RU1777610C - Method for desulfurization and alloying with titanium of corrosion-resistant steel - Google Patents

Abstract

The invention can be used in metallurgy in the smelting of corrosion-resistant steel. Essence: in the process of releasing melting from an arc furnace into the first ladle, desulphurization of corrosion-resistant steel and reduction of chromium from chromium oxides of furnace slag are simultaneously carried out by adding a mixture of lime and silicon in the ratio 1: (0.5-0.6 ) weighing 38-40 kg / t of steel, and then desulfurization is carried out a second time during the overflow of steel from the first ladle to the second ladle by adding a mixture of lime and fluorspar in the ratio 1:: (0.3-0.6) weighing 4- 10 kg / t of steel, with one desulfurization being carried out Temporarily titanium alloyed steel in the second ladle is first doped at the bottom of the second bucket containing materials titada- weight 10- 20 kg / t steel, and after draining 20-40; NY weight of the melt in the second bucket sits remainder five- tansoderzhaschih materials.

Description

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The invention relates to ferrous metallurgy and can be used in the production of corrosion-resistant steels in electric arc furnaces.

The aim of the invention is to increase the degree of desulfurization of steel and the absorption of titanium and chromium.

The essence of the invention lies in the fact that in the method of desulfurization and alloying with titanium of corrosion-resistant steel, which includes the release of metal with slag from an arc furnace into a first ladle, removing furnace slag from a ladle, pouring metal into a second ladle,

additive in the second ladle of titanium-containing materials and metal blowing in the second ladle with inert gas; first, in the process of melting from the arc furnace into the first ladle, corrosion-resistant steel is desulphurized and chromium is reduced from the chromium oxides of the furnace slag by the additive before the mixture is melted of lime and silicon in a ratio of 1: (0.5-0.6) weighing 38-40 kg / t of steel, and then desulfurization is carried out a second time during the overflow of steel from the first ladle to the WTO

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a swarm bucket by adding a mixture of lime and fluorspar in a ratio of 1: (O ,, 6) with a mass of 10 kg / t of steel, while desulfurization is carried out simultaneously with the alloying of steel with titanium in the second ladle by first adding titanium-containing materials to the bottom of the second bucket with a mass 10-20 kg / t of steel, and after draining 20-1 + 0% of the mass of the whole heat in the second ladle, the remaining amount of titanium-containing materials is planted.

The introduction of a mixture of lime and silicon prior to the release of the smelting weighing less than 38 kg / t of steel does not allow an increased reduction of chromium from the slag of the end of the oxygen purge.

With the mass of this mixture exceeding 0 kg / t, the degree of reduction of chromium and primary desulfurization of steel practically does not increase.

With a silicon fraction of less than 0.5, the conditions for the reduction of chromium from slag deteriorate due to insufficient deoxidation of the metal-slag system. When its values are more than 0.6, the likelihood of obtaining the silicon content in the finished steel increases above the upper limit, which, for example, for steel 12X18H10T is P, 80% 0

The use of less than 4 kg / t amount of desulfurizing mixture by overflow does not significantly reduce the sulfur concentration in steel. The introduction of more than 10 kg / t of its amount practically does not affect the increase in the degree of desulfurization, but only leads to an excessive consumption of lime and fluorspar and increases the likelihood of titanium slagging, especially when using low-percentage titanium-containing materials.

With a feldspar fraction of less than 0.3, the dissolution time of the desulfurizing mixture increases and the viscosity of the resulting slag increases, resulting in deterioration in the flow of steel desulfurization during overflow.

With a proportion of spar greater than 0.6, the steel desulfurization process is practically not improving, while the relatively expensive and rather scarce fluorspar is unjustifiably consumed (the price of lime is about 17 rubles / ton, and fluorspar is about 160 rubles / ton).

Entering titanium-containing materials to the bottom of the second bucket weighing less than

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with

5

0

5

about

5

0

5

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10 kg / t does not allow to obtain the titanium content in the finished steel within the required limits. As a rule, the titanium content in corrosion-resistant steel in accordance with the requirements of GOST 5632-72 is in the range of 0.3-0.8% by weight depending on the carbon content. The introduction of titanium-containing materials to the bottom of the second bucket weighing more than 20 kg / t does not allow to obtain a uniform distribution of titanium concentration over the volume of the bucket.

The introduction of the remaining amount of titanium-containing materials (in excess of 20 kg / t) and the desulfurizing mixture before discharge into the second ladle is less than 20% of the metal mass leads to an increase in the likelihood of slagging of titanium-containing materials and an uneven distribution of titanium throughout the volume of the ladle, and when they are introduced after discharge more than 40 % metal mass - steel desulfurization conditions are deteriorating.

