CN105603310A - Low-yield-ratio Q420GJ steel plate for buildings and production method of low-yield-ratio Q420GJ steel plate for buildings - Google Patents

Abstract

The invention belongs to the technical field of construction steel and discloses a low-yield-ratio Q420GJ steel plate for buildings and a production method of the low-yield-ratio Q420GJ steel plate for the buildings. The low-yield-ratio Q420GJ steel plate is chemically composed of, by weight, 0.06-0.08% of C, 0.35-0.45% of Si, 1.45-1.55% of Mn, P, S, 0.035-0.045% of Nb, 0.05-0.06% of V, 0.01-0.02% of Ti, 0.020-0.040% of Als and the balance Fe and impurities, wherein the weight percentage of the P is smaller than or equal to 0.015%, and the weight percentage of the S is smaller than or equal to 0.010%. The production method includes steps: step one, smelting; step two, continuous casting; step three, heating; step four, rolling and cooling; step five, finishing and flaw detection. Production cycle is shortened, cost is reduced, and finished steel plate products have excellent performances and can be applied to fields of high-rises, super high-rises, factories, mines, towers, large-span and large-scale structural engineering construction and the like.

Description

A kind of low yield strength ratio Q420GJ steel plate for building and production method thereof

Technical field

The present invention is specifically related to a kind of low yield strength ratio Q420GJ steel plate for building and production method thereof, belongs to and buildsBuild and use steel technical field.

Background technology

Steel building has superior shock resistance, environmental protection, quick construction is convenient, space availability ratio is high,The unique novelty of design model waits many advantages, has now become the developing direction of building structure in the world. For buildingSteel plate is mainly used in skyscraper, high-rise building, large span stadiums, airport, railway station, meetingThe stressed complexity such as exhibition center, steel-structure factory building and power transmission and transformation high tower, the heavy construction that reliability requirement is higherEngineering, requires steel plate just to have low yield strength ratio, good toughness and plasticity, narrow yield point fluctuation range and lessThickness effect, anti-lamellar tearing ability (thickness directional properties), good welding performance, good extensionPerformance and low-Cycle Fatigue Characteristics, have certain fire resistance.

Current domestic same level construction(al)steel patent and document have:

Chinese patent CN1O1343685A discloses that " a kind of yield strength is that 420MPa grade high-strength is for buildingHeat-Treatment of Steel method ", composition quality percentage is: C0.12～0.18, Si0.3～0.4%, Mn1.4～1.5、Nb0.03～0.05、V0.05～0.10、Ti0.01～0.02、P＜0.015、S＜0.005、All the other are Fe and inevitable impurity. Continuous casting billet is controlled cold method and is produced in the wrong after controlled rolling and controlled cooling, normalizingTake intensity at 420-440MPa, yield tensile ratio < 0.75 ,-60 DEG C of thick construction(al)steels of 45mm that ballistic work reaches 120JPlate. The method and be confined to 45mm steel plate.

Chinese patent CN101260495A discloses that " a kind of 590MPa level low yield ratio low carbon equivalent weight is for buildingThe manufacture method of steel plate ", chemical component weight percentage is: C:0.15, Si:0.37, Mn:1.41,P0.014, S≤0.005, Nb:0.031, V:0.081, Alt0.029, all the other are Fe and inevitableImpurity. Adopt two-stage control rolling and control cooling after, then quench through 760-810 DEG C of two-phase section andAfter 500 DEG C of tempering, obtain the heterogeneous structure that metallographic structure is tempered sorbite and granular ferrite, tensile strengthReach the construction(al)steel of 590MPa level. This invention adopts two-phase section to quench and tempering process, is subject to production equipment limitSystem, has extended the production cycle, has increased cost simultaneously.

Document " development and the application of Q420GJC steel for skyscraper " has been discussed the trial-production of Wuhan Iron and Steel Plant Q420GJC,Chemical composition is C:0.10～0.18%, Si:0.20～0.45%, and Mn:1.30～1.60%, P≤0.015％，S≤0.010％，Nb≤0.06，V≤0.07，,Ti≤0.03，Als：0.015～0.050％，Surplus is Fe and inevitable impurity. Adopt molten iron pretreatment, converter smelting, LF refining, vacuum placeReason, continuous casting, rolling, method cooling, normalizing are produced Q420GJC construction(al)steel. The method deficiencyPlace needs normalized treatment, has extended the production cycle, has increased cost simultaneously.

