| 摘要 |
<p>PURPOSE:To prevent the welding each other at graphitizing process, and to increase the yield rate with good welding, by using Fe alloy causing thin selective oxide film or Cr at the surface, for the material of sleeve at the lower end of internal sleeve of the double type sleeves. CONSTITUTION:The open cut 3 is placed toward inside for three directions at the lower end of the external sleeve 1. The base metal 5 is fitted at the top of the inside sleeve 4 made of nichrome and the third sleeve 6 is welded at the lower end. This sleeve is placed in the wet type hydrogen furnace and graphitizing process is made. Next, the third sleeve 6 in welded to the cut open 3 of the external sleeve, forming the coaxial duplex sleeve, and the heater 7 in inserted to the inside. With the cathode of the said constitution, at least one type of Co and Ni and the alloy added with Cr are used for the base of Fe for the third sleeve material, forming the thin selective oxide layer taking Cr as major material on the surface at manufacture. With this constitution, the defect due to welding of sleeve is prevented and without injuring the weldability, high temperature, greater strength, high yield rate and quality can be given.</p> |
