Tuesday, August 25, 2015

6 Useful Tips for Preventing Flux Core Welding Problems (Part 2)

With some tips and practice, you can avoid flux core welding problems and improve your FCAW welds.

See also: 

4. How to avoid weld undercutting and lack of fusion

Same as other weld defects, lack of fusion and undercutting can lower your welds quality and prevent them from going far in reduction of downtime and rework costs.
How to prevent undercutting
Undercutting is the aftermath of a groove melting in the base metal next to the weld toe but not being filled by weld metal. It weakens the toe of weld and often induces cracking. Applying appropriate welding voltage and current helps prevent this problem (don’t forget to conform to your welding parameters). Maintain the travel speed that enables the weld metal to completely fill the base metal’s melt-out areas. If you are applying the weaving technique, pause at the weld bead’s each side.

How to prevent lack of fusion
To avoid lack of fusion that eventuates due to the weld metal failing to completely fuse with the base metal (or the preceding weld bead in multi passes), maintain right work angle and heat input. Get the right angle by putting the stringer bead in its appropriate location at the joint, widening the groove or adjusting the work angle to approach the bottom during welding as necessary. Keep the arc on the welding puddle’s trailing edge, and maintain the gun angle drag of 15 - 45°. If you are applying a weaving technique, hold the arc on groove sidewalls for a moment during your welding. Raise your voltage range or/ and adjust wire-feed speed as needed to get complete fusion. In case you feel the wire is going ahead of the work puddle, such simple adjustments as applying higher welding current or raising travel speed can avoid problems.

Finally, make sure you clean the surface of base metal before welding to get rid of contaminants to avert lack of fusion.

5. How to prevent lack of penetration or excessive penetration

How to prevent incomplete and excessive penetration
Maintain proper heat input when welding is critical to preventing such problems as excessive penetration. The excessive penetration happens due to the weld metal melting through base metal and hanging underneath the weld. Most often, it is the consequence of too much heat. If you encounter the problem, choose a lower voltage range, decrease the wire-feed speed and raise the travel speed.

By contrast, choosing a higher voltage range, higher wire-feed speed or/ and reducing the travel speed can avert such problems as lack of penetration (i.e. shallow fusion between weld metal and base metal). Also, prepare the joint for permitting access to the groove bottom whilst maintaining appropriate extension of welding wire and arc characteristics. 

6. How to get qualified FCAW welds

Self-shielded FCAW is a trusted process for various construction applications though, getting qualified welds with it is not the luck of the draw. It results from good welding techniques, appropriate choice of parameters, and your ability to avert problems or quickly define and rectify them. Remember, preparing yourself with some essential information will enable you to avoid most common problems related to FCAW welding without sacrificing quality or time.


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