WO2004022808A1 - 構造用Cr鋼およびその製造方法 - Google Patents
構造用Cr鋼およびその製造方法 Download PDFInfo
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- WO2004022808A1 WO2004022808A1 PCT/JP2003/010908 JP0310908W WO2004022808A1 WO 2004022808 A1 WO2004022808 A1 WO 2004022808A1 JP 0310908 W JP0310908 W JP 0310908W WO 2004022808 A1 WO2004022808 A1 WO 2004022808A1
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- steel
- steel sheet
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Classifications
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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
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
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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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2261/00—Machining or cutting being involved
Definitions
- the present invention relates to a structural Cr steel, particularly a Cr steel for a refrigeration container, which is excellent in low-temperature toughness and impact characteristics, is less expensive than austenitic stainless steel, and has sufficient corrosion resistance.
- the lining material is a cold-rolled annealed sheet, which is often used without being painted, and because high low-temperature toughness is desired, the steel material is austenitic stainless steel JIS (Japanese Industrial Standard, Abbreviated as JIS>
- JIS Japanese Industrial Standard
- SUS 304 specified by G 4305 is used. This SUS 304 has excellent low-temperature toughness, large elongation, yield ratio (yield stress (Strength) is small, and the work hardening index is large, making it difficult for holes to be opened at the time of impact, making the stainless steel excellent in impact properties, but it is a major disadvantage in that it is expensive.
- Cold rolled annealed plates are used as the outer material, and SUS304, austenitic stainless steel, is used for high-grade frozen containers. cost Due to its high value, ferritic-martensitic stainless steels containing about 11% Cr, such as SUS410L and SUS410S specified in JIS G 4305, are also used. Hot rolled annealed plate is used for the aggregate, and 11% Cr manholetensitic stainless steel with reduced C and N is often used.
- Japanese Patent Publication No. 51-13463 Cr: 10 to 18 wt%, Ni: 0.1 to 3.4%, Si: 1 0.1 wt% or less Mn: 4.0 wt% or less, C: 0.03 wt% or less, N: 0.02 wt% or less,
- a martensitic stainless steel for welded structures has been disclosed in which a duct structure and a ductility and toughness performance of a weld heat affected zone are improved by generating a site structure.
- 57-28738 discloses that Cr: 10 to: L 3.5 wt%, Si: 0.5 wt% or less, and Mn: 1.0 to 3.5 wt%. , C: 0.02 wt% or less, N: 0.02 wt% or less, and by further limiting Ni to less than 0.1 wt%, pre-heating and post-heating before and after welding become unnecessary.
- a structural martensitic stainless steel excellent in weld toughness and weld strength 14 is disclosed. As disclosed in the Journal of the Japan Welding Society, vol. 57 (1988), No. 6, p. 432, this steel has been applied as various structural members including frame materials for marine containers.
- Such 1 l% Cr stainless steel is relatively inexpensive and is widely used as a material for container aggregates or external materials.
- Technology that can further reduce costs by overcoming the drawbacks of inferior low-temperature toughness and impact resistance compared to austenitic stainless steel SUS 304, reducing the amount of Cr, and saving on annealing of hot-rolled sheets. There are great expectations for the development of.
- Japanese Patent Application Laid-Open No. Hei 11-302795 discloses that Cr: 8 to 16%, Si: 0.05 to: L. 5%, and Mn: 0.05 to 1.5%. And then C: 0.005 to 0.1%, N: 0.05% or less, (C + N): 0.1% or less, and 50% or more martensite is formed in the heat affected zone by volume.
- a ferritic stainless steel for a building structure which is adjusted in such a manner, is disclosed.
- the steel disclosed in Japanese Patent Application Laid-Open No. 11-302795 does not provide sufficient low-temperature toughness for use in a refrigeration container, such as hot rolling, hot rolling, or further heat treatment, acid treatment. It is assumed to be used after washing, and no consideration is given to corrosion resistance after painting.
- JP-A-11-302737 discloses that Cr: 8 to 16%, Si: 0.05 to 1.5%, Mn: 0.05 to 1.5%, and Ni: 0.05 to 0.5%. : containing L 0/0, further C:. 0. 005 ⁇ 0 1%, N: 0. 05 or less, (C + N): heating 0.1 or less and the steel to 1 100 to 1,250 ° C A technique is disclosed in which hot rolling is terminated at 800 or more, winding is performed at 700 ° C or less, and the subsequent cooling rate is set to 5 ° CZ or less, thereby omitting annealing of the hot-rolled sheet. However, this technology is also premised on the use as hot rolled or after further heat treatment and pickling, and no consideration is given to the corrosion resistance after painting.
- Japanese Patent Application No. 2003-141462 (corresponding European Patent Application No. 030151 10.4, filing date: July 3, 2003) is a technology developed by the present inventors, but has a Cr: 8 mass. % Or more, 10 mass% or less, S i: 0.01 to 1. Oma ss% ⁇ Mn: 0.01 to 0.30 ma ss%, Cu: 0.01 to 1.0 ma ss% N i: 0.
