The hysteresis reason of the critical current when welding on direct polarity with the coated wire from the easily ionized substances.

When welding on small currents on direct polarity in carbon dioxide the Св-08Г2С the wire with coverings from the Cs and K or Cs and Na salts taken in a certain ratio observes the globular metal transfer. At gradual increase in wire speed Vw, the welding current increases also at its certain value equal critical, the globular metal transfer in steps passes into jet at the welding current equal to Ikp1 and the wire feed of Vw1.

If on the same wire to make welding on the droplet transfer in the beginning and to gradually reduce current, then spasmodic transition from the droplet transfer to Continue reading →

The hardness measurement. The Brinell’s method (Part 1).

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.

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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.

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