WO2013126022A2

WO2013126022A2 - Metal clays sintering at low temperature

Info

Publication number: WO2013126022A2
Application number: PCT/TR2012/000167
Authority: WO
Inventors: Mehmet AYKOÇ
Original assignee: Odak Sanat Hobi Ve Kraft Sanayi Dis Ticaret Limited Sirketi
Priority date: 2012-02-22
Filing date: 2012-10-23
Publication date: 2013-08-29
Also published as: WO2013126022A3

Abstract

The invention is a metal clay comprising powders of platinum, gold, silver and other precious metals and copper, nickel, chromium, zinc and tin and other non-precious metals or powders of their alloys and a mixtures of these powders, prepared by using a binder, that sinters at low temperatures. The invented metal clay allows use of onyx, marble, silicate based stones as well as non-precious stones with irregular shapes which can be found everywhere and semiprecious and precious metals with the metal clay without losing their characteristics owing to sintering at low temperatures within a short time.

Description

Patent Specification

METAL CLAYS SINTERING AT LOW TEMPERATURE

Technical Field

The invention is related with a metal clay which is sintered and easily shaped at lower temperatures as different from the conventional applications and thus allows production of decorative articles and various works of art at lower cost.

The invention is more specifically a metal clay which can be shaped more easily at lower temperatures to produce small size works of art or master models at workshop or home environment by a number of professionals such as decorative article manufacturers, jewelries, bijouterie's, sculptures, etc.

The metal clay in question is sintered at a temperature which is lower than the melting temperature (circa 500°C) of the metal. The metal clay consists of metal powders, a binder which binds the powder particles to turn the mixture into clay, a surfactant, and some additives which prevent sticking of the clay to the hands.

Known Status of the Technique

In the existing applications, especially in the designing of master models and the production of certain ornaments and objects in jewelry, tools and equipment such as roller, dice, press, casting machine, special welding machine, etc. must be used in general. In addition to these, specialists who can use the said tools and equipment as well as various consumables such as casting plaster, casting wax, etc. have to be used. The need for the said tools and equipment, specialist staff and consumables requires a substantial financial investment in the respective business. This discourages small size designers and manufacturers to embark on the business. This high investment cost prevents the genuine designers to engage in amateurish works and leads to loss of interest of handcraft lovers in the field.

One of the conventional methods used in the production of metal objects is the use of powder metal technologies. In these applications, resin-based binders and oils are mixed with metal alloy powders, molded and shaped by press. Following the aforesaid procedures, they are treated in an oven in a reducing atmosphere consisting of 95% Nitrogen and 5% Hydrogen. In this way, a mass having a pre-determined porosity is obtained, while a saving from power, raw material and auxiliary materials is achieved. With the said mass, pieces with complex forms and various machine components such as self-lubricating bearings can be made. By this method, decorative articles, jewelries, bijouterie items and sculptures can be produced. However, the need for ovens with special atmosphere, mixers, and presses in the application of the said method requires employment of persons specialized in this field. This prevents application of the said method at a workshop or home environment economically and practically.

Another method in the technical field is the method of use of the metal clays. It is the method of use of the metal clays obtained by mixing of metal powders with a binder and made available to the user. In this method, the metal clay is molded, shaped by hand and hand tools, dried and heated in an oven at such temperature and for such period recommended by the manufacturer or on a stove or by means of a torch which delivers the required temperature to sinter it.

There are commercial products in the market in this field, but availability of such products which can be sintered at lower temperature within shorter time will ensure saving from power used for sintering and facilitate the job of the user, and besides, the possibility of using of various ancillary materials, of which structure would otherwise sustain damage when treated at high temperatures in the oven, will enrich the designs of the users. Such ancillary materials are jewelry stones made of glass, non-precious natural stones, semi-precious stones and precious stones.

Soda glass allows ingress of metal into its body at near-melting temperatures, sustains discoloration, becomes dewy and losses its sheen. For this reason, it is not possible to realize such projects designed with such glasses (due to treatment of them with the metal clay in the oven) and to obtain a product which preserves the tones envisaged by the project.

While the use of non-previous natural stones together with metal clays promises broad capabilities to the designers, most of such stones cannot withstand high temperatures. They either lose their crystal water or are decomposed. Similarly, when precious and semi-precious stones are treated together with metal clays available commercially in the market in the oven, many of these stones crack along the veins within their body and loss their crystal water, becoming matt and discolored. This invention of us permits use of onyx, marble and silicate origin stones as well as many non-precious stones with unknown structure which are available everywhere, together with the metal clays. Achievement of sintering of the metal clay together with the said metals and ores at lower temperatures will ensure a substantial saving from energy used in the production of articles made of such clays as well as allow achievement of product quality and obtaining of products with differentiated appearance and value. In this way, jewelry stones made of glass, non-precious natural stones, and semiprecious and precious stones as ancillary materials can be used comfortably together with the metal clay. The patent US5376328 mentions a precious metal product obtained by sintering of a precious metal powder into a form in the solid phase. To produce the said precious metal product, a mixture containing the precious metal powder and a binder which evaporates when sintered is shaped into a pre-determined molded object and then the molded item is sintered. The most preferred moldable mixture contains 50-90% precious metal powder, 0.8-8% cellulose binder soluble in water and 0.08-3% surfactant, by weight. The precious metal preferably contains gold powder, silver or copper alloys and the gold is obtained by reduction by dipping.

