DD157807A1 - METHOD OF GENERATING A MODIFIED SOFTENER IN METALLURGICAL GEFAESSES - Google Patents

Abstract

The modified soft iron produced by the method according to the invention is for applications in electrical engineering / electronics, especially as a base metal for the production of bimetallic determined that is defined by special requirements for its chemical composition, in particular oxygen content. It is the object of the invention to produce a modified soft iron in the bottom-blowing oxygen converter by means of a special combination of several process steps, with which the required properties are achieved. The essence of the invention is a procedure for the production of a modified soft iron with less than 0.06% carbon, max. 0.10% manganese, max. 0.030% phosphorus, max. To develop 0.015% sulfur and min. 0.050% oxygen, which is a prerequisite for a good cooking movement in the subsequent remelting to increase the quality of the special iron-nickel-based materials and to reduce the rejection rates.

Description

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Title of the invention

Method for producing a modified soft iron in metallurgical vessels

Field of application of the invention

The invention relates to a method for producing a modified soft iron in metallurgical vessels, preferably in bottom-blowing oxygen converters, by combining several process steps with low carbon, silicon, manganese, phosphorus, sulfur and high oxygen contents as starting material for the production of Special materials based on iron-nickel.

Chara kt Eristik the known technical solutions

Soft iron is unalloyed steel with a high degree of purity and very low iron-carrier contents, in particular carbon.

The production of soft iron in metallurgical aggregates is a common, well-known experience of metallurgical practice. It is usually melted in the SM oven and in the oxygen converter. The use of soft iron is mainly after "quality and stainless steels", Verlag für Grundstoffindustrie Leipzig 1971, as a relay material in the electrical industry, for thermoforming purposes, for cold extrusion of profiles, as a gasket material, for electrodes in the tube industry, for Metallbadwannen and for the production of iron powder.

Processes or technological procedures for the production of soft iron or of soft steels are described in DE-OS 2 607 646, DE-OS 2 429 489, DE-OS 2 005 045, DD-AP. 82 950 and DE - AS. "-. 1 909 780 known.

It is a well-known metallurgical fact that in steelmaking processes where the carbon content of refrigerants falls below certain limits oxygen levels rise sharply. However, high levels of oxygen are undesirable particularly with soft iron since they cause a high level of non-metallic inclusions deteriorate the technological properties of steel. «

The known technical solutions for the production of soft steels therefore require special methods for reducing the oxygen content after the refining process. It is known to reduce the oxygen content by adding deoxidants and / or by vacuum treatment.

For example, DE - OS - 2 607 646 describes that a steel with low carbon contents is partially deoxidized with aluminum or silicon and then preferably becomes vacuum degassed.

DE-OS 2 005 045 also describes a process for the production of low-carbon mild steel in which the oxygen content is reduced by injecting aluminum wire before the vacuum degassing in order to shorten the treatment time in the vacuum installation.

According to DD - AP - 82 950 soft steels with low carbon and oxygen contents are produced by subjecting the steel to a vacuum treatment after tapping, during which fine - grained carbon is added during the vacuum treatment.

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A further procedure is set forth in DE-AS-1 909 780, wherein in soft steels with carbon contents of up to 0.05 % by flushing the melt and the fresh slag with nitrogen, a reduction in the oxygen contents is achieved. ,

In DE - OS - 2 429 489, a method is presented how soft steels with lowest carbon contents can be produced by simultaneously flushing with hydrogen with simultaneously low oxygen contents.

Soft iron is the starting material for the production of special iron-nickel-based materials. After the opposite, current state, the technology for this purpose, the soft iron produced in the converter, SM furnace or plasma furnace is remelted and mixed with a defined nickel content. However, the produced according to the prior art T / eicheisen with the relatively low oxygen content has a significant disadvantage, which is that the melting of special materials on iron Niekel ~ base only a small cooking movement of the melt. The consequence of this is high reject rates, reduced quality and low yield.

Object of the invention

The object of the present invention is to produce by a particular combination of several process steps in the bottom-blowing oxygen converter a modified Wex iron with a defined, relatively high oxygen content in the piece analysis, which eliminates the mentioned deficiency and as a starting material for the production of Sonderwerkstoff.en on iron Nickel base can be used.

G; the essence of the invention

The invention has for its object to develop a method for the production of a modified soft iron, which can be used as a starting material for the production of special materials on iron-nickel-Baeis »This modified soft iron should have a relatively high oxygen content of at least 0.050 % bring the prerequisite for a good cooking movement during subsequent remelting in the induction furnace in order to increase the quality of the special materials on egg nickel base and reduce the reject rates due to blistering.

According to the invention, the object is achieved by a special combination. nation of such process steps dissolved in the final product rolled less than 0.06 % carbon, traces of silicon, max. 0.10 % manganese, max. 0.030 % phosphorus, max. Guarantee 0.015 % sulfur and a minimum oxygen content of 0.050 % . The individual process steps are characterized in that a reduction of the oxygen contents is largely avoided.

