Installation for water quenching of oxidizing materials. For long-term annealing of metals and alloys in laboratory practice, vacuum furnaces of the type TGV-1, TBB-2, TVB-3, etc. are used with a heating temperature of up to 2000 ° C. Significant disadvantages of these furnaces are the duration of heating (at least 2-4 hours to 2000 ° C) and the lack of devices for rapid cooling. High-temperature laboratory furnaces with tungsten or molybdenum heating elements have a heating zone surrounded by a ceramic lining, which at high temperatures pollutes the atmosphere of the furnace.
At the Institute of Metallurgy of the Academy of Sciences of the USSR an installation was developed and manufactured in which the shortcomings of industrial laboratory furnaces produced by industry were eliminated.
The laboratory setup is designed for annealing and hardening of oxidizing alloys in flowing water, determining melting points, thermocouple calibration, calcining and annealing of oxides. The maximum temperature in the chamber is 2000 ° C, the power consumption is 3 kV⋅A. The installation consists of two main components: a vacuum chamber and a device for the rapid cooling of samples in running water (see figure). The vacuum chamber 1 is a seamless cylinder of steel Art. 3, supported by a vacuum gasket. The camera is fixed on the base with 2 four tension screws. Inside the chamber is a heater 3, which consists of two coaxially arranged tubes of 0.1 mm thick molybdenum tin, welded at the top.
Image1. General view of the installation.
The supply of current to the heater on one side allows the heater material to deform freely during heating and cooling. The electric current in the outer and inner tubes of the heater is opposite in direction, which is important when measuring temperatures with a thermocouple, as the electrical pickups are very small. Using an optical pyrometer, the sample temperature is measured through a viewing window 5 made of optical molybdenum glass located in the upper part of the vacuum chamber. The sample temperature can be measured with a tungsten-molybdenum thermocouple, which is introduced into the working space through a special
seal mounted at the base of the installation. To reduce the heat loss of radiation, the heater is closed with a system of suspended molybdenum tin screens 6. The insulating ring 7 at the bottom of the heater prevents short circuits.
In the lower part of the base of the installation, a device for sharp tempering of samples in running water 4 is installed, consisting of a glass 8 with running water, a spring mechanism 9, a rod 11, on the upper end of which a sample 10 is fixed, a tension nut 12 and a trigger 13. To power the heater electric current is a water-cooled current lead 14, insulated from the base of the installation with a PCB gasket; the other end of the current lead is attached to the base of the unit located on the bracket.
The test sample is introduced into the working space of the chamber from the bottom. The rod 11 with the sample 10 is connected to the base of the installation 2 through a Teflon sealing ring and tightened with a tension nut 12. The working chamber space is evacuated to 2⋅10-2 mm Hg, the argon of spectral purity flows into the chamber to a pressure of 500 mm Hg ; then turn on the power of the heater, carried out from a single-phase transformer OSU-20 and bring the sample to the desired temperature. After holding the tension nut 12 weaken trigger trigger 13 and the spring device 9 moves the sample from the working space in the glass with running water. A slight overpressure of argon in the chamber prevents air from entering it at the time of quenching, protecting the heater from oxidation. When using an installation for hardening alloys, the life of a molybdenum sheet heater is 25 cycles, with an annealing of 30-40 cycles. Installation is reliable and convenient in operation.
I. A. TREGUBOV, A. N. KOBYLKIN
ISSN 0026-0819. “Metallurgy and heat treatment of metals”, № 6. 1968
This article was taken from this resource.