Year: 1888

page_text: I HAYWARD AUGUSTUS HARVEY, of Orange, New Jersey, United States of
America, Mechanical Engineer 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 relates to a method of treatment by which the characteristic
qualities of refined crucible steel are imparted to steels of low grades, such as
Bessemer steel, basic steel etc., whereby such steels are made capable of taking any
prescribed temper, and are adapted to be manufactured into machinists' tools, axes,
knives, fine cutlery, or cutting or abrading instruments of any kind, and by which
such low steels are given increased tensile strength and are rendered weldable so that
they can be piled and reworked without difficulty.
The essential conditions of the method of treatment to which the ingot or other
body of steel is subjected are the presence of carbon, the absence of oxygen, and
high temperature, i.e., a temperature above 1500° F. the degree of temperature
being varied according to the degree of hardness which the product is required to
be capable of taking in the subsequent process of tempering. The higher the
temperature is, the higher is the temper which the product is rendered capable of
taking.
In carrying out the treatment, the ingots or other bodies of steel which are to be
treated are embedded in a finely powdered carbonaceous material, preferably hard
wood charcoal, contained in crucibles, boxes or receptacles made of plumbago or
some other refractory material, and provided with covers to prevent the charcoal
from being consumed.
No special kind of furnace is required, but in practice a furnace of the regenerative
type may be preferred both for the sake of economy in fuel and because of the
rapidity with which the heating operation can be performed.
The shape and dimensions of the furnace chamber will of course be governed by
the shapes and sizes of the ingots or other bodies of steel which are to be treated.
For example, ingots say two inches by three and eighteen inches long may be
treated in receptacles nine inches by ten inside and say twenty-four inches long.
Such a receptacle will serve to contain six ingots separated from each other and from
the walls of the receptacle by thicknesses of one inch of powdered charcoal, and
D71

page_text: separated from the bottom of the receptacle by a layer of one inch of powdered
charcoal, and from the cover by a layer of say three inches or more of powdered
charcoal.
The fire chamber or heating chamber may be proportioned with reference to
containing any desired number of boxes or other receptacles for the charcoal. The
boxes or other receptacles for the charcoal may be heated by direct contact with a
body of incandescent fuel in which they are embedded, or they may be deposited in
a heating chamber and he heated by contact with or radiation from the flames
conducted through such heating chamber. The time required for the heating
operation will depend of course upon the dimensions of the body or bodies of steel
under treatment and also upon the efficiency of the furnace employed.
The object to he accomplished is the uniform beating throughout of the body of
material under treatment, which for present convenience may be called raw steel.
If the raw steel is in a large mass or masses the heating operation will have to be
conducted more slowly in order that the interior of the mass of raw steel may be
raised to the required temperature without melting the crucible or box in which the
raw steel is packed. When the raw steel is embedded in powdered charcoal contained
in a covered crucible it may be raised above its ordinary melting point without being
melted, and certain excellent results are produced by raising the raw steel to
upwards of 3000° F. When the desired temperature has been reached, and the
heating operation has been so conducted or prolonged as to have insured the uniform
heating through of the material under treatment, the receptacle containing such
material is at once allowed to cool off, and if desired may be removed from the
furnace to hasten its cooling.
By this treatment raw steel, which previously could not be welded or tempered,
becomes weldable and undergoes a transformation by which its tensile strength is
increased, and by which it acquires the characteristics of refined crucible steel or
so-called tool steel of the higher grades.
There are a great variety of existing furnaces in which the process can be
conducted. Such furnaces of course vary in their efficiency, but a few trials by an
operator skilled in the management of any particular form of furnace will suffice to
determine the time required for conducting the process in such furnace, and also for
varying the process with reference to the qualities which it is desired the product
shall possess.
Thus, for example, if a product capable of taking a temper of a very high degree
of hardness be required, the material under treatment will be raised to a temperature
say of about 3000° F. The product which has been raised to about this temperature
and allowed to cool off to a temperature of say 200° or 300° F. before being removed
from the powdered charcoal in which it has been embedded, will on removal be
found very soft, will exhibit a clean surface of a dull grey or zinc color, and will be
capable of taking a temper so high that tools made from it, and hardened, will cut
chilied iron, and may be successfully used for turning chilled iron rolls.
By so varying the process as to lower the extreme limit of temperature to which
the material under treatment is raised, the product when cooled off will exhibit,a
clean surface of a slightly golden tint, and will be capable of taking a temper nearly
as high as that which the grey colored product is capable of taking.
By further lowering the limit of tomperature to which the material under treatment
is raised, the product when cooled will exhibit a surface of a pale blue tint, and will
be capable of taking a temper somewhat lower than that which the golden-tinted
product is capable of taking.
By still further lowering the limit of temperature to which the material under
treatment is raised, say for example to a temperature of about 1500° F. the product
when cooled will exhibit a surface of a dark purple color, but will be capable of
taking a low temper.
In practice, to raise the material under treatment to the temperature mentioned, it
will be necessary that the temperature of the furnace or heating chamber shall be
above the temperature at which cast iron melts.