- the present invention provides a structural Cr steel that has excellent low-temperature toughness and impact resistance, is less expensive than austenitic stainless steel, and has a sufficient corrosion resistance. It aims to provide steel.
- the present inventors investigated a number of effects of added elements on the above-mentioned properties based on Cr steel, and as a result, found that the Cr content was 6.0 to: L 0.
- the C and N contents By setting the C and N contents to 0.02% or less, it is possible to achieve both the corrosion resistance, toughness and impact resistance required for structural Cr steel, especially for frozen container steel.
- they have found that they can be manufactured at a lower cost than austenitic stainless steel, and can omit hot-rolled sheet annealing, and can be manufactured at a lower cost.
- the present invention has the following gist configuration. That is, in the present invention, in ma ss%, C: 0.002 to 0.02%, N: 0.002 to 0.02%, Si: 0.05 to 1.0%, Mn: 0.05 ⁇ : L.
- the present invention is a structural Cr steel containing the above invention steel and further containing 0.1% to 1.0% of Cu in mass%.
- the present invention provides the above steel according to the present invention, wherein, in terms of mass%, one or two selected from Ni: 0.1 to 1.0% and Mo: 0.1 to 1.0%. It is a structural Cr steel containing more than one kind.
- the present invention provides the above steel of the present invention further comprising one or two selected from mass T ?, Nb: 0.005 to 0.10%, and V: 0.005 to 0.20%. Structural Cr steel.
- the present invention provides, in terms of mass%, C: 0.002 to 0.02%,
- N 0.002 to 0.02%
- S i 0.05 to 1.0%
- Mn 0.05 to 1.0%, P: 0.04% or less, 3: 0.02% or less, A1: 0.001 to 0.10 / o, Cr: 6.0 to : 10.
- the steel material containing 0%, the balance of Fe and unavoidable impurities is re-heated, hot-rolled into steel strips, and then descaled in the hot rolling steel strip manufacturing process.
- This is a method for producing a hot rolled steel sheet for structural use, characterized in that the surface of the steel sheet is removed by 10 to 200 ⁇ .
- the present invention is the method for producing a structural Cr steel cold rolled steel sheet according to the above method for producing a steel sheet of the present invention, wherein the descaling treatment is performed, and then cold rolling, cold rolled sheet annealing, and pickling are performed. .
- the present invention is the method for producing a structural Cr steel sheet, wherein the steel material further contains Cu: 0.1 to 1.0%.
- the present invention also provides the method for producing a steel sheet according to the present invention, wherein the steel material is further selected from Ni: 0.1 to 1.0% and Mo: 0.1 to 1.0%. Or a method for producing a structural Cr steel sheet containing two or more types.
- the present invention provides the method for producing a steel sheet according to the present invention, wherein the steel material is further selected from Nb: 0.005 to 0.10 ° / o , and V: 0.005 to 0.20%.
- This is a method for producing structural Cr steel sheets containing one or two types.
- the present invention is the structural Cr steel, wherein the above-described steel of the present invention is for a refrigeration container. Also, the present invention is the method for producing a structural Cr steel sheet, wherein the structural Cr steel sheet is for use in a frozen container aggregate.
- the present invention is the method for producing a structural Cr cold-rolled steel sheet, wherein the structural Cr steel sheet is used for a cladding material for a frozen container.
- the present invention uses the above-described invention steel, or uses a Cr steel plate manufactured by the above-described method, processes it by forming, and further has a dry film thickness of 10 / zm or more on the surface of the steel plate. Is a refrigerated container having a coating film.
- the present invention is a structural Cr steel, wherein the above-mentioned invention steel is used for civil engineering and architectural structures. Further, the present invention is a method for producing a structural Cr steel hot-rolled steel sheet, wherein the above-mentioned invention steel is for civil engineering and building structures.
- the present invention is a method for producing a structural Cr steel cold-rolled steel sheet, wherein the invention steel is used for civil engineering and building structures.
- Fig. 1 A diagram showing the relationship between the removal amount of the steel sheet surface and SST (SaltSprayTestStng) n area ratio.
- Figure 2A Scanning electron micrograph of a steel sheet surface with a removal of 8 ⁇ m from the steel sheet surface.
- Figure 2B Scanning electron micrograph of a steel sheet surface with a removal rate of 40 / xm from the steel sheet surface.
- Fig. 3A A diagram showing the concentration profiles of Fe and Cr in the thickness direction from the steel sheet surface by glow discharge spectroscopy with a removal amount of 8 // m on the steel sheet surface.
- Fig. 3A A diagram showing the concentration profiles of Fe and Cr in the thickness direction from the steel sheet surface by glow discharge spectroscopy with a removal amount of 40 from the steel sheet surface.
