SU1102652A1 - Self-hardening sand for making casting moulds and cores - Google Patents

Abstract

SELF-CONTAINING MIXTURE FOR THE MANUFACTURE OF CASTING FORMS AND RODS, apply a fluid to a refractory filler, a floater, a floater, a process fluid, a substrate and a process additive, a process fluid. the ratio of ingredients, wt.%: Liquid glass 5.8-6.2 Propylene carbonate 0.9-1.1 Sodium carboxymethylcellulose 0.2-0.3 Refractory filler Remaining

Description

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The invention relates to foundry and can be used in the manufacture of molds and cores for steel and cast iron.

Known self-hardening mixture, including, wt.%:

Quartz sand Basis Liquid glass 5.5-6 Propylene carbonate 0.8-1 The mixture hardens very quickly on the ground, has a high final strength and low crushability Cl. However, the technological properties of this mixture are limited. The mixture has low plasticity, poor formability, short-term survivability. These drawbacks make it difficult to manufacture molds and large rods from it. In the manufacture of forms, it is difficult to remove models from the compacted form or even their destruction, and in the manufacture of large rods (with a core box filling time of more than 5 minutes), the lower, already hardened layers of the mixture are destroyed when compacted on a vibrating table. For this reason, large rods need to be manually compacted simultaneously with filling the crate with the mixture.

A known liquid mixture is used in which sodium carboxymethyl cellulose C 2.3 is used to improve the knockability.

However, this mixture can not be used in technical process involving the use of self-hardening mixture.

Closest to the invention to the technical essence and the achieved effect is a self-hardening mixture for the manufacture of casting molds and cores, which includes refractory filler, water glass, propylene carbonate and technological addition of phthalic ester СЗ.

However, an intense increase in the viscosity of liquid glass has a negative effect on the plastic properties of the mixture. In addition, the deterioration of the mixture worsens.

The purpose of the invention is to reduce the crushability of the forms and rods and stabilize their strength.

The goal is achieved by the fact that the self-hardening mixture for the manufacture of casting molds and cores, including refractory filler, liquid glass, propylene carbonate and technological additive, contains sodium carboxymethylcellulose as a technological additive in the following ratio of ingredients, wt.%:

Liquid glass 5.8-6.2

Propylene carbonate 0.9-1.1

Sodium carboxymethylcellulose - 0.2-0.3

Refractory

fillerEverything

Liquid glass (GOST 13078-67) is an aqueous solution of soluble sodium silicate. In the mixture is a binder. Liquid glass M 2,15, density 1480-1300 kg / m is used.

Propylene carbonate (TU-38-102-51-72) is a carbonic acid ester, colorless, a liquid with a characteristic smell of ether. The equipment is used for the synthesis of plastics and as a solvent for some organic compounds. It is used as a hardener in the mixture.

Sodium carboxymethylcellulose (Na-CMC) (GOST 5.588-70) is a sodium cellulose glycolic acid salt. The technique is used to stabilize clay suspensions, as an additive to detergents, for smoothing the warp threads and as a thickening agent for printing inks, as flotation reagents, for controlling the rheological properties of cement mortars, for the synthesis of water-soluble adhesives.

In this mixture, Na-CMC has been used as an additive to increase the vitality and improve the plastic properties of the self-hardening mixture. In addition, Na-CMC improves the knockability of the mixture.

The positive effect of Na-CMC is based on the fact that when it is dissolved in liquid glass, the latter increases the number of sodium ions relative to the number of SiO2 ions, thereby slowing down the coagulation of liquid glass, i.e. The incubation period for solid glass is lengthened. In addition, the presence of Na-CMC passivates liquid glass relative to propylene carbonate, and the effect of the latter on it becomes less active, the reaction of hydrolysis of liquid glass is slowed down. All this contributes to the fact that the survivability of the mixture increases.

