A Slip-Line Method for Calculating Extrusion Force of Steel Helmet with Cold Extrusion Moulding

This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.

Casting-cold extrusion of Al/Cu clad composite by copper tubes with different sketch sections

Casting-cold extrusion technology was presented to fabricate aluminum/copper clad composite,and copper tubes with different sketch sections were designed.The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves.The stress and strain in different deformation zones were analyzed.The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure.The maximum values of equivalent effective stress and radial stress appear in groove zones,and the maximum equivalent effective strain firstly is obtained also in groove zones.The grain size in groove zones is less than that in other zones.The experimental results are consistent with simulation results,which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.

Cold extrusion deformation behavior of medium carbon steel after quenching and tempering

By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angle of die (90 °-120 °), hardness after quenching and tempering (HRC21-29) and lubricated condition on the forming load was analyzed. The results show that there is no central bursting and micro crack in the inner of the extruded specimen, and the forming quality is good. The double-peak phenomenon takes place at the front-end of the specimen; the double-peak index increases with deformation extent, and larger deformation can avoid the double-peak phenomenon. The deformation extent is the most important influencing factor, and the lubricated condition almost has no influence, which means that the phosphate coating plus soap process is still a proper lubrication method for cold extrusion of medium carbon steel after quenching and tempering. By investigating the microscopic structure before and after deformation, the initial equiaxed grain is elongated in the extrusion direction, and this feature is more significant at the front-end of specimen.

EXPERIMENTAL STUDY ON OPEN－DIE COLD EXTRUSION FORMING TECHNIQUE FOR INVOLUTESPLINE SHAFTS

The deformation principles of the steady- state and the unsteady一state of open- die cold extrusion for involute spline shafts are analyzed by means of experiments. On one hand,based on the deformation principles of the steady- state, data for determining structural parameters of the die, the size of the billet and the constraint condition of this technique are given. On the other hand, according to the principles of the unsteady- state, data for modifying the shapes and sizes of the bil- lets are provided.

Novel Blasting-Like Lubricating Process for Cold Extrusion

A blasting-like lubricating process(combination of shot blasting and lubricating processes)is proposed.In this process,the specimens to be treated,alloy shots,and solid lubricating powder are rotated together in a roller.The surface pockets formed due to the impact by the shots can store lubricants,and the lubricant can also adhere to the specimen surface by hitting.The effects of process parameters,including rolling time,rotational speed,mass of alloy shots,and the diameter of shots,on the surface topography of the steel specimen are investigated using 13 experimental schemes.The distribution ratio and average depth of surface pockets on the defined areas of the specimen are quantitatively analyzed.Four selected schemes with the MoS_(2) solid lubricating powder are further carried out to lubricate the cylindrical billets,and the lubricating effect is evaluated using the steady combined forward and backward extrusion test.The indicated friction factor of the novel blasting-like process is smaller than that of the conventional phosphate-soap coating process.

Powder Extrusion Molding of Nanocrystalline WC-10Co Composite Cemented Carbide

The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.

Extrusion behavior of micro-nanostructured Al-18%Si alloy powders

The extrusion of Al-Si alloy powders with different particle sizes allows manufacture of different products with unique microstructures and therefore with unique mechanical properties. The effects of powder size on the extrusion behavior and process defect of Al-18%Si alloy were studied by means of microscopy (optical, scanning electron) and density determination. The main objective of the work is to demonstrate the influence of the powder material characteristics on final density and quality of bar. The results show that the bigger the powder particles, the better the performance of cold compacting. The surface of alloy bar extruded from big particles has good quality without cracking. While the smaller the powder particles, the higher the density and the better the microstructure and mechanical properties. For practice application, the mixed powders are better than single powder.

镍基高温合金深小孔的旋转冷挤压强化工艺优化

采用多级凸包硬质合金挤压工具对镍基高温合金平板中的深小孔进行旋转冷挤压及无旋转冷挤压(主轴转速为0)试验,研究了挤压率(2.4%,3.0%,3.6%)与主轴转速(0,66,200 r·min^(-1))对孔壁表面完整性及试样疲劳寿命的影响,确定了旋转冷挤压优化工艺。结果表明:与无旋转冷挤压强化工艺相比,旋转冷挤压强化后孔壁表面微裂纹较少,随着主轴转速的增加,微裂纹增多,表面粗糙增大,且相同主轴转速下,挤压率越大,粗糙度越小,表面硬度越高,残余压应力和压应力层厚度越大。优化旋转冷挤压工艺参数为主轴转速66 r·min^(-1)、挤压率3.0%,该工艺下的孔壁表面微裂纹少,塑性变形层较厚(约30μm),表层硬度提升(硬度峰值为515 HV),表面粗糙度较低(Ra为0.298μm),沿深度方向形成了厚度约为450μm、应力峰值为498 MPa的周向残余压应力层;在优化工艺下孔强化后试样的疲劳寿命约为未强化试样的6.6倍,疲劳裂纹源由孔壁表面向内部偏移了约45μm。

