JPH05287427A - Wear resistant aluminum alloy for cold forging and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a wear resistant Al alloy for cold forging having high strength by incorporating a specified amt. of Sr into an Al alloy having a specified compsn. constituted of Cu, Fe, Si, Mg, Mn, Cr, Ni, Ti and Al at the time of its casting. CONSTITUTION:At the time of casting an Al alloy contg., by weight, 1.0 to 3.0% Cu, 0.1 to 1.0% Fe, 6.0 to l0% Si, 0.2 to 1.5% Mg, 0.05 to 0.2% Mn, 0.05 to 0.5% Cr, 0.05 to 1.0% Ni and <=0.3% Ti, and the balance substantial Al, 0.02 to 0.10% Sr is incorporated therein. In this way, the objective wear resistant Al alloy excellent in both antinomic properties of strength as well as wear resistance and cold forgeability and capable of cold forging to a considerably complicated shape can be obtd. Furthermore, the conditional control in the process of the manufacture can surely and easily be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant aluminum alloy for cold forging, which can be cold-forged to a considerably complicated shape, and whose strength and wear resistance are greatly improved, and a method for producing the same. ..

[0002]

2. Description of the Related Art A is used as an automobile part, a machine part or the like which has conventionally been required to have wear resistance.
4032 (extruded material), which is an l-Si alloy, AC8A
(Casting), ADC12 (die casting) and the like have been used, but with the increasing demand for aluminum alloys, the required quality is changing and is becoming higher. That is, it has been pointed out that there are problems in performance such that the extruded material of the above-mentioned conventional alloy has insufficient wear resistance, and the casting and die casting have insufficient strength and toughness.

In addition to the above-mentioned conventional alloys, there is A390 as an alloy excellent in wear resistance, and a method of forging and using a cast or extruded material of A390 is being studied in order to further improve its strength and toughness. .. However, this alloy has poor forgeability, and it is necessary to perform warm or hot forging instead of cold forging, resulting in high manufacturing cost. Therefore, in order to refine the eutectic structure of the Al-Si alloy having the eutectic or hypoeutectic composition in the above alloy, an improvement treatment is carried out. As the improvement treatment agent, Na, Sr, Sb, etc. have been frequently used. Has been done. However, in this case, most of the actual operations for producing the extruded material are the improvement treatment of Na, and Sr and S
At present, b is used for another purpose.

By the way, the improvement treatment by Na is Al-S
By adding it to the molten alloy of the i-based alloy, the eutectic structure of the ingot of the Al-Si alloy obtained by solidification is refined. However, since Na is an extremely active metal, it is generally used. In addition, Na is added to the molten metal in the state of flux such as NaF or NaCl. However, the improvement treatment with Na is
In addition to the short improvement time of about 1 to 2 hours, there are problems that the molten metal is contaminated by flux components and that the hearth and the furnace wall are damaged. Further, in order to improve the quality of the product, a tubular filter may be used to clean the molten metal, but there is a problem that the tubular filter and the like are easily damaged by the flux component for Na addition.

[0005] Therefore, a substitute for Na as an improving treatment agent has been sought and various studies have been conducted. Of these, Sr has the advantage that it has a long duration of effect and is easy to handle, and since it can be added in the state of an Al-Sr intermediate alloy, the problem of contamination of the molten metal due to Sr addition does not occur. And so on. However, Sr
The improvement treatment is a state where it is used only for special casting products because the precipitation of Al-Sr intermetallic compound and the cost are higher than Na in actual operation.

[0006]

As a result of various investigations in view of the above, the present invention has revealed that even if it is an Al-Si alloy having a eutectic or hypoeutectic composition used in the fields of rolling, extrusion, casting, etc. We have developed a wear-resistant aluminum alloy for cold forging, which is capable of cold forging to complex shapes, and has greatly improved strength and wear resistance, and a method for producing the same.

That is, the alloy of the present invention has a Cu content of 1.0 to 3.0 wt.
%, Fe 0.1 to 1.0 wt%, Si 6.0 to 10 wt%,
Mg 0.2-1.5 wt%, Mn 0.05-0.2 wt%,
Cr0.05-0.5wt%, Ni0.05-1.0wt
%, Sr 0.02 to 0.1 wt%, Ti 0.3 wt% or less, and the balance being essentially Al.

