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分段控制法气体渗碳过程由排气、强渗、扩散和降温四个阶段组成。
排气阶段甲醇加入量为13.65mL/min，不加入煤油。
在渗碳的强渗阶段，炉温已升至900℃以上，煤油已能充分分解，改用加大煤油滴量、减少甲醇滴量的方法，以迅速提高炉气碳势，使工件表面大量吸碳，尽快提高表面碳含量，加速渗碳，从而缩短强渗时间。停止加入甲醇，煤油加入量为5.784822mL/min。
在扩散和降温阶段，煤油滴量适当减少，炉气碳势与最后要求相当即可。扩散阶段甲醇加入量为4.55mL/min，煤油加入量为1.1569144 mL/min。
降温阶段随炉冷至770℃，保温15~30min，使零件温度均匀，然后出炉淬火。
毕业论文关键词：凸轮轴；20钢；渗碳
20 steel carburizing heat treatment process design
Design notes: The main research design for camshaft carburizing process.
Everyone should not unfamiliar to the camshaft, valve, valve we often hear thetiming belt, timing chain, and it has a close relationship, the valve is in its place.Camshaft is one part of the engine valve mechanism, specifically responsible fordriving valve to open and close, role is to ensure that the engine work in the timing for the cylinder suction fresh fuel mixture, and promptly after the burning of waste gas discharged from the cylinder.
Synthesis of cam shaft work environment and failure analysis of the cam shaft, put forward with the following requirements:
(1) the camshaft must have certain flexural strength and enough toughness, can withstand a certain degree of resistance to torsional loads, ensure nodeformation force.
(2) the camshaft surface with high roughness, moderate intensity and hardnessand wear resistance, prevent the cam shaft work in defects in the wear, scratch,crack.
(3) the camshaft with wear resistance and excellent machining performance.
(4) the camshaft must have accurate size, shaft neck have the bending strengthmedium and anti torsion load and medium toughness and wear resistance.
20 steel is the high quality carbon steel, hardened steel, cold extrusion.The steel with low strength, toughness, ductility and weldability are good. Suitable for automobile, tractor and construction machinery manufacturing industry in the less important in small carburizing, carbonitriding parts.
Gas carburizing is a method of infiltration process of carbon workpiece in gaseous medium, can use hydrocarbons organic liquid, such as kerosene,acetone and other direct drop furnace vaporization. In the heat decomposition gas carburizing temperature, precipitation activated carbon atoms, the workpiecesurface infiltration. Can also use the gas furnace for certain components in advance of Walter prepared within, on carbonizing temperature decomposition ofcarbon atoms into the workpiece surface carburizing.
RQ series pit gas carburizing furnace is a batch type furnace, mainly used forsteel parts of the gas carburizing etc.. And the electric control cabinet withautomatic control and automatic temperature recording electric furnace.According to parts of the size, select the RQ3-105-9 pit type carburizing furnace.
In the carburizing medium of choice, single use kerosene is simple, but there are still many shortcomings in use, such as high temperature cracking is easy toproduce coke, gas composition and carbon potential instability, not easy to control. Using kerosene and methanol carburizing, methanol as carrier gas,kerosene as Fu gas, can give full play to different characteristics in differentstages of carburizing agent. Methanol cracking in low temperature, gas production, is not easy to form carbon black. While in the exhaust stage, low temperature, can drip drip a few drops into methanol, kerosene, the purpose is to eliminate the furnace oxidizing atmosphere as soon as possible.
Influence of carbon content of the surface carburizing temperature, carburizing speed and carbon concentration gradient. Enhance carburizing temperature canaccelerate carburizing speed, shorten the production cycle, but is in the steelgrain size not too big case. Because of too high carburizing temperature, easy to cause the coarse grain steel, increasing the deformation of parts, reduce the service life of equipment and tooling, and in the use of direct quenching after carburizing process, infiltration austenite more residual layer. In general,carburizing temperature between 900~950 ℃. In the lower temperature of Carburizing for small precision parts. To sum up, choose carburizing temperature is 920 ℃.
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