JP5983578B2 - Method for predicting appearance deformation of film, manufacturing method, and surface-coated metal plate - Google Patents

Description

  The present invention relates to a technique for deforming a surface-coated metal plate having a coating on at least one surface of a metal plate by press forming such as drawing or stretch forming into a desired shape of a processed product. The present invention relates to a technique capable of suppressing the appearance deformation of the surface film from being more than predetermined in the manufactured processed product. Here, the appearance deformation of the surface film refers to, for example, a phenomenon that the surface is whitened (whitened).

The surface-coated metal sheet is used after being processed into a desired shape in various industries, such as containers represented by automobiles, home appliances, building materials, cans, and the like. Here, the surface-coated metal plate imparts a film to the surface of the metal plate, thereby giving the metal plate as a substrate functions such as corrosion resistance, fingerprint resistance, and design properties such as gloss and color tone.
When processing a surface-coated metal sheet into a part, press work with excellent productivity such as drawing, overhanging, and bending is often used. If the surface coating is hard or difficult to deform compared to the underlying metal plate, press-molding the surface coated metal plate will not allow the coating to follow the deformation of the metal plate, so the coating will crack or peel, It is known that whitening may occur. When a crack or peeling occurs in the film, corrosion proceeds from there, and the peeled film enters between the mold and the metal plate, thereby causing problems such as wrinkling the metal plate. In addition, when the film is whitened more than a predetermined amount, the appearance quality of the product is impaired, resulting in a defective product.

For this reason, in order to prevent a crack, peeling, and whitening from arising in a film, the component and manufacturing method of a film suitable for press molding have been examined conventionally.
In patent document 1, the method of prescribing | regulating the gel fraction of the resin film at the time of a heating is proposed for the precoat aluminum plate. Patent Document 1 describes that the adhesion between the film and the aluminum plate is enhanced so that the film does not peel or whiten even when deep drawing or ironing is performed.
Moreover, there exists a technique of patent document 2 as a technique which evaluates peeling and adhesiveness of a film | membrane quantitatively. The method described in Patent Document 2 is a method for evaluating the limit at which the film does not follow the distortion of the substrate by measuring the distortion of the film on the substrate surface with a laser beam. On the other hand, as a technique for evaluating the whitening of the film, there is a method of visually determining the degree of whitening of the film by performing cylindrical drawing or tensioning as in Non-Patent Document 1, but conventionally, it is quantitative. There is almost no technology to evaluate.

Japanese Patent No. 4783051 Japanese Patent Laid-Open No. 11-142319

"Whitening Phenomenon and Drawing Mechanism in Pre-coating Aluminum Drawing" Light Metal, Vol. 57, No. 6 (2007) pp.228-233

When press-molding a surface-coated metal plate, various deformations occur in the metal plate, and the coating slides with the mold. When any deformation or sliding is applied to the metal plate and the coating, It is not clear how much whitening phenomenon will occur. Also, the degree of whitening of the film is considered to vary depending on the deformation characteristics of the metal plate and the film and the degree of sliding between the metal mold and the mold.
Here, as described in Patent Document 1, it is important to produce a surface-coated metal plate that does not cause whitening of the film. However, in the case of processing conditions with little deformation, peeling or whitening of the film occurs. In the case of processing conditions that cause difficult deformation, the method of Patent Document 1 may excessively limit the manufacturing conditions of the surface-coated metal sheet.

  Moreover, as in Non-Patent Document 1, it is simple to apply a deformation close to the actual press forming to the surface-coated metal plate and visually evaluate it. However, since this method is a sensory evaluation method, the results may vary depending on the measurer and measurement conditions, and the reliability is poor. As a quantitative evaluation method, there is also a technique described in Patent Document 2 that measures the amount of deformation (strain) at which the film peels off. However, before the metal plate and the film completely peel off, that is, there are fine cracks in the film. Since the whitening phenomenon occurs even at the stage of occurrence, detailed evaluation of the whitening phenomenon is considered difficult.

If the whitening phenomenon cannot be evaluated quantitatively, it is impossible to set production standards such as how much whitening is acceptable as a product. As a result, there has been a problem that it is impossible to predict whether a whitening phenomenon will occur in the film at the preparation stage for manufacturing a product using the surface-coated metal plate, for example, at the design stage of the mold or product shape.
The present invention has been made paying attention to the above points, and quantitatively evaluates the whitening phenomenon (appearance deformation) of the coating that will occur when the surface-coated metal sheet is press-molded. An object is to provide a technology capable of predicting a whitening phenomenon.

In order to solve the above problems, a method for predicting the appearance deformation of a film according to one aspect of the present invention is a method for press-forming a surface-coated metal plate having a film formed on at least one surface of the metal plate. A method for predicting the appearance deformation of a film for predicting the appearance deformation, estimating a sliding load that is a load applied to the film by sliding with a mold during the press molding, and obtaining the estimated sliding load. Based on this, the appearance deformation of the film generated by the press molding is predicted.
At this time, the sliding load may be based on the degree of damage received by the film by sliding as an index, and the deformation of the film caused by the press molding may be predicted from the degree of damage.

In addition, the relationship between the degree of external deformation of the film with respect to the sliding load is obtained in advance as a first relationship, and the sliding load estimated to be applied to the film by press forming the surface-coated metal plate and the above Based on the first relationship, the appearance deformation of the film on the metal plate may be predicted.
In addition, the pressure, the sliding speed, and the contact length, which is the length that the mold comes into contact with, when the film is rubbed from the mold when press-molding into the desired processing shape by the molding simulation, are determined. The sliding load or the appearance deformation may be evaluated from the damage state of the film surface after the test that is calculated as the sliding condition and after the sliding test is performed under the calculated sliding condition.