- Figure 4 Schematic diagram showing the scale / steel interface. BEST MODE FOR CARRYING OUT THE INVENTION
- the unit of the component content is mass%, hereinafter abbreviated as%.
- C is preferably as low as possible in order to improve the corrosion resistance after painting. This is because the formation of a dechromized layer accompanying the precipitation of carbonitrides is suppressed. However, 0.00
- the strength is insufficient, but if it exceeds 0.02%, the toughness and ductility are insufficient, and the impact resistance is reduced.
- the C content was set to 0.002 to 0.02%.
- a preferred range of the C content is 0.003 to 0.013%, more preferably 0.003 to 0.03.
- N is preferably as low as possible to improve corrosion resistance after painting. However, if it is less than 0.002%, the strength is insufficient, but if it exceeds 0.02%, the toughness and ductility are poor. The impact resistance decreases. In the steel of the present invention, it is important to reduce N to 0.02% or less. Also, by reducing the N content to 0.02% or less, it became possible to omit hot-rolled sheet annealing. Therefore, the N content was set to 0.002 to 0.02%. The N content is preferably 0.0030 to 0.0060% from the viewpoint of improving corrosion resistance after painting.
- Si is an element useful as a deoxidizing agent, but if its content is less than 0.05%, a sufficient deoxidizing effect cannot be obtained, so it must be 0.05% or more. However, if the Si content exceeds 1.0%, the toughness and ductility are insufficient, and the impact resistance is reduced. Therefore, the Si content was set at 0.05 to 1.0%. The preferable range of the amount added is 0.1 to 0.5% from the viewpoint of improving the low-temperature toughness.
- Mn is also an element useful as a deoxidizing agent like Si, but its content must be 0.05% or more because a sufficient deoxidizing effect cannot be obtained if it is less than 0.05%. You. However, if the Mn content exceeds 1.0%, Mn S inclusions increase and the corrosion resistance decreases. Therefore, the Mn content was set to 0.05 to 1.0%. From the viewpoint of improving the corrosion resistance after painting, the preferred range of the content is 0.10 to 0.30%.
- P is an element that not only deteriorates mechanical properties such as toughness and ductility, but is also harmful to corrosion resistance, especially when the P content exceeds 0.04%, because the effect becomes significant.
- the P content is restricted to 0.04% or less.
- S combines with Mn to form Mn S, which is the initial rusting point. Also, S Since it is also a harmful element that segregates at the crystal grain boundaries and promotes grain boundary brittleness, it is preferable to reduce it as much as possible. In particular, if the S content exceeds 0.02%, its adverse effect becomes significant, so the S content was restricted to 0.02% or less. In particular, when high corrosion resistance is required after painting, S It is desirable that the content be 0.006% or less.
- A1 is an element useful as a deoxidizing agent, and has an effect of spheroidizing an oxide to improve ductility at the time of bending, but a content of less than 0.001% is sufficient. Since no effect can be obtained, it must be 0.001% or more.
- the A1 content exceeds 0.1%, the amount of inclusions increases and the corrosion resistance decreases. Therefore, the content of 1 was set to 0.001 to 0.1%. If the content of A1 is large, inclusions may increase and mechanical properties may be degraded.Therefore, the upper limit of the A1 content is set to 0.05% so that the workability of the hot-rolled sheet is improved. Preferred from a viewpoint.
- Cr is an element indispensable for ensuring the corrosion resistance required for the refrigerated container material targeted by the present invention. Since the exterior of the frozen container material is painted, it is not required to have the same corrosion resistance as SUS 304, but even if it is less than 6.0%, the corrosion resistance cannot be secured. However, if the Cr content exceeds 10.0%, the toughness and ductility are insufficient, and the impact resistance is reduced. In the present invention, it is an important finding that it has been found that the corrosion resistance and toughness required for a frozen container material and the impact resistance are compatible at a Cr content of 6.0 to 10.0%. Also, by setting the Cr content to 10.0% or less, it became possible to omit the hot-rolled sheet annealing. In addition, in order to provide sufficient low-temperature toughness when the hot-rolled sheet annealing is omitted, the addition amount is preferably in the range of 6.0 to 9.5%. A more preferred range is 6.0 to 9.0%.
- Cu is a useful element for reducing the corrosion rate and improving the corrosion resistance, and also works effectively for suppressing crevice corrosion.
- corrosion resistance after painting which is a problem in the present invention
- corrosion in the gap structure at the part where the coating is partially peeled is a problem.
- Cu should be added. Is preferred.
- the content is less than 0.1%, the effect is poor.On the other hand, if the content exceeds 1.0%, the ductility and impact resistance tend to decrease, and the hot rolling Cracking easily occurs. Therefore, it is preferable to set the content of 11 to 0.1% to 0.1%.
- the upper limit of the addition amount is preferably 0.7% from the viewpoint of preventing hot cracking and workability.
