Porous polyimide composite retainer tube blank pre-heating, limiting and pressing process

Abstract

The invention discloses a porous polyimide composite retainer tube blank pre-heating, limiting and pressing process. The process comprises the following eight steps: 1, performing pretreating of vacuum drying on a raw material of polyimide; 2, weighing according to the weight percentage, and preparing a porous polyimide composite material; 3, forming the size of a retainer mould; 4, screening the porous polyimide composite material to remove small particles or impurities which are not mixed uniformly; 5, filling the porous polyimide composite material into the mould; 6, putting the mould filled with the material into a constant-temperature drying box, and preserving heat for 20-40 minutes; 7, taking out the mould, and limiting and pressing the mould; and 8, after demoulding, putting into a programmable sintering furnace for sintering and shaping. By the porous polyimide composite retainer tube blank pre-heating, limiting and pressing process, in a free sintering process, phenomena such as loose texture, low tensile strength and large pore size and porosity of a product due to a small forming pressure as well as stress cracking and poor consistency of material properties between tube blanks due to a large forming pressure can be avoided.

Description

technical field [0001] The invention belongs to the technical field of cages, and in particular relates to a preheating and position-limiting pressing process for a tube blank of a porous polyimide composite cage. Background technique [0002] The porous polyimide composite cage tube blank is based on polyimide, adding 15% polytetrafluoroethylene solid lubricant, mixed at high speed, pressed and sintered, and then sintered into one body. The pores make it have interpenetrating porous materials inside. The lubricating oil is immersed in the micropores under vacuum conditions, and the micropores become channels for the mutual communication of the lubricating oils. Realize the microcirculation of lubricating oil in the bearing. When the external conditions such as speed, load, temperature and lubricating oil characteristics are constant, a dynamic balance is established through operation. Porous polyimide composite cage has good mechanical properties, radiation resistance, an...

AI Technical Summary

Problems solved by technology

[0003] The common room temperature pressing, demolding and thermal firing process is free sintering. The product with low forming pressure has loose texture, low tensile strength, large pore diameter and porosity; the product with high forming pressure is prone to stress cracking and the material performance consistency between tube blanks is poor. and other phenomena

Applying another kind of pressing in the mold without removing the mold and placing it in the sintering furnace for sintering at 365~380°C, that is, constant volume sintering, will cause high energy consumption, high and low temperature alternation and easy loss of the mold, and a large amount of mold must be invested in order to improve efficiency.

These factors limit the application of free sintering and constant volume sintering

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