Welding apparatus and welding method

A welding apparatus for resistance-welding a tubular member and a bar member arranged in contact with one axial end surface of the tubular member, the welding apparatus comprising:

• a positioning jig configured to contact the bar member from a first side of the bar member in a direction perpendicular to an extending direction of the bar member;
• a first power supply jig configured to actively press the bar member from a second side of the bar member opposite the first side of the bar member, the first power supply jig actively pressing the bar member against the positioning jig in the direction perpendicular to the extending direction of the bar member;
• a second power supply jig located on an anti-bar member side of the tubular member, the second power supply jig being configured to actively press against respective contact surfaces of the bar member and the tubular member in the extending direction of the bar member, the bar member being actively pressed between the positioning jig and the first power supply jig, the second power supply jig actively applying pressure to the contact surfaces of the bar member and the tubular member;
• an electric current supplier supplying electric current to the first power supply jig, the bar member, the contact surfaces, the tubular member, and the second power supply jig, the bar member having a smaller heat capacity than the tubular member;
• and
• a controller configured to:
• receive a temperature of the tubular member measured by a temperature sensor;
• calculate a temperature of the bar member based on a rate of change of the measured temperature of the tubular member;
• and
• control the electric current supplied by the electric current supplier so as to:
• (i) maintain the temperature of the bar member, as calculated based on the measured temperature of the tubular member by the temperature sensor, at a constant value at a temperature that suppresses melting of the bar member for a predetermined period of time, which is after a start of the electric current supply and after the temperature of the bar member is increased to reach the temperature that suppresses melting of the bar member, and then (ii) increase the temperature of the bar member and the temperature of the tubular member to temperatures that melt the bar member and the tubular member.