CN104498826A - Continuously cast 140-mm thick plate Q345E and production method thereof - Google Patents

Abstract

The invention discloses a continuously cast 140-mm thick plate Q345E and a production method thereof. The continuously cast 140-mm thick plate Q345E comprises the following chemical components in percentage by weight: 0.10%-0.15% of C, 0.15%-0.35% of Si, 1.2%-1.45% of Mn, less than or equal to 0.010 of P, less than or equal to 0.003 of S, 0.020%-0.050% of Als, 0.020%-0.040% of Nb, 0.010%-0.020% of Ti and the balance of Fe and residual elements. According to the production method, by virtue of processes of KR hot metal pretreatment, converter smelting, argon blowing treatment, LF refining and VD refining, harmful elements, such as P and S which are adverse to the toughness of materials, of types of steel are strictly controlled, so that the purity of molten steel can be guaranteed, and the internal quality of the steel is improved; by utilizing relatively low heating temperature, the excessive growth of austenite crystals in the heating process can be avoided; in a stack cooling process of steel plates, the internal stress generated in controlled rolling and controlled cooling processes can be relieved, and hydrogen is substantially expanded, so that the internal quality of the steel plates is effectively improved; in a thermal treatment link, the temperature increase speed and the holding temperature as well as the cooling speed of the steel plates after the steel plates are discharged from a furnace are strictly controlled, crystal grains of the steel plates are uniformly refined, and the differences of grain structures in the thickness direction are reduced, so that the excellent comprehensive mechanical properties of the steel plates are guaranteed.

Description

A kind of continuous casting produces 140mmQ345E slab and production method thereof

Technical field

The invention belongs to Heavy Plate Production technical field, be specifically related to a kind of continuous casting and produce 140mm Q345E slab and production method thereof.

Background technology

In known technology, thickness adopts die casting to produce at the Q345E of more than 100mm, and this production line not only lumber recovery is low, and the production cycle is long, and cost is high, is unfavorable for low cost strategy under present steel form.

Summary of the invention

For the problems referred to above, the invention provides a kind of be easy to produce and can extensively use continuous casting produce 140mmQ345E slab and production method thereof.

A kind of continuous casting produces 120mmQ345E slab, chemical composition design (unit, wt%): C:0.10 ~ 0.15, Si:0.15 ~ 0.35, Mn:1.2 ~ 1.45, P :≤0.010, S :≤0.003, Als:0.020 ~ 0.050, Nb:0.020 ~ 0.040, Ti:0.010 ~ 0.020, other is Fe and relict element.

Carbon equivalent≤0.40 of described chemical composition.

For achieving the above object, described continuous casting produces the production method of 140mmQ345E slab, comprises the following steps:

(1) KR hot metal pretreatment: molten iron arrives at a station and must take off front slag and take off rear slag, and ensure liquid level thickness of slag layer≤20mm, molten iron reaches S≤0.005% after KR stirring desulphurization, simultaneously desulfurization time≤20min, desulfurization temperature drop≤20 DEG C;

(2) converter smelting: adopt 120 tons of top and bottom combined blown converters, enter in stove molten iron by mass percentage containing S≤0.003%, containing P≤0.070%, molten iron temperature >=1270 DEG C, molten iron Intake Quantity error is by ± 1 ton of control, process rifle position is by 1.0 ~ 1.3m in early stage, mid-term 1.2 ~ 1.6m, later stage 1.0 ~ 1.1m controls, slag making basicity R controls by 2.5 ~ 4.0, tapping target C: >=0.05%, P≤0.010%, S :≤0.003%, in ladle, Si-Al-Ba-Ca is added in tapping process, manganeseirom, ferro-silicon and lime, fluorite, with slag tapping before floating plug gear before tapping, slag stop cone pushing off the slag is adopted before tapping terminates, ensure thickness of slag layer≤30mm, omnidistance Argon is required in converter tapping process,

(3) Argon process: argon station is disposable adds aluminum steel, requires strong Argon 3min at argon station, flow 200 ~ 500NL/min, molten steel face bore hole diameter control, must not lower than 1570 DEG C from argon station temperature at 300 ~ 500mm;

(4) LF refining: omnidistance Argon in refining process, adds slag charge, basicity is pressed 4.0-6.0 and is controlled, add reductor, heating adopts electric current to heat, and heat-up time, one heating 7-12min, two heated 6-10min by twice control, reductor is added in two heat-processedes, and require that dry slag number of times is greater than 6 times, add silicon-calcium wire before leaving from station, before adding silicon-calcium wire, must argon gas be closed, do not adopt the upper steel temperature 1565 ± 15 DEG C of vacuum outgas, adopt the upper steel temperature 1610 ± 15 DEG C of vacuum outgas;

