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
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/12—Aluminium or alloys based thereon
• • 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
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12736—Al-base component
  • Y10T428/1275—Next to Group VIII or IB metal-base component
  • Y10T428/12757—Fe

Definitions

• the present invention relates to a hot-dip aluminum plated steel sheet excellent in strength and oxidation resistance at high temperatures and a method for producing the same.
• the present invention relates to a low alloy mesh plate with a fused aluminum plate that can be substituted for AIS I 409 or 410 as a material for an automobile exhaust gas system, and a method for producing the same.
• hot-dip aluminum-plated launders are broadly classified as heat-resistant and corrosion-resistant.
• the former is called an I-type aluminum-plated steel sheet, and the latter is called a type-II aluminum-plated steel sheet.
• the heat-resistant I-type aluminum loupe the presence of a small amount of Si in the A1 S suppresses the development of the Fe-Al alloy layer during high-temperature heating. The heat resistance of the steel sheet is improved.
• the service life of the conventional one is usually about 600, which is usually lower than that.
• type III aluminum-plated steel sheets use pure A1 as the coating material, and are superior in corrosion resistance to type I, but inferior to type I in heat resistance.
• Such a hot-dip aluminum-plated steel plate is usually made of a cold rolled plate of an aluminum chilled pot or a rimd pot, and is provided with a hot-dip aluminum coating.
• the rope slab is subjected to a hot rolling process, a bladder scale process,? Inter-rolling process, annealing ⁇
• the annealing process and the hot-dip aluminum plating process are carried out on a so-called Sendzimer-type hot-dip aluminum coating line equipped with in-line annealing equipment. It is generally performed by passing through a board.
• Japanese Patent Publication No. 53-15454 and the corresponding U.S. Pat. No. 3,881,880 disclose that carbon in a rope is contained in an almikilled carbon gauze having a carbon content of about 0.03 to about 0.25% by weight. It is proposed that the base material be one that is fixed to all and that contains enough titanium to leave about 0.1 to about 0.3% by weight of unbound titanium, and then be subjected to hot-dip aluminum plating. According to this, carbon is turned out as titanium carbide, and there is virtually no solid solution carbon in the iron. Therefore, an iron base in a state close to pure iron can be obtained. He teaches that when the coated steel sheet is heated to a high temperature, the A1 of the plating layer easily diffuses into the iron ground, and as a result, the high-temperature oxidation resistance of the steel ground surface is enhanced.
• Another object of the present invention is to provide a plate with a molten aluminum coating excellent in strength and oxidation resistance at high temperatures.
• the advantageous effects of the addition of titanium on the oxidation resistance as taught by the above-mentioned Japanese Patent Publication No. 53-15454 and the corresponding US Pat. No. 3,881,880 damage are as follows. It was found that even if an appropriate amount of Si and is added as an alloying element to the base metal with an extremely low amount, the target high-temperature strength can be exhibited without being hindered. This means that it is important to minimize the alloying components other than ⁇ 'and obtain an iron base close to pure iron as much as possible in order to promote A1 diffusion from the plating layer to the base material surface layer. It is surprising from the disclosure of the specification.
• Ti-added steels Both Si are known as elements that increase the strength of the net, and it is also known that Ti-added steels have a given secondary recrystallization temperature. It is therefore predictable that Ti-added Si-Mn steels will be able to develop sufficient strength at high temperatures up to the secondary recrystallization temperature.
• such Ti-added Si-Mn steel cold rolled gauze was manufactured under normal conditions using a normal industrial manufacturing line, and was then sent to a Sendjimi equipped with an in-line annealing facility. Attempts to commercially produce hot-dip aluminum-coated steel sheets with excellent strength and oxidation resistance at high temperatures by passing them through iron-type hot-dip aluminum-plated lines were unsuccessful. The resulting product had no spot-like spots and did not exhibit oxidation resistance at high temperatures.
