CN103392023B - The structural steel that weathering resistance is excellent - Google Patents

The structural steel that weathering resistance is excellent Download PDF

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CN103392023B
CN103392023B CN201280010266.3A CN201280010266A CN103392023B CN 103392023 B CN103392023 B CN 103392023B CN 201280010266 A CN201280010266 A CN 201280010266A CN 103392023 B CN103392023 B CN 103392023B
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steel
weathering resistance
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CN103392023A (en
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三浦进一
鹿毛勇
村濑正次
星野俊幸
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JFE Engineering Corp
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NKK Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

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  • Heat Treatment Of Steel (AREA)

Abstract

The invention provides the low and structural steel that weathering resistance is excellent of cost.Specifically, a kind of structural steel, wherein, in mass %, containing more than Cu:0.10% and less than 1.00%, more than Ni:0.10% and lower than 0.65%, more than W:0.05% and less than 1.00%, and containing more than Nb:0.005% and less than 0.200%, more than Sn:0.005% and less than 0.200% in one or both.Further, R value >=2.0 quality %.Wherein, R value=(R1 value+R2 is worth) 0.5, R1 value=[Cu] × 0.2+ [Ni] × 3+ [W] × 4+ [Nb] × 20+ [Sn] × 8.5, R2 value=(Log 1.5([W] 2+ 0.002)+16) × ((Log 2([Nb] × 0.1+0.001)+10)+(Log 2([Sn] × 0.1+0.001)+10) × 0.75) × 0.5 ([M] represents the content (quality %) of element M, is not set to 0 containing during element M).

Description

The structural steel that weathering resistance is excellent
Technical field
The present invention relates generally to the steel structure (SteelStructures) in outdoor application such as bridge (Bridge), is particularly suitable as the steel of the component requiring weathering resistance (atmospheric corrosionresistance) under the environment of near shore (coastal environment) contour air-borne salt (air-borne salt).
Background technology
All the time, in the steel structure in outdoor application such as bridge, atmospheric corrosion resistant steel (weathering steel) is used.Atmospheric corrosion resistant steel passes through in the environment being exposed to air (atmosphericenvironment) with high rusty scale (rust layer) covering surfaces of the protectiveness being enriched with the alloying elements such as Cu, P, Cr, Ni and makes corrosion speed (corrosion rate) significantly reduced steel.Known: to utilize the weathering resistance that it is excellent, use the bridge of atmospheric corrosion resistant steel usually can tolerate the use of decades under the state of non-application (paintless).
But; known: in the air-borne salt amounts such as near shore (amount of air-borne salt) how environment; be difficult to generate the high rusty scale of above-mentioned protectiveness; thus be difficult to obtain practical weathering resistance (hereinafter, air-borne salt amount is the value measured by the method for JIS Z2382).
According to non-patent literature 1, atmospheric corrosion resistant steel (JIS G3114: welded construction weathering resistance hot-strip) is in the past only 0.05mgNaCl/dm in air-borne salt amount 2/ day (hereinafter, uses mdd representation unit (mgNaCl/dm sometimes 2/ day)) following region can realize non-application and use.Therefore, in the environment that the air-borne salt amounts such as near shore are many, use after the anti-corrosive treatment such as application are implemented to common iron (JISG3106: Rolled Steel For Welded Structure).It should be noted that, dm represents decimetre (decimeter).
For application (coating), along with time process, there is deterioration in film (coating film), thus needs regular repairing (maintenance and repair).And, also to add the degree of difficulty of the soaring of labour cost (labor cost), application again (recoating).For this reason, the steel that current requirement can use when non-application, and high to the expectation of the steel that can use when non-application.
For this present situation, in recent years, as in the contour air-borne salt environment of near shore can in non-application the steel that use, develop containing various alloying element, steel particularly containing a large amount of Ni.
Such as, in patent documentation 1, disclose the high-weatherability steel be added with as the Ni improving more than the Cu of element of weathering resistance and 1 quality %.
In addition, in patent documentation 2, disclose the steel that the weathering resistance of Ni and Mo being added with more than 1 quality % is excellent.
