As mentioned earlier in Part 1 of this article, for the uniform determination of destruction nature, the successful prevention of premature and catastrophic destructions and, therefore, for the systematic increase in operational reliability of machines and designs, the unified fractures classification and common terminology for their description are created. The main fracture type’s classification is made on Continue reading →
The polymorphic transformations in metals (Part 1).
The polymorphic metals atomic packing provide the minimum value of the free energy potential in some circumstances and become unstable in others circumstances. In this case at the temperature and pressure change there is a polymorphic transformation. The modifications of polymorphic metal passing one into another with increasing temperature, designated by the α, β, γ and δ letters.
Fig. 1 shows the phase-rule diagrams and changes of the free energy potential of Continue reading →
The crystal growth (Part 2).
The outcrop of the crystal screw dislocation, Fig.1.
It creates conditions for the steps formation with the height equal to vector shift dislocation. Especially, they are important for the close-packed faces; in this case, the growth becomes possible even at low degrees of supercooling. The atoms joining to the step leads to spiral growth as each its area has in the initial state a Continue reading →
Welder Qualification Test (Part 2)
The requirements to welder qualification test vary for different weld configurations, including the sheet beveling, the sheets preparation to fillet welding, and also the pipe beveling. It is obvious that the qualification test for the sheet beveling allows you only partially to estimate the skills of pipes welding. However, if the welder is attested to the performance of the pipe welding; he is automatically attested to the sheet welding. Also it should be noted that the qualification test on sheet beveling in 3G and 4G positions allows you to attest the welder to all sheets positions. The qualification test for provisions of pipes 6G, 2G or 5G allows Continue reading →
The pore cluster
The pore cluster at the root of weld occurs because of the low current, high weld speed and irregular gas feed and lack of welding shielding against intake of moisture.
The pore cluster is a minor defect. The repair is regulated by the regulative documents on welding.
On the picture the pore cluster is visible in the form of the black points located without specified procedure.Continue reading →