eTheses Repository

# Bauschinger effect in Nb and V microalloyed line pipe steels

Kostryzhev, Andrii Gennadiovych (2009)
Ph.D. thesis, University of Birmingham.

 PDF (8Mb)

## Abstract

Chemical composition of structural steels with a ferrite-pearlite microstructure has been developing towards decreasing carbon content, to increase weldability, with increased microalloying element content, to provide grain refinement, solid solution and precipitation strengthening. During the UOE forming of large diameter (more than 400 mm) welded pipes the strength drop from plate to pipe, as a result of reverse deformation (the Bauschinger effect), depends on steel grade, namely microalloying element content, and processing. In this project the microstructure of two Nb- and V-microalloyed steels has been studied with optical, scanning and transmission electron microscopy. The dislocation density and (Ti,Nb,V,Cu)-rich particle diameter, volume fraction and number density were measured for as-rolled and annealed (30 min. at 400 $$^0$$C and 550 $$^0$$C) steels. The Bauschinger effect was measured during compression-tension testing for the same steel conditions. The yield stress drop during reverse deformation has been found to increase with an increase in forward pre-strain, dislocation density and particle number density within the effective particle diameter range of 12-50 nm. On the basis of dislocation-particle interaction analysis, a quantitative model of work-hardening behaviour dependence on particle number density and dislocation density has been derived for the reverse deformation of studied steel grades.

Type of Work: Ph.D. thesis. Strangwood, Martin and Davis, Claire Colleges (2008 onwards) > College of Engineering & Physical Sciences Department of Metallurgy & Materials TN Mining engineering. Metallurgy University of Birmingham 436
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.

Repository Staff Only: item control page