Abstract: A method of welding a noble metal tip of a spark plug to an electrode is provided. In the method of welding, in a waveform of a power of a laser beam according to a time of the laser welding, a power of a central portion thereof is smaller than those of both end portions thereof. In addition, the waveform of the power of the laser beam according to a time of the laser welding is a trapezoidal waveform which includes: a rising portion in which the power of the laser beam is gradually increased; a power maintaining portion in which the power of the laser beam after the rising portion is maintained uniform; and a falling portion in which the power of the laser beam after the power maintaining portion is gradually decreased.

Abstract: Provided is an ignition plug used for an internal-combustion engine. The ignition plug includes: a center electrode; an insulator disposed outside the center electrode; a metal housing disposed outside the insulator; a ground electrode having an end connected to the metal housing and the other end facing the center electrode; and an electrode tip fixed to one or more of the center electrode and the ground electrode. The electrode tip is made of an alloy of iridium Ir, hafnium Hf, and niobium Nb. Therefore, the ignition plug with the low-cost iridium can have high resistance to prevent an iridium element from oxidizing and vaporizing in high speed driving conditions.

Abstract: A method of welding a noble metal tip of a spark plug to an electrode is provided. In the method of welding, in a waveform of a power of a laser beam according to a time of the laser welding, a power of a central portion thereof is smaller than those of both end portions thereof. In addition, the waveform of the power of the laser beam according to a time of the laser welding is a trapezoidal waveform which includes: a rising portion in which the power of the laser beam is gradually increased; a power maintaining portion in which the power of the laser beam after the rising portion is maintained uniform; and a falling portion in which the power of the laser beam after the power maintaining portion is gradually decreased.

Abstract: Provided is an ignition plug used for an internal-combustion engine. The ignition plug includes: a center electrode; an insulator disposed outside the center electrode; a metal housing disposed outside the insulator; a ground electrode having an end connected to the metal housing and the other end facing the center electrode; and an electrode tip fixed to one or more of the center electrode and the ground electrode. The electrode tip is made of an alloy of iridium Ir, hafnium Hf, and niobium Nb. Therefore, the ignition plug with the low-cost iridium can have high resistance to prevent an iridium element from oxidizing and vaporizing in high speed driving conditions.