Note: Descriptions are shown in the official language in which they were submitted.
r~his in~vention relate~ to an improved method of restoring
or recollditioning worn or damaged engineering equipment~ sueh
as drive shafts, bearings and si~ilar equipment ~n the marine and
general en~ineering fields and provides a method of restorin~ orr
or damaged drive shafts or other components that have a circular
form and to which repair can be carried out7
It is known to restore worn area~ o~ drive shaft by a metal
praying process or flame plating but the repairs effected are
eub~ec-t to disadvantagesO Ir. particular5 the deposited metal may
not bo~d well to the ~haft and c,an therefore separate in use~ In
addition metal spraying by its nature ie porous, which in marine
en~ironments results in penetration of salt ~ater contributing to
early separation and resulting damage to bearings. Electrolytic
action or simply poor adhesion of the sprayed layer also
contribute to failure. It has also been proposed to fuse wire~
by ~elding in the longitudir.al direction along the dal~aged are~
of the ~haft~ '~his method, howe~er~ ls not only time consuming
and not readily adaptable to autol~atic processe~, but result3 in
considerable bending distortion of the ehaft wrhicll can only be
~r
.. .
1039~15 6
partly countered by laying uccessive wires on diametrically
opposed lines on the shaft, thi~ considerably complicates the
proces~. .
~ his invention seeks to provide a method which avoids the
aforementioned disadvantages and which can be applied to
restora-tion of shafts of all sizes.`
~ he object of thi~ invention is to provide a new method
which can be xeadily applied in many fields for xestoration of
~orn or corroded area~ and which will be acceptable by various
~ o~anis~ s
ID~ 4~ hnff~ as an approved proce3s.
According to this invention there i8 providea a method of
restoring worn or damaged metal dr~ve shafts or li~e components,
comprising O -
(a) cleaning the area of the shaft or the like to be re~tored,
(b) applying ~ wire of a metal compatible ~ith -the metal o~ the
shaft by winding, using a controlled feed and tra~7erse9
(c) subjecting the area at the junction of the ~ire and shaft
a~ ~inding progre~se~ to heat~ to weld or fuse the wire to
adjacent turns and to the sha~t, and
~D (d) subsequen~ly màchining the weld depo~1t so formed to provide
a ~ini~hed surface.
In a preferred example, the restoration of a marine
drive shaft, the worn or damaged area or areas are cleaned -
- chemically or mechanically 9 straightened, should this be
nece~sary, and then a metal wire fed onto the revolving
~IL0394~6
shaft, localised heat being applied to the junction of wire
and shaft to fuse both together and the said process being
continued by traversing along the damaged area until spiral
layers of deposited metal cover this area to a sufficient
depth to subsequently re-machine the surface to its original
size, or greater or smaller.
The applied wire is preferably~of the same or simi-
lar metal composition to the sha~t although widely different
metals can be applied~ subject to the ability to form an alloy
with ~he shaft. The w~ld is wound onto the shaft by rotating
the latter and feeding the welding wire thxough a gas or flux
shielded welding gun positioned close to the shaft and moved
longitudinally as the winding progresses. By this method a
homogeneous build-up of metal integral with the original shaft
metal is effected over the damaged area and by subsequent
machining the surface may be refonned to the original dimen-
sions and condition, or increased in diameter.
The method is particularly useful for remetalling
worn bearing areas of a shaft or corroded areas of a shaft.
The rate of rotation of the shaft, wire diameter,
type of wire, wox~ speed, current, shielding gas or gas
mixtures or flux, gas flow, electrode traverse speedJ wire
feed speed, voltage-work power scale, induction, electrode-
pclarity, work-polarity, voltage regulation and e~uipment
are related to the shaft diameter and welding process used.
The rotational speed of the work, its composition and wire
3L~394~6
size and composition, its feed rate and the r~lated vol~age
and current of the electric arc, including the shielding gas
or flux composition, are related and differ for each combina-
tion of work, wire and composition. These interrelationships
are complex and require experiment for optimum results. The
parameters for speciic embodiments are given herein by way
of examples.
The method may also be applied to the reconditioning
of gunmetal or aluminum bronze or alloy bearing sleeves on
marine propeller shafts. Hitherto such sleeves, when only
slightly wor~, were machined off and a new sleeve machined
and shrunk onto the shaft followed by machining and su~sequent
truing of the shaft.
When the process is applied to propeller shafts or
other marine components which have been subject to salt water
a chemical de-salination process will be applied as part of
the preliminary cleaning operation.
A continuous weld of metal identical, or compatible,
with the shaft is fused around the worn or damaged area of the
shaft by a circular motion instead of the more commonly used
lateral welding methods which can cause distortion and other
problems, or metal spraying which can be the subject of
porosity difficulties and lack of body strength. The continu-
ously fed wire coils are simultaneously welded to the shaft
and to each other as a deposition of compatible weld metal,
using an inert gas or flux shrouded electric welding process.
10394~
The voltage and current used ensures correct and even pene-
tration to suit the particular shaft and weld material con-
cerned. The process is continued until the deposit is suffi-
cient to permit machining of the areas to the required
dimensions. The laying-on of the weld is controlled by
varying the traverse and spindle speed of the lathe or other
machine being employed, such as a pipe rotating machine.
Stress relieving, or heat treatment, can be carried
out on completion of the process if necessary~ but one advan-
tage of the process is that in the majority of casss it isself-~ormalising and if the welding process is back-tracked
to a suitable finishing point to allow for heat dissipation,
it is unlikely that any surface cracking will occur.
It is not always neeessary to machine the surface
or prepare it by methods such as shot ~lasting, as the process
can be applied to any clean surface.
