JP4555500B2 - Hot-dip zinc-aluminum alloy-plated steel sheet with excellent workability and manufacturing method thereof - Google Patents

Description

【００２９】
（実施例２）
鋼スラブを溶製して通常の方法で薄鋼板を製造した板厚０．８ｍｍのＳＰＣＣ板をめっき原板とした。めっきは表２のようなめっき組成のものを、ゼンジミアタイプの連続溶融亜鉛めっきラインにて加熱、焼鈍、めっきを行った。焼鈍雰囲気は、１０％水素、残９０％窒素ガス雰囲気であり、露点を−３０度とした。焼鈍温度は７３０℃、焼鈍時間は３分である。めっき後は通常のワイピングによりめっき付着量を９０ｇ／ｍ^２とした。めっき後、調質圧延を１％行った。その後後処理を行った。後処理は無機酸化物を被覆し、合計で７０ｍｇ／ｍ^２から２４００ｍｇ／ｍ^２の範囲で行った。試験は円筒深絞りによる、限界絞り比を求めた。ポンチ径５０φ、ポンチ肩３Ｒ、ダイス肩３Ｒ、絞り比は２．１から２．３とした。無塗油で成形速度５ｍｍ／ｍｉｎとした。この結果を表２に示す。Ｎｏ．４５からＮｏ．８６までは本発明例を示す。Ｎｏ．８７からＮｏ．９０が、比較例であり、Ｎｏ．８７、Ｎｏ．８８はめっき上の酸化物皮膜処理厚みが小さすぎる。Ｎｏ．８９，Ｎｏ．９０は膜厚が厚く、摺動性が悪い。
【００３０】
【表２】

【００３１】
（実施例３）
鋼スラブを溶製して通常の方法で薄鋼板を製造した板厚０．８ｍｍのＳＰＣＣ板をめっき原板とした。めっきは表３のようなめっき組成のものを、ゼンジミアタイプの連続溶融亜鉛めっきラインにて加熱、焼鈍、めっきを行った。焼鈍雰囲気は、１０％水素、残９０％窒素ガス雰囲気であり、露点を−３０度とした。焼鈍温度は７３０℃、焼鈍時間は３分である。めっき後は通常のワイピングによりめっき付着量を９０ｇ／ｍ^２とした。めっき後、調質圧延を１％行い、溶剤脱脂後に表３に示す有機樹脂皮膜を施した。試験は円筒深絞りによる、限界絞り比を求めた。ポンチ径５０φ、ポンチ肩３Ｒ、ダイス肩３Ｒ、絞り比は２．１から２．３とした。無塗油で成形速度５ｍｍ／ｍｉｎとした。この結果を表３に示す。
Ｎｏ．１２６〜１２９は比較例であり、Ｎｏ．１２６、Ｎｏ．１２７は有機樹脂皮膜の皮膜厚が本発明範囲より小さいため、またＮｏ．１２８、Ｎｏ．１２９は逆に有機樹脂皮膜の皮膜厚が厚すぎるためにいずれも摺動性が悪い。
【００３２】
【表３】

