Method or Process of Reducing Metals or Mixtures of Metals Containing Oxygen.
Year: 1895

page_text: Date of Application, 27th Mar., 1895-Accepted, 11th May, 1895
COMPLETE SPECIFICATION.
[Communicated from abroad by Fried. Krupp, of Essen, Germany.]
Method or Process of Reducing Metals or Mixtures of Metals
Containing Oxygen.
I, AUGUST REICHWALD, of 9, New Broad Street, in the City of London,
Steel, Iron, Metal and Mineral Merchant, 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 :---
The present process has for its object to remove oxygen in a simple manner and
to render the same innocuous, in casting metals and metallic alloys which, such as
steel, ingot iron, nickel-steel, &c., contain oxygen in consequence of the mode of
their production.
As is well known the oxygen combines, unless it is prevented from so doing, with
the carbon (which is always present in the cast inetal) to form carbonic oxide; and
this combining action takes place rather slowly, and even during the setting or
solidification of the cast metal, so that blowholes are liable to be formed in the
latter. Heretofore attempts have been made to obviate this drawback by adding
to the fluid metal during the casting or pouring thereof, aluminium, either pure, or
in the form of aluminium-iron or aluminium-steel. By this means the oxygen,
which has a greater: chemical affinity for aluminium than for carbon and iron or
for the other metals contained in the casting, combined with the aluminium to
form therewith alumina in the shape of a fine powder which remains for the
greater part in suspension in the solidifying mass. Although the formation of
blowholes was prevented by this means, yet the alumina formed a certain impurity
in the metal casting. Now this impurity can also be prevented by adding to the
liquid casting either during the pouring or before the same, instead of aluminium
or its alloy with iron, an alloy consisting of one or more metals the chemical affinity
of which for oxygen is greater than that of the metals to be cast, and of one or
more electro-negative non-metallic elements, metalloids, such as silicon or boron.
The elements of this alloy are converted by taking up the oxygen from the casting
into single, double or multiple silicates, borates, &c., which produce a slag that is
readily fusible to a greater or less extent. This slag which is very quickly formed,
then rises in single drops up through the liquid and much heavier casting, and
renders the latter perfectly pure and free from blowholes.
For the de-oxidization (reduction) of steel, nickel-steel, and ingot-iron castings,
there are preferably employed as metallic additions, aluminium or even the metals
of the alkaline earths such as magnesium, that is to say, each metal separately, or
two or more metals in combination with one another, or even in combination with
one or more other metals of the earths, such as manganese or iron, whilst the
non-metallic addition consists preferably of silicon.
As the single silicates form more refractory slags than the double and multiple
silicates, it is always advisable to employ at least two metals together as an
addition. The alkali-metals, such as potassium, sodium &c., will generally not be
employed as additions, although they have the strongest chemical affinity for
oxygen, or rather for this very reason, because the intensity with which they
combine with oxygen, is very liable to cause explosions. Moreover their higher
price is also an objection to their use.

page_text: -
As a non-metallic addition, boron may in some cases be just as suitable, or in
many cases be more suitable than silicon, because the borates mostly become
volatilized at not too high temperatures, and escape immediately they are produced,
from the fluid casting in the form of vapour.
It is not intended here to exclude the substitution for silicon or boron, of
phosphorus or of a similar element, because the sole essential object of using the
non-metallic additions is based on the fact that, by absorbing the oxygen contained
in the casting, they form with the metals added to them, readily fusible or volatile
salts, and thereby prevent the formation of pulverulent precipitates.
A particularly suitable addition for steel castings has been found to consist of an
alloy of aluminium with manganese and silicon, the two last mentioned substances
being in the form of ferro-manganese and ferro-silicon; in a proportion of
5% of aluminium to 10 % of manganese and 10% of silicon, together with
75% of iron.
If the manganese be omitted from this mixture, it is probable that a double
salt consisting of aluminium-iron-silicate, will still be formed; but however the
presence of manganese affords a still greater security for the formation of a readily
fusible slag.
: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent, I declare that what I claim is :-
:.
1. Method of reducing metals or alloys of metals containing oxygen, consisting
in adding to the fluid casting before or during the pouring thereof, one or more
.metals, one at least of which has a stronger affinity for oxygen than the metal
being cast, and also one or more elements of such a nature as will form with the
added metals and with the oxygen, easily fusible salts.
2. One arrangement of carrying out the method specified in Claim 1, in which
the addition contains silicon and aluminium, or in place of the latter, magnesium,
and also one or more other metals.
3. Another arrangement of carrying out the method specified in Claim 1, in
which the addition is composed of aluminium, ferro-manganese and ferro-silicon.
4. Another arrangement of carrying out the method specified in Claim 1, in
which the addition consists of 5% of aluminium, 10 % of manganese, and 10% of
. silicon, to 75% of iron.
Dated this 27th day of March 1895.