CN109706375A - A kind of production method of the big thickness low-alloy high-tensile structural steel of 420~600mm - Google Patents

Abstract

The invention discloses the big thickness low-alloy high-tensile structural steels of 420~600mm of one kind, it includes following chemical components: C:0.12~0.15%, Si:0.20~0.5%, Mn:1.50~1.60%, P :≤0.013%, S :≤0.001%, Nb:0.04~0.06%, V:0.03~0.05%, Als:0.02~0.03%, and other is Fe and residual elements；Its production method includes following process flow: molten iron → converter → LF refining → VD vacuum processing → molding casting → steel ingot cleaning → steel ingot send in the 12h after cleaning out and rolls shove charge；Each chemical component dosage of the present invention is reasonable, under the premise of not reducing plasticity and toughness, gives full play to the double effects of solution strengthening and refined crystalline strengthening；Casting process, which is opened, to be poured surely, with flowing tightly；The toughness of steel can be enhanced using normalizing, using the microalloy super-thick steel plate after water water-cooled process normalizing is entered, occur that phase transformation after steel plate normalizing rapidly, crystal grain is refined, and part rolling stress is eliminated, increase the plasticity and toughness of steel plate under the premise of guaranteeing that armor plate strength requires.

Description

A kind of production method of the big thickness low-alloy high-tensile structural steel of 420~600mm

Technical field

The invention belongs to big thickness low-alloy high-strength steel plate production technical fields, and in particular to arrive 420~600mm of one kind The production method of big thickness low-alloy high-tensile structural steel.

Background technique

Domestic production 420-600mm thickness steel plate is able to satisfy client's service performance because of the limitation of equipment and technology at present It is required that manufacturer it is less, our factory Nanyang Chinese smelting special steel be promoted the market competitiveness, do the product that others is not bold enough to do, do others The product not gone for, company play the molding advantage that tonnage is big, internal soundness is stable, constantly developing, research and development super-thick steel plate production Process program has invented a kind of molding production work of the thickness beyond national standard range 420-600mm thick low-alloy high-strength structural steel Skill.

Summary of the invention

In view of the above-mentioned problems, the object of the present invention is to provide a kind of big thickness low-alloy high-tensile structural steels of 420-600mm Production method.

To obtain above-mentioned purpose, the technical solution adopted by the present invention is that the big thickness low-alloy high-strength of the 420~600mm Structural steel, it includes the chemical components of following mass percent: C:0.12~0.15%, Si:0.20~0.5%, Mn:1.50~ 1.60%, P :≤0.013%, S :≤0.001%, Nb:0.04~0.06%, V:0.03~0.05%, Als:0.02~ 0.03%, other is Fe and residual elements；Carbon equivalent ce V0.38~0.43；Its production method includes following process flow: molten iron (KR desulfurization) → converter (argon station) → LF refining → VD vacuum processing → molding casting (ingot shape selects 50T routine mould) → steel ingot is clear Reason (cleaning out in the 12h of ingot casting after demoulding) → steel ingot send in the 12h after cleaning out and rolls shove charge；

The pretreatment of a.KR molten iron: desulfurizing agent Mg powder or Mg powder+CaO, the molten iron that arrives at a station must take off preceding slag and take off rear slag, guarantee Liquid slag layer thickness≤20mm, molten iron guarantee molten iron S≤0.005% after KR stirring desulphurization, guarantee desulfurization cycle≤21min, Desulfurization temperature drop≤20 DEG C；

B. converter smelting: enter furnace molten iron S≤0.003%, P≤0.080%, molten iron temperature >=1270 DEG C, molten iron charge weight Error is controlled by ± 1t, and steel scrap strictly uses high-quality leftover pieces, and the 4/5 of lime total amount is added in the first batch of material；It is ore, light-burned white Marble will consider the needs of dephosphorization early period, by the content of MgO of clinker 10-12% with addition of light dolomite, open primary after blowing be added； Second batch slag charge regards process temperature and slugging situation is added, and high rifle position slugging dephosphorization as early as possible early period, oxygen presses 0.9MPa control, the After two batches of good slags of slag charge additionization, suitably drop rifle, blowing are steady；Aim carbon control [C]≤0.06%, S≤0.015%, P≤ 0.015%, [N]≤0.0020%；1640~1650 DEG C of tapping temperature, 1570~1590 DEG C of molten steel ladle temperature；

