【摘要】 针对汽车连杆用棒材44SMn28在生产中表面与内部裂纹频繁出现，基于低倍酸洗、光学显微观察、扫描电镜观察与能谱分析相结合的手段，对扒皮与黑皮44SMn28轧材的裂纹进行观察，对其中硫化物的析出、形貌、分布及其对裂纹产生的机理进行研究。结果表明：钢中存在大量的MnS夹杂物，尺寸在几百纳米到几百微米之间，成粒状、纺锤状或条带状分布于晶内与晶界；条带状硫化物是钢中裂纹产生的主要原因，其各向异性显著降低材料的横向机械性能，导致钢材在应力作用下沿其界面萌生裂纹；裂纹内部还存在大量氧化物，在氧化物与基体之间存在大量FeS，在热应力与机械应力作用下极易引起钢材开裂。与扒皮轧材相比，黑皮轧材表面裂纹显著减少、裂纹深度较浅，但在低温变形情况下轧材内部裂纹更易沿晶界扩展。更多还原

【Abstract】 In view of the frequent appearance of surface and internal cracks in the production of automobile connecting rod steel 44SMn28, based on the combination of pickling macro-detection, optical microscope, scanning electron microscope observation and energy dispersive spectroscopy analysis, the cracks of 44SMn28 rolled bar for peeling billet and black rolled billet were observed, and the precipitation, morphology, distribution of sulfide and the crack generation mechanism were also studied. The results show that there are a large number of MnS inclusions in the steel, ranging from hundreds of nanometers to hundreds of micrometers in size, distributed in granular, spindle or strip shape within the grain and grain boundaries. Banded sulfide is the main cause of cracks in steel, and its anisotropy significantly reduces the transverse mechanical properties of the materials, resulting in the initiation of cracks along its interface under stress. There is also a lot of oxide in the crack, and there is a lot of FeS between the oxides and the matrix, which is peculiarly prone to cause steel cracking under the action of thermal stress and mechanical stress. Compared with the peeled rolling materials, the surface cracks of the black rolled materials are significantly reduced, the crack depth is shallow. Moreover, the internal cracks of rolled materials are more likely to propagate along the grain boundary in the case of low temperature deformation.更多还原