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The paper presents the results of research on the influence of the time of annealing after welding at the temperature of 750°C on the mechanical properties of a homogeneous welded joint of T91 steel. The welded joints were annealed at 750°C for 0.5; 1.0; 1.5 and 2.0 hours. The research scope included the basic study, i.e. the measurement of hardness, the test of impact energy, the static tensile test, bending test, as well as the accelerated creep test. The results of the tests of mechanical properties indicate the possibility of using shorter annealing times for thin-walled welded joints, and thus the possibility of savings as a result of flexible heat treatments.

Resistance to stretching, a quality of specimen made by braze welding method were examined as well as usefulness of this method in industry was described. Technology and materials, which are used during braze welding, are depicted on the base of an inspection of joints. The results of macroscopic examinations of sample joints (base material, heat-affected zone and braze weld) are given. Furthermore, the results of the resistance, plasticity and hardness tests of sample joints are presented.

Research was conducted on welded joints of martensitic steel Thor 115 made with two filler materials - CrMo91 and Ni 6082. The scope of the investigations included: non-destructive and destructive testing. The macro- and microstructural investigations revealed correct structure of the weld, without welding imperfections. In the joint welded with Ni 6082, the so-called Nernst's layers and d-ferrite grains were visible. The investigations of the analysed joints showed that their properties, i.e. tensile strength and impact strength, were higher than the required minimum, whereas hardness was lower than the maximum value of 350 HV permitted for this group. [ABSTRACT FROM AUTHOR]

The results of a microstructure examination and mechanical properties of 15HM (13CrMo4-5) steel are presented in the article. The examined elements are the samples taken from the live steam pipeline serviced for about 420 000 hours at the temperature of about 510°C, and pressure of 11 MPa. It has been shown that after long-term operation the examined steel has a ferritic-pearlitic microstructure with a dominant content of quasipolygonal ferrite. The processes of fragmentation of lamellar precipitates and their spheroidization were observed in pearlite. On the grain boundaries, single lamellar precipitations were observed. Moreover, numerous precipitations at the interface of three grain boundaries were revealed. The examined steel, despite its long-term service time, was characterized by the strength properties (YS, TS) slightly lower than the required minimum, the impact energy value KV equal to 20 J, and the transition temperature shifted to a temperature above zero. Relatively low level of degradation of the microstructure and mechanical properties of the investigated steel can result from high stability of the ferritic-pearlitic microstructure. [ABSTRACT FROM AUTHOR]

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