In addition, a relationship between the degree of external deformation of the coating formed on the metal plate with respect to strain generated in the metal plate is obtained as a second relationship, and is added to the coating when the surface-coated metal plate is press-formed. The appearance deformation of the coating on the metal plate may be predicted based on the estimated sliding load and strain generated in the surface-coated metal plate, and the first relationship and the second relationship. .
Here, the strain is specified by using, for example, two parameters, a minimum strain and a maximum strain.

In addition, the above-described appearance deformation uses, for example, any one of film color, color difference, gloss, and light reflectance as an index.
Moreover, you may make it predict the membrane | film | coat position in which the external appearance deformation | transformation degree more than the preset threshold value generate | occur | produces with the said any external appearance deformation | transformation prediction method.
The manufacturing method according to one aspect of the present invention is a manufacturing method for manufacturing a machined part by press-molding a surface-coated metal plate in which a film is previously formed on at least one surface of the metal plate into a target processing shape. In addition, prior to processing the set processing shape by press molding, when it is determined that there is a film position where an appearance deformation degree equal to or greater than a preset threshold value is generated by the above-described appearance deformation prediction method for the film, the predetermined threshold value or more is set. According to the present invention, at least one of correction of the set processing shape and change of the coating material is performed according to the position of the film where the degree of appearance deformation occurs and the degree of appearance deformation at that position.

In addition, the surface-coated metal plate according to one aspect of the present invention has a degree of appearance deformation equal to or greater than a preset threshold value even if it is press-formed into a target processing shape based on the prediction result obtained by the above-described appearance deformation prediction method for a film. It is characterized in that a coating material capable of suppressing the occurrence of the above is used.
Here, the inventors observed a sample of a surface-coated metal sheet that was whitened by press working, and when the film peeled off and the metal plate or the base immediately below the surface film was exposed, the film appeared white In addition, it was confirmed that cracks generated in the film sometimes scatter light and make the film appear white. For this reason, it has been found that simply evaluating whether or not the film peels is insufficient.

Further, when the press-molded surface-coated metal plate was observed, it was found that the degree of whitening of the film was different between the film part rubbed by the mold and the film part not in contact with the mold. In other words, when damage was applied to the film by rubbing with the mold, the damage affected whitening of the film, and the effect was considered to vary depending on the damage (degree of damage).
In view of this, first, samples having various deformation forms (strain ratios) and deformation amounts (strain amounts) generated in the metal plate by press working were prepared. Next, various sliding tests were carried out on the samples using a sliding test apparatus in which sliding conditions were changed using the pressure and speed, and the contact length of the mold contacting the coating as parameters.

And the whitening phenomenon which generate | occur | produces in a film | membrane was investigated in detail with respect to each sample produced as mentioned above. As a result, it was found that the degree of influence differs depending on strain (strain amount and strain ratio) and film damage from the mold surface.
Furthermore, it was discovered that the degree of whitening of the film (degree of appearance deformation) can be quantified by measuring whiteness, color, color difference, gloss, light reflectance, etc. Ratio and strain), and the degree of whitening was related to the damage that the film received from the mold surface.

  Therefore, the strain generated on the surface-coated metal plate during press forming is reproduced by a uniaxial tensile test and an overhang test, and the damage that the film receives from the mold surface is reproduced by a sliding test to measure the whitening phenomenon that occurs on the film. Thus, the present inventors have found a method of mapping and using in detail the relationship between the strain generated in the film and the degree of whitening with respect to the damage (damage degree) due to sliding that the film receives from the mold surface. By digitizing the degree of whitening of the film, it is possible to evaluate with higher accuracy than conventional visual sensory evaluation and evaluation of ease of peeling of the film. Also, by calculating the strain generated in the molded product, the pressure and speed when the coating is rubbed on the mold surface, and the contact length by press molding simulation using the finite element method, the degree of whitening can be calculated from the above mapping. It was found that it can be predicted with high accuracy. Based on the above, the present invention has been conceived.

  According to the aspect of the present invention, when the target surface-coated metal plate is press-molded into a desired processed shape, it is possible to predict in advance how much the film is whitened, that is, the degree of appearance deformation of the film. For this reason, it can greatly contribute to the reduction of the defective rate of the press-formed product. In addition, it is possible to accurately predict the characteristics required for the coating of the surface-coated metal sheet at the material design stage. As a result, the development goal of the surface-coated metal sheet can be set, which can contribute to shortening the development period. Furthermore, there is an effect that it is possible to accurately predict whether or not the selection of the surface-coated metal plate used when press-molding various parts such as electrical products and automobile panel parts is appropriate.

It is an example of a sectional view of a surface covering metal plate concerning an embodiment based on the present invention. It is a figure which shows the example of a deformation | transformation form and a shaping | molding limit line. It is a figure which shows estimation of the limit line of a film | membrane damage. It is a figure which shows the example of the relationship between the molding height and glossiness by each deformation | transformation form. It is a figure which shows the example of the contour line of glossiness. It is a figure which shows the other example of the contour line of glossiness. It is a figure which shows the structure of a whitening prediction apparatus. It is a figure which shows the example of a driving sheet. It is a figure explaining the metal mold | die used for an overhang test. It is a figure explaining the distortion which generate | occur | produces in a uniaxial tension test. It is a figure explaining the distortion which generate | occur | produces in an overhang test. It is the figure which put together the strain deformation by the maximum principal strain and the minimum principal strain. It is a figure which shows the back cover component of the thin-screen television as an example of object. It is a figure explaining a sliding test. It is a figure when giving the glossiness when giving the distortion and the damage to the film. It is a figure when giving the glossiness when giving the distortion and the damage to the film. It is the figure which plotted the glossiness according to distortion for every test material. It is a figure which shows the contour line of glossiness for every test material. It is a figure which shows the result by visual observation of the conventional method. It is a figure which shows the result by this invention method.