• the hot rolled winding temperature in the manufacturing process is controlled to a low temperature that does not cause oxidation of Si and Mn in the steel, based on Ti-added Si-Mn ⁇ in which the gong component is appropriately adjusted. If this is done, it was found that an industrial product of a glazed board with molten aluminum with sufficiently high oxidation resistance and strength at high temperatures could be produced effectively.
• the present invention is intended to provide a method for industrially producing a hot-dip aluminum plated gauze plate based on such a Ti-added ultra-low carbon Si-steel as a substrate.
• a gong slab to which a sufficient amount of titanium added to the gong to be fixed and unbonded remains in the gong is produced, and is subjected to the maturing pressing process, the Teng scale process, the cold rolling process, the annealing process and In the usual method of manufacturing a molten aluminum coated glazed board, which is sequentially subjected to a molten aluminum coated immersion process to form a molten aluminum coated pierced board,
• C 0.020% or less
• Si 0.1 to 2.2M
• Mn 2.5% or less
• the present invention provides a method for producing a hot-dip aluminum plated launder plate characterized by the following.
• the hot-dip aluminum coated steel sheet according to the present invention which has excellent high-temperature strength and high-temperature oxidation resistance, has a C content of 0.020% or less, a Si content of 0.12.2% and a 2.5% weight or less.
• Ti 0.1 to 0.5% and (% Ti) / (% C + 3 ⁇ 4N) ⁇ 10, A1; 0.01 to 0.1%, N: 0.010% or less, the balance being Fe and unavoidable impurities, and substantial It consists of a Ti-added Si-Mn net substrate without internal oxidation and hot-dip aluminum coating on both sides.
• an intermediate layer consisting of an A1-Fe-Si alloy exists at the interface between the A1 plating coating (more precisely, Al-Si coating) and the base steel. .
• Internal oxidation is limited to the surface layer of the pan, but it can extend from a few micron to several tens of micron deep depending on the conditions (such as steel composition, winding temperature, and cooling rate after winding).
• the oxides of Si and Mn generated by the internal oxidation exude to the grain boundaries or grain boundaries and grains of the surface layer of the pot, and do not necessarily form a continuous layer. of The whole is referred to herein as an “inner oxide layer”. This is completely different in composition and form from the scale of the gong surface.
• FIG. 1 show the behavior of the internal oxide layer in various processes in the production of molten aluminum-coated lumber.
• FIG. 2 and () are cross-sectional micrographs (magnification, both X400x) before and after aluminum plating of the substrate where the internal oxide layer is present.
• Figures 3 (a), (b), (c) and (d) are cross-sectional micrographs (magnification, Izu) showing the behavior of the presence or absence of an internal oxide layer affecting the high temperature oxidation resistance. This is also X 400 times),
• Figures 4), (b), (c) and (d) show how the amount of Si and Mn in Si-Mn gong and the temperature affect the formation of the internal oxide layer. Graphical representation of the experimental results,
• Figure 5 shows the relationship between the occurrence of internal oxidation and the cooling curve of the hot rolled coil.
• Fig. 6 is a diagram showing the relationship between the Si content and the Si content in the base material stipulated by the present invention. Detailed description of the invention
• Fig. 1 is a schematic enlarged cross-sectional view of the steel surface immediately before hot-rolling and winding a Ti-bearing ultra-low carbon Si-Mn steel to which the amounts of Si and Si specified in the present invention are added.
• Scale 2 is generated on the surface of the gong base material 1.
• This scale 2 is usually called the secondary scale.
• the scale formed on the surface of the slab ripened to a high temperature in the ripening furnace is called the primary scale, and most of it is removed from the surface during the rolling process.
• Secondary scale 2 is generated during the period from finishing mill to coil winding.
• Fig. 1 (b) shows a similar cross section when hot rolled material with secondary scale 2 of Fig. 1 (a) is wound at a winding temperature exceeding 600 (for example, about 700) and allowed to cool.
• Fig. 1 (c) is a similar cross-sectional view after the hot-rolled material of Fig. 1 () has been descaled by pickling.