【００３３】
【発明の効果】
本発明によれば、加工性に優れた溶融亜鉛−アルミニウム系合金めっき鋼板を製造することが可能となり、自動車、建材等の産業上きわめて大きな効果を有している。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot dip zinc-aluminum alloy plated steel sheet excellent in workability and a method for producing the same.
[0002]
[Prior art]
In recent years, the use of surface-treated steel sheets has been expanded in order to cope with the prolonged service life of automobiles, household electrical products, building materials, and the like. In particular, the Zn-5 wt% Al hot dip galvanized steel sheet is used mainly for building materials and the like because it has superior corrosion resistance compared to conventional hot dip galvanizing. Recently, Zn-Al-Mg-based plated steel sheets have been developed, and further improvement in corrosion resistance has been achieved. However, the plating film workability of the Zn—Al-based alloy-plated steel sheet is not always sufficient, and there are some cases where the corrosion resistance is inferior in a portion subjected to severe processing. This is because an Fe-Al alloy layer is formed at the interface between the base metal and the plating film, and this layer is hard and brittle, so that powdering or the like occurs during press processing, or the processed part becomes the starting point of corrosion. Sometimes.
[0003]
As a technique for improving these points, Japanese Patent Laid-Open No. 58-177446 discloses a technique in which Si is added to a plating bath of a Zn—Al alloy for the purpose of suppressing the Fe—Al alloying reaction. However, the production of intermetallic compounds mainly composed of Fe—Al and Fe—Al—Si cannot be suppressed, and the workability of the film is not sufficient. Japanese Patent Application Laid-Open No. 9-143657 discloses a technique for suppressing microcracks by adding a small amount of Ti, B, Si or the like to Zn-Al-Mg plating containing 0.1 to 1.5% Al. However, there are problems such as insufficient corrosion resistance and severe occurrence of bath dross. Japanese Patent Application Laid-Open No. 10-176238 discloses that the Al content in the plating bath is 20 to 80%, and the steel components, particularly Si and P, are limited to suppress the Fe—Al—Si reaction and provide good workability. Although the technique to obtain is described, since Al concentration is too high, it cannot manufacture with a normal plating line, but has the problem of becoming high cost.
[0004]
[Problems to be solved by the invention]
In view of such a situation, it is an object of the present invention to provide a hot-dip zinc-aluminum alloy-plated steel sheet with improved workability of a conventional zinc-aluminum alloy-plated steel sheet.
[0005]
[Means for Solving the Problems]
It is important to suppress the formation of Fe—Al and Fe—Al—Si intermetallic compounds for the deterioration of the workability of the Zn—Al alloy plating. Therefore, the present inventors conducted extensive studies on the elements added to the plating bath and found that the addition of Mg is effective in suppressing deterioration of workability. Thereby, the production | generation of the said intermetallic compound is suppressed and plating adhesiveness becomes favorable. In addition, when the existence state of Si in the plating was investigated, and a more detailed investigation was made on a variety of metals such as Si, SiO ₂ and Mg ₂ Si, the size of the Si-based material in the plating layer was small and dispersed. It has been found that the plating adhesion is better and the slidability is better. This is considered to be because the slidability becomes unstable because the concentration of the Si-based material decreases around the large size, and the difference in local sliding resistance particularly on the surface layer increases.
[0006]
That is, the gist of the present technology is as follows.
[0007]
(1) A steel sheet having a plating layer composed of Al: 3 to 18%, Mg: 2.1 to 10%, the balance Zn and inevitable impurities in mass% on the surface of the steel sheet, and further in the plating layer The surface is characterized in that it contains 1 to 50% of Mg in the amount of Si and contains no more than 6 × 10 ³ Si-based substances having an area of 100 μm ² or more per unit cross-sectional area (mm ² ) of the plating layer. Hot-dip zinc-aluminum alloy plated steel sheet with excellent workability as a plating layer .
[0008]
(2) A hot-dip zinc-aluminum alloy-plated steel sheet having an excellent workability whose surface is a plated layer , further comprising Fe: 1% or less in the plated layer of the steel sheet described in (1) above.
[0009]
(3) The surface characterized by further containing 0.01 to 2.0% of at least one of Pb and Sn in the plating layer of the steel sheet according to (1) or (2). Is a hot-dip zinc-aluminum alloy-plated steel sheet with excellent workability.
[0010]
(4) Excellent workability characterized by having an inorganic oxide film in a range of 70 mg / m ^{2 to 2} g / m ² on the plated layer of the steel sheet according to any one of (1) to (3). Hot dip zinc-aluminum alloy plated steel sheet.
[0011]
(5) Melting excellent in workability characterized by having an organic resin film of 100 mg / m ^{2 to} 2.0 g / m ² on the plating layer of the steel sheet according to any one of (1) to (3) above. Zinc-aluminum alloy plated steel sheet.
[0012]
(6) When manufacturing a hot dip zinc-aluminum alloy plated steel sheet, by setting the plating bath temperature to less than 480 ° C., an Si-based material having an area of 100 μm ² or more is added to the plating layer in a unit cross-sectional area (mm ² 6 ) or less of ³ × 10 ^{3, wherein} the hot-dip zinc-aluminum alloy-plated steel sheet having excellent workability whose surface is a plated layer according to any one of the above (1) to (5) Method.
[0013]
(7) When manufacturing a hot-dip zinc-aluminum alloy-plated steel sheet, the plating bath temperature is set to less than 480 ° C., and cooling is continuously performed at a cooling rate of 10 ° C./s or more after plating, whereby 100 μm ² or more in the plating layer. The surface of the plating layer according to any one of (1) to (5) above, wherein 6 × 10 ³ or less of Si-based material having an area of 5 is included per unit cross-sectional area (mm ² ) of the plating layer The manufacturing method of the hot dip zinc-aluminum alloy plating steel plate excellent in workability which is .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below. First, the elements to be included in the plating layer will be described. Al in the plating layer is added to improve the corrosion resistance. If it is less than 3%, the corrosion resistance is inferior, and if it exceeds 18%, the effect of improving the corrosion resistance is saturated and the workability deteriorates.
[0015]
In general, Mg is often added because it has an effect of improving corrosion resistance. However, in the present invention, Mg is added in order to suppress the formation of an Fe—Al—Si intermetallic compound. If it is less than 2.1%, the formation of the Fe—Al—Si intermetallic compound cannot be suppressed, and the plating adhesion deteriorates. On the other hand, if it exceeds 10%, dross generation is large and plating becomes difficult.
[0016]
Si is an important element for the present invention, and is added to improve workability. If it is less than 1% of the amount of Mg added, both the plating adhesion and the slidability deteriorate. On the other hand, if it exceeds 50% of the added amount of Mg, the bath dross increases too much, so that it is 1 to 50% of the added amount of Mg.
[0017]
When the size of the Si-based material in the plating layer exceeds 100 μm ² , adhesion at the periphery tends to be deteriorated, and Si-based material having a size larger than this size is 6 × 10 ³ per unit cross-sectional area of the plating layer. If the number exceeds 1, the adhesion and slidability of plating both deteriorate, so the number of Si-based substances of 100 μm ² or more is set to 6 × 10 ³ pieces / mm ² or less.