D.LF refining: slag charge is added in whole Argon in refining process, and basicity is controlled by 4.0-6.0, and one heating of refining terminates Clinker must become white or yellow, the white slag retention time >=30min, it is desirable that the finishing slag for refining end is good fluidity, viscosity conjunction Suitable foam white slag；It makes white slag and carries out secondary desulfuration, white slag retention time 20-25min is made, using high temperature, high alkalinity, the high quantity of slag The abundant deoxidation of suboxides iron slagging process, deoxidier take calcium carbide, aluminum steel or aluminum shot；

E.VD is vacuum-treated: the pressure maintaining 18-23min at vacuum degree≤67Pa, carries out Ca processing immediately after vacuum breaker, finally H content≤1.2ppm；

F. it molds: online to use preceding ingot mould temperature≤120 DEG C, the feed trumpet control suitable for reading at a distance from collector nozzle of ladle when casting System is in≤140mm, and before casting, the mode that ingot casting powder half takes straw rope to hang is hung in ingot mould, and hanging height is higher than ingot 300~400mm of mould bottom, casting process, which is opened, to be poured surely, with stream tightly, is opened and is poured temperature control at 1550-1555 DEG C, ontology is poured 18- 21min, riser gating 8-10min, molding pouring temperature are controlled according to 1560-1565 DEG C；

G. heat: heating temperature and heating time are as follows: 600-650 DEG C of steel temperature, time 4-6h, heating speed are boiled in a covered pot over a slow fire after steel loading 100-120 DEG C/h is spent, 5h is kept the temperature when temperature rises to 900 DEG C, heating rate is unlimited when temperature rises to 1000 DEG C, and temperature rises to 14-15h tapping is kept the temperature at 1300 DEG C；

H. roll: steel ingot is tapped after dephosphorization, start rolling temperature >=1080 DEG C, into steel speed 1.5m/s, adds up reduction ratio > 45%, not cool steel hot rolling, 870~930 DEG C of finishing temperature；

I. heap is cold: cold using clamp high temperature nuclear reactor after offline, the cold temperature of heap is at 600-750 DEG C, with other hot-rolled steels after heap is cold Plate covering, forbids exposed, stack cold time >=96 hour；

J. it is heat-treated: being heat-treated after steel ingot finishing in outer machine furnace, 920-930 DEG C of heating temperature, heating coefficient T= 2.4mm/min, water cooling after tapping enter 785 DEG C of coolant-temperature gage >, water cooling 300-400S, general 550-600 DEG C of red temperature.

Wherein, C the main function of steel grade be improve intensity, be all to other performance it is unfavorable, in low-alloy high-strength In steel under conditions of guaranteeing some strength, reduces carbon content and be advantageous；Si can make the strength degree of steel, yield limit and Hardness improves, and so that elongation percentage, shrinking percentage and the impact flexibility of steel is decreased but not significant, so few in Hi-Stren steel The silicon of amount can be used to improve the intensity of steel, influence on other performances little；Mn is the reinforced alloys element of steel, and Mn content increases Stabilization of austenite can be improved, reduce critical cooling rate, reinforced ferrite improves the harden ability of steel, and can make to quench Tissue breakdown rate of transformation slows down in drawing process afterwards, increases resistance to tempering, improves tempered structure stability, but too high levels will Make steel grain coarsening at high temperature, and increase steel belt roof bolt brittleness tendency, with the increase of Mn/C, the brittle transition temperature of steel is aobvious Writing reduces, and Mn/C control is advisable in 18-19, improves carbon equivalent in addition, Mn is too high, unfavorable to weldability, therefore manganese is controlled In 1.50-1.60%；P, S: belonging to harmful element, and easy segregation reduces boundary surfaces energy in crystal boundary, reduces brittle fracture stress, Ductile-brittle transition temperature is influenced, therefore the lower content the better, P≤0.018% of the present invention, S≤0.007%；Nb: in micro alloyed steel Important function with crystal grain refinement, the carbonitride for the niobium that freezing period is precipitated, advantageously forms comparatively fine isometric casting Tissue, this tiny original austenite grains can inhibit growing up for austenite grain during heating, improve austenite Recrystallization temperature can promote the raw core of enrichment of γ-α phase transformation in the precipitation of low-temperature space Nb and strain induced precipitate behavior；In the area α, Ferrite crystal grain is inhibited to grow up, meanwhile, the additional amount of Nb should be also controlled in ingredient design, because Nb is in steel with solution In the presence of the precipitation of pro-eutectoid ferrite will be postponed, and postpone time of the austenite to perlitic transformation strongly；Nitrogen in V and steel The strain-aging of steel, another party are avoided so V can substantially reduce " freedom " N content in steel with stronger affinity Face, suitable N, which is added, in V-alloyed steel can give full play to the precipitation enhancement of V, and the precipitation strength effect of V (C, N) is with nitrogen in steel The increase of content and be incremented by, maximum intensity increment can reach 300MPa, and every nitrogen content for increasing by 10 × 10-6 can in V-alloyed steel To improve intensity 6MPa, optimize the precipitation of V by v n micro alloying, fining ferrite grains have given full play to refined crystalline strengthening And precipitation enhancement, significantly improve the obdurability of steel.

