JP2009092648A - Test piece preparation method and corrosion resistance evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a test piece preparation method that, even when metal plates to be jointed together differ in strengths, is able to evaluate the corrosion resistance of a mating structural part obtained with high accuracy, by jointing the processed metal plates together for use, and to provide a corrosion resistance evaluation method that uses the test piece. <P>SOLUTION: A test piece preparation method is a test piece preparation method for evaluating the corrosion resistance of the mating structural part between metal plates, and the method includes providing flat parts on bent surfaces of the metal plates formed, by processing the metal plates constituting the mating structural part; and forming the mating structural part by jointing the flat parts thus provided. Furthermore, a corrosion resistance method evaluates the corrosion resistance of a mating structural part between metal plates, by using a test piece prepared by the test piece preparation method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a test piece for evaluating the corrosion resistance in a laminated structure portion between metal plates, and a corrosion resistance evaluation method using the test piece.

  In recent years, there has been a social demand for extending the life of products such as automobiles, buildings, and home appliances and minimizing life cycle costs. The products and steel structures as described above are often used in a desired shape by overlapping metal plates and joining metal plates using welding, an adhesive, or the like. Further, from the viewpoint of securing the appearance of the product, it is general that after joining in a desired shape, a chemical conversion treatment step centering on phosphate and a coating treatment step such as electrodeposition coating are performed. These treatments not only ensure the appearance, but also contribute to improving the corrosion resistance by barriering the metal plate from corrosive substances such as oxygen, moisture, and chloride.

  However, the inside of the part where the above-mentioned metal plates are joined by welding or using an adhesive or the like (hereinafter, this part is referred to as the “matching structure”) is formed by chemical conversion treatment or electrodeposition coating. It is difficult to completely apply, and it is often a bare metal plate that is almost untreated. For this reason, once the corrosive material enters the corrugated structure of the metal plate, corrosion tends to occur, which greatly affects the life and durability of the product. For this reason, for products used in severely corrosive areas and corrosive environments, surface-treated metal plates, such as zinc- and aluminum-based hot-dip plating, electroplating, or those In many cases, the steel sheet is used by using a surface-treated steel sheet that has been subjected to alloying treatment, and a steel sheet in which a protective film such as an organic resin is applied to the surface of these surface-treated steel sheets.

  In addition, the surface-treated metal plate used in the above products is often used after being processed into a desired shape by bending or pressing, and the unpainted portion inside the metal plate mating structure Corrosion resistance is greatly affected by damage caused by processing of the surface-treated metal plate used. Therefore, the durability as a product is greatly influenced by the durability of the mating structure. For this reason, it is extremely important to accurately evaluate the corrosion resistance of the surface-treated metal plate in the mating structure.

However, when selecting the surface-treated metal plate to be used at the product design stage, the material itself or a corrosion resistance test in the processed state may be performed, but the processed surface-treated metal plate Normally, the corrosion resistance of the overlapping structure portion of the overlapped and joined portions is not considered. For example, Non-Patent Document 1 discloses that pre-coated steel sheets whose base materials are various galvanized steel sheets (hot dip galvanized steel sheets: GI, electrogalvanized steel sheets: EG, galvannealed steel sheets: GA) are subjected to rib machining by pressing. The results of evaluating the influence of the plating film on the corrosion resistance of the processed part are disclosed after being subjected to an outdoor exposure test.
Shioda, Hachiuchi, Ikijima, “CAMP-ISIJ”, Vol. 2, 1989, p. 608

  However, in the evaluation described in Non-Patent Document 1, the precoated steel sheet is coated before the steel sheets are joined. Therefore, as described above, the inside of the mating structure part deviates from the actually used state, and does not evaluate the corrosion resistance inside the mating structure part of the surface-treated steel sheet itself.

  In such a situation, the present inventors have repeated researches to solve the above problems. As a result, the surface of the sample to be evaluated is processed, the processed surfaces of the two surface-treated metal plates subjected to the processing are overlapped and bonded, and the corrosion test of the laminated structure formed at the bonded portion is performed. As a result, it was found that the corrosion resistance of the surface-treated metal sheet can be evaluated in a form close to the actual use state, and a patent application (Japanese Patent Application No. 2007-006852) was filed.