page_text: The tints referred to are similar to those which are exhibited upon the surface of a
piece of ordinary tool steel after it has been heated and while its temper is being
drawn. In the case of such a tool the color which it finally exhibits after the
tempering operation has been completed, indicates the degree of hardness which it
then possessos, different colors indicating different degrees of hardness. If the tool
is very hard, its surface may have a grey color; if it is slightly less hard, its surface
may have a straw color or golden tint, and if still less hard, its surface may exhibit a
blue tint, and if it possesses only a moderate degree of hardness, its surface may
have a dark purple tint. In the case of such tool steel, these colors are respectively
the invariable accompaniments of various degrees of hardness. On the contrary, in
the present process the several colors exhibited respectively by a number of objects
which have been heated to different degrees of temperature and allowed to cool before
being removed from their charcoal beds, do not indicate like differences in hardness
then possessed by those objects, the fact being that they are all of them comparatively
soft. What their colors do indicate is the extreme limit of hardness to which they
can be respectively brought in the operation of tempering them subsequently. Thus,
a product of pale blue tint can, in the process of tempering, be brought to the
condition of hardness which is ordinarily accompanied by the appearance of the blue
tint upon the surface, but cannot be made any harder. Its temper, however, can be
drawn, down so that it will be that indicated by a dark purple tint upon the surface.
Similarly, a product of the present process exhibiting a golden tint, or straw color,
can in tempering be hardened to straw color but no higher, and its temper can be
drawn down to a pale blue or to a dark purple. The same principle holds good as to
the product having the grey tint, which in tempering may be given the extreme
hardness indicated by the grey tint, and may have its temper drawn so that it
will exhibit in succession all the ordinary variations in color down to the dark
purple tint.
It will therefore be perceived that in practising the process herein described, the
color exhibited by the product upon its being removed from the charcoal after having
been allowed to cool off therein, affords a reliable indication of the character of the
product as to its capacity for tempering, so that it will not be necessary to actually
test the product before hardening it, to find what its qualities are.
In practice, it will not be necessary that the products which have been treated shall
remain in the charcoal bed until perfectly cool. They may be removed as soon as
they are cool enough to be handled.
If removed while hot, their surface will of course be more or less oxidized by
exposure to the air and they will be slightly harder. Such oxidation will to some
extent obscure their colors, but will do no material harm. The principal useful effects
produced result from the high temperature to which the objects under treatment are
subjected and do not depend upon the method of cooling. As the products of the
treatment exhibit different colors according to the temperature employed, so different
parts of the same ingot or bar may be made to exhibit different colors by subjecting
such parts to different temperatures. For example, the ingots or bars under treatment
may, if desired, be subjected to intense heat at one end and to a lower heat at the
other end, so that they will exhibit when removed from the charcoal a grey color at
the ends which have been most intensely heated and a blue or purple color at the other
ends and the regular series of intermediate colors between their grey and purple
portions. All parts of them however, will be found to have acquired the property of
weldability so that they can be readily piled and reworked.
After a furnace has been tested by trial, and the colors exhibited by the products
under different conditions of treatment have been observed, the character of the results
which will be produced by a prescribed duration of treatment in that furnace will be
known. Hence all that is required is to carefully reproduce, in repetitions of the
treatment, the conditions as to heat and duration which have previously been noted as
those which result in the yield of products having the required color; that is, products
having the capacity to take in tempering the degrees of hardness desired.
It is difficult and in the case of ordinary furnaces impossible to accurately measure