- Ni also reduces the corrosion rate and improves corrosion resistance. In addition, it is an effective component for improving toughness. However, if the content is less than 0.1%, these effects are poor.On the other hand, Ni is a very expensive element, and if its content exceeds 1.0%, the cost increases, so N
- the i content is preferably set to 0.1 to 1.0%. Note that the upper limit of the content is preferably set to 0.5% as long as hardening of the material and increase in cost are not caused.
- the content of] ⁇ 0 is preferably set to 0.1 to 1.0%. From the viewpoint of balance between corrosion resistance and strength and workability, the range of 0.1 to 0.5% is preferable. (12) Nb: 0.005 to 0.10%
- Nb precipitates as Nb carbonitride during hot rolling, has the function of suppressing the growth of crystal grains, and has the effect of greatly reducing the crystal grains of the hot-rolled steel sheet.
- the addition of Nb is effective. However, if the addition amount is less than 0.005%, the effect is poor. If the addition amount exceeds 0.10%, the toughness of the weld decreases, so the addition amount is 0.005 to 0.10%. did. From the viewpoint of weld toughness, the more preferable upper limit of the addition amount is 0.06%.
- V precipitates in the form of V carbonitride or V 4 C 3 during hot rolling has the effect of refining the crystal grains of the hot-rolled steel sheet, and improves the low-temperature morning resistance of the steel sheet.
- the amount is less than 0.005%, the effect is poor.
- the toughness of the welded part and the base metal is rather reduced. Therefore, the addition amount is set to 0.005 to 0.20%. From the viewpoint of improving the base metal toughness, the more preferable upper limit of the addition amount is 0.15%.
- Fe and unavoidable impurities are included.
- the steel produced by the technique of the present application has a substantially ferrite single phase structure.
- some of the steel may contain bainite, but the steel sheet after cold rolling has a substantially ferritic single phase structure.
- components are designed so that hard martensite is not generated in a state before working such as after hot rolling or cold rolling annealing.
- the composition is adjusted so that the martensitic structure has a low C content and a low N content, and sufficient low-temperature toughness can be obtained even after assembling by welding. Has features.
- the steel of the present invention is manufactured in the following manufacturing process.
- a smelting furnace such as a converter or an electric furnace
- molten steel adjusted to the component composition of the present invention by a refining method such as a VOD method, an AOD method, or an RH method is subjected to a continuous casting method or an ingot casting method.
- the slab is formed by the block rolling method.
- the slab is heated and formed into a hot-rolled steel sheet by a hot rolling process. It is also possible to insert the slab into a heating furnace before the slab is cooled to room temperature, or to directly hot-roll the slab after the slab is manufactured.
- the slab reheating temperature in hot rolling when performing slap reheating is not particularly specified, but it is necessary to raise the winding temperature in order to omit the annealing process of the hot rolled sheet.
- the slab reheating temperature is preferably at least 150 ° C.
- the reheating temperature exceeds 125 ° C, not only the loss due to oxidation of the surface of the slap during heating will increase, but also the problem that the slab will sag will occur.
- a part of the steel may be transformed into a ⁇ ferrite phase and the hot workability may be impaired.
- the rolling conditions and temperature conditions in the hot rough rolling are not particularly limited, but it is desirable to perform at least one pass of rolling at a rolling reduction of 30% or more.
- the high-pressure rolling refines the crystal grains of the steel sheet and improves the low-temperature toughness of the base metal.
- the finishing temperature in hot rolling is preferably 900 or more, and preferably more than 930, from the viewpoint of promoting softening after coil winding. By setting the finishing temperature in hot rolling to 900 ° C or more, the introduction of processed ferrite by rolling in the ⁇ + ⁇ two-phase region can be prevented, and the winding temperature can be kept high. The formation of a hard martensite phase during cooling of the steel can be suppressed.
- the winding temperature in hot rolling is preferably 800 ° C.
- hot-rolled sheet annealing may be performed as necessary.
- patch annealing at a temperature of 600 ° C or more or continuous annealing can be performed.
- the annealing time is preferably 1 hour or more.
- the removal amount in the descaling step is an important matter that determines the corrosion resistance after painting, which is the main feature of the present invention.
- the removal amount 1 of the steel sheet surface in the present invention is, as shown in the schematic diagram of FIG. 4, the thickness in the sheet thickness direction from the so-called scale Z steel sheet interface 2, and the internal oxidized layer 3 and the dechromized layer 4 including thickness.
- a scale layer 5 mainly composed of oxides of Fe and Cr is formed on the surface of the steel sheet after hot rolling or after hot rolling annealing, and a spinel phase (sinelstructure phase) mainly composed of Fe is formed on the outer layer.
- a spinel phase mainly composed of Fe and Cr is formed in the inner layer.
- the dechromized layer 4 is formed on the steel sheet side just below the scale due to the lack of time. If the dechromized layer 4 remains on the surface of the steel sheet after descaling, the corrosion resistance will be significantly reduced.Therefore, it is important to completely remove the dechromized layer 4 on the steel sheet surface during the descanning process. .
