CN103160739A - Continuously cast 80mm-thick bridge steel Q420qE and preparation process thereof - Google Patents
Continuously cast 80mm-thick bridge steel Q420qE and preparation process thereof Download PDFInfo
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Abstract
The invention discloses continuously cast 80mm-thick bridge steel Q420qE. The continuously cast 80mm-thick bridge steel Q420qE comprises the following chemical components in percentage by weight: 0.13-0.17% of C, 0.55-0.85% of Si, 1.05-1.70% of Mn, not more than 0.015% of P, not more than 0.005% of S, 0.160-0.200% of Ni, 0.050-0.070% of V, 0.020-0.040% of Nb, 0.010-0.020% of Ti, 0.015-0.035% of Als and the balance of Fe and residual elements. A production method of the continuously cast 80mm-thick bridge steel Q420qE comprises the following steps: KR molten iron pretreatment process, converter smelting process, argon blowing treatment process, LF (ladle furnace) refining process, VD (vacuum degassing) refining process and the like. According to the production method disclosed by the invention, the cleanliness of steel is ensured through the reasonable design of chemical components and an LF+VD process, and a high-temperature stack cooling process is adopted, so that residual stress caused by rapid cooling can be effectively avoided, the hydrogen content in a steel plate can be simultaneously greatly reduced, the thermal diffusion effect is fully realized, the detected defects of the steel plate are improved, and the 80mm-thick high-strength Q420qE steel plate is successfully developed through effective implementation of heating, rolling, quenching and tempering treatment and other processes.
Description
Technical field
The invention belongs to plate of moderate thickness Bridge Steel technical field, particularly a kind of continuous casting 80mm thickness Bridge Steel Q420qE and preparation technology thereof.
Technical background
As everyone knows, bridge plate Q420qE is mainly used in the significant points such as bridge structure, it requires to have higher intensity, hardness and toughness, be subjected to the effects limit such as high strength, high tenacity, this steel plate requires very strict to steel rolling, thermal treatment process, the productions such as therefore, its production difficulty is large, the tooling requirement is special are less.
At present, Chinese patent disclosed publication number on November 10th, 2010 is that the 101880824A application number is that 201010208305.3 patent of invention name is called and the invention discloses the special thick guaranteed cost of a kind of Q345q series, the guarantor bridge steel plate of detecting a flaw, and comprises the chemical composition of following quality amount per-cent: C:0.08～0.16, Si:0.20～0.50, Mn:1.15～1.60, P :≤0.020, S :≤0.010, micro alloying element (V+Nb+Ti+Ni) :≤0.12, AlS:0.010～0.050, other is Fe and relict element; Carbon equivalent :≤0.43.This bridge plate: yield strength is controlled at 315～350MPa, has on average reached 335MPa, than the rich 40MPa of standard; Tensile strength is controlled at 490～515MPa, has on average reached 500MPa, than the rich 30MPa of standard; Elongation is controlled at 29%～32%, on average reaches 28%, than standard affluence 8%;～20 ℃ of impact of collision power controls have on average reached 178J built in 144～256J, and still, for the desired intensity of the significant points such as bridge structure, hardness and toughness, its performance is relatively not high, and its processing requirement condition is relatively high, produces less.
Summary of the invention
The objective of the invention is for a kind of high strength, continuous casting 80mm thickness Bridge Steel Q420qE and preparation technology thereof that toughness is strong are provided.
