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Abstract: The first wall (FW) of China dual functional lithium lead-test blanket module (DFLL-TBM) for International Thermonuclear Experimental Reactor (ITER) contains rectangular helium flow channels, which will be fabricated by hot isostatic pressing (HIP)-diffusion welding with China low activation martensitic (CLAM) steel plates and rectangular tubes. Study on the rectangular tube fabrication process are being conducted. Rectangular tubes of 15mm×20 (inter dimensions of cross section)mm×2.2 (wall thickness)mm×1500 (length)mm were produced by hot piercing and cold rolling, and its dimensional deviation met the requirement of TBM assembly. The effects of tube rolling and heat treatment on microstructure and mechanical properties of CLAM rectangular tube were analyzed. It is found that soft annealing heat treatment after tube piercing was a suitable way to improve the ductility of the CLAM steel. The elongation should be less than 15% at every tube rolling step, and the favorable tempering temperature to release the stress caused by tube rolling was 800°C. [Copyright &y& Elsevier]

Based on detection technology of 1 H low-field nuclear magnetic resonance (NMR), this study developed a novel method for assessment and mechanism study of bleeding. This method is sensitive to bleeding water as well as water in cement paste and diluted grout, gives a vivid scenario of microstructure variation and provides important insights into mechanism of bleeding. In this study, influence of parameters such as cement type, water/cement ratio, chemical additives and environmental temperature on bleeding process was investigated. Results show that bleeding property of cements can be rapidly and precisely evaluated by the proposed method. It is found that peaks of T 2 distribution correlate with separated layers of fresh cement paste with bleeding, and the bleeding process generally consists of a significant growth, a relative stable period and a water-sucking stage. Results also demonstrate that retarder significantly increases bleeding, however, bleeding, to a certain extent, can be reduced by the addition of air-entraining agent. Furthermore, bleeding results of the cement paste under different temperatures (15.5 and 22.5 °C) suggest that higher temperature leads to a smaller T 2 value (around 10 ms) and a lower bleeding rate. The high precision of 1 H low-field NMR and linear correlation ( R ⩾ 0.921) between R t ( B ) and bleeding rate both evidenced the superiority and feasibility of the proposed method on study of bleeding. [ABSTRACT FROM AUTHOR]

In this paper the microstructure and mechanical properties of electron beam weld (EBW) joints for China low activation martensitic (CLAM) steel, which underwent a series of different post weld heat treatments (PWHTs) were studied. The aim of the study was to identify suitable PWHTs that give a good balance between strength and toughness of the EBW joints. The microstructural analyses were performed by means of optical microscope (OM) and scanning electron microscope (SEM). The mechanical properties were determined via tensile tests and Charpy impact tests. The results showed that the tensile strength of the as-weld joint (i.e. without any PWHT) were close to that of the base metal, but the impact toughness was only 13% of that of the base metal due to the existence of a delta-ferrite microstructure. To achieve a significant improvement in toughness a PWHT needs to be performed. If a one-step PWHT is applied tempering at 760°C for 2h gives EBW joints with high strength at a still acceptable toughness level. If a two-step PWHT is applied, a process involving quenching at 980°C for 0.5h followed by tempering at 740°C or 760°C for 2h gives EBW joints with high strength and toughness properties. Whenever possible a two-step PWHT should be applied in favor of a one-step process, because of higher resulting strength and toughness properties. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure of China Low Activation Martensitic steel (CLAM) and its influence on mechanical properties were investigated. The tensile test showed that the strength of CLAM (HEAT 0603A) was higher than that of HEAT 0408B at room temperature, and the reverse results were obtained at elevated temperatures. The results indicated that the microstructure was composed of dispersived carbide particles and lath martensite with high dislocation density. The main precipitation phases were Cr-rich M23C6 carbides precipitated mainly along the lath boundaries and prior-austenite grain boundaries and Ta-rich MX particles precipitated mainly in the laths and lath boundaries. The finer lath was the main reason for the higher strength of HEAT 0603A compared with HEAT 0408B at room temperature; contrasted with the lower strength at high temperature. Heavier hot forging deformation degree was considered as the main possible reason for the decrease of martensite lath width in HEAT 0603A. [Copyright &y& Elsevier]