TW567243B - Hot-dip Zn plated steel sheet excellent in luster-retaining property and method of producing the same - Google Patents

Abstract

Degradation of the surface luster of a hog-dip Zn-Al-Mg plated steel sheet is inhibited by controlling the contact temperature between the plating layer and a water stream in a water cooling step after plating layer solidification, thereby suitably controlling the strip temperature during contact with the water stream, and further by incorporating a small amount of a suitable readily oxidizing element in the plating bath to stabilize the oxidation state of the plating surface layer Al and Mg.

Description

567243 _ Case No. 9111 ^ £ | _Tohoku Year September ^ _ Amendment _____ V. Description of the Invention (3) [Technical Field to which the Invention belongs] The present invention relates to the prevention of hot dip in continuous hot dip steel plating production line Zn-A 1-Mg (Zinc-Ming-Town) is a technician who may deteriorate the surface gloss when dip-coated steel sheet. [Prior Art] Japanese Patent Publication No. 10- 2 2 6 8 6 5, Japanese Patent Publication No. 0- 3 0 6 3 5 7, and US Patent No. 6, 2 are related to the same applicant as the present applicant. No. 3 5, 4 1 0 (US 6, 2 3 5, 4 1 0B1), U.S. Patent No. 6, 3 7 9, 8 2 0 (118 6,379, 82 (^ 1), etc.) are used. : 4.0 to 10%, Mg: 1.0 to 4.0%, and Ti: 0.002 to 0.001%, B: 0.00 to 0.001%, and the remainder is determined by zn and A hot-dip Zn-Ab Mg-based immersion bath made of unavoidable impurities to make a hot-dip Zn steel plate, such as the immersion coating made of [Al / Zn / Zr ^ Mg ternary eutectic structure] The metal structure of [primary crystal A 1 phase] and [Zn single phase] is mixed in the blank, and an impregnated steel sheet having sufficient corrosion resistance and surface appearance as an industrial product can be prepared, and the publication also describes It contains the manufacturing conditions for producing this metal structure. The inventors have found that in the subsequent manufacturing process, in a hot-dip galvanized steel sheet containing a relatively large amount of such A 1 and Mg, depending on the manufacturing conditions, The surface gloss of the dip coating will deteriorate within 2 to 3 days "The surface gloss of the immersion bond layer is degraded" 彳 $ 彳 θ Although the surface of the immersion plating immediately after the manufacture has a beautiful metallic luster, it has passed with time (the fastest is 2 to 3 days later. After 4 to 7 hours), it has the meaning of a slightly blackish suspected interference color, and the degree of discoloration (a blackening phenomenon) of this polar surface layer can be quantified by the measurement of "luminosity"

567243 Amendment No. 91116441 V. Description of Invention (4). For example, if the lightness (L value) of the dip-plated surface immediately after manufacturing is originally around L 8 2, it will be reduced to around L72 after 7 days. Even if this L value drops, it does not mean that the corrosion resistance of the product will be particularly deteriorated. The physical and chemical properties of the dip-coated steel sheet will not be damaged in any way, but it is not ideal from the aspect of surface appearance. In particular, the entire surface is not deteriorated like the electroplated surface, but the discoloration of some parts is the real damage to the appearance. Such deterioration in surface gloss may be unique to the aforementioned hot-dip Zn-Ab and Mg-based steel sheet having a relatively large content of A 1 and Mg. This deterioration can be presumed to be caused by the degree of oxidation of Mg concentrated on the surface layer of the immersion bond or the complex participation of the oxidation state of surface layer A 1. To date, there have been no reported examples of the surface gloss deterioration mechanism or the suppression method thereof that occurs in such hot-dipped Zn-A 1-Mg based steel plates. [Disclosure of the Invention] Therefore, the present invention is directed to finding a means for suppressing the deterioration of the surface gloss which is unique to the hot-dip bond Zn-A 1-Mg-based steel sheet. As a result of various experimental studies conducted by the present inventors in order to solve the foregoing problems, the cause of the deterioration of the surface gloss of this hot-dip galvanized steel sheet was finally found to be between the surface of the dip coating and water during water cooling during the cooling process after immersion. When it is found that if you want to prevent the surface gloss from deteriorating, it is necessary to properly control the "contact temperature between the immersion coating and the water flow" in the water cooling process after the leaching layer solidifies, and then "when in contact with the water flow" The control of "material temperature" is an effective matter. Furthermore, the oxidized state of A 1 and M g of the surface of the immersion plating layer can be set to ill m _ ί by administering a suitable amount of "easily oxidizable elements" in the immersion plating bath. in

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3] 3885.ptc Page 7 2003.05.20.007 567243 _Case No. 91116441_ Year and month of the household) Public day _ ^ _ 5. Description of the invention (5) Finalization is a valid matter. Here, the temperature of the material when in contact with the water flow refers to the temperature of the material when it is cooled under the formation of a water film on the surface of the immersion coating during the cooling process after the immersion coating has solidified, and more specifically, it refers to the flow of water The temperature of the immersion coating layer when the immersion coating layer is cooled in a state where the surface of the immersion coating layer is capable of forming a water film on the solidified immersion coating layer. That is to say, after continuously immersing the steel strip in the aforementioned hot-dip Zn-Ab Mg-based bath and pulling it up, the surface of the immersion coating after the solidification is brought into contact with the water flow (for the immersion coating layer) When the surface is supplied with a quantity of water that can temporarily form a water film on the surface of the immersion plating layer, when the board is continuously passed through the water-cooled water-chilled zone, the material entering the water-chilled zone When the temperature is controlled below 105 ° C, the deterioration of the surface gloss of the immersion plating layer as described above can be suppressed. It is also clear that the temperature of the incoming material to the water-chilled zone depends on the equipment conditions, but it depends greatly on the thickness of the steel plate. If the thickness of the steel plate is thick, it is sometimes difficult to control the temperature of the material to the water-chilled zone. Below 105 ° C. In this case, if the element is a oxidizing element with a strong affinity for oxygen and has the stabilization effect of A 1 oxide, for example, a rare earth element, Y (era),

