JP2016113660A - Copper-based alloy for mold casting excellent in dezincification corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of copper alloy casting material hardly causing freezing cracking during mold casting and excellent in corrosion resistance.SOLUTION: There is provided a manufacturing method of a mold casting material consisting of a copper-based alloy containing, by mass%, Cu:65.1 to 69%, Pb:0.05 to 0.25%, 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% and one or more kind of Sb, As and P of total 0.03 to 0.2% and the balance Zn with impurities and heat treated at 450 to 550°C×30 minutes or more after casting.SELECTED DRAWING: None

Description

  The present invention relates to a copper base alloy excellent in dezincification corrosion resistance, and particularly relates to a copper base alloy for die casting excellent in corrosion resistance and a method for producing a mold casting material, which is optimal for faucets and valves.

  As a copper-based alloy that has excellent corrosion resistance and suppresses casting cracks by die casting, Japanese Patent No. 3461081 has a composition of Sn, Sb, As, P, Pb, Al, Fe, Zn, and Cu. In the alloy for alloy, the blending ratio of each component is Sn 0.05 to 0.2% by weight, any one or more of Sb, As or P 0.05 to 0.3% by weight, Zn = 1, Zinc equivalent calculated by Guillet's coefficient of Sn = 2, Pb = 1, Al = 6, Fe = 0.9 is 35.7-41.0% by weight, the balance is made of Cu, and the area occupation ratio of β phase An alloy for die casting characterized by having a solidification temperature range of 17 ° C. or lower with a content of 15% or lower is disclosed.

However, in the copper-based alloy disclosed in the publication, it is specified that Sn is 0.2% by weight or more and solidification cracking occurs when the mold is cast (when the solidification temperature range exceeds 17 ° C.).
By the way, in general, not only virgin materials but also recycled materials are used for the production of brass materials. However, when Sn is contained in the recycled materials of general free-cutting brass at most about 0.8% There is.
Therefore, the copper-based alloy disclosed in this publication can use only a small amount of recycled raw material, and the usage rate of virgin materials such as electrolytic copper and electrolytic zinc increases, resulting in an increase in cost.
Further, since the Sn component has an effect of improving erosion resistance and corrosion resistance, development of an alloy for die casting that allows the addition of Sn to some extent is desired.

Japanese Patent No. 3461081

  An object of this invention is to provide the manufacturing method of the cast material which consists of a copper base alloy for corrosion-resistant metal mold | die casting which does not raise | generate a solidification crack at the time of metal mold | die casting.

The copper base alloy used in the present invention is excellent in dezincification corrosion resistance and mold castability, and is a low Pb copper base alloy.
This alloy is, 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%, Si : 0.2-0.7%, Fe: 0.06-0.2%, Sn: 0.1-2.0%, and the total of any one or more of Sb, As and P: A copper base alloy comprising 0.03 to 0.2% and the balance of Zn and impurities is used.
The feature of the present invention lies in that in a copper base alloy (brass), the castability is improved by optimizing the combination of the Fe component and the Si component while improving the corrosion resistance by adding the Sn component.

  Moreover, the copper base alloy for die casting used in the present invention is, in mass%, Cu: 65.1 to 69%, Pb: 0.05 to 0.25%, Al: 0.2 to 0.7%, Mn: 0.2-0.7%, Si: 0.2-0.7%, Fe: 0.06-0.2%, Sn: 0.1-2.0%, Sb, As and P Any one or two or more of total: 0.03 to 0.2%, Te: 0.01 to 0.45%, Se: 0.02 to 0.45%, at least one of It contains an element, and the balance consists of Zn and impurities.

  Moreover, the copper base alloy for die casting used in the present invention is, 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%, Si: 0.2 to 0.5%, Fe: 0.06 to 0.2%, Sn: 0.1 to 2.0%, Sb, As, or Total of any one or more of P: 0.03 to 0.2%, Te: 0.01 to 0.45%, Se: at least one of 0.02 to 0.45% And / or Mg: 0.001 to 0.2%, Zr: 0.005 to 0.2%, at least one element is contained, and the balance is composed of Zn and impurities. To do.

In the present invention, the above alloy is preferably further added with 3 to 15 ppm of B component.
In the present invention, after die casting using this alloy, it is held at 450 to 550 ° C. for 30 minutes or more and 3 hours or less, so that the β phase area occupation ratio is 15% or less.

  The copper-based alloy according to the present invention can suppress the occurrence of casting cracks in die casting, and is excellent in dezincification corrosion resistance.

The component table | surface of the copper base alloy used for evaluation is shown. The evaluation result of the die casting material of a copper base alloy is shown. The mold structure used for evaluation of crackability is shown. The heat treatment results at Sn: 1.5% and 1.0% are shown. The heat treatment results at Sn: 0.8% and 0.4% are shown. The heat treatment results at Sn: 0.2% and 0.08% are shown. The dezincification test result is shown.

