CN103422021B - Low-yield-ratio structural steel with yield ratio equal to or larger than 550MPa and manufacturing method thereof - Google Patents
Low-yield-ratio structural steel with yield ratio equal to or larger than 550MPa and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses low-yield-ratio structural steel with a yield ratio equal to or larger than 550MPa. The low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa comprises, by weight, 0.03-0.10% of C, 0.30-0.60% of Si, 1.40-2.00% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.10-0.50% of Mo, 0.10-0.40% of Cr, 0.040-0.10% of Nb, 0.008-0.025% of Ti, 0.015-0.055% of Als, 0.0010-0.0080% of Ca, 0.0005-0.0050% of Mg, 10-30*10<-4>% of N, and 5-25*10<-4>% of O. A manufacturing method of the low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa comprises the steps of carrying out smelting and continuous casting to form a blank, heating the casting blank and carrying out heat insulation on the casting blank, rough rolling, finish rolling, and carrying out relaxation slow cooling on a steel plate. The mechanical properties of the low-yield-ratio structural steel are that RP0.2>=550Mpa, Rm>=700MPa, ductility A>=25%, -20 DEG C KV2>=200J, and RP0.2 / Rm <= 0.80. According to the low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa and the manufacturing method thereof, preheating is not needed after welding or the preheating temperature is not larger than 50DEG C, heat treatment is not needed after welding, and therefore welding efficiency is greatly improved; the cold and hot machining performance is good, and resistance to large deformation is achieved; cost is low, and the manufacturing processes are simplified.
Description
Technical field
The present invention relates to a kind of Kind of Steels Used in Engineering Structures and production method thereof, belong to low yield strength ratio structural steel and the production method thereof of yield strength >=550MPa particularly.
Background technology
Traditional high-strength steel generally takes the mode of quenching+tempering to produce, while intensity improves, yield tensile ratio is also improving constantly, especially when tensile strength reaches more than 600MPa, its yield tensile ratio just reaches more than 0.90, plasticity index also drops to less than 20%, based on the consideration of secure context, bridge, pipeline, construction work steel all limits to some extent to the yield tensile ratio of steel plate, especially Highrise buildings and public heavy construction must have good shock resistance, namely to the yield tensile ratio (less than 0.85) and plasticity index (more than 20%) that use steel, there is strict restriction, obviously, the yield tensile ratio that tradition high-strength steel is higher and lower unit elongation limit this kind of steel applying in such engineering.And in recent years, the steel plate once having bibliographical information to adopt two-phase region quenching+tempering mode to produce meets the technical requirements of such engineering, its metallographic structure type is ferrite+martensite, utilizes the rational proportion of soft phase ferritic structure to reach the object of low yield strength ratio.Its deficiency existed is that process of thermal treatment window is narrower, wayward in actual production, even needs to carry out repeatedly heat treatment process, substantially prolongs the technological process of production, add production cost, be unfavorable for applying.
Through retrieval: Chinese Patent Application No. is the patent documentation of 200910061106.1, disclose a kind of high strength low yield ratio welding structure steel and production method thereof, its deficiency is must containing expensive alloying elements such as higher Cr, Ni, and need to carry out stress relief tempering process, also requirement is not done to the unit elongation of steel plate.
Chinese Patent Application No. is the patent documentation of 201010599469.3, disclose a kind of 800MPa level low yield strength ratio structural steel and iron and production method thereof, this steel must containing more Cu, Ni element, and cost of alloy is high, and steel plate must carry out temper, adds explained hereafter cost.
The patent No. is the patent documentation of EP20010930007, disclose " THICK STEEL PLATE BEING EXCELLENT IN CTOD CHARACTERISTIC IN WELDING HEAT AFFECTED ZONE AND HAVING YIELD STRENGTH OF 460MPa OR MORE ", this invention steel adopts direct quenching+tempering or TMCP operational path to produce, but the steel plate adopting direct quenching+tempering to produce only has part yield strength at more than 550MPa, and yield tensile ratio is between 0.84-0.90, do not have anti-seismic performance, production technique cost is also higher; Adopt the steel plate yield strength of TMCP production all at below 550MPa, intensity rank is lower, and its yield tensile ratio is between 0.79-0.88, and anti-seismic performance is poor.The steel plate of above-mentioned two kinds of explained hereafter all limits the oxide particle number of Mg and Al of unit surface, controls difficulty comparatively large, is unfavorable for promoting at each metallurgy industry producing.
