Prediction device, prediction method, and prediction program

Abstract

The prediction device is provided with a prediction unit that calculates a first ratio in a first period and a second ratio in a second period of each phase constituting the plating layer based on the respective contents of multiple components contained in the plating layer, calculates a length of the first period until part of the corrosion of the plating layer reaches the base steel based on the corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase, calculates a length of a second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and the second corrosion rate of each phase, and calculates the sum of the length of the first period and the length of the second period as a predicted result of the corrosion resistance of the plating layer.

Description

[Technical field]

[0001] The present invention relates to a prediction device, a prediction method, and a prediction program. This application claims priority based on Japanese Patent Application No. 2023-186777, filed in Japan on October 31, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] Since steel corrodes when exposed to the atmosphere, it is necessary to subject the steel to anti-corrosion treatment such as plating in order to use the steel for a long period of time. Plated steel is less expensive than stainless steel. In recent years, from the viewpoint of carbon neutrality, importance has been attached to life cycle costs, and highly corrosion-resistant plated steel sheets that can protect steel from corrosion for a long period of time have been attracting attention. One example of highly corrosion-resistant plated steel sheets is zinc-aluminum-magnesium (Zn-Al-Mg) alloy plated steel sheet (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7136351 [Patent Document 2] Patent No. 7040695 Summary of the Invention [Problem to be solved by the invention]

[0004] Various properties such as corrosion resistance, sacrificial corrosion protection, workability, abrasion resistance, and color tone are required for plated steel sheets. However, the properties of plated steel sheets are evaluated independently by each steel company, and are not evaluated uniformly by all steel companies. For this reason, end users may have difficulty in selecting the most suitable plated steel sheet based on the properties.

[0005] Furthermore, these properties are highly dependent on the alloy components of the plating layer. In other words, the properties of the plating layer depend on the substances (phases) formed by the bonding of the elements of each metal component and the content of the substances. For example, a Zn-Al plating layer contains Zn and Al phases. Here, as the content of the Al component increases, the Al phase increases in the plating layer. As a result, the properties of the plating layer approach those of Al, and the corrosion resistance of the plating layer improves. On the other hand, the sacrificial corrosion protection, which is excellent in the Zn phase, decreases in a plating layer with a small amount of Zn phase.

[0006] Furthermore, if end users can know the corrosion resistance of plated steel sheets, they will be able to choose the most suitable plated steel sheets that place emphasis on life cycle costs. Also, by knowing the corrosion resistance of plated steel sheets, they will be less confused about the maintenance and replacement frequency of plated steel sheets. For this reason, many users are interested in the corrosion resistance (service life, life span) of plated steel sheets.

[0007] In order to improve the accuracy of predicting the corrosion resistance of the coating layer, it is desirable to calculate the corrosion rate based on the results of exposure tests and accelerated corrosion tests previously obtained for various types of coated steel sheets. However, in recent years, coating layers may contain not only Al and Zn but also Mg, and since the corrosion resistance of Al, Zn, and Mg differs, it has become even more difficult to predict the corrosion resistance of the coating layer. Thus, there is a problem that the accuracy of predicting the corrosion resistance of the coating layer cannot be improved.

[0008] In view of the above circumstances, an object of the present invention is to provide a prediction device, a prediction method, and a prediction program that are capable of improving the accuracy of predicting the corrosion resistance of a plating layer. [Means for solving the problem]

[0009] One aspect of the present invention is a prediction device including a prediction unit that calculates a first ratio in a first period and a second ratio in a second period of each phase constituting the plating layer based on the respective contents of a plurality of components contained in the plating layer, calculates a length of the first period until part of the corrosion of the plating layer reaches a base steel based on a corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase, calculates a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase, and calculates a sum of the length of the first period and the length of the second period as a predicted result of the corrosion resistance of the plating layer.

[0010] One aspect of the present invention is a prediction method executed by the prediction device described above, the prediction method including the steps of: calculating a first ratio in a first period and a second ratio in a second period of each phase constituting the plating layer based on the respective contents of a plurality of components contained in the plating layer; calculating a length of the first period until a part of the corrosion of the plating layer reaches a base steel based on the corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase; calculating a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase; and calculating a sum of the length of the first period and the length of the second period as a prediction result of the corrosion resistance of the plating layer.

[0011] One aspect of the present invention is a prediction program for causing a computer to execute the steps of: calculating a first ratio in a first period and a second ratio in a second period of each phase constituting a plating layer based on the content of each of a plurality of components contained in the plating layer; calculating a length of the first period until part of the corrosion of the plating layer reaches the base steel based on the corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase; calculating a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase; and calculating a sum of the length of the first period and the length of the second period as a prediction result of the corrosion resistance of the plating layer. Effect of the Invention

