Cut processed product and guardrail

Abstract

The present invention relates to a cut-processed product of a Zn-Al-Mg plated steel material having a parent steel material and a Zn-Al-Mg plating layer covering the surface of the parent steel material, and a guardrail using the cut-processed product, the cut-processed product comprising a Zn-Al-Mg plated steel material having a Zn-Al-Mg plated layer covering the surface of the parent steel material, the cut end surface of the cut processed product is covered with the Zn-Al-Mg plating layer at a coverage rate of 50-99% with respect to the cut end surface, and the non-plated surface of the parent steel material and the Zn-Al-Mg plating layer around the non-plated surface in the cut end surface of the cut processed product are covered with a repair coating film. The initial coating film resistance value in the repair coating film is 10-1000 Omega / cm2, the coating film resistance value after immersion of the cut processed product in 5 mass% saline water for 3 hours is 5-50 Omega / cm2, and the film thickness of the repair coating film is 10 [mu] m or more.

Description

Technical Field

[0001] The present disclosure relates to a cut-off product and a guard rail. Background Art

[0002] When the plated steel material is processed into a product shape, the plated steel material is cut, and the steel base of the steel material is exposed in a part of the cut cross section. The cut end surface not covered by the plating layer has reduced corrosion resistance, so it is necessary to improve the corrosion resistance of the cut end surface.

[0003] In order to improve the corrosion resistance of the cut end surface of the plated steel material, various methods and technologies have been studied. For example, there are known rust-proof processing technologies for the cut end surface, such as the inclined end surface method (Patent Document 1, etc.) in which a larger portion of the end surface cross section is covered with a plating layer than the conventional end surface cross section obtained by shearing, the slit processing method (Patent Document 2, etc.), and the laser cutting method (Patent Document 3, etc.).

[0004] However, it is difficult to cover the entire surface of the cut section with a plating layer, and there is a problem that a partially exposed cut end surface may generate red rust in the initial stage of exposure.

[0005] As a conventional corrosion protection technique for the cut end surface, a repair paint containing Zn-based metal powder (eg, Patent Document 4) is generally applied to the steel exposed surface of the cut end surface.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-32437

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-192989

[0008] Patent Document 3: Japanese Patent Application Publication No. 2021-087988

[0009] Patent Document 4: Japanese Patent Application Publication No. 2017-122186 Summary of the invention

[0010] Problems to be solved by the invention

[0011] It is expected that the above-mentioned combination of the rust-proofing technology of the cut end surface and the repair coating can impart higher corrosion resistance to the cut end surface.

[0012] However, in the cut end surface, since the area of ​​the steel substrate that serves as the cathode is significantly smaller than the plating layer that serves as the anode, the reduction reaction of water or oxygen is concentrated, causing cathodic peeling of the repair coating. Therefore, it is impossible to maintain sufficient corrosion resistance, especially for red rust suppression in the early stage of corrosion.

[0013] Furthermore, since cathodic peeling of the repair coating film occurs, long-term corrosion resistance cannot be expected.

[0014] Therefore, an object of the present disclosure is to provide a cut product which suppresses cathodic peeling of a repair coating film and has excellent corrosion resistance of a cut end surface for a long period of time from the initial stage, and a guardrail using the cut product.

[0015] Means for solving problems

[0016] Means for solving the problem include the following.

[0017] <1> A cut-off product is a cut-off product of a Zn-Al-Mg-based plated steel material having a base steel material and a Zn-Al-Mg-based plated layer covering the surface of the base steel material,

[0018] The cut end surface of the cut product is covered with the Zn-Al-Mg based plating layer at a coverage rate of 50 to 99% relative to the cut end surface.

[0019] The non-plated surface of the parent steel material in the cut end surface of the cut product and the Zn-Al-Mg-based plating layer around the non-plated surface are covered with a repair coating film.

[0020] The initial coating resistance value R1 in the repair coating is 10 to 1000 Ω / cm 2 The cut product is immersed in 5 mass % salt water for 3 hours and the coating resistance value R2 after immersion is 5 to 50 Ω / cm 2 ,

[0021] The repair coating film has a thickness of 10 μm or more.

[0022] <2> according to <1> In the cut product, the repair coating film contains Zn-based metal powder and a binder resin.

[0023] <3> according to <1> or <2> The cut-off product, wherein the cut-off end surface of the cut-off product has:

[0024] a first inclined surface including a first collapsed surface continuous from the first surface of the cut product and a first shear surface continuous from the first collapsed surface, and inclined from the first surface of the cut product toward the center in the plate thickness direction;

[0025] a second inclined surface including a second collapsed surface continuous from the second surface of the cut product and a second shear surface continuous from the second collapsed surface, and inclined from the second surface of the cut product toward the center in the plate thickness direction; and

[0026] a fracture surface formed between the first inclined surface and the second inclined surface,

[0027] At least a portion of the parent steel material located on the first inclined surface and the second inclined surface in the cut end surface of the cut product is covered with the Zn-Al-Mg based plating layer.

[0028] The non-plated surface of the base steel material including the fracture surface in the cut end surface of the cut product and the Zn—Al—Mg-based plating layer around the non-plated surface are covered with the repair coating film.

[0029] <4> according to <1> or <2> The cut-off product, wherein the cut-off end surface of the cut-off product has:

[0030] A side surface including a collapsed edge surface continuous from the first surface of the cut product and a shear surface continuous from the collapsed edge surface, and inclined along the plate thickness direction or from the first surface of the cut product toward the center; and

[0031] a fracture surface which is continuous from the side surface and reaches the second surface side of the cut product,

[0032] At least a portion of the parent steel material located on the side surface in the cut end surface of the cut product is covered with the Zn-Al-Mg based plating layer.

[0033] The non-plated surface of the base steel material including the fracture surface in the cut end surface of the cut product and the Zn—Al—Mg-based plating layer around the non-plated surface are covered with the repair coating film.

[0034] <5> according to <1> ~ <4> The cut product according to any one of the preceding claims, wherein an initial coating resistance value R1 in the repair coating is 300 to 500 Ω / cm 2 .

[0035] <6> according to <1> ~ <5> The cut product according to any one of the preceding claims, wherein the coating resistance value R2 of the repair coating after immersion is 10 to 45 Ω / cm 2 .

[0036] <7> according to <2> In the cut product, the Zn-based metal powder contains Zn and Al.

[0037] <8> according to <7> The cut product is characterized in that the content of Al in the Zn-based metal powder containing Zn and Al is 20 to 45% by mass relative to Zn.

[0038] <9> according to <7> The cut product is characterized in that the content of Al in the Zn-based metal powder containing Zn and Al is 28 to 34 mass % relative to Zn.

[0039] <10> according to <2> , <7> , <8> or <9> In the cut-off product, the content ratio of the Zn-based metal powder to the entire repair coating film is 60 to 80% by mass of the metal powder.

[0040] <11> according to <2> or <7> ~ <10> The cut product described in any one of the preceding claims, wherein the binder resin is at least one selected from the group consisting of a polystyrene resin and an epoxy resin.

[0041] <12> A guardrail having <1> ~ <11> The cut product according to any one of the above.

[0042] Effects of the Invention

[0043] According to the present disclosure, it is possible to provide a cut product that suppresses cathodic peeling of a repair coating film and has excellent corrosion resistance of a cut end surface for a long period of time from the initial stage, and a guardrail using the cut product. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic cross-sectional view showing a cut product 101 according to the first embodiment of the present disclosure.

