RESEARCH OF THE TECHNOLOGICAL MANUFACTURING OPERATIONS LIMITING THE RELIABILITY (FATIGUE STRENGTH) OF RIBBED TITANIUM PANELS

As it is known, titanium alloys due to a number of features (high specific strength, fatigue resistance, fracture toughness and corrosion resistance) are widely used in aerospace engineering, including ribbed panels. For products of this kind it is necessary to meet high requirements of quality of welded joints and dimensional accuracy of the construction. Fusion welding of titanium alloys results in the formation of inhomogeneities in the connection zone and in the reduction of technological and operational performance. The geometric dimensions of design are distorted due to occurrence of welding stresses, pores and microcracks appear in the weld metal, mechanical properties and other parameters are reduced. These facts require a comprehensive analysis of the manufacturing process of titanium ribbed panels: from the manufacturing of semi-finished products to the final stage of heat treatment of the finished product from the point of detection of the most significant in relation to defects in operations. The blank manufacturing operations, including their preparation for welding, welding and subsequent heat treatment regimes affect the cyclic and static strength of welded ribbed titanium panels depending on the number and total area of welding defects. The article presents the research that allows to predict the properties and reliability of welded structures and to achieve identity of the properties of basic metal and weld metal with the lack of a guarantee of both internal and external defects, depending on the choice of the complex technological measures. It is shown that a certain welding cooling rate in the range of phase transformation temperatures, finish milling, running and cleaning (degreasing and dehydration) of the surface of abutting edges, low annealing after welding in the air and subsequent sand cleaning; GLC in the auxiliary gas medium of nitrogen or argon or the combined GLC blanks and cutting by milling determine correspondence of properties and reliability of the welded joints of base metal of ribbed panels from VT20 alloy.

titanium alloys, preparation for welding, fusion welding, quality of connections

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