JPH038533A - Rare earth oxide slurry - Google Patents

Abstract

PURPOSE:To produce a casting having good dimensional accuracy by alternately applying a slurry contg. a rare earth oxide and water soluble polycarboxylic acid and granular ceramics on the surface of a lost wax pattern and drying the coatings at the time of casting a high melting active metal, such as Ti, by a lost wax method. CONSTITUTION:The slurry consisting of the aq. soln. contg. 0.1 to 2.5 pts.wt. alginate, such as sodium alginate per 100 pts.wt. oxide of the rare earth element having the grain size distribution of 30 to 100wt.%<=2mum is applied on the surface of the wax pattern having the same shape and size as the shape and size of the casting and the powder of the ceramics consisting of the oxide of the rare earth element used to the above-mentioned slurry is stuck thereon at the time of casting the metal, such as Ti or Ti alloy, having the high melting temp. and high activity by the lost wax casting method. Refractory coating layers are formed on the surface of the wax pattern by repeating this operation >=1 times and thereafter, the wax is melted away and the Ti, etc., are cast into the formed hole. The Ti casting which has no brittle reaction cured layers on the surface and has the high dimensional accuracy is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a slurry composition for lost wax casting molds, which is used for casting high melting point active metals such as titanium or titanium alloys, which has a rare earth oxide as a main ingredient.

(Prior Art) Rare earth oxides are used as raw materials for ceramics, and their properties are being utilized to expand their use in pigments, glazes, glasses, refractory crucibles, and the like. A non-aqueous ittria (y, o,) slurry is used as a surface coating agent for a mold in the lost wax casting method (see JP-A-63-115644). When manufacturing molds, SiO□ reacts with high melting point active metals such as titanium or titanium alloys when they are cast, creating a hard (and brittle) reaction hardening layer on the surface of the cast body.
In order to remove this, grinding and polishing such as chemical milling is required, making it impossible to obtain high dimensional accuracy.Also, since non-aqueous propylene glycol and ethyl ether are used, a large amount of cost is required for explosion-proof measures and work hygiene environment measures. There were some drawbacks, such as the need for

(Problems to be Solved by the Invention) The technical object of the present invention is to solve the above-mentioned disadvantages and drawbacks, and to obtain a lost wax cast product with high dimensional accuracy and no hardened layer on the surface of the cast product. An object of the present invention is to provide a rare earth oxide slurry for molding.

(Means for Solving the Problem) In order to solve the problem, the present inventors have investigated the characteristics of the mold coating layer, such as the particle size distribution of the rare earth oxide, the slurry concentration, the amount of water-soluble polycarboxylate added, and the concentration of the aqueous solution. As a result of repeated studies on the factors involved, the present invention has been completed.

The gist of the present invention resides in a rare earth oxide slurry made by adding an aqueous solution containing 0.1 to 2.5 parts by weight of a water-soluble polycarboxylate to 100 parts by weight of the rare earth oxide.

The present invention will be explained in detail below.

First, the rare earth oxide for slurry that is the object of the present invention is L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, D
In addition to oxides of Y, Ha, Er, Tm, Yb, Lu, etc., the present invention is applicable to one type or a mixture of two or more types selected from oxides of Y or Sc.

The particle size distribution of these oxides is such that particles of 2 jt m or less are 3
0 to 100% by weight (hereinafter referred to as wt%) is good (,
More preferably, 50 to 90 wt%, 2 μm or less
~5μm is 0~40wt%, and 5μm or more is 10~
It is 50wt%. If the amount of fine particles of 2 μm or less is less than 30 wt% and the amount of fine particles of 5 μm or more is 50 wt% or more, the strength of the coating layer after firing will be weak and it will easily peel off. The slurry concentration of rare earth oxide is preferably 40 to 80 wt%, preferably 5
It is 5 to 65 wt%. If it is less than 40 wt%, cracks will easily occur during drying, and if it is more than 80 wt%, the viscosity of the slurry will be too high, making it difficult to form a coating M with a desired thickness.