[0045] Figure 2 It is a schematic diagram for explaining the manufacturing method of the cut-off product 101 according to the first embodiment of the present disclosure.

[0046] Figure 3 It is a schematic cross-sectional view showing a cut product 101 according to a second embodiment of the present disclosure.

[0047] Figure 4 It is a schematic diagram for explaining the manufacturing method of the cut-off product 101 according to the second embodiment of the present disclosure.

[0048] Figure 5 It is a schematic cross-sectional view showing a cut product 101 according to a third embodiment of the present disclosure.

[0049] Figure 6 It is a schematic diagram for explaining the manufacturing method of the cut-off product 101 according to the third embodiment of the present disclosure.

[0050] Figure 7 This is a schematic diagram for explaining a sample for measuring the coating film resistance value. DETAILED DESCRIPTION

[0051] Hereinafter, an example of the coated steel sheet of the present disclosure will be described.

[0052] In addition, in this specification, the numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as a lower limit and an upper limit.

[0053] In the numerical ranges described in stages, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described in stages.

[0054] In the numerical range, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the Examples.

[0055] The term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0056] The "combination of preferred embodiments" is a more preferred embodiment.

[0057] In this specification, "Zn-Al-Mg-based plating layer" is also referred to as "plating layer".

[0058] The "Zn-Al-Mg-based plated steel material" is also referred to as a "plated steel material".

[0059] The “non-plated surface” refers to the surface of the base steel material of the plated steel material that is not covered with the Zn—Al—Mg-based plating layer.

[0060] The cut product disclosed in the present invention is a cut product of a Zn—Al—Mg-based plated steel material having a base steel material and a Zn—Al—Mg-based plating layer covering the surface of the base steel material.

[0061] The cut end face of the cut product is covered with the Zn-Al-Mg based plating at a coverage rate of 50 to 99% relative to the cut end face, and the non-plated surface of the parent steel material in the cut end face of the cut product and the above-mentioned Zn-Al-Mg based plating around the non-plated surface are covered with the repair coating.

[0062] The initial resistance of the repair coating is 10 to 1000 Ω / cm 2 The coating resistance value after immersion of the cut product in 5 mass % salt water for 3 hours (hereinafter also referred to as "coating resistance value after salt water immersion") is 5 to 50 Ω / cm 2 .

[0063] Furthermore, the film thickness of the repair coating film is 10 μm or more.

[0064] In the cut product disclosed herein, 50 to 99% of the cut end surface of the cut product is covered with a Zn-Al-Mg based plating layer, and the non-plated surface of the cut end surface and the plating layer around the non-plated surface are covered with a repair coating having the above-mentioned resistance characteristics.

[0065] By setting it as such a structure, the cathodic peeling of a repair coating film can be suppressed, and the fall of corrosion resistance in the initial stage of corrosion can be suppressed.

[0066] In addition, the components of the Zn-Al-Mg-based plating layer and the components of the repair coating film provide a chemical corrosion protection effect, thereby maintaining high corrosion resistance in long-term corrosion from the initial stage of corrosion.

[0067] Therefore, the disclosed cut product suppresses cathodic peeling of the repair coating film and has excellent corrosion resistance of the cut end surface for a long period of time from the initial stage.

[0068] The cut product of the present disclosure will be described in detail.

[0069] (Coated Steel)

[0070] Plated steel materials are steel materials that can be cut.

[0071] The plated steel material is a Zn-Al-Mg plated steel material having a base steel material and a plated layer covering the surface of the base steel material. Specifically, it is preferable that the plated steel material has a plated layer on both sides of the base steel material.

[0072] The base steel is the steel material on which the coating is to be formed.

[0073] The parent steel material is not particularly limited. Examples of the parent steel material include steel plates of an ultra-low C type (ferrite as the main structure), an Al-k type (a structure containing pearlite in ferrite), a dual-phase structure type (for example, a structure containing martensite in ferrite and a structure containing bainite in ferrite), a work-induced transformation type (a structure containing retained austenite in ferrite), and a fine crystal type (ferrite as the main structure).

[0074] The plating layer is a Zn-Al-Mg plating layer, which is a plating layer containing at least zinc, aluminum, and magnesium. The Zn-Al-Mg plating layer has higher corrosion resistance than the Zn plating layer or the Al plating layer because it contains Al and Mg.

[0075] Examples of the plating layer include zinc-aluminum-magnesium plating and known Zn-Al-Mg plating layers such as zinc-aluminum-magnesium-tin plating, zinc-aluminum-magnesium-silicon plating, and zinc-aluminum-magnesium-tin-silicon plating.

[0076] Examples of the plating layer include plating layers containing cobalt, molybdenum, tungsten, nickel, titanium, chromium, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic, and the like as a different metal element or impurity.

[0077] In particular, from the viewpoint of corrosion resistance, the zinc-based coating is preferably a coating containing aluminum in addition to zinc, or a coating containing aluminum and magnesium in addition to zinc. That is, if a zinc alloy-coated steel sheet is used for the original sheet, a more excellent corrosion resistance can be obtained compared to a galvanized steel sheet, and therefore it is preferred.

[0078] Specifically, the plating layer may include, by mass ratio, 65.0% of Zn, 5.0% to 25.0% of Al, and 2.0% to 12.5% ​​of Mg.

[0079] More specifically, the plating layer may have the following chemical composition: in mass %:

[0080] Zn: 65.0%,

[0081] Al: 5.0% to 25.0%,

[0082] Mg: 2.0% to 12.5%,

[0083] Sn: 0% to 20.0%,

[0084] Bi: 0% to 5.0%,

[0085] In: 0%~2.0%,

[0086] Ca: 0% to 3.00%,

[0087] Y: 0% to 0.5%,

[0088] La: 0% to 0.5%,

[0089] Ce: 0% to 0.5%,

[0090] Si: 0% to 2.5%,

[0091] Cr: 0% to 0.25%,

[0092] Ti: 0% to 0.25%,

[0093] Zr: 0% to 0.25%,

[0094] Mo: 0% to 0.25%,

[0095] W: 0%~0.25%,

[0096] Ag: 0% to 0.25%,

[0097] P: 0%~0.25%,

[0098] Ni: 0% to 0.25%,

[0099] Co: 0% to 0.25%,

[0100] V: 0%~0.25%,

[0101] Nb: 0% to 0.25%,

[0102] Cu: 0% to 0.25%,

[0103] Mn: 0% to 0.25%,

[0104] Li: 0% to 0.25%,

[0105] Na: 0% to 0.25%,

[0106] K: 0% to 0.25%,

[0107] Fe: 0% to 5.0%,

[0108] Sr: 0% to 0.5%,

[0109] Sb: 0% to 0.5%,

[0110] Pb: 0% to 0.5%,

[0111] B: 0% to 0.5%, and

[0112] Impurities.

[0113] The method for forming the plated layer is not particularly limited, and any method such as a known electroplating method, a hot dip plating method, a vapor deposition plating method, a dispersion plating method, and a vacuum plating method may be used.

[0114] The coating weight is not particularly limited, but is preferably 15 g·m -2 ~140g·m -2 More preferably, 30 g·m -2 ~90g·m -2 .

[0115] If the coating weight is 15 g·m -2 If the coating weight is 140 g·m -2 Below, the corrosion resistance is high and the phenomenon that the plating layer changes color to black can be suppressed.

