Quantitative effect of nitrogen on cracks in high Ti and Nb-bearing steels
In this paper,the influence of nitrogen(N)on the occurrence of transverse cracks in high Ti and Nb-bearing steels was quantitatively studied by experimental analysis,thermodynamic calculation and statistical analysis,and N-controlled quantitative standards were proposed.It shows that the high-temperature plastic changes of the steel are strongly correlated with the formation of N compounds.The precipitation of TiN at the end of solidification affects the first brittle zone,then the second brittle zone is related to the precipitation of Nb(C,N)compounds,and the third brittle zone has a relationship with the transformation of ferrite and the precipitation of AlN compounds.The temperature range of the second brittle zone spans from the precipitation point of Nb(C,N)to the point where the precipitation rate of Nb(C,N)begins to ease.The temperature range of the third brittle zone spans from the beginning of the precipitation of ferrite or AlN to the point where cementite begins to precipitate.The N control bottleneck of steel types lies in the precipitation of TiN at the end of solidification.The N control standard is established according to the TiN product,and the TiN product is 4×10-5-7×10-5(％·％).
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