SU1712445A1 - Mixture for modifying and alloying cast iron - Google Patents

Abstract

The invention relates to the field of metallurgy and can be used to modify cast iron for the manufacture of thin-walled castings. The purpose of the invention is to dispose of the waste, eliminate edge chill and increase the duration of the preservation of the modifying effect. Prepare a modifying mixture of the following composition, May. %: carbon. 5-10; waste of alumina boron-containing fiber 8-12, 'ferrosilicon remains 1 ^. The melt is cast iron and its modification is carried out at 1400-1420 ° gf. C. The application of the proposed modifier makes it possible to utilize the yields of aluminum-boron-containing fiber, eliminate edge chill and increase the duration of the modifying effect. Table 1. The invention relates to foundry, in particular, to modifier compositions for modifying gray iron, and can be used to make responsible thin-walled castings in mechanical engineering. The aim of the invention is to eliminate chamfer in castings, to increase the duration of preservation of the modifying effect and to reduce the cost of modifying! ** "turing while maintaining high strength properties. The goal is achieved by the fact that the mixture for modifying and alloying cast iron contains carbon, ferrosilicon FS75 and aluminum bullet waste and fiber in the following ratio of infectious substances, wt%; Carbon 5-10 Aluminous borsilicate fiber waste 8-12 Ferrosilicon Other Carbon in the mixture performs two functions: it serves as natural nuclei during the crystallization of the alloy and is a reducing agent for boron and aluminorderous debris and it is also used as a silver reducing agent and it is a good combination with its own body, and the aluminacers will first put on their own and they are boron-alumina and they are boron and aluminacers are already in offspring; carbon content is selected based on the most complete boron reduction conditions. The lower limit of carbon content

Description

BaOZ is easily reduced by free carbon, as well as partly by carbon from cast iron to metallic boron, by the following reax:

2 / ЗВ203 + 2С - 4 / ЗВ + 2СО.

It is also possible to reduce boron with silicon from ferrosilicon by the reaction:

2 / ЗВ20з + SI 4 / ЗВ + 8Ю2.

Reduced boron interacts with nitrogen in sufficient quantity in the melt to form boron nitride. The formation of stable boron nitride neutralizes the carbide-stabilizing effect of nitrogen and clears from it the boundaries of eutectic grains, increasing its strength. In addition, boron nitrides, located on the surfaces of graphite plates, prevent the formation of cementite and increase the survivability of the modification.

. The presence of aluminum oxide, magnesium, calcium oxides, which are active nucleation sites in the alumino borosilicate fiber, also makes it possible to significantly increase the duration of action of the modifying mixture.

The waste content of aluminosilicate fiber in the mixture below 8 wt.% Does not increase the strength characteristics. When the content of the waste is more than 12% by weight, an increase in the chill depth is observed.

The choice of 75% ferrosilicon as the leading component of the mixture is due to its strong graphitizing effect, albeit weaker than the silicobarium or silica gel; . But the absorption of ferrosilicon by liquid melt is higher than that of the indicated alloys, and the cost is lower.

Example. To study the mechanical and technological properties of cast iron modified by the known and proposed mixture, mixtures were prepared at the lower, middle and upper, as well as below the lower and upper levels of the ingredients for the proposed mixture and at an average level for the known mixture.

The technology of preparation of the mixture included grinding on a ball mill of FS75 ferrosilicon to a fraction of 0.5 mm in size, and waste of an aluminosilicate fiber to a fraction of 0.315 mm and subsequent mixing with carbon in a given proportion. The following materials were used to prepare the known and proposed mixtures: cryptocrystalline graphite GLS-3 (GOST 5420-74): FS75 ferrosilicon (GOST 1415-78): BC-grade aluminosilicate fiber waste {GOST10727-73); ferroboron FB2 (GOST 14848-69).

Comparative tests of the known and proposed modifying mixtures were carried out on cast iron of composition,%: carbon 3.2; silicon 1.8: manganese 0.45; chromium 0.06; sulfur 0.06; phosphorus 0.09. Melting of cast iron produced in an induction furnace EST102, and as the charge used to return the iron brand SCH20.

The modification was carried out at 1400-1420 ° C. .

To study the strength properties of the modifying mixtures, technological samples with a diameter of 30 mm were poured, from which samples were cut for tensile tests and for measuring hardness.

The duration of the preservation of the modifying effect was assessed by the chill of the wedge sample, which is poured every 2 minutes after the modification.

Elimination of edge chill was also assessed by chipping the wedge sample with an angle at the base of 15 ° and a height of 70mm.

The test results of the mechanical properties of cast iron after treatment with the known and proposed mixture are given in the table.

From the data it can be seen that the proposed mixture allows the casting of the metal 12 minutes after the modification, while it is known that it takes no more than 6 minutes.

The amount of chill off on a wedge sample of cast iron modified with a known mixture is 7-8 mm, while there is no chill on a wedge of cast iron modified with the proposed mixture. The mechanical properties of such a cast iron are slightly lower, although they also allow one brand strength to be raised.

Formula a and 3 about b reteni

The mixture for modifying and doping cast iron, predominantly thin-walled castings, containing carbon, ferrosilicon, and boron-containing component, characterized in that, in order to utilize waste, eliminate edge chill and increase the duration of preservation of the modifying effect, aluminum-containing waste fiber is used as a boron-containing component the following ratio of components, wt.%:

Carbon 5-10

Alumina-Bordered Fiber Waste8--12

Ferrosilicium Else

Claims (1)

Claim A mixture for modifying and alloying cast iron, mainly thin-walled castings, containing carbon, ferrosilicon and a boron-containing component, characterized in that, in order to utilize waste products, eliminate edge bleaching and increase the duration of the preservation of the modifying effect, aluminum-boron-containing fiber waste is used as a boron-containing component in the following ratio components, wt.%: Carbon 5-10 Waste Alumina-containing fiber 8-12 Ferrosilicon Else 1712445 6