Further, the manufacturing method of the present invention uses Cu1.0-
3.0 wt%, Fe 0.1-1.0 wt%, Si 6.0-1
0 wt%, Mg 0.2-1.5 wt%, Mn 0.05-0.
2 wt%, Cr 0.05-0.5 wt%, Ni 0.15-
When an aluminum alloy containing 1.0 wt% and Ti 0.3 wt% or less and the balance being substantially Al is cast, Sr0.
It is characterized by containing 02 to 0.10 wt%.

[0009]

The aluminum alloy is excellent in cold workability, but this not only means that the manufacturing process is easy and is suitable for mass production, but also has a great advantage that the dimensional accuracy of the product is significantly improved. In addition, various lubricants are generally used when making sliding surface parts by extrusion, etc., but in hot working, this lubricant often sticks to the sliding surface and contaminates the surface. Such troubles can be eliminated by processing, and a clean sliding surface can be formed. As described above, the Al-Si alloy having wear resistance and high strength and excellent cold workability is expected to be widely used.

In the present invention, the strength is improved by cold working,
The present invention also provides an Al-Si alloy having excellent wear resistance, to which Sr, which is not commonly used in conventional DC casting or the like, is applied as an improving treatment agent.

The reasons for limiting the content range of the alloy of the present invention will be described below. Although Si imparts wear resistance to the alloy, the content of Si is limited to 6 to 10 wt% because the effect is poor when it is less than 6 wt% and Sr exceeds 10 wt%.
This is because even if the alloy is added to perform semi-continuous casting and the solidification rate is increased, primary crystal Si is generated, making processing difficult and lowering the strength.

[0012] Cu imparts tensile strength to the aluminum alloy, and its content is limited to 1.0 to 3.0 wt% because the effect is insufficient if it is less than 1.0 wt%.
On the other hand, if it exceeds 3.0 wt%, even if Sr is added, the primary crystal Si and eutectic Si become coarse, making it difficult to process, remarkably lowering the cold forgeability, further lowering the corrosion resistance and causing stress corrosion cracking. This is because it is easy to do.

Although Mn has an effect of refining crystal grains and improves toughness, the content is limited to 0.05 to 0.2 wt% because the effect is insufficient if it is less than 0.05 wt%. If it exceeds 0.2 wt%, the wear resistance is reduced.

Although Cr improves wear resistance, the content of Cr is limited to 0.05 to 0.5 wt% because it is 0.05 wt%.
If it is less than 0.5% by weight, the effect is insufficient, and if it exceeds 0.5% by weight, quenching sensitivity is increased and strength is lowered.

Although Mg forms precipitates of Mg ₂ Si and gives strength, the content is limited to 0.2 to 1.5 wt% because the effect is insufficient if it is less than 0.2 wt%. Yes,
This is because if it exceeds 1.5 wt%, the elongation decreases and the plastic workability such as cold forgeability deteriorates.

Fe has the effect of increasing the hardness of the aluminum alloy. By containing Fe, the wear resistance of the aluminum alloy is improved, but the content is 0.1 to 0.1%.
The reason why it is limited to 1.0 wt% is that the effect is insufficient if it is less than 0.1 wt%, and if it exceeds 1.0 wt%, giant crystallized substances are generated.

Ni improves heat resistance (high-temperature strength) and wear resistance, but its content is limited to 0.05 to 1.0 wt% because the effect is insufficient if it is less than 0.05 wt%. This is because if the content exceeds 1.0 wt%, not only the effect is saturated but also the compound such as Al ₃ Ni is coarsened to deteriorate heat resistance and wear resistance.

Although Ti has a grain refining effect and an effect of improving strength and toughness, the content of Ti is limited to 0.3 wt% or less because the effect is saturated when the content exceeds 0.3 wt%. This is because. Although Ti is added in the form of Ti-B,
The amount of B is 1/10 to 1/20 of Ti.

In the present invention, 0.02 to 0.10 wt% of Sr is added as an improving treatment agent when casting the Al alloy having the above composition. By adding Sr in this way,
A long improvement duration of 4 hours can be obtained, the average Si grains of primary crystal Si and eutectic Si can be refined to 10 μm or less at the time of solidification of the alloy, and the average Si grain can be 5 even after extrusion.
Since it has a uniform fine Si grain structure of μm or less, wear resistance,
Although the strength, toughness and plastic workability were improved, the addition amount was limited to 0.02 to 0.10 wt% was 0.02 wt.
If it is less than 0.1%, the effect is insufficient, and if it exceeds 0.10% by weight, the effect is saturated and becomes supersaturated. Therefore, the Sr content is set within the above range, and other additive elements, particularly S
When the i content is within the above range, the Al-Sr intermetallic compound is not produced as described above.

