OA16222A - Alloy for reducing and doping steel. - Google Patents

Abstract

The invention relates to ferrous metallurgy, in particular to producing an alloy for reducing, doping and modifying steel. Said invention makes it possible to improve the quality of the steel treated with the inventive alloy owing to the deep reduction and modification of non-metallic impurities and the simultaneous microalloying of steel with barium, titanium and vanadium. Barium, titanium and vanadium are added into the inventive alloy, which contains aluminium, silicium, calcium, carbon and iron, with the following component ratio, in mass%: 45.0-63.0 silicium, 10.0-25.0 aluminium, 1.0-10.0 calcium, 1.0-10.0 barium, 0.3-0.5 vanadium, 1.0-10.0 titanium, 0.1-1.0 carbon, the rest being iron.

Description

The proposed invention is characterized by the following:

An alloy for reducing, doping and modîfyîng steel, containing aluminum, silicium, calcium, carbon and iron, that in addition contains barium, vanadium and titanium at the following ratio, in mass %:

Silicium	45,0-63,0
Aluminum	10,0-25,0
Calcium	1,0-10,0
Barium	1,0-10,0
Vanadium	0,3-5,0
Titanium	1,0-10,0
Carbon	0,1-1,0
Iron	remaining balance.

The content of reducing éléments in the composition of the alloy within specified lîmits allows to lower l,4-l,8-fold the amount of oxygen in the steel volume compared to the known alloy (the prototype). That permitted to raise the bénéficiai use of vanadium up to 90%. Recovery of manganèse from silico-manganèse into the steel was raised by 9-12% reaching 98,8% due to a deep réduction and oxygen shielding by active calcium, barium, aluminum and silicium. Barium and calcium within the specified limits, besides theîr reducing effect, also play a rôle of active desulphurizers; dephosphorizing agents and conditioning agents for non-metallic inclusions (NI), increasing their smelting capacity and due to complexity, signîficantly reduce total amount of non-metallic (NI) in the steel. In the presence of calcium, barium and titanium residual sulfur and oxides are înoculated into fine oxysulfides and complex oxides with equal distribution in the volume of steel without development of stringers and of theîr agglomération (pileups). The amount of residual

PCT/KZ2008/000004 18.09.2008 oxide non-metallic inclusions (NI) was reduced by 1,16-1,35 times than in the steel treatment with the alloy (the prototype).

Microdoping with vanadium and titanium in comparison to the use of the known alloy (the prototype) significantly împroves the mechanical properties of the 5 treated steel. Thus, impact hardness at (-40°C) has reached the values of 0,92-0,94 mj/m2.

The proposed alloy increases transfer of manganèse into steel during its treatment both with manganese-containing concentrâtes in direct doping, as well as from ferroalloys. Manganèse extraction was increased by 0,3-0,5%; the amount of 10 oxide inclusions was reduced by 20%; impact hardness increased by 0,04-0,06 mJ/m² higher than when using the known alloy (the prototype).

The alloy is made of high-ash coal-mîning coal wastes with addition of lowintensify splînt coal; lime; barium ore; vanadium-containing quartzite and ilmenite concentrate. Use of coke is elimînated. Spécifie power consumption is 10,0 15 10,9mW/h. In the process of alloy meltîng, as opposed to the known alloy (the prototype) a high-ash carbonaceous rock and splint coal are used. Carbonaceous rock contains 50-65% ashes, in which the amount of silicium oxide and aluminum oxide is not less than 90%, contains sufficient amounts of natural carbon for the reducîng processes, which is technologie al ly and economically justified. Splint coal additives 20 that hâve the properties of charge débonder, improve gas permeability of upper layers of the shaft top and the extraction of process gas. Power consumption in doping of the claimed alloy is 8,7% lower compared to the prototype.

Example. The claimed composition of the alloy being charged was melted in an ore-smelting fumace with transformer power 0,2MWA. The chemical and technical 25 compositions of the used charging materials are represented in Tables 2 and 3.

18.09.2008

PCT/KZ2008/000004

Table 2 - Technical analysis of carbonaceous rock and coal

Material	Content, %
Ac	Ve	W	Cj2	S
Carbonaceous rock	57,6-59,8	16,0	4,0	20,0-22,4	0,05
Coal	4,0	40,1	10,7	55,9	0,36

Table 3 - Chemical analysis of charging material

Material	Content, %
SiO?	AbO3	Fe2Oj	CaO	MgO	ΤίΟΐ	BaO	V	S	P
Carbonaceous rock	57,6	34,2	5,72	0,7	0,4	1,2	-	-	0,05	0,015
Coal	53,5	27,1	8,35	6,19	3,89	-	-	-	-	0,012
Vanadium-containing quartzite	94,3	1,1	1,2	0,4	0,3	-	-	0,8	-	0,15
Barium ore	35,7	1,0	1,0	2,0	-	-	44,0		8,57	0,02
llmenite concentrate	7,4	3,4	16,8	2,2	1,7	59,7	-	3,0	0,01	0,015
Lime	0,2	0,3	L5	92,0	5,95	-	-	-	0,02	0,03

As a resuit of tests it was established that the least spécifie power consumption; stable fumace operation and better gas permeability of fumace mouth correspond to the melting of the claîmed alloy composition. That approach excludes carbide forming and improves the technological properties of fumace mouth and as a resuit it improves rts operation.

