JPH0678580B2 - Aluminum alloy for forging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an aluminum alloy for forging,
More specifically, it relates to a high-strength aluminum alloy that has been used in recent years to reduce the weight of industrial machinery parts such as vehicles, and that also has wear resistance, machinability, and heat discoloration resistance. Is.

[Conventional technology]

Conventionally, Al-Si eutectic alloy is generally used as an aluminum alloy for forging that requires high strength and wear resistance, and typical ones are Al-Si eutectic alloys containing Cu, Mg, and Ni.
There is JIS A 4032 alloy with the addition of etc. In recent years, there have been increasing demands for improved properties, and therefore many proposals have been made for improving Al—Si-based eutectic alloys.

According to Japanese Patent Publication No. 53-20242, Al containing Cu and Mg is added.
-By quenching the Si eutectic alloy melt, high temperature strength,
An aluminum alloy having both wear resistance and free-cutting property is known. Further, this alloy can be forged in the ingot state without undergoing preliminary processing such as extrusion.

According to Japanese Patent Publication No. 53-20243, there is a proposal to improve the plastic workability by specifying the amount ratio of Cu and Mg added to the Al-Si eutectic alloy and making the silicon crystals in the eutectic structure fine particles. Has been done.

According to (A) Japanese Patent Laid-Open No. 62-149839, JIS A4
To improve the properties of 032 alloy, especially strength, 1.5-3.
0% Cu, 0.1-1.5% Mn, 0.2-1.5% Mg composition, 0.05
Proposals have been made to add ~ 1.0% Sb. In the description of this publication, it is stated that Sb has a function of refining primary crystal Si and eutectic Si which are likely to be coarsened by the influence of Cu.

Further, according to (B) Japanese Patent Laid-Open No. 62-44548, Pb, Sn and Bi are added to Cu alone or an Al-Si eutectic alloy containing Cu and Mg in order to improve machinability and seizure resistance. A proposal has been made for simultaneous addition, and according to JP-A-62-86142, (C) a proposal to add Zn to an Al-Si eutectic alloy containing Cu and g in order to improve wear resistance of the magnetic tape. Has been done.

[Problems to be Solved by the Invention]

As described above, in the alloy (A), by adding a small amount of Sb, the eutectic Si particles in the continuous forged ingot are refined and the crystallization of primary Si is suppressed, whereby the strength, wear resistance and forgeability are improved. Further, in the alloy (B), the addition of Pb, Sn and Bi improves the machinability and seizure resistance. Further above (C)
In alloy No. 3, the mechanical strength and magnetic tape abrasion resistance are improved by the addition of Zn. However, in spite of these effects, alloys of this type have common drawbacks, and there is a need to solve them.

That is, the Al-Si-Cu-Mg-based alloy as described above is subjected to heat treatment such as T6 after being hot forged or cold forged, but the Sb-containing alloy is black in this heat treatment performed in the air atmosphere. In addition, Zn, Pb, Sn and Bi containing alloys turn gray or dark gray, lose the original brilliance of aluminum alloys and deteriorate the commercial value of forged products due to the stain color.

Furthermore, the surface of the discolored aluminum alloy tends to impair the surface properties such as wear resistance and seizure resistance of the alloy body. Therefore, in order to maintain the commercial value and prevent the deterioration of surface properties, the discolored forged product should be surface-polished and cut at a depth of several tens of μm to several hundreds of μm to completely remove the deteriorated layer, or when only the appearance becomes a problem. Acid cleaning is required. Such a treatment is not costly, and the treated forged product is discolored again when it is placed in a heat environment or a heating environment during use, and therefore an essential solution is required.

Further, the forgeability of the Al-Si eutectic alloy is remarkably improved by the refinement of the structure as known in the above Japanese Patent Publication Nos. 53-2024 and 20243, and even if the eutectic refining agent such as Sb is not added. Since a fine eutectic alloy is produced, the stain color peculiar to Sb does not occur, but when an Al-Si eutectic alloy is melted using a recycled mass, a stain color due to inevitable impurities occurs. That is, in this case, the color of the same component was varied depending on the type and amount of impurities such as Zn and Pb, and the commercial value was significantly impaired. Further, in order to further improve the forgeability, it was necessary to make the macrostructure fine.

In view of the above-mentioned present situation, the present invention is strength, wear resistance, machinability,
While maintaining the excellent properties of the Al-Si eutectic alloy with improved forgeability etc., it retains the original beautiful luster without discoloration especially in the forging process, heat treatment process or thermal environment during use. It is an object of the present invention to provide an Al-Si-Cu-Mg-based forging alloy that has no deterioration of surface characteristics and further improves the forgeability by making the macrostructure finer and can reduce the occurrence of cracks. .

