RU2553125C1 - Modifying mixture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: modifying mixture contains the following components in wt %: barium carbonate 40-50, calcined soda 10-20, strontium carbonate 40-45.

EFFECT: invention increases physical and mechanical properties of treated melts of high-strength cast iron and copper alloys.

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Description

The invention relates to metallurgy, and in particular to modifiers used in the production of cast iron and copper alloys. Refining fluxes are known for processing copper group melts to remove harmful impurities dissolved in the molten metal.

To clean copper alloys, fluxes are used: (barium or sodium peroxide), (copper oxide, sulfuric acid barium and potassium). These fluxes are narrowly targeted, for example, for cleaning from mechanical impurities, from aluminum and antimony and are environmentally unfavorable (Handbook of a caster. M., Mechanical Engineering, 1971, 112-113 pp.).

Also known modifying mixture according to the patent of the Russian Federation for the invention No. 2298047 C22C 35/00, C21C 1/02, C22C 25/00 publ. 04/27/2007

The known modifying mixture is used in the production of castings from gray iron and aluminum alloys, contains barium carbonate and boric acid, additionally contains soda ash in the following ratio, wt. %:

Barium carbonate - 70-80

Boric acid - 10-17

Soda Ash - 8-15

Use in the production of gray cast iron and aluminum alloys can improve the mechanical properties and expands the capabilities of the modifying mixture.

Known modifying mixture is the closest in combination of essential features to the claimed invention and is selected by the applicant as the closest analogue.

The disadvantages of the known modifying mixture are the low physical and mechanical properties of the resulting metal and the possibility of using it only for gray cast iron and aluminum alloys. The known modifying mixture cannot be used in the modification of copper group alloys (brass, bronze) and in the modification of ductile iron.

The task at hand is the expansion of the operational capabilities of the modifying mixture.

The technical result of the claimed invention is to increase the physico-mechanical properties of the alloys.

The specified technical result is achieved in that the modifying mixture containing barium carbonate and soda ash, according to the invention additionally contains strontium carbonate in the following ratio, wt. %:

Barium carbonate - 40-45

Soda Ash - 10-20

Strontium Carbonate - 40-45

The specified modifying mixture can be used to increase physical and mechanical properties, both in the production of gray cast iron and especially high-strength cast iron, and copper alloys (see table).

An increase in the content of barium carbonate and soda ash over 45 and 20%, respectively, leads to an increase in non-metallic inclusions in the melt. A decrease in their content of less than 40 and 10%, respectively, weakens the modifying effect.

An increase in the content of strontium carbonate over 45% leads to the appearance of gas porosity and the appearance of a double eutectic in the structure. A decrease in its content below 40% leads to a violation of the ratio with barium carbon dioxide, reduces the degassing effect and the enlargement of structural components, which reduces the properties of the alloy.

All components of the modifying mixture are light-colored powders, which must be dried at 80-100 ° C for 20-30 minutes before use.

When barium carbonate and soda ash are introduced into cast iron, they dissociate with the formation of BaO (barium oxide), Na ₂ O (sodium oxide), CO ₂ (carbon dioxide). Due to the correspondence structure, barium oxide can be an additional nucleus for graphite inclusion, which accordingly contributes to the grinding of graphite.

Sodium oxide (Na ₂ O) forms a compound with sulfur, desulfurizing the melt, and the resulting sulfides can act as nuclei for graphite, i.e. activating the process of graphitization and grinding graphite inclusions, which helps to increase physical and mechanical properties. The emitted carbon dioxide degasses and mixes the cast iron, which contributes to the uniformity and stability of the structure.

When strontium carbonate is introduced into the melt, it dissociates into strontium oxide (SrO) and carbon dioxide (CO ₂ ). Strontium oxide acts as a graphite nucleus, enhancing the process of primary graphitization, and carbon dioxide is included in the previously described process.

The table shows that the introduction of a modifier consisting of barium carbonate, soda ash and strontium carbonate leads to desulfurization and degassing of the melt, the resulting refractory compounds serve as substrates for the crystallization of graphite, while the more active surface properties of Na, Ba and Sr contribute to grinding and improving the shape of graphite, which leads to grinding of graphite and a favorable change in its shape. This effect entails an increase in the physico-mechanical properties of cast iron.

The mechanism of the effect of strontium carbonate on copper alloys (brass) consists in the interaction of strontium with impurities (aluminum, iron) due to high surface-active properties with the formation of intermetallic compounds removed from the melt by bubbling with CO ₂ bubbles released from BaCO ₃ , Na ₃ CO ₃ , SrCO ₃ , upon their decomposition.

The introduction of Na and Ba leads to a refinement of the structure due to an increase in surface tension at the interface between the double eutectic and the melt – nucleus.

Chemical compounds formed during the decomposition of the modifier components and their interaction with the melt act as nuclei of the forming grains, contribute to their grinding, which, accordingly, increases the physicomechanical properties of the metal.

An example of implementation: the components of the modifier in the form of powders in the required quantities are poured into a paper bag. Cast iron melt, for example, grade СЧ15, melted in a cupola at a temperature of 1400 ° C, is discharged into a casting ladle and a modifier bag is introduced.

The modifier is introduced into the melt in the amount of 0.045-0.055% of the weight of the processed melt. Then the metal is poured into molds and the samples are poured for testing for mechanical properties (table).

A similar scheme is used to modify the melt of brass smelted in an induction furnace.

p / p Mixture composition Physical and mechanical properties SCH-15 LS-59 Hf-45 BaCO ₃ NaCO ₃ Srco ₃ σ _in kg / mm ² HB σ _in kg / mm ² δ,% HB σ _in kg / mm ² δ,% HB one 45 10 45 21.0 179 46.5 18.5 48,2 9.0 171 2 40 twenty 40 21.7 183 47.5 17.0 49.5 2,5 176 3 43 fourteen 43 23.5 190 48.0 15,5 51,4 10.0 176 four fifty fifteen 35 18.3 210 52,2 10.0 10.0 53.5 191 5 thirty twenty fifty 17.0 196 43.5 20.6 43.5 11.0 156 6 15.0 210 40,0 10.0 45.0 7.0 163 GOST 1583-92 GOST 17711-93 GOST 7293-85 7 prototype 19.5-20.0 210-220 - - - - -

Claims (1)

The modifying mixture used to process molten iron and copper alloys, characterized in that it contains components in the following ratio, wt. %:
Barium carbonate 40-45 Soda ash 10-20 Strontium carbonate 40-45