IE43211B1 - Method of restoring worn or damaged marine propeller shafts - Google Patents

Abstract

TITLE "Method of restoring worn or damaged drive shafts". A method of restoring worn bearing areas on a marine propeller shaft in which the area is cleaned and a wire compatible with the metal of the shaft is applied through an inert gas shielded arc welding gun, the wire being wound around the shaft by rotation thereof and fused to the shaft and adjacent turns during winding, the area being subsequently machined to produce a finished surface.

Description

This invention relates to a method of restoring a worn or damaged marine propeller shaft.

According to this invention there is provided a method of restoring a worn or damaged marine propeller shaft by the deposition and fusion of a metal to the shaft, characterised by the steps: (a) cleaning by exposing the base metal in the area of the shaft to be restored by chemical or mechanical means, (b) rotating the shaft in a lathe or similar machine about its longitudinal axis at an accurately controlled rate, (c) feeding the metal to be deposited as a single wire through an or similar machine inert gas shielded arc welding gun mounted on the lathe/and movable longitudinally thereof to the periphery of the rotating shaft with the wire itself forming a consumable electrode for the arc, (d) traversing the welding gun longitudinally along the shaft during rotation thereof while feeding said single wire therethrough and depositing the material of the wire as it is worn or consumed over the length of the/damaged area in the form of a continuously fused metal deposit, all while controlling the feed of the wire and maintaining a - 2 4 3 211 steady, continuous rotation of the shaft and traverse of the welding gun, (e) applying current tnrough the wire to the shaft as deeding ano rotation and tra/ersing progress deposited also to to effect fusion welding of the/material of the wire to the shaft and/adjacent deposited material / to form a homogeneous substantially uniforai metal deposit which blends with the base metal of the shaft, and (f) subsequently machining in a lathe the weld deposit to provide a finished surface.

The deposited metal covers the area of the repair to a sufficient depth the shaft in so that / may be subsequently machined to the original diameter.

The applied wire is preferably of the same or similar metal composition to the shaft although widely different metals can be applied, subject to the ability co form an alloy with the shaft. The weld is effected by feeding the wre through an inert gas shielded welding gun positioned close to the shaft and moved longitudinally as the I ceding wire progresses. By this method a homogeneous build-up of metal integral with the original shaft metal is effected worn or over thqfdamaged area and by subsequent machining the surface may be reformed.

The method is particularly useful for remetalling the worn bearing marine areas or corroded areas of a/propeller shaft. 2o Tne rate of rotation of the shaft, wire diameter, type of wire, work speed, current, shielding gas or gas mixtures, gas flow, electrode traverse speed, wire feed speed, volcage-wora power scale, induction, electrode-polarity, work-polarity, voltage regulation, and equipment are related to the shaft diameter of the shaft material and welding gun used. The rotational speed of the shaft and the composition/and wire size and its composition, feed rats ano the related voltage and current used and also tne swslaing gas. a re related ar.c differ for each combination of work, respective compositicnc. wire and their / ' These interrelationships are complex and require experiment for optimum results. Tne parameters for specific embodiments are given herein by way of examples. 3211 The method may also bo applied to the reconditioning of gunmetal or aluminium bronze or alloy sleeves on marine propeller shafts. Hitherto such a sleeve , when only slightly worn, was machined off and a new sleeve machined and shrunk onto the shaft followed by machining and subsequent truing of the shaft.

When the method is applied to propeller shafts 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 continuously fed wire is simultaneously welded to the shaft and to itself as a deposition of compatible weld metal, using an inert gas shrouded electric welding process. The voltage and current is selected to ensure correct and even penetration to suit the particular shaft and weld material concerned. The method is continued until the deposit is sufficient to permit machining of the area to the required dimensions. The laying-on of the weld is controlled by varying the traverse and rotation rate of the lathe or other similar machine being used, such as a pipe rotating machine.

Stress relieving, or heat treatment, can be carried out on completion of the method if necessary, but one advantage of the method is that in the majority of cases it is self-normalising and if the welding 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 necessary to machine the surface or prepare it by methods such as shot blasting, as the method can be applied to any cleaned surface.

Dissimilar metals may be used, for example stainless steel can be applied to mild steel and aluminium bronze to stainless steel, mild steel and bronze materials. Nickel-aluminium bronze also can be applied in cases where a - 4 43211 harder wearing surface is desired.

