Parameters control of steel diffusion layer in the process of thermochemical treatment

Abstract

Purpose. The aim of this study is to develop and to test management system TCT, which allows to get the required parameters of the diffusion layer - saturating concentration of the element C and the gradient of its distribution, as well as the thickness of the layer B to products of critical appointment. Methodology. As the material for research is selected the steel of the type 14ХГСН2МА which was influenced bu carburizing in solid carburizer at 1300 K. In order to study the kinetics of diffusion saturation (cementation) was used differential dilatometer. Findings. The laws of change of the linear dimensions of the sample tube differential dilatometer during the entire cycle of carburizing steel 14ХГСН2МА. The use of standard hollow instead of a solid, greatly improving the accuracy of fixing the beginning of diffusion saturation, which can be explained by more rapid heating of the hollow standard. This shown that the constructed dilatometric curves allow to identify and prevent saturation directly in the process of such undesirable processes as decarburization and sudden cessation of diffusion saturation with insufficient activity saturating the atmosphere. After reaching the temperature of carburizing steel 14ХГСН2МА (1300 K) there was an increase over time elongated tubular sample. These results confirmed the theoretical calculations of the length of the tubular sample based on the data dependence of the lattice parameter of austenite on the content of carbon in it. Also, using the results of chemical analysis and metallographic analysis supersaturation prototypes carbon steel 14ХГСН2МА and ways saturation mode to obtain the required parameters of cemented layer. Originality. For the first time to monitor and control the process suggested the use of steel TCT differential dilatometer. We give the design features, the operating principle of the device and its proper use as an example of carburizing steel 14ХГСН2МА. Practical value. It is shown that by using differential dilatometer and pre-constructed calibration curves can be directly during the TCT steel flexible to change the activity endopotential furnaces and therefore to amend the parameters of the diffusion layer. Simultaneous use of several dilatometers in carburizing furnace will identify problem areas of the furnace to eliminate their impact on the quality of processed products. Thus, the use of the developed device in the manufacturing process would significantly improve product quality by obtaining preassigned diffusion layer parameters.