[Means for Solving the Problems]

The first of the present invention is, by weight, Si 9-11%, Cu 2-4
%, Mg 0.3-0.6%, Mn 0.3-0.6, Sb 0.1-0.5%, B
The aluminum alloy for forging is characterized by containing 0.001 to 0.2% of e and 0.02 to 0.05% of B, and consisting of balance Al and impurities and having resistance to thermal discoloration. The second of the present invention is, by weight, Si. 9-11%, Cu 2-4
%, Mg 0.3-0.6%, Mn 0.3-0.6, Zn 0.05-1.5% and / or Pb, Sn, Bi 0.1-1.0% each, total 2.0% or less, B
e 0.001-0.2%, B 0.02-0.05%, balance Al and impurities, and a heat discoloration-resistant aluminum alloy for forging, characterized by the third aspect of the present invention. 9-11%, Cu 2-4
%, Mg 0.3-0.6%, Mn 0.3-0.6, Sb 0.1-0.5% and Z
n0.05-1.5% and / or Pb, Sn, Bi 0.1-1.0%, total 2.0% or less, Be 0.001-0.2%, B0.02-0.05%, balance Al and impurities, heat resistance It is an aluminum alloy for forging characterized by having discoloration.

The grounds for limiting the component range of the alloy of the present invention will be described below.

Silicon not only serves to strengthen the aluminum alloy matrix, but also forms an Al-Si eutectic structure to improve wear resistance.

In the content range of Si 9-11% of the present invention, eutectic Si is distributed almost all over the forged alloy to enhance wear resistance, and since coarse primary crystal Si is small, forgeability and machinability are also improved. It is good.

On the other hand, if the Si content is less than 9%, the proportion of eutectic Si is reduced and the forgeability is good, but the wear resistance is slightly inferior.
When the Si content exceeds 11%, the wear resistance is further improved, but the primary crystal Si is increased, so that the forgeability is deteriorated.

Copper is an element necessary for imparting heat treatment to an aluminum alloy and obtaining high strength. If the content of C is less than 2%, the strength cannot be obtained. On the other hand, if it exceeds 4%, the wear resistance is impaired, and primary crystal Si is apt to be generated, so that the forgeability is impaired.

Magnesium forms a solid solution in aluminum and serves to strengthen the alloy matrix, and also becomes an intermetallic compound of Mg ₂ Si by heat treatment and contributes to the improvement of strength and wear resistance. However
When the Mg content is less than 0.3%, strength and wear resistance are insufficient due to lack of solid solution strengthening and age hardening, while 0.
If it exceeds 6%, the forgeability deteriorates and the discoloration after heat treatment is affected.

Manganese enhances strength and wear resistance by solid solution strengthening and age hardening, but if it is less than 0.3%, it has little effect, and if it exceeds 0.6%, coarse intermetallic compounds tend to crystallize and forgeability is significantly impaired. become.

Boron has the effect of finely homogenizing the macrostructure and increasing the compressive strength during forging, but if it is less than 0.02%, the effect is not sufficient, and if it exceeds 0.05%, the effect is saturated.

Sb contained in the alloys of the first and third inventions refines Si crystal grains of eutectic structure.

Particularly in a large-diameter billet having a slow cooling rate, coarsening of eutectic Si is likely to occur, so that strength and wear resistance tend to be reduced. The addition of Sb is effective to prevent this, but Sb
If the content is less than 0.1%, its effect is small. On the other hand, if the Sb content exceeds 0.5%, an intermetallic compound containing Sb is crystallized and forgeability is deteriorated. Furthermore, when elements such as Zn, Pb, Sn, and Bi contained in the aluminum alloy of the recycled ingot are contained in the first invention alloy in large amounts as unavoidable impurities, the synergistic action of these impurities and Sb results in brightening. Property is lost, and it is difficult to recover the glitter even after adding Be, which will be described later. Therefore, the upper limit of the Sb content is 0.5%. Zn, P
Elements such as b, Sn, and Bi are usually impurities and do not need to be added.
When the alloy of the present invention is melted after the alloy containing them is melted, the amount increases to a considerable amount due to contamination in the furnace.

The alloy of the second invention does not contain Sb but contains at least one of Zn, Pb, Sn and Bi as a machinability improving component. But,
When Zn is 0.05% or more and Pb, Sn, and Bi are 0.1% or more, the original luster of aluminum is lost without the addition of Sb.

Further, if the content of Zn exceeds 1.5%, the forgeability and mechanical strength decrease, and if the contents of Pb, Sn, and Bi exceed 1.0% each, and the total content exceeds 2.0%, the wear resistance is impaired, and Since the glitter cannot be restored, the upper limit of the Zn, Pb, Sn, and Bi contents is determined by this.

In the alloy of the second invention, by producing a small-diameter ingot by the continuous casting method with a high cooling rate disclosed in Japanese Patent Publication No. 53-20243, it is possible to obtain the same or better performance as the Sb-added product in the large-diameter billet. It is possible to refine the crystal Si.

Beryllium added to the alloys of the first to third inventions has the function of suppressing the phenomenon of surface discoloration during high temperature heat treatment of aluminum alloys, but if the Be content is less than 0.001%, this effect cannot be achieved and 0.2 %, Mechanical properties, especially toughness, are deteriorated.

