Casing in the production prone to outer folding defects, affect product quality improvement, it needs to be controlled.
There are several outer folding edge oxide particles cause segregation of elements, with a folding, an oxide middle folding, the presence of an excess of Al, Mg, Ca, S, P, Mn, Si outer folding element, particularly at the grain boundaries have 20μm so brittle inclusions SiO2 and silicates, intergranular fracture occurs, and said brittle inclusions is the main reason for the formation of the outer fold.
1) To ensure that a pull carbon hit, after avoiding blowing carbon control endpoint> 0.10%;
2) Increase the effect of converter slag, slag under strict control, the departure process using slag, a steel ladle slag after thickness <50mm;
3) Double slag operation, control phosphorus content of the molten steel.
1) LF refining processing time ≥20min;
2) Strengthening deoxy go mixed results. Requirements refining slag basicity ≥2.5, slag ≤1%, white residue retention time ≥15min;
3) After the end of the bottom blowing argon refining to ensure soft blowing time ≥10min, to facilitate removal of molten steel inclusions.
1) Using a ladle, tundish, protective casting and seal argon, oxidation-free protective casting;
2) Casting temperature: tundish superheat less than 20 ℃;
3) The use of mold level brake control, electromagnetic stirring;
4) Using special flux, to ensure the quality of the slab surface.
To reduce the white spots caused by hydrogen induced cracking deal billets and bars the use of slow cooling process.