[0116] (Cut end surface of cut product)

[0117] -Coating coverage-

[0118] A portion of the cut end surface of the cut product disclosed in the present invention is covered with a Zn-Al-Mg based plating layer. Since a portion of the cut end surface is covered with a Zn-Al-Mg based plating layer having higher corrosion resistance than a Zn plating layer or an Al plating layer due to the presence of Al and Mg, high corrosion resistance is also imparted to the cut end surface.

[0119] The coverage of the plated layer on the cut end surface is 50 to 99%.

[0120] If the coverage of the plating layer is less than 50%, the coverage of the plating layer on the cut end surface is too low, so the corrosion resistance is reduced. On the other hand, if the plated steel material is cut, the plating layer on the surface of the plated steel material spreads to the cut end surface in a part of the cut end surface. However, it is difficult to spread the plating layer to the entire surface of the cut end surface.

[0121] Therefore, the coverage of the plating layer is set to the above range. The coverage of the plating layer is preferably 70 to 99%, and more preferably 90 to 99%.

[0122] The coverage of the plating layer was measured as follows.

[0123] The cut end surface of the cut workpiece to be measured is immersed in a solvent that dissolves the repair coating (ie, the binder resin) and washed with an ultrasonic cleaner for 1 minute or more to completely remove the repair coating.

[0124] Next, gold was vapor-deposited on the cut end surface to a thickness of about 10 nm to prepare a sample.

[0125] For the cut end surface of the sample, the distribution of Zn, Al and Mg elements in the coating composition was measured using an electron probe microanalyzer (EPMA) from the direction perpendicular to the plate thickness. Then, the ratio of the area where any one of Zn, Al and Mg was detected to the cut cross section was calculated as the coating coverage.

[0126] Here, in the measurement of the element distribution of the components of the coating layer by EPMA, the identification of the components of the coating layer and the components of the base steel material is determined by whether any one of the coating components of Zn, Al and Mg exists at 1 atm% or more in the EPMA quantitative analysis. Then, the region where it can be confirmed that any one of the coating components of Zn, Al and Mg exists at 1 atm% or more in the EPMA quantitative analysis is set as the region covered with the coating layer.

[0127] This operation was performed three times, and the average value was calculated.

[0128] The measurement conditions of EPMA were set as follows: measurement area = cut section width (ie, plate thickness) × 10 mm, acceleration voltage = 25 kV, and electron beam diameter = 10 μmφ.

[0129] -Repair coating-

[0130] The non-plated surface of the base steel material in the cut end surface of the cut product of the present disclosure and the Zn—Al—Mg-based plating layer around the non-plated surface are covered with a repair coating film.

[0131] Specifically, for example, the repair coating may cover the non-plated surface of the base steel and the plated layer at least 100 μm from the edge of the plated layer (i.e., the boundary between the non-plated surface of the base steel and the plated layer). Preferably, the repair coating is applied so as to cover the entire collapsed edge surface and the cut end surface.

[0132] Here, the formation state of the repair coating film was confirmed as follows.

[0133] The cut workpiece to be measured is cut in a direction perpendicular to the cut end surface and parallel to the plate thickness direction.

[0134] Next, the steel plate to be measured is embedded with an embedding resin mixed with an embedding curing agent in a specified ratio, and the embedded sample is mechanically polished to expose the cut surface obtained by cutting the cutting processing part, thereby preparing a sample with the cut surface as the observation surface.

[0135] The observation surface of the sample is observed using a SEM (Scanning Electron Microscope) with an EDS (Energy Dispersive X-ray Spectrometer) at a magnification of 50 to 100. In addition, the element distribution of Zn, Al, and Mg in the composition of the coating is also measured. Then, the edge of the coating is determined by the area where any one of Zn, Al, and Mg is detected. Then, the distance between the edge of the coating and the edge of the repair coating is calculated from the observation image obtained using the SEM. Among them, the distance between the edge of the coating and the edge of the repair coating is set as the distance along the surface of the coating.

[0136] By this operation, the formation state of the repair coating film can be confirmed.

[0137] It should be noted that the measurement conditions of EDS were set as follows: measurement area = cutting section width (ie, plate thickness) × 200 μm in cutting direction, acceleration voltage = 15 V, and electron beam diameter = 10 μm.

[0138] --Composition of repair coating--

[0139] The repair coating contains ingredients that have an alternative anti-corrosion effect.

[0140] Specifically, the repair coating film preferably contains Zn-based metal powder and a binder resin. The repair coating film may contain other additives as necessary.

[0141] The Zn-based metal powder is a metal powder containing Zn.

[0142] The Zn-based metal powder may be a metal powder containing Zn alone, or may be a metal powder containing Zn and a metal other than Zn.

[0143] The metal powder containing Zn and a metal other than Zn may be a mixed metal powder of a metal powder containing Zn alone and a metal powder containing a metal other than Zn alone, or may be an alloy metal powder containing Zn and a metal other than Zn.

[0144] Examples of metals other than Zn include Al, Si, Mg, Co, Ti, V, Cr, Mn, Fe, Co, Ni, and stainless steel.

[0145] Among them, Al is preferred as a metal other than Zn. That is, the Zn-based metal powder preferably contains Zn and Al. If Al is contained in the metal powder, it becomes easy to generate Zn alloy which is considered to have excellent corrosion resistance to the base steel material by Zn and Al. 6 Al 2 (OH) 16 CO 3 ·4H 2 O, so the corrosion resistance is improved.

[0146] Here, the content of Al in the Zn-based metal powder containing Zn and Al is preferably 20 to 45 mass %, more preferably 25 to 35 mass %, and particularly preferably 28 to 34 mass % relative to Zn.

[0147] When the Al content is set to 20 mass % or more, an excessive decrease in the coating film resistance values ​​R1 and R2 in the initial stage and after salt water immersion can be suppressed, and the corrosion resistance is improved.

[0148] When the Al content is 45 mass % or less, an excessive increase in the coating resistance value of R2 after salt water immersion can be suppressed, and cathodic peeling of the repair coating becomes less likely to occur.

[0149] The total content of Zn and Al in the Zn-based metal powder containing Zn and Al is preferably 90 mass % or more, more preferably 95 mass % or more, and particularly preferably 100 mass % based on the Zn-based metal powder.

[0150] That is, the total content of metals other than Zn and Al (particularly the content of V) is preferably 10 mass % or less, more preferably 5 mass % or less, and particularly preferably 0 mass % based on the Zn-based metal powder.

[0151] The average particle size of the Zn-based metal powder is preferably 1 to 20 μm, more preferably 1 to 10 μm. When the average particle size of the Zn-based metal powder is set within the above range, the surface area of ​​the Zn metal powder increases, and the chemical corrosion protection becomes easier to work, thereby improving the corrosion resistance.

[0152] In addition, the "average particle size" is a particle size at which the cumulative value from the smaller diameter side is 50% in a number-based particle size distribution determined by a dynamic light scattering method.

[0153] In addition, regarding the particle size of the Zn-based metal powder, the repair coating film (that is, the binder resin) was dissolved in a solvent, and the Zn-based metal powder was recovered by centrifugal separation, and the particle size was measured.

[0154] The content of the Zn-based metal powder is preferably 60 to 80% by mass, more preferably 65 to 75% by mass, based on the entire repair coating film.

