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INVENTION
Patent of the Russian Federation RU2105630
MIXTURE FOR MANUFACTURE OF FOUNDRY FORMS BY FLOATING MODELS
IN THE JEWELERY INDUSTRY
Applicant's name: Kondakov Yevgeny Nikolaevich
The name of the inventor: Kondakov Evgeniy Nikolaevich
The name of the patent holder: Kondakov Evgeniy Nikolaevich
Address for correspondence:
Date of commencement of the patent: 1993.05.12
Usage: in the foundry, mainly in the jewelry industry , in the manufacture of molds for investment models from noble models of precious and non-ferrous metals and alloys .
Essence: a mixture containing gypsum and water, as a siliceous material and a phosphorus-containing stabilizing additive, respectively contains calcined quartzite and dihydrogen phosphate with the following ratio of components, weight% : calcined quartzite 52.0 - 57.0 , gypsum 15.0 - 20.0 , Dihydrogenphosphate 0.0 - 2.2 , water - the rest.
DESCRIPTION OF THE INVENTION
The invention relates to foundry production, specifically to mixtures for the manufacture of molds for investment models, mainly in the manufacture of castings from noble and non-ferrous metals and their alloys, and is intended for industrial use in jewelry production, in precision instrumentation and engineering, and in local industry.
There are known import mixes for making foundry molds for the K-90 , Satinkast and Supercast models that contain fine-dispersed powders of natural cristobalite and high-strength gypsum [1] in neither the former USSR nor in Russia There is no natural cristobalite. Import supplies of any of these mixtures require exorbitant foreign exchange costs.
Domestic molding dinaso-gypsum mixtures are known , for example, the dental prosthesis mixture "Silauur-3b" , containing in the closed state, in weight. Dinas 53-57 , gypsum 14-18 , and water 27-30 [2] The mixture hardens too quickly for the production of jewelry and other products that are not associated with dental prosthetics ( 3-7 min ). In addition, "Silura -36" has an increased viscosity.
A mixture of DGA containing in weight is also known.
- Dinas 55.00-72.0
- Gypsum 2,5-14,5
- Technological additives:
Nitric acid 1.5-2.5
Oxalic acid 0.035-0.070 [3]
A significant disadvantage of the DGA mixture is the instability of the solidification start time, which varies jumpwise from one delivered batch to the other in a wide range from 3 to 90 minutes (with an allowable range of 12-30 minutes ). As a result, the average level of rejects of finished castings reached 40% and the mixture of DGA is currently not used in production.
The closest to the proposed for significant features and nature of industrial application is the mixture widely used in jewelry production for making casting molds for investment models, including gypsum, water and a stabilizing technological additive in the form of orthophosphoric acid, with the following content of components in weight.
- Dinas 60.0-64.0
- Gypsum 10.0-12.0
- Orthophosphoric acid 0.03-1.00
- Water Other [4]
This mixture, due to the use of a stabilizing technological additive in the form of orthophosphoric acid, provides a stable start of solidification of the mixture within 12-30 min and allowed to reduce the average level of rejects of finished castings to 7%
At the same time, the use of the prototype mixture in jewelry production has become much more complicated in recent years and has become economically and technologically inexpedient for a number of reasons:
- The source of the supply of dinas has long been the Krasnoarmeysky Combine, which, after the collapse of the USSR, was under the jurisdiction of Ukraine, which significantly increased the price of the dinas; Only for JSC "Russian gems" the purchase of a dinas at these prices translates into a figure of 47.5 million rubles. in year;
- At the same time, the quality of the supplied dinas decreased sharply-the ratio of its components to tridimide, cristobalite, and quartz.
- It has become far beyond the limits set by the technical conditions for the supply; Goes beyond these limits and the amount of harmful impurities of iron, aluminum and calcium in the supplied dinas;
- The above deviations have a negative effect on the stability of the physicochemical and technological properties of the mixture, on the quality of the casting molds and the finished castings.
The purpose of the invention was the development of a mixture for the production of casting molds for investment models having stable physicochemical and technological characteristics and ensuring a reduction in the cost of manufacturing it.
The goal is achieved due to the fact that the mixture for making casting molds for investment models of jewelry and similar products, containing gypsum and water in the closed state, contains calcined quartzite as a heat-resistant filler, and as a stabilizing technological additive, dihydrogen phosphate at the following ratio of components to weight .
