RU1349318C - Method of nitriding steel articles - Google Patents

Description

until the required layer thickness is reached. The choice of the temperature range is 500-680 ° C, the duration of both the first stage is 1-3 hours and the second 3-6 hours in ammonia and 0.5-1 hour and the mixture of ammonia and air is determined by type. in the first stage, 1 hour, in the second, 6 and 0.5 hours, respectively. For stainless ferritic and austenitic steels, 2.4 m 1 hour, respectively. For stainless austenitic steels especially high manganese - 3, 3 and 1 h. The choice of air concentration of 40-60 vol. The% volume is due to the high activity of the atmosphere, which provides a high rate of reduction of a high concentration of nitrogen in the nitride solution. A decrease in air concentration of less than 40% reduces the potential of the atmosphere, and an increase: an increase in excess of 60% leads to the rapid formation of an oxide layer. In both cases, the rate of penetration of nitrogen into the metal decreases, which leads to the need to increase the duration of the process.

Example, Nitriding according to the proposed method was subjected to samples of technical iron, structural and corrosion-resistant steels. Samples of des) 1si;) fell out with acetone, were loaded into a co vp viner, which was sealed, and the muffle and then into it

fed ammonia. Heating to isothermal holding temperature was carried out in an ammonia stream. Upon reaching the process temperature, a mixture of 30 or 50% was fed into the furnace

ammonia or 50 or 70% of the air for 1-3 hours, depending on the grade of steel .. Then the air supply was stopped and the treatment was carried out in an ammonia stream into which periodically every 3; 6 hours

About the course of 0.5; 1 h in an amount of 40 or 60 vol.%. The samples were cooled in an ammonia stream. In order to obtain comparative data, nitriding was carried out in parallel using a known method for samples of the same steels at the same temperatures, the total duration of the process and the technological parameters of the first stage. In the second stage, the composition of ha; the juvenile mixture was in all cases the same 60% LN3 to 40% air. Specific process data and values obtained. Tolcine diffusion layers are summarized in table. As can be seen from the table, the treatment according to the proposed method intensifies the saturation process by 1.2-1.5 times without reducing the surface hardness.

The technical and economic efficiency of the proposed method is determined by a higher saturation rate, which will reduce the duration of the nitriding process5.

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 Data on the known method are indicated below

Editor 3. Khodakova

Compiled by L. Burlinova

Tehred M. Morgenthal Corrector M. Kul

Order 567 Mintage

VNIIIPI of the State Committee for Inventions and Discover at the USSR State Committee for Science and Technology 113035, Moscow, Zh-35, Rauska nab., 4/5

Production and Publishing Plant Patent, Uzhhorod, 101 Gagarin St.

Table continuation