(5) VD refining: VD vacuum tightness must reach below 67Pa, dwell time is necessary >=15min, soft blow 2-5min or do not blow after vacuum breaker, in soft blow process, molten steel must not be exposed, online bag pumpdown time 1.7min, insulating covering agent ensures to be paved with molten steel face, must close argon gas, upper steel temperature 1565 ± 15 DEG C before adding insulating covering agent;

(6) continuous casting: adopt 350mm × 2320mm section continuous caster, continuous casting allusion quotation is drawn and is controlled at 10 ~ 20 DEG C according to the corresponding molten steel overheat of 0.80m/min(), crystallizer wide discharge 4400L/min, leptoprosopy discharge 560L/min;

(7) strand heating: adopt Three-section type heating: a heating <1000 DEG C, two heating 1200 DEG C, soaking zone 1180 DEG C, total 11 ~ 13min/cm control heat-up time, two heating and soaking zone total time 240min, steel billet upper and lower surface temperature head is no more than 20 DEG C;

(8) controlled rolling and controlled cooling: start rolling temperature is greater than 1020 DEG C, one-phase is rolling to 170mm and starts cool steel, two-stage start rolling temperature≤850 DEG C, finishing temperature 770 ~ 800 DEG C, roll rear employing ACC section cooling, be cooled to 610 ~ 630 DEG C of scopes with the temperature drop speed of 3 ~ 6 DEG C/s;

(9) steel plate cooling in heap: start stacking slow cooling when 350-500 DEG C after steel plates straightening, the slow cooling time is 48 hours;

(10) thermal treatment: steel plate is machine stove normalizing treatment outside, normalizing temperature is 890 ± 20 DEG C, and soaking time controls by 2.2 ~ 2.4mm/min, adopts aerosol to be cooled to 650 ± 10 DEG C, then start air cooling to room temperature after coming out of the stove.

The present invention is by KR hot metal pretreatment, converter smelting, Argon process, LF refining and VD refinery practice, and the strict harmful element controlling steel grade P, S etc. and be unfavorable for toughness of material, can not only ensure Molten Steel Cleanliness, and substantially increase steel internal soundness; Adopt lower Heating temperature can avoid excessively growing up of heat-processed austenite crystal, simultaneously the TiN that formed of trace Ti element can pinning austenite grain boundary in heat-processed, stops Austenite Grain Growth; Strict rolling temperature control in TMCP technological process, enter water temp and red temperature, can effective crystal grain thinning, for steel plate low-temperature flexibility provides organization foundation, Nb(C, N that Nb element is formed in ferritic transformation process at austenite) can transformation be stoped after ferrite crystal grain grow up, create good condition for steel plate obtains tiny ferrite crystal grain; Steel plate cooling in heap process can alleviate the internal stress formed in controlled rolling and cooling process, and significantly expands hydrogen, effectively improves internal quality of steel plate; Heat treatment link, by the speed of cooling after strictly controlling heat-up rate, holding temperature and steel plate and coming out of the stove, even refinement steel plate crystal grain, reduces thickness direction grain structure difference, guarantees the comprehensive mechanical property of steel plate excellence.

Embodiment

Of the present invention be easy to produce and can extensively use continuous casting produce 140mmQ345E slab chemical composition and comprise (unit, wt%): C:0.10 ~ 0.15, Si:0.15 ~ 0.35, Mn:1.2 ~ 1.45, P :≤0.010, S :≤0.003, Als:0.020 ~ 0.050, Nb:0.020 ~ 0.040, Ti:0.010 ~ 0.020, other is Fe and relict element.

Carbon equivalent [Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15] :≤0.40.