The patent US5702501 mentions a metal clay mixture for a product made of precious metal shaped by mold and a method for production of it. In order to obtain a molded product containing precious metal, the mixture actually contains powder of a precious metal and starch as well as organic resin as a water soluble organic binder, and water. Content of the starch and water soluble resin in the total organic binder and the precious metal power is 0.02- 3% by weight.

The patent US6290744 mentions sintering of noble metals and a method related with it. The mixture being the subject of the invention contains pure noble metal powders and noble metal alloy powders, a cellulose type resin soluble in water at the rate of 0.022-3% by weight, starch at the rate of 0.02-3% by weight and reticular macromolecular material at the rate of 0-05% by weight.

The patent US6572670 mentions colored metal clays and colored metals. For shaping of the metal objects, the mixture contains a first particle containing a jewelry metal and a second particle containing a refractory metal. It is stated that the mixture allows use of a very broad color spectrum for the preparation of metal jewelry.

The patent US6840979 mentions a clay mixture for shaping of noble metals and a method for sintering of the noble metal. The mixture being the subject of the invention contains as a main constituent a powder with a mean radius of 2.2-3.0 mum at the rate of 30-70% by weight and a powder with a mean radius of 5-20 mum at the rate of 70-30% by weight. The patent US7081149 mentions a silver clay containing silver powder. The said invention particularly claims a silver clay which can be obtained by sintering at lower temperatures. The silver powder for the silver clay mentioned here contains fine silver powders with a particle radius equal to or smaller than 2 at the rate of 15-50%) by weight. The rest of the mixture consists of particles with a radius larger than 2 mum and smaller than or equal to 100 mum.

Consequently, the need for a metal clay which can be sintered at lower temperatures in mixture with non-precious, semi-precious or precious metals, stones or various materials without any harm to the characteristics of such materials and inadequacy of existing solutions in this field has compelled us to make a development.

Purpose of the Invention

Purpose of the invention is to obtain a metal clay which can be sintered at lower temperatures in mixture with platinum, gold, silver and other precious metals and copper, nickel, chrome, zinc, tin and other non-precious metals or powder of alloys of such metals and a binder that binds the mixture of such powders without loss of characteristics of such materials.

Another purpose of the invention is to obtain a binder which will hold the metal powders in perfect plastic consistency which does not stick to hand and tools and a metal clay which will become workable by combining of the binder with various metal powders and sintering at lower temperatures without loss of characteristics of the precious and semi-precious metals or materials contained by it.

Brief Description of the Figures

Figure 1 shows the particle variety of the metal powder mixture being the subject of the invention.

Figure 1 (1) shows the amorphous metal particles

Figure 1 (2) shows the spherical/semi-spherical metal particles

Figure 2(a), (b) and (c) shows the steps of making of a necklace pendants with the metal clay being the subject of the invention.

Table 1 shows the test results.

Detailed Description of the Invention

Various professionals such as sculptors, jewelry and bijouterie makers, etc. who design and create ornaments or art objects which are visually impressive and at the same time resistant to environmental conditions shape metal clays to make an imaginary object real. However, one of the greatest disadvantages of this method is the need for very high temperatures for sintering of the metal clay, because soda glasses are added to the metal clay to obtain more original and luminous products in desired colors. However, any ancillary materials used to enrich the visual aspects of the design lose their characteristics at high temperatures. For this reason, product in the targeted quality cannot be obtained.

Any products suitable for sintering at lower temperatures within shorter times will ensure saving from energy required for sintering and facilitate the job of the user on the one hand and any ancillary materials which would otherwise lose their characteristics at high temperatures can be used in the metal clay safely and add richness to the designs of the users. Such ancillary materials are shaped jewelry stones made of glass, non-precious natural stones, semi-precious stones and precious stones.

Another advantage is that with reduced temperature, the metal clay can be processed at a small workshop and even at a home environment. In this way, the need for a number of additional machines, equipment and specialist staff required by the previous technique will be eliminated.

So, the present invention is a metal clay which offers the foreseen advantages by reducing the sintering temperature and shortening the sintering period as necessary to eliminate the said disadvantages.

Experiments showed that the characteristics of the metal particles used in the metal clay in relation with their sizes and shapes directly affected the sintering temperature and period. Magnitude of the ratio of the total surface areas (SA) and total edge lengths (EL) of the metal particles to the particle volume (PV) affects the sintering temperature reversely. In other words, how much the SA/PV and EL/PV increases, so much the sintering temperature decreases. (Considering that the metal particle is a three dimensional object, the said surface area is the total sum of all surface areas of the particle and the said edge length is the total sum of the edge lengths of the surfaces making up the object.)

