JPS5818418B2 - Manufacturing method of high-strength aluminum alloy for casting with excellent alumite properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [The present invention relates to a method for producing a high-quality aluminum alloy for casting that has good mechanical properties and excellent alumitability.

In recent years, A7 CIJ alloy, Al
-S i -M g alloy, AA -S i -Cu-
Various alloys such as Mg-based alloys have been proposed.

Among these alloys, for example, Ail can 24470sA7 coa is a 1-Cu-based test alloy.
X14Ly' AIl cast 67 has been proposed, and in both cases, the content of iron as an impurity is regulated to 0.20% by weight or less (all contents used in this specification are treated as weight%) to create a good machine. It has acquired the characteristics of

In putting the above-mentioned alloy into practical use, the present inventors found that although good mechanical properties were obtained, there were problems with alumite properties and pressure resistance, and attempted to solve these problems.

In other words, when aluminum alloy castings are generally subjected to alumite treatment, titanium is often added as an agent to disperse impurities that precipitate at grain boundaries; Color unevenness may occur, causing problems in terms of appearance5.

Furthermore, if the cooling rate during casting of the alloy is slow, the crystal grains may become coarse and the alumite property may be impaired.

Furthermore, if the cooling rate varies greatly in each part of the product, casting defects are likely to occur, making it difficult to obtain a product with sufficient pressure resistance and strength.

The present invention relates to a method for producing an alloy with high strength, high toughness, excellent pressure resistance, and excellent alumite properties, which was obtained through seeding experiments and diligent efforts in order to eliminate the above-mentioned drawbacks.

That is, the present invention contains 4.0 to 5.0% copper, 0.18 to 0.35% magnesium, and 0.0% silicon. '05~0.2
5%, titanium alone 0.03 to 0.11% or titanium and holon together in total 0.03 to 0.11%, and the titanium to holon quantitative ratio B / 'I' i is 1/100
~1/20, 0.05-0.3% chromium, 0 mankan
．． 0.05 to 0.4%, and optionally 0.8% silver.
% or more, and the remainder substantially consists of aluminum, the aluminium 1 is rapidly cooled from a solidification start temperature or higher and solidified at a cooling rate of 30°C/min or higher in the solidification zone. - A method for producing high-strength aluminum alloys for casting with excellent properties.The objective is to provide an appropriate cooling rate and reduce the titanium content to achieve good alumitability and superior mechanical properties. The goal is to obtain a refined alloy.

The reason for specifying the alloy components as described above in the present invention is as follows.

゛The reason why copper is limited to 40 to 5.0% is that if it is less than 40%, the specified strength cannot be obtained even after heat treatment.
If it is more than 5.0%, the alumite processability is poor, and 2 it impairs the castability, and hot cracking and shrinkage cavities are more likely to occur. 6 Magnesium increases heat treatment sensitivity due to the precipitation of Mg25i. Although it improves mechanical properties, if it is less than 0.18%, it has no effect, and if it is more than 0.35%, it becomes brittle and elongation decreases.

Silicon improves castability and pressure resistance, and improves mechanical properties by precipitating Mg25"i together with magnesium, so it should be contained in an amount of 0.05% or more, but if it is too large, the mechanical properties will deteriorate. Particularly when it exceeds 0.25%, the deterioration is remarkable.

The reason why titanium or titanium/boron is set at 0.03 to 0.11% is that if it is less than 0.03%, it has no effect on grain refinement, and if it is more than 0.12%, especially more than 0.15%, the titanium compound This is because intragranular segregation occurs, causing color unevenness during alumite treatment.

Furthermore, when titanium and boron are added at the same time, the addition ratio is limited to 1/100≦B/Ti≦1/20 because if B/Ti is not within this range, the grain refinement effect will not be achieved. This is because when 1/20<B/'l' i, there is an ability to refine the grain, but the negative effects of segregation occur.

Chromium is an element that improves mechanical properties and increases stress corrosion resistance, but if it exceeds 0.3%, mechanical properties deteriorate.

Further, the alumite property is improved by adding a small amount of chromium, but 0.05% or more is required.

Mankan is contained in an amount of 0.05% or more in order to improve corrosion resistance and alumite property, but if it is too large, castability and toughness are impaired, so the upper limit is set at 0.4%.

The reason why silver is set to 0.8% or less is that silver increases heat treatment sensitivity and dulls stress corrosion sensitivity, but adding more than 0.8% does not show any improvement effect and unnecessarily increases alloy conut. This is because it will happen.

It is desirable to suppress Fe as another impurity to 0.915% or less.

This is because iron has the effect of preventing high-temperature brittleness, but when the amount increases, the ternary compound N (A/ff7 Cu2 Fe) precipitates, reducing the heat treatment effect and impairing hardness and malleability.

Next, regarding the casting conditions, in the present invention, the reason why the soil is rapidly cooled from the solidification start temperature soil and each part of the product is cooled at a cooling rate of 30°C/min or more during the solidification period is as will be clarified in the examples described later. Unless processed under these conditions, a uniform fine macrostructure cannot be obtained, and mechanical properties and pressure resistance will be poor.
This is because the problem remains even when alumite treatment is applied.

Next, examples of the present invention will be shown together with comparative examples.

