Quantification of Nano-Sized Precipitates in Microalloyed Steels by Matrix Dissolution

Microalloyed steels possess good strength, toughness and excellent weldability, all of which are necessary attributes for oil and gas pipelines in northern climates. These properties are attributed in part to the presence of nano-sized Nb/Ti carbide precipitates. In order to understand the strengthening mechanisms and to optimize the strengthening effects, it is necessary to quantify the size distribution, volume fraction and chemical speciation of these precipitates. However, characterization techniques suitable for quantifying fine precipitates are limited. A matrix dissolution method has been developed to extract the nano-sized precipitates from microalloyed steels. The results from Grade 100 microalloyed steel are presented in this paper.