JPS619940A - Mold material for casting titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To attain easily thorough dimensional compensation by mixing preliminarily metallic powder which does not generate gas into a mold material, oxidizing the metallic powder in the stage of heating the mold and utilizing the expansion resulted from the oxidation. CONSTITUTION:The metallic powder which does not generate gas in the stage of hardening and heating the mold material and has the smaller free energy for forming oxide than titanium or titanium alloy is added into the magnesia mold material. The metallic powder is then oxidized in the stage of heating the mold and the volume of the mold is increased by the oxidation, by which the mold is expanded in volumn over the entire part. The casting conforming to the prototype is thereupon obtd. even if the molten metal cools down to a room temp. and shrinks dimensionally. The thorough dimensional compensation is thus attained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to the improvement of a mold material for casting titanium or a titanium alloy, which is used for casting dental castings and precision machine casting parts. It is.

(Prior art) Gold alloys, silver-palladium alloys, nickel-chromium alloys, cobalt-chromium alloys, etc. have been widely used in the casting of precision castings such as dental castings. are usually cast using gypsum-based molding materials based on glue or high-temperature phosphoric acid-based molding materials.

However, the gold alloys and silver-palladium alloys have problems in terms of price and corrosion resistance (Special Cζ silver alloy), and the cobalt-chromium alloys have problems with the stable supply of chromium and cobalt due to the expansion of underground capital. In addition to this, there is also the problem that it is hard to use for metals such as crown bridges.

Furthermore, in recent years, the biotoxicity of Ninokel-chromium alloy has been pointed out, and its use has been questioned.

Therefore, in recent years, titanium and titanium alloys, which have relatively abundant Cζ reserves as underground resources and have excellent biocompatibility, have been attracting attention as metals for casting in the dental world and elsewhere. That is, titanium (a) has excellent corrosion resistance and biocompatibility, (b1 has mechanical properties (strength, hardness) that are optimal as a dental metal, etc., and (C) nickel. The specific gravity is about 1/2 compared to chromium alloy ζ,
It has excellent properties such as being lightweight and being cheaper than nickel-chromium alloys, etc., considering its DL specific gravity. It is highly coveted.

However, titanium has a high melting point (approximately 1720°C), is easily oxidized at high temperatures, and has extremely high high-temperature activity (in addition, the amount of shrinkage of the cast body is quite large), so it remains unchanged as before. It is impossible to cast a cast body with desired dimensional accuracy using a mold material such as a high-temperature phosphate mold material or a magnesia mold material based on CJ.

Therefore, various experimental studies have been conducted to develop new mold materials for titanium or titanium alloys.The inventor of the present application has also developed (a) Aggregates whose main component is magnesia (MgO) to which alkali metal hydrogen carbonate, alkaline earth metal carbonate, etc. are added as hardening accelerators, and (b) whose main component is magnesia (MfO). Developed and released a molding material in which alkali metal hydrogen carbonate, alkaline earth metal carbonate, etc. are added as hardening accelerators to the aggregate, and fine aluminum powder is added as an expansion accelerator. are doing.

By the way, the mold material in which a curing accelerator and an expansion accelerator (aluminum fine powder) are added to the aggregate mainly composed of magnesia (LL) accelerates the solidification of the mold material kneaded with water, making it easier to manufacture molds. (b) When the mold material (green mold) mixed with water is cured, the green mold becomes 0.7~
It expands by about 0.8%.

Even during casting (approximately 700-800°C), the temperature of the mold is 0.5-0.
It has excellent practical effects, such as expanding by 7%, resulting in a mold expansion of about 1.5% as a whole, and (C) improving the compressive strength of the mold by the action of the hardening accelerator. be.

(Problems to be Solved by the Invention) However, the mold material still has many problems to be solved as described below.

(1) The expansion of the mold obtained by adding aluminum powder is about 1.5% at most, and the optimum value of mold expansion required in the case of titanium or titanium alloy1.
．． 8%, and as a result sufficient dimensional compensation cannot be achieved.