Next, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
In the present embodiment, the surface deformation of the coating 3 will be described by taking the whitening of the surface coating as an example.
Here, the surface-coated metal plate 1 includes a metal plate 2 and a film 3 applied to the surface of the metal plate 2 as shown in FIG. In the present embodiment, the surface-coated metal plate 1 in which the film 3 is formed on one surface of the metal plate 2 will be described as an example. Examples of the metal plate 2 include an aluminum plate, a SUS plate, and an iron plate. However, the metal plate 2 is not particularly limited as long as the metal plate 2 can be press-molded and can be provided with the coating 3. The film 3 includes, for example, a plating film, a chemical conversion film, a coating film, a film laminate film, a precoat film, or a film formed by laminating a plurality of them.

Here, basic deformation forms (strain ratio) generated by press-molding the metal plate 2 are roughly classified into uniaxial tensile deformation (ε ₁ = −2 · ε ₂ ) and plane strain deformation (ε ₂ / There are three forms: ε ₁ = 0) and equibiaxial deformation (ε ₁ = ε ₂ ). The forming limit forming limit line, which is the limit of crack deformation of the metal plate 2 due to deformation, can be represented by a curve having the maximum principal strain and the minimum principal strain as parameters, as shown in FIG. This forming limit line generally tends to be smaller in the vicinity of the plane strain state where the strain ratio (= minimum principal strain / maximum principal strain) = 0. That is, the forming limit differs depending on the deformation form of the metal plate 2.
Here, Table 1 describes the composition of each material shown in FIG.

The present inventors consider that there is some correlation between the deformation of the metal plate 2 and the appearance deformation of the surface coating 3 on the metal plate 2, and the distortion similar to the above forming limit line as shown in FIG. It was verified by assuming that a limit line of film damage due to correlated whitening could be assumed.
Then, when the relationship between the punch stroke amount (equivalent to the molding height) and the glossiness at the time of press working and the glossiness is obtained for each deformation mode, it is as shown in FIG. I understood that. Further, the degree of whitening is summarized as shown in FIG. 5 using the maximum main strain and the minimum main strain as parameters. That is, it was confirmed as described later that there is a correlation between the deformation mode (strain ratio) of the metal plate 2 and the degree of whitening. The degree of whitening is evaluated by the glossiness. Moreover, as shown in FIG. 6, the position of the contour line of the same glossiness changes with film | membrane materials. However, in either case, the contour line of the glossiness has a downward slope, which is different from the tendency of the molding limit line.

  Here, as the types of deformation forms (strain ratios) increase, the contour lines of glossiness can be obtained with higher precision. In this embodiment, the three types of uniaxial tensile deformation, plane strain deformation, and equal biaxial deformation are described above. The glossiness value in the deformed form was obtained as a representative value for each material, and information on strain and glossiness was accumulated in the whitening evaluation database 5 as data relating to the second relationship. Here, the glossiness in the deformation mode (strain ratio) between the three deformation modes is a value on a straight line connecting the same glossiness in the adjacent basic deformation modes as shown in FIG. Set. When actually obtained, contour lines are expressed by a line on a curve close to a straight line, and therefore it is estimated that the accuracy is not lowered so much even if linear approximation is performed. In addition, since the relationship between the deformation form other than the deformation form (strain ratio) of the actual measurement value and the whitening degree is an estimated value, it corresponds to the limit value of the whitening degree that is set in advance with a margin for the whitening degree. You may make it suppress the amount of distortion to carry out.

In addition, when a deformation is applied to a metal by press working, the portion where the deformation occurs while the surface of the coating slides on the mold surface (punch and punch) is not subject to sliding even if the deformation amount is the same. The external deformation is larger than that of the part.
Sliding between the above molds is performed with the sliding load (pressure) applied to the sliding part, the sliding speed, and the contact length with which the mold contacts when sliding as parameters. The sliding load received by the coating 3 varies depending on the sliding condition. That is, the sliding load can be expressed as a parameter (index) of the load during sliding, the sliding speed, and the contact length with which the mold comes into contact with the sliding. In addition, the sliding load which each membrane | film | coat position receives is the value which integrated | accumulated the load which consists of the load at the time of the said sliding, and a sliding speed. Since the integrated value is an integral of the time during which sliding is performed, the sliding load can also specify the load during sliding, the sliding speed, and the sliding time as parameters (indexes).

  In addition, the range of sliding load that will occur in normal press working (range of load, sliding speed, and contact length in the above-mentioned sliding) is that of the mold that is assumed to occur during actual processing. It can be calculated from a forming simulation using the moving speed, moving amount, and load applied to the plate as parameters. From such a calculation, the range of the sliding load that will occur in the assumed press working is obtained.

  Then, a plurality of representative values are sampled from the range for determining the obtained sliding load, and the sliding load conditions (load (pressure), sliding speed, and contact length) corresponding to each sampled representative value are determined. As a parameter, that is, as a sliding condition, a sliding experiment was actually performed using the target surface-coated metal plate 1 to evaluate whitening by sliding of the sliding portion (whitening degree). That is, the relationship between the sliding load conditions (load (pressure) and sliding speed and contact length) corresponding to each representative value sampled and the whitening evaluation value (whitening degree) is obtained and the relationship Was stored in the database 5 for whitening evaluation as data relating to the first relationship. This was done for each coating material that would be used. In addition, when using a value of a sliding condition that is not a representative value, that is, not previously stored in a database, it is calculated by interpolating a representative value existing in the vicinity.

