Continuous casting machine introduction

Continuous casting machine introduction I.1 Checking mould • Checking the each plate of the mould ensure the surface is smooth and without slag • The surface can not have any crack or hole – If in the surface with small crack or hole, it can be ground by abrasive paper; or grinding wheel – In case the surface with big crack (hole), impossible handle, it must be change new mold • Checking the dimension of the mould that includes width, thickness, and taper I.2 spray water • Checking the hose, if the flow rate invariable, water pressure in the hose decrease, the hose is leakage so it need to be changed new one • Checking the nozzle tip, the flow rate invariable, water pressure in the hose increase, the nozzle tip is clogged, it must be cleaned I.3 Tundish • Checking the temperature of tundish after preheating it is enough or not by infrared ray device • Castable in tundish collapsed or not • Checking SEN, stopper, shroud, sliding gate about broken or crack and their temperature Preheating time Tundish small fire normal ≧60 abnormal middle fire large fire ≧30 ≦90 ≧1100 ℃ ≧30 ≧90 ≧1100 ℃ SEN ≦60 ≦90 Long Nozzle ≧60 ≦90 ≧30 temp (±100℃) (±100℃) ≧900 ℃ ≧900 ℃ (±100℃) 10 I.5 torch cutter • After cutting, burn curve is too much, nozzle tip must be replace new one or COG/O2 ratio be adjusted • Countermeasure o Clean nozzle tip or change another o Align two burners in case of misalignment o Adjust O2/COG ratio 12 I.6 slab surface defect + Roller mark (regular in the surface of slab): caused by deep rolling affect onto slab surface  adjust pressure scratch onto slab surface if the hard slag or steel stick on roller + Crack (transverse, longitudinal ): caused by uneven cooling in the mould which leading to heat transfer is not homogeneous crack or depression - Countermeasure: checking the mould and cooling system, hydraulic pressure of unbending segment roller (it is sensitive to cause crack and affect to internal quality) -The pressure in the unbending segment, the single unbending point type is easier lead to crack than the multipoint type 13 14 confirm • Ladle temperature requirement • Chemical composition • Process route and treatment time • Casting parameter • conditioning 15 II.1 ladle temperature LD required temp = TL + superheat + temp drop  I.1.1 Tundish Temperature loss and super heat from L/D  T.D: the first heat 20~30 C, 2nd heat 10 ~150 C Steel grade Ladle requested temp.[0C] Superheat [0C] (in T.D) = T.D temp – Solidified temp Low carbon 1590~1595 35~45 Middle carbon 1575~1580 30~35 High carbon 1560~1570 20~25 Benefit For L.C steel  Δt high  facilitate inclusion floating remove For H.C steel  Δt low  mitigate segregation, increase equi-axed zone; but not too low  clogging and inclusion entrapped into solidified shell; if too high  easy to break out segregation, dendrite, internal crack TL ＝ 1538℃ － {F[%C] ＋ 13.0*[%Si] ＋ 4.8*[%Mn] ＋ 1.5*[%Cr] ＋ 2.0*[%Mo] ＋ 4.0*[%Ni] ＋ 5.0*[%Cu]} 16 If [%C] ＜ 0.5 ; F[%C] ＝ 55.5*[%C] ＋ 79.6*[%C]*[%C] II.1.2 L/D situation  New ladle: temp drop quickly  preheating  End life of ladle: temp also is dropped  relining  skull in ladle  de-skull II.1 Casting time temp drop 10 /4min II.1 Waiting time from refining finish to LD open (too long or short must be considered) II.2 Chemical composition: Examining meet the target or not, if not ask quality control people:  Re turn to melting shop to re-treating  casting but divert to new customer or hold 17 II Treating time and process route  final temp and stirring time (coolant and fluxes in ladle completed melted or not)  Waiting time: from the refining finish to the ladle open: too long – temp drop (In the static condition: 10 /3min) , too short – remaining scrap, fluxes  cause clogging II.4 Casting parameters Casting process parameters Casting speed  casting time Mold section Oscillation: stroke, frequency, NST Casting powder Cooling type: primary and secondary cooling Different Super heat with different steel grade & mold section Tundish; slide gate; SEN refractory  Clogging SEN: different product (SLB, BLM, BLT)  Different SEN type 18 ULC [%C] LC [%C] Peritectic [%C] MC [%C] HC [%C] 0.33 % ok ok no Special High quality steel grade no ok no As for FHS, cooling tank is necessary for shorten cooling time  more slab to be scarfed before charged to hot rolling mill Capacity: one set, about 20 ~30 pieces Cooling rate: 30 ~40 min/piece 22 -Checking scarfing  machine scarfing  handle scarfing If surface quality is good - Machine scarfing: hot scarfing ~ 800 0C; four faces simultaneously As for billet, don’t need to be ground, only