DE2447918A1 - Refining of steel - by using an alloy of calcium, aluminium and magnesium free of oxide - Google Patents

Abstract

Refining treatment, i.e. deoxidation and/or desulphurization, of a steel melt comprises the use of an alloy composed of 50-55% Ca, 39-44% Al and 6% Mg, which may contain in addn. about 0.04% C. The alloy, blown into the steel melt, is in atomized form and has an oxide-free surface, or the alloy is simultaneously atomized and blown direct into the steel melt, or the alloy is first atomized, and packed airtight, to prevent oxidation of its surface. Process is simpler and more economical than conventional deoxidation and desulphurization procedures. Undesirable elements such as Si and excess C are not introduced into the melt.

Description

Process for the deoxidation and / or desulfurization of iron melts due to oxide-free CaAlig (C) alloy When using steel, the producer nowadays ever greater demands are made.

It is therefore the task of metallurgy to use the already existing steel grades to improve even further.

For this it is necessary to correctly use the quality-reducing components to recognize in order to achieve a targeted improvement there.

Above all, the non-metallic ones have a negative effect on quality inclusions, such as sulfides, oxides or oxysulfides. In particular, these are Manganese sulphides, alumina inclusions and silicates, which are in the mechanical properties of the materials, e.g. toughness and Strength. The aim is therefore to produce a steel that is as free of sulfur and oxygen as possible.

Because the oxygen content is already greatly reduced in killed steels it will be based particularly on the desulfurization technology, preferably a method of simultaneous deoxidation and desulfurization, arrive to better Manufacture steel qualities without great expense. To remove the sulfur will be the melt is now subjected to multiple treatments, which is a great effort requires time and money.

-In the deoxidation and / or desulfurization are preferred elements that have a higher affinity for oxygen or sulfur are used than iron. As can be seen from the thermodynamic data, therefore, are the most effective Deoxidizers calcium, magnesium, aluminum, titanium, silicon, etc.For the Desulfurization comes from the elements of calcium, magnesium, sodium, manganese and others. in question.

Here mainly only manganese, cerium or mixed metals and calcium compounds are found in technology application.

The previously used deoxidation and desulphurisation alloys like CaSi, EgSi, ZrSiAl, CaC2, CaSiMn, CaSiAl, 0aSiIg etc. have the disadvantage that they also introduce unwanted accompanying elements such as Si and C into the melt.

The inclusions that form in the steel are predominantly linear and have a negative effect on the material properties.

The use of cerium and rare earth metals is high in cost tied together.

Try using pure calcium and magnesium for improved desulfurization and / or deoxidation are so far without tangible due to their low boiling points Success remained.

According to the invention, a new way is proposed, an alloy from Use calcium, magnesium and aluminum, which have an extraordinarily high level of desulphurisation and lesoxidation enabled. A composition of approx. 50-55% is required here Ca, 39-44 Al and 6% Mg, which already contribute to oxidation and sulfur uptake approx. 1,320 ° C a liquid phase with the composition of approx. 43-48 CaO, 46-51% Al 203 and 6% MgO forms, which then forms on the surface of the melt can deposit.

This metallic alloy also has the advantage that it has a Has a melting point of approx. 1,000 OC and is blown into the melt in powder form can.

Since this alloy has a high affinity for oxygen, there is the risk of the formation of an oxidized film, which has an extremely high melting point having.

When using grains covered with an oxidized film, the actual alloy is not effective, as this film acts as an insulating layer between the molten iron and the CasIMg alloy. This disadvantage affects the stronger the shorter the dwell time of the injected particles in the iron melt and thereby preventing the oxidized film from degrading.

According to the invention, an alloy with a composition of approx. 50-55% Ca, 39-44% Al and 6% Mg finely divided (powdery) and with oxide-free Surface are blown into the molten iron. The is also advantageous Presence of carbon in this alloy in a limit that the desulfurization reaction promotes, but a carburization of the steel bath is avoided. That can be achieved when the CaAlMg alloy is melted in a graphite crucible and using a head is atomized from graphite. Our results show one under these conditions Carbon content of 0.04%.

The alloy can be introduced indirectly in powder form or directly happen after atomization and is shown schematically in the accompanying figure.

The alloy is in a crucible (1), preferably made of graphite, melted and in a nozzle (2) with inert gas e.g. argon from the storage container (3) sprayed. The amount and grain size of the alloy being sprayed can be regulated via the pressure of the gas. The sprayed material gets into an expansion tank (4) and can with the atomizing gas either by means of a Lance (5) into the melt (6) from above or through a floor nozzle (7) from below into the melt (6) are blown in.

The proposed method of deoxidation and / or desulfurization promises the following advantages: 1. By melting the alloy in a graphite crucible In addition, small amounts of carbon arrive in our previous experiments approx.

0.04% total carbon, in the melt, so that the desulfurization is favored.

2. The argon flushing degassing process can be carried out at low cost combine. Here, the alloy with the argon as the carrier gas is introduced into the melt blown in.

3. The grain size and amount of the alloy can be changed during the process can be regulated as required, whereby a great flexibility is achieved.

4. The alloy can be produced, atomized and in one operation be blown directly into the melt. There can be no oxidation of the surface occur because inert gas is used.

5. There is no mechanical crushing of the powder, so that this no costs are incurred, which also reduces transport and storage costs will. If a powder is made from the alloy for later use, it must airtight packaging must be ensured. The oxides that form have one high melting point and thus become ineffective as reaction products.

6. The increased addition of calcium further reduces the influence of the any remaining inclusions on the mechanical properties of the steel favorably influenced. It can be increased from previously elongated oxide inclusions determine a more uniform and spherical shape of the inclusions.

Claims (1)

Claims "Process for the deoxidation and / or desulphurization of iron clay melts by oxide-free CaAlMg (C) alloy "Claim 1) Process for simultaneous deoxidation and / or desulfurization of the liquid steel d a d u r c h g e k e n n n z e i c Note that an alloy of approx. 5c-55CO Ca, 39-44% Al and 6% Mg is used. Claim 2) Method according to Claim 1 d a d u r c h g e -k e n n z It is clear that the CaAlMg alloy contains approx. o, o carbon. Claim 3) Method according to Claim 1 and 2 d a d u r c h g e k e Note that the alloy is in an atomized form with oxide-free Surface is blown into the molten steel. Claim 4) Method according to Claim 1, 2 and 3 d a d u r c h g e k It is noted that the alloy is atomized at the same time and directly into the molten steel is blown in. Claim 5) Method according to Claim 1, 2, 3 and 4 d a -d u r c h g e it is not indicated that the alloy is first atomized and packaged airtight to prevent oxidation of the surface skin.