Thus, in the database 5 for whitening evaluation, the second relationship between the deformation mode (strain ratio) and the degree of whitening, the index for specifying the sliding load (sliding condition), and the degree of whitening Data relating to the relationship 1 is stored in advance.
The whitening prediction device 4 predicts the whitening degree while referring to the data in the whitening evaluation database 5. As shown in FIG. 7, the whitening prediction device 4 includes an information input unit 4A, a whitening degree calculation unit 4B, and an output unit 4C.

The information input unit 4A inputs strain information, sliding information, and film material information.
Here, before the target surface-coated metal plate 1 is press-formed into a target shape, each strain applied by the press-forming to each part of the surface-coated metal plate 1 is subjected to a known technique such as a finite element method. It estimates with the distortion evaluation apparatus 6 to perform. Then, the information input unit 4A inputs the strain information estimated by the strain evaluation device 6.

Similarly, before the target surface-coated metal plate 1 is press-molded into a target shape, sliding conditions that will be applied from the mold to the coating 3 by the press-molding on each part of the surface-coated metal plate 1 are as follows. It estimates with the said strain evaluation apparatus 6 which performs a method well-known, such as a finite element method. Then, the information input unit 4A inputs an index (sliding condition) specifying the sliding load of each part estimated by the strain evaluation device 6 as sliding information.
Moreover, the information of film | membrane material is received from the control part etc. of the manufacturing line of the surface coating metal plate 1, for example.
The strain information here is a deformation mode (strain ratio) and a strain amount. The amount of strain is represented by, for example, the maximum principal strain. Further, the strain information may be two values of the maximum main strain amount and the minimum main strain amount. In this embodiment, position information on the metal plate 2 is added as strain information.

The sliding information includes a load (pressure) from the mold, a sliding speed, and a contact length with which the mold contacts. In addition, you may employ | adopt the contact time with a metal mold | die instead of the contact length which a metal mold | die contacts.
The whitening degree calculation unit 4B refers to the whitening evaluation database 5 using the strain information, the sliding information, and the film material information as parameters. And the whitening degree calculating part 4B acquires the whitening degree (glossiness in this embodiment) with respect to an index (sliding condition) for specifying each strain and sliding load. Each strain and sliding condition (equivalent to sliding load) are tied to each position on the metal plate 2.

Here, “the degree of whitening due to distortion” and “the degree of whitening due to sliding load” are individually acquired at the same position of the coating 3. The whitening degree calculation unit 4B may individually output the “whitening degree due to distortion” and the “whitening degree due to sliding load”. In this case, it can be distinguished whether whitening has occurred due to strain or sliding.
However, the relationship between the degree of whitening is obtained using a set of strain and sliding conditions as a parameter, and is stored in the whitening evaluation database 5, and one whitening is performed using the set of strain and sliding conditions as a parameter. You may comprise so that a degree may be acquired.

  Further, the whitening degree calculation unit 4B, for example, selects a higher one (select high) as the final whitening degree between “whitening degree due to distortion” and “whitening degree due to sliding load”. You may decide. Further, for example, as shown in the following formula, the “whitening degree due to sliding” after adding the correction gain k (<1) to the “whitening degree due to distortion” is added to obtain the final whitening degree. You may ask as.

Final degree of whitening =
"Whitening degree due to distortion" + k · "Whitening degree due to sliding load"
Furthermore, as shown in the following equation, both the “whitening degree due to distortion” and the “whitening degree due to sliding load” are multiplied by individual weighting factors α and β, respectively, and the subsequent values are added, thereby obtaining a final value. The degree of whitening may be determined.
Final degree of whitening =
α ・ “Whitening degree due to distortion” + β ・ “Whitening degree due to sliding load”
Here, α and β are weighting coefficients, and are set such that α + β = 1, for example.

The output unit 4C displays or prints the whitening degree due to each strain and sliding obtained by the whitening degree calculation unit 4B on the display unit 7 such as a display corresponding to the position of the metal plate 2. . At this time, for example, when the limit value of the whitening degree is set, the output unit 4C emphasizes and outputs the position of the metal plate 2 that has become the whitening degree exceeding the limit value of the whitening degree, for example. Or may be processed so that only that portion is displayed.
Here, the degree of whitening due to sliding and the degree of whitening due to distortion may be displayed individually or in different colors.

(Operation)
For each coating material, information on strain and whitening degree, sliding condition and whitening degree are collected and stored in the whitening evaluation database 5 in advance. In this embodiment, for the sake of simplicity, the strain is represented by three deformation forms such as uniaxial tensile deformation, plane strain deformation, and other biaxial deformation, and gloss information is collected in the three deformation forms to obtain the white color. Stored in the evaluation evaluation database 5. In addition, if information is separately collected for a plurality of film thicknesses for the same film material, more accurate data is obtained. Here, the sliding conditions are a load applied from the mold, a sliding speed, and a sliding time.

For example, as a preliminary evaluation before manufacturing the target surface-coated metal plate 1, if the target surface-coated metal plate 1 is press-formed into a target shape based on the material information of the metal plate 2, the metal Each strain applied to each part of the plate 2 by the press molding is estimated by a known method such as a finite element method.
Similarly, as a prior evaluation before manufacturing the target surface-coated metal plate 1, if the target surface-coated metal plate 1 is press-molded into a target processing shape, it is applied to each part of the metal plate 2 by the press-forming. Each sliding is estimated by a known method such as a finite element method.