Each chemical component dosage of the present invention is reasonable, under the premise of not reducing plasticity and toughness, gives full play to solution strengthening and thin The double effects that crystalline substance is strengthened, resulting high-strength high-toughness steel plate thickness 420-600mm belong to special thick molding plate；Casting process Open pour it is steady, tight with flowing, it is ensured that there is no micro-flaws, loose and empty etc., i.e. viability inside steel plate；It is not present inside steel plate The microsegregation of macroscopic view, semimacrosegregation and large area, i.e. homogenieity；Macroscopical, half macroscopical non-metallic inclusion is not present in steel plate, That is: pure property.The toughness that steel can be enhanced using normalizing, using the microalloy super-thick steel plate after water water-cooled process normalizing is entered, no Occur that phase transformation after steel plate normalizing rapidly, crystal grain is refined, and eliminates part rolling stress, is guaranteeing that steel plate is strong Degree increases the plasticity and toughness of steel plate under the premise of requiring.

Specific embodiment

The big thickness low-alloy high-tensile structural steel of 420~600mm of the present invention, it includes the changes of following mass percent It studies point:

C:0.12~0.15%, Si:0.20~0.5%, Mn:1.50~1.60%, P :≤0.013%, S :≤ 0.001%, Nb:0.04~0.06%, V:0.03~0.05%, Als:0.02~0.03%, other is Fe and residual elements；Carbon Equivalent CEV0.38~0.43；Its production method includes following process flow: molten iron (KR desulfurization) → converter (argon station) → LF refining → VD vacuum processing → molding casting (ingot shape selects 50T routine mould) → steel ingot cleaning (cleaning in the 12h of ingot casting after demoulding Finishing) → steel ingot send in the 12h after cleaning out and rolls shove charge；

The pretreatment of a.KR molten iron: desulfurizing agent Mg powder or Mg powder+CaO, the molten iron that arrives at a station must take off preceding slag and take off rear slag, guarantee Liquid slag layer thickness≤20mm, molten iron guarantee molten iron S≤0.005% after KR stirring desulphurization, guarantee desulfurization cycle≤21min, Desulfurization temperature drop≤20 DEG C；

B. converter smelting: enter furnace molten iron S≤0.003%, P≤0.080%, molten iron temperature >=1270 DEG C, molten iron charge weight Error is controlled by ± 1t, and steel scrap strictly uses high-quality leftover pieces, and the 4/5 of lime total amount is added in the first batch of material；It is ore, light-burned white Marble will consider the needs of dephosphorization early period, by the content of MgO of clinker 10-12% with addition of light dolomite, open primary after blowing be added； Second batch slag charge regards process temperature and slugging situation is added, and high rifle position slugging dephosphorization as early as possible early period, oxygen presses 0.9MPa control, the After two batches of good slags of slag charge additionization, suitably drop rifle, blowing are steady；Aim carbon control [C]≤0.06%, S≤0.015%, P≤ 0.015%, [N]≤0.0020%；1640~1650 DEG C of tapping temperature, 1570~1590 DEG C of molten steel ladle temperature；