, 2) The hydrogen gas generated when aluminum and water react causes the mold to expand (approximately 18%) during green mold hardening (mold condensation), but the mold is normally kept in the mold frame. Because it is hardened, its expansion in the lateral direction is restricted, resulting in an imbalance between the expansion in the vertical direction and the expansion in the lateral direction, which may cause deformation of the wax pattern in dental castings, etc. .

(3) It is quite difficult to control the amount of hydrogen gas in the mold material during curing to a desired value, and even if the mixing ratio of aluminum is the same, a constant expansion rate cannot always be obtained.

If hydrogen gas still remains in the mold, various problems will occur when the mold is heated.

The present invention aims to solve the above-mentioned problems with conventional mold materials, and involves pre-mixing metal powder that does not generate caulking gas into the mold material, and oxidizing the metal powder when the mold is heated. The aim is to take advantage of the expansion caused by oxidation. That is, when molten metal cools to room temperature, it shrinks in size more than when it was molten. However, if the mold is expanded by the amount of shrinkage during casting, a cast body that matches the original pattern (for example, wax pattern) can be obtained, and complete dimensional compensation can be achieved.

The present invention enables (a) to almost completely compensate for the shrinkage rate (approximately 1.8 inches) of the cast product when melt casting titanium or titanium alloy, and (1)) to reduce the expansion of the mold. , obtained during heating of the mold rather than during hardening of the mold, resulting in (
C) It is an object of the present invention to provide a mold material that does not cause deformation of the original model (wax pattern) and allows casting of extremely high-precision castings with almost no dimensional errors.

(Means for Solving the Problems) The present invention adds a metal powder that does not generate gas during curing and heating of the mold material into the mold material, and utilizes the expansion of the metal powder due to oxidation. The basic structure is to expand the mold by an appropriate amount during heating.

(effect) The volume of increases. As a result, the mold as a whole expands in volume, and the volume of the casting space after dewaxing also increases at a constant rate.

In addition, even if the mold is heated together with the mold while it is housed in a metal mold, the metal mold itself expands due to heating, so the expansion during hardening of the mold may occur. However, no inconvenience occurs due to restriction of expansion in the radial direction.

(Example) Various experiments regarding the mold material according to the present invention and their results will be explained below.

In the experiments related to the present invention, magnesia-based mold material (MD-105) manufactured by Taihei Shoji Co., Ltd. was used as the mold material, and the components of the magnesia-based mold material are as shown in Table 1. .

In addition, in the present invention, Zr, Fe, 3i, Sn powder manufactured by Hanui Chemical Industry Co., Ltd. and Cu, Ni, Ni powder manufactured by Japan Powder Metallurgical Industry Co., Ltd. are used as metal powders.
Cr powder is used in each case. Furthermore, among the above-mentioned metal powders, Zr powder has an oxide formation free energy smaller than that of titanium or titanium alloy, and as described later, among these metal powders, Zr powder is the most suitable for carrying out the present invention. It turned out to be a suitable metal.

In this example, using the magnesia-based mold material and metal powder, (a) measurement of dimensional change during mold hardening, #3
) Measurement of dimensional changes during mold heating, (c) Casting and compatibility tests were conducted. The above test methods and test results are as follows.

(a) Measurement of dimensional changes during mold hardening As shown in Figure 1, inner diameter D = 2511φ, height L = 30
The inside of the metal tube 1 of jEI is lined with Kao wool 2,
Fix it on the plastic plate 4 with wax 3.

Next, a mold material slurry is poured while being vibrated with a vibrator, a plastic plate (floating plate) 5 is placed on top of the slurry, and a differential transformer 6 is used to measure dimensional changes in the vertical direction.

Note that the load caused by the differential transformer 6 is approximately 5 fr.

(b) Measurement of dimensional changes during mold heating The mold material slurry was poured into silicone rubber split molds 7a and 7b as shown in Fig. 2 (a) and (b) while being vibrated, and the green strength was measured. At that point (approximately 18 hours after pouring), the molds 7a and 7b were taken out, heated at a rate of 5° C. per minute, and the dimensional change 1 was measured.

