AZ91镁合金管转角扩径分流挤压成形工艺分析及模具设计

Process analysis and die design of the expanding porthole extrusion process for AZ91 magnesium alloy tube angle

根据目前扩径挤压技术存在的问题,提出了一种新的镁合金管转角扩径分流挤压技术。扩径挤压的管材外径大于挤压坯料的外径,而传统的挤压管材外径小于挤压坯料外径。扩径分流挤压方法可实现小直径坯料挤压大口径管材,可降低挤压力以实现小吨位设备挤压大口径管材。还可利用转角剪切变形增加预焊合金属变形量,提高镁合金再结晶程度,提高生产效率,节约成本。设计了转角扩径分流挤压模具,并通过有限元法分析了AZ91镁合金扩径分流挤压成形过程。结果表明,整个挤压过程中金属流动顺畅,无折叠和充填不满等缺陷;通过控制工艺参数可控制温升在合理范围内,经过转角变形后等效应变达9.0左右,焊合室内焊合压力可达230 MPa,完全满足焊合要求;在所研究的参数范围内,焊合压力随着挤压速度的增加先增加后减小,随着挤压温度的增加焊合压力逐渐减小。

A new expanding porthole extrusion process for magnesium alloy tube angle is proposed based on the problems existing in the current expanding extrusion technology.The outer diameter of the expanded extruded tube is greater than the outer diameter of the extruded billet,while the outer diameter of the traditionally extruded tube is smaller than the outer diameter of the extruded billet.The expanding porthole extrusion can achieve the extrusion of large-diameter tubes from small diameter billets,and can reduce the extrusion pressure to achieve the extrusion of large-diameter tubes with small equipment tonnage.Angle shear deformation can also be used to increase the deformation of pre-welded metal,the recrystallization degree of magnesium alloy,the production and efficiency cost.We designed an angle expanding porthole extrusion die,and analyzed the forming process of AZ91 magnesium alloy through finite element method.The results show that the metal flow was smooth throughout the entire extrusion process,without defects such as folding or insufficient filling.By controlling the process,the temperature rise can be achieved within a reasonable range.After angle deformation,the equivalent strain can reach around 9.0,and the welding pressure in the welding chamber can reach 230 MPa,fully meeting the welding requirements.Within the studied parameter range,the welding pressure first increases and then decreases with the increase of extrusion speed,and gradually decreases with the increase of extrusion temperature.