The Department of Steel Metallurgy of the MGVMI has long studied aspects of the behavior of heats when different

methods are used to introduce reagents into the melt. It has been established that, under certain conditions, the introduction of

reagents into the volume of the melt may result in the formation of local zones in which chemical reactions will proceed dif-

ferently than in the rest of the melt. The efficiency of the use of the reagents can be changed by changing their composition

and the method used to administer them. These findings were used to develop and successfully test a technology for intro-

ducing composite blocks into melts (each block consists of a calcium–silicon core and a sheath composed of aluminum alloys).

Several positive results were obtained in a study of the calcium–silicon–aluminum blocks: an increase in the degree

of desulfurization of the steel and a decrease in its content of nonmetallic inclusions, with a simultaneous reduction in the

consumption of calcium–silicon and primary aluminum. Calculations showed that the block is melted almost instantaneous-

ly when the aluminum sheath is inserted into the liquid steel. The aluminum diffuses into the steel and deoxidizes it, form-

ing zones characterized by reduced oxygen activity around lumps of calcium–silicon. Taking this into account, we developed

a technology which conserves manganese-bearing materials.

One variant of the technology is the use of slags that contain oxides of manganese. Work on this variant was done

in the foundry of a factory equipped with 6-ton arc furnaces used to make steel 20LG. The production of this steel involves

the formation of a slag which contains a certain amount of manganese oxides. When the calcium–silicon–aluminum blocks

were used (to desulfurize the steel and reduce its content of nonmetallic inclusions), there was a stable increase (of at least

0.01%) in the concentration of manganese.

Additional studies that were performed showed the following:

• particularly favorable conditions for reducing manganese from the slag are created in the region where the calci-

um–silicon–aluminum blocks are introduced;

• the phenomenon of manganese reduction is most pronounced when the aluminum content of the steel increases to

~0.03%.

Allowing for these results, we arranged for the recycling of bank slags formed in the production of steels of type

20GL. The average composition of the slags, mass %: MnO – 20.6; SiO2 – 16.38; Al2O3 – 1.8; MgO – 4.2; CaO – 33.8;

P2O5 – 0.19; S – 0.131; Fetot – 18. Before use, the slag was subjected to crushing in order to obtain several different frac-

tions: 36% of the 40–80 mm fraction; 28% of the 20–40 mm fraction; 10.5% of the 12–20 mm fraction; <12 mm – the

remainder.

We tested two technologies for conducting heats: introduction of the slag into the furnace in small batches during

the heat, with the calcium–silicon–aluminum blocks being placed in the bottom of the ladle prior to tapping; addition of heat-

ed (white-hot) slag to the bottom of the ladle together with the blocks, followed by the injection of argon. The steel was

tapped with the furnace slag in both variants. We obtained positive results, but the best results were obtained in the second

variant (finishing temperature of the steel 1670–1680°C, slag consumption 25 kg/ton, residual aluminum content of the steel

about 0.03%, argon injection of the steel in the ladle for 2 min). The degree of manganese recovery from the bank slag reach-

es 73% in this case, while the savings of 78% ferromanganese is about 15 kg/ton in the production of steels of type 20LG

Metallurgist, Vol. 45, Nos. 9–10, 2001

TECHNICAL MEASURES FOR CONSERVING

MANGANESE-BEARING FERROALLOYS

G. A. Isaev and V. A. Kudrin UDC 669.18

Moscow State Evening Metallurgical Institute (MGVMI). Translated from Metallurg, No. 10, pp. 57–58, October,

2001.

0026-0894/01/0910-0417$25.00 ©2001 Plenum Publishing Corporation 417

and about 11 kg/ton in the production of steels of type (20–45)L. The positive results obtained in this stage of the study were

used to develop a new variant of the technology – the use of blocks of ferromanganese in a protective sheath composed of

inexpensive aluminum-bearing by-products (silumins). Attempts to apply the protective sheath to lumps of ferromanganese

showed that the latter reacts with the sheath. As a result,the sheath has the following average composition,mass %:Al –

69.75; Si – 27.05; Mn – 22.47; Mg – 5.14.

We developed regimes that ensure close contact between the protective sheath and the lumps of ferromanganese. We

also determined the main parameters needed to obtain a strong and dense protective sheath – the temperature of the alu-

minum-bearing melt,holding time, the relationship between the mass of a lump of ferromanganese and the time of preheat-

ing before immersion in the melt.

The initial laboratory studies showed that the composite ferromanganese–aluminum material is more effective than

ordinary ferromanganese for alloying steels.

Trial heats conducted by the given technology in a 10-ton arc furnace in an electric steelmaking shop showed that

the degree of assimilation of manganese is 8–24% greater than in the standard practice. We statistically analyzed the con-

sumption of ferromanganese and a large volume of data on heats of both manganese steels and carbon steels.

In the analysis,we examined the extent to which the actual degree of manganese assimilation by the steel and its

actual manganese content deviated from the top,middle, and bottom limits stipulated by the GOST. The methods of mathe-

matical statistics were used as qualitative and quantitative characteristics of the deviations.

The studies showed that the consumption of ferromanganese is traditionally calculated in such a way that the man-

ganese content of the steel corresponds to the upper limit. The use of this approach is no longer justified.

It follows from the data in Table 1 that in the production of low-manganese steels,most of the deviations (78.5%)

are seen in the production of steel with a manganese content 0.12–0.25% above the minimum specified for the grade. The

remaining deviations are seen when the manganese content exceeds the minimum by 0.02–0.11%. The latter figures are also

appreciably above the lower limit.

The results of the studies discussed here can be employed as a basis for recommending that the amount of ferro-

manganese used for residual alloying be calculated on the basis of the condition that the actual final manganese content be

0.1% below the content determined in the calculations normally performed as part of the production process. This will make

it possible to reduce the consumption of ferromanganese by roughly 1.5 kg/ton steel,which shows that ways can still be found

to save ferromanganese.

Conclusions. The amount of manganese saved in the alloying of steel can be increased further in the following

cases:the replacement of ferromanganese by a composite ferromanganese–aluminum material; the introduction of a man-

ganese-bearing slag into the ladle together with calcium–silicon–aluminum blocks; revision of the method used to calculate

the manganese content of the finished steel by lowering the maximum by 0.1% from the value traditionally used.

418

TABLE 1. Distribution of Deviations of the Actual Manganese Content of

Steel from the Minimum Specified for the Grade

Total number ∆MnNumber of heats mi in the

mi /nof heats n range of the deviations

28 0.02–0.06 2 0.071

28 0.07–0.11 4 0.142

28 0.12–0.16 11 0.392

28 0.17–0.21 8 0.285

28 0.22–0.26 3 0.107