  According to the method described in the above patent application, it was confirmed that the corrosion resistance of the metal plate mating structure can be evaluated with sufficient accuracy. However, in repeated examinations, when the strength of the metal plates to be joined is different, the shape after processing such as the degree of warping of the metal plate after processing is different, and therefore the corrosion resistance evaluation of the laminated structure portion It became clear that accuracy fell.

  Therefore, the present invention provides a method for producing a test piece capable of accurately evaluating the corrosion resistance in a mating structure portion when a metal plate subjected to processing is used by joining even when the strength of the metal plate to be joined is different. And it aims at providing the corrosion-resistance evaluation method using the test piece.

  The present inventors diligently studied a method that can accurately evaluate the corrosion resistance of the laminated structure even when the strength of the metal plates to be joined is different. As a result, (1) after processing the metal plate, the surface of the metal plate is flattened by subjecting the metal plate to a deep drawing process having a flat portion. By making a test piece in which the flat surfaces of the metal plates face each other and overlapping each other and joining, (3) performing a known corrosion test on the joint structure part of the joint, It was found that the corrosion resistance of the processed surface can be accurately evaluated even when the strength of the metal plates to be processed is different.

The present invention has been made based on the above findings and has the following characteristics.
[1] A method for producing a test piece for evaluating corrosion resistance in a mating structure portion between metal plates, which is formed on a curved surface of a metal plate formed by processing the metal plate constituting the mating structure portion. A method for producing a test piece, comprising providing a flat portion and joining the provided flat portions to form a combined structure portion.
[2] The method for producing a test piece according to [1], wherein the flat portion provided on the curved surface of the metal plate is formed by deep drawing.
[3] In the above [1] or [2], the depth of the curved surface is 2 mm or more, and the flat portion area (mm ² ) / depth (which is a ratio calculated from the flat portion area and the depth) mm) is 200 to 2000, deep drawing is performed to form a flat portion.
[4] The method for producing a test piece according to any one of [1] to [3], wherein the processing applied to the metal plate is sliding processing.
[5] The method for producing a test piece according to [4], wherein the processing applied to the metal plate is sliding processing including bending and bending back.
[6] In any one of the above [1] to [3], the processing performed on the metal plate is a tensile processing or an overhanging processing method.
[7] In any one of the above [1] to [6], after forming the mating structure portion, a chemical conversion treatment with phosphate is performed, and electrodeposition coating is further performed. .
[8] Corrosion resistance characterized by evaluating the corrosion resistance of the mating structure of metal plates using the test piece produced by the method for producing a test piece according to any one of [1] to [7]. Evaluation methods.

  ADVANTAGE OF THE INVENTION According to this invention, even when the metal plate to join differs, the test piece preparation method which can evaluate the corrosion resistance in the joining structure part in the case of joining and using the processed metal plate accurately And the corrosion-resistance evaluation method using the test piece is provided.

  Hereinafter, an example of the best mode for carrying out the present invention will be described.

  The method for producing a test piece for evaluating the corrosion resistance in the mating structure portion between the metal plates according to the present invention is a curved surface of the metal plate formed by processing the metal plate constituting the mating structure portion. A flat part is provided, and the provided flat parts are joined together to form a combined structure part. And the corrosion resistance evaluation method which concerns on this invention evaluates the corrosion resistance in the joining structure part which joined the metal plate which received the process using the test piece produced by the said method.

  As a metal plate which comprises the said matching structure part, the board which consists of steel, aluminum, copper, magnesium, these alloys etc. can be used, and there is no restriction | limiting in particular in those components. However, in practice, there is a strong demand for evaluation of the corrosion resistance of the laminated structure, and steel plates that are frequently used in automobiles and home appliances, among others, surface-treated steel plates that have been subjected to zinc-based plating, such as electrogalvanizing Steel plate, hot dip galvanized steel plate, alloyed hot dip galvanized steel plate subjected to alloying treatment after hot dip galvanization, hot dip galvanized steel plate with high aluminum content, and the above steel plate for the purpose of improving corrosion resistance It is preferable to use a steel plate or the like provided with a coating such as. Moreover, what is necessary is just to select the kind of two metal plates to join according to the condition of the mating structure part currently utilized for a motor vehicle, household appliances, etc., and it may be the same kind or a different kind. .

