Texture evolution and its simulation of cold drawing copper wires produced by continuous casting

The texture evolution of cold drawing copper wires produced by continuous casting was measured by X-ray diffractometry and electron back-scatter diffractometry,and was simulated using Taylor model.The results show that in the drawn poly-crystal copper wires produced by traditional continuous casting,111 and 100 duplex fiber texture forms,and with increasing strain,the intensities of 111 and 100 increase.In the drawn single-crystal copper wires produced by Ohno continuous casting,100 rotates to 111,and there is inhomogeneous distribution of fiber texture along radial direction of the wires,which is caused by the distribution of shear deformation.Compared with 100,111 fiber texture is more stable in the drawn copper wires.Comparison of the experimental results with the simulated results shows that the simulation by Taylor model can analyze the texture evolution of drawn copper wires.

Effect of electropulsing on deformation behavior of Ti-6Al-4V alloy during cold drawing

Electron backscattered diffraction （EBSD） and transmission electron microscopy （TEM） were used to investigate effect of electropulsing on microstructure and texture evolution of Ti-6Al-4V during cold drawing. Research results demonstrate that the electropulsing treatment （EPT） can enhance the deformability of the grains with unfavorable orientations, which makes the compatibility of deformation among grains much better. A comparison in texture evolution between conventional cold drawing and EPT cold drawing indicates that the EPT promotes prismatic 〈a〉 slip moving, restricts pyramidal 〈c＋a〉 slip occurring and accommodates the deformation with c-component by grain boundary sliding. The fraction decrease of low-angle grain boundaries for samples deformed with EPT reveals that the application of electropulsing restricts the formation of the incidental dislocation boundaries and the geometrically necessary boundaries.

Effects of stress state on texture and microstructure in cold drawing-bulging of CP-Ti sheet

Three different stress states of the combination of tensile（t） stress and compressive（c） stress,t t,t c and t c c,exist in the deformed commercially pure titanium（CP-Ti） sheet during cold drawing-bulging.The textures and microstructures in the different stress state regions were investigated by means of XRD and TEM analysis.Similar development of texture and microstructure is achieved with less thickness strain under multiaxial stresses in drawing-bulging than in cold rolling.The results show that texture and microstructure are much sensitive to multiaxial stresses.Twinning is more easily activated under compressive stress than tensile stress.Prism a slip is heavily affected by tensile stress,resulting in a remarkable change of the intensity of（0°,35°,0°） texture,while pyramidal c＋a slip,forming（20°,35°,30°） texture,weakens with the increase of thickness strain in spite of stress state.

Microstructures, Textures and Mechanical Properties Evolution during Cold Drawing of Pure Mg

Pure Mg wires with a maximum cumulative area reduction of 98% were obtained by successful cold drawing. Mechanical properties, microstructures and texture evolution of the as-drawn wires were investigated by tensile tests, transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). Depended on the mechanical properties and microstructure evolution, continuous dynamic recrystallization (DRX) had taken place during the cold drawing process. DRX during cold deformation has not been reported in other literatures before.

Microstructure Evolution and Its Effects on the Mechanical Behavior of Cold Drawn Pearlite Steel Wires for Bridge Cables

The microstructure evolution and its effects on the mechanical performance of 2000 MPa bridge cable steel wires were investigated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD),X-ray diffractometer(XRD)and mechanical tests.Experimental results reveal that,with the increasing strain from 0 to 1.42,a fiber structure and a<110>fiber texture aligned with the wire axis are gradually developed accompanied by cementite decomposition and the formation of sub-grains;the tensile strength increases linearly from 1510 to 2025 MPa,and the reduction of the area is stable with a slight decline from 44%to 36%.After annealing at 450℃for different times,pronounced changes in the microstructure occur.Cementite lamella fragment into coarser globules corresponding to a remarkable spheroidization process,while ferrite domains recover and recrystallize,and this process is associated to modifications in the mechanical properties.Furthermore,based on the observations on dislocation lines crossing through cementite lamellae,a possible mechanism of cementite decomposition is discussed.

