SU944723A1 - Mixture for producing casting cores - Google Patents

Description

(5} MIXTURE FOR THE MANUFACTURE OF CASTING RODS

one

The invention relates to foundry.

Castings, predominantly steel, of a complex configuration tend to form hot cracks. . Accelerated cooling of castings in places of possible formation of hot cracks prevents their occurrence due to more rapid growth of a hard crust. For this purpose, refrigerators or rods from mixtures with increased heat storage capacity are used; the mixture must have a high compliance in order to reduce the stresses causing the formation of hot cracks.

A known mixture for the manufacture of foundry molds and cores, containing quartz sand, bentonite, an anti-stick organic additive. In order to increase plasticity, an organic additive is added to the mixture - 33% aqueous latex solution 1

However, this mixture has a low coefficient of heat storage and its use does not lead to the elimination of the causes of the formation of hot cracks.

Also known is a mixture containing 93–9 mas ppm of quartz sand, chromite, magnesite, or chromium magnesite, wt. serpentine, dunite or mixtures thereof and bentonite as

10 binder .. Serpentine - silicate of iron and iron - is neutral () and does not burn to the casting, dunite refractory t2j.

15

When they are used in castings, the screws are not formed. They increase the fluidity of the mixture and bind excess water. The mixture allows to obtain high-quality castings, but

20, it is impossible to obtain high-quality steel castings (without cracks) with any combination of components of the mixture. This is due to low poltlivostyu

mixtures and relatively high heat storage coefficient.

Closest to the invention to the technical essence is a mixture containing, masd:

Fireproof

clay 18-2A

Corundum 18-22

Magnesitochromite 10, Yu

Orthophosphoric

acid21-24

Ground Chamotte

Graphite, the Rest

The compressive strength of the mixture before baking is 7.2-11.3 kgf / cm, and the afterburning is 320-4l6 kgf / cm.

The heat resistance of the mixture, determined by the relative strength drop per 1 thermal shift, is 20 0.9-1.7%, the coefficient of thermal conductivity of the mixture is (0.66-0.73) llTwcD.

The known mixture is designed to produce thin-walled iron castings, has a high strength of 25 and a low thermal diffusivity. The latter property allows to obtain castings without chill.

The aim of the invention is to increase the rate of solidification of steel castings by obtaining a given heat-accumulating capacity of the mixture and reducing the waste of castings by improving the flexibility of the mixture. 35

The goal is to achieve that the mixture for the manufacture of casting molds and rods, including gum refractory filler on the basis of acid magnesium, clay binder, technological additive, graphite and lumosilicate additive, contains as a silica-alumina additive, salt spar at the following ratio of 5 II ingredients, by weight .%:

Graphite5-15

Clayey

binder 5-10

Technological so

additive3-7

Feldspar3-8

Refractory

filler

based on 55

magnesium oxide Else

In addition, a mixture of magnesium oxide-based mate- rial contains magnesite, and, as a technological additive, a complex binder composition, wt.%: Oil-free universal fixer based on processing waste sulfur oil (UIC) 1-3

Binder based

water soluble

lignosulfonates 1-2

Phenolospirt2-3

The introduction of silver graphite achieves the necessary heat-accumulating effect. At the same time, the macro and microstructure of the metal is improved, the grain is crushed. In addition, an increase in the rate of movement of the crystallization front reduces the segregation of liquidation elements, which contributes to obtaining castings with a uniform distribution of elements over the cross section.

The introduction of feldspar improves the compliance of the mixture, which contributes to the reduction of casting stresses in case of difficult shrinkage. Feldspar is cheap material and available.

As a technological additive in the mixture, a complex binder is used, which consists of a oil-free universal fixer based on waste Eastern sulfuric oil (USC), a binder based on water-soluble lignosulfonates (CBI) and phenol-alcohol.

This combination of organic binders provides sufficient cheese strength, and the combination of USC and phenol alcohol acts to increase the strength in the dry state.

