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| Analysis of the characteristics of internal crack in[?350 mm]round billet of ASTM4130 continuous casting |
| LIU Ya-li，ZHANG Jun-ping |
| （The Special Steel Plant of Laiwu Breach Company， Shandong Iron and Steel Co.， Ltd.， Laiwu 271105 Shandong， China） |
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Abstract For analysis of internal crack problem of ASTM4130[?350 mm]continuous casting round billet in the Special Steel Plant of Shandong Iron and Steel Company， high temperature mechanics test， microstructure observation and analytical means such as scanning electron microscope were adopted. Systematic analysis of ASTM4130 as-cast organization in different high temperature mechanical properties， fracture morphology and organization transformation were conducted. Test results show that the main cause of internal cracks of ASTM4130 steel round billet is that the slab solidification organization is straightening at in 900-750 ℃ in the first Ⅲ brittleness temperature zone. At that time steel plastic is not high， and the steel billet straightening process force is large， this results in internal crack. According to the experiment data， through the optimization of continuous casting cooling parameters， slab surface temperature drop 150 ℃/m or less to ensure the slab transfered into the machine before the surface temperature ＞900 ℃. The 5 frames continuously straighteners replace the four 3-point straighteners used in the system. The working pressure of each tension machine was adjusted to 4MPa， which can avoid the casting billet crack by great stress or deformation in this temperature range.
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Received: 09 March 2018
Published: 29 September 2018
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2018, Vol. 37 
