JPH07197164A - Aluminum alloy having high strength and high workability and its production - Google Patents

Abstract

PURPOSE:To produce the alloy excellent in strength and abrasion resistance and also excellent in workability (cold forgeability, etc.) and suitable for compresser parts, etc., of an automobile and to provide a production method therefor. CONSTITUTION:This alloy is composed of 6.0-15.0wt.% Si, 0.1-1.0wt.% Fe 1.0-3.0wt.% Cu, 0.2-1.5wt.% Mg, 0.1-0.5wt.% Mn, 0.05-0.5wt.% Cr, 0.05-1.5wt.% Ni, 0.02-0.1wt.% Sr, <=0.3wt.% Ti and the balance Al with inevitable impurities. The molten aluminum alloy having this composition is casted to form a cast billet, then the cast billet is subjected to a homogenizing treatment under keeping it at 500-560 deg.C for more than 4hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable as a material for automobile parts required to have high strength, high abrasion resistance and high workability, for example, pistons, plates and scrolls used as compressor parts for air conditioners. The present invention relates to a high-strength and high-workability aluminum alloy and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, A is used for automobile parts and machine parts which are required to have high strength, high workability and high abrasion resistance.
JIS4032 alloy (extruded material) which is an l-Si alloy,
JISAC8A alloy (cast material), JISADC12 (die cast material) and the like have been used, but higher quality materials are required to expand the demand for aluminum. For example, iron-based materials have been used for parts that are subject to strong wear among compressor parts of room air conditioners and car air conditioners, but recently, aluminum alloys are often used for weight reduction. The JISAC8A alloy and the JISADC12 alloy have been used for such parts. However, due to the regulation of CFC gas, an aluminum alloy having excellent strength and abrasion resistance is required. Also, the shapes of these parts are becoming more complex,
There is a demand for a material having excellent workability during forming such as forging. With respect to these requirements, there is a problem that the extruded material of the conventional alloy has insufficient wear resistance, and the cast material and the die cast material have insufficient strength and toughness.

A390 alloy (Al-18 wt% Si-5 wt% as an alloy having strength and abrasion resistance superior to those of the conventional alloys described above.
Cu-0.6 wt% Mg alloy), and in order to further improve its strength and toughness, it is considered to use a cast or extruded material of A390 alloy by forging. However, this alloy has poor workability, and there is a problem in that forging must be performed by hot forging.

Further, in order to improve the workability of the above various Al-Si alloys, the shape of Si-based crystallized substances when Na is added to the molten metal in the state of flux such as NaF and NaCl to form an ingot Although an improvement treatment for making the particles spherical or granular and making them finer has also been performed, a sufficient effect has not been obtained, and there is a problem that the ceramic tube filter for filtering the molten metal during casting is easily damaged by the flux component.

[0005]

As a result of intensive studies in view of such a situation, the present invention is a high-strength and high-workability aluminum excellent not only in strength and wear resistance but also in workability such as cold forgeability. The alloy and its manufacturing method were developed.

That is, the first invention is Si 6.0 to 15.0 wt.
%, Fe 0.1-1.0 wt%, Cu 1.0-3.0 wt
%, Mg 0.2 to 1.5 wt%, Mn 0.1 to 0.5 wt
%, Cr 0.05 to 0.5 wt%, Ni 0.05 to 1.0
It is a high-strength and high-workability aluminum alloy characterized by containing wt%, Sr 0.02 to 0.1 wt% and Ti 0.3 wt% or less, and the balance being Al and inevitable impurities.

The second invention is Si 6.0-15.0 wt.
%, Fe 0.1-1.0 wt%, Cu 1.0-3.0 wt
%, Mg 0.2 to 1.5 wt%, Mn 0.1 to 0.5 wt
%, Cr 0.05 to 0.5 wt%, Ni 0.05 to 1.0
After casting an aluminum alloy melt containing wt%, Sr 0.02 to 0.1 wt%, and Ti 0.3 wt% or less, and the balance of Al and unavoidable impurities to form an ingot,
A method for producing a high-strength and high-workability aluminum alloy, which comprises performing a homogenizing treatment in which the temperature is held at a temperature of 00 to 560 ° C. for 4 hours or more.

