JPH0762480A - Low linear expansion aluminum alloy solidified by rapid cooling and its production - Google Patents

Abstract

PURPOSE:To obtain an Al alloy having a low coefft. of linear expansion and satisfactory machinability, excellent in mechanical characteristics after heating at a high temp. and especially useful for the screw rotor of the supercharger of an automobile or an industrial machine. CONSTITUTION:This Al alloy solidified by rapid cooling consists of 10-30% Si, 3-10% one or more among Fe, Mn and Ni and the balance Al and has <=10mum average grain diameter of Si grains and grains of AlSiFe, AlFe, AlMn and AlNi as intermetallic compds. and <=0.4% total amt. of alloying elements allowed to enter into solid soln. This alloy may further contain Cu and Mg. In a producing process, holding under heating at >=400 deg.C is carried out before or after hot working or cooling is carried out at <=5 deg.C/sec cooling rate in the temp. range from the hot working temp. to 200 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a low linear expansion rapidly solidified aluminum alloy and a method for producing the same, and particularly to high temperature strength and machinability suitable for a screw rotor of a supercharger used in automobiles, industrial machines and the like. Relates to a low linear expansion rapidly solidified aluminum alloy and a method for producing the same.

[0002]

2. Description of the Related Art Superchargers are widely used in automobiles and industrial machinery, but their screw rotors are used at 200 ° C.
Since the temperature of the screw rotor is high, the strength of the material for screw rotors is such that it can withstand plastic deformation and fracture due to high-speed rotation from room temperature to 200 ° C, and low linear expansion that can keep the clearance during rotation small even at high temperatures. Sex is required.

The screw rotor is also required to have excellent plastic workability and machinability in order to form a screw shape having strict dimensional accuracy. In addition, the screw rotor is made of PTFE after being molded into its final shape.
(Polytetrafluoroethylene) When performing a coating process, it must be strong enough to withstand this heating, as it will be subjected to a heat history of 100 h retention at 400 ° C.

It is considered to use aluminum for a screw rotor in order to reduce the weight, speed and performance of automobiles and industrial machines. However, in an aluminum alloy produced by a usual melting-casting method, Required performance above,
In particular, the strength characteristics cannot be satisfied.

On the other hand, as a method for giving excellent characteristics to an aluminum material, there are a powder metallurgy method and a spray forming method using a rapid solidification method. The powder metallurgy method is a method in which aluminum powder obtained by rapid solidification is compression-molded and processed by extrusion, forging, etc. to obtain a molded body. The aluminum alloy produced by these methods is put to practical use in some automobile parts and home electric appliance parts.

In order to apply the aluminum alloy by the powder metallurgy method and the spray forming method as a material for a screw rotor of a supercharger, the inventors have required various characteristics, particularly a combination of a linear expansion coefficient and an alloy component, and an alloy. Extensive basic research was conducted on the relationship between the solid solution of elements, the state of precipitation, and the manufacturing conditions of alloys.

[0007]

The present invention has been made based on the above basic research, and its purpose is to achieve all the above-mentioned various performances required as a material for a screw rotor of a supercharger. An object of the present invention is to provide a satisfying low linear expansion rapidly solidified aluminum alloy and a method for producing the same.

[0008]

A low linear expansion rapidly solidified aluminum alloy according to the present invention for achieving the above object comprises 10 to 30% of Si and one or more of Fe, Mn and Ni in total of 3 to 30%. 10% content, balance Al, Si particles and Al-Si-Fe system, Al-Fe system, Al-Mn
-Based, Al-Ni-based intermetallic compounds having an average particle size of 10 μm or less and a solid solution amount of an alloying element of 0.4% or less are the basic structural features, and Cu0.5-6% and Mg0.2 ~
3%, and optionally Zr, T
The second and third structural features are that i, Mo, and V are contained in a total amount of 0.2 to 3%.

