Classifications

• • 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
• • 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
• • 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
  • C22C38/06—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
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
  • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
• • 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
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • 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

Definitions

• the present invention relates to a structural steel material mainly used outdoors such as a bridge, and more particularly to a structural steel material excellent in weather resistance suitable for use in an environment with a large amount of incoming salt such as the vicinity of a coast. .
• weathering steel is used for steel structures used outdoors such as bridges.
• the weather-resistant steel material is a steel material in which the corrosion rate is remarkably reduced when the steel material surface is covered with a highly protective rust layer enriched with an alloy element such as Cu, P, Cr, or Ni in an air exposure environment. Due to its excellent weather resistance, it is known that bridges using weather-resistant steel can withstand service for decades without being painted.
• the conventional weathering steel (JIS G 3114: weathering hot rolled steel for welded structure) has an incoming salt content of 0.05 mg ⁇ NaCl / dm 2 / day (hereinafter, unit) the (mg ⁇ NaCl / dm 2 / day) may be referred by mdd) only in the following areas, has become it can be used in unpainted.
• Patent Document 1 discloses a highly weather-resistant steel material to which Cu and 1% by mass or more of Ni are added.
• Patent Document 2 discloses a steel material excellent in weather resistance to which 1% by mass or more of Ni and Mo are added.
• Patent Document 3 discloses a steel material excellent in weather resistance in which Cu and Ti are added in addition to Ni.
• Patent Document 4 discloses a steel material for welded structure containing a large amount of Ni and additionally containing P, Cu, Mo, Sn, Sb and the like.
• Patent Document 5 discloses a steel material excellent in corrosion resistance to which Sn is added.
• Japanese Patent No. 3785271 Japanese Patent Laid-Open No. 11-172370
• Japanese Patent No. 3846218 Japanese Patent Laid-Open No. 2002-309340
• Japanese Patent No. 3568760 Japanese Patent Laid-Open No. 11-71632
• the present invention has been developed in view of the above circumstances, and an object of the present invention is to provide a structural steel material that exhibits excellent weather resistance even in an environment that is low in cost and has a large amount of incoming salt.
• the inventors have made extensive studies on the component composition of steel from the viewpoint of weather resistance. As a result, it was found that the weather resistance of the steel material is significantly improved by adding a small amount of Nb and Sn in addition to a small amount of Cu, Ni, and Co. Furthermore, it discovered that the further improvement effect of a weather resistance was acquired by containing Cr.
• the present invention is based on the above-described novel findings.
• the gist configuration of the present invention is as follows. 1. % By mass C: 0.020% or more and less than 0.200%, Si: 0.10% or more and 1.00% or less, Mn: 0.20% or more and 2.00% or less, P: 0.003% or more and 0.030% or less, S: 0.0001% or more and 0.0200% or less and Al: 0.001% or more and 0.100% or less, and Cu: 0.01% or more and 1.00% or less, Ni: 0.01% or more and 0.65% or less Co: 0.002% or more and less than 0.220%, Nb: 0.005% or more and 0.200% or less and Sn: 0.005% or more and 0.200% or less, and the balance is a structural steel material having excellent weather resistance composed of Fe and inevitable impurities.
• Mo 0.001% or more and 1.000% or less
• W 0.005% or more and 1.000% or less
• Sb 0.005% or more and 0.200% or less, containing at least one selected from the above, but excellent weather resistance according to any one of 1 to 3 above Structural steel.
• Ti 0.005% or more and 0.200% or less
• V 0.005% or more and 0.200% or less
• Zr 0.005% or more and 0.200% or less
• B 0.0001% or more and 0.0050% or less containing one or more kinds selected from the above, and excellent weather resistance according to any one of 1 to 4 above Structural steel.
• REM 0.0001% or more and 0.0100% or less
• a structural steel material having excellent weather resistance can be obtained at low cost and in an environment with a large amount of incoming salt by compounding elements effective for improving weather resistance little by little. .