[0008]

First, the reasons for limiting the alloy composition of the alloy of the present invention will be described. Si is mainly present in the matrix of the aluminum alloy to improve the wear resistance and lowers the coefficient of thermal expansion. Also, increase the Young's modulus of aluminum alloy,
Since it reduces the density, it also contributes to weight reduction. The content is limited to 6.0 to 15.0 wt% because the effect is not sufficient if it is less than 6.0 wt%, and if it exceeds 15.0 wt%, the primary crystals are obtained even if the solidification rate during casting is increased. This is because Si becomes coarse, processing becomes difficult, and strength also decreases.

Fe increases the hardness of the aluminum alloy and improves the wear resistance, but its content is 0.1 to 1.0 wt.
%, The effect is not sufficient if it is less than 0.1 wt%, and if it exceeds 1.0 wt%, giant crystallized substances are generated and the workability deteriorates.

Cu enhances the strength of the aluminum alloy, and the reason why the content thereof is limited to 1.0 to 3.0 wt% is that the effect is not sufficient if it is less than 1.0 wt%.
This is because if it exceeds 0 wt%, primary crystal Si and eutectic Si are coarsened, workability such as cold forgeability is remarkably deteriorated, and corrosion resistance is also deteriorated to easily cause stress corrosion cracking.

Mg forms precipitates of Mg ₂ Si and enhances the strength, but the content is limited to 0.2 to 1.5 wt% because the effect is not sufficient if it is less than 0.2 wt%,
This is because if it exceeds 1.5 wt%, the elongation decreases and the workability such as cold forgeability deteriorates.

Mn has the effect of refining the crystal grains and improves the toughness, but the content is limited to 0.1 to 0.5 wt% because the effect is not sufficient if it is less than 0.1 wt%. If it exceeds 0.5 wt%, the wear resistance is lowered and a coarse intermetallic compound is formed.

Cr improves the wear resistance, but the content of Cr is limited to 0.05 to 0.5 wt% by 0.05 wt%
If it is less than 0.5% by weight, the effect is not sufficient, and if it exceeds 0.5% by weight, quenching sensitivity is increased and strength is lowered.

Ni improves heat resistance (high temperature strength) and wear resistance, but the content is limited to 0.05 to 1.0 wt% because the effect is not sufficient if it is less than 0.05 wt%. If the content exceeds 1.0 wt%, not only the effect is saturated, but also the intermetallic compound such as Al ₃ Ni is coarsened, and conversely the heat resistance and the wear resistance are deteriorated.

Ti has the effect of refining the crystal grains and improves the strength and toughness, but the content was limited to 0.3 wt% or less because the effect saturates when it exceeds 0.3 wt%. This is because the workability deteriorates.

Sr is added at the time of casting, and the grain size of primary crystal Si and eutectic Si at the time of solidification of the alloy is made fine, wear resistance, strength,
Improves toughness and workability, but adds 0.02%
The reason for limiting the content to 0.10 wt% is that the effect is not sufficient if it is less than 0.02 wt%, and the effect is saturated if it exceeds 0.10 wt%, resulting in an unnecessarily high cost.

Although the alloying elements of the alloy of the present invention have been described above, they may be contained as unavoidable impurities in an amount that is contained in ordinary aluminum ingots.

Next, the manufacturing method of the present invention will be described.
The production method of the present invention is characterized in that after the above-mentioned molten aluminum alloy is cast into an ingot, a homogenization treatment is carried out at a temperature of 500 to 560 ° C for 4 hours or more. Al-S
The homogenization treatment of i-based alloy is usually less than 500 ° C (450 to 4
It is applied at a temperature of about 80 ° C.), but in the present invention, the homogenization treatment is performed at the above temperature to increase elongation and improve workability. That is, the homogenization treatment temperature is 500
It was found that high elongation (high workability) can be obtained by making the crystallized substances generated during casting sufficiently solid-solution by finely precipitating Mn and Cr by making the temperature as high as ˜560 ° C. is there. If the homogenization temperature is less than 500 ° C, the above effect is not sufficient, and if it exceeds 560 ° C, eutectic melting (burning) or the like occurs to cause ingot cracking. If the holding time is 4 hours or more, the above effect can be obtained, and there is no problem even if the holding time is lengthened.

