1. Materials for shaft parts
① Shaft parts commonly used materials are 35, 45, 50 high-quality carbon structural steel, 45 steel is the most widely used, generally tempered, hardness of 230 to 260HBS.
② less important or less loaded shaft available Q255, Q275 and other carbon structural steel.
③ Shafts subject to higher forces and high strength requirements can be tempered with 40Cr steel with hardness of 230-240HBS or hardened to 35-42HRC.
④ If it is high-speed, heavy-duty conditions of the work of shaft parts, the choice of 20Cr, 20CrMnTi, 20Mn2B and other alloy structural steel or 38CrMoAIA senior quality alloy structural steel. These steels by carburizing quenching or nitriding treatment, not only high surface hardness, but also its heart strength is greatly improved, with better wear resistance, impact toughness and fatigue strength performance.
⑤ ductile iron, high-strength cast iron due to good casting performance, and vibration damping performance, commonly used in the manufacture of complex shape structure of the shaft. Especially our rare earth a magnesium ductile iron, impact toughness, but also has the advantages of friction absorption, low sensitivity to stress concentration, etc., has been used in automobiles, tractors, machine tools on the important shaft parts.
(6) without the final heat treatment to obtain high hardness of the screw, generally available tensile strength of not less than 600MPa of 45 and 50 medium carbon steel. Precision machine tool screws can be made of carbon tool steel T10, T12. After the final heat treatment to obtain high hardness of the screw, with CrWMn or CrMn steel manufacturing, can ensure that the hardness of 50 ~ 56HRC.
2. Technical requirements for shaft parts
① Dimensional accuracy
The dimensional accuracy of the main journal diameter is generally IT6~IT9, and the precision is IT5. For the step shaft, the length of each step is given tolerance according to the requirements of use, or the tolerance is assigned according to the requirements of the assembly size chain.
② Geometric accuracy
Shafts are usually supported on bearings with two journals, which are the assembly reference of the shaft. The geometric accuracy (roundness, cylindricity)) of the support journal should generally be required. The general accuracy of the journal geometry shape tolerance, should be limited to the diameter tolerance range, that is, according to the inclusion requirements in the diameter tolerance after the mark E, such as higher requirements, and then marked its allowable tolerance value (that is, after the size tolerance note E outside, and then add a box to mark its shape tolerance value).
③ Mutual position accuracy
Shaft parts with the journal (assembly transmission journals), relative to the support journal coaxiality is its mutual position accuracy of the general requirements. For the reason of convenient measurement, radial circular runout is commonly used to indicate. In addition, there are requirements for perpendicularity of axial positioning end face and axis center line, etc.
④ Surface roughness
In general, the surface roughness of the support journal is Ra0.16 ~ 0.63um, with the surface roughness of the journal is Ra0.63 ~ 2.5um. For general parts, typical parts, the above generally have the corresponding tables and information available.