Summary of the invention

Therefore, the object of the invention is to provide a kind of low yield strength ratio, has good plasticity and toughness, Yi JiyouGood anti-lamellar tearing performance, and production cost is lower, is not subject to produce equipment restriction, and the process-cycle is short, specificationControlled low yield strength ratio Q420GJ steel plate for building, yield strength >=420MPa, yield tensile ratio is less than 0.79,-40 DEG C of impact of collision merits are greater than 34J, and its chemical composition is by weight percentage: C:0.06～0.08%,Si:0.35～0.45％、Mn：1.45～1.55％、P≤0.015％、S≤0.010％、Nb：0.035～0.045％、V:0.05～0.06%, Ti:0.01～0.02%, Als:0.020～0.040%, all the other are Fe and can notThe impurity element of avoiding.

The present invention also provides the above-mentioned low yield strength ratio Q420GJ processing method of steel plate for building, described sideMethod comprises the following steps:

Step 1 is smelted:

Adopt the process pretreated molten iron of desulfurization and high-quality steel scrap as raw material, bottom-blowing of converter adopts omnidistance ArgonPattern, terminal hit at first time, causes molten steel nitrogen pick-up to reduce because re-blowing. The further deoxidation of LF ladle refining furnace,Desulfurization, remove be mingled with, adjusting component and temperature, strictly control Argon intensity,, mid-term strong according to early stagePrinciple strong, that the later stage is weak is formulated Argon curve, in ensureing deoxidation, dark desulfurization, alloying, subtractsSecondary oxidation and the nitrogen pick-up of few refining process. RH operation adopts the dark degasification technique of circulation, is ensureing liquid steel temperatureUnder stable prerequisite, significantly reduce the gas contents such as hydrogen, oxygen, nitrogen, reduce the unfavorable shadow of pernicious gas to steelRing, the percentage by weight that finally obtains molten steel be C:0.06～0.08%, Si:0.35～0.45%, Mn:1.45～1.55％、P≤0.015％、S≤0.010％、Nb：0.035～0.045％、V：0.05～0.06％、Ti：0.01～0.02%, Als:0.020～0.040%, surplus is Fe and inevitable impurity.

Step 2 continuous casting:

Step 3 heating;

In heating furnace, to plate slab heating, fully ensure plate slab heating-up temperature and soaking time. Add hot temperatureDegree is controlled at 1180 DEG C-1220 DEG C, and the heat time is controlled at 200-240min, ensures the abundant of alloying elementSolid solution, board briquette is even.

Step 4 rolling and cooling:

Rolling adopts two-stage control rolling, i.e. austenite recrystallization district controlled rolling (conventionally claiming rough rolling step)With austenite non-recrystallization zone controlled rolling (conventionally claiming the finish rolling stage). When roughing, strengthen pass deformation, openRolling temperature is 1160～1200 DEG C, and the relative reduction ratio of single pass has at least two passages to be controlled at above more than 20%,The each pass deformation of strict control when finish rolling, finish rolling start rolling temperature≤920 DEG C, open rolling thickness is 1.3-3.0Times finished product thickness, last percentage pass reduction > 10%. Finishing temperature 870-880 DEG C, rolls rear steel plate and adopts control coldBut, final cooling temperature 570-600 DEG C, metallographic structure is the tiny and uniform ferrite and pearlite of crystal grain.

Step 5 finishing and flaw detection.

Further, step 2 is specially:

Conticaster is straight circular-arc type continuous casting machine, employing solidification end dynamic soft-reduction, electromagnetic agitation and optimizationDynamic secondary cooling technology, by constant temperature, permanent pulling rate technique (0.9-1.1m/min), low overheat casting(15-25 DEG C), alleviates the defects such as continuous casting billet center segregation, center porosity, crackle, oscillation mark, final productionGo out the thick high-quality continuous casting steel billet of 250mm or 300mm.

Further, step 5 is specially:

The cooling rear line flaw detection that all carries out of hot rolled steel plate, after flaw detection, steel plate keeps dry, for can not be onlineThe steel plate flaw detection of rolling off the production line of flaw detection, carries out and judges according to the regulation of non-destructive testing standard JB/T4730.3, closesLattice rank is I level.

