Filling Rules of Bevel Gears in the Closed-die Cold Forging

The closed-died cold forging technology of the bevel gears used in Jada car was investigated. With the analysis of the strain field and velocity field of the plastic deformation and the endured forces of the dies, the filling rules for the metal were analyzed by the elastic-plastic finite element method （FEM）. The results show that there is a great difference among closed-die cold forging, extrusion and forging, as far as the metal flowing is concerned. The outer addendum cannot be filled completely in the closed-die cold forging of the bevel gears, and the round angle will be formed. But it does not influence the application of the bevel gears. At the beginning, the rigid area is formed in the cavity of the lower die. And then it will move upwards to supply the metal for the gear filling. For the closed-die cold forging of the bevel gears, the force acting on the upper die and the lower die is significantly different.

Controlled Rolling and Cooling Process for Low Carbon Cold Forging Steel

Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 ℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.

Volume calculation of the spur gear billet for cold precision forging with average circle method

Forging spur gears are widely used in the driving system of mining machinery and equipment due to their higher strength and dimensional accuracy.For the purpose of precisely calculating the volume of cylindrical spur gear billet in cold precision forging,a new theoretical method named average circle method was put forward.With this method,a series of gear billet volumes were calculated.Comparing with the accurate three-dimensional modeling method,the accuracy of average circle method by theoretical calculation was estimated and the maximum relative error of average circle method was less than 1.5%,which was in good agreement with the experimental results.Relative errors of the calculated and the experimental for obtaining the gear billet volumes with reference circle method are larger than those of the average circle method.It shows that average circle method possesses a higher calculation accuracy than reference circle method(traditional method),which should be worth popularizing widely in calculation of spur gear billet volume.

Experimental study of the mechanical property of barrel processed by cold radial forging

The cold radial forging process usually introduces some changes of the material, such as the increased strength, the decreased plasticity and the introduction of anisotropic mechanical prop- erty. To obtain the changes of mechanical property of barrel processed by cold radial forging, the tangential mechanical properties of the barrel blank and the forged barrel are measured with a de- signed test based on the plastic deformation analysis for a barrel and by applying internal pressure, and their axial mechanical properties are measured by the tensile test. The changes of mechanical property of barrel processed by cold radial forging are obtained by comparing the mechanical proper- ties of the barrel blank and the forged barrel. The tangential and axial flow stresses of the barrel blank and the forged barrel are also presented.

Finite element analysis and simulation for cold precision forging of a helical gear

To investigate the effects of billet geometry on the cold precision forging process of a helical gear,six different billet geometries were designed utilizing the relief-hole principle.And the influences of the billet geometry on the forming load and the deformation uniformity were analyzed by three-dimensional(3D)finite element method(FEM)under the commercial software DEFORM 3D.The billet geometry was optimized to meet lower forming load and better deformation uniformity requirement.Deformation mechanism was studied through the distribution of flow velocity field and effective strain field.The forging experiments of the helical gear were successfully performed using lead material as a model material under the same process conditions used in the FE simulations.The results show that the forming load decreases as the diameter of relief-hole d0 increases,but the effect of d0 on the deformation uniformity is very complicated.The forming load is lower and the deformation is more uniform when d0 is 10mm.

Fatigue Behavior of Cemented Carbide Die in Cold Forging of Steel

The fatigue behavior of cemented carbide die under service load in the multistage cold forging of steel was investigated. It was found that the fatigue cracks do not initiate at the stress concentration position and the crack initiation position can be classified to three types. The crack initiation position can be predicted by FEM only when the plastic deformation of the die is considered.

Numerical and experimental study on new cold precision forging technique of spur gears

A new cold precision forging technique is proposed to form a spur gear from a hollow billet, that is blocking the divided flow region and then final forging by the relief hole. 3D FEM simulation of the whole process of a pure aluminium spur gear is performed using DEFORM 3D TM . The load stroke curve, effective stress distribution, effective strain distribution, velocity distribution, and so on, are achieved. These results are compared with those achieved using the conventional closed die forging in the same conditions. The results show that this new technique has many advantages over the conventional one. The deformation load is reduced by near 30% and the filling ability of the tooth profile is also improved. Precision forging experiments of spur gears with the new process were performed using material Pb. The experimental results show a good agreement with the numerical results.

