SU1463766A1 - Inoculant composition for cast iron - Google Patents

Description

(21) 4262892 / 31-02

(22) 05/18/87

(46) 07.03,89o Bnsh. Number 9

(71) All-Union Correspondence Polytechnic Institute

(72) B.K. St. Tkin, MI Karpenko, Yu.G. Serebrkov and A.N. Bolotov

(53) 669.15-198 (088.8)

(56) USSR inventor certificate № 1081212, кп. C 21 C 1/10, 1984.

USSR Author's Certificate No. 973654, cl. C 22 C 35/00, C 21 C 1/10, 1982.

(54) MODIFIED MIXTURE FOR CAST IRON

(57) The invention relates to the field of foundry, in particular, to modifying mixture compositions for producing high-strength cast iron. The purpose of the invention is to increase the mechanical properties, crack resistance and density of cast iron by improving the deoxidizing ability of the mixture. The modifying mixture contains magnesium, graphite, silico-metal, ferrosilicon, silico-aluminum and manganese nitrides with the following ratio of components, wt.%: Magnesium 7-12, graphite 8-14, silico-metal 20-30, ferrosilicon 10-18, silico-aluminum 15-20, nitrides manganese 11-35. The additional addition of silicon dioxide and manganese nitrides to the mixture increases the acidification, graphitizing and stabilizing properties of the mixture, which leads to a significant (15–20%) increase in the mechanical properties, crack resistance and density of cast iron treated with this mixture Yew, 1 tab.

(ABOUT

SL

The invention relates to foundry, in particular, to the production of high-strength cast iron dp castings with increased crack resistance.

The purpose of the invention is to improve the mechanical properties, crack resistance and density of cast iron in castings by improving the deacidification of the mixture.

The goal is achieved by the fact that the modifying mixture containing magnesium, graphite, silico-metal and ferrosilicon, additionally contains silicon-aluminum and manganese nitrides with the following ratio of components, wt.%:

Magnesium 7-12

Graphite .8-14

Ferrosilicon Silikomishmetall

Silico-aluminum Nitrides of Manganese Iron

10-18

20-30 15-20 11-35 Else

4 O) 05

O5

SP)

The addition of silicon-aluminum increases the deoxidizing, graphitizing and stabilizing properties of the mixture, increasing the density and mechanical properties of the cast iron. At a concentration of silicoaluminium up to 10 wt.%, The density and mechanical properties of the modified cast iron are insufficient, and with an increase in its content (more than 20 wt.%), The stability of the modification process, the technological properties and the totality of the castings decrease.

Manganese nitrides are introduced into mixtures as effective modifying agents that reduce cracking resistance and residual thermal stresses. Their concentration is limited to 35 wt.%, Above which deoxidizing capacity, properties and density of cast iron decrease, and the lower limit (11 wt.%) Is due to high characteristics of residual stresses, tendency to cracks and porosity of cast iron at lower crn- x manganese nitrides.

The magnesium content in the mixture is limited by its lower limit (7 wt.%), 1 which is necessary for a stable production of nodular graphite in cast iron. An increase in the magnesium concentration of the IB mixture (more than 12 wt.%) Increases the pyro effect, the stability of the mixture’s iraxidative capacity decreases, and the residual thermal stresses of the iron in the cast iron significantly increase. Ferrosilicon in the modifying mixture in the amount of 10-18 wt. : enhances technological and mechanical1463766

and the upper limit is for cast irons containing alloying and demodifying elements. When the concentration of silica-metal more than 30 wt.% In the structure appears structurally

free cementite in thin sections of castings, reduced structure homogeneity in thick sections, increased residual thermal stresses in the castings, reduced the shape of graphite and the tightness of cast iron. With co. holding the silicomismetal to 20 wt.%, casting properties deteriorate;

15 graphite, reduced deoxidizing ability, characteristics of hardness and density, increases the content of non-metallic inclusions in the iron.

J-.V

20 To obtain modifying the mixture, silicon alumina, ferrosilicon, graphite granulated, manganese nitrides, obtained by saturating electrothermal nitrogen with nitrogen, are used.

25 metal marga: nata, silico-metal, smelted in an electric furnace, a1-1 inothermal method and supplied float in pieces weighing no more than 10 kg, and magnesium. Fine properties, stabilizes deoxidized crushed raw materials, achievable capacity, reduces cracks. 0.1-5 mm are mixed in mechanical runners for 6-12 minutes. The base iron is melted into arc heat resistance and residual thermal: stresses increase the density of the iron in the castings.