[0018]
Fe is mixed into the plating bath as an impurity from the plating kettle and the steel plate to form an Fe-Al-Si intermetallic compound, which adversely affects the plating adhesion, and Si in the plating layer is liable to dross out. Since the effect of improving the mobility deteriorates, the content is made 1% or less.
[0019]
Pb and Sn are elements added as necessary for improving the slidability, and at least 0.01% of addition is necessary for improving the slidability. If it exceeds 2%, the plating adhesion deteriorates, so the content was made 0.01 to 2%.
[0020]
Next, a manufacturing method will be described. There is no particular limitation on the plating plate to be used, and it can be used regardless of the steelmaking method, steel strength, hot-rolled pickling material, cold-rolled material and the like. The present technology can be applied to plating regardless of the manufacturing method such as Sendzimir type, flux type, or pre-plating type. If the plating bath temperature is too high, Fe from a steel plate, a plating pot, or plating equipment is mixed into the plating bath, and Fe—Al and Fe—Al—Si intermetallic compounds are generated, resulting in poor plating adhesion. Moreover, it leads to the corrosion of a plating pot and plating equipment. In order to suppress this, the plating bath temperature is set to less than 480 ° C. The cooling rate after plating is set to 10 ° C./s or more in order to suppress local precipitation of the Si-based material and ensure plating adhesion and sliding properties. Further, there is no particular problem even if an aqueous post-treatment with blackening resistance and corrosion resistance is applied, and of course, temper rolling may be performed.
[0021]
In particular, coating the plated layer after plating with at least one inorganic oxide selected from oxides of Si, Mg, Zr, Mo, Ce, and Ca further improves the effects of the present invention. Let In this case, for example, there is no problem in using a complex oxide such as phosphate. When the total of these is less than 70 mg / m ² , there is no effect of improving slidability. If the total of these exceeds ² g / m ² , the slidability deteriorates, so the range is from 70 mg / m ^{2 to 2} g / m ² .
[0022]
Further, instead of coating with an organic resin film, the effect of the present invention is improved. If it is less than 100 mg / m ² , this effect is small, and if it exceeds ² g / m ² , the workability is rather deteriorated, so the range is from 100 mg / m ^{2 to 2} g / m ² . The organic resin may be in any form of water-based resin, solvent-based resin, powder-based resin, and solvent-free resin. The water-based resin mentioned here includes, in addition to water-soluble resins, water-insoluble resins that are water-insoluble but can be in a state of being finely dispersed in water, such as emulsions and suspensions (water-dispersible resins). . The resin that can be used as the organic resin is not particularly limited, but polyolefin resin, acrylic olefin resin, polyurethane resin, acrylic resin, polycarbonate resin, epoxy resin, polyester resin, alkyd resin, phenolic resin Resins, other thermosetting resins, and the like can be exemplified, and crosslinkable is more preferable. Two or more kinds of organic resins may be mixed or copolymerized. Moreover, you may add crosslinking agents, such as various melamine resin and an amino resin, as needed. In addition to the organic resin, there is no problem with the addition of fine silica or a lubricant.
[0023]
As a coating method for forming these inorganic oxides or organic films, any method such as spray, curtain, flow coater, roll coater, bar coater, brush coating, dipping, and air knife squeezing may be used. The ultimate baking temperature is desirably 80 to 250 ° C. If it is less than 80 ° C, the water in the paint is difficult to completely volatilize and the corrosion resistance is lowered, and if it exceeds 250 ° C, the alkyl part of the resin, which is an organic substance, undergoes modification such as thermal decomposition, or the film is cured too much. Since corrosion resistance and workability will fall, it is not preferable. 70-160 degreeC is more preferable. Moreover, although it does not regulate in particular about drying equipment, the method by hot air blowing, the indirect heating method by a heater, the method by infrared rays, the method by induction heating, and the method of using these together can be employ | adopted. Further, depending on the type of organic resin to be used, it can be cured by energy rays such as ultraviolet rays and electron beams.
[0024]
【Example】
Example 1
A SPCC plate having a thickness of 0.8 mm obtained by melting a steel slab and producing a thin steel plate by a conventional method was used as a plating base plate. Plating was performed by heating, annealing, and plating in a Sendzimir type continuous galvanizing line. The annealing atmosphere was an atmosphere of 10% hydrogen and the remaining 90% nitrogen gas, and the dew point was −30 degrees. The annealing temperature is 730 ° C., and the annealing time is 3 minutes. The plating bath is Al: 2.5 to 20%, Mg: 1.5 to 10.5%, Si: 0.5% to 60% of the added amount of Mg, Fe: 0 to 1.5%, remaining Zn and inevitable Plating was performed at a plating bath temperature of 390 to 500 ° C., using a plating bath adjusted to a specific impurity. After plating, the amount of plating deposited was 100 g / m ² per side by ordinary wiping. After plating, temper rolling was performed at 1%, and then chromate treatment was performed at an adhesion amount of ²⁰ to 30 mg / m ² . For the Si-based material of the plated steel sheet manufactured as described above, the EPMA observation of the plating cross section is carried out, the observation is performed for each arbitrary field of 100 μm ² , the number of 100 μm ² or more is counted, Expressed as the number per area. The obtained plated steel sheet is shown in Table 1.
[0025]
About the dross of a plating bath, it judged visually and it was set as (circle), and the thing in which generation | occurrence | production of a little dross was seen was set as x, and (circle) was set as the pass. For the workability evaluation, an impact test and a slidability test were performed. The adhesion test is an impact test, using a 12 mm diameter die and a 12 mm diameter punch, dropping a weight of 1.6 kg from a height of 1 m, peeling the overhanging part with adhesive tape, and plating The degree of film peeling was visually determined. The case where peeling of the film was not observed was evaluated as ◯ (passed), the case where powdered peeling was partially observed was indicated as Δ, the case where peeling of the film was observed as ×, and Δ and X were determined as unacceptable.
[0026]
The sliding test was a cylindrical cup squeezing test. The punch diameter is 50φ, the punch shoulder is 5R, the die shoulder is 5R, the drawing ratio is 2.1, the molding speed is 5 mm / min without oiling, and 100 pieces are drawn continuously. Visual observation was performed to determine the state of slidability. ○ (Pass) when there was no plating peeling or adhesion to the mold of the cup, △ if powder peeling occurred, or if the cup was broken and the cup was broken X and Δ and x were rejected.
[0027]
Table 1 shows these results. No. 1 to No. 30 is an example of the present invention, and the workability is good. No. 31 to No. 42 is a comparative example. No. 31 contains too much Al. No. 32 has poor processability due to too little Mg. No. Since 33 has too much Mg, it has a lot of dross and is rejected. No. 34 to No. No. 36 has poor processability because Si is too small. No. Since 37 has too much Si, there are many dross and processability is bad. No. 38 to No. No. 40 has poor workability because of too much Fe. No. 41, no. 42, workability is not evil for Si-based material cooling rate is too small and there are too many.
[0028]
[Table 1]