预腐蚀条件下不同孔数冷挤压强化7075-T6铝合金板件疲劳寿命退化规律

目的研究腐蚀环境下单孔和多孔冷挤压强化铝合金板件的疲劳寿命退化规律和损伤机理。方法针对2种不同孔距的三孔冷挤压强化7075-T6铝合金板件,采用模拟热带海洋大气环境的实验室加速腐蚀谱,开展不同腐蚀时间下的预腐蚀疲劳试验。结果获得了3倍孔距的三孔挤压强化铝板以及单孔挤压强化铝板的C(t)曲线、疲劳S-N曲线和损伤形貌特征,分析了腐蚀后挤压强化试件的腐蚀机理及挤压强化作用。同时,将不同孔数试件的试验结果进行比较,探明了孔数对挤压强化铝板腐蚀和疲劳性能的影响。结论腐蚀后挤压强化铝合金板件的疲劳性能发生显著退化,腐蚀损伤主要为剥蚀,疲劳裂纹萌生位置由孔边转移至表面。挤压孔数量对挤压强化铝合金板件的疲劳和腐蚀疲劳性能的影响较小。

TC4钛合金飞机结构件开缝衬套冷挤压技术的探索

现代飞机机体上有百万颗连接件,连接件之间所对应的连接孔在运行过程中会产生疲劳。大量试验数据显示,飞机机体损伤中,绝大部分都来自机械连接处。开缝衬套冷挤压增强钻孔工艺主要应用于飞机制造、维修等行业,主要用于改善航空结构孔的疲劳寿命。通过仿真分析,研究开缝衬套冷挤压增强孔残余应力分布情况和疲劳寿命。采用有限元模型、分析、测试,确定开缝衬套冷挤压增强工艺中的TC4钛合金相对挤压率为6%和8%左右,疲劳寿命增益效应显著。

基于DEFORM-3D的齿轮冷挤压模具铣削工艺研究

汽车差速器齿轮冷挤压成形技术的关键是冷挤压模具的设计与制造。齿轮冷挤压模具设计已得到较为广泛的研究,但制造方面较少被提及。针对冷挤压模具制造现状,提出一种高速铣削加工方案。为解决模具铣削中材料硬度高、刀具磨损和让刀量大等问题,基于DEFORM-3D仿真软件,设计单因素仿真试验进行对比分析,合理分配加工余量,并优选出切削力较小、刀具磨损程度低的切削用量。该方法为研究冷挤压类模具加工工艺提供了思路。

高压电器产品中铜套冷装、压装与粘接的对比应用

铝青铜铜套具有较高强度、导热性、耐磨性及耐腐蚀性等优点,在高压电器产品中广泛应用,但在工程使用过程中,生产装配现场反馈部分小直径铜套有窜出现象。经分析,铜套窜出主要是受剪应力及滑动摩擦力影响产生的滑移现象,为进一步提升装配质量,综合材料特性、结构强度、可制造性、经济性等方面,在不改变原装配结构条件下,选择冷装、压装、粘接3种连接方式开展工艺研究。通过验证,使用压装与粘接复合工艺可提供更高的固持力,并提出一种在过盈配合基础上发挥粘接效果的设计结构,有效减小径向压力产生的摩擦力。

Low Cycle Fatigue and Strengthening Mechanism of Cold Extruded Large Diameter Internal Thread of Q460 Steel

large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.

高强钛合金冷轧管材显微组织及力学性能研究

采用Gleeble—3800型模拟试验机对Ti-1300钛合金进行冷压缩试验。通过室温拉伸性能测试和组织形貌观察,研究了挤压温度、冷轧变形量和热处理对Ti-1300钛合金冷轧管材显微组织和力学性能的影响。研究结果表明:Ti-1300钛合金冷轧管材在相变点挤压制备管坯,并控制冷轧变形量为30%,能够获得良好的强度-塑性匹配。冷轧管材经固溶处理后具有较低的强度和较好的塑性,其α+β两相区固溶组织主要由大量的球状或拉长的α相以及残留的亚稳定β相组成;β单相区固溶组织主要由等轴的β晶粒组成。时效态冷轧管材的强度显著提高,其组织主要由球状或拉长的初生α相、针状次生α相以及β基体组成。

