JPS62168633A - Casting mold - Google Patents

Abstract

PURPOSE:To obtain a casting mold suitable for casting an active metal and high melting point metal by forming the casting mold of a calcia refractory material contg. specific ratios of CaO and halide. CONSTITUTION:A binder is added as necessary to the calcia refractory material contg. >=40wt% CaO and 0.1-8wt% halide and the mixture is molded to the casting mold having a prescribed shape. After such molding is dried and calcined, the molding is sintered at about 1,200-1,800 deg.C. The raw materials in addition to the CaO and halide include oxide such as MgO, carbide such as silicon carbide, nitride such as aluminum nitride and carbon such as graphite. Limestone, etc. are used for the CaO source raw material and CaF2, etc., are used for the halide raw material. The high activity metal and high melting point metal, etc., are easily cast by such casting mold, by which the casting having no contamination on the casting surface is obtd. and the cost of casting is considerably reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to active metals such as titanium and zirconium, alloys thereof (hereinafter in the specification, alloys may also be simply referred to as metals), or active metals such as chromium and vanadium. The present invention relates to a mold suitable for casting high-melting point metals.

[Prior Art] Calcia refractories are thermodynamically stable even at high temperatures and have a unique refining action, so the present inventors have proposed that they can be applied to the melting of various high-melting point metals and highly active metals. This is becoming clear.

According to the melting method proposed by the inventors, it is possible to easily melt highly active and/or high melting point metals, which are difficult to melt using conventional methods. Moreover, the obtained molten alloy is extremely clean.

Therefore, in order to obtain a highly clean cast body, it is necessary to melt a highly clean molten metal and use a mold that does not contaminate the molten metal. Conventionally, molds for casting titanium or zirconium (including alloys), which are active metals, have been used as lambda molds, investment molds, water-cooled copper molds, and sand molds (
(Using zircon sand, oripin sand, etc.) are known. The rammed type is made of graphite powder as an aggregate, molded with a carbon-based or resin-based binder, dried, and then fired.

Investment molds include tungsten powder coated molds, which use tungsten in a slurry and a metallic binder, and oxide molds, which combine oxide slurry with an oxide binder.
There are three types of graphite molds made by hardening graphite-based slurry with a carbon-containing binder.

In addition, as mold materials for titanium or titanium alloys, hardening accelerators such as alkali metal hydrogen carbonate and aluminum powder are added to pure magnesia or magnesia mold materials mainly composed of magnesia, and aggregates mainly composed of magnesia. Mold materials are also known (Japanese Patent Publication No. 58-5749,
JP 59-218237).

[Problems to be Solved by the Invention] However, when active metals are cast into these molds, a reaction occurs with the mold material, and carbon is generated in the case of graphite mold materials, and carbon is generated in the case of graphite mold materials, and In the case of molds, oxygen contamination occurs, resulting in contamination of the casting surface. Furthermore, among the investment types, those based on oxide binders are subject to intrusion of not only oxygen but also nitrogen. Such contamination of the casting surface requires a step to remove the contaminated layer on the surface of the casting, making the manufacturing process extremely complicated. Further, in the casting method using a water-cooled copper mold, the mold is expensive and there are other problems such as the risk of water leakage.

Furthermore, in molds made of oxide or graphite other than water-cooled copper molds, the thermal conductivity is low, so that shrinkage cavities are likely to occur in the center of the casting, resulting in a poor casting yield. In addition, these oxide-based or graphite-based molds are dense and have low thermal shock resistance.
There were problems such as easy cracking, poor durability, and unsuitability for repeated use of the mold material.

[Means and effects for solving the problems] The mold of the present invention contains 40% by weight or more of CaO and contains no halide.
．． It is characterized by being calcia containing 1 to 8% by weight.

[Function] The mold of the present invention is made of calcia which has a high melting point and is thermodynamically stable at high temperatures.
Alternatively, highly active metals can be easily cast, and castings without contamination on the casting surface can be obtained. Further, since the mold of the present invention contains a halide, the mold surface is smooth, and therefore a smooth casting surface can be obtained.

In addition, the presence of halides makes firing easier,
It is also possible to improve moldability.

The present invention will be explained in more detail below.

The mold of the present invention is calcia. As mentioned above, calcia has a high melting point and is thermodynamically stable even at high temperatures. The mold of the present invention has improved stability and heat resistance as the content of CaO increases.
At least 40% by weight of O (% unless otherwise specified)
indicates weight %. ), preferably 70% or more, particularly 80% or more.

