IMPROVEMENTS IN REFINING CAST IRON, WROUGHT, AND OTHER MALLEABLE IRON, AND IN THE CEMENTATION OF IRON
Year: 1862

page_text: PROVISIONAL SPECIFICATION left by William Clark at the Office of
the Commissioners of Patents, with his Petition, on the 10th February
1862. A communication from abroad by Messrs. Louis Joseph Frédéric
Margueritte, Chemist, and Alfred Laloüel de Sourdeval, Proprietor, both
of 29, Boulevart St. Martin, Paris.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer and Patent Agent, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN REFINING CAST IRON, WROUGHT, AND OTHER
MALLEABLE IRON, AND IN THE CEMENTATION OF IRON," to be as follows:-
It has been already proposed to substitute coal for the charcoal usually
employed in the cementing troughs or cases in the manufacture of steel.
The experiments of Macintosh prove that the cementation may be effected
under. the influence of a current of carbonated hydrogen, while coal on being
calcined disengages large quantities of hydrocarburets. It has, however, been
found necessary to abandon both the process of Macintosh, and also the use of
coal, on account of the steel produced by the employment of said agents being
of bad quality.
Having ascertained the causes which render these processes defective, the
object of the present Invention is to find a remedy for them. Both lighting
gas and coal in the purest state possesses. sulphuretted products which would
combine with the iron, and as infinitesimal quantities of sulphur are sufficient
to entirely change the quality of the iron or steel, it will be apparent that it
is highly necessary to remove it. This may be effected in the most simple

page_text: and economical manner by adding to the coal a certain quantity of lime or
carbonate of lime, which at the high temperature to which the mixture is
raised becomes transformed into quicklime, and retains in the state of
sulphuret of calcium not only the sulphur resulting from the distillation of
the coal, but also that evolved in the furnace, which always filters into the
cementing cases. The presence of the lime prevents an excess of sulphur
being taken up by the iron, and also possesses the further advantage of
removing the greater part of that which it previously contained; it thus
purifies and refines the iron, and renders it more suitable for subsequent
cementation, and, in fact, enables good steel to be obtained from iron of
inferior quality. I effect this purification and desulphuration of the iron by
means of hydrogen, which possesses (as is well known) the property, when
passed over impure iron, of producing sulphuretted hydrogen readily decom-
posable in lime.
Carbonates of baryta, strontium, sóda, or potash may be employed for
producing the same result, but as these are either fusible or volatile, and also
much higher in price than lime, I prefer the latter alkali as being completely
infusible, and of a fixed nature, besides being the cheapest of all the matters
suitable for employment. The coal and quicklime or the carbonate are
pulverized and mixed together in the proportions of from 15 to 20 or 25 per
cent. of the quantity of coal employed. The coke residue of the cementing
process is employed for heating purposes in the next operation.
The apparatus I prefer to use áre small retorts and furnaces similar to
those used by the Vieille Montagne Company for the manufacture of zinc.
These retorts, by reason of their small dimensions, may be readily brought to
a red heat, which is the most favorable for the cementation, while it is very
difficult for the heat to penetrate to the centre of the ordinary cementing
cases.
It will be easily understood that a furnace similar to those above mentioned,
maining from 40 to 50 retorts, would produce after a few hours' continuous
action a considerable quantity of steel. The results obtained by calcining
bars and plates of iron of bad quality in a mixture of coal and quicklime or
carbonate of lime surpass all expectation, steel of very good quality being
produced from iron which previously was unsuitable both for forging and
bending. These improved processes may also be applied for the improvement
of cast and malleable cast iron. This Invention therefore consists, 1st, in the
simultaneous purification, refinement, and cementation of iron by calcining it'
in a mixture of coal and alkaline carbonate or earthy alkali, preference in all
cases being given to lime or its carbonate; 2ndly, in 'the use of furnaces and

page_text: retorts similar to those used in the manufacture of zinc, enabling the iron to
be raised to the most favorable temperature for cementation, also rendering
the operation continuous and economical by successive supplies of material;
3rdly, in the employment of any other combustible material as a substitute for
the coal capable of furnishing hydrogen by distillation, such as lignites,
anthracite, peat, wood, and other matters mixed with lime for the simul-
taneous purification and cementation of iron; 4thly, the simultaneous contact
of non-carbonated hydrogen and lime, with iron divided into thin sheets for
the purpose of purifying it only, without cementing it. In this case the
hydrogen may be produced by passing steam over charcoal, or by the action
of sulphuric or hydrochloric acid on zinc or iron. The hydrogen acting at a
high temperature on the iron in contact with lime has the effect of purifying
it, so as to change inferior iron into iron of very good quality.