The mixture is prepared as follows. A composition consisting of calculated amounts of liquid glass and sodium carboxymethyl cellulose is preliminarily prepared. The estimated amount of the composition is stirred for 1-1.5 minutes with sand, after which the introduction of propylene carbonate and mixing is continued for 1.5-2.0 minutes. The mixture can be prepared in a batch and batch mixer. The compositions of the mixtures and their physical-mechanical properties and technological properties are given respectively in Table. 1 and 2. Mixtures 1 and 5 have the content of Na-CMC below the lower and upper levels, mixtures 2 and 4 have the boundary content of Na-CMC and 3 with the optimum. To compare the properties of the proposed mixture, the mixture was tested as a prototype. From the data table. 2 follows that. If Na-CMC is present in the mixture below the lower limit, the survivability of the mixture slightly exceeds the survivability of the mixture due to the prototype, and the strength is close to the strength of the mixture adopted as the prototype. With the presence of cm-Na-CMC in the composition above the upper limit, the survivability of the mixture, although significantly increases and exceeds the survival rate of the mixture, taken as a prototype, 4 times, however, the strength is expected to decrease to a technologically unacceptable value. . The effect of Na-KMD on the interaction of propylene carbonate and liquid glass is illustrated in FIG. 1 and 2. In FIG. 1 and 2 (curves 1, respectively) it follows that Na-CMC decreases the viscosity of liquid glass-. This is due to the fact that when Na-CMC dissolves in liquid glass, the latter increases the number of sodium ions relative to the number of silicon ions and, moreover, does not hydrolyze the liquid glass. When phthalic acid is introduced into zerpher liquid glass, the viscosity of liquid glass begins to increase somewhat, because this compound somewhat hydrolyzes liquid glass, like some ethers that hardened liquid glass (propylene carbonate, triacetin, etc.). Thus, on the first step, the influence of Na-CMC and phthalic acid ester on the change in the viscosity of liquid glass was clarified. FIG. 1 and 2 (curves 2, respectively, e) it follows that in both cases the viscosity of liquid glass begins to increase, but with the combination of phthalic acid ester and propylene carbonate, the latter increases more intensively, because each of them hydrolyzes liquid glass .. This affects the plastic properties, vitality and dynamics of solidification of the mixture (Table 3). From the data table. 1 it follows that the survivability of the proposed mixture is not lower than that opposed (application No. 2819255), and the prevalence of compressive strength in the initial period of hardening is explained by the chemical factors that are given. In the subsequent time, the proposed mixture continues to gain strength, and in the opposed creep, it is established. From this it follows that the mixability of the mixture increases. The proposed mixture and the known mixture were tested as core and facing mixtures in the manufacture of cores and shapes. Manufactured in 10 rods and molds for steel castings. Forms were made according to the generally accepted technology: the tested mixtures were superimposed on the model, filled with them, and then compacted. Forms made from the proposed mixture did not harden after 1012 minutes, the mixture was still in a visco-plastic state, was easily trimmed and smoothed with a trowel. Removing the jelly from a mold made from izestnoy mixture, was difficult, because the mixture is almost solidified and strongly obama model. The surface of the castings, cast, in molds made from the mixture in question and the mixture taken from the prototype, had a clean surface. The economic effect of the proposed mix is obtained by improving the quality of the pouring and reducing the labor intensity of the log works. The composition and cost of the PSS with an otderitelya - propylene carbonate are shown in Table. four,

The composition and cost of PSS with hardeners, propylene carbonate and sodium carboxymethyl cellulose are given in table. five.

The economic effect of the plant Sibt Zhmash with a volume of 5,000 tons will be 3350 rubles.

Table 1

93,4593.1 Quartz sand Liquid glass. 5.65.8 M-2.15 0.80.9 Na-CMC propyl carbonate 0.150.20 Phthalic ester

10.09.0 8.0 7.0

12,011,010.0 9.0

14,012,011,010,0

0.30.30.30.30

Table 3

3

1815

ten

table 2

10.0 18.0 18.0 0.3

Continued table. 3

31218

241418

The precipitation rate,% 0,50,9 2,7592,492,05 92,75 6,06,26,4 1,01,11,2 0,250,30.0,35

1.00.50.

0.06060

 I

0.013000

Table 4

0.5 3.6 30.0

Table 5

Claims (1)

SELF-CURING MIXTURE FOR MANUFACTURE OF CASTING FORMS AND RODS, including refractory filler, water glass, propylene carbonate and technological additive, characterized in that, in order to reduce the crumbling of molds and cores and stabilize their strength, the mixture contains sodium-carboxymeth as the technological additive for the following additives ingredients, wt.%: Water glass Propylene carbonate Sodium carboxymethyl cellulose a Refractory filler 5.8-6.2 0.9-1, -1 0.2-0.3 Rest 1102652.