The similar phenomenon shall be watched also in case of drop metal transfer, but in a little smaller level. At the same time, it is necessary to consider that the greatest vapors concentration of the metal evaporating generally from the active spot on an electrode in connection with rounding of a drop the gas flow going from an electrode, most likely, will be not on an arc pole axis under a drop, and in its peripheral parts of a drop on each side, at the same time, the vapors concentration of the electrode over a drop shall be noticeable more, than under a drop. What also promotes lowering of conductance of plasma under a drop in connection with the smaller potential of vapors ionization of metal in comparison with the potential of Continue reading →
The lack of fusion between layers.
The lack of fusion between layers occurs due to low current and high welding speed.
The lack of fusion between layers is the acceptable defect. The repair is regulated by regulatory documents for welding.
Fig. 1. The lack of fusion between layers is seen in the form of two black Continue reading →
The defects found at the metals macro-analysis.
With the macro-analysis reveal defects that violate the metal continuity:
- The shrinkholes, gas blowholes, caverns, cracks in cast metal (slabs, moulding);
- The cracks occurring during heat treatment or pressure treatment to a rolled or hammered metal;
- The shrinkholes, gas blowholes arising during welding the weld seams;
The etching methods depend on the metal type. The macro-analysis allows you to determine in steels the following:
- The depth of the hardening zone, having the high hardness in comparison with the soft core.
- The depth of the cemented layer.
The hardness measurement. The Rockwell hardness test method and microhardness (Part 2).
Irrespective the Rockwell’s scale which is used, the main process operations of the tests in essence don’t change and are provided below:
- The preparation of the studied surface;
- The placement of the tests subject in the Rockwell test machine;
- The preliminary loading application;
- The main loading application;
- The loading removal;
- The instrument reading.
The preliminary loading serves for the compensation of possible errors or gaps in Continue reading →
The polymorphic transformations in metals (Part 5).
Upon the shift transition of one modification to another the atoms move to small distances, smaller interatomic. These movements are studied in cobalt in detail. At Т > 425°С in cobalt it is stable face-centered cubic lattice modification (β-Со), is below 425°C —modification (α-Со). Both packaging can be provided as the atomic layers alternating, packed by the identical method. The transformation of one packaging to another can be performed if to displace the closely packed atomic layer in parallel, the octahedral plane (111) β-Со from в position into а. Such shifts need to be made on every second layer.