Year: 1888

page_text: I, JOHN WESLEY BOOKWALTER of Springfield, Ohio, United States of America,
Engineer, at present residing at the First Avenue Hotel, Holborn in the County of
Middlesex, 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 fundamental condition in the conversion of molten crude iron into steel or
malleable iron, is, that the atmosphere should be brought into contact with every
portion of the metal contained in the molten mass in order that the combustible
elements held by the iron may be properly oxidised by the oxygen contained in the
atinosphere.
To carry through the conversion the air must come in contact with the metal in
order that the oxygen may reach the combustible elements held by the iron, and having
this object in view former inventors have not unnaturally adopted the practice of forcing
the air into the interior or body of the metal apparently under the impression that to
get the air and metal intimately commingled was all that was needed.
They introduced the blast vertically through the bottom of the convertor, horizon-
tally near the bottom of the convertor, and from above obliquely so as to penetrate into
the metal through the top surface. All these plans however where the air is forced
into the body of the metal are accompanied by the drawback that the scoria and
impurities are generated within the body of the metal itself (thus so intimately asso
ciating them with the metal as to render their removal extremely difficult) and the
confined air escaping at the surface produces such violent agitation and currents as to
prevent the accumulation of the scoria upon the surface and on the contrary to cause
it to become most intimately mixed with the metal being carried about in the metal
by the powerful currents induced by the strong blast which return it again and again
to the mouth of the tuyeres there to be exposed to the pounding effect of the blast.

page_text: As the compressed air will on escaping from the metal expand with more or less
explosive violence both metal and scoria will be cast up high in the convertor and
falling back the scoria will be broken and carried into the currents again and by them
returned to the tuyeres, so that altogether they get much broken up and the small
particles being in a state of intimate mechanical mixture with the metal can hardly
afterwards be eliminated.
The scoria also being formed chiefly at the bottom where the air being most com-
pressed the proportion of oxygen to metal is greatest, must pass through the mass of
metal to get to the surface, but even then is not allowed to stay there being as above
explained dragged down again by the currents and falling metal.
The process of conversion is also irregular being most violent and thorough near
the tuyeres and diminishing in intensity as the distance from them increases and the
air and scoria being split so much by the currents and eddies it seems reasonable to
infer that some of it would come within the limits of atomic attraction and be never
afterwards entirely got rid of.
Another objection to the existing processes is that when the air is caused to penetrate
into the interior or body of the molten metal a portion will find its way upward to the
surface between the lining of the convertor and the metal; this causes a wasting away
of the material of the lining necessitating more fréquent renewals than would be
necessary if the air did not so pass between the lining and the metal.
In my process while retaining the advantages of the rapid process of conversion I get
rid of the disadvantages hitherto attending it and avoid the above described drawbacks
in a very simple manner.
To avoid the inevitable bad results of blowing into and through the metal and
forming the scoria absolutely in the mass or body of the metal I apply the blast at
or near the surface and direct it so that it merely impinges upon a small portion of
the metal at the surface and never really enters into the body of it as in the
cases above referred to and thus avoid the formation of scoria within the metal, and
also avoid those violent commotions and disturbances at the surface which would
prevent the accumulation of the scoria in the only safe and proper place for it viz.: the
surface.
Generally the tuyeres are horizontal when the convertor is vertical but I do not
bind myself to this arrangement. I also prefer to arrange them in directions more or
less tangential to the inner circumference of the convertor for the purpose of imparting
to the metal a circular motion in a horizontal plane, the effect of this motion
combined with the circulation in a vertical plane resulting from the application of the
blast to the surface being to bring the whole of the metal again and again to the
months of the tuyeres. The blast being applied in this manner near the surface strip
off the small portions of metal presented immediately in front of it but seeking to
escape in the direction of least resistance its power to strip or blow off the metal only
extends to a comparatively short distance so that an inclined face is presented or
formed in front of the tuyere and the scoria as it is formed on the surface of the metal
is blown across to the opposite side of the convertor where it remains floating on.the
metal and kept from returning to the tuyeres by the force of the blast. So long as
the scoria does not approach too near the tuyeres it is not of importance if it be gently
circulated upon the surface of the metal as the force of the blast diminishes very
rapidly so that its dynamic effect at even a few inches from the orifice of the tuyere
is small compared with what it is at the orifice itself. The blast being thus applied
to what may be termed a corner of the metal causes it to revolve in a vertical plane
not violently but steadily at a constant rate so that fresh metal is constantly supplied
to be acted upon by the blast the effect of the vertical circulation combined with the
horizontal circulation caused by the tangential direction of the tuyeres being to bring
the whole of the metal again and again to the mouths of the tuyeres the movement not
being strong or violent enough to drag down into the metal the scoria whose less
specific gravity enables it to resist such currents as are formed and the blast merely
tending to keep it at the side of the convertor remote from the tuyeres and not to
force it into the metal. The movement of the scoria is thus away from the tuyeres to