In addition, in patent documentation 3, disclose the steel that the weathering resistance that is also added with Cu, Ti except Ni is excellent.
In addition, in patent documentation 4, to disclose containing a large amount of Ni and containing the steel for welded structures material of Cu, Mo, Sn, Sb and P etc.
On the other hand, although do not mention the weathering resistance in the contour air-borne salt environment of near shore, but as the corrosion-resistant steel used in the harsh corrosive environment (corrosion environment) that the ballast tank (ballast tank) etc. of boats and ships directly spatters at the spray of seawater, Patent Document 5 discloses containing W and Cr and corrosion-resistant steel material for ship and vessel containing Sb, Sn and Ni etc.
Prior art document
Patent documentation
Patent documentation 1: Japanese Patent No. 3785271 publication (Japanese Unexamined Patent Publication 11-172370 publication)
Patent documentation 2: Japanese Patent No. 3846218 publication (Japanese Unexamined Patent Publication 2002-309340 publication)
Patent documentation 3: Japanese Patent No. 3568760 publication (Japanese Unexamined Patent Publication 11-71632 publication)
Patent documentation 4: Japanese Unexamined Patent Publication 10-251797 publication
Patent documentation 5: Japanese Unexamined Patent Publication 2007-254881 publication
Non-patent literature
Non-patent literature 1: " the Bridge beam へ ying To Seki The Ru joint research Reported of weathering resistance Steel material accuses Books (the joint research report relevant with the application of weathering resistance steel in bridge) (XX) ", No. 88, in March, 1993, build economize building institute, (company) steel social hall, (company) Japanese bridge build association
Summary of the invention
Invent problem to be solved
But, when increasing the content of Ni as patent documentation 1,2, exist because cost of alloy rises and cause the problem that the price of steel rises.
In addition, in patent documentation 3, owing to taking Ti as essential element, when therefore adding Ti in a large number, toughness is deteriorated sometimes.
In addition, for increase as described in Patent Document 4 Ni content and containing Cu, Mo, Sn, Sb and P etc. steel for, due to cost of alloy rise and cause the price of steel to rise, and due to the content of P high, therefore weldability reduction.
In addition, steel disclosed in patent documentation 5 due to purposes different, therefore the environment that exposes of steel is also significantly different, and result, required corrosion resistance nature is different, does not address the weathering resistance in the contour air-borne salt environment of near shore.
The present invention in view of such situation, even if its object is to provide cost low and be the structural steel that in the environment of about 0.4mdd, weathering resistance is also excellent in air-borne salt amount.
For the method for dealing with problems
In the present invention, in order to solve the problem, from the view point of the weathering resistance in high air-borne salt environment, the one-tenth of steel is grouped into and conduct in-depth research.Found that, contain W and Sn and/or Nb by compound in containing the base steel of Cu, Ni, the weathering resistance of steel in high air-borne salt environment can be improved.
The steel plate thickness reduction that the steel plate thickness reduction (84 days) that known corrosion in drying and watering cycle corrosion test described later (wet and dry cyclic corrosion test) causes causes with corrosion when exposing 84 days in the actual environment of air-borne salt amount for about 0.4mdd is equal.Therefore, in the present invention, the method that drying and watering cycle corrosion test described later is the weathering resistance in the environment of about 0.4mdd in air-borne salt amount as evaluation is carried out.In addition, known a large amount of steel grade No.18 shown in table 1 described later containing Ni can be use in the environment of about 0.4mdd in air-borne salt amount all the time, the average thickness of slab reduction of this steel grade in drying and watering cycle corrosion test described later is 14.0 μm, therefore in the present invention, whether the evaluation of various steel reaches less than 14.0 μm for benchmark with the average thickness of slab reduction in drying and watering cycle corrosion test described later.
Result, compound contain steel that the steel of W with Nb or compound contain W with Sn and weather resisteant steel in the past, ordinary steel, use the combination of other elements to obtain weather resisteant steel compared with, value based on the steel plate thickness reduction of corrosion test is little, have the excellent tendency of weathering resistance, in addition, if be the composition after the component content in restriction further, adjustment steel, even if then compared with the steel grade many with Ni content, the more excellent result of weathering resistance also can be obtained.
