| 摘要 |
<p>The spool and/or the sleeve for the slide valve are wholly or partly made from silicon nitride, by extrusion, conventionally or isostatically, the latter using a dry powder and nitrided afterwards. Moulding in a press or by injection, can also be used allowing the ports and passageways to be formed. For other processes, shaping is done by grinding and lapping. The spool is provided with a stainless steel operating spindle through its axis and both components are given a final treatment by impregnation of the pores with a low friction material, such as polyetrafluorethylene.</p> |
