Study of Magnetic Properties of silicon steel Composite Synthesized by Dual-Jet Atomization and Additive Manufacturing

• Main Authors: De-HauTseng, 曾德豪
• Other Authors: Chi-Yuan Tsao
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/gx343n

碩士 === 國立成功大學 === 材料科學及工程學系 === 105 === Study of Magnetic Properties of silicon steel Composite Synthesized by Dual-Jet Atomization and Additive Manufacturing De-Hau Tseng Chi-Yuan A. Tsao Department of Material Science and Engineering, National Cheng Kung University, Tainan City 701, Taiwan(R.O.C) SUMMARY In this study, Fe-6.5wt.% Si prealloyed powders were prepared by Dual-jet atomization process to prepare fully alloyed iron-based metal spherical powders , The RSAed powder is pre-alloyed and thus has more uniform homogeneity. The effects of various laser power, scanning rate and segregation on the phase ratio, magnetic properties, microstructures, density, and mechanical property of SLM Fe-6.5wt. %Si bulks were investigated. INTRODUCTION Magnetic materials play an important role in our life, due to energy saving and environmental protection. Soft magnetic materials is often studied in the field, because the soft magnetic materials often used in the core material, and under the alternating current Such as transformers, generators, motors, etc., where often use of silicon steel material, mainly because the silicon can increase the resistance and reduce the coercive force to reduce energy loss. Reducing the spacing of insulating layer which is to reduce the thickness of silicon steel sheet can mainly reduce the eddy current loss. The current commercial specifications of the largest silicon steel sheet thickness of 0.37mm, special specifications of the silicon steel sheet thickness of 0.1mm, while the increase in resistance is by The magnetization of Fe-6.5Si alloy has a relatively high relative permeability (2.8 * 104), and the magnetic properties of the Fe-6.5Si alloy have a relatively high relative magnetic permeability (2.8 * 104) High resistance (80μΩ-cm), high saturation magnetic flux density (1.8T), relatively low iron loss (〉 0.77W / kg, 0.35mm, 1T, 60Hz)[1] , But because of its poor workability, the application is limited MATERIALS AND METHODS Material Fe-6.5wt. %Si pre-alloyed powders was synthesized by rapid-solidifying atomization Selective laser melting process These two powders were than consolidated into bulks of 7 mm Cylindrical and 4 mm height by selective laser melting (SLM) with different laser powers(150 to 180W) and scanning rates(650, 750, 850, 950 mm/s). RESULTS AND DISCUSSION Microstructure analysis Fig.1 Fe-6.5 Si Fe - 6.5 Si laser fusion. Can be observed inside the main two main defects, the first is a circular hole. The second is a crack, It can be observed the more to the border, The number of gradually increased, because the cooling rate is faster, stir into the gas too late to escape the material inside. In the laser input energy, the pool of agitation is more intense, more gas will be inserted into the material to form pores, resulting in a significant increase in porosity. The other can be observed 180W, 750mm / s and 170W, 850mm / s these two parameters of the cracks caused by the sudden increase in the porosity of the substrate surface with varying degrees of oxidation, it can result of different heating conditions, and these two parameters just in the low heating area, so there may be a large-scale cracks. It can be found that the internal grain of the material is the type of casting crystal, the direction is towards the BD (build direction), this phenomenon can be seen as Epitaxy (Epitaxy), the direction of the material according to the substrate grain Direction of growth, casting materials to form columnar crystal elements, SLM process also meet the necessary conditions, the necessary conditions are as follows 1. The direction of the single heat flow, the main heat flow direction for the BD direction (guide plot board), SD direction of the heat flow is very small, because the thermal diffusion coefficient between each powder than the bulk of the thermal diffusion coefficient to small, so the column The growth direction of the crystal is BD direction. 2. Each layer of the process of metal melting soup has a high overheating temperature, inhibit the equiaxed zone (Equiaxed zone) formation. 3. The experimental results show that the agitation inside the pool is not enough to interrupt the columnar crystals, providing heterogeneous nucleation sites to form equiaxed crystal regions. Phase analysis Figure 2 Fe-Si ingot block and pre-alloy powder XRD pattern, in the part of the ingot block, because the cooling rate is slow, so there is the DO3 order phase generation, as shown in Table 6, about 11.7 wt% While the pre-alloy powder is due to the faster cooling rate, only the presence of Alpha-Fe. CONCULUSION With the higher the laser power, the higher the scanning rate, the higher the amount of silicon.phase analysis, Order phase DO3 mostly in the laser scanning rate 650mm / s and 750mm / s found, because the order phase requires a slower cooling rate to form coercivity, DO3 phase, grain size and porosity are positively correlated with negative stress. Saturation magnetization of the part, did not find the saturation magnetic quantization with the laser parameters have a relationship