Even if Ni content also demonstrates the reason of excellent weathering resistance less like this, be presumed as follows.
That is, Cu, Ni make rusty scale densification, prevent the chloride ion as corrosion promotive factor from arriving iron-based through rusty scale.W forms composite oxides at the near interface of rusty scale and iron-based and Fe in anode portion, suppresses anodic reaction.In addition, by with the formal distribution of W acid ion in rusty scale, show cation selective perviousness, prevent as corrosion promotive factor chloride ion arrive iron-based through rusty scale.Nb is enriched in the near interface of rusty scale and iron-based in anode portion, suppresses anodic reaction, cathodic reaction.Sn and Nb is similarly enriched in the near interface of rusty scale and iron-based in anode portion, suppresses anodic reaction, cathodic reaction.But these effects are independent containing sometimes insufficient, and utilize the effect that is multiplied containing Cu, Ni, W and Nb and/or Sn based on compound, the corrosion-suppressing effect of Cu, Ni, W, Nb, Sn significantly improves.As a result, with contain separately the steel grade of Ni with high-content compared with, the result that weathering resistance is more excellent is obtained.
Based on this discovery, the present inventor conducts in-depth research the impact that weathering resistance produces further with regard to these elements, and have found following shown weathering resistance index R value.And find, by the component content regulating Cu, Ni, W, Nb, Sn in steel in the mode making this R value reach more than 2.0, the steel that excellent weather resistance and hard is good can be obtained.
R value >=2.0 quality %
Wherein, R value=(R1 value+R2 is worth) 0.5
R1 value=[Cu] × 0.2+ [Ni] × 3+ [W] × 4+ [Nb] × 20+ [Sn] × 8.5
R2 value=(Log 1.5([W] 2+ 0.002)+16) × ((Log 2([Nb] × 0.1+0.001)+10)+(Log 2([Sn] × 0.1+0.001)+10) × 0.75) × 0.5,
In addition, in above-mentioned, [M] represents the content (quality %) of element M, is not set to 0 containing during element M.
It should be noted that, R1 value is the effect estimating that from above-mentioned various tests etc. each composition is given separately weathering resistance and improved, and the presumption of semiempirical ground and the value that is made.In addition, R2 value is the value of the effect that is multiplied will evaluating each composition.About the effect that is multiplied, owing to observing tendency saturated gradually relative to addition, therefore consideration logarithmic function represents, and semiempirical ground sets, is made constant.About the raising effect to weathering resistance, be thought of as these independent effects and the effect sum that is multiplied, thus derive the formula representing R value of the present invention.
The present invention is based on above discovery to complete, its purport is as described below.
[1] structural steel that a kind of weathering resistance is excellent, it is characterized in that, in mass %, containing more than C:0.020% and lower than 0.140%, more than Si:0.05% and less than 2.00%, more than Mn:0.20% and less than 2.00%, more than P:0.005% and less than 0.030%, more than S:0.0001% and less than 0.0200%, more than Al:0.001% and less than 0.100%, more than Cu:0.10% and less than 1.00%, more than Ni:0.10% and lower than 0.65%, more than W:0.05% and less than 1.00%, and containing more than Nb:0.005% and less than 0.200%, more than Sn:0.005% and less than 0.200% in one or both, surplus is made up of iron and inevitable impurity, and meet following formula (1):
R value >=2.0 quality % ... formula (1)
Wherein, R value=(R1 value+R2 is worth) 0.5
R1 value=[Cu] × 0.2+ [Ni] × 3+ [W] × 4+ [Nb] × 20+ [Sn] × 8.5
R2 value=(Log 1.5([W] 2+ 0.002)+16) × ((Log 2([Nb] × 0.1+0.001)+10)+(Log 2([Sn] × 0.1+0.001)+10) × 0.75) × 0.5,
In addition, in above-mentioned, [M] represents the content (quality %) of element M, is not set to 0 containing during element M.
[2] structural steel that the weathering resistance as described in above-mentioned [1] is excellent, is characterized in that, in mass %, also containing Cr: more than 0.1% and below 1.0%.
