铸造镁合金中微孔对其组织和力学性能的影响

利用镁液定量测氢方法和定量金相技术,研究了镁合金中含氢量、试样厚度和除气方式对微孔的影响。结果表明,熔剂保护下熔炼的镁液含氢量比气体保护下的要高,相应的微孔也多;同一含氢量下随铸件厚度增加,微孔增多;在熔剂保护下Ar气除气后铸件微孔明显减少。力学性能试验表明,镁液在熔剂保护下熔炼并利用Ar气除气,铸件抗拉强度比不除气时提高了21%,伸长率提高了50%。     

超声振动对半固态铝合金浆料含气量的影响

在不同的温度以及不同的初始含氢量下对A356铝合金熔体实施超声振动,通过定量测氢仪直接测定含氢量,研究了超声振动在制备半固态A356浆料时对熔体含气量的影响及除气效果。结果表明,对A356液相线温度(615℃)以下20℃以内的半固态浆料,超声振动具有除气作用,最大除气率达15%左右。初始含氢量低时,半固态熔体的超声除气效率降低。熔体氩气除气结合半固态超声振动除气效果最好,含氢量可降至0.12cm3/100gAl以下。对在常压下制备的液态及半固态浆料凝固试样,气缩孔率随熔体含氢量的降低而减小,试样密度随含氢量的降低而增大。     

不同熔炼方法对Mg-Nd-Zn-Zr熔体品质影响

采用熔剂法(熔剂保护和熔剂精炼)和气体法(气体保护和气体精炼)两种熔炼方法制备Mg-Nd-Zn-Zr合金熔体,对Zr合金化阶段及最终熔炼效果进行对比研究。结果表明,熔剂法和气体法均能得到成分合格的镁熔体。两种方法都可以实现良好的晶粒细化效果,但气体法制备的镁熔体试样的晶粒比熔剂法更为细小。气体法与熔剂法均能有效保护熔体及降低镁熔体中夹杂,但与气体法相比,熔剂法对夹杂的控制效果更好。     

镁合金熔液含氢量的炉前快速检测研究

在提出了镁熔体含氢量测定的数学模型的基础上,采用微型计算机及控制电路,开发出适合于炉前使用的镁合金熔液快速测氢系统。利用该装置,对AZ91镁合金熔液进行了含氢量的炉前快速检测试验研究。结果表明,AZ91镁合金熔液在气体保护熔炼条件下,每100g镁熔液含氢量在6~14cm3范围内,并随温度的增加而提高。     

氮气和熔剂联合净化铝熔体

研究了SDJ 1型熔剂与氮气联合净化铝合金熔体的效果 ,并对熔剂净化机理以及FI法 (Fluxinjection)净化优势进行了探讨 ,揭示了除气过程中气体与熔剂的相互作用。结果表明 :采用FI联合精炼工艺 ,在适当的温度 (72 0℃ )和熔剂加入量 (0 .15 %SDJ 1)条件下 ,联合精炼工艺的除气效果远远优于生产中常用的氮气吹气法和熔剂法 ,联合净化法的优势在于提高了吸附能力以及加入具有固氢作用的降渣剂。FI工艺原理为 :气体与熔剂在熔体中均匀分布、密切接触 ,气体使熔剂快速上浮 ,熔剂的存在提供多而窄的通道 ,使氢容易聚集在通道附近 ,即使氢含量较低时 ,氮气仍能发挥作用 ,通道的存在有利于分散和离解气泡。     

镁合金精炼用新熔剂的研究

一、前言镁及其合金是一种极易氧化的金属,特别是在熔融状态下更易氧化燃烧,为了减少烧损,安全生产和保证金属内部纯洁度,在整个熔铸过程中需要用气体或熔剂加以保护。目前变形镁合金铸锭的生产是用粉状的二号熔剂作熔体表面的复盖保护。二号熔剂加10％(或15％)氟化钙制成粉状或块状作为镁合金熔体的精炼熔剂。铸造时用二氧化硫气体保护。二号熔剂主要成分为氯盐。氯盐熔剂的采用除对熔体起保护作用防止氧化燃烧外,还兼有精炼除渣、除气的作用。然     

