SU789220A1 - Modifying flux for centrifugal casting of cast iron blanks - Google Patents

Description

one

The invention relates to foundry production of ferrous alloys, mainly centrifugal cast iron billets4

The compositions of modifying and refining fluxes used in the centrifugal casting of steel, bronze and cast iron billets, containing metal oxides, fluorides and metal powders 11, are known.

The disadvantage of these compositions of fluxes is that they do not provide uniform hardness over the thickness of the casting, which is the wear resistance of the products.

This phenomenon is explained by the fact that Metallic materials included in the flux composition do not provide an increase in the content of pearlite in the macrostructure of castings.

The known composition of the modifying flux based on metal oxides and fluorides, containing, as a modifying component, iron chips in the following ratio of components, weight. %; metal oxides (Al.j.0%, S0a “Na, jO, BaO) 5–10, pig iron chips 60–85 2.

However, under the conditions of frequent heat changes of product,

using this flux, is prematurely destroyed. This is due to the fact that particles of melted chips are observed in the body of the casting, which

5 reduces the mechanical properties of cast iron when it is used in conditions of heat shift at the next operating cycle: HiarpeB products take a short time (5-10 minutes), work at high temperatures (2.50-40rs) for a long time (2-3 hours) , cooling to room temperature for 15–20 minutes, then repeating the cycle. The purpose of the invention is to create a flux composition that provides an increase in the thermal cyclic resistance of cast iron and, consequently, an increase in the reliability and durability of the products.

20 to achieve this goal, antimony was introduced into the composition of the flux based on metal oxides and fluorides, at. This content of all ingredients should be in the following ratios,

25 wt. % :. .

Metal oxides (AB-jO - 1 | 2, SiOi - 9-10, - 10-11, 5-7) 25-30.

Antimony45-55 - i

30 CryoliteEverything Else

Before dosing into the rotating form, the flux components are dried at 120-150 s, ground in ball mills to fractions of 0.05-0.02 mm, and mixed in the required ratios for 3-5 minutes.

When dispensing a flux of metal to be poured, falling into a rotating form, it is emulsified by centrifugal forces in the metal, as a result of which the surface of the metal with the flux increases.

Non-metallic flux components (metal oxides and fluorides) protect the cast alloy and antimony from oxidation, refin the metal from harmful impurities and non-metallic inclusions, and also insulate the free surface of the metal, creating the most favorable conditions for its directional from the outer surface to the internal solidification. The metallic component of the flux antimony — as a result of the development of a large contact surface, dissolves uniformly in the cast metal and grinds the metal grain and graphite inclusions during alloy crystallization, which contributes to an increase in the thermal cyclic resistance of the iron.

The quantitative optimal composition of the proposed flux has been tested experimentally. The optimum amount of metal oxides fluctuates within 25-30% and depends on the content of harmful impurities in the metal. With their content of 0.1-0.15%, it is necessary to use .25% of oxides, and with a content of 0.16-0.20% of impurities, 30% of oxides must be used.

When using oxides of less than 25% in the flux content, the maximum value of the coefficient

the distribution of harmful impurities and non-metallic inclusions between methyl and flux, and with an oxide content of more than 30%, the degree of removal of harmful impurities and non-metallic inclusions from the metal does not increase.

Cryolite in the composition of the flux performs the role of stabilizing the physicochemical and technological properties of the flux (surface tension, viscosity, fluidity) and with a content of 15-30% of cryolite in the flux, the optimum values of these properties are achieved. The content of cryolite depends on the pouring temperature of the cast iron, at the pouring temperatures of 1300-1320 C it is necessary to enter

15-20% of cryolite, with 1321-1340 from 20-25%, and with more it is necessary to enter 26-30%.

In tab. 1 shows the dependence of the antimony content in the flux on the thickness

castings.

Table 1.

40-45

46-50 51-55

When the antimony content is less than 40% in the flux, the metal grain and graphite inclusions are not crushed and, as a result, the thermocyclic resistance of cast iron does not increase, and when the content is more than 55%, the quality of the metal does not significantly affect.

The amount of flux offered. which is introduced in the centrifugal casting of cast iron billets, depends on. metal pouring temperature, which is determined by the alloy grade. Experienced found that at a pouring temperature of 1300-1320, you must enter 1-2% of the flux, at 1321-1E40 ° C, 2.1-3%, at 1321-1340 ° C - 2.1-3%, at over 1340C 3.1-4%.

Example. 6 batches of blanks weighing 40 kg each were cast and investigated, each made of cast iron; 3 batches,

5 to 3 each casting, under a known flux and 3 batches under the proposed one.

The pouring temperature of the metal, the amount of flux casting introduced in each batch is 2.5% by weight of the cast metal. Metal casting speed 3 kg / s. The diameter of the internal casting 170 mm. Casting thickness 70 mm. The shape is lined with a free-flowing mixture consisting of. from 90% of sand and 10% of powdered zircon. Lining thickness 8 mm. The flux is introduced into the form by a pneumatic conveyor (a special dispenser).

Features of the casting and the results of the study of experimental blanks are presented in Table. 2

Metal oxides-10,

Metal oxides-25, antimony-40, cryolite-35

Metal oxides-27, antimony-47, cryolite-26

Metal oxides-30, antimony-55, cryolite-15

As can be seen from the table. 2, the application of the proposed flux allows to increase the thermal cyclic resistance of cast iron by 2 times or more.

This makes it possible to increase the durability of products operating under thermal conditions, for example, cylinder liners of compressors for the nitrogen industry, by a factor of 2.

Claims (2)

The economic effect is 120-150 p. per 1 ton of good lithium. Formula of Invention Flux for modifying in center-casting cast iron billets, including metal oxides and cryolite Table 22, 22, 24 48, 50, 47 51, 50, 49 50, 49, 52 characterized in that, in order to increase thermal cycling iron resistance, reliability and durability of the workpieces, it additionally contains antimony in the following ratio of ingredients, weight. %: Metal oxides 25-30 Antimony30-55 CryoliteEverything Sources of information taken into account during the examination 1. USSR Author's Certificate No. 464376, В 22 О 13/00; 1974. 2. USSR author's certificate t 608603, cl. B 22 D 13/00, 1976.