JPS6024168B2 - Aluminum alloy for casting with high iron content - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for casting A-Si-Cu with a high iron content, such as a secondary alloy ingot mainly composed of returned material or returned material.
The purpose of the present invention is to economically provide alloys with improved toughness and good thermal shock resistance in A-based alloys or A-Si-Cu-Mg based alloys.

JIS standard AC2A, AC wave, A-Si-Cu alloy represented by AC, A〆-Si-Cu-Mg alloy represented by AC fox, AC group have excellent castability by heat treatment. Because of its high strength and toughness, it is widely used as an alloy for casting engine parts, safety parts, and other machine parts for automobiles, ships, etc.

However, when the iron content increases in this type of alloy, the strength and rice grain properties of the cast material decrease rapidly, making it impossible to use it for the above-mentioned purposes.

That is, Figure 1 illustrates the relationship between iron content and mechanical properties in A-7%Si-2.5%Cu (corresponding to AC) alloy castings, where the iron content is 0.2%. %, the tensile strength is 35k9/m or more and the elongation is 5% or more, but when the iron content approaches 0.5%, the strength and elongation decrease rapidly, and especially when the iron content approaches 0.7%, the tensile strength decreases to 30kg/m2. below,
The elongation is 2% or less, which significantly reduces the toughness.According to the research of the present inventors, this relationship is not limited to alloys with the above composition, but also applies to A-Si-Cu alloys of all compositions. ,
It has been confirmed that the neck orientation common to A-Sj-Cu-Mg alloys can be recognized. By the way, generally in foundries, from the viewpoint of resource and cost saving,
A large amount of returned material or secondary alloy ingots containing mainly returned material is used, but in this case, a large amount of iron is usually mixed in the returned material or secondary alloy ingots. Therefore, due to the above-mentioned circumstances, when this type of alloy is used for the above-mentioned purposes, especially in engine parts for automobiles, ships, etc., which require strict strength and toughness, foundries are using it as impurities. It is necessary to adjust the iron content to the lowest possible amount of 0.4% or less, and the alloy blending operation for this purpose has been an extremely troublesome problem.

The present invention was devised after repeated studies in view of the above circumstances, and the present inventors have developed an A-Si-Cu system or an A-Si-Cu system
As a result of research into the cause of the decrease in toughness due to an increase in the amount of iron in Si-Cu-Mg alloys, it was found that when the iron content in these alloys approaches 0.5%, the iron becomes more concentrated than the aluminum in the alloy component. Acicular A produced by reaction with silicon etc.
It has been found that the A-Fe-Si compound rapidly increases and becomes coarse, and since this A-Fe-Si compound is extremely brittle, this significantly reduces the strength and elongation of the alloy.

As a result of further research, the inventors found that approximately 0.6
When adding an appropriate amount of manganese and antimony to an alloy containing more than % iron, A〆-F crystallizes in the matrix.
It has been found that the morphology of the e-Si compound changes greatly and is dispersed as a fine compound having a spherical to granular morphology, and that the strength and elongation of the alloy are significantly improved.

Figures 2a and 2b show the results of the above-mentioned experiments conducted by the present inventors; For the Cu (equivalent to AC) alloy, b is the same as above alloy with 0.0% manganese.
7% and 0.8% of antimony within the range of the present invention are shown respectively. That is, as is clear from these microscopic structures, in Fig. 2a, a large amount of acicular A-Fe-Si compounds are crystallized, whereas in b, there are almost no acicular compounds, and these compounds are It can be seen that the compound is formed into fine spherules. The above-mentioned effects of the alloy of the present invention can only be obtained by the combined addition of manganese and antimony in alloys with a relatively high Fe content, and such effects cannot be obtained by adding antimony or manganese alone. do not have.
The present invention was made based on the above-mentioned discovery, and includes silicon containing more than 4.0% and up to 13.0% by weight; 2.
More than 5% up to 4.5% copper, more than 0.6% up to 1.5%
up to manganese and more than 0.2% up to 1.0% antimony, with or without up to 0.30% titanium, and 1.5% as impurities or significant elements
The present invention proposes an aluminum alloy for casting comprising up to 0.6% up to 1.2% of magnesium and over 0.6% up to 1.2% iron, with the remainder consisting of aluminum and unavoidable impurities other than the above-mentioned elements.

According to the present invention, the toughness of the alloy is significantly improved even though the iron content in the alloy is extremely high. There is no need to pay any attention to iron content adjustment when blending, and the inclusion of iron in the alloy as described above has the effect of improving the heat resistance properties, especially the thermal shock resistance, of the alloy. It is also possible to intentionally mix them.

Next, the reason for limiting the composition of each alloy component in the alloy of the present invention will be explained as follows.

A〆-Si-Cu alloy containing more than 4.0% and up to 13.0% silicon, more than 2.5% and up to 4.5% copper, and up to 1.5% magnesium, A〆- Si-Cu-Mg
In series alloys, silicon strengthens the alloy matrix and has the effect of improving flow, shrinkage, prevention of casting cracks, etc.; 4.
If it is less than 0%, the effect will be small, and if it is more than 13.0%, the toughness and thermal shock resistance will be significantly reduced.