[0012] According to the present invention, it is possible to improve the accuracy of predicting the corrosion resistance of a plating layer. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a prediction device in an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a model of a corrosion morphology of a Zn-Al-Mg plating layer in an embodiment. [Diagram 3] FIG. 2 is a diagram showing an example of the liquidus temperature of Zn—Al—Mg in an embodiment. [Figure 4] FIG. 2 is a diagram showing an example of the 1-molar molecular weight and density of each phase in an embodiment. [Diagram 5] FIG. 4 is a diagram showing an example of a database of area fractions of each phase in an embodiment. [Figure 6] 4 is a flowchart illustrating an example of a process for calculating the adhesion weight of each phase in the embodiment. [Figure 7] FIG. 4 is a diagram showing an example of the corrosion rate of each phase in a first time period in the embodiment. [Figure 8] FIG. 1 is a flowchart showing an example of a process for calculating the length of a period (first period) during which some corrosion can be confirmed on the surface of a plating layer, and the length of a period (second period) after some of the corrosion has reached the interface between the plating layer and a steel sheet in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. In the following, the prediction device, the prediction method, and the prediction program will be described using a zinc (Zn)-aluminum (Al)-magnesium (Mg) plating layer as an example of a plating layer, but the plating layer in the embodiments is not limited to a Zn-Al-Mg plating layer.

[0015] 1 is a diagram showing an example of the configuration of a prediction device 1 in an embodiment. The prediction device 1 is an information processing device that predicts the corrosion resistance of a plating layer, and is, for example, a personal computer or a smartphone terminal. The prediction device 1 includes a storage device 11, a storage unit 12, a prediction unit 13, a display unit 14, and a communication unit 15.

[0016] The storage device 11 is a non-volatile recording medium (non-transient recording medium). In the storage unit 12, a prediction program is loaded from the storage device 11.

[0017] The prediction unit 13 is, for example, a processor such as a CPU (Central Processing Unit). The prediction unit 13 is realized as software by executing a prediction program deployed from the storage device 11 to the storage unit 12. The prediction program may be recorded in a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), a CD-ROM (Compact Disc Read Only Memory), or a non-transitory recording medium such as a storage device such as a hard disk and a solid state drive (SSD) built into a computer system.

[0018] The prediction unit 13 may be realized using hardware including an electronic circuit (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integration circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), an FPGA (Field Programmable Gate Array), or the like.

[0019] The prediction unit 13 predicts the corrosion resistance of the plating layer based on the respective contents (input values) of Zn, Al, and Mg. For example, the prediction unit 13 calculates the ratio of each phase constituting the plating layer, and predicts the service life (service life) of the plating layer based on the calculated ratio.

[0020] The display unit 14 includes a display device such as a liquid crystal display, etc. The display unit 14 displays, for example, the prediction result.

[0021] The communication unit 15 executes communication with an external communication device (not shown) via a communication line such as the Internet, a LAN (Local Area Network), or a WAN (Wide Area Network). The communication unit 15 may transmit, for example, a prediction result to the communication device (not shown).

[0022] Next, the prediction device, the prediction method, and the prediction program will be described in detail. Ideally, it would be preferable to predict the service life of plated steel sheets based on a database of the results of exposure tests of plated steel sheets. However, plated steel sheets used in the field of building materials are required to have a service life (corrosion resistance) of 30 to 50 years or more. For this reason, it is practically difficult to create a database of recently developed plated steel sheets. However, it is possible to predict the corrosion resistance of plated steel sheets in exposure tests by accurately predicting the corrosion resistance of the plating layer based on the results (knowledge) of accelerated corrosion tests (e.g., cyclic corrosion tests) that have a certain degree of correlation with exposure tests.

[0023] Therefore, the prediction device 1 predicts the corrosion resistance of the plating layer based on accumulated knowledge about accelerated corrosion that has a certain degree of correlation with exposure tests. It is possible to change the acceleration level (corrosion rate) of the accelerated corrosion test by changing the salt water concentration and its cycle interval. In addition, if the corrosion rate of each substance (each phase) constituting the plating layer can be obtained, it is possible to predict the corrosion resistance of the plated steel sheet.

[0024] Furthermore, the prediction device 1 predicts the corrosion resistance of the plating layer using a corrosion model based on knowledge gained from many accelerated corrosion tests. In order to calculate the corrosion resistance (service life) of the plating layer, the corrosion form of the plating layer needs to be fully theoretically elucidated and knowledge of the corrosion form needs to be reflected in the corrosion model. In this regard, the relationship between the corrosion model and the accelerated corrosion tests and the relationship between the corrosion model and the exposure tests have been fully confirmed.

[0025] 2 is a diagram (cross-sectional view) showing an example of a model (corrosion model) of the corrosion form of a Zn-Al-Mg plating layer in an embodiment. The plating layer 101 is a Zn-Al-Mg plating layer. The plating layer 101 is present on the surface of a steel material 102, and thus has sacrificial corrosion protection properties against the steel material 102. For example, the plating layer 103-1 shows a range of a ternary eutectic structure.

[0026] In a corrosion period including period I (first period) and period II (second period) exemplified below, the plating layer 101 (Zn-Al-Mg plating layer) corrodes depending on the usage environment.

[0027] Stage I: This is the period when the plating layer partially corrodes from the surface. Phase II: This is the period when part of the corrosion of the plating layer reaches the interface between the plating layer and the steel material, and the plating layer corrodes while providing sacrificial protection to the base steel material (base steel). The steel sheet is protected from corrosion until the plating layer, which has sacrificial protection to the base steel sheet, disappears.