For achieving the above object, the production method that the present invention takes comprises: KR hot metal pretreatment, converter smelting, Argon process, LF refining, VD refining, continuous casting, strand heating, controlled rolling and controlled cooling, steel plate cooling in heap and thermal treatment.In described KR hot metal pretreatment, water arrives at a station and must take off front slag and take off rear slag, and ensure liquid level thickness of slag layer≤20mm, molten iron reaches S≤0.005% after KR stirring desulphurization, simultaneously desulfurization time≤20min, desulfurization temperature drop≤20 DEG C, in described converter smelting, adopt 120 tons of top and bottom combined blown converters, enter in stove molten iron by mass percentage containing S≤0.003%, containing P≤0.070%, molten iron temperature >=1270 DEG C, molten iron Intake Quantity error is by ± 1 ton of control, process rifle position is by 1.0 ~ 1.3m in early stage, mid-term 1.2 ~ 1.6m, later stage 1.0 ~ 1.1m controls, slag making basicity R controls by 2.5 ~ 4.0, tapping target C: >=0.05%, P≤0.010%, S :≤0.003%, in ladle, Si-Al-Ba-Ca is added in tapping process, manganeseirom, ferro-silicon and lime, fluorite, with slag tapping before floating plug gear before tapping, slag stop cone pushing off the slag is adopted before tapping terminates, ensure thickness of slag layer≤30mm, omnidistance Argon is required in converter tapping process, in described Argon process, argon station is disposable adds aluminum steel, requires strong Argon 3min at argon station, flow 200 ~ 500NL/min, and molten steel face bore hole diameter control, must not lower than 1570 DEG C from argon station temperature at 300 ~ 500mm, in described LF refining, in refining process, omnidistance Argon, adds slag charge, basicity is pressed 4.0-6.0 and is controlled, and adds reductor, and heating adopts electric current to heat, heat-up time is by twice control, one heating 7-12min, two heating 6-10min, add reductor in two heat-processedes, and require that dry slag number of times is greater than 6 times, silicon-calcium wire is added before leaving from station, must argon gas be closed before adding silicon-calcium wire, not adopt the upper steel temperature 1565 ± 15 DEG C of vacuum outgas, adopt the upper steel temperature 1610 ± 15 DEG C of vacuum outgas, in described VD refining process, VD vacuum tightness must reach below 67Pa, dwell time is necessary >=15min, soft blow 2-5min or do not blow after vacuum breaker, in soft blow process, molten steel must not be exposed, online bag pumpdown time 1.7min, and insulating covering agent ensures to be paved with molten steel face, argon gas must be closed, upper steel temperature 1565 ± 15 DEG C before adding insulating covering agent, in described casting process, adopt 350mm × 2320mm section continuous caster, continuous casting allusion quotation is drawn and is controlled at 10 ~ 20 DEG C according to the corresponding molten steel overheat of 0.80m/min(), crystallizer wide discharge 4400L/min, leptoprosopy discharge 560L/min, in described 2 Mo Steel Slab during Heating Process, adopt Three-section type heating: a heating <1000 DEG C, two heating 1200 DEG C, soaking zone 1180 DEG C, total 11 ~ 13min/cm control heat-up time, two heating and soaking zone total time 240min, steel billet upper and lower surface temperature head is no more than 20 DEG C, in described controlled rolling and controlled cooling process, start rolling temperature is greater than 1020 DEG C, and one-phase is rolling to 170mm and starts cool steel, two-stage start rolling temperature≤850 DEG C, finishing temperature 770 ~ 800 DEG C, rolls rear employing ACC section cooling, is cooled to 610 ~ 630 DEG C of scopes with the temperature drop speed of 3 ~ 6 DEG C/s, in described steel plate cooling in heap process, start stacking slow cooling after steel plates straightening when 350-500 DEG C, the slow cooling time is 48 hours, in described heat treatment process, steel plate is machine stove normalizing treatment outside, and normalizing temperature is 890 ± 20 DEG C, and soaking time controls by 2.2 ~ 2.4mm/min, adopts aerosol to be cooled to 650 ± 10 DEG C, then start air cooling to room temperature after coming out of the stove.

Example 1

By a kind of 140mmQ345E slab that KR hot metal pretreatment, converter smelting, Argon process, LF refining, VD refining, continuous casting, strand heating, controlled rolling and controlled cooling, steel plate cooling in heap and thermal treatment obtain, its chemical composition comprises (unit, wt%): C:0.14, Si:0.30, Mn:1.41, P :≤0.008, S :≤0.001, Als:0.035, Nb:0.025, Ti:0.014, other is Fe and relict element.

Example 2

By a kind of 140mmQ345E slab that KR hot metal pretreatment, converter smelting, Argon process, LF refining, VD refining, continuous casting, strand heating, controlled rolling and controlled cooling, steel plate cooling in heap and thermal treatment obtain, its chemical composition comprises (unit, wt%): C:0.13, Si:0.28, Mn:1.43, P :≤0.007, S :≤0.001, Als:0.032, Nb:0.024, Ti:0.015, other is Fe and relict element.

Mechanical mechanics property is analyzed

Composition and mechanical mechanics property perform by GB/T 1591/2008, and mechanical mechanics property specifically sees the following form.

140mmQ345E slab mechanical mechanics property

According to the inventive method, produce 20 batches as a trial, its mechanical mechanics property sees the following form.