Surface hardness can he maintained by using an appropriate metal, or subsequent heat treatment.

The metnod of the invention proves to be faster than known methods such as metal spraying and flame plating and is less liable to produce distortion in the shaft or affect the composition of the parent metal at greater depths.

In practice the shaft is rotated in a lathe, which is capable of rotation at an accurately controlled speed. The speed may be as low as 0.2 r.p.m. the depending on/diameter of the shaft and rate of metal deposition. Further the rate of traverse of the welding gun 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 unsatisfactory as the high current densities and attendant arcing destroys the bearing surfaces in the machine and leads to variations in weld current.

This problem is overcome by fitting the machine with electric motor brush-gear contacting the machine spindle or a sleeve tnereon, or by using a brush-gear band strapped to the workpiece to complete the circuit.

As an example a two inch diameter stainless steel shaft was rotated at four r.p.m. and a 0.8 mm stainless steel wire was fused to the shaft using a repaired Tow voltage shielded 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 prevising minimal heat input and reducing any possible detriments 1 effects to the parent metal or deposited weld.

Conventional repairs using metal spraying often fail due to the porosity of tne repair allowing alt water penetration and subsequent separation - 5 azn of the metal layers. This is avoided with the method of the invention.

The accompanying drawing shows one arrangement for carrying out the method of the invention using a conventional lathe. As shown the propeller shaft 1 to be restored is mounted for rotation 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 equipment. The saddle 5 also carries a cutting tool and mounting 9.

The following examples taken in conjunction with the tables illustrate the various parameters for a number of combinations and dimensions of shafts and wire.

In the examples the welding equipment used was by Norman Butter and Company Limited designated NBC 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 gun used on the opposite side to the welding/ on the workpiece to remove possible splatter which could cause pinpoints of porosity especially when subsequent layers are being applied. A constant voltage is to be maintained in all cases. - 6 43211 Weld Example Shaft Wire Equipment 1 Stainless Steel EN18C Aluminium Bronze BS2901 Part 3 NBC350 2 Aluminium Bronze DGS8452 II NBC500 3 Aluminium Bronze II II 4 Monel K500 Monel 60 NBC350 5 IE li NBC500 6 Stainless Steel EN18C Stainless 29/9R BS2901 Part 2 NBC350 7 Stainless Steel EN58J Inconel 625 (Regd. Trade Mark) NBC500 o u II ' II 9 Gun Metal BS1400 Phosnic (Ni 1,38:Mn 0.22: Si 0.46: P 0.021: Sn 5.22: Balance Cu) NBC350 10 Gun Metal BS1400 1959 Phosnic NBC500 11 Gun Metal,Admiralty Spec. DGS 203 or LG4 Phosnic N II 12 Mild Steel EN3C PZ.6000 BS 2901 Part 1, A16 NBC350 13 Mild Steel EN38 IE II 14 Mild Steel EN3C a NBC500 15 EN5K 0:0.25-0.35 Si :0.05-0.35 Mn:0.6-1.0 3:0.05 P:0.05 PZ.6000 0:0.25-0.3 Si 0.3-0.5 Mn: 1.3-1.6 S: 0.04 P:0.04 II 15 Mild Steel EN3L PZ.6000 BS 2901 Part 1 Al 6 II i 7 II II II 13 EK5K PZ.6000 II - 7 43 211 co <0- O CM 3-6 Cougar 35-45 COjtQ 57-65 30 280-300 S- CO 0.08 CO Cougar 35-45 0.15 «0 co 33 280-290 1 i ID CM CO o ID Cougar ι (See 1) i 45 n jio o 25 ο co CM tn 3 to 4 1.00 to 1.20 «0· Argon (Pure) 35-45 | 0.166 ’ 1 60-70 27 260-280 *0- CM 80 Ό to C φ o scn 3 S_ CL. 35-45 1 0.093 01 . «0· CM 130-150: co 3 to 4 CO o 2-9 Argon 35-40 0.166 6.2 ... J 28 CO co CM ^eoj co 6-8 | Argon 35-40 S L' 0 1 6.5 «0* CM o co 1 o CM CM co o to Argon in •0· LO 25 οει-οζι O J z J 3 ω - Q. E Shaft Di am. inches Wire Size, mm Work Speed, rpm Shield Gas Gas Pressure p.s.i. j Electrode traverse inches/revolution fO σ σ φ Φ (- CM Φ Φ £- Φ r- tn Potential (Volts) Current (Amps) fO X UJ (0 _Q a •σ Φ 4- σ) χ: •P·» CM Ο tS in CM 0) Ό ro S-σ ω u φ -Ρ (Λ Ο) Φ Cd U <0 cn Ο Ο rd •r~ Ό cn (0 -σ ω φ ψ. φ tφ •ρ ο CM Φ •Ρ Ο ζ — co — © ι © CM 0.3 Cougar ©rots f—— © © Γ-. © ΓΧ CM 270-290 o -a cm c o © O © un . c ♦ o © c». O o r— ft! I— *3* © 1 r— © < © o © 280- © © m OOM c © © © © • C · o •xT © η». © r— C& r— £. © rx. © © *=£ CO o © ¢0 © © i- O © Π3 co^o © o co © 3 © «3· © 1 o © 1 O © © CM CO © S~ © co o co to © © © © 3 1 •xi- co O © © co © © o © © © co o © c: o O © © o co CM . 1 © I I— © X © © © i- © • r— d © © — CM 30- r“ CM 08 © c: o © o j— 1 o © X o © © ί o o © © r- ΞΞ -stf· =£ CO ό CM 1 © © r- i-itt CO c © Γ- cn o co r— i—- © 1 r— © © .· a1 ' © C<~i CM © o CO IX ΐ. Cn o CO r— © 1 © © • © © O © © -ll © c ,n CM CO cn cn o P γo· «χ1· •st © O < CO r— CM © ©’ ·· ~1 -P o 22 C © Φ LU Q- E «3 JO u Φ '4- © - CQ tO < X I—- LU 2 11 TABLE 2.

