(1) Material shaft parts
The axial forging material is usually 45 steel: for medium precision and high speed shafts, 40Cr and other alloy structural steel can be selected; For shafts with higher accuracy, GCRL5 bearing steel and 65mn spring steel can be selected; For shafts with complex shapes, nodular cast iron can be selected. For shafts working under high speed and heavy planting conditions, low-carbon alloy steel or 38crmool nitriding steel can be selected, such as 20crmnTi, 20mn2b, 20cr, etc.
(2) Blank shaft parts
The most commonly used blanks for shaft parts are round bar material and forging; Some large shafts or shafts with complex structures are cast. After heating and forging, the fiber structure in the metal can be uniformly distributed along the surface, thus obtaining higher tensile, bending and torsional strength. Therefore, forgings are usually used for more important shafts. According to the size of batch production. The blank forging method is divided into free forging and die forging.
(3) Heat treated shaft parts
In addition to the type of steel selected, the service performance of axial components is also related to the heat treatment used. Before processing the forging blank, it is necessary to arrange normalizing or annealing treatment (carbon steel and alloy steel, carbon-containing equipment greater than=0.7%) to refine the grains in the steel. Eliminate forging stress, reduce material hardness and improve cutting performance.
In order to obtain better comprehensive mechanical properties, axial forgings usually need quality adjustment. When blank remains, the quality shall be adjusted after rough turning and semi-fine turning to eliminate the residual stress of rough turning. Small margin, quality adjustment can be arranged in front of rough car. Surface quenching is usually arranged before fine machining to correct local deformation caused by quenching. For the shaft with high precision requirements, after local quenching or rough grinding, it needs to be treated in time at low temperature (long-term low temperature in 160 ℃ oil) to ensure dimensional stability.
For nitrided steel (such as 38grMoal), quality adjustment and low-temperature timeliness treatment shall be carried out before oxygen infiltration. The quality requirements for quality regulation are also very strict. After quality adjustment, it is not only necessary to uniformly refine the sorbite structure, but also need to be 8? Away from the surface? The mass fraction of ferritic carbon in the 10mm layer shall not exceed Wc=5%, otherwise it will lead to nitriding brittleness and affect its quality.