Next, water-soluble polycarboxylate is added to maintain the stability of the rare earth oxide slurry, which is the most important feature of the present invention, to increase the dispersibility of the oxide fine particles, and to maintain the green strength when the coating layer dries. However, in the present invention, one selected from sodium alginate (hereinafter referred to as SAA), ammonium alginate (hereinafter referred to as AAA), amine alginate, sodium polyacrylate (hereinafter referred to as 5PAA), or ammonium polyacrylate. A mixture of two or more types is preferable, and among them, alginates are preferably used. The concentration of the aqueous solution is preferably 0.1 to 5 wt%, more preferably 0.5 to 2 wt%. If it is less than 0.1 wt%, there will be no binder effect, and if it is more than 5 wt%, the slurry will have a high viscosity and will not have the desired layer thickness. Addition to rare earth oxide] is 1.1 per 100 parts by weight of oxide.
-2.5 parts by weight is good, preferably 03-1.0 parts by weight. If it is less than 0.1 part by weight, cracks are likely to occur during drying, and if it is more than 2.5 parts by weight, the viscosity of the slurry is too high and it becomes impossible to mold.

This rare earth oxide slurry can be produced according to the conventional method (
First, a water-soluble polycarboxylate aqueous solution is dissolved and adjusted to a desired concentration without any undissolved matter, and while stirring, rare earth oxide fine powder whose particle size has been adjusted is added little by little to form a predetermined slurry. Next, this slurry is charged into a ball mill, an automatic mortar, etc., and sufficiently kneaded until undispersed particles disappear to produce a slurry. In order to prevent air bubbles from being mixed into the dehydrated molded product, it is preferable to add an antifoaming agent if necessary, and a silicone type or a POE-POP condensed ring type is used. The amount added is 0.00 parts by weight per 100 parts by weight of the rare earth oxide.
1 to 1.0 parts by weight of O is preferred.

Next, a method for manufacturing a high melting point active metal casting by a lost wax casting method using the above slurry will be described in detail.

■Prepare one or more wax models of the same shape as the desired cast product, and glue them to wax sprues and runners to form a so-called tree.

(2) The tree is immersed in the water-soluble polycarboxylate-containing rare earth oxide slurry, and the wax surface is coated with the slurry.

■ Once the slurry on the wax surface dries, apply ceramic granules (hereinafter referred to as stucco) evenly over the slurry coating layer. However, rare earth oxides used in the slurry are preferred.

■Repeat the steps of ■ and ■ above one or more times.

■After that, based on the conventionally known method, after immersing in a slurry consisting of colloidal silica or ethyl silicate hydrolyzed solution and ceramic fine powder such as zircon powder or fused silica powder, The operation of coating with is repeated until the thickness of the coating layer reaches a predetermined thickness.

■After the coating layer has sufficiently dried, the wax is eluted and the remaining mold is fired.

(2) A high melting point active metal such as titanium or titanium alloy is melted and poured into the mold. The method of melting these metals is not critical, but melting in a vacuum or in a non-oxidizing atmosphere is preferable.

■After the metal solidifies and cools in the mold, the mold is removed to take out the cast product, and the runners, sprues, etc. are removed to make the product.

The present invention will be specifically described below with reference to examples in which it is applied to a surface coating agent for lost wax casting molds, but the present invention is not limited to these examples. In the examples, all parts and percentages are by weight.

First, the properties of the mold will be described.

(Example 1) 1. Preparation of slurry Add 198 parts of water to 2 parts of ammonium alginate (AAA) to make a 1 wt% aqueous solution, and add Pluronic L-61 (trade name, manufactured by San Nobuco Co., Ltd.) as an antifoaming agent to this. Completely dissolved. Next, ittria (Y, O,
) to which 55 parts of the above aqueous solution was added and kneaded for 40 minutes to prepare a slurry. The particle size distribution of Ittria was as shown in Table 2 I-A.