- Burnt quartzite 52,0-57,0
- Gypsum 15.0-20.0
- Dihydrogen phosphate 0.05-2.0
- Water Other
Fired quartzite, in contrast to quartz sand used in Krasnoarmeysk for the production of dinas, has a monolith structure and has a composition stable in terms of the component ratio, which includes 20% cristobalite (the rest is crystalline and fused silica) and a very small amount of foreign impurities.
The stability of calcined quartzite in composition ensures the consistency of the composition of the molding mixture and the stability of its properties, which is necessary for the high quality of the foundry molds and the resulting finished castings. Deliveries of calcined quartzite are not associated with organizational and economic difficulties, since quartzite deposits in the monolith and enterprises for its extraction and processing are located in Russia, for example, in the Yekaterinburg region. The cost of the mixture with calcined quartzite is almost half that of the mixture on the Ukrainian dinas. The replacement of the technological additive in the form of orthophosphoric acid with dihydrogen phosphate simplifies the technology for making the mixture, since it is much easier to introduce small amounts of a powder component into the mixture than liquid acid.
Properties and advantages of the proposed mixture, as well as its industrial applicability and compliance with the established requirements of the following examples and tables. Table No. 1 illustrates the properties and cost of mixtures for the production of casting molds on investment models, depending on the composition and the ratio of the components. Table No. 2 contains the admissible values of the main parameters of the mixtures.
The process of making a molding mixture using calcined quartzite and dihydrogen phosphate is clear from the following example: after a five-hour calcination at a temperature of 1400 ° C , quartzite is crushed in crushers and ball mills to a powder state with a dispersion not larger than 0.08 mm ; A five-hour mixing of quartzite, gypsum and dihydrogenphosphate powders in a percentage ratio: quartzite 75% gypsum 23% dihydrogen phosphate 2% Thus, the powder part of the molding mixture is made, which is packed in polyethylene bags and cardboard drums weighing 40 kg and is supplied to consumers who Use the necessary amount of water to the powder part.
Example 1
Casting jewelry brooches, weighing 7 g . (Products from gold 585 o ).
For these castings of a large mass of gold, the molding mixture must have an increased strength, which is achieved by reducing the mass of water and the increased content of gypsum. Take a molding mixture with the following ratio of components in weight.
Quartzite calcined 52% gypsum 20 , dihydrogen phosphate 2 , water 26 (According to Table 1 , composition No. 4 ). Marriage rate of 5.6%
Example 2
Casting a delicate jewelry jewelry ring made of silver 925 o , weighing 2.5 grams .
For such jewelry, the composition of the molding mixture is selected, having increased fluidity, which is provided by a relatively high content of dihydrogen phosphate and water. In connection with this condition, the composition No. 6 of Table No. 1 in weight is used.
- Calcined quartzite 53.5
- Gypsum 18,0
- Dihydrogen phosphate 1.0
- Water 27.5
The correct choice of the composition of the mixture ensured a rather low level of rejection of ready castings 4.1%
Comparison of the data of Tables N 1 and N 2 shows that the compositions according to the invention have improved physicomechanical and technological properties and economic characteristics in comparison with the compositions of the prototype mixture, and the output of the components content beyond the limits specified by the set of essential characteristics leads to deterioration of properties Mixture and to increase the level of rejection of finished castings of jewelry and similar products.
INFORMATION SOURCES
Gutov L.A. Casting on the melted gold and silver alloys models. L. Mashinostroenie, 1974, p. 54-65;
Germer M.M. And Batovsky VM Fundamentals of Materials Science in Dentistry. M. Medicine, 1969, p.55;
Author's certificate of the USSR N 519272, cl. B 22 C 9/04, 1976;
Author's certificate of the USSR N 904869, cl. B 22 C 1/16, 1980.
CLAIM
Mixture for the production of casting molds for investment models for jewelry, comprising gypsum, a refractory silica-containing material, a phosphorus-containing stabilizing processing aid and water, characterized in that it contains calcined quartzite as the refractory siliceous material, and as the phosphorus-containing stabilizing technological additive, dihydrogen phosphate Component ratio, wt.
- Burnt quartzite 52,0-57,0
- Gypsum 15.0-20.0
- Dihydrogen phosphate 0.05-2.0
- Water Other
print version
Date of publication 16.11.2006гг
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