JPS61273233A - Molding material for precision casting and casting method using same - Google Patents

Abstract

PURPOSE:To obtain a molding material which can be used for metals having low to high m.p., metals having high activity and glass ceramics by adding a limited weight ratio of zirconium oxide having a limited average grain size to magnesium oxide having a limited average grain size. CONSTITUTION:A wax pattern having the shape of a casting object is set in a casting flask and the powder molding material prepd. by adding at least 5wt% of zirconium oxide having <=1.0mm average grain size to the magnesium oxide having <=1.0mm average grain size is packed into the casting flask. A molten metal is poured into the shell formed by a dewaxing stage after the above-mentioned stage and is precisely cast. The MgO-ZrO2 molding material for precision casting obtd. in the above-mentioned manner has excellent chemical stability at a high temp. and is the molding material consisting of a mixture composed of MgO and ZrO2 having the high resistance to heat and corrosion and therefore the molding material is usable for casting of metals having high m.p. and high activity such as Ti and Ti alloy and glass ceramics.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold material for precision casting of industrial metal materials, glass materials, etc., and a casting method using the same.

(Conventional technology) In general, casting technology is a unique processing technology that has a greater degree of freedom in terms of size, shape, number of pieces, etc. than other metal processing technologies such as forging presses and powder metallurgy. It is one of the important metal processing techniques that have been used. Among these, the precision casting method in particular has undergone various improvements and developments as a method that can cast products with much higher dimensional accuracy than the regular casting method without using a mold. Ta. Nowadays, it has become an essential technology in the manufacturing field of molds, general mechanical parts, aerospace parts such as jet engines, etc.

Now, by precision casting, aluminum, magnesium, titanium, copper and their alloys, steel, stainless steel,
Almost all metals, such as cobalt-based heat-resistant alloys and nickel-based heat-resistant alloys, can be cast using air-melted materials or vacuum-melted materials. It greatly depends on the mold material used and the casting process. The selection of mold material has become an extremely important factor for success.

By the way, silica, alumina, chamotte, magnesia,
Zircon gypsum and other materials have been widely used. However, each of these mold materials has advantages and disadvantages, and their range of application has been relatively limited. For example, silica is relatively cheap and has a high refractory temperature, so it has traditionally been most widely used in the foundry industry, and is also used as a basic raw material for investment casting mixtures, but it is also used in stainless steel casting. In this case, the casting surface may become rough due to the reaction with the chromium oxide that is generated.
Disadvantages include the inability to cast highly reactive metals such as pure titanium and titanium alloys.

In addition, gypsum is Ag, Mg to ^u181, Cus, and
It is widely used in the fields of dentistry and jewelry as a molding material that can produce good dimensional accuracy and excellent surface finish even in complex shapes with thin cross-sections for low-melting nonferrous metals such as these alloys. However, when casting higher melting point steel or heat-resistant alloys, the sulfur in the plaster chemically reacts at high temperatures, resulting in extremely poor casting surfaces.

(Problems to be solved by the present invention) As mentioned above, the range of casting metals to which conventional precision casting mold materials can be applied is limited, and there is a need for mold materials that can be applied to a wider range of metals. development was desired.

As one of these, a magnesia-based investment material has recently been developed as a mold material for titanium, but the quality of its cast products is still far from satisfactory.

Therefore, we aim to create a molding material that has good thermal stability and strength for metals ranging from low to high melting points, is extremely reactive, and can be applied to active metals and glass ceramics. be.

(Means for solving the problem) In order to solve the problem, the present inventors conducted tests on various mold materials including conventional mold materials, and found that magnesium oxide MgO and zirconium oxide Z・0□ The mold material consists of a mixture composition of
It has the characteristics of an excellent high-temperature refractory material in that it does not get wet with glass and is not affected by the furnace atmosphere, and it is also an extremely reactive metal, titanium.
It has been discovered that zirconium can be easily cast, and the quality of the cast product is also excellent.

(Example) Examples of the composition and casting method of the mold material for precision casting of metal, glass, etc. according to the present invention will be described below based on Examples.

"Example 1" Magnesia with a purity of 98% and an average particle diameter of 325 mesh pass and fused calcia-stabilized zirconia with a purity of 94% and an average particle diameter of 325 mesh pass were used as the base material of the mold material, and silica sol and acrylic were used as binders. A mud-like investment material was prepared by blending a system emulsion and trace amounts of a surfactant and an antifoaming agent in the following proportions.

Mold material composition MgO: 95% by weight/Zr0z: 5.0% by weight 1
00 parts silica sol 15 parts acrylic resin emulsion 15 parts surfactant
0.1 part defoaming agent
0.1 part wax pattern width 10mm length 3
011II11 Using a plate model with a thickness of 2 mm, a mold was made using a mold material with the above composition by a known investment method, and then stainless steel SOS 420 was used.
Casting of J-2 and SCM440 was carried out. the result,
There was almost no chemical reaction between the molten metal and the mold (and a cast product with no surface roughness was obtained.

"Example 2" As the base material of the mold material, magnesia with a purity of 98% and an average particle size of 200 mesh and a purity of 93% and an average particle size of about 10% are used.
Electrofused magnesia-stabilized zirconia with an average particle size of μ was used, and an inorganic binder, an organic binder, etc. were added as a binder in the following proportions to form a mud-like investment material.

Mold material composition MgOnia 0% by weight/Zr0z: 30% by weight 100
1 part silica sol 16 parts phenolic resin 16 parts surfactant
0.1 part Antifoaming agent 0.1 part Using the same wax pattern as in Example 1, aluminum alloy (AC4C) and formulation (beryllium copper) were cast.

The resulting cast products were comparable in mechanical strength and elongation hardness to those cast in plaster molds. In addition, the surface properties of the fibers were good.

