Precision piston rod material
Piston rod stress in tensile and compressive stress of alternate state, and is instantaneous, large impact load. Filler contact and friction heat, the temperature rise of itself. The working condition of its rough forging, the processing precision is high, has the very strong comprehensive mechanical properties, and the filler contact position and working temperature higher hardness, roughness can reach Ra0.16~0.32.
In order to get the high temperature wear resistance of , the piston rod surface with nitriding heat treatment. When added to steel to produce nitride element, in the low temperature nitriding process in production of fine dispersed surface hardness, itself is also very high nitride, which has very high hardness of nitrided layer. Al, Cr, Mo is better, especially aluminum nitride ( AlN ) to improve the nitride layer hardness of the most prominent, and the nitride at 600℃not aggregation and coarsening of the nitride layer, has the advantages of high red hardening. But the aluminum nitride ( AlN ) particle more brittle, the nitride layer is easy to peel, so the nitriding steel aluminum content should not be too much, generally choose 0.2%~1.2% can get more hard nitrided layer, the nitride layer depth did not negatively affect.
The nitride layer formed in the chromium chromium nitride ( Cr2N, CrN ), low hardness, but the nitride layer has better stability, and chromium can enhance nitriding parts matrix strength, so the chromium content should be selected in the range 1.3%~1.6%. In order to reduce the adverse effects of aluminum nitride, also be appropriate to add a small amount of molybdenum. Usually by adding a small quantity of molybdenum in 0.15%~0.25% is more appropriate. The piston rod of carbon content should be 0.25%~0.45%.（图/文）