This finding follows that instead of using spherical metal particles in the former technique, using of metal particles with amorphous surfaces as well reduces the sintering temperature. Amorphous particles have irregular shapes and their SA and EL values are higher compared with the spherical particles.

A sample application of the experiments done can be presented by using pure silver (Ag) powder. Here, we used silver powders divided into three classes in terms of their particle sizes and shapes. The silver powder in the first class consists of amorphous particles with particle size between 0.01 and 300 microns. The silver powders in the second and third classes have spherical/semi-spherical particles with particle sizes between 0.1 and 20 microns and between 0.1 - 52 microns, respectively. The metal particles in the first class offer sintering at lower temperature, while the others were used as filler to create an effect that would reduce the diminishing. In addition, a binder mixture was used to keep the particles in the said three classes together in clay consistency. As a result of the experiment, it was found that the sintering temperature of the metal clay obtained which is the subject of this invention could be 500°C lower than the melting temperature of the metal used. The binder is a dilution of starches, cellulose derivatives, natural and synthetic gums, polymers, resins, surfactants, one or more oils in water and other solvents.

So, sintering of the metal clay being the subject of the invention at a lower temperature within a shorter time allows use of semi-precious and precious stones, as well as onyx, marble, silicate based stones and even non-precious stones with irregular shapes which are found everywhere with the metal clay without losing their characteristics. Consequently, possibility of using of the said stones and metals that can melt at lower temperatures with the metal clay being the subject of the invention owing to sintering of the metal clay at lower temperatures within shorter times provides a low cost solution on the one hand and allows creation of more original art objects with much broader design capabilities.

In the particle distribution shown in Figure 1, how much larger is the total surface areas and edge lengths of the amorphous particles with irregular shapes (2), so much lower can be the sintering temperature of the resulting metal clay. Ratio of the spherical/semi-spherical metal particles (3) to the total metal powder mixture (1) serves to minimization of diminishing of the desired metal clay. The said amorphous metal particles (2) account for 2 - 100% of the total metal powder mixture (1). The ratio of the said metal powder mixture to the metal clay mixture (1) is 10 - 96%. The binder accounts for 2 - 90% of the metal clay mixture. The size of the said spherical and/or semi-spherical metal particles (3) is 0.1 - 100 microns. The size of the said amorphous metal particles (2) is 0.01 - 300 microns.

In the design of necklace pendant, the first stage is to slab the metal clay by means of a roller and cut it into oval as shown in Figure 2a. In the second stage, the center of the slab is cut and removed as shown in Figure 2b. Figure 2c shows placement of a pebble stone onto the metal clay and encircling of it with a strand made of metal clay. The object so obtained is heated to sinter at appropriate temperature, so that sintering is achieved without discoloration or loss of luminosity of the pebble stone and at the end an object consisting of the pebble stone + metal is obtained.

Claims

1. The invention is a metal clay mixture which sinters at a low temperature and/or within a short time, comprising a mixture of metal powders in amorphous metal particles and a binder which holds the said particles together in a clay consistency.

2. As per the Claim 1, a metal clay comprising the said metal powders at the rate of 10 - 96%, while the binder at the rate of 2 - 90%, of the whole mixture (2).

3. As per the Claim 1, a metal clay comprising amorphous metal particles (2) of the said metal powder or a mixture of amorphous metal particles and spherical/semi-spherical metal particles (3).

4. As per the Claim 1, a metal clay comprising the said binder in a group selected from dilutions or dispersions of cellulose derivatives, acrylates, starches, oils, resins, polymers and similar generally organic materials in water or other solvents.

5. As per the Claim 2, a metal powder mixture (1) comprising the said amorphous metal particles (2) representing 2 - 100% of the total metal powder mixture (1).

6. As per the Claim 2, a metal powder mixture comprising the said metal powder being the powder of a precious or non-precious metal in pure state.

7. As per the Claim 2, a metal powder mixture comprising the said metal powder being the powder of an alloy of more than one metal.

8. As per the Claim 2, a metal powder mixture comprising the said metal powder being a mixture of powders of more than one metals in pure state.

9. As per the Claim 2, a metal powder mixture comprising the said metal powder being a mixture of metal powders in pure state and powders of metal alloys.

10. As per the Claim 2, a metal powder mixture comprising the said metal powder being a mixture of powders of metal alloys.

11. As per the Claims 1 and 9, a metal clay comprising the said spherical and/or semi- spherical metal particles (3) in size of 0.1 - 100 microns.

12. As per the Claims 1 and 9, a metal clay comprising the said amorphous metal particles (2) in size of 0.01 - 300 microns.

13. As per the Claim 4, a binder comprising solid substance at the rate of 0.2 - 0.99% and liquid substance at the rate of 75% - 99.8%.