Further, when heat-treated, copper significantly imparts alloy strength through age hardening, but if it is less than 2.5%, this effect is small, and if it is more than 4.5%, it reduces graininess. Magnesium is used to precipitate M&Si through heat treatment to strengthen the alloy matrix.
For g-based alloys, 0.4
% or more, but addition of 1.6% or more is not preferable because it significantly reduces plowability.

In the present invention, A-Si-Cu within the specified composition range is used.
iron as an impurity or a significant additive element in Cu-Mg alloys exceeding 0.6% 1.2
This applies to alloys containing up to %.

In alloys with an iron content of 0.6% or less, the strength of the alloy cannot be said to be permanently low, and therefore there is no need for improvement, and in cases where the iron content exceeds 1.5% This is set as the upper limit because the effect of improving toughness according to the present invention cannot be sufficiently exhibited. In the present invention, as mentioned above, A-Si-Cu alloy with high iron content or A-Si-Cu-Mg
>0.6% up to 1.5% manganese and >0.20% up to 1.0%, preferably 0.25%
This is a composite addition of antimony up to 0.8%, but when antimony coexists with manganese, it significantly refines the needle-shaped coarse A-Fe-Si compounds that crystallize in the alloy matrix. It also has the effect of dispersing it as a granular or spherical compound. Additions below the respective lower limits will have little effect, and additions above the respective upper limits will actually reduce the strength of the alloy, which is not preferable. When the alloy of the present invention is cast, there is no problem in adding up to 0.3% of titanium or further adding up to 0.05% of shelving elements to refine the alloy, as has been conventionally done.

In particular, proactively incorporating up to 0.30% titanium into the alloy has the effect of improving the shrinkage of castings in addition to the above-mentioned refinement effect.
It has the effect of preventing money from breaking.

In addition, when the alloy of the present invention contains magnesium, 0
．． It is also possible to appropriately prevent oxidation by adding up to 0.5% beryllium. Next, embodiments of the present invention will be described as follows.

The alloy according to the present invention and its comparative examples are shown in Table 1 below.

Table 1 K Impurities (including those contained as repeating materials) Table 1 '11~[4 JISAC2A, AC Spot, AC Monument, AC Mountain D and A containing a large amount of iron as impurities
Alloy a has a chemical composition corresponding to each alloy of C, and alloy b has a composite addition of manganese and antimony within the scope of the present invention. The molds were cast in a mold testing station, subjected to solution treatment, then exposed to water or hot water, and then subjected to artificial aging treatment.The mechanical properties of these were measured.The results are also shown on the right side of Table 1.

The heat treatment conditions for each sample are as follows.

．． Kinki U Solution treatment Akirairi Artificial aging treatment repair (1
)510°C
0°C x 10 vaguely charged water dawn 160°C x 7 Wu style punishment (4
) 510C x 4 Koraden Mizuaki entry 220℃ x 5 mountain pass belt Based on the results in Table 1, the example location. In all of {1} to ■, Alloy B has higher measured values of tensile strength and elongation than Alloy A, that is, all alloys {1} to [4} have Fe content of 0.6 to It can be seen that strength and toughness are improved by the combined addition of manganese and antimony when the content is as high as 1.2%.

As described above, the present invention uses A-Sj-Cu alloys or A-Sj-Si alloys that contain a large amount of iron and have significantly reduced rice toughness.
The technical facts regarding the A-Fe-Si compounds of Cu-Mg alloys have been elucidated, and the toughness can be greatly improved, so there is no need to worry about adjusting the iron content in places like foundries. In addition, heat resistance and other properties can be improved depending on the iron content, and of course, it is economical to use recycled materials or alloy ingots mainly made of recycled materials and the composition can be adjusted relatively easily. It is possible to provide an aluminum alloy for casting having such characteristics and passing it through various engine parts, etc., and it can be said that it is extremely effective industrially.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and FIG. 1 is a chart showing the relationship between iron content and mechanical properties in A-Si-Cu alloy castings, and FIG. A photomicrograph at a magnification of 20 pm showing a comparison of the structure of an A-Si-Cu alloy containing 1% manganese and antimony with and without the addition of manganese and antimony; a contains manganese and antimony; "b" indicates those containing both of them. Figure 2 Figure 2

Claims (1)

[Scope of Claims] 1. More than 4.0% and up to 13.0% silicon by weight; 2.
More than 5% up to 4.5% copper, more than 0.6% up to 1.5%
Manganese up to 0.20% and up to 1.0% antimony, and up to 1.5% magnesium and over 0.6% 1 as impurities or significant additive elements.
．． An aluminum alloy for casting with a high iron content, containing up to 2% iron, with the remainder consisting of aluminum and unavoidable impurities other than the above-mentioned elements. 2 more than 4.0% and up to 13.0% silicon by weight; 2.
More than 5% up to 4.5% copper, more than 0.20% 1.5
% manganese, more than 0.20% up to 1.0% antimony, and more than 0.02% up to 0.30% titanium, and as impurities or significant added elements 1.5
% magnesium and more than 0.6% up to 1.2% iron, with the remainder consisting of aluminum and unavoidable impurities other than the above-mentioned elements.