Summary of the invention
The object of the invention is to the deficiency overcoming prior art existence, a kind of R is provided
p0.2>=690MPa, Rm>=800MPa, unit elongation A>=22% ,-20 DEG C of KV
2>=180J, R
p0.2/ Rm≤0.80, and production process is simple, cost is low, is easy to low yield strength ratio structural steel and the production method thereof of the yield strength>=690MPa of scale operation.
Realize the technical measures of above-mentioned purpose:
A low yield strength ratio structural steel of yield strength>=550MPa, its component and weight percent content are: C:0.03-0.10%, Si:0.30-0.60%, Mn:1.40-2.00%, P≤0.010%, S≤0.005%, Mo:0.10-0.50%, Cr:0.10-0.40%, Nb:0.040-0.10%, Ti:0.008-0.025%, Als:0.015-0.055%, Ca:0.0010-0.0080%, Mg:0.0005-0.0050%, N:10-30 × 10
-4%, O:5-25 × 10
-4%, all the other are Fe and inevitable impurity; Meet: Ca/S=1.2-2.8,2Cr+Mn=2.00-2.60%, Als/N=12-20, Pcm=C+Si/30+Mn+Cu+Cr simultaneously)/20+Ni/60+Mo/15+V/10+5B≤0.25%; Mechanical property is: R
p0.2>=550MPa, Rm>=700MPa, unit elongation A>=25% ,-20 DEG C of KV
2>=200J, R
p0.2/ Rm≤0.80.
It is: being added with weight percent content is: V≤0.10%, Ni≤0.30%, B≤0.0020%.
Produce the method for the low yield strength ratio structural steel of a kind of yield strength >=550MPa, it walks Zou:
1) smelt also continuous casting and become base;
2) heat strand and be incubated, heating and temperature control is at 1180 ~ 1220 DEG C;
3) carry out roughing: 1160-1180 DEG C, total reduction is 60-80%, and roughing end temp is 1040-1080 DEG C;
4) finish rolling is carried out: control finishing temperature at 800 ~ 860 DEG C, total reduction is 70 ~ 80%, and rolling pass is in 6 ~ 8 roads;
5) carry out relaxation slow cooling to steel plate, speed of cooling is 2-5 DEG C/s, and cooling termination temperature is 740-820 DEG C; Carry out section cooling subsequently, speed of cooling is 10-20 DEG C/s, and cooling termination temperature is 300-500 DEG C; Last air cooling is to room temperature.
It is characterized in that: the upper and lower water of section cooling is than being 0.50-0.85, and roller speed is 0.5-1.4m/s.
Mechanism and the effect of chemical composition and main technique in the present invention are below described in detail in detail:
C content of the present invention is selected strongly to improve the intensity of steel at 0.03 ~ 0.10%, C by gap displacement solution strengthening, is guarantee one of requisite element of hardness of steel.C belongs to and expands austenite phase field element, when C content lower than 0.03% time,
Transformation temperature obviously promotes, and causes TMCP narrow process window, and causes the raising of steel strength deficiency and yield tensile ratio.When C content higher than 0.10% time, the welding cold crack sensitivity coefficient of the tendency of carbon segregation, Gang Zhong M-A island amount and steel increases, thus worsens plasticity and toughness and the welding property of steel, affects the cold and hot working performance of steel.Therefore C content is defined as 0.03 ~ 0.10%.
It is solution strengthening and deoxidation that Si content of the present invention is selected at the Main Function of 0.3 ~ 0.60%, Si in steel.The element of stronger bonding force is had owing to adding Mg, Ca, Als etc. and [O], therefore, Si mainly solution strengthening effect in steel of the present invention.When Si content lower than 0.3% time, its solution strengthening effect is not obvious, and especially tensile strength can not meet the demands, cause yield tensile ratio to raise simultaneously, when Si content higher than 0.60% time, will the ratio on MA island, welded heat affecting zone be increased, worsen base material and HAZ low-temperature impact toughness and ductility.Therefore Si content is defined as 0.3-0.60%.
It is guarantee steel obdurability and the indispensable element of welded heat affecting zone performance that Mn content of the present invention is selected at 1.40 ~ 2.0%, Mn.Another vital role of Mn is the forming core core that the tiny sulfide formed with Ca, S can be used as acicular ferrite, when Mn content lower than 1.4% time, these limited use; When Mn content higher than 2.0% time, then can form the sulfide inclusion of more large size complexity, reduce the low temperature fracture toughness of steel and the low-temperature flexibility of welded heat affecting zone, worsen the welding property of steel.Meanwhile, Mn expands austenite phase field, reduces A
c1and A
c3transformation temperature, when Mn content higher than 3.50% time, suppress ferritic transformation, after proper temperature starts fast cooling, will cause ferritic transformation amount seldom, the yield strength of steel will sharply raise, and be unfavorable for that yield tensile ratio controls.Therefore Mn content is defined as 1.4 ~ 2.0%.