  The corrosion resistance evaluation method according to the present invention evaluates the corrosion resistance in a mating structure where bonded metal plates are joined. Therefore, in the present invention, after processing and flattening by providing a flat portion on the surface treatment surface of the curved metal plate, they are overlapped facing each other, and then joined by, for example, spot welding or an adhesive. To form a mating structure. Then, the joined metal plates are subjected to a corrosion test as they are or after being cut into an appropriate size as necessary.

  As a method of providing a flat portion on the surface-treated surface of the curved metal plate, it is preferable to form by deep drawing. Other methods of flattening include overhang molding, tensile molding, rolling, etc., but these require further processing after processing the surface-treated surface of the metal plate, making certain evaluation difficult. Therefore, it is not preferable. Deep drawing is particularly preferable because after the surface-treated surface of the metal plate is processed, no further processing is applied to the surface to be evaluated, and a certain evaluation can be obtained.

The flatness of the flat portion formed by deep drawing is affected by the processing depth and the area of the flat portion after processing. The inventors have studied by changing the processing depth and the area of the flat portion. As a result, it was found that sufficient flatness can be obtained when the flat area (mm ² ) / depth (mm), which is a ratio calculated from the flat area and depth, is 200 or more and 2000 or less. If it is smaller than 200, not only the variation in evaluation is increased because the area of the flat portion is reduced, but also drawing is severe, and the material may be limited. When the value is larger than 2000, the amount of drawing in the flat portion is too low, and it is not preferable because sufficient flatness cannot be maintained. When the ratio is larger than 200, the flat portion area is increased, so that not only variation in evaluation is reduced, but also drawing is easy, and the material is not limited. In the case of 2000 or less, since the amount of drawing of the flat portion is an appropriate amount, it is preferable because sufficient flatness can be maintained.

  However, when the processing depth is shallower than 2 mm, it becomes difficult to sufficiently planarize any area. When the processing depth is 2 mm or more, it is easy to sufficiently flatten any area. Therefore, the processing depth is preferably 2 mm or more.

  In addition, there is no restriction | limiting in the method of confirming the planarization condition of the formed flat part. For example, it is possible to use a method of calculating the curvature with a laser microscope. As a simple method, it is possible to determine whether or not the surface is flat by placing a level on a flat surface.

  In order to evaluate the corrosion resistance in a form close to the product state actually used, it is preferable that the processing applied to the metal plate is a sliding processing. This is because a product generally has a product shape often obtained by press working, and there are many sites where durability (corrosion resistance) can be rubbed on a flat surface.

  In recent years, the product shape has become complicated, and in order to obtain the shape, there are many cases where a bead is provided in a die of a press machine. Therefore, in order to simulate the bead passage portion with higher accuracy, it is more preferable to perform a sliding process including bending and bending back.

  Furthermore, depending on the application site of the steel plate that is actually used, the processing applied to the metal plate is preferably tensile processing or bulging processing. This is because there are many cases where the steel sheet stretches due to processing such as pressing, and the substantial plating adhesion amount before and after the processing changes greatly. In particular, when the plated film of the plated steel sheet is not ductile, it is easy for the plated film to be detached during tensile processing and overhanging processing, and it is necessary to simulate the damage to the plated film according to the application site. . Furthermore, in the case of a steel plate with a coating of organic resin or the like on the surface of the plated steel plate, the soundness of sliding is maintained, but the coating of organic resin or the like cannot follow the tensile stress or compression stress. In some cases, a local defect occurs, and corrosion proceeds from that site. In order to accurately simulate the corrosion resistance when such a plating film or a film formed on the plating film is damaged, it is preferable to perform a tensile process or an overhang process.

