SI22628A - PROCESS OF MANUFACTURE OF DENTAL ALLOYS WIT HIGH CONTENT OF Au - Google Patents

Abstract

The subject of invention is a process of manufacture of dental alloys with high content of Au and belongs to the subject area of working technology. A technical problem the invention is solving is the manufacture of the dental alloy with the chemical composition 77 wt% Au, 1.2 wt% Pd, 4.5 wt% Pt, 10 wt% Ag, 6 wt% Cu and 1.3 wt% Zn. In the said process of manufacture, exact sequence of technological procedures is shown on the embodiment example, by which Au dental alloy plates of required dimensions and properties can be produced. The process of manufacture of Au dental alloy consists of melting and casting into a metal ingot mould, of procedures of cold forming of cast raw shapes, such as profile rolling, intermediate recrystallisation glowing, flat rolling, burnish rolling and of cut up of tapes to required plate dimensions.

Description

The subject of the invention is a method of manufacturing dental alloys with high gold content (Au) - hereinafter referred to as dental dental alloys. The inertia, remodeling, and yellow color of gold represent the elements that rank Au dental alloys among t i. natural materials for the dental environment. Dental alloys with high Au content are those with Au mass fraction above 77% and therefore have excellent biocompatibility. A technical problem solved by the process of manufacturing dental dental alloys is the production of these alloys with the required attainment of properties. In addition to the required chemical composition, they must have an adequate melting interval (about 100 ° C) and casting temperature (above 1290 ° C), hardness above 170 HV, elongation above 6%, tensile strength R 'and above 680 N / mm ² and a plasticity limit exceeding 550 N / mm ² . The required chemical composition can fluctuate +/- 2% in each component, melting interval + / 10 ° C, casting temperature +/- 30 ° C, hardness +/- 10 HV, elongation +/- 2%, while tensile strength and the plasticity limit fall only by 10 N / mm ² according to the required values. Au dental alloys must meet all requirements in dental technology, where material is used for fixed crowns and longer multi-link bridges (standard EN ISO 9693: 2000). Otherwise, they can also be used for inlays, MOD inlays, onlays, partial crowns, bridges (also multiple joints), for cast bases, overlays - that is, for use in porcelain technology. In the case of the use of Au dental alloys in porcelain, it is necessary to satisfy the conditions of the coefficient of thermal expansion (CTE) of the alloy, which must be compatible with the CTE coefficient of the porcelain used. As porcelain can withstand higher compressive stresses than tensile, it is desirable that the thermal expansion of Au dental alloy be slightly larger than porcelain (CTE _with ij _t .> CTEpo _rc ). With this condition fulfilled, it can be expected that, after baking the toothbrush and during cooling it, compressive stresses will be generated in the porcelain shell. It will also prevent high internal stresses from occurring during the cooling of the dental object from baking temperature to room temperature, especially in the outer - bright surface of the porcelain bake. High internal stresses on this surface would be extremely unfavorable, as high local biting pressures could cause the porcelain coating to rupture immediately.

These requirements can be achieved by the described technological procedures, the most important of which is the thermo-mechanical treatment of Au dental alloys, where, with the correct combination of mechanical and thermal treatment, the required required properties are achieved at the required dimensions

Today, there are many different technological processes that are the basis of machining technology, which differ in their function partially or substantially, and enable the production of various forms of objects, including Au dental alloys. They can generally be divided into four main groups:

- primary design comprising refinement and casting, etc .;

- cold forming comprising rolling, profile rolling, flat rolling, etc .;

- processing or t i. heat treatment comprising improvement: external by surface treatment or internal by thermal treatment,

- splitting comprising shearing, cutting, trimming, etc.

The characteristics of individual technological processes are as follows:

When casting, pour molten metal into a mold cavity in which it solidifies and retains its shape. In this way, the mold gets the final shape that will be retained for further processing and use. In a simple and economical casting process, we make a shape that we couldn't otherwise have, or we could make it with difficulty. Castings replace forged products, although they have better mechanical properties due to their fine-grained structure. Castings, on the other hand, have the same strength in all directions, which has a beneficial effect on subsequent mechanical treatment.

