Oil casing folding defect solution

Sleeve in the production of prone to folding defects, affecting the improvement of product quality, need to be controlled.


Several out-folded oxide particles cause segregation of elements, with folded, folded oxides present with Al, Mg, excess Ca, S, P, Mn, elements folded outside the temple, especially at the grain boundaries 20 meters, μ brittle inclusions SiO2 and silicate, along the crystal rupture said that the main reason for the formation of external folds of brittle inclusions.


Smelting process:
1) to ensure that after carbon hits, avoid blowing carbon control end point> 0.10%;
(2) Strict control of converter slag, slag effect, the use of slag pretreatment process, the slag thickness of 50mm or less;
3) double slag operation, control of molten steel phosphorus content.


Refining process:
1) LF refining treatment time ≥20min;
2) to strengthen the result of deoxidation to mix. Requires refining alkalinity ≥ 2.5, slag ≤ 1%, white residue retention time ≥ 15min;
3) at the end of blowing argon to ensure soft blowing time ≥ 10min after the end, easy removal of molten steel inclusions.


Casting process:
(1) the use of ladle, tundish, casting protection and sealed argon non-oxidation protection pouring;
2) pouring temperature: tundish overheat less than 20;
3) the use of mold liquid level brake control, electromagnetic stirring;
4) Adopt special flux to ensure the surface quality of slab.


Finishing process:
To reduce the white spots caused by hydrogen cracking, billets and rods are cooled slowly.