In order to shorten the nitriding cycle and make the nitriding process independent of the steel type, two new nitriding processes, soft nitriding and ion nitriding, have been developed on the basis of the original nitriding process in the last one or two decades
Soft nitrocarburizing is essentially low-temperature carbonitriding, which is mainly nitriding. At the same time as the nitrogen atoms of the steel are penetrated, a small amount of carbon atoms are infiltrated. The treatment result is harder than the general gas nitrogen mentioned above. Low brittleness, so it is called soft nitriding. Cryogenic treatment
1. Soft nitriding method. The soft nitriding method is divided into two categories: gas nitrocarburizing and liquid nitrocarburizing. At present, the most widely used in domestic production is gas nitrocarburizing. <, br> Gas nitrocarburizing is low-temperature carbon and nitrogen co-infiltration in an atmosphere containing activated carbon and nitrogen atoms. Commonly used co-infiltration media are urea, formamide and triethanolamine, which generate heat at the temperature of nitro nitration The decomposition reaction produces activated carbon and nitrogen atoms. Cryogenic treatment
Activated carbon and nitrogen atoms are absorbed by the surface of the workpiece, and penetrate into the surface layer of the workpiece through diffusion, thereby obtaining a carbonitriding layer mainly composed of nitrogen.
Gas nitrocarburizing temperature is usually 560-570 ℃, because the hardness value of the nitride layer is the highest at this temperature. The nitriding time is usually 2-3 hours, because over 2.5 hours, the depth of the nitride layer increases slowly with time. Cryogenic treatment
2. Soft nitriding layer structure and soft nitriding characteristics: After the steel is nitrocarburized, the outermost layer of the surface can obtain a white layer of a few microns to tens of microns, which is made of ε phase, γ` phase and nitrogen-containing The carbon body Fe3 (C, N) is composed of a sub-layer of 0.3-0. 4 mm diffusion layer, which is mainly composed of γ` phase and ε phase.
Soft nitriding has the following characteristics:
(1) The processing temperature is low, the time is short, and the workpiece deformation is small. Cryogenic treatment
(2) Not limited by steel types, carbon steel, low alloy steel, tool steel, stainless steel, cast iron and iron-based powder unmetallurgical materials can be soft nitriding. The surface hardness of the workpiece after soft nitriding is related to the nitriding process and materials. Cryogenic treatment
3. Can significantly improve the fatigue limit, wear resistance and corrosion resistance of the workpiece. Under dry friction conditions, it also has anti-scratch and anti-seizure properties.
4. Because there is no brittle ξ phase in the soft nitride layer, the nitride layer is hard and has a certain toughness, which is not easy to peel. Cryogenic treatment
Therefore, in the current production, soft nitriding is widely used in the treatment of wear-resistant workpieces such as molds, measuring tools, high-speed steel tools, crankshafts, gears, cylinder sleeves and so on.
It should be noted that the current problem of gas soft nitriding is that the thickness of the iron-nitrogen compound layer in the surface layer is thin (0.01-0.02mm), and the hardness gradient of the nitride layer is steep, so it is not suitable to work under heavy load conditions. In addition, during the nitridation process, HCN, a toxic gas, will be generated in the furnace, so attention should be paid to the sealing of the equipment in the production to prevent the furnace gas from leaking and polluting the environment. Cryogenic treatment
Nuoruida (Tianjin) science and Technology Co., Ltd. is committed to research, development, and sales of liquid nitrogen cryogenic equipment which is establish in 2002. Using European and American technology, we provide a variety of equipment. The main equipment is liquid nitrogen equipment, cryogenic furnace, cryogenic processing equipment, low temperature assembly equipment, cryogenic assembly equipment, and so on.
