| Although existing laser additive manufacturing(SLS and SLM)and electron beam additive manufacturing technologies can form parts with good quality and high forming precision,their equipment cost and forming efficiency limit their industrial applications.In order to improve the forming efficiency and reduce the cost of additive manufacturing,the technology of additive manufacturing using arc as heat source has become a new trend.In this paper,microbeam plasma arc is used as the additive manufacture heat source to study the dimensional accuracy and characteristics of 316 L stainless steel parts formed by microbeam plasma arc additive manufacture.The main research results and contents are as follows:(1)single-pass research: the process window of current and welding speed,current and powder delivery speed to form stability welding pass was made,and the forming mechanism of discontinuity(spheroidization,discontinuity),wide welding pass and powder splash was revealed.The influence rule of single-layer single-pass size was studied: when the current changes from 30 to 55 A,the width of single-layer single-pass increases and the height decreases.When the overburden velocity changes from 300 to 600mm/min,the width and height of the layers decrease.When the speed of powder delivery is from 6 to 11g/min,the width and height of each layer increase..In addition,the optimal model of cross section profile of single flue was studied.By comparing the error between model area and real area,the parabolic linear model is obtained as the optimal model.(2)single-pass and multi-pass research: the regression equation of width and height of single-pass and multi-pass straight arm was established,and the average error of Prediction and truth was no more than 10%.The actual verification of the two sets of parameters shows that the error rate is less than 5%.The influence of process parameters on the width of the model is as follows: welding current > feeding speed > welding speed;The influence on the layer height is: powder feeding speed > welding current > welding speed.The tensile strength and fracture elongation of the straight arm are greater than those of the casting parts.The tensile strength(575MPa)and elongation at fracture(49.07%)in the horizontaldirection is both greater than that in the vertical direction(560MPa\49.07%).The micro-hardness of the straight arm presents a "high-low-high" trend from the bottom to the top in the vertical direction.In the horizontal direction,the hardness at the center is the highest and the hardness at both ends is low.(3)multi-channel lap and suspension characteristics: based on the determination of the optimal model,the optimal lap rate was calculated to be 33%.The three groups were set with the bonding rate of 28%,33% and 38%,and the surface flatness test was carried out.It was found that the flatness was the smallest under the condition of 33% bonding rate.Analysis of different slope Angle welding forming condition,set up 30 °,45 °,60 °three groups of different slope Angle,and It was found that 60 °oblique Angle can barely form structure,and under 60 °oblique Angle failed to form a suspended structure.(4)application verification: for 7 parts of 2 categories,the forming strategy and program realization are introduced,the forming surface morphology is analyzed,the problems in the forming process are explored,and the process parameters are optimized.By analyzing the forming rate and powder utilization rate,it was found that the forming rate and powder utilization rate of the straight arm parts were higher than that of the other kind,among which the forming rate and powder utilization rate of the cylindrical thin wall parts were the highest.the dimensional accuracy of milling forming cylindrical straight arm is around ±0.12mm... |
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