treatment at 450 to 550 ° C for 30 minutes or more; Contains Cu: 65.1~69%; Pb: 0.05~0.25%; Al: 0.2~0.7%; Mn: 0.2~0.7%; Si: 0.2~0.7%; Fe: 0.06~0.2%; Sn: 0.1~2.0% ; a total of one or more of Sb, As, and P: 0.03 to 0.2%; further containing at least one of Te: 0.01 to 0.45%, Se: 0.02 to 0.45%, or / and Mg: 0.001~ 0.2%, Zr: at least one of 0.005 to 0.2%; the remainder is Zn and impurities. The method for producing a mold cast material comprising a copper-based alloy according to any one of claims 1 to 3, wherein the copper-based alloy further contains 3 to 15 ppm of B.