Repair of Welded Joints Made of Steel P91 (X10CrMoVNb9-1) by a Backing Run of the Selected Site with Heat Treatment

Power Technology and Engineering - The results of complex studies of welded joints made of steel P91 (X10CrMoVNb9-1) with repair welding performed in OAO VTI are presented. A control weld joint was...     

Structure of an edge-dislocation wave originating in plane-wave diffraction by a half-plane

A new treatment of the well-known Sommerfeld solution of the problem of plane-wave diffraction from a perfectly conducting half-plane is reported. We show, in both theory and experiment, that the diffraction field (E-polarization) can be represented as a superposition of real physically existing waves, in contrast to geometrical and boundary waves postulated in Sommerfeld's representation. Our representation includes two pairs of wave components: one pair propagates along the direction of the incident wave, and the other in a mirror-reflected direction. Each wave pair consists of a plane-wave component with an amplitude half that of the incident wave and a nearly plane-wave component with an infinitely extended edge dislocation. On the basis of the proposed interpretation, all features of the half-plane diffraction are explained.     

Analysis of the development of damage in a welded junction in the hot intermediate superheat steam duct of 800-MW generator units

Data from a metallographic study of a damaged weld junction in a hot intermediate superheat steam duct and a computational model for crack development (in the damaged zone) by a creep mechanism are described. Anumerical calculation confirms the possibility of crack development to the known final size over a time of approximately 15,000 h, which corresponds to the operating time for the steam duct from the last time it was inspected until the time of a through fault, under conditions such that a 2.5-mm-deep surface crack (with a length of ∼50 mm along the surface) had been overlooked during this last inspection. Translated from élektricheskie Stantsii, No. 10, October 2008, pp. 29–35.     

On Some Features of Repair Welding Without Heat Treatment of Power-Generating Equipment Made of Pearlite Steels

Power Technology and Engineering - Features of welding heat-resistant steels when repairing cased power-generating equipment without heat treatment are outlined. It is shown that, by adjusting the...     

Physical approach to analytic simulation of Fresnel integrals

Fresnel integrals continue to find new applications in various areas of human activity, including technology and music. However, performing calculations with them is often hindered by a mathematical peculiarity of these integrals, which is the rapidly oscillating functions of the basic variable. This circumstance complicates the numerical calculations when these integrals need additional integral transformation: convolution, Fourier transform, etc. The suggested solution of the problem consists of replacement of the complex Fresnel integral by a single rational function that simulates this integral in the entire area of its existence with an accuracy up to 10(-6). The advantages of the suggested approach are confirmed by the concrete example.     

Plane wave diffraction by a perfectly transparent half-plane

The exact solution is found for plane wave diffraction by an arbitrary phase step. The analysis is performed by using the Huygens-Fresnel principle and the superposition integral, where every secondary wave was identified with the surface element field of the actual electromagnetic wave. The dependence of the total field structure on the height of the phase step is analyzed. The formation algorithm is demonstrated for the primary wave component of the edge diffraction, which has a singular nature and determines nearly all physical properties of this phenomenon.     

Study of the structure and properties of metal of the major steam lines of a CCGT-420 unit made from high-chromium Х10CrMoVNb9-1 (P91) steel

The technology of manufacture of live steam lines and hot reheat lines at FINOW Rohrsysteme GmbH are discussed. These pipelines are designed for high-performance CCGT units and are made from high-chromium martensitic steel X10CrMoVNb9-1 (P91). The principles of certification and evaluation of conformance of thermal and mechanical equipment made from new construction materials with the TRCU 032-2013 technical regulation of the Customs Union are detailed. The requirements outlined in Russian and international regulatory documents regarding the manufacture of pipes and semifinished products for pipeline systems are compared. The characteristic features of high-chromium martensitic steel, which define the requirements for its heat treatment and welding, are outlined. The methodology and the results of a comprehensive analysis of metal of pipes, fittings, and weld joints of steam lines are presented. It is demonstrated that the short-term mechanical properties of metal (P91 steel) of pipes, bends, and weld joints meet the requirements of European standards and Russian technical specifications. The experimental data on long-term strength of metal of pipes from a live steam line virtually match the corresponding reference curve from the European standard, while certain experimental points for metal of bends of this steam line and metal of pipes and bends from a hot reheat line lie below the reference curve, but they definitely stay within the qualifying (20%) interval of the scatter band. The presence of a weakened layer in the heat-affected zone of weld joints of steel P91 is established. It is shown that the properties of this zone govern the short-term and long-term strength of weld joints in general. The results of synthesis and analysis of research data support the notion that the certification testing of steam lines and other equipment made from chromium steels should necessarily involve the determination of long-term strength parameters.     

Studying the metal of steam boiler drums made of grade 16GNM steel after its long-term operation

Results from a study of the structure and properties of the metal of drums made of Grade 16GNM steel that have been in operation for a long period of time are presented. A change in the strength characteristics and fracture ductility of metal with respect to its initial properties indicated in its certification data is analyzed. It is shown that changes in the strength properties of the metal of drums do not demonstrate any stable trends with an increase in the time of its operation.     

Reasons for and nature of weld joints failure in hot reheat steam lines of 800-MW power units

The nature of and reasons for weld joint failure in the hot reheat (HRH) steam lines of an 800-MW power unit are analyzed. It is shown that the weld joint destruction happened in the softened area and is typical for the weld joints operating for a long time under creep conditions. Numerical simulation demonstrated that the weld joint exhausted its lifetime due to the impact of equivalent stresses that exceeded design values, this being the reason for the failure.