• Nb is concentrated in the rust near the surface of the ground iron to prevent chloride ions, which are corrosion accelerating factors, from passing through the rust layer and reaching the ground iron. Suppresses the reaction. Sn is concentrated in the rust in the vicinity of the surface of the ground iron, and by making the rust layer finer, the permeation of the corrosion promoting factor through the rust layer is suppressed, and the anode reaction and cathode reaction of the steel material are suppressed.
• these effects are not sufficient when each component is contained alone.
• the corrosion resistance is significantly improved for the first time. Achieved.
• C 0.020% or more and less than 0.200%
• C is an element that improves the strength of the structural steel material, and in order to ensure a predetermined strength, it is necessary to contain 0.020% or more.
• the C content is in the range of 0.030% or more and less than 0.200%.
• they are 0.03% or more and 0.18% or less, More preferably, they are 0.06% or more and 0.16% or less.
• Si 0.10% or more and 1.00% or less Si is an important component in the present invention, and the rust grains of the entire rust layer are refined to form a dense rust layer, thereby improving the weather resistance of the steel material. Has an effect. Moreover, it has the effect of preventing cracks on the surface of the steel material during hot rolling. In order to acquire these effects, it is necessary to make it contain 0.10% or more. On the other hand, when it contains excessively exceeding 1.00%, toughness and weldability will deteriorate remarkably. Accordingly, the Si amount is set to a range of 0.10% to 1.00%. Preferably they are 0.15% or more and 0.70% or less, More preferably, they are 0.40% or more and 0.60% or less.
• Mn 0.20% or more and 2.00% or less
• Mn is an element that improves the strength of the structural steel material, and in order to ensure a predetermined strength, it is necessary to contain 0.20% or more. On the other hand, when it contains excessively exceeding 2.00%, toughness and weldability will deteriorate. Accordingly, the amount of Mn is set in the range of 0.20% or more and 2.00% or less. Preferably they are 0.40% or more and 1.8% or less, More preferably, they are 0.60% or more and 1.65% or less.
• P 0.003% or more and 0.030% or less
• P is an element that improves the weather resistance of the structural steel material. In order to obtain this effect, it is necessary to contain 0.003% or more. On the other hand, if it exceeds 0.030%, weldability deteriorates. Therefore, the P content is 0.003% or more and 0.030% or less. Preferably it is 0.020% or less.
• S 0.0001% to 0.0200%
• weldability and toughness deteriorate.
• the content is reduced to less than 0.0001%, the production cost increases. Therefore, the S content is set to 0.0001% or more and 0.0200% or less.
• Al 0.001% or more and 0.100% or less
• Al is an element necessary for deoxidation at the time of steelmaking. In order to obtain this effect, it is necessary to contain 0.001% or more as the amount of Al. On the other hand, if the content exceeds 0.100%, the weldability is adversely affected. Therefore, the Al amount is set to 0.001% or more and 0.100% or less. Preferably they are 0.005% or more and 0.07% or less, More preferably, they are 0.010% or more and less than 0.05%.
• Cu 0.01% or more and 1.00% or less
• Cu which is an important component in the present invention, has the effect of remarkably improving the weather resistance of steel by coexisting with Ni, Co, Nb and Sn.
• Cu refines the rust grains of the rust layer to form a dense rust layer, and has an effect of suppressing transmission of chloride ions, which are corrosion promoting factors, to the ground iron. This effect is obtained when the content is 0.01% or more.
• the amount of Cu is made 0.01% or more and 1.00% or less.
• they are 0.03% or more and 0.45% or less, More preferably, they are 0.10% or more and 0.36% or less.
• Ni 0.01% or more and 0.65% or less
• Ni is an important component in the present invention, and has the effect of remarkably improving the weather resistance of steel by coexisting with Cu, Co, Nb and Sn.
• Ni has an effect of forming a dense rust layer by refining rust grains, thereby improving the weather resistance of the steel material.
• it is necessary to contain 0.01% or more.
• the cost rise accompanying Ni consumption increase will be caused. Therefore, the Ni content is set to 0.01% or more and 0.65% or less.
• they are 0.03% or more and 0.50% or less, More preferably, they are 0.20% or more and 0.40% or less.