Next, with reference to the data of the whitening evaluation database 5, information on the degree of whitening of each part of the plate surface generated on the surface of the processed product after processing the target surface-coated metal plate 1 is obtained. For example, the location of the metal plate 2 that is greater than or equal to a preset whitening degree (in the present embodiment, less than the glossiness) is displayed in association with the position in the shape after processing or the position in the metal plate 2 before processing. .
And when the location which becomes more than preset whitening degree (in this embodiment, below glossiness) exists, for example, the coating material to be used is changed, for example, a material having higher viscosity and viscoelasticity as the coating material In other words, the pre-evaluation process is performed until there is no portion where the whitening degree is equal to or higher than the preset whitening degree (in the present embodiment, the glossiness is lower).

Or, for example, as a pre-evaluation before manufacturing the target surface-coated metal plate 1, based on the material information of the metal plate 2, if the target surface-coated metal plate 1 is press-molded into a target processing shape, The maximum strain generated in the metal plate 2 is obtained for each deformation mode. For example, the maximum value of the maximum principal strain amount is obtained for each of the three types of deformation.
Then, referring to the data of the whitening evaluation database 5 with the maximum value of the maximum principal strain amount for each of the three types of deformation as a parameter, for example, for each of the three types of deformation for the coating material to be used The glossiness is obtained, and it is determined whether it is less than or equal to the preset whitening degree (in this embodiment, greater than or equal to the glossiness). Alternatively, referring to the data of the whitening evaluation database 5 using the maximum value of the maximum principal strain amount for each of the three types of deformation as a parameter, the glossiness is equal to or less than the preset whitening degree (in this embodiment, Obtain a list of coating materials that have a glossiness of at least. At this time, in order to select the coating 3, the strength condition of the coating 3 may be input.

  Further, as described above, referring to the data of the whitening evaluation database 5, information on the degree of whitening occurring on the surface of the processed product after processing the target surface-coated metal plate 1 is obtained and set in advance. When there is a portion that is equal to or higher than the degree of whitening (in this embodiment, equal to or lower than the glossiness), the composition of the metal plate 2 is changed or the processing shape of the portion that is equal to or higher than the preset whitening degree is changed. The pre-evaluation process is performed until there is no place where the whitening degree is equal to or higher than the preset whitening degree (in this embodiment, the glossiness is lower).

In addition, if the reason why the whitening degree exceeds a predetermined value is the case of sliding, even if the sliding conditions are the same, the coating material can be changed to a material with a small whitening degree, or the whitening degree exceeding the predetermined value can be achieved. The machining shape is changed so that the sliding load of the portion where the degree is generated is reduced.
By performing as described above, it is possible to predict in advance how much the coating 3 is whitened when the target surface-coated metal sheet 1 is press-formed into a desired shape, that is, the degree of appearance deformation of the coating 3. For this reason, it can greatly contribute to the reduction of the defective rate of the press-formed product.

In addition, the characteristics required for the coating 3 of the surface-coated metal plate 1 can be accurately predicted at the material design stage. Therefore, the development goal of the surface-coated metal sheet 1 can be set, which can contribute to shortening the development period. Furthermore, there is also an effect that it is possible to accurately predict whether or not the selection of the surface-coated metal plate 1 used when press-molding various parts such as electrical products and automobile panel parts is appropriate.
Thus, since it is rarely restricted by the material of the base metal plate 2 used as a target, the characteristics of the surface coating 3, and the manufacturing method, it can be applied to various surface-coated metal plates 1. In addition, when parts such as industrial and consumer devices and can products are produced by press-molding the surface-coated metal plate 1, whitening of the coating 3 can be predicted in advance. The characteristics themselves can be selected in advance.

(Modification)
Here, in the above description, an index (sliding condition) for identifying the sliding load is used as sliding information, and the relationship between the sliding condition and the degree of whitening is obtained in advance and stored in the whitening evaluation database 5. As explained in the case of using.
Instead of this, with the index (sliding condition) for specifying the sliding load, the surface-coated metal plate 1 is actually subjected to a sliding experiment to determine the damage (damage degree) of the coating 3. Damage may be used as sliding information. That is, the sliding load may be evaluated by damage caused by sliding, and the damage and the degree of whitening may be related in advance as the first relationship and accumulated in the whitening evaluation database.

  Here, the damage of the film 3 is evaluated by, for example, the ratio of the surface roughness of the film 3 after the sliding test to the surface roughness of the film 3 before the sliding test. At the same time, the degree of whitening of the film 3 after the sliding test is evaluated as described above, and the relationship between the damage (degree of damage) of the film 3 due to sliding and the degree of whitening is obtained as a first relationship, Accumulate in the database for whitening evaluation. In this case, it is possible to include the difference due to the coating 3 such as the coating material in the damage information by associating the damage caused by sliding with the degree of whitening.

In this case, after an index (sliding condition) corresponding to the target sliding load is calculated by a molding simulation, a sliding test is performed under the sliding condition, and the surface of the coating 3 before and after the sliding test is performed. Information on damage is obtained by obtaining roughness, and the degree of whitening corresponding to the obtained damage is obtained from the whitening evaluation database 5. If past sliding test results are recorded, the information may be referred to.
Here, the relationship between the sliding condition and the damage for each coating material may be separately obtained and accumulated as a third relationship. In this case, when the sliding condition is obtained by molding simulation, damage is obtained from the third relationship using the obtained sliding condition and the coating material as parameters, and the damage and the first relationship are obtained. The degree of whitening is obtained from

(Effect of this embodiment)
This embodiment has the following effects.
(1) Estimating a sliding load, which is a load applied to the coating 3 by sliding with a mold during the press molding, and the coating generated by the press molding based on the estimated sliding load 3 appearance deformation is predicted.
According to this configuration, when the target surface-coated metal plate 1 is press-formed into a desired shape, the degree to which the coating 3 is whitened by sliding with the mold, that is, the degree of external deformation of the coating 3 is determined. Is predicted in advance. For this reason, it can greatly contribute to the reduction of the defective rate of the press-formed product.
(2) The sliding load uses the degree of damage received by the film 3 by sliding as an index, and predicts the appearance deformation of the film 3 caused by the press molding from the degree of damage.
As a result, the sliding load can be evaluated based on the degree of damage.

