The amount of metal evaporating from the cathode spot (Part 1).

When welding with the direct polarity, the dimensions of the anode spot determine the width of the weld. At the same time, at the given current and voltage, on the arc from the width of the seam depends on the depth of penetration of the product, since it is determined by the arc pressure on the weld pool. Thus, the size of the anode spot affects not only the technological parameters of the welding process, but also the strength properties of the welded joint. The size of the anode spot is directly influenced by the diameter of the column of the arc, which in turn depends on the composition of the arc gas, which is significantly influenced by metal vapor from the cathode spot on the electrode. Similarly, when welding on the reverse Continue reading →

The crystals shape (Part 1).

The shape formed in the melt of the crystals depends on the growth conditions (overheating and supercooling liquid heat removal direction, and other impurities) and the metal nature. In conditions close to equilibrium, properly cut crystals are formed. They grow slowly; their surface is smooth, although it contains steps necessary for the construction of faces. If the impurities are small and the temperature of the liquid increases with the distance from the surface of the crystal, the zone advanced for some reason or another enters the zone with the Continue reading →

The polymorphic transformations in alloys (Part 4).

The polymorphic transformations in alloys lying outside the eutectoid (KML) and peritectoid (MKL) lines do not differ from the one considered earlier (see Fig. 1).

The transformations begin with the appearance of embryos of the new modification and end with a complete transition of the high-temperature modification β into one of the low-temperature α1 or α2. The polymorphic Continue reading →

The static volt ampere characteristic of the arc. The external characteristic of the power source.

The static characteristic of the arc is the dependence of the arc voltage on the current Uд = f(Icв)  at the constant length (lд = сonst).

The numerous studies have established that, although there are differences for different arcs (inessential), the common for all arcs is that the dependence for the arc Uд = f(Icв) – the static characteristic of the arc is nonlinear (Fig. 1). This arc distinguishes from other energy consumers, for example, the resistor that has a linear characteristic (U = f(I) the dependence in accordance with Ohm’s law is linear). This is due to another mechanism of electrical conductivity in the arc than Continue reading →

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