page_text: which nothing but the metal to be acted upon and free from scoria is presented with
the natural result that the metal produced is exceedingly free from impurities and
homogeneous in quality.
The eating away of the lining by the air getting between the lining and the metal to
which I have already drawn attention is obviated by my process for the simple reason
that the air blast being applied close at the surface and escaping upwards without
penetrating into the metal does not get between the metal and the lining except at the
point of introduction which is of no great importance as the metal is at that point
blown right away from the lining, thus the length of time during which one lining will
last is very greatly increased.
By this process I am able to attain and maintain a very much higher temperature
than has been possible with previous systems and this increased temperature of the
metal is attended with important advantages.
1st. The metal being as a consequence more fluid and retaining its liquid condition
much longer it therefore runs into the moulds with greater certainty and facility
thus rendering it well adapted to the production of castings of great perfection and
quality.
:
2nd. The greater fluidity of metal resulting from this higher temperature favors the
more complete separation of impurities from the metal, since the more viscid the
liquid mass is the greater is the tendency of impurities to adhere to and remain in
the molten metal.
3rd. This higher fluidity causes a freer movement of the molecules of the metal thus
enabling the air blasts in their action on the metal to effect a more complete displace-
ment and circulation of all the particles of iron, bringing them thus with greater
freedom and certainty to be acted upon by the air.
In order to more clearly explain the different effects which result from the different
modes of applying the blast I have appended diagrams in which I have attempted to
indicate roughly what may be imagined to take place in a convertor.
The diagrams are all supposed to represent a vertical section of the metal in a
convertor, Fig. 1 showing the blast introduced vertically at the bottom; Fig. 2
horizontally at or close to the bottom; Fig. 3 at or near the top but directed into the
body of the metal though but slightly downwards and Fig. 4 the blast introduced in a
practically horizontal direction a little below the surface.
In figure 1 the air is shown ascending to the whole body of the metal causing violent
combustion and disturbance every where throwing up the metal and impurities high
above the surface which fall back again as already explained, the arrows showing the
return currents bringing down the scoria to be again subjected to the pounding
effects of the blast by reason of the exceedingly powerful currents produced by the
heavy blast and the impurities being driven into these currents by the falling metal.
In figure 2 blasts are shown entering from opposite sides of the convertor and
although these will not cause such violent disturbances as in figure 1 it will never-
theless be seen that the air permeates the greater part of the metal and that the return
currents come from the surface so as to drag down the scoria to the blast to be
pulverized. This blast also being at a high pressure causes very violent disturbance so
that the scoria cannot remain quiescent upon the surface as in my process.
In figure 3 the blast enters near the surface but is driven at once into the metal
with the result that violent agitation takes place and the scoria is formed in the metal
instead of upon it as in my process and rises to the surface where it floats about but
cannot get clear of the metal on account of the agitation and is drawn into the
powerful currents produced by the strong blast which must be used, or the air would
not enter the metal, which is the very aim and object of all processes previous to
mine. My own process is illustrated in figure 4. In this case the blast is applied at
or near the surface and in a direction and of a power such that whilst sufficient to
strip off or blow away the metal close to it the combined inclination and power are
not sufficient to cause it to penetrate the metal in the same way as in the previous
instances. The metal being forced back by the blast presents an inclined surface
to it whilst the scoria is formed practically at the surface and is blown to the

