SU905325A1 - Method for chemical and heat treatment - Google Patents

Description

Isobreggenie relates to chemical-thermal treatment, in particular, to the process of nitriding of pig iron in a plasma discharge. Methods are known for the chemical-thermal treatment of cast iron and, in particular, its nitriding in a glow discharge, consisting in heating, holding at a constant ature rate and cooling in plasma. Til The disadvantage of this method is that the gas pressure is not optimized due to the saturation temperature. for the identification of yours. the process of nitriding of cast iron. Lowest to the proposed technical solution is the nitriding process, which is the process of expressing nitrogen in steel in a glowing plasma of ammonia atmosphere with nitrogen, consisting of heating, isothermal holding at optimum pressure and cooling 121. However, the method does not allow for a change in the pressure optimization depending on the temperature during the heating and cooling process. Thus, the method does not take into account the features of aeration of the industrial bulk tank when it is necessary to optimize the pressure during heating and cooling, since they have a long heating and cooling time. cooling, often exceeding the isothermal holding time. In addition, the method does not take into account the need to optimize the pressure during heating and cooling of proca 1sha1a to products with a complex configuration (also requiring slow heating and cooling). No invention - the intensification of the formation of the nitrided layer. This goal is achieved by the fact that when heated in the temperature range of 500-7OO ° C, the pressure is continuously increased. , gas from 1 to 7 mm Hg. Art., and schzh cooling reduce gas pressure

7 to 1 mmHg. Art. With this,

ammonia when heated

Extender {cooling and cooling according to

Р "339 - 1.74 + 0.2938-lO tV

- Oh, 160777.

The proposed method is carried out as follows.

The nitrided product in the working end tanker is the catopes, in the chamber itself the anode. Air from the working volume of the donerteine is pumped out to the mouth. Art. The chamber is then purged with ammonia 1O min at a pressure of 10 mm Hg. Art. Then the gas from the chamber pumps out with up to 0.3 mm Hg. Art. A voltage of 1OOO B is applied to the electrodes, at which a cathode sputtering stage is carried out for 10 to 15 minutes to clean the surface of the electrode and. At the end of this stage, the voltage decreases to 1OO B, and the pressure increases to 1.0 mm Hg, st. Then

the voltage increases smoothly, and the atura rate rises to 500 s. When this temperature is reached, the pressure rises in accordance with a further degree of temperature using the indicated formula. Moreover, the required pressure can be set manually at regular intervals and automatically spun. When the temperature and pressure of the isothermal holding are reached, the change in parameters is stopped. The product is maintained under these conditions, the necessary, and then cooling begins with a simultaneous decrease in pressure by the same formula. Below the temperature, the pressure varies arbitrarily.

Claims (2)

Examples of nitriding, the depth of the azoT1 layer according to the proposed and known methods, depending on the technological parameters, are given in the table. Thus, the technical effect of the cue effect obtained from using this method speeds up the process of nitriding and shortens its duration. As evidenced by the act of tests that were conducted at the MADI metal department, the formula for pressure versus temperature was obtained based on the analysis of experimental data. The latter show that the maximum depth of the nitrated layer is achieved with a strictly defined ammonia pressure, optimal for a given isothermal holding temperature. At optimal pressure is 1.0 mm Hg. Art.} at - 2.0 mm Hg. v .; with BPT - 5, O mm Hg v .; at 700 ° C 7 mm Hg. Art. Using the least squares method, we derive a formula representing the correlation dependence of the optimal ammonia pressure on temperature. The application of this formula for setting gas pressure values when heated to the holding temperature and when cooled thereafter shows significant efficiency, which is reflected in, presented in. Moreover, the choice of optimal pressures for isothermal holding is carried out by the same formula. Claims method of chemical heat treatment, including heating, isothermal shadder and cooling products in a glow discharge in an atmosphere of ammonia, characterized in that, with the chain of intensification of nitrogenous formation, when heated in the temperature range of 5OO-700 ° C is continuous) increase the pressure of the ammonia from 1 to 7 mm Hg. Art., and when cooled, the pressure is reduced from 7 to 1 mm Hg. at that, the pressure of ammonia during heating, isothermal exposure and cooling is determined by the formula:, where K.- 339; KI - 1.74; 0,2938lOr -; Cf- 0.160777-10-; t is temperature, C; p is the desired pressure, mm RT. Art. Sources of information taken into account during the examination 1. Lakhtin, Yu. M., et al. Nitriding high-strength cast iron in a glow discharge. Metallurgy and thermal processing of metals. 1964, No. 3, p. 37-41. 2. Butenko O. I.. Investigation of a glow discharge for chemical thermal processing. Mitom, Mb 3, 1967, p. 7-10.