JPS63220962A - Manufacturing method for magnesium alloy products with complex shapes - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] ``Object of the Invention'' The present invention relates to a method for manufacturing a magnesium alloy product having a complicated shape, and having a complex structure in terms of shape or thickness and a healthy structure. The purpose of the present invention is to provide a method for accurately manufacturing magnesium alloy products.

(Industrial Application Field) Technology for manufacturing parts with complex configurations used in transportation equipment, electronic equipment, etc.

(Prior art) Magnesium and magnesium alloys are the best in light weight and have outstanding properties such as vibration isolation, so they are used in parts of transportation equipment such as wheels, data arms, servo arms, and clamps. It has also begun to be used for various products with complex shapes, such as parts for electronic devices such as.

However, as a method for obtaining the above-mentioned parts, the die-casting method has excellent productivity and is suitable for mass production and has been adopted for manufacturing various products. Therefore, this die-casting method is also used for the above-mentioned magnesium products. has been adopted.

As an alloy material for magnesium products, MDCInlA (JIS standard), which has good die-casting properties, is used.
The composition is AJ: 8.5-9.5%, Zn: 0.45-0.
9%, balance Mg and impurities).

(Problems to be Solved by the Invention) However, it is natural that this magnesium product should be of good quality, and the above MDCI
A product made of NlA alloy simply cast by a normal die casting method cannot adequately meet such requirements.

That is, when the above-mentioned MDCIn alloy is cast by the ordinary die casting method, air in the die casting mold cavity generates dispersed gas pores, making it impossible to obtain a healthy structure. Therefore, it is natural that it is not always possible to obtain a product that is preferable in terms of strength, durability, etc., and this poses a major obstacle to the effective use of the above-mentioned products.

In order to address the above-mentioned problems, the present inventors have developed an active gas substitution die casting method in which the air in the mold cavity is replaced with a gas active against magnesium such as oxygen gas, and We considered obtaining the above-mentioned magnesium products using non-porous die-casting methods such as vacuum die-casting methods, in which air is sucked out and cast, but in this case, gas pores were no longer observed in the product. However, there remains a tendency for external shrinkage to occur in the product, and especially in parts with complex structures, problems such as casting cracks occur along with this external shrinkage. Can not.

"Structure of the Invention" The present invention was developed after studying to solve the above-mentioned problems, and includes: All: 3.7 to 4.8 wt%, Mn: 0.2
When casting a magnesium alloy containing 2 to 0.48 wt% Si, 0.69 to 1.4 wt% Si, residual force < qg, and impurities using a non-porous die casting method, the mold temperature was set to 100%. This is a method for manufacturing a magnesium alloy product having a complicated shape, characterized by a temperature of ~150°C.

(Effect) -t% (hereinafter simply referred to as %), All: 3,7-4.
8%, Mn: 0.22-0.48%, Si: 0.69
It has been confirmed that by casting a magnesium alloy containing ~1.4% by a non-porous die casting method, the product generally has no gas pores and the occurrence of external shrinkage is reduced. However, parts with large changes in wall thickness such as wheels, data arms, servo arms, clamps, etc., and products with complex shapes and structures with openings and bosses can be manufactured using non-porous die casting using the above magnesium alloy. Even when casting using this method, there remains the problem that casting cracks occur in areas where the thickness of the product changes significantly. This problem can be solved by nonporous die casting of the magnesium alloy at a mold temperature of 100 to 150°C, resulting in a sound magnesium alloy product.

AI imparts mechanical strength to the alloy, and 3.
If it is less than 7%, the effect is poor, and if it is more than 4.8%, shrinkage tends to occur and casting cracks are also observed, so it is necessary to set it to 3.7 to 4.8%.

Mn provides the alloy with the property of avoiding a decrease in corrosion resistance caused by Fe, and in order to properly obtain this effect, it is necessary to contain it in an amount of 0.22% or more. But 0
．． If it exceeds 48%, it is undesirable because crystallized substances are formed and the mechanical properties are deteriorated, so the upper limit should be 0.48%.