[0028] The end of the II period marks the end of the useful life of the plating layer. When the II period ends, dot-like red rust that has developed on the steel material due to corrosion can be seen from the surface of the plating layer. That is, the prediction device 1 calculates the number of cycles at which the adhesion weight of the plating layer remaining on the surface of the steel sheet decreases in the accelerated corrosion test and the adhesion weight or thickness of the plating layer given as the input value (initial value) finally becomes 0 as the useful life (corrosion resistance) of the plating layer.

[0029] The reason for distinguishing the corrosion period (service life) into such stages I and II is that in Stage I, the corrosion rate is specific to the phase that constitutes the plating layer. In contrast, in Stage II, the corrosion of the plating layer is accelerated by protecting the steel sheet (base steel). Therefore, in Stage II, the corrosion rate in Stage I (first corrosion rate) must be multiplied by the acceleration rate to use a corrosion rate corrected for each phase (second corrosion rate).

[0030] The prediction device 1 calculates the corrosion rate of each phase constituting the plating layer for each period of Period I and Period II based on the configuration of the plating layer (input value). The prediction device 1 calculates the overall corrosion resistance (service life) of the plating layer by summing up the service life corresponding to the corrosion rate of each phase.

[0031] FIG. 3 is a diagram (liquidus diagram) showing an example of the liquidus temperature of Zn-Al-Mg in an embodiment (Reference 1: P. Liang, T. Tarfa, J. A. Robinson, et al., "Experimental investigation and thermodynamic calculation of the Al±Mg±Zn system," Thermochimica Acta 314 (1998) 87-110).

[0032] The liquidus lines in the liquidus diagram shown in FIG. 3 correspond to contour lines in a map. For example, the thick liquidus lines in the liquidus diagram shown in FIG. 3 correspond to valleys in a map. The thick liquidus lines represent the solidification process of the Zn-Al-Mg alloy. That is, in the liquidus diagram shown in FIG. 3, when a predetermined position is given to the prediction device 1 as an input value (initial value) of each content of Zn-Al-Mg, the solidification of the Zn-Al-Mg alloy progresses so that the temperature becomes lower along the thick liquidus line at a position close to that position.

[0033] <Input> Information on the plating layer for which the corrosion resistance (service life) is to be calculated is provided to the prediction unit 13. Specifically, in order to confirm the change in corrosion resistance due to the difference in the components of the Zn-Al-Mg plating layer, the components of Al and Mg are provided to the prediction unit 13 in "at%" or "mass%". The total of the percentages of the Zn, Al and Mg components is 100%. Therefore, it can be expressed as "(Zn at%, Al at%, Mg at%) = (100-xy, x, y)". The atomic weights of Zn, Al and Mg are Zn = 65.38, Al = 26.98 and Mg = 24.305. Using these, "mass%" equivalent to "at%" is calculated.

[0034] The density of each of the components Zn, Al, and Mg is also provided to the prediction unit 13. The prediction unit 13 calculates the theoretical density "ρ" based on the density of each of the components Zn, Al, and Mg. Here, the density of Zn is "ρZn=7.14 g / cm 3 " and the density of Al is "ρAl = 2.7g / cm 3 " and the density of Mg is "ρMg = 1.738g / cm 3 The prediction unit 13 calculates the theoretical density "ρ" based on the density and "mass%" of each component.

[0035] In addition to the components of the plating layer to be predicted, the thickness of the plating layer "L μm" and the deposition weight of the plating layer must be provided to the prediction unit 13. The deposition weight of the plating layer is, for example, 5 to 100 μm and 20 to 630 g / m 2 When converting between plating thickness and coating weight, the result of multiplying the plating thickness by the theoretical density "ρ" is the coating weight. Also, the result of dividing the plating coating weight by the specific gravity is the plating thickness [μm].

[0036] In the embodiment, a numerical value related to the coating weight is used in the prediction calculation. Here, "coating weight=ρL g / m 2 " is given to the prediction unit 13. For example, in the case of 100% Zn plating, 2 The equivalent plating thickness is 100 ÷ 7.12 ≒ 14 μm.

[0037] The thinner the plating layer, the shorter its service life. If the plating layer is thick, even if it corrodes a lot, it is still thick enough to withstand the corrosion, so period I "τ1" is longer and the timing of the start of period II "τ2" is delayed. In contrast, if the plating layer is thin, period I "τ1" is shorter and the timing of the start of period II "τ2" is earlier.

[0038] In addition, in the case of a Zn-Al-Mg-based plating layer having a plating thickness of 20 μm, the second period "τ2" tends to start when 30% of the entire plating layer is corroded. In the case of a Zn-Al-Mg-based plating layer having a plating thickness of 30 μm, the second period "τ2" tends to start when 50% of the entire plating layer is corroded. Therefore, it is necessary to input the proportion of the plating layer corroded in the first period "τ1" "G = 0.0 to 1.0" to the prediction unit 13 as the proportion of the plating layer at the timing when the second period "τ2" starts (= 1-G). If it is assumed that the structure of the plating layer is homogeneous, the formulas (1) and (2) are established based on the proportion "G" and the plating adhesion weight "ρL".

[0039] TM1 = ρL G … (1) TM2=ρL (1-G) …(2)

[0040] Here, "TM1" represents the adhesion weight (corrosion weight loss) of the plating layer corroded in the first period "τ1". "TM2" represents the adhesion weight (corrosion weight loss) of the plating layer corroded in the second period "τ2".

