RUDDER TABS

PATTES DE GOUVERNAIL

English Abstract

The invention relates to a method of connecting metals together and articles produced thereof and more specifically to connecting metals together to construct the ships rudder wherein the metals have dissimilar thermal expansion rates to one another including the steps of: pre-heat treating a transition plate along with a first metal; welding the transition plate to the first metal; stress relieving the resulting weld; and welding a second metal to the at least one transition plate.

French Abstract

L'invention se rapporte à un procédé permettant de raccorder ensemble des métaux et à des articles produits à partir de ce procédé et, de façon plus précise, au raccordement de métaux les uns aux autres pour construire un gouvernail de navire, les métaux présentant des coefficients de dilatation thermique différents les uns par rapport aux autres, ledit procédé comprenant les étapes consistant à : préchauffer une plaque de transition conjointement avec un premier métal ; souder la plaque de transition au premier métal ; réduire les tensions de la soudure résultante ; et souder un second métal à ladite ou auxdites plaques de transition.

Claims

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CLAIMS:
1. A rudder manufacturing method of manufacturing a rudder for a marine
vessel, the rudder comprising a rudder stock and a rudder blade, the rudder
stock comprising a first metal material and the rudder blade comprising a
second metal material, the first metal material and the second metal material
each having a thermal expansion rate, the thermal expansion rate of the first
metal material being different to the thermal expansion rate of the second
metal material, the method comprising the steps of: providing a transition
plate having opposed first and second connection portions comprising a
metal material having a rate of thermal expansion that is substantially equal
to the thermal expansion rate of the second metal material, the first
connection portion for making a welded connection directly to the first metal
material of said rudder stock and the second connection portion for making a
welded connection directly to the second metal material of said rudder blade;
preheating said transition plate and said rudder stock; connecting, by
welding, the metal material of the first connection portion of the preheated
transition plate directly to the first metal material of the preheated rudder
stock, thereby forming a first welded connection; heating said first welded
connection connecting said first connection portion of said transition plate
directly to said rudder stock to relieve stress in the first welded
connection;
and, after said heating to relieve said stress in said first welded
connection,
connecting, by welding, the metal material of the second connection portion
of said transition plate directly to the second metal material of said rudder
blade to form said rudder, with the rudder stock and the rudder blade being
spaced apart and connected by said transition plate.
2. The method according to claim 1, wherein the first metal material of the
rudder stock is a forged steel having a carbon content that is higher than any
carbon content of the second metal material.
3. The method according to claim 1 or claim 2, wherein the second metal
material of the rudder blade is DH36 steel or a stainless steel containing 18%
nickel, 20% chromium, 6.1% molybdenum, 0.2% nitrogen and 0.01% carbon.
Date Recue/Date Received 2022-01-31

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4. The method according to any one of claims 1 to 3, wherein the metal
material
of the transition plate is the same as the second metal material.
5. The method of claim 4, wherein the second welded connection is formed
without preheating the rudder blade before the second welded connection is
formed.
6. The method of claim 4 or 5, wherein the second welded connection is
formed
without preheating the transition plate after heating the transition plate to
relieve said stress and before the second welded connection is formed.
7. The method of claim 4, wherein the second welded connection is formed
without the transition plate and the rudder blade being in a preheated state.
8. The method of any one of claims 4 to 7, wherein the rudder is
manufactured
without heating the second welded connection to relieve stress after the
second welded connection is formed.
9. The method of any one of claims 1 to 8, wherein the transition plate is
elongate and has opposed longitudinal edges along its length, and one of the
opposed longitudinal edges abuts an edge of said rudder blade.
10. The method of claim 9, wherein another one of the opposed longitudinal
edges of the transition plate abuts the rudder stock.
11. The method of any one of claims 1 to 8, wherein the transition plate is
elongate and has opposed longitudinal edges along its length, and one of the
opposed longitudinal edges abuts the rudder stock.
12. A rudder for a marine vessel, the rudder comprising a pre-heated rudder
stock comprising a first metal material, a rudder blade comprising a second
metal material, and a preheated transition plate comprising a metal material
and having opposed first and second connection portions, the metal material
of the first connection portion being welded directly to the first metal
material
of said preheated rudder stock and the metal material of the second
connection portion being welded directly to the second metal material of said
Date Recue/Date Received 2022-01-31

