JPH036346A - Aluminum alloy for forging - Google Patents

Abstract

PURPOSE:To obtain an Al alloy for forging having high strength, wear resis tance, machinability, and heating discoloration resistance by specifying a compo sition consisting of Si, Cu, Mg, Mn, Be, and, as impurities, Sb, Zn, Pb, Sn, and Bi, and Al. CONSTITUTION:The above alloy is an Al alloy for forging having a composition consisting of, by weight, 3-9% Si, 2-4% Cu, 0.3-0.6% Mg, 0.3-0.6% Mn, 0.001-0.2% Be, and, as impurities, <0.1% Sb and >=0.05% Zn and/or >=0.1%, in total, of one or more elements among Pb, Sn, and Bi, and the balance Al with other impurities, and further, this alloy has superior strength, wear resistance, machinability, and forgeability and also has heating discoloration resistance causing neither discoloration nor deterioration in surface characteristics in a thermal environment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum alloy for forging,
More specifically, the present invention relates to aluminum alloys for forging that have high strength, wear resistance, and machinability in response to the recent trend toward lighter weight industrial machine parts such as vehicles.

[Prior Art] Conventionally, Al-St eutectic alloys have been generally used as aluminum alloys for forging that require high strength and wear resistance, and a typical example is Al-8t eutectic alloys. There is a JISA4032 alloy to which Cu, Mg, Ni, etc. are added. In recent years, there has been an increasing demand for improved properties, and many proposals have been made to improve AQ-8i eutectic alloys.

According to Japanese Patent Publication No. 53-20242.

An aluminum alloy is known that has high-temperature strength, wear resistance, and free machinability by rapidly cooling a molten AQ-6i eutectic alloy to which Cu and Mg are added.

Furthermore, this alloy can be forged in its ingot state without undergoing any preliminary processing such as extrusion.

According to Japanese Patent Publication No. 53-20243, a proposal was made to improve plastic workability by specifying the quantitative ratio of Cu and Mg added to the AQ-St eutectic alloy and by making the silicon crystals in the eutectic structure into fine particles. being done.

(A) According to JP-A No. 62-449839, in order to improve the properties of JISA4032 alloy, especially its strength, 1.5-3.0% Cu, 0.1-1.5% Mn
, 0.2-1.5% Mg, 0.05-1.0
It has been proposed to add %sb. The explanation in this publication is good. However, despite these effects, these types of alloys have common drawbacks that need to be solved. That is, AQ Si as above
-Cu-Mg alloys are hot-forged or cold-forged and then subjected to heat treatment such as T6. During this heat treatment, which is carried out in the air, sb-containing alloys turn black and Zn
, Pb, Sn, and Bi-containing alloys discolor to gray or dark gray, losing the original color tone of the aluminum alloy and damaging the commercial value of the forged product due to the contaminating color.

Furthermore, the surface of an aluminum alloy that exhibits discoloration tends to lose its inherent surface properties such as wear resistance and seizure resistance. Therefore, in order to maintain commercial value and prevent deterioration of surface properties, discolored forged products are
It is necessary to completely remove the altered layer by surface polishing and cutting to a depth of micrometers, or to perform acid cleaning or alkaline cleaning when only the appearance is a problem. Such treatment not only increases the cost, but also the treated forged products generate heat during use and discolor again when placed in a heated environment.SB is an action that aims to refine primary Si and eutectic Si, which tend to become coarse due to the influence of Cu. It is stated that there is.

Furthermore, (B) JP-A-62-44548 discloses that in order to improve the eutectic alloy properties and seizure resistance of an Al-8i-based eutectic alloy containing Cu alone or Cu and Mg, Pb,
It has been proposed to add Sn and Bi simultaneously.

(C) According to JP-A No. 62-86142, Zn0.2 to 1.5 is added to the eutectic AQ-31-Cu-Mg alloy.
It has been proposed to improve magnetic tape abrasion resistance by adding %.

[Problems to be Solved by the Invention] As mentioned above, in the alloy (A), the addition of a small amount of sb refines the eutectic Si particles in the continuous casting ingot, suppresses the crystallization of primary Si, and thereby The strength, wear resistance, and forgeability are improved, and the alloy (B) above has Pb, Sn, and Bi.
The addition of Zn improves the machinability and seizure resistance.Furthermore, in the alloy (C), the wear resistance is improved by the addition of Zn, so a fundamental solution is required.

In addition, if an alloy with a fine eutectic structure can be obtained by controlling the casting conditions such as rapid cooling continuous casting of small diameter billets without adding a eutectic phase refiner such as sb,
Although the heating contamination color peculiar to b does not occur, the eutectic mwL thinning effect by adding sb is an extremely effective means in continuous casting of normal diameter billets I, and is generally widely adopted. Heating stain color is inevitable. Furthermore, recycling of aluminum has become widespread, and AgSi-based eutectic alloys are generally produced by mixing recycled ingots, and in this case too, contamination color occurs due to impurities. That is, in this case, even if the parts are the same, the color tones vary depending on the type and amount of impurities such as Zn, Pb, Sn, and Bi, which significantly reduces the commercial value.