use blast shooter for inspection - Piling: Slab yard management: auto-tracking system: crane indication for lifting up slag with Identity Number  avoid slab transportation to wrong destination IV.5.2.Bloom hot charging for delivery for hot rolling mill IV.5.3 Billet  Storage for  inspection  blast shooter  R.M 23 24 Continuous casting procedures 1) Ladle put on the ladle turret then turn around to the casting position 2) Tundish preheat stop and left up and transferred to casting position by transfer car 3) Tundish lower down to the mold and align the SEN to the center of the mold 4) Long nozzle is connected to the CNT (connect nozzle tip) of bottom of ladle and open the L/D slide gate (using oxygen lancing if not naturally open) 5) T/D powder shall be charged when liq Steel reach over the L/N tip 6) Teeming the liquid steel into the mold normally 40 % ~60% of TD or more if T.D preheating is not enough 7) Casting powder is also put into mold when liquid steel reach above port of SEN, to avoid this powder entrapped into liquid steel 8) Start casting when the mold level reach to certain level, normally keep liquid steel at level of 100 mm below the mold edge during casting 9) Taking the sample to follow up the composition is meet or not come from the secondary refining and measuring the temperature in tundish, normally three times or more  to adjust casting speed 260 ton, 200 ton, 150 ton, 100 ton, 50 ton THANKS FOR YOUR ATTENTION! 26 [...]... finish to the ladle open: too long – temp drop (In the static condition: 10 /3min) , too short – remaining scrap, fluxes  cause clogging II.4 Casting parameters Casting process parameters Casting speed  casting time Mold section Oscillation: stroke, frequency, NST Casting powder Cooling type: primary and secondary cooling Different Super heat with different steel grade & mold section Tundish; slide gate;... IV.5.2.Bloom hot charging for delivery for hot rolling mill IV.5.3 Billet  Storage for  inspection  blast shooter  R.M 23 24 Continuous casting procedures 1) Ladle put on the ladle turret then turn around to the casting position 2) Tundish preheat stop and left up and transferred to casting position by transfer car 3) Tundish lower down to the mold and align the SEN to the center of the mold 4) Long nozzle... mold normally 40 % ~60% of TD or more if T.D preheating is not enough 7) Casting powder is also put into mold when liquid steel reach above port of SEN, to avoid this powder entrapped into liquid steel 8) Start casting when the mold level reach to certain level, normally keep liquid steel at level of 100 mm below the mold edge during casting 9) Taking the sample to follow up the composition is meet or... ladle: temp also is dropped  relining  skull in ladle  de-skull II.1 3 Casting time temp drop 10 /4min II.1 4 Waiting time from refining finish to LD open (too long or short must be considered) II.2 Chemical composition: Examining meet the target or not, if not ask quality control people:  Re turn to melting shop to re-treating  casting but divert to new customer or hold 17 II 3 Treating time and process... cooling time  more slab to be scarfed before charged to hot rolling mill Capacity: one set, about 20 ~30 pieces Cooling rate: 30 ~40 min/piece 22 -Checking scarfing  machine scarfing  handle scarfing If surface quality is good - Machine scarfing: hot scarfing ~ 800 0C; four faces simultaneously As for billet, don’t need to be ground, only use blast shooter for inspection - Piling: Slab yard management:... Slab - Receiving of slab - Sampling, in the commissioning stage all of slab need sampling, but after production is stable may be it’s not necessary For IF, Si steel,starting and tail out slab  scarfing machine Sampling by sulfur print or etch : extend of carbon centerline segregation -Cooling: spray water, air cooling (scatter) or soft cooling, it is depended on the steel grade or C equivalent content... unbending segment, the single unbending point type is easier lead to crack than the multipoint type 13 14 confirm • Ladle temperature requirement • Chemical composition • Process route and treatment time • Casting parameter • conditioning 15 II.1 ladle temperature LD required temp = TL + superheat + temp drop  I.1.1 Tundish Temperature loss and super heat from L/D  T.D: the first heat 20~30 0 C, 2nd heat... edge during casting 9) Taking the sample to follow up the composition is meet or not come from the secondary refining and measuring the temperature in tundish, normally three times or more  to adjust casting speed 260 ton, 200 ton, 150 ton, 100 ton, 50 ton THANKS FOR YOUR ATTENTION! 26