Work Hardening in Ferritic Steel Containing Ultra-fine Carbides

Kosaka, Noriaki; Funakawa, Yoshimasa

doi:10.2355/isijinternational.isijint-2015-218

Cited by 10 publications

(4 citation statements)

References 22 publications

(21 reference statements)

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“…Kosaka et al 8,9) reported a strong correlation between the trapped-hydrogen concentration and the amount of precipitation strengthening of carbide precipitated steel, which indicated the possibility of coherent strain at the carbide/matrix interface is the trapped-hydrogen sites due to carbide precipitation. They used the Gerold-Haberkorn equation, used the calculated lattice constant and precipitation amount obtained by Thermo-Calc, and assumed spherical carbide with a size of 10 nm when evaluating the amount of precipitation strengthening.…”

Section: Factors Controlling Hydrogen Trapping By Alloy Carbidesmentioning

confidence: 99%

“…There are various reports on the hydrogen trapping behaviour of alloy carbides. Kosaka et al 8,9) reported that the MC carbides of NbC, TiC, and VC exhibited high hydrogen trapping capacities, and they presumed that the main factor affecting the hydrogen trapping was the coherent strain field at the carbide/matrix interface. Yamasaki et al 10) reported that the trapped hydrogen concentration per unit MC particle in V/Mo added steel increased as the increase of Mo fraction at the MC metal atom site (M site).…”

Section: Introductionmentioning

confidence: 99%

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Carbide Precipitation and Hydrogen Trapping Behavior in Mo and V Added Tempered Martensitic Steel

Kameya,

Taniguchi,

Kobayashi

et al. 2024

ISIJ Int.

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To investigate the hydrogen trapping effect of the combined addition of V to Mo-added steel, 0.1C-2Mn-1.6Mo mass% steel (Steel A) and 0.1C-2Mn-1.6Mo-0.2V mass% steel (Steel B) were prepared, quenched, and tempered at 873 K. The hydrogen trapping effect was investigated by thermal desorption hydrogen analysis of hydrogen-charged specimens, and Steel B showed a higher hydrogen trapping capacity than Steel A. According to thermodynamic equilibrium calculations, hydrogen trapping site of Steel A and B after tempering were predicted as M 2 C carbides. However, according to TEM observation of these specimens, not only coarse M 2 C but fine MC carbides precipitated in Steel A, and only fine MC precipitated in Steel B. Chemical composition of these precipitates were investigated by the three-dimensional atom probe analysis. MC of both Steel A and B show a composition close to MC 0.5 , in which Mo is the primary element in metal sites. It was found that the carbon-site vacancy (C vacancy) ratio of MoC 0.5 in the present work is higher than that of V 4 C 3 (VC 0.75 ). The hydrogen trapping capacity showed a good correlation with the product of the area of Fe-MC interface and the C vacancy ratio in MC. The reason of the higher hydrogen trapping capacity of Steel B than that of Steel A is considered as below. 1) The combined addition of V to Mo assisted the precipitation of MC instead of coarse M 2 C. 2) C vacancies in MC were increased by the partitioning of Mo into MC, and the vacancies acted as hydrogen trapping sites.

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Section: Factors Controlling Hydrogen Trapping By Alloy Carbidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Carbide Precipitation and Hydrogen Trapping Behavior in Mo and V Added Tempered Martensitic Steel

Kameya,

Taniguchi,

Kobayashi

et al. 2024

ISIJ Int.

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“…A detailed analysis of work-hardening in the interphase precipitation-strengthened steels has been started. 61,62) Recently, the precipitation pathway of (Ti, Mo)C has been investigated by the HR-TEM and 3D-AP techniques. 63) HR-TEM observation indicated that embryo clusters that were coherent with ferrite grew into NaCl type nanometer-sized carbides through the GP zone.…”

Section: (B) Ferritic-martensitic Steelmentioning

confidence: 99%

Interphase Precipitation and Application to Practical Steels

Funakawa¹

2019

Mater. Trans.

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Interphase precipitation is a phenomenon in which precipitates are generated on interphase boundaries during phase transformation, creating carbides having a form like bands or fibers in micro-alloyed steels. In isothermal transformation, a lower transformation temperature reduces the carbide diameter and band spacing, and a higher cooling rate reduces them in the continuous cooling process. Various interphase precipitation mechanisms have been suggested, and some models for the ledge mechanism attempted to explain the regular band spacing in steels containing carbide-forming elements quantitatively. Recently, as the orientation relationship in the grains of the interphase boundary is not consistent with the ledge mechanism, three-dimensional interface structures have been suggested to explain the experimental results of observation by transmission electron microscopy in low carbon steel. The newly-proposed interphase structure model may explain both the ledge and quasi-ledge mechanisms. Steels with tensile strength of more than 590 MPa, which are manufactured by using interphase precipitated carbides, have been developed and used practically not only in plate and sheet products but also in forged products to improve formability. In steels consisting of ferrite and a second hard phase, interphase precipitated carbides are used to realize high local ductility and to reduce the difference of hardness between the two phases. Ferritic steels strengthened by nanometer-sized carbides are developed to achieve excellent formability, realizing precipitationstrengthening of more than 300 MPa.

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“…For example, Ashby-Orowan model [4] is well known, which formulated the increment of yield strength by inter-particle spacing. Furthermore, in recent years, effect of precipitated particles on work hardening behavior has been studied [5][6][7]. However, the effect of precipitated particles on toughness has not been understood enough yet.…”

Section: Introductionmentioning

confidence: 99%

Effect of Precipitation State on Strength and Toughness of Precipitation Hardened Hot Rolled Steel Sheet

Yokoyama

Taniguchi

2018

MSF

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In this work, to clarify the effect of carbide precipitation state on strength and toughness, Ti,V alloyed precipitation hardened ferrite single phase steel sheets with different carbide size were investigated. In order to change the precipitated particle size, cooling conditions after hot rolling were changed. Under condition A, steel sheets were cooled to 873K by water spray (for fine precipitation). Under condition B, steel sheets were air-cooled from 1053K for 20sec, then cooled by water spray to 873K (for coarse precipitation). The experimental results were following. The balance of tensile strength and Charpy absorbed energy was better in condition B. (Ti,V)C were observed in both conditions, but the size of (Ti,V)C were larger in condition B. From the above, it was suggested that as the carbide size become larger, the decrease in toughness per strengthening amount becomes smaller.

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Work Hardening in Ferritic Steel Containing Ultra-fine Carbides

Cited by 10 publications

References 22 publications

Carbide Precipitation and Hydrogen Trapping Behavior in Mo and V Added Tempered Martensitic Steel

Carbide Precipitation and Hydrogen Trapping Behavior in Mo and V Added Tempered Martensitic Steel

Interphase Precipitation and Application to Practical Steels

Effect of Precipitation State on Strength and Toughness of Precipitation Hardened Hot Rolled Steel Sheet

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