| 摘要 |
PURPOSE:To improve durability and quick heatability by using a composite core material having a positive high resistance temperature coefficient and covered with a metal or an alloy having a higher oxidation resistance than that of the core material for heating element. CONSTITUTION:An iron core metal 2 having a positive high resistance temperature coefficient is inserted into an alloy tube 1 made of heat proof metals, such as Ni-Cr, Ni-Cr-Fe and Fe-Cr-Al for covering. Through this constitution, a temperature in a complex resistance wire is first increased quickly as the conductivity depends on iron up to a temperature of about 700 deg.C. Then, when specific electric resistance of the core material 2 becomes almost equal to that of the heat resistant alloy tube 1, the heat generated by the resistance becomes controllable with the heat resistant alloy, the temperature dependence is lowered and the Joule heat attains the limit at a fixed temperature without a special control circuit. Then, the heat resistane is improved and preheating time can be reduced. |
