A Study On NdFeB Flow And Heat Transfer Law In Single-roll Constant Capacity Of Casting

Accelerating melt spinning process has many advantages, due to the process of casting NdFeB slab, so that it attracts the industry's extensive attention. Single roller melt spinning process is the primary means of preparing and researching amorphous materials, but there are very few studies on making NdFeB thin ribbon. To test liquid NdFeB composition distribution, body temperature field and the cooling rate in launder by experimental method is very difficult, so it has positive theoretical significance and applying value to make an research on NdFeB flow and heat transfer and process parameters during the process of single-roll constant capacity o casting.In the process of NdFeB casting, the average thickness and uniformity of the thin ribbon is very essential for the quality of NdFeB. This paper took a research institute's jilt bell furnace as the prototype, and took casting, launder, revolving water-cooled rolls as the research object. This paper established the crucible rotation and flow function formula through mathematical modeling, and the function relationship is divided into two sections, which respectively use matlab to solve the relationships of crucible rotation and flow in casting and validate the results, and then fit the function formula about constant capacitance casting angle and temporal change, and calculate the fitting error and select the appropriate fitting manner. The main purpose is to make NdFeB keep equithickness in the continuous casting process.Only constant capacity of casting can not guarantee thin ribbon even thickness during molding, so this paper made an research by changing the size of the flow channel and other parameters to study their effect on the flow field, and made the use of fluent software, adopted numerical simulation method, and got the two-phase distributions of free surface shape in the flow channel, NdFeB liquid in the flow field and weak gas through simulation. These parameters have extremely important effect on the thickness uniformity of accelerating thin ribbon. This paper mainly by changing dip angle, the length of launder and the shape of sprue to study their effects on flow field, and the simulation results show that the greater the angle is, the more disordered the flow field is, the more unstable NdFeB free surface is, and when the inclination is 2°, the thickness of the smooth surface is superior then the inclination of 8°. The longer the length of launder is, the more stable the flow field is, and the more stable the free surface of NdFeB is, but when the length is too long, it will expand the vacuum chamber, and when the length is over 550, the effect of the flow channel's length on the thickness uniformity decreases gradually. Simulation results show that under the condition of ensuring the other parameters remain unchanged, the shape of sprue has no effect on the distribution of NdFeB flow field.This paper adopted Ansys software to simulate NdFeB cooling speed and the distribution of NdFeb strip temperature field. It mainly simulates the effect of body temperature, roller surface and other process parameters on strip temperature field and the cooling rate. The Body temperature cooling rate affects the crystal structure of NbFeB and also affects whether NbFeB can roll off timely, and ensure the casting process continues smoothly. The simulation results show that when the body temperature between 1300? and 1450?, NbFeB strip can roll off smoothly in the experienced time, and the cooling rate decreases with the increases of the body temperature. when the body temperature is over 1500?, body can not successfully roll off in the experienced time, which may lead to rollers clamping and interrupting the production. Through simulating the effect of rolling surface temperature on cooling rate, and it found that body cooling rate decreases with the rolling surface temperature increases. When the initial temperature of roll surface is below 600?, the cooling rate of NbFeB decreases as the roller surface temperature increases, and can roll off smoothly in the experienced time. When the initial temperature of roller surface is above 650?, the maximum temperature of NbFeB strip can't be cooled to a solid phrase line, otherwise it will affect continuous production, and result in rollers clamping.