• Co 0.002% or more and less than 0.220%
• Co is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel material by coexisting with Cu, Ni, Nb and Sn. Co is distributed throughout the rust layer, and forms a fine rust layer by refining rust grains, thereby having an effect of improving the weather resistance of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.002% or more.
• the content is 0.220% or more, the cost increases with an increase in Co consumption. Therefore, the Co content is set to be 0.002% or more and less than 0.220%. Preferably they are 0.003% or more and 0.100% or less, More preferably, they are 0.010% or more and 0.030% or less.
• Nb 0.005% or more and 0.200% or less
• Nb is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel by coexisting with Cu, Ni, Co and Sn.
• Nb is concentrated near the interface between the rust layer and the ground iron in the anode part to suppress the anode reaction and the cathode reaction. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more.
• the Nb amount is set to be 0.005% or more and 0.200% or less. Preferably they are 0.008% or more and 0.100% or less, More preferably, they are 0.010% or more and 0.030% or less.
• Sn 0.005% or more and 0.200% or less
• Sn is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel by coexisting with Cu, Ni, Co and Nb.
• Sn forms an oxide film containing Sn on the surface of the steel material, and improves the weather resistance of the steel material by suppressing the anode reaction and cathode reaction of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.200%, the ductility and toughness of the steel are deteriorated. Therefore, the Sn amount is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.100% or less, More preferably, they are 0.020% or more and less than 0.050%.
• the balance is Fe and inevitable impurities.
• N and O are mentioned as main unavoidable impurities, it is permissible at N: 0.0100% or less and O: 0.0100% or less, respectively.
• This equation (1) serves as an indicator of weather resistance in an atmospheric environment, and as the content of Cu, Ni, Co, Nb, Sn effective for improving weather resistance increases, the weather resistance increases.
• the target weather resistance can be obtained when the value is larger than 02. Preferably it is 0.05 or more. More preferably, it is 0.08 or more.
• the upper limit value of the formula (1) is preferably 25.00. More preferably, it is 22.00. More preferably, it is 18.00.
• Cr 0.01% or more and 1.00% or less
• Cr is an element that forms a dense rust layer by refining rust grains and improves weather resistance. In order to acquire this effect, it is necessary to make it contain 0.01% or more.
• Cr when Cr is excessively contained exceeding 1.00%, weldability is deteriorated. Therefore, when Cr is contained, the content is set to 0.01% or more and 1.00% or less. Preferably they are 0.04% or more and 1.00% or less, More preferably, they are 0.10% or more and 0.50% or less.
• Mo 0.001% or more and 1.000% or less
• Mo is a corrosion-promoting factor chloride because MoO 4 2- is eluted with the anode reaction of steel and MoO 4 2- is distributed in the rust layer. It functions to prevent ions from passing through the rust layer and reaching the iron. Moreover, it has the effect
• W 0.005% or more and 1.000% or less
• W is a corrosion-promoting factor chloride by elution of WO 4 2- with the anode reaction of the steel material and distribution as WO 4 2- in the rust layer.
• WO 4 2- electrostatically prevents ions from passing through the rust layer and reaching the base iron.
• action which suppresses the anode reaction of steel materials because the compound containing W precipitates on the steel material surface.
• a content of 0.005% or more is necessary.
• the content exceeds 1.000%, a cost increase accompanying an increase in W consumption will be caused. Therefore, when W is contained, the W amount is set to 0.005% or more and 1.000% or less.
• they are 0.010% or more and 0.500% or less, More preferably, they are 0.030% or more and 0.300% or less.
• Sb 0.005% or more and 0.200% or less
• Sb is an element that suppresses the anode reaction of the steel material and suppresses the hydrogen generation reaction that is the cathode reaction, thereby improving the weather resistance of the steel material. In order to sufficiently obtain such effects, it is necessary to contain 0.005% or more. On the other hand, when Sb is contained excessively exceeding 0.200%, toughness is deteriorated. Therefore, when Sb is contained, the amount of Sb is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.100% or less, More preferably, they are 0.020% or more and 0.050% or less.