The basis of cold forming is limited to plastic deformation transformation methods, in which the microstructure of the material being transformed is changed, whether it is a cast or already transformed microstructure. These methods include rolling, which is a process of continuous transformation of a metal between two cylindrical pressure surfaces (cylinders) rotating in opposite directions, with a distance less than the thickness of the rolled object. The material moves through the workspace due to friction between the cylinders and the roller; in doing so, the roller extends in the direction of the main load of the compression, but at the same time it extends perpendicularly and longer. Roller deformation is greatest in the direction of minimum resistance (in the direction of rolling). As the time unit enters between the cylinders the same amount of material as it exits, and the cross-section of the opening between the cylinders decreases in the direction of rolling, the speed of the cylinder increases in approximately the same proportion as its thickness decreases. We can briefly summarize the following general characteristics of rolling:

- the exit velocity of the cylinder is greater than the constant circumferential velocity of the cylinders,

- the plastic deformation process takes place between cylinders having the same diameter and the same rotational speed,

- the axes of the cylinders belonging to one frame are parallel and lie in the rolling plane,

- Adjust the opening between the cylinders by adjusting the cylinders (with special screw spindles manually, mechanically or hydraulically).

- the rolling direction is perpendicular to the rolling plane,

- the contact arc surfaces across the width of the roller, the roller opening and the jump limit the forming area in which the material is plastically deformed.

Profile rolling is used in the production of various profiles, where the change of the entire cross section of the roll has an important role. The changes in the thickness and width of the roller are determined by the shape and size of the profile enclosed by the rollers. The production of profiles is faster and more economical, the greater the ratio of the cross-section of two successive plugs. For this reason, it is very important to determine, as a rule, the sizes and number of individual plugs required to complete the final profile. With a small number of plugs we can shorten the rolling time, but this number of plugs or passes of the roller through the rolling hole is limited by the maximum allowable ratio of the deformation of the cross section between the individual plugs.

Heat treatment is a process of heating, annealing, cooling and subsequent annealing, which achieves the intended properties or microstructural state of the alloy. It consists of heating to a certain temperature, isothermal holding for a certain period of time and various rapid cooling. In this way, the unbalanced state of the microstructure resulting from cooling is altered in a controlled manner. Heat treatment of metallic materials can greatly improve an individual property or several properties at once and achieve a useful combination of properties. The heat treatment is aimed at reducing the internal stresses of the metal, releasing the hardening due to cold deformation and increasing the ductility by repairing and recrystallization, changing the microstructure or improving the microstructure of homogeneity. The possible heat treatments depend on the characteristics of the structure of the material (constitution) as can be seen in their phase diagram. The goals of homogenization or diffusion annealing are to achieve a homogeneous or uniform chemical composition in the microstructural components. Objectives of voltage annealing reduce internal stresses in the material. These annealing is carried out at temperatures at which the microstructure of the material and thus its other properties change as little as possible. Recrystallization annealing is a heat treatment that softens materials that have been hardened by cold plastic deformation. Solvent annealing dissolves the secretions and produces a homogeneous solid solution

The purpose of the technological separation process, which includes shearing, is to separate one part of the material (sheet) from the other part, or to prepare the material for further transformation or to obtain a definite final shape. There are two methods of shearing: shear on Shears and shear with special cutting tools. In the first case of shearing, we are talking about an open cut between the cutting edges of two knives, which can be straight or circular. Known open cut procedures are trimming and trimming. In the second example of shearing, we have a closed cut formed by individual parts of the tool. These cutting methods include cutting, punching, trimming and cutting.