a kind of continuous casting 80mm thickness Bridge Steel Q420qE, the mass percent of its chemical composition and each composition: C:0.13～0.17, Si:0.55～0.85, Mn:1.05～1.70, P :≤0.015, S :≤0.005, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.015～0.035, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
The function analysis of described chemical composition is as follows:
C: be most basic strengthening element in steel, improve intensity;
Si: be the solution strengthening element, favourable to the intensity that improves steel plate;
Mn: be the solution strengthening element, all favourable to intensity and the toughness that improves steel plate;
P: unfavorable to welding, and have certain cold shortness, and belong to harmful element in this steel grade, that should control is as far as possible low;
S: easily form the MnS type impurity, have certain red brittleness, belong to harmful element in this steel grade, that should control is as far as possible low;
Ni: both strongly improved on the one hand the intensity of steel, another aspect makes again the toughness of iron keep high level all the time, its temperature that becomes fragile is extremely low, lattice parameter and the γ～iron of Ni are close, so can become continuous solid solution, this just is conducive to improve the hardenability of steel, and Ni can reduce stagnation point and increase austenitic stability, so its quenching temperature can reduce, hardening capacity is good.
V, Nb, Ti: can be combined with C, N in steel, form fine carbide or carbonitride, can play crystal grain thinning and dispersion-strengthened action, thereby reach the net effect of the obdurability of effective raising steel.
Al: can play the grain refining intensificatiom effect;
The production method of a kind of continuous casting 80mm thickness Bridge Steel Q420qE comprises the steps:
The a.KR hot metal pretreatment technology: guarantee liquid level thickness of slag layer≤20mm, molten iron guarantees molten iron (by mass percentage) S≤0.005% after the KR stirring desulphurization, guarantees desulfurization cycle≤21min, desulfurization temperature drop≤20 ℃
B. converter smelting process: enter stove molten iron (by mass percentage) S≤0.005%, P≤0.080%, molten iron temperature 〉=1270 ℃ slag making basicity R controls by 2.5～4.0, tapping P≤0.015%, C 〉=0.05%, S≤0.012%, argon blowing process: the disposable aluminum steel that adds in argon station, at the strong Argon 3min of argon station requirement, flow 200～500NL/min, molten steel face bore hole diameter control be at 300～500mm, must not be lower than 1570 ℃ from argon station temperature.
The c.LF refinery practice: basicity is controlled by 4.0～6.0, and one heating 7～12min, two heating 6～10min in two heat-processedes, added reductor, and required the dry slag number of times greater than 6 times by twice control heat-up time.Add silicon-calcium wire before leaving from station, close argon gas, 1565 ± 15 ℃ of upper steel temperature (not adopting vacuum outgas)/1610 ± 15 ℃ (employing vacuum outgas) before adding silicon-calcium wire.
The d.VD refinery practice: VD vacuum tightness must reach below 67Pa, and the dwell time is necessary 〉=15min, soft blow 2～5min or do not blow after vacuum breaker, and in the soft blow process, molten steel must not be exposed, 1565 ± 15 ℃ of upper steel temperature.
E. continuous casting process: adopt the production of 300mm section, middle bag superheating temperature is controlled in 15～25 ℃ of scopes, and pulling speed of continuous casting is carried out according to 0.72m/min, the two cooling water meters of cold employing 8#, the cooling employing of crystallizer 2# cooling curve.
F. heating process: one-phase Heating temperature≤950 ℃, the two-stage heating and temperature control is at 1220～1240 ℃, and the soaking zone temperature is controlled at 1200～1220 ℃, is controlled at 5～6h left and right total heat-up time.
G. rolling technology: 1020 ℃～1120 ℃ of one-phase start rolling temperatures, reduction in pass is 35mm; 800～830 ℃ of two-stage start rolling temperatures, last pass draft 〉=15%, 770～800 ℃ of finishing temperatures; It is 760 ℃～780 ℃ that cooling control technology requires into water temp, and red temperature is controlled at 600～630 ℃.
H. cooling in heap technique: the stacking slow cooling temperature is not less than 450 ℃, cooling in heap time 〉=72 hour.
I. thermal treatment process: adopt normalizing+fast cold thermal treatment process, 920 ± 10 ℃ of normalizing temperatures, t=2.0min/mm, water-cooled red temperature are controlled at 560～580 ℃.
