[en] Constitutive equations were developed to describe plastic deformations in the framework of the TNO-research programme on inelastic analysis of structural components within the SNR-300 fast breeder reactor. Two types of steel, the austenitic steel WN 1.4948 and the ferritic steel WN 1.6770 were investigated. The experimental verification of the mathematical description was performed for biaxial states of stress but also for cyclic and nonradial load histories. The description of plastic deformation was based on the so-called fraction model of BESSELING, in some cases indicated as sub-layer or overlay model. It was concluded that the main source of the discrepancies between the theory and experiments on the austenitic steel (WN 1.4948) could be found in the description of the gradual transition from elastic to fully plastic behaviour after a load reversal. During this transition process the isotropic hardening plays an important role in the steel considered. It was also found that during cyclic straining the linear elastic range diminishes when the number of cycles increases. This effect can be considered as a softening effect. So, it may be stated that in the transition region we have to do with competing processes of hardening and softening. Consequently, the curvature in the transition region after a load reversal is much smaller than one would expect observing the curvature of the transition region in the initial load curve. This paper discusses the mathematical description of these effects, including the determination of the model parameters. (orig.)

[en] Dynamic fracture mechanics and notch impact bending tests were carried out for the tank material 1.6770 of the KNK reactor. As far as possible, the tests were done and evaluated based on the J integral Standard E 813. Lacking a functioning method for measuring the length of cracks for fracture mechanics, one had to fall back on the multi-sample method. The 'stop block' method used to produce a defined small extension of cracks at high speeds of loading was described. The process is very expensive and excites great vibration in the samples. If the force and deflection are measured directly on the sample and using a suitable process, it supplies plausible J_0.2 and K_1d results. Compared to this, the notch impact bending test results evaluated by fracture mechanics methods from J_max in the transition range gives results about 30 C lower. The explanation of the difference in the results lies in the different procedures: a) Fracture mechanics values J_0.2 from crack resistance curves (with energies from defined crack extensions); b) Notch impact energies only determined from the maximum force (associated length of crack cannot be measured). The different sample geometries B/W and the type of loading in the bending devices may be responsible for the remaining difference. (orig.)

[en] In order to study the feasibility of 2.25 Cr-1 MoNiNb steel heavy section forging, the chemical composition, melting practice and ingot making, hot working and heat treatment conditions by using laboratory heats and by production tests. Based on the results of the investigation, the actual forgings such as hollow cylinders with maximum 290 mm thickness, solid cylinder with 420 mm diameter and plates with maximum 185 mm could be supplied for application in the helical coiled SG of the FBR SNR 300. Statistical analysis of the products showed the sufficient and isotropic material properties, which fulfill the requirements of the basic safety rules. (orig.)

[en] Diffusion coefficients of Sb and Si in 2 1/4 Cr-1Mo-NiNb stabilized ferritic steel (DIN 1.6770) were determined from concentration profiles measured using energy dispersive x-ray microanalysis in the scanning electron microscope. Activation energies Q and frequency factor D/sub 0/ was calculated for different ranges of temperature for Sb and Si. The values of diffusion coefficients of Sb were found to be higher than those of Si in this alloy. (author) 8 figs

[en] Alloy 617M and 10%Cr ferritic-martensitic steel are candidate rotor materials under consideration for steam turbine of India Advanced Ultra Super Critical (AUSC) coal fired power plants. Therefore, there is a dissimilar metal welding (DMW) between 10% Cr steel rotor parts to Alloy 617M rotor parts. This DMW will be executed by hot-wire narrow-gap TIG welding process using Alloy 617 filler (ERNiCrCoMo-1) wire. Narrow- Gap TIG (NGTIG) welding is carried out using specially designed TIG torch on a narrow-groove joint preparation. Welding procedure has been developed for joining 10%Cr steel to Alloy 617M by two methodologies. Ferrite grain size at weld nugget was finer compared to the base metal. Heat-affected zone also experienced phase transformation and exhibited enhancement in ferrite grain size in comparison to base metal with marginal drop in microhardness. From this investigation, it is concluded that the tool exhibited microstructural stability at elevated temperatures and thus dynamic recrystallisation was also achieved during FSW process

