No. 45 steel is called in GB and S45C in JIS, AS It is called 1045080M46 in TM and C45 in DIN. It is often called No. 45 steel in China, and also called "oil steel" shaft parts. The functions, structural characteristics and technical requirements of shaft parts are one of the typical parts often encountered in machines. It is mainly used to support transmission zero
Components that transmit torque and bear loads. Shaft parts are rotating parts, whose length is greater than the diameter, and are generally composed of cylinder Face, cone face, inner hole, thread and corresponding end face. According to the different structural shapes, shaft parts can be divided into optical shaft, stepped shaft, hollow shaft and crankshaft. The shaft with a length diameter ratio less than 5 is called a short shaft, and the shaft with a length diameter ratio greater than 20 is called a slender shaft. Most shafts are between the two. The shaft is supported by bearings, and the shaft section matched with the bearing is called the journal. The journal is the assembly benchmark of the shaft, and their accuracy and surface quality are generally required to be high. Their technical requirements are generally formulated according to the main functions and working conditions of the shaft, and generally include the following:
（1） In order to determine the position of the shaft, the journal that plays a supporting role in dimensional accuracy usually requires high dimensional accuracy (IT5~IT7). The dimensional accuracy of journal for assembling transmission parts is generally required to be low (IT6~IT9).
（2） Geometric form accuracy The geometric form accuracy of shaft parts mainly refers to the roundness and cylindricity of journal, outer cone, Morse taper hole, etc. The tolerance should be generally limited to the size tolerance. For inner and outer circular surfaces with high accuracy requirements, their allowable deviations shall be marked on the drawings.
（3） Mutual position accuracy The position accuracy requirements of shaft parts are mainly determined by the position and function of the shaft in the machine. Generally, the coaxiality requirements of the journal of the assembled transmission parts on the supporting journal should be ensured, otherwise the transmission accuracy of the transmission parts (gears, etc.) will be affected and noise will be generated. For ordinary precision shafts, the radial runout of the mating shaft segment to the bearing journal is generally 0.01~0.03mm, and for high-precision shafts (such as the main shaft), it is generally 0.001~0.005mm. （4） The surface roughness is generally Ra2.5~0.63 μ m for the shaft diameter matched with the transmission parts, and Ra0.63~0.16 μ m for the bearing diameter.
Blank and material of shaft parts (I) Blank of shaft parts Blank of shaft parts can be in the form of bar stock, forging and other blanks according to the use requirements, production type, equipment conditions and structure. For shafts with small difference in outer circle diameter, generally bar stock is the main material; For stepped shafts or important shafts with large differences in outer circle diameters, forgings are often used, which can save materials, reduce machining workload and improve mechanical properties. According to the different production scale, there are two forging methods of blank: free forging and die forging. Free forging is mostly used for small and medium-sized production, and die forging is used for mass production. （2） The material of shaft parts shall be different according to different working conditions and use requirements heat treatment Specification (such as quenching and tempering, normalizing, quenching, etc.) to obtain certain strength, toughness and wear resistance. 45 steel is a common material for shaft parts. It is cheap. After quenching and tempering (or normalizing), it can obtain better cutting performance, and can obtain higher strength, toughness and other comprehensive mechanical properties. After quenching, the surface hardness can reach 45~52HRC. 40Cr and other alloy structural steels are suitable for shaft parts with medium precision and high speed. After quenching, tempering and quenching, these steels have good comprehensive mechanical properties. Bearing steel GCr15 and Spring Steel 65Mn, after quenching and tempering and surface high-frequency quenching, the surface hardness can reach 50~58HRC, and it has high fatigue resistance and good wear resistance, which can produce high precision shafts. accuracy Machine tool 38CrMoAIA nitrided steel can be selected as the main shaft of (such as grinder grinding wheel shaft, coordinate boring machine main shaft). After quenching, tempering and surface nitriding, this steel can not only obtain high surface hardness, but also maintain a soft core, so it has good impact resistance and toughness. Compared with carburized and quenched steel, it has the characteristics of small heat treatment deformation and higher hardness. No. 45 steel is widely used in machinery manufacturing, and its mechanical properties are very good. However, this is a medium carbon steel with poor quenching performance. No. 45 steel can be hardened to HRC42-46. Therefore, if the surface hardness is required and the superior mechanical properties of 45 # steel are desired, the surface of 45 # steel is often quenched (high-frequency quenching or direct quenching) to obtain the required surface hardness.
