冷镦钢开裂的原因分析及改进
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摘要
为了研究冷镦钢开裂的原因和过程,取样分析了某钢厂生产中存在开裂的试样,利用带有能谱仪的扫描电镜(SEM-EDS)观察开裂区域宏观形貌和微观组织并表征夹杂物的形貌和成分。结果发现,部分魏氏体混杂在基体中,降低了冷镦钢的塑性和韧性;开裂区域发生穿晶断裂和氧化脱碳现象,其完全脱碳层的平均厚度为28μm,说明表面缺陷在轧制前就已经存在,导致冷镦钢轧制时开裂;残留在钢中的铝镁钙复合夹杂物也直接导致了表面缺陷和开裂。同时,提出改善微观组织、减少夹杂物的改进措施。
In order to study the causes and processes of cracking of cold heading steel,the specimens with cracking produced in a steel mill were sampled and analyzed.Scanning electron microscopy(SEM-EDS)with an energy dispersive spectrometer was used to observe the macroscopic morphology and microstructure of the cracked area and characterize the morphology and composition of the inclusions.It was found that part of the Widmanstatten structure was mixed in the matrix,which reduced the plasticity and toughness of the cold heading steel.Transgranular fracture and oxidative decarburization occurred in the cracked zone,and the average thickness of the complete decarburized layer was 28μm,which indicated that the surface defects existed before rolling,resulting in cracking of the cold heading steel during rolling.The residual aluminum-magnesium-calcium composite inclusions in steel also directly led to surface defects and cracking.At the same time,improvements were proposed to improve the microstructure and reduce inclusions.
In order to study the causes and processes of cracking of cold heading steel,the specimens with cracking produced in a steel mill were sampled and analyzed.Scanning electron microscopy(SEM-EDS)with an energy dispersive spectrometer was used to observe the macroscopic morphology and microstructure of the cracked area and characterize the morphology and composition of the inclusions.It was found that part of the Widmanstatten structure was mixed in the matrix,which reduced the plasticity and toughness of the cold heading steel.Transgranular fracture and oxidative decarburization occurred in the cracked zone,and the average thickness of the complete decarburized layer was 28μm,which indicated that the surface defects existed before rolling,resulting in cracking of the cold heading steel during rolling.The residual aluminum-magnesium-calcium composite inclusions in steel also directly led to surface defects and cracking.At the same time,improvements were proposed to improve the microstructure and reduce inclusions.
引文
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[16]Todorov R P,Khristov K G.Widmanstatten structure of carbon steels[J].Metal Science and Heat Treatment,2004,46(1):49.
[2]鲁欣武.杭钢冷镦钢生产技术发展[J].中国冶金,2006,16(5):19.
[3]MIN Yi,JIANG Mao-fa.Exergy analysis and optimization of ladle furnace refining process[J].Journal of Iron and Steel Research,International,2010,17(11):24.
[4]Suzuki H G,Nishimura S,Nakamura Y.Improvement of hot ductility of continuously cast carbon steels[J].Transactions of the Iron and Steel Institute of Japan,2006,24(1):54.
[5]You D,Michelic S K,Wieser G,et al.Modeling of manganese sulfide formation during the solidification of steel[J].Journal of Materials Science,2017,52(3):1797.
[6]许涛,邹长东,赵家七,等.含铝冷镦钢塞棒侵蚀原因分析与改进[J].钢铁,2016,51(12):41.
[7]Petrus B,Zheng K,Zhou K,et al.Real-time,model-based spray-cooling control system for steel continuous casting[J].Metallurgical and Mater Transactions B,2011,42(1):87.
[8]Rian Dippenaar,Christian Bernhard,Siegfried Schider,et al.Austenite grain growth and the surface quality of continuously cast steel[J].Metallurgical and Mater Transactions B,2014,45(2):409.
[9]WANG Biao,JI Zhen-ping,LIU Wen-hong,et al.Application of hot strength and ductility test to optimization of secondary cooling system in billet continuous casting process[J].Journal of Iron and Steel Research,International,2008,15(4):16.
[10]帅习元,陈洪伟,周勇,等.冷镦钢冷镦开裂原因及其改进措施[J].中国冶金,2008,18(4):33.
[11]Zahid G H,Huang Y,Prangnell P B.Microstructure and texture evolution during annealing a cryogenic-SPD processed Alalloy with a nanoscale lamellar HAGB grain structure[J].Acta Materialia,2009,57:3509.
[12]王利军,阮士朋,王宁涛,等.高强度螺栓用非调质钢的研制与应用[J].钢铁,2018,53(11):102.
[13]Valiev R Z,Mulyukov R R,Ovchinnikov V V,et al.Direction of a grain-boundary phase in submicrometre-grained iron[J].Philosophical Magazine Letters,1990,62:253.
[14]Valiev R Z,Sergueeva A V,Mukherjee A K.The effect of annealing on tensile deformation behavior of nanostructured SPD titanium[J].Scripta Materialia,2003,49:669.
[15]孔祥华.SCM440与ML40Cr大盘卷脱碳与冷镦开裂行为研究[C]//2011年全国高品质特殊钢生产技术研讨会论文集.西宁:中国金属学会,2011:266.
[16]Todorov R P,Khristov K G.Widmanstatten structure of carbon steels[J].Metal Science and Heat Treatment,2004,46(1):49.