The metallurgy of zinc-coated steel

The cold rolling texture of low and extra low carbon steels is primarily made up of a nearly perfect normal direction (ND) fibre and of two other components, centred at 001 and 112 , which...

Cold rolling and annealing textures in low carbon and extra low carbon steels

A series of dual-phase (DP) steels containing finely dispersed martensite with different volume fractions of martensite (Vm) were produced by intermediate quenching of a boron- and vanadium-containing microalloyed steel The volume fraction of martensite was varied from 03 to 08 by changing the intercritical annealing temperature The tensile and impact properties of these steels were studied and compared to those of step-quenched steels, which showed banded microstructures The experimental results show that DP steels with finely dispersed microstructures have excellent mechanical properties, including high impact toughness values, with an optimum in properties obtained at ∼055 Vm A further increase in Vm was found to decrease the yield and tensile strengths as well as the impact properties It was shown that models developed on the basis of a rule of mixtures are inadequate in capturing the tensile properties of DP steels with Vm>055 Jaoul-Crussard analyses of the work-hardening behavior of the high-martensite volume fraction DP steels show three distinct stages of plastic deformation

Influence of martensite content and morphology on tensile and impact properties of high-martensite dual-phase steels

Heavy-duty liquid detergents containing anionic surfactant, fatty acid, builder, proteolytic or amylolytic enzyme, boric acid or a boron compound capable of forming boric acid in the composition, and calcium ion are disclosed. Boric acid provides improved enzyme stability in the compositions.

Liquid detergents containing boric acid to stabilize enzymes

Dislocation structures in the ferrite of a C-Mn-Si dual-phase steel intercritically annealed at 810°C were characterized at various tensile strains by transmission electron microscopy At strains which corresponded to the second stage on a Jaoul-Crussard plot of strain hardening behavior, the dislocation density in the ferrite is inhomogeneous, with a higher density near the martensite. The third stage on a Jaoul-Crussard plot corresponds to the presence of a well-developed dislocation cell structure in the ferrite. The average cell size during this stage is smaller than the minimum size reported for deformed iron, and the cell size was inhomogeneous, with a smaller cell size near the martensite.

Dislocation substructure as a function of strain in a dual-phase steel

A\" the baris oJ cOlltilluum model , theoretical equatioll which describes a stressstraill cllrve oJ dual phase steel is built up Jrom the stressstraill curves oJ each composite phase. The comparisoll oJ theorelical result, with experimenla l onts is made on the cOlltilll/ously alll/ealed dual phase steel which is composed oJ Jerrite and martensite . Agreemenl betweell them is essell tially good Jor volume Jraction oJ martensite below 0.2. The theoretica l equation makes clear the wa)'s Jor improvillg ductility oJ high slrenglh dual phase <teets. They are im/Jroving the tensile slrellglhelongation relalionship oJ soft phase, strellgthening the hard phase (IS high as p ossible, desirably to Ihe level oJ martellsite, and cOlilrollilig Ihe volume fraction oJ hard phase below 0 .2.

Work Hardening of Continuously Annealed Dual Phase Steels

The effects of surface microstructure and chemical compositions on characteristics of Fe-Zn compounds which formed on continuously galvanized steel sheets have been investigated by using ultra low carbon and low carbon steels.From SEM observation, morphology of Fe-Zn compounds formed at interface between steel and plating layer were classified into three types; outburst structure, fine granular structure, and pillar-like structure.The amount of outburst structure increases with decreasing solute carbon content in steels. Phosphorus inhibited the formation of outburst structure when solute carbon was combined with a carbide forming element such as Nb or Ti.A comparison between distribution of Fe-Zn compounds and corresponding steel surface indicated that the outburst structure formed preferentially at grain boundaries exposed on the steel surface, whereas fine granular structure formed mainly at the interior of surface grains.

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Effects of Surface Microstructure and Chemical Compositions of Steels on Formation of Fe-Zn Compounds during Continuous Galvanizing

When a cold reduced steel of which chemical composition is substantially controlled within the range of 10x[S]% to 2.00% [Mn], 0.003 to 0.02% [N] and (<5×1031 4)/[N]% [Al] is subjected to a full continuous annealing process comprising a heating-up step of Ac1 to 900° C × 5 to 180 sec., a rapid cooling step of the heating-up temperature to about room temperature by water-spray, reheating step of the room temperature to 150° C to 450° C × 5 to 300 sec., and then final cooling- and coiling step, high bake-hardenability and excellent non-aging property are given to the above steel with ease.

Process of making a high strength cold reduced steel sheet having high bake-hardenability and excellent non-aging property

PURPOSE:To obtain a steel plate suitable for deep drawing as a galvanized steel plate by adding Ti and B to an Nb steel having a specified composition so as to satisfy specified relations and by restricting conditions during rolling and annealing. CONSTITUTION:A killed steel consisting of 0.001-0.005% C, 0.005-0.50% Si, 0.06-0.25% Mn, 0.005-0.100% P, 0.001-0.020% S, 0.010-0.060% sol. Al, =900 deg.C, coiled at 650-700 deg.C, descaled, cold rolled and subjected to box annealing or continuous annealing at a temp. represented by equation V (where T is the annealing temp., t is a time for which the steel plate is kept at a temp. above the annealing temp., and log t is the common logarithm of the annealing time). By this method a galvanized steel plate with >=1.7 Lankford value is obtd.

Galvanized steel plate for deep drawing and its manufacture

PURPOSE:To obtain a composite structure steel sheet having excellent ductility and workability and high strength by hot rolling a specifically composed C-Si- Mn steel at a specified finishing temp. and controlling cooling and coiling temp. thereby optimizing the structure. CONSTITUTION:A steel consisting of 0.30-0.65wt% C, 0.7-2.0% Si, 0.5-2.0% Mn and the balance Fe with inevitable impurities is hot rolled at the finishing temp. specified to Ar3-Ar3+50 deg.C. Such steel sheet is held for 4-20sec in a 450-650 deg.C range and is coiled at =10% ferrite, >=10% austenite and the balance bainite or martensite is obtd. by such temp. control. The hot rolled composite structure steel sheet having high strength and high workability is obtd. by the above- mentioned method without requiring any special alloy element.

Kazuhide Nakaoka

Papers

Work Hardening of Continuously Annealed Dual Phase Steels

Effects of Surface Microstructure and Chemical Compositions of Steels on Formation of Fe-Zn Compounds during Continuous Galvanizing

Process of making a high strength cold reduced steel sheet having high bake-hardenability and excellent non-aging property

Galvanized steel plate for deep drawing and its manufacture

Production of hot rolled composite structure steel sheet having high strength and high workability