芯轴悬挂器高强度螺纹结构设计及评价研究

为了防止芯轴下端连接螺纹强度不足而造成失效事故,采用高温高压套管柱设计计算方法、有限元数值模拟和实验手段,对芯轴材料进行了力学性能实验,开发了一种用于芯轴悬挂器高强度螺纹结构,并在极限复合载荷下对该螺纹进行了三维有限元计算。研究结果表明,拉扭压复合载荷对外螺纹强度影响较大,压缩载荷对内螺纹内台肩第一牙应力影响较大,内外螺纹其余部位相对安全。拉伸载荷在一定程度缓解了上扣扭矩对内外螺纹台肩部位的影响。从计算结果得到内外螺纹整体上应力小于材料允许的屈服极限,且螺纹接头接触压力均大于外在流体压力,可以形成有效密封,研究结果为芯轴悬挂器螺纹结构的选型和使用提供理论基础。

Development of Technology and Equipment for Non-destructive Testing of Defects in Sewing Mandrels of a Three-roll Screw Mill 30-80

The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.

基于芯棒校准探头定位误差的齿轮精度在线测量

主流的齿轮测量设备大都通过参考球进行探头位置校准,相较于参考球,芯棒不仅安装与操作方便,同时还可以检测机床的静态精度。因此对开发的新型齿轮磨床进行齿轮在线测量时,采用芯棒进行探头校准来实现齿轮测量。为了提高探头定位精度,初步利用最小二乘法(least square method,LSM)拟合芯棒中心来进行探头定位,并在此基础上使用基于AitkenΔ^(2)迭代的算法来补偿LSM的定位误差,进而实现探头位置校准。该方法将非线性拟合迭代过程用线性收敛的数值序列代替,不仅具有较快的收敛速度,同时数值趋于稳定。通过齿廓偏差评估实验证明了该方法的有效性,可对其他齿轮测量时的探头位置校准提供参考。

基于光谱共焦探针的Wolter-Ⅰ型X射线显微镜芯轴高精度检测

Wolter型X射线显微镜具有高分辨率和集光区域,在先进光源和高能激光器中有重要的应用价值。基于镍电镀成形的复制法是制备Wolter型X射线显微镜的有效方法之一,其中,芯轴的表面精度和质量会直接影响X射线成像的性能。高精度检测技术是芯轴制备的基础,而传统检测装置难以测量具有圆周回旋对称特征的Wolter型表面轮廓。为了解决Wolter型芯轴检测难和测量精度低的问题,搭建了基于光谱共焦探针的离线检测装置实现芯轴表面中低频轮廓的高精度测量,分析了该装置的各类系统误差和随机误差,并采用双探针与标准镜来校准测试过程,将测试中的温湿度漂移和随机误差的PV值降低至23 nm。最后,开展了该检测装置和CGH干涉检测法的检测对比实验。通过Wolter芯轴表面测试结果比较,两种测试方法的偏差PV值约为60 nm,证明了该检测装置的合理性和检测方法的准确性。

芯轴式套管悬挂器金属密封设计及性能分析

为了避免芯轴式套管悬挂器密封失效,根据芯轴式套管悬挂器的结构及密封工作原理,设计了一种新型的金属密封结构。建立了芯轴式悬挂器密封性能有限元模型,研究了不同顶丝压力和套管悬重对密封锥面变形及接触压力的影响。结果表明:随顶丝推力的增加,上、下密封锥面上平均接触压力都增加,有利于实现密封;随套管悬重的增加,上密封锥平均接触压力增加,下密封锥平均接触压力减小,除下内锥面外,均能满足密封要求。研究结果可为芯轴式悬挂器密封部位的结构设计提供参考。

基于蚁群算法的绝热层缠绕路径优化

为解决绝热层缠绕成型过程中胶带撕裂褶皱和间隙控制等问题,本文提出一种基于多因素改进蚁群算法的缠绕路径优化方法。优化策略包括:构建蚂蚁决策空间,改变启发式函数,引入带隙缩放系数。利用ACIS几何造型库构建芯模、胶带三维模型,提出一种胶带应变计算方法,以评估胶带撕裂褶皱程度。缠绕仿真及试验验证结果表明:该方法能够有效优化绝热层缠绕路径,解决胶带撕裂褶皱问题,并满足缠绕胶带带隙要求,提高绝热层缠绕成型质量。本文研究为绝热层缠绕成型工艺提供了一种新型的路径优化方法。