• Ti 0.005% or more and 0.200% or less
• Ti is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.200%, the toughness is deteriorated. Therefore, when Ti is contained, the Ti amount is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.10% or less, More preferably, they are 0.020% or more and 0.050% or less.
• V 0.005% or more and 0.200% or less
• V is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, when the content exceeds 0.200%, the effect is saturated. Therefore, when V is contained, the amount of V is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.15% or less, More preferably, they are 0.030% or more and 0.100% or less.
• Zr 0.005% or more and 0.200% or less
• Zr is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, when the content exceeds 0.200%, the effect is saturated. Therefore, when Zr is contained, the amount of Zr is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.10% or less, More preferably, they are 0.020% or more and 0.050% or less.
• B 0.0001% or more and 0.0050% or less B is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0050%, the toughness is deteriorated. Therefore, when B is contained, the B content is set to 0.0001% or more and 0.0050% or less. Preferably, it is 0.0005% or more and 0.0040% or less, and more preferably 0.0010% or more and 0.0025% or less.
• REM 0.0001% or more and 0.0100% or less REM is distributed over the entire rust layer, and has an effect of forming a dense rust layer by refining rust grains and improving the weather resistance of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more, but when it exceeds 0.0100%, the effect is saturated. Therefore, when REM is contained, the REM content is 0.0001% or more and 0.0100% or less.
• Ca 0.0001% or more and 0.0100% or less Ca is an element effective for fixing S in steel and improving the toughness of the weld heat affected zone. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0100%, the amount of inclusions in the steel increases, which leads to deterioration of toughness. Therefore, when Ca is contained, the Ca content is set to 0.0001% or more and 0.0100% or less.
• Mg 0.0001% or more and 0.0100% or less Mg is an element effective for fixing S in steel and improving the toughness of the weld heat affected zone. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0100%, the amount of inclusions in the steel increases, which leads to deterioration of toughness. Therefore, when Mg is contained, the Mg amount is set to 0.0001% or more and 0.0100% or less.
• the structural steel material having excellent weather resistance according to the present invention is a molten steel prepared in the above component composition, made into a slab by a normal continuous casting or a block method, and then the obtained slab is subjected to hot rolling to a thick plate or a shape steel. It is obtained by using steel materials such as thin steel plates and steel bars.
• the heating conditions and rolling conditions in the hot rolling may be appropriately determined according to the required material, and a combination of controlled rolling, accelerated cooling, reheating heat treatment, or the like is also possible.
• the content of each element can be determined by spark discharge emission spectrometry, fluorescent X-ray analysis, ICP emission spectroscopy, ICP mass spectrometry, combustion method, and the like.
• the conditions of the corrosion test are as follows. The drying process at a temperature of 60 ° C. and a relative humidity of 35% RH is performed for 3 hours, and then the transition time is set to 1 hour, then the temperature is set to 40 ° C. and the wetting process at a relative humidity of 95% RH is set to 3 hours. Time was taken to make one cycle for a total of 8 hours. After repeating the said process 8 cycles, the drying process for 8 hours was implemented. Furthermore, after repeating the said process 11 cycles, the drying process for 8 hours was implemented. Moreover, the artificial seawater solution adjusted so that the amount of salt adhering to the test piece surface might be 0.30 mdd during the drying process for 8 hours was sprayed on the test piece surface. Under these conditions, 84 cycles of tests were conducted in 12 weeks.
• the test piece is immersed in an aqueous solution of hexamethylenetetramine in hydrochloric acid and derusted, and then the weight is measured. The difference between the obtained weight and the initial weight is obtained, and the tape seal portion is removed. From the surface area of the test piece to be removed and the density of iron, the average reduction in thickness on one side was determined and used as the amount of corrosion.
• Table 1-1 and Table 1-2 the results of the investigation on the corrosion amount (average thickness reduction amount) and the value of Equation (1) are also shown. In addition, if this corrosion amount (average thickness reduction amount) is 15 ⁇ m or less, it can be said that the weather resistance is excellent.

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• 2016
  • 2016-08-12 MY MYPI2018700476A patent/MY186926A/en unknown
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