| 摘要 |
<p>The method involves carbonitriding a piece in conditions such that a surface zone has an average quantity of nitrogen, of about 0.2 percent by weight, in austenite. The transformation of austenite into martensite is carried out in two steps. One of the steps is provided for obtaining a profile of a quantity by weight of austenite that decreases between two values. The other step is provided for reducing the quantity of austenite and for obtaining a profile of a quantity by weight of austenite that decreases between two values, by using a cryogenic treatment. The values defined in the former transformation step lie between 20 and 50 percent in the surface and intermediate zones of the piece, between 0 and 25 percent by weight in a core zone of the piece and the rest is formed of a percentage of iron precipitates containing carbon and nitrogen and a percentage of martensite issued from the transformation. The values defined in the latter transformation step lie between 10 and 40 percent in the surface zone, 10 and 30 percent in the intermediate zone, 0 and 25 percent by weight in the core zone and the rest is formed of a percentage of iron precipitates containing carbon and nitrogen and a percentage of martensite issued from the transformation. An independent claim is also included for a bearing including an inner ring, an outer ring and a rolling body placed between the rings.</p> |