The present invention is by rational chemical composition design, LF+VD technique guarantees the cleanliness factor of steel, employing high temperature cooling in heap technique can effectively be avoided the unrelieved stress because of quick cooling generation, can greatly reduce simultaneously the content of hydrogen in steel plate, fully realize thermal diffusion effect, improve the steel plate inspection defective, and effectively implement by techniques such as heating, rolling and modifier treatment, successfully developed 80mm high strength Q420qE steel plate, its yield strength is controlled at 430～500MPa, tensile strength is controlled at 540～620 MPa; Elongation is controlled at 20%～25%;～40 ℃ of V-type ballistic works are controlled at 150～210 J.
Embodiment
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.13～0.17, Si:0.55～0.85, Mn:1.05～1.70, P :≤0.015, S :≤0.005, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.015～0.035, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
the preparation technology of continuous casting 80mm thickness Bridge Steel Q420qE of the present invention comprises the high-quality molten iron, the KR hot metal pretreatment technology, converter smelting process, argon blowing process, the LF refinery practice, the VD refinery practice, continuous casting process, heating process, controlled rolling and controlled cooling, cooling in heap technique, thermal treatment process, in described KR hot metal pretreatment technology, the molten iron that arrives at a station must be taken off front slag and take off rear slag, guarantees liquid level thickness of slag layer≤20mm, and molten iron guarantees molten iron (by mass percentage) S≤0.005% after the KR stirring desulphurization, guarantee desulfurization cycle≤21min, desulfurization temperature drop≤20 ℃ in described converter smelting process, enter stove molten iron (by mass percentage) S≤0.005%, P≤0.080%, molten iron temperature 〉=1270 ℃, molten iron Intake Quantity error is controlled by ± 1t, and steel scrap strictly adopts the high-quality scrap stock, and 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, and slag making basicity R controls by 2.5～4.0, tapping target P≤0.015%, C 〉=0.05%, S≤0.012%, in tapping process in the ladle Si-Al-Ba-Ca, manganeseirom, ferro-silicon and lime, fluorite.tap with slag before the floating plug gear before tapping, before finishing, tapping adopts the slag stop cone pushing off the slag, guarantee thickness of slag layer≤30mm, require omnidistance Argon in converter tapping process, in described argon blowing process, the disposable aluminum steel that adds in argon station, at the strong Argon 3min of argon station requirement, flow 200～500NL/min, molten steel face bore hole diameter control is at 300～500mm, must not be lower than 1570 ℃ from argon station temperature, in described LF refinery practice, omnidistance Argon in refining process, Argon intensity is regulated according to different link needs, add refining slag, basicity is controlled by 4.0～6.0, the refinement and deoxidation agent is with calcium carbide, aluminum shot, ferrosilicon powder is main, add-on is according to oxygen level in molten steel and make the white slag situation and add in right amount, heat-processed is more than needed according to rhythm selects suitable electric current to heat with temperature conditions, heat-up time is by twice control, one heating 7～12min, two heating 6～10min, require according to the slag making situation in two heat-processedes, add reductor, and require the dry slag number of times greater than 6 times.Add silicon-calcium wire before leaving from station, must close argon gas before adding silicon-calcium wire, 1565 ± 15 ℃ of upper steel temperature (not adopting vacuum outgas)/1610 ± 15 ℃ (employing vacuum outgas), in described VD refinery practice, VD vacuum tightness must reach below 67Pa, dwell time is necessary 〉=15min, and soft blow 2～5min or do not blow after vacuum breaker, in the soft blow process, molten steel must not be exposed.The normal online bag pumpdown time: (vacuumizing front liquid steel temperature-target temperature leaving from station)/1.7min.insulating covering agent, assurance is paved with the molten steel face, must close argon gas before adding insulating covering agent, 1565 ± 15 ℃ of upper steel temperature, in described continuous casting process, adopt the production of 300mm section, whole process