RU2525870C2 - Method of ladle spheroidising modification of high-strength cast irons - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used in machine building and automotive industry for productions of casts of high-strength cast iron with spherical and vermicular shape of graphite. Spheroidising modifier as ferromagnesium silicon foundry alloy is placed at ladle bottom rear, opposite the tip, so that coverage of ladle bottom does not exceed the radius of bottom circle. Then, ladle is filled with iron melt for 30-60 s. Note here that at teeming, iron melt jet is fed closer to ladle tip.

EFFECT: higher efficiency.

2 cl, 1 dwg

Description

The invention relates to metallurgy, in particular to a method for bucket spheroidizing modification of molten iron to produce high-strength cast iron with spherical and vermicular graphite.

It is widely known that to obtain high-strength cast irons with spherical and vermicular graphite by light alloys (the specific gravity is less than the specific gravity of the molten iron), such bucket spheroidizing modifications are used as the “sandwich process”, “ladle with a lid”, etc. (Knustad, О Problems encountered in the production of high-strength cast irons. Overview of existing methods for producing high-frequency cast iron and modifiers used [Text] / O. Knustad // Foundry worker of Russia. - 2011. - No. 4. - P.19-26; Kosnikov, GA. foundry [Text] / GA Kosnikov. - C St. Petersburg: SPbSPU, 2002. - 204 p .; Alexandrov, N. N. High-quality cast iron for castings [Text] / NN Aleksandrov. - M: Engineering, 1982. - 222 p .; RF patent No. 2074894; copyright certificate No. 1786086).

However, all existing methods of bucket spheroidizing modification involve the use of special technological schemes for placing a modifier, for example, such as a reaction pocket for a modifier on the bottom of the bucket, and / or additional equipment for filling the bucket with molten iron from the furnace, such as a tank lid with a storage hole molten iron from the furnace and dosed to the ladle, forklift to remove and put on the lid on the ladle, etc.

The disadvantages of all known methods of bucket spheroidizing modification of cast iron are: increased complexity, the need for additional equipment and machinery, reduced productivity.

The objective of the invention is to reduce the complexity, the rejection of the use of additional equipment and technology, increasing productivity.

The technical result in the implementation of the invention is to create a simplified compared to the "sandwich process" method of ladle modification of ductile iron, which does not require the use of additional equipment and technology and allows you to stably obtain the required quality of cast iron in castings.

No prior art analogues have been identified.

The problem is solved in that a method of bucket spheroidizing modification “pouring from above” was developed (Fig. 1), according to which, in the back of the bottom of the bucket (opposite the toe) using a special filling funnel (Fig. 1a) or by turning the bucket back on 45 ° (clockwise) (fig. 1b,) a spheroidizing modifier (“light” alloy type FSMg) is placed so that the overlap of the bottom of the bucket does not exceed the radius of its circumference, while the erosion of the hitch ra and his fumes. After that, over a period of 30 ... 60 s, the bucket is filled with molten iron from the furnace.

When filling the bucket with metal, the melt stream should be fed closer to the bucket nose to avoid erosion and premature reaction of the modifier with cast iron melt. The metal jet from the waiting furnace is fed continuously, and the time of filling the ladle with molten iron is estimated from the expression:

- эквивалентный диаметр носка печи, м; v_ч -кинематическая вязкость расплава чугуна при температуре заливки, м²/с; S_ч - живое сечение потока чугуна, м²; Re - число Рейнольдса.where t _k is the time of filling the bucket with a molten iron, s; V _to - the volume of the bucket, m ³ ; $$D_{\mathrm{uh}\mathrm{to}\mathrm{at}}^n$$

- equivalent diameter of the toe of the furnace, m; v _{h -} kinematic viscosity of the molten iron at pouring temperature, m ² / s; S _h - live section of the flow of cast iron, m ² ; Re is the Reynolds number.

When filling the ladle with filling of the “light” spheroidizer in accordance with the “top-down” technology, it is necessary that the mode of motion of the molten iron from the waiting furnace into the ladle be unsteady, that is, Re≈3000 ... 6000.

In the turbulent mode of motion of the molten iron from the furnace to the ladle (with a strong jet Re> 6000), due to the fast filling of the ladle, there is a splash of metal and emission of particles of unreacted modifier. All this makes the modification process unstable, worsens the environmental situation and imposes a restriction on the operation of this technology in an open bucket.

In the laminar mode of motion of the molten iron from the furnace to the ladle (with a weak jet Re <3000), due to the slow filling of the ladle, most of the modifier floats on the mirror and reacts with atmospheric oxygen, which leads to an accelerated extinction of the modifying effect due to premature magnesium fumes.

Therefore, the bucket filling time is inversely proportional to the Reynolds number and should fall within the recommended range. In particular, assuming that the metal consumption of the ladle is 0.17 m ³ , the equivalent diameter of the furnace toe is 0.367 m, the living flow cross section is assumed to be 2/3 of the furnace toe section is 0.0176 m ^2, and the kinematic viscosity of the molten iron is 2 · 10 ^-5 m ² / s there are known and constant values, when substituting the range of Reynolds numbers 3000 ... 6000 into the formula, they calculate the optimal range of bucket filling time with the best absorption of magnesium from the modifier: t = 30 ... 60 s.

Studies conducted on the sources of patent and scientific and technical information showed that the claimed method for producing high-strength cast iron with spherical and vermicular form of graphite by ladle modification with light alloys is unknown and does not explicitly follow from the studied prior art, that is, meets the criteria of "novelty" and " inventive step ".

The inventive method of modification can be used in the conditions of iron production and meets the criterion of "industrial applicability".

Claims (2)

1. The method of bucket spheroidizing modification of high-strength cast irons, including placing a spheroidizing modifier on the bottom of the bucket and filling the bucket with molten cast iron, characterized in that the spheroidizing modifier in the form of a ferrosilicomagnesium ligature is placed in the back of the bottom of the bucket, opposite the toe, so that part of the bucket did not exceed the length of the radius of its circumference, after that within 30 ... 60 s the bucket is filled with molten iron, and when the bucket is filled with metal, the melt stream and cast iron is served closer to the toe of the bucket. 2. The method according to claim 1, characterized in that the time of filling the bucket with molten iron is determined by the formula:

where t _k is the time of filling the bucket with a molten iron, s; V _to - the volume of the bucket, m ³ ; D ⁿ _equiv - equivalent toe diameter of the furnace, m; v _h - kinematic viscosity of the molten iron at pouring temperature, m ² / s; S _h - live section of the flow of cast iron, m ² ; Re = 3000 ... 6000 is the Reynolds number characterizing the mode of motion of the melt from the furnace to the ladle.

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