基于感应加热的无孔型轧制数值模拟探讨

采用有限元分析软件模拟了高速线材生产中铸坯感应加热过程和粗轧无孔型轧制1~3道次的热连轧过程。计算并分析了感应加热过程温度的变化,分析了轧制过程中轧制力、等效应变和温度的变化。计算结果表明,当铸坯表面温度在950~1 100℃范围内时,表面温度越低,粗轧过程中铸坯断面变形相越均匀,变形更易渗透到铸坯中心位置。     

钛合金无缝管热连轧温度场模拟

采用有限元法分析了钛合金无缝管多机架连轧下的温度状态。模拟结果表明：随轧制道次的增加,辊底下的外表面温度以逐渐减缓的速率降低,中心温度整体上以逐渐减缓的速率上升,而辊缝下外表面温度持续升高。中心温度的周向不均匀性在奇数道次时减小,在偶数道次时增大,而外表面温度分布的不均匀性与此相反。前一机架压下量与后机架辊缝处温升呈负相关,降低前一机架压下量可显著提升后机架周向温度不均匀性。温度测量和晶粒形貌分析的结果表明,模拟结果与实验结果吻合度较高。     

基于二次开发的AZ31镁合金热轧有限元模拟和实验研究

利用ABAQUS提供给用户自定义材料本构模型的Fortran程序接口,对AZ31镁合金进行了材料模型的二次开发,编写了自定义的用户材料子程序(UMAT),并对AZ31镁合金热轧过程进行了有限元数值模拟。主要研究了初始轧件温度为673 K,不同压下率的条件下,板材变形区内厚度方向的温度和应变场的变化情况。数值模拟结果表明:板材在变形区内表面附近和中心位置的温度变化情况不同。随轧制的进行,表面温度先是骤降,然后有小幅度的上升;板材心部温度先是有小幅度的升高,然后大幅度的下降,表面和中心温差在30~40 K之间。板材近表面的应变高于中心层,随压下率的增加应变逐渐增加。微观组织观察结果表明:板材近表面的较大应变导致动态再结晶程度明显高于中心位置。     

5052铝合金板材热轧过程塑性变形及应力分布的三维热力耦合模拟

对5052铝合金板材热轧过程进行了三维热力耦合模拟,综合考虑热轧过程中轧制速度、变形温度、道次压下量和摩擦系数等因素对热轧过程中轧件变形区内塑性变形和应力分布的影响,建立了多参数的热力耦合热轧模型。结果表明,在轧件变形区内,因加工硬化与动态软化的综合作用,其流变应力呈典型的动态再结晶特征。在变形区内轧件表面因金属流动剧烈,其等效塑性应变和应变速率远远大于轧件心部,塑性变形显著。轧制速度是轧件温度场分布最重要的影响因素之一,轧制速度越大,轧件的温升就越高;而温度是影响等效应力大小的主要因素,温度升高和应变速率降低都使得流变应力降低。     

阳极板多道次辊弯成形过程数值模拟

利用有限元软件MAC.MARC,根据按辊弯成形工艺建立的辊花图,对阳极板多道次辊弯成形过程进行了数值模拟。基于动力显示算法,采用刚性辊轮沿板材长度方向运动的方式建立了阳极板多道次辊弯成形有限元模型。分析了成形过程中阳极板的Y向位移、等效应力与等效塑性应变的变化,重点研究了板材成形时等效塑性应变在弯曲角处的变化。结果表明,等效塑性应变的极值主要出现在当前道次所成形的弯曲角位置,且随成形弯曲角度的增大而增大。     

GH4169异型材单轧槽轧制工艺

采用轧制工艺生产GH4169合金异型材,结合实验条件,基于有限元模拟软件建立了单轧槽少道次轧制过程的三维刚塑性有限元模型。采用异型坯作为坯料,分析了轧制过程中孔型充满度、变形温度、等效应变和等效应力的分布情况。模拟结果表明,采用Φ160 mm×200 mm轧机时,初轧温度为1070℃,断面收缩率为45%,单轧槽两道次轧制成形,孔型充满度良好,等效应变约为0.3~1.4。结合模拟结果,在轧机上进行了热轧实验,轧件厚度满足尺寸要求,宽度比成品小2 mm,没有发生晶粒细化。这主要是由于多火次、多次数轧制,使得加热引起的晶粒长大程度大于小变形量引起的晶粒细化程度,使得晶粒未细化,宽度不够。     

