RU2233907C1 - Stainless steel "dentalit" for orthopedic stomatology - Google Patents

Abstract

FIELD: metallurgy, medicine, stomatology.

SUBSTANCE: invention relates to stainless corrosion-resistant chrome-nickel steels designated for making cast dental crowns and fixed bridge-like prostheses, among them with plastic facing. The claimed stainless steel for orthopedic stomatology comprises carbon, silicon, manganese, chrome, nickel, molybdenum, rare-earth elements and iron. Also, steel comprises additionally copper, calcium and magnesium in the following ratio of components, wt.-%: carbon, 0.10-0.20; silicon, 1.5-2.0; manganese, 1.3-1.8; chrome, 19.5-22.0; nickel, 16.0-19.0; molybdenum, 2.8-4.0; copper, 0.5-1.5; calcium, ≤ 0.02; magnesium, ≤ 0.04; rare-earth elements, ≤ 0.05; iron and inevitable impurities, the balance. Chrome content and carbon content are depended by the following ratio: Cr/C ≤ 200. Invention provides enhancing the technological effectiveness of steel in making dental prostheses by improving cast indices of steel and by its treatment capacity also by abrasives, polishing capacity, reducing content of alloying components and retention of the enhanced level of mechanical properties, high corrosion stability, nontoxicity in the mouth cavity.

EFFECT: improved, enhanced and valuable properties of steel.

2 tbl, 1 ex

Description

The invention relates to the field of metallurgy, and in particular to stainless (corrosion-resistant) chromium-nickel steels, intended for the manufacture of cast dental crowns and bridges, including with plastic lining.

Cast metals used in orthopedic dentistry should:

- to provide high-precision casting of thin-walled dentures;

- it is well processed by dental abrasives and polished;

- have sufficient strength to prevent deformation of the thin-walled prostheses made from them in the patients mouth;

- have high corrosion resistance in saliva, blood, gastric juice, not be toxic, i.e. meet all modern sanitary-chemical and toxicological requirements.

Known stainless steel designed for medical instruments, mainly for surgical implants operated inside a living organism, which contains the following components, wt.%:

Carbon 0.01-0.03

Chrome 16.5-18.5

Nickel 14.5-17.5

Molybdenum 2.6-3.1

Silicon 0.2-0.6

Manganese 1.0-2.0

Aluminum 0.03-0.25

Magnesium 0.005-0.03

Iron Else

(Copyright certificate SU No. 1678894 A1, IPC C 22 C 38/44, publ. 09/23/1991).

The use of this steel makes it possible to increase the operational reliability of surgical implants inside a living organism by increasing their resistance to pitting corrosion.

However, the presence of a low carbon content in steel worsens its casting characteristics, and in combination with a low chromium content it does not provide the strength properties necessary for the manufacture of long-length thin-walled bridges.

Known iron-nickel alloy Virolloy E (Wirolloy E) for dental crowns with a plastic lining, containing the following components, wt.%:

Chrome 21

Nickel 25

Molybdenum 5

Copper 1.5

Manganese 1.5

Iron 46

. Wilh. Herbst GmbH & Co, 5m792/ BD 7858 Best №82007, 1992 by BEGO).(Germany, BEGO company, gold processing, Wilhelm Herbet GmbH and Co. Bremen; BEGO Bremer

. Wilh. Herbst GmbH & Co, 5m792 / BD 7858 Best No. 82007, 1992 by BEGO).

This alloy has lower strength characteristics: yield strength σ _0.2 = 240 N / mm ² and hardness HV10 = 135, which complicates its use for thin-walled bridges, especially of great length, and therefore can be used in accordance with the recommendation of the company only for single crowns.

The closest analogue to the combination of elements is corrosion-resistant steel “Dentan” for dentures, containing the following components, wt.%:

Carbon 0.003-0.05

Silicon 2.3-3.0

Manganese 1.0-2.1

Chrome 23.5-26.5

Nickel 19.0-21.0

Molybdenum 1.8-2.2

Cerium 0.05-0.15

Iron Else

(RF patent No. 2017857 C1, IPC C 22 C 38/44, 38/58, publ. 08/15/1994 - prototype).

The patent indicates high mechanical properties:

tensile strength, σ _in = 60-80 kg / mm ² ;

yield strength, σ _0.2 = 50-60 kg / mm ² ;

elongation, δ ₅ = 50-60%.

However, as follows from the description of the patent, these properties are obtained on samples made of hot-deformed bar after rolling, while in the molded state (working: dentures are made by centrifugal casting) these properties will be significantly less.

A low carbon content in steel (less than 0.05%) reduces its fluidity, worsening casting properties, and a high chromium content (up to 26.5%) reduces the workability and polishability of steel.

The problem to which the invention is directed is to create stainless steel for cast dentures having the following set of properties:

- increased casting characteristics;

- good machinability with dental abrasives and polishability;

- increased mechanical properties, providing reliability and durability of a thin-walled denture, including a bridge, of great length;

- high corrosion resistance in the oral cavity that meets all modern sanitary-chemical and toxicological requirements;

with a decrease in the content of the main alloying elements.

