JP5428571B2 - Fuel tank for vehicles - Google Patents

Description

The present invention relates to a fuel tank for a vehicle .

Conventionally, Pb—Sn alloy-plated steel sheets having excellent corrosion resistance, workability, solderability (weldability) and the like have been mainly used as fuel tank materials, and are widely used as fuel tanks for automobiles.
On the other hand, Sn—Zn alloy-plated steel sheets have been mainly produced by an electroplating method in which electrolysis is performed in an aqueous solution containing Zn and Sn ions, for example, as in Patent Document 1. Sn-Zn alloy-plated steel sheets mainly composed of Sn are excellent in corrosion resistance and solderability and have been used in many electronic parts. This Sn-Zn plated steel sheet has been found to have excellent characteristics in automotive fuel tank applications, and in the following Patent Documents 2 to 4, molten Sn-Zn plated steel sheets have been disclosed.

  Pb-Sn alloy-plated steel sheets that have been used as fuel tank materials for automobiles have been used habitually because they have recognized various excellent properties (for example, workability, fuel tank inner surface corrosion resistance, solderability, seam weldability, etc.). In recent years, with the increasing awareness of the global environment, we are shifting to the direction of Pb-free.

  On the other hand, Sn—Zn electroalloy plated steel sheets have been used in applications where the corrosive environment is not so severe, mainly as electronic parts that require solderability and the like. However, since the inner surface of the steel plate constituting the fuel tank for automobiles is exposed to automobile fuel such as gasoline, it is subjected to a relatively severe corrosive environment. In addition, automobile fuel such as gasoline may be deteriorated to generate organic acid, and the steel sheet may be exposed to automobile fuel containing organic acid, which may lead to a more severe corrosive environment. In addition, the Sn-Zn plated steel sheet may cause pitting corrosion due to Zn segregation even in a flat portion that has not been processed. From the above, in order to further improve the sacrificial anticorrosive ability, it has been studied to adjust the amount of Zn added in the Sn—Zn plating.

Japanese Patent Laid-Open No. 52-130438 Japanese Patent No. 3126622 Japanese Patent No. 3126623 International Publication No. 1996/30560

  By the way, a fuel tank for automobiles is manufactured by deep drawing a steel plate to manufacture a part called a shell, and then superposing a pair of shells and welding them together. Recently, the shape of the fuel tank is becoming more complex due to the weight reduction of the tank, the complexity of the vehicle body design, and the relationship of the storage location of the fuel tank. In order to manufacture such a complex-shaped fuel tank, processing is performed while restraining the end of the steel plate so as not to cause wrinkles in the steel plate when deep drawing the steel plate. The steel plate at this time has a portion that undergoes large machining and a portion that undergoes little machining. As described above, the corrosion resistance of the steel sheet when subjected to partial large processing has not been studied so far.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel tank for excellent vehicle corrosion resistance.

When the present inventors diligently studied the relationship between the degree of processing of steel sheets and corrosion, it was speculated that the Zn crystals deposited on the hot dipped layer would be the starting point of plating cracks during the processing of the steel sheets. It has been found that prevention of plating cracking leads to improved corrosion resistance. The gist is that
( 1 ) A steel plate, formed on the surface of the steel plate, and formed on the base plating layer, the base plating layer containing 15% by mass to 40% by mass Ni and the remainder Fe. It consists that is in a molten plated steel sheet ing to and a hot dip plated layer containing 4 wt% or more 8.8% mass% of Zn and the balance to Sn, wherein the molten plated steel sheet, sheet thickness There is a part where the reduction rate is 15% or more and 30% or less, and the hot dip plated steel sheet is a mold having a convex side R3 to 5 mm, a concave side R1.5 to 2.5 mm, and a convex part length 1 to 6 mm. The total length of plating crack defects in the hot-dip plated layer that occurs when draw bead processing is performed at a speed of 100 to 300 mm / min and a sheet thickness reduction rate of 15% to 30% is 10 mm in the drawing direction of the steel sheet during draw bead processing. The A fuel tank for a vehicle, which is a hot dip plated steel sheet to be 0.5mm or less.
( 2 ) The hot-dip galvanized steel sheet is a mold having a mold convex side R3 to 5 mm, a concave side R1.5 to 2.5 mm, and a convex part length 1 to 6 mm, a drawing speed of 100 to 300 mm / min, and a thickness reduction rate. It is a hot-dip plated steel sheet in which the number of plating crack defects in the hot-dip plated layer that occurs when the draw bead processing is performed at 15% to 30% is 50 or less per 10 mm in the drawing direction of the steel plate during the draw bead processing. The fuel tank for vehicles according to ( 1 ).

