Ferrite grain refinement by controlled rolling of lovv-carbon and microalloyed steel

Deformation dilatometry has been used to simulate controlled hot rolling followed by controlled cooling of a Nb microalloyed pipeline steels, the microstructure and transformation characteristics in the steel and the effect of deformation on transformation are studied. According to the results of both dilatometry measurements and microstructure observations, the continuous cooling transformation curves (CCT) of the tested steels are constructed. The results show that Nb content and deformation enhance the formation of acicular ferrite; the microstructure of the steel range from PF, QF to AF with increasing of cooling rates from 0.5 to 50°C /s in a two stages controlled rolling and the microstructure revolution is sensitive to cooling rates when it is lower than 5°C /s, however, when the cooling rate increasing further, the microstructure didn’t change very much but M/A constituents in matrix is refined and dispersed.

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Effect of semifinished rolled product cooling rate during controlled rolling on the condition of microalloyed steel hot-worked austenite, final microstructure, and mechanical properties. Part 2. Study of the effect of semifinished rolled product cooling rate on ferrite-bainite structure formation*

Metallurgist ◽

10.1007/s11015-012-9549-0 ◽

2012 ◽

Vol 56 (1-2) ◽

pp. 137-146

Author(s):

Yu. D. Morozov ◽

I. F. Pemov ◽

E. A. Goli-Oglu ◽

D. V. Nizhelsky

Keyword(s):

Mechanical Properties ◽

Cooling Rate ◽

Structure Formation ◽

Rolled Product ◽

Microalloyed Steel ◽

Controlled Rolling ◽

Microstructure And Mechanical Properties ◽

Bainite Structure ◽

Final Microstructure

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Effect of Finishing Temperature on Mechanical Properties of a Nb-Microalloyed Steel Sheet

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.129-131.1022 ◽

2010 ◽

Vol 129-131 ◽

pp. 1022-1028

Author(s):

Daavood Mirahmadi Khaki ◽

A. Akbarzadeh ◽

Amir Abedi

Keyword(s):

Mechanical Properties ◽

Microalloyed Steel ◽

Total Elongation ◽

Controlled Rolling ◽

Recrystallization Temperature ◽

Effective Parameters ◽

Steel Sheets ◽

Intercritical Range ◽

Nb Microalloyed Steel ◽

Hot Rolled

Thermo mechanical processing and controlled rolling of microalloyed steel sheets are affected by several factors. In this investigation, finishing temperature of rolling which is considered as the most effective parameters on the final mechanical properties of hot rolled products has been studied. For this purpose, three different finishing temperatures of 950, 900 and 850 °C below the non-recrystallization temperature and one temperature of 800 °C in the intercritical range were chosen. It is observed that decreasing the finishing temperature causes increase of strength and decrease of total elongation. This is accompanied by more grain refinement of microstructure and the morphology was changed from polygonal ferrite to acicular one. Findings of this research provide suitable connection among finishing temperature, microstructural features, and mechanical properties of hot rolled Nb-microalloyed steel sheets.

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Rosenhain Centenary Conference - 3. Materials development present and future 3.2 Controlled rolling

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1976.0119 ◽

1976 ◽

Vol 282 (1307) ◽

pp. 289-303 ◽

Cited By ~ 18

Keyword(s):

Grain Size ◽

Grain Refinement ◽

Low Temperatures ◽

Controlled Rolling ◽

Processing Conditions ◽

Materials Development ◽

Fine Grain ◽

Heat Treated ◽

Grains Refinement ◽

Major Consideration

Controlled rolling is a means whereby the properties of steel can be improved to a level equivalent to those of more highly alloyed or heat-treated steels. The processing conditions are controlled to refine the austenite structure and thereby give fine ferrite grains. Refinement of the structure is aided by the addition of micro-alloying elements such as Nb, V or Ti. The improved strength and toughness of controlled rolled steels are shown to be a result of the fine grain size. A further increase in strength beyond that due to grain refinement can be obtained by finishing rolling at low temperatures in the y + oc or cc regions. Commercial controlled rolling in various mill layouts, together with some properties obtained are described and it is pointed out that optimization of productivity is a major consideration when controlled-rollmg procedures are being planned.

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