The proposed blend can be used to make raw forms. To do this, it is necessary to introduce water into the mixture, which allows the mixture to give the necessary moisture and strength without the use of binders.

The compositions of the mixtures are given in table 1 and the properties in table. 2

The mixture of compositions according to the table. 1 are prepared in mixers. Initially magnesite, graphite, bentonite and feldspar are placed in a mixer in a weight ratio. These components are mixed for 1-2 minutes. Water or complex binder is then added. The mixture is stirred for 5-8 minutes, after which the prepared mixture is suitable for use.

A mixture of 1 with a minimum content for forms and rods of graphite and feldspar has a heat storage capacity of 502, 4/2

52 kcal / m, -hour-hail. In this case, conditions for the formation of hot cracks appear as the flexibility of the mixtures decreases.

A mixture of 2 with a maximum content for forms and rods of graphite and feldspar has an increased heat storage capacity of 78 kcal / m-hail, but low crude-strength - 0.6-0.65 kgf / s (for forms) and 0.3 -0.35 kgf / cm (for rods) and gas permeability (units), which adversely affects the quality of castings.

When the content of graphite in the mixture is lower than b%, the necessary heat-accumulating effect is not achieved, as a result of which hot cracks can form in the castings. The use of graphite over S% is impractical due to the deterioration of gas permeability and decrease in the strength of the mixture.

The content of feldspar in the mixture is below 3 wt. does not have a significant effect on the compliance and anti-stick properties of the mixture, and above 8 wt. leads to a decrease in the refractoriness of the mixture.

The use of mixtures containing more than 85 wt.% And less than b5 wt. | magnesite does not produce the desired results due to the low strength in the first case and low gas permeability in the second.

The best indicators are obtained when using a mixture of 3.

As follows from the table. 2, the low dry and wet strength of the mixtures according to the invention during the period of crystallization and cooling of steel castings of a complex configuration in the form, significantly reduce the linear stresses in the castings, which

ultimately, it contributes to a sharp decrease in the formation of such a type of marriage as hot cracks. Most, it is rational to have a heat storage capacity of the mixture equal to 60-75 kcal / m hail. This is due to the fact that 4fo increase in the heat-accumulating capacity of the mixture above 75-80 kcal / mIh / hour, hail does not have a significant effect. the time of crystallization of castings, and the use of mixtures with lower heat-accumulating capacity than it turned out, increases the time of crystallization and cooling of castings, which can be undesirable for their structure (possible increased elimination of sulfur over the section of castings, as well as the formation of shrinkage porosity and cracks).

Claims (3)

1. A mixture for the manufacture of casting cores used predominantly in the preparation of steel castings of complex configuration, including refractory filler based on magnesium oxide, clay binder, technological additive graphite and aluminosilicate additive, characterized in that In order to increase the rate of solidification of castings by obtaining a given heat-storage capacity of the mixture and reduce waste rejection by improving the flexibility of the mixture, the latter contains feldspar as an aluminum silicate additive in the following ratio of ingredients, wt .: Graphite5-15 Clayey binder 5-10 Technological additive3-7 Feldspar 3-8 Refractory filler based magnesium oxide Else 2. A mixture according to claim 1, characterized in that the quality of the material based on magnesium oxide contains magnesite. 3. A mixture according to claim 1, characterized in that, as 11 technological additives, it contains a complex binder of composition, wt. Oil-free universal fixer based on reprocessing of sulfurous eastern oils (UIC) 1-3 Binder based on 12 water-soluble or glucose sulfonates1-2 Phenolospirt 2-3 Sources of information taken into account during the examination 1. USSR author's certificate M 550217, cl. 22 C T / 00, 1975. 2. Patent Czechoslovakia № 10 cl. 31 C 1/01, 1965. 3. USSR Copyright Certificate W 732068, cl. B 22 C 1/18, 1976,