[0018]

EXAMPLES The present invention will now be described in more detail with reference to examples. Melts of various aluminum alloys having the alloy compositions shown in Table 1 were cast by ordinary water cooling casting to produce an ingot having a diameter of 219 mm. When Na was added during casting, a waffle-like flux was added, and when Sr was added, an Al-Sr rod was added. The macrostructure and microstructure (Si grain size) of these ingots were examined, and after these ingots were homogenized under the conditions shown in Table 1, extrusion was carried out at a temperature of 400 ° C. to obtain a round bar having a diameter of 27 mm. The test piece was taken from the above, and the extruded structure (Si grain size), the mechanical properties of O material and T6 material,
Cold forgeability and wear resistance were investigated.

The main test methods are as follows. (1) Measurement of Si particle size A microphotograph of a predetermined portion taken with a metallurgical microscope at a magnification of 400 times is image-analyzed by an image analyzer, and the Si particle area is replaced with an area-equivalent circle. The particle size distribution of the Si particles was determined by the circle equivalent diameter method that uses the particle size of the Si particles. This measured the average particle size. (2) Cold forgeability (upset forgeability) A cylindrical test piece having a diameter of 27 mm and a height of 20 mm is compressed by a press. When a microcrack occurs on the free deformation surface, the compression is stopped, and the following formula is used. The upsetting ratio at that time was obtained, and this upsetting ratio was used as the limit workability, and the cold forgeability was evaluated by the limit workability. (3) Abrasion resistance Using an Ogoshi abrasion tester, the specific abrasion amount of the test piece was measured under the following conditions to evaluate the abrasion resistance. Lubrication conditions: Gear oil (GL-5) Wear distance: Wet 200 mm Load: 19.7 kg Mating material: SCM21 Wear rate: 1.36 m / sec These results are shown in Table 2.

[0020]

[Table 1]

[0021]

[Table 2]

As is apparent from Table 2, alloy No. 1 of the present invention
Nos. 4 to 4 have strengths and abrasion resistances equal to or higher than those of the conventional alloys Nos. 8 to 10, and cold forgeability is remarkably excellent. On the other hand, it is understood that the cold forgeability of Comparative Alloys Nos. 5 to 7, which have alloy compositions and manufacturing conditions outside the range of the present invention, are inferior.

[0023]

As described above, according to the present invention, a high-strength and high-workability aluminum alloy which is excellent in strength, wear resistance and cold forgeability and is suitable for compressor parts of automobiles and the like. Is obtained, and has a remarkable industrial effect.

Claims (2)

[Claims] 1. Si 6.0-15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 3.0 wt%, Mg 0.2 ~
1.5 wt%, Mn 0.1 to 0.5 wt%, Cr 0.05 to
0.5wt%, Ni0.05-1.0wt%, Sr0.02
~ 0.1 wt%, Ti less than 0.3 wt%, the balance is A
A high-strength and high-workability aluminum alloy, which is characterized by comprising 1 and unavoidable impurities. 2. Si 6.0-15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 3.0 wt%, Mg 0.2 ~
1.5 wt%, Mn 0.1 to 0.5 wt%, Cr 0.05 to
0.5wt%, Ni0.05-1.0wt%, Sr0.02
~ 0.1 wt%, Ti less than 0.3 wt%, the balance is A
After casting a molten aluminum alloy consisting of 1 and unavoidable impurities into an ingot, the ingot is subjected to a homogenizing treatment in which the ingot is held at a temperature of 500 to 560 ° C. for 4 hours or more. Processable aluminum alloy manufacturing method.