How to choose the processing material of camshaft blank?
How to choose the processing material of camshaft blank?
1. Material selection
1) Spheroidal graphite cast iron: the cast iron with spheroidal graphite is obtained by spheroidizing molten iron close to the composition of gray cast iron with magnesium or magnesium alloy or other spheroidizing agent. Graphite is spherical, which greatly reduces the segmentation and sharp mouth effect of graphite on the matrix. Ductile iron has high strength, wear resistance, resistance, shock absorption and small notch sensitivity.
Nodular cast iron camshafts are generally used in single cylinder internal combustion engines, such as S195 diesel engines. Nodular cast iron used as camshafts is QT600-3 or QT700-2. It is required that the spheroidization is grade 2 (graphite spheroidization rate is 90-95%) and the graphite particle size is greater than grade 6. The overall hardness of camshaft is hb230-280.
2) Alloy cast iron: add Mn, Cr, Mo, Cu and other elements to the molten iron close to the composition of gray cast iron. Thereby forming an alloy with pearlite and reducing the amount of ferrite. Alloy cast iron camshafts are generally used for high-speed camshafts. Such as cac480 camshaft, the overall hardness of camshaft is hb263-311.
3) Chilled cast iron: it is generally used for the surface cooling treatment of low alloy cast iron, so that the outer layer is white cast iron or pitted cast iron, and the core is still gray cast iron. For example: 372 camshaft. The camshaft made of chilled cast iron is in dry friction or semi dry friction working state, and has the ability to bear large bending and contact stress. The surface layer of the material is required to be anti-wear and high strength, and the core still has certain toughness. There are mainly two types of chilled cast iron: chromium, molybdenum and copper chilled cast iron and chromium, molybdenum and nickel chilled cast iron. The metallographic structure of the chilled layer: ledeburite + pearlite (sorbite) chilled cast iron has a hardness of hrc45-52. At present, the hardness of domestic chilled cast iron is about hrc47.
4) Medium carbon steel: generally used for large engine camshafts. For example, 6102 engine is forged by die forging. Some are also used for motorcycle camshafts. The forming is simple. After die forging, annealing treatment is generally required to facilitate machining.
2. Selection of coarse datum
The circular surface of the blank outer cylinder and one side surface of the blank outer cylinder supporting the journal are often selected as the positioning reference. End face processing: domestic manufacturers use milling processing, and some foreign manufacturers use milling instead of milling.
1) For the blank is a die forging, especially for the precision grinding forging, the precision of the blank is determined by the forging die, with high precision and small machining allowance.
2) For the blank, especially the precision casting, it not only has good machinability, but also has high machining allowance. The precision of the blank is higher than that of the forging. It can be positioned.
3) In the process of Camshaft Machining, the uniform and reasonable distribution of machining allowance should be considered when selecting the rough datum.
3. Selection of fine reference
For the rough machining, semi finishing and finishing of the outer surface of each support shaft, timing gear, gear journal and connecting journal, and the finishing of the support shaft and timing gear journal, the semi finishing, finishing and finishing of the cam and eccentric are all based on the two holes. For the rough machining of the cam and eccentric, the processed support journal and timing gear journal are generally used as the positioning reference, Before the surface finishing and after the heat treatment, the center hole trimming process is usually arranged. When trimming the center hole, the support shaft is used for positioning, and the common method is grinding.
Guang'an Jinzhan Machinery Manufacturing Co., Ltd. covers an area of 11 mu, with more than 80 employees and 22 professional and technical personnel; It is located in Qingtan foundry Park, Linshui Industrial Development Zone. It mainly produces motorcycles, automobiles, agricultural machinery and various special-shaped iron castings. Its main products are automobile camshafts, various types of general air-cooled cylinders and special water-cooled cylinders of motorcycles
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