is taked the protection cast, prevent that molten steel is air-breathing, middle bag superheating temperature is controlled in 15～25 ℃ of scopes, pulling speed of continuous casting is carried out according to 0.72m/min, the two cooling water meters of cold employing 8#, the cooling employing of crystallizer 2# cooling curve, in described heating process, delivering to continuous oven after the strand cooling in heap heats, one-phase Heating temperature≤950 ℃, the two-stage heating and temperature control is at 1220～1240 ℃, the soaking zone temperature is controlled at 1200～1220 ℃, be controlled at 5～6h left and right total heat-up time, in described rolling technology, adopt two stage rolling, 1020 ℃～1120 ℃ of one-phase start rolling temperatures, adopt high temperature low speed to depress greatly rolling, reduction in pass is 35mm, 800～830 ℃ of two-stage start rolling temperatures, the two-stage takes to depress greatly rolling, last pass draft 〉=15%, 770～800 ℃ of finishing temperatures, it is 760 ℃～780 ℃ that cooling control technology requires into water temp, red temperature is controlled at 600～630 ℃, in described cooling in heap technique, the stacking slow cooling temperature is not less than 450 ℃, and cooling in heap time 〉=72 hour are in described thermal treatment process, adopt normalizing+fast cold thermal treatment process, 920 ± 10 ℃ of normalizing temperatures, t=2.0min/mm, water-cooled red temperature are controlled at 560～580 ℃.
Embodiment one
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.13, Si:0.55, Mn:1.05, P:0.015, S:0.005, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.015, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
the preparation technology of continuous casting 80mm thickness Bridge Steel Q420qE of the present invention comprises the high-quality molten iron, the KR hot metal pretreatment technology, converter smelting process, argon blowing process, the LF refinery practice, the VD refinery practice, continuous casting process, heating process, controlled rolling and controlled cooling, cooling in heap technique, thermal treatment process, in described KR hot metal pretreatment technology, the molten iron that arrives at a station must be taken off front slag and take off rear slag, guarantees liquid level thickness of slag layer≤20mm, and molten iron guarantees molten iron (by mass percentage) S≤0.005% after the KR stirring desulphurization, guarantee desulfurization cycle≤21min, desulfurization temperature drop≤20 ℃ in described converter smelting process, enter stove molten iron (by mass percentage) S≤0.005%, P≤0.080%, molten iron temperature 〉=1270 ℃, molten iron Intake Quantity error is controlled by ± 1t, and steel scrap strictly adopts the high-quality scrap stock, and 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, and slag making basicity R controls by 2.5～4.0, and the mass percent of tapping target P is 0.015%, the mass percent of C is 0.05%, the mass percent 0.012% of S, in tapping process in the ladle Si-Al-Ba-Ca, manganeseirom, ferro-silicon and lime, fluorite.tap with slag before the floating plug gear before tapping, before finishing, tapping adopts the slag stop cone pushing off the slag, guarantee thickness of slag layer≤30mm, require omnidistance Argon in converter tapping process, in described argon blowing process, the disposable aluminum steel that adds in argon station, at the strong Argon 3min of argon station requirement, flow 200～500NL/min, molten steel face bore hole diameter control is at 300～500mm, must not be lower than 1570 ℃ from argon station temperature, in described LF refinery practice, omnidistance Argon in refining process, Argon intensity is regulated according to different link needs, add refining slag, basicity is controlled by 4.0～6.0, the refinement and deoxidation agent is with calcium carbide, aluminum shot, ferrosilicon powder is main, add-on is according to oxygen level in molten steel and make the white slag situation and add in right amount, heat-processed is more than needed according to rhythm selects suitable electric current to heat with temperature conditions, heat-up time is by twice control, one heating 7～12min, two heating 6～10min, require according to the slag making situation in two heat-processedes, add reductor, and require the dry slag number of times greater than 6 times.Add silicon-calcium wire before leaving from station, must close argon gas before adding