曲轴铸改锻日趋明显

发动机曲轴的作业标准偏差，在工作上受交替变化负载所造成的变形和剪应力的功效，因此对传动轴的疲惫耐磨损和抗压强度等特性均有较高的规定。伴随着载货汽车向功率大的超重型载重车发展趋势，小汽车向速、轻量发展趋势，对汽车发动机的各类特性需求也愈来愈高，铸造发动机曲轴迫不得已遭遇严峻形势。由于发动机曲轴绝大多数是由配重块斜面分模发动机曲轴于弯折疲惫而毁坏，锻钢发动机曲轴的最大优势是不锈钢板材具备较高的弯折疲劳极限，并且大部分与抗压强度正相关。而球墨铸铁发动机曲轴因为存有高纯石墨主骨、磷化处理物与铝合金因素的位错缩松，因而其疲劳极限较低，且不与抗压强度正相关。据美国福特汽车公司实验证实，针对相同的发动机曲轴和曲轴颈支撑点面总宽，铸造发动机曲轴的使用寿命仅有煅造发动机曲轴的一半。

伴随着大功率油耗低、低排放量的规定，汽车发动机的出现工作压力从8MPa~9MPa升高到12MPa,乃至14MPa,球墨铸铁发动机曲轴承受不住如此高的出现工作压力，因此近些年世界各国铸造发动机曲轴的占比在降低而煅造发动机曲轴的占比在升高，发动机曲轴铸改锻的发展趋势日趋显著。例如我国某柴油机厂由原应用铸造发动机曲轴，现改成70%应用煅造发动机曲轴。

Crankshaft casting and forging are becoming increasingly obvious

The working conditions of the crankshaft are extremely poor. The bending and shear stress caused by the alternating load during the work, so the fatigue wear resistance and strength of the crankshaft have extremely high requirements. With the development of trucks to high-power and heavy-duty trucks, and the development of cars to speed and light weight, the performance requirements of engines have become higher and higher. Casting crankshafts have to face severe tests. Because most of the crankshaft is damaged by bending fatigue due to the curved block split mold crankshaft, the biggest advantage of the forged steel crankshaft is that the steel has a higher bending fatigue strength, which is basically proportional to the tensile strength. Ductile iron crankshafts have low fatigue strength and are not proportional to tensile strength due to grain boundary segregation of graphite voids, phosphides, and alloying elements. According to the test of Ford Motor Company, for the same crankshaft and connecting rod neck support surface width, the life of the cast crankshaft is only half of that of the forged crankshaft.

With the requirements of high power, low fuel consumption and low emissions, the explosion pressure of the engine has risen from 8MPa to 9MPa to 12MPa, or even 14MPa. Ductile iron crankshafts cannot withstand such high explosion pressures, so the proportion of cast crankshafts at home and abroad has declined in recent years. The proportion of forged crankshafts is increasing, and the trend of crankshaft casting to forging is becoming increasingly apparent. For example, a domestic diesel engine factory changed from of cast crankshafts to 70% of forged crankshafts.

以上是《曲轴铸改锻日趋明显》的介绍，原文链接：http://xcmjd.com/cncjmjjg/8257.html