[3] structural steel that the weathering resistance as described in above-mentioned [1] or [2] is excellent, it is characterized in that, in mass %, also containing be selected from more than Co:0.01% and less than 1.00%, more than Mo:0.005% and less than 1.000%, more than Sb:0.005% and less than 0.200%, more than REM:0.0001% and less than 0.1000% in more than one.
[4] structural steel that the weathering resistance according to any one of above-mentioned [1] ~ [3] is excellent, it is characterized in that, in mass %, also containing be selected from more than Ti:0.005% and less than 0.200%, more than V:0.005% and less than 0.200%, more than Zr:0.005% and less than 0.200%, more than B:0.0001% and less than 0.0050%, more than Mg:0.0001% and less than 0.0100% in more than one.
It should be noted that, in this manual, represent that the % of the composition of steel is all quality %.In addition, in the present invention, " structural steel that weathering resistance is excellent " refers to the structural steel meeting the high-weatherability can applied in the high air-borne salt environment of below 0.4mdd in practical.
Invention effect
According to the present invention, the low and structural steel that weathering resistance is excellent of cost can be obtained.
In structural steel of the present invention, contain the effective element of raising weathering resistance by compound, can not the expensive elements such as Ni be contained in a large number thus realize low cost, practical weldability can be had, and excellent weathering resistance can be had in the environment that the air-borne salt amounts such as near shore are many.Particularly in the high air-borne salt environment of air-borne salt amount more than 0.05mdd, there is significant effect.But the upper limit of air-borne salt amount is expected for below 0.4mdd.
Accompanying drawing explanation
Fig. 1 represents the condition of corrosion test and the schematic diagram of circulation.
Embodiment
Below describe the present invention in detail.
More than C:0.020% and lower than 0.140%
C is the element that the intensity of structural steel is improved, and in order to ensure the intensity of regulation, needs containing more than 0.020%.On the other hand, if be more than 0.140%, then weldability and toughness deterioration.Therefore, C content is set as more than 0.020% and lower than 0.140%.Be preferably more than 0.060% and less than 0.100%.
More than Si:0.05% and less than 2.00%
Si as reductor during steel-making, and as making the intensity of structural steel improve and guaranteeing the element of intensity of regulation, needs to contain more than 0.05%.On the other hand, excessive in sometimes more than 2.00%, toughness and weldability are significantly deteriorated.Therefore, Si content is set as more than 0.05% and less than 2.00%.Be preferably more than 0.10% and less than 0.80%.
More than Mn:0.20% and less than 2.00%
Mn is the element that the intensity of structural steel is improved, and in order to ensure the intensity of regulation, needs containing more than 0.20%.On the other hand, excessive in sometimes more than 2.00%, toughness and weldability deterioration.Therefore, Mn content is set as more than 0.20% and less than 2.00%.Be preferably more than 0.20% and less than 1.50%.
More than P:0.005% and less than 0.030%
P is the element that the weathering resistance of structural steel is improved.In order to obtain this effect, need containing more than 0.005%.On the other hand, when content is more than 0.030%, weldability deterioration.Therefore, P content is set as more than 0.005% and less than 0.030%.Be preferably more than 0.005% and less than 0.025%.
More than S:0.0001% and less than 0.0200%
When S content is more than 0.0200%, weldability and toughness deterioration.On the other hand, make content be reduced to lower than 0.0001% time, production cost increase.Therefore, S content is set as more than 0.0001% and less than 0.0200%.Be preferably more than 0.0003% and less than 0.0050%.
More than Al:0.001% and less than 0.100%
The necessary element of deoxidation when Al is steel-making.In order to obtain this effect, as Al content, need containing more than 0.001%.On the other hand, during more than 0.100%, detrimentally affect is caused to weldability.Therefore, Al content is set as more than 0.001% and less than 0.100%.Be preferably more than 0.010% and less than 0.050%.It should be noted that, about Al content, measure acid-soluble Al.
More than Cu:0.10% and less than 1.00%
Cu has and to form fine and close rusty scale by making the miniaturization of rust grain thus make the effect that the weathering resistance of structural steel improves.This effect can obtain when content is more than 0.10%.On the other hand, during more than 1.00%, the cost increase produced with Cu addition increases can be caused.Therefore, Cu content is set as more than 0.10% and less than 1.00%.Be preferably more than 0.20% and less than 0.50%.