When trace amounts of Zr (zirconium), Si (silicon), etc. are added to the dipping bath (actually, it is added in the range of 0.02 to 0.05% by mass). The fact that the temperature of the incoming material is lowered below 105 ° C (ie, even above 105 ° C) can also suppress the deterioration of the surface gloss. Therefore, the present invention provides a method for manufacturing a hot-dip galvanized steel sheet with good gloss retention, characterized in that the steel strip is continuously immersed in a Zn bath containing 4.0 to 15% by mass of A1 and 1.0 to 4. 0% by mass of Mg hot-dip galvanizing bath,

3] 3S85.ptc Page 8 2003. 05.20. 008 567243 _Case No. 91116441_ > Revised Years and Years _ V. Description of the invention (6) After being pulled up, the continuity through the plate will cause the surface and water flow of the immersion coating after solidification is completed. The water-chilled zone in which water cooling is performed under contact, and at this time, the temperature of the material entering the water-chilled zone is controlled below 105 ° C to control the deterioration of the gloss of the immersion coating. The hot-dip galvanizing bath is preferably in terms of mass%, A 1: 4.0 to 15%, Mg: 1.0 to 4.0%, Ti (titanium) 0.0 to 01 to 0.1%, B (Boron): 0 · 0 0 1 to 0 · 0 4 5%, the rest: those made of Zn and unavoidable impurities. Furthermore, the present invention provides a method for manufacturing a hot-dip galvanized steel sheet with good gloss retention, which is characterized by containing 4.0 to 15 mass% of A1 and 1.0 to 4.0 mass% of Mg in a Zn bath. 0 0 2 至 0.05 mass% after adding at least one kind of rare-earth element Y, Zr or Si easily oxidizable element to the hot-dip galvanizing bath, the steel strip is continuously immersed in In this bath, the continuous through plate is pulled in a water-chilled zone in which the surface of the immersion plating layer is brought into contact with water flow after solidification is completed, and at this time, it enters the water-chilled zone. The temperature of the side material is controlled above 105 ° C and below 300 ° C to control the deterioration of the gloss of the surface of the dip coating. This hot-dip galvanizing bath is preferably in terms of mass%, A 1 ·· 4. 0 to 15%, Mg · · 1. 0 to 4.0%, Ti · · 0.01 to 0.1%, B: 0. 0 0 1 to 0.04 5%, at least one kind of rare-earth element Y, Zr or Si easily oxidizable element ·· 0 0 0 2 to 0. 05%, the rest ··· Made of Zn and unavoidable impurities. In addition, as a hot-dip ore zinc steel sheet produced by such a manufacturing method, the present invention is provided for use, and contains A 1: 4.0 to 1 5% by mass%,

Mg: 1.0 to 4.0%,

3J3885.ptc Page 9 2003.05. 20.009 567243 _ Case No. 91116441 Sound Year y / yyyyyyyyy 7> Day_ifi__ V. Description of the invention (7) It can be re-contained as required

Ti: 0. 01 to 0. 1%, B: 0. 001 to 0. 045%, preferably further containing at least one oxidizable element selected from rare earth elements Y, Zr, or Si. 0 0.02 to 0.05%, the remainder is a hot-dip galvanized steel sheet with good gloss retention obtained by hot-dip galvanizing bath made of Zn and unavoidable impurities for hot-dip galvanizing of a steel strip. This immersion coating has "primary A1 phase" or "primary A1 phase" and "r Zn phase" mixed in the blank of "eight 1/211/2112 ^ 18 ternary eutectic structure" and / or "ZrigMg phase" metal structure. [Embodiment] In this specification, the term "steel strip" is used in the description of the hot-dip plating production line in principle, and the term "steel sheet" is used in the description of the finished product. The same. Figure 1 shows the outline of the equipment for manufacturing hot-dip galvanized steel sheet. The steel strip 2 that has been maintained at a predetermined temperature through the furnace 1 will be continuously sent to the immersion bath 3 ^ Once the '/ qian 3' comes out, use a Wiping nozzle 4 to adjust the amount of adhesion. When the air-jet cooler is 5 ^, the solidification of the bell layer will be completed. Next, the gas-water cooling zone 6a or 6b and ^, and the cooling zone 1 4 are operated in combination or alone, or they are passed through a water shock 7 punching zone 7 and the rice is tempered and cold-rolled by a skin pass mill 7 without running. After being subjected to the tension tester (tensi η 1 eve 1 1 er) 9 through the centrifugal ratio, it was taken up by the tension reel (tensi ο nree 1) 10 after the inspection process. E.g.

Page 10 2003. 05. 20. 〇10 567243 _ Case No. 91Π6441_ Household year 5 ~ month "> Revision _ V. Description of the invention (8) When the acid treatment is formed, it is subjected to roller tension straightening. After the machine 9, it is processed by the roller coating machine 11 and passes through the drying zone 1 2 and the air cooling zone 13 and is taken up by the tension winder 1 0 a. When a hot-dip bond Z η-A 1-M g steel sheet (hereinafter referred to as "Mg-containing hot-dip steel sheet") containing relatively large amounts of A 1 and Mg is manufactured as described above, from the viewpoint of surface properties It is important to properly control the cooling rate or the position of solidification after the immersion coating is solidified. Therefore, the temperature of the material when passing through the gas cooling zone 5 must be tightly controlled according to the plate speed or thickness. Then, in order to perform the light slab cold rolling in the flattening rolling mill 8 correctly, it is necessary to make the flattening by cooling in the gas water cooling zone 6 (and the gas cooling zone 1 4) or the water quenching zone 7 (Ski η pass) The material temperature on the inlet side is below the approximate temperature (for example, below 70 ° C). The cooling load in these cooling zones varies in conjunction with the plate speed and plate thickness. Generally, the spray of water or aqueous solution is supplied in the gas-water cooling zone, the airjet is supplied in the gas-cooled zone, and the surface of the immersion plating layer is supplied with sufficient water film in the water-chilled zone. Water flow. Therefore, in the latter water-chilled zone, the cooling operation in the water-chilled zone is ensured regardless of the change of the cooling load because the surface of the immersion bond layer can be in contact with the water flow to ensure a greater cooling rate. The efficiency is better. The water or aqueous solution in the air-water cooling zone 6 is sprayed together with the air stream, but does not supply the amount of water that can form a water film on the surface of the immersion coating layer, but mainly removes heat by evaporation latent heat. Therefore, the heat removal system in contact with the water current like the water-chilled zone is different in the form of heat removal and the cooling rate is also different. However, studies have found that the temperature of the incoming material towards the water-chilled zone