旋转喷吹氩气在Al-Si合金熔体净化中的应用

对ZL101熔体分别采用熔剂处理、旋转喷吹氩气处理,检测处理前后的含氢量。将未净化及采用两种不同工艺处理的ZL101熔体分别浇注砂型、金属型铸件,对比两种处理方法对铸件针孔度的影响。结果表明,旋转喷吹氩气的除气效果明显优于熔剂处理;旋转喷吹氩气后,不论是砂型还是金属型,铸件针孔度都可达到一级。     

预热惰性气体对铝熔体除气效果的影响

为了充分发挥惰性气体对铝熔体的除气效果而又避免环境污染,提出预热惰性气体除气的新思路,设计简易预热装置,提高惰性气体气泡的入液温度。除气试验结果表明,在相同的熔炼条件下,预热惰性气体除气法可产生细小弥散的入液"热气泡",气泡不易长大且延长了气泡溢出液面的时间,当静置时间为20 min时,熔体含氢量可低至0.15 mL/(100 g Al),除气效果优于常规低温气体除气法的,是一种有效的环保型物理除气新工艺。     

一种配制不同含氢量铝合金熔体装置研制

氢是唯一大量溶于铝熔体的有害气体,极易使铸件产生气孔等缺陷。为提高铝合金铸件的质量,铝熔体的除气和炉前检测是必不可少的。在评价除气效果或测氢精度时,需提供全量程内不同氢含量铝熔体作为样本。基于此,研制出用于配置不同含氢量的铝合金熔体装置,介绍了装置的原理、组成及不同含氢量铝熔体的配制试验结果。     

吹入气体和熔剂混合物精炼铝合金

为了精炼铝合金采用各种方法:用惰性气体吹洗熔体、用熔剂进行处理及其他方法。此时,用一种方法除气效果不错,但从金属中清除氧化物颗粒效果较差(吹气法)或者与此相反(熔剂处理法)。吹入惰性气体时,熔体除气速度慢,只好增加吹气时间和增多气体耗量。通常采用的气体(氮、氩)含有一定量的氧和水蒸气,它们活泼地氧化铝熔体,在气泡表面     

Influence of hydrogen levels on porosity and mechanical properties of Mg alloy castings

Abstract

The effects of hydrogen levels on microstructure of porosity and mechanical properties of magnesium alloy castings were investigated. The hydrogen content of AZ91 alloy melt under Ar+HFC-134a mixed gas protection was 103 cm³ kg^?1, which was less than that of 139 cm³ kg^?1 under flux protection, therefore the effect of gas protection was better. The porosity ratio in microstructure of castings melted under gas protection was 1˙8%, which was also less than that of 2˙6% under flux protection. The hydrogen content of melt under flux protection and degassed with Ar gas was 70 cm³ kg^?1, and the corresponding porosity ratio in microstructure of castings was only 0˙6%. The density of the samples was increased with decreasing hydrogen content. The tensile strength of AZ91 alloy casting sample under flux protection and degassed with Ar gas was 21% higher than that of undegassed one, and the elongation was also 50% higher.     

镁合金中的氢及其除气方法

由于镁合金回炉料的回用增多,镁合金铸造方法多元化以及AZ91镁合金对显微气孔的敏感性,都要求镁合金熔炼时进行除气处理,但当前对镁合金中除气方法研究甚少.本文论述了镁合金中氢的来源及其机理,介绍了镁合金中几种除气方法,并对这些方法进行了评价和展望.     

The effects of purge gases on the hydrogen content and mechanical properties of spray-degassed Al

Spray degassing was used to remove hydrogen dissolved in aluminum melt. In order to investigate the effects of different purge gases on aluminum melt during spray degassing, different kinds of purge gases were used in experiments. The results show that, as a purge gas in the process of spray degassing, nitrogen leads in increasing the hydrogen content and inclusion content of the aluminum melt. The mechanical properties of the specimens are very poor.     

