At less plastic metals the differences in the characteristics which are obtained in areas of elastic deformation and plastic deformation can be not so noticeable. Therefore, to determine the yield point it is hardly possible to use the «Drop of the Beam» method. The method which is called the «Offset» method gives other opportunities. The dependence curve between tension and deformation is typical for the less plastic metals and is shown in Fig. 1.Continue reading →
Macroanalysis by the fractures’ type (Part 1)
Fracture is the failure surface of a product or the whole piece of metall. According to cracks fracture cracks, holes, blowholes, stratifications, gaps, large slag inclusions and other defects are well identified.
The fracture contains information on features and causes of failure, which can be fragile, viscous and mixed – fatigue. The viscous fracture is common to the high strength fine grained metal with high mechanical properties; the fragile fracture is common to the Continue reading →
The assessment methods of the weld metal tendency to hot cracking (Part 2).
During the process of crystallization the weld metal continuously undergoes to lateral deformations, due to which the longitudinal crystallizational crack can be formed in the weld metal.
The initial strain rate A is selected so large that the crack initiation was guaranteed, and in process of movement the arc along a sample decreases monotonically (Fig. 1). The crack which has occurred at the beginning of the weld develops deep into the crystallizing metal after the moving arch. The effort necessary to deform the Continue reading →
The line of pores in the welded seam.
The line of pores in the welded seam occurs because of low current, high weld speed and irregular gas feed or high humidity.
The line of pores is a minor defect. The repair is regulated by the regulative documents on welding.
Growth of crystals (part 1).
Growth of nucleuses happens as a result of migration of liquid atoms to them. However, in a lot of cases, it doesn’t come to this one-faced atoms transfer. Atom, which belongs to a liquid, not necessary stays on closed-packed faced when gets on it. The possibility of its returning to liquid depends on how strongly it is held by adjacent atoms. Single atom (fig. 1)