The lack of root penetration arises because of small current and high welding speed.
The lack of root penetration is admissible defect. Repair of the lack of root penetration is regulated by regulating documents on welding.
Dividing of the real welding arc column into two parts (Part 2).
The reflected plasma flow when wire welding Св-08Г2С with a diameter of 1,6 mm with a covering from К2СО3 in СО2 on the reverse polarity, promoting the arc column expansion, allows to receive the droplet transfer at the welding voltage of 32 V and welding current of 320 … 330 A. At the same time, the arch column length over the product surface is 1,5 … 2 mm and in this case even the external part of the arc column is covered by the reflected plasma flow that does this way of welding in CO2 to the most optimal from all known processes in terms of the arc energy loss. The wire welding covered with К2СО3 in СО2 allows to receive optimum formation Continue reading →
The crystal growth (Part 3).
At the large overcooling, the mechanism of the crystals growth by means of dislocations and steps is replaced normal, is not connected with the origin of new atomic layers in usual sense. In these conditions the prize of thermodynamic potential when hardening is so huge that the crystal can become covered by rough and step sides with big excess of energy. On these sides, there are many places convenient for fixing of atoms. Therefore with such crystals growth there is no need for formation of new steps. The crystals of all metals can have the rough Continue reading →
Welder Qualification Test (Part 4).
For some welding technologies when changing the electrodes type provided in technical requirements it may be necessary to repeat the welder qualification test. For example, on Fig. 1 the various types of the metal coated electrodes which are grouped taking into account skill levels, required for their use are shown.
The polymorphic transformations in metals (Part 2).
The second feature of the phase transformations in solid metals is connected with smaller, than in liquid, atoms mobility. The diffusion velocity in liquid metals is enormously higher, than in solid metals. Therefore, at the identical difference of chemical potentials (Δμ), the crystals growth as a result of individual transitions of atoms happens faster in liquid metal, than in solid metals. This distinction is most noticeable if the polymorphic transformation happens at temperatures much below than a melting point.
The specified features of phase transformations in a solid state lead to the fact that recrystallization comes at big deviations from equilibrium temperatures, than Continue reading →