It should be noted that, patent documentation 5 relates to corrosion-resistant steel material for ship and vessel.The half in the life-span (20 years) that life-span (being generally speaking 10 years) of the protection against corrosion film of the ballast tank of boats and ships is boats and ships, within remaining 10 years, maintain erosion resistance by carrying out Repair Coatings, consider from such present situation, the object of the corrosion-resistant steel material for ship and vessel described in patent documentation 5 is, under the harsh corrosive environment that seawater or its spray are directly splashed on the ballast tank of boats and ships etc., play excellent erosion resistance when the condition of surface not by steel affects, the time till Repair Coatings can be extended and then reduce Repair Coatings operation.On the other hand, structural steel of the present invention is applied to the steel structure in outdoor application such as bridge, its object is to, can use in the high air-borne salt environment of the about 0.4mdd such as near shore when non-application, compared with the steel described in patent documentation 5, use the environment of steel significantly different with object.Therefore, for the steel described in patent documentation 5, do not need containing Cu, but for the present invention, need form fine and close rusty scale containing Cu thus the weather resisteant of steel is improved.Therefore, as mentioned above, in the present invention, containing more than 0.10% Cu.
More than Ni:0.10% and lower than 0.65%
Ni has and to form fine and close rusty scale by making the miniaturization of rust grain thus make the effect that the weathering resistance of structural steel improves.In order to fully obtain this effect, need containing more than 0.10%.On the other hand, when Ni is more than 0.65%, the cost increase produced with Ni consumption increases can be caused.Therefore, Ni content is set as more than 0.10% and lower than 0.65%.Be preferably more than 0.15% and less than 0.50%.
More than W:0.05% and less than 1.00%, more than Nb:0.005% and less than 0.200% and/or more than Sn:0.005% and less than 0.200%
W is important condition in the present invention, by existing with Nb and/or Sn simultaneously, has the effect that the weathering resistance of steel in high air-borne salt environment is significantly improved.In addition, with the anodic reaction of steel, stripping WO 4 2-and with WO 4 2-formal distribution in rusty scale, prevent for electrostatically thus as corrosion promotive factor chloride ion arrive iron-based through rusty scale.In addition, the compound precipitation containing W, at steel surface, suppresses the anodic reaction of steel thus.In order to fully obtain these effects, W needs containing more than 0.05%.On the other hand, during more than 1.00%, the cost increase produced with W addition increases can be caused.Therefore, W content is set as more than 0.05% and less than 1.00%.Be preferably more than 0.10% and less than 0.70%.
Nb is important condition in the present invention, by existing with W simultaneously, has the effect that the weathering resistance of steel in high air-borne salt environment is significantly improved.In addition, in anode portion, be enriched in the near interface of rusty scale and iron-based, suppress anodic reaction, cathodic reaction.In order to fully obtain these effects, Nb needs containing more than 0.005%.On the other hand, during more than 0.200%, toughness can be caused to reduce.Therefore, Nb content is set as more than 0.005% and less than 0.200%.Be preferably more than 0.010% and less than 0.050%.
Sn is important condition in the present invention, by existing with W simultaneously, has the effect that the weathering resistance of steel in high air-borne salt environment is significantly improved.In addition, form the oxide film thereon containing Sn at steel surface, suppress the anodic reaction of steel, cathodic reaction, make the weathering resistance of structural steel improve thus.In order to fully obtain these effects, Sn needs containing more than 0.005%.On the other hand, during more than 0.200%, the deterioration of the ductility of steel, toughness can be caused.Therefore, Sn content is set as more than 0.005% and less than 0.200%.Be preferably more than 0.010% and less than 0.050%.
In addition, if containing in Nb and Sn at least any one, just can realize effect of the present invention.But, if containing Nb and Sn, then there is the effect significantly improving weathering resistance further.The reason of the effect containing Nb and Sn is also indefinite, but think because, in drying process and moistening process environment repeatedly, Nb and Sn significantly plays the condition of effect (such as, the environment such as salt concentration in temperature, relative humidity or rust) different, therefore to be complemented each other respective effect and significantly improve weathering resistance further by Nb and Sn.