• the scale 2 is removed by pickling, but the deposited oxide remains in the grains. Then, a part of the oxide deposited at the grain boundaries is removed, and gaps 3 are formed at the grain boundaries.
• Fig. 1 (d) is a similar cross-sectional view of Fig. 1 () after cold-rolled hot-rolled material.
• the surface of the cold-rolled material is not smooth, and gap 3 is enlarged by cold rolling.
• the internal oxide layer remains even after cold rolling ⁇
• the gap 3 on the surface of the cold-rolled material that has been expanded and deformed is susceptible to the rolling oil and other contaminants used in the cold rolling process. May not be completely removed by annealing in
• Figures 1 ⁇ and (f) show the same results after passing the cold-rolled material of Fig. 1 (d) through an in-line annealed hot-dip aluminum plated line and applying molten aluminum plating.
• FIG. Foreign matter that has entered the grain boundary "gap" on the cold rolled material surface is completely removed by annealing at the plating line.
• OMPI If it is not removed, the aluminum coating may not adhere to that part as shown in Fig. 1 (e).
• 4 is the aluminum-coated S layer (Al-Si layer), and 5 is the interface between the aluminum-plated coating layer 4 and the lure base metal 1. This shows the A 1—Fe—Si alloy layer to be used, and the unplated layer 6 in Fig. 1 (e).
• Figures 2) and (b) are micrographs (400x magnification) before and after plating of the case where such non-plating occurred. Even if such unplating does not occur, as shown in Fig. 1 (f), the AI-Fe-Si alloy formed at the interface between the A1-Si coating layer 4 and the gong base metal layer 1
• the thickness of layer 5 tends to be larger than usual. This is probably because the surface area of the cold-rolled material becomes larger than it seems due to the existence of the grain boundary “gap 3”. If the thickness of the A1-Fe-Si alloy layer 5 is large, plating separation is likely to occur when hot-dip aluminum-coated steel sheets are processed. The presence of "gaps 3" deep (tip) After-out catastrophe also "pores 7 55 next likely. Holes 7 also to pull the plated ⁇
• Fig. 3 (a, micrograph of the cladding material corresponding to Fig. 1 (f) (magnification
• Such internal oxide layers form when the aluminum-plated steel sheet is heated to a high temperature.
• ⁇ ⁇ ⁇ Fig. 3 (>) is a micrograph of the same magnification after heating the cladding material of Fig. 3 (a) in air at 800 for 20 hours. It can be seen that the high-temperature oxidation resistance of the yum-plated steel plate is significantly impaired, and that such high-temperature heating causes the internal oxide layer itself to progress deeper into the steel substrate.
• the present invention it is important to obtain, after the scale process, a pan surface substantially free of an internal oxide layer when manufacturing a base steel for a molten aluminum-plated steel sheet. It is. According to the present invention, this can be achieved by controlling the temperature of the 10 sheets immediately before winding on the coiler in the hot rolling process to a sufficiently low level just before winding on the coiler.
• Table 1 shows the chemical composition of the test pan plate (plate thickness 1.0 mm) used for the test. Show. Each test was prepared by forging, hot rolling (thickness: 7.0 mm), grinding (thickness: 5. Oram), and cooling (thickness: 1.0 mm). Table 1 (Chemical composition of test material by weight%)
• FIG. Fig. 4 (a) shows the result at 550, but no internal oxide layer is formed irrespective of the content of Si and.
• Fig. 4 (0) shows the results for 600 cases.
• a slight increase occurred in the case of test specimens ⁇ 5, 6, and 7, but not in the other test networks.
• there is no difference due to the decrease in the Si content but this may be due to the difference in the form of the scale formed on the surface.
• a deep internal oxide layer is formed except for the test mounds ⁇ 1 and ⁇ 3, where Si and are extremely low. Deeper oxide layer is formed Cheating.
• the winding temperature in the hot rolling process should be about 600'c or less, preferably about 570'c or less. It seems that most preferably it needs to be controlled below about 550'c.