P≤0.010% of the present invention, S≤0.005%, P, S are the detrimental impurity elements in steel.High P easily causes segregation,
Affect the homogeneity of structure of steel, reduce the toughness of steel; S and Mn easily forms MnS and is mingled with, very unfavorable to low-temperature flexibility.
Mo content of the present invention is selected in 0.10-0.50%, the effect of Mo in steel mainly solution strengthening effect, and a small amount of Mo separates out with the form of carbide, improves the intensity of steel further.Mo is stabilization of austenite element, and promote that the bainite and martensite of high density dislocation substructure is formed, utilize build up to improve the intensity of steel, appropriate Mo can also reduce the yield tensile ratio of steel, improves the anti-seismic performance of steel.Want to reach above-mentioned effect, Mo content must not be less than 0.10%, but Mo is precious alloy
Element, the Mo more than 0.50% not only easily obtains a large amount of martensitic stuctures in quick process of cooling, also easily obtains martensitic stucture, be degrading the over-all properties of base material and heat affected zone in welding cooling.
Cr content of the present invention is selected in 0.1-0.4%, Cr is the element effectively improving armor plate strength, also be the element improving steel plate hardening capacity, ferritic phase apparition is moved to right, the cooling rate widening bainitic transformation is interval, promotes the formation of middle temperature transformation tissue, simultaneously, when Cr and Ni compound is added, more contribute to the hardening capacity and the weather resistance that improve steel.But when Cr content is more than 0.40%, then significantly can reduce the toughness of base material and heat affected zone.
Ni content of the present invention selects at≤0.30%, Ni little to steel strength contribution, but obviously can improve steel
Low-temperature flexibility, significantly improves the low-temperature flexibility of steel.Particularly high to solution strengthening element content such as Cr steel, its effect improving low-temperature flexibility is just more obvious.Ni amount is too high, and except increase production cost, surface of steel plate easily produces the iron scale being difficult to come off.
Nb content of the present invention is selected 0.04 ~ 0.10%, Nb is a kind of carbide, there is strong Grain refinement, austenite recrystallization temperature can be significantly improved, expand rolling technology scope, make invention steel abundant thinning microstructure in II stage rolling process, guarantee that steel have good obdurability coupling.In the operation of rolling, the carbonitride particle that Nb is formed in steel, can effectively suppress growing up of austenite crystal, improves obdurability and ductility.In steel of the present invention, when Nb content lower than 0.04% time, cause yield strength not enough, when Nb content higher than 0.10% time, the appearance because of MA island tissue in welding process of cooling is worsened its performance by welded heat affecting zone.
V≤0.10% of the present invention, V is a kind of quite strong carbide forming element, and appropriate V has obvious precipitation hardening effect.When Nb and V compound adds fashionable, obviously can improve the generation of transverse crack phenomenon, significantly improve the recrystallization temperature of steel.But V too high levels, precipitation strength effect is remarkable, but base material and heat affected zone degraded toughness.
Ti of the present invention selects 0.008 ~ 0.025%, Ti is also a kind of strong carbonitride-forming elements, Mg, Als superfine oxide particle separates out tiny TiN, Ti(CN) or Nb the composite carbon nitride of Ti, the effective dimensions of these particles is below 1.0 μm, effectively can stop Austenite Grain Growth in heating and welding process, make grain refining, improve the low-temperature flexibility of steel.Ti and Nb adds simultaneously, can improve steel austenite recrystallization temperature further, expand rolling technology scope.But when Ti is greater than 0.025%, the carbonitride particle size of the Ti separated out will reach several even tens μm of orders of magnitude, cause the inadequate refinement of crystal grain, worsen the toughness of base material and welded heat affecting zone, when Ti is less than 0.008%, unit surface endoparticle quantity not sufficient, do not have grain refinement effect, therefore Ti is defined as 0.008 ~ 0.025%.