313885.ptc Page 11 2003. 05.20.011 567243 Amendment No. 91116441 V. Description of the invention (9) The fact that the gloss maintenance performance of the dip-plated surface will be different. If the temperature is 105 ° C or higher, the aforementioned deterioration of the surface gloss is liable to occur. The reason is not clear, but it can be presumed that when the water temperature is above 100 ° C when entering the water-chilled zone, a boiling phenomenon will occur when the water film is formed on the surface of the immersion coating. The surface of the coating will become rich in reactivity, and the behavior of A 1 due to the presence of water at atmospheric pressure will be about 1 1 0 ° C as the boundary. At this time, A 1 20 3 · 3 Η 20 (Or A 1 (Ο Η) 3) The compound is stable, so the A 1 compound generated on the surface of the immersion coating in the water-chilled zone due to the temperature of the incoming material will be different and related. [Al / Zn / Zr ^ Mg binary eutectic structure] The Mg-containing Mg-containing metal structure of [primary A 1 phase], [Zn phase], and [Zn2Mg phase] is contained in the blank. In the hot-dip galvanized steel sheet, the outermost surface of the ternary eutectic blank will change to an easily oxidized form due to the chemical reaction as described above, and a brightness change may occur within 2 to 3 days after dip-dip The surface gloss is deteriorated. It has been found through research that, if the temperature of the material entering the water-chilled zone is below 105 ° C, the surface gloss deterioration of the hot-dip galvanized steel sheet containing Mg is approximately as shown in the examples described below. Preventer. In this case, the cooling operation before entering the water-chilled zone does not mean that the solidified immersion plating surface is supplied with water capable of forming a water film to quench it like the water-chilled zone, but must be cooled with gas and water ( Mist water spray) or gas cooling (such as jet cooler) light cooling operation. This is because when the rapid cooling operation that can form a water film is performed before entering the water-chilled zone, the temperature of the material entering the water-chilled zone is below 105 ° C. Operation 313885.ptc

Page 12 2003.05.20.012 567243 Amendment V. Description of the invention Even if it becomes nothing, it still goes down. However, the material temperature makes the plate speed at the freezing point. However, if the affinity is strong, for example, the rare-earth material can effectively suppress some elements, the outermost surface of these coatings can be compared with this phenomenon, and the chilling bands can be suppressed. The effect mass% has the meaning of being dissolved in the dipping case No. 91116441 (10). Although it has a relationship with the thickness of the plate and the speed of the plate, air-water cooling can make the temperature of the material entering the water-chilled zone at 105 ° C. When the plate thickness is thick, sometimes the water-chilled zone The entry side of the domain has its difficulties at 105 ° C. Even in the case of a thick plate, if the degree becomes slower, the cooling capacity of the air-water cooling zone can be increased. However, it is not the best strategy because of problems in control or reduction of productivity. Immediately after the solidification is complete, a moderate amount of easily oxidizable elements, such as Y, Zr, Si, etc., are present in the dip-plating surface with oxygen and have the stabilization effect of A1 oxide, even if they enter the water-chilled zone If the temperature is 105 ° C or more, the surface gloss is deteriorated as shown in the examples described later. Except for the rare earth elements Y, Zr, and Si, there are elements that can exhibit the same effect, but only this is known at present and others have not known. The easily oxidizable element has the property that it is still concentrated in the part of the immersion coating layer after the immersion and solidification process of the hot-dip galvanized steel sheet containing Mg or has been solidified. Therefore, even if it is added in a small amount in the immersion bonding bath, Since the concentration exists in the outermost surface portion of the immersion plating surface, it is possible to suppress surface reactants in water that originally had an adverse effect on the maintenance of surface gloss. However, if the amount of these easy oxygen additions in the immersion bond bath is 0.02 mass% or less, the content must be added to the composition of the immersion plating bath at 0.02 2% because it cannot be exerted. on. On the other hand, if it is added too much, it will cause difficult bathing. Even if it can be dissolved, it will make these elements overwhelming.

313885.ptc Page 13 2003.05.20.013 567243 _Case No. 91116441_Eve May 2 > Amendment 2) V. Description of the invention (11) Residual precipitation near the grain boundaries of the surface layer of the immersion plating will only make the surface The effect of suppressing the deterioration of gloss is saturated, so the content in the immersion bath is 0. 10 mass% or less, as appropriate, 0.8 mass% or less, preferably 0. 05 mass% or less, more preferably 0. It may be added in an amount of 0.3% by mass. The addition of easily oxidizable elements is as described above. When the temperature of the material at the entrance side of the water-chilled zone is above 105 ° C, the effect of preventing surface gloss degradation is most effectively exerted. When the temperature of the side material is below 105 ° C, these oxidizable elements can still be added to the dipping bath for safety reasons. In addition, the temperature of the incoming material in the water-chilled zone may be higher than 105 ° C. If the temperature exceeds 300 ° C, it may be caused by the temperature in the water-chilled zone. The cooling load is too large to sufficiently reduce the entrance temperature of the sh i η pass, so it is preferably controlled below 300 ° C. In a normal manufacturing production line, if the plate thickness is less than 1.6mni, it is relatively easy to make the temperature of the material entering the water-chilled zone below 105 ° C, thereby ensuring gloss retention. If the thickness of the plate is more than 1.6mm, it is better to ensure the gloss by adding the easily oxidizable element in practice to forcibly cool the temperature of the material entering the water-chilled zone to 105 ° C. Good job. In the present invention, since the surface gloss of the Mg-containing hot-dip galvanized steel sheet is prevented from being deteriorated in such a manner, the target is a Mg-containing hot-dip zinc-containing steel sheet that causes surface gloss deterioration. Such a hot-dip galvanized steel sheet containing Mg can be exemplified by using a mass percentage of A 1 ·· 4.0 to 10% and Mg: 1. 0 to 4.0% as basic examples. Contains Ti: 0.001 to