Impurities such as Zn may be contained in ordinary Al ingots.

The Al alloy of the present invention prevents the generation of Sr-based compounds despite the addition of Sr as an improving agent, stably casts a high-quality ingot, and further extrudes Si grains into a uniform fine grain. It is what That is, the alloy of the present invention is used mainly as a material for cold forging such as a cast rod or an extruded rod to facilitate cold forging.

[0022]

EXAMPLES The present invention will be described below with reference to examples. Table 1
Inventive alloys (No. 1 to 4) and comparative alloys (No. 5 to No. 5)
7), conventional alloys (Nos. 8 to 10) were made into test materials by the following method, and macroscopic and microstructures after casting, mechanical properties, cold forgeability, and wear resistance were examined. The results are shown in Table 2.

As the test material, an aluminum alloy having the components and component ratios shown in Table 1 was melted by a usual method (DC casting), and Sr or Na was added as an improving treatment agent as shown in Table 1. At this time, Na is a waffle-like flux and Sr is A
It was added using an l-Sr rod, and the improved holding time was also checked at any time, and an ingot was prepared for each. The obtained ingot was homogenized at 470 ° C. for 12 hours, excluding the conventional alloy No. 9, and extruded into a round bar having a diameter of 27 mm at a temperature of 400 ° C. to obtain a test material.

Next, the test method of the main test materials will be described. Cold forgeability (upset forgeability); test piece has a diameter of 2
A cylindrical rod of 7 mm in height and 20 mm in height is compressed by a press. When a micro crack is generated on the free deformation surface, the compression is stopped, and the installation rate (limit workability) at that time is set. Sought by. That is, the difficulty of the upsetting forgeability was expressed by the upsetting rate.

Measurement of primary crystal and eutectic Si particle shapes: A Miku photograph taken at a predetermined magnification of 400 times with a metallurgical microscope was subjected to image analysis by an image analyzer (aspect), and the Si particle area was converted into an area-equivalent circle. Substituting, the particle diameter distribution was determined by the circle equivalent diameter method using the circle as a representative and the Si particle diameter. This measured the average particle diameter.

Abrasion resistance: Using the Ogoshi-type abrasion tester, the specific abrasion loss of the test material was measured under the following conditions to evaluate the abrasion resistance. Lubrication condition: Unlubricated Wear distance: Dry type 1200mm Load: Dry type 19.7kg Mating material: SCM21 Wear rate: 1.36m / sec Working oil: Gear oil (GL-5)

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from Table 2, the alloy of the present invention (N
o.1 to 4) have a balance of strength, wear resistance, and cold forgeability as compared with comparative alloys (No. 5 to 7) and conventional alloys (No. 8 to 10) that are out of the structural range of the present invention. In terms of texture, the effect of Sr is confirmed even in the average Si grain size due to the macrostructure (DAS, etc.) of the ingot and the improvement treatment. It was also confirmed that the improved retention time of the alloy of the present invention during DC casting was superior to the comparative alloy and the conventional alloy.

[0030]

As described above, according to the present invention, the obtained aminium alloy is excellent in both strength and wear resistance and cold forgeability, which cannot be achieved by conventional aluminum alloys, and Industrially significant effects such as reliable and easy management of conditions during the manufacturing process are achieved.

Claims (2)

[Claims] 1. Cu 1.0 to 3.0 wt%, Fe 0.1 to
1.0 wt%, Si 6.0-10 wt%, Mg 0.2-1.
5wt%, Mn0.05-0.2wt%, Cr0.05-
0.5wt%, Ni0.05-1.0wt%, Sr0.02
A wear-resistant aluminium alloy for cold forging, characterized in that it contains 0.1 to 0.1 wt% and 0.3 wt% or less of Ti, and the balance substantially consists of Al. 2. Cu 1.0 to 3.0 wt%, Fe 0.1 to
1.0 wt%, Si 6.0-10 wt%, Mg 0.2-1.
5wt%, Mn0.05-0.2wt%, Cr0.05-
0.5wt%, Ni0.05-1.0wt%, Ti0.3wt
% Sr 0.02 to 0.10 wt% at the time of casting of an aluminum alloy containing 0.1% or less and the balance substantially consisting of Al. A method for producing a wear resistant aluminum alloy for cold forging.