Improvements in the Hearths or Bottoms of Mill and other Furnaces Used for Heating Iron and Steel.
Year: 1895

page_text: Date of Application, 6th July, 1895
Complete Specification Left, 27th Mar., 1896-Accepted, 16th May, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Hearths or Bottoms of Mill and other
Furnaces Used for Heating Iron and Steel.
ALEXANDER EDWIN TUCKER of 35 Paradise Street Birmingham Metallurgist
and FRANK WILLIAM HARBORD of Egham in the County of Surrey Metal-
lurgist do hereby declare the nature of this invention to be as follows:-
When iron or steel is reheated in a furnace having a siliceous hearth or bottom
a great waste of iron is experienced by the oxide of iron formed uniting with the
silica to form a fusible slag. On the other hand if a hearth is wholly composed of
sbrunk basic material a too highly refractory slag is produced & the hearth
gradually grows thicker & thicker.
We find that a very suitable hearth can be made by using a highly calcareous
silicate containing alumina & in some cases phosphate of lime: We thus are able
to produce a nearly neutral body as follows:-We mix blast furnace slag when
molten or otherwise with basic phosphatic slag from the converter or open hearth
furnace molten or otherwise, or with limestone lime or dolomite in suitable propor-
tions to get the required composition sometimes using only two of these bodies &
at other times all of them the object being to obtain a material of as neutral a
character as possible which at same time is capable of resisting the temperature
required, & we vary the proportions of these bodies to suit the special metallurgical
conditions.
We find it is often advisable after grinding & mixing instead of using the
material in this state at once for the furnace bottoms to frit or fuse the mixture
together at a very high temperature & afterwards crush & regrind to required
fineness. We find that the product thus obtained either by admixture with molten
slags or by grinding alone or by fritting or fusing together at a high temperature
in a suitable furnace, is of great density & infusibility & when made in proper
proportions forms an excellent material for the hearths & bottoms of mill & similar
furnaces on which iron is treated. The best method of making such hearths we
find is first to place lumps of the above material & to fill in with fine finally
placing a layer of fine on the top to form a level surface, & glazing the whole.
Dotad this 4th day of July 1895.
ALEX. E. TUCKER.
F. W. HARBORD.
Improvements in the Hearths or Bottoms of Mill and other
Furnaces Used for Heating Iron and Steel.
We, ALEXANDER EDWIN TUCKER, of No. 35 Paradise Street, Birmingham
Metallurgist, and FRANK WILLIam Harbord, of Egham, Surrey, Metallurgist,.
do hereby declare the nature of our invention and in what manner the same, is to
be performed to be particularly described and ascertained in and by the following;
statement :-
Our invention has reference to furnaces used for heating iron and steel, such for,

page_text: example as the furnaces commonly known as mill furnaces used for heating masses
or piles of iron or steel and furnaces for raising strips of iron, and steel to a
welding heat in the manufacture of iron and steel tubes and in furnaces used for
other like purposes.
In furnaces of the kind referred to it is desirable that the hearth or bottom
should be so hard and infusible as to permit of the ready motion upon it of the
iron or steel being heated. It is further desirable that the said hearth or bottom
should have no tendency to promote the oxidation of the heated steel or iron
resting upon it; that is, that it should contain practically no free silicic acid as
heated silicic acid forms with oxide of iron a fusible slag and the presence of silicic
acid promotes the oxidation of the iron or steel being heated.
In order to produce according to our invention hearths or bottoms of mill and
other heating furnaces having the desirable properties herein before referred to we
proceed as follows:-We take the slag produced in that method of manufacturing
steel known as the Thomas Gilchrist or basic method (which said slag is highly
basic consisting essentially of oxide of iron, free lime, silica together with a con-
siderable percentage of phosphate of lime and which slag we will hereinafter call
basic slag) and we also take the slag produced in the ordinary blast furnace which
said slag we will hereinafter call blast furnace slag. The two slags referred to
may either be mixed in a molten state or one only may be molten and the other in
a solid state introduced into the molten slag. Or both slags may be taken in a
solid state and after being reduced to powder mixed and used in the manner herein-
after explained. The two kinds of slag which we employ have approximately the
following compositions.
Basic slag has approximately the following composition by weight :-
Silica
Oxide of iron
Phosphoric acid
Lime and magnesia
Oxide of manganese
Alumina -
-
-
. 9.00
- 12.00
22.00
50.00
4.00
2.00

page_text: welding heat. In order to give the required infusibility to the compound slag
we employ in making the hearths or bottoms of furnaces for raising iron or steel
to a welding heat, we reduce the proportion of silicic acid to lime. In some cases
this may be effected by increasing the quantity of basic slag. Or where from the
compositions of the slags or for other reason this cannot be readily effected by
varying the proportions of the two slags we proceed as follows. We mix the two
slags in the manner hereinbefore described and we add to the mixture either in a
molten or solid state such an amount of limestone or dolomite (magnesium limestone)
as will produce the required infusibility.
In applying the materials hereinbefore described to the hearth or bottom of a
furnace we prefer first to place lumps of the compound slag on the bed of the
furnace and to fill in the spaces between the said lumps with ground compound
slag or a mixture of ground compound slag with powdered limestone or dolomite;
the surface of the hearth or bottom being made level and smooth by a layer of the
fine powder.
By heating the hearth or bottom of the furnace before using the furnace for
heating iron or steel its surface is raised to a temperature which will produce
incipient fusion whereby a smooth or glazed surface of the hearth or bottom is
produced.
Where we employ materials in addition to those contained in basic slag and blast
furnace slag we prefer to heat the powdered mixture of slags and the additional
materials such as limestone or dolomite to a temperature which will produce
incipient fusion in the said mixture of the materials and we grind to powder
the frit or semi fused mass thus produced and apply it in the manner hereinbefore
described.
Having now particularly described and ascertained the nature of our inven-
tion and in what manner the same is to be performed we declare that we
claim as our invention of "Improvements in the hearths or bottoms of mill and
other furnaces used for heating iron and steel."
Making the said hearths or bottoms of a mixture of basic slag and blast furnace
slag, or of a mixture of basic slag, blast furnace slag and limestone or dolomite, the
said materials being treated and applied to the bed of the furnace substantially in
the manner herein before described.
Dated the Twenty-fifth day of March 1906
ALEXANDER EDWIN TUCKER.
FRANK WILLIAM HARBORD.