page_text: such high temperatures, and in view of this fact, and also in consideration of the
varying efficiency of different furnaces and of different fuels, the more practical
method of conducting the process will be by regulating the duration of the heating
operation, after having first ascertained by trial what length of time is taken in the
particular furnace, and with the particular fuel employed, whether solid or gaseous, to
heat the material under treatment to such a temperature as will produce a product of
the desired colour.
The temperatures herein mentioned are to be regarded simply as approximations to
the actual temperatures employed in practice. It is not necessary that these tempera-
tures, which cannot easily be measured, shall be herein accurately prescribed because
the observation of the periods of time occupied in the particular furnace, and the
observation of the colours which the treated ingots respectively exhibit, with the
particular fuel which may be employed affords all the information required for the
subsequent successful production of ingots having like colours, by the use of similar
fuel in the same furnace.
A single ingot, say two by three inches and eighteen inches long, deposited in
powdered charcoal in a crucible say five inches in diameter and twenty-four inches
long, can be successfully treated by keeping such crucible embedded in a free burning
coke fire for a period of from four to six hours. A larger ingot or a number of ingots
contained in a larger crucible may require a longer time, as say fifteen or twenty
hours, to ensure uniform heating throughout to the required temperature.
The product produced by this mode of treatment will be found to be free from scale
and without blisters upon its surface. As there is no oxidation upon its surface,
finished articles, such as knives, cutlery, files and other cutting or abrading instru-
ments, made of low steel, may be subjected to the treatment without injury, and the
material of which they are composed be thereby transformed into steel of fine quality.
It is to be remembered that the smaller the area in cross section of the article under
treatment, the less will be the time required for their treatment under the high
temperature herein prescribed, and the duration of the treatment will therefore be
varied as found to be necessary in view of the sizes of the articles to be treated, as well
as in view of the efficiency of the furnace and of the fuel which may be employed.
It has long been known that iron could be transformed into steel by depositing it
in a bed of carbonaceous material and subjecting it to a high temperature for several
days. The bars of steel so produced have their surfaces covered with blisters and the
product is hence known as blister steel. It is also well known that such steel is not
adapted for making tools for working wood or metal.
A costly product known as Mushet steel has also been made by fusing malleable
iron with carbonaceous matters in crucibles. The Mushet steel is of extraordinary
hardness and has hence been employed for turning chilled iron rolls and other
analogous purposes.
It will be found not only that tools made from the grey coloured product produced
by the process herein described will do perfectly well all the kinds of work which
tools made from Mushet steel are capable of doing, but that they are superior to
tools made from any other steel whatever for certain purposes, such for example as
boring deep holes in chilled iron or steel, or turning or planing the surfaces of
thin-shelled chilled iron or steel castings, which, by reason of their shape cannot be
supported directly opposite the tool and are hence liable to spring when the point
of the tool is pressed hard against them.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is :-
First. The herein described process of treating ingots or other objects composed
of low steel, such as Bessemer steel, for the purpose of imparting to the metal of
which such objects are composed the qualities of refined crucible steel; which
consists essentially in embedding the object or objects to be treated in a body of
granulated or powdered carbonaceous substance such as wood, charcoal, deposited
in a crucible or receptacle made of plumbago or any other suitably refractory

page_text: material and provided with a cover to prevent the combustion of the charcoal, and in
heating such receptacle and its contents in a furnace or heating chamber the tem-
perature of which is above the melting point of cast iron, for such length of time that
the objects treated, when removed from the charcoal will exhibit clean unblistered
surfaces of a prescribed colour or colours, as herein set forth, and will possess the
capacity of taking in tempering the degree or degrees of hardness ordinarily indicated
by such colour or colours.
Second. The herein described process of treating ingots or other objects composed
of low steel, such as Bessemer steel, for the purpose of increasing the tensile strength
of the metal of which such objects are composed and giving it the quality of
weldability, so that it can be piled and reworked in the ordinary manner; which
consists essentially in embedding the object or objects to be treated in a body of
granulated or powdered carbonaceous substance such as wood charcoal, deposited in a
crucible or receptacle made of plumbago or other suitably refractory material and
provided with a cover to prevent the combustion of the charcoal, and in then heating
such receptacle and its contents in a furnace or heating chamber the temperature of
which is above the melting point of cast iron, for such length of time that the objects
treated will, on removal from the charcoal, exhibit clean unblistered surfaces of a
prescribed colour or colours, as herein set forth.
1007
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.