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为净化汽车排气和降低单位油耗,主要采用提高排气温度和降低车身重量的方法。为了适应这些要求,开发了成本低且具有耐热性的铁素体系不锈钢YUS450(14Cr-0.3Nb-0.1Ti-0.5Mo)。发现通过复合添加Nb-Ti,可以延长热疲劳寿命,这是作为排气歧管用材料使用时最重要的特性;同时满足高温应用环境中的刚性以确保减薄,从900℃附近的高温强度和防止晶粒成长的观点出发,取0.3Nb-0.1Ti。为确保900℃附近的抗氧化性,Cr量为14Cr。发现通过添加少量的Mo,可以减少高温盐蚀造成的腐蚀减薄量,Mo量定为0.5Mo。开发的钢种与现有的SUS430J1L(YUS180:19Cr-0.4Nb-0.4Cu)相比,在耐热疲劳特性和耐高温盐蚀性等高温特性方面均良好,而且由于降低合金添加量,实现了成本的降低。
In order to purify the vehicle exhaust and reduce unit fuel consumption, the main method is to increase exhaust temperature and reduce body weight. In order to meet these requirements, a low-cost and heat-resistant ferritic stainless steel YUS450 (14Cr-0.3Nb-0.1Ti-0.5Mo) was developed. It has been found that the thermal fatigue life can be extended by the compound addition of Nb-Ti, which is the most important characteristic when used as an exhaust manifold material, and at the same time, satisfies the rigidity in a high-temperature application environment to ensure thinning, from high temperature strength From the viewpoint of preventing grain growth, 0.3Nb-0.1Ti is taken. In order to ensure the oxidation resistance near 900 ° C, the amount of Cr is 14 Cr. It is found that by adding a small amount of Mo, the amount of corrosion reduction caused by high-temperature salt corrosion can be reduced, and the amount of Mo is set at 0.5 Mo. Compared with the conventional SUS430J1L (YUS180: 19Cr-0.4Nb-0.4Cu), the developed steels are excellent in high-temperature characteristics such as thermal fatigue resistance and high-temperature salinity corrosion resistance, and since the alloy addition amount is reduced, Cost reduction.