FIB and TEM Studies on the Bainitic Microstructure in Low Carbon HSLA Steels

This paper deals with the development of low carbon NbTiB micro-alloyed high strength low alloy steel for heavy plates with high wall thickness. In the production of heavy plate it is remarkably difficult to achieve a combination of high strength and good low-temperature toughness. Bainitic microstructures have shown the capability to attain such requirements. To achieve a bainitic microstructure even for heavy wall products the formation of bainite can be promoted and supported by the use of small amounts of boron as a micro-alloying element. This industrial research project is based on the addition of small amounts of boron to promote the desired bainitic structure. Mill rolling trials were carried out to determine the optimum process parameters. The results of experimental mill rolling trials on 35 mm plates will be presented in this paper.

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FIB and TEM Studies on the Bainitic Microstructure in Low Carbon HSLA Steels

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.26-28.73 ◽

2007 ◽

Vol 26-28 ◽

pp. 73-76 ◽

Cited By ~ 6

Author(s):

J.S. Kang ◽

S.S. Ahn ◽

C.Y. Yoo ◽

Chan Gyung Park

Keyword(s):

Acicular Ferrite ◽

Focused Ion Beam ◽

Ion Beam ◽

Bainitic Ferrite ◽

Granular Bainite ◽

Low Carbon ◽

3 Dimensional ◽

Hsla Steels ◽

Bainitic Microstructure ◽

Lath Structure

In the present study, focused ion beam (FIB) technique was applied to make site-specific TEM specimens and to identify the 3-dimensional grain morphologies of bainitic microstructure in low carbon HSLA steels such as granular bainite, acicular ferrite and bainitic ferrite. Granular bainite consisted of fine subgrains and 2nd phase constituents like M/A or pearlite located at grain and subgrain boundaries. Acicular ferrite was characterized by an aggregate of ramdomly orientated and irregular shaped grains. The high angle boundaries between adjacent acicular ferrite grains caused by intragranular nucleation during continuous cooling process. Bainitic ferrite revealed uniform and parallel lath structure within the prior austenite grain boundaries and its’ packet size could effectively decreased by the formation of intragranular acicular ferrite.

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Microstructure and Mechanical Properties of Bainite Containing Martensite and Retained Austenite in Low Carbon HSLA Steels

Materials Transactions JIM ◽

10.2320/matertrans1989.32.715 ◽

1991 ◽

Vol 32 (8) ◽

pp. 715-728 ◽

Cited By ~ 29

Author(s):

Masaaki Katsumata ◽

Osamu Ishiyama ◽

Tsuyoshi Inoue ◽

Tsutomu Tanaka

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Low Carbon ◽

Microstructure And Mechanical Properties ◽

Hsla Steels

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Statistical Evaluation of Some Hot Rolling Theories

Journal of Engineering Materials and Technology ◽

10.1115/1.3225035 ◽

1982 ◽

Vol 104 (1) ◽

pp. 47-52 ◽

Cited By ~ 8

Author(s):

A. Murthy ◽

J. G. Lenard

Keyword(s):

Experimental Data ◽

Hot Rolling ◽

Laboratory Experiments ◽

Statistical Evaluation ◽

Low Carbon ◽

Flow Strength ◽

Hsla Steels ◽

Accuracy And Precision ◽

Hot Strip ◽

Hot Strip Mills

The accuracy and precision of four mathematial models of varying complexity are evaluated by comparing their predictions to experimental data generated in carefully controlled laboratory experiments and to production logs obtained from the finishing trains of several Canadian, American, and European hot strip mills. The materials rolled are low carbon and HSLA steels; the models used are Orowan’s formulation with Shida’s flow strength and Ford and Alexander’s formulation with Shida’s flow strength; then both these formulations are combined with Ekelund’s flow strength equation. It is concluded that Orowan’s formulation with Shida’s flow strength relation is the most consistently accurate technique of analysis. Further, the behavior of HSLA steels is not well described by either Shida’s or Ekelund’s equations.