In addition, the sample made from the split mold shown in Fig. 2 (a) (5 chickens φ
jlJ1) was measured using a thermal expansion analyzer (Thermoflex) manufactured by Rigaku Denki Kogyo Co., Ltd., and as shown in Fig. 2(b).
Samples (4 m x 10 m x 10 m) were prepared using a thermomechanical analysis device (TM-2) manufactured by Shimadzu Corporation.
0) to measure the amount of dimensional change. The load measured by the measuring device etc. is about 5 g.

(c) Casting test and suitability test of cast products Add a specified amount of water to the mold material and first premix it. The amount of water was kept to a minimum without impairing operability, and preliminary kneading was carried out by hand kneading for several seconds.

After that, a vacuum automatic kneader (CO) manufactured by Towa Giken Co., Ltd.
NEL) for 2 minutes, and then buried with a wax pattern while being vibrated with a vibrator. After drying the buried mold material at room temperature for about 16 hours, it was heated in an electric furnace under various heating conditions (using or not using a heating ring, heating speed, heating temperature, etc.), and was heated at Iwatani Sangyo Co., Ltd. Casting was carried out using an argon arc melting casting machine (CASTMATIC) manufactured by Co., Ltd. Pure titanium KS~50 (purity of 99.8% or more) manufactured by Kobe Steel, Ltd. was used as the casting metal for the compatibility test, casting surface roughness, and seizure test.

The form of the buried wax pattern is shown in Figure 3 (
As shown in a) to FIG. 3(d), (a) mold (9a), (
b) MOD-Inlay (9b), (C) Clinical pattern (
There are four types: 9C) and (d) Bridge (9d), and the casting body of each pattern should be investigated for surface roughness, seizure, etc. d) Compatibility test of cast products The compatibility of the cast products is shown in Figure 4 (a). ) to FIG. 4(C), the amount of uplift (5) between the abutment tooth 8 and the cast body 9 was investigated by measuring it using a sliding microscope. still,
The measurement points for the amount of uplift are shown at A in FIG. 4, but the amount of uplift is not measured for the bridge because the measurement points are complicated.

Next, the results of each of the above tests will be explained.

(1) Preliminary test regarding casting and compatibility First, a test was conducted using the Magnesia molding material MD-105 as a base material and adding 5% by weight of various metal powders thereto. The test results are shown in Table 2.

Table 2 Magnesia mold material Addition amount of MD-105 metal powder 5% by weight Type of wax pattern Mold (2) Measurement results of dimensional changes during mold hardening From the results of the preliminary casting and compatibility tests mentioned above, relatively good results were obtained. In the case where the zirconium powder for which the test results were obtained was added, dimensional changes were measured using the amount added as a parameter. The results are shown in Fig. 5, and the curve C1 shows that Zr is 3w.
t%, C2 is 4 wt%, C3 is 5 wt%, C4 is 6 wt%, and C5 is 6.54 wt%.
Moreover, C6 shows the case where Zr=Qwt%. There is no correlation between the amount of Zr powder added and the dimensional change during curing. In conclusion, when Zr powder is added to MD-105, the maximum shrinkage during curing is about 0.2%, excluding the influence of the measurement load (about 0.2%).

(3) Measurement results of dimensional changes during mold heating The measurement results of dimensional changes during heating are shown in Figure 6. In addition, in FIG. 6, the curve Dl has a Zr content of 3 wt%, and the curve D2 has a Zr content of 4 wt%.
t%, D3 is 5 wt%, D4 is 5wL%, D5 is 6
．． The case of 54 wt% is shown respectively.

It is clear from Figure 6 that the dimensional change during heating is
It is approximately proportional to the amount of powder added.

When 5 wt% of Zr powder is added, the dimensional change rate at 900℃I is +2.25%, and considering the shrinkage (approximately 0.2 to 0.4%) when the mold hardens, the total expansion amount is is approximately 1.85% (900°C). That is, Zr powder 5w
The addition of L% will achieve the required mold expansion.