  In the case of metal plates used in automobiles and home appliances, chemical conversion treatment with phosphate etc. or electrodeposition coating is performed for the purpose of improving durability as well as obtaining a beautiful appearance after pressing. There are many cases. In this case, corrosion under the coating film by electrodeposition coating is often different from the corrosion behavior of a bare metal plate. Therefore, when simulating the use with electrodeposition coating, make a test piece that has been subjected to chemical conversion treatment with phosphate, etc. and electrodeposition coating, and evaluate the corrosion resistance using this test piece. Is preferred.

  In addition, there is no particular limitation on the corrosion test method when performing the corrosion resistance evaluation using the test piece according to the present invention, and conventionally used exposure tests, salt spray tests, salt spray and dry / wet repetition, A combined cycle test in which a temperature change is applied can be used. The combined cycle test has various conditions. For example, a test method defined by JASO-M-609-91 or a corrosion test method defined by SAE-J2334 defined by the American Society of Automotive Engineers may be used. it can.

  The effects of the present invention will be described below with reference to examples.

[Metal plate processing]
Table 1 shows test materials used as metal plates.

  As shown in Table 1, the base material is a soft cold-rolled steel plate (mild steel) represented by a steel plate symbol SPC, and a surface-treated steel plate (steel plate symbol: Zn-Ni30, GA45, GI60, surface-treated). A total of nine types of test steel sheets were prepared: GI100, Zn-Al, GA45 + organic coating) and high-strength steel (H4-SPC, H6-SPC). A primary test piece having a width of 80 mm and a length of 350 mm is prepared from these steel plates (plate thickness of 0.8 mm), and bending and bending back are included using a jig imitating a die 1 and a bead 2 as shown in FIG. A draw bead process, which is a sliding process, was performed. As a result, a slide having a length of 150 mm or more was caused between the evaluation surface of the steel plate and the die shoulder and the bead portion to obtain a secondary test piece having a shape as shown in FIG.

In the draw bead processing, the radii of curvature of the die shoulder and bead portion of the jig used were 2 mmR and 5 mmR, respectively. The pressing pressure of the die 1 was 5.88 × 10 ⁴ N / m ² and the drawing speed was 2 m / min. Furthermore, the test piece was coated with 1.5 g / m ^{2 of} Preton 303PX2 manufactured by Sugimura Chemical Co., Ltd. as a lubricating oil on both sides and then subjected to draw bead processing.

[Planarization processing]
The steel sheet subjected to the draw bead processing was subjected to a flattening process for providing a flat portion. As the flattening process, first, the steel sheet was cut out to a predetermined size and then deep-drawn to obtain a tertiary test piece. Table 2 shows the levels of deep drawing.
Incidentally, deep drawing uses two dice the area 3600 mm ^2, 800 mm ^2, the inner pressure 294200N (30tf), a blank pressure 49033N (5tf), Sugimura Chemical Co. as lubricating oil: a Pureton 303PX2 to one side 3 g / m ² was applied to both sides and then carried out.

The flatness of the tertiary test piece subjected to deep drawing was evaluated. Further, the flatness of the sample not subjected to the flattening treatment was also evaluated as a comparison. The flatness was evaluated by placing the tertiary test piece on a horizontal plane, placing a commercially available level on the surface of the tertiary test piece, and examining the flatness in the draw bead drawing direction. The evaluation criteria are as follows. In addition, when a level is placed, if the bubble comes to the center of the circle on the level, it will be “flat”, if the bubble is displaced within the range of the circle, it will be “slightly shifted”, and the range of the circle will be The case where bubbles were shifted beyond this was evaluated as “large shift”.
“◎”: When all five locations are flat.
“◯”: When four places are flat and a slight deviation is observed at one place.
“Δ”: When three or more locations are flat and a large shift is observed at one or more locations.
“X”: When a large shift is observed at two or more locations.