Als content of the present invention is selected usually to add in steel as deoxidant element at 0.015 ~ 0.055%, Als.Als N in steel is combined and forms AlN particle, is improved intensity and the low-temperature flexibility of steel by Grain Refinement Effect.Als in the present invention
Another vital role and Mg and [O] combine and form fine oxide particle, Mn sulfide depends on these oxide particles and separates out, the tiny precipitate of this complexity can be used as again grain boundary ferrite and the ferritic forming core core of lath, thus refinement base material and HAZ tissue.If Als content is lower than 0.010%, TiN amounts of particles and the oxide particle deficiency as forming core core is formed in steel, worsen base material and HAZ impelling strength, if Als content higher than 0.055% time, the oxide inclusion of Al in steel is easily caused to increase, size is comparatively large, reduces purity and the plasticity and toughness of steel, worsens welding heat affected impelling strength.
Ca of the present invention is deoxidant element, and be also desulfurization element, its content controls 0.001 ~ 0.008%.Add appropriate Ca in steel by Sulfide inclusion nodularization, be conducive to the low-temperature flexibility and the HAZ toughness that improve base material.In order to improve its deoxidization desulfuration effect, improve substrate mass and heat affected zone performance, Ca content should be not less than 0.001%; When Ca content is more than 0.008%, then can form many large-scale oxide compounds containing Ca and sulfide mixing is mingled with, be unfavorable for the impelling strength of base material and heat affected zone.
Mg of the present invention controls 0.0005 ~ 0.005%.Mg is a very important element in product of the present invention.Mg and Als and [O] combine and form tiny oxide particle, and TiN separates out tiny complex granule with it for forming core core depends on these oxide surfaces, refinement base material and heat affected zone tissue; As transformation core and therefore Mg can also accelerate MnS inclusion on these oxide compounds, separate out complicated particle, refinement base material and heat affected zone tissue.When Mg content in steel lower than 0.0005% time, in these oxide compound complex granules, Mg content is lower, MnS is difficult to separate out on the oxide particle of Mg, also it changes core effect as Intragranular Acicular Ferrite is just lost, unit area oxide amounts of particles simultaneously as the forming core core of TiN is not enough, and the low-temperature flexibility of base material and HAZ toughness can not get ensureing.When Mg content is 0.005%, the effect of Mg reaches capacity, even if the content of Mg is more than 0.005%, forms the large size complex inclusion that Mg content is high, worsens the impelling strength of base material and heat affected zone.
B of the present invention selects interpolation to be no more than 0.002%, the effect of B mainly improves the hardening capacity of steel, postpones austenite and changes to ferrite and pearlite, when B content is more than 0.002%, low-temperature impact toughness will be caused to decline and instability, worsen the welding property of steel simultaneously.
N content of the present invention is selected 10 ~ 30 × 10
-4in %, N and steel, the element such as Nb, Ti, Al, V, C forms nitride or carbonitride, is the important element making steel mother metal tissue and weld structure grain refining.If N content is lower than 10 × 10
-4%, then in N and steel, Ti, Als form unit nitride particles quantity not sufficient, can not effectively refinement base material and weld structure.When N content is higher than 30 × 10
-4during %, in steel solid solution N measure increase, to base material and welded heat affecting zone performance unfavorable, be also unfavorable for the surface quality of steel billet.
O content of the present invention is selected 5 ~ 25 × 10
-4%, generally, O belongs to obnoxious flavour in steel, for guaranteeing the total amount of oxide inclusion in purity of steel and steel, O content strictly need be limited in lower level.But when O content is lower than 5 × 10
-4during %, then in steel, unit surface is not enough as the fine oxide amounts of particles of Mg, Als of forming core core.For avoiding occurring too much oxide-based large size complex inclusion in steel, in steel, O upper content limit is limited in 25 × 10
-4within %.
Above-mentioned chemical composition also must meet simultaneously: Ca/S=1.2-2.8, Als/N=12-20,2Cr+Mn=2.0-2.6%, Pcm=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B≤0.25%.
In steel of the present invention, as Ca/S < 1.2, the rotten spheroidization of Ca to Sulfide inclusion is not obvious, as Ca/S > 2.8, by forming many large-scale oxide compounds containing Ca and sulfide mixing inclusion in steel, be unfavorable for the performance of steel;
As Als/N < 12, unit surface AlN amounts of particles is not enough, and its Grain refinement is not obvious, as Als/N > 20, containing large size aluminate in steel, the performance of base material and heat affected zone is all had a negative impact;
As 2Cr+Mn < 2.0%, cause hardness of steel not enough, as 2Cr+Mn > 2.6%, worsen base material and heat affected zone; Steel of the present invention belongs to high-strong toughness height ductile steel, and for guaranteeing intensity and the welding property of steel, Pcm value must be less than or equal to 0.25%.
