Patent ID: 9617690
Date: 2017-04-11
CPC Classifications: B23K,E01B

Claim:
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.