The évaluation of the reducing and doping capacity of the claîmed alloy and of the known (prototype) alloy was performed in an open coreless induction fumace IST-0,1 (capacity 100kg) in melting of low-alloyed steel grades (17GS, 15GUT). Scrap métal with 0,03-0,05% of carbon and up to 0,05% of manganèse content was used as a meta! charge,

A fier obtaining the metallic melt and heating it up to the température of up to 1630-1650°C the métal was poured into a ladle. Réduction with the claîmed alloy and the known alloy (the prototype) was performed in a ladle together with silîcomanganese SMnl7 based on obtaining up to 1,4% of manganèse in the steel. The manganèse extraction rate into the alloy was determined by the chemical

PCT/KZ2008/000004 i 8.09.2008 composition of métal samples. The métal was ladled into ingots that later were rolled into 10-12mm sheets. Results of réduction and doping are shown in Table 4,

The claimed alloy was used in steel treatment in experimental production No 3 - 11 The best results of reducing, doping and modifying steel were obtained when the 5 steel was treated with alloys No. 5-9 (Table 4). In these productions the maximal recovery of manganèse from silicomanganese into steel was 96,0-98,9%, which is 912% higher than in using the prototype alloy. Increase of manganèse extraction can be explained by fuller steel réduction due to high content of silicium and aluminum, as well as the presence of calcium, barium and titanium in the claimed alloy. Oxygen 10 content in experimental steel treated with alloys No. 5-9 was reduced by 1,4-1,8 times to the values of 0,002-0,0026% , compared to the steel treated with the prototype alloy - 0,003-0,0036% respectively.

In order to evaluate qualîties and mechanîcal properties of the obtained métal the quantity of nonmetallic inclusions was determined according to GOST 1778-70.

During réduction with the claimed alloy nonmetallic inclusions were smaller and of globular form, with no alumina stringers or accumulations of oxides, unlike in using the known alloy (the prototype). Thîs is provided because of the calcium and barium presence in the content of the alloy, which, along with desulphurizing and dephosphorîzing capacity, also show inoculating properties that are analogical to capillary active substances, which is évident from oxides coagulation into easily fusible complexes that are easy to remove from the steel volume. Content of residual oxide NI was reduced to 0,007-0,0075% compared to réduction with the known alloy (the prototype), which amounted to 0,0084-0,0097%. Microdoping with vanadium and titanium in the claimed alloy permîtted to increase the impact hardness, 25 moldabîlity and hardness of the experimental steel. The impact hardness at (-40°C) increased to 0,92-0,94 mJ/m² versus 0,82-0,88mJ/m²; flow limit (σ_τ) - 490-5 lOmPa; relative extension (o_s) - 35-37%; temporary résistance (ob) - 610-629mPa. The

PCT/KZ2008/000004 18.09.2008 obtaîned composition of components în the claimed alloy corresponds to the optimal and allows its use for réduction and doping of semikîlled and low-alloy grades of steel, ensuring even formation of easily fusible complex NI that are easily removed from the steel volume, and transforming residual NI into finely dîspersed and of optimal globular shape.

Accepted limits of components ratio in the alloy are rational. In particular, the reduced concentration of calcium, barium, vanadium and titanium which are lower than the established limit in the alloy does not ensure the desired effect of réduction; doping and modifying of residual NI in steel treatment. Thus, steel treatment with alloy obtaîned in meltîng No. 3 with low content of silicium, calcium and barium, in spite of high content of aluminum and titanium does not reduce steel sufficiently; contains high amount of alumina and oxide NI stringers, and the mechanical properties are at the level of steel treated with the known alloy (prototype).

At the same time exceeding the acceptable limits of concentration of these éléments is unreasonable as it încreases the spécifie power consumption in the process of obtaining the claimed alloy and the positive properties that result from its application do not differ much from the claimed limits in the composition.

Thus, compared to the prototype, due to the additional content of barium, vanadium and titanium in the alloy, the proposed invention permits to:

- perform deeper steel réduction;

- significantly reduce the content of nonmetallic inclusions;

- modify (inoculate) residual nonmetallic inclusions into favorable complexes equally dîstributed in steel volume;

- increase the rate of manganèse extraction into steel;

- increase impact hardness of steel;

PCT/KZ2008/000004 l 8.09.2008

Moreover, the economical feasîbility of alloying has to do with the use of inexpensive high-ash carbonaceous rocks, excluding the use of expensive coke.

The results of experimental productions of 17GS and 15GUT grades steel had shown high effectiveness of the claimed alloy.

Claims (1)

1. An alloy for steel réduction and doping containing aluminum, silicium, calcium, carbon and iron, characterized in that it also contains barium, vanadium and titanium with the following corrélation of the components, in mass%:

   Silicium 45,0-63,0 Aluminum 10,0-25,0 Calcium 1,0-10,0 Barium 1,0-10,0 Vanadium 0,3-5,0 Titanium 1,0-10,0 Carbon 0,1-1,0 Iron remaining balance.