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 presenceof an excess of Al, Mg, Ca, S, P, Mn, Si outer folding element, particularly atthe grain boundaries have 20μm so brittle inclusions SiO2 and silicates,intergranular fracture occurs, and said brittle inclusions is the main reasonfor the formation of the outer fold.

Smelting process:
1) To ensure that a pull carbon hit, after avoiding blowingcarbon control endpoint> 0.10%;
2) Increase the effect of converter slag, slag under strictcontrol, the departure process using slag, a steel ladle slag after thickness<50mm;
3) Double slag operation, control phosphorus content of themolten steel.

Refining process:
1) LF refining processing time ≥20min;
2) Strengthening deoxy go mixed results. Requirementsrefining slag basicity ≥2.5, slag ≤1%, white residue retention time ≥15min;
3) After the end of the bottom blowing argon refining toensure soft blowing time ≥10min, to facilitate removal of molten steelinclusions.

Casting process:
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, electromagneticstirring;
4) Using special flux, to ensure the quality of the slabsurface.

Finishing processes:
To reduce the white spots caused by hydrogen induced cracking deal billets and bars the use of slow cooling process.