ADVANTAGE OF THE INVENTION According to this invention, the fuel tank for vehicles excellent in corrosion resistance can be provided.

FIG. 1 is a diagram showing a cross-sectional shape of a mold used in draw bead processing. FIG. 2 is a diagram showing the results of elemental analysis by the EPMA method of the example of the present invention. FIG. 3 is a diagram showing the results of elemental analysis by the EPMA method of the comparative example.

The present invention is described in detail below.
The hot dip galvanized steel sheet for a fuel tank of a vehicle according to this embodiment includes a steel sheet, a base plating layer formed on the surface of the steel plate, and a hot dip plating layer formed on the base plating layer. Examples of the steel plate include steel plates that have been annealed through a series of steps such as hot rolling, pickling, cold rolling, annealing, and temper rolling of steel slabs, or rolled materials. Regarding steel components, it must be a component system that can be processed into a complex shape of the fuel tank, the thickness of the alloy layer at the steel-plating layer interface can be thin to prevent plating peeling, and the progress of corrosion inside and outside the fuel tank is suppressed. It must be a component system. In particular, it is desirable to apply IF steel (Interstitial atom Free), which is excellent in workability, only to parts that require high workability. Furthermore, in order to ensure weld hermeticity, secondary workability, etc. after welding. A steel sheet with several ppm added is desirable. The representative component ranges of this IF steel are C ≦ 0.003 mass%, Si <0.01 mass%, Mn: 0.10 mass% to 0.20 mass%, P <0.025 mass%, and S: 0. 0.005 mass% to 0.02 mass%, Ti: 0.040 mass% to 0.060 mass%, balance: Fe and inevitable impurities are preferable, and it is more preferable that B is further contained in an amount of about 5 ppm. For example, C: 0.003% by mass, Si: 0.01% by mass, Mn: 0.20% by mass, P: 0.01% by mass, S: 0.01% by mass, Ti: 0.06% by mass, balance : IF steel composed of Fe and inevitable impurities. In hot rolling, after slab heating at around 1150 ° C, it is rolled to about 3 to 6 mm, cold-rolled to about 0.5 to 1.5 mm after pickling, and surface rolling oil and iron powder are removed by alkaline electrolysis. After annealing. The annealing is preferably continuous annealing from the viewpoint of cost, but can also be manufactured by batch annealing. Thereafter, temper rolling is performed, Fe—Ni alloy pre-plating is performed, and hot dip plating is performed by a plating method generally called a flux method.

  The hot-dip plating layer is composed of 4 to 8.8% by mass of Zn and the balance of Sn: 91.2 to 96.0% by mass and inevitable impurities. The plating composition Zn is limited in consideration of the balance of corrosion resistance between the inner surface and the outer surface of the fuel tank. The outer surface of the fuel tank is painted after the fuel tank is molded because perfect rust prevention capability is required. Therefore, although the coating thickness determines the rust prevention ability, the material prevents red rust by the anticorrosion effect of the plating layer. In particular, the anticorrosive effect of the plating layer is extremely important at the part where the coating is poor. Addition of Zn to Sn-based plating lowers the potential of the plating layer and provides sacrificial anticorrosive ability. For this purpose, it is necessary to add 4% by mass or more of Zn. Addition of excess Zn exceeding the Sn-Zn binary eutectic point of 8.8% by mass causes an increase in melting point that promotes the growth of coarse Zn crystals. As a result, the intermetallic compound layer (so-called alloy layer) under the plating layer grows excessively. For these reasons, the Zn content must be 8.8% by mass or less. The coarse Zn crystal is not problematic in that it exhibits the sacrificial anticorrosive ability of Zn, but on the other hand, selective corrosion is likely to occur in the coarse Zn crystal part. In addition, since the intermetallic compound itself is very brittle, the growth of the intermetallic compound layer under the plating layer tends to cause plating cracking during press molding, and the corrosion protection effect of the plating layer is reduced.

