scispace - formally typeset
Search or ask a question
Topic

Microalloyed steel

About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the morphology of the obtained intragranular microstructures has been found to depend on the steel composition, the prior austenite grain size, and the density of particles able to promote intra-granular nucleation.
Abstract: Acicular ferrite formation, promoted by the intragranular nucleation of ferrite plates, is well known to be beneficial for achieving a good combination of mechanical properties. However, the set of microstructures that can be obtained during the subsequent development of the transformation from the primary plates generated at particles can be quite complex and depends on a certain number of variables: steel composition, temperature range, prior austenite grain size, and particle density. In the present work, acicular ferrite microstructures have been produced by isothermal treatments in three different steels with different active particle types and densities. The morphology of the obtained intragranular microstructures has been found to depend on the steel composition, the prior austenite grain size, and the density of particles able to promote intragranular nucleation. Electron backscattered diffraction (EBSD) techniques have been used to define the microstructural unit controlling toughness in these types of microstructures.

265 citations

Journal ArticleDOI
TL;DR: In this article, a theory of anisotropic ductile fracture is outlined and applied to predict failure in a low alloy steel, and a rate-dependent version of the theory is employed to solve boundary value problems.

265 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures.
Abstract: The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of martensite-austenite (M-A) constituents and of “crystallographic” bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probabilistic models (the “Master-curve” (MC) approach, the Beremin model, and a “double-barrier” (DB) model) are applied to account for the ductile-to-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.

257 citations

Journal Article
TL;DR: In this paper, the role of V in microalloyed steels with a particular address as to how it affects microstructural evolution and mechanical properties is emphasised, based on work carried out at the Swedish Institute for Metals Research (SIMR).
Abstract: The overall objective of the present paper is to review the role of V in microalloyed steels with a particular address as to how it affects microstructural evolution and mechanical properties. Its role in thermomechanical controlled processing (TMCP) is emphasised. The review is largely based on work carried out at the Swedish Institute for Metals Research (SIMR) during the last 25 years, but also includes reference to other relevant, published work. A specific aim is to demonstrate the present scientific knowledge of the subject. Therefore the understanding and interpretation of essential phenomena related to microstructure formation and properties are thoroughly examined, ranging from the influence of microalloying on prevention of austenite grain growth and recrystallisation, to precipitation in ferrite and its effect on strength. Within the well-known thermodynamic database, Thermocalc, a special microalloy database has been developed at SIMR, allowing reliable predictions of phase equilibria and thermodynamic functions for phase transformations in microalloyed steels. A comprehensive account is given of the role of V in the most important processing steps that the microalloyed steels are subjected to, viz. TMCP, continuous casting and welding. Compared to the other microalloying elements, Nb and Ti, V exhibits essential differences. In particular, the solubility of its carbonitrides is much larger and the solubility of its nitride is about 2 orders of magnitude smaller than its carbide, contrary to Nb but similar to Ti. For optimal alloy design and thermomechanical processing, proper allowance must be made for these differences. To reach the maximum ferrite grain refinement, ∼4 μm, repeated recrystallisation in a series of rolling reductions is used in TMCP of V-microalloyed steels, so-called Recrystallisation-Controlled-Rolling (RCR), as opposed to traditional controlled rolling of Nb-steels where heavy rolling at low temperatures in the non-recrystallisation regime is the means of attaining grain refinement. RCR presents some important advantages, in particular a more economical hot rolling practice by allowing low reheating and high finishing temperatures. As compared to Nb, V has certain further advantages as a microalloying element due to its greater solubility in austenite. The tendency for hot cracking of cast slabs is much less pronounced and dissolution of coarse V(C,N) compounds is more easily achieved prior to hot rolling than for the corresponding NbC. It is demonstrated that the relatively large solubility of V(C,N) and the much lower solubility of VN than VC makes V an eminent choice for strong and easily controllable precipitation strengthening. A corollary of the difference in VN and VC solubilities is that N becomes an essential microalloying element in V-steels, because it largely determines the density of V(C,N) precipitation and thereby the degree of precipitation strengthening. Moreover, since pure ferrite dissolves more N than C, the total N-content of the steel is normally dissolved in the ferrite before V(C,N) precipitation, whereas only a fraction of the C-content, given by the austenite/ferrite or ferrite/ cementite equilibrium, is dissolved in ferrite. Hence, by precise additions of N, this circumstance facilitates the control of V(C,N) precipitation strengthening.

231 citations

Journal ArticleDOI
TL;DR: In this paper, the precipitation behavior of a commercial high-strength low-alloy (HSLA) steel microalloyed with 0.086 wt pct Nb and 0.047 wtpct Ti has been investigated using transmission electron microscopy (TEM) and mechanical testing.
Abstract: The precipitation behavior of a commercial high-strength low-alloy (HSLA) steel microalloyed with 0.086 wt pct Nb and 0.047 wt pct Ti has been investigated using transmission electron microscopy (TEM) and mechanical testing. The emphasis of this study is to compare an industrially hot-rolled steel and samples from a laboratory hot torsion machine simulation. From TEM observations, the Ti and Nb containing precipitates could be grouped according to their size and shape. The precipitates in order of size were found to be cubic TiN particles with sizes in the range of 1 µm, grain boundary precipitates with diameters of approximately 10 nm, and very fine spherical or needle-shaped precipitates with sizes on the order of 1 nm. The needlelike precipitates were found on dislocations in ferrite and constituted the dominant population in terms of density. Thus, they appear to be responsible for the precipitation strengthening observed in this steel. Aging tests were carried out at 650°C to evaluate the precipitate strengthening kinetics in detail. The strengthening mechanisms can be described with a nonlinear superposition of dislocation and precipitation hardening. The mechanical properties of torsion-simulated material and as-coiled industrial material are similar; however, there are some microstructural differences that can be attributed to the somewhat different processing routes in the laboratory as compared to hot strip rolling.

229 citations


Network Information
Related Topics (5)
Alloy
171.8K papers, 1.7M citations
84% related
Microstructure
148.6K papers, 2.2M citations
84% related
Deformation (engineering)
41.5K papers, 899.7K citations
82% related
Grain boundary
70.1K papers, 1.5M citations
81% related
Welding
206.5K papers, 1.1M citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202288
202164
202090
201986
201888