基于动态收敛长度模型的异形结构芯模编织控制策略

近年来,复合材料广泛地代替金属材料应用在复杂结构件上。在异形结构预成型体的编织过程中,针对芯模半径连续变化导致编织角不稳定等问题,本文提出一种机器人牵引速度的控制方法。首先对异形结构芯模进行离散化处理得到每段的半径,然后对机器人的牵引速度进行优化计算,通过计算得到的牵引速度对编织角进行调整同时得出推进距离与实际编织长度的关系。最后通过机器人二次推进对编织长度进行补偿,并基于动态收敛长度进行下一段芯模的编织。试验结果证明,该控制方法能有效降低异形结构芯模的编织角误差并维持在±3°以内,对实际生产中编织角的严格把控以及任意曲率芯模的编织具有重大意义。

基于均质与细晶化的高性能限动芯棒生产工艺优化与实践

随着全球无缝钢管行业的蓬勃发展,高性能限动芯棒作为关键工艺装备,其生产工艺的优化与创新日益受到关注。本文通过对其生产加工的国内外研究现状及工艺特点难点的深入分析,以对芯棒加工中的均质化、细晶化、热处理工艺等方面研究优化为方向,开发出具有自主知识产权的高性能限动芯棒生产工艺,提高了芯棒的力学性能和冲击韧性,确保了产品质量的稳定性和可靠性,为我国高性能限动芯棒的自主化生产奠定了坚实基础。

弯曲参数对304不锈钢管材大曲率无芯弯曲成形性的影响

针对管材无芯弯曲多缺陷耦合的成形问题,以管材壁厚变化率及截面短轴变化率作为成形指标,在不同弯曲参数下进行304不锈钢管材大曲率无芯弯曲试验,结合硬度测试及微观组织表征,研究了弯曲参数对弯曲成形及微观组织演变的影响规律。结果表明:随着弯曲速度、弯曲角度及相对管径的增大,壁厚变化率呈增加趋势,且壁厚增厚率始终大于壁厚减薄率,同时,弯管截面畸变程度加剧。在各弯曲参数下,管材弯曲内外侧均发生奥氏体向马氏体转变,马氏体组织含量及硬度与壁厚变化率呈正相关关系,中性层几乎不存在马氏体。通过选择合适的工艺,最终弯制出相对弯曲半径为1.4的合格弯管。

60t高速五线旋转式冷拔机组浅析

本文实现了一种具有竖直提升上料、多模式毛管横移布料、芯棒水平穿芯、双工位旋转式芯棒台为特征的高速无缝钢管冷拔机组。该机组实现了冷拔管生产过程散料、提升上料、下位拔制、下料等工序自动运行;可实现最多五支直径φ28~φ63.5mm、壁厚3.5~10mm、长度8~26m碳钢及低合金钢管同时拔制;机组公称拔制力最大60t,拔制速度最高50m/min。该设备提升了国内冷拔管材生产机组设计、制造水平以及企业生产技术水平,对促进我国钢管行业技术装备发展具有深远意义。

基于半开放扇形件支座的加工工艺分析

针对半开放扇形件加工周期长、在三轴数控铣床翻面次数多且拼装复杂、外圆?40f7无法通过车床常规加工完成等问题,通过分析零件结构和加工工艺,采用快速进给、四轴加工方案、涨开心轴和特制专用车刀,解决了该半开放扇形件的加工难题,使加工效率得到提升,缩短了加工周期,保证零件达到设计要求。

超超临界火电机组用F92钢法兰件锻造工艺优化

某超超临界火电机组中的F92钢法兰锻件,采用传统的冲孔和芯轴拔长工艺成形后,锻件内孔处经常出现裂纹和外凹缺陷,产品合格率仅有25%。对锻件成形过程进行数值模拟,研究其等效应变场的分布规律,发现裂纹产生处等效应变达到最大值15.170,同时锻件内孔产生外凹,最大直径达到669.421 mm。为解决此问题,提出一种小压量多道次拔长和近净成形挤压铆镦工艺相结合的优化方案。模拟结果显示,实施优化方案后,压下量为60 mm左右时得到最佳效果,等效应变值降至11.310,外凹最大直径减小到630.682 mm,同时锻件金属流线变化均匀。生产试制表明,法兰锻件裂纹和外凹缺陷消失,力学性能良好,微观组织细小均匀,产品合格率由25%提升至80%。

500 kV直线塔复合绝缘子断串原因分析

运用外观检查、解剖检查、染料渗透试验、红外测温试验,对一起500 kV某线路72号直线塔复合绝缘子断串故障原因进行分析。结果表明,故障相绝缘子护套存在自身缺陷、密封不严等问题,导致其芯棒与外界空气、雨水等接触,在强电场、酸液、潮湿空气等长期作用下芯棒受腐蚀,进而造成复合绝缘子中承力作用的玻璃纤维在电化反应下断裂,绝缘子在导线自重等综合作用下断串。