重轨BD2异形孔型可逆轧制过程的有限元模拟分析

通过翻转和平移轧辊的方法来实现轧件翻钢和侧向推钢过程,并通过给轧件加载一个加速度来实现可逆轧制,在此基础上对60 kg·m-1的U71Mn钢重轨轧制BD2异形孔可逆轧制过程进行了三维热力耦合有限元模拟,分析了轧件在各道次轧件横断面等效应变分布、温度场变化以及轧制力数据。结果表明:轧件的中心存在一个较大的低变形区域,并且随着轧制进行被分隔成两个部分,最终在轨头以及轨底的中心位置形成两个低变形区域,这种变形规律不利于铸坯心部缺陷的修复,轧件内部最高温度出现在轧件心部到表面的中间位置。温度和及轧制力的实测值与模拟值吻合良好,验证了模型的有效性。     

热连轧带钢立-平辊多道次轧制热力耦合三维有限元模拟

对热连轧Q345B窄带钢精轧立-平辊多道次轧制进行了三维热力耦合有限元模拟,分析了轧制过程中轧件温度场、等效应力-应变场及轧件表面特征点流动规律。结果表明,模拟计算的带钢断面中心点温度及平轧各道次稳态轧制压力与实测值吻合良好;宽度方向轧件边、角部与中心温差较大是导致边部金属应变不协调,上翻至带钢边部表面的主要原因;轧件角、边部由于冷缩效应存在一定拉应力,会影响轧件角部缺陷的愈合或扩展;采用立辊侧压调宽对轧件边部减薄和翻平宽展可能造成的边部缺陷有明显的改善作用。表面节点位置变化规律可为现场轧制生产中轧件边部缺陷的溯源分析提供便利。     

Ⅰ型扁钢轧制工艺优化

应用MSC.Marc软件建立了Ⅰ型扁钢4道次连续轧制过程中的三维有限元模型。以坯料30 mm×6 mm、成品25 mm×5 mm×3 mm的Ⅰ型扁钢热轧过程为例,研究了该轧件在不同轧制温度和轧制速度下的等效应力、等效塑性应变以及轧制压力的变化规律。结果表明,当初轧温度1150℃、终轧速度1.1m/s时轧制压力较低且较平稳,轧件的等效应力、等效塑性应变分布比较均匀,可以有效地改善产品质量。     

工艺路线对等径角挤压变形均匀性的影响

等径角挤压被认为是制备块体超细晶材料最有前景的工艺方法之一.采用刚塑性有限元法分析了不同路线多道次等径角挤压后的等效应变分布.结果表明:一道次等径角挤压后坯料中间主要变形区下部坯料的等效应变较低.A路线多道次挤压后,变形更加不均匀,上下表面的等效应变差值增大;C路线挤压后等效应变分布呈上下表面小,中间较高的分布特征,且随挤压次数的增加,中心和上下表面的等效应变差异增大.B_c路线多次挤压后的等效应变分布较均匀,等效应变较高的区域应变相差较小且所占区域较大.模拟结果对于等径角挤压工艺的制定可起到指导作用.     

I型扁钢轧制过程数值模拟

本文I型扁钢的生产坯料为钢带经卸卷、分条轧制后的窄钢条。采用有限元软件Msc.Marc建立了规格为25 mm×5 mm×3 mm的Q235 I型扁钢4道次热连轧的弹塑性有限元模型,研究了轧件在轧制过程中的变形情况、等效应力、等效塑性应变的变化规律。结果表明：轧件在立轧道次会出现轻微的狗骨形,平轧道次会出现轻微的单鼓形;轧件横断面的中间部位等效塑性应变较大;轧件边角部等效应力较大,轧制过程中易出现质量缺陷。     

Investigation and numerical analysis of strain distribution in the twist extrusion of pure aluminum

The effects of performing three twist extrusion passes on high purity aluminum samples were studied in this paper in regard to numerical analysis and experimental studies. The finite element analysis of the von-Mises stress and the equivalent plastic strain in the outer longitudinal and transverse cross-sections, which are parallel and normal to the billet axis respectively, was carried out. The simulation results showed that the end of the workpiece underwent more equivalent plastic strains in contrast to the head of the sample. Moreover, the corner regions experienced more strains than the center zone did. However, the heterogeneity in strain distribution in both longitudinal and transverse cross-sections decreased by performing the sequential twist extrusion passes. The experimental outcomes such as microstructure evolutions, microhardness and tensile tests validated the simulation results.     