313885.ptc Page 14 2003.05.20.014 567243 _Case No. 91116M1, May two years: ^ Yue _ V. Description of the invention (12) 0 · 1%, B: 0 · 0 〇1 to 〇 · 0 4 5%, The rest is a hot-dip galvanizing bath made of Z η and unavoidable impurities. The dip coating is made of [A 1 / Z n / Z n 2M g ternary eutectic structure] and mixed with the blank [ Primary crystal A 1 phase]; or a metal structure mixed with [primary crystal A 1 phase] and [Zn phase] and / or [Zn 2Mg phase], can have hot-dip Zn plating with excellent corrosion resistance and surface appearance -A 1 -Mg steel plate. Here, [A1 / Zn / Zn2Mg ternary] is preferred in the metal structure in which [primary A 丨 phase] is mixed in the embryo of [A 1 / Z n / Z ng ternary eutectic structure]. The total amount of the eutectic structure] + [primary crystal A 1 crystal] is 80% by volume or more, particularly preferably 95% by volume or more. The remaining parts are [z n phase], [Z n 2M g phase], and a small amount of [Zn / Zn2Mg binary eutectic] and [Al / Zn2Mg binary eutectic] may be mixed in a small amount according to circumstances. In addition, if S i is added, a small amount of [s 丨 phase], [Mg 2S 丨 phase], [Al / Mg2Si binary eutectic], and the like may be mixed. Therefore, the present invention can provide the use of A 1: 4 · 0 to i 5% by mass%,

Mg: 1.0 to 4.0%,

Ti: 0. 001 to 0.1%, B: 0. 〇〇1 to 〇. 045%, at least one selected from the rare earth elements Y, Zr, or easily oxidizable elements in Si: 0. 0 0 2 to 0.05%, the remainder: Zn and unavoidable impurities, a hot-dip galvanized steel sheet with a good gloss retention obtained by applying hot-dip plating to a steel strip. The immersion coating layer is mixed with [primary crystal A 丨 phase] or [primary crystal A1 phase] and [Zn phase] in the blank of [A1 / Zn / Zn2Mg ternary eutectic structure] and / Or [& 2 仏 phase] metal structure, and

Page 15 2003.05.20.015 567243 _Case No. 91116441_ ^ year and month _ ^ _ V. Description of the invention (13) The outermost surface of the plating layer is concentrated in the place where the aforementioned easily oxidizable elements are concentrated, which has the characteristics of organization. Here, the addition amount of A 1, M g, T i, B, etc. constituting the composition of the immersion bath, and their effects can also be exerted in the case where the easily oxidizable element is added according to the present invention, and T i and B In other words, if the metal structure of the dipped bond layer is made into a Zn 2M g binary eutectic metal structure as described above, it can provide Z ng which suppresses the bad influence on the appearance and survivability # 目 之For the purpose of generation and growth, its addition is beneficial. In order to obtain this effect, when Ti, B or Ti-B alloy or compound is added to the bath, the content in the bath can be such that Ti: 0.001 to 0.1%, B: 0.001 to 0.04 5% Just add it. If it contains more than this, precipitates may grow in the immersion plating layer, which may cause unevenness (equivalent to the nickname of the term in the field), and affect the appearance. A 1 in the immersion plating layer serves to improve the corrosion resistance of the immersion-plated steel sheet and suppress the occurrence of scum during the manufacture of the immersion-bonded steel sheet. If the content of A 1 is less than 1.0% by mass, the effect of improving the corrosion resistance is insufficient, and the effect of suppressing the floating of Mg oxides is also low. 0% 质量 为。 Preferably the A 1 content is 4.0% by mass or more. On the other hand, if the content of A 1 exceeds 15% by mass, the growth of the F e-A 1 alloy layer at the interface between the immersion plating layer and the base material steel plate is intense, resulting in poor immersion plating adhesion. Preferably, the A 1 content is 4.5 to 13.0 mass%, more preferably the A1 content is 5.0 to 10.0 mass%, and the particularly preferred A1 content is 5.0 to 7.0 mass%. Mg in the dip bell layer provides a role for generating uniform rot I insects on the surface of the dip plating layer to significantly improve the residual resistance of the dip-plated steel sheet. Such as Mg content

313885.P1C Page 16 2003.02.500.016 567243-Emperor No. 91116441 Astronomy correction of the moon _ V. Description of the invention (14) " When the content is less than 1.0% by mass, the effect of uniformly generating such corrosion products is not significant. Adequately, on the other hand, if the content of Mg exceeds 4.0% by mass, the effect of improving the surname of Mg will be saturated, and because the scum of the Mg oxide system is easily generated, the Mg content is based on It is preferable that it is 1 to 4% by mass. The preferred Mg content is 1.5 to 4.0 mass%, the more preferred content is 2.0 to 3.5 mass%, and the particularly preferred Mg content is 2.5 to 3.5 mass%. As shown in the lower part of Fig. 1, after the production line of hot-dip galvanized steel sheet containing Mg is used, if a light coating machine 11 is used to form the coating, for example, a chromate coating (Chromate Coatng), non- Chromate-based bell film (CChfoinate-ffee conversion coating), Chromic acid-containing organic tree month ✓ Organic film containing chromium acid, silicate film containing Chromiuii ^ acid At the same time, it is known from the research results that the aforementioned problems of surface gloss deterioration will also occur. Even in dipped garments with a formed film. Mouth 'also has the phenomenon that its brightness decreases after a few days and the surface gloss deteriorates. It is exactly the same as that of a non-forming treatment. Depending on the manufacturing conditions, it may sometimes occur & Therefore, according to the research results, it is known that this problem can be solved in accordance with the method of the invention 'through the aforementioned material temperature entering the water-chilled zone and the addition of easily oxidizable elements in / into the wall. With the fact of avoidance. Fo Yi 1 ′ After the plate is passed through the water-chilled zone, if the plate is then passed through to form a processing zone, it is also the same as the manufacturing method of the aforementioned Mg-containing hot-dip galvanized steel sheet.