The indicated limits of the content of graphite in the mixture are selected as the optimal I for the given numerical values of magnesium and manganese nitrides. KoTopjjie Enhance deoxidizing | the ability and stability of the modification process 1:

The content of graphite in a mixture of more than 14 wt.% Reduces the hardness, density, strength of cast iron and its technological properties; . Lowering the graphite concentration to less than 8 wt.%) Reduces the stability of the modification process, the degree of absorption of magnesium and increases the residual thermal stresses,

Silikomishmetall strengthens the deoxidizing ability and stabilizes, the process of modifying with some fluctuations in the chemical composition of the original iron. The lower limit of silico-metal is used to modify cast iron with a low content of non-metallic inclusions that do not contain demodifiers.

35

40

The following furnaces of chemical composition, wt.%: carbon 3.5-3.7, silicon 2.0-2.2j manganese 0.3-0.5; phosphorus 0.02-0.06; Nickel to 2 ,,: chrome to 0.05; sulfur to 0.08; titanium to O, (33; iron else. The release of cast iron into heated casting buckets is carried out at 1380-1420 ° C. Modifying mixtures, mixed mechanically in runners, are introduced into the ladle in a packed form when the cast iron is released from the furnace. Flow g modified mixtures of 1% by weight of the melt.

The compositions are the modified mixtures used to process the cast irons of the experimental heats, as well as the results of testing the proposed composition of the mixtures: in comparison with the known, they are listed in the table.

To determine the tendency of modified cast irons to form hot cracks, a star-like process sample is used. The absolute crack resistance is determined by the total length of cracks on the surface of the process sample. Absolute

50

and the upper limit is for cast irons containing alloying and demodifying elements. When the concentration of silica-metal more than 30 wt.% In the structure appears structurally

loose cement in thin sections of castings, reduced structure homogeneity in thick sections, residual thermal stresses in castings decrease, the shape of graphite and tightness of cast iron deteriorate. With co. holding the silicomismetal to 20 wt.%, casting properties deteriorate;

graphite, reduced deoxidizing ability, characteristics of hardness and density, increases the content of non-metallic inclusions in the iron.

J-.V

To obtain a modifying mixture, silicoaluminium, ferrosilicon, granite graphite, manganese nitrides, obtained by saturating electrothermal nitrogen with nitrogen, are used.

metal marga: nca, silico-metal, smelted in an electric furnace, a1-1-inothermal method and supplied float-in in pieces weighing not more than 10 kg, and magnesium. Out5

0

The following furnaces of chemical composition, wt.%: carbon 3.5-3.7, silicon 2.0-2.2j manganese 0.3-0.5; phosphorus 0.02-0.06; Nickel to 2 ,,: chrome to 0.05; sulfur to 0.08; titanium to O, (33; iron else. The release of cast iron into heated casting buckets is carried out at 1380-1420 ° C. Modifying mixtures, mixed mechanically in runners, are introduced into the ladle in a packed form when the cast iron is released from the furnace. Flow g modified mixtures of 1% by weight of the melt.

The compositions are the modified mixtures used to process the cast irons of the experimental heats, as well as the results of testing the proposed composition of the mixtures: in comparison with the known, they are listed in the table.

To determine the tendency of modified cast irons to form hot cracks, a star-like process sample is used. The absolute crack resistance is determined by the total length of cracks on the surface of the process sample. Absolute

0

The total density values are determined on standard cast samples of 030 mm, and the deoxidation capacity is determined by the concentration of extracted oxygen from modified and unmodified cast iron. Samples for oxygen content are taken at 1350-5 ° C.

these mixtures. The economy from the use of the mixture is 5.1-13.6 rubles / ton of pig iron.

Claims (1)

Invention Formula Determination of toughness of a modifying mixture for cast iron containing magnesium, graphite, silica gel on samples of 10-10-55 mm with V-for-metal and ferrosilicon, from l and h - with a different notch with a depth of 2 mm. The fact that, for the purpose of mastering the components of the modifying mixture, is determined by the total absorption of manganese, graphite, rare-earth metals, silicon, aluminum and magnesium nitrides from their d6 content in the modifying mixture. The determination of the content of components is carried out by the method of differentiated Quantitative analysis on samples taken from cast samples. As follows from the obtained results, the application of the proposed mixture leads to an increase of 15-20% of the mechanical properties of cast iron, its density and fracture capacity due to "a higher level of ability to mix / these mixtures. The economy from the use of the mixture is 5.1-13.6 rubles / ton of pig iron. Invention Formula sh; mechanical properties, cracking resistance and density of cast iron by improving the deoxidation ability of the mixture, it additionally contains silicon-aluminum and manganese nitrides in the following ratio, wt.%: Magnesium 7-12 Graphite8-14 Silikomishmetal Ferr osilitsy 0 Siliko Aluminum 5 Manganese Nitride 20-30 10-18 15-20 11-35 Table continuation