Flash butt welding method of rail steel
View Patent ↗This welding method is a flash butt welding method of a pair of track rail steel pieces, having: a preheating process in which electric current is made to flow for a predetermined time in a state in which the welding surfaces of a pair of track rail steel pieces are forcibly brought into contact with each other, and vicinities of the welding surfaces are heated by resistance heating; a former flashing process in which flashing is partially caused in the welding surfaces, and the welding surfaces are heated by the resistance heating and arc heating of the flashing; and a latter flashing process in which the flashing is furthermore caused throughout the entire welding surfaces, and the entire welding surfaces are uniformly heated by the resistance heating and arc heating of the flashing, in which a latter flashing velocity is 2.1 mm/sec to 2.8 mm/sec in the latter flashing process.
1. A flash butt welding method of a pair of track rail steel pieces, comprising:
applying, in an initial flashing process, a voltage to the pair of track rail steel pieces, and welding surfaces, which are the end surfaces of the pair of track rail steel pieces, are slowly brought close to each other so that short-circuit currents are made to flow locally, the welding surfaces are heated and welded through resistance heating, furthermore, flashing is caused in the welding surfaces, and the welding surfaces are heated by the resistance heating and arc heating of the flashing;
causing to flow, in a preheating process, after the initial flashing process, an electric current for a predetermined time in a state in which the welding surfaces are forcibly brought into contact with each other, and vicinities of the welding surfaces are heated by the resistance heating;
partially causing, in a former flashing process, after the preheating process, the flashing in the welding surfaces, and the welding surfaces are heated by the resistance heating and the arc heating of the flashing;
furthermore causing, in a latter flashing process, after the former flashing process, the flashing throughout the entire welding surfaces, and the entire welding surfaces are uniformly heated by the resistance heating and the arc heating of the flashing; and
abruptly bringing close to each other, in an upsetting process, after the latter flashing process, the welding surfaces by a large welding pressure, a majority of a molten metal on the welding surfaces is exhausted outside, and rear portions of the welding surfaces, which are heated to a high temperature, are pressurized and deformed, thereby forming a welded portion,
wherein a velocity at which the pair of the rail steel pieces are brought close to each other in the former flashing process is defined as a former flashing velocity and a velocity at which the pair of the rail steel pieces are brought close to each other in the latter flashing process is defined as a latter flashing velocity,
wherein the former flashing velocity is more than 0 mm/sec, and
wherein the latter flashing velocity in the latter flashing process is 2.1 mm/sec to 2.8 mm/sec and is increased to higher than the former flashing velocity in the former flashing process.
2. The flash butt welding method according to claim 1 , wherein a latter flash-off distance in the latter flashing process is 10 mm to 60 mm.
3. The flash butt welding method according to claim 1 , wherein a latter flash-off distance in the latter flashing process is in the range defined in equation 1:
60 mm≧[latter flash-off distance]≧{22.6−(6×[erosion amount per second in the latter flashing process])}mm (equation 1).
4. The flash butt welding method according to claim 1 , wherein each of the pair of track rail steel pieces contains Carbon (C): 0.85% to 1.20% by mass %.
5. The flash butt welding method according to claim 1 , wherein a Heat Affected Zone (HAZ) width in a welding joint portion is 27 mm or less, and a softened width is 10 mm or less.
6. A flash butt welding method of a pair of track rail steel pieces, comprising:
causing to flow, in a preheating process, an electric current for a predetermined time in a state in which welding surfaces of the pair of track rail steel pieces are forcibly brought into contact with each other, and vicinities of the welding surfaces are heated by resistance heating;
partially causing, in a former flashing process after the preheating process, a flashing in the welding surfaces, and the welding surfaces are heated by the resistance heating and arc heating of the flashing;
furthermore causing, in a latter flashing process after the former flashing process, the flashing throughout the entire welding surfaces, and the entire welding surfaces are uniformly heated by the resistance heating and the arc heating of the flashing; and
abruptly bringing close to each other, in an upsetting process after the latter flashing process, the welding surfaces by a large welding pressure, a majority of a molten metal on the welding surfaces is exhausted outside, and rear portions of the welding surfaces, which are heated to a high temperature, are pressurized and deformed, thereby forming a welded portion,
wherein a velocity at which the pair of the rail steel pieces are brought close to each other in the former flashing process is defined as a former flashing velocity and a velocity at which the pair of the rail steel pieces are brought close to each other in the latter flashing process is defined as a latter flashing velocity,
wherein the former flashing velocity is more than 0 mm/sec, and
wherein a latter flash-off distance in the latter flashing process is in the range defined in equation 1 and the latter flashing velocity in the latter flashing process is increased as compared to the former velocity in the former flashing process:
60 mm≧[latter flash-off distance]≧{22.6−(6×[erosion amount per second in the latter flashing process])}mm (equation 1).
7. The flash butt welding method according to claim 6 , wherein a latter flashing velocity in the latter flashing process is 0.5 mm/sec to 2.8 mm/sec.
8. The flash butt welding method according to claim 6 , wherein the track rail steel contains Carbon (C): 0.85% to 1.20% by mass %.
9. The flash butt welding method according to claim 6 , wherein a Heat Affected Zone (HAZ) width in a welding joint portion is 27 mm or less, and a softened width is 10 mm or less.
10. The flash butt welding method according to claim 2 , wherein each of the pair of track rail steel pieces contains Carbon (C): 0.85% to 1.20% by mass %.
11. The flash butt welding method according to claim 2 , wherein a Heat Affected Zone (HAZ) width in a welding joint portion is 27 mm or less, and a softened width is 10 mm or less.
12. The flash butt welding method according to claim 7 , wherein the track rail steel contains Carbon (C): 0.85% to 1.20% by mass %.
13. The flash butt welding method according to claim 7 , wherein a Heat Affected Zone (HAZ) width in a welding joint portion is 27 mm or less, and a softened width is 10 mm or less.