汽车排气阀软氮化工艺的研究.doc

毕业论文 汽车排气阀软氮化工艺研究 院（系）名称 工学院机械系 专业名称 材料成型及控制工程 汽车排气阀软氮化工艺研究 摘 要 我国汽车工业近几年飞速发展，产量持续增长，品种不断增加。汽车排气阀是发动机上重要的工作部件及易损件，其工作条件异常恶劣，要在高温、高压、腐蚀性燃气中经受频繁往复的高速运动和摩擦，冲击负荷大，因此要求有较高的高温性能、耐磨性能、耐腐蚀性能，抗疲劳等，故制备排气阀的材料要求也极为苛刻。自从发动机问世以来，气阀钢的材料已经历了碳钢和低合金钢，硅铬型不锈钢，奥氏体型耐热钢等多个发展阶段。目前，国内外使用最多的是奥氏体型耐热钢，而这种耐热钢系列中，常见的有：4Cr10Si2Mo，4Cr9Si2，5Cr21Mn9Ni2N(21–2N)，5Cr21Mn9Ni4N(21–4N)等。 本文主要研究了21–4N奥氏体耐热钢的表面预处理，并将预处理后的21–4N钢制汽车排气阀进行软氮化及表面强化。该预处理工艺为奥氏体耐热钢进行软氮化提供了必要的准备。进而对21–4N钢制汽车排气阀软氮化的工艺进行了对比实验研究，得出最优化的软氮化工艺规范。 关键词：排气阀，软氮化，耐热钢，抗疲劳 Automobile Exhaust Valve Soft Nitride Process Research Abstract The automobile industry in our country developed fast during these years with continual increasing of volume and variety. the working conditions of the exhaust valve extremely rigorous, high temperature, high pressure, corrosive gas withstand frequent in the high-speed reciprocating movement and friction, impact load, therefore require higher temperature properties, wear resistance, corrosion resistance, and so on, the exhaust valve of the material requirements are also extremely harsh. Since the advent of the engine, the valve steel materials has experienced low carbon steel and alloy steel, silicon-chromium stainless steel, austenitic steel, and other heat-development stage. At present, the largest number of domestic and international use of austenitic heat-resistant steel, which is heat-resistant steel series of common: 4 Cr10Si2Mo, 4Cr9Si2, 5Cr21Mn9Ni2N (21-2N), 5Cr21Mn9Ni4N (21-4N). This article studies on a 21-4 N austenitic heat-resistant steel surface preparation and pretreatment of 21-4 N steel automobile exhaust valve nitride and the soft surface strengthening. The pre-treatment for heat-resistant steel austenitic soft nitride provided the necessary preparations. Then to 21-4 N steel automobile exhaust valve soft nitride process were compared experimental research, produce the most optimal soft nitride process norms. Key words: Exhaust valve, Soft nitride, High-temperature steel, Antif