STEEL PRODUCTION METHOD AND CORRESPONDING INSTALLATION

Claims

1. A method for producing steel (50b) comprising at least a first direct reduction stage in which a direct reduction unit (11) reduces iron ore (20) using gas to produce an iron-containing material (30), characterized in that it comprises at least a second stage consisting solely of melting, in which an electric melting furnace (12) melts said iron-containing material (30) to form a volume of slag (21) and a volume of liquid metal (40), the latter having a percentage of carbon less than or equal to about 1%.

2. The method according to claim 1, characterized in that in the presence of at least one blast furnace (110) supplying part of the material for the production of said steel (50b), it subsequently includes at least a third stage of carburization, in which in a carburization station (13) a desired amount of carbon is added to said liquid metal (40) to obtain a carburized metal (50c) with a desired percentage of carbon in the range from 1% to 3% 3. The method according to claim 2, characterized in that it includes a fourth oxidation stage, in which, by means of at least one basic oxygen furnace (120), said carburized metal (50c) is mixed with a certain amount of pig iron (50a) produced in said at least one blast furnace (110), and together they are subjected to at least one oxygen blow to oxidize excess carbon in order to obtain said steel (50b), which is then sent to the continuous casting stage.

4. The method according to claim 3, characterized in that it includes a mixing step in which, in a mixing station (14), said carburized metal (50c) is mixed with a certain amount of pig iron (50a) produced in said at least one blast furnace (110), before being introduced into said oxygen converter furnace (120).

5. The method according to paragraph 3 or 4, characterized in that after dismantling the said at least one blast furnace (110), the third stage of carburization is eliminated together with the said oxygen converter (120), and in the said carburization station (13) out-of-furnace treatment processes take place to obtain the said steel (50b), which is cast at the said continuous casting stage.

6. The method according to paragraph 5, characterized in that at the said second stage, consisting exclusively of melting, in the said electric furnace (12) the processes of refining the liquid metal (40) also take place.

7. The method according to any one of the preceding claims, characterized in that said iron ore (20) used in said first stage of direct reduction has an iron concentration in the range of from 62% to 68%.

8. A method according to any of the preceding claims, characterized in that said reducing gas comprises hydrogen gas in combination with, or predominates in relation to, a gas mixture consisting primarily of carbon monoxide, methane, light hydrocarbons and a small percentage of other gases.

9. The method according to any of the preceding claims, characterized in that the oxidation to which the iron-containing material (30) obtained by direct reduction is subjected in said second stage, consisting exclusively of melting, uses approximately 5 Nm 3 / t up to 15 Nm 3 / t O2, and the fact that the said slag (21) has an iron oxide concentration in the range of approximately 10% to 15% 10. The method according to any one of paragraphs 2-9, characterized in that at the said third stage of carburization, graphite in pieces or flux-cored wire containing graphite or CaC2 is used.

11. The method according to any of the preceding paragraphs, characterized in that at said second stage, consisting exclusively of melting, said electric furnace (12) is also loaded with scrap metal (15).

12. An installation (10, 110) for producing steel (50b) comprising at least one direct reduction iron installation (11) configured to reduce iron ore (20) using natural gas to produce an iron-containing material (30), characterized in that it comprises at least one electric smelting furnace (12) located downstream of said direct reduction installation (11) and suitable for melting said iron-containing material (30) to form a volume of slag (21) and a volume of liquid metal (40), the latter having a percentage carbon content of less than or equal to about 1% 13. The installation (10, 110) according to claim 12, characterized in that in a first configuration, said installation (10, 110) comprises at least one carburizing station (13) located after said at least one electric melting furnace (12) and suitable for adding the required percentage of carbon to said liquid metal (40) to obtain a carburized metal (50c) with the required percentage of carbon, at least one blast furnace (110) suitable for feeding a certain amount of pig iron (50a) for the production of said steel (50b), and at least one basic oxygen furnace (120) suitable for receiving and oxidizing excess carbon contained in said carburized metal (50c), said pig iron (50a) and / or scrap metal;and in that, in the second configuration, transformed in relation to the said first configuration, the said at least one electric furnace (12) is also configured to carry out refining processes of the said liquid metal (40), and the said carburizing station (13) is configured to carry out processes of out-of-furnace treatment of the said refined liquid metal (40) in order to obtain the said steel (50b).; 14. The installation (10) according to paragraph 13, characterized in that in said second configuration, said installation (10) does not have blast furnaces (110) and an oxygen converter furnace (120).