Wei Kong

The System #2 flow loop used in this study is a 4−inch−diameter, high−temperature, high−pressure system. In situ corrosion and electrochemical measurements were performed using a homemade flat corrosion specimen and a three−electrode probe. The experiment results show that temperature has an accelerated influence on the corrosion of antibacterial alloy steel. With the increase of temperature and the presence of O₂ in the environment, a loose and porous corrosion product film was formed on the surface of the resistant steel, which made it easier for the corrosion medium to enter the corrosion product film from the pore, thus accelerating the corrosion.

There are always differences between the magnetic properties (core loss and magnetic induction) of the head and those of the tail, with the same chemical composition, in a medium-grade non-oriented silicon steel coil (or MGNO for short). To work out the reason leading to the differences and get methods to increase the magnetic properties, this paper studied the types and the distribution of the inclusions in MGNO, and the effects of the inclusions on the magnetic properties of the MGNO, by using SEM + FEEM observation and statistic analysis. The results show that there are oxide inclusions, sulfide inclusions, nitride inclusions and composite inclusions in the MGNO. More inclusions shorter than 500 nm are bad for the magnetic properties of the MGNO. On a lower order of the sizes, the number of the inclusions would more obviously affect the MGNO on its magnetic properties. The Al₂O₃ shorter than 1 µm and the MnS whose size is 100∼500 nm are the main inclusions that decrease the magnetic properties of the MGNO. In order to get better magnetic properties of the MGNO, the steelmaking process and the hot rolling process should be improved, chiefly the RH and the heat furnace.

To figure out the reason causing ladle nozzle clogging during a continuous casting process (or CC for short) for the silicon steel and get away to solve it, this paper studied the theoretical calculation of flow rates during casting, inclusions around the slide gate where ladle nozzle clogging happened, and Ca-treatment on refining units for producing the silicon steel. The results showed that: The bigger diameter of a nozzle or less nozzle clogging can guarantee an enough flow rate for reaching the target casting speed. Ladle nozzle clogging can be predicted by analyzing the percentage of a slide gate being opened. Al ₂ O ₃ and its composite inclusions were the main ones which cause the nozzle clogging during the CC process of the silicon steel. Ca-treatment could transform those high melting point inclusions into C12A7 by adding Si-Ca wires and prevent the ladle nozzle clogging of the silicon steel.

The submerged entry nozzle (SEN) clogging has been happening during continuous casting (or CC for short) for nonoriented silicon steel. To solve the problem, the paper studied a flow rate through SEN, a node attached to one of them, and the impact on the clogging. The results showed that when SEN is clogged seriously, the casting speed has to decrease below the target casting speed and that SEN clogging can be predicted by comparing the actual value and the theoretical one of a casting speed. Al2O3 and its composite inclusions caused the SEN clogging and the addition of Ca can solve SEN clogging during CC of the silicon steel both theoretically and practically. Furthermore, the impact of the addition of Ca on the magnetic properties of the steel were analyzed. The results showed that the core loss and the magnetic induction of the silicon steel decreased by using the addition of Ca, which generated more dissolved Aluminum, and the addition of Ca generated more harmful textures, which reduced the magnetic induction.