| Austenitic stainless steels have good mechanical properties, easy molding and low costadvantages, meanwhile the corrosion resistance is also excellent, for which are widely used inbiomedical materials.In this paper, the main subject of study is austenitic stainless steel screws. The austeniticstainless steel screws are basically used to implant in the human body. During the surgery, thetorque and torsion angle are increasing with the screw forward. If the toughness of screw is lowwhich may result in the twisting off of screws , surgery will fail and increase the patient'ssuffering. This subject aims at improving the plasticity of stainless steel screws by heattreatment,, building on the premise that do not change the screws'shape, while the strength ofaustenitic stainless steel screw will not be reduced, so the stainless steel screw has high strengthand plasticity.This paper studied the effect of different heat treatments on the torque and torsion angle.The process of the heat treatments are as follows, solid solutionized at 950℃and air-cooled,solid solutionized at 1050℃and air-cooled, solid solutionized at 950℃and water-cooled, andsolid solutionized at 950℃, then the samples are heated to 750℃and preserved for 7h. Theresults show the torsion angle is greatly increased, while torque is reduced in varying degreesthrough the first three heat treatments, and the torsion angle is also increased and the torqueachieve national standard through the fourth treatment. The grains grow to varying degrees bythe first three heat treatments and grains are uniformity by the last heat treatment. Optimizingheat treatment process parameters ,the optimum solution heat treatment temperature is solidsolutionizing at 950℃for 1h, air cooling and then heat preserving at 750℃for 7 hours, whichleads to the well fit of torque(4.63N ? m), and torsion angle(1544.84°). The torsion angle of isover ten times than the one of untreated screw when the torque keep invariant, which are fullymeet the national standards. |
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