The method for producing a low linear expansion rapidly solidified aluminum alloy according to the present invention comprises Si 10 to 30%, Fe and M.
When hot-working a rapidly solidified body containing at least one of n and Ni in a total amount of 3 to 10% and the balance being Al, it is heated and maintained at a temperature of 400 ° C. or higher before or after hot-working. The basic characteristic of the constitution is to include a step or a step of cooling up to 200 ° C. at a cooling rate of 5 ° C./s or less after hot working, and Cu 0.5 to 6% and Mg 0.2 to 3% are added. And optionally further Zr, Ti, Mo,
The second and third structural features are that one or more of V is contained in a total amount of 0.2 to 3%.

The basic composition of the aluminum alloy according to the present invention is 10 to 30% of Si and 3 to 10% of at least one of Fe, Mn and Ni, and the balance is Al. 6% and Mg 0.2 to 3% may be contained, and one or more kinds of Zr, Ti, Mo and V may be added in a total amount of 0.2 to 3%. Si is an element that acts to reduce the linear expansion coefficient of the aluminum alloy. The preferred content range of Si is 10 to 30%, and if the content is less than 10%, the effect of lowering the linear expansion coefficient is small, and
If it exceeds%, the machinability deteriorates.

Fe, Mn, and Ni are aluminum alloys.
It has the effect of suppressing the decrease in strength after heating at 200 to 400 ° C.
A preferable content range is 3 to 10% in total. If it is less than 3%, the effect is small, and if it exceeds 10%, the machinability is deteriorated.
Cu and Mg coexist to form an Al ₂ CuMg phase by aging and precipitating the alloy to enhance the strength at room temperature. The preferred content ranges are 0.5 to 6% and
If it is less than the lower limit, the effect is small, and if it exceeds the upper limit, the machinability and corrosion resistance of the alloy are impaired.

Zr, Ti, Mo and V are Al-Zr type, Al-Ti type, Al-Mo type and Al-V type in the alloy.
It forms an intermetallic compound of the system and suppresses the decrease in strength after heating at high temperature. The preferred content range is 0.2 to 2% in total. If it is less than 0.2%, the effect is small, and if it exceeds 2%, the machinability is impaired.

The first property requirement in the present invention is Si particles which are crystallized or precipitated in the alloy, and Al--Fe--.
The average particle size of Si-based, Al-Fe-based, Al-Mn-based, and Al-Ni-based intermetallic compound particles is to be 10 μm or less, and high strength can be obtained by finely dispersing these particles in the alloy matrix. Thus, high strength can be maintained even after holding at 400 ° C. for 10 hours. In addition, excellent machinability is given, and it becomes possible to process into a screw shape with strict dimensional accuracy. Average particle size is 10μ
If it exceeds m, strength improvement due to dispersion strengthening cannot be obtained, and plastic workability and machinability also deteriorate.

The second property requirement in the present invention is that the total solid solution amount of the alloying elements is 0.4% or less, and the supersaturated solid solution element is precipitated as an aluminum-based intermetallic compound, that is, The linear expansion coefficient of the alloy is reduced by using a composite system of aluminum and a compound. Preferably, the solid solution amount of the alloying elements such as Si and Fe is set to less than 0.2% to sufficiently precipitate these elements.
The solid solution amount can be measured based on this value by obtaining the lattice constant by X-ray diffraction.

In order to provide the above-mentioned property requirements, when heating the rapidly solidified body of the aluminum alloy having the composition of the present invention, which is produced by the powder metallurgy method utilizing rapid solidification or the spray deposition method, before hot working. Or a step of heating and holding at a temperature of 400 ° C or higher after hot working, or a step of cooling up to 200 ° C after hot working at a cooling rate of 5 ° C / s or less

If the heating and holding temperature before or after hot working is less than 350 ° C. and / or after hot working 200
If the cooling rate up to ° C exceeds 5 ° C / s, the alloying elements will form a solid solution and the sufficient effect of reducing the linear expansion coefficient cannot be obtained. If the heating and holding temperature exceeds 530 ° C, the precipitates become coarse and the average particle size of the intermetallic compound exceeds 10 µm, and the strength of the alloy decreases.

