Search

P91 and P92 steels are widely used in power plants and petrochemical industry for long-term service components. Due to high resistance to creep, fatigue and corrosion, the use of grade 91 and grade 92 steels allows ultrasupercritical conditions (600 °C, 300 bar). To achieve this goal the alloy design was based on the following metallurgical concepts: stable tempered martensitic microstructure, precipitation strengthening through M23C6 (Cr, Fe, Mo or W carbides) and fine MX (V, Nb carbides), solution hardening through elements as Mo or Mo/W and high Cr content. This study is focused on the microstructure evolution of grade 91 and grade 92 steels under aging and creep conditions. Three sets of laboratory-aged specimens heated in oven at 550°C, 600°C and 650°C were examined. Furthermore, the influence of stress on the microstructure was evaluated. The microstructures were characterized by several means of investigations and the results were compared to literature. [ABSTRACT FROM AUTHOR]

This paper presents an emerging market sourcing risk assessment and management model for sourcing components and sub-systems to emerging markets. The model was developed, tested and implemented by a US automotive manufacturer but the principles and tool discussed here are broadly applicable. We gathered a comprehensive list of risk factors through an intensive literature review and subject matter expert (SME) interviews. We used a process failure mode effect analysis (PFMEA) structure to characterize the risks and developed a simulation model to quantify risk factors in terms of dollars so that an OEM can evaluate risk mitigation strategies. The spreadsheet simulation ranks causes of failures and failure modes and calculates total risk in terms of dollars. In addition to analysing risk, the model evaluates the impact of different inventory levels on the costs of delays in the supply chain. The model can also be used to evaluate and select suppliers that offer minimum risk. We demonstrate the model with a real-world case study involving a North American auto company considering sourcing a component to an emerging market. [ABSTRACT FROM AUTHOR]

As part of a European research project, partially funded by the Steel Research Fund (RFS-CR-03049), the potential benefits derived from the use of synchronized tandem wire welding (STW) technology applied to structural plates, in place of the currently used arc techniques, have been evaluated. In particular, two welded joint types have been investigated: T joints and butt joints in S355 grade structural plate, 6 and 12 mm thick. Considering the variables that characterize the process, also depending on the type of tandem torch, i.e. variable or fixed electrode configuration, the influence of the distance between the electrodes, stick-out, the type of arc and weld speed on the process characteristics have been examined. The joints obtained have been compared with those produced using traditional technology in terms of overall joint deformation, structural integrity, microstructural analysis and mechanical performance (toughness and fatigue strength). The results have demonstrated that the STW process is an effective technology for increasing both the weld speed, at the same penetration and the quantity of metal deposited, by about 50% compared to GMAW welding, with only slightly higher but relatively modest heat input (1 kJ/mm). These operating conditions have allowed the preservation of a level of joint quality (EN ISO 5817 quality level B) and structural integrity, comparable with those of GMAW and SAW welded joints, in addition to significant reductions in distortion. Furthermore, the fatigue strength of STW joints has also been in compliance with the reference class (butt joint, FAT class 100). The objective of the project (RFS-CR-03049), partially supported by the Research Fund for Coal and Steel, was to explore and quantify the benefits of STW applied to structural steels as an alternative technology to established arc welding technologies. T joints and butt joints of 6 and 12 mm steel grade S355 plates have been investigated using two different types of welding gun configuration, i.e. fixed electrodes and variable electrodes configuration. The influence of electrodes distance, stick-out, arc types and welding speed have been examined. The optimized joints have been characterized in terms of structural integrity, microstructure, mechanical performance (impact fracture toughness and fatigue resistance), total deformation and compared to traditional arc welding joints. STW technology allowed an increase of about 50% in both the welding speed, at the same penetration and deposited metal compared to GMAW with a not much greater heat input (1 kJ/mm) maintaining the same level of joint quality (EN ISO 5817 quality level B) and structural integrity with a reduction of joint distortion. In addition, fatigue resistance of STW joints was in compliance with the requirement (FAT Class 100 MPa)[image omitted]. [ABSTRACT FROM AUTHOR]