The template of the present invention contains a halide in addition to CaO. Examples of the halides include fluorides, salts, and compounds of alkali metals, alkaline earth metals, and lead, and double salts containing them. Specifically, for example, CaF2. M
gF2. BaF2, S r F 2 , N a F
, L i F , K F , P b F 2
, Cs F , N a 3A I F a ,
Ca Cl 2 , Mg0 sentence 2. Examples include Nac sentences and KC sentences.

Many of these halides have much higher digestion resistance than CaO and have a low melting point, so in addition to improving hydration resistance by their presence, they also promote sintering of the base material during firing. It has the effect of increasing the density of the sintered body structure, and these effects combine to give the mold excellent hydration resistance. In addition, the sintering promotion effect significantly improves the strength of the resulting mold. Note that halides are present in large amounts at grain boundaries, and a layer containing a large amount of halides comes to encapsulate CaO particles, which is also thought to improve the water resistance of the mold. If the amount of this halide added is too large, it will reduce the fire resistance of the mold, so the content should be 8% or less, preferably 5% or less. Also, of course, if the amount added is too small, the above effects cannot be obtained, so 0.1% or more, preferably 0.3%
The content should be above.

Moreover, the template of the present invention can contain oxides, carbides, nitrides, and carbon (C) as substances other than CaO. Specifically, oxides with high melting points such as magnesia (MgO) and zirconia (Z r O2) are suitable.

Examples of carbides and nitrides include silicon carbide, silicon nitride, and aluminum nitride. Graphite is suitable as the carbon raw material. There are two types of graphite: natural graphite and artificial graphite, and either of them can be used. Note that graphite has a scaly shape and therefore has poor formability, and is inherently poor in reactivity and difficult to form a ceramic pound, so the strength of the sintered body tends to decrease. Therefore, when using graphite as a calcia mold material, it is effective to add a small amount of metallic aluminum. When aluminum is fired in a non-oxidizing atmosphere, it produces highly corrosion-resistant reaction products such as aluminum carbide and aluminum nitride, which increases the corrosion resistance of the mold and increases the bond between graphite and surrounding tissue, improving the strength of the mold. It becomes like this.

In addition, the raw materials used to manufacture the calcia mold include limestone, quicklime obtained by calcining it or fully calcining it,
In addition to dead burnt lime, fused calcia melted in an arc furnace, calcium hydroxide, etc. may also be used. Furthermore, minerals containing CaO, such as ralite, melwinite, anorsite, and dolomite, may also be used.

In order to manufacture the mold of the present invention, such a calcia raw material and a halide, and if desired, one or two of the above-mentioned oxides, carbides, nitrides, and carbons are used in combination as the main raw material. do. Then, an appropriate binder is added to this main raw material as necessary, and a mold is formed by molding and firing.

A non-aqueous binder is used as this binder.

The non-aqueous binder may be either liquid or solid. Liquid types include alcohol (-hydric or polyhydric alcohol) in which anhydrous calcium chloride or mastic rubber is dissolved, oleic acid dissolved in toluene, oleic acid dissolved in alcohol, and oil. A solution of oleic acid dissolved in carbon tetrachloride, a solution of beeswax dissolved in carbon tetrachloride, or isobutyl acetate are suitable, but non-aqueous liquids that do not digest calcia, such as mineral oil, animal oil, or vegetable oil, are suitable. It can be used if there is one.

As solid binders, polyethylene, polypropylene, cellulose acetate, acrylic resins, thermoplastic resins such as polyvinyl alcohol, thermosetting resins such as novolak, paraffin, etc. can be suitably used, but they can impart moldability. Other materials may also be used.

As the molding method, various methods are used, such as mold molding, slip casting, rubber press, injection molding, warm press, and stamping.

Note that hot press molding may be performed without using a binder or using a small amount of binder.

The molded body or stamped mold is dried if necessary, then preferably calcined at a temperature lower than the main firing temperature, and then main fired and sintered.

The firing temperature is 900℃ or higher, especially 1200 to 180℃.
0°C is preferred. The firing atmosphere may be an atmospheric atmosphere, but may be another atmosphere.

Using the mold of the present invention, high melting point and/or highly active metals can be easily cast. For pure metals with high melting points such as chromium and vanadium, or alloys containing large amounts thereof, it is preferable to use a mold with a high CaO content, such as one containing 80% by weight or more of CaO. Also,
Even when casting highly active pure metals such as titanium and zirconium, or alloys containing large amounts thereof, it is preferable to use a mold with a high CaO content.

The metal elements with high melting point and high activity constituting the metal suitable for casting with the mold of the present invention include the following, and the alloy thereof includes one or more of these elements. Includes: Sc, Y, La, lanthanoid elements such as Ce and Pr with atomic numbers 58 to 71, Ti
, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn
, Tc, Re, Ru, Os, Co, Nf, Rh, Pd,
Ir, Pt.