The reason that main technologic parameters controls:
For making the abundant austenitizing of strand, Mo, Cr are dissolved in austenite sufficiently uniformly simultaneously, must by strand 1180 ~ 1220 DEG C of heating, when temperature is lower than 1180 DEG C, then must increase heat-up time, add cost, Cr and Mo can not be dissolved in austenite completely simultaneously, reduce its effect, also make steel plate each position intensity uneven; When temperature is higher than 1260 DEG C, thick austenite crystal will be obtained, cause intensity not portion, impaired low temperature toughness, also worsen the welding property of steel.
Steel is carried out roughing in complete austenitic area, for obtaining the austenite crystal of abundant refinement, adopt the large pressure of 3-5 passage, must guarantee that total reduction is 60-80%, control finishing temperature is 1040-1080 DEG C, when temperature is lower than 1040 DEG C, then easily obtain mixed grain structure, when temperature is higher than 1080 DEG C, before finish rolling, the waiting time is long, austenite is grown up, and easily causes undercapacity.
Finish rolling is in complete non-recrystallize stage rolling, and for guaranteeing finish rolling stage percentage pass reduction, obtain abundant thinning microstructure, rolling pass is restricted to 6-8 road, and total reduction is 70-80%, and finishing temperature is 800-860 DEG C.
The steel plate relaxation time is less than or equal to 10s, and speed of cooling is 2-5 DEG C/s, and cooling termination temperature is 740-820 DEG C, and when the relaxation time is greater than 10s, proeutectoid ferrite grain growth, causes undercapacity; When speed of cooling is lower than 2 DEG C/s, need the longer relaxation time steel billet temperature could be chilled to 740-820 DEG C, grain coarsening, when higher than 5 DEG C/s, the proeutectoid ferrite scale of construction is very few does not even have ferrite to separate out, and causes steel plate yield tensile ratio higher than 0.80.
The beginning temperature of section cooling is subsequently 740-820 DEG C, and section cooling speed is 10-20 DEG C/s, and cooling termination temperature is 300-500 DEG C; Last air cooling is to room temperature.When cooling beginning temperature and being less than 740 DEG C, have a large amount of ferrites and separate out, cause undercapacity; When cooling beginning temperature higher than 820 DEG C, then separate out without ferrite in steel, then yield tensile ratio is higher, and unit elongation sharply declines, and can not meet steel requirement of the present invention.When speed of cooling is lower than 10 DEG C/s, in steel, there is pearlitic structure, cause the low-temperature flexibility of steel to be deteriorated, worsen the welding property of steel; When speed of cooling is higher than 20 DEG C/s, in steel, there is a large amount of martensitic stuctures, worsen the welding property of steel.In order to the steel plate that the structure and properties obtaining abundant refinement is splendid, cooling termination temperature controls as 300-500 DEG C.In order to ensure steel plate template, performance is uniform and stable and obtain good comprehensive mechanical performance, and must control the upper and lower water of section cooling than being 0.50-0.85, roller speed is 0.5-1.4m/s.
What deserves to be explained is, through validation trial, strict adopt chemical composition of the present invention, the steel plate of rolling technological parameter and the manufacture of process for cooling parameter could meet steel requirement of the present invention.
The present invention compared with prior art mechanical property is: R
p0.2>=550MPa, R
m>=700MPa, unit elongation A>=25% ,-20 DEG C of KV
2>=200J, R
p0.2/ R
m≤ 0.80; And postwelding does not need preheating or preheating temperature not higher than 50 DEG C, postwelding does not need thermal treatment, substantially increases welding efficiency; There is good cold and hot working performance, there is Chinese People's Anti-Japanese Military and Political College's resistance to deformation; Steel of the present invention is non-hardened and tempered steel, and have with low cost, manufacturing process is simple.
Accompanying drawing explanation
Accompanying drawing is metallographic structure figure of the present invention.
Embodiment
Below the present invention is described further
Table 1 is various embodiments of the present invention and the list of comparative example chemical composition value;
Table 2 is various embodiments of the present invention and the list of comparative example main technologic parameters value;
Table 3 is the mechanical property test result of the embodiment of the present invention.