- a dense layer mainly composed of Cr 2 O 3 is continuously formed further inside the above-mentioned spinel layer, so that the steel is applied from the outside to the steel sheet. Of oxygen is suppressed. Therefore, the thickness of the dechromized layer 4 is at most less than 1 0 ⁇ ⁇ from the scale / / steel plate interface.
- C r containing organic amount as in the present invention is 1 0% or less and low, since the C r 2 0 3 layer is not continuously formed, significantly ingress of oxygen in the external force, as shown in FIG. 4 The so-called internal oxidation layer 3 is formed. It is.
- the internal oxide layer 3 is formed by preferential oxidation of elements having a high affinity for oxygen, such as Cr and Si, and when the cross-sectional structure of the steel sheet is observed, preferential oxidation at the grain boundaries of the steel sheet 6 And oxide formation in grains7.
- the portion including the internal oxide layer 3 formed inside the scale / steel plate interface 2 and the decapping layer 4 formed in association with this is removed by descaling treatment. Is important, and this significantly improves the corrosion resistance after painting.
- the inventors have further studied diligently from the viewpoint of coating adhesion.
- the paint will not flow sufficiently into the grain boundary eroded area due to insufficient wettability of highly viscous paint. Therefore, it was found that the adhesion between the steel sheet and the paint was reduced.
- the chromium content at the grain boundaries is particularly likely to decrease, so that grain boundary erosion is likely to occur. If the coating adhesion decreases, a gap structure is easily formed between the coating film and the steel sheet, and the corrosion resistance after coating decreases.
- Table 1 and Fig. 1 show the removal of the steel sheet surface by using a hot rolled 9% Cr steel sheet manufactured on an actual machine and performing descaling with a shotplast, sulfuric acid, and hydrofluoric acid / nitric acid pickling in the laboratory.
- 5 is an example of a result of evaluating the corrosion resistance of a steel sheet and the corrosion resistance after painting when the amount is changed. From these results, in the steel containing 6.0 to 10.0% Cr as in the present invention, the corrosion resistance of the steel sheet is improved by removing the surface of the steel sheet by 10 ⁇ m or more in the descaling step.
- the coating adhesion is improved and the corrosion resistance after painting is improved.
- making the Cr concentration difference of 1% or less (Cr concentration inside the steel sheet) less than 1% (Cr concentration on the steel sheet surface) not only improves the corrosion resistance of the surface of the steel sheet itself, As shown below, by reducing irregularities due to grain boundary erosion, It has the effect of improving the corrosion resistance after painting.
- the amount of steel plate removed is l Oiim or more
- the difference in the Cr concentration of (Cr concentration inside the steel plate)-(Cr concentration on the steel plate surface) is 1% or less. In this case, the corrosion resistance after painting was good.
- the Cr concentration inside the steel sheet is the Cr concentration near the center of the steel sheet thickness without the influence of the Cr removal layer. Refers to the Cr concentration in the internal part beyond m. In the case of a cold-rolled annealed sheet, it refers to the Cr concentration in the portion inside tZ4 or more with respect to the sheet thickness t.
- the Cr concentration inside the steel sheet can be determined by analysis using EPMA, EDX, X-ray fluorescence, etc., solid-state emission spectroscopy, or high-frequency inductively coupled plasma-atomic analysis after chemical dissolution. Emission (hereinafter, referred to as IC JP method) or a method such as quantification by titration.
- IC JP method high-frequency inductively coupled plasma-atomic analysis after chemical dissolution.
- Fig. 2 shows the results of scanning electron microscope observation of the steel sheet surface when the steel sheet surface removal amount was 8 ⁇ m and 40 ⁇ m.
- the surface removal amount is 8 m
- the grain boundaries are preferentially deeply eroded.
- the surface of the steel sheet was removed by 40 ⁇ , no remarkable grain boundary erosion was observed.
- Figure 3 shows the results of measuring the Fe and Cr concentration profiles from the steel sheet surface in the thickness direction by glow discharge spectroscopy (GDS).
- GDS glow discharge spectroscopy
- the whiteness index of the steel sheet surface was measured in accordance with JISZ 8715, and as a result, the whiteness index of the 8 m-removed material was about 62, while that of the 40 ⁇ m-removed material was 68.
- the whiteness index was approximately 65 or more, significant grain boundary erosion was eliminated and the coating corrosion resistance of the steel sheets was improved.
- a more preferred removal amount of the steel sheet surface is 15 ⁇ or more, and further preferably 20 ⁇ or more.
- the present invention aims to control the steel sheet surface properties accompanying the removal of the steel sheet surface of Cr steel and to improve the corrosion resistance after painting by removing the internal oxide layer 3 and the dechromized layer 4.
- the steel plate surface was removed by 1 ⁇ or more, more preferably 15 ⁇ m or more, even more preferably 20 ⁇ or more, and the Cr concentration on the surface of the steel plate was reduced to ( It has been found that by setting the Cr concentration inside the steel sheet to be equal to or greater than 1 lmass%), the coating corrosion resistance is significantly improved.
