PURPOSE: To absorb any harmful influence due to differential thermal expansion by attaching each ceramic plate to the metal base of a valve element so as to form a specified clearance in space between the ceramic plates adjoining with each other in a cold state at time of disuse.

CONSTITUTION: The tip of a valve element 4 is covered with plural ceramic plates 14 with abrasion resistance, and each ceramic plate 14 is clamped to a heat resistant base plate 15 welded to the valve element 4 with a securing pin 16. In addition, a ceramic cap 17 is installed as covering a head part of the securing pin 16. Each ceramic plate 14 is attached to the ceramic plate 15 so as to get a specified clearance 19 formed between ceramic plates adjoining to each other in a cold state at time of disuse, namely, at the initial state. The valve element 4 is retractable by operation of a valve stem, and thereby a flow rate is controlled but a wearing action works strongly at a tip part of the valve element 4 in particular. However, the tip of the valve element 4 is ensured with abrasion resistance by the ceramic plate 14, through which a thermal expansion difference to be produced between the ceramic plate 14 and the base plate 15 at time of use at high temperature is well absorbed by the clearance 19.