Abstract：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 ductile-brittle 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-Al2O3 and CaO-SiO2-Al2O3 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.
李南, 王春芳, 罗志强, 李继康. 硅酸盐夹杂在集装箱底侧梁脆性开裂过程中的作用[J]. 冶金分析, 2019, 39(1): 21-27.
LI Nan, WANG Chun-fang, LUO Zhi-qiang, LI Ji-kang. Role of silicate inclusion in brittle cracking process ofbottom side rail of container. , 2019, 39(1): 21-27.
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 20Cr13 stainless steel hot-rolled round bar[J].China Metallurgy,2014,24(7):17-21.
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 of 14MnMoVN 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.