Protection behavior of fluorine-containing cover gases on molten magnesium alloys

The sulphur hexa-fluoride gas（SF6）, which is commonly used as the cover gas of molten magnesium alloys in the magnesium industry today, has an extremely high global warming potential（GWP）. The protection mechanism of SF6 containing cover gases on molten magnesium alloys was presented. The cover gas protects the melt by reacting with the melt to form a coherent protective film on the melt surface. The film contains MgO and MgF2. Particles containing MgF2 form on the interface between the oxide film and the bulk magnesium alloy, which correspond to the concave areas from the surface observation. These particles increase the Pilling and Bedworth ratio of surface film and enhance the protective capability of the films. Based on the understanding of the mechanism of SF6, a melting technology in a sealed furnace was proposed, and the protection behavior of magnesium alloys in the sealed melting furnace was investigated under the protective atmosphere containing HFC-134a. The morphology and composition of the surface film were also studied. Experiments to evaluate the protective effect of two other fluorine containing gases with low GWPs on AZglD alloy in the sealed furnace were also carried out, and the results show that the new gases are potential substitutes for SF6.     

Purification of scrap aluminum foil and aluminum melt covering and protecting & atomic purification theory

1　INTRODUCTIONTherecycleofaluminumscrapshasbeengivenimportanceby governmentsandresearchersallovertheworldforenvironmentprotecting ,energysavingandresourcesregenerating .Aluminumfoilisoneofthemostextensivelyusedaluminumproductsandtheoutputofthescrapaluminumfoilreachesmorethanonemilliontons .Therearemuch greasydirtandmanyoxidesonthesurfaceofthescrapaluminumfoil.Becauseofthehighproductioncostofaluminumfoil,propermethodshouldbeadoptedtopurifyscrapaluminumfoilsoastoavoidenergywasteandcostin c…     

镁合金铸造技术进展

综述了近年来国外在镁合金熔炼气体保护方法、熔炼炉设计和铸造工艺方法方面的最新研究成果。     

Degassing effect of ultrasonic vibration in molten melt and semi-solid slurry of Al-Si alloys

In the process of semi-solid slurry preparation with direct ultrasonic vibration (UV) by dipping the horn into the melt, one of the questions is whether the gas content in the melt would be increased or not by the cavitation effect of ultrasonic vibration. By application of quantitative gas content measurement technique, this paper investigated the effect of the ultrasonic vibration on the gas content of both the melt and the semi-solid slurry of Al-Si alloys, and the variations of the gas contents in two kinds of aluminum alloys, i.e., A356 alloy and Al-20Si-2Cu-1Ni-0.6RE alloy (Al-20Si for short). The results show that ultrasonic vibration has an obvious degassing effect on the molten melt, especially on the semi-solid slurry of Al-Si alloy which is below the liquidus temperature by less than 20 ℃. The ultrasonic degassing efficiency of the A356 alloy decreases with the reduction of the initial gas content in the melt, and it is nearly unchanged for the Al-20Si alloy. The gas content of both alloys decreases when the ultrasonic vibration time is increased. The best vibration time for Al-20Si alloy at the liquid temperature of 710 ℃ and semi-solid temperature of 680 ℃ is 60 s and 90 s, respectively; and the degassing efficiency is 48% and 35%, respectively. The mechanism of ultrasonic degassing effect is discussed.     

Al-Si-Mg系铝合金熔体吸氢热力学研究

通过建立铝合金熔体吸氢的热力学过程模型,分析了影响Al-Si-Mg系铝合金熔体吸氢的热力学因素。结果表明,降低空气湿度、熔炼温度、压力有利于降低铝液吸氢速率;Si、Mg含量与空气/铝液界面处的氢含量成线性关系,提高Si含量、降低Mg含量有利于降低空气/铝液界面处的氢含量,从而降低铝液的吸氢速率。