"Example 3" Magnesia with a purity of 98.5% and an average particle diameter of 350 mesh passes and a purity of 95% and an average particle diameter of approximately 20μ are used as the base material of the mold material.
Ittria partially stabilized zirconia, the following inorganic binder, organic binder, etc. were added as a binder to form a mud-like investment agent.

Mold material composition MgO: 30% by weight/Zroz 0% by weight 10
0 parts zirconia sol 13 parts urea resin
13 parts surfactant
0.2 parts Antifoaming agent 0.2
Using the same wax pattern as in Example 1 above,
Titanium and titanium alloy Ti-6AI-4V were cast.

Casting was performed using an argon arc melting pressure casting machine.

As a result, there was no cranking or seizure phenomenon on the mold surface, and the surface properties of the pickled surface of the cast product were also good.

In addition, internal inspection of these cast products using an xwA fluoroscope was conducted, but no internal defects such as internal cysts were found.

"Example 4" Using magnesium oxide and zirconium oxide having the same properties as in Example 1 as the base material of the mold material, a mud-like investment material having the following composition was formed.

Mold material composition MgO: 10% by weight/Zr0z: 90% by weight 1
00 parts Zirconia sol 10 parts Acrylic resin emulsion 10 parts Surfactant
0.1 part antifoaming agent 0
．． One part of the crown wax pattern in the form of a model is dipped into this slurry, and the thickness of the coating layer is 0.7-1.
It was set to 0+++m. Next, after naturally drying it in the air, it was placed in a cylinder lined with asbestos ribbon inside a metal ring with an inner diameter of 4011ffi and a height of 50 mm.
The surrounding area was filled with gypsum slurry for investment casting and backed up. After burying the pattern, about 1-2
After leaving it in a greenhouse for an hour, a slurry was applied to the sprue surface to coat the plaster surface. This was heated in an electric furnace to dewax and fire it.

Casting was performed in the same manner as in Example 3 using titanium alloy Ti-6Al-4V.

As a result, the heat resistance and mechanical strength of the coating layer against the molten titanium alloy were sufficient, no reaction was observed with the plaster as a backup material, and there was no damage to the mold. The surface quality of the obtained cast product after acid treatment was beautiful, and the quality was comparable to that of Example 3.

"Example 5" A glass ceramic having the following composition was cast using the same casting method as in Example 4.

Glass composition: Nazo 5.0% by weight Kto 0.5% by weight MgO 3,0% by weight Ca0 33.0% by weight 5i(h 45.0% by weight PzOs 13.5% by weight) As a result, mechanical strength without cracks is achieved. An excellent glass image-receiving cast body was obtained.

Now, although not shown in the above examples, Mg according to the present invention
O-ZrOt mixed mold material and magnesium oxide MgO
A comparison experiment was conducted on the properties and performance of titanium alloy and zirconium oxide ZrO alone.

As a result, in the case of 100% MgO, the tensile strength of the obtained cast body is excellent at over 100 kg 7 mm, but the elongation is very small at around 3%, and as a result of observation with an X-ray fluoroscope, internal cysts etc. are often observed. Furthermore, this mold material hardened rapidly and had problems with the stability of the slurry.

On the other hand, the tensile strength of 100% ZrO□ is Mg.
On the other hand, the elongation was smaller than that with O added, and on the other hand, the elongation was in the 6 to 7% range.

And almost no cysts were observed.

From these series of experiments, it has been found that it is desirable that the amount of ZrO added to MgO is at least 5.0% by weight.

Next, the average particle size of MgO and ZrO is 1.0m+
If it is more than n, the air permeability is sufficient, but the bonding force is not sufficient in terms of maintaining mold strength, and the resulting cast body has the disadvantage that it is difficult to obtain a delicate casting surface. In addition, as a backup material, it is preferable to use gypsum for the purpose of obtaining a cast body with excellent dimensional accuracy, but other scoter materials (
refractory sand) may be used. Furthermore, binders, surfactants,
Antifoaming agents and the like can be used in any combination within an appropriate range, as long as they do not cause aggregation, precipitation, etc. when added or mixed.

(Effects of the Invention) As described above, the MgO-ZrO□-based precision casting mold material according to the present invention is a mold material made of a mixture of MgO and ZrO□, which has excellent chemical stability at high temperatures and is rich in heat resistance and corrosion resistance. Therefore, not only metals with low melting points such as aluminum alloys and copper alloys, but also metals with high melting points and high activity such as titanium and titanium alloys, which are normally difficult to cast, and metals such as glass ceramics. It can also be used for casting, making it possible to perform precision casting of a wide variety of metals and other materials that have never been possible before.

Claims (3)

[Claims] (1) A mold material for precision casting, characterized in that at least 5% by weight or more of zirconium oxide with an average particle size of 1.0 mm or less is added to magnesium oxide with an average particle size of 1.0 mm or less. (2) A wax model in the shape of the object to be cast is set in a mold, and in the mold, zirconium oxide with an average grain size of 1.0 mm or less is added to magnesium oxide with an average grain size of 1.0 mm or less. A casting method characterized in that, after a step of filling a powdered mold material with at least 5% weight addition, molten metal is injected into a shell formed through a dewaxing step. (3) A powdered casting material made by adding at least 5% by weight of zirconium oxide with an average particle size of 1.0 mm or less to magnesium oxide with an average particle size of 1.0 mm or less, and a solution containing a binder. After passing through the process of kneading and making a slurry, a model forming the object to be cast is immersed in the slurry or the slurry is applied to the surface of the wax model to form a wax model with a coating layer of mold material on at least the surface of the wax model. A casting method characterized by filling a backup material such as gypsum, silicate, or phosphate into a mold for the model, and injecting molten metal into the shell after the dewaxing process.