  On the other hand, corrosion on the inner surface of the fuel tank is not a problem when only normal gasoline is used, but a severe corrosive environment appears due to water contamination, chlorine ion contamination, and production of organic carboxylic acids due to oxidative degradation of gasoline. there's a possibility that. If gasoline leaks outside the fuel tank due to piercing corrosion, it can lead to serious accidents, and these corrosions must be completely prevented. When the deteriorated gasoline containing the above corrosion-promoting components was prepared and the performance under various conditions was examined, it was confirmed that Sn-Zn alloy plating containing 8.8% by mass or less of Zn exhibits extremely excellent corrosion resistance. .

When the pure Sn or Zn content containing no Zn is less than 4% by mass, the plated metal has no sacrificial anticorrosive ability to the ground iron (material to be plated) from the initial stage of exposure to the corrosive environment. For this reason, pitting corrosion at the plating pinhole portion on the inner surface of the fuel tank and early red rust on the outer surface of the tank are problematic.
On the other hand, when Zn is contained in a large amount exceeding 8.8% by mass, Zn is preferentially dissolved, and a large amount of corrosion products are generated in a short time. For this reason, there is a problem that the carburetor for an engine is likely to be clogged when a hot-dip plated steel sheet is used for a fuel tank. In terms of performance other than corrosion resistance, the Zn content increases, the workability of the plating layer also decreases, and good press formability, which is a feature of Sn-based plating, is impaired. Furthermore, the solderability is significantly reduced due to the melting point increase of the plating layer and the Zn oxide due to the increased Zn content.

  Therefore, in the present embodiment, the Zn content in the hot dipped layer is in the range of 4 to 8.8% by mass, and in order to obtain a more sufficient sacrificial anticorrosive action, it is desirable to be in the range of 6 to 8.8% by mass.

  As described above, sacrificial anticorrosive ability is imparted by the inclusion of Zn in the Sn-based plating of the hot dipped layer. This effect is used to control corrosion on the inner and outer surfaces of the fuel tank. However, in such a corrosive environment, Zn itself has a high elution rate, so the presence of coarse Zn crystals as described above will form a Zn segregation part in the plating layer, and there is this Zn segregation part. Only that part elutes preferentially, and it becomes a state in which perforation corrosion tends to occur at that part.

In the plating composition region of the hot-dip plating layer of this embodiment, the hot Sn-Zn plating structure usually tends to be a solidified structure in which a Sn primary crystal and a cellular binary Sn-Zn eutectic structure are mixed. At this time, Zn is particularly easily segregated at the eutectic cell-eutectic cell grain boundary. The reason why Zn tends to segregate at the eutectic cell-eutectic cell grain boundary is not clear, but the following reasons are considered.
(A) Influence of a trace amount of impurities having high affinity with Zn.
(B) The eutectic structure tends to be coarsened at the eutectic cell-eutectic cell grain boundary in the final solidified part.
(C) Since Zn is a preceding phase of Sn—Zn eutectic solidification, each preceding Zn phase of different eutectic cells is bonded at the eutectic cell-eutectic cell grain boundary.
Zn segregated at this eutectic cell-eutectic cell grain boundary becomes a starting point of corrosion as described above, and facilitates selective corrosion.

  Such segregation of Zn can be eliminated by positively growing Sn primary crystals and suppressing the growth of eutectic cells. In the composition range of the hot-dip plating layer of this embodiment, Sn crystallizes as an initial crystal, so if Sn dendrite is spread over the plating layer in the early stage of solidification in a network form, a cellular Sn- Zn binary eutectic cannot be developed greatly because its growth is suppressed by the dendrite arm. Therefore, the huge eutectic cells do not collide with each other, Zn that segregates at the eutectic cell-eutectic cell grain boundary disappears, and the corrosion resistance on the inner and outer surfaces of the fuel tank is remarkably improved.