Beneficial effect of the present invention is: a kind of low yield strength ratio Q420GJ of the present invention steel plate for building,By rational Design of Chemical Composition, make finished steel plate obtain better mechanical property, production of the present inventionMethod, directly adopts normalizing rolling, without off-line normalizing heat treatment, has shortened the production cycle, also falls simultaneouslyLow production cost, finished steel plate of the present invention has excellent comprehensive mechanical performance. Can be applicable to high level, superThe fields such as high level, factories and miness, pylon, large span and large scale structure engineering construction.

Brief description of the drawings

Fig. 1 is the flow chart of the production method of a kind of low yield strength ratio Q420GJ of the present invention steel plate for building;

Fig. 2 is the metallographic structure figure at embodiment 3 steel plate 1/2 thickness places.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described:

Low yield strength ratio Q420GJ of the present invention steel plate for building, yield strength >=420MPa, yield tensile ratio is littleBe greater than 34J in 0.79,0 DEG C of impact of collision merit, chemical composition is by weight percentage: C:0.06～0.08%,Si:0.35～0.45％、Mn：1.45～1.55％、P≤0.015％、S≤0.010％、Nb：0.035～0.045％、V:0.05～0.06%, Ti:0.01～0.02%, Als:0.020～0.040%, all the other are Fe and impurity.The flow process of steel plate processing method as shown in Figure 1.

Embodiment 1

Raw material molten iron is through Deep Desulphurization of Hot Metal, converter top and bottom blowing, ladle argon-blown, LF external refining, RHApplication of vacuum and continuous casting process obtain the 250mm heavy slab of the percentage of chemical component weight shown in table 1. Slab1200 DEG C of heating-up temperatures, heat time 220min, 1180 DEG C of first stage start rolling temperatures, single pass is relativeReduction ratio has at least two passages to be controlled at above more than 20%, in the time that rolled piece thickness is 60mm, on roller-way, treatsTemperature, to 910 DEG C, is carried out second stage rolling subsequently, and finishing temperature is 870 DEG C, and finished steel plate thickness is 20mm.After rolling finishes, steel plate enters cooling (ACC) equipment of acceleration, is cooled to 600 DEG C, heat with the speed of 5 DEG C/sAfter rectifying, cold bed is cooling. Carry out afterwards line flaw detection and finishing processing, finally can obtain steel plate finished product.

Embodiment 2

Embodiment is with embodiment 1, and wherein heating-up temperature is 1200 DEG C, heat time 213min, the first rankThe start rolling temperature of section rolling is 1180 DEG C, and the start rolling temperature of second stage rolling is 900 DEG C, and rolled piece thickness is125mm, finishing temperature is 876 DEG C, finished steel plate thickness is 50mm. Steel plate cooling velocity is 8 DEG C/s, eventuallyCold temperature is 580 DEG C. It is cooling that heat is rectified rear cold bed. Detect a flaw afterwards and finishing processing, finally can obtainSteel plate finished product.

Embodiment 3

Embodiment, with embodiment 1, adopts 300mm heavy slab, and wherein heating-up temperature is 1200 DEG C, heatingTime 230min, the start rolling temperature of first stage rolling is 1185 DEG C, the start rolling temperature of second stage rolling is890 DEG C, rolled piece thickness is 128mm, and finishing temperature is 880 DEG C, and finished steel plate thickness is 80mm. Steel plate is coldBut speed is 8 DEG C/s, and final cooling temperature is 570 DEG C. It is cooling that heat is rectified rear cold bed. Detect a flaw afterwards and finishing placeReason, finally can obtain steel plate finished product. The metallographic structure figure at embodiment 3 steel plate 1/2 thickness places is as Fig. 2 instituteShow, metallographic structure is the tiny and uniform ferrite+pearlitic structrure of crystal grain.

The chemical composition (wt%) of embodiment 1～3 is as shown in table 1.

Table 1

Embodiment	C	Si	Mn	P	S	Nb	V	Ti	Als
										1	0.06	0.35	1.45	0.006	0.003	0.035	0.050	0.010	0.020
2	0.07	0.40	1.50	0.010	0.005	0.040	0.055	0.015	0.030
										3	0.08	0.45	1.55	0.012	0.006	0.045	0.060	0.020	0.040

The steel plate of embodiment 1～3 is carried out to conventional mechanical property, Z-direction tensile property, impact property inspection,The results are shown in Table 2.

