Boron in Heat‐Treatable Steels: A Review

Sharma, Mamta R.; Ortlepp, Isabell; Bleck, Wolfgang

doi:10.1002/srin.201900133

Cited by 41 publications

(27 citation statements)

References 154 publications

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“…In contrast, alloy L4 is hyperstochiometrically alloyed with aluminum to completely ensure that boron nitride formation is not possible. In addition, investigations reported in the literature have shown that around 0.0030 wt% boron gives a saturation level of grain boundary strengthening, [29] although this cannot be rebutted or confirmed by this study. Nevertheless, boron effectively strengthens the grain boundaries and increases the impact energy.…”

Section: Discussioncontrasting

confidence: 56%

“…Therefore, nitride-forming elements, such as titanium and aluminum, are alloyed, consuming the nitrogen and forming nitrides to keep the boron free. [29][30][31] Figure 8. Monotonic yield strengths from initial loading curve and cyclic yield strengths R* p0.2 from IST of the QþT steel 42CrMo4, [16] the LHD steel LHD-11, [19] and the alloys L1-L5.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, nitride‐forming elements, such as titanium and aluminum, are alloyed, consuming the nitrogen and forming nitrides to keep the boron free. [ 29–31 ] Therefore, higher boron contents require also the alloying of higher amounts of titanium or aluminum. The alloy LHD‐11, with 0.0029 wt% boron, shows a higher Charpy V‐notch impact energy than L1, with a boron content of 0.0016 wt% (Figure 7).…”

Section: Discussionmentioning

confidence: 99%

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Behavior of Forging Steels under Cyclic Loading—the Benefit of Air‐Hardening Martensites

Schmiedl

Gramlich

Schönborn

et al. 2020

steel research int.

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The development of air-hardening martensitic forging (LHD: luft härtend duktil) steels offers high material performance with a short and simple process route. In this study, five alloys (L1-L5), based on the existing LHD alloy concept but with different contents of aluminum, titanium, boron, and molybdenum, are cast at laboratory scale. The casted blocks are hot forged into semifinished products and cooled in air (uncontrolled). The tensile properties, the Charpy V-notch impact energy, the cyclic material behavior, and the fatigue strength of the alloys L1-L5 are opposed to each other. Furthermore, the material properties are compared with the standard quench and tempered (QþT) steel 42CrMo4 (reference material) and ranked against previously developed forging steels. The tensile properties and Charpy V-notch impact energy are comparable with those of the reference material, whereas the new alloy concepts show a significantly higher cyclic yield strength and fatigue strength.

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Section: Discussioncontrasting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Behavior of Forging Steels under Cyclic Loading—the Benefit of Air‐Hardening Martensites

Schmiedl

Gramlich

Schönborn

et al. 2020

steel research int.

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“…Furthermore, combined alloying of Nb and B as well as Mo and B has been described in the literature as enhancing boron's hardenability effect [2][3][4][5][6]. Both elements prevent boron from forming boron carbides (Fe 23 (C,B) 6 ) in the austenite grain boundaries that would reduce solute boron's effect of obstructing ferrite nucleation [7].…”

Section: Introductionmentioning

confidence: 99%

Toughness Property Control by Nb and Mo Additions in High-Strength Quenched and Tempered Boron Steels

Zurutuza

Isasti

Detemple

et al. 2021

Metals

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The synergetic effect on hardenability by combining boron with other microalloying elements (such as Nb, Mo and Nb + Mo) is widely known for high-strength medium carbon steels produced by direct quenching and subsequent tempering treatment. The improvement of mechanical properties could be reached through optimization of different mechanisms, such as solid solution hardening, unit size refinement, strain hardening, fine precipitation hardening and the effect of carbon in solid solution. The current study proposes a procedure for evaluating the contribution of different microstructural aspects on Charpy impact toughness. First, the effect that austenite conditioning has on low-temperature transformation unit sizes and microstructural homogeneity was analysed for the different microalloying element combinations. A detailed crystallographic characterization of the tempered martensite was carried out using electron backscattered diffraction (EBSD) in order to quantify the effect of unit size refinement and dislocation density. The impact of heterogeneity and presence of carbides was also evaluated. The existing equations for impact transition temperature (ITT50%) predictions were extended from ferrite-pearlite and bainitic microstructures to tempered martensite microstructures. The results show that microstructural refinement is most beneficial to strength and toughness while unit size heterogeneity has a particularly negative effect on ductile-to-brittle transition behaviour. By properly balancing alloy concept and processing, steel having a yield strength above 900 MPa and low impact transition temperature could be obtained by direct quenching and tempering.

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“…The distribution of boride is improved by modification of the alloy molten with V, Ti, and RE-Mg [ 17 ], which improves the toughness of a high boron iron-based alloy. Moreover, the addition of a small amount of Nb or Mo can help to enhance boron’s hardenability in the steel, and prevent boron from forming boron carbides in the grain boundary [ 18 , 19 , 20 , 21 ], thereby reducing the obstructing effect of solute boron on ferrite nucleation [ 22 ]. Except for these, the net-like Fe 2 B can be disconnected by high temperature austenization [ 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Quenching and Partitioning (Q&P) Heat Treatment on the Microstructure and Mechanical Properties of High Boron Steel

et al. 2021

Materials

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High boron steel is prone to brittle failure due to the boride distributed in it with net-like or fishbone morphology, which limit its applications. The Quenching and Partitioning (Q&P) heat treatment is a promising process to produce martensitic steel with excellent mechanical properties, especially high toughness by increasing the volume fraction of retained austensite (RA) in the martensitic matrix. In this work, the Q&P heat treatment is used to improve the inherent defect of insufficient toughness of high boron steel, and the effect mechanism of this process on microstructure transformation and the change of mechanical properties of the steel has also been investigated. The high boron steel as-casted is composed of martensite, retained austensite (RA) and eutectic borides. A proper quenching and partitioning heat treatment leads to a significant change of the microstructure and mechanical properties of the steel. The net-like and fishbone-like boride is partially broken and spheroidized. The volume fraction of RA increases from 10% in the as-cast condition to 19%, and its morphology also changes from blocky to film-like. Although the macro-hardness has slightly reduced, the toughness is significantly increased up to 7.5 J·cm−2, and the wear resistance is also improved.

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Boron in Heat‐Treatable Steels: A Review

Cited by 41 publications

References 154 publications

Behavior of Forging Steels under Cyclic Loading—the Benefit of Air‐Hardening Martensites

Behavior of Forging Steels under Cyclic Loading—the Benefit of Air‐Hardening Martensites

Toughness Property Control by Nb and Mo Additions in High-Strength Quenched and Tempered Boron Steels

The Effect of Quenching and Partitioning (Q&P) Heat Treatment on the Microstructure and Mechanical Properties of High Boron Steel

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