(3) The relationship of the external deformation degree of the coating 3 formed on the metal plate with respect to the sliding load on the surface-coated metal plate 1 is obtained in advance as a first relationship, and the surface-coated metal plate 1 is press-molded. Based on the sliding load estimated to be applied to the film 3 and the first relationship, the appearance deformation of the film 3 on the metal plate is predicted.
According to this configuration, by referring to the first relationship obtained in advance, when the target surface-coated metal plate 1 is press-molded into a desired shape, the film 3 is slid by sliding with the mold. It is possible to predict the degree of whiteness to some extent, that is, the degree of appearance deformation of the film 3 easily and in advance. For this reason, it can greatly contribute to the reduction of the defective rate of the press-formed product.

(4) According to the molding simulation, when the coating 3 is rubbed from the mold when press-molding into a target processing shape, the pressure received by the coating 3, the sliding speed, and the length that the mold is in contact with A certain contact length is calculated as a sliding condition, and the sliding load or appearance deformation is evaluated from the damaged state of the film surface after the test after the sliding test is performed under the calculated sliding condition.
According to this structure, it becomes possible to evaluate with a more reliable index by utilizing the damage state of the surface of the film generated in practice.

(5) The relationship of the degree of external deformation of the coating 3 formed on the metal plate with respect to the strain generated in the metal plate is obtained as a second relationship, and the coating is formed when the surface-coated metal plate 1 is press-formed. 3 is predicted based on the sliding load estimated to be applied to 3 and the strain generated in the surface-coated metal plate 1 and the first relationship and the second relationship. To do.
According to this configuration, it is possible to predict the appearance deformation of the coating 3 from two viewpoints of distortion and sliding.

(6) The strain is specified using two parameters, minimum strain and maximum strain, as parameters.
According to this configuration, it is possible to evaluate the degree of appearance deformation of the coating 3 with higher accuracy.
Here, the evaluation may be made more simply by one strain amount such as the maximum principal strain amount without looking at the deformation form. For example, when attention is paid only to the deformation near the plane strain deformation, the evaluation may be made using only the maximum principal strain amount.

(7) The above-described external deformation is determined by using any one of the color, color difference, gloss, and light reflectance of the coating 3 as an index.
Such an index can be objectively measured and evaluated by a measuring device such as a gloss meter.
Here, in the above-described embodiment, the glossiness is exemplified as an index of the degree of whitening as the degree of appearance deformation. However, an amount that can be measured by the measuring device, such as a color saturation or a light reflectance, may be used as the index value.
Moreover, although whitening is illustrated as an external appearance deformation | transformation of the membrane | film | coat 3, if it changes from the external appearance used as references | standards, such as blackening and greening, and a change of an external appearance can be measured with a measuring device, this invention is applied. I can do it.

(8) Predict the film position where the degree of appearance deformation equal to or greater than a preset threshold value occurs.
As a result, the occurrence position of the degree of appearance deformation that becomes a problem can be predicted in advance, so that it is possible to cope in advance.
(9) If it is determined that there is a film position where an appearance deformation degree equal to or greater than a preset threshold is generated by the appearance deformation prediction method of the film prior to processing the set processing shape by press molding, the predetermined threshold or more According to the film position where the degree of appearance deformation occurs and the degree of appearance deformation at that position, at least one of the modification of the set processing shape and the change of the film material is performed.
According to this configuration, the press shape can be optimized in advance. Alternatively, optimization of the film 3 can be performed in advance.

(10) Based on the prediction result of the appearance deformation prediction method of the film 3, a film material that can suppress the occurrence of the appearance deformation degree equal to or higher than a preset threshold value is used even if the target processing shape is press-molded. A surface-coated metal plate 1 is used.
According to this configuration, it is possible to provide the surface-coated metal plate 1 that is more suitable for the intended processing shape and processing conditions.

  The metal plate 2 is processed into a JIS No. 5 tensile test piece and a 200 mm square test piece. At this time, a test piece for measuring the degree of whitening of the coating 3 and a test piece for measuring strain are prepared. In addition to the measurement of glossiness, the measurement method of the degree of whitening of the film 3 is a quantitative measurement of changes in the film 3 such as whiteness, yellowness, blackness, brightness, color difference, or light reflectance. Any method may be used as long as it can be measured.

  The test piece for measuring the glossiness is measured in advance for comparison before and after the test. The test piece for measuring strain is marked on the back surface of the contact portion with the punch 11 with a distance between the gauge points of 0.5 to 50 mm. If the distance between the gauge points is smaller than 0.5 mm, the reading error of the gauge position becomes so large that it cannot be ignored with respect to the measured strain value, which is not suitable. When the distance between the gauge points is larger than 50 mm, the strain change between the gauge points is averaged, so that the measurement accuracy of the strain may be lowered. The marking method may be any method as long as strain can be measured, such as a scribed circle, laser marking, etching, or marking. In addition, distortion may be measured using image processing such as digital image correlation (DIC).

