| Amorphous alloys are a kind of "double green" soft magnetic functional material for green preparation and green application.And their manufacturing is also a shortened process,which can save about 80%energy compared to the production process of cold-rolled silicon steel sheets.At present,the 1k101 Febased amorphous alloy,which is currently being produced commercially,has a saturated magnetic induction strength(Bs)of 1.56T,being about 20%lower than that of silicon steel materials.The Bs of magnetic materials is directly related to the power density of the device,so improving the Bs of amorphous alloy materials has become a research hotspot in the field.Hitachi Metal first developed Metglas2605HB1(Fe82Si4B13C1)amorphous alloy,with the Bs up to 1.64 T.However,due to the low glass forming ability(GFA)of this alloy,the process manufacturing is very difficult,and Hitachi Metal has formed a patent monopoly and market blockade in China.In view of this,the urgent demand of China’s amorphous industry is to develop a new alloy composition system with high Bs and high GFA,and to achieve breakthroughs in industrial production integration technology by solving key basic scientific problems faced in industrial production.This thesis is focused on solving the problems of low GFA and narrow production process window of Fe-Si-B-C(HB1)amorphous alloy system.Based on the Fe83Si5B11C1 alloy,a new Fe-Co-Si-B-P-C amorphous alloy system with high GFA and high Bs was successfully developed by adjusting the atomic mismatch and mixing enthalpy of the alloy via the blending of metalloid element such as Si,P and C and increasing the saturation magnetic induction of the alloy via the doping of ferromagnetic element Co.In view of the large amount of inclusions in low-cost raw materials required for industrial production,the integrated technology of bottom argon blowing and foam ceramic filtration was developed by controlling the morphology of inclusions in melt,and the thermodynamics and dynamics of inclusion formation,which greatly improved the cleanliness of melt and the quality of produced ribbons.The pilot scale production of new Fe-Co-Si-B-P-C amorphous alloy strip was successfully realized with industrial pure raw materials.The main results have been achieved as follows:(1)Based on the theories of glass formation,a new Fe83Si5-xB11PxC1(x=1,2,3,4 at.%)amorphous alloy system with high GFA was successfully developed by replacing Si with P element in the base Fe83Si5B11C1 amorphous alloy.Among them,it has been found that Fe83Si1B11P4C1 amorphous alloy has the best GFA and can be prepared into amorphous ribbon with a thickness of 36μm.After the heat treatment at 360℃,Fe83Si4B11P1C1 amorphous alloy showed the best comprehensive soft magnetic properties,and its Bs and coercivity(Hc)were 1.62 T and 2.6 A/m,respectively.However,the analysis of thermophysical parameters showed that substitution of P for Si will reduce the thermal stability of amorphous phase in the alloy system.(2)Based on the composition of Fe83Si1B11P4C1 alloy with high GFA,different content(1～5 at.%)of Co was added to improve its Bs.The results show that the Bs of the alloy increases from 1.57 T to 1.72 T with the increase of Co content from 1 to 5 at.%.However,the increase of Co content will also increase the Hc of the amorphous alloys,when adding Co content is lower than 3 at.%,the Hc of amorphous alloy is controlled within 10A/m.When the content of Co is more than 3 at.%,the Hc of amorphous alloy rapidly increases to 18.7 A/m.The results show that 3 at.%Co is the best,and its Bs can reach 1.68 T and Hc is 9.8 A/m.(3)In order to solve the problem that the surface of amorphous alloy is easily oxidized in Fe-Co-Si-B-P-C system with high P content,a low-temperature preoxidation heat treatment process for amorphous alloy was developed.The results show that when heat treated in the temperature range of 240～300℃,the Hc of the sample after pre-oxidation heat treatment is significantly lower than that of the sample after vacuum heat treatment.The Hc of the sample after annealing at 280℃ for 10 min in air is 4.4 A/m,which is lower than 5.9 A/m of the sample after vacuum heat treatment.In the pre-oxidation process,it has been found that there are elements migration on the surface of the amorphous alloy,and Co element migrates from the outside surface to the oxidation front,and the P element migrates from the inside part to the oxidation front.At the same time,there are a few of element atoms(mainly Co and P)gathered at the junction between the oxide layer and the amorphous matrix,which improves the magnetic properties of the amorphous alloy.However,if the pre-oxidation time is too long and the oxide layer becomes thicker,Hc for this amorphous alloy will increase.(4)The corrosion resistance of Fe-Co-Si-B-P-C amorphous alloy after preoxidation and non oxidation heat treatment was studied.It is found that the pre oxidation heat treatment can improve the corrosion resistance of Fe-Co-Si-B-PC amorphous alloy.The Ecorr value is increased from-0.736 V to-0.668 V,which is easy to generate a passivation platform.The oxide layer after pre-oxidation treatment is divided into two layers:the inner layer is amorphous,the outer layer is crystalline,and the main oxide is Fe2O3.In the oxidation process,Co and P elements gather at the oxidation interface to form phosphorus and cobalt oxides with high corrosion resistance,thus improving the corrosion resistance of the amorphous alloys.(5)A new type of permeable brick structure has been designed and developed,which has been changed from a porous slit type permeable brick structure to a new type of dispersive gas permeable brick structure.By using this new type of permeable brick structure combined with a ceramic foam filter,the diameter of the argon can be controlled within 3 mm,and the melt inclusion content can be reduced from about 500 pcs/mm2 to less than 200 pcs/mm2 by bottom blowing argon for 30 minutes.By controlling the purity of the melt,it greatly improved the smoothness of industrial production and the strip grabbing rate can be increased from 60%to 95%。It can also significantly improve the quality of the amorphous ribbon,the horizontal range can be controlled within 2μm,no scratch and defect on the surface,and the lamination coefficient can reach 0.89. |
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