[0155] When the content of the Zn-based metal powder is 60% by mass or more, an excessive increase in the resistance value of the coating film in the initial stage and after immersion in salt water can be suppressed, and cathodic peeling of the repair coating film becomes less likely to occur.

[0156] When the content of the Zn-based metal powder is 80% by mass or less, an excessive decrease in the resistance value of the coating film in the initial stage and after immersion in salt water can be suppressed, and the corrosion resistance is improved.

[0157] Therefore, the content of the Zn-based metal powder is preferably within the above range.

[0158] Examples of the binder resin include well-known resins such as polystyrene resins, polyester resins, epoxy resins, urethane resins, polyolefin resins, acrylic resins, and phenolic resins.

[0159] Among them, the binder resin is preferably at least one selected from polystyrene resin and epoxy resin. If these resins are used, it becomes easy to control the coating film resistance value after salt water immersion to a preferred range, and it is easy to improve the corrosion resistance.

[0160] The binder resin may be a cross-linked resin or a non-cross-linked resin, but is preferably a cross-linked resin from the viewpoint of improving corrosion resistance.

[0161] As the crosslinking agent for forming the crosslinked resin, known crosslinking agents such as melamine, isocyanate, silane compound, zirconium compound, and titanium compound can be used depending on the type of the resin to be crosslinked.

[0162] The content of the binder resin is preferably 20 to 40% by mass, more preferably 25 to 35% by mass, based on the repair coating film.

[0163] When the content of the binder resin is set to 20% by mass or more, an excessive decrease in the resistance value of the coating film in the initial stage and after immersion in salt water can be suppressed, and the corrosion resistance is improved.

[0164] When the content of the binder resin is 40% by mass or less, an excessive increase in the resistance value of the coating film in the initial stage and after immersion in salt water can be suppressed, and cathodic peeling of the repair coating film becomes less likely to occur.

[0165] Therefore, the content of the binder resin is preferably within the above range.

[0166] Other additives in the repair coating include pigments (MgO, Al 2 O 3 , precipitated barium sulfate, barium carbonate, calcium carbonate, carbon, magnesium carbonate, etc.), dispersants, defoaming agents, preservatives, thickeners, film-forming aids, etc.

[0167] --Film thickness of repair coating--

[0168] If the film thickness of the repair coating is too low, the corrosion resistance is reduced. There is no particular upper limit on the thickness of the repair coating, but if the film thickness becomes too thick, not only the coating cost per cut end face becomes high, but also the drying time after the repair coating is applied becomes longer.

[0169] Therefore, the film thickness of the repair coating film is 10 μm or more. The film thickness of the repair coating film is preferably 10 to 100 μm, and more preferably 20 to 30 μm.

[0170] The film thickness of the repair coating film was measured as follows.

[0171] The cut workpiece to be measured is cut in a direction perpendicular to the cut end surface and parallel to the plate thickness direction.

[0172] Next, the cut-processed component to be measured is embedded in an embedding resin mixed with an embedding curing agent in a specified ratio, and the embedded sample is mechanically polished to expose the cut surface obtained by cutting the cut-processed component, and a sample is prepared with the surface in the orthogonal direction of the cut end surface as the observation surface.

[0173] The observed surface of the sample was observed by SEM (Scanning Electron Microscope) at a magnification of 50 to 100 times, and the film thickness of the repair coating film formed at any position of the non-plated surface of the base steel material was measured.

[0174] The film thickness measurement was performed on three embedded samples, and the average value of the three measured values ​​was calculated.

[0175] --Repair coating film resistance value--

[0176] If the initial coating resistance R1 in the repair coating is less than 10Ω / cm 2 , the metal powder in the repair coating is slowly oxidized, and the chemical corrosion resistance of the repair coating is inactivated at an early stage, so the corrosion resistance is reduced.

[0177] If the initial coating resistance R1 in the repair coating is higher than 1000Ω / cm 2 , the chemical corrosion protection of the repair coating will not work at all, and red rust may be generated in the steel substrate under the repair coating due to the influence of moisture in the atmosphere, thereby reducing corrosion resistance.

[0178] Therefore, the initial coating resistance value R1 is set to 10 to 1000 Ω / cm 2 .

[0179] It should be noted that the initial coating resistance value R1 in the repair coating refers to the coating resistance value when the proportion of the total amount of metal powder in the repair coating that is not corroded is 80% or more. If the proportion of the total amount of metal powder in the repair coating that is not corroded is 80% or more, the coating resistance value R1 in this state becomes 10 to 1000Ω / cm 2 From the above viewpoint, the initial coating film resistance value R1 is preferably 300 to 500 Ω / cm 2 .

[0180] Here, the initial coating resistance value R1 refers to the coating resistance value when the cut product is stored in a non-corrosive environment or used in a corrosive environment, provided that the proportion of the total amount of metal powder in the coating that is not corroded is 80% or more.

[0181] Specifically, the coating resistance value in the repair coating of the cut product stored in a non-corrosive environment during the period from the time the cut product is made until the cut product is put to use (for example, until the cut product is installed as a beam as a guardrail) is equivalent to the "initial coating resistance value R1".

[0182] Furthermore, if the proportion of non-corroded metal powder in the repair coating is 80% or more, the coating resistance value in the repair coating of the cut product used as a guardrail beam in a corrosive environment also corresponds to the "initial coating resistance value R1".

[0183] The corrosion ratio of the total amount of metal powder is set as the total ratio of the oxidation ratio and the hydrogen oxidation ratio of the metal powder. The corrosion ratio of the metal powder is measured by analyzing the cross-sectional image of the repair coating film. Specifically, it is as follows.

[0184] The central region of the cut end surface of the cut workpiece to be measured, excluding the range of 10 mm from the end of the repaired coating film, was cut in a direction perpendicular to the cut end surface and parallel to the plate thickness direction.

[0185] Next, the cut processed part of the measurement object is embedded in an embedding resin mixed with an embedding curing agent in a specified ratio, and the embedded sample is mechanically polished to expose the cut surface obtained by cutting the cut processed part and the repair coating film, and a sample is prepared with the surface in the orthogonal direction of the cut end surface as the observation surface.

[0186] The observation surface of the sample was subjected to mapping analysis using a SEM (Scanning Electron Microscope) equipped with EDS (Energy Dispersive X-ray Spectroscopy). The observation magnification was set to a magnification that allowed the entire repair coating to be observed in the film thickness direction from the interface between the repair coating and the base steel material to the coating surface, and the interface between the repair coating and the base steel material of 100 μm or more to be observed.

[0187] This visual field observation was performed at three locations per one embedded sample, and this visual field observation was performed at a total of nine locations for the three embedded samples, and the corrosion ratio of the metal powder in each visual field was calculated.

[0188] The corrosion ratio (%) of the metal powder was calculated by "(the number of corroded metal powders / the total number of metal powders)×100" in the field of view.

[0189] Corroded metal powder can be identified by mapping analysis using an SEM equipped with EDS, based on the coincidence of detection positions of metal elements such as Zn and oxygen.

[0190] However, the corroded metal powder does not contain MgO and Al that were initially added to the coating in an oxidized state. 2 O 3 The ratio after removing these additives from the entire corroded metal powder is calculated as follows.

