PRETREATMENT METHOD OF HEATING CHAMBER OF VACUUM CARBURIZING FURNACE

• Main Authors: TANAKA TATSUMI, OSHIRO RIKIYA, MIYAKOSHI NOBORU, HARAI SATORU, MACHI TETSUJI
• Format: Patent
• Language: English
• Published: 27.03.2008
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

PROBLEM TO BE SOLVED: To provide a pretreatment method of a heating chamber of a vacuum carburizing furnace which is less wasteful in consumption of carburization gas, energy or the like, and less wasteful in process, and to prolong the lifetime of a zirconia type oxygen sensor. SOLUTION: Any work is not conveyed into a heating chamber 6 of a vacuum carburization furnace 1, but the heating chamber is closed and sealed, and heated and evacuated to discharge adsorbed oxygen in a structure in the furnace until the oxygen partial pressure in the heating chamber reaches not higher than a predetermined value. After re-starting the heating chamber, the heating chamber is heated and evacuated. When the oxygen partial pressure in the heating chamber is not lower than the predetermined value, and if the amount of the adsorbed oxygen from the structure in the heating chamber after the completion of burnout, after the exchange of the structure in the furnace or the like, the pretreatment is performed. The temperature in the heating chamber is set to be lower than the vacuum carburization temperature, and the predetermined value of the oxygen partial pressure in the heating chamber is set to be ≤1×10-19.6atm. A zirconia type oxygen sensor is used for measuring the oxygen partial pressure. During the vacuum carburization, the zirconia type oxygen sensor and the hydrocarbon gas in the heating chamber are not subjected to the contact reaction with each other. COPYRIGHT: (C)2008,JPO&INPIT