JPH07197165A - High wear resistant free cutting aluminum alloy and its production - Google Patents

Abstract

PURPOSE:To obtain a high wear resistant free cutting aluminum alloy being suitable to a compressor parts, etc., of an automobile having excellent strength, wear resistance, machinability and workability (cold forging property, etc.). CONSTITUTION:This aluminum alloy has composition contg. 1.0-15.0wt.% Si, 0.1-1.0wt.% Fe, 1.0-5.0wt.% Cu, 0.2-1.5wt.% Mg, 0.1-0.5wt.% Mn, 0.05-0.5wt.% Cr, 0.05-1.0wt.% Ni, <=0.3wt.% Ti and the balance Al with inevitable impurities and if necessary, containing 0.02-0.1% Sr and further, at least 2 kinds of 0.1-2.0wt.% Pb, 0.1-2.0wt.% Sn, 0.1-2.0wt.% Bi. This aluminum alloy is cast to make a cast ingot and, thereafter, a homogenizing treatment is executed to the ingot at 500-600 deg.C for >=4hr to obtain the high wear resistant free cutting aluminum alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automobile parts required to have high strength, high wear resistance, free-cutting property and corrosion resistance, such as pistons, plates and scrolls used as compressor parts for air conditioners. The present invention relates to a high wear-resistant free-cutting aluminum alloy suitable as a material and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, automobile parts and machine parts which are required to have high strength and high abrasion resistance are JIS4032 alloy (extruded material) which is Al-Si alloy, JISAC8A.
Although alloys (cast materials), JIS ADC12 (die casting materials), etc. have been used, 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. For such parts, JI
SAC8A alloy and JIS ADC12 alloy have been used, but due to the CFC gas regulation, an aluminum alloy having more excellent strength and abrasion resistance is required. In addition, the shapes of these parts have become complicated, and there is a demand for a material that is excellent in workability during forming such as forging, has good machinability during machining, and can prolong the life of the cutting tool. In order to meet these requirements, the extruded materials and cast rods of the conventional alloys have insufficient wear resistance, and the cast materials and die cast materials have insufficient strength and toughness. As for machinability, S contributes to wear resistance for all materials to improve machinability.
There is a problem that the addition amount of hardening elements such as i, Mg and Cu is restricted.

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, the forging process must be performed by hot forging, and since the Si content is high,
There is a problem that the machinability is poor and the life of the cutting tool is shortened and the manufacturing cost is high.

The machinability of the above various Al--Si alloys,
In order to improve workability, when Na is added to the molten metal in the state of flux such as NaF or NaCl to form an ingot, S
The i-type crystallized product has been spherical or granular, and improvements have been made to refine it, but sufficient effects have not been obtained and the ceramic tube filter that filters the molten metal during casting due to the flux component is damaged. There is a problem that it is easy to do.

[0005]

As a result of intensive studies in view of such a situation, the present invention is a high wear-resistant free-cutting aluminum alloy excellent not only in strength and wear resistance but also in machinability and workability. And its manufacturing method were developed.

That is, the first invention is Si 1.0 to 15.0 wt.
%, Fe 0.1-1.0 wt%, Cu 1.0-5.0 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
wt%, Ti less than 0.3 wt%, Pb0.1
~ 2.0wt%, Sn0.1 ~ 2.0wt%, Bi0.1
A high wear-resistant free-cutting aluminum alloy containing at least two of 2.0 wt% and the balance being Al and unavoidable impurities.

The second invention is Si 1.0 to 15.0 wt%,
Fe 0.1-1.0 wt%, Cu 1.0-5.0 wt%, M
g 0.2-1.5 wt%, Mn 0.1-0.5 wt%, Cr
0.05-0.5 wt%, Ni 0.05-1.0 wt%, S
r 0.02-0.1 wt%, Ti 0.3 wt% or less, Pb 0.1-2.0 wt%, Sn 0.1-2.
It is a high wear-resistant free-cutting aluminum alloy, characterized by containing two or more of 0 wt% and Bi 0.1-2.0 wt%, and the balance being Al and unavoidable impurities.

