Pores in welded joint (part 1).

According to AWS A3.0 document the porosity is determined as “continuity transgression in the form of hollow space, formed by captured gas in consolidation process”. Thus we have a right to examine pores as certain hollow spaces or gas pockets inside consolidated metal of welded joint. Thanks to characteristic spherical form the pores are considered to be the least dangerous continuity Continue reading →

Welding cracks and their classification.

According to dimensions and influence on metal density are there two categories of cracks (local ruptures): microcracks (their dimensions are comparable to dimensions of crystal lattice parameters; are available almost always in real crystals) and macrocracks which appear in weld joint in the course of welding or use of product (are dangerous defect – reason for structural failure).

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Crystals nucleation in liquids (Part 2).

For formation of nucleuses of critical size there is not enough energy, exuded during atoms transfer from liquid to crystals. It compensates these energetic consumptions for two thirds, connected with surface energy or for half of energy, released owing to atoms transfer from liquid to crystal phase.

Nucleus critical size is decreasing with increasing of overcooling. The value of Continue reading →

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