In the first phase, the melt is refined in the bottom-blowing oxygen converter in a conventional manner to a carbon content below 0.06%. After the slagging, a second blowing phase with oxygen of at least 1 minute, preferably 2 minutes, follows. In this second blowing phase, it softens, i. H. blown with reduced oxygen loading in order to achieve a high iron slag and thus a further increase in the oxygen contents.

For the purpose of temperature and sulfur correction, burn lime, limestone or fresh ore is added during the 1 st of the 2 "blowing phase. 2. Hach this blowing phase to the melt of at least 0.080%, preferably 0.100% oxygen, _s contain deal with security in the rolled end product has an oxygen content of at least 0.050.% ', Preferably 0.060% to .erreichen "

During tapping, the melt is allowed to melt for max. 0.6 kg PeMn per ton of steel, preferably 0.4 kg PeMn per tonne of steel, and max. 0.04 kg Al per tonne steel, preferably 0.02 kg Al per tonne steel. The goal of this minor deoxidation is not to reduce oxygen levels, but only to reduce the heavy boiling of the steel during tapping.

Dex casting of the blocks takes place in falling casting. The weight of the blocks should be max. 4 t, preferably 3 t, during the casting, no aluminum is added. The blocks need to freeze.

After parboiling, a 5 to 10 cm thick surface layer, the blocks are covered with lids and / or Y / alzzunder, so that the block head closes immediately.

embodiment

The invention will be explained in more detail with reference to an exemplary embodiment:

In a bottom-blowing oxygen converter, a batch is blown using 22 t of molten pig iron and 5 t of scrap. ,

The pig iron was desulphurised to a sulfur content below 0.015 % before use. The oxygen loading during spraying is 4000 bt il / h. On the basis of the anticipated endpoint, the Prischproseß is broken off, a sample taken from the melt and the temperature measured. The Stahlbadtemperatur is after the first blowing phase i680 ⁰ C. The carbon content is 0.04%, the phosphorus content of 0.030% _t the manganese content was 0.12% and the sulfur content of 0.013% ·.

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After the slagging, the 2 * blowing phase follows. The oxygen supply is during this 2nd blowing phase

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3000 m iN / h »10 seconds after the start of the second blowing phase, 200 kg burnt lime and 10 kg kg of fresh ore are added · 90 seconds after the start of the second blowing phase, this is stopped« The converter is transferred with oxygen blowing of the blowing nozzles, from the melt one taken sample and the temperature measured · the Stahlbadtemperatur is I69O ⁰ C, the carbon content is 0.02% _9, the manganese content 0.06%, the phosphorus content of 0.022% and the sulfur content of 0.011% · the oxygen content after the blowing is 0.098% ·

When the residual slag is stiffened, tapping is carried out. About 1/4 of a ladle filling, 8 kg of FeMn and 0.5 kg of aluminum are added.

The casting of the steel takes place to 3-t blocks, "During the casting, no aluminum is added. · Wax Boiling an approx. 7 cm thick surface layer, a lid is placed on the block head. The service life of the blocks in the molds is 40 minutes.

The foundry sample of this iron / iron melt gave 0.04% carbon, 0.08 % manganese , 0.023 % phosphorus and 0.011 % sulfur . The oxygen content of the casting sample was 0.068 % .

Claims (5)

228 79 9 6 7 Claim for invention " 1. A method for producing a modified soft iron in. metallurgical vessels, preferably in bottom-blowing oxygen converters, by combining several process steps with low carbon, silicon, manganese, phosphorus, sulfur and oxygen contents as starting material for the production of special iron-nickel-based materials, characterized in that is not degraded by the combination of the process steps, the oxygen content of the melt, but by an additional freshness with oxygen before tapping to a level of min. 0.080 % ₉ preferably 0.100 %, is held in the first blowing phase in a conventional manner the Melt is refined to carbon contents below 0.06 % and enriched in the 2nd blowing phase, the melt with oxygen. , 2. The method according to item 1, characterized in that the melt is abgeschlackt after the first Blasphase. Method according to items 1 and 2, characterized in that the second blowing phase is at least 1 minute, preferably 2 minutes, in which the second blowing phase is soft blown in order to achieve high iron slagging, for the temperature and sulfur correction burnt lime Limestone and / or ore is used and the amount necessary for the correction is added in the 1st third of the 2nd blowing phase. 4 · Process according to items 1 to 3> characterized in that the melt is not deoxidized and alloyed, but only during the tapping max. 0.6 kg PeMn per ton of steel, preferably 0.4 kg PeMn per ton of steel and max · 0.04 kg of aluminum per ton of steel, preferably 0.02 kg of aluminum per tonne of steel, are added, so that the mortar overcooking the Melt is avoided. Method according to items 1 to 4, characterized in that the casting of the steel in falling casting takes place in blocks of max. 4 tons, preferably 3 tons, while aluminum is not added during casting and after 5 to 10 cm Edge layer the blocks are covered with lids or mill scale. 6 _e method according to item 1 to 5 »characterized in that in the piece analysis of the modified soft iron less than 0.06 % carbon, max * 0.10 % manganese, max« 0.030 % phosphorus, max «0.015 % sulfur and min % _t before preferably 0.060 % _s oxygen can be achieved ,,