Deformation behaviors of magnesium alloy AZ31 sheet in cold deep drawing

To investigate how the popular magnesium alloy AZ31 sheet(aluminum 3%,zinc 1%)behaves in cold working,deep drawing experiments at room temperature,along with finite element(FE)simulation,were performed on the cold forming sheet of the AZ31 alloy after being annealed under various conditions.The activities were focused on the fracture pattern,limit drawing ratio(LDR),deformation load,thickness distribution,anisotropic effect,as well as the influences of the annealing conditions and tool configuration on them.The results display that punch shoulder radius instead of die clearance,has much influence on the thickness distribution.The anisotropy is remarkable in cold working,which adversely impacts the LDR.The fracture often happens on the side wall at an angle to axis of the deformed specimen.The results also imply that the LDR for the material under present experimental conditions is 1.72,and annealing the material at 450 ℃ for 1 h may be preferable for the cold deep drawing.

Textures of high-strength and low-expansion Fe-Ni alloy wires during cold-drawing processes

Textures of high-strength and low-expansion Fe-Ni alloy wires during cold-drawing processes were investigated using X-ray diffraction （XRD） and electron back scatter diffraction （EBSD） techniques. The experimental results show that the 〈111〉 and 〈100〉 fibre textures are the main texture components, and crystalline grains in the surface are more fine and uniform than those in the center of Fe-Ni alloy wires during cold-drawing processes. It is found that the volume fraction of the 〈111〉 fibre texture component determined by quantitative regression calculation of the Gaussian distribution function reaches more than 60% and the strong 〈111〉 fibre texture component favors the torsional property of Fe-Ni alloy wires.

Microstructures and properties of cold drawn and annealed submicron crystalline Cu-5%Cr alloy

The microstructures and properties after cold drawing and subsequent annealing of submicron crystalline Cu-5%Cr (mass fraction) alloy were investigated. The results show that, the microstructure of submicron crystalline Cu-5%Cr can be further refined by cold drawing. After cold drawing, the grains of Cu-5%Cr alloy with grain size of 400-500 nm can be refined to be cellular structures and subgrains with size of 100-200 nm. Both strength and ductility of Cu-5%Cr alloy can be enhanced by cold drawing, and the optimal mechanical properties can be achieved with drawing deformation increasing. It is suggested that dislocation glide is still the main mechanism in plastic deformation of submicron crystalline Cu-5%Cr, but grain boundary slide and diffusion may play more and more important roles with drawing deformation increasing. When the cold drawn Cu-5%Cr wires are annealed at 550 ℃, fine recrystal grains with grain size of 200-300 nm can be obtained. Furthermore, there are lots of fine Cr particles precipitated during annealing, by which the recrystallization softening temperatures of the cold drawn Cu-5%Cr wires can be increased to 480-560 ℃. Due to the fact that Cr particles have the effect of restricting Cu grains growth, a favorable structural thermal stability of the submicron crystalline Cu-5%Cr can be achieved, and the submicron grained microstructure can be retained at high temperature annealing.

Microstructures of Ti–Ni–Fe wire after severe cold-drawing and annealing

The microstructures and mechanical properties of Ti–47 at%Ni–3 at%Fe shape memory alloy wire under the condition of severe cold-drawing at room temperature and different postdeformation annealing processes were intensively investigated using transmission electron microscope(TEM),X-ray diffraction(XRD),Vickers microhardness tester and electron tensile tester.It is indicated that the structure of the alloy evolves into a predominant amorphous structure with a trace of nanocrystalline B2 phase after the cold-drawing of 76%areal reduction.Postdeformation annealing process exerted significant influence on the microstructure and mechanical properties.Crystallization occurs when the cold-drawn wire was annealed at 300℃ for 30 min.The ultimate tensile strength and ductility as well as the superelasticity of the wire are improved significantly by cold-drawing plus postdeformation annealing.

