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.

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.

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.

Study of the influence of heat treatment procedure on the microstructure and mechanical properties of H13 mandrel steel

In this study,the microstructural evolution of H13 mandrel steel during its manufacturing process and the influence of the preheat treatment procedure and the second-step tempering temperature on its microstructural and mechanical properties were investigated.The experiment results showed that,using an H13 mandrel steel billet in the as-annealed condition produced by Baosteel as a raw material,the preheat treatments of normalization,spheroidization annealing,or normalization plus spheroidization annealing,as described in this paper,had no significant effect on the final mechanical properties after quenching and tempering.H13 mandrel steel met all the mechanical property requirements via quenching and tempering without preheat treatment.In the temperature range from 600 to 680 t,with an increase in the second-step tempering temperature,the strength gradually decreased whereas the plasticity and toughness gradually improved.Using the quenching-plus-first-tempering procedure of 1030℃/l h/oil cooling+600℃/5 h/air cooling,good balance between strength and toughness could be achieved by selecting 650℃ as the second-step tempering temperature.The test results also showed that the holding time of the second tempering played a big role in the mechanical properties.When this holding time was extended from 1 to 2 h,the hardness of the H13 mandrel steel decreased and the extent of this reduction increased with an increase in the second-step tempering temperature.In the temperature range of 1030 to 1090℃,the yield strength,tensile strength,and hardness gradually increased,however,the impact toughness decreased with increases in the quenching temperature.

卷曲机WINDING UNIT卷芯MANDREL效能提升措施

电解电容生产设备卷曲机核心部位零部件MANDREL为生产中主要消耗零部件,现对其生产工艺,使用效能进行实验分析提出改进措施,从而提高零部件的使用性能及国产化质量。

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.

Deforming mechanism of non-mandrel drawing process of circular aluminium tube by simulation

The aluminium tubes with high strength and smooth outer-surface can be produced by non-mandrel drawing process. It is an effective method to study forming mechanism of drawing process by simulation, based on which the relevant dies with reasonable dimensions can be designed to ensure tube precision. The dynamic model and elasto-plastic finite element model of the forming process were established based on FEM software Deform-3D, then the simulation was performed. The expressions about drawing load were deduced, and the influence of friction coefficient on drawing load was computed by the expressions and software respectively. Based on simulation results the deformation mechanism of drawing process without plug was expounded. According to flowing speed vector graph the law of material flowing was summarized, by which the deformation regions were partitioned. Furthermore, some potential problems of drawing process such as diameter shrinking, thickness varying were forecast and analyzed quantificationally.

Influence of mandrel-cores filling on size effect of cross-section distortion of bimetallic thin-walled composite bending tube

Two new size factors of cross-section hollow coefficient and bending degree are introduced to reveal the size effect of bending forming of bimetallic composite tube.Hollow coefficient and bending degree can limit the commonly used bent tube to the size description range of(0,2.00).The evolution laws of the cross-section distortion forms in the hollow coefficient-bending degree interval are revealed as well as the action of the mandrel-cores on the size effect.Results show the mandrel-cores filling can expand the forming limit of the bent tube,but also bring two other forming defects of wrinkle and rupture.The identification factor(hollow coefficient multiply bending degree)provides a method for querying the cross-section distortion forms of all composite bending tubes.In the identification factor interval(0,1.00),the distribution area of bending forming defects of the composite tube is continuous.The thin-walled composite bending tube collapses when identification factor in(0,0.39),wrinkles when identification factor in[0.39,0.50),and ruptures when identification factor in[0.50,1.00).The mathematical model of size effect is derived,by which the average cross-section distortion rate is found to distribute like a radial leaf in the hollow coefficient-bending degree qualified forming space.The best forming zone is hollow coefficient 0.46-0.68,and bending degree 0.25-0.47.

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。

Friction Coefficient Between Rolling Tube and Mandrel of Full Floating Mandrel Mill

In the process of steel tube production, continuous tube rolling is the foremost forming procedure and the critical step that decides the dimension precision and the surface quality. In the actual production of the 4140 mm full floating mandrel mill in Steel Tube Branch in Baosteel, steel T91 was chosen to be the typical sample, self-made rolling force transducer and mandrel velocity testing equipment were used, and a series of comprehensive tests on rolling parameters including the rolling force and mandrel velocity were carried out. After the experiment, the friction state between rolling tube and mandrel was analyzed. The friction coefficient was calculated and the values of 0. 033 - 0. 074 in each mill were obtained. The friction coefficient increases obviously along the rolling direction.

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。

Influence of Pass Parameters on Retained Mandrel Rolling Process

Roller pass is one of the key factors affecting the product quality in the retained mandrel rolling process. The metal flow condition of rolling deformation area was researched using the FEA （finite element analysis） software Marc. The influences of the pass bottom radius, the sidewall radius, the sidewall angle, the roller shoulder fillet radius, as well as the roller gap on the rolling process under the conditions of different friction were discussed. Based on these results, the changes of the workpiece exit width, the mandrel axial force, the rolling force, and the rolling torque associated with various parameters were determined, which would provide the basis for designing the pass and determining the rolling condition reasonably.

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。

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。

Mandrel degradation model of combined fast and slow processes

In this paper, we report the study of degradation for a kind of ideal mandrel material called poly-α-methylstyrene based on theoretical and experimental methods. First-principles calculations reveal two types of process: depolymerization and hydrogen-transfer-induced chain scission. The energy barrier for the former(0.68–0.82 eV) is smaller than that for most of the latter(1.39–4.23 eV). More importantly, reaction rates suggest that the former is fast whereas the latter is mostly slow, which can result in a difference of 5–31 orders of magnitude at 550 K. Furthermore, a thermogravimetric experiment shows that the activation energy of 2.53 eV for degradation is between those of fast and slow processes,corresponding to the theoretical average value of multiple reaction paths. Thus, a mandrel degradation model combining fast and slow processes is established at the atomic level. Our work provides a direction for research into the key technology of target fabrication in inertial confinement fusion.

限动芯棒连轧管机组生产节奏提升策略

介绍了连轧管机组的几种不同芯棒循环轧制方式。指出,作为当前连轧管机组的绝对主流,限动芯棒连轧管机组仍然存在生产节奏偏慢问题。为了解决该问题,可以对影响机组技术“瓶颈”的穿孔过程和连轧过程进行一系列技术优化,特别是通过对其前台芯棒及毛管上下料设备结构、芯棒循环工艺流程进行创新,有望实现限动芯棒连轧管机生产节奏质的提升。

航空制孔垂直度快速检测方法

针对现场环境下的航空制孔垂直度检测问题,提出了一种基于激光测距的快速高精度测量方法。首先,利用膨胀芯轴在被测孔内稳定支撑并模拟孔的轴线,通过安装在芯轴上的激光测距传感器和角度编码器获取孔的端面点云数据,并拟合出端面法向量;最后,计算该法向量与被测孔轴线之间的夹角作为垂直度误差。为了提高装置测量精度,提出了基于RANSAC的三维点云重建算法,并通过向量合成法补偿由膨胀芯轴体现基准时所产生的系统误差。利用不同垂直度标准环规对所述装置进行了标定,并完成了平面样件及曲面样件的制孔垂直度测量实验。实验结果表明:该装置的测量重复性<0.01°,最大示值误差<±0.1°,单个孔的测量时间<1 min,能够满足航空制孔垂直度的现场检测精度与速度要求。