(4) Casting and compatibility test (1) 7) Results Tests were conducted by changing the heating conditions during casting and the conditions such as using or not using an IJ song during heating. Oxidation of Zr powder There is a close relationship between the degree of molding and the compatibility of the casting.

(al in Table 3 is the result of the compatibility test,
b) shows the heating conditions, and in any case, no seizure or surface roughness occurs in each cast body.

Table 3 (-1 Mold Compatibility Test Results Table 3 To
) Heating conditions (1) and (2), (2) and (3), (5) and (6) in Table 3 for the compatibility test This is a comparison of whether it is better to heat the ring with the ring attached to it, or whether it is better to heat it without the ring attached.
In both cases, the use of the ring provides better compatibility than the case without the ring.

In addition, (7), (8), and (9) are results of examining the difference in oxidation depending on the buried position of the wax pattern, and from Figure 6, the temperature range for Zr oxide formation is approximately 600 to 700°C. Therefore, this temperature range was heated at a low heating rate. As a result (under force), the surface side had been stretched well, but the center side had little elongation, resulting in considerable distortion.
There was almost no difference in the molds of 8) and (9) when the molds were wide horizontally and long vertically. In other words, if the wax pattern to be embedded is fixed at the center of the mold, a cast body with almost no distortion can be obtained.

Finally, regarding α-kiri and (1B, α-rito (to)),
We investigated whether there is a difference between a ring and a ringless type when slowly heated in the Zr oxide formation temperature range (approximately 600 to 700°C). The temperature range for slow heating is 600-750℃ for safety, and the heating rate is 0.8
It was 0/min. (In (13), the ring is clearly more suitable than the ringless. (1 [
Comparing UL and UL), it seems that the ringless version has better compatibility, but the U casting had air bubbles on the inside of the cup due to poor burial, so I scraped off the air bubbles. This is thought to have led to a decrease in compatibility during fitting. Therefore, in this case (slow heating between 600 and 7500), it was found that using a ring was more effective than using a ringless one.

Furthermore, when comparing (1) and (13) in which 5 wt% of Zr was added, 031 has considerably better compatibility. From this, the temperature range for Zr oxide formation (60
It was found that slow heating at tζ (between 0 and 700'C) provides better compatibility.

To summarize the above results, in order to completely oxidize the Zr powder in the mold material without deforming the casting, the heating rate should be slow (especially between 600 and 700°C), a ring should be used, and the inside of the Since the method of spreading Kao wool seemed to be optimal, subsequent heating was performed using this method.

(5) Results of casting and compatibility test (2) As shown in FIG. 7, using the investment ring 10 formed by pasting Kao wool paper 10b on the inside of a stainless steel ring tOa, the wax pattern 11 was attached to the spool 121ζ. After fixing it on the cone 13 and pouring mold mud odor into it, it was dried for about 16 hours. Thereafter, the gold 14 and the truncated cone 13 were removed and heated as they were in an electric furnace to 900° C. according to the schedule shown in FIG. 8, and various wax patterns were cast.

Incidentally, the results of the casting are similar to those of the first embodiment, and no roughening of the casting surface or seizure is observed in any of the cast bodies.

Next, a compatibility test was conducted on each cast body cast by the above method. Table 4 shows the results.

Table 4 Compatibility results for various wax patterns In the compatibility test using clinical patterns, the compatibility improved as the amount of Zr powder added increased. However, Zr 5 w
There is only a difference of 0.0211 between Zr powder addition and Zr 5 w% addition, and since the mold is disposable, taking economic aspects into consideration, it seems appropriate for the amount of Zr powder added to be about 5 wt%.

This is because, in clinical applications, the lifting amount is approximately the same as that of the alloy currently in use (approximately 0.0611), so there is no problem.

In addition, in a compliance test using a MOD-inlay with 5 wt% of Zr powder added, the lifting amount was 0.44 mm, which seems not to be very suitable, but even when conventional dental alloys are used, lifting to this extent is amount.