page_text: L
opposite side of the convertor where it remains upon the surface of the metal while
an equable current or circulation is imparted to the body of the metal which
is thus returned again and again to the mouth of the tuyere.. The violent operations
take place at the surface and near the tuyeres while the bulk of the metal remains
comparatively quiet while as each particle of the metal as it comes within the influence
of the blast is blown clear away from the rest of the metal it is clear that all the metal
is most thoroughly acted upon by the air.
Except directly in front of the tuyeres and for a short distance from them the surface
of the metal is sufficiently calm and undisturbed to allow the scoria to collect upon it
whereas in all process where the blast is introduced into the body of the metal the
(surface upon which the scoria would float is constantly broken up and violently
agitated by the escaping air which divides up the scoria and causes it to be dragged
down again into the metal as elsewhere explained.
I will now briefly recapitulate the chief objects that I have in view in this
invention.
First: To avoid the formation of scoria in the metal and thereby avoid having to
solve the difficult problem of how to get it out.
Second: To avoid or prevent the undue agitation of the surface and thereby permit
of the scoria and impurities collecting and remaining there in practical separation
from the body of the metal.
Third To keep the air from entering into the mass of the metal and so avoid
any risk of its being retained there, or getting between the metal and the lining
.of the convertor excepting at the point of introduction; whereby a great cause of
waste of the lining is avoided and the life of the lining thereby greatly lengthened.
Fourth Notwithstanding the preceding clause to thoroughly oxidise every particle
of the metal by subjecting it to the action of the air blast in the manner described.
Fifth To produce an extremely high temperature in the molten metal resulting
in the advantages enumerated above.
i
:
From the foregoing it clearly appears that the blast must be applied during the whole
of the time at practically the same position upon the metal; it must not be too deep
or it enters into the metal; and it must be deep enough or it will escape without
producing the desired results. But it must also be remembered that the bulk of the
metal diminishes during the conversion by reason of the elimination of the impurities
which form a very important proportion of the total bulk, consequently the level of
the surface of the metal falls during the process and as a consequence of this the
blast must be brought to its former position relatively to the metal. This may be
done in various ways two of which naturally present themselves: first by bringing
the blast down to the metal and second by bringing the metal up to the blast. The
former proceeding may be most conveniently accomplished by using a tilting con-
vertor and turning it upon its trunnion; or in a fixed convertor by having the
tuyeres movable as for example by making them vertically telescopic and dropping
them as required though the difficulties in effecting this would be considerable. The
raising of the level of the metal could be effected by means of a false bottom which would
raise the whole of the metal, or inserting some refractory body (as for example) a plunger
located in the wall of the convertor and adapted to be further immersed in the
metal, or lumps of similar material placed in the bath from time to time as required
which by occupying part of the space previously occupied by the metal would restore
the surface level. Of these the tilting convertor is doubtless the most practical and
is what I prefer to use; the others are merely suggestions to show how the same
result might be attained.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent and in what manner the
same is to be performed, I declare that what I claim is :-
1. In the conversion of molten cast or crude iron into malleable iron or steel the
application of the air blast or blasts in such manner that while oxidising the

page_text: combustible elements held in the iron practically no scoria or impurities will be
generated within the body of the metal substantially as and for the purpose specified.
2. In the conversion of molten cast or crude iron into malleable iron or steel the
application of the blast or blasts in such manner that the impurities or scoria
generated or liberated in the process of conversion will be kept in a state of practical
separation from the body of the metal substantially as and for the purpose specified.
3. In the conversion of molten cast or crude iron into malleable iron or steel the
application of the air blast or blast in such manner as to impart to the whole mass of
metal such circulating currents as will bring rapidly, certainly and smoothly the
whole of the metal into contact with the blast substantially as and for the purpose
specified.
4. In the conversion of molten cast or crude iron into malleable iron or steel
restricting the act of conversion to a small portion of the metal by so apportioning
the strength and direction of the blast that while impinging upon or even to a
small extent entering the metal it does not penetrate into the body thereof sub-
stantially as and for the purpose specified.
5. In the conversion of molten cast or crude iron into malleable iron or steel
keeping the violent interaction of the air and metal and the scoria and liberated
impurities at or near the surface of the metal and separate from the bulk or main
body thereof by so introducing the blast at or near the surface that it does not
extensively penetrate into the metal substantially as and for the purpose specified.
6. In the conversion of molten cast or crude iron into malleable iron or steel con-
verting the metal without at any period of the blow allowing the air to mix with
more than a small portion of the metal at once and at or near the surface sub-
stantially as and for the purpose specified.
7. In the conversion of molten cast or crude iron into malleable iron or steel
the introduction of the blast in such manner as to blow the scoria and impurities as
formed or liberated away from the mouth of the tuyere and retain them there upon
the surface of and practically separate from the main body of the metal substantially
as and for the purpose specified.
8. In the process of converting pig iron into malleable iron or steel a complete
blow or converting operation in which the blast is never allowed to penetrate into the
body of the metal substantially as and for the purpose specified.
9. In the conversion of crude or pig iron into malleable iron or steel the intro-
duction of the blast in such manner as to prevent the air from getting between the
metal and the lining of the convertor except at the point of introduction substantially
as and for the purpose specified.
10. In the conversion of crude or pig iron into malleable iron or steel the main-
taining of the proper relative positions of the metal and blast during the process of
conversion substantially as and for the purpose specified.
11. The maintaining of the proper relative positions of the blast and the metal
during the process of conversion by lowering the tuyere or source of the blast in
equal ratio with the fall of the surface of the metal substantially as specified.
12. The maintaining of the proper relative positions of the blast and the metal
during the process of conversion by maintaining the same surface level of the metal
throughout the process substantially as specified.