DE927387C - Process for producing high quality steel - Google Patents

Description

Method of making high quality steel During manufacture of steel, the cooking process is of crucial importance, because through it and. the vigorous bath movement brought about by the gases dissolved in the bath, in particular the hydrogen which promotes the formation of flakes, expelled and existing slag particles be eliminated. Boiling the steel, however, is dependent on the use of a high-carbon, preferably partly bound from pig iron existing insert, mostly under Addition of oxygen carriers, e.g. B. Ores, is refined.

This way of working now fails in the production of low-carbon Steels, e.g. B. case-hardening steels with less than 0.2% carbon, because low-carbon Melt the boil is finished before the dissolved gases in sufficient quantities are away. In addition, such melts are exposed to the risk of over-freshening, whereby an increased expenditure of deoxidizing agents is caused, which in turn the Favors the formation of non-metallic inclusions. In addition, even well-cooked ones hot melts from the furnace atmosphere often absorb gases again, which then form difficult or impossible to remove. The material is as a result susceptible to flake and bubble formation. Also, it is usually not possible to use the Alloying elements of an insert consisting of alloyed scrap before burn-up to protect. Valuable alloy elements are then initially lost; You need to be recovered from the slag in costly processes. That Process according to the invention dispenses with the use of pig iron containing or higher-carbon inserts and it still achieves that those dissolved in the bath Gases and the slag particles are completely removed. A particular advantage of the. Process is the great accuracy with which high-quality steels, z. B. at 'higher temperatures, parts that are subject to severe stress can be generated can.

According to the invention, an insert made of scrap without pig iron and melted down without other carbon-rich aggregates, the bath overheated and then molecular hydrogen or another molecular, reducing one Gas, e.g. B. acetylene or carbon oxide, blown through the bath.

In itself is the use of hydrogen or other reducing agents Gases known in steel production. So is z. B. has been proposed by a refreshed bath reducing gases, e.g. B. a mixture of C O and C 02, optionally blown through with the addition of nitrogen. Hydrogen on the other hand is because of the decrease the reducing power rejected at higher temperatures. It was also suggested in the converter process to remove that which has been absorbed from the bath during freshening Oxygen to conduct hydrogen through the bath, thereby replacing solid Deoxidizer works. Escapes through the slag layer lying on the bath at the same time water vapor. Another suggestion is to blow hydrogen in atomic form Form through the steel bath and thereby achieves, in addition to deoxidation, a Reduction of the carbon content.

Furthermore, reducing gases are used, e.g. B. the mixtures of CO and C 02, for the production of materials with low cold brittleness, blue brittleness and good homogeneity. Known ist_ it, such gases -during the casting effect will be, by the current flowing from the anne Pf jet sucks in the deoxidizing gas. The deoxidizing effect of hydrogen is canceled out by the absorption of atomic hydrogen by the melt.

In contrast, the invention consists in the fundamentally new knowledge of the insolubility of molecular hydrogen or other reducing molecular Gases in steel melts. From this is the steelmaking process according to the invention designed according to the pressure and amount to be blown through the steel bath Gases are dimensioned so that, despite the emerging bath movement, the molten steel protective slag cover is not breached.

The temperature of the bath when the gas is blown in must be selected so that the melt appears clear and fluid after treatment. To This process step ends with treatment of the melt by blowing in of gases repeated before the last deoxidation.

Surprisingly, the molecular hydrogen flowing through it will not absorbed by the steel melt, but rather it drives it in the melt dissolved gases, in particular atomic hydrogen, largely from. Be at the same time Metal oxides reduced and slag particles brought to the surface.

Example An insert consisting of 550o kg forge waste and 280o kg of chips of the same were melted at a high temperature.

The bath had the following composition: carbon o, 20/0, manganese 0.280/0, silicon 0.0r1 / 0, chromium 2.2%, tungsten 0.461 / u, vanadium 0.291 / o, molybdenum 0.50 / 0, phosphorus 0.08%, sulfur 0.0150 / 0.

During the melting, in addition to Mn and Si, about 0.5% was Cr and 0.02 / 0 V has been slagged. Then about 30001 molecular hydrogen were initially carried through blown the bath.

The analysis of the subsequently taken sample showed: carbon 0.21 / a, Manganese 0.28%, silicon 0.28%, chromium 2.06%, tungsten 0.5%, vanadium 0.340 / a, molybdenum 0.5%, phosphorus 0.0071 / o and sulfur 0.5%, 6%.

The amount of gas escaping when the sample blocks solidified was not larger than the first sample. After the slag had been changed, the melt was alloyed and before deoxidizing, repeated gas blowing. This was the melt clearer, thinner and less gas. After the addition of ferro-silicon it became smooth potted and processed further without fuss.

The method according to the invention can be used to produce any success Alloyed or unalloyed steels are used as it is the melting of a very pure, coarse-grained steel with no tendency to form flakes or marginal blistering or coarse crystal properties guaranteed.

Claims (3)

PATENT CLAIMS: i. Process for producing high quality steel, whereby. Hydrogen or other reducing gases passed through the superheated steel bath are, characterized in that one consisting of scrap and not carbon-rich Components, e.g. B. in the form of pig iron, containing insert melted down and while avoiding the boiling process, molecular hydrogen or another reducing agent acting molecular gas with such a pressure and in such an amount through the Bath is blown through that a breakthrough of the slag cover on the part of the molten steel not taking place. 2. The method according to claim i, characterized by the use of low-carbon scrap without the addition of pig iron or other high-carbon scrap Surcharges as stakes. 3. The method according to claims i and 2, characterized through the use of inserts made from alloyed scrap with grades of easily oxidizing components such as chromium or vanadium.