【作者】 帅美荣；

【导师】 黄庆学；

【作者基本信息】 太原科技大学 ， 机械设计及理论， 2012， 博士

【摘要】 钛及钛合金是20世纪90年代发展起来的一种新型金属材料，具有熔点高、比强度高、耐高温、抗腐蚀、无磁性、无毒等特点，广泛应用于航空航天、海洋船舶、生物工程、民生用品等领域。近年来，市场对小直径钛合金棒材产品需求量越来越大。然而，棒材生产工序复杂、产品尺寸精度低、成材率低、能源浪费严重。欲使其成为普及型金属，必须降低成本。因此，整合钛加工设备、开发可连续工业化生产的冶炼技术、开发低成本的钛合金品种是钛工业发展面临的重大课题。本课题来源于山西省青年科技研究项目，旨在开发钛合金棒材短流程、近终成型技术。采用三辊Y型轧机连轧生产小直径钛合金棒材省略了横列式轧制过程中重复加热（均热）、重复退火、重复修磨等工序；避免了二辊高速轧机连轧钛棒设备利用率低的弊端；同时，满足了钛合金棒材小批量、多品种的产品要求。但是由于钛合金塑性变形特性与钢、铝、铜等显著不同，尤其对于有强度要求和特殊后续加工特性要求的钛合金棒材，其孔型设计合理与否，直接影响产品的质量和成材率等。所以，本文采用有限元分析软件模拟了钛合金棒材八道次连轧过程；建立了适用于三辊轧制小直径钛合金棒材的孔型设计模型；并在自行研制的Y型轧机上进行试验。本文主要研究内容如下：（1）本文以TC4钛合金为研究对象，在GLEEBLE-1500热模拟机上进行压缩实验，深入研究了TC4钛合金的热塑性变形行为规律和流变应力。采用回归方法确定了钛合金高温塑性变形时峰值应力和稳态应力的本构关系，并考虑应变的影响，用指数型硬化函数和软化方程建立了TC4钛合金新型的流动应力方程。这些分析结果对研发塑性成型产品、优化生产工艺以及提高产品质量都具有非常重要的理论意义和实用价值。（2）考虑到平三角轧件在圆孔型中轧制稳定，且圆孔型可以生产不同直径的圆棒，选择“平三角-圆”孔型系统。运用ANSYS商用有限元模拟软件，结合本文建立的TC4钛合金本构关系，虚拟仿真了8机架Y型轧机连轧TC4钛合金棒材的全过程；分析了棒材在三辊孔型中纵向变形和横向宽展，横截面上不同区域金属的温度、等效应力、等效应变分布规律，以及各道次轧制力的变化趋势。在整个连轧过程中，轧件轧制平稳、变形均匀、没有出现“开裂”、“耳子”、“皱褶”等现象。（3）通过有限元模拟可知，钛合金棒材在三辊热连轧过程中，轧件在孔型中受到正反交替六个方向的压缩变形，轧件表面及内部温度、变形抗力、宽展、连轧常数等不断发生变化。由于钛合金棒材采用的是多机架（20架以上）、紧凑式（机架间距在1m以内）连轧，故上述参数的轻微波动会立刻影响连轧的稳定性甚至导致连轧过程中断。为了保证连轧的顺利进行以及控制产品尺寸精度，开展孔型设计方面的研究是至关重要的。本文提议了一种新型的、适合于钛合金棒材轧制的三辊孔型设计模型，与传统孔型设计的根本区别在于避免了孔型填充系数的选取。（4）应用正交试验和有限元相结合的方法，分析了影响钛合金棒材宽展的主要因素，建立了小直径TC4钛合金棒材宽展模型，并在实验样机上进行验证，为平三角和圆孔型设计提供了理论基础。通过分析轧件与轧辊接触区的几何形状，应用获得的本构关系，建立了三辊孔型轧制小直径TC4钛合金棒材的轧制力模型，并在实验样机上进行测试。结果表明：轧制力计算值与测量值偏差在工程计算允许范围内。（5）借助MATLAB计算、逻辑推导功能，开发了钛合金棒材计算机辅助孔型设计软件。本CARD软件适用于三辊Y型轧机所有孔型（平三角、圆三角、弧三角），能够实现孔型参数、轧件参数、力能参数等的计算，计算结果用EXCEL输出，孔型图用AUTOCAD输出。以Φ12mmTC4钛合金棒材孔型设计为例，验证了CARD系统的准确性。该软件界面友好，操作简单，能有效缩短孔型设计周期，提高工作效率与设计精度。更多还原

