304不锈钢的电脉冲辅助车削与声电耦合表面加工研究
发布时间：2018-09-12 09:07
【摘要】：本研究在自行设计和搭建的综合实验平台上,进行了304不锈钢的电脉冲辅助车削与声电耦合(即超声表面滚压和电脉冲耦合)表面加工实验。深入研究了电脉冲对304不锈钢的切削加工性及超声表面滚压加工表面强化层性能的影响规律,并提出了相应的机制进行解释。电脉冲辅助车削加工研究发现:与普通车削相比,参数优化的电脉冲可显著降低304不锈钢车削加工的主切削力和轴向表面粗糙度,减小加工硬化;切削区的塑性变形能力显著增强,车削变质层流变厚度有所增加,切屑形成方式由原来的剪切塑性变形向剥离撕裂转变;实验所用的YG6X刀具前刀面的磨损形态从机械磨损向黏结磨损转变,且黏结磨损随电流密度增大而加剧;电脉冲过大会引起加工表面微弱氧化,表面粗糙度和显微硬度上升,恶化加工表面质量;在本研究的实验条件下,较理想的电脉冲参数为:均方根电流密度1.28A/mm2,峰值电流密度9.15A/mm2,脉冲频率600Hz;研究引入量子力学的物质波理论和摩擦学的共振选择摩擦能量逸散理论对电脉冲辅助车削加工的内在作用机理做出了探索解释。声电耦合表面加工研究发现:与单纯超声表面滚压加工相比,参数优化的电脉冲可进一步显著提高304不锈钢超声表面滚压加工表面强化层的显微硬度和表面光洁度,显著促进表面微裂纹愈合;强化层表面的耐摩擦磨损性能得到进一步提高,获得了更高的表面残余压应力,材料的抗拉强度增强;电脉冲导致304不锈钢的层错能升高,使得其塑性变形机理从以形变孪生为主转变为以位错滑移为主;强化层中的形变孪晶数量大幅减少,同时马氏体含量增加,晶粒更加细化;最终形成的表面强化层是少量较软的奥氏体和大量较硬的马氏体形成的软硬镶嵌结构;电脉冲过大会造成加工表面显微硬度下降,残余压应力释放,恶化表面加工质量,但同时会增加表面强化层的作用深度。在本研究的实验条件下,较理想的电脉冲参数为:均方根电流密度1.03A/mm2,峰值电流密度7.66A/mm2,脉冲频率600Hz。研究从电脉冲对位错增殖和位错运动的影响角度出发,提出了电脉冲辅助塑性加工临界电流密度的概念,对声电耦合表面加工的内在作用机理做出了探索解释。本研究工作对以304不锈钢为代表的难加工金属材料的高效切削和表面强化处理具有一定的指导意义!
[Abstract]:In this study, the surface processing experiments of 304 stainless steel were carried out on a comprehensive experimental platform designed and constructed by means of electropulse-assisted turning and acousto-electric coupling (i.e. ultrasonic surface rolling and electric pulse coupling). The influence of electric pulse on the machinability of 304 stainless steel and the properties of surface strengthening layer by ultrasonic surface rolling were studied, and the corresponding mechanism was put forward to explain the effect of electric pulse on the machinability of 304 stainless steel. It is found that compared with ordinary turning, the main cutting force and axial surface roughness of 304 stainless steel turning can be significantly reduced by the electrical pulse with optimized parameters, and the working hardening can be reduced. The plastic deformation ability of the cutting zone is obviously enhanced, the rheological thickness of the turning metamorphic layer is increased, and the forming mode of chip is changed from the original shear plastic deformation to the peel tear. The wear pattern of the front tool face of the YG6X tool used in the experiment changed from mechanical wear to bonding wear, and the bonding wear increased with the increase of current density, the surface of the machined surface was slightly oxidized and the surface roughness and microhardness increased due to excessive electrical pulse. Deterioration of machined surface quality; under the experimental conditions of this study, The ideal parameters of electric pulse are as follows: RMS current density 1.28A / mm2, peak current density 9.15A / mm2, pulse frequency 600Hz.Study on matter wave theory introduced quantum mechanics and resonance selective friction energy fugacity theory of tribology for electric pulse assisted turning The internal mechanism of processing is explored and explained. It is found that compared with pure ultrasonic surface rolling, the microhardness and surface finish of surface strengthening layer of 304 stainless steel can be further improved by optimized electric pulse, compared with pure ultrasonic surface rolling. The friction and wear resistance of the strengthened layer was further improved, and the surface residual compressive stress was increased, the tensile strength of the material was enhanced, and the stacking fault energy of 304 stainless steel was increased by electric pulse. The plastic deformation mechanism is changed from deformation twinning to dislocation slip, and the number of deformation twins in the strengthening layer is greatly reduced, and the martensite content is increased, and the grain size is more refined. The resulting surface strengthening layer is a soft and hard inlaid structure formed by a small amount of soft austenite and a large number of hard martensite. But at the same time, it will increase the action depth of the surface strengthening layer. Under the experimental conditions of this study, the ideal parameters are as follows: root mean square current density 1.03A / mm2, peak current density 7.66A / mm2, pulse frequency 600Hz. From the point of view of the effect of electric pulse on dislocation proliferation and dislocation movement, the concept of critical current density in electrically pulsed assisted plastic machining is proposed, and the internal mechanism of acoustoelectric coupling surface machining is explored and explained. This study has certain guiding significance for high efficiency cutting and surface strengthening treatment of refractory metal material represented by 304 stainless steel.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG51;TG661