[Evaluation of corrosion resistance]
The evaluation surfaces of the tertiary test pieces prepared as described above were overlapped and joined by spot welding to prepare a test piece for corrosion resistance evaluation as shown in FIG. Thereafter, Palbond manufactured by Nihon Parkerizing Co., Ltd. was used for this test piece for corrosion resistance evaluation, and immersed in standard conditions (35 ° C., 120 seconds) to perform phosphate chemical conversion treatment. Subsequently, electrodeposition coating and baking treatment were performed using an electrodeposition paint manufactured by Kansai Paint. In addition, the film thickness of electrodeposition coating was set to 20 μm after baking, and measurement was performed using a commercially available electromagnetic film thickness meter. In addition, in order to evaluate the influence of sliding on the corrosion resistance, an unprocessed test piece and a sample not subjected to the flattening treatment were also prepared and used for evaluation.

Next, the test piece for corrosion resistance evaluation produced as described above was subjected to a combined cycle corrosion test comprising the steps of drying, wetting and salt spraying as defined in SAE-J2334 as shown in FIG. In addition, corrosion resistance evaluation of each steel plate was implemented in the following procedures.
1) The spot weld is punched out and the mating structure is disassembled.
2) Peeling of paint (Deoscoat 300, manufactured by Neos, 15 minutes immersion).
3) Plating and rust removal (dilute hydrochloric acid immersion).
4) The maximum erosion depth (L) generated in the mating structure was measured with a point micrometer manufactured by Mitutoyo Corporation.

Next, the accuracy in the corrosion resistance test was evaluated. The evaluation was carried out by performing five sets of tests for each level and by the variation in the maximum erosion depth (L). Here, the variation of each level is the difference (ΔL = L _max ) obtained by subtracting the minimum maximum erosion depth (L _min ) from the maximum maximum erosion depth (L _max ) for each of the five sets of combined structures. -L _min ) was calculated and evaluated as follows.
“◎”: ΔL ≦ 0.05 mm
“◯”: 0.05 mm <ΔL ≦ 0.1 mm
“Δ”: 0.1 mm <ΔL ≦ 0.2 mm
“×”: 0.2 mm <ΔL
The validity of the evaluation result of the corrosion resistance test was evaluated based on the relationship between the coating amount and the maximum erosion depth. In the automotive field, it is known from the analysis results of automobiles that are actually running that, for SPC, GA45, GI60, GI100, and Zn-Ni30, there is a negative correlation between the amount of plating and the maximum erosion depth. The validity of the results of the corrosion resistance evaluation method can be evaluated by investigating the correlation between the amount of plating and the maximum erosion depth. Then, from the result evaluated by the corrosion resistance evaluation method according to the present invention, the correlation between the plating adhesion amount and the maximum erosion depth was investigated, and the validity of the result of the corrosion resistance evaluation method according to the present invention was evaluated.

  The evaluation results obtained above are shown in Table 3 together with the test piece preparation conditions.

  From the evaluation results shown in Table 3 above, the following matters were clarified.

  (1) Sample No. Nos. 1 to 9 are examples of the present invention, sample No. 10 to 18 are comparative examples in which the flattening process was not performed. In Examples 1 to 9 of the present invention in which the flattening process was performed, the results of the flatness evaluation were good, and it was found that the flatness was improved. Furthermore, as a result of the accuracy evaluation of the corrosion resistance evaluation, it can be seen that ΔL is significantly reduced in Invention Examples 1 to 9 compared to Comparative Examples 1 to 9, and the accuracy is greatly improved.

(2) Sample No. 3 and no. Reference numerals 19 to 22 are examples of the present invention in which the processing depth in the flattening processing is changed. Sample No. with a flat area (mm ² ) / depth (mm) of 3600 19 (Invention Example 10) is a sample No. that has not been flattened. Although the accuracy of the corrosion resistance evaluation is improved as compared with 12 (Comparative Example 3), the effect is not so remarkable. On the other hand, Sample No. with a flat portion area (mm ² ) / depth (mm) of 180 was obtained. Although 22 (Invention Example 13) has sufficient accuracy in corrosion resistance evaluation, the maximum erosion depth average value (mm) is larger than that in other Invention Examples. From this, sample no. In No. 22, it is expected that the steel plate surface is damaged during the flattening process, and the plating film is detached. From these results, it is understood that when the flat part area (mm ² ) / depth (mm) is 200 or more and 2000 or less, the durability (corrosion resistance) of the mating structure part can be evaluated with higher accuracy.