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Development of Low Carbon Microalloyed Ultra High Strength Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.500-501.551 ◽

2005 ◽

Vol 500-501 ◽

pp. 551-558 ◽

Cited By ~ 6

Author(s):

A. Ghosh ◽

Brajendra Mishra ◽

Subrata Chatterjee

Keyword(s):

Room Temperature ◽

High Strength Steels ◽

High Strength ◽

Low Carbon ◽

Hsla Steels ◽

Finish Rolling ◽

Ultra High Strength Steels ◽

Rolling Temperatures ◽

Carbon Microalloyed ◽

Carbon Concentrations

In the present study HSLA steels of varying carbon concentrations, alloyed with Mn, Ni, Cr, Mo, Cu and micro-alloyed with Nb and Ti were subjected to different finish rolling temperatures from 850oC to 750oC in steps of 50oC. The microstructure of the steel predominantly shows martensite. Fine twins, strain induced precipitates in the martensite lath along with e-Cu precipitates are observed in the microstructure. With an increase in carbon content the strength value increases from 1200MPa UTS to 1700MPa UTS with a negligible reduction in elongation. Impact toughness values of 20-26 joules at room temperature and −40oC were obtained in sub-size samples.

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Issues in Welding of HSLA Steels

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.365.44 ◽

2011 ◽

Vol 365 ◽

pp. 44-49 ◽

Cited By ~ 12

Author(s):

Sandeep Jindal ◽

Rahul Chhibber ◽

N.P. Mehta

Keyword(s):

Structural Integrity ◽

Hsla Steel ◽

Weight Ratio ◽

Welding Process ◽

Pressure Vessels ◽

Carbon Steels ◽

Low Carbon ◽

Line Pipe ◽

Hsla Steels ◽

Selection Of

The application of High Strength Low Alloy (HSLA) steels has expanded to almost all fields viz. automobile industry, ship building, line pipe, pressure vessels, building construction, bridges, storage tanks. HSLA steels were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higher-strength materials. Due to higher-strength and added excellent toughness and formability, demand for HSLA steel is increasing globally. With the increase of demand; other issues like the selection of filler grade and selection of suitable welding process for the joining of these steels have become very significant. This paper discusses the various issues regarding selection of suitable grade and selection of suitable welding process for joining of HSLA steels and issues concerning the structural integrity of HSLA steel welds.

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Behaviour of low-carbon and HSLA steels during torsion-simulated continuous and interrupted hotrolling practice

Metals Technology ◽

10.1179/030716979803276534 ◽

1979 ◽

Vol 6 (1) ◽

pp. 325-331 ◽

Cited By ~ 38

Author(s):

J. Sankar ◽

D. Hawkins ◽

H. J. McQueen

Keyword(s):

Low Carbon ◽

Hsla Steels

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Grain Refinement by Rapid Transformation Annealing of Cold Rolled Low Carbon Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.500-501.771 ◽

2005 ◽

Vol 500-501 ◽

pp. 771-778 ◽

Cited By ~ 8

Author(s):

P. Álvarez ◽

C. Lesch ◽

Wolfgang Bleck ◽

Hélène Petitgand ◽

Joachim Schöttler ◽

...

Keyword(s):

Grain Refinement ◽

Rapid Heating ◽

Carbon Steels ◽

Low Carbon ◽

Steel Sheets ◽

Hsla Steels ◽

Mn Content ◽

Cold Rolled ◽

Equiaxed Grains ◽

Rapid Transformation

A novel thermal treatment, rapid transformation annealing (RTA), has been applied to six different cold rolled low-carbon (LC) steel sheets with the aim of refining their microstructure. The process involves rapid heating to just above the austenite (g) to ferrite (a) transformation temperature and subsequent rapid cooling to room temperature. Grain sizes around 2 µm in two different Nb-Ti HSLA steels, 5 µm in a Ti-LC steel and 6 µm in a plain LC (0.037%C) steel have been produced using fast cooling rates (200°C/s). Non-equiaxed structures are obtained in a Nb-Ti HSIF steel and in a plain LC (0.135%C) (CM) steel due to their higher Mn content. However, very fine equiaxed grains (2 µm) are obtained by rapid intercritical annealing (RIA) in the CM steel. Irrespective of the microalloying concept, the grain growth of recrystallized a grains before their transformation was inhibited in CM and in both HSLA steels. This inhibition is connected with the overlapping of a recrystallization and a-g transformation processes which is essential in order to achieve extreme grain refinement either by RTA or RIA.

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