Fabrication Of High Silicon Iron Alloy By Direct Powder Rolling Technique

In this thesis, the fabrication technique of the high silicon-iron strips near to 6.5wt.% Si by the Direct Powder Rolling (DPR) technique were studied. The reaction mechanism between the iron and silicon powders was clarified. The final high silicon-iron strips were fabricated with the optimal rolling coefficient and the magnetic properties were investigated.Firstly, basing on the knowledge of soft magnetic materials fabricated by the Powder Metallurgy (MP), we brought forward a new ideal about the composite powder, which is to distribute brittle metal powders (Si) to the surface and gaps of the plastic ones (Fe), then composite particles in which plastic metal powder is packaged by brittle ones are formed by further deformation. The effect of rolling coefficients was analyzed, and the optimal coefficients were gotten, therefore the continual coiled green strips in a certain thickness could be produced which have a good mechanical property. The structure evolution and reaction mechanism of silicon-iron composite powders treated at the temperature ranging from 700 C to 1200 C respectively were carefully investigated through XRD, SEM, EPMA, DSC. It was found that the chemical formula, Fe + Si - Fe (Si) + Fe3Si (Si), controls the reaction process, and the reaction mechanism of powder homogenization was clarified. Following this principle, the final specimens were successfully fabricated with the concentration of 6.0 - 6.5wt.% Si. The saturation magnetization of the sample is 1.79T close to the theoretical value of the same composition alloy. The core loss of specimens indicated an excellent soft magnetic performance in high frequencies of 1-10 KHz. The specimens during fabrication process can be cut and final strips have a good mechanical property.Furthermore, a new method to measure the concentration of ferromagnetic alloys was exhibited, and its reliability was also confirmed, which is to measure the Curie point of specimens by the DSC analysis and then compare the data with ones of standard specimens so that to observe the concentration of specimens. The average component of the alloy can be evaluated as well as the inhomogeneity using this measure. It is indicated that the degree of the reaction diffusion among powders.The results show that the production technique of the high silicon-iron strip byDPR has many advantages, such as low energy loss and simple production technique, and it has a great potential of continuous industrial production.