2. Production of lost wax casting mold■ Prepare a wax mold in the shape of the desired casting,
The mold is immersed in the slurry to coat the wax surface with the slurry.

■The slurry on the wax surface dries (first, apply ittria stucco on top of the slurry coating layer without any overlap).

■The second layer and subsequent layers are coated with stucco using mullite refractories after being immersed in a slurry made of colloidal silica and zircon powder, based on a conventionally known method. Repeat until it is.

■After the coating layer has sufficiently dried, the wax is eluted and the remaining mold is fired.

Next, the appearance and cross section of the surface coating layer (Yutria slurry and Yetria stucco layer) of about 1 mm in thickness of the produced mold were observed and evaluated. There were no cracks on the surface of the coating, and no bubbles were present in the cross section of the coating layer. Table 1 shows the composition of this slurry and the results of evaluating the appearance of the surface coating layer of the mold.

(Example 2, Comparative Example 1.2) Example 2 was carried out in the same manner as Example 1 except that no antifoaming agent was added. Table 1 shows the slurry composition and the evaluation results of the surface coating layer of the mold.

(Example 3.4) In Example 3.4, the particle size distribution of Ittria was I-B in Table 2.
, I-C was used in the same manner as in Example 1, and the evaluation results of the slurry composition and the surface coating layer of the mold were
Shown in the table.

(Example 5.6) Examples 5 and 6 were carried out in the same manner as in Example 1 except that the rare earth oxides were changed to cerium oxide and erbium oxide, respectively, and the conditions and results are shown in Table 1. Furthermore, the particle size distribution of the rare earth oxides is shown in Table 2.

(Comparative Example 3.4) Comparative Example 3.4 was carried out in the same manner as Example 1, except that the slurry concentration of yttria and the amount of water-soluble polycarboxylate added to yttria were changed, and the conditions and results were It is shown in Table 1.

(Example 7.8) Example 7.8 is the same as Example 1 except that the water-soluble polycarboxylate as the binder was changed to SAA and 5PAA, respectively, and the aqueous solution concentration of these binders and the amount added to itria were changed. The same procedure was carried out, and the conditions and results are shown in Table 1.

Next, the conditions and results when titanium alloy was cast into the mold shown in the above example will be described.

(Example 9.10, Comparative Example 5.6) The mold prepared in Example 1.8 as Example 9.10 and the slurry and stucco shown in Table 3 as Comparative Example 5.6 were used as the first layer, and thereafter The molds produced under the same conditions as in Example 1 were combined into a series of molds sharing one sprue. A titanium alloy containing 6% aluminum and 4% vanadium was melted in an electron beam melting furnace and centrifugally cast into the mold.

After the titanium alloy had solidified and cooled, the mold was removed and the hardened surface layer depth and surface roughness were measured after sandblasting. The results are shown in Table 3.

(Effects of the Invention) The rare earth oxide slurry blended with the water-soluble polycarboxylate of the present invention is suitable when used as a slurry for a surface coating agent of a lost wax casting mold, and does not cause roughness on the surface of the mold. It has high dimensional accuracy and can produce precision cast products without bubbles or voids, making it extremely useful in industry.

Claims (1)

[Claims] 1. A rare earth oxide slurry obtained by adding an aqueous solution containing 0.1 to 2.5 parts by weight of a water-soluble polycarboxylate to 100 parts by weight of the rare earth oxide. 2. After applying a refractory powder slurry to a wax model having a predetermined shape, repeating the step of scattering ceramic granules one or more times to form a refractory coating layer on the model and drying it; In a method for manufacturing a high melting point active metal molded article, in which a mold is prepared through a step of eluting wax from a model and firing it, and a molded product is obtained by injecting a metal melt into the mold, the slurry is the slurry according to claim 1. A method for producing a high melting point active metal molded article with excellent surface properties, characterized by using a rare earth oxide slurry.