拉速对30Cr13连铸板坯中碳化物尺寸和分布的影响

Effect of casting speed on size and distribution of carbide in 30Cr13 continuous casting slab

30Cr13是一种优秀的刀具用马氏体不锈钢,连铸技术的发展使其生产效率大大提高。拉速是连续铸钢过程中一个重要的工艺参数和技术指标,当连铸拉速不适当时,极易形成大量分布不均匀的碳化物,而碳化物的尺寸和分布是影响连铸板坯质量的关键因素。以30Cr13连铸板坯为研究对象,利用电镜、光镜、X射线衍射技术等,对拉速为0.75、0.80和0.85 m/min的连铸板坯中不同凝固组织处碳化物的形状、尺寸和类型进行了分析统计。结合凝固组织形貌研究了拉速对30Cr13连铸板坯中碳化物的影响,总结了拉速对碳化物影响的规律。研究表明,碳化物的主要形状为簇状、块状和条状,主要组成元素为铁、铬和碳,并确定了碳化物的主要类型为(Fe,Cr)_(7)C_(3)和(Fe,Cr)(23)C_(6)。发现“白亮带”处无碳化物存在,在“白亮带”之间的试样中出现了大量碳化物,连铸板坯中心处碳化物最多。拉速对碳化物的形状、类型和存在位置影响较小,而对碳化物的数量、尺寸影响较大。随着拉速的增大,碳化物总面积占比和数密度先减小再增大,在拉速为0.8 m/min时连铸板坯中碳化物面积占比和数密度最低,这一变化与不同拉速下碳偏析指数偏离正常值的程度趋势相同。随着拉速的增大,小尺寸碳化物占比逐渐增大,大尺寸碳化物占比几乎为0。采用0.80 m/min的拉速可以很好地控制连铸板坯中碳化物的尺寸分布,改善连铸板坯的质量。

30Cr13 is a high quality stainless steel for cutting tools.The development of continuous casting technology has greatly improved its production efficiency.Casting speed is an important process parameter and technical indicator in the continuous casting process.When the casting speed is not suitable,it is easy to form a large amount of unevenly distributed carbides,and the size and distribution of carbides are key factors affecting the quality of continuous casting slabs.Taking 30Cr13 continuous casting slab as the research object,the morphology,size,and type of carbides in different solidification structures in continuous casting slabs of 0.75 m/min,0.80 m/min,and 0.85 m/min were analyzed by Scanning electron microscope,Light microscopy,X-ray diffraction.The effect of casting speed on carbides in 30Cr13 continuous casting slab was studied based on the solidification microstructure morphology,and the effect law of casting speed on carbides in continuous casting slab was summarized.The results show that the main morphology of carbides is clusters,blocks,and strips,and the main components are Fe,Cr,and C.The main types of carbides have been determined to be(Fe,Cr)_(7)C_(3)and(Fe,Cr)(23)C_(6).And it was found that there were no carbides present at the"white bright band",and a large amount of carbides appeared in the sample between the"white bright bands",with the most carbides appearing at the center of the slab.The casting speed has no effect on the shape,type,and location of carbides,but has a greater impact on the quantity and size of carbides.As the casting speed increases,the proportion of total carbide area and number density first decrease and then increase.When the casting speed is 0.80 m/min,the proportion of carbide area and number density in the continuous casting slab is the lowest.This change is consistent with the trend of the degree of deviation of the C segregation index from the normal value under different casting speeds.With the increase of casting speed,the proportion of small-sized carbides increases gradually,while that of large-sized carbides are almost zero.The speed of 0.80 m/min can effectively control the size distribution of carbides in continuous casting slab and improve the quality of the slab.