The above described methods describe methods and influential process parameters that allow the production of certain dimensions and properties of different types of semi-finished products, while the solution of the correct sequence of technological procedures for the production of Au dental alloys is not given. There is no specific solution for the control of thermo-mechanical treatment of Au dental alloys by which the desired properties of these dental alloys can be achieved in the chosen chemical composition.

A technical problem solved by the invention is the process of manufacturing Au dental alloys. In the manufacturing process, the following examples indicate the exact sequence of technological procedures by which the Au dental alloy with the required properties can be produced. The solution of a technical problem enables the reliable achievement of the quality of Au dental alloys.

The following is a process for manufacturing a dental alloy with a high Au content according to the invention with a detailed technological description for each individual manufacturing step separately:

(i) melting of feedstocks - pre-alloys (Ag / Pd, Cu / Zn) and Au dental alloys;

(ii) casting molten pre-alloys (Ag / Pd, Cu / Zn) into a metal mold and Au dental alloys into a graphite mold; rolling and rolling;

(iv) thermal treatment of intermediate dental alloy semi-finished products: recrystallization annealing with appropriate regimes in the selected atmosphere;

(v) trimming of Au dental alloy tiles on both sides of the Shear and stamping.

At the end of the descriptions, a derivative example of a manufacturing process for an Au dental alloy is provided.

(j) Ag-Pd pre-alloy

The melting of the Ag / Pd pre-alloy (50:50 wt.%) Takes place in an induction furnace at T = 1473 K in a protective atmosphere Ar (with a flow rate of 31 / min and a pressure of 1.03 bar) and represents a change in the solid aggregate state of silver and palladium in liquid by supplying thermal energy through high frequency induction. This is based on an electronic generator that produces high frequency current (~ 170 kHz). It flows over the surface of a hollow copper conductor, which, like a coil, is surrounded by a few threads of a vertically standing melting pot. The current generates an alternating electromagnetic field with the highest concentration of magnetic forces in the center of the graphite retort, where Ag and Pd are deposited. The electromagnetic field induces high-frequency current in metals - Ag and Pd, which heats them strongly and finally also relatively quickly.

Oi)

The molten Ag / Pd pre-alloy is poured into a flat metal mold of dimensions. 120mm>lOOmm> 15mm. This is followed by cooling in a metal mold and immediately quenching in water until equilibration with T _VO de Before further thermo-mechanical treatment, the cast preform of the Ag / Pd pre-alloy needs to be further cleaned, which means washing and brushing the casts with a mixture of water and detergent and final drying. with compressed air.

(iii)

In the case of flat Ag / Pd preforms with dimensions of 120 mm χ 100 mm ^x 15 mm, rolling in the first stage should be carried out on a rolling machine with smooth cast steel cylinders with a hard surface (recommended thickness of cemented layer is at least 6 mm) , about 250 mm in diameter. This rolling is performed in steps of 0.5 mm to final = 0.6 mm. After rolling, the Ag / Pd preform is cut to 15mm I5mm.

(i) Cu-Zn pre-alloy - (MS 63)

Melting of Cu / Zn pre-alloy (66:33 wt.%) Takes place in an induction furnace at T = 1273 K in a protective atmosphere Ar (with a flow rate of 31 / min and a pressure of 1.03 bar) and represents a change in the solid aggregate state of copper and zinc in liquid by supplying thermal energy through high frequency induction. This is based on an electronic generator that produces high frequency current (~ 170 kHz). It runs over the surface of a hollow copper conductor, which, like a coil, surrounds a vertically standing melting pot with some windings. The current creates an alternating electromagnetic field with the highest concentration of magnetic forces in the center of the graphite retort, where Cu and Zn are deposited. The electromagnetic field induces high-frequency current in metals - Cu and Zn, which heats up strongly and finally also relatively quickly.