313885.ptc Page 17 2003.05. 20.017 567243 _ Case No. 91116441 Years May > ^ Days Amendment _ V. Description of the invention (15) The surface gloss of the Mg-containing hot-dip zinc steel sheet produced by the formation process is deteriorated. Therefore, the present invention can also provide the use reason, in terms of mass%, A 1: 4 · 0 to 1 5%,

Mg: 1.0% to 4.0%,

Ti: 0. 001 to 0. 1%, B: 0. 001 to 0. 0 4 5%, at least one kind of oxidizable element selected from rare earth elements Y, Zr, or Si: 0. 0 0 2 to 0 · 0 5%, the remainder: Zn and unavoidable impurities, the hot dip plating bath formed by hot dip plating on the steel strip, and then applied (f 〇rmati ο η) to the dip coating Hot-dip bell zinc steel with good retention. Example 1 Using the equipment shown in FIG. 1, heat including zinc containing A 1: about 6% by mass, Mg: about 3% by mass, Ti: about 0.05% by mass, and B: about 0.01% by mass was performed. In the bath of dip galvanizing bath, the metal structure of the immersion plating layer has [primary crystal A1 phase] and [Z η phase] and [Z η phase] in the blank of [Al / Zn / Zn2Mg ternary eutectic structure] and [Z n 2M g phase] structure of a M g hot-dip zinc-containing steel sheet (plate thickness: 0.8 to 1.0 mm). At this time, the temperature of the material on the exit side of the gas cooling zone 5 is below 3 3 5 ° C, the solidification of the immersion coating is completed in the cooling zone, and the gas water cooling zones 6a, 6b, and the gas cooling zone 1 4 The cooling conditions and through-plate speed in the water-chilled zone 7 are set to be substantially constant, so that the temperature of the material entering the water-chilled zone 7 is below 100 ° C, and the temperature is below about 70 ° C.板 至 平整 滚 Mill8. The surface gloss of the obtained Mg-containing hot-dip bell-zinc steel plate is good

313885. ρκ Page 18 2003.05.20.018 567243 _Case No. 91116441 Lunar Fork and Moon Amendment_ V. Description of the invention (16) The phenomenon of surface gloss deterioration did not occur. Under the same conditions as the foregoing, the result of passing a steel strip with a plate thickness of 1.6 mm or more, although the temperature of the material entering the water-chilled zone 7 rose to about 120 to 150 ° C. However, the operation itself is not faulty, and it is possible to produce a Mg-containing hot-dip galvanized steel sheet with good surface gloss similar to the foregoing. However, after 2 to 3 days, the surface gloss of these steel plates decreased slightly, and it was seen everywhere that the brightness L value decreased from 8 2 immediately after manufacturing to 75 degrees after 2 days. Therefore, the cooling capacity in the gas-water cooling zone 6a, 6b is increased to reduce the temperature of the material entering the water-chilling zone 7 to below 105 ° C. As a result, the phenomenon that the surface gloss is deteriorated has disappeared. In the case of chromate treatment, the presence or absence of deterioration in surface gloss is caused by the temperature of the material entering the water-chilled zone 7 on the side of the material. That is, it can be seen that the phenomenon of surface degradation occurs in the same way as in the case without chromate treatment. Example 2 Based on the experience of the previous example, the degree of deterioration of the surface gloss of the immersion plating layer was checked by tests under various conditions. The surface gloss is evaluated by the lightness (L) measured using a spectrophotometer based on the L value of the Lab method. First, when the hot-dip Zn-Ab and Mg-based steel sheets are manufactured under the following "dipping conditions", from the completion of the solidification of the dip coating to the material temperature of about 30 ° C, Conditions "The air-water cooling (spraying of mist water) and water quenching (current projection) are performed on the immersion coating. Then, while measuring the L value immediately after the immersion plating of the obtained test piece of each of the immersion-plated steel sheets, the test piece was installed in a constant temperature and humidity tank maintained at 60 ° C at a relative humidity of 90% from the immediately after immersion plating

313885.ptc Page 19 2003.02.500.019 567243 _Case No. 91116441_ • Yiyiyueyue Amendment_ V. Description of the invention (17) Enter and keep in the tank for 20 hours and measure the L value after this constant temperature and humidity test To assess the degree of deterioration of surface gloss. (Dip plating conditions) Treatment of steel strip: hot-rolled steel strip dipping bell bath with a thickness of 2.0 mm Composition: A 1 29.0% by mass, Mg = 2.3% by mass, and the remaining two Zn dipping bath temperature: 4 3 0 ° C Weight per unit area: 90g / m2 Passing speed: 80m / niin (cooling conditions) (1) Air-water cooling nozzle: 2 fluid nozzle fluid: water (water pressure = 12.5kPa) + air (empty Air pressure = 4. OkPa) Spray water volume: The spray air volume is shown in the first table: The average mist water particle size is shown in the first table: about 5 0 // m The temperature of the material at the time of spraying the fog water: shown in the first table Material temperature at the end of spraying mist water: shown in Table 1 (2) Water-chilled water flow projection device: 1 0 0 flat nozzles (f 1 apspray η ο zz) 1 e) set of 7 headers. Use fluid: water (water pressure = 2.5 kg f / cm2) Water volume: Table 1 shows the temperature of the material at the beginning of the projected water flow: Table 1 shows

3] 3885.ptc Page 20 2003. 05.20.020 567243 * p _Case No. 91116441_   7th and 7th month _ ^ _ V. Description of the invention (18) Material temperature at the end of the projected water flow: shown in Table 1 Table 1 shows the L value of each dip-coated steel sheet immediately after the dip-plating obtained when the material temperature (the temperature of the material entering the water-chilled zone on the side of the water-cooled zone) is changed according to the above conditions, and the above-mentioned 2 0 Measurement result of L value after one hour constant temperature and humidity test. In addition, the metal structure of the immersion plating layer was examined from a microscope observation of the immersion plating section of each immersion plating steel plate. As a result, all the steel plates had [primary crystal A1] in the blank of the [Al / Zn / Zn2Mg ternary eutectic structure]. Phase], and optionally a metal structure of [Zn phase] and [Zn2Mg] (hereinafter referred to as the metal structure of [Z ng 糸]].