In order to develop Sn primary crystals actively, the growth start point (nucleation site) of Sn should be increased. In the solidification process of hot dipping, since the heat removal on the steel plate side is large, it solidifies from the interface side of the plating / base metal. Therefore, the growth starting point (nucleation site) of the Sn primary crystal dendrite can be created by providing fine irregularities on the lower alloy layer of the hot dip plating layer or fine irregularities on the base iron itself.
The most effective method for providing the nucleation site is the form control of the alloy phase (generated by the reaction between the base iron and the molten metal) in the lower layer of the hot dip plating layer. In order to influence the nucleation of Sn, fine irregularities are effective, and it is only necessary to control how the alloy phase is generated. That is, the part where the generation of the alloy phase is progressing is convex, the part where the generation of the alloy phase is suppressed is concave, and this control is performed by the base plating prior to the hot dipping bath temperature, hot dipping time, and hot dipping. This is possible by applying a layer to the steel sheet.

  Even if Zn is 8.8% by mass or less, if the growth of the Sn primary crystal is not sufficient, a minute Zn crystal may be present. Such a Zn crystal is a starting point for defects in the hot-dip plated layer when the steel sheet is subjected to a large processing. Therefore, the smaller the number of Zn crystals, the better. The existence frequency of the Zn crystal can be evaluated by the length of the defect and the number of defects after the draw bead processing. The hot-dip plated steel sheet with fewer defects and fewer defects after the draw bead processing has fewer Zn crystals, and the corrosion resistance of the hot-dip plated layer can be enhanced on the inner and outer surfaces of the fuel tank. In order to reduce the fine Zn crystals, it is preferable to optimize the base plating layer.

In the hot-dip galvanized steel sheet of the present invention, it is preferable to form a plating layer made of an Fe—Ni alloy as the base plating layer. In the area where the Fe-Ni plating layer is covered by the base plating, alloying proceeds between the base plating Fe and the hot-plated Sn-Zn metal during the solidification process of the hot-dip plating. Alloying is suppressed between the hot-dip Sn-Zn metal. As a result, a fine uneven alloy phase is generated. There is no problem if the composition of the Fe—Ni alloy plating layer is not extremely biased with respect to either element. However, in order to suppress the precipitation of Zn crystals in the hot dip plating layer, it is better that the Ni composition ratio is small. Thereby, generation | occurrence | production of the defect of the hot dip plating layer at the time of draw bead processing can be suppressed. Accordingly, the composition ratio of Ni in the base plating layer is preferably in the range of 15 to 40% by mass, and more preferably in the range of 15% by mass or more and less than 21% by mass. When the Ni composition ratio is in the range of 15 to 40% by mass, there is no influence of the composition of the underlying plating layer. Moreover, if it is this range, it will become an area | region where Sn primary crystal production | generation is more stable. Fe-Ni alloy plating bath can be used with nickel sulfate 240-350 g / L, nickel chloride 30-60 g / L, boric acid 30-45 g / L and iron sulfate 40-100 g / L. . There is a positive correlation between the Fe-Ni plating composition and the Fe-Ni alloy plating bath composition. By changing the ratio of Ni ²⁺ and Fe ²⁺ within the range of these Fe-Ni alloy plating bath compositions, It is possible to control the Ni plating composition. The plating conditions are pH = 2.5 to 4.5, bath temperature 40 to 60 ° C., and current density ^{2 to} 10 A / dm ² . As for the amount of plating, the Fe-Ni alloy plating layer does not need to be non-uniformly coated, so there is no need to set an upper limit, but economically, the amount of base plating is 0.01 to 2.0 g / m ² per side. Is appropriate.