[0191] First, the corrosion rate of the metal powder is calculated by visual observation, and then the additives (MgO, Al 2 O 3 Specifically, the corrosion ratio (%) of the metal powder obtained by field observation is subtracted from the corrosion ratio (%) of the metal powder. 2 O 3 The ratio (%) of the additives added initially.

[0192] That is, the corrosion ratio (%) of the metal powder is calculated by "(the number of corroded metal powders - the number of additives) / the total number of metal powders × 100" in the field of view.

[0193] In this way, the measured value of the additive ratio is subtracted from the measured value of the corrosion ratio in the above-mentioned 9 viewing fields, and the average value of the obtained ratios is calculated.

[0194] Then, the value obtained by subtracting the average value (%) of the obtained ratio from 100% (=100-the average value of the obtained ratio) is defined as "the ratio of the non-corroded metal powder in the total amount of the metal powder in the repair coating film".

[0195] It should be noted that MgO and Al contained in the coating material in an oxidized state 2 O 3 By calculating the increase in the oxides in the repair coating film from the oxides derived from the additives in the paint, it is possible to distinguish them from corroded metal powder.

[0196] On the other hand, if the coating resistance R2 after the repair coating is immersed in salt water is less than 5Ω / cm 2 , the metal powder in the repair coating is rapidly consumed in a corrosive environment, and the chemical corrosion protection of the repair coating becomes inactivated at an early stage, thereby reducing the corrosion resistance.

[0197] If the coating resistance R2 after the repair coating is immersed in salt water is higher than 50Ω / cm 2 In a corrosive environment, the oxygen reduction reaction is concentrated on the exposed portion of the steel substrate directly below the repair coating. Due to the change to an alkaline environment, intermolecular forces such as hydrogen bonds become less likely to work, resulting in cathodic peeling of the repair coating, resulting in reduced corrosion resistance.

[0198] The coating resistance value R2 after the repair coating is immersed in salt water is preferably 10 to 45 Ω / cm 2 , more preferably 25 to 40 Ω / cm 2 .

[0199] Here, the coating resistance value after immersion in salt water in the repair coating is the coating resistance value after immersion of the cut workpiece in 5 mass % salt water for 3 hours. More specifically, it is the coating resistance value after at least the cut end surface of the cut workpiece is immersed in 5 mass % salt water at a liquid temperature of 25° C. for 3 hours.

[0200] The initial coating resistance values ​​R1 and R2 in the repair coating and after the salt water immersion can be adjusted by, for example, the film thickness of the repair coating and the type and amount of the metal powder.

[0201] The coating film resistance value was measured as follows.

[0202] The cut workpiece of the object to be measured is cut into 10 mm squares to obtain a cut piece having a cut end face with a repair coating formed thereon. The cut end face of the obtained cut piece is used as the measurement face, and a conductor is connected to the portion other than the measurement face by a method that does not hinder conduction, such as spot welding or soldering. Only a certain area of ​​the cut end face of the object to be measured is exposed, and the other portions are insulated and sealed to obtain a sample of the repair coating (refer to Figure 7 ).

[0203] The coating film resistance value was determined by measuring the AC impedance of the repair coating film on the exposed cut end surface of the obtained sample.

[0204] This operation was performed twice, and the average value of the coating film resistance was calculated.

[0205] It should be noted that Figure 7 In the figure, 400 indicates a sample, 402 indicates a cut piece of a cut product, 404 indicates a wire, 404A indicates a connecting portion of the wire, 406 indicates an insulating seal, and 408 indicates a repair coating film on the exposed cut end surface.

[0206] (Specific form of the cut end surface of the cut product)

[0207] As specific aspects of the cut end surface of the cut product of the present disclosure, the cut products according to the first to third embodiments of the present disclosure will be described with reference to the drawings.

[0208] However, in the following description, “the first surface and the second surface of the cut product” refer to surfaces facing each other in the plate thickness direction.

[0209] The “collapsed surface” refers to a surface that is plastically deformed in a curved shape due to tensile stress acting on the surface of the plated steel material when the plated steel material is cut.

[0210] The "shear surface" refers to a surface cut by a shear force when the plated steel material is cut.

[0211] The “fracture surface” refers to a surface formed when a crack generated in the plated steel material during the cutting process serves as a starting point and the plated steel material breaks.

[0212] Furthermore, the "collapse surface", "shear surface" and "fracture surface" are continuous surfaces, and constitute the cut end surface of the cut product.

[0213] It should be noted that in Figure 1 to Figure 6 In the diagram, the plate length direction of the plated steel material is set as the X direction, the plate width direction is set as the Y direction, and the plate thickness direction is set as the Z direction.

[0214] exist Figure 1 to Figure 6 In the drawings, the same reference numerals are used to denote the same components or the same parts.

[0215] -First Embodiment-

[0216] like Figure 1 As shown in , the cut end surface 101C of the cut product 101 according to the first embodiment of the present disclosure has a first inclined surface 102 , a second inclined surface 104 , and a fracture surface 106 .

[0217] The first inclined surface 102 includes a first collapsed surface 102A that continues from the first surface 101A of the cut product 101 and a first sheared surface 102B that continues from the first collapsed surface 102A.

[0218] The first inclined surface 102 is inclined in the plate thickness direction from the first surface 101A toward the center of the cut product 101. That is, the first shearing surface 102B is a surface having a predetermined inclination angle with respect to the plate thickness direction of the plated steel material 10.

[0219] The second inclined surface 104 includes a second collapsed surface 104A continuous from the second surface 101B of the cut product 101 and a second sheared surface 104B continuous from the second collapsed surface 104A.

[0220] The second inclined surface 104 is inclined in the plate thickness direction from the second surface 101B toward the center of the cut product 101. That is, it is a surface having a predetermined inclination angle with respect to the plate thickness direction of the plated steel material 10.

[0221] The fracture surface 106 is formed between the first inclined surface 102 and the second inclined surface 104 .

[0222] The fracture surface 106 is formed when the plated steel material 10 is fractured when the plated steel material is cut. Therefore, it is difficult for the fracture surface 106 to be covered with the plating layer 14, and the base steel material 12 becomes a non-plated surface.

[0223] At least a portion of the base steel material 12 located on the first inclined surface 102 and the second inclined surface 104 in the cut end surface 101C of the cut product 101 is covered with the plating layer 14 .

[0224] Specifically, when the plated steel material 10 is cut, the first inclined surface 102 is covered by the plating layer 14 covering the base steel material 12 located on the first surface 101A. When the plated steel material 10 is cut, the second inclined surface 104 is covered by the plating layer 14 covering the base steel material located on the second surface 101B.

[0225] That is, the first inclined surface 102 and the second inclined surface 104 are respectively covered with the plating layer 14 continuous from the plating layer 14 of the cut product 101 .

[0226] By adjusting the area of ​​the plating layer 14 covering the base steel material 12 located on the first inclined surface 102 and the second inclined surface 104 , the coverage of the cut end surface of the cut product 101 by the plating layer 14 is adjusted.

[0227] It should be noted that the entire surface of the base steel material 12 located on the first inclined surface 102 and the second inclined surface 104 may be covered with the plating layer 14 .

[0228] On the other hand, the non-plated surface of the base steel material 12 including the fracture surface 106 in the cut end surface 101C of the cut product 101 and the plating layer 14 around the non-plated surface are covered with the repair coating film 16 .