Modelling and simulation of contact force in cold rotary forging

Cold rotary forging is an advanced and complex metal forming technology with continuous local plastic deformation.Investigating the contact force between the dies and the workpiece has a great significance to improve the life of the dies in cold rotary forging.The purpose of this work is to reveal the contact force responses in cold rotary forging through the modelling and simulation.For this purpose,a 3D elastic-plastic dynamic explicit FE model of cold rotary forging is developed using the FE code ABAQUS/Explicit.Through the modelling and simulation,the distribution and evolution of the contact force in cold rotary forging is investigated in detail.The experiment has been conducted and the validity of the 3D FE model of cold rotary forging has been verified.The results show that: 1) The contact force distribution is complex and exhibits an obvious non-uniform characteristic in the radial and circumferential directions; 2) The maximum contact force between the upper die and the workpiece is much larger than that between the lower die and the workpiece; 3) The contact force evolution history is periodic and every period experiences three different stages; 4) The total normal contact force is much larger than the total shear contact force at any given time.

Effect of key factors on cold orbital forging of a spur bevel gear

Cold orbital forging is an advanced spur bevel gear forming technology. Generally, the spur bevel gear in the cold orbital forging process is formed by two steps: the preforming step and the final step. Due to the great importance of the final step to gear forming and its complication with interactive factors, this work aims at examining the influence of key factors on the final step in cold orbital forging of a spur bevel gear. Using the finite element(FE) method and control variate method, the influence rules of four key factors, rotation velocity of the upper tool, n, feeding velocity of the lower tool, v, tilted angle of the upper tool, γ, friction factor between the tools and the billet, m, on the geometry and the deformation inhomogeneity of the cold orbital forged gear are thoroughly clarified. The research results show that the flash becomes more homogeneous with increasing v, increasing m, decreasing n or decreasing γ. And the deformation of the gear becomes more homogeneous with increasing v, decreasing n or decreasing γ. Finally, a corresponding experiment is conducted, which verifies the accuracy of FE simulation conclusions.

Deformation and Densification Laws of Powder Cold Forging

The deformation and densification laws of preform upsetting and closed-die forging were researched based on experimental results of cold forging of deoxidized Fe powder sintering porous material under different initial conditions such as friction factor, ratio between height and diameter and relative density. The fracture limit criteria＂ for powder cold-forging upsetting and the limit strain curve were achieved. The effect of friction facto,, ratlt, between height and diameter and relative density on fracture strain limitation was emphatically analyzed. The limit process parameter curves for the deformation of upsetting were also confirmed. Laws of deformation, densification and density distribution for closed-die forging of powder perform during cold-forging were further analyzed and discussed with the help of experimental phase analysis. As a result, this experiment established theoretical foundations for the design of preform and die as well as optimization of technological process parameters.

Homogeneity of microstructure and Vickers hardness in cold closed-die forged spur-bevel gear of 20Cr Mn Ti alloy

Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.

半轴齿轮的热—冷复合锻造中冷锻充不满缺陷的成形数字仿真及工艺研究

针对半轴齿轮热—冷复合锻造中冷锻整形时出现的充不满缺陷,利用UG、Geomagic-Design和Deform-3D等软件,对冷锻毛坯(热锻成形的工件)进行了重新设计和冷锻整形工序仿真模拟,全面考查齿厚、齿高参数变化对产品质量的影响。从模拟结果来看,当冷锻整形开始合模时,毛坯初始位置齿顶和冷锻模具型腔之间的间隙越大(齿厚增加越大/齿高减小越大)时,终锻时所需的锻压力越大,在产品小端齿顶处越易形成折叠缺陷。毛坯初始位置齿顶与型腔贴合(齿厚增加量为零或为负),则不易产生折叠缺陷,齿侧和冷锻模具型腔之间的间隙越大(实际齿厚越小),所需锻压力越大。经过实际生产验证,在相应的齿轮参数条件下,冷锻毛坯比冷锻模具型腔轮廓的齿高增加0.1 mm、齿厚不变时,冷锻整形后齿槽和齿高全部压满,成型质量好,产品废品率达到预期要求。

锻钢冷轧工作辊表面剥落原因

某冷轧厂锻钢冷轧工作辊表面发生剥落事故,采用宏观观察、化学成分分析、硬度测试、超声检测、金相检验等方法分析表面剥落原因,结果表明:轧制过程中有异物压入,使冷轧工作辊表面局部产生应力集中点并萌生裂纹,裂纹在轧制力的作用下沿晶界扩展;冷轧辊表面缺陷和次表层夹杂是轧辊表面剥落的根本原因。

