Develop a sustainable welding procedure for chromium manganese austenitic stainless steel using the ATIG process

Chromium manganese austenitic stainless steel is exhibiting an admirable amalgamation of higher strength and stress corrosion resistance. This economical steel is developed to fulfill the requirement of a variety of consumers for high temperature and structural applications. Hitherto, the limitation associate with the TIG welding process is a low depth of penetration which reduces productivity. Activated tungsten inert gas welding (ATIG) is the best suitable option to overcome this problem and satisfy the sustainable welding requirement. Welding procedure has been developed for chromium manganese austenitic stainless steel during ATIG welding using a box behken design (BBD) to improve penetration depth and productivity. The activated flux using SiO2 and TiO2 flux indicates improvement in penetration 5.3 mm and 5.1 mm as compared to TIG welding. The ATIG welded test coupon has strength and hardness of 495 MPa and 195 HV when using SiO2 flux, and 487 MPa and 190 HV when using TiO2 flux, compared to 435 MPa and 165HV for the TIG welded test coupon. ATIG welds have higher strength and hardness because of their finer grain size when compared to TIG welded test coupons.

Vortex phase diagram in 1111-type CaFe0.89Co0.11AsF single crystal

Studying the vortex properties in high-Tc superconductors is crucial for understanding the high temperature superconducting mechanism. However, until now, only few vortex studies have been performed in 1111-type iron-based superconductors due to their smaller-sized single crystals. In this study, we have synthesized the millimeter-sized CaFe0.89Co0.11AsF single crystals by self-flux method. Three dimensional vortex nature was confirmed in the thermally activated flux flow region. Second magnetization peak was observed on the isothermal magnetization curves. Meanwhile, the dominated role of the normal point pinning was also confirmed. Finally, the various phase boundaries of the vortex were determined based on the analysis of the resistivity and magnetization data, and a complete vortex phase diagram of CaFe0.89Co0.11AsF single crystals was established.

Emphasis of Weld Time, Shielding Gas and Oxygen Content in Activated Fluxes on the Weldment Microstructure

The activated-TIG (A-TIG) process is a recognised process for achieving higher depth-of- penetration (DoP) and it could be used for various stainless-steel grades welding. The oxygen content of oxide based activated fluxes provide the extra heat during decomposition of flux and result into deep penetration. This study reveals the effect of short weld time of 2 sec in stationary arc, shielding environment (Ar and Ar + 2.5 % H2) and an effect of oxygen element in activated flux (CrO3 and SiO2) on the microstructure and weld metal micro-hardness. Use of hydrogen mix shielding gas during A-TIG process has significant impact on the dilution rate, grain size and dendrite arm spacing. The fraction of oxygen in the flux and the presence of silicon in SiO2 flux play a significant role in achieving higher DoP. To evaluate the impact of different shielding environment on grain growth, the samples were investigated with weld pool morphology, depth of penetration, weld chemistry, optical microscopy and SEM analysis. The extra heat produced due to oxygen fraction in activated flux and H2 induced shielding have been quantified in the study. The ferrite and austenite grain growth as well as the dendrite arm spacing found to be increased due to presence of H2 in shielding gas.