US937486A - Process of producing steel free from protoxids. - Google Patents

Description

UNITED STATES PATENT OFFICE: 1 A

o'r'ro THALLNER, or nrsmnncxnfi'rrn, GERMANY, ASSIGNOR TO THE FIRM :ZF

' BIs nncKHti'r'rE, or BIsMARcKHijT'rE, GERMANY.

rnocnss or rnonucnve STEEL-FREE rnom rno'roxrns.

No Drawing.

To all whom it may concern: 1 Belt known that I, O'i'ro' THAL 'NER, met.-

- allurgist, a subject of the King of Prussia,

and resident of Bismarckhiitte, in the Provinceof Upper Silesia, German Empire, have invented a new and useful Process for Producing Steel Free from Protoxid's, of which the following isa specification.

'- This invention relates to a process for producing steel free from protoxids of iron or manganese and which has the acid properties ofcrucible steel, 1

.It is already known to apply silicon for .the deoxidation of steel and slag. In-de- -ametal that. it is not capable of separating out in the short time before pouring. The result. s that onlya small quantity of the purev silicon remains in solution in the steel and as this small quantity'only acts for a short time it has practically no influence on the mternal structure of the-steel. :On the contrary the fine emulsified silicic acid has a disadvantageous action on the internal structure. If it is desired to cause-the silicon to act advantageously on the internal structure the metal .must contain a greater quantity of the silicon and be subjected to the protracted action of the silicon at the melting temperature." It is known that in the Martin furnace a strong blowing action is obtained in consequence of the gases of combustion, that is to say, there is a constant excess of oxygen present inthe slag and this oxygen has a constant blowin action on the metal bath below it. It is t eref ore impossible to obtain a constant percentage of carbon in the metal in a basic lined furnace of this kind as the carbon in contact with the slag which is rich in oxygen is subjected to constant changes asalso 18 the manganese in the metal bath. This oxygen of course also afiects the silicon as the silicon has a great affinity for the oxygen 1n the slag, and passes over into,the slag as silicic acid. It appears therefore to be unpossible to retain pure silicon dissolved Specification of Letters Patent.

Application filed April 20,

Patented Oct. 19, 1909.

1909 Serial No. 491,104.

pears also impossible to obtain afavorable.

ture of the steel. There still remains the possibility-of adding the silicon before tapping or in the ladle. Silicon of course always out of the. slag in a Martin furnace. The object aimed at however was diflicult to obtain as the metal below the slag might still remain rich in oxygen and in addition very large quantities of silicon were necessary to slag constantly took up oxygen from the combustion gases and this oxygen had to be continuously removed. The slag was'therefore always more acid in its nature and increased in 'its tendency to give up oxygen to Y the metal bath. It may therefore be as sumed as a practical impossibility to melt metal in a basic flame-heated furnace and still retain a reasonable proportion of silicon in solution.

I have discovered that the protoxids may be removed and pure silicon taken up in soan electric furnace with a basic lining and heating the steel together with siliconin said lining in consequence of the hightemperatures obtained retains the slag in a much more basic character than was at all possible in a Martin furnace. The consequence is that the slagis lem liable to take u oxygen. from the air as there is no oxidi mg flame present in the electric furnace. The proof of metal may be heated for several hours in an electric furnace with a basic lining without altering the percentage of carbon and manseen in that the slag may be retained free of iron for several hours. This circumstance alone permits the carrying out ofthe following process.

from any other blowing apparatus 15 passed into a basic electric furnace. Suflicient ferrosilicon is added either in the electric furnace or when tapping into the ladle to completely deoxidiz'e the metal and so that a fixed amount of pure silicon remains in solution. When added.in the electric-furnace the ferrosilicon may be laid in the furnace bring about the permanent silicizing as the.

this may be found in the fact that the The Martin I steelorthe melted product and. the metal poured thereon or the ferro with a basic lined Martin furnace and it apaction of the silicon on the internal struc- Y reduces the protoxid of iron and manganese v .80 lution by the steel by treating blown steel in furnace. The electric furnace with a basic ganese in the metal. The proof is also to be 1 addition of silicon on a basic Martin furnace v sible to add part of'the silicon to the metal before passing the ,same in the electric furnace and the other part after. The chemical action which results, is as'follows: The

product of the deoxidation which is emulsified 1D. the metal has time during the melting in the electric furnace to separate out and" this product passes in the form of silicic acid into the slag. The pure silicon held in solution ,is neutral as regards the basiclining. In consequence the basic lining of the furnace is not attacked whereas the excessive led to the formation of large quantities of I silicic acid which attacked the lining of the furnace very severely. If the. slag in the electric furnace still contains iron-protoxid, the iron in the slag is gradually extracted by means of the silicon in the bath and this reduction takes place at the contact surface between the slag and the metal bath. The reduction further takes place until the whole content of silicon has been used up or until the slag is free of iron. vIn order to retard theloss of silicon it isnecessary to accelerate the deoxidation of"the'slag. This maybe effected by throwing on charcoal or the like or aluminium compounds or even pulverized ferrosilic'on. It isto be mentioned that. a part of the deoxidizing agent burns with the air whilethe deoxidizing means which act on the slag from below act without loss.

When thedeoxidation iscomplete in the slag, it becomes white or falls to a powder when exposed to the cooling action of the air. When.

the slag becomes white or falls to apowder k 40 in the air, the metal bath below the slag may Witnesses:

beassumed as in a proper state is; taking up pure silicon, and that the silicon remaining in solution in the metal will no longer be used up. In consequence if further additions of ferrosilicon are made, the silicon acts on the internal structure of the metal upward that is to say from the metal bath upward, is also an important feature of the r metallurgic action.

I claim l. The process of producing steel free from protoxids, consisting in blowing the steel and. passing it to a basic electric furnace, adding silicon to said steel and heating said metal in said furnace together with the silicon till the metal and slag are'deoxidized. 2. The process of producing steel free from protoxids, consisting in blowing the steel and passing the blown steel to a basic electric furnace, adding silicon to said steel, heating said metal in'said furnace-together with the silicon till the metal and slag are deoxidized, and then adding further silicon.

3 In witness whereof I have hereunto set my hand in the presence of two witnesses.

OTTO THALLNER.

HERMAN PLISOHKE, MAX ZIEncHE.