Effects of Silicon and Manganese Contents on V-Bending in High-Strength TRIP-Aided Dual-Phase Steel Sheets with Polygonal Ferrite Matrix

Dual Phase (DP) steel sheets, mainly 590 MPa TS grade steel, have been applied to structural parts of automobile because of their good formability, large bake hardenability and high crash worthiness. Although the concept of DP steel was established as early as the mid-1970th, the literature contains little discussion of Zn-coated DP steel, which has been the main application in recent years. In manufacturing Zn-coated DP steel, chemical composition which secures adequate Zn coatability and appropriate heat cycles, including galvannealing, must be considered. In this paper, the effect of Nb on the tensile properties, stretch flange formability and bake hardenability of 590 MPa TS grade DP steel is discussed. The base chemical composition was 0.05%C-2%Mn-0.5%Cr steel. The effect of Nb on the above-mentioned properties was studied using 0.05%Nb added steel and found that the addition of 0.05%Nb results in improved elongation, stretch flangeability and bake hardenability with higher tensile strength under both simulated GA and GI heat cycles. These improved properties by the addition of Nb are brought about by the grain refinement of ferrite matrix and finer dispersion of martensite.

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Tribological Characteristics of Coarse and Ultra-Fine Grained Ferrite-Martensite Dual Phase Steel Fabricated by Equal Channel Angular Pressing

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.124-126.1389 ◽

2007 ◽

Vol 124-126 ◽

pp. 1389-1392 ◽

Cited By ~ 1

Author(s):

Yong Suk Kim ◽

Hyun Seok Yu ◽

Dong Hyuk Shin

Keyword(s):

Dual Phase Steel ◽

Sliding Friction ◽

High Strength ◽

Ferrite Matrix ◽

Bearing Steel ◽

Dual Phase ◽

Tribochemical Reaction ◽

Wear Characteristics ◽

Wear Rates ◽

Fine Grained

The dual phase steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, is known to possess high strength, toughness, and superior wear resistance. However, the detailed wear mechanism of the steel has not yet been understood thoroughly. In the present study, dry sliding friction and wear characteristics of an ultra-fine grained ferrite-martensite dual phase steel has been investigated at room temperature. Wear tests of the steel were carried out using a pin-on-disk wear tester against an AISI 52100 bearing steel ball at loads ranging from 1N to 10N. Normalizing heat treatment was also performed on the steel to produce a ferrite-pearlite microstructure, and the wear characteristics of the normalized specimen were compared with that of the dual phase steel. The dual phase steel exhibited lower wear rates than the normalized steel, but the steady-state friction coefficients of the two steels were similar. The wear of the dual phase steel proceeded with a tribochemical reaction on the wearing surface accompanied with subsurface strain hardening, which explained the lower wear rate of the steel.

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On the Practice of the Microstructure Adjustment to Improve the Strength-Plastic Comprehensive Performance of a C-Si-Mn Alloyed High-Strength Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.631-632.467 ◽

2013 ◽

Vol 631-632 ◽

pp. 467-471

Author(s):

Shuang Kuang ◽

Guo Sen Zhu ◽

Ying Hua Jiang

Keyword(s):

Tensile Strength ◽

Trip Steel ◽

Dual Phase Steel ◽

High Strength ◽

Residual Austenite ◽

Ferrite Matrix ◽

Continuous Annealing ◽

Dual Phase ◽

Metastable Austenite ◽

Multi Phase

Four continuous annealing cycles were adopted to get four kinds of multi-phase steels using 0.2C-1.5Si-1.8Mn [wt%] alloyed raw steel and the microstructures and mechanical properties were investigated. The results show that traditional ferrite-martensite dual phase steel has a tensile strength of more than 1000MPa, but has the lowest strength-plastic product of only 18GPa%. The traditional ferrite, bainite and residual austenite TRIP steel has the highest elongation of 31% and hardening exponent of 0.24, but its tensile strength is just over 800MPa. Introducing hard matrix such as acicular bainitc ferrite or martensite to replace the polygonal ferrite matrix, meanwhile introducing metastable austenite, is conducive to obtain high strength and good ductility. Those kinds of modified TRIP steel with hard matrix can reach above 20GPa% of the strength-plastic product on the 1000MPa grade.

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