US2577883A - Treatment of metals - Google Patents

Description

Patented Dec. 11, 1951 TREATMENT OF METALS Jean Charles Fourmanoit, Brussels, Belgium No Drawing. Application January 3, 1950, Serial No. 136,641. In Belgium January 21, 1949 I 1 Claim.

This invention relates to a process for the manufacture of metals, more particularly of steel Without however being limited to this latter manufacture.

The invention has for its main object to permit a desulfurization, and/or de-phosphorizing and/or de-oxidation of the metal, which shall be as complete as possible.

According to the present invention, pieces of calcined basic substance in rock form, such as lime or dolomite which have retained a porous structure similar to the natural rock from which they have been obtained, and impregnated with one or more alkaline substances, are added to the charge of metal to be subjected to melting or in the course of the melting operation.

As such alkaline substances, use may advantageously be made of sodium or potassium compounds. Anhydrous caustic soda gives particularly good results.

Preferably, the pieces of calcined basic rocky substance are graded for size, the usual dimensions of the pieces being approximately 30/30 The impregnation of the pieces by the alkaline substance or substances may be effected under vacuum, or/and by pressure, or by baking under naked fire.

The impregnated pieces may be added to the charge simultaneously with the other substances employed in the manufacture of the metal. For instance, they may be used in the manufacture of steel with the well-known product consisting of pieces of calcined limestone impregnated with hydrocarbons, such as pitch and/or bitumen.

The pieces of calcined basic rocky substance impregnated according to the present invention may be covered, by immersion for instance, with a coating of hydrocarbon which protects them against hydration when they are stocked, and they may be used thus coated in the process of metal manufacture.

The invention may also be applied to the manufacture of cast-iron, by introducing the pieces of basic substance in rocky form impregnated with alkaline substance, into the charge of a cupola furnace, in a mixture with the usual limestone.

The impregnated pieces may also be used for desulfurizing the metal in a melting vessel, or in a mixing vessel, or in a casting ladle.

Example Limestone in block form is calcined, a high vacuum (70 cm. Hg) is promptly applied to the calcined limestone while in lump form to remove air from its pores, the lumps are treated with an excess of caustic soda at elevated temperature (about 300 C.) uniformly to impregnate and saturate the pores with the caustic soda. The excess of caustic soda is drained off to obalmost entirely,

tain a product in lump form which has the structure of the original limestone, with the said anhydrous caustic soda substantially uniformly distributed throughout the entire cross-section of the pieces of lime or the like.

A charge is introduced into an open-hearth steel-producing furnace, which charge comprises 50 tons of steel scrap, 3 tons of pieces of lime impregnated with pitch and 0.150 ton of pieces of lime impregnated as explained above with caustic soda and containing about 30% of soda. The operation is carried out as usual for the manufacture of steel in an open-hearth furnace, and a steel is finally obtained which is entirely, or desulfurized, de-phosphorized and de-oxidized.

It should be noted that the pieces impregnated according to the present invention (lime for instance) have retained the porous structure of a natural rock (of the limestone before calcina tion) and retain such'form until the metal has been melted or after. The impregnated substance is liberated gradually during the melting of the metal and this may explain the very good results obtained.

What I claim is:

In the desulfurizing and dephosphorizing of ferrous metals, the process which comprises melting down in a furnace a charge of a ferrous metal containing impurities of sulfur and phosphorus, said charge containing lumps of lime having the rock structure of the original limestone of a size ranging from about 30 to 80 mm. Whose pores are thoroughly impregnated throughout their cross section with of the order of about 30 per cent by weight of caustic soda; said impregnated lime lumps having been impregnated with caustic soda by contacting them with an excess of caustic soda at a temperature of the order of 300 C. followed by draining off the excess.

JEAN CHARLES FOURMANOIT.

REFERENCES CITED The following references are of record in the 3 file of this patent:

UNITED STATES PATENTS Number Name Date 196,671 Kay Oct. 30, 1877 696,410 Broodsky Apr. 11, 1902 1,549,313 Jackson Aug. 11, 1925 1,590,731 Evans June 29, 1926 2,159,977 Nicholas May 30, 1939 2,334,499 Millard Nov. 16, 1943 FOREIGN PATENTS Number Country Date 13,843 Great Britain "g- 1888 443,277 Belgium May 5, 1942 444,167 Belgium July 11, 1942 447,397

Belgium Oct. 31, 1942