In view of the above-mentioned current situation, the present invention has been developed to improve strength, wear resistance, machinability,
While maintaining the excellent properties of AgSi-based eutectic alloys, which have improved forgeability, etc., they do not discolor during the forging process, heat treatment process, or in the thermal environment during use, and retain the alloy's original beautiful color tone, as well as surface properties. AlS with no deterioration, further improved forging workability, and no cracking
The object of the present invention is to provide an i-Cu-Mg alloy for forging.

[Means for Solving the Problems] The first alloy of the present invention contains less than 3-9% Si, C
u2-4%, Mg0.3-0.6%, Mn0.3-0.
6%, Be0.001-0.2%, and S as an impurity.
b less than 0.1%, Zn 0.05% or more and/or P
An aluminum alloy for forging characterized by containing one or more of B, Sn, and Bi in a total amount of 0.1% or more, with the remainder consisting of Al and other impurities, and having heat discoloration resistance, the present invention The second alloy contains, by weight, less than 3-9% Si, C
u2-4%, Mg0.3-0.6%, Mn0.3-0.
6%, sbo, 1-0.5%, Be0.001-0.2
It is an aluminum alloy for forging, which is characterized by having heat discoloration resistance, containing 7%, the balance being Al and impurities, and having heat discoloration resistance. Processing becomes difficult.

Copper is an element necessary to impart heat treatability to aluminum alloys and obtain high strength. The content of Cu is 2%
If it is less than 4%, no strength will be obtained, while if it exceeds 4%, wear resistance will be impaired and forging workability will also be reduced.

Magnesium forms a solid solution in aluminum and helps strengthen the alloy matrix, and also forms intermetallic compounds such as Mg2Si through heat treatment, contributing to toughening and improved wear resistance through heat treatment. However, if the Mg content is less than 0.3%, strength and wear resistance will be insufficient due to lack of solid solution strengthening and age hardening, while if it exceeds 16% O, forging workability will deteriorate and the Affects discoloration.

Manganese increases strength and wear resistance through solid solution strengthening and age hardening, but if it is less than 0.3%, it has little effect;
If it exceeds %, coarse intermetallic compounds tend to crystallize, which significantly impairs forging workability.Less than %, Cu2-4%, Mg0
．． 3-0.6%, Mn0.3-0.6%, 5bO11~
0.5%, Be 0.001-0.2%, Zn 0.05% or more and/or one or more of Pb, Sn, and Bi as impurities, totaling 0.1% or more, and the balance is AI2.
This is an aluminum alloy for forging, which is composed of aluminum and other impurities, and is characterized by its resistance to heat discoloration.

The basis for limiting the range of components of the alloy of the present invention will be described below.

Silicon not only helps strengthen the aluminum alloy matrix, but also forms an Al-Si eutectic and improves wear resistance.

When the Si content is less than 3-9%, which is the content range of the present invention, eutectic Si is dispersed and crystallized to improve strength and wear resistance. S
If the i content is less than 3%, the amount of eutectic Si will decrease, resulting in poor strength and wear resistance. If the Si content exceeds 9%, the eutectic Si will become coarse and primary Si will be seen everywhere.

sb contained as an alloying element in the alloy of the second invention
refines the SL crystal grains in the eutectic structure. In particular, in large-diameter billets whose cooling rate is slow, the eutectic Si tends to coarsen, which tends to reduce strength and wear resistance. Addition of sb is effective in preventing this, but the effect is small if the sb content is less than 0.1%. On the other hand, if the sb content exceeds 0.5%, intermetallic compounds containing sb will crystallize, and forging workability will deteriorate.

The aluminum alloy of the first invention contains sb, Zn, Pb, S
The target is those containing n, Bi, etc. as impurities. These impurities are contained in a non-negligible amount when the recycled lump is used as a raw material, and cause heat staining color. These elements are impurities and do not need to be added, but when the alloy of the present invention is melted by using recycled ingots or after melting an alloy containing them, the amount increases to a considerable extent due to contamination in the furnace.

Among these impurities, sb has a particularly remarkable effect on discoloration, and in the presence of other impurities, it acts synergistically with these and causes a significant loss of brightness. The content of sb that does not reach, i.e. 0
．． The upper limit is 1%. On the other hand, when Zn is contained in an amount of 0.05% or more and/or Pb, Sn, and Bi are contained in a total of 0.1% or more, the problem of color staining occurs. Therefore, Zn is 0.05
% or more -1 The target is an alloy in which the total content of Pb, Sn, and Bi is 0.1% or more.