(ii)

The molten Cu / Zn pre-alloy is poured into a flat metal mold of dimensions: 120m ^x lOOmm ^; 15mm. This is followed by cooling in the metal coke and immediately quenching in water to equalize the temperature with T _{vo <fc} . Before further thermo-mechanical treatment, the cast preform of the Cu / Zn pre-alloy needs to be further cleaned, which is the rinsing and brushing of the casts with a mixture of water and detergent and final drying with compressed air.

(iii)

In the case of flat Cu / Zn shaped preforms with dimensions 120 mm ^x '100 mm ^x ' 15 mm, rolling in the first stage should be carried out on a rolling machine with smooth cast steel cylinders with a hard surface (recommended thickness of cemented layer is at least 6 of about 250 mm in diameter. This rolling is performed in steps of 0.6 mm to a final L = 0 6 mm. After rolling, the Ag / Pd preform is cut to 15mm ^x 15mm.

(i) dental alloy with high Au content

The melting of the Au dental alloy (Ag / Pd, Cu / Zn, Au, Pt, Pd, Ag, Cu, a small spoon of charcoal) takes place in an induction furnace between T = 1573 and 1623 K in a shielding atmosphere Ar (with a flow rate of 31 / min and pressure 1.03 bar) and represents the change in the solid aggregate state of the pre-alloys in the form of 15mm ^x 15mm tiles and other components of the dental alloy into liquid by supplying heat through high-frequency induction. This is based on an electronic generator that produces high frequency current (~ 170 kHz). It runs over the surface of a hollow copper conductor, which, like a coil, surrounds a vertically standing melting pot with some windings. The current creates an alternating electromagnetic field with the highest concentration of magnetic forces in the center of the graphite retort, into which the necessary components of the Au dental alloy are deposited. The electromagnetic field induces a high-frequency current in the metal, which it strongly heats and finally also relatively quickly melts.

(u)

The molten Au dental alloy is poured into a graphite mold with a recommended diameter (Φ) of 16 mm. This is followed by 1-1.5 min cooling of the dental alloy in the graphite coke and immediately quenching in water to equalize the temperature with T _{vo <} j _e . After extinguishing, a 1 cm cut should be made on the upper surface of the cast at the point where the material shrunk. Before further thermo-mechanical treatment, the cast preform must be further cleaned, which means flushing and brushing the casts with a mixture of water and detergent and finally drying with compressed air.

(iii) and (iv)

For molded preforms with φ = 16 mm from Au dental alloy, profile rolling in the rolling machine must be performed in the first stage. The working cylinders must be made of steel for improvement (in our case we used cylinders made of OHV4 or DIN 86CRMOV7 material from Metal Straight), with a diameter of about 160 mm and with an open square caliber shape without touching the cylinders. This profile rolling is performed in 0.25-0.3 mm increments to a wire of - 5.3 mm. This is followed by cutting the wire to a length of 500 mm. Due to high internal stresses and too high hardening of the Au dental alloy wire, an intermediate recrystallization isothermal insult in a flow furnace at 1093 K at a flow rate of 200 mm / min in a protective atmosphere (H ₂ : N ₂ = 80: 20) is required. After annealing, allow the wire to cool slowly to air at room temperature. Before further thermo-mechanical treatment, the wire has to be cleaned, which is a rinse and brush with a mixture of water and detergent and final drying with compressed air. From this dimension of the square profile, it is necessary to carry out a flat rolling on a rolling machine, which should have flat working cylinders made of steel for improvement (in our case we used cylinders made of material with the code 0HV4 or the mark according to DIN 86CRMOV7 of the manufacturer Metal Straight) with a diameter of about 120 mm. This flat rolling is made from - 5.3 mm in 0.2 mm increments into a 2.8 mm strip. Due to the re-emergence of high internal stresses and over-hardening of the Au dental alloy tape, it is necessary to re-intermediate the recrystallization isothermal insulation of the strips in a flow furnace at 1093 K at a flow rate of 200 mm / min in a protective atmosphere (H ₂ : N ₂ = 80: 20 ). After annealing, allow the strips to cool slowly in air to room temperature. Before further thermo-mechanical treatment, the tapes need to be cleaned, which is to rinse and brush the castings with a mixture of water and detergent and finally to dry with compressed air. This is followed by the flat rolling of the strips zd = 2.8 mm into the strips zd 1.8 mm and a width of 7 mm with 0.25 mm steps. The final transformation process is a polishing roll. It is rolled on a rolling machine having a polishing cylinder of about 120 mm diameter and having a hardness comparable to that of a carbide solid (1000 HV). This requirement must be respected at this stage of transformation in order not to cause a high roughness of the Au dental alloy during the rolling process due to insufficiently hard cylinders. The rolling process is performed in two steps d = 0.2 mm into a strip of 1.40 mm (+ 0.05 / -0) thickness and 7 mm width. After rolling, the high-Au dental alloy strips are cut using double-sided Tile Scissors. 7mm (± 0.3)> 7mm (± 0.3) * 7mm (± 0.3).

