SU900926A1 - Mixture for producing casting moulds - Google Patents

Description

This invention relates to a foundry, in particular to mixture compositions for the manufacture of disposable casting molds.

It is known to use in the foundry industry uniform molding compounds, which include liquid carbon-sodahering additives to improve the nonstick properties. One such additive is fuel oil 1.

However, the use of fuel oil in mixtures has a number of significant disadvantages, the main of which include the increased tendency of the mixture to clumping during the preparation process, as well as a significant gassing during pouring. .

A more effective antiburning agent in the composition of sandy-clay mixtures for the manufacture of disposable casting molds is an extract for the selective purification of oil distillates for oil 2.

However, the sandy-clayey mixture with this additive is characterized by increased gas production.

The closest in technical essence and the achieved result

To the proposed is a mixture for the manufacture of casting molds, containing, wt.%: circulating mixture 82.1-86.1, quartz sand 8-10, water-clay suspension with a density of 1.2 g / cm 5.27, 2 and anti-stick an additive of 0.60, 8, in which the potassium hydrophobic agent GFK-1 3 is used.

However, molding compounds with the addition of GFK-1. have a good anti-burning effect only to obtain thin-walled (up to 25 mm) castings of small and medium casting weighing up to 80 kg, which is associated with the formation of

15 of the corresponding pyrocarbon content. Upon receipt of more (over 100 kg) thick-walled (over 25 1m) Castings, the use of an additive in a mixture of GFK-1 does not always allow

20 receive casting without burns.

The purpose of the invention is to increase the flowability and improvement of the antiburning properties of a single molding mixture at the floor of large thick wall cast iron castings.

This goal is achieved by the fact that the mixture for the manufacture of casting molds, including a circulating mixture, quartz sand, water-clay slurry and carbon-containing

additive-, contains as a carbon-containing additive plasticizer oil - a mixture of compounded, residual and distillate: extracts of phenolic oil purification from sulfur crude oil in the following ratio of ingredients, wt.% 2

Quartz sand8-10

Clay water slurry 2-7 Plasticizer oil 0.1-0.9 Recycled mix Else Plasticizer oil is a mixture of compounded, residual and distillate extracts of phenolic oil purification from sulfur oils (PN-B), GOST 12861-67, refers to the high molecular weight aromatic compounds, it is a brown-green liquid with a kinematic viscosity at 100 ° C of 30-35 cC (grade PN-6K) and 35-40 cSt (grade PN-6Sh).

The main factor in the purity of the surface of iron castings is the presence in the surface layer of the shape of a thin film of shiny carbon — a product of thermal decomposition of carbon-containing additives, which prevents the formation of ferrous silicate and is not wetted by liquid metal. The formation of bright carbon is determined by two main factors, the nature of volatile hydrocarbons and the temperature of their thermal decomposition. High molecular weight aromatic compounds have the greatest tendency to form brilliant carbon. - The higher the molecular weight and the more aromatic rings in a molecule, the greater the yield of brilliant carbon during pyrolysis is the product,

In tab. 1 compares the indicators characterizing carbon-containing additives, which are included in the compositions of the compared mixtures (PN-B, grade PN-BK and PN-BS) in the proposed mixture and GFK-1 in the known mixture.

As can be seen from the data presented in table. 1, a greater amount of bright carbon is produced during pyrolysis from the PN-BK and PN-BS additives. Due to this, the addition of the product PN-6 provides higher antiburning properties of sandy-clay or sandy-bentonite mixture.

.If the content of plasticizer Petroleum PN-6 in the composition of the molding mixture below the lower limit (0.1 wt.%), The required nonstick properties of the mold are not provided when producing thick-walled iron castings, and when its content is above the upper limit (0.9 wt.% individual defects are found on the surface of the castings in the form of grooves and folding, due to the known negative effect of the excess amount formed in the conditions of flashing brilliant carbon.

The slurry of molding clay or bentonite in water with a preferred density of 1.2 r / cMi is used as the water-clay suspension according to the invention.

The mixing of the ingredients of the mixture is carried out in a roller mixer in the usual order for single molding mixtures.

In tab. 2 shows the compositions of the proposed mixtures (1-7) and known 8.

Properties of mixtures 1-8 are given in table. 3

Given in Table. 3 indicators relating to the assessment of the quality of the surface of castings, obtained in the manufacture of castings from medium frequency walls with a thickness of 25-50 mm and with a different mass

From the comparison of the results presented in table. 3, it follows that the proposed mixtures already with the content of a plasticizer of oil PN-b 0.4 wt.% Provide higher indicators of non-stick properties (see the assessment of the surface quality in Table 3) and flowability than the mixture with the content of a known non-stick additives GFK-1 0.7 wt.%. The more this difference is expressed at equivalent contents in the compositions of the compared mixtures of the specified nonstick additives, as well as with a higher content of the plasticizer PN-6 plasticizer (for example, compare the properties of mixtures 3 and 8).

Thus, the proposed mixture provides improved flowability (and, consequently, the shape of the ability), and also has improved antiburning properties, which has a positive effect on quality. the surface of the thick-walled (25 mm thick) cast iron castings.

Ta b l and c a i

table 2

86,486,185,688,6

9 99 9

4,54,54,5 2

0,10,40,9 0,4

83.6 87.1 85.1 85.8 9.8 10 9

7 4,5 4,5 4,5

0.4 0.4 0.4

0.7

Claims (1)

Claim A mixture for the manufacture of 45 foundry molds, including a reverse mixture, quartz sand, a water-clay suspension and a carbon-containing additive, characterized in that, in order to increase the fluidity and improve the non-stick properties of the mixture when producing large thick-walled cast iron castings, as carbon-containing additives it contains petroleum plasticizer - a mixture of compounded, residual and distillate extracts of phenolic purification of oils from sulfur oils in the following ratio of ingredients, wt.%: Quartz sand 8-10 Water-clay suspension 2-7 Oil plasticizer 0.1-0.9 Working mixture Else