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rudder blade, wherein the first metal material has a carbon content that is
higher than any carbon content of the second metal material, and each of the
first metal material of the rudder stock, the second metal material of the
rudder blade and the metal material of the transition plate has a rate of
thermal expansion, wherein the rate of thermal expansion of the metal
material of the transition plate is substantially equal to the rate of thermal
expansion of the second metal material, and the rate of thermal expansion of
the first metal material is different from the rate of thermal expansion of
the
metal material of the transition plate.
13. The rudder according to claim 12, wherein the first metal material of the
rudder stock is a forged steel.
14. The rudder according to claim 12 or claim 13, wherein the second metal
material of the rudder blade is DH36 steel or a stainless steel containing 18%
nickel, 20% chromium, 6.1% molybdenum, 0.2% nitrogen and 0.01% carbon.
15. The rudder of any one of claims 12 to 14, wherein the transition plate is
elongate and has opposed longitudinal edges along its length, and one of the
opposed longitudinal edges abuts an edge of said rudder blade.
16. The rudder of claim 15, wherein another one of the opposed longitudinal
edges of the transition plate abuts the rudder stock.
17. The rudder of any one of claims 12 to 14, wherein the transition plate is
elongate and has opposed longitudinal edges along its length, and one of the
opposed longitudinal edges abuts the rudder stock.
18. The rudder of any one of claims 12 to 17, wherein the metal material
of the
transition plate is the same as the second metal material.
Date Recue/Date Received 2022-01-31

Description

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RUDDER TABS
This invention relates to a method of connecting metals together and articles
produced thereof and more specifically to connecting them to construct a
ship's
rudder.
Before two metals of specific grades are welded to one another, a pre-heating
step is used. Pre-heating involves heating the metals to be welded to a
predetermined, minimum temperature. This is done to remove any moisture and/or
hydrogen from the weld area to prevent delayed hydrogen cracking and to lower
the
thermal gradient to reduce distortion and residual stress. Stress relieving
after
welding is another heat treatment which removes internal or residual stresses
that
may be present from the welding operation. Stress relief after welding reduces
the
risk of brittle fracture.
Currently, ships' rudders are fabricated by balance welding rudder blades to a
rudder stock and then stress relieving once fabrication has been completed. A
rudder stock is made of a Forging having a higher carbon equivalent to that
used for
the rudder blades. A preferred Forging rudder stock has a high carbon content
which
means that it requires pre-heat treatment and, after welding, for stress
relieving.
Sometimes, rudder blades are manufactured from a metal which is different to
that
used to make the rudder stock. As the metals are different, the thermal
expansion
rates will be different which means that it is not possible to apply stress
relief to the
metals whilst maintaining the resulting rudder within the required tolerance
range of
6mm (+- 3mm). It can be very expensive to make a rudder from rudder stock and
blades of the same material as a superior quality is needed for the blades
compared
to the stock.
According to an aspect of the present invention, there is provided a rudder
manufacturing method of manufacturing a rudder for a marine vessel, the rudder
comprising a rudder stock and a rudder blade, the rudder stock comprising a
first
metal material and the rudder blade comprising a second metal material, the
first
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metal material and the second metal material each having a thermal expansion
rate,
the thermal expansion rate of the first metal material being different to the
thermal
expansion rate of the second metal material, the method comprising the steps
of:
providing a transition plate having opposed first and second connection
portions
comprising a metal material having a rate of thermal expansion that is
substantially
equal to the thermal expansion rate of the second metal material, the first
connection
portion for making a welded connection directly to the first metal material of
said
rudder stock and the second connection portion for making a welded connection
directly to the second metal material of said rudder blade; preheating said
transition
plate and said rudder stock; connecting, by welding, the metal material of the
first
connection portion of the preheated transition plate directly to the first
metal material
of the preheated rudder stock, thereby forming a first welded connection;
heating said
first welded connection connecting said first connection portion of said
transition plate
directly to said rudder stock to relieve stress in the first welded
connection; and, after
said heating to relieve said stress in said first welded connection,
connecting, by
welding, the metal material of the second connection portion of said
transition plate
directly to the second metal material of said rudder blade to form said
rudder, with the
rudder stock and the rudder blade being spaced apart and connected by said
transition plate.
According to another aspect of the present invention, there is provided a
rudder for a marine vessel, the rudder comprising a pre-heated rudder stock
comprising a first metal material, a rudder blade comprising a second metal
material,
and a preheated transition plate comprising a metal material and having
opposed first
and second connection portions, the metal material of the first connection
portion
being welded directly to the first metal material of said preheated rudder
stock and
the metal material of the second connection portion being welded directly to
the
second metal material of said rudder blade, wherein the first metal material
has a
carbon content that is higher than any carbon content of the second metal
material,
Date Recue/Date Received 2022-01-31