挤压工艺对冷锻用6061合金棒材组织的影响

本文采用热挤压、冷锻造及高低倍观察等方式研究了合金成分、挤压温度及挤压速度对冷锻毛坯组织的影响。结果表明:合金中添加Cr和Mn合金元素能显著改善挤出棒材的内部晶粒组织形貌;采用高温高速的挤压工艺可以使低Cr和Mn合金挤出棒材整个截面呈完全细晶状态,满足了冷锻工艺对原材料品质的需求,同时也大幅提升了挤压生产效率,是最经济、有效的工业化生产方案。

基于Forge的止动片冷锻冲裁成形数值仿真

针对有孔较厚板材的成形问题,结合冷锻及冲裁工艺特点得到了某型止动片有孔板材冷锻冲裁成形工艺,分析了其冷锻冲裁成形原理。运用仿真软件Forge建立了止动片冷锻冲裁成形数值仿真模型,对其在不同冷锻冲裁时间下的等效应力、等效应变和应变能变化规律以及成形损伤特性进行了研究。结果表明:止动片在不同冷锻冲裁时间下,其等效应力、等效应变及应变能分布区域存在差异,但等效应力、等效应变及应变能变化趋势基本一致,最大值都出现在冲裁孔边缘。

Evaluation of dry-in-place lubricants for cold forging by using an optimal steady combined forward and backward extrusion testing method

This study evaluated dry-in-place lubricants used for cold forging.A group of isothermal compression tests with a strain rate(ε)e&range of 0.001–1 s^(−1) and temperature(T)range of 30–400℃ were completed.The flow stress(σ)curves of annealed steel S45C were obtained,and a corresponding Hensel–Spittel model was developed to support finite element(FE)simulation.The sensitivity of the steady combined forward and backward extrusion(SCFBE)test proposed in another study was improved by approximately 20%after it was optimized using the results of the FE simulations.Key parameters were identified,and the calibration curves after optimization were obtained.On the basis of the optimized test,a friction testing setup with a heating system was developed,in which the die temperature could be adjusted from room temperature(RT)to 230℃.Three dry-in-place lubricants and conventional phosphating lubricant were tested,and the friction factors(m),forming loads,and ejection loads were measured.The surface features of the specimens after testing were also investigated.According to the testing results,of the three tested dry-in-place lubricants,the mica type was the best.In addition,the optimized friction testing design was verified as effective.

冷温锻压力机下顶料机构优化设计

本文对冷温锻压力机下顶料装置进行结构优化设计。通过结构优化,降低了零件重量,有效减少了加工装配工作量,方便顶出时间的调整,节省安装时间,维修方便。

基于COLDFORM的汽车万向节接头多级冷锻成形数值仿真

针对高精度汽车万向节接头力学性能高、表面质量优和形状复杂的情况,先对其原有成形工艺进行分析,再对其成形工艺进行改进。针对改进后的成形工艺,建立了有限元仿真模型。运用专业有限元软件COLDFORM对其成形过程进行数值仿真,得到了汽车万向节接头在多级冷锻成形过程中的锻压力、锻压温度及等效应力等。结果表明：多级冷锻成形过程中镦头工序压力最大,冷锻成形工序压力最小。结果能为高精度、高强度汽车万向节接头成形及工艺优化提供参考。

变速箱长柄法兰轴工艺分析及模具关键结构设计

目的根据长柄法兰轴的结构特点,制定一套产品的成形工艺方案并投入到生产中。方法法兰轴是双离合器变速器输出端与差速器连接的重要零件,其形状复杂,成形难度较大,根据产品的特点,制定温锻-冷锻联合成形的工艺方案。针对温锻工序中锻件内腔难以充满的问题,利用DEFORM对工艺中的关键步骤进行模拟仿真,并根据模拟结果对模具进行补偿设计,使锻件内腔底部与模具之间的间隙降至0.3 mm以下。考虑到金属的剧烈流动会加重模具的磨损,设计一套模具润滑系统,以提高模具的使用寿命。而锻造过程中模腔内形成密闭空间,压缩的空气会阻碍金属充填型腔,因此,在凹模与凸模上设计出一套模具排气系统,以避免塌角缺陷的产生。结果实现了长柄法兰轴工件的工业化生产,生产效率可达每分钟12.5只。结论根据数值模拟的结果对模腔面进行优化,设计了一套模具的润滑结构与排气结构,避免了锻造缺陷的产生,为双离合器变速箱长柄法兰轴产品的温冷锻工艺生产提供了经验依据。