Trial production 140mmQ345E slab mechanical mechanics property

The described 20 batches of 140mmQ345E slabs of upper table, detect a flaw by JB/T 4730, steel plate all closes three grades, unification level 14 pieces, ratio 70%; The percentage of A-class goods 100% examined outward by steel plate, produces a desired effect.

Claims (2)

1. a continuous casting produces 140mm Q345E slab, the chemical composition mass percent that it comprises: C:0.10 ~ 0.15, Si:0.15 ~ 0.35, Mn:1.2 ~ 1.45, P :≤0.010, S :≤0.003, Als:0.020 ~ 0.050, Nb:0.020 ~ 0.040, Ti:0.010 ~ 0.020, other is Fe and relict element.

2. continuous casting produces a production method for 140mm Q345E slab as claimed in claim 1, and described continuous casting produces the production method of 140mmQ345E slab, comprises the following steps:

(1) KR hot metal pretreatment: molten iron arrives at a station and must take off front slag and take off rear slag, and ensure liquid level thickness of slag layer≤20mm, molten iron reaches S≤0.005% after KR stirring desulphurization, simultaneously desulfurization time≤20min, desulfurization temperature drop≤20 DEG C;

(2) converter smelting: adopt 120 tons of top and bottom combined blown converters, enter in stove molten iron by mass percentage containing S≤0.003%, containing P≤0.070%, molten iron temperature >=1270 DEG C, molten iron Intake Quantity error is by ± 1 ton of control, process rifle position is by 1.0 ~ 1.3m in early stage, mid-term 1.2 ~ 1.6m, later stage 1.0 ~ 1.1m controls, slag making basicity R controls by 2.5 ~ 4.0, tapping target C: >=0.05%, P≤0.010%, S :≤0.003%, in ladle, Si-Al-Ba-Ca is added in tapping process, manganeseirom, ferro-silicon and lime, fluorite, with slag tapping before floating plug gear before tapping, slag stop cone pushing off the slag is adopted before tapping terminates, ensure thickness of slag layer≤30mm, omnidistance Argon is required in converter tapping process,

(3) Argon process: argon station is disposable adds aluminum steel, requires strong Argon 3min at argon station, flow 200 ~ 500NL/min, molten steel face bore hole diameter control, must not lower than 1570 DEG C from argon station temperature at 300 ~ 500mm;

(4) LF refining: omnidistance Argon in refining process, adds slag charge, basicity is pressed 4.0-6.0 and is controlled, add reductor, heating adopts electric current to heat, and heat-up time, one heating 7-12min, two heated 6-10min by twice control, reductor is added in two heat-processedes, and require that dry slag number of times is greater than 6 times, add silicon-calcium wire before leaving from station, before adding silicon-calcium wire, must argon gas be closed, do not adopt the upper steel temperature 1565 ± 15 DEG C of vacuum outgas, adopt the upper steel temperature 1610 ± 15 DEG C of vacuum outgas;

(5) VD refining: VD vacuum tightness must reach below 67Pa, dwell time is necessary >=15min, soft blow 2-5min or do not blow after vacuum breaker, in soft blow process, molten steel must not be exposed, online bag pumpdown time 1.7min, insulating covering agent ensures to be paved with molten steel face, must close argon gas, upper steel temperature 1565 ± 15 DEG C before adding insulating covering agent;

(6) continuous casting: adopt 350mm × 2320mm section continuous caster, continuous casting allusion quotation is drawn and is controlled at 10 ~ 20 DEG C according to the corresponding molten steel overheat of 0.80m/min(), crystallizer wide discharge 4400L/min, leptoprosopy discharge 560L/min;

(7) strand heating: adopt Three-section type heating: a heating <1000 DEG C, two heating 1200 DEG C, soaking zone 1180 DEG C, total 11 ~ 13min/cm control heat-up time, two heating and soaking zone total time 240min, steel billet upper and lower surface temperature head is no more than 20 DEG C;

(8) controlled rolling and controlled cooling: start rolling temperature is greater than 1020 DEG C, one-phase is rolling to 170mm and starts cool steel, two-stage start rolling temperature≤850 DEG C, finishing temperature 770 ~ 800 DEG C, roll rear employing ACC section cooling, be cooled to 610 ~ 630 DEG C of scopes with the temperature drop speed of 3 ~ 6 DEG C/s;

(9) steel plate cooling in heap: start stacking slow cooling when 350-500 DEG C after steel plates straightening, the slow cooling time is 48 hours;

(10) thermal treatment: steel plate is machine stove normalizing treatment outside, normalizing temperature is 890 ± 20 DEG C, and soaking time controls by 2.2 ~ 2.4mm/min, adopts aerosol to be cooled to 650 ± 10 DEG C, then start air cooling to room temperature after coming out of the stove.