D.LF refining: slag charge is added in whole Argon in refining process, and basicity is controlled by 4.0-6.0, and one heating of refining terminates Clinker must become white or yellow, the white slag retention time >=30min, it is desirable that the finishing slag for refining end is good fluidity, viscosity conjunction Suitable foam white slag；It makes white slag and carries out secondary desulfuration, white slag retention time 20-25min is made, using high temperature, high alkalinity, the high quantity of slag The abundant deoxidation of suboxides iron slagging process, deoxidier take calcium carbide, aluminum steel or aluminum shot；

E.VD is vacuum-treated: the pressure maintaining 18-23min at vacuum degree≤67Pa, carries out Ca processing immediately after vacuum breaker, finally H content≤1.2ppm；

F. it molds: online to use preceding ingot mould temperature≤120 DEG C, the feed trumpet control suitable for reading at a distance from collector nozzle of ladle when casting System is in≤140mm, and before casting, the mode that ingot casting powder half takes straw rope to hang is hung in ingot mould, and hanging height is higher than ingot 300~400mm of mould bottom, casting process, which is opened, to be poured surely, with stream tightly, is opened and is poured temperature control at 1550-1555 DEG C, ontology is poured 18- 21min, riser gating 8-10min, molding pouring temperature are controlled according to 1560-1565 DEG C；

G. heat: heating temperature and heating time are as follows: 600-650 DEG C of steel temperature, time 4-6h, heating speed are boiled in a covered pot over a slow fire after steel loading 100-120 DEG C/h is spent, 5h is kept the temperature when temperature rises to 900 DEG C, heating rate is unlimited when temperature rises to 1000 DEG C, and temperature rises to 14-15h tapping is kept the temperature at 1300 DEG C；

H. roll: steel ingot is tapped after dephosphorization, start rolling temperature >=1080 DEG C, into steel speed 1.5m/s, adds up reduction ratio > 45%, not cool steel hot rolling, 870~930 DEG C of finishing temperature；

I. heap is cold: cold using clamp high temperature nuclear reactor after offline, the cold temperature of heap is at 600-750 DEG C, with other hot-rolled steels after heap is cold Plate covering, forbids exposed, stack cold time >=96 hour；

J. it is heat-treated: being heat-treated after steel ingot finishing in outer machine furnace, 920-930 DEG C of heating temperature, heating coefficient T= 2.4mm/min, water cooling after tapping enter 785 DEG C of coolant-temperature gage >, water cooling 300-400S, general 550-600 DEG C of red temperature.

Wherein, C the main function of steel grade be improve intensity, be all to other performance it is unfavorable, in low-alloy high-strength In steel under conditions of guaranteeing some strength, reduces carbon content and be advantageous；Si can make the strength degree of steel, yield limit and Hardness improves, and so that elongation percentage, shrinking percentage and the impact flexibility of steel is decreased but not significant, so few in Hi-Stren steel The silicon of amount can be used to improve the intensity of steel, influence on other performances little；Mn is the reinforced alloys element of steel, and Mn content increases Stabilization of austenite can be improved, reduce critical cooling rate, reinforced ferrite improves the harden ability of steel, and can make to quench Tissue breakdown rate of transformation slows down in drawing process afterwards, increases resistance to tempering, improves tempered structure stability, but too high levels will Make steel grain coarsening at high temperature, and increase steel belt roof bolt brittleness tendency, with the increase of Mn/C, the brittle transition temperature of steel is aobvious Writing reduces, and Mn/C control is advisable in 18-19, improves carbon equivalent in addition, Mn is too high, unfavorable to weldability, therefore manganese is controlled In 1.50-1.60%；P, S: belonging to harmful element, and easy segregation reduces boundary surfaces energy in crystal boundary, reduces brittle fracture stress, Ductile-brittle transition temperature is influenced, therefore the lower content the better, P≤0.018% of the present invention, S≤0.007%；Nb: in micro alloyed steel Important function with crystal grain refinement, the carbonitride for the niobium that freezing period is precipitated, advantageously forms comparatively fine isometric casting Tissue, this tiny original austenite grains can inhibit growing up for austenite grain during heating, improve austenite Recrystallization temperature can promote the raw core of enrichment of γ-α phase transformation in the precipitation of low-temperature space Nb and strain induced precipitate behavior；In the area α, Ferrite crystal grain is inhibited to grow up, meanwhile, the additional amount of Nb should be also controlled in ingredient design, because Nb is in steel with solution In the presence of the precipitation of pro-eutectoid ferrite will be postponed, and postpone time of the austenite to perlitic transformation strongly；Nitrogen in V and steel The strain-aging of steel, another party are avoided so V can substantially reduce " freedom " N content in steel with stronger affinity Face, suitable N, which is added, in V-alloyed steel can give full play to the precipitation enhancement of V, and the precipitation strength effect of V (C, N) is with nitrogen in steel The increase of content and be incremented by, maximum intensity increment can reach 300MPa, and every nitrogen content for increasing by 10 × 10-6 can in V-alloyed steel To improve intensity 6MPa, optimize the precipitation of V by v n micro alloying, fining ferrite grains have given full play to refined crystalline strengthening And precipitation enhancement, significantly improve the obdurability of steel.