The third invention is Si 1.0 to 15.0 wt%,
Fe 0.1-1.0 wt%, Cu 1.0-5.0 wt%, M
g 0.2-1.5 wt%, Mn 0.1-0.5 wt%, Cr
0.05 to 0.5 wt%, Ni 0.05 to 1.0 wt%, T
i 0.3 wt% or less, and Pb 0.1 to 2.0
wt%, Sn 0.1-2.0 wt%, Bi 0.1-2.0 wt
% Of the aluminum alloy and the balance is Al and inevitable impurities, and a molten aluminum alloy is cast into an ingot, and the ingot is held at a temperature of 500 to 560 ° C. for 4 hours or more. A method for producing a high wear-resistant free-cutting aluminum alloy, characterized by performing homogenization treatment.

The fourth invention is Si 1.0 to 15.0 wt%,
Fe 0.1-1.0 wt%, Cu 1.0-5.0 wt%, M
g 0.2-1.5 wt%, Mn 0.1-0.5 wt%, Cr
0.05-0.5 wt%, Ni 0.05-1.0 wt%, S
r 0.02-0.1 wt%, Ti 0.3 wt% or less, Pb 0.1-2.0 wt%, Sn 0.1-2.
After casting an aluminum alloy melt containing two or more of 0 wt% and Bi 0.1 to 2.0 wt% and the balance of Al and unavoidable impurities to form an ingot, 500 is cast into the ingot.
A method for producing a high wear-resistant free-cutting aluminum alloy, characterized by carrying out a homogenizing treatment for holding at a temperature of ˜560 ° C. for 4 hours or more.

[0010]

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 1.0 to 15.0 wt% because when it is less than 1.0 wt%, the effect is not sufficient, and when it exceeds 15.0 wt%, primary crystal Si and eutectic Si are coarsened and processed. This is because it becomes difficult to perform cutting, the machinability is deteriorated, and the life of the cutting tool is significantly shortened.

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 workability and machinability deteriorate.

Cu enhances the strength of the aluminum alloy, and the reason why the content thereof is limited to 1.0 to 5.0 wt% is that the effect is not sufficient if it is less than 1.0 wt%.
This is because if it exceeds 0 wt%, the workability is remarkably reduced, the corrosion resistance is also lowered, and stress corrosion cracking is likely to occur.

Mg forms precipitates of Mg ₂ Si to enhance 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 plastic workability such as cold forgeability deteriorates.

Mn has an effect of refining crystal grains and improves 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 decreases and a coarse intermetallic compound is produced.

Although Cr improves the 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 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 abrasion 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 conversely, the heat resistance and 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.

Pb, Sn, and Bi are all contained in order to improve the machinability and prolong the life of the cutting tool, but the content is limited as described above.
Only one of b, Sn and Bi, or if the content of each is less than 0.1 wt%, the effect is not sufficient, and if the content of each exceeds 2.0 wt%, crystallized substances increase, and Properties, surface treatment property after cutting, and corrosion resistance are deteriorated.

Sr is added at the time of casting to reduce the grain sizes of primary crystal Si and eutectic Si during solidification of the alloy, to improve wear resistance, strength,
The toughness, plastic workability and corrosion resistance are improved, but the addition amount is limited to 0.02 to 0.10 wt% to 0.02.
If it is less than wt%, the effect is not sufficient, and if it exceeds 0.10 wt%, the effect is saturated, which unnecessarily increases the cost.

Although the alloying elements of the alloy of the present invention have been described above, they may be contained in the usual aluminum ingot as unavoidable impurities.

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 has been found that a high elongation can be obtained by making the crystallized substances formed during casting sufficiently solid-solution by finely precipitating Mn and Cr by setting the temperature to 560 ° C. 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.

