The E.O. Paton Welding Institute1 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

The E.O. Paton Welding Institute 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 Institute4 Drawing of the Edge of Spindle, where Threaded Holes to be Repaired are Placed

The E.O. Paton Welding Institute 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 Institute6 1 – clad tube; 2 – cladding tube; 3 – explosive It’s obvious that to apply explosion welding for solving the problem the internal concentric scheme should be used

The E.O. Paton Welding Institute7 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 Institute8 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 Institute9 Typical Macrosection of Repaired Threaded Hole Typical microstructure of joint (cladding material is on top), Х200

The E.O. Paton Welding Institute 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. The Scheme of Fatigue Testing 1 – edge of the spindle; 2 – cartridge; 3 – bolt; 4 - holder

The E.O. Paton Welding Institute The Results of Fatigue Testing Fatigue Crack Life Ν р, cycles Specimen Number Fatigue Crack Life Ν р, cycles Specimen Number Repaired Threaded HolesNew Threaded Holes The following minimal fatigue crack life values were received after treatment of the results: - for the new threaded holes Νmin = cycles; - for the repaired threaded holes Νmin = cycles.

The E.O. Paton Welding Institute New Threaded Holes after TestingRepaired Threaded Holes after Testing General View of Threaded Holes after Testing

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The E.O. Paton Welding Institute14 THANK YOU FOR YOUR ATTENTION