Method for controlling a flash-butt resistance welding process

A flash-butt resistance welding process comprising the steps of:

• flashing of parts being welded;
• upsetting the parts being welded;
• changing the direction of motion of the parts being welded during said flashing step by bringing together and separating the parts being welded;
• measuring during said flashing step, at the same moment of time, the useful electric power and an electric parameter of the flashing process which is related to said useful electric power by a function which maximizes the useful power at a predetermined value of said electric parameter;
• determining during said flashing step an increment in said useful electric power and an increment in said electric parameter of the flashing process within the same period of time;
• determining during said flashing step the value and the sign of the ratio of said increments in said useful electric power and electric parameter of the flashing process;
• ensuring during said flashing step the bringing together of the parts being welded up to a first moment when said ratio of said increments in said useful electric power and electric parameter of the flashing process reverses its sign;
• ensuring during said flashing the separation of said parts being welded from said first moment to a second moment when said value of said ratio of said increments in said useful electric power and electric parameter of the flashing process reaches a preset value selected to suit the resistance of the welding circuit and the cross sectional area of the parts being welded.