Nitrogen pore formation
Nitrogen porosity forms when supersaturated nitrogen in the weld pool rapidly decreases in solubility during solidification, creating gas holes in the cast structure. This can lead to cracking and reduced mechanical properties.
Physical-Chemical Mechanism of Action
Nitrogen is dissolved in the melt, but suddenly becomes insoluble during solidification. This leads to a sudden volume increase and the formation of pores in the cast structure.
Metallurgical Relevance & Welding Risks
Nitrogen pore formation can lead to destruction, reduced mechanical properties, and shortened material life. It increases susceptibility to cracking and distortion.
Workshop Practice & Action Guidelines
To minimize nitrogen pore formation, keep the melting temperature as high as possible to slow down the spread of nitrogen. In addition, use pore-inhibiting materials or processes to control the volume increase from nitrogen.