Three-Dimensional Thermo-mechanical Coupled FEM Simulation for Hot Continuous Rolling of Large-Diameter Mandrel Bar

Based on the important boundary conditions of rolling simulation including friction, heat conduction and interactionsof the workpiece and rolls, the hot continuous rolling processes of large-diameter mandrel round bar (200 mm indiameter) in 6VH-stand hot tandem mill are successfully simulated by three-dimensional coupled thermomechanicalelastoplastic finite element method (FEM). The distributions of stress, strain, temperature and the rolling force andtorque for the two-pass and four-pass continuous rolling are calculated respectively. Thus, the two and four-passroll schedules are verified, respectively. The simulation results show that it is safe to produce 200 mm round barby the two-pass (oval pass and round pass) continuous rolling on the existing equipment compared to the four-passcontinuous rolling. There are concave surfaces and increased widths occurring at the end of rolled billet due touneven deformations between the outside and inside of the workpiece as well as the free spreading close to the rollgap of the final pass.

Effects of quenching temperature on microstructure and mechanical properties of H13 mandrel steel

Optical microscope, stereomicroscope, scanning electronic microscope （SEM） and mechanical property testing were used to research the effects of different quenching temperatures on the microstructure and mechanical properties of the H13 mandrel steel. The results indicate that following an increase in the quenching ,the degree of alloying is enhanced due to the carbides dissolving gradually in austenite, which improves the hardenability of the specimens, as well as their room and high-temperature strength. At the same time, the fracture toughness increases due to the increment of the martensite number and the interparticle distance of impact toughness. Optimal performance Consequently,the service life of the H13 the carbides. However, extremely coarse grain and martensite can decrease the can be obtained after quenching at 1 060℃ and double tempering at 620℃mandrel steel is extended significantly.

Effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel

This study researches the effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel steel and compares these effects with those of the conventional treatment. The results indicate that both carbide particles and grains were refined, carbide particles were uniformly distributed by the refining treatment, and therefore,the strength and toughness of H13 mandrel steel were improved. Rapid cooling after the solution treatment may inhibit intra-granular precipitation of carbide particles, which is favorable to enhancing toughness. Consequently, high- performance H13 mandrel steel can be produced by proper refining treatment.

Evolution of microstructure of aluminum alloy hollow shaft in cross wedge rolling without mandrel

During the process of cross wedge rolling of aluminum alloy hollow shaft, the evolution of its microstructure has an important influence on the mechanical properties of the rolled piece. In order to obtain the microstructure evolution law of aluminum alloy hollow shaft in cross wedge rolling without mandrel, a finite element model is constructed through the finite element software Deform-3D. The influences of rolling temperature, sectional shrinkage,spreading angle and forming angle on the average grain size of rolled piece are studied by numerical simulation of microstructure evolution. The cellular automata method reveals the inherent relationship between the process parameters and the evolution of the microstructure, and provides a reference for optimizing the rolling process parameters of aluminum alloy hollow shafts and improving the forming quality. The results show that the average grain size of the rolled piece increases with the increase of the rolling temperature, decreases with the increase of the sectional shrinkage,and decreases first and then increases with the increase of the spreading angle, and changes little with the increase of the forming angle.

Effect of mandrel on cross section quality of thin-walled tube numerical controlled bending

The effect of mandrel with the structure of ball and socket on the cross section quality of thin-walled tube numerical controlled(NC) bending was studied by numerical simulation method, combined with theoretical (analysis) and experiment. Influencing factors of the mandrel include the count of mandrel heads, the diameter of mandrel and its position. According to the principle of NC tube bending, quality defects possibly produced in thin-walled tube NC bending process were analyzed and two parameters were proposed in order to describe the cross section quality of thin-walled tube NC bending. According to the geometrical dimension of tube and dies, the range of mandrel protrusion was derived. The finite element model of thin-walled tube NC bending was established based on the DYNAFORM platform, and key technological problems were solved. The model was verified by experiment. The effect of the number of mandrel heads, the diameter of mandrel and the protrusion length of mandrel on the cross section quality of thin-walled tube NC bending was revealed and how to choose mandrel parameters was presented.

Finite element analysis of the bulge defect forming and eliminating on tube continuous rolled by full floating mandrel mill

Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.

Study on the mechanical properties and service life of H13 mandrels

The microstructures and mechanical properties of H13 mandrels made by Baosteel and foreign companies were investigated in this study. Based on the comparison research, the processes were optimized, such as steelmaking, heat treatment and multiple forging processes. The quality of Baosteel mandrels was greatly improved by increasing the homogenizing of an annealing temperature and refining processes. The results of the pilot trial showed that the average number of piercing steel tubes for Baosteel mandrels was over 3000 ,which reached the level of imported mandrels.