In the alloy of the first invention, the above-mentioned Japanese Patent Publication No. 5320243
By producing a small-diameter ingot using the continuous casting method with a high cooling rate disclosed in No. 1, it is possible to refine the eutectic Si to a level equivalent to or higher than that of a large-diameter billet in terms of sb addition.

Be added to the alloys of the first to third inventions has the function of suppressing the phenomenon of surface discoloration during heat treatment of aluminum alloys, but if the Be content is less than 0.001%, this effect cannot be achieved. , if it exceeds 0.2%, mechanical properties, especially toughness, deteriorate.

1 [Examples and Comparative Examples] The present invention will be explained in detail below using Examples and Comparative Examples.

The alloys of the present invention and comparative examples having the compositions shown in Table 1 were melted and 50
This cast rod was heated at 350 to 450° C. and hot upsetting forging was performed at a processing rate of about 60% to form a rod body of 18 mmφ.

Then, after solution heat treatment was performed at 530° C., the color tone of the surface was observed. The results were as shown in Table 2.

(Hereinafter, blank space) In the alloy of the present invention, up to 0.7% of Fe can be tolerated as an unavoidable impurity. If this amount is exceeded, Al-F
This is not preferable because the development of e-3i needle crystals impairs the toughness of the alloy.

[Function] It is known that when an aluminum alloy containing Mg is heated in an oxidizing atmosphere, an oxidation reaction occurs on the alloy surface at a depth of several tens of micrometers to several hundreds of micrometers, producing spinel Al203.nMgo.

It is thought that when the aluminum alloy further contains sb, pb, Sn, Bi, etc., these elements combine with spinel in the form of oxides or metals, and become surface contaminants. Therefore, the aluminum alloy after heating changes to various colors depending on the type of oxidation reaction product. It is presumed that Be, which is a feature of the present invention, forms an extremely thin film on the surface of the Al alloy to cover the A alloy and prevents the reaction with oxygen and the formation of spinel thereby.

2. Surface color tone [Effects of the invention] (1) The aluminum alloy forged products of the first to third inventions do not exhibit contaminating colors such as black or gray even after being subjected to heating environments such as heat treatment, and retain the silvery white metal inherent to aluminum alloys. It gives a glossy appearance and increases the value of the product. Furthermore, since there is no deterioration of the surface of the product, there is no need to remove the surface by polishing or the like, and furthermore, there is no need for treatment to restore color tone and gloss by pickling or the like, which eliminates a factor that increases costs.

(2) The alloys of the first to third inventions are Si, Cu, Mg and M.
By adding n, it exhibits high strength and wear resistance. In addition to these common elements, in the second invention alloy, by adding sb, the eutectic Si can be made finer and the above performance can be improved.

<3) The alloy of the first invention contains Sb, Zn and/or P
Since B, Sn, Bi, etc. are allowed to be mixed in as impurities, the cost of raw materials can be reduced by using recycled lumps. Further, although the amount and type of these impurities vary depending on the type of raw materials used, it is possible to manufacture a forged product with a constant color modulation despite this.

Therefore, the burden of raw material management is greatly reduced, and consumers can also receive products of a constant quality.

Adding sb as a significant component, Zn and/or Pb
The alloy of the third invention containing , Sn, and Bi as impurities is an Al-Si-
It is useful as a Cu-Mg-Mn alloy.

(4) According to the first to third inventions, there is no altered structure on the surface of the forged product that has undergone a heating process such as heat treatment, and eutectic A such as α-AI2, eutectic Si, Mg2Si, and intermetallic compounds of sb
It is composed of the original structure of l-8i alloy. Also, Mg
, Sb, etc. are not lost as spinel and exhibit the desired characteristics, so an alloy with excellent surface characteristics, which is important for wear resistance, can be obtained.

Claims (3)

[Claims] 1. By weight, less than 3-9% Si, 2-4% Cu, Mg0
．． 3-0.6%, Mn0.3-0.6%, Be0.00
1-0.2%, and as impurities, less than 0.1% Sb, Z
For forging, containing 0.05% or more of n and/or 0.1% or more of one or more of Pb, Sn, and Bi in total, the remainder consisting of Al and other impurities, and having heat discoloration resistance. Aluminum alloy. 2. By weight, less than 3-9% Si, 2-4% Cu, Mg0
．． 3-0.6%, Mn0.3-0.6%, Sb0.1-
0.5%, Be 0.001-0.2%, balance Al
An aluminum alloy for forging, which is characterized by having heat discoloration resistance and consisting of impurities. 3. By weight, less than 3-9% Si, 2-4% Cu, Mg0
．． 3-0.6%, Mn0.3-0.6%, Sb0.1~
0.5%, Be 0.001-0.2%, and as impurities Zn 0.05% or more and/or Pb, Sn, Bi
An aluminum alloy for forging, characterized in that it contains at least 0.1% of one or more of the above in total, with the remainder consisting of Al and other impurities, and has heat discoloration resistance.