[0041] The corrosion resistance of a plating layer varies depending on the proportion of each phase (each constituent phase) that makes up the plating layer. As the proportion of highly corrosion-resistant phases (phases that corrode slowly) increases, the service life of the plating layer will be longer. Note that corrosion resistance here refers to the pure corrosion weight loss (amount of wear) of the plating layer, excluding the steel material. It is to be distinguished from the effect of protecting the steel material from corrosion by the plating layer corroding in place of the steel material (sacrificial corrosion protection) and corrosion resistance.

[0042] When the coating layer contains Zn, Al, and Mg, the phases that make up the coating layer can be classified into six types. These six types (phases 1 to 6) are classified according to the solidification process of Zn, Al, and Mg alloys. Therefore, the ranges (input ranges) of the content of each of Zn, Al, and Mg are limited. For example, the input range of Zn component is "25 to 85 at%", the input range of Al component is "10 to 73 at%", and the input range of Mg component is "2 to 18%".

[0043] An example of the definition of each phase is shown below. The first phase, the “Pure_Al phase”, is a phase containing a trace amount (content “up to 16.5 at %) of Zn and Al. The second phase, "Al-Zn(α) phase", is a mixed phase of Al phase and Zn phase (Zn content is 16.5 at%). The third phase, the "Zn-Al (β) phase," is a mixed phase of Zn and Al (Zn content is 59 at%). The fourth phase, "Pure_Zn(η) phase", is a phase containing a trace amount of Al (content "up to 16.5 at %) and Zn (Zn content is 98.4 to 100 at %). The fifth phase, "MgZn2 phase", is a single phase (crystal grain) that is formed from the liquid phase at the same time as or first after the formation of the Pure_Al phase. Usually, the size of the "MgZn2 phase" is 1 μm or more. The sixth phase, "ternary eutectic structure," is a phase consisting of fine Pure_Al, fine Pure_Zn, and fine MgZn2, and is a mixed structure formed by a ternary eutectic reaction. The overall composition is "Zn-9at%Al-5at%Mg."

[0044] These definitions clarify the definition of each phase based on its atomic constitution, so that it is possible to theoretically calculate the molecular weight and density of each phase.

[0045] 4 is a diagram showing an example of the 1-molar molecular weight and density of each phase in an embodiment. When the component composition of the plating layer and the molecular weight of each constituent phase are given, if the volume fraction of each phase is known, it is possible to calculate the weight and number of moles of each phase constituting the plating layer.

[0046] Fig. 5 is a diagram showing an example of a database of the area fraction of each phase in an embodiment. Fig. 5 shows a part of the database in a table format. The database includes actual measurement results of the correspondence between each component of Al-Zn-Mg and the area fraction SP (≈volume fraction VP) of each phase. Using the database, the component composition of the plating layer, and the molecular weight of each phase, the prediction unit 13 calculates the weight and number of moles of each phase constituting the plating layer.

[0047] To create the database shown in Fig. 5, a plating layer similar to the Zn-Al-Mg plating layer shown in Fig. 2 was prepared. The prepared plating layer was subjected to cross-sectional observation using an EPMA (Electron Probe Micro Analyzer). The proportion of each phase was calculated so that each phase was classified into a value close to its component value, and the area fraction SP (≒volume fraction VP) of each phase was calculated based on the calculated proportion of each phase.

[0048] A hot-dip galvanizing simulator developed by the company was used to prepare the plated steel sheets for creating the database. This hot-dip galvanizing simulator is capable of full nitrogen replacement throughout the test. This hot-dip galvanizing simulator can perform a series of plating operations in an oxygen-free state (less than 5 ppm), and can also monitor the temperature during the process.

[0049] Metals with a purity of 99% or more were used to prepare the plating bath, and Zn-Al-Mg alloys were produced by vacuum melting. Cold-rolled steel sheets of 1.2 mm (JIS G 3141), which are general structural steels, were used as the base steel for the plating sheets. In order to suppress the reactivity between iron (Fe) and the plating layer, a coating of Cr: 0.1 g / m2 was applied to the plating surface, which had been thoroughly degreased, washed and pickled. 2 " and "Ni: 0.1g / m 2 " were deposited in sequence.

[0050] This was used as the original sheet for plating, and the temperature of the original sheet for plating was raised to 800°C at a rate of 10°C / sec., after which 20% H2-N2 gas was sprayed onto the original sheet for plating and held for 60 seconds, and surface reduction was performed on the original sheet for plating. After the original sheet for plating was cooled to the plating bath temperature, the original sheet for plating was immersed in the plating bath for 1 second. After the plated steel sheet was pulled out of the plating bath, the plated steel sheet was wiped with N2 gas, and the thickness of the plating layer was controlled to be 25 μm in each case. The flow rate of the sprayed gas N2 was controlled so that the time from the melting point to 380°C (temperature at the end of solidification) was 20 seconds. The plating bath temperature was set to the melting point (= the liquidus temperature described in the above-mentioned Reference 1) + 20°C.