Hereinafter, the components of the copper base alloy used in the present invention will be described.
The Cu component is preferably in the range of 65.1 to 69%.
If the Cu component is less than 65%, the β phase increases and the corrosion resistance decreases.
Increasing the Cu component improves corrosion resistance such as dezincification corrosion resistance, but becomes expensive, so the content 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 is added as necessary, but if it exceeds 0.25%, the elution value of lead increases. , 0.25% or less.

As described above, the Sn component is liable to cause solidification cracking during casting. In the case of using a copper base alloy for die casting, it was generally said that the Sn component had to be set to 0.2% or less.
In the present invention, casting cracks can be prevented in the range of Sn: 0.05 to 2.0%.
Moreover, in order to provide dezincing resistance, 0.1% or more of Sn is necessary.

The Fe component promotes refinement of crystals, suppresses cracking during casting, and improves castability.
The Fe component is preferably in the range of 0.06 to 0.2%.
When the Fe component is controlled within this range, casting cracks due to the addition of Sn are suppressed.
In particular, in the range of Fe: 0.06 to 0.1%, casting crack does not occur even if Sn is increased to 2.0%.

  The Al component improves the hot water flowability, but if it is too much, the resistance to dezincification decreases, so the range is 0.2 to 0.7%, preferably 0.2 to 0.5%. .

Si component also contributes to improvement of castability, promotes refinement of crystals, suppresses solidification cracking during casting, and improves castability.
In particular, when 0.2% or more of Si was added, the effect was great, and it became clear that casting cracks could be prevented in the range of Sn: 0.05 to 2.0%.
In particular, it has been said that the amount of Sn added is preferably 0.20% or less in the past, but in the present invention, sufficient castability can be secured even in the range of Sn: 0.21 to 2.0%. .
However, Si has a large zinc equivalent of 10, and if the amount is large, the β phase increases and the dezincification corrosion resistance is impaired. Therefore, the upper limit of Si is set to 0.7%.

  The Mn component strengthens the matrix but combines with Fe to form a hard intermetallic compound and impair the machinability, so the content was made 0.2 to 0.7%.

The Sb component is preferably added in an amount of 0.03% or more in order to improve the corrosion resistance. However, if it exceeds 0.2%, it is liable to cause coagulation cracking.
In addition, 0.05% to 0.2% of As or P that acts in the same manner as Sb may be added instead of Sb, or these may be added in combination.
When adding in combination, the upper limit of the total is 0.3%.

  The Te component improves the machinability, but is effective at 0.01% or more, and the upper limit is set to 0.45% from the viewpoint of obtaining an effect corresponding to the addition amount and economical efficiency.

The Se component improves machinability, but is suppressed as much as possible because the material unit price is expensive.
Moreover, since hot workability worsens, 0.45% or less is desirable.
When adding Se component, the range of 0.02 to 0.45% is preferable.

The Mg component has an effect of improving strength by crystal refining, improving hot water flow, and deoxidizing / desulfurizing effects.
When 0.001% or more of Mg is contained in the molten metal, the S component in the molten metal is removed in the form of MgS.
On the other hand, if Mg exceeds 0.2%, it is oxidized, and the viscosity of the molten metal is increased, which may cause casting defects such as oxide entrainment.
Therefore, the Mg component has an effect in the range of 0.001 to 0.2%.

The Zr component has a crystal grain refining effect.
The effect appears with addition of 0.005% or more.
Zr has a strong affinity for oxygen, and when it exceeds 0.2%, it oxidizes, increasing the viscosity of the molten metal, and may cause casting defects such as oxide entrainment.

Next, heat treatment will be described.
The alloy of the present invention has an α + β two-phase structure in an as-cast state, but the β phase is reduced by heat treatment at 450 to 550 ° C., and the corrosion resistance is increased.
In addition, if the heat treatment time is less than 30 minutes, it is difficult to reduce the β phase, so it is necessary to keep it for 30 minutes or more.
Moreover, since the heat treatment effect does not change even if it exceeds 3 hours, it is set to 30 minutes or more and 3 hours or less.