[Work]

It is known that when an aluminum alloy containing Mg is heated in an oxidizing atmosphere, an oxidation reaction occurs on the surface of the alloy having a depth of several 10 μm to several 100 μm to generate spinel Al ₂ O ₃ .nMgO.

When the aluminum alloy further contains Sb, Zn, Pb, Sn, Bi and the like, it is considered that these elements combine with spinel in the form of an oxide or in a metal state to form surface contaminants.

Therefore, the aluminum alloy after heating changes its color to various colors depending on the kind of the oxidation reaction product. Be, which is a feature of the present invention, forms an extremely thin film on the Al alloy surface.
It is presumed that it coats Al and interferes with the reaction with oxygen and thus the formation of spinel.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 Alloys having the compositions shown in Table 1 were continuously cast into 50 mmφ, and this casting rod was heated at 350 to 450 ° C. to forge with a working rate of about 60%.
Performed with a 600 ton hammer.

After that, solution treatment was performed at 530 ° C. in a kerosene burner furnace, and then the results of observing the surface color are shown in Table 2.

Example 2 A small-diameter continuous casting rod having a diameter of 50 mmφ was produced from the invention alloy having the composition of No. 1 in Table 1 and the comparative alloy of No. 9, which was homogenized at 490 ° C. and then upset test of diameter 45 mmφ. Molded into pieces. Upset forging was performed at 400 ° C with a hydraulic press. As a result of performing upsetting forging tests at various processing rates with different processing rates, the test piece No. 1 has a processing rate of 92%.
No cracks occurred until the test piece No. 9 had a processing rate of 84%
With the above, cracks occurred.

〔The invention's effect〕

(1) According to the first to third inventions, the forged product has a metallic luster without exhibiting a contaminated color such as black or gray even after being subjected to a heating environment such as heat treatment, and enhances the value of the product. In addition, since the deterioration of the product surface caused by the loss of metallic luster is eliminated, it is not necessary to remove the surface by polishing, etc., and the yield reduction is avoided, and the treatment of metallic luster recovery such as pickling is also impossible. The cost increase factor is eliminated because it becomes necessary.

(2) The alloys of the first to third inventions exhibit high strength and wear resistance by adding Si, Cu, Mg and Mn. In addition, B addition improves the forgeability by miniaturizing the macro group. In addition to these common elements, in the first invention alloy, addition of Sb makes it possible to further refine the eutectic Si and improve the above performance.

Since the alloy of the second invention allows Zn, Pb, Sn, Bi and the like to be mixed in as impurities, the cost of raw material can be reduced by using the recycled mass. The alloy of the third invention is Sb
In addition, since Zn, Pb, Sn, Bi and the like are allowed to be mixed in as impurities, the effects of the two inventions can be obtained at the same time.

(3) According to the first to third inventions of the present application, there is no altered structure on the surface of the forged product that has undergone a heating process such as heat treatment, and the intermetallic compound of α-Al, eutectic Si, Mg ₂ Si, Sb, etc. It is composed of the original set of eutectic Al-Si alloys. Further, the additive elements such as Mg and Sb exhibit desired characteristics without being lost as spinel and the like, so that a metal having excellent surface characteristics important for wear resistance can be obtained.

(4) When forging of a shape that easily produces burrs, the alloys of the first to third inventions are useful for reducing cracks entering the burrs.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyuki Shiosato 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. Sekiguchi Tsunehisa 43-13, Kaminogidai, Kanagawa-ku, Kanagawa-ku, Kanagawa Prefecture (72) Inventor Ryoichi Kondo 431, Kamisugada-cho, Hodogaya-ku, Yokohama-shi, Yokohama, Kanagawa Prefecture

Claims (3)

[Claims] 1. Si 9-11%, Cu 2-4%, Mg by weight
0.3-0.6%, Mn 0.3-0.6%, Sb 0.1-0.5%, Be
An aluminum alloy for forging which is characterized by containing 0.001-0.2% and B 0.02-0.05%, the balance being Al and impurities, and having heat discoloration resistance. 2. Si 9-11%, Cu 2-4%, Mg by weight
0.3-0.6%, Mn 0.3-0.6%, Zn 0.05-1.5% and / or Pb, Sn, Bi 0.1-1.0% each, total 2.0% or less, Be
An aluminum alloy for forging which is characterized by containing 0.001-0.2% and B 0.02-0.05%, the balance being Al and impurities, and having heat discoloration resistance. 3. By weight, Si 9-11%, Cu 2-4%, Mg
0.3-0.6%, Mn 0.3-0.6%, Sb 0.1-0.5% and Zn
0.05-1.5% and / or Pb, Sn, Bi 0.1-1.0%, total 2.0% or less, Be 0.001-0.2%, B 0.02-0.05%, balance Al and impurities, heat resistance to heat discoloration An aluminum alloy for forging which is characterized by having.