SU733847A1 - Self-drying pickup preventing paint for casting moulds and cores - Google Patents

Description

(54) SELF-HANDLING PAINTING PAINT FOR CASTING RODS The invention relates to the field of foundry, and to the composition of the self-rising anti-stick. 1pasok for casting cores and molds. The compositions of self-drying anti-stick paints are known, including a refractory filler and hydrolyzed ethyl silicate l. However, when these paints are used for large steel castings with a casting time (} over 60 seconds, the paint cracks and peels off in the upper parts of the mold and forms due to this fact on the surface of the castings. The composition of self-hardening nonstick paint, including hydrolyzed ethyl silicate, is known - 6-12% silicon dioxide and fluorite additive 2. Limit to the content of dioxide of the cream or ethyl silicate in the application of fluorite eliminate the raster ": nodding of paint and FORM. Increase its sediment However, the production RcnbrfaHHR of the well-known Kryski showed that on steep steel castings with a casting time of 6O-12C in the upper parts of the mold the paint cracks and peels off the mold, consequently on the castings there is formed a scarlet. The chain of the invention is to prevent paint cracking , improving the covering ability of its sedimentation stability, for this self-rising anti-stick paint for casting cores and ({yurm, including refractory filler and hydrolyzed etilsipikata solution contains as ethyl silicate solution hydrologo Call crude product with 3-12% silica and 0.5-1.5% acetic acid and further comprises polivinilbutnral adhesive with the following ratio of ingredients, wt. with,; A hydrolyzed solution of ethyl silicate with 3-12% silicon dioxide and 0.5-1.5% acetic acid 39.5-49.5 polyvinyl butyral 1.2-1.8 glue Refractory fill. body As a refractory filler, fused magnesite, electrocorundum, zircon, etc. can be used. The glue polyvinyl butyr al can be of the grade KA or KB (GOST 9439-60). The amount of silica in hydro-ethylated ethyl silicate (3-12%) depends on the casting duration Forms Beli casting lasts less than 1 min. It is allowed to have 12% PLN in hydrolyzed ethyl silicate. With a casting time of about 2 minutes, 3% SiO2 in hydrolyzed ethyl silicate is allowed. When going beyond the specified limits on the content of S-i O. in hydrolyzed ethyl silicate, the heat resistance of the paint decreases. When the content of polyvinyl butyral adhesive is below the lower limit, the heat resistance of the paint is reduced, and when its content is above the upper limit, the nonstick properties of the paint are deteriorated. . Polyvinyl butyral is injected into the paint to improve the sedimentation stability of the paint and improve toughness. The ethyl silicate hydrolyzed in the presence of acetic acid has higher plastic properties than that hydrolyzed in the presence of hydrochloric acid, and therefore the anti-adhesive paint on ethyl silicate with acetic acid is less prone to cracking. The content of acetic acid in the paint is 0.11-0, 33 wt. % or in terms of 1OO weight. % non-hydrolyzed ethyl silicate 0.5-1.5 weight. % When the content of acetic acid is lower than the lower limit, the heat resistance of the paint decreases due to the formation of products of incomplete hydrochloride with a burn-out temperature of 200-ZOO C, and when it is higher than BepxHOix), the paint's ability to deteriorate. In the case of lacTBo-reactors, hydrolysis is applied to t acetone, alcohol, solvent 646. The hydrolysis of ethyl silicate is carried out in two stages. The first stage is hydrolysis itself. Acetic acid is used as a catalyst in the amount of 0.5-1.5 wt.% of ethyl silicate is non-hydrolyzed, water is contained in an amount of 13-19 wt.% of non-hydrolyzed ethyl silicate. Ethyl silicate 32 is poured into the hydrolyzer and acetone is added. The agitator is turned on. The mixture of ethyl silicate with acetone is stirred for 30-40 s. Then, it is not stopped. mixing, pour ode acidified with acetic acid. The hydrolysis is carried out for 2O-4O minutes, after which the hydrolyzed solution is held to complete the hydrolysis for at least 6 hours. The content of silica in the solution after the complete hydrolysis should be about 18%. In the hydrolyzed method described ethyl silicate contains, wt.%; Ethyl silicate 3252-59 Water 8-11,8 Acetic acid. 0.5-1.5 Acetone or alcohol 35-40 Second stage - diluting the hydrolyzed solution with organic solvents to the required (3-12 weight. %) silica content of the solution. The paint is prepared as follows. Polyvinyl butyral (PVB) is introduced with mixing with a refractory filler in a dry form, in powder form. The purpose of mixing is to evenly distribute the PVB between the particles of the refractory filler. Such a distribution increases the rate of subsequent dissolution of PVB and prevents the formation of stuck lumps of PVB. The thus prepared dry mixture of refractory filler and PVB is introduced into a hydrolyzed solution of ethyl silicate and stirred until a homogeneous suspension is obtained with an approximate density of 2.1 g / cm. Examples of compositions are given in the table.

