Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/30—Regulating or controlling the blowing
  • C21C5/32—Blowing from above

Definitions

• the invention relates to a method for producing steel with a low phosphorus content from pig iron with the usual phosphorus content, in which the pig iron in a metallurgical vessel, in particular a converter, in which a fresh gas consisting predominantly or completely of technically pure oxygen is blown onto the melt from above and an inert stirring gas, in particular blown into the melt from below, in a single process step, is simultaneously decarburized and dephosphorized.
• a method for further reducing the phosphorus content in which a pig iron is poured into a converter and fresh oxygen is blown onto the pig iron from above with a slag-forming agent and at the same time a gas from the group of inert gas, nitrogen, Oxygen, carbon monoxide, carbon dioxide or their mixtures are blown into the melt from below. It is essential in this process that a desilicated pig iron is introduced into the converter. This means that desilication involves a separate process step. Due to this separate process step, temperature losses of the melt occur; there are also additional quantities of slag which lead to increased iron losses.
• This fresh process is aimed at a final phosphorus content of 0.010% by mass or less; The published specification contains no information about the influence of the manganese content of the pig iron used on the setting of the lowest phosphorus content in the steel.
• the unstilled steel melt in the fresh vessel is after or shortly before the end of the usual fresh process, ie in the region of a carbon content of less than 0.4% and after extensive removal of the fresh slag with the aid of a conveying gas CaC0 3 and Na 2 C0 3 in a ratio of 1: 1 with the addition of fluorspar and / or iron oxide in an amount of up to 30% by mass in% of the carbonate mixture so deeply introduced into the melt that the total slag is mixed and then the steel is added Retention of the treatment slag is tapped and finished in the pan in a manner known per se. In this way, phosphorus levels in the steel of less than 0.001% should be achievable.
• the steel in the converter is not or only insignificantly dephosphorized after decarburization and then at a temperature which essentially occurs after the carbon has been burned into a heated pan poured, in which then dephosphoric agents are blown in in a conventional manner.
• the invention is based, to reduce the usual phosphorus content of pig iron, which is usually up to 0.2% to 0.005 mass content in% or less, without additional effort during a single-stage combined blow molding process.
• this object is achieved according to the invention in that pig iron with a manganese content of less than 0.2% by mass is used in% and the refining up to a final phosphorus content in the steel at the end of the bubble of 0.005 mass content in% or less is carried out.
• the manganese content of the pig iron used is generally about 0.4 to 0.8%, e.g. DE-Z “Stahl und Eisen” 104 (1984) No. 16, pp. 767 to 773.
• Figure 6 on p. 769 shows a manganese content of the pig iron used of around 0.50 to 0.60%.
• the final phosphorus content after freshening is between 0.020 and 0.010%, depending on the converter size.
• B. pictures 4, 9 and 12 on pages 37 to 39 show.
• the invention is now based on the knowledge that when using pig iron with a manganese content of less than 0.2% final phosphorus content can be achieved after refining 0.005% and less. This is made possible without disadvantages that are inherent in the known processes.
• pig iron with a reduced manganese content can be achieved without difficulty and without costs by using inexpensive ores with low manganese content in the blast furnace and by not having to reuse manganese-containing steel slags in the blast furnace furnace.
• the pig iron is used with a silicon content of 0.15 to 0.35% by mass in%, preferably less than 0.30% by mass in%, there is a further advantage in terms of reducing the required amount of lime, which can amount to 20 to 40 kg / t crude steel when freshening. This also results in a reduction in the amount of slag produced.
• the lower amount of lime corresponds to the lower silicon content in the specified range.
• the pig iron with low silicon and manganese content can then be refined to low carbon, sulfur and especially phosphorus content in a single blowing process without upstream dephosphorus and without changing slags.
• a metallurgical vessel in particular in a converter
• technically pure oxygen is blown from above onto the surface of the molten bath by means of a lance.
• an inert stirring gas is blown into the melt from below. This can be done continuously or temporarily from the start of oxygen inflation until the fresh steel is cut off.
• intermittent or intermittent blowing in of the stirring gas it is important to blow the gas in during the first and last third of the total treatment time.
• the invention is illustrated by the following examples.
• the percentages correspond to mass contents in%.
• Technically pure oxygen was used again as fresh gas, which was blown onto the pig iron melt from above.
• the amount of lime added was 51 kg / t crude steel.
• a comparison of the results from the comparative example with the exemplary embodiments 1 and 2 according to the invention shows that when pig iron with manganese contents of less than 0.20% is used in the converter, the final phosphorus contents can be reduced with approximately the same initial phosphorus contents of 0.005% and less . There is no increased iron slagging or other process disadvantages. The amounts of lime used can also be further reduced if the Si content in pig iron is reduced, s. Example 2. This reduces the amount of slag. Another advantage over the comparative example is that the blowing process runs smoothly and the known ejection of slag and steel is largely eliminated.
• the process according to the invention is suitable for freshening pig iron low in phosphorus with an initial phosphorus content of up to 0.2%, preferably up to 0.15%.
• the lime is added in pieces (8 to 40 mm) at the beginning of the blowing process.
• the amount of lime added when carrying out the method according to the invention essentially depends on the silicon content and is not greater than when carrying out the generic method without the measures according to the invention.
• the final blowing temperature should not exceed 1650 ° C.

Priority Applications (1)

Applications Claiming Priority (3)

Publications (2)

Family

ID=25742039

Family Applications (1)

Country Status (14)

Families Citing this family (8)

Family Cites Families (15)

• 1984
  • 1984-09-22 DE DE3434894A patent/DE3434894C2/de not_active Expired
• 1985
  • 1985-08-21 AT AT85110495T patent/ATE39497T1/de active
  • 1985-08-21 DE DE8585110495T patent/DE3567031D1/de not_active Expired
  • 1985-08-21 EP EP85110495A patent/EP0175924B1/de not_active Expired
  • 1985-08-22 AU AU46540/85A patent/AU569412B2/en not_active Ceased
  • 1985-08-28 ZA ZA856561A patent/ZA856561B/xx unknown
  • 1985-08-28 FI FI853294A patent/FI77694C/fi not_active IP Right Cessation
  • 1985-09-04 ES ES546700A patent/ES8703936A1/es not_active Expired
  • 1985-09-05 MX MX8889A patent/MX164702B/es unknown
  • 1985-09-11 US US06/774,632 patent/US4604138A/en not_active Expired - Fee Related
  • 1985-09-12 CN CN85106853.7A patent/CN1005276B/zh not_active Expired
  • 1985-09-13 JP JP60201953A patent/JPS6179709A/ja active Granted
  • 1985-09-16 IN IN655/CAL/85A patent/IN163954B/en unknown
  • 1985-09-20 BR BR8504605A patent/BR8504605A/pt not_active IP Right Cessation
  • 1985-09-20 CA CA000491216A patent/CA1234989A/en not_active Expired

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events