Device Design And Process Research Of Horizontal Continuous Casting For Magnesium Alloy Ingots

Magnesium alloy is one of the lightest metal structure materials in practical application,which is known as "21st century green engineering materials".The large-size magnesium alloy ingots are prepared by the vertical continuous casting method.This technique has a poor working environment.It is likely to cause secondary oxidation of the melt before casting,lowering the quality of the melt,poor surface quality of the ingot,large machining allowance,and high economic cost.So it does not meet environmental standards.In horizontal continuous casting,the holding furnace is sealed with the crystallizer.This technology uses the bottom pouring method to prevent secondary oxidation and inclusions well and reduce the oxide inclusions and other doping contents in the alloy.The ingot produced inside has less porosity and porosity.At the same time,the technology has high crystallization speed,good organization structure and high density;in addition,the heat conductivity of the mold is concentrated on the front end,and the cooling of the second cooling zone is uniform and the speed is fast,which makes the surface quality of the casting blank good.Therefore,it is of great practical significance to develop and research horizontal continuous casting technology for large size magnesium alloy round billet.Electromagnetic stirring technology,as a processing technology with no contact,good controllability,no pollution,etc.,is an important modification method in the grain refinement method,which can improve the uniformity of the solute field and temperature field in the melt.To ensure the uniformity of the internal organization.AZ31 magnesium alloy was selected as the research material.This article developed a horizontal continuous casting equipment and preparation process for Ф160mm diameter magnesium alloy ingots.The following conclusions can be drawn:(1)The horizontal continuous casting system for preparing large-diameter magnesium alloy round billets mainly includes designed and reformed smelting furnaces,crystallizers,electromagnetic stirring systems,cooling water systems,casting systems,lubrication protection systems,and atmosphere protection systems.The magnesium alloy smelting furnace independently designed in this experiment has been optimized and optimized by several columns.The smelting and liquid control system can be applied to the production of horizontal continuous casting.The requirements on the temperature at the gate are high.It is necessary to ensure that the magnesium alloy is in the molten state at the gate of the continuous casting.The setting of the lining can significantly improve the problem.(2)The magnesium alloy ingot prepared under the technological conditions of pouring temperature is 720 ℃,the preheating time of the dummy bar is 20 min,the casting speed is 50mm/min,and the drawing method is selected as a combination of pull and stop,first cooling water flow rate is 50L/min,and the second cooling water flow rate is 20L/min,ensuring the quality of the melt is good,has good surface quality and no defects such as loose shrinkage holes in the cross section.(3)There is a serious specific gravity segregation of solute elements in ordinary horizontal continuous casting,and it is extremely necessary to improve the solute distribution through electromagnetic stirring.Relative to the center position,the local segregation degree of Al and Zn elements in the round cross section obtained the minimum values at the top of the ingot,which were-2.2% and-3.6%,respectively,and the maximum at the bottom of the ingot was 40.7% and 59.0%.The overall grain size of the ingot is small but unevenly distributed.The average grain size at the bottom of the ingot is the smallest at 112μm.The middle part of the ingot is relatively coarse columnar crystals with an average grain size of 254μm.All of these need to be improved by electromagnetic stirring.