Bauschinger effect in Nb and V alloyed line-pipe steels

The UOE process is used for cold forming of large diameter steel line-pipes. Pipe strength has been found to increase (work hardening) or decrease (Bauschinger effect) after the UOE process compared to the plate depending on the steel grade, plate and pipe processing history. The steel chemistry, through the presence of microalloy precipitates, and prior processing, through the size and distribution of microalloy precipitates and presence of retained work hardening, affects the magnitude of the Bauschinger effect. In this paper the microstructures of two (Nb and Nb-V alloyed) steel plates, in terms of (Nb,V)(C,N) particle distributions and dislocation densities, have been related to the Bauschinger parameters in the as rolled and annealed initial conditions. The Bauschinger stress parameter increases with microalloy particle number density and dislocation density increase and the relative importance of the two effects is discussed

Sports materials special issue editorial

Materials are key to the world of sport [...

Mechanical property development during UOE forming of large diameter pipeline steels

Mechanical properties of large diameter welded steel pipes depend on the thermomechanically controlled rolled (TMCR) plate microstructure and UOE pipe-forming cold deformation sequence. Strength from plate to pipe may increase (work-hardening) or decrease (the Bauschinger effect). Bauschinger effect parameters depend on steel composition and plate processing history. The present study is examining two pipeline grades: X60 (Nb-alloyed) and X65 (Nb- and V-alloyed). Mechanical properties are determined by grain refinement, solid solution, precipitation strengthening mechanisms, and work-hardening (work-softening). The reverse deformation yield drop increases with an increase in the precipitate particle volume fraction and pre-strain. Annealing, leading to a decrease in the dislocation density, reduces the yield drop. The Bauschinger parameters are being quantitatively related to the particle type, size, and volume fraction, and the dislocation density

Characterisation of precipitation and carbide coarsening in low carbon low alloy Q&T steels during the early stages of tempering

In order to ensure that appropriate tempering conditions are used to obtain desired strength and toughness for low carbon low alloy quench and tempered (Q&T) steel plates in a range of thickness, it is desirable to be able to predict the effect of composition and tempering conditions (time and temperature) on the microstructure and hence the hardness evolution for these steels. In this paper, carbide precipitation and coarsening behaviour in three low carbon low alloy Q&T steels have been investigated during tempering at 600 °C up to 16 hours to determine the role of alloying additions of Mo, V, Cr and Si. It has been found that auto-tempering occurs during water quenching with ε’-carbide and cementite being present within the martensite laths for all three steels. In the Base steel, cementite becomes the stable second phase after 2 hours tempering and has an elliptical (sometimes spherical) shape, which coarsens with time during tempering from 2 h to 16 h. However, in the Base-Mo-V and Base-Cr-Mo-V-Si steels, elliptical and needle-shaped cementite (shown to contain Mn, Mo and Cr) both exist during tempering; furthermore, finer elliptical secondary Mo-V-rich carbides are observed after tempering for 4 h. The coarsening of cementite contributing to the softening process in the three steels has been quantified with, most significantly, the inter- and intra-lath carbides coarsening independently. Although fine secondary alloy carbides are observed after 4 hours tempering, they do not result in any noticeable secondary hardening peak in the Base-Mo-V and Base-Cr-Mo-V-Si steels

Modeling the effects of pore arrays on the electrical and mechanical properties of copper

Abstract</jats:p

Magnetic characterisation of microstructural feature distribution in P9 and T22 steels by major and minor BH loop measurements

This paper investigates the magnetic properties and parameters measured from major/minor loops and used to characterise different microstructural feature distributions in P9 and T22 steel in different heat treatment or service conditions. The present study introduces a non-destructive way of selecting microstructural features of interest and/or excluding those of little relevance by examination of minor loop measurements at a selected range of applied fields and discusses the fundamental mechanism in terms of domain processes. There is remarkable consistency in magnetic behaviours and properties such as initial/incremental permeability values between the measurements by different techniques. This behaviour has been ascribed to the similar underlying domain processes and hence similar selected microstructural features that are affecting the domain processes

Effect of strain-induced precipitation on the recrystallization kinetics in a model alloy

The effects of Nb addition on the recrystallization kinetics and the recrystallized grain size distribution after cold deformation were investigated by using Fe-30Ni and Fe-30Ni-0.044 wt pct Nb steel with comparable starting grain size distributions. The samples were deformed to 0.3 strain at room temperature followed by annealing at 950 °C to 850 °C for various times; the microstructural evolution and the grain size distribution of non- and fully recrystallized samples were characterized, along with the strain-induced precipitates (SIPs) and their size and volume fraction evolution. It was found that Nb addition has little effect on recrystallized grain size distribution, whereas Nb precipitation kinetics (SIP size and number density) affects the recrystallization Avrami exponent depending on the annealing temperature. Faster precipitation coarsening rates at high temperature (950 °C to 900 °C) led to slower recrystallization kinetics but no change on Avrami exponent, despite precipitation occurring before recrystallization. Whereas a slower precipitation coarsening rate at 850 °C gave fine-sized strain-induced precipitates that were effective in reducing the recrystallization Avrami exponent after 50 pct of recrystallization. Both solute drag and precipitation pinning effects have been added onto the JMAK model to account the effect of Nb content on recrystallization Avrami exponent for samples with large grain size distributions

Implications of Rigid Gripping Constraints on Clubhead Dynamics in Steel Golf Shafts

Research and equipment testing with golf robots offers much greater control and manipulation of experimental variables compared to tests using human golfers. However, whilst it is acknowledged that the club gripping mechanism of a robot is dissimilar to that of a human, there appears to be no scientific findings on the effects of these gripping differences on the clubhead at ball impact. Theoretical and experimental strain propagation rates from the clubhead to the grip and back to the clubhead were determined during robot testing with a 9-iron to determine if this time interval was sufficiently short to permit the gripping mechanism to have an effect on the clubhead during impact. Longitudinal strain appears to propagate the most quickly, but such deflections are likely to be small and therefore of little meaningful consequence. Shaft bending was not a primary concern as modes of large enough amplitude appear to propagate too slowly to be relevant. Torsional strain propagates at a rate which suggests that constraints at the grip end of a golf club could potentially influence impact dynamics for steel shafted irons; however, this effect seems unlikely to be significant, a likelihood that decreases further for longer irons. As such, it is considered reasonable to treat the influence of a robot’s gripping mechanism on clubhead dynamics at impact as negligible, and therefore comparisons between robot and human data in this regard are valid