As the copper-based alloy, melts having various alloy compositions as shown in FIG. 1 were prepared, and the following evaluation tests were performed.
The result is shown in the table of FIG.
<Evaluation test>
(1) Casting crack test Cast cracking property was evaluated by a both-end restraint test method.
The shape of the mold used is shown in FIG.
A beryllium copper alloy was used as the material of the mold.
In FIG. 3, the heat insulating material 1 is provided at the center so that the cooling at the center is delayed from the both-end restraining portion 2.
The restraint distance L was 150 mm, and the length of the heat insulating material 1 was 100 mm.
In the test, the both ends were constrained by quenching the constrained portion, and it was determined by examining whether the generated solidification shrinkage force caused cracks in the central portion of the test piece serving as the final solidified portion.
In the evaluation, a case where no crack occurred in the central portion was indicated as “◯”, a portion where cracks were partially observed but not broken was indicated as “Δ”, and a case where fracture occurred at the central portion was indicated as “X”.
(2) Dezincing resistance test The test piece evaluated in the casting crack test was heat-treated at 470 to 550 ° C. for 3 hours, and then the test material was made of CuCl ₂ · 2H ₂ O 12 at 75 ± 3 ° C. according to the ISO method. It was immersed in a 7 g / l solution for 24 hours, the dezincification corrosion depth was measured, and evaluated according to the following criteria.
Those having a dezincification depth of 100 μm or less were accepted (◯), and those having a dezincification depth exceeding 100 μm were rejected (x).

<Discussion>
Example Alloy No. 2 (Sn: about 0.4%) and No. 2 4 (Sn: about 0.2%) and No. 4 5 (Sn: about 1.5%) and No. 6 (Sn: about 1.0%) and No. 6 No. 7 (Sn: about 0.8%) and the amount of Sn added and Comparative Example No. With respect to Sn of 21: 0.08%, structural photographs after heat treatment are shown in FIGS.
As a result of heat treatment at 470 ° C. and 550 ° C. for 3 hours, No. Only 21 has a large amount of β phase remaining.
Other alloys have almost lost the β phase.
This β phase is known to be inferior in dezincing resistance.
FIG. 7 shows a structure photograph after the dezincing test.
No. 5, no. 6, no. 7 shows a dezincing test after heat treatment at 470 ° C. for 3 hours.
The dezincing depth is no. 5 (Sn: about 1.5%) is 60 μm, No. 5 6 (Sn: about 1.0%) is 48 μm, no. 7 (Sn: about 0.8%) is 36 μm and 100 μm or less, respectively, and is excellent in dezincing resistance.
No. 2 (Sn: about 0.4%), No. 2 4 (Sn: about 0.2%) and No. 4 No. 21 was subjected to a dezincing test after heat treatment at 550 ° C. for 3 hours.
The dezincing depth is No. 2 is 16 μm. 4 is 12 μm and 100 μm or less, respectively. Sn: 0.08% corresponding to 21 is 100 μm or more, and dezincification corrosion occurs as a whole.
Therefore, when Sn is less than 0.1%, dezincing resistance cannot be maintained even if heat treatment is performed.
Moreover, No. of the comparative example. 23 causes casting cracks.
From the above, Sn is preferably 0.1% or more and 2% or less. Further, if Sb is 0.02%, the corrosion resistance is poor, and if it exceeds 0.2%, casting cracks occur. Therefore, the range of Sb is preferably 0.03% or more and 0.2% or less.

1 Thermal insulation material 2 Both ends restraint part

Claims (4)

  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%, Si: 0.00. 2 to 0.7%, Fe: 0.06 to 0.2%, Sn: 0.1 to 2.0%, and any one or more of Sb, As, and P: 0.03 A die casting material made of a copper base alloy, which is die cast using a copper base alloy comprising ~ 0.2% and the balance Zn and impurities, and then heat-treated at 450 to 550 ° C for 30 minutes or longer Manufacturing method.   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%, Si: 0.00. 2 to 0.7%, Fe: 0.06 to 0.2%, Sn: 0.1 to 2.0%, and one or more of Sb, As and / or P: Copper containing 0.3 to 0.2%, further containing at least one element of Te: 0.01 to 0.45%, Se: 0.02 to 0.45%, the balance being Zn and impurities A method for producing a die casting material made of a copper base alloy, characterized in that die casting is performed using a base alloy, followed by heat treatment at 450 to 550 ° C. for 30 minutes or more.   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%, Si: 0.00. 2 to 0.7%, Fe: 0.06 to 0.2%, Sn: 0.1 to 2.0%, and any one or more of Sb, As, and P: 0.03 -0.2%, Te: 0.01-0.45%, Se: 0.02-0.45%, at least one element or / and Mg: 0.001-0.2 %, Zr: 0.005 to 0.2%, at least one element is contained, and the remainder is die-cast using a copper-based alloy composed of Zn and impurities, and then 450 to 550 ° C. × 30 A method for producing a die casting material made of a copper-based alloy, characterized by heat-treating for at least a minute.   The method for producing a die casting material made of a copper-based alloy according to any one of claims 1 to 3, wherein the copper-based alloy is further added with 3 to 15 ppm of B.