Английский для сварщиков. Гричин С.В. - 94 стр.

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Since the tool gets red hot, it is necessary to protect it against the

environment using a shielding gas. A possible use of FSW in the welding of

steels is in the context of stainless steels. Austenitic stainless steels can easily

be welded using conventional arc welding and other processes. However,

FSW can offer lower distortion, lower shrinkage and porosity. More

important is the avoidance of fumes containing hexavalent chromium which

is carcinogenic. In addition, chemical segregation effects associated with

welding processes involving solidification are avoided. Such segregation can

lead to a degradation of corrosion resistance since electrochemical cells are

set up between solute-rich and poor domains.

Friction Stir Welding of Cast Aluminium Alloy

The most popular aluminium casting-alloy contains about 8 wt% of

silicon. It therefore solidifies to primary aluminium-rich dendrites and a

eutectic mixture of aluminium solid-solution and almost pure silicon. The

latter occurs as coarse silicon particles which tend to be brittle. The cast alloy

usually has some porosity. Friction stir welding has the advantage that it

breaks up the coarse silicon particles and heals any pores by the mechanical

processing, as illustrated below.