In addition, also tool has the following advantages: on the basis of mechanical properties, weldability etc. of guaranteeing steel, reduce the addition of Nb, Sn when not enabling weathering resistance deterioration respectively.For this reason, be preferred invention mode containing Nb and Sn.
Surplus is Fe and inevitable impurity.At this, as inevitable impurity, below N:0.010%, below O:0.010%, below Ca:0.0010% can be allowed.In addition, when the Ca contained as inevitable impurity exists in a large number in steel, make the toughness deterioration of welding heat affected zone, be therefore preferably less than 0.0010%.
Except mentioned component element, following alloying element can also be added as required.
Cr: more than 0.1% and below 1.0%
Cr is the element forming fine and close rusty scale by making the miniaturization of rust grain thus improve weather resisteant, and in order to fully obtain this effect, content needs more than 0.1%.On the other hand, during more than 1.0%, weldability can be caused to reduce.Therefore, containing sometimes, Cr content, for more than 0.1% and below 1.0%, is preferably more than 0.2% and less than 0.7%.
In addition, in the present invention, for following reason, can containing be selected from Co, Mo, Sb and REM more than one.
More than Co:0.01% and less than 1.00%
Co is distributed in whole rusty scale, has and to form fine and close rusty scale by making the miniaturization of rust grain thus make the effect that the weathering resistance of structural steel improves.In order to fully obtain this effect, need containing more than 0.01%.On the other hand, during more than 1.00%, the cost increase produced with Co consumption increases can be caused.Therefore, containing sometimes, Co content is more than 0.01% and less than 1.00%, is preferably more than 0.10% and less than 0.50%.
More than Mo:0.005% and less than 1.000%
Mo is with the anodic reaction stripping MoO of steel 4 2-, and MoO 4 2-be distributed in rusty scale, prevent the chloride ion as corrosion promotive factor from arriving iron-based through rusty scale thus.In addition, the compound precipitation containing Mo, at steel surface, suppresses the anodic reaction of steel thus.In order to fully obtain these effects, need containing more than 0.005%.On the other hand, during more than 1.000%, the cost increase produced with Mo consumption increases can be caused.Therefore, containing sometimes, Mo content is more than 0.005% and less than 1.000%, is preferably more than 0.100% and less than 0.500%.
More than Sb:0.005% and less than 0.200%
Sb is by suppressing the anodic reaction of steel and suppressing cathodic reaction namely to produce H-H reaction and make the element that the weathering resistance of structural steel improves.In order to fully obtain this effect, need containing more than 0.005%.On the other hand, during more than 0.200%, toughness deterioration can be caused.Therefore, containing sometimes, Sb content is more than 0.005% and less than 0.200%, is preferably more than 0.020% and less than 0.060%.
More than REM:0.0001% and less than 0.1000%
REM is distributed in whole rusty scale, has and to form fine and close rusty scale by making the miniaturization of rust grain thus make the effect that the weathering resistance of structural steel improves.In order to fully obtain this effect, need containing more than 0.0001%.On the other hand, during more than 0.1000%, its effect is saturated.Therefore, containing sometimes, REM content is more than 0.0001% and less than 0.1000%, is preferably more than 0.0010% and less than 0.0350%.
In addition, in the present invention, for following reason, can containing be selected from Ti, V, Zr, B and Mg more than one.
More than Ti:0.005% and less than 0.200%
Ti is the element for improving needed for intensity.In order to fully obtain this effect, need containing more than 0.005%.On the other hand, during more than 0.200%, toughness deterioration can be caused.Therefore, containing sometimes, Ti content is more than 0.005% and less than 0.200%, is preferably more than 0.010% and less than 0.100%.
More than V:0.005% and less than 0.200%
V is the element for improving needed for intensity.In order to fully obtain this effect, need containing more than 0.005%.On the other hand, more than 0.200% time, effect is saturated.Therefore, containing sometimes, V content is more than 0.005% and less than 0.200%, is preferably more than 0.010% and less than 0.100%.
