TWO-STEP INDUCTION HEAT TREATMENT OF CYLINDRICAL PARTS

• Main Author: TAGAWA TOMIHIRO
• Format: Patent
• Language: English
• Published: 03.12.1993
• Edition: 5
• Subjects: CHEMISTRY; CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION ORPROCESSING OF GOODS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE

PURPOSE:To harden steel parts to a prescribed hardness with quenching without devel oping quench crack by induction-heating the outer surface of the steel parts at the time of quenching the cylindrical steel parts from a specific temp. or higher with a heat treatment apparatus arranged in the hollow part. CONSTITUTION:The temps. of the inner surface and the outer surface of the cylindrical steel parts W are heated at the Ac3 transformation point or higher so that the temp. gradient becomes the straight line while vertically moving a first induction heating device 1 in the hollow part of the cylindrical body W with a rod 3. While heating by vertically moving a second induction heating device 6 arranged near the outer surface of the cylindrical body W with a rod 7 so as to synchronize the shifting of the first induction heating device 1, by injecting cooling water from a cooling water injecting device fitted to the first induction heating device 1, the quenching is executed to make the inner surface high hardness martensitic structure. As the second induction heating device 6 heats the outer surface of the cylindrical body W at the same time, the outer surface of the cylindrical body is cooled at slower cooling rate than the critical cooling rate in the continuous cooling transformation curve (CCT curve) of thus steel, and the hardness is lowered and the development of the quench crack caused by expansion is reduced.