• the lower limit of the winding temperature is not critical and depends on the capacity of the coiler. Winding at temperatures usually below about 400'c is not practical.
• the hot-rolling temperature has been important as a recipe for controlling the physical properties of the net obtained.
• Ti-added low-carbon steel which evolves Ti as Ti carbonitride and improves the ductility and workability of the pot, raising the winding temperature to 600 ° C, for example, The aim was to control the size of the carbonitride in Ti to an appropriate range by exceeding the temperature, more preferably at 700 or more.
• carbon and nitrogen are fixed by Ti.
• the carbon content is limited to a very low value of less than 0.02% ), It is intended to improve the strength by positively adding appropriate amounts of Si and Mn.
• the aluminum-plated gauze plate is manufactured on an industrial scale by actually applying the winding temperature, which has been conventionally recommended for Ti-containing gongs, to the Ti-containing ultra-low carbon Si-Mn steel according to the present invention. I tried to. However, as shown in Failure Example A of Example 1 below, this was a defective product for the Luo I product with aluminum plating.
• the present inventors have conducted studies to overcome this reality, but found the cause in the internal oxide layer as described above, and as a prescription for suppressing the formation of this internal oxide layer, have conventionally been recommended in Ti addition glows. Contrary to the high-temperature winding that has been performed, it has been found that low-temperature winding is essential.
• the hot rolling process consists of roughly rolling a slab, finish rolling it, and winding it up into a coil, during which time the primary scale is removed.
• the post-coating high-scale process is a normal chemical or thermal rising scale process, which is basically a process to remove the secondary scale inevitably generated in the hot press process. Most commonly, pickling is performed. As described above, the internal oxide layer is not removed in this (2) scale process.
• the cold pressing process is a process of cold rolling with or without intermediate annealing to a desired thickness of a hot rolled slab of ⁇ scale.
• the method for producing a molten aluminum plated launder according to the method of the present invention has a special significance on the chemical composition of the base steel applied to this method. Below is the effect of each component of this base material
• C is a harmful component to the high-temperature oxidation resistance of aluminum-plated netting.
• the first point of the detrimental effect of c is that it significantly reduces the ability of A1 to diffuse from the coating layer into the base steel, and that when the aluminum pan plate is heated to a high temperature. The point is that a large amount of voids and voids are generated at the interface between the base material and the adhesion layer. The formation of these voids and voids occurs more frequently when the diffusion rate of Fe from the substrate pan into the plating layer is higher than the diffusion rate of A1 from the plating layer into the substrate.
• the second point of the detrimental effect of C is to enhance the separation of the plating layer at high temperatures.
• the addition of Ti sufficient to fix the content makes it possible to obtain a net product with stable strength characteristics and excellent surface cleanness. It becomes difficult.
• the titanium carbide (and Ti nitride) has The amount of output is extremely large, and the form of this output changes even with slight changes in various conditions in the hot rolling process and also in the annealing process.
• the strength characteristics of the gongs and the extensibility characteristics vary greatly depending on the difference in the form of this projection. Therefore, it is practically difficult to produce a product having stable strength characteristics.
• the strength improvement due to carbonitride of Ti is not expected, and the C content is reduced to a low range, and the necessary amount of added Ti is reduced accordingly, and secondary recrystallization by Ti addition is performed.
• the improvement of high-temperature strength which is the object of the present invention, is to be achieved by maintaining the strength improving effect of the addition of Si and Mn up to the secondary recrystallization temperature.
• the C content needs to be as low as possible, with the upper limit being 0.02%, preferably 0.017%, and more preferably 0.015%.
• the extremely low C content can be achieved by adding a vacuum-gas treatment method to the normal converter steelmaking method.
• the lower limit of the C content is not critical, and can be 0.001% or more, which can be achieved by combining ordinary converters with vacuum and gas equipment.
• Si is an element that contributes to the improvement of high-temperature strength, which is the main object of the present invention, and also contributes to high-temperature oxidation resistance.