More than Zr:0.005% and less than 0.200%
Zr is the element for improving needed for intensity.In order to fully obtain this effect, need containing more than 0.005%.On the other hand, more than 0.200% time, effect is saturated.Therefore, containing sometimes, Zr content is more than 0.005% and less than 0.200%, is preferably more than 0.010% and less than 0.100%.
More than B:0.0001% and less than 0.0050%
B is the element for improving needed for intensity.In order to fully obtain this effect, need containing more than 0.0001%.On the other hand, during more than 0.0050%, toughness deterioration can be caused.Therefore, containing sometimes, B content is more than 0.0001% and less than 0.0050%, is preferably more than 0.0010% and less than 0.0050%.
More than Mg:0.0001% and less than 0.0100%
Mg makes the S in steel fix thus to improving the effective element of toughness of welding heat affected zone.In order to fully obtain this effect, need containing more than 0.0001%.On the other hand, during more than 0.0100%, the amount of the inclusion in steel increases, and causes the deterioration of toughness on the contrary.Therefore, containing sometimes, Mg content is more than 0.0001% and less than 0.0100%, is preferably more than 0.0020% and less than 0.0050%.
In addition, in order to the effect of the weather resisteant in high salt time-sharing environment that is fully improved, the scope that R value demand fulfillment following by definition specifies.
R value >=2.0 quality %
Wherein, R value=(R1 value+R2 is worth) 0.5
R1 value=[Cu] × 0.2+ [Ni] × 3+ [W] × 4+ [Nb] × 20+ [Sn] × 8.5
R2 value=(Log 1.5([W] 2+ 0.002)+16) × ((Log 2([Nb] × 0.1+0.001)+10)+(Log 2([Sn] × 0.1+0.001)+10) × 0.75) × 0.5
In addition, in above-mentioned, [M] represents the content (quality %) of element M, is not set to 0 containing during element M.
Above-mentioned R value is the index of the weathering resistance representing steel, and in order to obtain excellent weathering resistance in high salt time-sharing environment, R value is set as more than 2.0.
The structural steel that weathering resistance of the present invention is excellent can obtain in the following manner: utilize converter (steel converter), the steel with mentioned component composition is carried out melting by ordinary method by the melting means such as electric furnace (electric furnace), will by common continuous casting (continuouscasting), the steel billet (slab) that cogging method obtains carries out hot rolling (hot rolling), make slab (steel plate) thus, shaped steel (shaped steel), steel sheet (steel sheet), the steel such as bar steel (bar steel).Heating, rolling condition suitably can be determined according to required material, also can combine controlled rolling (controlled rolling), accelerating cooling (accelerated cooling) or reheat (reheating) such thermal treatment etc.
In addition, by using the structural steel obtained in the above described manner as the structural member of steel structure, the steel structure in the many environment of the air-borne salt amounts such as near shore with excellent weathering resistance can be formed in.
Embodiment
The steel of chemical constitution shown in table 1 is carried out melting, carries out hot rolling (hotrolling) after being heated to 1150 DEG C, air cooling (air cooling), to room temperature (room temperature), manufactures experimently into the steel plate of thickness 6mm.Then, the test film (test specimen) of 35mm × 35mm × 5mm is cut from obtained steel plate.For test film, effects on surface carries out ground finish (grindingprocessing), to make surfaceness (surface roughness) Ra be less than 1.6 μm, by end face (edge face), the back side (back side) with adhesive tape (tape) sealing (seal), be that the mode of 25mm × 25mm is also by surface rubber belt sealing with the area of surperficial exposed division (exposed area).
For the test film obtained in the above described manner, carry out the drying and watering cycle corrosion test of the method as the weathering resistance evaluated in 0.4mdd environment, and measure thickness of slab reduction.Drying and watering cycle corrosion tests and thickness of slab reduction measuring method as follows.
