Powder/Wire Mesh Composite Rolling Micron Pore Porous Plate And Its Application For Aerostatic Bearings

Powder/wire mesh composite micron pore porous plate is a new type of porous metal material with numerous interpenetrating pores,which is made of metal powder and wire mesh by composite rolling and solid-state sintering.Porous aerostatic bearing is a hydrostatic lubrication bearing with porous material as restrictors and gas as lubricant.Because the porous material has various micron-sized pore structures,it does not need to additionally process of the micron pore structure.So,it has the advantages of high bearing capacity,good stability and lower processing cost compared with the aerostatic bearing with small orifice throttling.Current applications of porous materials for restrictors include porous graphite,porous ceramics,porous metal powder metallurgical materials.However,porous graphite is easy to deformation and fall off,porous ceramic is brittle and difficult to machining,and traditional porous metal powder metallurgy materials are difficult to have effective permeability and mechanical properties at the same time.In order to obtain a porous metal material with plenty of microns sized pore structures and excellent permeability and mechanical properties,this paper used of metal powder sintered easily available micron pore and continuous dense metal wire mesh the characteristics of high intensity,proposed a manufacturing method of a new type of powder/wire mesh composite rolling micron pore porous plate,and developed processing equipment,explored the processing technology.The pore sizes distribution,microstructure and phase,permeability,mechanical properties of the material and its practical application in aerostatic thrust bearings and journal bearings were investigated.In this paper,an integrated rolling equipment including powder wire mesh laying device,rolling device,and winding device was developed.It has high processed efficiency and is convenient to realize large-scale industrial production.Based on the flatness control theory,the mechanism of wavy defect caused by buckling instability of porous strip was analysed.A novel wet process rolling method was proposed and the effect of roller speed on rolling effect was studied.Reducing the rolling speed was useful to improve the rolling effect.Specifically,the phenomenon of wavy defect of the porous strip can be eliminated by decreasing the roller speed to 1 r/min and supplemented by wet process rolling.The air permeability of the coarse powder porous composite thin plates reaches 2.31×10^-12 m².The ultimate tensile strength of the fine powder porous composite thin plates reaches 157 MPa.Its manufacturing process is environment-friendly and efficient without binder and degreasing.A new type of powder and wire mesh composite porous plate was fabricated by composite rolling and vacuum solid-state sintering of the porous thin plate and wire mesh.The microstructure of the composite porous plate was mainly composed of austenite and ferrite.The effects of wire mesh volume content,diameter and sintering temperature on impact and tensile mechanical properties of the material were investigated.Impact toughness of the composite porous plates decreases with increasing wire mesh volume fraction,and increases first and then decreases with increasing wire mesh diameter,and increases with increasing sintering temperature.When the sintering temperature increased to 1360°C,the impact toughness increased to 72.95 J/cm².Low volume fraction and small diameter of wire mesh and sintering temperature over 1310°C were beneficial for composite porous plates to obtain higher impact toughness.The tensile strength of the composite porous plate decreases first and then increase with increasing mesh volume fraction and mesh diameter and increase with increasing sintering temperature.When the volume fraction of the wire mesh is 65.7%,the diameter of the wire mesh is 120μm,and the sintering temperature is 1360°C,the tensile strength of the composite porous plate increased to 593 MPa,which are much higher than those of the wound steel wire material and the wire mesh porous plate.Based on particle filling technology and powder metallurgy technology,a new method of fabricating powder wire mesh composite gradient porous plate by using powder and wire porous plate was presented in this paper.A novel stainless steel gradient porous plate with porosity ranging from 15%to 26%and the average pore size below 10μm was fabricated.The effects of porosity and sintering temperature on pore size distribution,permeability and tensile properties were investigated.The permeability decreases and the tensile strength increases of the material with the decrease of porosity and the increase of sintering temperature.When the porosity is 23.56%and the sintering temperature is 1330°C,the air permeability of the porous gradient plate reached 1.27×10^-13 m²,and the tensile strength reached 258 MPa.A new type of three-dimensional porous stainless steel was fabricated by compression moulding and vacuum sintering of stainless wire mesh,and its anisotropic permeability,tensile and compressive properties were investigated.The results indicated that the radial air permeability reached 3.1×10^-11 m².The axial compressive strength was higher than the radial compressive strength and reached 1249 MPa.Porous aerostatic thrust bearing and porous aerostatic journal bearing were fabricated by using the powder wire mesh composite micron pore porous plate as the restrictors,and the static and dynamic performance test system of the aerostatic bearing was established.Based on the basic equations of hydrodynamics,the gas pressure distribution and load capacity of porous aerostatic thrust bearings and journal bearings were analyzed.The static load performance of porous aerostatic thrust bearings and journal bearings was numerically calculated by Fluent software.When the diameter of the porous restrictors is 45 mm and the air pressure is 0.5 MPa,the maximum load capacity of the porous aerostatic thrust bearing reached 727 N.A novel combined porous aerostatic journal bearing which can adjust the pressure difference between upper and lower was proposed.When the upper bearing bush was supplied pressure with 0.5MPa and the lower was 0.1 MPa,the maximum load capacity reached 290 N.The vibration reduction ratio of the porous aerostatic journal to the high-speed motorized spindle in the radial direction reached 23.63%,and in the axial direction reached 54.3%.This paper has a guiding significance for the practical application of powder/wire mesh composite micron pore porous plate in porous aerostatic bearings.