Roll Compaction And Subsequent Heat Treatment Of Fe-Si Composite Powder

6.5wt%Si silicon-iron strips are one kind of soft magnetic with excellent property. It has higher relative permiability , saturation magnetization intensity, and lower magnetostriction and core loss, compared with conventional silicon-iron materials. In this paper, the process of fabricating silicon-iron strips by direct powder rolling was studied. The changes of density and phase composition and structure evolvement were mainly studied.The powder synthesis fluid testing instrument, powder testing instrument and SEM which are used for the testing of Fe-6.5%Si composite powder were applied, then the effect of powder component and mixing time for the powder fluid and loose density was analyzed . In powder rolling, the influences of powder properties and process coefficients on thickness and density of the green strips were studied. The influence of roll gap, feeding height and the width of green strips on the thickness and the density of green strips were analyzed. Choosing proper heat treatment coefficients, 6.5wt%Si silicon-iron strips were fabricated. The reaction mechanism was explained. Magnetic properties of the final strips were characterized.A simple and efficient means of synthesizing Fe-Si composite powder which takes on good fluid and big loose density was found. The results showed that continuous green strips could be manufactured by the laboratory scale ordinary duo mill (roll diameter is 50mm and roll velocity is 0.2 m / s). The properties of the composite powder, roll gap, feeding height and the width of green strips had the influence on the thickness and density of green strips during roll compaction. With the increasing of roll gap the thickness of green strips increased and the density decreased.After the research of the sintering mechanism, it is found that powder properties and rolling coefficients all had influences on the properties and structures of the final strips .Strips with a bigger density had better magnetic properties. Choosing proper silicon particle size, a local graded structure, Fe-Fe(Si)-Fe₃Si(Si)-Si, forms when sintering at 1000℃ for 3 hours. The local graded structure plays an important role in the DPR process. Fe₃Si(Si) phasekeeps higher content of Si, and Fe(Si) phase remains the state with much lower Si-content, thus provides good mechanical proprieties of rolling and cutting for the compacts. Then, the subsequent sintering at high temperature of about 1200°C improves the density and makes the distribution of Si homogeneous in the final products of high silicon iron sheets. The magnetic properties of the final strips were tested, the core loss of specimens indicated an excellent soft magnetic performance in high frequencies.