silicon-calcium wire, 1565 ± 15 ℃ of upper steel temperature (not adopting vacuum outgas)/1610 ± 15 ℃ (employing vacuum outgas), in described VD refinery practice, VD vacuum tightness must reach below 67Pa, dwell time is 15min, soft blow 2～5min or do not blow after vacuum breaker, and in the soft blow process, molten steel must not be exposed.The normal online bag pumpdown time: (vacuumizing front liquid steel temperature-target temperature leaving from station)/1.7min.insulating covering agent, assurance is paved with the molten steel face, must close argon gas before adding insulating covering agent, 1565 ± 15 ℃ of upper steel temperature, in described continuous casting process, adopt the production of 300mm section, whole process is taked the protection cast, prevent that molten steel is air-breathing, middle bag superheating temperature is controlled in 15～25 ℃ of scopes, pulling speed of continuous casting is carried out according to 0.72m/min, the two cooling water meters of cold employing 8#, the cooling employing of crystallizer 2# cooling curve, in described heating process, delivering to continuous oven after the strand cooling in heap heats, one-phase Heating temperature≤950 ℃, the two-stage heating and temperature control is at 1220～1240 ℃, the soaking zone temperature is controlled at 1200 ℃, be controlled at 5～6h left and right total heat-up time, in described rolling technology, adopt two stage rolling, 1020 ℃～1120 ℃ of one-phase start rolling temperatures, adopt high temperature low speed to depress greatly rolling, reduction in pass is 35mm, 800～830 ℃ of two-stage start rolling temperatures, the two-stage takes to depress greatly rolling, last pass draft 〉=15%, 770 ℃ of finishing temperatures, it is 760 ℃～780 ℃ that cooling control technology requires into water temp, red temperature is controlled at 600 ℃, in described cooling in heap technique, the stacking slow cooling temperature is not less than 450 ℃, and cooling in heap time 〉=72 hour are in described thermal treatment process, adopt normalizing+fast cold thermal treatment process, 920 ± 10 ℃ of normalizing temperatures, t=2.0min/mm, water-cooled red temperature are controlled at 560～580 ℃.
Embodiment two
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.14, Si:0.60, Mn:1.30, P:0.012, S:0.004, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.020, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
The preparation technology of this Bridge Steel and embodiment one are basic identical, and its difference is: in converter process, the mass percent of tapping target P is 0.014%, the mass percent of C is 0.06%, the mass percent 0.011% of S.
In described VD refinery practice, VD vacuum tightness must reach below 67Pa, and the dwell time is 17min.
In described heating process, the soaking zone temperature is controlled at 1205 ℃.
In described rolling technology, 776 ℃ of finishing temperatures.
In described cooling control technology, red temperature is controlled at 606 ℃.
Embodiment three
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.165, Si:0.70, Mn:1.65, P:0.006, S:0.002, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.025, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
The preparation technology of this Bridge Steel and embodiment one are basic identical, and its difference is: in converter process, the mass percent of tapping target P is 0.013%, the mass percent of C is 0.07%, the mass percent 0.010% of S.
In described VD refinery practice, VD vacuum tightness must reach below 67Pa, and the dwell time is 20min.
In described heating process, the soaking zone temperature is controlled at 1210 ℃.
In described rolling technology, 782 ℃ of finishing temperatures.
In described cooling control technology, red temperature is controlled at 612 ℃.
Embodiment four
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.168, Si:0.75, Mn:1.68, P:0.003, S:0.001, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.030, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
The preparation technology of this Bridge Steel and embodiment one are basic identical, and its difference is: in converter process, the mass percent of tapping target P is 0.013%, the mass percent of C is 0.08%, the mass percent 0.009% of S.
In described VD refinery practice, VD vacuum tightness must reach below 67Pa, and the dwell time is 20min.
In described heating process, the soaking zone temperature is controlled at 1216 ℃.
