Dimension Control of Workpieces on the Machining of Bearing Steel in Supercooled Austenite
1984 Volume 70 Issue 3 Pages 404-411
Details
1984 Volume 70 Issue 3 Pages 404-411
On machining of bearing steel in supercooled austenite, the dimensions of a workpiece change due to the thermal contraction and the martensitic transformation in the cooling process after cutting.
In order to obtain the precise dimensions of the workpiece at room temperature, it is necessary to predict the dimension changes and to adjust the tool paths to compensate for them in the machining process of the steel in supercooled austenite. A method to predict the dimension change was estabished. A dimension control system for an NC machine tool was designed and its performance was proved by experiments.
The obtained results are summarized as follows;
(1) The thermal contraction rate of supercooled austenite of bearing steel SUJ3 is 2.2×10-5/ °C.
(2) The final dimension (L) of a workpiece is expressed by the following equation in terms of the temperature (T°C) of the workpiece during cutting and the machined dimension (l) of supercooled austenite. L=l(1.0077-2.2×10-5×T)
(3) In the case when the tool wear rate is small, the final dimension is controled precisely by means of the developed dimension control system which makes the compensation of the machining dimension for the dimension change predicted at each temperature of workpieces on the basis of the thermal contraction rate of supercooled austenite.