  The prepared specimens are processed with different strain ratios (ratio of maximum and minimum principal strains) and strain amounts. Here, in order to produce test pieces having different strain ratios, a uniaxial tensile test and a truncated cone extension test of FIG. 9 using the driving sheet 10 having different plate widths W shown in FIG. 8 are performed. Although the structure of the mold is not particularly limited, as will be described later, a sliding test can be performed on the film 3 and a flat portion having a sufficiently wide area that can measure the degree of whitening of the film 3 is provided. It is preferable to set the shape of the top of the punch 11 in advance. However, the tip shape of the punch 11 may be spherical as long as the degree of whitening of the film 3 can be measured as long as it is limited to the strain test. Since the test piece is deformed following the deformation of the driving sheet 10, the driving sheet 10 is preferably made of mild steel having better deep drawability (higher Rankford value) than the test piece. Lubricating oil is applied to the interface between the driving sheet 10 and the punch 11 and does not need to be applied to other portions. By changing the width W of the driving sheet 10 in a range that is larger than the hole diameter D at the center and smaller than the distance between the beads (Φ180 mm), a wider strain ratio can be added to the test piece.

  The amount of strain is changed by changing the tensile distance in the uniaxial tensile test and the molding height in the truncated cone extension test. If the strain is measured from a scribed circle with respect to a test piece to which various strains are applied, a test piece in which the strain ratio and the strain amount are changed as shown in FIGS. 10 and 11 can be produced. When the strain of each test piece is displayed on the same graph, it can be described as shown in FIG. In FIG. 12, the horizontal axis represents the minimum principal strain and the vertical axis represents the maximum principal strain.

  Next, the damage (degree of damage) that the film receives by rubbing against the mold surface is reproduced on the test piece. In order to reproduce the damage, it is necessary to reproduce the sliding conditions such as pressure, speed and contact length when the coating 3 is rubbed. More preferably, the roughness and material of the mold surface, the type of lubricating oil between the coating 3 and the mold surface, and the like should be matched with the molding conditions in actual press molding. The pressure, speed, and contact length are preferably calculated by forming simulation based on the finite element method. This is because, during press molding, complicated phenomena such as material movement, pressure, and strain change occur simultaneously, making it difficult to actually measure.

  When the position where the whitening of the film 3 is likely to occur is investigated for the back cover part of the flat-screen television shown in FIG. 13, the film 3 is likely to be whitened at the vertical wall portion A where the mold and the film 3 are in contact. discovered. Therefore, a molding simulation was performed based on the mold shape, and the pressure, speed, and contact length with which the coating 3 was rubbed on the mold surface were calculated. The LS-Dyna ver.9.71 was used as the molding simulation solver, and the simulation was performed using the dynamic explicit method. The friction coefficient between the mold and the blank was 0.15, and the mesh size was 1.25 mm. The wrinkle presser force was also set to 40 tons by setting the inflow rate to be equal between the forming simulation and the press experiment. The conditions for performing the forming simulation may be set in any way as long as the above pressure, speed, and contact length can be calculated under conditions simulating actual press forming.

  Based on the above calculation results, a sliding test is performed on the strained test piece. The test piece that has been stretched is cut into a dimension that allows a sliding test on a flat portion on the punch. For the sliding test, a method of fixing the test piece and moving the tool (slider) on the test piece as shown in FIG. The contact pressure was 130 MPa, the moving speed of the tool was 1 m / min, and the contact length was 4 mm. Tool material, surface roughness, and lubricating oil were combined with actual press molding. The test method may be any method as long as the tool can rub on the coating 3 of the surface-coated metal plate 1 and the friction coefficient can be measured.

  When the glossiness is measured for each of the test pieces to which the strain and the damage to the film 3 are added, it is as shown in FIG. If the glossiness at each strain is connected with contour lines, the relationship between the strain applied to the surface-coated metal plate 1 and the degree of whitening of the coating 3 against damage applied to the coating 3 as shown in FIG. Can do. In this embodiment, the degree of whitening due to both strain and sliding is associated with the above damage, but the degree of whitening due to sliding and the damage may be associated with each other.

  In addition, when evaluating in more detail, what is necessary is just to measure the whitening degree of the membrane | film | coat 3 by adding strain ratios other than biaxial deformation, such as uniaxial tension deformation and plane strain deformation, to a test piece. In particular, since the unequal biaxial deformation region between plane strain deformation and equal biaxial deformation is a strain ratio that is likely to occur in press forming, the strain ratio of the unequal biaxial region may be evaluated in detail. Moreover, if the strain ratio generated at the time of press molding is known in advance, it is efficient to evaluate the degree of whitening of the coating 3 with respect to the strain around the strain ratio.

If the relationship between the strain and the degree of whitening of the film 3 with respect to the damage to the film 3 is evaluated in advance, the strain generated when molding a press-molded product, the surface pressure and the speed at which the film 3 rubs the mold surface. The whitening degree of the film 3 can be predicted from the contact length. In addition, if a certain degree of whitening of the film 3 is provided as an acceptable standard for a molded product, the presence or absence of whitening of the film 3 can be predicted in advance at the production preparation stage.
This will be described more specifically.
Three types of metal plates shown in Table 2 were prepared.

The characteristics of the film 3 of each test material are as shown in Table 2, and the film 3 is mainly composed of a polyester resin, a curing agent, and carbon black. Further, the hardness of the film 3 is a hardness in a state where it is coated on a metal plate, and was measured by a Fischer hardness meter (manufactured by Fischer Instrument Co.). As the curing agents, Cymel 327 and Cymel 701 (both registered trademarks, Mitsui Cyanamid Co., Ltd.) were used. Carbon black is added to complement the bridging action by being added simultaneously with the curing agent.
The test material (1) is an organic film electroplated steel plate, the test material (2) is an organic film electroplated steel plate, and the test material (3) is a precoated aluminum alloy plate.