[0229] The cut product 101 can be cut, for example, by Figure 2 The cutting tool 121 shown in FIG. Figure 2 As shown in FIG. 1 , when viewed from the plate width direction (Y direction), the punch 122 includes a first base portion 122A having a wedge-shaped first blade portion 122B, and a die 124 includes a second base portion 124A having a wedge-shaped second blade portion 124B. The wedge-shaped first blade portion 122B and the second blade portion 124B extend in the plate width direction (Y direction), and the plated steel material 10 is cut along the direction in which the first blade portion 122B and the second blade portion 124B extend.

[0230] The plated steel material 10 cut by the first blade portion 122B of the die 124 and the second blade portion 124B of the punch 122 is arranged between the die 124 and the punch 122 in a state where both ends thereof are held by a binder ring (not shown). At this time, the die 124 and the punch 122 are arranged so that the first blade portion 122B and the second blade portion 124B face each other. Then, the plated steel material 10 is cut by pressing the punch 122 relative to the die 124.

[0231] When the punch 122 is pressed into the die 124, the cutting tool 121 causes the plating 14 on the surface of the plated steel material 10 to enter the cut end face 101C by the tensile stress generated between the first blade portion 122B and the second blade portion 124B and the plated steel material 10, so that a part of the cut end face 101C is covered with the plating 14. That is, the plating 14 on the surface of the plated steel material 10 follows the movement of the first blade portion 122B and the second blade portion 124B relative to the plated steel material 10 when the punch 122 is pressed into the die 124, so that the plating 14 enters the cut end face 101C. Thus, the plated steel material 10 can be cut, and at least a part of the first inclined surface 102 and the second inclined surface 104 in the cut end face 101C of the cut product 101 is covered with the plating 14.

[0232] The shape of the cut end surface 101C of the cut product 101 cut by the cutting tool 112 is caused by the shapes of the first blade portion 122B and the second blade portion 124B. Since the first blade portion 122B and the second blade portion 124B are wedge-shaped, the cut end surface 101C of the cut product 101 is not a shape along the plate thickness direction, but a shape of the first inclined surface 102 and the second inclined surface 104 having inclined surfaces along the wedge shape.

[0233] In the cutting tool 121, the shapes of the first blade portion 122B and the second blade portion 124B are set to be wedge-shaped, so that the plating layer 14 on the surface of the plated steel material 10 can easily follow the movement of the first blade portion 122B and the second blade portion 124B along the inclined surface of the wedge shape when the plated steel material 10 is cut. As a result, the plating layer 14 on the surface of the plated steel material 10 can follow not only the first collapsed edge surface 102A and the second collapsed edge surface 104A of the cut end surface 101C, but also the first sheared surface 102B and the second sheared surface 104B.

[0234] Therefore, by adjusting the inclination angles of the first shearing surface 102B and the second shearing surface 104B, it is possible to adjust the coverage of the plating layer 14 with respect to the cut end surface 101C of the cut product 101. Specifically, by increasing the angles of the wedge-shaped inclined surfaces of the first blade portion 122B and the second blade portion 124B with respect to the plate thickness direction of the plated steel material 10, the plating coverage is increased.

[0235] - Second Embodiment -

[0236] like Figure 3 As shown in , a cut end surface 201C of a cut product 201 according to the second embodiment of the present disclosure has a side surface 202 and a fracture surface 206 .

[0237] The side surface 202 includes a collapsed surface 202A that continues from the first surface 201A of the cut product 201 and a sheared surface 202B that continues from the collapsed surface 202A.

[0238] The side surface 202 is inclined in the plate thickness direction from the first surface 201A toward the center of the cut product 201. That is, the side surface 202 is a surface having a predetermined inclination angle with respect to the plate thickness direction of the plated steel material 10.

[0239] The fracture surface 206 is a surface that is continuous from the side surface 202 and reaches the second surface 201B side of the cut product 201 .

[0240] The fracture surface 206 may include a fin portion 206A (that is, a burr) protruding from the second surface 201B on the second surface 201B side of the cut product 201 .

[0241] At least a portion of the parent steel material 12 located on the side surface 202 in the cut end surface 201C of the cut product 201 is covered with the plating layer 14 .

[0242] Specifically, when the plated steel material 10 is cut, the side surface 202 is covered with the plating layer 14 covering the base steel material 12 located on the first surface 201A.

[0243] That is, the side surface 202 is covered with the plating layer 14 that is continuous from the plating layer 14 of the cut product 201 .

[0244] By adjusting the area of ​​the plating layer 14 covering the base steel material 12 located on the side surface 202 , the coverage of the cut end surface of the cut product 201 by the plating layer 14 is adjusted.

[0245] It should be noted that the entire surface of the base steel material 12 located on the side surface may be covered with the plating layer 14 .

[0246] On the other hand, the non-plated surface of the base steel material 12 including the fracture surface 206 in the cut end surface 201C of the cut product 201 and the plating layer 14 around the non-plated surface are covered with the repair coating film 16 .

[0247] The cut product 201 can be cut, for example, by Figure 4 It is manufactured by the cutting processing tool 221 shown in FIG.

[0248] The cutting tool 221 includes an upper slit blade 222 and a lower slit blade 224 .

[0249] The upper longitudinal cutting knife 222 and the lower longitudinal cutting knife 224 are as shown in FIG. Figure 4As shown in the figure, when observing from the plate width direction (Y direction), when the plated steel 10 is cut, the surface opposite to the cut end surface 201C has a first surface 226A along the plate thickness direction of the plated steel 10 and a tapered surface 226B inclined outwardly relative to the first surface 226A.

[0250] The upper slitting blade 222 and the lower slitting blade 224 extend in the plate width direction (Y direction), and the plated steel material 10 is cut along the direction in which the upper slitting blade 222 and the lower slitting blade 224 extend.

[0251] The plated steel material 10 cut by the upper slitting knife 222 and the lower slitting knife 224 is arranged between the upper slitting knife 222 and the lower slitting knife 224 with both ends thereof held by a material holding ring not shown. Then, the plated steel material 10 is cut by pressing the upper slitting knife 222 and the lower slitting knife 224 relatively.

[0252] When the cutting tool 221 presses the upper slitting blade 222 into the lower slitting blade 224, the tensile stress generated between the upper slitting blade 222 and the lower slitting blade 224 and the plated steel material 10 causes the plating layer 14 on the surface of the plated steel material 10 to enter the cut end face 201C, so that a part of the cut end face 201C is covered with the plating layer 14. That is, the plating layer 14 on the surface of the plated steel material 10 follows the movement of the upper slitting blade 222 and the lower slitting blade 224 relative to the plated steel material 10 when the upper slitting blade 222 is pressed into the lower slitting blade 224, so that the plating layer 14 enters the cut end face 201C. In this way, the plated steel material can be cut, and at least a part of the side surface 202 in the cut end face 201C of the cut product 201 is covered with the plating layer 14.

[0253] The shape of the cut end face 201C of the cut product 201 cut by the cutting tool 121 is caused by the shapes of the upper slitting blade 222 and the lower slitting blade 224. Since the upper slitting blade 222 and the lower slitting blade 224 have a first surface 226A along the plate thickness direction of the plated steel material 10 and a tapered surface 226B inclined outwardly with respect to the first surface 226A, the cut end face 201C of the cut product 201 is not a shape along the plate thickness direction, but a shape of the side surface 202 having an inclined surface along the tapered surface 226B.

