Study on continuous cooling transformation and strength-toughness of X70 pipeline steel with high deformability
by Bin Wang; Cui Zhou; Jia-xiang Zhu; Xiao-yu Tian
International Journal of Microstructure and Materials Properties (IJMMP), Vol. 9, No. 2, 2014

Abstract: Microstructure evolution and mechanical properties of X70 pipeline steel with high deformability was studied in this paper, phase transformation of this steel was investigated by continuous cooling transformation (CCT) method on Formastor-FII automatic transformation instrument. It was concluded that the phase transformation of the steel mainly occurred at 800∼500ºC with Ac1 = 730ºC and Ac3 = 890ºC. Furthermore, as the cooling rate increased, the phase transformation temperature decreased and the hardness of the steel increased. When the cooling rates was 5~20ºC/s, the microstructure was composed of quasi-polygonal ferrite and bainite, the content of bainite increased as cooling rates increased; when the cooling rates were lower than 2ºC/s, bainite disappeared, the microstructure was polygonal ferrite and pearlite. The stress-strain curve of X70 pipeline steel with high deformability exhibited round-house type and the steel had excellent strength-toughness and uniform elongation(>10%), low yield ratio (<0.8), high strain hardening exponent, the brittle-ductile transition temperature was between −100∼−120ºC.

Online publication date: Thu, 30-Apr-2015

The full text of this article is only available to individual subscribers or to users at subscribing institutions.

 
Existing subscribers:
Go to Inderscience Online Journals to access the Full Text of this article.

Pay per view:
If you are not a subscriber and you just want to read the full contents of this article, buy online access here.

Complimentary Subscribers, Editors or Members of the Editorial Board of the International Journal of Microstructure and Materials Properties (IJMMP):
Login with your Inderscience username and password:

Username:        Password:          Forgotten your password?

Want to subscribe?
A subscription gives you complete access to all articles in the current issue, as well as to all articles in the previous three years (where applicable). See our Orders page to subscribe.

If you still need assistance, please email subs@inderscience.com