This is because MOD-inlays do not fit into the abutment teeth if the cast body is too large or too small. According to the suitability test using MOD-inlay, the amount of Zr powder added was 5 wt%.
It seems appropriate.

Compatibility tests using bridges have also shown similar compatibility to those using conventional dental alloys.

As described above (in this example, 2 to 7 wL% is added to MD-1.05, which is a magnesia-based molding material).

By preferably adding 5 wL% of Zr powder, it is possible to obtain a cast body without roughening of the casting surface or seizure, and almost complete dimensional compensation can be achieved.

Furthermore, although high purity titanium (purity of 99.8% or higher) is used as the cast metal in this example, it is also possible to use titanium of lower purity or an alloy of titanium and other metals. However, substantially the same results as in each of the above embodiments can be obtained. For example, in the case of an alloy containing 50 to 5 Qwt% of titanium, it has been confirmed that the desired purpose can be sufficiently achieved by adding 2 to 3% of Zr powder.

Furthermore, in this example, the M D
-105 is used, but the mold material is M D -1.
, 05, and other types of mold materials may of course be used.

(Effects of the Invention) In the present invention, since an appropriate amount of metal powder is added to the mold material and the expansion due to oxidation is utilized,
It is possible to obtain an extremely high expansion coefficient of the mold during heating, and it is possible to easily achieve almost complete dimensional compensation.
Casting surface roughness or burning.

Casting can be performed without any problems.

Further, in the present invention, unlike the prior art, there is no need to expand the mold by the generated gas, so there is no adverse effect from the gas, and a cast body that substantially matches the original mold can be obtained.

Furthermore, in the present invention, the mold expands only when it is heated, and no expansion occurs when the mold hardens, so there is no adverse effect on the wax pattern fζ compared to the prior art, and an extremely high-precision cast body can be obtained. can be obtained.

As mentioned above, the present invention has excellent practical utility.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for measuring dimensional changes during mold hardening. FIG. 2 is a perspective view of a silicone rubber split mold used to measure dimensional changes during mold heating. FIG. 3 is a perspective view of various wax patterns used in casting tests. FIG. 4 is an explanatory diagram showing the measurement points of the lifting amount of each of the four types of wax parquets. FIG. 5 shows the rate of dimensional change during curing of the mold. Figure 6 shows the dimensional change rate during heating of the mold. Figure 7 is a perspective view of the casting equipment in another casting test. Figure 8 shows the heating of the mold. This is the Sukeshiel curve. 1 Metal tube 2 Kao wool 3 Wax 4 Plastic plate 5 Floating plate 6 Differential transformer 7a, 7b Split mold 8 Support tooth 9 Casting body A Lifting amount Fig. 1 Fig. 4 Fig. 3 (a) (b) Figure 7 Procedure Amendment (Method) Indication of case Patent application 1982-1334982 Title of invention
Mold material for casting titanium or titanium alloys 3 Relationship with the case of the person making the amendment Address of the applicant: 1-15-18 Tenjinnomori, Nishi-ku, Osaka Name Kenji Tsugaya 4 agents and 1 other person 5 Amendment order Date September 25, 1980 6 Subject of amendment Drawing attached to application 7 Contents of amendment

Claims (1)

[Claims] 1. A metal powder that does not generate gas when the mold material is hardened or heated is added to the mold material, and the expansion of the metal powder due to oxidation is used to expand the mold in an appropriate amount when heated. A mold material for casting titanium or a titanium alloy, characterized in that it is made to expand. 2. Titanium or titanium according to claim 1, in which the molding material is a magnesia-based molding material, and the metal powder to be added is a metal powder having a smaller free energy of oxide formation than titanium or a titanium alloy. Mold material for alloy casting. 3. The mold material for casting titanium or titanium alloy according to claim 1 or 2, wherein zirconium or zirconium alloy powder is added as the metal powder. 4. The mold material for casting titanium or titanium alloy according to claim 3, wherein the added zirconium component is 2% by weight to 7% by weight.