http://jultika.oulu.fi/files/nbnfi-fe2018062726516.pdf

Slurry erosion of steel – Review of tests, mechanisms and materials

Formation mechanism and control methods of acicular ferrite in HSLA steels: A review

Hydrogen permeation and embrittlement susceptibility of X80 welded joint under high-pressure coal gas environment

Acicular ferrite is a microstructure nucleating intergranularly on non-metallic inclusions and forming an arrangement of fine, interlocking grains. This structure is known to improve steel properties, especially steel toughness, essentially. The formation of acicular ferrite is mainly affected by steel composition, cooling rate, inclusion landscape and austenite grain size. In recent decades, extensive research has been conducted to investigate these factors. The present paper provides an overview of the impact of published results and the state of knowledge regarding acicular ferrite formation. Special attention is paid to the effect of carbon, manganese and titanium addition to steel, as well as the optimum size, number and composition of non-metallic inclusions. In addition, the reactions during the nucleation and growth of acicular ferrite needles are briefly addressed. Further, characteristics of acicular ferrite and bainite are summarized, which should help to distinguish these similar structures.

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Acicular Ferrite Formation and Its Influencing Factors - A Review

Online prediction of mechanical properties of hot rolled steel plate using machine learning

Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

Three kinds of X70 steels with the same chemical composition and different microstructures fabricated by varying processes were compared in aspect of the microstructures and mechanical properties using SEM, TEM and tensile testing machine. The experimental results showed that the steel 1 with acicular ferritic microstructure fabricated by thermal-mechanical processing with online accelerated cooling (TMCP) exhibited an excellent combination of strength and toughness, but provided high yield ratio of 0.85, low uniform elongation of 8.3% as well as low strain hardening exponent of 0.09, indicating poor deformability. In contrast to above steel 1, the steel 2 and steel 3 having ferrite-bainite dual-phase microstructure respectively fabricated by TMCP and intercritical annealing exhibited the improved deformability in terms of the low yield ratio of 0.69 and 0.68, high uniform elongation of 12.8% and 11.8%, and strain hardening exponent of 0.157 and 0.155. It is argued that the optimum properties combination of strength, toughness and deformability can best be achieved by obtaining a ferrite-bainite dual-phase microstructure. This kind of ferrite-bainite dual-phase pipeline steel is appropriate to transmitting oil and natural gas in seismic zone and permafrost.

/pdf/study-of-pipeline-steels-with-acicular-ferrite-j08achnwja.pdf

Study of Pipeline Steels with Acicular Ferrite Microstructure and Ferrite-bainite Dual-phase Microstructure

Anti-large-deformation pipe line steel prepared by thermal treatment method and preparation method thereof

This study aims to investigate the effect of initial microstructures on the properties of ferritemartensite dual-phase pipeline steels with strain-based design. For this purpose, the as-received acicular ferrite steels were first austenitized at 920 °C for 15 minutes followed by air cooling and water quenching to produce ferrite-pearlite and ferrite-martensite microstructure, respectively. Subsequently, the steels with ferrite-pearlite, ferrite-martensite and as-received acicular ferrite microstructure were intercritically annealed at 820 °C for 10 minutes followed by water quenching to produce three different ferrite-martensite dual-phase microstructures. Tensile tests, Vickers hardness and Charpy impact tests were carried out to investigate the mechanical properties. Scanning electron microscope was used to analyze the microstructures and tensile fractographs. The results showed that all the tensile specimens of these three different ferrite-martensite dual-phase steels fractured in ductile mode, however, their microstructures and mechanical properties varied significantly. By contrast, the ferrite-martensite dual-phase steel derived from acicular ferrite initial microstructure had optimal combination of the strength, toughness and deformability, which provided a good candidate for the pipeline steels with strain-based design used in severe geological environments.

/pdf/effect-of-initial-microstructures-on-the-properties-of-4h0fcyl6rk.pdf

Effect of initial microstructures on the properties of Ferrite-Martensite Dual-Phase pipeline steels with Strain-Based design

The invention discloses a hot-rolling large-deformation-resistance pipeline steel and a preparation method thereof. The hot-rolling large-deformation-resistance pipeline steel comprises the following components in percentage by mass: not more than 0.12% of C, not more than 0.35% of Si, not more than 2.0% of Mn, not more than 0.02% of P, not more than 0.01% of S, not more than 0.11% of Nb, not more than 0.08% of V, not more than 0.05% of Ti, not more than 0.06% of Al, not more than 0.012% of N, not more than 0.50% of Cu, not more than 0.60% of Cr, not more than 0.50% of Mo, not more than 0.60% of Ni, not more than 0.005% of B, not more than 0.01% of Ca and the balance of Fe and inevitable impurities. The preparation method comprises the following steps of: carrying out air cooling after hot rolling, and then carrying out water cooling to 100-300 DEG C or immediately carrying out water cooling to 100-300 DEG C after hot rolling, wherein the tensile strength of the steel is not less than 600MPa. The hot-rolling large-deformation-resistance pipeline steel has higher strain hardening index, larger uniform elongation and lower yield ratio, thereby having higher deformation-resistance capacity than that of the common pipeline steels. A steel plate with the thickness of 10-25mum is made into a steel pipe so that the pipeline steel can meet the high-pressure conveying requirements of petroleum and natural gas.

Xiurong Zuo

Papers

Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

Study of Pipeline Steels with Acicular Ferrite Microstructure and Ferrite-bainite Dual-phase Microstructure

Anti-large-deformation pipe line steel prepared by thermal treatment method and preparation method thereof

Effect of initial microstructures on the properties of Ferrite-Martensite Dual-Phase pipeline steels with Strain-Based design

Hot-rolling large-deformation-resistance pipeline steel and preparation method thereof