High-strength low-alloy steel

About: High-strength low-alloy steel is a research topic. Over the lifetime, 625 publications have been published within this topic receiving 7232 citations. The topic is also known as: High Tensile Strength Steel; HTSS.

Multicomponent High-Strength Low-Alloy Steel Precipitation-Strengthened by Sub-nanometric Cu Precipitates and M 2 C Carbides

Abstract: HSLA-115 is a novel high-strength low-alloy structural steel derived from martensitic Cu-bearing HSLA-100. HSLA-100 is typically used in conditions with overaged Cu precipitates, to obtain acceptable impact toughness and ductility. Present work on HSLA-115 demonstrates that incorporating sub-nanometric-sized M2C carbides along with Cu precipitates produces higher strength steels that still meet impact toughness and ductility requirements. Isothermal aging at 823 K (550 °C) precipitates M2C carbides co-located with the Cu precipitates and distributed heterogeneously at lath boundaries and dislocations. 3D atom-probe tomography is used to characterize the evolution of these precipitates at 823 K (550 °C) in terms of mean radii, number densities, and volume fractions. These results are correlated with microhardness, impact toughness, and tensile strength. The optimum combination of mechanical properties, 972 MPa yield strength, 24.8 pct elongation to failure, and 188.0 J impact toughness at 255 K (−18 °C), is attained after 3-hour aging at 823 K (550 °C). Strengthening by M2C precipitates offsets the softening due to overaging of Cu precipitates and tempering of martensitic matrix. It is shown that this extended yield strength plateau can be used as a design principle to optimize strength and toughness at the same time.

Influence of Ti on non-metallic inclusion formation and acicular ferrite nucleation in high-strength low-alloy steel weld metals

Abstract: The phase transition behaviors of non-metallic inclusions as a function of Ti content were investigated by monitoring changes in the microstructure and mechanical properties of high-strength low-alloy steel multipass weld metals Weld metals with Ti contents ranging from 0007 to 017 wt% were prepared using a gas metal arc welding process The inclusion analysis was performed based on thermodynamic calculations and transmission electron microscopy, accompanied by energy-dispersive spectrometry and selected area electron diffraction With increase in the Ti content of weld metals, the chaotic arrangement of ferrite laths in the columnar zone was transited to a well aligned arrangement and the impact toughness of the weld metals drastically deteriorated in response to the decrease in the Mn content of the inclusion The effective inclusion phase for intragranular nucleation contained considerable amounts of Mn and a Mn depleted zone was observed around the effective nucleant

Microstructural characteristics and impact fracture behavior of a high-strength low-alloy steel treated by intercritical heat treatment

Abstract: Effects of the intercritical heat treatment (IHT) on microstructural evolution and Charpy impact fracture behavior of a high-strength low-alloy (HSLA) steel were investigated. The toughening mechanism was clarified by analyzing microstructural characteristics and crack propagation paths. Results showed that a composite microstructure of ferrite phase separated by globular, rod and irregular shape martensite was obtained by adding the intercritical quenching to the conventional heat treatment of quenching and tempering. And 3.6% retained austenite was detectable in the microstructure. The percentage content of high-angle (15° or more) boundaries reached 78.5%. It was also found that the steel had a high ratio of propagation energy (average: 152 J) to the total absorbed energy (average: 212 J) during impacting at −40 °C. Two crack propagation path models were observed: along the long axis direction of banded ferrite, and across the grains and corresponding interfaces. The improvement of impact toughness was attributed mainly to the retained austenite, the interlocking arrangement of banded ferrite and the ferrite–martensite interfaces with high-angle misorientation, which exhibited effective resistance to the crack propagation.