JPS5842744A - Nickel-chromium alloy for cast dental plate - Google Patents

Abstract

PURPOSE:To obtain an alloy enabling the use of a gypsum burying material, free from Be harmful to the human body, and having satisfactory mechanical properties by adding Zr to an Ni-Cr alloy in place of Be and increasing the Mo content. CONSTITUTION:This alloy consists of, by weight, 15-20% Cr, 8.5-15% Mo, 1-5% Al, 2-7% Mn, 0.3-2.0% Zr and the balance Ni with impurities. Mo has an effect of making the crystal grains fine and strengthening the alloy matrix. Since the mechanical properties are deteriorated by adding Zr, in case of less than the lower limit of Mo, satisfactory mechanical properties are not obtd., yet more than the upper limit of Mo makes the alloy brittle. When the alloy is cast in a gypsum burying material, Zr produces an effect of preventing the surface roughening of the casting. In case of less than the lower limit of Zr, the effect is insufficient, yet more than the upper limit of Zr deteriorates the mechanical properties.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nickel-chromium alloy for use in dental casting beds, which is a type of dental prosthesis.

Conventionally, nickel-chromium alloys for dental casting floors that use gypsum-based investment materials have contained beryllium, which is considered harmful to the human body, as an essential component to prevent the surface of the cast from becoming rough.

The alloy of the present invention does not contain beryllium, but by containing zirconium, which is harmless to the human body, the surface roughness of the cast body has been significantly improved. It is characterized by containing molybdenum, which improves the mechanical properties to the point where it is fully satisfactory as a nickel-chromium alloy for dental casting floors.

Cobalt-chromium alloys have been widely used as base metal alloys for dental casting floors, but since this type of alloy has a high melting point of around 1400°C, phosphoric acid with high fire resistance is used as an investment material. It would have been difficult if I hadn't used a salt-based investment material. Phosphate-based investment materials are sintered and hardened by incineration heating, so they do not have high strength, and after casting, it is difficult to remove the cast material from the investment material without deforming it, and the work time is long because the incineration temperature must be high. Become.

Since the curing time is fast, there are problems in that there is no margin for handling during technical work.

In recent years, in order to solve the problems of phosphate-based investment materials mentioned above,
A nickel-chromium alloy that can be used as a gypsum-based investment material with excellent operability and easy removal of the cast body after casting has appeared, and has become widely used.0 However, currently commercially available gypsum-based The nickel-chromium alloy used as the investment material contains beryllium as an essential component, as shown in Table 1, for example.

Table 1: Margin below Gypsum-based investment materials have the advantages mentioned above, but because they use anhydrite as a binding material, they have low fire resistance and when cast with high melting point alloys, they have the disadvantage of causing surface roughness on the surface of the cast object. have.

Although beryfluorium contributes to increasing mechanical properties, it is actually included as an essential component because it has a remarkable effect on preventing roughening of the surface of the cast body.

However, when humans inhale the gas, dust, and fume of beryllium compounds, acute beryllium poisoning occurs.

It is known that chronic poisoning can lead to respiratory disorders, heart failure, etc., and people involved in melting, casting, and polishing are at particularly high risk and must be extremely careful. For this reason, there is a strong demand for the development of nickel-chromium alloys that do not contain harmful components.

Taking these circumstances into consideration, the present inventors have developed a new external dental casting bed that can use gypsum-based investment material and has satisfactory performance in terms of mechanical properties and does not contain beryllium, which is harmful to the human body. As a result of conducting research with the aim of creating a nickel-chromium alloy for aluminum alloys, it was discovered that zirconium is extremely effective in preventing roughening of the surface of cast objects. By incorporating molybdenum, the mechanical properties were improved and an alloy with satisfactory performance as a nickel-chromium alloy for dental casting floors was successfully produced.

The alloy according to the present invention is 1) 15 to 20 inches of chromium, 8.5 to 15 inches of molybdenum, 1 to 5 inches of aluminum, and 2 inches of manganese.
7% zirconium, 0.6-2.0% zirconium, and the balance nickel and impurities. 2) A nickel-chromium alloy for dental casting beds comprising 0.0005-0.5% calcium. Regarding the nickel-chromium alloy for dental casting floors described in item 1, after casting using a gypsum-based investment material, it maintains good cast surface properties and maintains consistent tensile strength.
It is elastic, corrosion resistant, and self-hyperchromic.

All claims in the present invention are expressed in weight percent. Next, the reason for limiting the range of each component as described above will be described.

Chromium is an indispensable element for maintaining the corrosion resistance and discoloration resistance of base metal alloys, and its effect was fully recognized in the alloy of the present invention at 15%. But 2
If it exceeds 0%, the tensile strength will decrease and the melting point will increase, so it was limited to a range of 15 to 20 inches.