• the high temperature strength improvement effect of Si is due to solid solution strengthening, and the effect increases as the Si content increases.
• the Si content exceeds 2.2%, the high-temperature strength is further increased, but not only the cold workability and weldability are deteriorated, but also the aluminum plating properties are remarkably deteriorated, resulting in a sound aluminum plating. It becomes difficult to obtain a coating.
• the upper limit of the Si content is 2.2%. If the Si content is less than 0.1%, the effect on high-temperature strength and high-temperature oxidation resistance is extremely small. Therefore, the lower limit is set to 0.1%, preferably 0.2%, and more preferably 0.2%. 0.5% is the lower limit.
• Mn is an element that contributes to the improvement of high-temperature strength, which is the main object of the present invention.
• the effect of Mn to improve the strength of the module is due to the effect of solid solution strengthening, and the effect increases as the Mn content increases.
• the Mn content exceeds 2.5%, the high-temperature strength is further increased, but not only the cold workability and weldability are significantly degraded, but also the 800 ' During high temperature use in the temperature range below C,
• ⁇ ⁇ r has the effect of lowering the transformation temperature.
• FIG. 6 shows the relationship between the Si content and the Mn content defined by the present invention. According to the present invention, the hatched area in FIG.
• the preferred Si and Mn contents are points A (0.1, 2.5), K (0.1, 1.47), L (0.67, 0.33), Q (2.2, 1.1) and D (2.2, 2.5) in Fig. 6. It is represented by a point within the defined pentagon.
• Ti is one of the basic elements that effectively diffuses A1 in the plating layer into the substrate network.
• C and N in the base material as ⁇ (C, ⁇ ) substances, the diffusion of A1 from the plating layer into the base material steel becomes remarkably easy, and the base material adheres to the base material. The amount of voids and voids generated at the interface with the layer is drastically reduced.
• outermost surface is composed mainly of Alpha 1 2 0 3
• An o-Fe layer having a high concentration of A1 covered with a stable and dense oxide layer is formed, and excellent high-temperature oxidation resistance is exhibited. If Ti is added in an amount at least 10 times the (C + N) amount, a sufficient amount of Ti can be present in the form of a solid solution in the base material , further improving the high-temperature oxidation resistance of the coated steel sheet Yes.
• This Ko ⁇ is the interface between the oxide layer to a- Fe layer ⁇ the A1 high hand above at a high temperature heating (A1 diffusion layer) mainly composed of A 1 2 0 3, Ti is selectively by being acid into, [pi to the interface 'concentrated believed because to the oxide layer of the a l 2 0 3 as a main component more stable and dense ones. Also, since Ti raises the secondary recrystallization temperature, the ferrite grains of the base metal are stabilized at a high temperature, and the solid solution strengthening effect of Si and Mn according to the present invention is maintained at a high temperature. Will be provided.
• the overall effect of Ti as described above does not increase even if the Ti content exceeds 0.5% and is added in a large amount, but rather only increases the surface quality of the substrate steel. Limit the value to 0.5%. In addition, if the content is less than 0.1%, even though it is sufficient to fix C and N in the base steel, the amount of solute Ti in the base pan is reduced and the above A 1 2 0 3 stable and dense things to et the oxide layer mainly composed of i 8
• the lower limit is 0.1%.
• M is added for the purpose of sulfuric acid in molten steel, but in the present invention it is also important as a reserve sulfuric acid element to yield Ti and to be added well. From this viewpoint, the lower limit was set to 0.01%. Addition of ⁇ in excess of 0.1% not only does not significantly improve the acid effect, but also increases the risk of spoiling the surface properties of the gauze plate, so the upper limit is set to 0.1%.
• This example explains the importance of the winding temperature specified by the present invention in the commercial-scale production of hot-dip aluminized steel sheets, and A is a failure example and B is a success example. .
• the low-carbon glow was melted in an 80-ton LD furnace.
• the smelt produced in the converter was subjected to ladle refining by the VAD method, and coal was coalesced by vacuum heating.