Table 2

As can be seen from Table 2, steel plate normal tensile property of the present invention meets this rank skyscraper steel plate completely and makesWith requiring, and have larger surplus capacity ,-40 DEG C of impact of collision merits are much larger than the 34J of standard-required, Z-directionThe stretching contraction percentage of area, more than 47%, meets Z35 steel plate rank completely, illustrates that steel plate of the present invention hasGood anti-lamellar tearing ability. Steel plate yield tensile ratio≤0.79, much smaller than 0.85 of standard-required, shows steelPlate has excellent shock resistance, and steel plate inspection I level is qualified, and in a word, steel plate of the present invention has excellent combiningClose mechanical performance. Can be applicable to high level, Super High, factories and miness, pylon, large span and large scale structure engineeringDeng.

The above is the preferred embodiment of the present invention, it should be pointed out that common for the artTechnical staff, is not departing under the prerequisite of principle of the present invention, can also make some improvement andRetouching, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (4)

1. a low yield strength ratio Q420GJ steel plate for building, yield strength >=420MPa, yield tensile ratio is less than0.79 ,-40 DEG C of impact of collision merits are greater than 34J, it is characterized in that, described low yield strength ratio Q420GJ is for buildingThe chemical composition of steel plate is by weight percentage: C:0.06～0.08%, Si:0.35～0.45%, Mn:1.45～1.55％、P≤0.015％、S≤0.010％、Nb：0.035～0.045％、V：0.05～0.06％、Ti：0.01～0.02%, Als:0.020～0.040%, all the other are Fe and impurity.

2. a production method for low yield strength ratio Q420GJ as claimed in claim 1 steel plate for building,It is characterized in that, said method comprising the steps of:

Step 1 is smelted:

Adopt the process pretreated molten iron of desulfurization and high-quality steel scrap as raw material, bottom-blowing of converter adopts omnidistance ArgonPattern, the further deoxidation of LF ladle refining furnace, desulfurization, removal are mingled with, adjusting component and temperature, according toEarly stage is strong, mid-term is strong, principle that the later stage is weak is formulated Argon curve, and RH operation adopts the dark degassed work of circulationSkill, the percentage by weight that finally obtains molten steel be C:0.06～0.08%, Si:0.35～0.45%, Mn:1.45～1.55％、P≤0.015％、S≤0.010％、Nb：0.035～0.045％、V：0.05～0.06％、Ti：0.01～0.02%, Als:0.020～0.040%, all the other are Fe and impurity;

Step 2 continuous casting:

Step 3 heating;

In heating furnace, to plate slab heating, heating and temperature control is at 1180 DEG C-1220 DEG C, and the heat time is controlledBuilt in 200-240min;

Step 4 rolling and cooling:

Rolling adopts two-stage control rolling, the i.e. non-recrystallization of the controlled rolling of austenite recrystallization district and austeniteDistrict's controlled rolling, when roughing, start rolling temperature is 1160～1200 DEG C, the relative reduction ratio of single pass has twice at leastInferior above being controlled at more than 20%, the each pass deformation of strict control when finish rolling, finish rolling start rolling temperature≤920 DEG C,Open rolling thickness is 1.3-3.0 times of finished product thickness, has twice reduction ratio at least > more than 20%, extreme trace is depressedRate > 10%, finishing temperature 870-880 DEG C, rolls rear steel plate and adopts control cooling, final cooling temperature 570-600 DEG C,Obtain the tiny and uniform ferrite+pearlitic structrure of crystal grain;

Step 5 finishing and flaw detection.

3. the production method of low yield strength ratio Q420GJ as claimed in claim 2 steel plate for building, its spyLevy and be, in described method, step 2 is specially:

Conticaster is straight circular-arc type continuous casting machine, employing solidification end dynamic soft-reduction, electromagnetic agitation and optimizationDynamic secondary cooling technology, by constant temperature, permanent pulling rate technique, pulling rate 0.9-1.1m/min, final production goes out 250mmOr the thick high-quality continuous casting steel billet of 300mm.

4. the production method of low yield strength ratio Q420GJ as claimed in claim 2 steel plate for building, its spyLevy and be, in described method, step 5 is specially:

The cooling rear line flaw detection that all carries out of hot rolled steel plate, after flaw detection, steel plate keeps dry, for can not be onlineThe steel plate flaw detection of rolling off the production line of flaw detection, carries out and judges according to the regulation of non-destructive testing standard JB/T4730.3, closesLattice rank is I level.