FLASH BUTT WELDING OF RAILS 1 PRINCIPLE Softening

FLASH BUTT WELDING OF RAILS 1

PRINCIPLE • Softening of interface by electric current • Rails are butt under pressure welding • Shortening of rails by 25 -30 mm 2

COMPONENTS OF MACHINE • Clamping mechanism • Forging mechanism – Bring the rails in contact at low force – Application of high force on completion of welding cycle • Step down voltage from 400 -500 V to 4 -12 V and current between 30, 000 Amp to 80, 000 Amp 3

OPTION OF FBW • Fixed site depot • Mobile flash butt welding plant 4

AT FIXED DEPOT • • • Rail storage & transfer table Straightening End cleaning Welding Stripping 5

CONT. . • Post weld treatment – Rail joint straightening – Rail head profiling • Inspection • Outgoing conveyor system 8

FBW PROCESS • INITIAL BURN OFF - in this stage rails are moved closer & away in a cyclic manner for 20 -30 cycles in 10 -15 seconds. Voltage 9 -10 V, current approx. 40000 Amps. • PREHEATING – in this stage rails are moved closer & away in longer cycles in which contact period is 45 seconds & separation for 1 seconds. This is done for 45 -60 seconds keeping Voltage 9 -10 V, current approx. 40000 Amps. 14

• FINAL FLASHING – in this stage rails are kept in touch for 15 -20 seconds Voltage 9 -10 V, current approx. 40000 Amps. Continuous flashing takes place. • FORGING (UPSETTING) – rails are butted at high pressure for 10 seconds. Actual welding of rails takes place. • STRIPPING – done in hot state to shave off projected metal which has come out while forging. 15

BUTTING PRESSURE • 72 UTS – 5 Kg/mm 2 • 90 UTS – 6 Kg/mm 2 • 110 UTS – 7 Kg/mm 2 16

SUITABILITY OF RAIL FOR WELDING 17

SUITABILITY OF RAIL FOR WELDING 18

CHECKING OF JOINT AFTER WELDING WITH NEW RAIL 19

CHECKING OF JOINT AFTER WELDING WITH OLD RAIL 20

CHECKING OF FINISHING OF JOINT AFTER WELDING 21