الفهرس 
Dual Phase Steel (DPOnly 14 pages are availabe for public view
 |  | from | 90 |  |  |
| | | from | 90 | | |
Abstract
The design of new steel grades and microstructures is mostly motivated by the necessity of steel industry to process always better suited high strength / toughness steel with low production costs. Automotive customers are asking for more steel options to meet increased specifications for strength/toughness, crash worthiness, and energy absorption. To meet these requirements, new developed types of steel known as Advanced High- Strength Steels (AHSS) were introduced e.g.: DP steel ”Dual Phase”. In the present work it was found that dual phase produced in continuous production at ”EZZ STEEL ” compact strip mill steel containing 0.068% C, 0.385% Si, 1.042% Mn and 0.651% Cr with different thicknesses 2.8, 3.2 and 3.8 mm, is characterized by microstructure consis8ng of dispersion of 15 ~ 35% of hard martensite islands in a so9 ductile ferrite matrix, Moreover no cracks or voids linked to martensite islands formed at center line due to higher Mn% were revealed. Mechanical tes8ng showed low values for yield/tensile strength ra8o (Yield Strength =352 413 MPa, Tensile Strength = 546 ~ 649 MPa), where average ra8o of YS/TS about 0.61 was obtained. For the elonga8on values, it varied between 22 ~ 29% , average grain size was ~11.9 and average strain hardening index ” n-value” is 0.14 for all tested samples. Mathematical analysis for different combinations of production parameters (holding temperature, holding time and coiling temperature) were applied to find the best combination of rolling parameters to achieve the targeted properties, holding temperature range (650 ~710 °C) was used for holding 8me range from 2.7 to 4.8 seconds and coiling temperatures ranged between (100 ~380 °C). Mathematica and Minitab software showed that the optimum holding temperature is recommended to be around 675 to 695 °C with coiling temperature just below 265°C and holding 8me star8ng from 3sec. to achieve the required proper8es of DP600.