[en] The cyclic polarization method was applied in the fast detection of the effect of metallurgical factors on the resistance of steel 21/4Cr1MoNiNb to local corrosion in water with a low level of alkalis and chlorides. A procedure was suggested of controlling the optimization of the chemical composition and the final heat treatment of the steel used for some sections of the fast reactor steam generator. Immediately upon immersing the samples in a solution of 2x10^-3M NaOH + 1x10^-3M NaCl at 22 degC, each sample was subject to five subsequent triangular potential pulses within -1,200 to +475 mV at a potential change rate of 10 mV/s. The hysteresis loop charge was measured during the 5th pulse. Based on the results of measurements, the effects are discussed of the chemical composition of the steel on the size of the hysteresis loop charge and the effective stabilizing ratio Nb_total/C⁺ where C⁺ is the effective carbon content in the steel. The procedure also tested the possibility of indicating the optimum stabilizing ratio necessary to provide improved steel resistance to local corrosion, and allowed its determination. (J.B.). 3 figs., 3 tabs., 10 refs

[en] The behavior was tested in actual conditions of the material for the steam generator of the BOR 60 fast reactor. Steel 08Cr2.25Mo1NiNb (commercial designation HT8X6) was used for the evaporator and the heater. The reheater was manufactured of 05Cr21Ni32Ti0.5Al (S31) and 03Cr18Ni11 (3R12) alloys. The evaporator tubes were exposed at a sodium temperature of 410 degC and the material of the reheater at a temperature of 480 degC. Changes in the structure and weight, material susceptibility to intergranular corrosion, the composition of corrosion products, basic mechanical properties, refractoriness and fatigue properties of the materials were investigated. The results are tabulated or graphically represented. On the basis of the results, an estimate was made of residual life with regard to corrosion effects on structure, of corrosion fatigue strength and material service life. Manifestations of operating conditions served to assess that the life of steam generator tubes should not be less than 200,000 operating hours. (E.S.). 21 refs., 12 figs., 8 tabs

[en] With regard to the manufacture of fast reactor steam generators the following materials were tested: Cr20Ni35Ti (S31), Cr18Ni11 (3R12) and Cr2.25Mo1Nb (HT8X6). Mechanical properties are adequate to values of non-exposed steels. Creep tests showed that at operating temperatures of up to 500 degC no changes appeared in the refractory properties due to the effects of sodium or the water/steam mixture. The plastic properties (ductility) remained unchanged. Tests of the effect of the water/steam mixture on fatigue showed in Cr2.25Mo1Nb steel a decrease by one order of resistance to high cycle fatigue. This was caused by local corrosion of tubes. For an undisturbed internal surface with compact magnetite layer, the fatigue properties of tubes remained unchanged. Cracks near to the surface have a mixed character with prevalence of intergranular failure. (Pu)

[en] A 40,000-hour corrosion test was carried out of structural materials on the 30 MW BOR-1 steam generator in Dimitrovgrad in the USSR. Tested in liquid sodium were the following structural materials: HT8X6 (Cr2.25Mo1Nb), 3R12 (Cr18Ni11) and S31 (Cr20Ni35Ti). The materials preserved their good mechanical properties, including unchanged structures of welded joints. Changes in carbon concentration were studied by gradual sampling of successive layers 25 μm in thickness. Carburization of all used materials was only found to have taken place in surface layers to a depth of 100-150 μm. Tests of intergranular corrosion only showed sensitization in S31 tubes, this most pronounced at the sodium inlet to the superheater, i.e., at 480 degC. A 10,000-hour corrosion experiment was made in liquid sodium at a temperature of 550 degC under conditions of convection flow. The test showed that uniform corrosion due to sodium does not affect the planned service life of used structural materials. Structural changes of the materials are described resulting from exposure to corrosion in the BOR-1 steam generator. Possible uses of HT8X6 and 3R12 for fast reactor steam generators are discussed. (Pu)

[en] The material properties were studied in detail of samples removed from experimental reactor BOR-60 after 35,000 hours of operation in the sodium-water steam mixture in order to establish the effects of radiation, high temperatures and corrosion on materials used in fast reactor steam generators. Microstructure changes, fatigue properties and creep strength were investigated of materials of the 03Cr18Ni11, 05Cr21Ni32Ti0.5Al and 08Cr2.25Mo1NiNb types. The test results are shown in graphs and discussed in detail. They show that most problems arise with pitting corrosion in material 08Cr2.25Mo1NiNb which, at more exposure, will result in reducing the material fatigue resistance. (Z.M.)