[0022]

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 these ingots were homogenized under the conditions shown in Table 1 and then extruded at a temperature of 400 ° C. to obtain a round bar having a diameter of 30 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, wear resistance, machinability and corrosion 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 condition: Gear oil (GL-5) Wear distance: Wet 200 mm Load: 19.7 kg Counterpart material: SCM21 Wear speed: 1.36 m / sec (4) Cutting performance Cutting with two types of side feed cutting and parting cutting The machinability was evaluated by the chip shape and the surface roughness after cutting. 3. Horizontal feed cutting tool; HTi DNMA431 feed; 0.5 mm / rev peripheral speed; 50, 100 rpm cut; 0.5 cm cut-off cutting tool; UTi 20T EGT3 feed; 0.05 mm / rev peripheral speed; 50, 100 cut; 0 (5) Corrosion resistance Corrosion resistance was evaluated by a cass test based on the pitting depth after 100 and 500 hours of holding and the weight reduction amount. The results are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

As is apparent from Table 2, alloy No. 1 of the present invention
Nos. 5 to 5 have the same or higher strength and abrasion resistance as compared with the conventional alloys Nos. 9 to 11, and are markedly excellent in cold forgeability, machinability and corrosion resistance. On the contrary, Comparative Alloys Nos. 6 to 8 whose alloy compositions and manufacturing conditions are out of the range of the present invention are inferior in cold forgeability and machinability.

[0027]

As described above, according to the present invention, high wear resistance suitable for automobile compressor parts and the like which is excellent in strength, wear resistance, cold forgeability, and machinability. A high-quality free-cutting aluminum alloy is obtained, which has a remarkable industrial effect.

Claims (4)

[Claims] 1. Si1.0 to 15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 5.0 wt%, Mg 0.2 ~
1.5 wt%, Mn 0.1 to 0.5 wt%, Cr 0.05 to
0.5wt%, Ni0.05-1.0wt%, Ti0.3wt
% Or less, Pb 0.1 to 2.0 wt%, Sn
High wear-resistant free-cutting aluminum, containing two or more of 0.1 to 2.0 wt% and Bi of 0.1 to 2.0 wt% and the balance being Al and inevitable impurities. alloy. 2. Si1.0 to 15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 5.0 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
.About.0.1 wt%, Ti 0.3 wt% or less, further P
b 0.1-2.0 wt%, Sn 0.1-2.0 wt%, Bi
A high wear-resistant free-cutting aluminum alloy, characterized by containing two or more of 0.1 to 2.0 wt% and the balance being Al and inevitable impurities. 3. Si1.0 to 15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 5.0 wt%, Mg 0.2 ~
1.5 wt%, Mn 0.1 to 0.5 wt%, Cr 0.05 to
0.5wt%, Ni0.05-1.0wt%, Ti0.3wt
% Or less, Pb 0.1 to 2.0 wt%, Sn
0.1 to 2.0 wt%, Bi 0.1 to 2.0 wt%, containing at least two kinds, the balance is cast aluminum alloy molten metal consisting of Al and unavoidable impurities, A method for producing a high wear-resistant free-cutting aluminum alloy, which comprises subjecting the ingot to a homogenizing treatment for holding at a temperature of 500 to 560 ° C. for 4 hours or more. 4. Si1.0 to 15.0 wt%, Fe0.1
~ 1.0 wt%, Cu 1.0 ~ 5.0 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
.About.0.1 wt%, Ti 0.3 wt% or less, further P
b 0.1-2.0 wt%, Sn 0.1-2.0 wt%, Bi
After casting an aluminum alloy melt containing two or more of 0.1 to 2.0 wt% and the balance being Al and unavoidable impurities to form an ingot, the ingot is heated to 500 to 560 ° C. A method for producing a high wear-resistant free-cutting aluminum alloy, which comprises performing a homogenizing treatment for holding at a temperature for 4 hours or more.