The selection of shaft parts:

　　Shaft parts are selected according to the requirements on bearing properties, size, rotation speed, accuracy and roughness, as well as the presence of impact and other comprehensive consideration.

　　1. Less loading Shaft. The main consideration is shaft rigidity, wear resistance and precision. For example, for some rotation shaft with low working stress, strength or toughness, the usually used material is low and middle carbon steel( 35#,45# steel) after normalizing. If trunnion is requested to have certain Wear resistance, then 45# is suitable after hardening with tempering heat treatment, the trunnion is treated by quenching and low temperature tempering.

　　2. Shaft bearing alternating bending loading or alternating torque (such as gear transmission shaft, engine crankshaft, spindle, etc.).Because of uneven when the entire section, the surface stress is big, the core stress is small, so don't need to choose high hardenability steel, often chosen steel is 45,40Cr,40MnB steel, etc., which can be quenched and tempered first, then trunnion is treated by high, medium frequency hardening and tempering at low temperature.

　　3. Shat bearings alternating bending (or the reverse) and pull, pressure loading (such as hammer rod, Marine propeller shaft, etc.).The stress distribution of the shaft center is uniform, the core stress is big also, high hardenability of steel should be chosen, such as 30CrMnSi, 40CrMnMo, etc. Generally quenching and tempering , then quenching to the shaft trunnion and tempering at low temperature.

　　4. Shaft withstand overloading, impact and high demand on abrasion resistance (such as automobile, tractor transmission gear, etc.) , 18Cr2Ni4WA,20CrMnTi are selectable, carburizing first , quenching and tempering treatment at low temperature.

　　5. Shaft with overloading, larger impact and high precision (such as high precision grinding machine spindle, coordinate boring machine spindle, etc.) 38CrMoAlA is often selected with quenching and tempering then nitriding.