52
2 Model of Quasi-Steady Weld Pool Dynamics and Numerical Simulation
direction. The shape of both the upper and lower surfaces of weld pool is open.
This indicates that the surface tension gradient of free surface of weld pool plays an
important role in heat transfer of weld pool.
2.6.2 Effect of Welding Speed and Laser Power on Weld Pool
Size
Under the assumption that the laser beam is CO 2 laser, the radius of focal plane
is 0.2 mm and the defocus is 0, the relationship between laser weld pool, welding
speed and laser input power is simulated. Figure 2.23 shows the relationship between
weld width and welding speed during laser welding of titanium alloy at laser power
of 3000 W. Welding speed is an important factor affecting the length and width of
weld pool. When the laser power is constant, increasing the welding speed means
that the energy of the welding body decreases. On the other hand, with the increase
of welding speed, the interaction time between laser beam and titanium alloy is
relatively shortened. Therefore, the laser energy of input material decreases in unit
time, and the width of weld pool is decreases.
Fig. 2.23 Weld pool width dependence on traveling speeds of workpiece