In described rolling technology, 788 ℃ of finishing temperatures.
In described cooling control technology, red temperature is controlled at 618 ℃.
Embodiment five
continuous casting 80mm thickness Bridge Steel Q420qE of the present invention, the mass percent of its chemical composition and each composition: C:0.17, Si:0.80, Mn:1.65, P:0.009, S:0.003, Ni:0.160～0.200, V:0.050～0.070, Nb:0.020～0.040, Ti:0.010～0.020, Als:0.030, other is Fe and relict element, on described continuous casting 80mm thickness Bridge Steel Q420qE, be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of lower top layer, wherein: ferrite volume fraction is 80～90%, Martensite Volume Fraction is 20～10%, the steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
The preparation technology of this Bridge Steel and embodiment one are basic identical, and its difference is: in converter process, the mass percent of tapping target P is 0.010%, the mass percent of C is 0.08%, the mass percent 0.010% of S.
In described VD refinery practice, VD vacuum tightness must reach below 67Pa, and the dwell time is 20min.
In described heating process, the soaking zone temperature is controlled at 1220 ℃.
In described rolling technology, 795 ℃ of finishing temperatures.
In described cooling control technology, red temperature is controlled at 623 ℃.
Following table is the continuous casting 80mm thickness Bridge Steel Q420qE mechanical property table according to above-described embodiment gained.
The continuous casting 80mm thickness Bridge Steel Q420qE of this trial production all reaches standard-required, and its its yield strength is controlled at 430～500MPa, and tensile strength is controlled at 540～620 MPa; Elongation is controlled at 20%～25%;～40 ℃ of V-type ballistic works are controlled at 150～210 J.Simultaneously, performance index have satisfied standard and customer requirement fully.
Technical process of the present invention:
KR hot metal pretreatment technology → converter smelting process argon blowing process → LF refinery practice → VD refinery practice → continuous casting process → heating process → controlled rolling and controlled cooling → cooling in heap technique → thermal treatment process → outer inspection → flaw detection → warehouse-in.
Chemical Composition: C is main forms carbide with other element, plays build up and precipitation strength effect, the raising armor plate strength; Mn mainly plays solution strengthening and reduces transformation temperature, works to improve armor plate strength; Nb plays the refined crystalline strengthening effect, and during Heating Steel Ingots, the Nb of solid solution can stop Austenite Grain Growth; Rolling through the two-stage, the C of V, N compound are separated out, and improve armor plate strength; P, S content are controlled in a lower scope, and in a word, whole Composition Control is more stable, satisfy the Composition Design requirement of continuous casting 80mm thickness Bridge Steel Q420qE.
Claims (3)
1. continuous casting 80mm thickness Bridge Steel Q420qE, it is characterized in that: the mass percent of its chemical composition and each composition: C:0.13-0.17, Si:0.55-0.85, Mn:1.05-1.70, P :≤0.015, S :≤0.005, Ni:0.160-0.200, V:0.050-0.070, Nb:0.020-0.040, Ti:0.010-0.020, Als:0.015-0.035, other is Fe and relict element.
2. continuous casting 80mm thickness Bridge Steel Q420qE as claimed in claim 1, it is characterized in that: be the ferrite/martensite tissue of grain-size 2～3um in each 0.5～1.0mm thickness of described continuous casting 80mm thickness Bridge Steel Q420qE upper and lower top layer, wherein: ferrite volume fraction is 80～90%, and Martensite Volume Fraction is 20～10%; The steel plate centre portions is the higher ferrite/martensite tissue of martensite content, and wherein: Martensite Volume Fraction is 50～70%, and ferrite volume fraction is 50～30%.
