Abstract
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.
Highlights
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
Summary
ИССЛЕДОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ОПЕРАЦИЙ ИЗГОТОВЛЕНИЯ ЛИМИТИРУЮЩИХ НАДЕЖНОСТЬ (УСТАЛОСТНУЮ ПРОЧНОСТЬ) РЕБРИСТЫХ ТИТАНОВЫХ ПАНЕЛЕЙ. В том числе подготовка их под сварку, режимы сварки и последующей термической обработки влияют на статическую и цикловую прочность сварных ребристых титановых панелей в зависимости от количества и суммарной площади дефектов сварного шва. Анализ [1] результатов испытаний сварных соединений ребристых панелей показал, что их механические свойства укладываются в допустимые пределы значений для основного металла, но при этом прочность сварного соединения на 8 – 12 % меньше прочности основного металла. В работах [1 – 5] показано, что причиной ухудшения механических свойств сварных соединений являются как режимы термического цикла сварки (ТЦС), так и образование пористости в металле сварного шва. Основное влияние на свойства сварных соединений титановых сплавов оказывают технологические операции раскроя и последующей обработки перед сваркой, связанные с образованием пор в металле шва Как видно из данных табл. 2 и рис. 3, малоцикловая усталость сварных образцов таврового сечения, как и стыковых соединений, выполненных проплавлением по традиционным режимам для ребристых панелей, существенно зависит от режимов отжига, независимо от формы и методов испытания специальных образцов
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