Embodiment is produced according to following steps:
1) smelt also continuous casting and become base;
2) heat strand and be incubated, heating and temperature control is at 1180 ~ 1220 DEG C;
3) carry out roughing: 1160-1180 DEG C, total reduction is 60-80%, and roughing end temp is 1040-1080 DEG C;
4) finish rolling is carried out: control finishing temperature at 800 ~ 860 DEG C, total reduction is 70 ~ 80%, and rolling pass is in 6 ~ 8 roads;
5) carry out relaxation slow cooling to steel plate, speed of cooling is 2-5 DEG C/s, and cooling termination temperature is 740-820 DEG C; Carry out section cooling subsequently, speed of cooling is 10-20 DEG C/s, and cooling termination temperature is 300-500 DEG C; Last air cooling is to room temperature.
The chemical composition (wt, %) of table 1 various embodiments of the present invention and comparative example steel
Chemical composition contrast (wt, %) (two) of table 1 steel of the present invention
Table 2 various embodiments of the present invention and comparative example main technologic parameters value list ()
Table 2 various embodiments of the present invention and comparative example main technologic parameters value list (two)
The mechanical property list of table 3 various embodiments of the present invention and comparative example
As can be seen from Table 3, through carrying out normal tensile property ,-20 DEG C of impact of collision tests to steel plate of the present invention, and contrast with compared steel, its result: under normal temperature, steel yield strength of the present invention and compared steel are in same level, and tensile strength exceeds a lot than compared steel, steel yield tensile ratio (R of the present invention
eL/ R
m) be all less than 0.80 and higher extension property, and comparative steel yield tensile ratio is more than 0.86, unit elongation less than 20%, this illustrates that steel of the present invention has more excellent anti-seismic performance and extension property; At steel of the present invention-20 DEG C, ballistic work is all at about 300J, and far above compared steel, this illustrates that steel of the present invention has excellent low-temperature flexibility.
Above-described embodiment is only the best and exemplifies, and is not the restriction to embodiments of the present invention.
Claims (4)
1. a low yield strength ratio structural steel of yield strength>=550MPa, its component and weight percent content are: C:0.075-0.10%, Si:0.30-0.60%, Mn:1.40-2.00%, P≤0.010%, S≤0.005%, Mo:0.10-0.50%, Cr:0.10-0.40%, Nb:0.040-0.10%, Ti:0.008-0.025%, Als:0.015-0.055%, Ca:0.0022-0.0080%, Mg:0.0005-0.0012% or 0.0021 ~ 0.0050%, N:(10-30) × 10
-4%, O:(5-25) × 10
-4%, all the other are Fe and inevitable impurity; Meet: Ca/S=1.2-2.8,2Cr+Mn=2.00-2.60%, Als/N=12-20, Pcm=C+Si/30+(Mn+Cu+Cr simultaneously)/20+Ni/60+Mo/15+V/10+5B≤0.25%; Mechanical property is: R
p0.2>=550MPa, Rm>=700MPa, unit elongation A>=25% ,-20 DEG C of KV
2>=200J, R
p0.2/ Rm≤0.80.
2. the low yield strength ratio structural steel of a kind of yield strength >=550MPa as claimed in claim 1, is characterized in that: being added with weight percent content is: V≤0.10%, Ni≤0.30%, B≤0.0020%.
3. the method for the low yield strength ratio structural steel of a kind of yield strength >=550MPa described in production claim 1, its step:
1) smelt also continuous casting and become base;
2) heat strand and be incubated, heating and temperature control is at 1180 ~ 1220 DEG C;
3) carry out roughing: 1160-1180 DEG C, total reduction is 60-80%, and roughing end temp is 1040-1080 DEG C;
4) finish rolling is carried out: control finishing temperature at 800 ~ 860 DEG C, total reduction is 70 ~ 80%, and rolling pass is in 6 ~ 8 roads;
5) carry out relaxation slow cooling to steel plate, speed of cooling is 2-5 DEG C/s, and cooling termination temperature is 740-820 DEG C; Carry out section cooling subsequently, speed of cooling is 10-20 DEG C/s, and cooling termination temperature is 300-470 DEG C; Last air cooling is to room temperature.
4. method of producing the low yield strength ratio structural steel of a kind of yield strength >=550MPa as claimed in claim 3, is characterized in that: the upper and lower water of section cooling is than being 0.50-0.85, and roller speed is 0.5-1.4m/s.
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| CN108754335B (en) * | 2018-08-22 | 2019-09-10 | 武汉钢铁有限公司 | A kind of the welding structure fire-resistant and weather-resistant steel and production method of yield strength >=550MPa |
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