钢管斜轧穿孔过程的三维有限元数值模拟及分析

本文以某厂狄舍尔(D iescher)穿孔机为研究对象,应用DEFORM-3D非线性有限元分析软件对实心圆坯二辊斜轧穿孔过程进行了三维热力耦合数值模拟,通过分析圆坯的应力应变场和温度场及顶头穿孔过程中的温度场分布特征,得出管坯最大应力、应变、温度最高处位于管坯与轧辊、导盘接触区。顶头轴向温度梯度明显,头部温度最高。为改善顶头的工作环境和提高其使用寿命提供了理论依据。     

高温合金圆坯穿孔时力和变形参数的测定

φ30mm二辊斜轧穿孔机使用高温合金圆坯穿孔,在不同加热温度、轧辊转速、辊面角和前进角条件下,测定了轧辊入口锥和出口锥轧制力、顶头的轴向力、穿孔时间和坯料扭转变形程度。     

AZ31镁合金无缝管斜轧穿孔新工艺研究

为了解决镁合金无缝管难加工问题,研究了AZ31镁合金斜轧穿孔制备管坯新工艺。根据镁合金热加工本构关系确定加工温度和应变率范围为300~450℃、0.001~1 s~(-1),根据斜轧理论与现有的三辊斜轧设备初步确定工艺参数,对Φ40 mm×300 mm镁合金棒材进行穿孔过程热力耦合数值模拟及实验研究,取穿后毛管试样进行金相分析。结果表明:采用斜轧穿孔方式完全可以制备AZ31镁合金无缝管;在400℃下,选择合适的顶头前伸量、送进角、轧辊转速、孔喉直径能够顺利穿制Φ40 mm×5.5 mm×615 mm镁合金毛管;轧后组织成等轴状均匀分布且晶粒明显细化,达到3μm,相应力学性能得到改善。此工艺可代替传统挤压工序生产无缝镁合金管,提高生产效率、降低成本,便于后续成品管的生产。     

AZ31镁合金无缝管斜轧穿孔数值模拟

提出采用三辊斜轧穿孔方法制备镁合金无缝管,基于AZ31镁合金塑性变形特点和斜轧穿孔成形原理分析,建立AZ31镁合金的力学模型,设定AZ31镁合金斜轧穿孔的工艺和模具参数。利用Deform-3D有限元分析软件对AZ31镁合金在300~400℃温度范围内进行斜轧穿孔数值模拟,得到各个成形阶段坯料的等效应力分布和金属流动速度矢量图。模拟结果表明在350℃、0.01 s-1变形条件下,AZ31镁合金斜轧穿孔保持稳定轧制。根据模拟结果进行试验验证,结果表明在此工艺条件下斜轧穿孔后的AZ31镁合金管力学性能良好,验证了斜轧穿孔制备镁合金无缝管的可行性和有效性,为镁合金无缝管新的生产方法提供理论依据。     

镍基高温合金锥筒形件拉深旋压成形机理研究

针对镍基高温合金因加工硬化严重成形时极易产生破裂和起皱等典型缺陷的问题,以锥筒形壳体类零件为对象,提出了一种由锥形预制坯经过真空固溶处理后拉深旋压成形锥筒形件的方法,并对其成形机理进行了研究。基于Abaqus/Explicit平台,建立了锥筒形件拉深旋压有限元模型,分析了成形过程中的瞬态等效应力、等效塑性应变、切向应力、壁厚及三向应变分布规律。结果表明:在旋压成形过程中,最大瞬态等效应力位于旋轮接触区及附近区域、最大瞬态等效塑性应变位于坯料口部;瞬态切向压应力最大值位于旋轮接触区,而瞬态切向拉应力最大值位于旋轮接触区附近的两侧区域。筒形段中部壁厚减薄,而坯料口部壁厚增厚。旋压成形试验表明,锥形预制坯经拉深旋压后可获得壁厚均匀的锥筒形件。     