- the corrosion resistance of the steel sheet in Table 1 was evaluated based on the area ratio after performing a 4-hour saltwater mist test in accordance with JISZ 2371, and the steel sheet having an area ratio of 20% or less was evaluated as good.
- the corrosion resistance after coating was determined by applying a JIS coating on the surface to an acryl resin coating with a target dry film thickness of 5 O / zm, A salt water spray test was performed for 1000 hours according to Z2371, and a case where there was no remarkable flow that would cause a puddle at the lower part of the sample was evaluated as good.
- the measurement of the amount of steel sheet surface removal is specifically performed by measuring the weight and the size after removing the scale mechanically using a shot blast, and the weight after performing acid pickling.
- the descaling method of the hot rolled sheet in the present invention is not particularly limited.
- the steel sheet after descaling can be used as the steel of the present invention. Further, the steel sheet after the descaling is cold-rolled to a predetermined thickness and then annealed and pickled may be used as the steel of the present invention. Since the surface of the cold-rolled annealed sheet is sufficiently smooth, it is considered that the corrosion resistance does not decrease due to poor coating adhesion as described above.However, if the descaling of the hot-rolled sheet is insufficient, Sufficient corrosion resistance cannot be obtained even after annealing.
- the steel of the present invention in which the internal oxide layer 3 and the dechromized layer 4 immediately below the scale are completely removed by the descaling treatment of the hot-rolled sheet, it is possible to obtain sufficient corrosion resistance even in the steel sheet after cold rolling annealing.
- the rolling reduction in the cold rolling is preferably 30% or more.
- the steel sheet after cold rolling is preferably annealed for the purpose of softening, and the annealing condition at this time is preferably 600 ° C. or more. After cold rolling annealing, the steel sheet can be pickled or subjected to a similar treatment, and then can be given various surface finishes specified in JIS G430. In consideration of corrosion resistance after painting, it is preferable to use No. 2B finish.
- the paint is applied by spraying or brushing, etc.
- the paints include acrylic resin paint, phthalate resin paint, epoxy resin paint, polyurethane resin paint, etc.
- Various paints as described in ISK550 are used. Before painting, various primers may be applied to prevent initial damage. If necessary, an undercoat or an intermediate coat using various anticorrosive paints or resin paints may be applied.
- the steel of the present invention itself has higher corrosion resistance than ordinary steel and also has excellent adhesion between the steel sheet surface and the top coating, so that primer coating, undercoating and intermediate coating can be omitted. It is also possible to apply a high topcoat paint directly to the steel sheet. When considering use as a refrigeration container, the thickness of the coating film must be 10 ⁇ or more to obtain sufficient corrosion resistance. It may not be necessary to apply the paint depending on the application where it is used, such as when used as a structural material for a house or in a material that does not require high corrosion resistance.
- the value of the Charpy impact value as a toughness index one 2 5 ° C at 5 0 J / cm 2 or more is required.
- the temperature should be at least 80 cm 2 at 25 ° C.
- the yield ratio is a value that is an index of the difficulty of processing and the seismic performance when used in a house. It is desirable that the yield ratio be as low as possible, but the structural material must be 80% or less. It is less than 75%.
- Steel raw materials are melted by vacuum melting to the chemical composition shown in Table 2.
- a 50 kg steel ingot is manufactured by ingot, heated to 1200 ° C, held for 1 hour, and hot-rolled to a 4 nun thickness heat. It was a rolled sheet.
- Half of these hot-rolled sheets were subjected to uniform annealing (hot-rolled sheet annealing) at 650 ° C for 10 hours.
- the hot-rolled steel sheet whose hot-rolled steel sheet and the hot-rolled steel sheet were annealed was shot-plasted and then descaled by pickling with a mixture of hydrofluoric acid and nitric acid to remove the steel sheet surface by about 15 ⁇ m. did.
- the amount of removal from the steel sheet surface was measured by measuring the weight and dimensions after mechanically removing scale by shot blasting and the weight after pickling, and the difference between these weights was measured as the surface area of the sample.
- the removal thickness ( ⁇ ⁇ ) of the steel sheet was determined using the steel sheet density (7.8 g / cm 3 ).
- pickling use l ⁇ 2 mass% hydrofluoric acid-13 ⁇ 15 mass% nitric acid solution at a temperature of 40 ⁇ 60 ° C, take out every 30 seconds and measure the weight after washing. By repeating this, a desired steel sheet surface removal amount was obtained.
- a sheet with a thickness of X50X100 is cut out and spray-coated on the surface to produce an acrylic silicone resin paint with a target dry film thickness of 50 / zni (Kansai Paint Co., SILICOTECT AC overcoat, SILI Coated by COTE CT AC TOP C OAT), and a cross-cut X-shaped sample was placed on the sample.
