Zheng an Hu

Effect of Thread Helix Angle on the Axial Metal Flow of Cross Wedge Rolling Thread Shaft

When rolling thread shaft in cross wedge rolling, forming quality of thread is affected by many process parameters such as the thread helix angle, which is a special and complex parameter. However, there is few study of the effect of the thread helix angle on thread shaft forming. In this paper how thread helix angle affects axial metal flow was analyzed from the perspective of rolling force and the forming process of thread shaft was simulated with different helix angles by the deform-3D software. Through the measurement of the point coordinates, the effect of the helix angle on the axial metal flow of rolled pieces was analyzed. Finally, the conclusion was obtained that helix angle causes the asymmetry of axial metal flow with small difference values for asymmetry and the axial metal flow of rolled pieces increases as the helix angle increases. The rolling thread segment can be ensured in the middle of rolled pieces by moving the blank a suitable distance in the reverse direction of the axial flow direction.

Numerical Simulation and Experiment of Hot Roll Forming Large Module Gear

To compare with the other gear manufacturing methods, the hot roll forming process is applied in forming large module gear. The hot gear rolling theory is realized by modeling in Solidworks and Deform-3D, the finite element model (FEM) that coupled deformation and heat transfer was established, and the FE model velocity boundaries were set by converting the workpiece rotation into the revolution speed of the roller. The total displacement of metal flow, folding angel of teeth, effect strain and the temperature distribution of the part were obtained in the whole process of hot gear rolling, also the rolling force was predicted by simulation. The simulation results reveal the forming mechanism, and the rolling experiments were carried out with self-designed rolling mill, which verify that the hot roll forming large gear is feasible.

Effects of Die Tooth Profile on Forming Helical Tooth Shaft in Cross Wedge Rolling

The study on forming helical tooth shaft processes in cross wedge rolling can contribute to the advantages of material-saving and efficient. Die tooth profile is an important process parameter of cross wedge rolling helical tooth shaft. Three kinds of forming process of die helical teeth were simulated by DEFORM-3D finite element analysis software to analyze three different die helical tooth. According to the tooth forming characteristics, the effects of three kinds of die tooth profile on forming of a polled piece were analyzed. When rolling a polled piece using the die with the same addendum width, it is convenient for die processing and the effect of polled piece forming is better; when using the die with the narrow front and gradually wider rear, the defects of uneven tooth bottom and larger pitch may happen. The rolling experiment was made by using the die with the same width at the tooth bottom. The results are in good agreement with the simulation. Therefore, we should use the die with unchanged addendum width, tooth height and the sidewall proportional increased when designing the die.

The Numerical Simulation of GH4169 Alloy during Cross Wedge Rolling

The metal microstructure of a product formed by cross wedge rolling (CWR) has much effect on the comprehensive properties of the final product. The microstructure model of GH4169 alloy was programmed into the rigid-plastic finite element software DEFORM-3D by the secondary development in this paper, so the microstructure evolution during the CWR process can be simulated. The finite element model (FEM) that coupled deformation, heat transfer and microstructure evolution was established. Based on the model, the evolution of microstructure of GH4169 alloy in the process of CWR was realized with the simulation. The strain, strain rate, temperature and the distribution of grain size of the part were obtained in the whole process of CWR. The simulation results show that the dynamic recrystallization is the main grain refinement mechanism for the CWR process and the grain refining effect of the workpiece during the CWR process is remarkably.

The Effect and Experiment Research of Forming Angle on Internal Defect of Valve Roughcast Formed by Single Cross Wedge Rolling

Cross wedge rolling valve roughcast is charactered by minor diameter, long stretching and heavy section shrinkage; however, it is hard to select a set of suitable machining process parameter and prone to rolling internal defect. In order to research this problem, a whole forming process of valve roughcast by single cross wedge rolling is simulated with finite element simulation software DEFORM-3D 6.0, which focuses on the stress and strain of the center point of rolled piece under different forming angles. The rolling experiment under different forming angles was done on H500 rolling mill to calculate and analysis of the areas of the centre holes for each rolled piece. The influence of forming angle on internal defect is discovered by a method combining finite element simulation and experiments. At last, it is concluded that forming angle of 28°can improve the internal defect of valve roughcast formed by single cross wedge rolling.

Effect of Blank Shape and Size on the Forming Quality of Thread Shaft Rolling in Cross Wedge Rolling

The defects of the lower tooth height and of larger pitch in thread portion of rolled pieces are prone to appearing when rolling thread shaft in cross wedge rolling. To solve this problem, changing the blank shape and size were tried. Two types of concave conical and round blanks are designed with concave conical blanks obtained by rolling in the cross wedge rolling. Because the design of the rolling die is simple, good precision of blank can be ensured. Multiple size types of blanks were designed and the rolling experiment was made in the rolling mill of model H630. By measuring the values of the tooth height and pitch, the effect of blank shape on thread shafts rolled in the wedge rolling were investigated carefully. The reasonable size range of the blank shape was obtained. The conclusions above pave the theoretical foundation for the in-depth study on this technology.

Analysis of the Wedge Tip Fillet for Central Defeats in the Process of Cross Wedge Rolling 4Cr9Si2 Valve

Forming process of 4Cr9Si2 martensite refractory steel by cross wedge rolling was simulated by means of rigid-plastic finite elementDEFROM-3D software. From wedge tip angle to analyze the central defeats: The increase of maximum stress and its duration time is resulted from the rise of wedge tip fillet (R); the maximum shear stress and maximum shear strain did not change significantly, but its duration time will enlarge with increasing of wedge tip fillet; these factor will lead to the higher possibility of internal defeats. Rolling experiments are carried out to verify the correctness of the FEM and feasibility of simulation results by the experiment: internal defeats have appeared in the conditions of R=12mm.

Study on 4Cr9Si2 Martensitic Heat-Resistant Steel in CWR

4Cr9Si2 Martensitic heat-resistant steel is inlet valve and the exhaust tappet materials. This paper is based on the constitutive relationship of 4Cr9Si2 Martensitic heat-resistant steel obtained by isothermal compression; a finite element model of Cross Wedge Rolling was build up for 4Cr9Si2 Martensitic heat-resistant steel. In the model the heat conduction between billet and the die, the convection of heat transfer, and the thermal conversion of plastic work and friction work were taken in account, the value of damage was obtained in the rolling and central porosity was analysis. Then verify the correctness of the FEM and feasibility of simulation results by the experiment

The Analysis of the Stress and Strain in Skew Rolling

In this paper, three-dimensional finite-element model for the skew rolling (helical-groove rolling) process has been used to characterize the workpiece material stress,strain and deformation behavior. Particular attention has been paid to representative cross section and the center, edge and mid-radius points of the billet

Effect of Process Parameters on the Temperature of 4Cr9Si2 Martensite Refractory Steel during CWR

Based on the constitutive relationship of 4Cr9Si2 martensite refractory steel obtained by Gleeble-1500 hot simulation isothermal compression, a finite element model of Cross Wedge Rolling was build up for 4Cr9Si2 Martensite and the heat conduction, convection, plastic work and friction work were taken in account in the model. The forming process of 4Cr9Si2 martensite refractory steel by cross wedge rolling was simulated by means of DEFORM-3D software. The influence regularities of temperature of rolling process parameters were obtained: temperature rise rapidly result from plastic work and friction work in the cross-section at the process of rolling, with the completion of rolled piece cross-section, temperature descending due to heat conduction and radiation with atmosphere. The rolled piece temperature difference decrease with rolling speed and die preheat temperature increasing, the billet heating temperature is little for rolled piece temperature difference compared with rolling speed and die preheat temperature.