[0051] The deposition process suppressed the formation of an intermetallic compound layer containing Fe and Al between the plating bath and the plated steel sheet. This ensures that the plating layer is almost identical in composition to the plating bath, eliminating the effect of Fe. However, because the plating layer is an extremely thin film, the diffusion of Fe into the plating layer is inhibited when the plated steel sheet is immersed in the plating bath, but Fe immediately diffuses into the plating bath after plating. As a result, almost no traces of these (Ni layer, Cr layer) remain in the plating layer, and the interface alloy layer is almost nonexistent in the plating layer. This makes it possible to minimize the effect of the base steel on the plating alloy layer.

[0052] The cooling rate of 20 seconds refers to the normal time (20 seconds) between immersion in the plating bath and reaching the top roll. In order to prevent the plating bath from wrapping around the top roll, the temperature of the plated steel sheet is adjusted by gas blowing during the plating solidification process so that the plated steel sheet passes through after it has completely solidified. Also, plated steel sheets of 20 mm square are cut out from the center of the plated steel sheet. A vertical resin filling is made on the plated steel sheet, and the plated steel sheet is polished.

[0053] The cross section of the plating layer of the polished plated steel sheet was observed with an EPMA. Here, it was confirmed that the Al-Fe alloy layer and the like remained near the interface, and that plating bath make-up components became plating layer components, as well as the thickness of the plating layer. A scanning electron microscope (SEM) image was obtained in the field of view where the plating layer thickness was confirmed, and a Zn, Al, and Mg component map image (EPMA map image) was obtained by EPMA at the position where the scanning electron microscope image was obtained. From this, the area ratio of each phase was determined in the database.

[0054] Normally, the coating layer solidifies from the surface, so the final solidification part in the solidification process is located near the interface between the base steel material and the coating layer. As a result, a structure with biased components is formed in the horizontal cross section of the coating layer. For this reason, the area ratio of each phase is measured from the cross section of the coating layer.

[0055] To confirm the area ratio of each phase, the plating layer was observed at a magnification of 500 times using a scanning electron microscope, and the measurement of the area ratio of each phase was repeated until the total field of view of the plating layer reached 100,000 μm. A partial image of the plating layer was cut out from the EPMA image, and the cut out partial image was divided into a 5 μm x 5 μm mesh.

[0056] A phase in which Al and Zn are detected, the Zn content is 16.5 at% or less, and the contents of other components are 5 at% or less is classified as the first phase, "Pure_Al phase." A phase in which Al and Zn are detected and the Zn content is 16.5 to 37.75 at % is classified as a second phase, the "Al-Zn(α) phase." A phase in which Zn and Al are detected and the Zn content is 37.75 to 59 at % is classified as the third phase, the "Zn-Al (β) phase." A phase in which Zn and Al are detected and the Zn content is 59 to 98.4 at % is classified as the third phase, “Zn-Al (β) phase”, and the fourth phase, “Pure_Zn (η) phase”. A phase in which the Mg content is 33.3 at% (±3 at%) and the Zn content is 66.6 at% (±3%) is classified as the fifth phase, "MgZn2 phase" (single phase). A phase in which Zn, Al, and Mg are detected, the Zn content is 80 at% or more, the Mg content is 1 to 10 at%, and the Al content is less than 5 to 15 at%, is classified as Phase 6, a "ternary eutectic structure."

[0057] As shown above, in many cases, phases can be classified based on the Zn content. As an exception, the interface between the plating layer and the steel material and the resin interface may be classified as "other." Therefore, the area ratio of each phase is confirmed in the range other than the range classified as "other."

[0058] In the following, the letter subscript represents the phase number (nth phase). For example, the area ratio "SP 1 " represents the area ratio of the first phase. For example, the volume ratio "VP 2 " represents the volume fraction of the second phase.

[0059] SP 1 ~SP 6 (≒ volume ratio VP 1 ~VP 6 ) can be confirmed in the database. Therefore, the total volume of each phase that constitutes the plating layer, V = V 1 +V 2 +V 3 +V 4 +V 5 +V 6 " and the density of the nth phase "ρ n "The volume ratio "VP n Based on this, the prediction unit 13 calculates the volume "V n " is calculated using equation (3).

[0060] V n =VP n ÷100÷V …(3)

[0061] Density of nth phase "ρ n " and the volume of the nth phase "V nBased on the above, the prediction unit 13 calculates the content (weight) of each phase in the plating layer "m n " is calculated using equation (4).

[0062] m n =V n ×ρ n …(4)

[0063] The total content (weight) of each phase in the plating layer, "M", is expressed by formula (5).

[0064] M=m 1 +m 2 +m 3 +m 4 +m 5 +m 6 …(5)

[0065] When the "Mass%" display is used, the prediction unit 13 calculates the content (weight) of each phase "m n " and the content (weight) of each phase "MS n " (mass%) as shown in equation (6).

[0066] MS n =m n / M×100 …(6)

[0067] The prediction section 13 is a calculation section for calculating the content (weight) of each phase, "MS n " by the total adhesion weight of the plating layer "ρL" to obtain the weight of the nth phase contained in the plating layer "RM n " is calculated as shown in equation (7).

[0068] RM n =ρL×MS n …(7)

[0069] The prediction unit 13 calculates the weight of the nth phase "RM n " and molecular weight "N n " and the number of moles of the nth phase "mol n " may be calculated as shown in equation (8).

[0070] Moln =RM n / N n …(8)

[0071] The total number of moles, "MOL", is expressed as in formula (9).