(3) Sample No. 23 and 24 are examples of the present invention in which the evaluation was performed by changing the area of the flat portion. The flat part area (mm ² ) / depth (mm) is 800 and the processing depth is 1 mm. In the case of Sample No. 23 (Invention Example 14), sample No. Although the accuracy of the corrosion resistance evaluation is improved as compared with 12 (Comparative Example 3), the effect is not so remarkable. From this, it can be seen that the processing depth is preferably 2 mm or more.

  (4) In FIG. 1 to 5 and FIG. The relationship of the plating adhesion amount and the maximum erosion depth average value about 10-14 is shown. In FIG. 5 (a) and FIG. 5 (b), the R-2 power value which is a determination coefficient is described. Comparing the R-2 power values of the inventive example and the comparative example, it can be seen that the inventive example is largely close to 1 and the linearity is improved. From this, it can be seen that the method of the present invention is an effective test method, and the accuracy of corrosion resistance evaluation is further improved.

[Metal plate processing]
As a test material used as a metal plate, No. 1 in Table 1 was obtained. Five types of test materials 1, 3, 4, 5, and 7 were prepared. And these steel plates were subjected to tensile processing or overhang processing by the following method.
-Tensile processing A primary test piece having a width of 80 mm and a length of 350 mm was prepared from the five kinds of test materials, and the tensile processing was performed. FIG. 6 shows a conceptual diagram of the tensile processing test. When the elongation in the longitudinal direction of the steel plate of the test material reached 15%, the processing was finished and a secondary test piece was obtained. As a preliminary test, a scribed circle was printed on the surface of the test material, a tensile test was performed, and the area change of the test material was measured. As a result, it was confirmed that the ratio was 1.05.
-Overhang processing A primary test piece of 300 mm square was prepared from the above five kinds of test materials, and overhang processing was performed to obtain a secondary test piece. The conditions are as follows.
Punch: 150mmΦ
Dice: 160mmΦ
Blank hold force: 980665N (100tf)
Processing amount: 20%
FIG. 7 shows a conceptual diagram of the overhanging test. In addition, as a preliminary test, a scribed circle was printed on the surface of the test material to perform overhanging, and the change in the area of the test material was measured. As a result, it was confirmed that the ratio was 1.4 times.
Moreover, the comparative test piece which does not implement a tension process and an overhang process was also prepared.

[Planarization processing]
After the secondary test piece and the comparative test piece are cut out to a predetermined size, the deep drawing process is performed on the test material subjected to the above-described tensile process or the overhang process and the comparative test piece not subjected to the tensile process and the overhang process. This was carried out to obtain a tertiary test piece. As for the flattening processing method, the level No. in Table 2 is used for any steel plate. The flat portion area described in C was 3600 mm ² and the processing depth was 5 mm.

  The flatness of the tertiary test piece subjected to deep drawing was evaluated. The evaluation of flatness is the same as in Example 1.

[Evaluation of corrosion resistance]
The evaluation surfaces of the tertiary test pieces produced as described above are overlapped and joined by spot welding, and the same phosphate treatment and electrodeposition coating as in Example 1 are performed, and a test for corrosion resistance evaluation as shown in FIG. Pieces were prepared, and the average value of the maximum corrosion depths in the five sets of mating portions was determined in the same manner as in Example 1.

  The validity of the evaluation result of the corrosion resistance test was evaluated based on the relationship between the coating amount and the maximum erosion depth. In the automotive field, it is clear that the corrosion resistance of the GA + organic coating (epoxy resin) is equivalent to that of GA in the case of an actual press product in a processing mode mainly composed of tensile processing and overhang processing. In addition, regarding SPC, GA45, GI60, and GI100, it is known that a negative correlation is recognized between the plating adhesion amount and the maximum erosion depth, and the correlation between the plating adhesion amount and the maximum erosion depth is investigated. Therefore, it is possible to evaluate the validity of the result of the corrosion resistance evaluation method. Then, from the result evaluated by the corrosion resistance evaluation method according to the present invention, the correlation between the plating adhesion amount and the maximum erosion depth was investigated, and the validity of the result of the corrosion resistance evaluation method according to the present invention was evaluated.

