Soft nitriding process in steel heat treatment characteristics

In order to shorten the nitrogen cycle, and make the nitriding process is not restricted by steel, in close to a, 20 years on the basis of the original nitriding process developed soft nitriding and ion nitriding two new nitriding process soft nitriding is essentially nitriding temperature carbonitriding, steel the nitrogen atom of permeability and at the same time, there is a small amount of carbon atoms, the processing result compared with the general gas nitrogen, low permeability layer hardness and brittleness is small, so called soft nitriding. 1. Soft nitriding method, soft nitriding method is divided into flexible gas soft nitriding and liquid nitriding two kinds big. The current domestic production is the most widely used in gas soft nitriding. Gas soft nitriding is in the atmosphere of activated carbon, nitrogen atoms low temperature carbon and nitrogen altogether permeability, commonly used in seepage medium with urea, formamide and triethanolamine, they are soft nitriding temperature pyrolysis reaction, to produce activated carbon and nitrogen atoms. Activated carbon, nitrogen absorbed by the workpiece surface, through diffusion into the workpiece surface, which is given priority to with nitrogen carbonitriding layer. 560 - commonly used gas soft nitriding temperatures Nitride layer under the temperature 570 ℃, as the highest hardness value. For 2 - nitriding time often 3 hours, because more than 2. 5 hours, with the extension of time, nitride layer depth increases slowly. 2. Soft nitriding layer organization and soft nitriding features: steel after soft nitriding, the outermost layer on the surface of a few microns to dozens of micrometers can be obtained of white layer, it is by the epsilon phase, gamma ` cementite Fe3 and nitrogen ( C, N) The composition, second layer of 0. 3 - 0. 4 mm of diffusion layer, it is mainly composed of gamma ` and epsilon phase. Soft nitriding has the following characteristics: ( 1) Low processing temperature, and time is short, the workpiece deformation is small. ( 2) Without being limited by the grade of steel, carbon steel, low alloy steel and die steel, stainless steel, cast iron and iron-based powder metallurgy materials are not soft nitriding process can be performed. The surface of the workpiece after soft nitriding hardness and nitride process and related materials. 3. Can dramatically improve the fatigue limit, abrasion resistance and corrosion resistance. Under the condition of dry friction also has properties, such as abrasion resistance and resistance to bite. 4. Because of the soft nitriding layer there is no brittle phase is deduced, so the nitride layer hard and has a certain toughness, not easy peeling off. As a result, the production of soft nitriding has been widely used in mould, measuring tool, high speed steel tools, crankshaft, gear, such as cylinder liner wear workpiece processing. Should pay attention to the present problem is the gas soft nitriding surface iron nitrogen compound layer thickness is thinner, 0. 01 - 0. 02mm） And the nitride layer hardness gradient is steep, so the unfavorable work under overload conditions. In addition, in the process of nitride, produces HCN this toxic gas in the furnace, so production will pay attention to the sealing device, so as to avoid furnace gas leakage pollution environment.