Dissimilar metal~ may be used, for example stainless
steel can be applied to mild steel and aluminum bronze to
stainless steel, mild steel and bronze materials. Nickel-
aluminum bronze also can be applied in cases where a harderwearing surfa~e is desired.
Surface hardness can be maintained by using an
appropriate metal, or subsequent heat treatment.
The method o~ the invention proves to be faster than
known processes such as metal spraying and flame plating and
is less liable to produce distortion in the shaft or affe~t
--5--
~39~86
the composition o~ the parent metal at lower levels.
A modification provides for the resurfacing of a
flat surface by laying-on the wire in a helix across the
surface and a further modification provides for internal appli-
cation of the wire to the inside surface of a cylinder where
sufficient space is available to receive the welding gun.
In practice repair of worn shafts or the like is
carried out by rotating the shaft in a lathe, or similar
machine, which is capable of rotation at an accurately con-
trolled gpeed. The speed may be as low as 0.2 r.p.m. depend-
ing on diameter of the shaft and rate of metal deposition.
Further the rate of traverse of the welding head across the
area of the shaft being restored is variable and accurately
controlled in relation to the rotational speed by means of an
independent variable speed motor controlled from a variable
potentiometer.
Existing machines may be easily modified to carry
out the method of the invention with particular attention
being given to protection of the machine slideways from weld
splatter and the method of current feed to the shaft, Because
of the high direct currents employed, feeding through the
machine bearings is generally unsatisfactory as the high
current densities and attendant arcing destroys ~he bearing
surfaces in the machine and leads to variations in weld current.
This problem is overcome by fitting the machine with motor
brushgear contacting the machine spindle or a contact sleeve
--6--
~3~48Çi
thereon, or a brushgear band strapped to the workpiece to
complete the circuit.
As example a two inch diameter stainless steel shaft
was rotated at four r.p.m. and a 0.8 m.m. stainless steel wire
was fused to the shaft and fed through a low voltage shiPlded
argon arc. The area of the shaft was then turned and ground
to the final dimensions. This type of work can be carried out
in accordance with predetermined data thereby minimising the
heat input and reducing any detrimental effects to the parent
metal or deposited weld.
Conventional repairs using metal spraying may f~il
due to the p0~0sity of the repair allowing salt water penetra
tion and subsequent separation of the metal layers. This is
avoided with the method of the invention.
With marine propeller shafts a chemical de-salting
process is effected as a preliminary step.
The accompanying drawing shows one arrangement for
carrying out the method of the invention using a conventional
lathe. As shown the shaft 1 to be restored is mounted for
rot~tion by the machine headstock drive 2 in steadying bearings
3 and 4. The lathe saddle 5 carries the arc welding equipment
6 with feeds for shielding gas and wire 7. An adjustment 8
provides for variation of the height of the welding eguipment.
The saddle 5 also carries a cutting tool and mounting 9.
The following examples taken in conjunction with the
table illustrate the various parameters for a number of
3~486
combinations and dimension of shafts and wire.
In the examples the welding equipment used was by
Norman Butter and Company Limited designated ~BC 350 or NBC
500 being 350 amp and 500 amp respectively and the parameter
"wire feed speed" is the dial reading on this equipment. In
all examples the polarity was, welding electrode-positive,
and workpiece-negative. Other sizes of different diameters
can be calculated from the data presented in order to achieve
satisfactory results. A wire brush is used on the opposite
side to the:~weld gun on the workpiece to remove possible
splatter which cou~ cause pin points of porosity especially
when subsequent layers are being applied. A constant voltage
is to be ma.intained in all cases.
~¢J 3~ 6
Example Shaft Wire Weld
Equipment
1 Stainless Steel ENl8C Aluminium Bronze NBC350
BS2901 Part 3
2 Aluminium Bronze " NBC500
DGS8452
3 Aluminium Bronze
4 Monel K500 Monel 60 NBC350
" " NBC500
6 Stainless Steel EN18C Stainless 29/9R NBC350
BS2901 Part 2
7 Stainless Steel EN58J Inconel 625 NBC500
8 ll ~, "
9 Gun Metal BS1400 Phosnic NBC350
(Ni 1.38:Nn 0.22:
Si 0.46: P 0.021:
Sn 5.22:
Balance CU)
Gun Netal BS1400 Phosnic NBC500
1969
ll Gun Metal, Admiralty Phosnic N "
Spec. DGS 203 or LG4
12 Mild Steel EN3C PZ.6000 BS 2901 NBC350
Part 1, Al 6
13 Mild Steel EN3B
14 Mild Steel EN3C " NBC500
EN5K C:0.25-0.35 PZ.S000 C:0.25-0.3 "
Si:0.05-0.35 Si 0.3-0.5
Mn:0.6-1.0 MN:1.3-1.6
S:0.05 P:0.05 S:0.04 P:0.04
16 Mild Steel EN3L PZ.6000 BS 2901 "
Part 1 Al 6
17 "
18 EN5K PZ.6000 ~'
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1~3~4136
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TA13LE 2. 1~39486
__ _ ~ ~
E~MPLE: NO. S~TTING ON SPECIFI~D EQUIPMENT
. _ __
Cour~e Vol~ e Power Fine Induc~ance
Scal~ Voltag~ Con~x~l
~. _ . _ _ _ _ . _
. D LOW Q . 100
2 ~ LOW 5 100
3 D LOW 2 100
4 D I.OW 4 100
C LOW 4-6 100
6 D . LO~ 4 100
7 C I~oryJ 5-6 605
8 D LOW 35 70
9 D LOW 4~5 O
D LOlil 5 O
11 A HIGH 3 O
12 :1) LOW 4 100
13 D I,OW 4 100
14 C LOW 5 6 6i~5
D LOW 3 70
16 D LOW 3 70
17 . LOW 3 70
18 _ HIGH 1 7 0
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