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Патент USA US3097982

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July 16, 1963
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A. 1.. F. HYDEN
3,097,972
DI-PHASE PICKLING PROCESS
Filed Sept. 26. 1960
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United States Patent 0 ”v in
3,097,972
Patented July 16, 1963
1
2,
3,097,972
preferably made in running water. This can be arranged
by adding water to the upper portion of the water column,
and withdrawing water from the lower portion of said col—
urnn, near the boundary layer between the pickling liquid
DI-PHASE PICKLING PROCESS
Anders Lennart Fredrik Hydén, Farsta, Sweden, assignor
to Aktiebolaget Atomenergi, Stockholm, Sweden, a
company of Sweden
Filed Sept. 26, 1960, Ser. No. 58,223
Claims priority, application Sweden Oct. 19, 1959
2 Claims. (Cl. 134-—28)
and the rinsing liquid. If desired the pickling liquid,
too, can be changed continually, by adding pickling liquid
to one end of the pickling liquid column, and withdrawing
pickling liquid from the other end of the column.
The above described process and the apparatus referred
This invention relates to pickling processes in general, 10 to are illustrated in the accompanying drawing which is
a front view of the vertically disposed cylindrical vessel.
i.e. processes of treating a metal object with a liquid,
Referring to the drawing, 1 is the rinsing ‘zone, 3 is the
usually an acid, for affecting the surface of the metal,
pickling zone and‘ 2 is the dividing zone in which the
usually for removing metal oxides. The following spec
boundary layer between the pickling and rinsing liquids
i?cation refers to one particular pickling process, but it
is evident to any body skilled in the art that the invention 15 is maintained. Water is passed through the rinsing zone
1 by introducing fresh water at pipe 4 and withdrawing
is not limited to that particular process.
water contaminated with pickling liquid at pipe -5 which
In many pickling processes it is important that the
is provided with an open tube 6, preferably transparent,
objects to be pickled are transferred as rapidly as possi
for observing the level of liquid in the zone 1. The over
ble from the pickling bath to the subsequent rinsing bath.
One example of such a process is the pickling of objects 20 ?ow pipe 7 serves to prevent the liquid from over?owing
the top‘ of the vessel. The pickling zone 3- is double
of zirconium and zirconium alloys in a mixture of nitric
walled or jacketed and is cooled by introducing water
acid and hydro?uoric acid, for the purpose of removing
into the jacket through the pipe 10‘ and withdrawing it
from the surfaces of the objects such impurities as might
through the pipe 1. Pickling liquid is introduced
othenwise produce damage due to corrosion. If such
objects are lifted from the pickling bath in the conven 25 through the pipe 9 and the three thermometers ‘8, 8, 8
serve for observation and control of the temperature of
tional way and are then lowered into the rinsing bath,
the pickling liquid. The apparatus ‘may be used for either
this must be done within a ‘few seconds, because otherwise
batch or continuous operation. In batch operation zone
there are precipitated on the metal surface chemical com.
pounds which are di?icult to dissolve and to remove by
3 is ?lled with acid up to zone 2 while a flow of water
is maintained through zone 1. When the pickling acid
30
rinsing, and which jeopardize the result of the pickling.
The present invention relates to a method which makes
it possible to transfer the objects from the pickling bath
to the rinsing bath directly and without transporting them
in the air. The method of the invention is characterized
by arranging a pickling liquid, having one speci?c weight,
and a rinsing liquid, having a different speci?c weight,
as strati?ed liquids, the lighter liquid (forming a layer upon
the heavier liquid, treating the object to be pickled in
the pickling liquid and then transferring it into the rins 40
ing liquid through the boundary layer between the two
liquids.
becomes exhausted it is withdrawn through pipe 9 and
zone 3 is then re?lled with fresh pickling acid. In con
tinuous operation acid is introduced continuously or inter
mittently through the pipe 9 and is permitted to rise to
the level of the outlet of pipe 5 and to over?ow there
through along with the rinsing (water from zone 1. Thus
the boundary layer or mixed zone is maintined in the
zone 2. No dif?culty is encountered in keeping the rins
ing layer and the pickling layer separate. In the con
tinuous operation described above the upper boundary
of the mixed zone will of course rise to the level of
the outlet to pipe 5.
The rinsing liquid is usually water, and water is lighter
The pickling and rinsing liquids have a tendency of get
than the pickling liquid and is consequently strati?ed to
ting mixed with each other at the boundary layer between
‘form a layer upon the pickling liquid. It is possible, 45 the two liquids, viz. by diffusion and by the movements
however, to stratify a lighter pickling liquid to form a
layer upon a heavier rinsing liquid, for instance a com
partively concentrated sulphuric acid solution. In this
caused by the objects passing through the boundary layer.
It has been found, however, that it is possible to main
tain the boundary between the two liquids sut?ciently
sharp for practical purposes. It is possible to control
rinsed, be lifted up thorugh the overlaying pickling liquid 50 the height of the mixed zone, for instance by continually
layer, but must be removed from the apparatus while en
changing the pickling and rinsing liquids, as suggested
tirely surrounded by the rinsing liquid, for instance
above. In this case, the height of the mixed zone is de
case the object must not, of course, after having been
through a U-shaped chamber.
The pickling of objects of zirconium and its alloys may
termined by the distance between the two levels at which
the pickling and rinsing liquids are withdrawn from the
be carried out in a vertical cylinder. The lower portion 55 apparatus. The position of the mixed zone may be
of the cylinder is ?lled with an aqueous solution contain
checked by means of bodies which float in the liquid
ing 39% by volume nitric acid having a speci?c gravity
of 1.42, and 3.5% by volume of a hydro?uoric acid solu
tion containing 52% by weight hydro?uoric acid. Water
and which have known specic weights between that of
the pickling liquid and that of the rinsing liquid. These
bodies place themselves at a level where the speci?c
The 60 weight of the liquid is equal to that of the body.
objects to be pickled are lowered through the open top
What is claimed is:
end of the cylinder, through the water layer into the
1. A method of pickling objects of zirconium and
is strati?ed to form a layer upon the acid solution.
pickling liquid. When the pickling is ?nished the ob
zirconium alloys which comprises establishing a strati?ed
jccts are lifted into the water layer where they are rinsed,
for instance for a time of ?ve minutes. The rinsing is
solution of nitric acid and hydro?uoric acid, a lighter top
bath consisting of a heavier bottom layer of an aqueous
3,097,972
4
3
layer of Water and a boundary layer of a mixture of the
liquids of said top and bottom layers, the liquids of said
References Cited in the ?le of this patent
UNITED STATES PATENTS
layers being miscible with each other in all proportions,
supplying Water to said top layer adjacent to the upper
surface thereof and Withdrawing Water mixed with said 5
aqueous solution from said top layer at a point adjacent
to said boundary layer, and moving said objects from said
bottom layer through said boundary layer into said top
layer.
1,329,467
2,310,569
2,399,205
2,894,860
2,923,648
2. A method as de?ned in claim 1 in which said bottom 10
layer is maintained by adding said solution thereto near
the lower surface thereof.
Miskella _____________ __ Feb. 3,
BOOth _______________ __ Feb. 9,
Campbell ____________ __ Apr. 30,
Engelhardt __________ __ July 14,
K’Burg _______________ __ Feb. 2, 1960
FOREIGN, PATENTS
577,571
Canada ______________ __ June 9,
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