CS210758B1 - Carbon additive to foundry molding and core mix - Google Patents

Abstract

Carbonaceous additive for foundry molding and core mix for gray iron castings, reducing the roughness of the casting surface. The additive is formed from anthracene oil, which contains cyclic hydrocarbons with a boiling point in the range of 343 to 400 UC. The additive is contained in the foundry molding and core mix in an amount of 0.4 to 2.0% by weight.

Description

BACKGROUND OF THE INVENTION The present invention relates to a carbon additive to a foundry molding and core composition for cast iron castings, reducing the surface roughness of the castings.

Increasing requirements for dimensional accuracy of castings can only be met if the surface roughness of the castings, especially the surface from the mold, is reduced. In the production of small to medium gray iron castings, cast into raw molds without coating, the surface roughness of the same grinding material and the type and binder content depend on two basic mold characteristics:

on the other hand, at the compression stage of the mold, given the constant compression rate of the ability of the mixture to form a dense mold with minimal pores. This ability is evaluated, for example, by the compressibility, flowability or formability of the compositions.

On the one hand, it is the ability of the mixture to prevent liquid metal from penetrating into the mold pores during casting and the formation of regular protrusions on the surface of the castings, referred to as surface roughness.

Presently, liquid additives such as bitumen solutions or emulsions or mineral oils are added to the molding composition to improve the moldability. Their beneficial effect on the roughness of the casting surface lies in the reduction of the porosity of the mold and in the direct protective action of the carbonaceous substances in the mixture against the penetration of metal into the pores of the mold.

The second group of substances used are powder additives such as coal flour, ground asphalt or ground coal pitch, which effectively protects the mold surface against caking and thus reduces the roughness of the castings.

The disadvantages of these types of materials are, in particular, the lower protective efficacy of petroleum asphalts and oils in liquid additives, so that even if the porosity of the mold is reduced, the surface of the castings is not sufficiently smooth. The disadvantage of powdered substances is their unfavorable influence on the compressibility and flowability of the mixtures. The molds of the mixtures with these additives have an increased porosity, so that even with a high protective action of the substances themselves against the penetration of the metal into the mold, low roughness of the castings is not obtained. Powder substances of various types, for example, coal flours and petroleum bitumen, are sometimes combined to improve efficiency. Faster decomposing asphalts complement slower reacting but longer acting coal. even in these cases, however, the resulting effect is reduced by the unfavorable effect of the powder substances on the compressibility of the mixture and thus on the porosity of the mold.

The aforementioned disadvantages are eliminated and the surface roughness of the gray iron castings cast into the clay mixture is greatly improved by the carbonaceous additive to the foundry and molding composition according to the invention, characterized in that the additive consists of anthracene oil containing cyclic hydrocarbons having a boiling point. 343 to 400 ° C and is present in the foundry and molding core mixture in an amount of 0.4 to 2.0% by weight.

The anthracene oil additive combines the advantages of liquid lubricants with a lubricating effect, improving the blendability of the blend and very effective hard coal protectors. This results in improved compressibility and flowability of the compositions, reduced porosity of the mold and substantially lower surface roughness of the castings. In the recovery of the present mixture in the foundry, a small addition of anthracene oil is sufficient, the addition of bentonite and lower moisture is reduced compared to mixtures with conventional black meal. Similarly, the anthracene oil components dissolved or suspended in a liquid such as a mineral oil, solution, suspension or emulsion of asphalt have a similar effect.

For ease of dispensing, it is advantageous to combine anthracene oil with latex additives to increase their effectiveness on the surface of the castings. Combinations with carbonaceous substances, for example 30 to 60 wt. or 30 to 66 wt. % asphalt powder. Similarly, anthracene oil can be pre-soaked in 25 to 75 wt. 56 and add to the mixture in the form of a powder or liquid.

Examples of the foundry molding and core composition with the carbonaceous additive of the invention.

Example 1

The bentonite base mixture, containing Lozorno sand (d ^ Q = 0.26 mm) and 7% of the branganite bentonite, after compression at a constant pressure of 0.4 MPa, gave these roughnesses of the test casting with the addition of various additives. The content of the ingredients is given in% by weight.

% bituminous flour% milled asphalt gilsonite% bitumen solution in kerosene% asphalt aqueous suspension 2% fuel oil% anthracene oil II (mixture humidity 3.5%)% anthracene oil IX (mixture humidity 2.7%) roughness = 160 yum roughness R _z = 114 / um roughness R _z = 110, um roughness R _z = 160 / im roughness R _z = 110 / µm roughness R _z = 84 (Um roughness R _z - 69 µm

Thus, the addition of anthracene castings of 26 to 45 µm against oil resulted in a reduction in the surface roughness of the test bituminous materials and by 76 to 91 A ™ P ^rot and bituminous meal.

Example 2

By combining the powder constituents of the molding composition with anthracene oil, i.e. by pre-activating them with an oil additive, these roughnesses of the test castings from the bentonite mixture were obtained, pressed at a specific pressure of 0.6 MPa;

a) Lozorno sand mixture with 7% bentonite without any additive with 3% charcoal powder with 2% anthracene oil (added separately) with 2% anthracene oil (soaked in bentonite)

R _z = 114 µm R _z = 112 µm R _z = 71 µm

R _z = 73 / um

(b) a mixture of Lozorno sand with 7% bentonite and the following ingredients soaked in a 1: 2 ratio in black powder:

black coal content. meal type and content of activator roughness R _z (/ um) 4% 2% mixture of anthracene oil and black oil (1: 1) 67 2% 1% of the same mixture 69 4 * 2% mixture of anthracene oil and asphalt solution (1: 1) 67 2% 1% of the same mixture 63

The examples confirm the possibility and efficacy of anthracene oil activation of powdered substances. The consistency of the preparation can be adjusted by the ratio of the powder substances.

Example 3

While circulating in a test foundry with a basic sand mix of Lozorno with 7% bentonite and 2% blend (anthracene oil with petroleum bitumen solution, ratio 3: 2), it was revived by adding 0.3% bentonite and 0.1% additive. The surface roughness of the thin-walled castings ranged between R _z = 50 to 70 µm on horizontal surfaces and R _z = 70 to 85 µm on vertical surfaces. These roughnesses were clearly lower than those normally found in foundries (80-160 µm).

Anthracene oil and its components protect the casting surface even when sprayed onto the mold. The effect of the additive is manifested by its soaking into the top layers of the mixture and is evident from the achieved surface roughness of the castings. Thin spraying with the solution of the above substances onto the raw forms made it possible to obtain the following surface roughness of the castings:

anthracene oil R _z = 40 to 50 μαα anthracene R _z = 45 µm carbazole R _z = 40 to 45 µm

Claims (1)

Carbonaceous additive for foundry molding and core mixture for gray iron castings, characterized in that it is anthracene oil containing cyclic hydrocarbons boiling in the range of 343 to 400 ° C and is present in the foundry molding and core mixture in an amount of 0, 4 to 2.0% by weight.