- a 1000-hour salt spray test (5% NaC 1, 35 ° C, The pH was adjusted to 6.5 to 7.2), and the time until a remarkable flow, which caused a puddle at the bottom of the sample, was measured.
- the dry film thickness of the paint was determined by examining the cross section of the paint film by an electromagnetic film thickness gauge using a magnetic method.
- the dry film thickness was approximately 50 xm. Also, both surfaces of the steel sheet were ground by 0.75 mm to a thickness of 2.5 mm, and a sub-size Charpy impact test specimen conforming to JIS Z 2202 with a 2 raraV notch perpendicular to the rolling direction was sampled. The Charpy impact value (J / cm 2 ) at ⁇ 25 ° C. was measured. The results are shown in Table 3. The Charpy impact value of cold-rolled steel sheets of 2 mmt or less cannot be measured by ordinary methods, but generally the toughness increases as the steel sheet thickness decreases (see, for example, Journal of the Japan Welding Society, Vol.61 (1992), No.8).
- the cold rolled steel sheet is also structurally more advantageous than the hot rolled steel sheet for the Charpy impact value. Therefore, the Charpy impact value of the cold rolled steel sheet at -25 ° C is Equal to or greater than the value in. Therefore, if the Charpy impact value of a hot-rolled steel sheet with a large thickness shows a sufficient value, the The Charpy impact value of a cold rolled steel sheet having a small thickness is also a sufficient value.
- a 0.7 mm thick cold-rolled and annealed sheet was prepared using a No. 2 steel sheet that had not been subjected to hot-rolled sheet annealing, and a 0.7 mm-thick 2 mm V notch Charpy specimen was prepared. Create and small (1
- the above hot-rolled and pickled steel sheets were each cold-rolled to a thickness of 0.7 mm, then annealed at .750 ° C for 1 minute, and then subjected to descaling by neutral salt electrolysis and nitric acid electrolysis to obtain cold-rolled steel products.
- Neutral salt electrolysis conditions with 20% N a 2 SO 4 solution as the liquid temperature at 70-80, and the condition of the electrical quantity 100 ⁇ 200 CZdm 2.
- the nitric acid electrolysis condition was a condition in which the amount of electricity was 20 to 40 CZ dm 2 in a 10 ° / oHNO 3 solution at a liquid temperature of 50 to 60.
- JIS13B tensile test specimens were sampled in the rolling direction and subjected to a tensile test according to JIS Z 2241 to measure elongation and yield ratio. Furthermore, an X50 X 100 (mm) thick plate is cut out and spray-coated on the surface to give an acrylic silicone resin paint (Kansai Paint Co., Ltd., Silicotect AC overcoat, S
- Table 3 shows that steels 1 to 10 and steels 18 to 19, which are examples of the present invention, show whether or not hot-rolled sheet annealing was performed. Notwithstanding, there toughness (Sharubi impact value) N 50 J m 2 or more, a force one elongation of 33% or more, Le., Ru further yield ratio falls below 75%. In addition, good corrosion resistance with no run-off was shown in a 1000-hour saltwater fog test. On the other hand, the comparative steels 11 to 17 in which the steel composition is out of the range of the present invention have good toughness, elongation, yield ratio, and / or corrosion resistance regardless of the presence or absence of hot-rolled sheet annealing. Level had not been reached.
- the steel of the present invention is relatively inexpensive.
- the steel of the present invention has a lower Cr—low C—low N compared to SUS304 or 11% Cr stainless steel, so that hot-rolled sheet annealing can be omitted. By omitting, further cost reduction is achieved.
- taking advantage of the excellent mechanical properties and low cost of the steel of the present invention it can be applied to various structural materials such as housing structural materials, and has sufficient performance especially for use in cold regions. Demonstrate.
