ZHANG Chao-lei
,
LIU Ya-zheng
,
ZHOU Le-yu
,
JIANG Chao
钢铁研究学报(英文版)
The secondary hardening, the austenite grain coarsening and the surface decarburization phenomenon of Nb-bearing spring steel were investigated, and the effects of niobium on tempered microstructure was studied using scanning electron microscope. The results show that the micro-addition of niobium increases the tempering resistance and produces secondary hardening. The effect of niobium on the size and distribution of cementite particles is one of the primary reasons to increase the hardness after tempering. The grain-coarsening temperature of the spring steel is raised 150 ℃ due to Nb-addition. Furthermore, both the secondary hardening and the austenite grain coarsening phenomenon congruously demonstrate niobium begins observably dissolving above 1100 ℃ in the spring steel. Besides, niobium microalloying is an effective and economy means to decrease the decarburization sensitivity of the spring steels.
关键词:
spring steel
,
microalloying
,
secondary hardening
,
grain coarsening
,
surface decarburization
ZHANG Chaolei
,
LIU Yazheng
,
JIANG Chao
,
XIAO Jinfu
钢铁研究学报(英文版)
Influence of vanadium and/or niobium additions on delayed fracture behavior in high strength spring steel was studied by hydrogen permeation method and slow strain rate technique (SSRT), and its mechanism was analyzed. The results show that apparent diffusion coefficient of hydrogen in microalloyed spring steels NbVsteel and Nbsteel is lower than that in nonmicroalloyed steel 60Si2MnA. Percentage of strength reduction in SSRT in air after precharged hydrogen of the microalloyed steels is smaller than that of 60Si2MnA. Addition of the microalloys changes the fracture characteristics. Thence, vanadium and/or niobium additions are a very effective and economy means to improve the hydrogeninduced delayed fracture resistance of high strength spring steel.
关键词:
spring steel
,
microalloy
,
hydrogeninduced delayed fracture
,
slow strain rate technique
,
hydrogen permeation