EXAMPLE NO. SETTING ON SPECIFIED EQUIPMENT Coarse Voltage Power Scale Fine Voltage Inductance Control 1 D LOW 4 100 2 B LOU 5 100 3 D LOW 2 100 4 D LOW 4 100 5 C LOW 4-6 100 6 D LOW 4 100 7 C LOW 5-6 6.5 8 0 LOW 3-5 70 9 D LOW 4-5 0 10 D LOW 5 0 11 A HIGH 3 0 12 D LOW 4 100 13 D LOU 4 100 14 C LOW 5-6 6.5 15 D LOW 3 70 16 D LOW 3 70 17 D LOW 3 70 18 A HIGH 1 70

Claims (5)

1. A method of restoring a worn or damaged marine propeller shaft by the deposition and fusion of a metal to the shaft, characterised by the steps: (a) cleaning by exposing the base metal in the area of the shaft to be restored by chemical or mechanical means, (b) rotating the shaft in a lathe or similar machine about its longitudinal axis at an accurately controlled rate, wire (c) feeding the metal to be deposited as a single/through an inert gas or similar machine shielded arc welding gun mounted on the lathe/and movable longitudinally thereof to thr- periphery of the rotating shaft with the wire itself forming a consumable electrode for the arc, (d) traversing the welding gun longitudinally along the shaft during rotation thereof while feeding said single wire therethrough and depositing the material of the wire as it worn or is consumed over the length of the/damaged area in the form of a continuously fused metal deposit, all while controlling the feed of the wire and maintaining a steady, continuous rotation of the shaft and traverse of the welding gun, (e) applying current through the wire to the shaft as feeding and rotation and traversing progress to effect fusion welding of the deposited material of the wire to the shaft and also to adjacent deposited material to for!:: /a homogeneous substantially uniform metal deposit which blends with the base metal of the shaft, and (f) subsequently machining in a lathe the weld deposit to provide a finished surface.

2. A iiiethod in accordance with Claim 1, wherein the wire is of the same material as the shaft.

3. A metnod in accordance with Claim 1 or 2, wherein an electrical gun circuit fo'' the welding /is completed through brush-gear associated with shaft.

4. A method according to any preceding claim, wherein the cleaning includes a desalination process. - 11 4 3 211

5. A method as claimed in Claim 1, substantially as herein described with reference to any one of the examples herein.