The degree of whitening of the film 3 before and after applying strain and damage to the film 3 was measured using a gloss meter. On the test piece, a scribed circle having a distance between the gauge points of 6.35 mm was transferred to the back surface of the contact portion with the punch, a uniaxial tensile test and a truncated cone test were performed, and various strains were applied. Thereafter, the strain was measured from the change in the circle diameter before and after applying the strain.
Furthermore, a sliding test was performed on the test piece in order to damage the coating 3. Assuming the back cover parts of the flat-screen television shown in FIG. 13 as the test conditions, the surface pressure was 130 MPa, the tool moving speed was 1 m / min, and the contact length was 4 mm.

If the strain and glossiness of the test piece prepared as described above are measured, the relationship between the degree of whitening of the film 3 with respect to the strain and damage to the film 3 can be shown as shown in FIG. Furthermore, if the distribution of the glossiness with respect to the maximum principal strain and the minimum principal strain is connected with contour lines, the relationship of the strain with respect to the whitening degree of the coating 3 of each metal plate can be evaluated as shown in FIG.
FIG. 19 shows a comparison between the conventional method and the method of the present invention. In the conventional method, the case where the test piece was visually whitened was determined as x, the case where slight whitening was observed was evaluated as Δ, and the case where whitening did not occur was determined as ○. By the method of the present invention, the degree of whitening of the film 3 with respect to the strain ratio and the strain amount could be quantitatively evaluated.

  Next, the degree of whitening of the film 3 is predicted for the back cover component of a thin television. First, press molding was performed on the specimens (1), (2), and (3), and the glossiness at position A shown in FIG. 13 was measured. The strain generated in the specimen was obtained by performing press forming simulation using the finite element method. Here, the strain may be obtained by adding a marking to the test material, press-molding, and measuring the distance between the marking marks. FIG. 20 shows a comparison between the mapping of the inventive method and the results of press molding. By using the press molding simulation using the finite element method and the mapping of the present invention from the shape of the part or the mold, the degree of whitening occurring in the coating 3 could be predicted with high accuracy.

DESCRIPTION OF SYMBOLS 1 Surface coating metal plate 2 Metal plate 3 Film | membrane 4 Whitening prediction apparatus 4A Information input part 4B Operation part 4C Output part 5 Database for whitening evaluation 6 Evaluation apparatus 11 Punch

Claims (9)

A method for predicting the appearance deformation of a film for predicting the appearance deformation of the film produced by press-molding a surface-coated metal plate having a film formed on at least one surface of the metal plate,
Estimating the sliding load, which is the load applied to the film by sliding with the mold during the press molding,
Based on the sliding load was the estimated, the appearance deformation of the film caused by the press-molding to predict,
The prediction is
The relationship of the degree of appearance deformation of the film with respect to the sliding load is obtained in advance as a first relationship,
The appearance deformation of the coating on the metal plate is predicted based on the sliding load estimated to be applied to the coating by press forming the surface-coated metal plate and the first relationship. A method for predicting the appearance deformation of a film. In the first relationship, the sliding load is characterized by an index of a degree of damage received by the film by sliding, and an appearance deformation of the film caused by the press molding is predicted from the degree of damage. The method for predicting the appearance deformation of a film according to claim 1. By molding simulation, when the film is rubbed from the mold when it is press-molded into the target processing shape, the pressure applied to the film, the sliding speed, and the contact length that is the length that the mold contacts are slid. As a condition,
The film according to claim 1, wherein the sliding load or the appearance deformation is evaluated from a damaged state of the film surface after the test after the sliding test is performed under the calculated sliding condition. Appearance deformation prediction method. Separately from the first relationship, a relationship between the degree of external deformation of the film formed on the metal plate with respect to strain generated in the metal plate in advance is obtained as a second relationship,
Based on the sliding load estimated to be applied to the film when the surface-coated metal plate is press-formed, the strain generated in the surface-coated metal plate, and the first relationship and the second relationship, the metal plate appearance deformation prediction method of coating as claimed in any one of claims 1 to claim 3, characterized in that predicting the appearance deformation of the film above. The above strain is an external deformation prediction method of coating according to claim 4, characterized in that two of the minimum principal strain and the maximum principal strain and parameters, respectively. The appearance of the film according to any one of claims 1 to 5 , wherein the appearance deformation is based on any one of color, color difference, gloss, and light reflectance of the film. Deformation prediction method. An appearance deformation prediction of a film characterized by predicting a film position where an appearance deformation degree equal to or greater than a preset threshold is generated by the method for predicting an appearance deformation of a film according to any one of claims 1 to 6. Method. A manufacturing method for manufacturing a machined part by press-molding a surface-coated metal plate having a film formed in advance on at least one surface of a metal plate,
Prior to processing the set processing shape by press molding, if it is determined by the method for predicting the appearance deformation of a film according to claim 7 that there is a film position at which an appearance deformation degree equal to or greater than a preset threshold value is generated, the preset position is set. A manufacturing method characterized in that at least one of the above-described modification of the processed shape and change of the coating material is performed in accordance with the position of the film where the degree of appearance deformation equal to or greater than the threshold value occurs and the degree of appearance deformation at that position. The occurrence of a degree of appearance deformation exceeding a preset threshold value even if press-molding to a target processing shape based on a prediction result by the method for predicting appearance deformation of a film according to any one of claims 1 to 7. A surface-coated metal sheet characterized in that a coating material capable of suppressing the above is used.

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