大圆钢轧制三维塑性变形有限元模拟

使用ANSYS/LS-DYNA通用有限元分析软件对大圆钢轧制过程进行模拟仿真,得到了采用成品前单圆弧椭圆孔型的大圆钢轧制的等效应力场、等效应变场,分析了轧件横截面的等效应变和等效应力分布情况。成品前孔型改为双圆弧椭圆孔型后重新模拟轧制过程,根据模拟结果比较,得出采用成品前双圆弧椭圆孔型有利于改善成品道次的应力、应变分布。     

Research on continuous multi-point forming method for rotary surface

In order to realize high efficient and flexible manufacturing for 3-D surface, continuous multi-point forming (CMPF) is researched. Firstly, principle of CMPF is described, and its characteristics are analyzed by comparing with the conventional spinning methods. Secondly, FEA model of CMPF for disc-shape surface is established, forming load is analyzed theoretically, equivalent stress and plastic strain distributions of disc-shape surface are analyzed. Thirdly, wrinkling is analyzed through simulation results. Fourthly, forming process of tube-shape surface is studied. Finally, CMPF equipment is developed, and experiments are carried out. Results indicate: For disc-shape surface, equivalent stress in regions of center fixture and flexible roller exceeds yield stress; the maximum plastic strain is generated in center region; plastic strain in region of flexible roller takes the second place; shell elements in wrinkling region generate tangent direction compress deformation. For tube-shape surface, maximum value of equivalent stress appears in region of flexible roller; plastic strain field presents annular distribution, its maximum value appears in marginal region. Measure results of curvature radius of disc-shape surface and tube-shape surface almost accord with simulation results. Simulation results of stress field, strain field and wrinkling almost accord with practical situation.     

Microstructure and texture development of pure aluminum and aluminum alloy processed by high speed hot rolling

The microstructure and texture development of pure aluminum and aluminum alloy processed by high speed hot rolling are investigated. The aluminum sheets are rolled at temperatures ranging from 410°C to 560°C at a rolling speed of 15m/s without lubrication and quenched into water at an interval of 30 ms after rolling. The redundant shear strain induced by high friction increases beneath the surface at a reduction above 50% for Al alloy (AA5052) and above 60% for pure Al (AA1050). Dynamic recrystallization occurs in the surface region when the equivalent strain exceeds a critical value that depends on rolling temperature, while only recovery occurs in the center region. The critical equivalent strain for the occurrence of recrystallization in AA5052 is lower than that in AA1050. When the large strain is introduced beneath the surface, the shear texture, the main components of which are {001}<110> and {111}<110>, develops. In the center region, Cu-orientation and cube orientation develop. The shear texture beneath the surface is weak when recrystallization occurs.     

蛇形热轧中轧制参数对7075铝合金厚板变形分布的影响

介绍了蛇形轧制的实现方式。运用数值模拟方法,在Deform 3D上分析单道次轧制过程中蛇形轧制和对称轧制7075铝合金厚板的流动速度及应力应变分布情况,分析异速比、上下轧辊错位量和压下量对蛇形轧制变形区内轧板等效应变和剪切应变的影响规律。结果表明：蛇形轧制中,由于下辊速度快,轧板下层金属流动比上层快,蛇形轧制中轧板下层等效变形大于上层,且随着异速比的增大,上下层金属变形差距增大;对称轧制中厚板心部的剪切应变几乎为0,蛇形轧制中由于有“搓轧区”的存在,厚板心部的剪切应变远大于对称轧制的,且随着异速比的增加和错位量的增加,轧板心部的剪切变形增大。这种附加的剪切变形有利于使变形向厚板心部渗透,从而改善厚板高向变形的不均匀性。     

Nano-grained pure copper with high-strength and high-conductivity produced by equal channel angular rolling process

Equal channel angular rolling, based on the equal channel angular pressing, is a severe plastic deformation process which can develop the grains below 1 μm in diameter. Microstructure, mechanical properties and electrical conductivity of commercial pure copper strips processed by equal channel angular rolling were investigated. Scanning electron microscopic micrographs of the strips produced by ten passes of equal channel angular rolling process showed nano-grains ∼70-200 nm in size. Also yield and tensile strengths and microhardness of samples increased with increasing the number of passes, whereas their ductility decreased. The electrical conductivity varied slightly. So via equal channel angular rolling process and by producing nano-grained pure copper, the strips can be strengthened with a little decrease in electrical conductivity but it has shortcomings of low elongation and strain hardening.     

高速线材减定径轧制变形特点与热模拟参数研究

为分析高速线材减定径轧制的变形特点,利用有限元模拟方法研究了四道次减定径轧制过程。轧制产品规格为φ12 mm的圆钢,孔型系统为椭圆-圆-椭圆-圆。研究表明,四道次减定径轧制轧件最大累积等效塑性应变达1.890,最大温升达76.7℃,轧件平均变形速度大于429.4 s-1。限于热模拟条件的限制,仅能对减定径轧制轧件的变形程度进行准确模拟。