Welding Defects In Automotive Fabrication – Causes & Remedies

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Uncertainties and imperfections do exist in manual working. It can be either human error or any error arising from the usage of the equipment. So, the fact “humans are prone to errors” is undeniable.

But the best thing you should inculcate while working is that preciseness and focus can minimize all sorts of defects.

Similarly, welding is a process that is exposed to multiples defects. But the best of welders are those who try to find out the cause and the way out of it.

Major Categories of Welding Defects In Automotive Fabrication

The welding defects in automotive fabrication are categorized as followed:

➔   Dimensional Uncertainty

These defects are caused due by improper setup, deformity, and Inappropriate welding sequence. Furthermore, such defects are easily identified by physical appearance.

➔   Discontinuities

Discontinuity is caused due to disturbance in the physical composition of a material. Yet, the discontinuities exceeding a tolerance limit are only regarded as welding defects. Therefore, an object with some discontinuity can be liable for some applications and not for others.

➔   Errors in Material properties

Material properties vary a lot due to welding defects. For instance, it can lead to an increase in hardness level, lower material strength, et cetera.

What are some of the most common welding defects?

❏    Weld Crack

Cracks are considered to be one of the most criticized defects. Welds with cracks aren’t accepted to meet the required standards. The cracks mostly appear on the outside of the materials.

The temperature supplied while welding can lead to different sorts of cracks, such as

Hot cracks

These cracks mainly occur during the crystallization process of a weld joint. Excessive temperatures, for example, temperatures over 10000C, are its leading cause.

Cold Cracks

These cracks occur after the completion of the welding process. Also, these cracks occur at lower temperatures and are mainly found to develop in steel due to the deformities in its formation.

Crater cracks

Crater cracks are developed due to an incorrect ending to the welding process, i.e., the erroneous termination of arc and high welding currents.

To avoid carter cracks, ensure that when the weld cools and solidifies, it must have enough volume to surpass the contraction of weld metal.

Causes

  • Use of hydrogen while welding a metal-containing iron;
  • High Shrinkage stress;
  • Metal with carbon and sulfur composition;
  • No, preheat before the welding process;
  • Inappropriate joint design;
  • Metal impurity.

Way Out

  • Select the appropriate metal;
  • Driveaway any material impurity;
  • Heat the metal beforehand;
  • Stick with the required current and welding speed;
  • Cool the requisite weld area adequately;
  • Don’t leave the crater unoccupied.

❏    Porosity

Porosity is the result of weld metal impurity and contamination. Wormholes, blowholes, and porosity are likely to pop up due to gases confined within the weld. It loosens and weakens the weld.

Causes

  • Use of a longer arc;
  • Existence of dampness and moisture;
  • Use of deficient electrode de-oxidant;
  • The tainted surface of weld metal;
  • Exertion of high gas flow;
  • Poor gas shield;
  • Existence of rust, grease, and oily fluids.

Way Out

  • Purify the materials before welding;
  • Use appropriate and dry electrodes;
  • Utilize the standard arc and alter the arc distance as desired;
  • Examine your gas meter and configure accurate pressure and flow settings;
  • Make use of the ideal welding process.

❏    Undercut

The reduction of a cross-sectional thickness of the base metal is known as undercutting. It’s usually the formation of a hollow at the weld toe. Hence, there’s a substantial reduction in the strength of weld and workpieces.

Cause

  • Welding at excessive currents;
  • Speedy welding;
  • Use of large electrodes;
  • Non-required heat supply due to the use of uneven angles;
  • Inadequate gas shielding;
  • Improper welding procedures.

Way Out

  • Make use of suitable electrodes along with meticulous angles;
  • Shorten the arc length;
  • Make use of the multi-pass technique, allowing you to access diversified weld joints and plate thickness;
  • Try directing more heat towards thicker elements of the material;
  • Pick the correct shielding gas as per material properties.

❏    Incomplete Fusion

The lack of fusion (bonding) between the weld metal and the base metal leads to this sort of welding defect. These lead to gaps between joints where molten metal can’t accumulate.

Cause

  • Low heat supply;
  • Impurity layer over the metal surface;
  • Incorrect use of electrode and electrode angle;
  • Fast travel speed;
  • Large weld pool.

Way Out

  • Use of relevant welding current and arc voltages;
  • Remove the layer of contamination;
  • Utilize the correct electrode;
  • Shrink discharge rate;
  • Keep the molten pool from inundating the arc.

❏    Lack of Penetration

This sort of defect occurs when the weld metal doesn’t wholly stretch out to the weld joint.

Cause

  • Messed up and distorted procedures;
  • Unsuitable joint;
  • Inappropriate electrodes;
  • Ample space between metals;
  • The quick movement of the welding beads leading to incomplete deposition;
  • Low current.

Way Out

  • Proper alignment;
  • Use of suitable electrodes;
  • Increase amperage current;
  • Lower welding speed.

❏    Slag inclusion

Slag is a derivative of stick-welding, flux core arc welding, and submerged arc welding.

This defect is evident and apparent all in the weld. This is likely to happen when flux(solid preserving material) melts on the weld or on its surface.

Cause

  • Poor cleaning standards;
  • Speedy welding;
  • Improper welding angles;
  • Quick cooling of the weld pool;
  • Low welding current.

Way Out

  • Increase current supply;
  • Modify the welding speed;
  • Control rapid cooling.

❏    Spatter

This tends to happen when molten particles from the weld bead splash all around while welding. It frequently occurs in gas metal arc welding. This issue can be cut down to some extent but not completely.

Cause

  • High electric current supply;
  • Low voltage supply;
  • Reversed polarity;
  • Impure material surface;
  • Incorrect electrode angle;
  • Varying wire.

Way Out

  • Shorten arc length;
  • Make amendments to the current supply;
  • Check out for polarity;
  • Larger electrode angle.

❏    Overlap

When the weld metal extends over the base weld toe and cools down, the defect is considered to overlap.

Cause

  • Ample supply of weld metal;
  • Low welding speed;
  • Poor welding techniques;
  • Use of large electrodes.

Way Out

  • Use larger electrodes and better angles;
  • Restrict the amount of weld metal used;
  • Speed up the welding process.

Last Words

There are lots of welding defects. Out of so many of them, the defects mentioned above are evaluated as the concerning ones.

The description of all these creates an idea of dealing with any of the above occurring situations. To ace your welding tasks and be renowned as one of the experts and professional welder, you must kick out these happenings.

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