Journal Published Online: 24 September 2018
Volume 8, Issue 2

Distortion-Free Heat Treatment of Thin Rods in Magnetic Field



The problem of distortion during the quenching of thin rods (shafts, rollers, sewing needles, etc.) is serious, making vital the need for straightening (often by hand). The device for the heat treatment of thin rods was developed. The use of the device avoids distortion of the rods and improves their structural characteristics. A distinctive feature of the device is the use of a constant magnetic field (intensity up to 800 kA/m). The magnetic field performs an orienting function. When the part is immersed in the hardening liquid, the magnetic field of the solenoid orients the rod vertically. This ensures the magnetic fixation of the part. In addition, the magnetic field controls the heating temperature for quenching. The device was used for heat treatment of sewing needles made of U10A (UNS T72301) steel. The needles are held vertically in the upper part of the tube furnace by means of a magnetic field. When heated to a temperature of 740°C–750°C, the steel parts lose their ferromagnetic properties and fall vertically downwards. During the fall, they are further heated to a quenching temperature of 780°C. For this purpose, the height of the furnace (in this case 1,000 mm) is specially calculated. In the quench tank, the needles are in a strictly vertical position. In addition, the effect of the magnetic field on quenching leads to an enhancement of the martensitic transformation. The dispersity of individual crystals and laths of martensite increases. The volume fraction of lath martensite in alloys with a mixed morphology is increasing. The degree of self-tempering increases. The preferential arrangement of martensite crystals in the direction of the magnetic field lines is present. Thus, the device improves the structural characteristics of thin rods and excludes their distortion.

Author Information

Pustovoit, Viktor Nikolaevich
Department of Physical and Applied Material Science Department, Don State Technical University, Rostov-on-Don, Russia
Dolgachev, Yuri Vychislavovich
Department of Physical and Applied Material Science, Don State Technical University, Rostov-on-Don, Russia
Pages: 5
Price: $25.00
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Stock #: MPC20170159
ISSN: 2379-1365
DOI: 10.1520/MPC20170159