Comprehensive various elements effect, good plasticity and low-temperature flexibility have been taken into account while guaranteeing armor plate strength, has been formulated Such as the chemical component of following table:

(explanation: CEV=C+Mn/6+ (Mo+V+Cr)/5+ (Ni+Cu)/15, remaining is Fe and residual elements)

Each chemical component dosage of the present invention is reasonable, under the premise of not reducing plasticity and toughness, gives full play to solution strengthening and thin The double effects that crystalline substance is strengthened, resulting high-strength high-toughness steel plate thickness 420-600mm belong to special thick molding plate；Casting process Open pour it is steady, tight with flowing, it is ensured that there is no micro-flaws, loose and empty etc., i.e. viability inside steel plate；It is not present inside steel plate The microsegregation of macroscopic view, semimacrosegregation and large area, i.e. homogenieity；Macroscopical, half macroscopical non-metallic inclusion is not present in steel plate, That is: pure property.The toughness that steel can be enhanced using normalizing, using the microalloy super-thick steel plate after water water-cooled process normalizing is entered, no Occur that phase transformation after steel plate normalizing rapidly, crystal grain is refined, and eliminates part rolling stress, is guaranteeing that steel plate is strong Degree increases the plasticity and toughness of steel plate under the premise of requiring.

Example

By the pretreatment of KR molten iron, converter smelting, Argon processing, LF refining, VD refining, molding, heating, hot rolling, heap it is cold, Heat treatment process obtains a kind of low-temperature impact Q345E grades of special thick molding plates, it includes the chemical component of following mass percent (unit, wt%): C:0.14, Si:0.26, Mn:1.58, P:0.012, S:0.001, Als:0.021, V:0.040, Nb: 0.040, CEV:0.41, other is Fe and relict element.

Mechanical mechanics property analysis

Ingredient and mechanical mechanics property are executed by GB/T 1591-2008, and mechanical mechanics property specifically see the table below

500mm low alloy series Q345E mechanical mechanics property

Standard requirements (since thickness exceeds national standard, performance is referring to 400mm thickness performance in GB-T 1591-2008)

Produce plate property

Sample batch	Thickness/mm	Rel/MPa	Rm/MPa	A%	KV2/J(-40℃)
						1	500	341	498	27	277、232、262
2	500	342	542	22	286、232、211
						3	500	348	498	25	259、251、245

This trial production 500mm thickness Q345E, using hot rolling+normalizing rapid cooling technique, in which: yield strength control 341~ 348MPa, tensile strength control exist in 498~542MPa, elongation control in 22%-27%, -40 DEG C of V-type ballistic work controls 211~286J fully meets 500mm thickness Q345E's by Q345E maximum gauge performance requirement in GB/T 1591-2008 standard Standard.

Outer inspection and flaw detection: examining certified product rate 100%, detect a flaw by JB/T 47030 outside steel plate, closes three-level.