[Example 1] Using the aluminum alloy test materials shown in Table 1, ingots of 90 mm x 1207 ui were manufactured in a unidirectional solidification furnace under varying cooling conditions (listed in Table 1).

Macro photographs of the cross section of the obtained ingot are shown in FIGS. 1, 2, and 3.

Figure 1 shows the alloy of specimen A-1 at 64 degrees below the solidification start point.
This is a photograph of the macrostructure after slowly cooling to 0°C and then rapidly cooling from 640'C. As a result of heating, the cooling rate in the solidification section at this time was 106"C7'min
Met.

Figure 3 is a macro photograph of the ingot cross section of sample A-'3, which was solidified by changing the cooling rate at the bottom, center, and top of the ingot. min% 68℃/m at the top of the ingot
The cooling rate was in.

Comparing FIG. 1 and FIG. 2, the macrostructure in FIG. 1, which was rapidly cooled from a temperature below the freezing point, shows a coarser structure.

However, since both have a uniform macrostructure, when anodized, there is no problem with low titanium content, but even with a rapidly cooled fine structure, a beautiful alumite finish can be obtained when the titanium content is high. is difficult.

Additionally, materials solidified from below the freezing point have inferior mechanical properties compared to materials rapidly cooled from above the freezing point.

. Same - When the cooling rate is changed within the sample, Figure 3 1
As shown, coarsening of crystal grains occurs in areas where the cooling rate is slow, and a uniform fine structure cannot be obtained, and when alumite treatment is applied to this, color unevenness occurs.

[Example 2] 1-4.5% Cu -0.3% Mg -0.3%M
n -0.2% Cr -0.06 to 0.23% TI alloy Samples obtained by varying the cooling rate from 670°C above the solidification initiation temperature were solution treated at 535°C for 6 hours and then water quenched. Table 2 shows the results of testing the mechanical properties, alumite properties, and pressure resistance of the products that were subjected to artificial aging treatment at 160°C for 10 hours. 8625(1)T
The test was carried out according to ype I C1ass 1 under the following conditions.

Electrolyte: Cry37511/It aqueous solution Current: 5
00A or less Voltage: 40±IV Bath temperature: 34±1℃ Time 260 minutes Pressure test was performed by processing the sample material to 3mm thickness and applying air pressure to 5yJJ
I checked to see if there was any leakage.

According to Table 2, the cooling rate is 4°C/min, 23'C7
In the case of min, satisfactory mechanical properties could not be obtained.

In addition, the cooling rate is 41'C/min, 106°C/f.
n1. In the case of n, good mechanical properties can be obtained, but if the titanium content is high, intragranular segregation will occur, and color unevenness will occur when alumite treatment is performed.

Therefore, it has been found that good results in both mechanical properties and alumite properties can be obtained when the cooling rate is 30°C//'□in or more and the titanium content is 0.03 to 11%.

[Example 3] Samples were cast by casting the molten metals of the test materials shown in Table 3 into sand molds and metal molds and giving various cooling rates, and after solution treatment at 5351°C for 6 hours, water quenching was carried out to 160°C. Artificial aging treatment was performed for 10 hours.

The alumite treatment was carried out using an aqueous solution of 375 g of Cr O/A' at a bath temperature of 34±1° C., a current of 500 A or less, and a bath voltage of 40±IV for 60 minutes.

Table 4' shows the results of testing the mechanical properties, alumite properties, and pressure resistance of the samples thus prepared.

As is clear from Table 4, the alloy according to the present invention controls the quenching start temperature and solidification zone cooling rate compared to the comparative example.
And the amount of titanium or titanium/boron added is 0.03 to 0.
．． By suppressing the content to 11%, alumite properties, pressure resistance, and mechanical properties are improved.

[Brief explanation of drawings]

Figures 1, 2, and 3 are sample materials A-1 (comparative example), A-2 (invention), and A-3 shown in Table 1 of Examples, respectively.
Ingot (90pmvt×12
0 mm) is a photograph of a cross-sectional macrostructure.

Claims (1)

[Claims] 1. 4.0 to 5.0% copper and 0.18 to 5.0% magnesium
0.35%, silicon 0.05-0.25%, titanium alone 0.03-0.11% or titanium and poro. In coexistence with the titanium and the titanium, the total amount is 0.03 to 0.11%, and the amount ratio B/Ti of titanium and the boon is 1/100 to 1/20.
Chromium 0.05-0.3%, Mn 0.05-0
．． 4% and the remainder substantially consists of aluminum, the alloy has excellent alumite properties, characterized by being rapidly cooled from the solidification start temperature or higher and solidified at a cooling rate of 30°C/min or more in the solidification zone. Manufacturing method of high strength aluminum alloy for casting. 2 4.0~5.0% copper, 0.18~0.18% magnesium
0.35%, silicon 0.05-0.25%, titanium alone 0.03-0.11% or coexistence of titanium and boron, total 0.03-0.11%, and titanium and boron. Quantity ratio B/Ti is 1/100 to 1/20, chromium is 0.05 to 0.3%, Mn is 0.05 to 0.4%
and alumite, which is characterized by casting an alloy containing 0.8% or less of silver and the remainder substantially consisting of aluminum, which is rapidly cooled from a solidification initiation temperature or higher and solidified at a cooling rate of 30°C/min or higher in the solidification zone. A method for producing a high-strength aluminum alloy for casting with excellent properties.