[0072] MOL=mol 1 +mol 2 +mol 3 +mol 4 +mol 5 +mol 6 …(9)

[0073] The prediction unit 13 is a prediction unit for predicting the mole percentage of the n-th phase, “mol% n " may be calculated as shown in equation (10).

[0074] mol% n =mol n / MOL …(10)

[0075] In this way, the prediction unit 13 calculates the proportion of each phase in the plating layer. Based on the proportion of each phase, the prediction unit 13 uniformly distributes each phase in a model of the corrosion morphology of the plating layer. The prediction unit 13 calculates the corrosion weight loss in each of the I period "τ1" and the II period "τ2". This makes it possible to obtain the corrosion resistance (service life) of the plating layer. It should be noted here that there is an order in which each phase corrodes.

[0076] In exposure tests and accelerated corrosion tests (combined cyclic corrosion tests), each phase corroded in order of lowest corrosion potential. Specifically, the order of corrosion (corrosion order) was confirmed by cross-sectional observation of the plating layer in many corrosion tests conducted by the company: third phase "Zn-Al (β) phase", sixth phase "ternary eutectic structure", fifth phase "MgZn2 phase", fourth phase "Pure_Zn (η) phase", second phase "Al-Zn (α) phase", and first phase "Pure_Al phase".

[0077] Next, an example of the operation of the prediction device 1 will be described. FIG. 6 is a flowchart showing an example of a process for calculating the adhesion weight of each phase in the embodiment. Since each phase corrodes in the order described above, the ratio of phases with low corrosion potential increases in the I period "τ1". The ratio of phases with high corrosion potential increases in the II period "τ2". The prediction unit 13 calculates the ratio of each phase of the adhesion weight "TM1" of the plating layer corroding in the I period "τ1" and the ratio of each phase of the adhesion weight "TM2" of the plating layer corroding in the II period "τ2" as follows.

[0078] In the example below, "SUM" is a variable that represents the total weight. The total weight "SUM" is substituted with the total weight according to the processing content at each step. The total weight "SUM" is used to determine whether the timing for the end of the I period "τ1" has arrived. In other words, the total weight "SUM" is used to determine whether corrosion has reached the boundary between the plating layer corroded in the I period "τ1" and the plating layer corroded in the II period "τ2". Here, the timing for the end of the I period "τ1" is determined based on the proportion "G" of the plating layer corroded in the I period "τ1".

[0079] The prediction unit 13 initializes the total weight "SUM" (variable) with the adhesion weight of the third phase (step S101). The prediction unit 13 determines whether the adhesion weight "TM1" of the plating layer corroding in the first period - the total weight "SUM" is equal to or less than 0 (step S102).

[0080] When the adhesion weight "TM1" of the plating layer corroded in the first period - the total weight "SUM" is equal to or less than 0 (step S102: YES), the prediction unit 13 calculates the adhesion weight "TM2" of the plating layer corroded in the second period. Here, the adhesion weight "TM2" is calculated by the following formula: "TM2 = SUM - TM1 + RM 6 +RM 5 +RM 4 +RM 2 +RM 1 " (step S103-1).

[0081] If the adhesion weight "TM1" of the plating layer corroding in the first period - the total weight "SUM" exceeds 0 (step S102: NO), the prediction unit 13 selects one phase for each iteration from step S106 in the order of the fifth phase, fourth phase, second phase, and first phase. The prediction unit 13 calculates the adhesion weight "RM n The prediction unit 13 adds the adhesion weight of the first phase "RM 1 It is then determined whether " has been added" (step S105).

[0082] If it is determined that the adhesion weight of the phase other than the first phase has been added to the total weight "SUM" (step S105: YES), the prediction unit 13 determines whether the total weight "SUM" minus the adhesion weight "TM1" of the plating layer corroding in the first period is equal to or less than 0 (step S106). If it is determined that the total weight "SUM" minus the adhesion weight "TM1" of the plating layer corroding in the first period exceeds 0 (step S106: NO), the prediction unit 13 returns the process to step S104.

[0083] When it is determined that the total weight "SUM" - the adhesion weight "TM1" of the plating layer corroded in the first period is equal to or less than 0 (step S106: YES), the prediction unit 13 returns the process to step S103. Here, in step S104, the prediction unit 13 subtracts the adhesion weight "RM 6 " is added, the adhesion weight "TM2" is "TM2 = SUM-TM1 + RM 5 +RM 4 +RM 2 +RM 1 In step S104, the total weight "SUM" is added to the adhesion weight of the fifth phase "RM 5 " is added, the adhesion weight "TM2" is "TM2 = SUM-TM1 + RM 4 +RM 2 +RM 1 In step S104, the total weight "SUM" is added to the adhesion weight of the fourth phase "RM 4" is added, the adhesion weight "TM2" is "TM2 = SUM-TM1 + RM 2 +RM 1 In step S104, the total weight "SUM" is added to the adhesion weight of the second phase "RM 2 " is added, the adhesion weight "TM2" is "TM2 = SUM-TM1 + RM 1 " (step S103-5).

[0084] The total weight "SUM" is added to the first phase adhesion weight "RM 1 If it is determined that " has been added" (step S105: YES), the prediction unit 13 returns the process to step S103. Here, the adhesion weight "TM2" is "TM2 = SUM - TM1" (step S103-6).