【Abstract】 Titanium and Titanium alloy is a kind of new metal material developed in1990’s. It is not only characterized by high melting point, high specific strength,high temperature resistance as well as corrosion resistance, but alsonon-magnetic and toxic-free. It is widely used in the area of aerospace, marine,bioengineering, livelihood and others. The market for small-sized titanium alloyrod is becoming more and more demanding in recent years. However, there existsome disadvantages of titanium alloy, such as complicated technology，lowaccuracy, low rolling yield and high energy consumption in the manufacturingprocess. In order to make titanium alloy become a popular metal, it is veryimportant to decrease its cost. Therefore, an important subject which aims atintegrating equipment, developing sustainable smelting technology and loweringcost variety is facing in titanium industry.This subject originated from province young research program of Shanxi isto develop a short and near-shape machining technique for titanium alloy rod.Compared with open-train mill, the continuous rolling process of Y-type cancelsrepeated heating (soaking), annealing and repair grinding. Compared withtwo-roll mill, it increases efficiency of roll. Meanwhile, the requirement ofsmall-batch and multi-variety of titanium alloy rod production is met.However, the deformation characteristics are significantly differentbetween titanium and steel, aluminum as well as copper. Especially for titaniumrod of strength and subsequent machining requirement, the pass design has animportant influence on quality and rolling yield. Therefore, in this paper thedeformation behavior of TC4alloy has been researched systematically, thecontinuous rolling process has been simulated by FEM software, pass designmodel for small-sized titanium alloy has been established, and experiment hasalso been done on self-development Y-type mill.Main contents are as follows.(1) Take TC4alloy as the study subject, this study conducts compressiontests on TC4alloy by Gleeble-1500thermal simulator and examines TC4alloy’s deformation behavior and flow stresses. The constitutive equationscorresponding to the peak and stable stresses have been determined respectivelyusing regression method. Furthermore, taking into the strain account, the flowstress equation has also been established by combining exponentially hardeningand softening function. The simulated results are believed to be important todevelop production, optimize process and improve quality of TC4alloy rod.(2) Pass system of “flat triangle–round” is applied not only because theflat triangle workpiece is relatively stable in round groove, but also the differentdiameter round rod could be produced from round groove. Based on theestablished flow stress equations, continuous rolling process of TC4alloy oneight Y-type mills has been virtually simulated using ANSYS software.Extension and spread deformation have been analyzed. Temperature, equivalentstress as well as equivalent strain of different deformation zone and rolling forceof per mill have been illustrated. The whole rolling process is smooth withoutcrack, edges and folds, which shows that the proposed rolling process isfeasible.(3) It could be concluded from FEM simulation above, the TC4alloy rod iscompressed from six directions and its surface and interior temperature,resistance deformation, spread and continuous rolling constant changeconstantly in hot rolling process. Furthermore, considering the compact distanceof the adjacent stands (no more than1m) and multi-stand (more than20stands)during rod rolling, the stability of continuous rolling is very easy to beinfluenced and even interrupted due to the slight fluctuation of the mentionedparameters. Therefore, there is a significant need to engage in research ongroove design so as to ensure the stability of the continuous rolling andproduction accuracy of titanium alloy. In this paper, a new groove design modelfor Y-type process of TC4rod has been established, whose difference from thetraditional pass design lies in avoiding fill ratio of groove.(4) By combining FEM with orthogonal test, spread model for TC4alloyrod has been established, and experiments have also been done on modelmachine. It provides theoretical foundation for flat triangle and round groove design. By analyzing contact zone shape of workpiece and roller, three-rollrolling force model for TC4alloy rod has been modified based on constitutiveequations. And experiments have also been done on model machine. The resultshave shown that the difference between calculated value and measured value isin the allowable range.(5) Computer aided pass design software for continuous rolling titaniumalloy is developed using MATLAB function of calculation and logic deduction,which is suit to all of pass types of Y-type mill including flat triangle, round andarc triangle. It can calculate many parameters for pass, workpiece andmechanics, etc. Numerical results are outputted by EXCEL and multi-passgrooves are drawn by AUTOCAD. Pass design for Φ12mm TC4alloy rod hasproven the validity of CARD. With friendly interface and simple operation, theCARD software could be used to shorten period, improve efficiency andaccuracy of pass design.更多还原