(Hot plating bath temperature, immersion time)
Both the hot dip bath temperature and the immersion time affect the growth of the alloy phase.
When the hot dip bath temperature is significantly low, the alloy phase does not grow, and when it is extremely high, the alloy phase is promoted to grow. However, from the viewpoint of operability, the hot dipping bath temperature is often set to the liquidus temperature of the molten metal +10 to 50 ° C., and the upper limit is set to the liquidus temperature + 100 ° C. at most. If the bath temperature is low, there is a risk of solidification of the molten metal due to variations in bath temperature in the hot dipping bath. On the other hand, when the bath temperature is high, there are disadvantages such as excessive alloy phase growth, the need for cooling capacity for solidification after hot dipping, and uneconomical. In the Sn-Zn-based plating of the hot-dip plating layer of the present embodiment, 240 to 300 ° C. is an appropriate hot-dip bath temperature range in consideration of the Sn-Zn composition range. It is possible to generate an alloy phase having fine irregularities by combining the immersion times.

  As for immersion time, the growth of the alloy phase is generally insufficient on the short time side, and the growth of the alloy phase tends to be excessive on the long time side. However, in this embodiment, the alloy phase has already grown by immersion for 1 second, and the growth of the alloy phase is gradually saturated even if immersed for a long time. In actual continuous hot dipping, the dipping time takes at least about 2 seconds, and it is usually not dipping for more than 15 seconds due to the size of the hot dipping pot. A long immersion time means a reduction in productivity and is uneconomical. In the immersion time range of 2 to 15 seconds, an alloy phase having fine irregularities can be generated by a combination of the base plating and the hot dipping bath temperature.

  Further, as a condition for developing the Sn primary crystal, there is also an influence of a cooling rate after gas wiping performed for controlling the amount of plating adhesion. In the Sn primary crystal and the binary Sn—Zn eutectic structure, the Sn primary crystal solidifies first, but in order to sufficiently develop the Sn primary crystal, a slower cooling rate is preferable. When manufactured in combination with the pre-plating method, the cooling rate of the molten Sn—Zn plating layer is preferably 30 ° C./second or less. The lower limit is not particularly set, but if the cooling rate is too slow, the productivity is lowered. Therefore, a cooling rate of 10 ° C./second or more is preferable in actual production.

  The hot dip galvanized steel sheet of the present invention is not particularly limited as long as it is within a manufacturable range with respect to the thickness of the steel sheet used and the coating adhesion amount. In the processing used for processing parts such as ordinary fuel tanks, the reduction rate of the thickness of the steel sheet is 30% or less, but corrosion particularly in a region where the thickness is 15% or more becomes a problem. The plate thickness reduction rate referred to here is a numerical value defined by (initial steel plate thickness−steel plate thickness after processing) × 100 / (initial steel plate thickness). This is because the plating damage occurs with an increase in the degree of processing and acts as a starting point of corrosion. In the hot-dip plated steel sheet of the present invention, when the thickness reduction rate is 15% or more, defects penetrating the plating layer are generated and corrosion occurs. May be induced.

  The plating crack defect of the hot-dipped layer in the present invention refers to a defect caused by a crack that penetrates the hot-dipped layer and reaches the steel plate from the plating surface. It does not include cracks that occur only in the plating layer and do not reach the steel sheet, or cracks in the alloy layer between the base plating layer and the hot dipping layer. Since the plating crack defect reaches the steel plate, the plating cracked steel plate can be detected by detecting Fe, which is a main constituent element of the steel plate. Specifically, Fe may be detected by the EPMA method, and one region where Fe is detected may be regarded as a plating crack defect. The inventors have found that this plating crack defect is more likely to occur as the number of Zn crystals in the hot-dip plating layer increases, and the inventors have found that the corrosion resistance after processing can be evaluated by measuring the number and size of defects. Is heading.

