Hardness is the metal’s ability to resist the introduction or breakdown. The metal’s hardness gives an idea of its tensile strength. Therefore, the hardness measurement is carried out by means of any penetrator type pressed into the surface of the tested subject. Depending on the hardness measurement method, either diameter, or depth of the impression is measured. Hardness can be measured also by means of various electronic or ultrasonic devices testing, but generally, it is the pressing.
The cast metal macrostructure.
The dendrite structure and the crystallization zones of cast metal can be detected by the deep etching of macrosection in 15% water solution of ammonium persulphate (NH4)2S2O8 and to give the opinion about the cooling speed of the ingot or casting.
To defect the casting location the casting control is carried out:
the shrinkholes are cavities which borders in steel are concentrated with C, P, S, nonmetallic inclusions; shrinkholes are formed due to volume reduction of metal at crystallization and are situated in the central and mainly top part of the killed ingot;Continue reading →
Dividing of the real welding arc column into two parts (Part 1).
In the real welding arches the arch column is divided into two parts, significantly differing among themselves under the terms of existence: the arch column which is under the surface of the product and over its surface. These differences include not only available the cooling surface of the product crater for the column which is under the product surface, but also available the thermal effect on this column part of the reflected plasma flow covering this part of the column and protecting it from cooling with crater walls. The reflected gas flow as a result of the crater gas flow Continue reading →
Welder Qualification Test (Part 3).
AWS come forward with the proposal to use of the sheets additional configuration for the tests intended for weld test in horizontal position. For this purpose, the same joint angle of sheet beveling (45°) is applied, as well as to the lower position, but the edge is mown only at the top sheet. Thanks to it, the tray on which the welder can build up the layers of the weld pass is formed and to fill with simpler way the space between edges.
Macroanalysis by the fractures’ type (Part 2).
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 →