313885.pic Page 21 2003. 05.20.021 567243 Case No. 91116441 The year and the month outside the office V. Description of the invention (19)

7 ^ >-CO >-CO >-No. oo Water volume 1 m3 / h pi 丰 丰 cn 〇〇0¾ g — oo ο 3 < swim 3 p ro oo 〇 ro oo o ro oo 〇h- * CD OO i Material temperature at the beginning of spraying mist water iTC to XW cn tsD ts〇CO H- * CO ►- * Material temperature at the end of spraying mist water ^ ° c ►— * · — * »— ^ s Water flow yellow m V h Water-chilled 03 l \ 3 H- »CO ►— * CO ro 1¾ 〇 ° 涔 CO CO CO CJ Material 1 at the end of projection 1 mild ec 1 oo OO CO oo ro oo to just dip plating L value m to oo oo ro r4 to pi Quotient 1 Dison 1® S Γ concentrated test comparative example comparative example of the present invention example of the present invention eiiV [full green cognizant ·· Α1Π9.0 鹓 _ 次- Mgn2.3 mantis t%-lacquer soap zn] 313885.ptc page 22 2003. 05. 20. 022 1111 567243 _ case number '9Π16441_Θ year y month y > a amendment _ V. Description of the invention (20) From Table 1 It can be seen that if the temperature of the material entering the water-chilled zone is above 105 ° C, the fact that the value of the brightness L after dip plating tends to decrease as its temperature increases will increase. On the other hand, if the temperature is below 105 ° C, the brightness immediately after the dip-plating is maintained in spite of a long period of time. It can be seen that the Mg-containing hot-dip galvanized steel sheet with good surface gloss retention has been produced. . Example 3 The surface gloss deterioration of a hot-dip galvanized steel sheet containing Mg was examined in the same manner as in Example 2 under the following dip plating conditions and cooling conditions after the solidification of the dip coating was completed. The results are shown in Table 2. The result. (Dip plating conditions) Processed steel strip: Hot rolled steel strip with a thickness of 3.2 mm. Dip bath composition: A 1 = 6.3% by mass, M g = 3.2% by mass,

Ti = 0.0 0 8% by mass, B = 0 · 0 0 2% by mass, remainder = Zn Dip bath temperature: 3 9 0 ° C Weight per unit area: 120g / m2 Pass-through speed ·· As shown in Table 2 Way changed. (Cooling conditions) (1) Gas cooling (only with gas cooling zone cooling) Nozzle: Plate-shaped nozzle with a gap of 5mm. Gas used: Air (wind pressure = 4kPa) Air volume .. · Start gas as shown in Table 2 Material temperature during cooling: Table 2 shows the material temperature at the end of gas cooling: Table 2 shows

333885.ptc Page 23 2003.05. 20.023 567243, < _Case No. 91116441_ Years and Days Amendment _ V. Description of the invention (21) (2) Water-chilled water flow projection device · will press 1 50 in the direction of the panel There are 10 rows of flat nozzles in the in-in space. Set 7 rows of fluids. Use fluid: water (water column = 2 · 2 kg f / cm 2) Water volume: Table 2 shows the material temperature at the beginning of the projected water flow: No. 2 The table shows the material temperature at the end of the projected water flow: Table 2 shows

313885.ptc Page 24 2003.05.20.024 567243 Case No. 91116441 Amendment Form 2 Nly 2 4¾ 2 々 身 Γν Description > Five C / 1 oa 1 B-3 cd 1 CO CO 1 ►— * No. 〇Ί CD PO OJ Through plate speed mX min 2500 1200 2500 2500 o Air volume m Vmin system ΓΟ Η- »ro H- * CO cn OO cn i— * O) 1 Material temperature · degree 1 ° C L--.- _ ►- cn H— Ol oo o CNO cn 1 The material temperature at the beginning of cooling is mild ° C * — * s 1— * s h- * 1— * wh »— * water flow surplus mV h water-chilled cooling Η- * CO ►— * 1— · Bu 'oo »— * CD ro oo tvD oo ro The material at the beginning of the project is mild. C CO w CO CO Material temperature at the end of projection ° C OQ oo CO oo oo L value immediately after dipping Η -3 CO oo CO r · r〇pi ® ° 1¾ * 5 1¾ Comparative example Comparative example Example of the present invention Example of the present invention Example of the present invention aB? Ί 〔^ 瀹 shirtindene: A1M6 · 3 鹓 一: 次 ig = 3-—st ^ lrjfilrlo.glsf, ΒΠ0.002 鹓 一: 次-# ^? Nj,

313885.ptc Page 25. 2003. 05.20. 025 567243 ^ _Case No. 91116441 > Year / Month / Day Amendment_ V. Description of the invention (23) As can be seen from the results of Table 2, this example is also the same as Example 2. If the temperature of the material entering the water-chilled zone is above 105 ° C, the decrease in the brightness L value after dip plating increases as its temperature increases, but the temperature is below 105 When the temperature is below ° C, the brightness just after dipping is still maintained after 20 hours of constant temperature and humidity test. In addition, the metal structure of the immersion plating layer was observed through a microscope observation of the cross-section of the immersion plating layer of each of the immersion plating steel plates. As a result, all the steel plates were stabilized to obtain a metal structure of "Z η 2M g". Example 4 Regarding No. B-2 to No. B-5 of Example 3, the immersion plating surface after the water-chilled zone was formed under the following conditions, and the same as that of Example 2 was performed. The brightness after 20 hours of the constant humidity test is shown in Table 3. (Formation and processing conditions A) Coating method: spraywringerr ο 1 1) treatment solution: yak clone 3 3 8 7 N (full chromium concentration in the liquid: 10g) / l) Chromium adhesion amount: 10 mg / m2 (Formation processing condition B) Coating method: Report-type bell-coating method treatment solution · A solution with a fluorinated junction lg / 1 in Sinclair 3 3 8 7 ( Total chromium concentration in the liquid: 20g / 1) Chromium adhesion amount: 40 mg / m2 (Formation treatment condition C) Coating method · Professional coating method