  The evaluation results obtained above are shown in Table 4 together with the test piece preparation conditions.

From the evaluation results shown in Table 4 above, the following matters were clarified.
(1) Sample No. Nos. 25 to 29 are examples of the present invention, sample No. 35 to 39 are comparative examples in which no processing was performed. FIG. 8 shows the relationship between the plating adhesion amount after the overhang processing and the average maximum corrosion depth. In the example of the present invention, a negative correlation was found between the plating adhesion amount after processing and the maximum corrosion depth, and the validity of the test became clear.
In addition, in the GA + organic film (sample No. 39) that was not processed as a comparative example, a remarkable corrosion resistance improvement effect was recognized as compared with GA (sample No. 36), and actual parts could not be simulated. On the other hand, in the case of the inventive example GA + organic film (sample No. 29) subjected to the overhang molding, it is confirmed that the corrosion resistance is equivalent to that of GA (sample No. 26), and an actual part can be simulated. I understand that
(2) FIG. 9 shows the relationship between the amount of plated coating after tensile processing and the average maximum corrosion depth. Sample No. Reference numerals 30 to 34 are examples of the present invention subjected to tensile processing. Since GA + organic film (sample No. 34) has the same corrosion resistance as GA (sample No. 31), it can be seen that an actual part can be simulated. And the validity of the test became clear from the fact that a negative correlation was found between the amount of plated deposit after processing and the maximum corrosion depth.

It is a figure which shows an example of the jig which performs the draw bead process to the test piece used in the Example which concerns on this invention. It is a figure which shows an example of the shape of the secondary test piece produced in the Example which concerns on this invention. It is a figure which shows an example of the shape of the test piece for corrosion resistance evaluation produced in the Example which concerns on this invention. It is a figure which shows an example of the process of the combined cycle corrosion test performed in the Example which concerns on this invention. In the Example which concerns on this invention, it is a figure which shows the result of having investigated the relationship between the plating adhesion amount and the maximum erosion depth about the example of this invention and a comparative example. It is a figure which shows an example of the jig used in the Example which concerns on this invention which performs a tensile process to a test piece. It is a figure which shows an example of the jig used in the Example which concerns on this invention which performs an overhanging process to a test piece. In the Example which concerns on this invention, it is a figure which shows the result of having investigated the relationship between the plating adhesion amount and the maximum erosion depth about the example of this invention and a comparative example. In the Example which concerns on this invention, it is a figure which shows the result of having investigated the relationship between the plating adhesion amount and the maximum erosion depth about the example of this invention and a comparative example.

Explanation of symbols

1 Dice 2 Bead 3 Punch

Claims (8)

  A method for producing a test piece for evaluating corrosion resistance in a mating structure part between metal plates, wherein a flat part is formed on a curved surface of a metal plate formed by processing the metal plate constituting the mating structure part. A test piece manufacturing method, wherein the provided flat portions are joined together to form a combined structure portion.   The method for producing a test piece according to claim 1, wherein the flat portion provided on the curved surface of the metal plate is formed by deep drawing. In the curved surface, the depth is 2 mm or more, and the flat area (mm ² ) / depth (mm), which is a ratio calculated from the flat area and depth, is 200 or more and 2000 or less, The method for producing a test piece according to claim 1, wherein a deep drawing process is performed to form a flat portion.   The method for producing a test piece according to claim 1, wherein the processing applied to the metal plate is sliding processing.   The method for producing a test piece according to claim 4, wherein the processing applied to the metal plate is sliding processing including bending and bending back.   The method for producing a test piece according to any one of claims 1 to 3, wherein the process applied to the metal plate is a tensile process or an overhang process.   The method for producing a test piece according to any one of claims 1 to 6, wherein after the mating structure portion is formed, chemical conversion treatment with phosphate is performed, and further, electrodeposition coating is performed.   The corrosion resistance evaluation method characterized by evaluating the corrosion resistance in the joining structure part of metal plates using the test piece produced by the test piece production method as described in any one of Claims 1-7.

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