Wednesday, August 26, 2015

10 Powerful Ways to Avoid Lack of Fusion in Welding

Make sure your welders know those causes and ways of preventing lack of fusion in welding…

Lack of fusion in welding occurs when there isn’t fusion between weld metal and the surfaces of base plate. Most commonly, this problem is the consequence of poor welding technique. Using very wide weld joint can also be conductive to lack of fusion. Heat input, position, electrode and work angle are also very important for obtaining best fusion results. Along with causes of lack of fusion, practicable ways to prevent the defects of welding are specified below. You can refer and ensure your welders are equipped with enough skills to stay away from this problem.

1. Good welding techniques

Too large weld puddle (too slow travel speed) would end up with lack of fusion. In this case, keep the arc on the leading edge of puddle. By so doing, the weld puddle won’t be too large and cushion the arc.

2. Making the weld joint narrower

Lack of fusion can result from using very wide weld joint. If you direct the arc down the joint center, the molten weld metal won’t melt the side walls of base plate but just flow and cast against them. The arc heat must be used to melt base plate. To do so, make the joint narrower or direct the arc toward the base plate’s side wall. When you multiple pass weld thick material, use a split bead technique whenever possible after root passes. Avoid large weld beads that bridge the whole gaps.

3. High heat input

Less heat input would be conductive to poor fusion. Heat supply is related to welding current, voltage and travel speed. It is directly related to voltage and current, and inversely associated with travel speed. Low current/ voltage settings lead to insufficient heat supply. On the other hand, the same problem would result from faster travel. Then adjust maximum allowable current, and blend the weld metal with moderate space.

4. Oxide/ Scale removal

Weld joints can be prone to atmospheric contamination. Oxide film or any unwanted particle may hamper the fusion process and do harm to weld properties. That’s why it’s recommended to get rid of any strange overlay on the joint. Clean the joint before welding will help prevent lack of fusion.

5. Correct angles

Electrode and work angles are important for attaining best fusion results. Ensure correct electrode angle with moderate pace, as wrong electrode handling would make liquid weld interrupt the arc activity.

6. Bead orientation

Slot and fissure between weld beads can appear if you incorrectly position them along the joint wall. Slot developed may induce slag inclusions and thereby lack of fusion. Your welder must be trained enough to correctly place the beads and ensure complete blend of weld along the side wall.

7. Vertical uphill position

Partial fusion may eventuate due to root pass with vertical downhill position creating disruption in the process. For this problem prevention, vertical uphill is preferred.

8. Edge preparation

Good preparation of edge would contribute to perfect welding. Variation in root attributes results from joint pieces unaligned in the same plane. Also, in case of too large root face, the weld metal won’t completely fuse at root. Meanwhile, small root opening can influence aspects of fusion, resulting in un-fused output. Then it’s recommended to confirm the right root opening before starting the welding procedure.

9. Proper welding parameters

The penetration depth decreases as you raise the voltage but change no other parameters. Choose welding parameters (high level of current, short arc length, not too high welding speed) for promoting penetration into joint side wall without causing flooding.

10. Right voltage and inductance

For short circuiting mode in the Mig/ Mag process, inductance might surpass the given level, inducing serious fusion problems. Indeed, the magnetic field generated by immoderate inductance hinders the welding current from rising. In this case, the wire tip metal isn’t heated enough and doesn’t fuse with the parent metal. There requires proper adjustment of voltage and inductance settings to avert spattering and lack of fusion because too low inductance would lead to serious spatter. Appreciably, employ modern equipment with advanced power source that offers regulated voltage and inductance values.


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