Relationship between temperature at cut front edge and kerf quality in fiber laser cutting of Al–Cu aluminum alloy

• Temperature at cut front edge of fiber laser cutting of Al alloy, Tce is studied firstly.
• Optimal Tce range for accepted kerf quality is found, which is 1800–1950 °C.
• The mechanism is discussed by the calculation of the forces acting on molten pool.
• Kerf quality is dependent on the angle of the resultant to downward direction.

The characteristics of the temperature at cut front edge (Tce) during fiber laser cutting of AA2219 aluminum alloy were studied. A temperature monitoring system employing an infrared laser thermometer was established to record the time-domain Tce. A series of experiments was carried out to explore the relationship between the Tce and kerf quality. There was an optimal Tce range of 1800–1950 °C for accepted kerf. By calculating the forces acting on molten pool, the existence of the optimal Tce range was demonstrated, and the effect of the Tce on kerf quality was discussed. The kerf quality was mostly dependent on the angle of the resultant to the downward (θ). Only when the θ was around the minimum of 38° that is corresponding to optimal Tce range, the kerf was accepted because the liquid metal was pushed away smoothly, although the resultant value was small. When increasing or decreasing the Tce outside the optimal range, the kerf was bad because the increased θ intended to push the liquid metal backward to attach on the kerf rather than push them away.