SU531624A1 - Nonstick coating for casting molds and cores - Google Patents

Description

(54) ANTI-GRUNT COATING FOR CASTING FORMS AND RODS

The invention of the ognosigs to the field of liginal production.

The composition of the nonstick coil for the foundry is known: molds and cores, containing a refractory filler (dunite) and an organic binder, 1

However, gas shells and subcortical porosity are formed due to the high gas content in castings obtained in forms with a covered surface.

Closest to the essence and the result achieved, as described by Texiin4ecKOE, is a coating containing a refractory filler, an aqueous solution of magnesium phosphate and bentonite,

However, this coating has low sedimentation stability and does not provide a clean surface from molts.

The aim of the invention is to increase the sedimentation stability of the coating and to improve the surface cleanliness of the steel castings. For this, the proposed nonstick coating additionally contains magnesium oxide (Md-O) or substances containing at least 9O% magnesium oxide (for example, magnesite), and cryolite, in the following ratio of ingredients, wt%:

Aqueous solution of magnesium phosphate 4O-5O Magnesium oxide 4-5

Cryolit 0.7 5-1,

Refractory filler Else.

An aqueous solution of magnesium phosphate is prepared by introducing powdered mineral brucite Mg- (OH) in 50% orthophosphoric acid (H PO) with continuous stirring with subsequent dilution with technical water to a density of 125 - 1.35 g / cm. Dry components (refractory filler, cryolite) are used in the form of powders supplied by the industry with the voice of CM TU O 5-2 9-67, TU 48-01-53-71, GOST 9077-59, GOST 10561-69, As a component containing MgO, magnesite powder is used, obtained by grinding the waste magnesite brick (GOST 4689-63) and sifting them through a sieve with a cell O, 16 mm. All components have a heat of 20 ° C. Prepare a non-stick coating as follows. 5000 cm of an aqueous solution of magnesium phosphate with a density of 1.25 g / cm are poured into a stainless steel tank, then, with continuous stirring, refractory filler and cryolite are introduced for 20 minutes. The magnesite powder was introduced immediately before coating the mold with it being stirred in a liquid state for 5 minutes. Vs

Ingredient

An aqueous solution of magnesium phosphate

Oxy magnesium Criolig

Filler (zircon) Time hardening Coefficient Composition of the devi, min sedimentation of aeration, cm 1,95 10 2,15 102, 05 10

Table 1

Content, weight,%

D. I

30 354045

50 30

4.5 5.0

5.5 3.5 1.5 2.0 2.5 0.5

Claims (2)

Table 2. A weld coating is applied on the surface of the casting molds and cores in two layers. The first layer of the coating is dried in air for 30 minutes, the second is in an oven for 2 hours. The molds are loaded into a cold furnace, then the temperature of the furnace is raised to ZZO ° C. B for 2 hours and 3 hours is held. In tab. Table 1 shows the compositions 1-6 of the nonstick coating, in table. 2 - their technological properties. Icr n Evaluation of the cast surface profile When applying Neravnesti on the net over the surface Cast with a brush Pure without a burn Pure without a burn Oxlo 8O% clean surface Observed About 70% of the pure namshi surface When applying Irregularity of tacking the brush 3, the best is the composition 3 When using electrocorundum and quartz sand as a filler, the optimal compositions of nonstick coatings contain, in weight,% 1 and 0.75, cryolite 5 and 4 magnesium oxide, respectively. The implementation of the invention will lead to a reduction in the labor intensity of casting production by eliminating cleaning operations. Claims of the Invention Non-stick coating for casting molds and cores, used mainly in the preparation of steel castings, including a refractory filler and an aqueous 53 24 6 solution of magnesium phosphate, which is so that, in order to increase the sedimentation stability of the coating and surface purity of steel castings, it additionally contains magnesium oxide and cryolite in the following ratio of ingredients, weight,%: Aqueous solution of magnesium phosphate 40-50 Magnesium oxide 4-5 Cryolite 0.75-1.5 Refractory filler Others. Sources of information taken into account in the examination: 1. Auth. St. USSR № 394153, M, Cl. In 22 SZ / OO, 1970. 2. Auth. St. USSR № 354933, M. Kl. B 22 C 3/00, 1969.