SU732068A1 - Mix for preparing gasting molds preferably for use - Google Patents

Description

(54) MIXTURES FOR THE MANUFACTURE OF CASTING FORMS MOSTLY MULTIPLE The invention relates to foundry, in particular, to mixtures used to make cast-in-position casting molds. Nanbs its closest to the technical essence and the achieved result is a caster mixture for the manufacture of foundry, mainly reusable, containing ground graphite, refractory clay, corundum, magnesitocromite and orthophosphorous acid | l. The known mixture is characterized by insufficient high strength and high thermal conductivity, which leads to the squeezing of thin-walled cast iron castings, as well as insufficient accuracy of the resulting casting, resulting in increased allowances for machining of castings. The purpose of the invention is to increase the strength in the wet state and after firing, to prevent the atbel of thin-walled cast-iron castings and to increase the accuracy of the casting. USES The achievement of the delivered mixture for mold casting, mainly multiple use, including graphite, refractory clay, corundum, magnesitochromite, orthophosphoric acid, additionally contains chamotte in the following ratio of ingredients, vol. %; Refractory clay12-18 Corundum 9-11 Magnesitechromite 5-7 Ortsphosphoric acid 14-16 Ground chamotte 8-28 Graphite Else. When the content of ground chamotte falls below the lower limit, the strength of the mold decreases and the accuracy of castings deteriorates, and when it is above the upper limit, the heat resistance of the mixture decreases and the casting decreases. service life of the form. The formation of strength in the raw state is determined by the reactions between phosphoric acid, 373 of magnesium oxide in the composition of chromium magnesite and fine particles of clay. It is preferable to use orthophosphoric acid with a density of 1.45-1.55 g / C, since at a lower density, the mixture becomes overwetted and sticking to the equipment, which reduces the surface quality of the forms, and at higher density, the viscosity of the mixture increases, its flowability decreases and deteriorates the quality of the imprint of the model during shaping. An increase in the content of chromomagnesite above the stipulated limit leads to a reduction in the survivability of the mixture, which worsens the conditions of qualitative shaping. An increase in the clay content above the stipulated limit leads to the formation of cracks in the mold during shrinkage of the clay, and a decrease in its content below the lower limit leads to a loss of strength of the mixture in its wet state. Fireclay

Ingredients and properties

Contents of ingredients, vol.%: And indicators of properties for mixtures №№. 68A, given that it has a linear expansion coefficient close to graphite. This determines the absence of higher thermal stresses when the mold is cast at the contact points of the chamotte grains and graphite particles. The cost of fireclay is low and it is easily accessible. By varying the ratio between graphite and chamotte within conditional limits, one can adjust the properties of a half-molded mold. With a relative increase in the content of graphite, the thermal conductivity and heat resistance of the mold increase, however, its strength characteristics decrease both in the raw state and after calcination and the accuracy of the resulting iron castings decreases somewhat. After packing, the forms from the proposed mixture are colored and dried at 300-400 0 8-12 hours. The table shows the compositions of the proposed mixtures and their basic properties.

16 18 181412

11 10 9 911

75667

Compressive strength before firing, kgf / cm

Compressive strength after firing, kgf / cm

Heat resistance,%

4t

according to the relative strength drop for 1 heat changes;

The known mixture provides the following indicators: Compressive strength, kgf / cm before firing 3.6-4.2

after firing, ЗО2-ЗЗЗ

Heat resistance,.% 0.8-1.12

8.5 10.4 11.3 7.2 8.5

416 37O 377 362 32O 1.71.0 1.41.10.9

Claims (1)

From a comparison of the properties of the proposed mixture and the known one, it follows that we propose 1 mixture that increases the strength in the raw state by about 2 times and in the burnt condition - by 10-2 5%. This contributes to the reduction of defects in the form of breakage, chipping and cracking, to obtain a higher quality model imprint and, as a result, to improve the accuracy of casting and reduce the allowances for machining by 25-30%. The coefficient of thermal diffusivity of the mixture according to the known is (2.0-2.2) 10, and in the proposed mixture it is 2.5-3 times lower. Due to this, it is possible to obtain thin-walled iron castings without chill, with a stable structure, accurate dimensions and good surface quality. The heat resistance of the proposed mixture is 10-15% lower than that known, however, saving metal and reducing casting processing costs not only compensate for losses caused by reduced mold durability, but also cover them, which reduces the cost of 1 ton of iron castings by about 2O The invention of the mixture for the manufacture of casting molds, mainly reusable, including graphite, refractory clay, corundum, Gedesitrohromite, orthophosphoric acid, is one that, in order to increase the strength of the mixture s in the cf state and after firing, preventing the chipping of thin-walled iron castings and improving the accuracy of the casting,. It additionally contains ground chamotte in the following ratio of ingredients, vol.%: 12-18 Refractory clay 9-11 Corundum 5-7 Magnesite-chromite 14-16 Orthophosphoric acid 8-28 Ground chamotte Rest Graphite Sources of information taken into account during examination 1 USSR Author's Certificate in Application No. 2181746 / О2, cl. B 22 C 1/18, 1975. /