Example 1. When smelting steel grade 12X18H10T in a 100-ton electric arc furnace after melting the charge and oxidative decarburization, a metal was obtained containing 0.08% carbon, 15.0% chromium, 10.0% nickel, 0.025% sulfur . Chromium fumes for oxygen purge amounted to 2 kt. After introducing cooling additives, 2.5 tons of lime and 2.1 tons of 65% ferrosilicon (ratio of lime to silicon 1: 0.55) were added to the furnace and also after obtaining a homogeneous fluid slag over the entire surface of the bath ferrochrome and nickel. Slag was not downloaded during the recovery period. After the release of the melt, the slag was drained from the ladle by tilting it with a crane. The residual slag mass was (measured with a metal ramrod) about 1 ton. The chemical composition of the metal in the bucket: carbon — 0.09%, chromium — 17.7%, nickel — 10.0%, sulfur — 0.022%. Metal temperature -. Then they started pouring metal through the nose of the first ladle into the second steel pouring ladle, onto the bottom of which 1.5 tons of 70% ferrotitanium were preloaded. After draining, about 30% of the total metal mass (visually determined) was added from the top to the second bucket with 0.8 tons of desulfurizing mixture (0.6 tons of lime and 0.2 tons of fluorspar). After overflow temperature

517

the metal was 1580 ° С „Having purged steel with argon through a lance in the bottom of the ladle for min, the ladle with finished steel was cast at metal temperature. The chemical composition of the obtained steel: carbon - 0.09%, chromium - 17.5%, nickel - 10.0%, sulfur - 0.015%, titanium - 0.60% (the same in all samples during casting). Through assimilation of chromium was 89%, titanium - 57%, the total degree of desulfurization - 0%. The melting time was 1 $ min shorter than with conventional two-slag technology.

Example 2. The same as in example 1. After introducing cooling additives into the furnace, 2.5 tons of lime and 3.3 tons of ferrosilicochrome grade were added (lime to silicon ratio 1: 0.53). The temperature of the metal after release is 1 60 ° C. 1.5 tons of 30% ferrotitanium were charged to the bottom of the second bucket. After draining 30% of the mass of metal, 2.5 tons of 30% ferrotitanium and 0.6 tons of desulfurizing mixture (0.4 tons of lime and 0.2 tons of spar) were sequentially added to the second bucket. The temperature of the metal after overflow is 1570 ° C, after purging with argon for 30 minutes -. The chemical composition of the obtained steel: carbon - 0.09%, chromium - 17.5%, nickel - 10.0%, sulfur - 0.016%, titanium - 0.60%. Through assimilation of chromium - 89%, titanium - 55%, the total degree of desulfurization - 36%.

The results of pilot melts, shown in tables 1-3, indicate the advantages of desulfurization and alloying with titanium of stainless steel according to the proposed method, i

The application of the proposed method of alloying with titanium and steel desulfurization will increase the through absorption of chromium from 85 to, increase O6

Claims (1)

to reduce the furnace productivity by about 5% by reducing the duration of the recovery period of electric melting as a result of the transition to single-slag technology, to increase the absorption of titanium, to use low-percent titanium-containing materials for out-furnace alloying, to ensure satisfactory desulfurization of corrosion-resistant steel The method of desulfurization and alloying with titanium of corrosion-resistant steel containing 0.3-0.8% titanium, including the release of metal with slag from the arc furnace into the first ladle, removal of furnace slag from the ladle, overflow of metal into the second ladle, addition of titanium-containing materials to the second ladle and blowing in the second ladle with an inert gas, characterized in that, in order to increase the degree of desulfurization of steel, the absorption of titanium and chromium, steel is desulfurized and chromium is reduced simultaneously in the process of melting from the arc furnace into the first ladle and chromium oxides of furnace slag by means of an additive prior to melting, a mixture of lime and silicon in a ratio of 1:: (0.5-0.6) kg / t of steel, and then desulfurization is carried out a second time during the overflow of steel from the first ladle to the second by additives in the second bucket of a mixture of lime and fluorspar in a ratio of 1: (0.3-0.6) with a mass of kg / t of steel, while desulfurization is carried out simultaneously with the alloying of steel; titanium in the second ladle, first an additive to the bottom of the second ladle of titanium-containing materials with a mass of 0-20 kg / t of steel, and after draining the entire smelting mass, an additive to the second ladle of the remaining amount of titanium-containing materials Table 1