Year: 1887

page_text: Date of Application, 22nd Feb., 1887.
Complete Left, 28th June, 1887.
Complete Accepted, 29th July, 1887.
I, JOHANNES DAHL of Kiel, in the Empire of Germany, Manufacturer, do hereby
declare the nature of this invention, to be as follows :-
:-
The pieces of steel to be annealed are placed in layers in a receptacle of iron or
brickwork, the inner sides of which are coated with a freshly mixed mortar of dust
of fire bricks and are strewed with white lead in the following manner.
A quantity of fuel consisting of crushed white-beech-wood or other wood, turf and
charcoal mixed in equal parts, is spread on the bottom of the receptacle and a number
of the steel pieces to be annealed, strewn with white lead are placed on it.
On the latter are laid at certain intervals flat fire bricks and the intervals filled up
with the said fuel, so as to completely surround the steel pieces. Subsequently a
second layer of steel, again covered with fuel, follows, then a third layer, on which
are laid in the above described manner fire bricks and fuel, care being taken, that the
single layers of steel may be, as far as possible of the same thickness. This is con-
tinued until the receptacle is filled when it is closed by a cover, coated with fire-brick
mortar.
Subsequently the receptacle is exposed for about 1 to 2 hours to a charcoal fire,
until its walls if they are of iron, appear dark red. Now the fire is covered or
damped and the receptacle allowed to slowly cool. The whole process lasts about
6 or 8 hours.
The steel pieces annealed by this improved process excel by extraordinary softness
and great capacity of being hardened, without the steel being impaired in toughness.
Dated this 22nd day of February 1887.
HERBERT & Co.,
67, Strand, W.C.,
Agents to Applicant.

page_text: I, JOHANNES DAHL of Kiel, in the Empire of Germany, Manufacturer, 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 pieces of steel to be annealed are placed in layers in a receptacle of iron or
brickwork, the inner sides of which are coated with a freshly mixed mortar of dust
of fire-bricks and are strewn with white lead or oxide of lead respectively in the
following manner :
A quantity of fuel consisting of a mixture of pulverised charcoal, turf, or crushed
white beach-wood-charcoal, intermixed with fine chips of forged iron, is spread on the
bottom of the receptacle and a number of the steel pieces to be annealed, strewn with
oxide of lead or white lead are placed on it. On the latter are laid at certain intervals
flat fire bricks and the intervals filled up with one of the said sorts of fuel, so as to
completely surround the steel pieces. Subsequently a second layer of steel, strewn
with white-lead or oxide of lead and again covered with fuel, follows, then a third
layer, on which are laid in the abovedescribed manner fire-bricks and fuel, care being
taken, that the single layers of steel may be, as far as possible, of the same thickness.
This is continued until the receptacle is filled, when it is closed by a cover, coated
with fire-brick-mortar.
Subsequently the receptacle is exposed for about 1 to 2 hours to a charcoal fire,
until its walls, if they are of iron, appear dark red. Now the fire is covered or
damped and the receptacle allowed to slowly cool. The whole process lasts about
6 or 8 hours.
The purpose of strewing the steel pieces to be annealed with whitelead or oxide of
lead is believed to be explained by the following:
With the heating of hardened-and so-called special steel for the purpose of easier
working, oxidizing influences frequently occur, produced partly by non-combusted
air in the fire, partly the formation of silicic acid. By the presence of silicic acid
between the molecules of the steel, the tenacity of the same decreases considerably
while its hardness is increased.
The silicic acid is removed during the annealing process by combining with the
oxide of lead to form silicate of lead, whereby the steel becomes extraordinarily soft
and richer in its contents of carbonic acid under the influences of the glowing
material.

page_text: Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed, I declare that what I claim is:
The described process for annealing steel, consisting in placing the pieces to be
annealed layer-wise on fire bricks between crushed fuel from white-beech-wood, turf
or charcoal, intermixed with small chips of forged iron, in a receptacle coated with
fire-brick mortar and in the application of white-lead or of oxide of lead with which
the single pieces of steel and the walls of the vessel are strewn.
Dated this 28th day of June 1887