[0085] <Corrosion rate> The prediction unit 13 calculates the service life of the plating layer based on the adhesion weight "TM1" and the corrosion rate "r1" in the I period "τ1" and the adhesion weight "TM2" and the corrosion rate "r2" in the II period "τ2". Hereinafter, the corrosion rate of the n-phase in the I period "τ1" is referred to as "r1 n The corrosion rate of the nth phase in the second period, “τ2”, is expressed as “r2 n " should be written.

[0086] In accelerated corrosion tests (combined cyclic corrosion tests), the corrosion rate is the corrosion weight loss per specified cycle. Therefore, the units of the corrosion rates of the plating layer, "r1" and "r2", are "g / m 2 In exposure tests, the units of the corrosion rates of the plating layer, "r1" and "r2", are "g / m 2 / year (day, month)". The corrosion rates "r1" and "r2" of the plating layer change depending on the corrosive environment of the accelerated corrosion test or exposure test.

[0087] In order to prevent the alloy components of each phase from being rapidly cooled, single-phase metal specimens were prepared, and the corrosion rates of each phase were determined by subjecting the metal specimens to various corrosion tests.

[0088] FIG. 7 is a diagram showing an example of the corrosion rate of each phase in a first period in an embodiment. In a cyclic corrosion test (JIS H 8502 JASO M609-91), the corrosion rate is as shown in FIG. 7. In the corrosion rate "r2", the acceleration of corrosion depends on the components of the steel plate. When general mild steel is used in the test, in the cyclic corrosion test (JIS H 8502 JASO M609-91), the corrosion rate "r2" is often 30 to 50 times the corrosion rate "r1".

[0089] 8 is a flowchart showing an example of a process for calculating the length of a period (first period) during which some corrosion can be confirmed on the surface of the plating layer, "TIME1," and the length of a period (second period) after some of the corrosion has reached the interface between the plating layer and the steel sheet, "TIME2," in an embodiment. Each of steps S201 to S206 illustrated in FIG. 8 is similar to each of steps S101 to S106 illustrated in FIG. 6.

[0090] If the adhesion weight "TM1" of the plating layer corroded in the first period - the total weight "SUM" is equal to or less than 0 (step S202: YES), the prediction unit 13 calculates the adhesion weight "TM2" of the plating layer corroded in the second period (step S203-1). The prediction unit 13 also calculates the period length "TIME1" of the first period and the period length "TIME2" of the second period. Here, "TIME1=SUM / r1 3 " Also, "TIME2 = (SUM-TM1) / r2 3 +RM 6 / r2 6 +RM 5 / r2 5 +RM 4 / r2 4 +RM 2 / r2 2 +RM 1 / r2 1 " (step S207-1).

[0091] When it is determined that the total weight "SUM" - the adhesion weight of the plating layer corroding in the first period "TM1" is equal to or less than 0 (step S206: YES), the prediction unit 13 returns the process to step S203. In addition, the prediction unit 13 calculates the period length of the first period "TIME1" and the period length of the second period "TIME2". Here, in step S204, the prediction unit 13 subtracts the adhesion weight of the sixth phase "RM 6 " has been added, "TIME1=RM 3 / r1 3 +(SUM-RM 3 ) / r1 6 " Also, "TIME2 = (SUM-TM1) / r2 6 +RM 5 / r2 5 +RM 4 / r2 4 +RM 2 / r2 2 +RM 1 / r2 1 " (step S207-2). In step S204, the total weight "SUM" is added to the adhesion weight of the fifth phase "RM 5 " has been added, "TIME1=RM 3 / r1 3 +RM 6 / r1 6 +(SUM-RM 3 -RM 6 ) / r1 5 " Also, "TIME2 = (SUM-TM1) / r2 5 +RM 4 / r2 4 +RM 2 / r2 2 +RM 1 / r2 1 " (step S207-3). In step S204, the total weight "SUM" is added to the adhesion weight of the fourth phase "RM 4 " has been added, "TIME1=RM 3 / r1 3 +RM 6 / r1 6 +RM 5 / r1 5 +(SUM-RM 3 -RM 6 -RM5 ) / r1 4 " Also, "TIME2 = (SUM-TM1) / r2 4 +RM 2 / r2 2 +RM 1 / r2 1 " (step S207-4). In step S204, the total weight "SUM" is added to the adhesion weight of the second phase "RM 2 " has been added, "TIME1=RM 3 / r1 3 +RM 6 / r1 6 +RM 5 / r1 5 +RM 4 / r1 4 +(SUM-RM 3 -RM 6 -RM 5 -RM 4 ) / r1 2 " Also, "TIME2 = (SUM-TM1) / r2 2 +RM 1 / r2 1 " (step S207-5).

[0092] The total weight "SUM" is added to the first phase adhesion weight "RM 1 If it is determined that "TIME1=RM" has been added (step S205: YES), the prediction unit 13 returns the process to step S203. The prediction unit 13 also calculates the period length "TIME1" of the first period and the period length "TIME2" of the second period. Here, "TIME1=RM 3 / r1 3 +RM 6 / r1 6 +RM 5 / r1 5 +RM 4 / r1 4 +RM 2 / r1 2 +(SUM-RM 3 -RM 6 -RM 5 -RM 4 -RM 2 ) / r1 1 " Also, "TIME2 = (SUM-TM1) / r2 1" (step S207-6).

