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Effect of ferrite on DWTT performance of pipeline steel
- Oct 30, 2018 -

DWTT (drop hammer tearing performance) is an important performance parameter of pipeline steel.

For the pipeline steel used in the production of oil and gas pipelines, not only a certain strength, but also a certain degree of toughness, so the production of pipeline steel are required to carry out DWTT test testing, and this parameter is closely related to the ferrite in the body.

 

A multilateral ferrite or needle-like ferrite is generally formed in pipeline steel.

The role of the multilateral ferrite is to:

1) Coordinate deformation.

Because the multilateral ferrite belongs to the phase with low strength and good plasticity, the existence of the appropriate amount of polygon ferrite can improve the coordination and deformation ability of various tissues, in addition, the existence of grain boundary pearlite also limits the coordinated deformation of ferrite, the deformation resistance increases, the formation work and expansion of cracks increase, and thus the toughness is also improved.

2) passivation crack tip. The multilateral ferrite belongs to the ductile tissue and the strength is low, which can make the crack tip produce large plastic deformation, hinder the crack propagation, and at the same time make the stress of the crack tip relax and the crack tip passivation.
In addition, the existence of a certain number of multilateral ferrite grains will force cracks to continue to cross between the pearlite tissue and the multilateral ferrite, a large number of interfaces inhibit crack propagation, resulting in increased toughness.