Medium-carbon Steel High-temperature Rapid Carburizing Treatment Process And Performance

Since the carbon content of surface of medium-carbon steel established, the room for improvement of surface hardness is limited, in the face of some rather high wear resistance of the working environment, it can not be reused and highlight its excellent mechanical properties. While the hardness of the steel and steel carbon content are closely related, improving the carbon content of the steel surface by a chemical heat treatment process is one of the most effective ways to increase the surface hardness of steel. The usual carburizing process is often targeted at the lower surface of the carbon content of low-carbon steel or low carbon alloy steel, therefore the carburizing treatment process for medium-carbon steel needs to be further explored, to establish a complete fit in medium-carbon steel surface hardening carburizing processes.This paper put forward the concept of high-temperature reducing carburizing time,which means high-temperature carburizing(>850℃-950℃).And in order to prevent excessive high carburization temperature during carburizing resulting crystal grains coarsening, this paper select paste carburizing process, and through the re-selection of a new formulation of Paste carburizing agent to improve the atmosphere activity of carburizing, combined with the preparation of a certain strength and a relatively high density of protecting paste ointment applied to carburizing surface, forming a dense and narrow carburizing confined space, to further improve the speed of the carburizing and short the time of carburizing.We found:On the basis of the traditional paste carburizing agent proportion of ingredients,choose finer (particle size<100 mesh) toner to provides activated carbon atoms, and choose the considerable thermal stability Na2CO3 powder as a catalyst penetration at the same time, and choose the often used as an anti-caking agent CaCO3 powder to prevent sintering carburizing agent, while the percentage of Na2CO3 powder weight increased to nearly 50%, measured by carburizing case depth comparison found that the paste carburizing agent at elevated temperatures exhibit a very high activity.After the selection has good adhesion and have a relatively high strength cured Na2SiO3·H2O as the main component, and add a particle size less than 100 mesh Al2O3 powder to make carburized protecting paste, after a series of coating, drying process, making comparative test with a brand inorganic adhesive protecting paste, through the comparison of depth of carburized layer find that using the self-made carburizing protection shell and inorganic adhesive paste as a protective layer respectively obtained similar protection and similar effect by measuring the carburized layer.However, on the use of technolog,due to the making and drying process of carburizing protection shell is more complex and spending more time, and therefore to evaluate the use of carburizing protection shell effect is not as good performance on the market inorganic adhesive as a whole,so the carburizing protection shell needs further exploration.In the depth of the carburized layer measurement innovative use of EPMA of the carburized layer,and according to the dynamic relationship between the case depth and the carburizing time to make linear fitting,and to make comparison with traditional metallurgical thickness measurement method to find the respective advantages and disadvantages.According to the knowledge about the dynamics, through design different carburizing temperature and different holding time test to obtain different case depth, to draw out the linear fitting of the function between the case depth and the carburizing time of medium-carbon steel high-temperature carburizing,and depend on this curve we can design the suitable carburizing time and carburizing temperature to obtain the case depth that meet the requirements of use and under the premise of grain not coarsening.At the same time,after the high-temperature carburizing,to quench the medium-carbon steel at a appropriate temperature,through the HRC measurement of carburized layer to compare with the non-treatment medium-carbon steel,we found that,the HRC of carburized layer was obvious higher than the non-treatment medium-carbon steel,prove that the high-temperature carburizing surface hardening technology is ideal.