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Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE60326247T DE60326247D1 (de) | 2002-09-03 | 2003-08-28 | Cr-STAHL FüR DIE BAUANWENDUNG UND HERSTELLUNGSVERFAHREN DAFüR |
US10/523,880 US20050241737A1 (en) | 2002-09-03 | 2003-08-28 | Cr steel for structural use and method for producing the same |
EP03794112A EP1538230B1 (en) | 2002-09-03 | 2003-08-28 | Cr STEEL FOR STRUCTURAL USE AND METHOD FOR PRODUCING THE SAME |
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JP2002-257229 | 2002-09-03 | ||
JP2002257229 | 2002-09-03 |
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WO2004022808A1 true WO2004022808A1 (ja) | 2004-03-18 |
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PCT/JP2003/010908 WO2004022808A1 (ja) | 2002-09-03 | 2003-08-28 | 構造用Cr鋼およびその製造方法 |
Country Status (7)
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US (1) | US20050241737A1 (ja) |
EP (1) | EP1538230B1 (ja) |
KR (1) | KR100665128B1 (ja) |
CN (1) | CN1303242C (ja) |
DE (1) | DE60326247D1 (ja) |
TW (1) | TWI306123B (ja) |
WO (1) | WO2004022808A1 (ja) |
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JP4959937B2 (ja) * | 2004-12-27 | 2012-06-27 | 株式会社日立産機システム | 腐食診断部品を設けてなる配電用変圧器 |
DE102006062348B4 (de) * | 2006-12-22 | 2016-10-06 | Mitsubishi Hitachi Power Systems Europe Gmbh | Oberflächengestrahlte Dampferzeugerbauteile oder Kraftwerkskomponenten |
CA2807637C (en) * | 2010-08-24 | 2018-09-11 | Tomoyuki Ozasa | Method for preventing elution of bi from copper alloy |
DK2736393T3 (en) * | 2011-07-29 | 2018-05-22 | Moba Group Bv | DEVICE FOR THE PROCESSING AND PROCESSING OF FOOD PRODUCTS AND FOOD INGREDIENTS |
KR101921595B1 (ko) * | 2016-12-13 | 2018-11-26 | 주식회사 포스코 | 리징성 및 표면품질이 우수한 페라이트계 스테인리스강 및 그 제조방법 |
KR101889193B1 (ko) * | 2016-12-22 | 2018-08-16 | 주식회사 포스코 | 내식성 및 가공성이 우수한 냉연강판 및 그 제조방법 |
KR101923922B1 (ko) * | 2016-12-23 | 2018-11-30 | 주식회사 포스코 | 표면특성이 우수한 오스테나이트계 스테인리스강 가공품 및 이의 제조 방법 |
CN111349850B (zh) * | 2018-12-24 | 2022-03-18 | 宝山钢铁股份有限公司 | 一种高耐蚀耐候钢及其制造方法 |
WO2023121295A1 (ko) * | 2021-12-22 | 2023-06-29 | 주식회사 포스코 | 무방향성 전기강판, 그 제조 방법 및 그를 포함하는 모터 코어 |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH08143959A (ja) * | 1994-11-24 | 1996-06-04 | Nippon Steel Corp | 高温特性の優れた鋼管の製造方法 |
JPH10147848A (ja) * | 1996-11-19 | 1998-06-02 | Nisshin Steel Co Ltd | 高温強度及び高温酸化特性に優れたエンジン排ガス経路部材用フェライト系高Cr鋼 |
JP2002161312A (ja) * | 2000-11-21 | 2002-06-04 | Nkk Corp | 高靭性高クロム鋼板の製造方法 |
Family Cites Families (3)
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US6544356B2 (en) * | 1996-12-05 | 2003-04-08 | Nisshin Steel Co., Ltd. | Steel sheet for use as an electrode-supporting frame member of a color picture tube and manufacturing method thereof |
TW504520B (en) * | 1997-03-27 | 2002-10-01 | Kawasaki Steel Co | Chromium-containing hot rolled steel strip and its production method |
US20040003876A1 (en) * | 2002-07-04 | 2004-01-08 | Jfe Steel Corporation, A Corporation Of Japan | Structural Fe-Cr steel sheet, manufacturing method thereof, and structural shaped steel |
-
2003
- 2003-08-28 KR KR1020057003628A patent/KR100665128B1/ko not_active IP Right Cessation
- 2003-08-28 DE DE60326247T patent/DE60326247D1/de not_active Expired - Lifetime
- 2003-08-28 US US10/523,880 patent/US20050241737A1/en not_active Abandoned
- 2003-08-28 WO PCT/JP2003/010908 patent/WO2004022808A1/ja active Application Filing
- 2003-08-28 EP EP03794112A patent/EP1538230B1/en not_active Expired - Fee Related
- 2003-08-28 CN CNB038209276A patent/CN1303242C/zh not_active Expired - Fee Related
- 2003-09-02 TW TW092124190A patent/TWI306123B/zh not_active IP Right Cessation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08143959A (ja) * | 1994-11-24 | 1996-06-04 | Nippon Steel Corp | 高温特性の優れた鋼管の製造方法 |
JPH10147848A (ja) * | 1996-11-19 | 1998-06-02 | Nisshin Steel Co Ltd | 高温強度及び高温酸化特性に優れたエンジン排ガス経路部材用フェライト系高Cr鋼 |
JP2002161312A (ja) * | 2000-11-21 | 2002-06-04 | Nkk Corp | 高靭性高クロム鋼板の製造方法 |
Also Published As
Publication number | Publication date |
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TWI306123B (en) | 2009-02-11 |
EP1538230A4 (en) | 2007-11-14 |
DE60326247D1 (de) | 2009-04-02 |
EP1538230B1 (en) | 2009-02-18 |
KR100665128B1 (ko) | 2007-01-09 |
CN1303242C (zh) | 2007-03-07 |
CN1678766A (zh) | 2005-10-05 |
EP1538230A1 (en) | 2005-06-08 |
TW200404904A (en) | 2004-04-01 |
KR20050057106A (ko) | 2005-06-16 |
US20050241737A1 (en) | 2005-11-03 |
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