[0017]

In the present invention, Si, Fe, Mn, N
Combination of alloy elements such as i in a specific range, precipitation of Si particles and fine particles of Al-Si-Fe system, Al-Fe system and other intermetallic compounds, and synergistic effect of solid solution amount in a specific range of alloy elements Thereby, a rapidly solidified aluminum alloy having a low coefficient of linear expansion, excellent strength after high temperature heating and excellent machinability can be obtained.

[0018]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. The powder metallurgy method, spray forming method and melt casting method in the examples and comparative examples are as follows. Powder metallurgy method: Molten molten aluminum alloy is made into powder by the helium gas atomization method with an average cooling rate of about 10 ³ to 10 ⁴ ° C / s, and precompressed (up to 70 to 80% of true density) -Aluminum container encapsulation-A billet with a diameter of 67 mm was manufactured by a vacuum degassing process at 400 ° C.
This is hot extruded into a bar with a diameter of 18 mm. Spray forming: A molten aluminum alloy melt was sprayed with argon gas in an argon gas atmosphere, and was rapidly cooled and solidified and deposited on a cylindrical collector to produce a billet with a diameter of about 260 mm and a length of 900 mm.
This billet was hot extruded at an extrusion ratio of 10. Melt casting method: Billet is manufactured by normal continuous casting,
The billet was hot extruded at an extrusion ratio of 10.

Example 1 The aluminum alloys shown in Table 1 were melted, a powder metallurgy method and a spray forming method were applied to prepare a billet, and the billet was held at each temperature shown in Table 2 before hot extrusion.
Hot extrusion was performed, and after extrusion processing, samples were prepared from the materials cooled to 200 ° C. at each cooling rate shown in Table 2, and the average particle size of Si particles and intermetallic compounds and the total solid solution amount of alloy elements were measured. The linear expansion coefficient, the proof stress after high temperature heating, and the surface roughness after turning were measured. The measurement results are shown in Table 2.

For turning, a carbide single-edged bite (rake angle 0
°, clearance angle 5 °, cutting edge angle 0 °, nose radius 0.4 mm), 43 mm diameter sample cutting speed 162 mm / min, cutting depth 1 m
After turning under the conditions of m 2 and a feed rate of 0.05 mm / rev., the surface roughness of the turned surface of the sample was measured. According to Table 2, all the samples produced according to the conditions of the present invention had a low linear expansion coefficient, excellent proof stress after high temperature heating, and a smooth surface after turning.

[0021]

[Table 2]

[0022]

[Table 2]

Comparative Example 1 Aluminum alloys having the compositions shown in Table 3 were manufactured into billets by applying the usual melting casting method, powder metallurgy method and spray forming method, and were made to the temperature shown in Table 4 before hot extrusion. After heating and hot extrusion, the temperature up to 200 ° C is shown in Table 4.
A sample was prepared by cooling at the cooling rate shown in
The average diameter of the i particles and the intermetallic compound particles, the total solid solution amount of the alloy elements, the linear expansion coefficient, the proof stress after high temperature heating, and the surface roughness after turning were measured. The results are shown in Table 4.
The turning conditions were the same as in Example 1. Those that do not satisfy the conditions of the present invention are underlined.

