Welding device, and welding method employing welding device

A gas shielded arc welding method using a welding device, wherein

• the welding device is a device including
• a portable welding robot mounted with a welding torch including a nozzle that guides jetting of shielding gas and a contact tip that performs energization on a consumable electrode,
• a feeding device that supplies the consumable electrode to the welding torch,
• a welding power source that supplies electric power to the consumable electrode via the contact tip,
• a gas supply source that supplies the shielding gas to be jetted from an end of the nozzle, and
• a control device that controls the portable welding robot, in which, when the welding torch is seen from a side of jetting of the shielding gas,
• the contact tip is placed in an inside of an opening of the nozzle,
• the nozzle and the contact tip have a relatively movable structure, and
• an inner diameter of the end of the nozzle is within a range of not less than 10 mm and not more than 20 mm,
• a flow rate of the shielding gas is within a range of not less than 15 L/min and not more than 50 L/min, and
• a flow velocity of the shielding gas is within a range of not less than 1 m/sec and not more than 10 m/sec,
• wherein a welding current supplied from the welding power source has a pulse waveform in which a combination of a first pulse and a second pulse is set as one period, the first pulse has a higher peak current value than the second pulse, and the second pulse has a longer peak span than the first pulse,
• wherein a peak current value of the first pulse is within a range of not less than 400 A and not more than 600 A, a peak current value of the second pulse is within a range of not less than 300 A and not more than 500 A, a peak span of the first pulse is within a range of not less than 0.5 msec and not more than 3.5 msec, and a peak span of the second pulse is within a range of not less than 1.5 msec and not more than 5.5 msec,
• wherein the welding power source includes
• a voltage detector that detects a welding arc voltage,
• a current detector that detects a welding current, and
• a droplet detachment detection section that detects detachment of a droplet formed at an end of the consumable electrode,
• wherein the droplet detachment detection section, when it has detected the detachment of the droplet on a basis of at least one of the welding current, the arc voltage, and a ratio between an arc voltage and a welding current (V/I:resistance) obtained from the voltage detector and the current detector in a peak span of the first pulse, causes a peak current value of the first pulse to be reduced, and
• wherein, when a cable length of a power cable that connects the welding power source and the portable welding robot together is denoted by L mm and a cable cross sectional area is by S mm2, a rate of L to S (L/S;
• unit:
• 1/mm) has a relationship of L/S≤10000.

A multilayer welding method that is a gas shielded arc welding method for multilayer welding using a welding device, wherein

• the welding device is a device including
• a portable welding robot mounted with a welding torch including a nozzle that guides jetting of shielding gas and a contact tip that performs energization on a consumable electrode,
• a feeding device that supplies the consumable electrode to the welding torch,
• a welding power source that supplies electric power to the consumable electrode via the contact tip,
• a gas supply source that supplies the shielding gas to be jetted from an end of the nozzle, and
• a control device that controls the portable welding robot, in which, when the welding torch is seen from a side of jetting of the shielding gas,
• the contact tip is placed in an inside of an opening of the nozzle,
• the nozzle and the contact tip have a relatively movable structure, and
• an inner diameter of the end of the nozzle is within a range of not less than 10 mm and not more than 20 mm,
• a flow rate of the shielding gas is within a range of not less than 15 L/min and not more than 50 L/min,
• a flow velocity of the shielding gas is within a range of not less than 1 m/sec and not more than 10 m/sec,
• wherein a welding current supplied from the welding power source has a pulse waveform in which a combination of a first pulse and a second pulse is set as one period, the first pulse has a higher peak current value than the second pulse, and the second pulse has a longer peak span than the first pulse,
• wherein a peak current value of the first pulse is within a range of not less than 400 A and not more than 600 A, a peak current value of the second pulse is within a range of not less than 300 A and not more than 500 A, a peak span of the first pulse is within a range of not less than 0.5 msec and not more than 3.5 msec, and a peak span of the second pulse is within a range of not less than 1.5 msec and not more than 5.5 msec,
• wherein the welding power source includes
• a voltage detector that detects a welding arc voltage,
• a current detector that detects a welding current, and
• a droplet detachment detection section that detects detachment of a droplet formed at an end of the consumable electrode,
• wherein the droplet detachment detection section, when it has detected the detachment of the droplet on a basis of at least one of the welding current, the arc voltage, and a ratio between an arc voltage and a welding current (V/I:resistance) obtained from the voltage detector and the current detector in a peak span of the first pulse, causes a peak current value of the first pulse to be reduced,
• wherein, when a cable length of a power cable that connects the welding power source and the portable welding robot together is denoted by L mm and a cable cross sectional area is by S mm2, a rate of L to S (L/S;
• unit:
• 1/mm) has a relationship of L/S≤10000, and
• in a case of the multilayer welding,
• (1) only a first layer,
• (2) the first layer to a second layer, or
• (3) the first layer to a third layer
• are welded using, as a welding current supplied from the welding power source, a direct current of a constant voltage not using a pulse waveform, and
• remaining layers are welded using, as the welding current, a welding current having a pulse waveform in which a combination of a first pulse and a second pulse is set as one period,
• the first pulse has a higher peak current value than the second pulse, and
• the second pulse has a longer peak span than the first pulse.