• Each of the scaled hot rolled sheets was cold rolled with a thickness of 1.55 mm using a tandem type four-stage cold fsl rolling mill.
• the sheet After subjecting each cold-rolled sheet to a surface cleaning treatment, the sheet was passed through a stainless steel-type hot-dip aluminum plating apparatus equipped with an in-line baking equipment, and was subjected to A1-Si (9% Si) plating. did. More specifically, the temperature of the strip in the line is at most .700 at N 0 F, followed by H Z
• the temperature in the (heat zone) was 810-830.
• the atmosphere of HZ was AX gas (decomposed ammonia gas).
• Pan plate plated Te this good Unishi is coating weight by a pair of di
• We Tsu Towaipa is adjusted to 80 gZm 1 in both total, it is moderately cooled After that, it was wound up in a coil.
• the plated coil was arrested by the dull roll at an elongation of about 1.0%.
• Figure 3 (a) shows a cross-sectional micrograph (magnification: 400x) of the area where no plating is applied to the plated steel sheet. This photograph shows that the internal oxide layer remains after plating.
• Fig. 3 (W) shows a cross-sectional micrograph (magnification: X 400 times) of the same steel sheet after the steel sheet was heated in the air at 800'C for 20 hours in the atmosphere shown in Fig. 3 (a).
• the diffusion layer was not formed on the surface layer of the gauze substrate, but that Fe scale was formed immediately below the plating layer and that the internal oxide layer was formed further deeper. ⁇ Plates cannot be said to be industrial products that satisfy the requirements for high-temperature oxidation resistance.
• FIG. 3 (c) shows a cross-sectional micrograph (magnification: 400x) of the plated steel sheet in Fig. 3 (c) after heating at 800'c for 20 hours in air. According to this photograph, the Al diffusion layer contributing to high-temperature oxidation resistance was formed, and no Fe scale was formed at the interface between the plating layer and the substrate, and no internal oxidation progressed. You can see the fact.
• Example 2 shows a cross-sectional micrograph (magnification: 400x) of the plated steel sheet in Fig. 3 (c) after heating at 800'c for 20 hours in air. According to this photograph, the Al diffusion layer contributing to high-temperature oxidation resistance was formed, and no Fe scale was formed at the interface between the plating layer and the substrate, and no internal oxidation progressed. You can see the fact.
• Example 2 shows a cross-sectional micrograph (magnification: 400x) of the plated steel sheet in Fig. 3 (c) after heating at 800'c for 20 hours in air
• Samples A, B and C are comparative examples in which the contents of Si and Hn in the base steel were outside the range of the present invention, and the Ti content and TiZ (C + N) ratio were varied. . These three samples, whose Si and content are outside the range of the present invention, have uniformly low strength at 600, regardless of the Ti content. Comparing these three samples, the increase in oxidation of sample C, which has the highest Ti content and the ⁇ ⁇ / (C + N) ratio, is the lowest, and the effect of Ti on the oxidation resistance is clear. However, this sample C has a low high-temperature strength and cannot achieve the object of the present invention.
• Samples D and E are comparative examples in which the Si and Mn contents exceed the upper limit of the present invention, respectively.
• Sample D has high temperature strength but low ductility at room temperature. Sample D had non-plating. For this reason, the amount of oxidation is also increasing.
• Sample E has high strength at high temperatures and low oxidation weight increase, but the mechanical properties at room temperature are likely to change significantly depending on the annealing conditions.
• Sample F is a comparative example in which the Si content and the content are within the range of the present invention but no Ti is added. Although this sample has excellent temperature strength, it is inferior in high temperature oxidation resistance.
• Sample G to Sample K are within the scope of the present invention. Comparing these five samples with sample C, Si and n do not impair the high-temperature oxidation resistance and contribute to the improvement of room-temperature strength and high-temperature strength in such a Ti-added steel. I understand.

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• 1983
  • 1983-07-04 JP JP58121277A patent/JPS6013053A/ja active Granted
• 1984
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