Axial parts material selection cases:
1.The machine tool spindle
Machine tool spindle mainly under alternating bending stress and the torsion stress, sometimes undertake impact loading, shaft neck and cone hole surface will be rubbed. Spindle should, therefore, has the good comprehensive mechanical properties, spline, shaft and cone hole should have a higher surface hardness and wear resistance. Such as CA6140 machine tool spindle (as shown in figure 10-1), under torsion and bending stress at work, if loading is not big, with middle speed, 45 # steel can be chosen, specific processing craft route is:
Blanking-forging - normalizing - rough machining – quenching and tempering - half finish turning cylindrical - center holes - milling keyway - partial quenching –turning empty slot + coarse grinding cylindrical + Rolling milling spline -hob spline high frequency quenching – low tempering - fine grinding
The effect of heat treatment process in this route is : the shaft blank and processing flow can be obtained from forging; Normalizing treatment can eliminate stress, improve forging organization; Hardness is 200-230 HBW after quenching and tempering,which is sorbite organization, the purpose is to make the main shaft with high comprehensive mechanical properties, , inside cone and outside cone surface hardness can be 45-52HRC after salt bath partial quenching and tempering; Spline parts is heated by high frequency quenching and tempering to ensure its wear resistance and high precision.
2.The internal combustion engine crankshaft
As shown in figure 10-2, the internal combustion engine crankshaft bears torsion and bending with impact, which requests high strength, certain impact toughness and resistance to bending and torsion fatigue strength while working , in the journal should have high hardness and wear resistance. Small and medium-sized power internal combustion engine crankshaft most commonly used material is 45 steel and nodular cast iron, alloy steel commonly used for high-speed high-power internal combustion engine crankshaft, such as 35CrMo, 43CrMo and so on.
45# steel crankshaft processing route:
anking - forging - normalizing - rough machining – quenching and tempering - finishing - shaft neck surface quenching + tempering at low temperature - fine grinding
QT700-2 steel crankshaft processing route:
Smelting -casting - high temperature normalizing (950 ℃) - high temperature tempering (560 ℃) - machining - journal gas nitriding (nitriding temperature 570 ℃) - fine grinding