Hardness of tempered martensite in carbon and low-alloy steels

Grange, R. A.; Hribal, C. R.; Porter, L. F.

doi:10.1007/bf02646882

Cited by 293 publications

(143 citation statements)

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“…The effect is due to tempering of martensite. Tempering of martensite occurs at temperatures below the lower critical Ac 1 and was also reported as the main reason for softening in martensitic steels [24][25][26].…”

Section: Introductionmentioning

confidence: 78%

Use of the Aging Effect to Change the Local Properties of Structure Components

Asadi

Schulze

Palkowski

2010

AMR

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Abstract. This research deals with processes leading to local strengthening effects in Advanced High Strength Steels (AHSS). Dual phase (DP), retained austenite (RA) -both hot and cold rolledand complex phase (CP) steels have been investigated to examine the effect of thermal and mechanical processing parameters on local properties. For this purpose, a method has been investigated to achieve local strengthening, namely local deformation and local heat treatment. Samples were locally deformed by bending and embossing processes. A local deformation with defined pre-strains leads to enhanced hardness and strengthening. A subsequent aging treatment leads to a further increase in mechanical properties. Local heat treatment was applied using a laser and an electron beam. Following local heat treatment with selected parameters, the microstructure of the surface and the cross section as well as the mechanical properties were evaluated by light optical, scanning as well as transmission electron microscopy, hardness measurement, tensile testing and thermal modelling. It can be stated that with partial heat treatment, local high strengthening can be produced. At lower heat treating temperatures, this effect could be attributed to bake hardening. With increased heat treating temperature, the initial microstructure near the surface is affected. A model can be improved, which defines the correlation between the influencing parameters and the local properties. The influence of over-aging in locally strengthen regions has been studied. For this investigation, parameters are stable to locally adjust the strengthening effect. Partial strengthening of AHSS by local deformation or local heat treatment can open up new fields of applications for locally using the strengthening effect to only influence relevant areas of interest, thus providing the potential for saving energy and designing the component's behaviour. Introduction:

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Section: Introductionmentioning

confidence: 78%

Use of the Aging Effect to Change the Local Properties of Structure Components

Asadi

Schulze

Palkowski

2010

AMR

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“…Although, there is an important quantity of data about different alloying elements influence on the martensite hardness, 9,10) a few data are found about the substitutional elements influence on the strain hardening of martensitic steels. 11) In the present work, Mn effect on the strain hardening of martensitic steels is characterized.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Modeling of Manganese Effect on Strength and Strain Hardening of Martensitic Carbon Steels

et al. 2013

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Carbon and manganese combined effect on the mechanical behavior of martensite was characterized and analyzed using literature and new experimental data of various carbon-manganese steels. A synergy effect of carbon and manganese on the martenstite strength and strain hardening was detected and was then taken into account in a specific way in the simplified model, based on a Continuous Composite Approach. Model was adjusted with only one fitting parameter and the obtained results are in good agreement with experimental stress-strain curves.

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“…This concept is supported by the well known fact that vanadium is effective in resisting softening and indeed producing secondary hardening during tempering of martensitic microstructures in tool steels. 5) Hence, it was decided to perform an exploratory investigation as to what base alloying is required to generate bainite in a low carbon hot strip steel after finish rolling and, furthermore, whether V-microalloying will be capable of adding strength above 600 MPa in such steels.…”

Section: Introductionmentioning

confidence: 99%

Vanadium Microalloyed Bainitic Hot Strip Steels

et al. 2010

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The aim of the present study was to investigate the possibilities of reaching yield strengths beyond 600 MPa for low carbon bainitic hot strip steels by vanadium microalloying together with suitable base alloying. The processing conditions and levels of carbon and nitrogen chosen in this laboratory investigation correspond to those of a typical 8 mm hot strip steel containing 0.04 mass% carbon and 0.010 mass% nitrogen from electric arc furnace practice processed in conventional or compact strip mills. It was found that a base alloying corresponding to 1.4 mass% Mn, 1.0 mass% Cr and 0.25 mass% Mo is required to form a fully bainitic structure after coiling at 400°C. The decisive factors determining the strength of bainitic hot strip steels are firstly the bainite transformation temperature and secondly the extent to which recovery of the densely dislocated bainitic ferrite can be prevented. The results of this study demonstrate that vanadium microalloying effectively prevents the recovery of the bainitic ferrite and leads to retention of the strength of the virgin bainite after coiling. This is primarily due to retardation of recovery by fine vanadium carbonitrides precipitates on dislocations and only to a lesser extent to true precipitation strengthening. With 0.08 mass% V together with 0.010-0.020 mass% N the yield strength lies in the range of 750-790 MPa compared to 680 MPa for a similar reference steel without vanadium. By raising the chromium content to 2 %, yield strengths in the range of 840-880 MPa have been reached. This is attributed to a lowering of the bainite transformation temperature resulting from the higher base alloying.KEY WORDS: high strength steel; bainite; alloying; hot rolling; cooling; microstructure; mechanical properties.* 1 This paper is dedicated to Michael Korchynsky, who recently retired from Stratcor Inc. after 60 years service to steel and vanadium microalloying. The authors of this paper, as well as former colleagues in Stockholm, are indebted to him for his profound engagement in our research and for countless rewarding discussions over the years. * 2 All steel compositions in this paper are expressed in mass%. Alloy Design and Experimental SteelsOut of the normal alloying elements, manganese, molybdenum and chromium are the most effective for raising the hardenability of steel, defined as their ability to prevent formation of ferrite and pearlite during hardening. Their hardenabilities expressed as the Grossman coefficient 6) are all high but decline somewhat in the order Mn, Mo and Cr, viz. 4.10, 3.14 and 2.83. In the present case, the retardation of bainite formation is particularly significant. Here, the coefficient differs more between these three elements, Mn 4.10, Cr 1.16 and Mo 0. 7) Hence, to stimulate bainite formation and at the same time prevent formation of ferrite/pearlite, molybdenum is most effective, followed by Cr and then Mn. In accordance with this, 1.4% Mn, 1.0% Cr and 0.25% Mo were chosen as the standard composition to create an adequate base hardenabilit...

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Hardness of tempered martensite in carbon and low-alloy steels

Cited by 293 publications

References 1 publication

Use of the Aging Effect to Change the Local Properties of Structure Components

Use of the Aging Effect to Change the Local Properties of Structure Components

Characterization and Modeling of Manganese Effect on Strength and Strain Hardening of Martensitic Carbon Steels

Vanadium Microalloyed Bainitic Hot Strip Steels

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