JP4858436B2 - Zinc rich primer coated steel with excellent iron rust resistance - Google Patents

Description

The present invention relates to a zinc-rich primer coating steel which is excellent in resistance to rust generation resistance, particularly, were superior especially of zinc-rich primer coating steel formed by coating a zinc-rich primer on the surface of the steel material such as steel plate having耐鉄rust resistance, excellent relates zinc-rich primer coating steel resistant to rust generation resistance.

Steel materials such as thick steel plates not only have high strength and excellent workability, but also have the advantage of being inexpensive and easy to obtain, so steel structures such as bridges, steel towers and tanks, buildings, etc. Widely used in transportation industry such as steel buildings and ships.
Steel materials used for these applications are generally coated to prevent corrosion, and the steel materials are subjected to surface treatment before coating. Surface treatment is divided into primary surface treatment and secondary surface treatment. The primary surface treatment is aimed at preventing the occurrence of iron rust during the processing or assembling process of steel materials, and the steel skin and iron rust are removed at steelworks and shipyards, after which a primer is applied. The The secondary surface treatment is a treatment of removing primer pinholes or iron rust generated from damaged parts during the processing or assembling of the steel material and applying the primer again. As means for removing rust, sandblasting and power tool (grinder etc.) processing are mainly performed. As a primer, there are a wash primer and a zinc rich primer, but a zinc rich primer is often used from the viewpoint of corrosion resistance. For the coating applied after the secondary surface treatment, a resin-based paint such as butyral resin, polyester resin, or epoxy resin is used.

The steel materials with improved corrosion resistance in the coating film defects after painting are disclosed in Patent Document 1 and Patent Document 2.
JP-A-10-330881 JP 2000-169939 A

  As described above, the secondary surface treatment is performed in order to remove iron rust generated from primer pinholes and damaged parts during the processing or assembling of the steel material, which has been a heavy load. Generation | occurrence | production of this iron rust was not able to be suppressed with the steel materials which improved the corrosion resistance in the coating-film defect part after the painting disclosed by patent documents 1-2. That is, there has been a demand for a steel material that reduces the occurrence of iron rust from primer pinholes and damaged parts in order to reduce the load of secondary surface treatment.

The present invention, in order to meet such demands, and to provide a zinc-rich primer coating steel with improved耐鉄rust resistance, excellent resistance to rust generation resistance by the interaction of the zinc-rich primer and steel .

  The corrosion protection function of zinc-rich primer-coated steel is as follows: 1) Suppression of water, oxygen, chloride and other corrosive factors from the environment to the steel by the zinc-rich primer film 2) When placed in an environment where the steel corrodes 3) Effect of Zn contained in zinc rich primer on sacrificial corrosion protection of steel, 3) Permeation of corrosion factors such as water, oxygen and chloride from environment to steel by corrosion products of steel and Zn It is thought that it is done. For 1), the higher the ion permeation resistance of the zinc rich primer film, the higher the sacrificial anticorrosive ability of Zn for 2), and the higher the ion permeation resistance of the corrosion product layer for 3), the higher the anticorrosion effect. Get higher.

In the present invention, the anticorrosion effect of the zinc-rich primer-coated steel material, that is, the iron rust resistance is improved by increasing 2) and 3). The iron rust resistance here refers to the ability to prevent red rust, which is a corrosion product of steel.
First, with regard to 3), it was examined to increase the ion permeation resistance of the corrosion product layer of Fe and Zn. In general, the ion permeation resistance of the corrosion product layer is related to the size of the corrosion product particles, and the finer the corrosion product particles, the higher the ion permeation resistance. Therefore, the element which can make the corrosion product particle | grains of Fe and Zn fine was examined. The corrosion products of Fe here are iron oxide, iron oxyhydroxide and the like, and the corrosion products of Zn are basic zinc carbonate, zinc oxide, zinc hydroxide, basic zinc chloride and the like. A steel piece to which alloying elements such as Ni, Cu, Cr, and Mo are melted and solidified is hot-rolled to form a steel plate, and after removing the scale, a zinc rich primer is applied to produce a small exposure test piece. did. The specimen was exposed to the coastal environment for 6 months. Then, the size of the formed corrosion product particles of Fe and Zn was evaluated by half width by X-ray diffraction and observation with an electron microscope. As a result, for any alloy element, the effect of making the corrosion product particles fine was recognized, but the effect of Ni was the greatest.

  Next, regarding 2), a mechanism that can enhance the sacrificial anticorrosive ability of Zn is considered. In sacrificial protection, Zn is corroded instead of being protected from Fe. For this reason, Zn is gradually consumed, and Fe cannot be prevented from being corroded. Therefore, it is necessary to reduce the consumption rate of Zn. In order to reduce the consumption rate of Zn, it is necessary to reduce the sacrificial anticorrosive current. For that purpose, it is necessary to increase the ion permeation resistance of the corrosion product between Zn and Fe. Therefore, it is considered that Ni is the most effective as a result of the above examination. Therefore, an experiment was conducted to verify this. In this experiment, a steel piece to which a steel added with alloy elements such as Ni, Cu, Cr, and Mo was melted and solidified was hot-rolled to form a steel plate, scale was removed, and no zinc rich primer was applied. A test piece was prepared, which was exposed to the coastal environment for 6 months to prepare a sample covered with a Fe rust layer. This sample and a Zn plate were coupled in artificial seawater, and the current value between the sample and the Zn plate was measured. As a result, the current value in the steel to which Ni was added was significantly reduced. This confirms that the Ni-added corrosion product layer is indeed effective in reducing sacrificial anticorrosive current.

