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EXPLOSION WELDING PROCESS
FOR REPAIRING WORN
THREADED HOLES IN THE
SPINDLES OF RAILWAY WHEELS
Prof. L.D. Dobrushin*, Ing. S.Yu. Illarionov**
The E.O. Paton Electric Welding Institute, Kiev, Ukraine
[email protected], [email protected]
The E.O. Paton Welding Institute
1
One of the most widespread and hard-to-eliminate defect of the
spindle is a damage or wear of threaded holes M 20 that are
used for the bolt fixtures of the roller bearing stop bars. Just light
mechanical damage of threaded hole element leads to crippling
of the whole spindle that must be used during 8…15 years.
The E.O. Paton Welding Institute
State of the Art in Solving of the Problem
1) Arc melting in CO2 with the following drilling and thread cutting. This
method has some lacks:
- high cost of equipment and consumables;
- great probability of cracks occurring because of spindles are made of steel
that is considered as difficult to weld;
- shrink shortenings leads to prohibitive decreasing of diameter.
2) Bigger diameter thread cutting with the following screwing of hollow
insert that has inner diameter M 20. The main lack is:
- low reliability because an unscrewing of the hollow insert occurs when it
runs.
The E.O. Paton Welding Institute
Drawing of the Edge of Spindle, where
Threaded Holes to be Repaired are Placed
The E.O. Paton Welding Institute
4
The explosion welding can be proposed for solving
the problem as alternative to described above
methods of repairing.
The process has some advantages:
- low cost of equipment and consumables;
- strength of joint is more than strength of less strong
material in the bond;
- thermal effect on the base metal is significantly less than
in case of arc melting when it leads to undesirable
structure changing;
- shrink shortenings and corresponding decreasing of
diameter of the edge part of the spindle do not occur.
The E.O. Paton Welding Institute
It’s obvious that to apply explosion welding for solving the
problem the internal concentric scheme should be used
1 – clad tube; 2 – cladding tube; 3 – explosive
The E.O. Paton Welding Institute
6
Materials that are Used for the
Repairing Cladding Process
1. Base material (axle steel) has the following mechanical properties:
- UTS = 600…650 MPa;
- Elongation = 6%
2. Cladding material (Steel 20) has the following mechanical properties:
- UTS = 420…425 MPa;
- Elongation = 42%.
* It was chosen with the thought that it must has a good plasticity and be able
to strengthen significantly.
3. Thickness of the wall of cladding tube is 2.5 mm and external diameter is 17 mm
* Selection of such a thickness is required by the following conditions:
- internal diameter of clad hole must be less than 17.3 mm giving possibility to
make the treaded hole M 20;
- the hole expends during explosion loading;
- thinning of cladding tube due to its expansion.
The E.O. Paton Welding Institute
7
Some Technological Features of Explosion Welding
Process for Repairing Worn Threaded Holes
1. Previous boring of worn threaded hole to 20.4 mm in diameter.
2. Setting cladding tube in the hole to be clad in a manner that does
not allow placing gap fixtures between surfaces to be welded for
avoiding lack of sound joint.
3. Usage of external concentric anvil to avoid expansion of the edge
part of the spindle.
The E.O. Paton Welding Institute
8
Typical Macrosection of Repaired Threaded Hole
Typical microstructure of joint (cladding material is on top), Х200
The E.O. Paton Welding Institute
9
The Scheme of Fatigue Testing
Shown device provides fatigue testing of two
specimens simultaneously in a following
mode:
Рmax = 98,0 kN and Рmin = 49,0 kN,
frequency of cycling = 5 Hz.
Repaired threaded holes and new ones for
comparison as a base were tested.
Only two first turns of thread were exposed to
loading.
1 – edge of the spindle;
2 – cartridge; 3 – bolt; 4 - holder
The E.O. Paton Welding Institute
The Results of Fatigue Testing
New Threaded Holes
Specimen
Number
Fatigue Crack
Life Νр, cycles
Repaired Threaded Holes
Specimen
Number
Fatigue Crack Life
Νр, cycles
1
156 000
1
145 000
2
134 000
2
124 000
3
142 000
3
145 000
4
165 000
4
150 000
The following minimal fatigue crack life values were received
after treatment of the results:
- for the new threaded holes Νmin = 127 000 cycles;
- for the repaired threaded holes Νmin = 122 000 cycles.
The E.O. Paton Welding Institute
General View of Threaded Holes after Testing
New Threaded Holes after Testing
Repaired Threaded Holes after Testing
The E.O. Paton Welding Institute
The E.O. Paton Welding Institute
13
THANK YOU FOR YOUR ATTENTION
The E.O. Paton Welding Institute
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