The number of plating crack defects and the total length are the number of defects in each specimen and the total length of cracks caused by the defects by the following method for multiple specimens cut out from various locations on the steel sheet after draw bead processing. It can be calculated from the average of these.
That is, an imaginary straight line having a length of 10 mm is randomly set along the drawing direction of the draw bead processing for the cut steel piece. A defect that overlaps the virtual line is detected by the EPMA method. The number of defects may be determined by detecting Fe by the EPMA method, setting one region where Fe is detected as one plating crack defect, and measuring the number of plating crack defects overlapping the virtual line. Moreover, what is necessary is just to let the sum total length of the plating crack defect (Fe detection area | region) which overlaps a virtual straight line be the total length of a plating crack defect about the total length of a plating crack defect. Then, what is necessary is just to average the number and the total length of the plating crack defect of all the steel pieces.

  In the hot dip galvanized steel sheet of the present invention, the total length of plating crack defects is preferably 0.5 mm or less per 10 mm in the drawing direction of the draw bead processing. If the total length of plating crack defects exceeds 0.5 mm, the corrosion resistance of the hot dip plated steel sheet is lowered, which is not preferable. Moreover, the number of plating crack defects should just be 50 or less per 10 mm of drawing directions of the said draw bead process. If the number of plating crack defects exceeds 50, the corrosion resistance of the hot dip plated steel sheet is lowered, which is not preferable.

  In addition, as a result of intensive investigations on a method for simply evaluating the corrosion resistance after processing, the plating damage status after actual pressing corresponds extremely well to the plating damage that occurs in draw bead processing that specifies the die conditions and processing conditions. Corrosion resistance after processing corresponds to the occurrence of plating crack defects. Therefore, it becomes possible to evaluate the corrosion resistance after processing by grasping the plating crack defect of the sample that has been subjected to the draw bead processing under specific conditions.

  That is, FIG. 1 shows a cross-sectional shape of a mold used in draw bead processing. In FIG. 1, reference numeral 8 denotes a convex side R, reference numeral 9 denotes a concave side R, reference numeral 10 denotes a convex portion length, and reference numeral 11 denotes a drawing direction. The present inventor processed with various changes in the shape of the mold and the drawing speed of the draw bead, and reduced the plate thickness, the number of plating cracks penetrating the plating layer per 10 mm in the drawing direction, and the crack length in the plating surface layer. When the total of the thickness was measured, by drawing bead processing at a drawing speed of 100 to 300 mm / min with a mold having a mold convex side R3 to 5 mm, a concave side R1.5 to 2.5 mm, and a convex length 1 to 6 mm, It became clear that the relationship between the plate thickness reduction rate and plating cracking defect in the actual press can be reproduced. Moreover, as a result of investigating the post-coating corrosion resistance of the material subjected to the draw bead processing under these conditions, the relationship between the plating damage and the corrosion resistance in the actual press can be reproduced. When producing the hot dip galvanized steel sheet of the present invention, a part of the hot dip plated steel sheet is cut out and subjected to draw beading, and the number of plating crack defects and the total length of the processed steel sheet are measured. May fall within the scope of the present invention.

  In addition, the fuel tank of the present embodiment can be manufactured by deep-drawing the hot-dip plated steel sheet according to the present invention to manufacture a part called a shell, and then superimposing a pair of shells and welding them together. it can. The outside of the fuel tank may be painted to improve corrosion resistance.

Examples of the present invention are shown below.
An Fe-Ni plating bath (nickel sulfate: 240 g / L, nickel chloride: 30 g / L, boric acid: 30 g / L, iron sulfate: 0) 30g, 40, 50, 55, 100, 150g / L, pH = 2.5) Fe-Ni plating or Ni plating of various compositions 1.0g / m ² (bath temperature 50 ° C per side, current density 10A / dm ² ) gave. The steel sheet was coated with a plating flux containing zinc chloride, ammonium chloride and hydrochloric acid, and then introduced into a Sn-Zn hot dipping bath having various compositions at 250, 300 and 350 ° C. After reacting the plating bath and steel plate surface for 2, 5, 10, 15, 20 seconds, pull out the steel plate from the plating bath, adjust the adhesion amount by gas wiping method, and apply the plating adhesion amount (total Sn + Zn adhesion amount). Controlled to 40 g / m ² (per side). After gas wiping, the cooling rate was variously changed with an air jet cooler to solidify the hot-dip plated layer.

