SU568681A1 - Method of carburizing steel component in circulating gas flow under pressure - Google Patents

Description

one

The invention relates to the field of metallurgy, mainly to the chemical and heat treatment of metals, and can be used as a method for surface saturation of steel products with carbon.

The known method of gas cementation of steel products, which consists in heating and holding them in a regenerated gas stream in a closed system 1. A gaseous medium (60% nitrogen, 40% oxide and carbon dioxide) is produced by passing air through heated charcoal. Charcoal is heated to a temperature slightly lower than the temperature of steel products.

However, the known method of cementation is not very productive; it does not allow to increase the saturation rate of the product surface without changing the process temperature and gas flow rate; varies. Mala performance of the known method of cementation due to the low difference between the equilibrium content of carbon monoxide in the gaseous medium and the equilibrium content of carbon monoxide in the gaseous medium with the same components, but neutral with respect to the steel product. This difference is still

more reduced due to the different temperatures to which the steel products and the gas environment are heated.

The purpose of the invention is to increase the productivity of the process and to obtain uniformly carbon-saturated diffusion layers that provide high performance properties, as well as to use the spent gaseous medium by circulating it in a confined space in the presence of solid carbon.

The goal is achieved by the fact that, according to the proposed method of cementation, steel products, a gaseous medium consisting of oxide and. carbon dioxide and solid carbon (charcoal) are heated to the same temperature in the range of 850-1000 ° C.

In addition, in the process of chemical heat treatment, the direction of the circulating gas flow is periodically reversed.

Claims (2)

By varying the pelvic flow rate, diffusion layers can be obtained with different depths and with different carbon concentrations. Changing the direction of the circulating gas flow during operation produces an equal depth of the cemented layer in different parts of the surface of the steel products. The drawing shows an installation diagram for carrying out the proposed cementation method. Sugar 1, provided with an inlet 2 with a valve 3, is hermetically closed by a lid 4 with a fan 5 and a pressure gauge 6, which makes it possible to measure the pressure of the gaseous medium in the muffle. In addition, an internal cylindrical shield 7 filled with steel products 8 and charcoal 9 used as solid carbon is placed in the muffle. The method is carried out as follows. Chemical heat treatment of products made of steel bar size 20X20 mm is carried out. Composition of steel (20KhZMVF),%: Carbon 0.19 2.67 0.35 Tungsten Vanadium 0.72 0.49 Molybdenum Else Iron From the prepared air is pumped out of the muffle to work. A muffle with products and solid carbon is heated to 920 ° C and a small portion of carbon dioxide is fed into it through the inlet. After reacting CO2 with hot carbon in a muffle, a pelvic environment consisting of carbon monoxide and carbon dioxide is created. The chemical heat treatment is carried out for 6 hours under a pressure of a gaseous medium of 6 kgf / cm and a speed of a circulating gas flow of 1.1 m / s. The data of physical properties obtained after cementation by the proposed (1) and limestone (2) method are presented below. 12 ° С 920+ 920+ Tehsherat} cementation, ° С Holding time, h66 Gas pressure, 61 Circulation speed ha -1.11.1 per m / sec Cemented depth 1.5 + 1.55 0 , 63 + 0.65 layers, mm Surface hardness 750,610 Carbon concentration at 1,781.34 surfaces,% Thus, during the cementation of the proposed method, the rate of saturation of the surface of steel products with carbon and, consequently, productivity increases. The method of cementation of steel parts in a circulating gas flow under pressure, including heating and holding parts in a gaseous environment, characterized in that, in order to accelerate the process of chemical heat treatment and improve the uniformity of the diffusion layer, the process is carried out in the presence of solid carbon the gaseous medium, solid carbon and steel parts are heated to the carburizing temperature, and the pressure of the circulating gas flow during the carburizing process is periodically changed to the Opposite. Sources of information taken into account during the examination 1. USSR author's certificate No. 67018, cl. C 23C 11/12, 1944. 2. Raits VB “Technologists of chemical heat treatment, 1965, pp. 82.