Zn-Al合金热型连铸定向凝固的晶体生长机理

对热型连铸条件下Ｚｎ－Ａｌ系列合金引锭时的晶体形核和随后的多晶体的竞争生长过程进行了探讨.组织观察表明：单向热流条件下引锭端部生核的晶粒当其枝晶择优生长方向与热流方向一致时才能生长，其它取向的晶粒逐渐被淘汰．合金的凝固特性对选晶过程有极大的影响． ＺＡ５和 ＺＡ８合金由于凝固范围窄，晶体直接由引锭端部的晶粒通过竞争生长获得往状晶组织ＺＡ１２， ＺＡ２２和 ＺＡ２７含 Ａｌ量高．凝固范围宽，其平行柱状晶组织是从引锭端部的等轴晶区发展而来的·

水平连铸机的现状和发展(续四)

4.2 连铸工艺 4.2.1 拉坯参数的确定在水平连铸中,结晶器振动式铸机采用的是在线连续式拉坯制度,而结晶器固定式铸机采用的是拉—停、拉—推、拉—推—停、拉—停—推或拉—停—推—停的间隙式拉坯制度。因后者更为普遍,故这里主要讨论结晶器固定式铸机的拉坯参数。水平连铸拉坯参数中有三个最基本的量:拉坯频率、推(停)拉时间比和反推量。 4.2.1.1 拉坯频率对于不同的水平连铸机。

浅谈连续铸造行业熔炼浇注过程的自动化

近年来国家对绿色制造、智能制造越来越重视,铸造行业也跟随国家的步伐,进行了深入的改革,但是在连续铸造行业中从熔炼炉到保温炉的铁水转运过程一直无法实现自动化,大大制约了行业的发展。本文阐述了一种基于自流槽的铁水转运系统,自流槽的铁水转运系统通过熔炼炉与保温炉高低错位布置,实现了铁水从熔炼炉到保温炉以自流形式转运的功能,为连续铸铁行业的铁水转运提供借鉴。

Effect of ultrasonic power and casting speed on solidification structure of 7050 aluminum alloy ingot in ultrasonic field

With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting speed on solidification structure in ultrasonic field were also analyzed. The experiment and simulation results show that the solidification structure of the ingot is homogeneously distributed, and its grain size is obviously refined at ultrasonic power of 240 W. The average grain sizes, which can be seen from the Leica microscope, are less than 100 μm. When the casting speed is 45-50 mm/min, the best grain refinement is obtained.

Numerical simulation of solidification morphologies of Cu-0.6Cr casting alloy using modified cellular automaton model

The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental results.In numerical simulation aspect, finite difference(FD)method and modified cellular automaton(MCA)model were used to simulate the macro-temperature field, micro-concentration field,nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting operations.From the observed casting experiment,the preliminary grain morphologies are the directional columnar grains by the VCC process.The solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.

Solidification of Be-free Ni-based dental alloy

A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuouscasting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy startedwith the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent：FCC-γ＋G-phase, which replaced the low-melting eutectic （FCC-γ＋NiBe） in the Be-bearing alloys. AlNi6Si3 and γ′ formed during theterminal stages of solidification by investment casting, while the formation of AlNi6Si3 was suppressed by continuous casting. TheScheil solidification model agreed very well with the experimental results.

Microstructure and mechanical properties of AZ31 alloy ingot fabricated by semi-continuous casting

The AZ31 alloy ingot with diameter of 110 mm and length of 3500 mm was fabricated successfully. The compositions and microstructure morphologies of the ingot at different locations were performed, which indicated that the chemical composition distributed homogeneously through the whole alloy ingot and the average grain size increased from the surface to the center. The results of the EDS and element face-scanning illustrated that the eutectic compounds mainly consisted of fl-Mg17Al12 and a small amount of fl-Mgl7（AlZn）12. Furthermore, slight improvements of the strength and ductility were observed from the center to the surface along the axial direction of the alloy ingot, while both the strength and elongation to failure of the samples along the radial direction are higher than that along the axial direction. The fine grain strengthening was the main contributors to the strength of the as-casted AZ31 alloy.

Effect of high-intensity ultrasonic field on process of semi-continuous casting for AZ80 magnesium alloy billets

Under the high-intensity ultrasonic field,AZ80 magnesium alloy was semi-continuously cast.The effects of ultrasonic intensity on the as-cast microstructures and mechanical properties were investigated.The results show that the microstructures of the alloy cast under high-intensity ultrasonic field are fine and uniform,and the grains are equiaxed,rose-shaped or globular with an average size of 257μm.High-intensity field significantly decreases the grain size,changes the morphologies of theβ-Mg17Al12 phases and reduces their area fraction.It is also shown that a proper increase in ultrasonic intensity is helpful to obtain fine,uniform and equiaxed as-cast microstructures.The optimum ultrasonic parameters are that frequency is 20 kHz and ultrasonic intensity is 1 368 W.The mechanical tests show that the mechanical properties of the as-cast AZ80 magnesium alloy billets cast under ultrasonic field are greatly improved,and with increasing the ultrasonic intensity,the mechanical properties of the entire alloy billets are much higher and more uniform than those of the alloy without ultrasonic field.

Rheological behavior of continuous roll casting process of aluminum alloy

The rheological behavior of aluminum alloy and its influencing factors in physical simulation of continuous roll casting process were studied by using a Gleeble-1500 thermal-mechanical simulation tester with a set of special clamp system. The relationships between the flow stress and the strain rate in the deformation process of simulating roll casting experiment were obtained. The results show that four different characteristic stages exist in the temperature range of the whole rheological process. The first occurs when the temperature is higher than 600 ℃, which belongs to the creep deformation stage; the second occurs when the temperature lies in the range of 500600 ℃, and it can be regarded as the high temperature and low stress level deformation stage; the third occurs when the temperature decreases to the range of 300500 ℃, it is considered to be the middle stress level deformation stage; the last occurs when the temperature is less than 300 ℃ and the strain rate is less than 1.00 s -1, it belongs to middle stress level deformation stage. But when the strain rate is larger than 1.00 s -1,it belongs to the high stress level deformation stage. And the relative constitutive models suitable for the four different stages of continuous roll casting process were established through multivariate linear regression analysis of the experimental data.

Increasing Production Efficiency through Casting Quality Improving by Electromagnetic Field Applying

The increased production efficiency of heat treatable A1 alloys, as the result of applied electromagnetic field during continuous casting process was investigated. The applied frequency of the electromagnetic field （EMF） during the AI alloys continuous casting was changing from 30 Hz to 50 Hz, while some castings were obtained without the EMF influence. The mechanical characterization of continuous casted AI alloys EN AW 2007 and En AW 2024 was done on testing machine Zwick/Roell Z 100. The microstructure of as-cast samples was examined, as well. When the frequency decreases （from 50 Hz to 30 Hz）, the grain size decreases as well, what is noticeable through the finer microstructure and its uniformity throughout the cross-section. These results have shown that low frequency electromagnetic field significantly influenced the microstructure and therefore the mechanical properties of as cast ingots. Thus, through improved castings quality, operation time and energy savings, the production efficiency was increased.

连续铸铁型材的应用与发展

随着铸铁型材的应用领域不断扩大,连续铸铁型材技术和装备日臻完善。铸铁型材连续铸造主要分为水平连续铸造型材和垂直连续铸铁空心型材两类,本文综述连续铸铁型材生产方式及特点的基础上,总结了铸铁型材的应用方向和发展趋势,对发挥铸铁型材优势,从而提高我国装备制造业水平作出展望。