[0029]
(Example 2)
A SPCC plate having a thickness of 0.8 mm obtained by melting a steel slab and producing a thin steel plate by a conventional method was used as a plating base plate. Plating was performed with a plating composition as shown in Table 2 by heating, annealing, and plating in a Sendzimir type continuous hot dip galvanizing line. The annealing atmosphere was an atmosphere of 10% hydrogen and the remaining 90% nitrogen gas, and the dew point was −30 degrees. The annealing temperature is 730 ° C., and the annealing time is 3 minutes. After plating, the plating adhesion amount was 90 g / m ² by ordinary wiping. After plating, temper rolling was performed 1%. Thereafter, a post-treatment was performed. Postprocessing covers the inorganic oxide was performed in the range of 70 mg / ^{m 2} of 2400 mg / ^{m 2} in total. In the test, the limit drawing ratio was determined by cylindrical deep drawing. The punch diameter is 50φ, the punch shoulder is 3R, the die shoulder is 3R, and the drawing ratio is 2.1 to 2.3. The molding speed was 5 mm / min without oil coating. The results are shown in Table 2. No. 45 to No. Examples up to 86 show examples of the present invention. No. 87 to No. 90 is a comparative example. 87, no. No. 88 has an oxide film treatment thickness on plating too small. No. 89, no. 90 is thick and has poor sliding properties.
[0030]
[Table 2]