From the above examination, it was found that the addition of Ni to the steel increases the ion permeation resistance of the corrosion product layer, and at the same time, this corrosion product reduces the consumption rate of Zn. Thus, it was confirmed that the zinc rich primer life could be extended and the iron rust resistance could be improved.
The present invention has been made based on such knowledge. That is, the present invention is as follows.
(1) In a zinc rich primer-coated steel material obtained by applying a zinc rich primer to the surface of a steel material from which scale has been removed, the composition of the steel material is C: 0.001 to 0.20%, Si: 0 in mass%. .60% or less, Mn: 0.1 to 2.0%, P: 0.030% or less, S: 0.01% or less, Al: 0.004 to 0.08%, Ni: 0.1 to 0 .35%, and in addition, by mass%, Cu: 0.2 to 0.5%, Cr: 0.2 to 0.5%, Mo: 0.1 to 0.5% Alternatively, a zinc-rich primer-coated steel material excellent in iron rust resistance, comprising two or more types, and comprising the balance Fe and inevitable impurities .

  According to the present invention, since the iron rust resistance of the primer-coated steel material during the processing or assembling of the steel material is improved, there is an effect that the load of the secondary surface treatment can be reduced.

First, the reasons for limiting the composition of the steel material used in the present invention will be described.
C: 0.001 to 0.20%
C is an element necessary for ensuring the strength of the steel material. If the C content is less than 0.001%, sufficient strength for use as a steel building, steel structure, industrial machine or the like cannot be obtained. On the other hand, if it exceeds 0.20%, the toughness and weldability of the steel material deteriorate. Therefore, C needs to be in the range of 0.001 to 0.20%. In addition, Preferably it is 0.001 to 0.16%.

Si: 0.60% or less Si is an element that has a deoxidizing action and improves the strength of the steel material by solid solution strengthening. When the amount of Si exceeds 0.60%, the toughness and weldability of the steel material deteriorate. Therefore, Si is limited to 0.60% or less. In addition, Preferably it is 0.10 to 0.50%.
Mn: 0.1 to 2.0%
Mn is necessary to ensure the strength of the steel material. If the amount of Mn is less than 0.1%, sufficient strength for use as a steel building, steel structure, industrial machine or the like cannot be obtained. On the other hand, if it exceeds 2.0%, the toughness and weldability of the steel material deteriorate. Therefore, Mn needs to be in the range of 0.1 to 2.0%.

P: 0.030% or less P is an element contained in steel as an impurity, and is preferably reduced as much as possible in order to deteriorate the toughness of the steel. In particular, when the content exceeds 0.030%, the toughness of HAZ is significantly deteriorated. For this reason, P was limited to 0.030% or less. In addition, since excessive P reduction raises refining cost and becomes economically disadvantageous, it is preferable to set it as 0.005% or more.

S: 0.01% or less Since S is a harmful element that deteriorates toughness and weldability, it must be reduced as much as possible. Therefore, it was limited to 0.01% or less.
Al: 0.004 to 0.08%
Al needs to be 0.004% or more in terms of deoxidation of steel, and if added over 0.08%, the toughness of the base metal is lowered and at the same time the toughness of the weld metal part is deteriorated by dilution into the weld metal part. . Therefore, it limited to 0.004 to 0.08% of range.

Ni: 0.1 to 0.35%
As described above, Ni makes the Fe corrosion product and Zn corrosion product dense, increases the permeation resistance of the corrosion factor to steel, reduces the sacrificial anticorrosion current of Zn and steel in the zinc rich primer, It works to reduce the consumption rate. This effect is manifested at 0.1% or more. Although this effect is recognized even if it exceeds 1.0%, since it becomes economically disadvantageous, it limited to 0.1 to 1.0% of range. However, in the present invention, the upper limit of Ni is set to 0.35% .

Cu: 0.2-0.5%, Cr: 0.2-0.5%
Cu and Cr have the same action as Ni, but the effect is not as great as Ni. However, in view of the fact that it is not an expensive metal like Ni, it can be supplementarily added. It can also be used to increase the strength of steel. If it is less than 0.2%, the effect is small in terms of corrosion resistance and strength. On the other hand, if it is 0.5% or more, the corrosion resistance effect is saturated. Therefore, it was made into the range of 0.2 to 0.5%.

