机械性质的HSLA贝氏体钢.pdf

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Matcrials Science and Enginccring A283(2000)136-143
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Mechanical properities of an HSLA bainitic steel subjected to
controlled rolling with accelerated cooling
P C.M. Rodrigues a, E V. Pereloma b.*. D B. Santos
Department of Mechanica/ Engineering, FUWREL, Sto odo del Rei, MG, Brazil
b Department of Materials Engineering, Monash University, Clayton, VIC 3800. ustrali
Department of Metallurgical and Materials Engineering, UFMG, Belo Horizonte, MG, Brazil
Received 6 September 1999; received in revised form 6 December 1999
Abstract
Controlled rolling followed by accelerated cooling was utilised in laboratory simulations to study the microstructure and
mechanical properties of an HSLA low carbon bainitic steel. The effects of processing parameters, such as cooling start
temperature and cooling rates, on the final microstructure and mechanical properties were studied. Optical microscopy and
transmission electron microscopy were used to cvaluate the complex microstructures consisting of polygonal ferrite, pearlite
bainite and martensite retained austenite constituent. The use of the multiple regression analysis allowed establishment of the
relationships between mechanical properties and accelerated cooling variables: cooling rates and cooling start temperatures
O 2000 Elsevier Science S.A. All rights reserved
Keywor: Bainitic teel Controlled Tollin; Accelerated cooling Mechanical properties: Microstructural characterisation
1. ntroduction
Accelerated cooling after controlled rolling produces
a refined final microstructure and favours the formation
HSLA low carbon steels with multiphase microstruc
of low transformation temperature products, lik
Ire have been extensively studied in the last two
bainite and martensite-austenite (MA) constituent
[1-4]. These steels have high tensile strength,
(7, 8]. The majority of works has been directed towards
good toughness and weldability. This combination o
the study of microstructural evolution during acceler
properties has led to their application in the automotive
ated cooling 4, 9]. However, only a limited amount o
industry, in manufacturing of large diameter pipes for
research was carried out on the effect of accelerated
gas and oil transportation in the areas of low tempera
cooling variables on the mechanical properties of steels
ture and as plates for naval ships construction
he objective of the present work was to study the
Multiphase microstructures consisting of polygona
influence of cooling rate and accelerating cooling start
ferrite, pearlite, bainite and martensite can be produced
emperature on the mechanical properties(Vickers mi
in a great variety of HSLA low carbon steels as a result
crohardness. vield strength, tensile strength and total
of an appropriate combination of chemical composi-elongation) of a HSLA low carbon bainitic steel and to
tion, thermomechanical processing and accelerated establish the correlation between them
cooling conditions. The choice of optimum parameters
for accelerated cooling, such as accelerated cooling start
and finish temperatures and cooling rate, also depends 2 Experimental procedure
on the chemical composition of the steel and the ther
mo