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[en] Austenitic materials have tended to pose something of a challenge for conventional ultrasonic techniques. However, some advanced techniques, involving a high degree of mechanisation, are now proving capable of giving reliable results and are described here. (author)
[en] Highlights: • First report on hot cracking behavior of carbide-free bainitic (CFB) weld metals • CFB weld metals show comparable hot cracking resistance to most austenitic steels. • Strategies for optimization of CFB weld metal compositions discussed In this work, hot cracking behavior of a carbide-free bainitic weld metal was investigated using Varestraint tests and Gleeble hot ductility tests. The results show that the carbide-free bainitic weld metal is as resistant to hot cracking as many of the standard austenitic stainless steel weld metals. The effects of composition, solidification mode, and impurity content on hot cracking susceptibility of carbide-free bainitic steels are discussed. Some guidelines for optimizing their compositions for superior hot cracking resistance are also presented.
[en] The effects of creep damage and stressing history on the further creep behaviour after a change in the direction of stress were investigated. The measured creep fracture times were found to be strongly dependent on the change in the direction of stress. This behaviour is explained by a tensorial nonlinear theory in which the influence of predamage is represented by a two-stage tensor
[en] The effect of strain induced martensite on the low cycle fatigue behavoir of AISI 304 austenitic stainless steel was investigated. During low cycle fatigue, the austenitic stainless steel showed continuous cyclic hardening. The extent of cyclic hardening was increased with decreasing austenite stability. The austenite stability was controlled by annealing time and temperature, which resulted in different carbide morphology. The continuous cyclic hardening behavior was considered to be resulted from the continuous martensitic transformation during low cycle fatigue. The amount of transformed martensite was measured with ferrite scope. (Author)
[en] An approach on variations of stresses during plant start-stop cycles, reduced power conditions and thermal gradients on materials SS 304 HCu has been studied. A procedure has been established that permit estimation of the cumulative damage under changing exposure conditions. Cyclic creep stress 200 MPa at 973 K has been carried out with variations start from 2 to 20 % with 15 minutes at interval of 1 hour. The cumulative life fraction approached the value of unity for specimens pre-damaged to life fractions of 0.75, 0.86, 0.91, 0.94, 0.92 and 0.75. Rupture life on cyclic creep nature is less than the uni-axial creep value of the materials. Cree-creep damage factor is predominantly existing during cyclic creep loading and an interestingly life fraction is 0.95 gives maximum damage occurred point. Rupture ductility has been increased with increased variations of stress cyclic. Microstructure of the steel changes during cyclic creep conditions will be carried out. (author)