硅酸盐夹杂在集装箱底侧梁脆性开裂过程中的作用
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摘要
某集装箱底侧梁在正常使用过程中发生开裂,事故发生时箱内载重未超过箱体允许的承重极限。通过对开裂的底侧梁进行化学成分光谱分析、拉伸及冲击性能测试、梁正常部位及断口毗邻区域金相检验、断口分析以及夹杂物综合分析等,分析了底侧梁开裂的原因,研究并解释了夹杂物在开裂过程中所起的作用。检验及分析结果表明,底侧梁钢板强韧性低下,且表面脱碳,存在表面强度进一步低于基体的现象,在服役过程中导致裂纹易于在表面萌生。酸溶铝(Als)含量极低,这也导致钢板存在较高的韧脆转变温度,服役过程中存在较大的安全隐患。同时钢板内存在大量大尺寸的MnO-SiO2-Al2O3系和CaO-SiO2-Al2O3系硅酸盐塑性夹杂,该夹杂在热加工过程中被严重拉长,分布于晶界和晶内,严重破坏了钢材基体连续性,导致其强韧性低下并促进了裂纹的扩展。服役过程中底侧梁R角处作为应力集中部位首先发生开裂,进而裂纹以沿晶+穿晶解理的方式快速扩展,最终脆性开裂。
The bottom side rail of one container was cracked in normal service condition.The load in container did not exceed the allowable weight limit when the accident occurred.The cracked bottom side rail was characterized by chemical composition spectral analysis,tensile and impact property test,metallographic examination of normal position and fracture-adjacent region,fracture analysis and comprehensive analysis of inclusions.The cracking reasons of bottom side rail analyzed.The role of inclusions in cracking process was studied and explained.The examination and analysis results showed that the obdurability of bottom side rail steel sheet was low.Moreover,the surface decarburization was observed.The surface strength was further lower than that of matrix.As a result,the cracks were easily initiated on surface in the course of service.The content of acid soluble aluminum(Als)was very low,leading to high ductilebrittle transition temperature of steel sheet.Therefore,great safety risk existed in the course of service.Meanwhile,there were a lot of large-size MnO-SiO2-Al2 O3 and CaO-SiO2-Al2 O3 plastic silicate inclusions in steel sheet.These inclusions were severely stretched in hot-working process and distributed in grain boundary and grains,which seriously destroyed the continuity of steel matrix,leading to the low obdurability and the expansion of cracks.The R angle was the stress concentration position of bottom side rail in the course of service and firstly cracked.Then the cracks were rapidly extended in the mode of intergranular fracture and transgranular cleavage,and finally causing brittle cracking.
The bottom side rail of one container was cracked in normal service condition.The load in container did not exceed the allowable weight limit when the accident occurred.The cracked bottom side rail was characterized by chemical composition spectral analysis,tensile and impact property test,metallographic examination of normal position and fracture-adjacent region,fracture analysis and comprehensive analysis of inclusions.The cracking reasons of bottom side rail analyzed.The role of inclusions in cracking process was studied and explained.The examination and analysis results showed that the obdurability of bottom side rail steel sheet was low.Moreover,the surface decarburization was observed.The surface strength was further lower than that of matrix.As a result,the cracks were easily initiated on surface in the course of service.The content of acid soluble aluminum(Als)was very low,leading to high ductilebrittle transition temperature of steel sheet.Therefore,great safety risk existed in the course of service.Meanwhile,there were a lot of large-size MnO-SiO2-Al2 O3 and CaO-SiO2-Al2 O3 plastic silicate inclusions in steel sheet.These inclusions were severely stretched in hot-working process and distributed in grain boundary and grains,which seriously destroyed the continuity of steel matrix,leading to the low obdurability and the expansion of cracks.The R angle was the stress concentration position of bottom side rail in the course of service and firstly cracked.Then the cracks were rapidly extended in the mode of intergranular fracture and transgranular cleavage,and finally causing brittle cracking.
引文
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[2]Atkision H V,Shi G.Characterization of inclusions in clean steels:a review including the statistics of extremes method[J].Progress in Material Science,2003,48:457-520.
[3]张德堂.钢中非金属夹杂物鉴别[M].北京:国防工业出版社,1991:255-290.
[4]王鑫潮,王红娜,成国光,等.20Cr13不锈钢热轧板材夹杂物研究[J].中国冶金,2014,24(7):17-21.WANG Xin-chao,WANG Hong-na,CHENG Guo-guang,et al.Characteristics of inclusions in 20Cr13stainless steel hot-rolled round bar[J].China Metallurgy,2014,24(7):17-21.
[5]黄一新,尹雨群,李晶,等.X70管线钢中夹杂物控制试验研究[J].江苏冶金(Jiangsu Metallurgy),2007,35(5):26-28.
[6]王旭红.高强船板钢中硅酸盐类夹杂物的研究[J].河北冶金,2011(4):7-9.WANG Xu-hong.Study about silicate inclusion in highstrength ship board steel[J].Hebei Metallurgy,2011(4):7-9.
[7]李双江,李阳,姜周华,等.304奥氏体不锈钢夹杂物冶金行为[J].东北大学学报:自然科学版,2010,31(3):402-405.LI Shuang-jiang,LI Yang,JIANG Zhou-hua,et al.Metallurgical behavior of inclusion in 304austenitic stainless steel[J].Journal of Northeastern University:Natural Science,2010,31(3):402-405.
[8]刘林飞.Q195连铸板坯中非金属夹杂物的研究[D].重庆:重庆大学,2004.
[9]戴为志.建筑钢结构焊接工程层状撕裂的产生机理及防止[J].焊接技术(Welding Technology),2007,36(3):27-30.
[10]戴丽娟.14MnMoVN钢层状撕裂敏感性研究[J].包头钢铁研究学院学报,2001,20(1):40-42.DAI Li-juan.Research on the layer tearing sensitivity of14MnMoVN steel[J].Journal of Baotou University of Iron and Steel Technology,2001,20(1):40-42.
[11]罗怀晓,李云,刘延坪.某高压输电线路铁塔腿根部断裂原因分析[J].热加工工艺,2018,47(2):259-261.LUO Huai-xiao,LI Yun,LIU Yan-ping.Analysis on causes of fracture in tower leg of high-voltage transmission lines[J].Hot Working Technology,2018,47(2):259-261.