Pearlite

About: Pearlite is a research topic. Over the lifetime, 6028 publications have been published within this topic receiving 65695 citations.

Superhigh strength hot-rolled steel sheet excellent in workability, and its production

Abstract: PROBLEM TO BE SOLVED: To obtain a hot-rolled steel sheet excellent in workability by allowing it to have a specified compsn., also allowing the contents of specified elements to have a specified relation and allowing it to have a metallic structure composed of bainite of a specified volume fractional rate as the main phase and at least one kind among pearlite, ferrite or the like as a 2nd phase, and in which the bainitic phase has the specified average grain size. SOLUTION: The steel sheet having a compsn. contg., by weight, 0.05 to 0.20% C, 0.05 to 0.50% Si, 1.0 to 3.5% Mn, <=0.05% P, <=0.01% S, 0.005 to 0.30% Nb, 0.001 to 0.10% Ti, 0.01 to 1.0% Cr, <=0.10% Al, and the balance Fe with inevitable impurities, and in which each content of Si, P, Cr, Ti, Nb and Mn satisfies the relation expressed by the inequality is prepd. Moreover, its metallic structure is the one composed of bainite of 60 to <90% in a volume fractional ratio as the main phase and at least one kind among pearlite, ferrite, residual austenite and martensite as a 2nd phase, and in which the average grain size of the bainitic phase is controlled to <4 μm.

Isothermal decomposition of supercooled austenite in steels

Abstract: A brief rationalisation is made of the isothermal decomposition kinetics of supercooled austenite in steels. From the experimental evidence of the past several decades, it is concluded that each type of isothermal decomposition product, i.e. grain boundary allotriomorphs, Widmanstatten ferrite (and cementite), pearlite, upper bainite, lower bainite, lath martensite, and twinned martensite, has its own independent C-curve in time–temperature–transformation (TTT) diagrams. Special emphasis is placed on the isothermal transformation kinetics of martensite. It is demonstrated that martensite transformation follows C-curve kinetics in isothermal conditions; this is a general rule and holds for all steels. The reason why most experimental TTT diagrams fail to display separate C-curves for different products is briefly explained. A temperature–composition–product (TCP) diagram is constructed for Fe–C alloys (plain carbon steels) to depict the general pattern of the decomposition process and to display th...

Effects of Plastic Warm Deformation on Cementite Spheroidization of a Eutectoid Steel

Abstract: The warm compression tests were performed on the eutectoid steel to investigate the evolution of cementite morphology. Several processing parameters, such as temperature, strain rate and reduction, were changed to analyze the effect of each parameter on spheroidization of cementite. The results showed that the warm compression promoted the fragmentize and the spheroidization of lamellar cementites. When the specimen was compressed with reduction of 50% at 700 °C and in the strain rate of 0. 01 s−1, the excellent spheroidized cementite was obtained. The mechanism of fragmentation and spheroidization of lamellar cementites during compression was discussed by using transmission electron microscope. The formation of spheroidized cementite was related to the time of compression process. The fragmentize of lamellar cementites was due to the extension of sub-grain boundary in the cementite. The spheroidization of cementite depended on the diffusion of carbon atoms at the tip of bended and breakup cementite.

Deformation Behavior and Mechanical Properties of Ferrite-Bainite-Martensite (Triphase) Steel

Abstract: The effect of microstructures on the mechanical properties of multi-phase steels has been studied. The amount and nature of low temperature transformation products of the steels are changed through heat treatment and controlled cooling after hot rolling. Ferrite plus bainite steel has superior stretch- flangeability and fatigue strength while it is inferior in strength-uniform elongation relationship to ferrite plus martensite (“dual-phase”) steel.Introduction of a small amount of martensite to ferrite plus bainite steel gives rise to a decrease in yield ratio and increase in work hardening rate. The microscopic examination shows that pearlite and martensite particles nucleate cracks easily and replacement of pearlite and martensite particles by more ductile bainite particles results in improved ductility. Stretch-flangeability of triphase steel is also improved by decreasing martensite particle size. It is concluded that ferrite-bainite-martensite (triphase) steel may be preferred to ferrite-martensite steel in automobile applications.