本文编号：2238547
[Abstract]:In this study, the surface processing experiments of 304 stainless steel were carried out on a comprehensive experimental platform designed and constructed by means of electropulse-assisted turning and acousto-electric coupling (i.e. ultrasonic surface rolling and electric pulse coupling). The influence of electric pulse on the machinability of 304 stainless steel and the properties of surface strengthening layer by ultrasonic surface rolling were studied, and the corresponding mechanism was put forward to explain the effect of electric pulse on the machinability of 304 stainless steel. It is found that compared with ordinary turning, the main cutting force and axial surface roughness of 304 stainless steel turning can be significantly reduced by the electrical pulse with optimized parameters, and the working hardening can be reduced. The plastic deformation ability of the cutting zone is obviously enhanced, the rheological thickness of the turning metamorphic layer is increased, and the forming mode of chip is changed from the original shear plastic deformation to the peel tear. The wear pattern of the front tool face of the YG6X tool used in the experiment changed from mechanical wear to bonding wear, and the bonding wear increased with the increase of current density, the surface of the machined surface was slightly oxidized and the surface roughness and microhardness increased due to excessive electrical pulse. Deterioration of machined surface quality; under the experimental conditions of this study, The ideal parameters of electric pulse are as follows: RMS current density 1.28A / mm2, peak current density 9.15A / mm2, pulse frequency 600Hz.Study on matter wave theory introduced quantum mechanics and resonance selective friction energy fugacity theory of tribology for electric pulse assisted turning The internal mechanism of processing is explored and explained. It is found that compared with pure ultrasonic surface rolling, the microhardness and surface finish of surface strengthening layer of 304 stainless steel can be further improved by optimized electric pulse, compared with pure ultrasonic surface rolling. The friction and wear resistance of the strengthened layer was further improved, and the surface residual compressive stress was increased, the tensile strength of the material was enhanced, and the stacking fault energy of 304 stainless steel was increased by electric pulse. The plastic deformation mechanism is changed from deformation twinning to dislocation slip, and the number of deformation twins in the strengthening layer is greatly reduced, and the martensite content is increased, and the grain size is more refined. The resulting surface strengthening layer is a soft and hard inlaid structure formed by a small amount of soft austenite and a large number of hard martensite. But at the same time, it will increase the action depth of the surface strengthening layer. Under the experimental conditions of this study, the ideal parameters are as follows: root mean square current density 1.03A / mm2, peak current density 7.66A / mm2, pulse frequency 600Hz. From the point of view of the effect of electric pulse on dislocation proliferation and dislocation movement, the concept of critical current density in electrically pulsed assisted plastic machining is proposed, and the internal mechanism of acoustoelectric coupling surface machining is explored and explained. This study has certain guiding significance for high efficiency cutting and surface strengthening treatment of refractory metal material represented by 304 stainless steel.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG51;TG661
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