3. the production method of continuous casting 80mm thickness Bridge Steel Q420qE as claimed in claim 1, is characterized in that: comprise the steps:
The a.KR hot metal pretreatment technology: guarantee liquid level thickness of slag layer≤20mm, molten iron guarantees molten iron (by mass percentage) S≤0.005% after the KR stirring desulphurization, guarantees desulfurization cycle≤21min, desulfurization temperature drop≤20 ℃;
B. converter smelting process: enter stove molten iron (by mass percentage) S≤0.005%, P≤0.080%, molten iron temperature 〉=1270 a ℃ slag making basicity R presses 2.5-4.0 and controls, tapping P≤0.015%, C 〉=0.05%, S≤0.012%, argon blowing process: the disposable aluminum steel that adds in argon station, at the strong Argon 3min of argon station requirement, flow 200-500NL/min, molten steel face bore hole diameter control be at 300～500mm, must not be lower than 1570 ℃ from argon station temperature;
The c.LF refinery practice: basicity is pressed 4.0-6.0 and is controlled, heat-up time is by twice control, one heating 7-12min, two heating 6-10min, in two heat-processedes, add reductor, and require the dry slag number of times greater than 6 times, add silicon-calcium wire before leaving from station, close argon gas before adding silicon-calcium wire, 1565 ± 15 ℃ of upper steel temperature (not adopting vacuum outgas)/1610 ± 15 ℃ (employing vacuum outgas);
The d.VD refinery practice: VD vacuum tightness must reach below 67Pa, and the dwell time is necessary 〉=15min, soft blow 2-5min or do not blow after vacuum breaker, and in the soft blow process, molten steel must not be exposed, 1565 ± 15 ℃ of upper steel temperature;
E. continuous casting process: adopt the production of 300mm section, middle bag superheating temperature is controlled in 15-25 ℃ of scope, and pulling speed of continuous casting is carried out according to 0.72m/min, the two cooling water meters of cold employing 8#, the cooling employing of crystallizer 2# cooling curve;
F. heating process: one-phase Heating temperature≤950 ℃, the two-stage heating and temperature control is at 1220-1240 ℃, and the soaking zone temperature is controlled at 1200-1220 ℃, is controlled at the 5-6h left and right total heat-up time;
G. rolling technology: 1020 ℃～1120 ℃ of one-phase start rolling temperatures, reduction in pass is 35mm; Two-stage start rolling temperature 800-830 ℃, last pass draft 〉=15%, 770～800 ℃ of finishing temperatures; It is 760 ℃-780 ℃ that cooling control technology requires into water temp, and red temperature is controlled at 600-630 ℃;
H. cooling in heap technique: the stacking slow cooling temperature is not less than 450 ℃, cooling in heap time 〉=72 hour;
I. thermal treatment process: adopt normalizing+fast cold thermal treatment process, 920 ± 10 ℃ of normalizing temperatures, t=2.0min/mm, water-cooled red temperature are controlled at 560-580 ℃.
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| CN108148941A (en) * | 2017-11-22 | 2018-06-12 | 南阳汉冶特钢有限公司 | A kind of smelting process of ultralow boron steel |
| CN108914008A (en) * | 2018-08-10 | 2018-11-30 | 武汉钢铁集团鄂城钢铁有限责任公司 | A kind of economical high-ductility 360MPa level structure steel plate and its manufacturing method |
| CN109092893A (en) * | 2018-07-03 | 2018-12-28 | 新疆八钢铁股份有限公司 | 60 meters of overlength Plate Production techniques |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103397251A (en) * | 2013-08-05 | 2013-11-20 | 武汉钢铁(集团)公司 | 150-190 mm thick bridge steel produced by continuous casting slab and technology thereof |
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| CN108148941A (en) * | 2017-11-22 | 2018-06-12 | 南阳汉冶特钢有限公司 | A kind of smelting process of ultralow boron steel |
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| CN109868412A (en) * | 2019-02-18 | 2019-06-11 | 山东钢铁股份有限公司 | Exempt to preheat 500MPa grades of high-strength steel of big thickness low-carbon-equivalent and its manufacturing method before a kind of weldering |
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