Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1998-03-25
1999-08-17
Yee, Deborah
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148625, 148626, 266251, 266254, C21D 900
Patent
active
059388668
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION AND PRIOR ART
The present invention concerns a method for the treatment of components by means of a gas mixture comprising mainly a first light gas and in a minor amount a second gas being heavier than the first gas, said method comprising a first step in which the gas mixture is utilized for the treatment of the components in a treatment chamber and a second step in which the gas mixture is subjected to a concentration and purification process in which the concentration of the First gas is increased, the gas mixture after the treatment in the treatment chamber being discharged for the supply thereof to the purification step. Furthermore, the present invention concerns an apparatus for the treatment of components by means of a gas mixture comprising mainly a first light gas and, in a minor amount, a second gas being heavier than the first gas, said apparatus comprising a treatment chamber, being arranged to allow the treatment of the components by means of the gas mixture, and a concentration and purification device being arranged to concentrate and purify the gas mixture to increase the concentration of the first gas.
It has been known for a long time, when hardening steel articles and components after heat treatment, to cool these rapidly by means of a fluid, i.e. oil. However, such a cooling may give rise to deformations of the articles and stresses in the material, because certain parts are cooled more rapidly than others. Furthermore, such a cooling requires a subsequent purification of the articles, and the use of oil may cause environmental problems. To solve these problems it has been suggested that the articles should be cooled by means of a gas. Such a gas cooling has as well the advantage of improving the possibility to control the cooling process.
U.S. Pat. No. 5, 158, 625 discloses a hardening device in which articles to be hardened are introduced in a furnace. After heating of the articles to a desired hardening temperature, they are cooled by means of helium at an absolute pressure of 2,5 bar. The helium is circulated in the furnace by a fan and is cooled by a heat exchanger. When the cooling has been finished, the contaminated helium is transported from the furnace to a buffer tank by means of a vacuum pump, so that a vacuum is obtained in the furnace. Then, the contaminated helium is transported by a compressor to a purification apparatus, comprising a filter for the removal of oil impurities and a purification member for the removal of water and oxygen from the helium. The thus purified helium is subsequently brought back to a second buffer tank and may from there be supplied to the furnace and thus be recirculated. The purification member is not described more closely in U.S. Pat. No. 5,158,625. The vacuum pumping of the furnace after the cooling has been performed results in a relatively large rest amount of helium in the furnace, since a complete vacuum may not be reached under practical conditions. Thus, this amount of helium is lost. Furthermore, vacuum pumping is time-consuming, requiring a relatively long cycle time for each batch to be treated.
SUMMARY OF THE INVENTION
The object of the present invention is to improve, when performing a treatment with gas, the possibilities to separate and recirculate the gases involved in the treatment.
Said object is attained by the initially mentioned method characterized in that said discharge comprises moving the gas mixture upwardly and out through an outlet member provided in an upper part of the treatment chamber by introducing additional gas, being heavier than the first gas, from below in the treatment chamber. Thereby, in the first place the lighter first gas will leave the treatment chamber and a first separation of the two gases is achieved. Advantageously, the additional gas is constituted of the second gas. Since the second gas is heavier than the first gas, it will not reach the outlet member but instead force the first gas upwards towards and out through this member. According to an embodiment,
REFERENCES:
patent: 5158625 (1992-10-01), Lhote et al.
Andersson Goran
Brunskog Ante
Eriksson Tore
Holm Torsten
Wingbro Torgny
AGA Aktiebolag
Yee Deborah
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