313885.pic Page 26 2003. 05.20.026 567243 _Case No. 91116441_f Two years y__ Five. Description of the invention (24) Treatment liquid: 50g / 1 magnesium phosphate, 1 Og / 1 titanium potassium fluoride, organic Amount of metal component in aqueous solution containing 3 g / 1 of acid as main component: 50 mg / m 2 (Formation treatment condition D) Form a thin film (lower layer) according to the following two steps Coating method ·· Squeezing and drying (S h 〇wer W ringer) method treatment liquid: Sinclair 3 3 8 7N (total chromium concentration in the liquid: 1 Og / 1) chromium adhesion amount: 10 mg / m 2 (upper layer) Coating method: roller coating method Organic thin film: urethaneresi η (thickness: 1 · 5 // m) Table 3 Forming treatment with forming treatment applied Surface gloss Note Immersion coating conditions L value constant temperature and humidity (L after 20 hours) Number B-2 A 81 81 Inventive example number B-4 A 81 72 Comparative example number B-3 B 81 80 Inventive example number B-5 B 81 70 Comparative example number B-3 C 81 8} Inventive example number B _ 4 C 81 73 Comparative example number B-2 D 81 81 Inventive example number B-5 D 81 72 Comparative Examples

313S85.ptc Page 27 2003. 05.20.027 567243 __Case No. 91116441_ > Year y Month Revision_ V. Description of the invention (25) From the results in Table 3, it can be seen that in any kind of formation treatment, such as water quenching When the temperature of the material on the side of the zone is below 105 ° C, the brightness L value will decrease with the change of time after immersion plating. However, when the temperature is below 105 ° C, it will be maintained even if the time is long. The fact that there is lightness immediately after immersion plating. (Example 5) When the immersion plating was performed under the following immersion plating conditions and cooling conditions, the deterioration of the surface gloss in the case where an easily oxidizable element was added to the immersion bath was checked. The results are shown in Table 4. (Dip plating conditions) Process steel strip: Hot-rolled steel strip dip plating bath with a thickness of 1.6 mm Composition: The temperature of the dip plating bath listed in Table 4: 4 5 0 ° C Weight per unit area: 190g / m2 Passing speed : 60 to 12 0m / min (cooling conditions) (1) air-water cooling nozzle: 2 fluid nozzle fluid: water (water pressure = 1.0 to 3.5 kg f / cm2) + air (air pressure = 2.5 S5.0kgf / cm2) Spray water volume: 0 to 8m3 / h Spray air volume: 0 to 60 0 m 3 / mi η Average mist water particle size: 10 to 30 // m (2) Gas cooling

3] 3S85.ptc Page 28 2003. 05.20.028 567243 Today _ case number 91116441_ / year yyyy > Mody _ Charm _ V. Description of the invention (26) Nozzle: plate-shaped nozzle with 5mm gap Gas: Air (wind pressure = 4kPa) Air volume: 0 to 3500m V min (3) Water-chilled water flow projection device: Set punches with 1 0 0 flat nozzles at 150 mm intervals towards the web direction 7 Fluid used in the column: Water (water pressure = 3.0 kg f / cm2) Water volume: 180m3 / h Material temperature at the beginning of projecting water flow: shown in Table 4

313885.ptc Page 29 2003.05.20.029 567243 Case No. 91116441 Year of birth y Amendment V. Description of invention (27) Table 4

C 丨 么 C 丨 5? 6? 7 C-IOO C- 9 0-10? 11? 12? 13 0 丨 r? 1? 2 7 3

13. 11 · 10. 13. 006 .050 -008 006 -073 .024 046 0.050 S7 024 005 PS6 -012 -009 3001 .038 009 006 002 003 004 001 -015 • 009 020 -003 0.020 -005 010 r

Si

Si

Si «熥 YX aa C e 0028 si 021 001 埘 埘 I» 0. so -os, 007 -010 -S8 003 029 21 S3 004 -001 -QQ1 003 ▼ so 023 洳 尹 irrsMI 鲋 鸿 鲋 跃 兹 铒 ( Mwo \ oo \: # ¾ Z Π) 167 145

Is 146 237 131 103 1300 100 s H6 174 131 198 100 ^ Select- > Tank Piping 0〇198 96. 155 埘 C4 ^ B) Xie »埘 (l ^ ll ^ lc) w (^^ c) 81 is 8ro 81 81 002 s82 s 002 81 81 82 col 82 1-H- 盘 涛 窆 1¼ 硌 运 窆 入 ti

313885.ptc Page 30 2003. 05.20.030 567243 _Case No. 91Π6441_Year of the Year "Revised_ V. Description of the invention (28) As can be seen from Table 4, in Examples 2 to 3, even at constant temperature After 20 hours in the constant humidity test, if the lightness L value drops to a level of 71, the decrease of the lightness L value can still be suppressed due to the addition of an easily oxidizable element. The Mg-containing hot-dip galvanized steel sheet No. C-7 to which Si as an easily oxidizable element was added, and the result of dipping the elements in the surface layer portion according to ESCA (electron spectroscopy for chemical analysis) was confirmed to be S The fact that i is almost entirely concentrated in the electrode surface layer portion and the inside of the immersion plating layer hardly exists. In addition, according to the ESC A analysis, if the side where the lightness L value decreases (No. C-10) after 20 hours in the constant temperature and humidity test, and the case where the lightness L value does not decrease (No. C-5), In the former example, it is found that Mg tends to be biased to the surface layer portion of the immersion electrode. In addition, in Table 4, an example of forming the immersion plating layer after the water-chilled zone (No. C-12 to No. C-15) is given. It can be seen that the With or without addition, the degree of decrease in brightness L value varies, and the addition of an easily oxidizable element can suppress the decrease in brightness L value. As described above, according to the present invention, it is possible to effectively prevent the phenomenon of deterioration of the surface gloss peculiar to the Mg-containing hot-dip galvanized steel sheet. Therefore, a Mg-containing hot-dip galvanized steel sheet having good corrosion resistance and excellent surface gloss retention can be provided.

