Tempering of the Bainite and the Bainite/Martensite Duplex Structure in a Low-Carbon Low-Alloy Steel

Ohmori, Yasuya; Ohtani, Hiroo; Kunitake, Tatsuro

doi:10.1179/msc.1974.8.1.357

Cited by 70 publications

(25 citation statements)

References 8 publications

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“…Experts on steel materials developed low alloy steels of 600-800 MPa grades by means of different strengthening methods, however, relatively high amount of different alloy elements were used, which make the production cost high and requires more strict production conditions. [7][8][9][10][11][12][13][14] This article gives the experimental results for the development of Ti-microalloyed bainite-ferrite multi-phase steel with perfect comprehensive properties by Ti-microalloying which has relative lower cost comparing with niobium and vanadium alloying. The developed steels make use of the interaction among alloy elements like Mn and Ti, rolling control, rapid cooling after rolling and the effect of precipitation strengthening and grain refinement strengthening of Ti.…”

Section: Introductionmentioning

confidence: 99%

A Bainite-Ferrite Multi-Phase Steel Strengthened by Ti-Microalloying

Wang

Ai-da

2011

Mater. Trans.

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Ti-microalloyed bainite multi-phase steels were prepared in laboratory scale. The tensile strength of examined steels are all higher than 775 MPa and the maximum value is 875 MPa, with at least 27 J impact energy at 253 K which shows a good balance of high strength and high toughness. The examined steels have uniform and fine multi-phase structure with bainite as main phase and ferrite as minor phase, the ratio of ferrite phase gradually decreases with the cooling speed of post-rolling increasing. Most of the precipitates are nano scaled particles of TiN and TiC, which disperse at grain boundaries, dislocations and other places, having effect of grain refinment strengthening and precipitation strengthening.

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Section: Introductionmentioning

confidence: 99%

A Bainite-Ferrite Multi-Phase Steel Strengthened by Ti-Microalloying

Wang

Ai-da

2011

Mater. Trans.

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“…For example, in low alloy quenched-and-tempered steels, if austenite grains are separated into several parts by fine bainite laths nucleating at austenite grain boundaries during quenching prior to the martensite transformation, the mean martensite packet size will be largely reduced, the ductile/brittle transition temperatures being significantly lowered. 1,2) The mean lath packet size has often been referred to as the effective grain size 3) or the unit crack path. 1) Since the microstructural controls can be achieved by heat treatments, the mechanisms of phase transformations in steels have been the subjects of numerous investigations from kinetic and crystallographic points of view.…”

Section: Introductionmentioning

confidence: 99%

Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

Ohmori

2001

ISIJ International

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The studies on the crystallographic features of diffusional transformation of austenite in various steels have been reviewed. A primary ferrite forming at an austenite grain boundary is related to at least one of the austenite grains separated by the boundary with the Bain correspondence. In the case of the microstructures containing both ferrite and carbides such as pearlite, degenerate pearlite, interphase precipitation of alloy carbides, and upper and lower bainites, the crystallographic relationships between ferrite and carbides provide further information to elucidate the transformation mechanisms. In the present report, therefore, the orientation relationships between ferrite, carbide and austenite as well as the habit planes of platelike transformation products and the mechanisms of transformations are discussed.

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“…The boundaries between grains having different orientations of 15 deg or higher are high-angle boundaries, and these grains are generally considered to be effective grains. [30] The measurement data of the effective grain size are shown in Table V. The grain size of the M1-50 specimen is smaller (49 lm) than that of the M4-30 specimen (28 lm).…”

Section: Microstructure Of Simulated Haz Of Api X80 Linepipe Steelsmentioning

confidence: 99%

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

Sung

Sohn

Shin

et al. 2014

Metall Mater Trans A

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This study is concerned with effects of complex oxides on acicular ferrite (AF) formation, tensile and Charpy impact properties, and fracture toughness in heat affected zones (HAZs) of oxidecontaining API X80 linepipe steels. Three steels were fabricated by adding Mg and O 2 to form oxides, and various HAZ microstructures were obtained by conducting HAZ simulation tests under different heat inputs. The no. of oxides increased with increasing amount of Mg and O 2 , while the volume fraction of AF present in the steel HAZs increased with increasing the no. of oxides. The strengths of the HAZ specimens were generally higher than those of the base metals because of the formation of hard microstructures of bainitic ferrite and granular bainite. When the total Charpy absorbed energy was divided into the fracture initiation and propagation energies, the fracture initiation energy was maintained constant at about 75 J at room temperature, irrespective of volume fraction of AF. The fracture propagation energy rapidly increased from 75 to 150 J and saturated when the volume fraction of AF exceeded 30 pct. At 253 K (À20°C), the total absorbed energy increased with increasing volume fraction of AF, as the cleavage fracture was changed to the ductile fracture when the volume fraction of AF exceeded 45 pct. Thus, 45 vol pct of AF at least was needed to improve the Charpy impact energy, which could be achieved by forming a no. of oxides. The fracture toughness increased with increasing the no. of oxides because of the increased volume fraction of AF formed around oxides. The fracture toughness did not show a visible correlation with the Charpy absorbed energy at room temperature, because toughness properties obtained from these two toughness testing methods had different significations in view of fracture mechanics.

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Tempering of the Bainite and the Bainite/Martensite Duplex Structure in a Low-Carbon Low-Alloy Steel

Cited by 70 publications

References 8 publications

A Bainite-Ferrite Multi-Phase Steel Strengthened by Ti-Microalloying

A Bainite-Ferrite Multi-Phase Steel Strengthened by Ti-Microalloying

Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

Effects of Oxides on Tensile and Charpy Impact Properties and Fracture Toughness in Heat Affected Zones of Oxide-Containing API X80 Linepipe Steels

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