SU996076A1 - Method of producing castings of high-strength iron - Google Patents

Description

(3) METHOD OF OBTAINING HIGH-STRENGTH CAST IRON CURVES

one

The invention relates to foundry, in particular, to technologies for modifying and producing castings from high-strength cast iron in centrifugal casting.

There is a method of centrifugal casting pipes made of nodular cast iron. A distinctive feature of this method of production of cast iron pipes is the treatment of cast iron, modified spheroidizing graphite rozagents, granulated flux in order to improve the quality of pipe castings, the flux being fed to the centrifuged melt outside the stream of cast iron. Such a two-step technological cycle of processing ensures the production of castings from cast iron, which also has a spherical shape of graphite and a very homogeneous structure due to the processing of the melt with a special granular flux; supplied to the melt separately 1.

However, the application of this method for the production of centrifugal castings requires the presence of special reagents, spheroidizing graphite, and a device for carrying out the modification of cast iron, special fluxes, as well as a device for granulating the flux and for feeding it into the melt.

Closest to the proposed

10, according to the technical solution, is a method for producing castings from high-strength cast iron, including the introduction of complex modifiers containing dispersed gra15 fit 121 into the melt.

However, this method does not allow to obtain dense castings from nodular cast iron, for example, such as cylinder liners, oil mats, directly in the mold casting mold.

The purpose of the invention is to obtain castings from nodular cast iron without shrinkage defects and structurally free carbides.

This goal is achieved by the fact that according to the method for producing castings from high-strength cast iron, which includes melt processing in a casting form with complex-modifiers containing graphite powder, complex modifiers are introduced into a rotating casting mold BEFORE the casting and cast iron melt.

The melt processing of the pig iron in a rotating form is carried out in the following manner.

Finely crushed complex modifier mixed with fluorspar and graphite powder is introduced into a rotating mold, the rotation speed of which ensures that this modifying mixture is retained on the working surface of the mold. After the introduction of this modifying additive, the metal is poured into a rotating mold. At the same time, the modifying mixture, as a lighter phase (specific gravity of 3.2-L, 5 g / cm), is pressed before the metal is poured by centrifugal forces to the machine of the rotating form, after the iron is cast (specific gravity is more than 7.5 g / cm) 1 ) is displaced by the action of centrifugal forces on the free surface of the forming casting, i.e. passes through a layer of liquid nugun. Due to the interaction of finely crushed modifier and graphite powder with liquid nugun, de-sulfugation, dephosphorization and graphite formation occur in it, with calcium, barium, magnesium, and rare-earth metals being part of the complex modifier, providing, in addition to refining the metal, spherical graphite in cast iron at the base centers of graphitization, introduced by graphite powder and distributed during the passage of modifying, carrying through the layer of liquid iron during the formation of the casting throughout its cross section.

The proposed method of modifying the cast iron directly in the rotating form allows the furnace to modify the furnace and cupola melting.

According to the proposed method, in the same way as in other known methods for modifying cast iron, fluorspar is introduced into the modifying mixture;

, combining the complex modifier with a cast iron due to the creation of a fluxing environment near the front of the interaction

complex modifier particles with

melt.

The graphite powder introduced into the modifying mixture shifts the inclusions nucleation process (Spherical graphite on the basis of graphite-forming centers introduced by it towards higher temperatures, which leads to more complete graphitization of pig iron in a liquid-solid and liquid state. Modification of cast iron is only one complex modifier without the addition of graphite powder leads to the fact that the formation and growth of inclusions, spheroidal graphite in cast iron, partially occurs in the liquid-solid state. For this reason, when modifying In a cast iron in a rotary mold of a centrifugal machine with a complex modifier alone, when the casting method itself determines the absence of the gating system and feed profit, it is impossible to obtain dense healthy castings (see table), the presence of graphite in the mixture eliminates these casting defects.

The proposed modifying method, in which the modifying mixture interacts with cast iron at temperatures close to the liquidus temperature, excludes the possibility of forming structurally free carbides in the cast iron structure (see table).

Experiments on the production of cylinder liners from high-strength nodular cast iron by the centrifugal method show that the aging of modified cast iron in the ladle before pouring the mold of the centrifugal machine contributes to the nucleation of iron carbides (see table). When modifying in the form due to the short time of crystallization of cast iron, the process of carbidization in it does not proceed (see table). Modified cast iron treated with the complex modifier alone without graphite additive has shrinkage defects, so the casting of the liner has shrinkage defects centered on its inner working surface (see table), which sharply reduces the operational reliability and durability of the sleeves. The table shows the data characterizing the effect of the addition of potting powder to the modifying agent during the modification of cupola iron in the mold during centrifugal casting on the density of the casting, the influence of the modifying method, the formation of chill in the liners. 4 2.1-2.5 0.6-0.9 0, -0.6 0.25-0.35 0.15-0.25 overheated in an induction mixer to UOO-l 2d ° C. The modification is carried out with a complex composition modifier, wt.%: S Wl Ba 3.5 Ca- 5.4 REM 3.5 Md 7.5 Fe Else The consumption of the complex modifier is 3 of the mass of liquid iron, the ratio between the number of complex modifier and fluorspar 10: 1. The consumption of graphite, which is part of the modifying mixture according to the proposed method, is 0.25-0, the mass of the casting.

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year

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Claims (2)

Invention claims are introduced, rotational The method of producing high-melting cast iron, high-strength cast iron, including o6pai- Sources of information, melt processing in a mold, a set taken into account when examining with lex modifiers containing 1. French Patent No. 579869: graphite powder, about l and h and y y and y cl. At 22 D 13/10, 1977. so that, with the chain of receipt 2. Borgeand, R., Les inoculants et, cast iron 9 and rovid gra-. nodullsants en fonderle de fonte. fit-free shrinkage defects and structure-1c Horames et fonderle, 1977, fP 80, torn free carbides, complex. 25-30. 4th mold to fill