Example completed:

DENTAL ALLOY WITH HIGH Au CONTENT (77 m.% Au, 1.2 m.% Pd, 4.5 rn.% Pt, 10 m.% Ag, 6 m.% Cu, 1.3 Zn)

Description of the manufacturing process:

1. Cabinet:

a) Preliminary drawings of Au dental alloy components and preparation of pre-alloys (at least in the amount of total impurity without dirt):

- Require pre-alloys Ag / Pd, Cu / Zn

- control of weathered pre-alloys

b) weigh according to the recipe:

- control of total dentition of dental alloy components: Au, Ag, Pt, Pd, Cu, Zn

2. Smelter: use of dedicated graphite pots for dental alloys

a) Pre-fabrication of Ag / Pd pre-alloy:

- compression of the individual pre-alloy components: Pd and Ag

- casting in an induction furnace at T = 1473 K (in atmosphere Ar 5.0, flow Ar = 31 / min)

- pouring molten Ag / Pd pre-alloy into Fe mold 120mm χ lOOmm χ 15 mm. quenching in H2O

- casting cleaning (trimming, water, detergent, brush, drying - compressed air)

- weighing

b) pre-fabrication of Cu / Zn pre-alloy 66:34:

- Alloying and casting in an induction furnace at T = 1273 K (in atmosphere Ar 5.0, flow Ar = 31 / min)

- pouring molten Ms pre-alloy into Fe mold 120mm ^x lOOmm * 15 mm, quenching in H ₂ O

- casting cleaning (trimming, water, detergent, brush, drying - compressed air)

- weighing

c) casting of Au dental alloy in an induction casting furnace:

- alloying (loading of components into the furnace: Cu / Zn, Ag / Pd, Pt, Au, Pd, Ag, Cu, small spoon of charcoal) and casting in an induction furnace by manual mixing with a carbon rod at T = 1573-1623 K (in atmosphere Ar 5.0, flow Ar = 31 / min)

- pouring molten alloy into graphite mold (Φ = 16 mm)

- cooling (holding) the alloy in a graphite mold for 1-1.5 min in air, then quenching in water

- casting cleaning (trimming, water, detergent, brush, drying - compressed air)

- weighing

3. Cabinet:

- casting weighing, sorting

- casting control

4. Production preparation: plastic transformation of pre-alloys and Au dental alloys on cleaned and dry cylinders

a) preliminary transformation and cutting of Ag / Pd pre-alloy:

- profile rolling on a flat cylinder with steps of 0.5 mm to a final Π = 0.6 mm (machine AUR.0 0315)

- cut to approx 15mm * 15mm

- weighing

b) Pre-conversion and cutting of Cu / Zn pre-alloy:

- profile rolling on a flat cylinder with steps of 0.6 mm to a final U = 0.6 mm (machine AURO 0315)

- cut to approx I5mm χ I5mm

- weighing

c) Plastic transformation and cutting of Au dental alloy:

- profile rolling of bars from Φ = 16 mm into wire = 5.3 mm with steps 0.25-0.3 mm (machine ZC 0439)

- cutting wire to 500 mm length

- annealing of 5 wires together in a flow furnace at 1093 K at 200mm / min in a N2 / H2 protective atmosphere

- cooling the wire in air to T _room

- Cleaning the wire with soft curly Ms wire brush, water and detergent

- flat rolling of wire 7 = 5.3 mm into a strip of 2.8 mm thickness (± 0.2 mm) with 0.2 mm steps (AURO 0315 machine)

- insulting 5 strips together in a flow furnace at 1093 K at 200mm / min in a N ₂ / H ₂ protective atmosphere

- Cooling the air strips to T _rooms does not

- Cleaning strips with soft curly Ms wire brush, water and detergent

- flat rolling of tape with d = 2.8 mm into tape with d = 1.8 mm and W = 7 mm with 0.25 mm steps (AURO Oj »15 machine)

- polishing roll of tape with steps of 0.2 mm in thickness of 1.40 mm (+ 0,05 / -0) and width of 7 mm (machine AURO 0319)

- Tile cut 7 mm (+0,3) χ 7 mm (+0,3) ^x 1,4 mm (+ 0,05 / -0) with stamping S (machine AURO 0429)

PATENT APPLICATIONS

Claims (14)

1. The process of manufacturing dental alloys with high Au content is characterized by the fact that it consists of melting and casting, cold forming of Au molded preforms, heat treatment and cutting of Au strip into dimension-appropriate tiles. 2. The method according to the preceding claim, characterized in that the melting of the Au dental alloy is carried out by an inductive method between T = 1573 and 1623 K in a protective atmosphere Ar (at a flow of 3 l / min and a pressure of 1.03 bar). Method according to the preceding claims, characterized in that the molten Au dental alloy is cast into a 0 16 mm metal mold. The process according to the preceding claims, characterized in that the molded Au dental alloy molds in the metal molds are cooled for 1-1.5 minutes at room temperature and then extinguished in water. 5. The method according to the preceding claims, characterized in that, in the case of molded Au dental alloy preforms with 0 = 16 mm, a 1 cm long trim is to be made on the upper surface. A The method according to the preceding claims, characterized in that it is carried out by means of a profundal roll for casted preforms with 0 = 16 mm of Au dental alloy. Method according to the preceding claims, characterized in that it proceeds in steps of 0.25-0.3 mm to a wire diameter of 0 = 5.3 mm. 8. The method according to the preceding claims, characterized in that intermediate recrystallization isothermal annealing of Au dental alloy wire with 0 = 5,3 mm in a flow furnace at a rate of 200 mm / min at 1093 K and in a protective atmosphere (H) is required. ₂ : N2 = 80: 20). After annealing, allow the wires to cool slowly in air to room temperature and clean them in water and detergent with a brush. The method according to the preceding claims, characterized in that it is carried out by means of flat rolling of Au dental alloy wire with diameter 0 = 5.3 mm. 10. The method according to the preceding claims, characterized in that it proceeds in steps of 0.25 mm to a strip thickness of d = 2.8 mm. 11. The method according to the preceding claims, characterized in that another intermediate recrystallization isothermal annealing of an Au-dental alloy strip d = 2.8 mm is required in a flow furnace at a rate of 200 mm / min at a temperature of 1093 K and in a protective atmosphere (H ₂ : N2 = 80: 20). After annealing, allow the strips to cool slowly in air to room temperature and clean them in water and detergent with a brush. 12. The method according to the preceding claims, characterized in that it is carried out by polishing the Au dental alloy strip with a thickness d = 2.8 mm. 13. The method according to the preceding claims, characterized in that it proceeds in steps of 0.2 mm to a strip thickness of d = 1.4 mm. 14. The method of the preceding claims, characterized in that the Au-dental alloy strip of d-1.4 mm is to be cut into 7mmx7mmxl .4mm tiles.