IMPROVEMENTS IN THE TREATMENT OF STEEL AND OTHER METALS PREPARATORY TO CASTING."
Year: 1877

page_text: LETTERS PATENT to John Bourne, of Mark Lane, in the City of London, Civil
Engineer, for the Invention of "IMPROVEMENTS IN THE TREATMENT OF STEEL
AND OTHER METALS PREPARATORY TO CASTING."
PROVISIONAL SPECIFICATION left by the said John Bourne at the Office.
of the Commissioners of Patents on the 7th July 1877.
JOHN BOURNE, of Mark Lane, in the City of London, Civil Engineer. "IM-
PROVEMENTS IN THE TREATMENT OF STEEL AND OTHER METALS PREPARATORY TO
CASTING."
These improvements have for their object the attainment of soundness and the
exemption from blown holes and air bubbles in castings made from wrought iron,
steel, or other metals. This end is attained by pumping out or extracting from such
metals, while in the molten state, the gas or gases by which "honeycombing" is
produced.
The pumping or extraction may be effected by any convenient mechanical means,
such as a common pump, or by an exhausting jet of steam or other fluid, or by any
suitable arrangement of apparatus by which a vacuum more or less perfect is
produced. The molten metal, preferably in a state of minute subdivision, is
exposed within a suitable vessel to the action of the vacuum, by which means the
gases, which would otherwise produce cavities in the metal, are sucked away and
expelled.
The mould for the reception of the molten metal may be placed within the vessel
in which the vacuum is maintained, or the metal may be merely cleared of its gases
within that vessel, and may be conducted thence while still fluid into moulds exposed
to the atmosphere in the usual manner.
The exhaustion necessary for the extraction of the gases from the molten metal
may, it is obvious, be produced by the hydrostatic gravitation of a column of the
molten metal itself, or the gases may be mechanically expelled by repeated heating
and cooling of the molten metal itself under such arrangements as will prevent
their reabsorption.

page_text: The exhaustion may be maintained by suitable mechanical arrangements within
the crucible or furnace in which the metal is melted, or the metal may be melted
while exposed to the ordinary pressure of the atmosphere, and the gases be subse-
quently extracted, as before described.
The metal, if cooled too much in the operation of extracting the gases to retain
suitable fluidity for casting, may be reheated in vacuo to prepare it for casting.
·SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Bourne in the Great Seal Patent Office on the 7th January
1878.
"IM-
JOHN BOURNE, of Mark Lane, in the City of London, Civil Engineer.
PROVEMENTS IN THE TREATMENT OF STEEL AND OTHER METALS PREPARATORY TO
CASTING."
My present Invention has for its object the attainment of soundness and the
exemption from blow troles or honey combing in castings made from molten wrought
iron, steel, or other metals. This end is attained by extracting, in the manner
hereafter described, from such metal while in the molten state the gas or gases by
which honeycombing is produced.
The removal of the gases may be effected by the aid of any mechanical means
capable of producing rarefaction, such as a common pump, an exhausting jet of
steam or other fluid, the hydrostatic gravitation of a column of the molten metal
itself, or any other exhausting expedient by which a vacuum more or less perfect is
produced. The molten metal must be exposed to the action of the vacuum in such
way as to ensure the disengagement of the gas from the metal, and for this purpose
I submit the metal to the vacuum preferably in a state of minute subdivision. This
may be accomplished by allowing the molten metal to run through perforations in a
fire-clay block into a tall cylinder, within which a vacuum is maintained. By thus
subdividing the metal and discharging it in the form of a metallic rain into an
exhaust chamber the gases are separated from the metal, and are sucked away by
the pump or other extractor in cominunication with the exhaust chamber..
:
I may remark that it is not intended to subdivide the molten metal (without the
aid of a vacuum) for the removal of the gases, nor to attempt to suck away the
gases from a vessel filled with molten inetal by producing a vacuum above the
metal, as the hydrostatic pressure of the metal itself would under such circum-
stances retain the gases within the metal, notwithstanding the existence of the
vacuum above it; but according to my Invention I extract the gases by the conjoint
action of the vacuum and of the subdivision, as above explained, or by analogous
or equivalent means embodying the same conditions.
As a modification of the above-described process I melt the metal in a crucible
provided with a horizontal division plate having one or more holes-therein, through
which holes the metal as it melts flows drop by drop into the bottom part of the
erucible. I also make the crucible with a top or cover, which is luted on, and I
conduct a pipe from this cover or other convenient part of the crucible to a pump
or extractor; by which a vacuum is maintained within the crucible itself. Each
successive thin layer of metal as it melts is thus exposed to the action of the
vacuum, whereby the gases are sucked away in much the same manner as when the

page_text: molten metal is poured through a perforated block, as above described. In either
case the gas-retaining influence of a column of liquid metal, which produces a
hydrostatic pressure within the body of metal itself, is neutralized.
The mould for the reception of the molten metal may, it is obvious, be placed
within the vessel in which the vacuum is maintained when that course is convenient,
or the metal may be merely cleared of its gases within the exhausted vessel or
chamber, and may be conducted thence while still fluid into moulds exposed to the
atmosphere in the usual manner.
Should the metal be cooled too much in the operation of pumping out the gases
to retain the necessary fluidity for casting, it may be reheated previous to casting
either in vacuo or in the atmosphere by the aid of a suitable crucible.
As water in the act of freezing expels the air with which it was charged, and as this
air, if rapidly expelled, makes the ice opaque, by reason of the minute air bubbles
entangled in its substance, so metals in the act of solidifying tend to expel their gases,
and as their solidification is necessarily rapid, a portion of the gases is imprisoned,
and honeycombing is naturally produced. I aid the operation of expulsion of the
gases during the cooling of the molten metal, for as the metal cools, the gases,
besides being expelled, will be pumped away, and cannot therefore be re-absorbed.
.
Having now set forth the nature of my Invention of "Improvements in the
Treatment of Steel and other Metals Preparatory to Casting," and explained the
manner of carrying the same into effect, I wish it to be understood that under the
above in part recited Letters Patent I claim submitting molten steel and other
metals to the action of a vacuum, in the manner and for the purpose above
described.
In witness whereof, I, the said John Bourne, have hereunto set my hand and
seal, the Seventh day of January, in the year of our Lord One thousand
eight hundred and seventy-eight.
JOHN BOURNE. (L.S.)