工件底孔直径对42CrMo4内螺纹冷挤压成形的影响

为了提高螺纹的成形质量,借助有限元模拟和试验相结合的方法,对影响内螺纹冷挤压成形的关键工艺参数工件底孔直径进行了研究。采用数值模拟的方法研究了工件底孔直径与加工过程中最高挤压温度、最大挤压扭矩之间的关系,获得4种底孔直径下挤压温度、扭矩的变化曲线与成形后螺纹的牙形状况。通过试验对挤压后的内螺纹牙高、表层形貌进行了检测,同时对数值模拟得到的牙形结果进行了验证。数值模拟与试验结果表明,挤压过程中的扭矩与温度随着工件底孔直径的增大而减小,成形后的螺纹牙高同样随着底孔直径的增大而减小。对于42CrMo4钢材冷挤压M22×2的内螺纹,在保证螺纹的连接强度的条件下,为了降低挤压过程中的温度与扭矩,预制工件底孔直径选择应选择φ21.15~φ21.20mm。

超声振动辅助孔挤压强化装置研制及试验

为探究超声振动辅助孔挤压强化工艺,设计超声振动辅助孔挤压强化装置。利用ANSYS软件对设计的装置进行模态分析,测量装置的谐振频率及位移,开展孔结构件挤压强化试验。研究结果表明:模态分析中装置的谐振频率为25 542.5 Hz,测试装置的谐振频率为26 918 Hz,相对误差为5.39%;测量装置中挤压芯棒工作环部位的位移,其最大值为3.38μm;与无超声挤压强化相比,超声挤压强化后孔壁表面粗糙度降低程度大,装配孔直径增加范围为6~17μm。

汽车轻量化连接用自流钻螺钉挤压成形工艺研究

目的针对自流钻螺钉现有工艺生产效率低、易产生晶粒粗大等问题,提出了一种新的多工步冷挤压成形工艺——利用模腔控制螺钉尾部形状,并验证了该工艺的可行性。方法利用有限元软件DEFORM-3D对提出的3种不同冷挤压方案成形过程中的金属流动规律、材料填充情况、成形力进行了数值模拟,讨论了方案一和方案二中锻造缺陷产生的原因,最后根据方案三的模拟结果设计了相应模具并进行了试验验证。结果根据方案三成形出的自流钻螺钉充填饱满,第一道工序是将圆棒坯料一端直接挤压成螺钉特定的尾部形状,该工序所需成形力为42.4kN。第二道工序是将螺钉头部镦粗,该工序所需成形力为58.2kN。第三道工序是终锻成形,该工序所需成形力为287.4kN。结论通过有限元模拟,确定了自流钻螺钉三工步冷挤压成形工艺,提出了能够避免折叠产生的预制坯形状和模具结构,实现了自流钻螺钉尾部的可控成形。通过试验验证,形成了稳定的成形工艺窗口和可靠性较高的模具结构,实现了该产品的批量生产。

冷挤压工艺参数对内螺纹疲劳寿命的影响试验研究

为研究冷挤压加工工艺对42CrMo4高强度钢内螺纹疲劳性能的影响,借助ABAQUS非线性动力学软件和FE.SAFE疲劳分析软件进行联合仿真,建立冷挤压内螺纹加工模型和疲劳寿命仿真模型,分析冷挤压内螺纹残余应力的分布,探讨底孔直径、丝锥锥角和摩擦因数等典型工艺参数对冷挤压内螺纹疲劳寿命的影响。开展切削与冷挤压内螺纹的疲劳性能测试,分析内螺纹冷挤压加工工艺的强化机理。结果表明:冷挤压内螺纹的疲劳寿命明显优于切削内螺纹,是因为经过冷挤压加工,残余应力场的存在使螺纹表面疲劳源的位置由表层转移至螺纹内部的过渡部位。减小工件底孔直径能明显提升疲劳寿命,但过小的底孔直径会导致疲劳寿命下降;增大丝锥的锥角有助于改善挤入面的疲劳寿命;过大的摩擦因数会降低冷挤压内螺纹的疲劳寿命。

基于上限法的闭式冷正挤压棒料脱膜状态分析

考虑一种非磷系润滑膜的脱膜长度,通过上限法分析模型对棒料的闭式冷正挤压工艺进行了分析。通过实验获得了脱膜长度随锥模半角和断面收缩率的变化规律。实验结果表明,随断面收缩率的增长,脱膜长度快速增长。随着锥模半角的增长,脱膜长度也在增长,但是锥模半角增大到一定程度后,脱膜长度的增长幅度减小。求得总功率为最小时的最佳锥模半角,范围是15°~28°,最佳锥模半角随脱膜长度的增加而增加。在成形载荷方面,与DEFORM商用有限元分析软件的仿真结果进行了比较,上限法算得的成形载荷略大于有限元仿真结果,而且两者的载荷曲线较为相近,证明了该上限法分析模型的合理性,也表明上限法更有利于成形设备的选型。