[0024]

[Table 3]

[0025]

[Table 4]

As can be seen from Table 4, Sample No. 1 in which the total solid solution amount of alloying elements is larger than the condition of the present invention has a high linear expansion coefficient, and Sample No. 2 in which the Si content is small is also High coefficient of linear expansion. Sample No. 3 and Fe containing too much Si
Sample No. 4, which has an excessively large content, has poor machinability and thus has a large surface roughness after turning. In addition, since the samples produced by the melt casting method have large Si particles and intermetallic compound particles, the mechanical properties are poor and the surface roughness after turning is large. A4032 alloy (Al-12.3% Si-
0.5% Fe-0.9% Cu-1.1% Mg) is made into a billet by normal continuous casting, heated and held at a temperature of 400 ° C before hot extrusion, then hot extruded to a temperature of 5 ° C up to 200 ° C. Sample made of material cooled at a cooling rate of / s (Si particle average diameter
5 μm, average diameter of intermetallic compound 2.8 μm, total solid solution amount of alloying elements 0.13%) has a high linear expansion coefficient of 19.9 (× 10 ^-6 / K), and strength characteristics are proof stress 130 MPa at room temperature and heating at 150 ° C. Later yield strength
The values were 107 MPa and 102 MPa after heating at 200 ° C, which were both low values.

Comparative Example 2 An aluminum alloy containing 20% of Si and 5% of Fe and the balance of Al was melted, a billet was manufactured by applying a spray forming method, and hot extrusion was performed at 340 ° C. After processing and heating at the temperature shown in Table 5, 200
Samples were prepared from materials cooled at a cooling rate shown in Table 5 up to ℃, and the average diameter of Si particles and intermetallic compound particles,
The total solid solution amount of alloy elements, the yield strength after high temperature heating, and the surface roughness after turning were measured. The measurement results are shown in Table 5.
The turning conditions were the same as in Example 1.

[0028]

[Table 5]

As shown in Table 5, Sample No. 12 having a heating and holding temperature after hot extrusion processing lower than the condition of the present invention has a large solid solution amount of alloying elements and has a linear expansion coefficient reducing effect. I can't. Sample No. 13 has a high heating and holding temperature after the hot extrusion process, so that the precipitates are coarsened, the mechanical properties are deteriorated, and the machinability is also deteriorated.

[0030]

As described above, according to the present invention, there is provided an aluminum alloy having a low linear expansion coefficient, excellent mechanical performance after heating at high temperature, and good machinability, particularly for automobiles and industrial machines. It is useful as a material for a screw rotor of a supercharger.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazuhisa Shibue 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries, Ltd. (72) Inventor Makoto Otani 5-11-3 Shimbashi, Minato-ku, Tokyo No. Sumitomo Light Metal Industry Co., Ltd. (72) Inventor Shinichi Tani 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (6)

[Claims] 1. Si 10 to 30% (weight%, the same applies hereinafter),
It contains at least one of Fe, Mn, and Ni in a total amount of 3 to 10%, the balance is Al, and Si particles and Al-Si-F.
The average particle size of the e-based, Al-Fe-based, Al-Mn-based, and Al-Ni-based intermetallic compound particles is 10 μm or less, and the total solid solution amount of Si, Fe, Mn, and Ni among the alloy elements is 0.4%.
A rapidly solidified aluminum alloy for a screw rotor of a supercharger, characterized in that: 2. A low linear expansion rapidly solidified aluminum alloy according to claim 1, which contains Cu 0.5 to 6% and Mg 0.2 to 3%. 3. The low linear expansion rapidly solidified aluminum alloy according to claim 1, wherein Zr, Ti, Mo and V contain at least one of 0.2 to 2% in total. 4. Hot-working when forming a rapidly solidified body containing 10 to 30% of Si and at least 3 to 10% of at least one of Fe, Mn, and Ni, and the balance being Al by hot working. Low linear expansion rapid cooling characterized by including a step of heating and holding at a temperature of 350 ° C or more before or after hot working, or a step of cooling up to 200 ° C after hot working at a cooling rate of 5 ° C / s or less Method for producing solidified aluminum alloy. 5. The method for producing a low linear expansion rapidly solidified aluminum alloy according to claim 3, which contains Cu 0.5 to 6% and Mg 0.2 to 3%. 6. The method for producing a low linear expansion rapidly solidified aluminum alloy according to claim 4, wherein one or more of Zr, Ti, Mo and V are contained in a total amount of 0.2 to 2%.