SU662236A1 - Ceramic composition for making moulds and cores - Google Patents

Description

(54) CERAMIC MIXTURE FOR THE MANUFACTURE OF FORMS AND STEM

The invention relates to a foundry, in particular, to compositions of mixtures used to obtain ceramic and metal shell with a ceramic coating forms, mainly by constant models, as well as rods.

Blends are known in which marshalite, quartz sand, hydrolyzed ethyl silicate, aqueous alkali solution are introduced in various combinations 1, 2, 3.

The main disadvantages of the known mixtures are low gas permeability before and after calcination. Furnace calcination greatly lengthens the technological cycle of making molds and cores.

Closest to the described invention to the technical essence and the achieved effect is a mixture of the following composition 4, wt.%:

Marchalit55,6

Quartz sand 16,8

Hydrolyzed

ethyl silicate26,0

15% aqueous solution

alkalis1,6

The mixture has the following characteristics: compressive strength of 16 kg / cm; tensile strength at stretching 2.5 kg / cm, gas permeability after free burning 30;

gas permeability after calcination for at least 1 h in a furnace 40.

Known mixture has a low gas permeability after the free-burning part of the volatile substances. As a consequence, ceramic and metal-coated with ceramic coating forms and rods made from this mixture are baked in an oven at 850-950 ° C for complete removal. volatile substances from the mixture. However, after high temperature

calcining in a furnace known mixture has a low gas permeability.

The long-term calcination of ceramic and metal-shell molds and cores in a furnace significantly lengthens the technological cycle of casting, and for metal-shell molds it further reduces the durability of the metal sheath and increases its wear. To reduce wear of the metal sheath, calcining of the ceramic coating of metal-shell molds with portable burners is used, however, the calcining cycle at the same time lengthens by 8-10 times as compared to calcination in a furnace. The aim of the invention is to increase the gas permeability of the forms and rods and reduce the time to manufacture them. This goal is achieved by the fact that the known mixture containing marshallite, quartz sand, ethyl silicate and a 15 ° / aqueous alkali solution, additionally contains sovelit at the following ratio of components, wt.%; Sovelit 0.25-2.5 Ethyl silicate 22.0-26.5 15 / o-water. 1.15-1.55 alkali solution 17.0-20.6 Quartz sand Else: Marshalite GOST 6788-74 is applied to the so-called thermal insulation products. Co-efficient products are intended for thermal insulation of industrial installations, equipment and pipelines at a temperature of insulated surfaces up to 500 ° C. Depending on the bulk density, sovelite products are subdivided into brands 350 and 400. The cost of 1 meter of brand 400–30 rubles. , ps -, - -.:- Name of the component Mixture number 1

Hydrolyzed

24.5

24.5 24.5 ethyl silicate

15% water

1,31,31,3 alkali solution

Table 1

24,524,524,5

1,31,31,3 Death Mix No. 2№ 3 Mixtures are given in table. 1, and their physico-mechanical properties in table. 2. As can be seen from Table 2, the gas permeability values of the mixture increase, and the limits of compressive and tensile strength decrease slightly depending on the content of sovelite compared with the same values of known composition. The optimal addition of sovelit is within 0.25-2.5 wt.%, And with a further increase in its amount, the strength properties of the mixture decrease significantly, and with a decrease, the gas permeability decreases. Higher gas permeability of the mixture allows to reduce the duration of calcination in the furnace, 2 times and the duration of calcination, burners 4 times. For example, the time for calcining molds and cores from a known mixture for castings weighing 0.5 tons with burners is 4-5 shifts, in a furnace 4-5 hours. There is 1 shift, in some 2 hours. In addition, an increase in the gas permeability of the molds and cores improves the quality of castings, reducing the number of defects in gas vents. The composition of the mixture Mixture Mixture Mixture number 4№ 5№ 6

Claims (4)

1. Certificate of Certificate No. 301212, cl. At 22 C 9/04, 07/16/68. 2.Patent of France No. 2070366 ,, class. B 22 C 1/00, 1971. 3. "Foundry production, No. 5, 1973, p. 40-41. 4. Collector, Progressive Methods for the Manufacture of Casting Molds, Chel Binsk, 1973, p. 88