[0254] In the cutting tool 221, the upper slitting blade 222 and the lower slitting blade 224 have the tapered surface 226B, so that when the plated steel material 10 is cut, the plating layer 14 on the surface of the plated steel material 10 can easily follow the movement of the upper slitting blade 222 and the lower slitting blade 224 along the inclined surface of the tapered surface 226B. As a result, the plating layer 14 on the surface of the plated steel material 10 can follow not only the collapsed edge surface 202A of the cut end surface 201C, but also the shear surface 202B.

[0255] Therefore, by adjusting the width of the first surface 226A of the upper slitting blade 222 and the lower slitting blade 224 along the plate thickness direction of the plated steel material 10 , the coverage of the plated layer 14 on the cut end surface 201C of the cut product 201 can be adjusted.

[0256] -Third Embodiment-

[0257] like Figure 5 As shown in FIG. 1 , a cut end surface 301C of a cut product 301 according to the third embodiment of the present disclosure has a side surface 302 and a fracture surface 306 .

[0258] The side surface 302 includes a collapsed surface 302A that continues from the first surface 301A of the cut product 301 and a sheared surface 302B that continues from the collapsed surface 302A.

[0259] The side surface 302 is along the plate thickness direction.

[0260] The fracture surface 306 is a surface that is continuous from the side surface 302 and reaches the second surface 301B side of the cut product 301 .

[0261] The fracture surface 306 may include a fin portion 306A (that is, a burr) protruding from the second surface 301B on the second surface 301B side of the cut product 301 .

[0262] At least a portion of the parent steel material 12 located on the side surface 302 in the cut end surface 301C of the cut product 301 is covered with the plating layer 14 .

[0263] Specifically, when the plated steel material 10 is cut, the side surface 302 is covered with the plating layer 14 covering the base steel material 12 located on the first surface 301A.

[0264] That is, the side surface 302 is covered with the plating layer 14 that is continuous from the plating layer 14 of the cut workpiece 301 .

[0265] By adjusting the area of ​​the plating layer 14 covering the parent steel material 12 located on the side surface 302 , the coverage of the cut end surface of the cut product 301 by the plating layer 14 is adjusted.

[0266] It should be noted that the entire surface of the base steel material 12 located on the side surface may be covered with the plating layer 14 .

[0267] On the other hand, the non-plated surface of the base steel material 12 including the fracture surface 306 in the cut end surface 301C of the cut product 301 and the plating layer 14 around the non-plated surface are covered with the repair coating film 16 .

[0268] The cut product 301 can be cut, for example, by Figure 6It is manufactured by the cutting processing tool 321 shown in FIG.

[0269] The cutting tool 321 includes an upper slitting blade 322 and a lower slitting blade 324 .

[0270] The upper longitudinal cutting knife 322 and the lower longitudinal cutting knife 324 are as follows Figure 6 As shown in , when viewed from the plate width direction (Y direction), a bent portion 326A is provided at a corner portion that faces the plated steel material 10 and faces the cut end surface 301C when the plated steel material 10 is cut.

[0271] The upper slitting blade 322 and the lower slitting blade 324 extend in the plate width direction (Y direction), and the plated steel material 10 is cut along the direction in which the upper slitting blade 322 and the lower slitting blade 324 extend.

[0272] The plated steel material 10 cut by the upper slitting knife 322 and the lower slitting knife 324 is arranged between the upper slitting knife 322 and the lower slitting knife 324 in a state where both ends thereof are held by a material holding ring (not shown). Then, the plated steel material 10 is cut by pressing the upper slitting knife 322 and the lower slitting knife 324 relatively.

[0273] When the cutting tool 321 presses the upper slitting blade 322 into the lower slitting blade 324, the tensile stress generated between the upper slitting blade 322 and the lower slitting blade 324 and the plated steel material 10 causes the plating layer 14 on the surface of the plated steel material 10 to enter the cut end surface 301C, so that a part of the cut end surface 301C is covered with the plating layer 14. That is, the plating layer 14 on the surface of the plated steel material 10 follows the movement of the upper slitting blade 322 and the lower slitting blade 324 relative to the plated steel material 10 when the upper slitting blade 322 is pressed into the lower slitting blade 324, so that the plating layer 14 enters the cut end surface 301C. In this way, the plated steel material can be cut, and at least a part of the side surface 302 in the cut end surface 301C of the cut product 301 is covered with the plating layer 14.

[0274] In the cutting tool 321, the upper slitting blade 322 and the lower slitting blade 324 have the curved portion 326A, so that the tensile stress applied to the plating layer 14 on the surface of the plated steel material 10 is relieved when the plated steel material 10 is cut. As a result, the plating layer 14 on the surface of the plated steel material 10 can follow not only the collapsed edge surface 302A of the cut end surface 301C, but also the shear surface 302B.

[0275] Therefore, by adjusting the curvature radius of the curved portion 326A of the upper slitting blade 322 and the lower slitting blade 324 , the coverage of the cut end surface 301C of the cut product 301 by the plating layer 14 can be adjusted.

[0276] (Application of cutting processed products)

[0277] The cut processed products disclosed herein can be applied to guardrails (specifically, guardrail components, especially guardrail beams), steel sections for plastic greenhouses or agricultural greenhouses, pillars, beams, soundproof walls, soundproof walls, components for electrical equipment, components for safe environments, structural components, steel plates used in solar brackets, etc.

[0278] The cut-off processed product of the present disclosure is obtained by cutting the plated steel material and then subjecting it to processing such as press forming according to the above-mentioned use.

[0279] Example

[0280] Hereinafter, the present disclosure will be described in further detail with reference to examples, but these examples do not limit the present disclosure.

[0281] (Preparation of plated steel sheet)

[0282] The following types of plated steel materials were prepared.

[0283] Zn-6%Al-3%Mg: Zn-Al-Mg plated steel sheet (sheet thickness = 4.5 mm, plating composition = Al: 6 mass%, Mg: 3 mass%, balance: Zn, single-sided plating weight = 120 g / m 2 )

[0284] Zn-11%Al-3%Mg: Zn-Al-Mg plated steel sheet (sheet thickness = 4.5 mm, plating composition = Al: 11 mass%, Mg: 3 mass%, balance: Zn, single-sided plating weight = 120 g / m 2 )

[0285] Zn-19%Al-6%Mg: Zn-Al-Mg plated steel sheet (sheet thickness = 4.5 mm, plating composition = Al: 19 mass%, Mg: 6 mass%, balance: Zn, single-sided plating weight = 120 g / m 2 )

[0286] Zn: Hot-dip galvanized steel sheet (sheet thickness = 4.5 mm, coating weight = 120 g / m 2 )

[0287] (Paint for repair)

[0288] Repair paints having the compositions shown in Table 1 were prepared.

[0289] (Example)

[0290] According to the conditions in Table 2, the plated steel sheet was cut using a cutting tool to obtain Figure 1 , Figure 3 or Figure 5The sample with the cut end surface shown in . It should be noted that the shape of the cutting tool was adjusted so that the coverage of the plating layer on the cut end surface was set as shown in Table 2.

[0291] Next, under the conditions shown in Table 2, a repair coating was applied on the non-plated surface of the base steel material of the plated steel sheet and the plating layer around the non-plated surface at the cut end surface of the sample to form a repair coating film.

[0292] The film thickness of the repair coating was set as shown in Table 2. The initial coating resistance and the coating resistance after immersion in salt water (i.e., the coating resistance after immersion of the cut product in salt water of mass % for 3 hours) were as shown in Table 2.