313885.pic Page 31 2003.05. 20. 031 567243 _Case No. 91116441_pyyyyyyyyyy > 丨 Revised_ Brief description of the drawing [Simplified illustration of the drawing] The first drawing shows the manufacture of the Mg-containing hot-dip coating according to the present invention Schematic diagram of a dip plating line for an example of equipment for zinc steel plate 〇1 furnace 2 steel strip 3 dip bath 4 sweeping nozzle 5 gas cooling zone 6a, 6b gas water cooling zone 7 water quench zone 8 flat rolling mill 9 rolls Tension straightening machine 10 '10a Tension coiler 11 Xingkun coating machine 12 Drying zone 13 Air cooling zone 14 Gas cooling zone

313885.pic Page 32 2003. 05.20.032

Claims (1)

567243 Case No. 9111 Pan 44 Correction Supplement 丨 A method of manufacturing a hot-dip galvanized steel sheet with a good guarantee, characterized by continuous impregnation of the steel strip in a Zn bath containing 4.0 to 15% by mass of A 1 And 1 · 0 to 4 · 0 mass% of Mg hot-dip galvanizing bath. After being pulled up, the continuous sign is counted, and the chemist passes through the water-cooled water to quench the surface of the immersion coating after the solidification is completed. A method of manufacturing a hot-dip galvanized steel sheet having a good gloss retention property by controlling the temperature of the material entering the water band in this zone and at this time to be lower than 105 ° C to suppress the deterioration of the gloss of the dipping surface. , Its characteristics: the continuous impregnation of the steel strip contained in the Zn bath; by mass% Α1: 4. 0 to 15%, Mg: 1.0 to '4. (m X Ti: 0 · 001 to (] .: 1% Λ B :(). () 01 to 0.04 5%, the rest • Zn and unavoidable impurities, a hot-dip galvanizing bath made of 9 After being pulled up, the continuous pass plate is allowed to solidify Dip coating The temperature of the water-cooled water-cooled region under contact with the water flow and the temperature of the inlet side entering the water-chilled zone is controlled below 1 () 5 ° C to prevent the gloss of the surface of the immersion coating. Poor gloss retention. A method for manufacturing a hot-dip galvanized steel sheet, which is characterized in that: in a Zn bath, 4.0 to 15 mass% of A1 and 1.0 to 4.0 mass% of Mg are added to a hot-dip galvanized zinc bath, and At least one kind selected from rare earth elements Y, Z] or easily oxidizable elements of 0.0 to 0.25% by mass 313885.ptc Page 33 2003.05.20. 033 567243 _Case No. 91116441 / > amended on yyyyyyyy_ _ After the scope of the patent application, the steel strip is continuously immersed in the bath, and the continuity after pulling up The through plate is water-cooled in a water-chilled zone in which the surface of the immersion coating is brought into contact with the water flow after solidification, and at this time, the temperature of the incoming material entering the water-chilled zone is controlled to 105 ° Above C and below 300 ° C in order to suppress the gloss deterioration of the surface of the immersion plating layer. 4. A method for manufacturing a hot-dip galvanized steel sheet with good gloss retention, characterized in that the steel strip is continuously impregnated; in mass%, A 1: 4.0 to 1 5%, Mg: 1 · 0 to 4.0%, Ti: 0.001 to 0.1%, B: 0.001 to 0. 045%, at least one oxidizable element selected from rare earth elements Y, Zr or Si One type: 0 · 0 0 2 to 0 · 0 5%, the rest: Zn and unavoidable impurities, a hot-dip galvanizing bath made of Zn and unavoidable impurities. After being pulled up, the continuous continuous plate is passed on the surface of the immersion coating after solidification is completed. In the water-chilled zone where water is cooled under contact with the water flow, and at this time, the temperature of the material entering the water-chilled zone is controlled to be above 105 ° C, and below 300 ° C to suppress the immersion coating. Deterioration of surface gloss. 5. The manufacturing method of the hot-dip galvanized steel sheet with good gloss retention as described in any one of the scope of application for patents 1 to 4, wherein the plate is passed through the water-chilled zone and then passed through the plate. Form a processing zone. 6. — A type of hot-dip galvanized steel with good gloss retention. It is used by reason. 313885.ptc Page 34 2003.05.20.034 567243 _Case No. 91116441_ & yyyyyyyy__ Six, the scope of patent application A1: 4. 0 to 15%, Mg: 1. 0 to 4.0%, selected from rare earths At least one of the easily oxidizable elements of the elements Y, Z r or Si: 0 · 0 02 to 0.05%, the balance: Zn and unavoidable impurities, a hot-dip ore bath made of steel, for steel Made with hot dip bond. 7. —A type of hot-dip ore steel plate with good gloss retention, used by quality; A 1: 4 · 0 to 1 5%, Mg: 1 · 0 to 4 · 0%, Ti: 0 · 001 To 0.1%, B: 0.001 to 0.045%, at least one selected from the rare-earth elements Y, Zn, or Si, and easily oxidizable elements. 0. 0 0 2 to 0. 0 5 %, The rest: hot dip bond bath made of Zn and unavoidable impurities, which is obtained by applying hot dip ore to the steel strip. 8. The hot-dip galvanized steel sheet with good gloss retention as described in item 6 or 7 of the scope of the patent application, in which the easily oxidizable elements are concentrated in the outermost surface of the dip coating. 9. The hot-dip galvanized steel sheet with good gloss retention as described in item 6 or 7 of the scope of patent application, in which the dip coating layer has an embryo in an "Al / Zn / Zn2 M g ternary eutectic structure" The material is mixed with "primary crystal A 1 phase", or mixed with "primary crystal A1 phase" and "Zπ phase" and / or "Zr ^ Mg" metal structure. 313885.ptc Page 35 2003.05.21.035 567243 _Case No. 91Π6441_ > Year 5 ^ Refer to the amendment_ VI. Application for patent scope 1 0 — A kind of hot-dip galvanized steel sheet with good gloss retention, used by reason; by mass , A1: 4.0 to 15%, Mg: 1.0 to 4.0%, at least one selected from the rare-earth elements Y,, Zn or Si, and easily oxidizable elements: 0. 0 0 2 to 0.0 5 % Remaining parts: Zn and unavoidable impurities, hot-dip coating bath made of hot-dip bond to the steel strip, and then forming treatment on the dip coating layer 0 A hot-dip galvanized steel sheet with good gloss retention, Department of use; by mass, A1: 4 _ 0 to 15%, Mg: 1.0 to '4.0% Ti: 0. 001 to (K: 1% B: (}. 丨 0 0 1 to 0.045 %, At least one selected from the rare-earth elements Y,, Zn η or Si oxidizable elements: (). 0 0 2 to 0.0 5% remainder • Zn and unavoidable impurities, heat generated Dip bath y applies heat to the steel strip Plating, immersion plating and then administering the forming process and the winner 0 313885.pic Page 36 2003.05. 20.036