JPS5816038A - Manufacture of die cast aluminum product with high damping capacity - Google Patents

Abstract

PURPOSE:To obtain the titled die cast Al product by keeping a molten Al-Si alloy contg. a specified amount of Si at a temp. below the liquidus line to crystallize proeutectic Si and by die casting the molten alloy contg. the proeutectic Si. CONSTITUTION:A molten Al-Si alloy contg. 20-35% Si is kept at a temp. >=20 deg.C, especially >=30 deg.C below the liquidus line to crystallize proeutectic Si, and the molten alloy contg. the proeutectic Si is die cast by an ordinary method to obtain a die cast Al product with high damping capacity and superior mechanical strength. When the Si content of the molten alloy is <20%, high damping capacity is not provided, and >35% Si content deteriorates the machinability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for manufacturing aluminum die-cast products with excellent anti-vibration properties. More specifically, the present invention relates to a method of manufacturing a guicast product with excellent vibration damping properties using a hypereutectic Al-1-U-Si alloy.

In many types of mechanical equipment, vibrations generated in its own moving parts are transmitted to other parts, or external vibrations are transmitted to the equipment, reducing the performance of the equipment. , may cause noise generation. As a countermeasure for this,
In addition to proper design of the building equipment, it is important to use materials with good vibration-proofing properties that do not generate vibrations or absorb vibrations and prevent them from being transmitted to other parts. From this point of view, various anti-vibration alloys have been proposed.

Example, tt? JP-A No. 74-31gl14NIC proposes an alloy that has a damping capacity of 4X10-1 or more when subjected to cold working of 114 or more to an aluminum alloy containing silicon of l to 0s. In addition, one of the inventors of the present invention previously proposed an aluminum-silicon casting alloy containing silicon JO~J!t%f and having an average diameter of primary silicon of 0011 m or more and having excellent vibration damping properties ( 4!i-Gansho 1
! -10!2, see issue 4).

Although this alloy has excellent deformability, it suffers from low production efficiency because it is slowly cooled during casting. It is also desired to further improve the mechanical properties of the resulting product. The present inventors have discovered that by die-casting a molten metal of this alloy in a state in which primary silicon has crystallized, it is possible to produce products with high vibration damping properties and excellent mechanical properties with high efficiency. , completed the invention.

That is, in the present invention, a molten aluminum alloy containing 20 to 33 silicon is kept at a temperature lower than the liquidus line to form a molten metal containing crystallized primary silicon, and die casting is performed using this molten metal. This is a method of manufacturing an aluminum die-cast product with excellent vibration-proofing properties.

To explain the present invention in more detail, the method of the present invention uses a molten aluminum alloy containing silicon in an amount of 0 to 3j (by weight % 1 in the alloy composition of the present invention). In general, the higher the silicon content, the better the vibration-proofing properties of a die-cast product can be obtained, so the silicon content needs to be equal to or higher than 0. However, as the silicon content increases, the hardness of the product increases, but the tensile strength and Young's modulus decrease. Also.

The greater the silicon content, the lower the machinability (cutting properties) of the product. Furthermore, when the silicon content increases, the melting temperature of the alloy increases, making melting treatment difficult. Therefore, taking these points together, the upper limit of silicon content is 3! It should be 1, preferably 30-. Also, the presence of alloying elements other than silicon generally improves the mechanical properties of the product, but reduces vibration isolation. Therefore, in order to improve die castability, it is preferable to avoid the presence of alloying elements other than iron to the extent of 1%.

In the method of the present invention, first, a molten metal of the above-mentioned aluminum-silicon alloy is prepared, and then this is maintained at a temperature below the liquidus line of the alloy to crystallize primary silicon. When the molten metal is kept at a low temperature, the amount of primary silicon crystallized increases, and the vibration damping properties of the resulting product improve.

Therefore, it is usually λO℃ or more than the liquidus line, preferably 30℃
Maintain at i1 degrees lower than ℃. However, if the holding temperature is too low, the viscosity of the molten metal increases, making it difficult to stir the molten metal to make its composition uniform and to pour the molten metal into a die-casting machine. Therefore, it is preferable to maintain the molten metal at a temperature higher than (liquid phase m - 70°C). The size of primary silicon that crystallizes while the molten metal is maintained at a predetermined temperature of Ii degrees is generally 100 to 1000 μm, and this is thought to contribute to the vibration damping performance of the product. Although there are some coarse primary crystals exceeding 1000μ in size, the formation of such large primary crystals results in the formation of primary crystals with a size of θO ~ 1000μ, which is thought to contribute most to vibration damping performance. To reduce the number of crystals, stir the molten metal well while holding it.
Preferably, K is applied to prevent such coarse primary silicon crystals from crystallizing.

Die casting in the method of the present invention is carried out according to a conventional method using the molten metal in which the above-mentioned primary silicon crystals are crystallized.

Primary silicon has a slightly lower specific gravity than the molten aluminum-silicon alloy.

It is preferable to thoroughly stir the molten metal to make its composition uniform before pouring it into the die-casting machine.

According to the method of the present invention, aluminum-silicon alloy molded products with excellent vibration-proof properties and mechanical strength can be produced with high efficiency.

The present invention will be explained in more detail with reference to Examples below, but the gist of the present invention can be summarized as follows.

The following examples are limited to but not 0, and rto℃
After holding at 700 CK for 1 hour, the temperature was raised to a predetermined temperature over about 1.5 hours, and held at a turbidity of about 10 minutes. The liquidus line of this alloy is about 76
It was 0°C. Using this molten metal, the casting capacity r to
Vd, sprue speed Jf / j WL/aθC and plate (ko,!
Thickness width xro xizo length) was cast.

A test piece having a length of lλOWt, a width of 711111, and a thickness of I■ was prepared by cutting, and its internal friction *t was measured using a transverse vibration type internal friction measuring device.

That is, this test piece was subjected to J4. Suspended at the position of f■, and vibrated at the resonant frequency of the test piece using a vibrator @/X
After vibrating at 10-' and /X/0-'',
Free damping was performed, and internal friction (q-9) was determined from the logarithmic damping rate (a') at the time of free damping using a linear equation.

Mu δ = - E (Mu 0 / Mu n) = WQ - Here AO = Resonance width A11 = Amplitude of n-th vibration during free decay n = Number of vibrations during free decay The results are shown in Table 1. show.

In addition, Table 1 also lists the measured values of Young's modulus and tensile strength of Gui-cast products. From Table 1, the molten metal is held at a temperature lower than the liquidus line and primary silicon crystallizes. It is clear that by die-casting a die-cast article with high internal friction is obtained.

IIE/table

Claims (1)

[Claims] (1) A molten metal of Al-1-Um-Silicon alloy containing 20 to 31% silicon is maintained at a temperature lower than the liquidus line to obtain a molten metal containing monocrystalline silicon, and this molten metal is used. A method for manufacturing aluminum die-cast products with excellent vibration-proofing properties, which is characterized by die-casting using a method of die-casting.