A kind of method that reduces CSP casting billet surface longitudinal micro-crack, wrinkle defective
Technical field:
The invention belongs to this technical field of smelting iron and steel and continuous casting, relate to the smelting and the continuous casting process of CSP technology, particularly as the smelting and the continuous casting process of the CSP hot rolled coil of cold-rolling galvanization board raw material.
Background technology:
Up to 70~80%, this can reduce production costs the CSP hot rolled coil as the cold rolling feeds ratio at present, but CSP hot rolled coil surface and inherent quality problem are rolled the galvanizing production blemish with Xing raw food.The strand that traditional long flow process coiled sheet production technology is produced is thick, and pulling rate is low, but the check table planar defect is removed then after the strand cooling, and the strand post bake after the removal of defects is carried out hot rolling.The sheet billet that CSP technology has, high pulling rate, surperficial iron scale be thick and fine and close, directly characteristics such as rolling make casting billet surface easily produce vertical micro-crack and wrinkle defective, and this defective can not equally can be rolled after cleaning casting billet surface defective to traditional handicraft, these defectives can not be eliminated after hot, cold rolling simultaneously, thereby form the belt steel surface longitudinal crack.
Smelting and the following S content<80ppm of continuous casting process that present CSP technology generally adopts, tundish covering flux adopts MgO-CaO, and crystallizer section 70mm, oscillating curve are sine curve, and copper plate of crystallizer exists slight scuffing or micro-crack sometimes.These technologies cause that casting billet surface produces vertical micro-crack and wrinkle defective and finally makes cold-rolling galvanization plate surface crack defective greater than 30/1000 meters.Above defective is by uncoiling range estimation gained.
Summary of the invention:
Technical problem to be solved by this invention provides the method for a kind of CSP of minimizing casting billet surface longitudinal micro-crack, wrinkle defective, and this method can finally reduce cold-rolling galvanization plate face crack quantity, improves product quality.
The technical scheme of technical solution problem of the present invention is: a kind of method that reduces CSP casting billet surface longitudinal micro-crack, wrinkle defective comprises LF refining procedure, CSP continuous casting working procedure:
A kind of minimizing CSP casting billet surface longitudinal crackle and wrinkle defective method comprise LF refining procedure, CSP continuous casting working procedure:
In the CSP continuous casting working procedure: described tundish covering flux is high basicity coverture, the width of crystallizer end face is 90-100mm, the oscillating curve of crystallizer is non-just profound curve, high-frequency small amplitude motion, does not have naked eyes scratches visible and crack on the copper coin, tundish molten steel protection cast;
In the LF refining procedure: control molten steel [S] weight percentage≤0.003%, sour molten aluminium weight percent [Al
s]=0.02%~0.06%, total oxygen T.O weight percent<0.0025%.
The present invention is directed to CSP casting billet surface longitudinal micro-crack and wrinkle, take following technology;
A, the little amplitude of employing high frequency, non-just profound vibration improves the covering slag lubricant effect, reduces frictional force between strand and copper coin; Adopt the wide CSP crystallizer of 90-100mm, increase the gap between SEN mouth of a river outer wall and the copper coin, reduce steel stream initial solidification shell is washed away, guarantee that shell thickness is even.
B, molten steel [S] content≤0.003%, sour molten aluminium [Al
s]=0.02%~0.06% reduces the reaction between CaS generation and S, Als and the covering slag; Total oxygen T.O<0.0025% reduces disperse Al in the steel
2O
3Change the covering slag performance Deng field trash.
C, the online and off-line copper plate of crystallizer surface quality of control.
The present invention can effectively reduce casting billet surface longitudinal crackle and wrinkle, reduces the blemish of hot rolled coil, finally reduces the cold-rolling galvanization surface defects of products, and cold-rolling galvanization plate surface cracks defective by dropping to less than 5/1000 meters greater than 30/1000 meters.Above defective is by uncoiling perusal statistics gained
The specific embodiment:
Below in conjunction with embodiment the present invention is done detailed explanation:
Of the present inventionly be mingled with, roll up slag by galvanization roll uncoiling inspection, carry out the perusal statistics.
Embodiment 1:
In the CSP continuous casting working procedure: described tundish covering flux is Al
2O
3-CaO, the width of crystallizer end face are 90mm, and the oscillating curve of crystallizer is non-just profound curve, high-frequency small amplitude motion, does not have naked eyes scratches visible and crack on the copper coin, and the tundish molten steel is poured into a mould under argon envelope protective condition;
In the LF refining procedure: control molten steel weight composition is 0.020%C, 0.01%Si, 0.08%Mn, 0.005%≤P, 0.001%S, 0.02%[Al
s], molten steel total oxygen T.O content is less than 0.0025%.
It is 4/1000 meters that embodiment 1 cold-rolling galvanization plate surface cracks defective.
Embodiment 2:
In the CSP continuous casting working procedure: described tundish covering flux is Al
2O
3-CaO, the width of crystallizer end face are 95mm, and the oscillating curve of crystallizer is non-just profound curve, high-frequency small amplitude motion, does not have naked eyes scratches visible and crack on the copper coin, and the tundish molten steel is poured into a mould under argon envelope protective condition;
In the LF refining procedure: control molten steel weight composition is 0.040%C, 0.025%Si, 0.01%Mn, 0.01%P, 0.002%S, 0.045%[Al
s], molten steel total oxygen T.O content is less than 0.0025%.
It is 2/1000 meters that embodiment 2 cold-rolling galvanization plate surfaces crack defective.
Embodiment 3:
In the CSP continuous casting working procedure: described tundish covering flux is Al
2O
3-CaO, the width of crystallizer end face are 100mm, and the oscillating curve of crystallizer is non-just profound curve, high-frequency small amplitude motion, does not have naked eyes scratches visible and crack on the copper coin, and the tundish molten steel is poured into a mould under argon envelope protective condition;
In the LF refining procedure: control molten steel weight composition is 0.055%C, 0.04%S, 0.12%Mn, 0.015%P, 0.003%S, 0.06%[Al
s], molten steel total oxygen T.O content is less than 0.0025%.
It is 1/1000 meters that embodiment 3 cold-rolling galvanization plate surfaces crack defective.