EMF CHANGES MADE BY COLD DRAWING AND HEATING TREATMENT IN TYPE K HEAVY-GAUGE SHEATHED THERMOCOUPLE CABLES

The electromotive force (EMF) changes in type K heavy gauge sheathed thermocouple cables was investigated. To cope with this discrepancy owing to EMF steep reduction and understand the difference between type K heavy gauge sheathed thermocouple cables and small ones, the affects of EMF from sheath pipe, drawing times, annealing temperature, annealing time and annealing way were mainly studied and appropriately analyzed. The results show the change in the thermal EMF is related with the residual stress and crystal defects, which are imparted by cold work during manufacture. The affects of cold work can be removed by annealing. Finally, a feasible way of fabricating heavy gauge sheathed thermocouples was suggested according to practical situation.

Microstructure and texture evolution of cold-rolled deep-drawing steel sheet during annealing

In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. （111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of （111} advantageous texture components in the annealing texture increases from 55vo1% to 65vo1%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.

Study on Modification of Polymer Properties by the Cold Drawing Process

Polymers have a wide diversity of applications, ranging from therapeutics delivery to tissue engineering. While advances in polymer chemistry have facilitated synthesis and development of new polymers, increasing efforts have also been directed to engineer properties of existing polymers. One of the common approaches to modify polymer properties is cold drawing, which can align polymer chains and orient the chains in a crystalline manner. Regarding the industrial significance of cold drawing in polymer engineering, this study used semi-crystalline high density polyethylene (HDPE) as a model to examine the effect of cold drawing on the anisotropic mechanical properties of polymers. During cold drawing, the yield strength of the polymer was shown to be in a positive relationship with the strain rate, and the hardness of the cold-drawn region was demonstrated to be significantly enhanced. Our results confirmed the feasibility of engineering the properties of polymers by applying tension for plastic deformation, and highlighted the importance of precise control of the strain rate in the treatment.

金属拉拔工艺中的摩擦与腐蚀交互作用研究进展

综述了金属拉拔成形中的摩擦特点及影响摩擦的主要因素,总结分析了电致塑性和电化学促进金属表面塑化的作用机制,以及电化学冷拉拔中电解液环境下的腐蚀与磨损交互作用对工艺及工件的影响,以期为提高拉拔成形技术中加工金属的表面质量,延长模具使用寿命提供理论基础,为金属塑性成形技术的发展以及关键材料的生产提供重要参考。

单晶铜拉拔过程组织及织构演变

目的通过分析单晶铜线材在冷拉拔过程中不同位置微观结构的变化情况,得到变形过程中组织及织构的演变规律。方法采用冷型下引连铸装置制备得到ϕ8 mm高纯铜铸态杆坯,并在大拉机中进行多道次拉拔,获得了真应变分别为0.5、1.3、2、2.7和3.4的铜线样品;采用电子背散射衍射技术分别对铸态及拉拔态试样纵截面的显微组织以及织构进行观测。结果拉拔开始后,在试样纵截面上部的次表层率先观察到与轴向呈45°的滑移带,试样下部开始分裂出平行于拉拔方向的柱状晶。随着应变的增加,位于次表层的滑移线数目显著增多,滑移带间距更加紧密,随后在试样芯部也观察到与轴向呈30°的滑移带,试样边部晶粒的裂化程度更加显著,形成大量平行于轴向的纤维晶粒。当真应变增加至3.4时,少量倾斜于轴向的晶粒在外力作用下被拉至与轴向平行,最终形成致密的纤维组织。在整个拉拔过程中,铜线纵截面上下2个边部由初始的<001>织构先后演化出<114>、<112>、<433>、<111>织构,芯部演化出<112>、<111>织构。结论在拉拔过程中,不同位置的变形程度不同,组织及织构的演变也表现出较为明显的差异。总体表现为,线材边部比芯部变形程度更加剧烈,组织纤维化程度更高,织构演变也更加复杂。