St gives the alloy high temperature creep resistance and cast crack prevention properties, and in order to effectively obtain these effects, it is necessary to contain 0.69% or more. On the other hand, if this Si exceeds 1.4%, external shrinkage is likely to occur as in the case of A1, and casting cracks are also likely to occur, so this is set as the upper limit.

The nonporous die casting method in the present invention is a die casting method that limits the generation of gas pores caused by the air in the mold cavity. There are nine laminar flow die casting methods, in which a molten metal shut-off valve is provided in the communication section, and the valve is closed by the pressure of the injected molten metal, and the air inside the cavity is exhausted while casting.
Furthermore, either a cold chamber type or a hot chamber type can be applied to the method of the present invention.

By the way, since magnesium generally has poor fluidity, the mold temperature is usually kept high, and the mold temperature is maintained at about 220 to 250° C. for casting. However, the present inventors believe that in order to accurately prevent the above-mentioned casting cracks, it is not preferable to set the mold temperature to 220°C or higher, and it is recommended to set the mold temperature to a considerably lower temperature than 150°C. We have confirmed through many experiments that it is effective. If the mold temperature is kept at a low temperature such as 150°C or lower, defects due to poor flow will occur when casting a magnesium alloy with poor fluidity.
The non-porous die-casting method adopted in the method of the present invention has less effect on the flow of molten metal due to the air inside the cavity than the ordinary die-casting method, so even alloys with poor fluidity are free from defects due to poor molten metal circulation. Can be cast without forming.

The mold temperature referred to in the art is the surface temperature of the mold cavity that obtains the product form, and if the temperature is below 100°C, the moisture in the mold release agent or mold coolant cannot be sufficiently evaporated. This is undesirable as it causes gas pores to form.
Furthermore, if the temperature exceeds 150°C, casting cracks will occur, such as in areas where the thickness changes, which is undesirable. A more preferable range is 110 to 140°C.

(Example) Specific examples of the present invention will be described below.

A molten magnesium alloy having a composition shown in Table 1 below was cast using a 250 t cold chamber die casting machine.

Table 1 The obtained cast body is a part for an electronic device as shown in the attached drawing, and the part body 1 with a thickness of 5 days has a plurality of openings 2.
The data arm is formed with a ring-shaped boss portion 5 having an inner hole 4 and a recessed portion 3, and its casting conditions are as shown in Table 2 below.

2. Regarding the products obtained in this way, the presence or absence of gas pores and external shrinkage was determined by observation after taking an X-ray photograph, and casting cracks were determined by color checking, and these results are summarized. The results are shown in Table 3 below.

In other words, according to Table 3, it is clear that the product according to the present invention does not have external shrinkage or gas pores, and can be cast even if it is an unrestricted and complicated product as described above and has various wall thicknesses. It was confirmed that no cracking occurred and a sound product was obtained.

"Effects of the Invention" According to the present invention as explained above, it is possible to not only completely eliminate gas pores and external shrinkage, but also to appropriately obtain products without casting cracks even in products with complex shapes and configurations. In addition, it is possible to accurately manufacture magnesium alloy products with complex shapes that have good water flow, a healthy structure, and a good finish, and is an industrially highly effective invention.

[Brief explanation of the drawing]

The drawings illustrate the technical content of the present invention, and are explanatory diagrams showing one example of a product manufactured by the method of the present invention. However, in this drawing, 1 is the component body, 2 is the opening,
Reference numeral 3 indicates a recessed portion, 4 an inner hole, and 5 a ring-shaped boss portion.

Claims (1)

[Claims] Al: 3.7 to 4.8 wt%, Mn: 0.22 to 0.4
8 wt%, Si: 0.69 to 1.4 wt%, and the balance consists of Mg and impurities when casting by non-porous die casting method, the mold temperature is set at 100 to 150°C. A method for manufacturing a magnesium alloy product having a complex shape, characterized by: