The Influence Of Fe2+ On 45# Steel Loose Layer Of Liquid Nitrogen

The crankshaft, as a key component of the engine, works under the joint action of the cyclically-changing gas force, inertia force and its torque to withstand the bending and torsional cyclic loading. After the nitriding salt bath, the crankshaft has excellent wear resistance, fatigue resistance strength and improved corrosion resistance.This paper uses Weichai WD615 engine crankshaft as an example of the main reason that why lossening happens in the nitriding salt bath. By testing with all kinds of reasons like nitriding temperature, nitriding time, the CNO-concentration of salt and iron content, it can be concluded that:in the actual production process, nitriding temperature, nitriding time and salt of the CNO-concentration are the three factors relatively stable, while the iron content in the nitriding salt bath is the main reason for the lossening. Here in this paper, the impact of the iron content on nitride layer is analyzed, and the idea of when porous layer depth of nitride is less than 1/2, we have to control the salt content in the upper limit of iron is raised. In addition, the experimental results show that the surface quality of the crankshaft before nitriding, often completely slag and the occasional high-temperature correction of the nitriding salt bath are the effective methods for keeping away the loose layers.In the end, we use micro hardness tester with the method of wave generator to test the nitrided layer brittleness, and the results show that using liquid nitriding will bring more brittleness than using gas nitriding.