Czech Welding Institute (Czechia)

The main generic feature of the hyolithid genus Pterygotheca Novlk, 1891 - the fringe on the lateral edges and on the dorsal side of the conch - is interpreted here as a colony of a tabulate coral, Hyostragulum gen. n. This coral covered the living specimens of different hyolithid species in the Bohemian and Moravian Lower and Middle Devonian and occasionally also of nautiloids and gastropods. Because of this discovery it is necessary to withdraw the order Pterygothecida Syssoiev, 1968 and probably also the family Ptery-gothecidae Syssoiev, 1958. The genus Pterygotheca is questionable, but further study may prove its validity. The character of the epifaunal coral strongly supports the interpretation of a benthic life of hyolithids.

This article describes the overlay welding of a cobalt alloy. This overlay is made by the plasma transfer arc (PTA) welding technology. Cobalt alloy is overlaid on a creep resistant steel as the seat of a high-pressure steam valve. High-pressure steam valves are used in the energy, nuclear, petrochemical, oil, gas and pharmaceutical industries. Creep resistant high alloy steels are weldable with proper welding conditions, including stress relieving. Cobalt alloys, on the other hand, have worse weldability. Overlay welding of these heterogeneous materials is possible as well with meeting specific conditions especially proper welding parameters. In this article, the whole experiment is described, including design of the part that is overlaid by plasma arc welding. The technological procedure of overlay welding is described, including a description of the welding equipment, subsequent evaluation and all standards and specified inspections needed for welding procedure qualification (WPQR). WPQR qualification of overlay welding was also done and finished with Notify Body.

Abstract Mit dieser Arbeit wird an frühere Analysen der Gattung Festuca Sect. Festuca in Böhmen angeschlossen ( TOMAN 1974, 1976). Etwa 500 Proben sind qualitativ, semiquantitativ und quantitativ bearbeitet worden; dabei wurden nicht nur morphologisch‐taxonomische sondern auch ökologisch‐chorologische Fragen behandelt. Die Untersuchungen wurden durch langjährige Kultivierungs‐Versuche an etwa 50 ausgewählten Populationen ergänzt. Zusätzlich wird die starke Variabilität einiger Merkmale beschrieben, einschließlich solcher, die man üblicherweise für stabil hält und die deshalb of taxonomisch benutzt worden sind. Das Material wurde mathematisch ausgewertet; von den angewandten Methoden ist z. B. neu die mathematische Hilfsmethode bei der Artbestimmung, die Methode zur Auswahl der Typenkollektionen der Arten sowie die einfache Veranschaulichung der Beziehungen zwischen den quantitativen Merkmalen mittels Modell. Es scheint, daß letztere ein Charak‐teristikum der genetischen Gesetzmäßigkeit ist. Abschließend folgen einige Änderungen zu den Methoden der Faktor‐ und Variationsanalyse.

The aim of the paper is to explain the reason why the creep rupture on welded joints at high temperatures is often observed in the heat affected zone (HAZ), especially in the so called intercritical zone (IC-HAZ). The creep rupture strength (CRS) of cross-weld joints is usually about 20 to 30% lower than that of the base material in the case of the creep resistant modified chromium steel. Precipitation strengthening (PS) depends on the interparticle spacing (IPS) of secondary phases — M23C6 and nanoparticles of MX. With increasing IPS of secondary phases the proof stress and creep rupture strength decreases, while creep rate increases. To estimate the IPS in HAZ the modelling technique was used for estimation of the microstructure and properties. The microstructure of HAZ modelled regions was analysed by transmission electron microscopy. The Smitweld machine was used to reproduce the thermal cycles in HAZ. Real creep tests were carried out on specimens with HAZ modelled regions and also on the P91 real welded joints. It was found that interparticle spacing of secondary phases in the HAZ is much higher than that in the base material. Therefore the proof stress and hardness as well as creep rupture strength of HAZ is much lower than that of the base material. It was observed that CRS in the HAZ is about 20% lower than that of the base material.

Abstract The efficiency of power plants is depending on the steam temperature and/or the steam pressure. Efficiency increasing from 35% to 42-45% require increasing of the steam temperature over 600°C and the pressure over 26 MPa. According to the designer opinion it is not profitable to use classical low alloy creep resistant steels 16Mo3, 13CrMo4-5 or 10CrMo9-10 for membrane waterwall construction for these service condition. New modified low alloy creep resistance T23 and T24 (7CrMoVTiB10-10) steels were developed for membrane waterwalls. Welding of these steels with small thickness (around 6.3 mm) should be enabled without preheating and post weld heat treatment (PWHT) due to the lower carbon content below 0.1%. High creep rupture strength (CRS) values are achieved by Ti, N and B elements alloyed to T24 steel. The original expectation that the welding small thickness without preheating was early overcome and was wrong. According to the present experience the T24 steel is welded with preheating at 150-250°C depending on the wall thickness and welded joint toughness in order to achieve required hardness and impact toughness values. Opinions on the T24 welded joints post weld heat treatment (PWHT) requirements are still inconsistent. Especially the membrane waterwalls of the supercritical power plants are still produced without PWHT.

Geografie > Archive > 1969, Vol. 74 > Issue 4 > Historie a současný stav výzkumu eroze… Geografie 1969, 74, 303-312 https://doi.org/10.37040/geografie1969074040303 Historie a současný stav výzkumu eroze půdy v České socialistické republice Otakar Stehlík Geografický ústav ČSAV; Mendelovo nám. 1, Brno, Czechia « Previous article Next article »

This paper describes the welding procedure qualification of the multilayer “lamellar” flange for modern bridge construction made in the Czech Republic. The fine-grained structural steel was used for construction and welding qualification. Weldability of this steel grade is briefly mentioned. Technological and proposed welding processes including weld joint preparation are described. FCAW welding in the overhead position is carried out by the seamless flux cored wire and SAW welding using solid wire in the flat position is applied. All required tests on the multilayer weld joint including tensile test, bend test, hardness distribution, impact test, and macroscopic evaluation are investigated. All test results are in good agreement with EN ISO 15614-1 standard requirements. Based on the satisfactory results, the proposed welding procedure for the multilayer flange weld joint can be qualified.

Import 23/07/2015