Welding is done to join the metals by melting the metal ends and then joining them. It is mainly helpful in joining large pieces of metal or when the new metal structure cannot be formed. In railways, it is done with the help of road-rail vehicles, which can move on both roads as well as on rails. FLASH BUTT WELDING RAIL is did to weld the tracks.
To weld the rails preparation has to be done which is as follows:
- Pre-straightening of rails: There are some geometric principles in rails that are to be followed, if these principles are not followed then they have to be adjusted before welding with the help of pre-straightening device to match the standards.
- Reducing the difference between head width: The actual head width of rails is to be examined as to reduce the variation between the head width of rails ends that are to be connected. Deviations should be labeled on the railheads, to choose the least deviation for welding.
- End-cleaning: Before welding is done, the end faces of the rails on which welding is to be done, are cleaned to eliminate any presence of rust and paint through brushing and grinding which will help in good electrical contact and will prevent arcing. With the aid of carbon tetrachloride or benzene, oil and grease can be eliminated. If there is any inner defect like piping then rail will not be welded.
The process of rail welding is as follows:
- Electrical contact: The electrical contacts like copper and electrodes in the welding machine should be cleaned with the aid of air pistol which assures the freedom from any oxides and other materials to prevent arcing at the contact points on the rail.
- Rail adjustment: To prevent the step defects, the running area of rails at the interface should be perfectly aligned.
- Welding Order: The welding order is as follows:
- Aligning: The running area of rails at the interface should be perfectly aligned.
- Primary burn off: It is done to assure that the welding link has a good connection. Control is modified according to the specs of the rail and welding machines.
- Preheating: The rail ends are linked to enable the current flow which helps in preheating the rail ends.
- Flashing: Rail is moved in the beginning constantly at same speed and in the end at a faster speed. It is done to prevent short-circuiting and rails end also gets burn-off.
- Forging: To butt the rail ends collectively, pattern movement is accelerated through a strong butting power and magnitude depending upon the manufacturing of the welding machine.
- Stripping: A stripper that is installed near the welding machine, strips the hot upset metal about the rail section so that the least grinding is needed to attain last finished profile at the weld. When the automatic stripper is not fitted, manual withdrawal of upset metal is done with the help of pneumatic chisel.
The above discussed is the process of rail welding. In RESISTANCE FLASH WELDING, no filler metals are used to join the metals and is more effective in comparison to other techniques of welding and that’s why it is used in rails.