Why does alkali embrittlement occur in the weld bead when carbon steel is used with NaOH at temperatures above 50°C?
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Why does alkali embrittlement occur in the weld bead when carbon steel is used with NaOH at temperatures above 50°C? The bonding of carbon steel with NaOH is carried out by welding; at higher temperatures (50°C), the weld seam is prone to alkali embrittlement, leading to cracks at the weld joint.
This post was last edited by Shutong on 2020-6-8 at 16:33. For the alkali embrittlement of steel, three conditions generally need to be met simultaneously. One is a solution of sodium hydroxide at a high concentration. Tests have shown that an alkali solution with a concentration of over 10% is sufficient to cause alkaline embrittlement in steel. Second is the higher temperature; the temperature range for alkaline embrittlement is wide, but the temperature at which alkaline embrittlement occurs most easily is around the boiling point of the solution. Third is tensile stress, which can be caused by external loads, residual stresses, or a combination of both. Although the magnitude of tensile stress is a factor affecting alkaline embrittlement, a more important factor is whether the stress is uniform; localized tensile stress is what most easily leads to alkaline embrittlement.
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