From the obtained steel sheet, a 40 × 300 mm sample was cut out for draw bead processing, and 1 to 2.5 g / m ^{2 of} rust preventive oil mainly composed of mineral oil was applied, followed by convex side R4 mm, concave side R2 mm, and convex part length. A draw bead process was performed with a 4 mm metal mold (material SKD-11, Cr plating 20 μm) at a drawing speed of 200 mm / min so that the plate thickness reduction rate was 15 to 30%. By cutting out a part of the sample after processing and detecting Fe by the EPMA method, the total number of plating crack defects penetrating the plating layer confirmed per 10 mm in the draw bead processing direction, and the total crack length of the plating crack defects Was measured.

Then, after carrying out alkali degreasing and removing the applied rust preventive oil, the corrosion resistance was evaluated by the following method.
Corrosion resistance in the salt damage environment on the outer surface of the fuel tank was evaluated by the red rust generation area ratio after SST 960 hours, and the red rust area ratio was 10% or less.
The corrosion resistance of the inner surface of the fuel tank was performed by the following method. Corrosion solution was prepared by adding 10vo1% water to forced deteriorated gasoline left at 100 ℃ for 24 hours in a pressure vessel. In 350 ml of this corrosive solution, a plated steel sheet with a bead drawn (plate thickness reduction rate 15%, 30 x 35 mm end face / back face seal) was subjected to a corrosion test at 45 ° C for 3 weeks. The ion species and the amount of elution were measured. The amount of elution was considered good when the total metal amount was less than 200 ppm.

The results are shown in Tables 1 and 2. As for the hot-dip plated steel sheet of the present invention example, the occurrence of plating cracks after draw bead processing is greatly reduced, and as a result, both the outer surface corrosion resistance and the inner surface corrosion resistance are good. Or B.
2 shows the result of elemental analysis by the EPMA method of the present invention example (sample No. 1), and FIG. 3 shows the result of elemental analysis by the EPMA method of the comparative example. The comparative example is Sample No. except that the base plating is pure Ni plating. 1 is a hot dip galvanized steel sheet manufactured in the same manner as in No. 1.
As is clear from the comparison between FIG. 2 and FIG. 3, it can be seen that the steel sheet of the example of the present invention has a significantly lower Fe detection region than the comparative example. Moreover, in the steel plate of this invention example, it turns out that the segregation of Zn is low significantly.
In Tables 1 and 2, the results of comprehensive evaluation of each sample are shown as follows.
A: Good, good corrosion resistance B: Fair, usable C: Bad, unusable

Claims (2)

A steel plate, formed on the surface of the steel plate, and formed on the base plating layer, a base plating layer containing 15 to 40% by mass of Ni and Fe in the balance. consists dip plated steel sheet ing to and a hot dip plated layer containing 4 wt% or more 8.8% mass% of Zn and the balance of Sn and a,
The hot-dip plated steel sheet has a portion with a thickness reduction rate of 15% to 30%,
The hot-dip galvanized steel sheet is a mold having a convex side R3 to 5 mm, a concave side R1.5 to 2.5 mm, and a convex part length 1 to 6 mm, a drawing speed of 100 to 300 mm / min, and a plate thickness reduction rate of 15% or more. It is a hot dip galvanized steel sheet in which the total length of plating crack defects in the hot dip plating layer generated when the draw bead processing is performed at a condition of 30% or less is 0.5 mm or less per 10 mm in the drawing direction of the steel sheet during the draw bead processing. A fuel tank for vehicles. The hot-dip galvanized steel sheet is a mold having a convex side R3 to 5 mm, a concave side R1.5 to 2.5 mm, and a convex part length 1 to 6 mm, a drawing speed of 100 to 300 mm / min, and a plate thickness reduction rate of 15% or more. The number of plating crack defects in the hot-dip plated layer generated when the draw bead processing is performed under a condition of 30% or less is a hot-dip plated steel plate that is 50 or less per 10 mm in the drawing direction of the steel plate during the draw bead processing. Item 2. A fuel tank for a vehicle according to Item 1 .

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