Model-based parameter identification of comprehensive friction behaviors for giant forging press

A new experimental apparatus was set up to investigate the actual fi-iction characteristics on the basis of speed control of the serve system.A modified friction model was proposed due to real time varying deformation resistance.The approach to identify the parameters of comprehensive friction behaviors based on the modified model was proposed and applied to the forging press.The impacts on parameters which the external load had were also investigated.The results show that friction force decreases with velocity in the low velocity regime whereas the friction force increases with the velocity in the high velocity regime under no external load.It is also shown that the Coulomb friction force,the maximum static friction force and the vicious friction coefficient change linearly with the external load taking the velocity at which the magnitude of the steady state friction force becomes minimum as the critical velocity.

Design of a 70 MPa Two-Way Proportional Cartridge Valve for Large-Size Hydraulic Forging Press

For an ultra-high-pressure hydraulic transmission system of a large-size hydraulic forging press(LHFP),a 70 MPa two-way proportional cartridge valve has been developed to improve the power weight ratio of the hydraulic forging press.In this study,a nominal diameter 25 mm(DN25)cartridge valve is taken as the research object.A longer concentric cylindrical annular gap is set to effectively prevent the ultra-high-pressure oil from flowing to the pilot stage and a seated valve structure is set to form the linear sealing zone in the closing state of the main valve port.Electric-displacement feedback is adopted to realize precise control of the main valve port flow and the features of this valve are investigated.In order to verify the strength and static and dynamic characteristics,the finite element model and a simulation model of the valve proposed above are built.There is a little deformation which does not affect the main valve spool movement,and the main valve port flow meets the design demands.Then,the prototype of DN2570 TPCV is manufactured and a ultra-high-pressure experimental platform is developed.The experimental results show that the DN2570 TPCV designed in this study has the advantage of fast response,high control precision,and low leakage,which can meet the requirements of LHFPs.

Microstructure and Carbides Characteristics of Spray Formed 9V High Vanadium Steels

To develop advanced high speed steel with high vanadium content,a kind of vanadium content 9% high speed steel in the form of circular ring was spray formed under certain thermal conditions.The carbides topography of as-cast and as-sprayed 9V steel were observed.The effects of post thermo-mechanical processing（hot isostatic pressing and hot forging） and heat treatment on the microstructure and carbides distribution were investigated.The spray formed 9V steel typically consists of fine,homogeneous and angular-shaped MC carbides with diameters ranging from 1 to 2 μm.Spray formed 9V steel shows an excellent hot workability following increase of forging ratio due to fine homogeneous carbides.After heat treatment,spray formed 9V steel is composed of MC carbides,martensite and retained austenite.The hardness value of heat treated materials is inversely proportional to the volume fraction of residual austenite.Fine dispersed MC carbides have significant influences on the dislocation motion of spray formed 9V steel.

Numerical Analysis of Unconventional Forging Process of Hollowed Shaft from Ti-6Al-4V Alloy

This paper presents theoretical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy in a three-slide forging press.This method in comparison with other metal forming methods allows for obtaining of hollowed products.The designed process is verified theoretically by means of numerical simulations based on finite element method with assumption of 3D state of strain.The following factors are considered in the analysis:material flow kinematics,strain distribution,temperature distribution and force of process.On the basis of results,it is stated that the application of designed technology allows for obtaining of a product of assumed quality.A comparison is made between material consumption in analyzed process and material consumption in typical metal forming methods,also in used at present technology of shaft manufacturing by machining only.It is stated that the application of forging in the three-slide forging press allows for a considerable decrease of manufacturing costs due to material savings and decrease of labor consumption of operations at finishing.