Aluminum is nickel and N15AJ! This forms an intermetallic compound that contributes to improving the tensile strength and elastic limit of the alloy, but at the same time reduces the elongation.

In the alloy of the present invention, if it is less than 1%, the tensile strength and elastic limit will not be sufficient, and if it exceeds 5%, the elongation will be greatly reduced, so it is limited to a range of 1 to 5%.

Manganese plays the role of cleaning other metal compounds during melting, that is, as a deoxidizing agent, but if it is less than 2%, the deoxidizing effect is insufficient, and if it exceeds 7%, it will cause the alloy to become brittle.
It was limited to a range of ~7%.

Since molybdenum makes crystal grains finer, it is effective in strengthening the alloy matrix, and is therefore added as a component that contributes to increasing the tensile strength, elastic limit, and hardness of the alloy. As mentioned above, it is essential to contain zirconium in order to maintain a good cast surface, and since this zirconium deteriorates the mechanical properties, molybdenum is less than 8.5% in the alloy of the present invention. If it exceeds 15 degrees, the alloy becomes brittle, so it is necessary to keep it in the range of 8.5 to 15 degrees.

The mechanical properties that should be satisfied as an alloy for the casting floor are a tensile strength of 80 KVmm2 or more, and an elastic limit of 65 KVmm2 or more.

The elongation is 1.5 to 5.0 inches, and a good cast surface has a ten-point average roughness of 14 microns or less.

Zirconium is an element that is extremely effective in preventing surface roughness of the cast object when it is cast into a gypsum-based investment material.
If the number is less than 6, the effect will not be sufficient, and if it exceeds 2, the mechanical properties will deteriorate.

Therefore, the amount of zirconium needs to be within the range of 6 to 2.0%. Zirconium oxidizes preferentially to form a thermally stable oxide film, which acts as a protective film and is effective in preventing roughening of the surface of the cast body.

Table 2 shows the composition, physical and mechanical properties, and surface roughness test results of the Examples and Table 6 of the Comparative Examples.

As can be seen from the second table, in order to maintain a good casting surface and obtain an alloy with satisfactory mechanical properties, the amount of molybdenum should be 8.5 to 15, and the amount of zirconium should be 0.6 to 2. .0
Correlations that limit the range of relationships are required.

Calcium exhibits an excellent deoxidizing effect even in small amounts, and when melted, the surface of the molten metal easily becomes mirror-like, making it easier to determine the timing of casting. Therefore, casting can be performed without overheating, and an ingot with fewer cavities can be manufactured. For this purpose, it is better to add calcium, but if it exceeds 0.5 g, the mechanical properties of the alloy deteriorate as seen from Comparative Example 6, so 0.0005 -
It is necessary to limit the range to 0.5 inches.

The reasons for limiting the range of the alloy components of the present invention have been explained above, but dental alloys are different from general industrial alloys! l)
Since they are always used under the harsh conditions of the oral cavity, they must have particularly excellent corrosion resistance and discoloration resistance.

The alloy of the present invention was tested with artificial saliva and four other test fluids used in dentistry and was found to have excellent corrosion resistance and discoloration resistance.

Next, Table 4 shows a comparison of the physical and mechanical properties and surface roughness between the alloy of the present invention and a commercially available nickel-chromium alloy for the same purpose.

Table 4 Tensile tests were conducted by preparing tensile test pieces according to A, D, A, 8 No., 14, and the hardness was determined by thickness i, 5 mm.
A test piece with a width of 10 mm and a length of 15 mm was prepared, and its Vickers hardness (Hv) was measured. The melting point (liquidus point) was determined by differential thermal analysis.

The surface roughness was determined by preparing a disk with a thickness of 5 mm and a diameter of 50 mm, and measuring the 10-point average roughness according to JIS B [1+SO1.

The alloy according to the invention maintains a good casting surface.

In addition, it has high mechanical properties, especially a large elastic limit, which makes it possible to manufacture a casting bed with less warping.

When a dental casting bed was actually manufactured using the alloy of the present invention, the castability,
The gloss after final polishing and the compatibility with the original model were both good.

The above describes a nickel chromium alloy for dental casting floors that can be used with a gypsum-based investment material that does not contain beryllium. It is a junior college that contributes to the improvement of dental prosthetic technology.

Claims (1)

[Claims] 1 15-20% chromium, 8.5-15% molybdenum, 1-5% aluminum, 2-7% chromium, 0.6-2.0% zirconium, the remainder being nickel and impurities. Made of nickel-chromium alloy for dental casting floors. 2 Contains 0.0005 to 0.5 of calcium-
A nickel-chromium alloy for dental casting floors according to claim 1.