The mold of the present invention can be applied not only to an outer mold but also to an inner mold called a core. Furthermore, since CaO has digestibility, the template of the present invention can be removed by utilizing this digestibility.

For casting in the present invention, the atmosphere is preferably a vacuum or an inert gas atmosphere such as argon.

[Examples] Examples will be described below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

Example 1 85 parts by weight of fused calcia (CaO purity 99%) crushed and classified to 0.2 mm or less, reagent grade 1 CaF
100 parts by weight of raw material powder was prepared by mixing 5 parts by weight of No. 2 and 10 parts by weight of magnesia clinker crushed into pieces of 0.2 mm or less.

Also, add anhydrous calcium chloride to ethyl alcohol at a concentration of 4.
10 parts by weight of the solution was prepared. These were mixed and molded.

After drying this molded body at 100'C for 1 hour,
Sintering was performed at ℃ for 3 hours.

All firings were performed in an air atmosphere. The sintered body thus obtained had the shape and dimensions shown in FIG.

Pure Ti was cast using this mold. The atmosphere during casting was Arl pressure, and the temperature of the molten metal during casting was 1700°C. Table 1 shows the results of chemical analysis of O and N on the surface of the casting after the molten metal was poured into the mold and solidified.

Example 2 A mold was produced and casting was carried out in the same manner as in Example 1 except that the conditions were changed as shown in (a) to (f) below.

(a) The composition of raw materials is as follows.

Dolomite clinker (Ca064.3%, Mg030.
9%, F e 2032, 3%, 5i021.8%,
90 parts by weight of A (2030.4%) crushed and classified to 0.3 mm or less, 3 parts by weight of CaO, 1 part by weight of limestone.
10 parts by weight crushed into pieces smaller than mm.

(b) An alcoholic solution of calcium chloride (5%) is used as a binder.

(c) The mixing ratio of the above solid raw material and binder is Zoo:1
Set to 0.

(d) The conditions for the main firing are 1100°C x 3 hours.

(E) The casting alloy is 60% Zr and 40% Co.

(f) The temperature of the molten metal during casting is 1550°C.

Table 1 shows the results of chemical analysis of the surface of the obtained casting.

Example 3 A mold was produced and casting was carried out in the same manner as in Example 1, except that the conditions were changed as shown in (a) to (f) below.

(a) The composition of raw materials is as follows.

Commercially available quicklime (Ca098.0%, SiO20.0
85 parts by weight of pulverized and classified 8%) to 0.1 mm or less, 25 parts by weight of MgCu, and 10 parts by weight of dolomite clinker (same as Example 2) crushed to 0.1 mm or less.

(b) An alcoholic solution of calcium chloride (5%) is used as a binder.

(c) The mixing ratio of the above solid raw material and binder is Zoo:1
Set to 0.

(d) The conditions for the main firing are 1350°C x 3 hours.

(E) The casting alloy is made of 68% Ni and 32% La.

(f) The temperature of the molten metal during casting is 1400°C.

Table 1 shows the results of chemical analysis of the surface of the obtained casting.

Comparative Example 1 A mold was produced and casting was performed in the same manner as in Example 1, except that the conditions were changed as shown in (a) to (d) below.

(a) Use only commercially available silica sand powder (SiO298%) as the raw material.

(b) Water glass was used as a binder and hardened with CO2 gas.

(c) The mixing ratio of the solid raw material and binder is 100:5.
shall be.

Comparative Example 2 A mold was produced and casting was performed in the same manner as in Example 2, except that commercially available silica sand was used as the raw material for the mold.

Table 1 shows the results of chemical analysis of the surface of the obtained casting.

Comparative Example 3 A mold was produced and casting was performed in the same manner as in Example 3, except that commercially available silica sand was used as the raw material for the mold.

The results of chemical analysis of the surface of the obtained castings are shown in Table 1. FIG. 1 is a dimensional drawing showing the shape of the mold.

Table 1 [Effects of the Invention] As is clear from the explanation in 1- below, according to the present invention, highly active metals, high melting point metals, or alloys thereof can be easily cast. The resulting casting is highly clean without contamination such as C, O, N, etc., and post-treatment such as removal of the casting surface contamination layer is not necessary. Furthermore, the mold material of the present invention is inexpensive and can be recovered after casting and used repeatedly for molding, making it possible to significantly reduce casting costs.

[Brief explanation of drawings]

Claims (1)

[Claims] (1) A mold made of a calcia refractory material containing 40% by weight or more of CaO and 0.1 to 8% by weight of a halide.