微合金元素Nb对低碳铸钢强度和冲击韧性的影响

doi:10.11896/j.issn.1005-023X.2018.02.016

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Abstract

Microalloyed cast steels with different amount of niobium (Nb) were produced by medium frequency induction furnace. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to investigate the effect of microalloying element Nb on microstructure, strength and toughness of low carbon cast steels. The results indicated that the grain size of low carbon cast steels were refined by 20.8%—34.6% and fine NbC particles were formed by niobium addition. Meanwhile, yield strength (YS), ultimate tensile strength (UTS) and room temperature toughness of the microalloyed steels were improved significantly. Grain refining and precipitation were proved to be the main strengthening mechanisms. When the content of Nb was 0.044 wt%, the YS, UTS and impact energy of the microalloyed steel were 350 MPa, 520 MPa and 119.7 J, respectively. They were improved by 20.7%, 7.2% and 25.6% with retained ductility, respectively, as compared to Nb-free steel.

Key words： low carbon cast steel Nb microalloying microstructure strength toughness

Published: 25 January 2018

CLC number:

TG142.1+3

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	Articles by authors
	Dingfa FU
	Yu LENG
	Wenli GAO

Cite this article:

Dingfa FU,Yu LENG,Wenli GAO. Effect of Microalloying Element Niobium on the Strength and Toughness of Low Carbon Cast Steels[J]. Materials Reports, 2018, 32(2): 237-242.

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http://www.mater-rep.com/EN/10.11896/j.issn.1005-023X.2018.02.016 OR http://www.mater-rep.com/EN/Y2018/V32/I2/237

Chemical composition (wt%) of the investigated steels

Microstructure of the investigated steels after normalizing at 900 ℃ and tempering at 550 ℃ with different Nb contents:(a)0%, (b)0.016%, (c)0.044%, (d)0.072%

Grain morphology and size analysis of the investigated steels with different Nb contents by EBSD: (a)0%, (b)0.016%, (c)0.044%, (d)0.072%

Grain size of the investigated steels with different Nb contents

Precipitates analysis of the niobium microalloyed steels (0.044% Nb) by TEM

Relationship between Nb content and strength/ductility of the investigated steels

Relationship between Nb content and room temperature impact toughness of the investigated steels

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