The technical result of the invention is to improve the casting characteristics of steel, as well as its machinability with dental abrasives, polishability while reducing the content (saving) of alloying elements and maintaining a high level of mechanical properties, high corrosion resistance, non-toxicity in the oral cavity.

The specified technical result is achieved by the fact that stainless steel for orthopedic dentistry, containing carbon, silicon, manganese, chromium, nickel, molybdenum, rare-earth metals and iron, according to the invention, to increase manufacturability in the manufacture of dentures additionally contains copper, calcium and magnesium in the following ratio of components , wt.%:

Carbon 0.10-0.20

Silicon 1.5-2.0

Manganese 1.3-1.8

Chrome 19.5-22.0

Nickel 16.0-19.0

Molybdenum 2.8-4.0

Copper 0.5-1.5

Calcium ≤0.02

Magnesium ≤0.04

REM ≤0.05

Iron and inevitable impurities

while the content of chromium and carbon are related by the following relationship: Cr / C≤200.

When the carbon content in the steel is less than 0.10%, good fluidity of the steel is not provided, and when the carbon content is more than 0.20%, the corrosion resistance decreases.

A silicon content of less than 1.5% does not provide good casting characteristics of the steel, and when its content exceeds 2.0%, ductility is reduced.

Manganese in the range of 1.3-1.8% provides good fluidity of steel, with a manganese content of more than 1.8%, its corrosive properties deteriorate.

A chromium content of less than 19.5% reduces the corrosion resistance of steel, and over 22.0% degrades the workability and polishability of steel, and also reduces the yield of steel during metallurgical processing (ingot deformation on a bar).

Nickel in the specified range of 16.0-19.0% provides a plastic non-magnetic austenitic structure. An increase in the content of deficient nickel over 19% leads to a rise in the price of metal.

When the molybdenum content is less than 2.8%, the necessary corrosion resistance and strength of steel are not provided, and when its content is more than 4.0%, the melting temperature increases and ductility decreases.

Alloying with copper lowers the melting point of steel, increases its ductility in the cold state and, as a consequence, workability and polishability. Alloying with copper less than 0.5% is not effective, but more than 1.5% leads to a decrease in hot deformability during metallurgical processing.

The introduction of rare-earth metals is limited to 0.05% due to the additional alloying with modifying additives of calcium and magnesium in amounts of not more than 0.02 and 0.04%, respectively. Complex microalloying of rare-earth metals, calcium and magnesium increases the processability of steel during hot processing from ingot to bar and thereby increases the yield of “suitable” for metallurgical processing.

The dependence Cr / C≤200 limits the alloying of steel with chromium at the upper limit when the carbon content is at the lower limit, which allows, without reducing the corrosion resistance, to additionally increase the hot ductility and yield during metallurgical processing, as well as the workability of steel while saving chromium.

The invention is illustrated by the following examples.

DENTALIT steel was smelted in compliance with the strict regime of technology in a vacuum induction furnace on a clean charge with casting into an ingot. After high-temperature heating, the ingot was forged on a hammer onto a bar, which was subsequently cut into measured billets of ~ 15 grams.

Test samples were cast from these preforms using a centrifugally cast method using the technology adopted in dental practice.

The chemical composition and properties of the proposed steel in cast condition are shown in table 1 and 2, respectively.

From the results of determining the mechanical properties obtained in the molten state, it follows: the proposed steel has an increased level of mechanical properties, allowing the manufacture of dentures, including long bridges, with a thinner wall, which makes it possible to conduct gentle preparation with minimal removal of the patient’s dental tissue .

Machinability and polishability of steel was evaluated by the complexity in the manufacture of prostheses. The results showed that the new steel is easily treated with dental abrasives and polished due to its lower chromium content and additional alloying with copper.

To assess the fluidity of steel by centrifugal casting, as in the manufacture of dentures, thin-walled specimens of complex configuration were cast with a wall thickness of 0.2 mm.

All parts on the casting of the proposed steel turned out to be clear and of a given geometry due to the increased fluidity due to the higher carbon content. Moreover, as the carbon in the steel increased to 0.19%, the fluidity of the steel increased.

Determination of the melting temperature showed that the proposed steel is not high and is not more than 1330 ° C.

Thus, the proposed "DENTALIT" steel is characterized by increased manufacturability in the manufacture of dental prostheses, namely, the best casting characteristics, machinability with dental abrasives and polishability, which reduces the complexity and reduces the time of manufacture of dental prostheses, and also contains less basic alloying elements up to 19 %

Corrosion, sanitary-chemical and toxicological tests of the proposed DENTALIT steel showed that it fully meets all modern medical requirements for materials for dental prosthetics.

Claims (1)

Stainless steel for orthopedic dentistry containing carbon, silicon, manganese, chromium, nickel, molybdenum, rare-earth metals and iron, characterized in that it additionally contains copper, calcium and magnesium in the following ratio, wt.%: Carbon 0.10-0.20 Silicon 1.5-2.0 Manganese 1.3-1.8 Chrome 19.5-22.0 Nickel 16.0-19.0 Molybdenum 2.8-4.0 Copper 0.5-1.5 Calcium ≤0.02 Magnesium ≤0.04 REM ≤0.05 Iron and inevitable impurities while the chromium content and carbon content are related by the following relationship: Cr / C≤200.