in a solution of egypsinate;

Claims (2)

In the prototype paint, the hydrupized solution of ethyl silicate contains 0.5% hydrochloric acid. The ability of the proposed paint and the known to resist cracking is determined as follows. In an induction furnace with a capacity of 20 kg, gray cast iron of grade 18-36 melted and overheated to 1500 ° C. The metal mirror was cleared of slag and oxides, and at a distance of 40 mm from the metal mirror, a sample from a liquid self-hardening liquid mixture painted with the test paint was visually observed. The proposed paint cracked in 2.5-3.5 minutes, and is known in 1-2.5 minutes. The paint coverage is tested by the following procedure. A paint of a certain composition is prepared, prepared afterwards, and it is kept in a closed container for at least 3 minutes for complete dissolution of the polyvinyl butyral. After aging, the paint is mixed again and poured into an open container. In the paint glass plate. In the same position as in the course of dipping, the paint on the plate is dried for 30 minutes. The thickness of the ink layer on the plates is measured micromet1X) M. The optimum covering ability according to the experiments corresponds to the thickness of the layer O, 2-O, 5 mm. The proposed test kit, when tested in accordance with the described method, provides for obtaining a thickness of the paint layer of 0.4 mm, and the known does not provide for obtaining the thickness of the full-thickness layer in the optimal range of 0.2-0.5 mm). To determine the sedimentation stability of paint, a standard technique for quick-drying inks was used (GOST 298-62). As a refractory filler fused magnesite fraction less than 30 microns. As a result of the tests, it was found that the sedimentation stability of the dye using ethyl silicate hydrolyzed on acetic acid and ethyl silicate hydrolyzed on hydrochloric acid depends on the percentage of silicon in terms of Si O in ethyl silicate. Moreover, in either case, it is less with a higher SiOo content, therefore, to compare the sedimentation stability of the paint, we chose a hydrated ethyl ethyl acetate (Table 1, example) containing a maximum of SA02 (12%). The sedimentation stability of the paint using ethyl silicate, hydrolyzed on hydrochloric acid (prototype), is equal to 7O%, and the sedimentary stability of paint using ethyl silicate, hydrolyzed on acetic acid (proposed) - 80%. Thus, the proposed non-stick paint has an increased trehino-resistance, good covering power, sufficient sedimentation stability, and high erosion resistance. It is advisable to use the proposed paint for molds and cores of both small and heavy cast steel. 77 Claims of the Invention A self-drying non-stick paint for casting cores and molds, comprising a refractory filler and a hydrolyzed ethyl silicate solution which, in order to prevent paint cracking | improvement of the covering ability of its sedimentation stability, as a hydrolyzed solution of ethyl silicate, it contains a technical product with 3-12% of silica and 0.5-1.5% of acetic acid and additionally contains polyvinyl butyral adhesive in the following ratio of ingredients, weight. %: Hydrolyzed solution of ethyl silicate with 3-12% silicon dioxide and 0.5-li5% acetic acid 39.5-49.5 polyvinyl butyral 1.2-1.8 glue Refractory on the Other. Complement Sources of information that are considered in the examination 1.Sb. Proceedings of TsNIITMASH,, 102, p. 117-138. 2.Avtorskoe svchechelstvo USSR 383511, cl. In 22 S ZOOOO, 197O.