Drying and watering cycle corrosion test
For above-mentioned test film, as shown in Figure 1, humiture circulation is carried out under single side surface being adhered to state salty.In humiture circulation, the drying process of temperature 40 DEG C, relative humidity 40%RH is set as 11 hours, transit time is set as 1 hour, then be 25 DEG C by temperature, relative humidity be the moistening operation of 95%RH be set as 11 hours, transit time is set as 1 hour, be a circulation with 24 hours, carry out 12 weeks (84 circulations).About the attachment of salinity, carry out with every seven humiture circulation times (before the drying process of humiture circulation) before humiture circulation starts, carry out 12 times altogether.Now, the specified amount of the artificial seawater solution of preparation is applied to the surface of test film, makes the salt component be attached on surface of steel plate reach 1.4mg/dm 2.
The mensuration of thickness of slab reduction
After drying and watering cycle corrosion test, in 37% hydrochloric acid (hydrochloric acid) 500mL, vulkacit H (hexamethylene tetramine) 3.5g, ヒ PVC ロ Application (inhibitor (inhibitor) that ア イ コ ー ケ ミ カ Le company manufactures) 3mL, add distilled water (distilled water) makes it reach 1L, obtained deruster, test film is impregnated in this deruster, and after de-rust gravimetry.It should be noted that, the mensuration of weight is according to the method recorded in the 145th corrosion-protection against corrosion symposium " high precision int of corrosive wear evaluation method ".In addition, obtain the difference of obtained weight and initial stage weight, and the area in subjects face divided by test film, calculate the average thickness of slab reduction of test film one side thus.
The corrosion test result obtained by the way is grouped into one-tenth, is illustrated in together with R value in table 1-1 ~ table 1-6.
From table 1-1 ~ table 1-6, be that in the example of the present invention of more than 2.0, thickness of slab reduction is 11.8 ~ 13.9 μm, has excellent weathering resistance in R value.
On the other hand, in the comparative example departing from the scope specified in the present invention, R value is lower than 2.0, and thickness of slab reduction is 14.3 ~ 17.7 μm, larger than the present invention's example, and weathering resistance is poor.

Claims (5)

1. a structural steel, in mass %, containing more than C:0.020% and lower than 0.140%, more than Si:0.05% and less than 2.00%, more than Mn:0.20% and less than 2.00%, more than P:0.005% and less than 0.030%, more than S:0.0001% and less than 0.0200%, more than Al:0.001% and less than 0.100%, more than Cu:0.10% and less than 1.00%, more than Ni:0.10% and lower than 0.65%, more than W:0.05% and less than 1.00%, and containing more than Nb:0.005% and less than 0.200%, more than Sn:0.005% and less than 0.200% in one or both, surplus is made up of iron and inevitable impurity, the Ca wherein contained as inevitable impurity is less than 0.0010%, and meet following formula (1):
R value >=2.0 quality % ... formula (1)
Wherein, R value=(R1 value+R2 is worth) 0.5
R1 value=[Cu] × 0.2+ [Ni] × 3+ [W] × 4+ [Nb] × 20+ [Sn] × 8.5
R2 value=(Log 1.5([W] 2+ 0.002)+16) × ((Log 2([Nb] × 0.1+0.001)+10)+(Log 2([Sn] × 0.1+0.001)+10) × 0.75) × 0.5,
In addition, in above-mentioned, [M] represents the content (quality %) of element M, is not set to 0 containing during element M.
2. structural steel as claimed in claim 1, wherein, in mass %, also containing Cr: more than 0.1% and below 1.0%.
3. structural steel as claimed in claim 1 or 2, wherein, in mass %, also containing be selected from more than Co:0.01% and less than 1.00%, more than Mo:0.005% and less than 1.000%, more than Sb:0.005% and less than 0.200%, more than REM:0.0001% and less than 0.1000% in more than one.
4. structural steel as claimed in claim 1 or 2, wherein, in mass %, also containing be selected from more than Ti:0.005% and less than 0.200%, more than V:0.005% and less than 0.200%, more than Zr:0.005% and less than 0.200%, more than B:0.0001% and less than 0.0050%, more than Mg:0.0001% and less than 0.0100% in more than one.
5. structural steel as claimed in claim 3, wherein, in mass %, also containing be selected from more than Ti:0.005% and less than 0.200%, more than V:0.005% and less than 0.200%, more than Zr:0.005% and less than 0.200%, more than B:0.0001% and less than 0.0050%, more than Mg:0.0001% and less than 0.0100% in more than one.
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