Weld Defects
For expert welding advice, you can rely on Welding Engineers as a solid source of welding information. In this Weld Defects Resource Section, we offer advice on causes and remedies for some common defects we have seen in welding projects across New Zealand.
Weld imperfections & preventive measures in CO2 arc welding
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- Weld Defects
In this article we explore various welding imperfections, their causes and preventative measures.
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Stress Relief Cracking
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Postweld heat treatment (PWHT) is generally carried out to relieve residual stresses, remove diffusible hydrogen, and temper hard transformation microstructures of the weld, thereby preventing brittle fractures and obtaining the desired properties of the product.
Porosity
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What is Porosity in welding?
Porosity refers to cavity-type discontinuities or pores formed by gas entrapment during the solidification of molten weld metal. Porosity reduces the strength of a weld. In arc welds, it is caused by dissolved gases that are usually present in a molten weld metal.
Hot Crack: How it occurs and how it can be prevented
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What is Hot Crack?
Hot crack can be defined as cracking formed at high temperatures near the solidus of the metal, where the metal has coherence but is completely brittle. It can occur in weld metals and the heat-affected zone.
Hydrogen Cracking – Diffusible Hydrogen and how to avoid it
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What is diffusible hydrogen?
In welding, hydrogen is generated from the dissociation of water vapor or hydrocarbons in the welding arc. Metals such as steel and aluminum at or near their melting temperatures diffuse hydrogen at a very high rate.
More: Hydrogen Cracking – Diffusible Hydrogen and how to avoid it
Cold Cracks in Fillet Welds
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Variations of cold cracks
Cold cracks are defined as cracks that occur at temperatures of 200-300°C or lower in carbon steel and low-alloy steel welds. Cold cracks can occur in both butt welds and fillet welds; however, this article will focus on those occurring in fillet welds.
Weld defects due to incomplete fusion
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- Weld Defects
Weld defects can occur in the best of workshops and invariably lead to higher costs due to re-work and downtime. One typical defect we have seen examples of recently is incomplete fusion.
Cold Cracking-Low Hydrogen
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Cold Cracking – Use of Low Hydrogen Filler Metals to Reduce Risk
We have seen several instances of cold cracking in welds when visiting customers. The standard of welding work and adherence to correct procedure was not an issue, so the question was why it occurred and what can be done to avoid a repetition.
