SU1614884A1 - Self-hardening sand for making moulds and cores when casting magnesium alloys - Google Patents

Abstract

This invention relates to a foundry, in particular, to compositions of self-hardening mixtures for the manufacture of molds and cores in the casting of magnesium alloys. The purpose of the invention is to prevent the oxidizing effect of the mixture on the magnesium alloy and the tendency of the mixture to form gas defects in the castings of magnesium alloys. The composition of the mixture, wt.%: Powdered material based on calcined magnesium oxide, treated with surfactants anionic or non-ionic class 1.0 ... 2.5, phosphoric acid 2.0 ... 3.5, water 0.25 ... 0.30, boric acid 0.5 ... 1.5, sulfur 0.5 ... 1.0, sodium fluoride or cryolite 0.5 ... 2.5, refractory material based on silica, the rest. The implementation of the invention prevents the oxidizing effect of the mixture on the magnesium alloy (and thus avoiding the formation of oxidizing burns on the surface of the castings), and also prevents the formation of gas defects in the castings without applying staining or dusting of the forms and rods with protective additives. 2 tab.

Description

The invention relates to foundry, namely, to compositions of self-hardening (cold hardening) mixtures based on inorganic binders for the manufacture of molds and cores during the casting of magnesium alloys.

The purpose of the invention is to prevent the oxidizing effect of the mixture on the magnesium alloy and the tendency of the mixture to form gas defects in the castings of magnesium alloys.

SUMMARY OF THE INVENTION The essence of the invention is the additional addition of boric acid, sulfur and sodium fluoride or cryolite to the mixture.

Protection of mastic alloys at different stages of mold casting and metal crystallization is carried out by creating a protective atmosphere that prevents the metal from contacting with oxygen of the air and creating protective films on the crystallization metal.

The proposed composition provides a protective atmosphere, the most durable films and obtaining defect-free castings at all temperatures cast in the temperature range 700-770 ° C. and without the use of protective fumes and paints.

For experimental verification of the proposed composition, six compositions of self-hardening mixtures are prepared (Table 1). The preparation of the mixtures is carried out in a paddle batch mixer. Binder, additives and orthophosphoric acid are introduced into the filler (quartz sand) with mixing.

aa

When assembling molds and cores for pouring dust and protective paints, they are not used.

The molds of the proposed self-hardening mixture are filled with typical melts of ML 5 alloy (of various sizes with a pouring temperature of 720-760 ° C).

The data are given in Table 2.

The use of the invention prevents the oxidizing effect of the mixture on the magnesium alloy and thereby avoiding the formation of oxidizing burns on the surface of the castings, as well as eliminating the formation of defects in the castings without using staining or dusting of the forms and rods with protective additives.

Formulas of the Invention A self-hardening mixture for the manufacture of molds and cores for the casting of magnesium alloys, including a refractory material based on silica, a powdery material based on annealed magnesia, treated with surfactants ano-

an active or non-ionic class, orthophosphoric acid and water, characterized in that, in order to prevent the oxidizing effect of the mixture on the magnesium alloy and the tendency of the mixture to form gas defects in magnesium alloy castings, the mixture additionally contains boric acid, sulfur and fluoride sodium or cryolite in the following ratio of ingredients, May,%: Powdered material based on calcined magnesium oxide, treated with surfactants of anionic or non-ionic class1.0-2.5

Orthophosphorus

acid2.0-3.5

Water 0,25-0,30

Borna acid 0,5 -1,5

Sulfur-0.5-1.0

Sodium fluoride

or cryolite 0.5-2.5

Silica-based refractory material Else

Table 1

table 2

Continued table. 2

Claims (1)

Claim Self-hardening mixture for the manufacturer? molds and rods for casting magnesium alloys, including silica-based refractory material, powdered material based on calcined magnesium oxide treated with an anionic or nonionic surfactant class, phosphoric acid and water, characterized in that, in order to prevent the oxidizing effect of the mixture on magnesium alloy and the propensity of the mixture to form gas defects in castings of magnesium alloys, the mixture additionally contains boric acid, sulfur and sodium fluoride or cryolite in the following ratio and ents, May. %: Powdered material based on calcined magnesium oxide treated with anionic surfactant or nonionic class 1.0-2.5 Phosphoric acid 2.0-3.5 Water 0.25-0.30 Boric acid 0.5 -1.5 Sulfur -0.5-1.0 Sodium fluoride or cryolite 0.5-2.5 Refractory material silica based Rest Table 1 Components Content Components, May. % 1 2 3 4 5 6 Quartz sand 95.25 95.25 91.5 91.5 88.7 88.7 Calcined processed magnesium oxide Surfactant 1,0 1,0 2.0 2.0 2,5 2,5 Technical phosphoric acid 2.0 2.0 3.0 3.0 3,5 3.5 Water 0.25 0.25 0.3 0.3 0.3 0.3 Sulfur 0.5 0.5 0.7 0.7 1,0 1.0 Boric acid 0.5 0.5 1,0. 1,0 1.5 1.5 Fluoride triy 0.5 - 1,5 - 2,5 - Cryolite - 0.5 - 1.5 - 2,5 table 2 Parameters Indicators of the properties of mixtures and the quality of castings 1 2 -3 4 5 6 The curing time of the mixture, min Shedding · rods,% 18-20 Less than 0.2 18-20 less than 0.2 10-15. 0.3 10-15 0.3 13-15 0.5 13-15 0.5 Continuation of the table. 2 Parameters Indicators of the properties of mixtures and the quality of castings 1 I · 2 · | 3 i 4 J 5 I 6 Quality of Suitable casting; no oxidative burning; gas defects in section khvos.ti castings no castings are observed Compiled by S. Teplyakov Editor I. Derbak Tehred M. Morgenthal Corrector L. Pilipenko Order 3946 Circulation 629 Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.