Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1.
A METHOD OF ATTACHING A FIRST
METAL PLATE TO A SECOND METAL PLATE
The present invention relates to a method of
5. attaching a first plate of a first metal, such as
titanium, alloy steel or a similar material, to another
plate of a second metal.
In connection with lining of receptacles and
vessels having a round or rectangular shape with
10. titanium plates it has previously been customary to
attach the titanium plates against the inside of the
vessel by drilling holes from the inside through the
titanium plate into the outer shell of an unalloyed or
stainless material. The blind hole has thereupon been
15. threaded and a correspondingly threaded pin of titanium
has been screwed into it. The pin has then been welded
around thè circumference against the titanium plate in
order to obtain a seal.
This method is time consuming and troublesome to
20. execute. The titanium pin thus has a tendency to cut
into the material of the outer plate, thus makiny the
screwing step very slow. At the same time the titanium
plate has a tendency to move outwardly on the pin and
thus lift from the surface of the outer plate. This is
25. very disadvantageous since the risk of oxygen absorb-
ation at the weld root increases, which can result in
deterioration of the weld. Furthermore, if the
titanium plate is very thin, which is often the case,
there is a risk that it can be da~aged around the weld.
30- This is due to the fact that the pin, which is coarser
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2.
than the thickness of the titanium plate, must be supplied
with comparatively more heat during the welding process,
which in turn implies that the titanium plate will be
heated too much...and can melt through. At worst a piece
5. of the titanium plate can be destroyed and the plate
has to be cut away and replaced by a new plate. E~en if
the titanium plate is not destroyed, perpendicular
stresses will ar.ise in it which, in unfavourable cases,
can lead to fractures later on.
10. One object of the present invention is to provide
a method of attaching.a plate of one material to a second
plate which does not suffer these disadvantages.
According. to the invention there is provided a method
for attaching a first plate of a first metal to a second
15. plate of a second metal, including the steps of forming
a hole through the plates; introducing a pin shaped
attaching member into the hole, the attaching memb.er
being made of the first metal, or a metaL weldable
thereto, and having one end which has been provided with
20. a sidewardly bendable edge portion, the attaching member
being introduced into the hole 50 that the said end
extends outside the first plate so that it cannot mo~e
axially outwardly from the first plate; bending the
edge portion over sidewards towards the surface of the
25. first plate so that the plates are drawn together by
the reaction force around the hole; and welding the edge
portion circumferentially to the first plate.
Due to the fact that the plates are pressed together
around the hole the risk of o~ygen heing admitted between
30. the plates at the root of the weld is reduced, and so
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the qua]ity of the weld around the pin is improved.
Preferably, the edge portion is melted during the
welding process, which may be completed without any
welding wire.
5. The heat needed for melting the comparatively thin
~ent over edge portion 14 o~ the shank 10 may be small
enough to ensure that there will ~e no risk of melting
through the lining plate due to too much heat. In fact,
a very thin lining plate can be used without involving
10. any such ris~. Also due to the fact that welding must
not be commenced and carried out until after the pin
has been located and been bent over at its end, the
assembly work may be far simplified. Furthermore, the
welding can be carried out by unskilled welders due to
15. the fac~ that, normally, no welding wire is re~uired.
Finally, compared with the earlier method described
above further advantages of the present invention are
that threading of the attaching element and the hole is
not required, the weld quality around the attaching
20. member tends to be better, and the welding time may be
significantly reduced.
Preferably, one end of the attaching member is of
such a shape and size that following welding, the welded
portion and the welded end extend essentially level
25. with the sur~ace of the first plate.
Preferably, the hole is drilled straight through
the plates and~as the attaching member a headed pin is
used, the head of which is brought into contac-t with
the outside of the second plate. Con~eniently, the one
30. end of the attaching member has a central recess, the
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edge wall of which forms the bendable edge portion.
The invention also extends to an attachment member
suitable for use in the methods in accordance with the
invention described above.
5. The method according to the invention is by no means
limited to lining new receptacles and Yessels. It can
also be used to great advantage for lining older
vessels, in which the thickness of the outer shell has
been reduced due to corrosion, since a method in
lO. accordance with the inYentiOn does not require a blind
hole in the outer shell, as in the earlier known method.
Another area of use is scar~ing in rolling mills in
connection with changing from milling plate of one
material to milling plate of another material. For this
15. purpose blast welding of the seam has thus far been
used. It transpires that the great stresses in the
rolling mill inYolve a great risk that the blast wela
may fail. HoweYer, the joining method according to the
invention may eliminate the risk of the plates
20. separating from each other.
The inYentiOn may be carried into practice in
various ways and one embodiment will now be described by
way of example with reference to the accompanying
drawings in which Figures l to 3 illustrate three
25- successive steps in carrying out the method according
to the in~ention.
The three Figures illustrate in section a small
portion of the wall of a receptacle or a vessel with a
round or rectangular shape. An inner lining in the
form of a titanium plate is designated 2 and the outer
shell of the vessel is designated 4.
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The outer shell consists of unalloyed or stainless
steel.
In order to attach the lining 2 to the shell 4,
a number of through holes are drilled through the
S. titanium plate 2 and the lining plate 4. One of these
holes is shown in the Figures and is designated 6.
From the outside a pin shaped attaching member with a
head 8 and a shank 10 is introduced into the hole so
that the head is brought into contact with the plate 4.
10. The shank 10 has a central recess 12 in its end that
leaves an edge portion 14. The attaching member is of
the same material as the lining plate 2 or alternatively
is o~ a material that is easily weldable to this
material.
15. By means of a mandrel indicated at 16 the edge
portion 14 of the recess 12 is bent outwardly so that it
is brought into contact with.the edge of the lining
plate 2 and thereby the plates 2 and 4 are drawn together
around the hole 6 between the head 8 a~d the edge
20. portion 14 thus bent. Practical experiments haYe shown
that bending the end portion of the shank outwardly
through approximately 45 is enough., as is indicated in
Figure.2.
Welding, so called TIG-welding in the conte~mplated
25. embodiment, is now commenced by melting down the bent
over edge portion 14. Then the weld is completed
without the aid of any welding wire, so that a weld 18
with a root indicated at 20 and ~ith the appearance
indicated in Figure 3 is obtained. Only in exceptional
30. ~a~es is the addition of material in the form of welding
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wire necessary. The end of the shank 10 and the surface
o~ the weld facing outwardly are thus essentially left
level with the inside of the lining plate 2.
As an example, the following suitable dimensions of
5. the attaching element are given.
Protruding length o~ the s~,iank abo~e the lining plate
2 = Thickness of the lining plate 2.
Depth of the recess 12 = Thickness of the lining
plate 2.
10. Height of the head 8 = Thickness of the lining plate
2 + 1 mm.
Diameter of the head 8 = Thickness of the shank
lo ~ 5 mm.
Generally, the length of the pin is adapted and the
15. protruding pin end is shaped so that said end contains
the correct amount of material to be able to serve as
the additional material required in connection with the
TIG-welding process.