Claims (1)

1. the production method of the big thickness low-alloy high-tensile structural steel of 420~600mm of one kind, it is characterised in that described 420~ The big thickness low-alloy high-tensile structural steel of 600mm includes the chemical component of following mass percent: C:0.12~0.15%, Si: 0.20~0.5%, Mn:1.50~1.60%, P :≤0.013%, S :≤0.001%, Nb:0.04~0.06%, V:0.03~0.05%, Als:0.02~0.03%, other is Fe and residual elements；Carbon equivalent ce V0.38~0.43；Its production method includes following technique Process: molten iron → converter → LF refining → VD vacuum processing → molding casting → steel ingot cleaning → steel ingot is after cleaning out It is sent in 12h and rolls shove charge；Pre-process in a.KR molten iron: desulfurizing agent Mg powder or Mg powder+CaO, the molten iron that arrives at a station must take off preceding slag and take off Slag afterwards guarantees that liquid slag layer thickness≤20mm, molten iron guarantee molten iron S≤0.005% after KR stirring desulphurization, guarantees desulfurization cycle ≤ 21min, desulfurization temperature drop≤20 DEG C；

B. converter smelting: enter furnace molten iron S≤0.003%, P≤0.080%, molten iron temperature >=1270 DEG C, molten iron charge weight error is pressed ± 1t is controlled, and steel scrap strictly uses high-quality leftover pieces, and the 4/5 of lime total amount is added in the first batch of material；Ore, light dolomite are wanted The needs for considering dephosphorization early period open primary after blowing be added by the content of MgO of clinker 10-12% with addition of light dolomite；Second batch Slag charge regards process temperature and slugging situation is added, high rifle position slugging dephosphorization as early as possible early period, and oxygen presses 0.9 MPa control, second batch After the good slag of slag charge additionization, suitably drop rifle, blowing are steady；Aim carbon control [C]≤0.06%, S≤0.015%, P≤ 0.015%,[N] ≤0.0020%；1640~1650 DEG C of tapping temperature, 1570~1590 DEG C of molten steel ladle temperature；

D.LF refining: slag charge is added in whole Argon in refining process, and basicity is controlled by 4.0-6.0, and one heating of refining terminates clinker It must become white or yellow, the white slag retention time >=30min, it is desirable that it is suitable for good fluidity, viscosity to refine the finishing slag of end Foam white slag；It makes white slag and carries out secondary desulfuration, white slag retention time 20-25min is made, using high temperature, high alkalinity, high quantity of slag hypoxemia Change the abundant deoxidation of iron slagging process, deoxidier takes calcium carbide, aluminum steel or aluminum shot；

E.VD is vacuum-treated: the pressure maintaining 18-23min at vacuum degree≤67Pa, carries out Ca processing immediately after vacuum breaker, final H contains Amount≤1.2ppm；

F. mold: online to use preceding ingot mould temperature≤120 DEG C, the feed trumpet distance controlling suitable for reading with collector nozzle of ladle exists when casting ≤ 140mm, before casting, the mode that ingot casting powder half takes straw rope to hang is hung in ingot mould, and hanging height is higher than ingot mould bottom 300~400mm of portion, casting process, which is opened, to be poured surely, with stream tightly, is opened and is poured temperature control at 1550-1555 DEG C, ontology is poured 18- 21min, riser gating 8-10min, molding pouring temperature are controlled according to 1560-1565 DEG C；

G. heat: heating temperature and heating time are as follows: 600-650 DEG C of steel temperature, time 4-6h, heating rate are boiled in a covered pot over a slow fire after steel loading 100-120 DEG C/h, 5h is kept the temperature when temperature rises to 900 DEG C, heating rate is unlimited when temperature rises to 1000 DEG C, and temperature rises to 1300 DEG C when heat preservation 14-15h tapping；

H. roll: steel ingot is tapped after dephosphorization, start rolling temperature >=1080 DEG C, into steel speed 1.5m/s, adds up reduction ratio > 45%, no Cool steel hot rolling, 870~930 DEG C of finishing temperature；

I. heap is cold: cold using clamp high temperature nuclear reactor after offline, the cold temperature of heap is covered after heap is cold with other hot rolled steel plates at 600-750 DEG C Lid, forbids exposed, stack cold time >=96 hour；

J. it is heat-treated: being heat-treated after steel ingot finishing in outer machine furnace, 920-930 DEG C of heating temperature, heating coefficient T=2.4mm/ Min, water cooling after tapping enter 785 DEG C of coolant-temperature gage >, water cooling 300-400S, general 550-600 DEG C of red temperature.