[0093] In this manner, the prediction unit 13 calculates the period "TIME1" in the first period "τ1" and "TIME2" in the second period "τ2." The prediction unit 13 calculates the corrosion resistance (service life) of the plating layer "TIME=TIME1+TIME2."

[0094] As described above, the prediction unit 13 (proportion calculation unit) calculates the proportion (first proportion) of each phase constituting the plating layer in the first period and the proportion (second proportion) of each phase constituting the plating layer in the second period based on the respective contents of the multiple components contained in the plating layer. The prediction unit 13 (first period calculation unit) calculates the length of the first period until part of the corrosion of the plating layer reaches the base steel based on the corrosion ranking of each phase, the first proportion of each phase, and the first corrosion rate of each phase. The prediction unit 13 (second period calculation unit) calculates the length of the second period following the first period based on the corrosion ranking of each phase, the second proportion of each phase, and the second corrosion rate of each phase. The second corrosion rate is a rate obtained by correcting the first corrosion rate in accordance with the promotion of corrosion of the plating layer by protecting the base steel. The prediction unit 13 (prediction result calculation unit) calculates the sum of the period length of the first period and the period length of the second period as a prediction result of the corrosion resistance of the plating layer.

[0095] In this way, the prediction unit 13 calculates the length of the corrosion period (service life) based on the corrosion rank of each phase, the ratio of each phase, and the corrosion rate of each phase. This makes it possible to improve the accuracy of predicting the corrosion resistance of the plating layer. It is possible for end users of plated steel sheets to efficiently select materials based on the prediction results. In addition, it is possible to reduce labor costs because it is possible to shorten the time until the adoption of the plated steel sheet is approved.

[0096] In this way, the prediction unit 13 may distinguish the corrosion period (service life) into period I and period II. That is, the prediction unit 13 may calculate the corrosion period in period I separately from the corrosion period in period II. This makes it possible to further improve the accuracy of predicting the corrosion resistance of the plating layer.

[0097] (Modification) In order to improve the accuracy of predicting the corrosion resistance (service life) of the plating layer, the actual data of the corrosion test may be reflected in the corrosion resistance prediction result. By fitting the predicted service life "TIME" to the service life "TIME'" (actual data) obtained by the corrosion test using the correction function "f" (TIME' = f(TIME)), a high prediction accuracy can be obtained.

[0098] Examples of individual data points obtained in the corrosion tests are shown below. (Zn, Al, Mg) = (80, 13, 7) at%, plating thickness 20 μm, red rust generation cycle = 210 (Zn, Al, Mg) = (80, 17, 8) at%, plating thickness 20 μm, red rust generation cycle = 240 (Zn, Al, Mg) = (70, 22, 8) at%, plating thickness 20 μm, red rust generation cycle = 300 (Zn, Al, Mg) = (70, 24, 10) at%, plating thickness 20 μm, red rust generation cycle = 300 (Zn, Al, Mg) = (52, 34, 13) at%, plating thickness 20 μm, red rust generation cycle = 840 (Zn, Al, Mg) = (25, 73, 2) at%, plating thickness 20 μm, red rust occurrence cycle = 840

[0099] The corrosion test may further increase the number of data points, and the prediction unit 13 may correct the prediction result of the useful life using a technique such as machine learning (for example, supervised learning) based on many data points.

[0100] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0101] 1... prediction device, 11... storage device, 12... storage section, 13... prediction section, 14... display section, 101... plating layer, 102... steel material, 103... plating layer

Claims

1. a prediction unit which calculates a first ratio in a first period and a second ratio in a second period of each phase constituting the coating layer based on the contents of each of a plurality of components contained in the coating layer, calculates a length of the first period until a part of the corrosion of the coating layer reaches a base steel based on a corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase, calculates a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase, and calculates a sum of the length of the first period and the length of the second period as a predicted result of the corrosion resistance of the coating layer. A prediction device comprising:

2. The prediction device according to claim 1 , wherein the second corrosion rate is a rate obtained by correcting the first corrosion rate in accordance with accelerated corrosion of the plating layer due to corrosion protection of the base steel.

3. A prediction method executed by a prediction device, comprising: calculating a first ratio in a first period and a second ratio in a second period of each phase constituting the plating layer based on the contents of each of a plurality of components contained in the plating layer, calculating a length of the first period until a part of the corrosion of the plating layer reaches a base steel based on a corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase, calculating a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase, and calculating a sum of the length of the first period and the length of the second period as a predicted result of the corrosion resistance of the plating layer. A prediction method including:

4. On the computer, a step of calculating a first ratio in a first period and a second ratio in a second period of each phase constituting the coating layer based on the contents of each of a plurality of components contained in the coating layer, calculating a length of the first period until a part of the corrosion of the coating layer reaches a base steel based on a corrosion ranking of each phase, the first ratio of each phase, and a first corrosion rate of each phase, calculating a length of the second period following the first period based on the corrosion ranking of each phase, the second ratio of each phase, and a second corrosion rate of each phase, and calculating a sum of the length of the first period and the length of the second period as a predicted result of the corrosion resistance of the coating layer. A prediction program for executing the above.

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