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and each of the first metal material of the rudder stock, the second metal
material of
the rudder blade and the metal material of the transition plate has a rate of
thermal
expansion, wherein the rate of thermal expansion of the metal material of the
transition plate is substantially equal to the rate of thermal expansion of
the second
metal material, and the rate of thermal expansion of the first metal material
is different
from the rate of thermal expansion of the metal material of the transition
plate.
According to another aspect, there is provided a method of connecting metals
having dissimilar thermal expansion rates to one another including the steps
of: pre-
heat treating a transition plate along with a first metal; welding the pre-
heated
transition plate to the pre-heated first metal; and welding a second metal to
the
transition plate after stress relieving the resulting weld between the
transition plate
and the first metal.
According to another aspect, there is provided a rudder comprising a pre-
heated first metal welded to a pre-heated transition plate, the transition
plate being
further welded to a second metal with a lower carbon content to the first
metal and
manufactured by the method described above.
According to another aspect, there is provided a method of connecting metals
having dissimilar thermal expansion rates to one another including the steps
of: pre-
heat treating a transition plate along with a first metal; welding the
transition plate to
the first metal; stress relieving the resulting weld; and welding a second
metal to the
transition plate.
The transition plate may be welded to the first metal by MIG or MAG welding.
The second metal may be welded to the transition plate by MIG or MAG welding.
The use of transition plates means that similar or dissimilar metals can be
connected to each other, with the weld undergoing pre-heat treatment and
stress
relief, without causing stress to the welds by different rates of thermal
expansion.
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This maintains the resulting product within the desired tolerances as no
welding
needs to be carried out directly on the now stress relieved rudder stock.
In some embodiments the transition plates are made of DH36 steel.
In some embodiments, the first metal is a forged-steel measuring 100 mm
thick and which has high carbon content. The second metal may be DH36 steel or
Super austenitic Avesta Sheffield 2545M0O which is a stainless steel
containing
18% nickel, 20% chromium, 6.1% molybdenum, 0.2% nitrogen and 0.01% carbon.
The first metal is used to make a rudder stock and the second metal is used to
make
a rudder blade insert. 2545M0O may be used as it has improved wear and
corrosion resistance properties.
The different grades of steel of the first metal and second metal expand and
contract at different rates to one another. For example, the expansion rate of
Avesta
Sheffield 254SM0O is double that of the high-carbon forged steel which can be
used
for the rudder stock. It is evident that stress relief of the conventional
weld joining the
blade and the stock will cause the steel components to expand at different
rates.
However, the present invention overcomes this problem and results in a rudder
which
is either not distorted or distorted within an acceptable tolerance range.
In some embodiments, the transition plate and the second metal have
comparable expansion rates.
There is no need to preheat the transition plates and rudder blades. Also,
there is no need to stress relieve the weld joining the blade to the
transition plate.
Date Recue/Date Received 2021-10-25

CA 02934139 2016-06-16
WO 2015/091681 PCT/EP2014/078282
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The method can be applied to rudder stabilisers or steel fabrication that
requires tight tolerances and metals that require stress relieving.
In a further aspect of the invention there is provided a rudder comprising
a first metal welded to a transition plate, the transition plate being further
welded
to a second metal wherein the first metal has a higher carbon content than the
second metal.
An embodiment of the invention will now be described by way of example
only and with reference to the accompanying drawing of which:-
Figure 1 shows a view of a ship's rudder and transition plate according to
the present invention.
Turning to Figure 1 there is provided a ship's rudder 10 comprising a
rudder stock 11 made from a first metal and a rudder blade 12 made from a
second metal. Both the rudder stock 11 and rudder blade 12 are abutted
against a transition plate 13 and welded along the length of joints 14 and 15,
in
accordance with the methods of the invention. For simplicity Figure 1 shows
the welds at joints 14 and 15 as butt joints, however, these could be other
types
of joint, for example, lap joints, modified butt joints, modified lap joints
or a
combination of butt and lap joints.
Variants, modifications, additions and omissions relating to the
description above are possible within the ambit of the invention and will be
readily apparent to the skilled addressee.

Representative Drawing