Mo: 0.1 to 0.5%
Mo has an action similar to that of Ni, and further has an action of suppressing permeation of chloride ions to the steel, and is effective for preventing corrosion of the steel. The effect appears at 0.1% and saturates at 0.5% or more. It is also an element that increases strength and can be used for that purpose. If it exceeds 0.5%, the toughness and weldability will be adversely affected. From these things, it was set as 0.1 to 0.5% of range.

Other than the components described above, Fe and unavoidable impurities. As unavoidable impurities, N: 0.010% or less and O: 0.010% or less are acceptable.
Next, a method for producing the zinc-rich primer-coated steel material of the present invention will be described.
Steel having the above composition is melted, and the obtained molten steel is solidified by a conventional technique such as a continuous casting method or an ingot-making method to produce a steel piece. The method for melting steel is not particularly limited. A conventional technique such as a converter, electric furnace, vacuum degassing, ladle refining or the like may be used alone or in various combinations to melt the steel having the above composition.

  The steel slab thus manufactured is hot-rolled to manufacture steel materials such as thick steel plates, thin steel plates, and shaped steels. Prior to hot rolling, the steel slab is charged into a heating furnace and heated to a temperature at which hot rolling is possible. In the present invention, the heating temperature of the steel slab by the heating furnace is not particularly limited. However, if the heating temperature of the steel slab is less than 1000 ° C., the deformation resistance of the steel slab is large, so the hot rolling load increases. On the other hand, when it exceeds 1250 ° C., the crystal grains of the steel material become coarse and the mechanical properties deteriorate. Accordingly, the heating temperature of the steel slab is preferably in the range of 1000 to 1250 ° C. In addition, if the steel slab that has solidified molten steel by continuous casting method or ingot-making method has a temperature that can be hot-rolled when fed to the hot-rolling equipment, it is charged in the heating furnace. Alternatively, hot rolling may be performed as it is.

In forming the zinc rich primer film on the surface of the steel material thus manufactured, the scale of the steel material surface generated in the steel material manufacturing process is removed prior to the formation of the film. Thereby, the adhesiveness of a zinc rich primer film | membrane and steel materials improves. The means for removing the scale is not particularly limited, and any conventional technique such as shot blasting, sand blasting or brush keren can be used. A zinc rich primer containing Zn is applied to the surface of the steel material after scale removal to form a coating film. The formed zinc rich primer film needs to contain 70% or more of Zn . As long as that is the case, the application method is not particularly limited, and any conventional technique such as spraying, brushing, or roll coater may be used.

Using a converter, the steel having the composition shown in Table 1 is melted and made into a slab by continuous casting. The slab is charged into a heating furnace and heated to 1150 ° C., and then hot-rolled to a thick steel plate ( A steel material having a thickness of 10 mm and a width of 3000 mm was obtained . Or comb specimen from the obtained steel material (thickness 10 mm, width 100 mm, length 300 mm) cut out to remove the scale by a shot blasting treatment to the surface thereof, the surface after the descaling, organic zinc-rich Primer was applied. The coating thickness is 15 μm. Next, a scratch having a length of 50 mm was put on the surface of the test piece after the coating film was formed, so that the coating film was partially damaged and subjected to an exposure test. The scratches reached the railway, and the exposed area was a point 20 m from the coast of Tokyo Bay (incoming salt content: 0.35 mg / dm ² / day). In addition, the amount of flying salt is a value measured by the gauze method of JIS Z2381. After 6 months, the test piece was collected and the area of red rust generated from the scratch was measured. Each measured value is expressed as a ratio to the base (Comparative Example H), and this is shown in Table 1 as the red rust occurrence area ratio (base ratio).

Reference Examples A and B and Reference Examples C and D were made using Ni-added steel materials, and the red rust generation area ratio (base ratio) was as good as 50% or less. Moreover, it turns out that the effect (red rust prevention effect) becomes remarkable as Ni amount increases. Inventive examples E, F, and G using steel materials in which Cr, Mo, and Cu are further added to 0.35% Ni steel added with a relatively small amount of Ni (used in Reference Example B) are also effective. Can be seen to improve. On the other hand, in Comparative Examples I, J, and K using steel materials to which only Cr, Mo, and Cu were added without adding Ni, the area ratio of red rust generation (base ratio) was reduced, but only about 80%. Is small. In Comparative Example H in which Ni, Cr, Cu, and Mo are not added, the red rust generation area ratio (base ratio) is the worst at 100%.

Claims (1)

In a zinc rich primer-coated steel material obtained by applying a zinc rich primer to the surface of a steel material from which scale has been removed, the composition of the steel material is C: 0.001 to 0.20%, Si: 0.60% in mass%. Mn: 0.1 to 2.0%, P: 0.030% or less, S: 0.01% or less, Al: 0.004 to 0.08%, Ni: 0.1 to 0.35% In addition, one or two of Cu: 0.2 to 0.5%, Cr: 0.2 to 0.5%, and Mo: 0.1 to 0.5% in mass%. A zinc-rich primer-coated steel material excellent in iron rust resistance, characterized by comprising the above, and remaining iron and inevitable impurities .