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The inner surface of pressure vessel steel used in the petrochemical industry is often coated with corrosion resistant materials. The industrial process that combines increased productivity with controlled dilution is ESSC (ElectroSlag Strip Cladding). The paper aims to overcome the current ESSC process limitations, analyzing the possible benefits introduced by Multi Strip technology, Twin type. The tests with combinations of carbon steel coated with Alloy 625 and Type 347 deposit on creep resistant low alloy steel were conducted. [ABSTRACT FROM AUTHOR]

For dissimilar metal welds, between austenitic stainless steels and ferritic steels, an austenitic stainless steel filler material with an adequate composition is normally used. To minimize the risk of hot cracking, the weld zone should preferably be constituted by an austenitic microstructure with a small amount of ferrite δ. During solidification, the microstructures depend on filler material and base material compositions. Useful indications of the weld zone microstructures can be drawn from such diagrams, for example the Schaeffler diagram, which defines the fields of existence of the phases as a function of composition expressed in terms of chromium equivalent (Creq%) and nickel equivalent (Nieq%). Recently alternative diagrams to Schaeffler diagram have been proposed. An amendment was introduced in one of these diagrams to better characterize the boundary area between martensitic-austenitic structure and fully austenitic structure. In this paper, by means of the experimental test results of austenitic stainless steel and ferritic steel joints, welded with laser beam process, some specimens were obtained with a weld zone composition near to the boundary between martensitic and austenitic zone in the Schaeffler diagram. The content of the elements was calculated by energy dispersive microanalysis (EDS). The microstructures were examined by optical microscopy and scanning electron microscopy (SEM) and by Vickers microhardness tests. For some microstructures, which were fully austenitic, the position of the corresponding points were located in the martensitic-austenitic zone below the line defined by the original Schaeffler diagram, while they were in accordance with the new definition of the boundary zone of the modified Schaeffler diagram. [ABSTRACT FROM AUTHOR]

EST Plant (Eni Slurry Technology) consists of about 300 pressure vessels in the following principal units and section: * EST unit (unit 90); * Hydrogen production plant (Unit 95); * SWS sulphur recovery and tail gas treatment (Unit 92 and 94). More than 100 "critical" equipments exist in the EST complex, divided in units and sections on the basis of their type of service. In detail, the considered critical items include: carbon steel and low alloy steels heavy wall pressure vessels for high temperature, high-pressure hydrogen service; carbon steel pressure vessels in sour (wet H^S service) and amine service. For fabrication of such "critical" items special base materials and filler metals were adopted according to specific material requirement, special welding processes and fabrication sequences (including advanced automatic systems for non destrucutive testing) were used. This paper shows an overview on some critical aspects and experience of fabrication of main "critical" equipments of EST Plant. [ABSTRACT FROM AUTHOR]

Presently, many economical and technical efforts are made by pipeline industry aimed to satisfy the needs to transport gas from far away regions to the final market and to set new solutions in terms of both design criteria and new high performance materials. Due to the fact that easy Oil and Gas is largely exploited and new fields will be more and more in deeper water (it means water depths greater 305 m), that means higher pressures and temperatures and more corrosive environments, material requirements are increasing. In this situation low-alloy carbon steels tend to be structurally satisfactory, but lack in terms of corrosion resistance. On the other hand stainless steels and nickel alloys resist to corrosion environments but are lack in terms of strength or extremely costly. Clad pipes, low-alloy carbon steel with a thin layer of a corrosion-resistant alloy, is presently considered, more and more, a suitable solution to the most demanding requirements of strength, corrosion resistance and cost-effectiveness. In a cladded pipe, the (generally) unalloyed carbon steel outer pipe handles the internal and external pressure, while the high-alloy cladding provides the corrosion protection. The paper describes the pipes and fittings production starting from metallurgical clad plates. In particular the experience developed by Allied Group is described. The developed products and components represent the ideal candidate for the most severe offshore and subsea applications typical of the Oil&Gas sector. [ABSTRACT FROM AUTHOR]

High carbon steels are commonly used in modem mechanical industry due to their good mechanical properties and to their relatively low cost. Unfortunately, when dealing with welding processes, these materials must be set aside because of their very high crack susceptibility and more refined and expensive steels must be taken into consideration, such as HSLA, DP and TRIP ones, thanks to their lower carbon equivalent and similar, or even better, mechanical properties. In micro-scale components industry the use of high carbon steels is also very common, in particular in precision mechanics, watch and MEMS industry. Considering the very low thicknesses typical of these components and the intrinsic welding difficulty related to the material, several studies stressed on the possibility to exploit nanosecond pulsed lasers in welding this kind of steels. These sources, taking advantage from the short duration of the pulse and from a repetition rate as high as 1 MHz, allow a very accurate control of the heat input delivered to the material and pave new ways in micro-welding of medium and high carbon steels. The present paper deals with the exploitation of a 20 W nanosecond pulsed laser source in welding low thickness C70 (AISI 1070) plain carbon steel. The process is studied by evaluating the influence of the main parameters on its feasibility. The activity pointed out that, by properly selecting the main parameters, it is possible to achieve sound and crack-free weld beads with a maximum penetration as high as 200 fim and a very small heat affected zone. The main interesting point concerning this specific welding process is related to the fact that, by simply selecting the proper process parameters, it is possible to achieve high productivity working cycles involving laser cutting, welding and marking on the same machine and exploiting the same workpiece positioning. [ABSTRACT FROM AUTHOR]