[0293] Through these operations, samples of cut products were obtained.

[0294] (evaluate)

[0295] The following evaluations were performed on the cut end surfaces of the obtained cut product samples.

[0296] - Cathodic disbonding resistance -

[0297] The combined cyclic corrosion test according to CCT-JASO M609 was carried out for 30 cycles.

[0298] Thereafter, a tape ("Sellotape (registered trademark)" manufactured by Nichiban Co., Ltd.) was affixed to the repair coating film-forming surface of the cut end surface of the cut product sample and then peeled off.

[0299] Then, the peeled tape was observed, and the ratio of the area of ​​the repaired coating film peeled by the tape to the area of ​​the repaired coating film attached to the tape (hereinafter referred to as "peeled area ratio") was calculated and evaluated according to the following criteria. It should be noted that "A" and "B" were set as pass.

[0300] A: Peeling area rate is 0%

[0301] B: The peeling area ratio is more than 0% and less than 5%

[0302] D: The peeling area rate exceeds 5%

[0303] -Long-term corrosion resistance 1-

[0304] The combined cyclic corrosion test according to CCT-JASO M609 was carried out for 120 cycles.

[0305] The red rust generation area on the cut end surface of the cut product sample was measured and evaluated according to the following criteria. It should be noted that the pass was set as "A" or "B".

[0306] A: Red rust area rate is 0%

[0307] B: The red rust area ratio is more than 0% and less than 10%

[0308] C: Red rust area ratio is more than 10% and less than 20%

[0309] D: Red rust area rate exceeds 20%

[0310] B or above is qualified

[0311] -Long-term corrosion resistance 2-

[0312] The combined cyclic corrosion test according to CCT-JASO M609 was carried out for 180 cycles.

[0313] The red rust generation area on the cut end surface of the cut product sample was measured and evaluated according to the following criteria. It should be noted that the pass was set as "A" or "B".

[0314] A: Red rust area rate is 0%

[0315] B: The red rust area ratio is more than 0% and less than 20%

[0316] D: Red rust area rate exceeds 20%

[0317] B or above is qualified

[0318] [Table 1]

[0319]

[0320] [Table 2]

[0321]

[0322] From the above results, it is understood that the examples of the present disclosure suppress cathodic peeling of the repair coating film as compared with the comparative examples, and have excellent corrosion resistance of the cut end surface from the initial stage for a long period of time.

[0323] The symbols are explained as follows.

[0324] 10 Coated steel

[0325] 12 Parent steel

[0326] 14Zn-Al-Mg coating

[0327] 16 Repair coating

[0328] 101 Cutting Processing

[0329] 101A Cutting the first surface of the processed product

[0330] 101B Cutting the second surface of the processed product

[0331] 101C Cutting end surface of the processed product

[0332] 102 1st inclined surface

[0333] 102A collapsed edge

[0334] 102B Shear surface

[0335] 104 2nd inclined surface

[0336] 104A 2nd collapsed edge

[0337] 104B Second shear plane

[0338] 106 fracture surface

[0339] 201 Cutting products

[0340] 201A Cutting the first surface of the processed product

[0341] 201B Cutting the second surface of the processed product

[0342] 201C Cutting end surface of cut products

[0343] 202 Side

[0344] 202A collapsed edge

[0345] 202B Shear plane

[0346] 206 fracture surface

[0347] 301 Cutting products

[0348] 301A Cutting the first surface of the processed product

[0349] 301B Cutting the second surface of the processed product

[0350] 301C Cutting end surface of cut products

[0351] 302 Side

[0352] 302A collapsed edge

[0353] 302B Shear surface

[0354] 306 fracture surface

[0355] It should be noted that the disclosure of Japanese Patent Application No. 2022-157062 is incorporated into this specification by reference in its entirety.

[0356] All documents, patent applications, and technical standards described in this specification are incorporated into this specification by reference to the same extent as if each document, patent application, and technical standard was specifically and individually described as being incorporated by reference.

Claims

1. A cut product, which is a cut product of a Zn-Al-Mg-based plated steel material having a base steel material and a Zn-Al-Mg-based plated layer covering the surface of the base steel material, The cut end surface of the cut product is covered with the Zn-Al-Mg based plating layer at a coverage rate of 50 to 99% relative to the cut end surface. The non-plated surface of the base steel material in the cut end surface of the cut product and the Zn-Al-Mg-based plating layer around the non-plated surface are covered with a repair coating film. The initial coating resistance value R1 in the repair coating is 10 to 1000 Ω / cm 2 The cut product is immersed in 5 mass % salt water for 3 hours and the coating resistance value R2 after immersion is 5 to 50 Ω / cm 2 , The repair coating film has a thickness of 10 μm or more.

2. The cut product according to claim 1, wherein: The repair coating film includes Zn-based metal powder and a binder resin.

3. The cut product according to claim 1, wherein: The cut end surface of the cut product has: a first inclined surface including a first collapsed edge surface continuous from the first surface of the cut product and a first shearing surface continuous from the first collapsed edge surface, and inclined from the first surface of the cut product toward the center in the plate thickness direction; a second inclined surface including a second collapsed edge surface continuous from the second surface of the cut product and a second shear surface continuous from the second collapsed edge surface, and inclined from the second surface of the cut product toward the center in the plate thickness direction; and a fracture surface formed between the first inclined surface and the second inclined surface, At least a portion of the parent steel material located on the first inclined surface and the second inclined surface in the cut end surface of the cut product is covered with the Zn—Al—Mg-based plating layer, The non-plated surface of the base steel material including the fracture surface in the cut end surface of the cut product and the Zn—Al—Mg-based plating layer around the non-plated surface are covered with the repair coating film.

4. The cut product according to claim 1, wherein The cut end surface of the cut product has: A side surface including a collapsed edge surface continuous from the first surface of the cut product and a shear surface continuous from the collapsed edge surface, and inclined along the plate thickness direction or from the first surface of the cut product toward the center; and a fracture surface which is continuous from the side surface and reaches the second surface side of the cut product, At least a portion of the parent steel material located on the side surface in the cut end surface of the cut product is covered with the Zn—Al—Mg-based plating layer, The non-plated surface of the base steel material including the fracture surface in the cut end surface of the cut product and the Zn—Al—Mg-based plating layer around the non-plated surface are covered with the repair coating film.

5. The cut product according to claim 1, wherein The initial coating resistance value R1 in the repair coating is 300 to 500 Ω / cm 2 .

6. The cut product according to claim 1, wherein: The coating resistance value R2 of the repair coating after immersion is 10 to 45 Ω / cm 2 .

7. The cut product according to claim 2, wherein: The Zn-based metal powder contains Zn and Al.

8. The cut product according to claim 7, wherein: In the Zn-based metal powder containing Zn and Al, the content of Al relative to Zn is 20 to 45 mass %.

9. The cut product according to claim 7, wherein: In the Zn-based metal powder containing Zn and Al, the content of Al relative to Zn is 28 to 34 mass %.

10. The cut product according to claim 2, wherein: The content ratio of the Zn-based metal powder to the entire repair coating film is 60 to 80% by mass of the metal powder.

11. The cut product according to claim 2, wherein: The binder resin is at least one selected from polystyrene resin and epoxy resin. 12 . A guardrail comprising the cut product according to claim 1 .

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