大扩径斜轧穿孔过程的热-力耦合分析

采用自行设计的五段式扩径顶头的大扩径斜轧穿孔工艺,将实心圆管坯一次穿制成大口径空心毛管,可以将扩径率提高至70%,突破了锥形辊穿孔扩径率30%的极限,大大减少能源消耗,提高金属成材率,减少管坯规格,显著降低大口径热轧无缝钢管的生产成本。本文借助于有限元分析软件Simufact对大扩径斜轧穿孔过程进行三维热力耦合模拟,分析大扩径斜轧穿孔过程中的应力/应变状态、力能参数、运动学参数、温度分布、以及大口径毛管的尺寸精度等,为大扩径斜轧穿孔的工具设计及调整参数优化提供科学依据。     

基于加工图的新型钛合金斜轧穿孔温度预测

采用GLeeble-3500热模拟机对新型海洋用钛合金Ti80进行压缩试验,研究了该合金流动应力在不同变形参数下的变化,并建立了高温本构方程和热加工图。由加工图中优化出的高功率耗散安全区,初步判断斜轧穿孔法制备Ti80合金无缝管坯时的棒料初始温度；并由有限元模拟及物理实验予以验证。结果表明：在同一应变速率下,Ti80合金流动应力对温度的敏感程度不同,在两相区变形,流变应力会随温度的降低而急剧增大；在单相区变形,流动应力则相差不大。建立的应变补偿型Arrhenius双曲正弦函数,经验证能够准确预测流动应力的变化。所绘热加工图明确指出了Ti80合金热塑性成型时两个优化的工艺窗口：一是在两相区低应变速率,即925-975℃/0.01-0.1s_-1附近；二是在单相区中等应变率,即1050-1100℃/0.1-1s_-1附近。进一步对棒料初始温度在950、1050和1100℃条件下的斜轧穿孔过程进行三维热力耦合有限元模拟,发现950℃穿孔时顶头轴向力会激增为单相区穿孔时的5-6倍,从而导致扎卡；而单相区穿孔均能顺利进行。为降低能耗,最终确定棒料初始温度1050℃为最优穿孔温度,并且在狄舍尔斜轧穿孔机上一火次成功试制出Ti80合金无缝管坯。     

Ti-6Al-4V合金多道次热轧过程有限元模拟与实验

采用热力耦合方法对Ti-6Al-4V合金进行了多道次热轧模拟,研究了不同道次温度和等效塑性应变的分布特点。模拟结果表明,轧制过程表面温度低于心部的温度,随轧制道次的增加,表面温度整体表现为降低过程,中心温度整体表现为先升高后降低过程。中心位置比表面位置的等效塑性应变大,表面位置与中心位置的等效塑性应变均随变形道次的增加而增大。结果表明,随着轧制道次的增加,中心显微组织变形大于表面。中心区域组织易于发生动态球化。     

文摘

<正> 采用曼内斯曼穿孔机穿孔,毛管内表面产生有呈螺旋分布的半圆环状裂纹,严重影响成材率和生产率的提高。对此,日本川崎制铁公司钢铁研究所对裂纹缺陷产生机理进行了模拟试验,试验采用焊接热循环试验,使用SUS 316L不锈钢管坯。当压缩率为90％、加热温度高于1300℃时,金属塑性处于零塑性区。毛管穿孔采用的是简化二次元对称轴热传导解析模型,模拟出材料、轧辊、顶头温度曲线。当毛管内表面温度超过1300℃以上时,毛管内表面产生裂纹,这种裂纹属于晶间裂纹。     

钛合金环件径轴向轧制过程温度场模拟与分析

用Deform-3D有限元软件对钛合金环件轧制成形过程进行了模拟,分析了环件成形过程中的温度分布规律.结果表明:高温区在中心,低温区在外表面;由于受轴向轧制力的影响,较高的温度出现在端面.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.