[0031]
(Example 3)
A SPCC plate having a thickness of 0.8 mm obtained by melting a steel slab and producing a thin steel plate by a conventional method was used as a plating base plate. Plating was performed with a plating composition as shown in Table 3 by heating, annealing, and plating in a Sendzimir type continuous hot dip galvanizing line. The annealing atmosphere was an atmosphere of 10% hydrogen and the remaining 90% nitrogen gas, and the dew point was −30 degrees. The annealing temperature is 730 ° C., and the annealing time is 3 minutes. After plating, the plating adhesion amount was 90 g / m ² by ordinary wiping. After plating, temper rolling was performed at 1%, and after organic solvent degreasing, the organic resin film shown in Table 3 was applied. In the test, the limit drawing ratio was determined by cylindrical deep drawing. The punch diameter is 50φ, the punch shoulder is 3R, the die shoulder is 3R, and the drawing ratio is 2.1 to 2.3. The molding speed was 5 mm / min without oil coating. The results are shown in Table 3.
No. Nos. 126 to 129 are comparative examples. 126, no. No. 127 has a thickness of the organic resin film smaller than the range of the present invention. 128, no. On the other hand, 129 has poor slidability because the thickness of the organic resin film is too thick.
[0032]
[Table 3]

[0033]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture the hot dip zinc-aluminum alloy plating steel plate excellent in workability, and has a very big effect on industries, such as a motor vehicle and a building material.

Claims (7)

A steel plate having a plating layer composed of Al: 3 to 18%, Mg: 2.1 to 10%, the balance Zn and unavoidable impurities in mass% on the surface of the steel plate, and further containing Si in the plating layer The surface is a plating layer characterized by containing 6 to 10 ³ or less Si-based substances having an area of 100 μm ² or more per unit cross-sectional area (mm ² ) , including 1 to 50% of the amount of Mg. molten zinc excellent in certain workability - aluminum alloy coated steel sheet. The hot-dip galvanized-aluminum alloy-plated steel sheet having excellent workability whose surface is a plated layer , further comprising Fe: 1% or less in the plated layer of the steel sheet according to claim 1. The plated layer of the steel sheet according to claim 1 or 2, further containing 0.01 to 2.0% of at least one of Pb and Sn , wherein the surface is a plated layer. molten zinc excellent in certain workability - aluminum alloy coated steel sheet. Hot-dip zinc excellent in workability characterized by having an inorganic oxide film in the range of 70 mg / m ^{2 to 2} g / m ² on the plated layer of the steel sheet according to claim 1. Aluminum alloy plated steel sheet. A molten zinc-aluminum alloy excellent in workability, characterized by having an organic resin film of 100 mg / m ^{2 to} 2.0 g / m ² on the plated layer of the steel sheet according to any one of claims 1 to 3. Plated steel sheet. When manufacturing a hot-dip zinc-aluminum alloy-plated steel sheet, by setting the plating bath temperature to less than 480 ° C., an Si-based material having an area of 100 μm ² or more in the plating layer is 6 per unit cross-sectional area (mm ² ) of the plating layer. The manufacturing method of the hot dip zinc-aluminum alloy plated steel plate excellent in workability whose surface is a plating layer in any one of Claims 1 thru | or 3 characterized by containing x10 < ³ > or less. When manufacturing a hot-dip zinc-aluminum alloy-plated steel sheet, the plating bath temperature is set to less than 480 ° C., and cooling is continuously performed at a cooling rate of 10 ° C./s or more after plating, whereby an area of 100 μm ² or more is formed in the plating layer. of claims 1 to 3 further characterized in that the inclusion of Si-based material unit cross-sectional area of the plating layer (mm ²⁾ per 6 × 10 ³ or less, the surface is excellent in workability is plated layer molten A method for producing a zinc-aluminum alloy plated steel sheet.