变形量对冷拉拔低碳镀锌钢丝力学性能的影响

冷拉拔低碳镀锌钢丝以良好的耐蚀性能、焊接性能、与力学性能协同匹配的良好综合性能和低廉的价格广泛应用于轻工业及建筑行业,其中变形量是影响其力学性能、生产成本及良品率的关键因素。通过显微组织分析、力学性能测定、断口观察,研究了Q235冷拉拔低碳镀锌钢丝不同变形量下的加工硬化过程,并分析了断丝及钢丝表面出现箭头状裂纹的原因。结果表明:真应变从0增加到2.41的过程中,抗拉强度、横纵截面硬度随应变量增加呈抛物线状增加,抗拉强度从586.8 MPa增加到1157.1 MPa,横截面硬度比纵截面增加了5.8 HV。塑性变形初期,加工硬化率最大,为364.7 MPa。真应变从0增加到1.91过程中,加工硬化率从364.7 MPa降低到162.2 MPa,真应变从1.91增加到2.41的过程中,加工硬化率又增加到了172.0 MPa。钢丝中存在CaO夹杂物是导致钢丝出现断丝和表面箭头状裂纹的主要原因。

电流密度对单晶铜棒材电化学冷拉拔的影响

通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最小,且拉拔后棒材的表面硬度也最小。不同的电流密度使单晶铜棒材的塑化程度不同,其主要原因是由于晶体内滑移系激活数量不同引起,导致位错易于运动,使得位错缠结减少。而在更高的电流密度下,由于表面腐蚀层厚度的增加,激活的滑移系数量减少,继而摩擦力增大,位错密度增大,使得拉拔力再次增大。

冷拉变形对7050铝合金丝材组织与性能的影响

对7050铝合金丝材经冷拉变形后过时效态以及冷加工变形态的组织与性能进行了研究。结果表明,随着冷变形量的增加,晶粒拉长,屈服强度、抗拉强度和剪切强度增大。与冷拉态相比较,过时效态丝材的这些指标增加不明显;晶粒越均匀细小,合金丝材冷镦时越不易发生开裂。

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。

预应力钢绞线用YL82B钢冷拉断裂原因

某钢厂生产的预应力钢绞线用YL82B钢在冷拉过程中发生多次断裂现象。采用宏观观察、化学成分分析和金相检验等方法对盘条断裂的原因进行分析。结果表明:笔尖状、喇叭状断口产生的原因为热轧后冷却速率较慢,珠光体相变增多,导致材料的强度变小,且中心碳偏析使材料形成严重网状碳化物,最终导致盘条断裂;平断状、斜断状断口的产生原因为材料表面发生磕碰、冷拉时氧化皮去除不干净、润滑不当、对焊不规范使材料发生点状烧伤,以及焊后未及时正火等。

烘干温度对线切割钼丝冷拔用石墨乳使用性能的影响

为研究不同烘干温度下所制备的钼丝表面石墨乳烘干涂层厚度、碳氧含量变化及其对钼丝冷拔加工的润滑效果(模产、钼丝表面)影响,本文按3个插值点烘干温度(600、700、800℃)进行钼丝在线热拉压延后单独涂覆石墨乳烘干以获得相应的石墨乳涂层,并继续后面冷拔加工对比测试。结果表明:不同烘干温度会导致石墨乳涂层的厚度及碳、氧含量变化,从而影响石墨润滑性能,进而影响后续钼丝冷拔加工的润滑效果。相比较3个烘干温度点中,烘干温度在700℃时,石墨乳涂层厚度最大且碳、氧含量比例适中,此时的石墨润滑性能大增,因此,该温度点下制备的石墨乳涂层在后续钼丝冷拔加工中体现出较好润滑效果,其模产水平高、成品丝材表面质量好。通过本次研究,可以为线切割钼丝冷拔加工的润滑效果优化提供参考。