Year: 1898

page_text: Date of Application, 6th Apr., 1898-Accepted, 20th May, 1898
vou
I, FRITZ SCHADELOOCK, of The Crucible Steel Works, Tergeste, Trieste, in the
Empire of Austria, Steel Maker, do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This invention has for its object an improved process for the manufacture of
crucible steel.
I make crucible cast steel from a mixture of molten Siemens-Martin iron,
preferably free from sulphur and phosphorus, and of grey pig free from sulphur and
phosphorus.
The oxidation of the carbon arising hitherto in the process did not allow of steel
having a predetermined amount of carbon contents being produced. This oxidation,
which has hitherto been ascribed to the admission of atmospheric air, is caused much
more by oxygen contained in the raw materials, as actually the crucible is never
surrounded by oxidising but only by reducing gases. I avoid a de-carbonisation of
the iron according to the formula iron oxide + iron carbide iron carbon oxide
by carefully removing the oxides of iron in the molten iron partly by hand-picking,
partly by mechanical scouring or even by chemical means, and in the case of the
grey pig by melting the same in crucibles in a reducing atmosphere and subsequently
removing the bodies containing oxygen (oxides) in the above mentioned manner.
Both raw materials are then weighed into the crucible in pieces of about 1-5 cubic
centimetres in volume.
In order to prevent the steel bath being rendered impure by the diffusion of gas
or the silicate substance of the crucible, it is preferable to reduce to a minimum the
period of contact between the crucible and the metal. This is obtained especially by
the raw materials being inserted in the above mentioned sizes, as when the pieces are
larger the transmission of heat is more defective, and when smaller the air has too
great an insulating effect.
As however, even where the above mentioned conditions are most scrupulously
observed, it is impossible to attain the desired carbon contents, that is to say the
entire removal of all oxidising substances (ferric oxide, ferro silicate and the like),
I reduce these bodies, before they still can produce a de-carbonisation of the steel
bath, by the addition of a metal which has greater affinity for oxygen than iron and
on which it exerts no deleterious influence.
For this object I employ aluminium, magnesium or other well known similarly
acting metal, but I avoid any excess as in my special case it is only a question of
the removal of the oxygen and not the formation of ferro-aluminium.
In consequence of the great difference in the specific gravity of iron and
aluminium, magnesium, or the like, it is necessary to stir the latter (atmospheric
oxygen being excluded as far as possible) that is to say so long as the crucible is
exposed to the fire gases.
On the oxidation of the added reducing metal, so much heat is released that the
steel bath becomes very fluid and easier opportunity of escape is afforded to the

page_text: enclosed gases.
Numerous experiments have shown the good quality of steel
produced in this way and among others the co-efficients of quality obtained.
The process herein before described may of course be employed with any crucible
steel alloys.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
"
The improvements in the manufacture of crucible cast steel and its alloys, which
consists in-
a The removal by hand picking, mechanical scraping, or chemical means, of
oxidising compounds which decarbonise the iron and thus render impossible the
production of steel with exactly pre-determinable carbon contents;
b/ The addition of reducing metals (aluminium, magnesium, or other known
similarly acting metal) at a suitable moment with the object of removing the quite
unavoidable traces of oxides (bodies containing oxygen); .
c/ The agitation of the reducing metals in already existing or created, reducing
atmospheres ;
d/ The application of the raw materials in pieces of such a size (about 1-5 cubic
centimetres) that the duration of the process is reduced to a minimum; substantially
as herein before described.
Dated this 5th day of Anril 1000
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.