SU1420034A1 - Method of extra-furnace treatment of steels in ladle with mixture of ferrotinanium and ferrocerium - Google Patents

Abstract

The invention relates to methods for the deoxidation and modification of cast nitrogen-containing steels and can be used to produce high-quality steels, for example H2I49MAFL. The purpose of the invention is to increase ductility and toughness at low temperatures. The method includes the following operations: 4.4-2.5 kg / ton of nitrated ferrochrome are placed in the furnace before casting, the steel is processed in a ladle with a combined additive of ferrotitanium, ferrovanadium and ferroceri in amounts, respectively, kg / t: 2.0-5, 0; 4.25-11.25 and 1.0-2.6 to ensure the content of titanium, vanadium, cerium and nitrogen in the finished metal in accordance with the expressions TiKN

Description

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with f

The invention relates to metallurgy and can be used to obtain high-quality steels.

I The purpose of the invention is to increase the plasticity and impact toughness at ideal temperatures.

It was experimentally established that with the introduction of ferrotitanium is less than 2.0 kg / t or with a ratio of

k 1,2-10 in the finished steel does not achieve deep deoxidation and modification, since all titanium is used to remove oxygen, and the formation of titanium nitrides, which serve as additional centers of crystallization, does not occur and does not reach the required degree from | Grain grinding,

 With the addition of ferrotitanium over kg / ton or with a ratio of tTilCN i p 2.2 10, accumulations of oxy and carbonitride inclusions are formed, which reduce the impact strength at low temperatures,

I Vanadium nitrides are separated from a solid solution of steel at 900-1050 ° C and are finely dispersed inclusions that are effective

Modify the structure of cast steel,

hr introduction of ferrovanadi less

4.25 kg / ton or at a ratio of VJCNJ

4.5 The amount of vanadium nitrides is small and the effect of modification is weak. With the addition of ferrovanadium of more than 11.25 kg / ton or with a Cv ratio of N 6.4-1.0, a large number of vanadium nitrides and carbonitrides are formed; diy leads to an overvoltage of the metal matrix and a decrease in cold resistance.

Cerium effectively modifies nonmetallic inclusions, is a strong deoxidizing agent and desulfurizer, improves the toughness of steel. The addition of cerium to less than 1.0 kg / t or with a Ce UN ratio of 0.5–10 in the finished metal is ineffective, since it has little effect on the nature of non-metallic inclusions. With the introduction of ferroce

At over 2.6 kg / ton or at a ratio of 71.5-10, cerium suppresses the nitride formation process with the participation of titanium and vanadium due to a decrease in nitrogen activity, which tones the effect of modification. In addition, cerium forms complex oxy sulfonitride inclusions of a large size, located irregularly

Q

,

five

Q

five

0

0

five

but in terms of steel volume, which drastically reduces toughness, and the cold resistance threshold shifts to the freezing temperature range.

An increase in cold resistance of the steels treated by the proposed method is achieved by the joint introduction of these elements with nitrogen, which provokes the formation of dispersed excess phases at different temperature-time stages of the formation of a steel casting. .

The invention is illustrated by examples, the results of which are shown in Tables 1 and 2.

The steels are smelted in an induction ram of magnesite crucible.

After melting, iron is set in steel and FS75 is fermented by ferrosilicon. Then, at 1600 ° C, chrome is melted and expanded. temperature up to 1620 C. Nitrided ferrochrome PCHN600A (7.9% nitrogen) is added to a 30 min liquid melting period. After downloading the slag at (20-2650 ° C), the metal is poured into a ladle, seated on a jet of ferrotitanium PTI35a, ferrovanadium FBdZZa and ferrocerium (50% cerium). Then, slag is removed from the surface of the metal in the ladle and cast into dried sand and clay forms. The obtained ingots are subjected to heat treatment (high-temperature homogenization and double normalization with high tempering) and make samples for the study of properties.

The test results are shown in table 2.

Claims (1)

Comparison of test results for steels treated with known soba and proposed shows the advantages of the latter for higher values of plastic and cold-resistant properties, which allows to increase the reliability of parts manufactured from them. Invention Formula The method of out-of-furnace treatment of steels in a ladle with a mixture of ferrotitanium and ferrocerium, characterized in that, in order to increase plasticity and toughness at negative temperatures, 4.4-2.5 kg / ton of nitrated ferrochrome are applied to the furnace before pouring steel in the ladle is carried out by joint addition of ferrotitanium, ferrovanadium and ferroceri in amounts of 2.05, 0, respectively; T ,, 25; 1.0-2.6 kg / t and the provision in the finished metal of titanium, vanadium and nitrogen in accordance with the expressions:   (1.2 - 2.2) .10 VltN (4.5 - 6, A) -10 CelfN (0.5 - 1.5) -10 Table 1