JP2006283188A - Zn PLATED STEEL SHEET HAVING EXCELLENT CORROSION RESISTANCE AND WORKABILITY, AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a galvanized steel sheet having excellent corrosion resistance and workability, and to provide a method for producing the steel sheet without exchanging a plating bath and peripheral apparatus such as a roll in the bath. <P>SOLUTION: The galvanized steel sheet having excellent corrosion resistance and workability is characterized in that: (a) a metal(s) and/or an intermetallic compound(s) composed of the metal(s) formed inside a plating layer applied to the surface of a steel sheet by thermal spraying, which has a particle diameter of 0.5 to 50 μm by the diameter of the equivalent circle and has an ionization tendency higher than that of Zn is dispersedly present at a ratio of 0.2 to 30% by average volume%, and also; (b) the maximum depth of craters present in the surface of the plating layer is <20% of the average plating layer thickness, and is produced by thermally spraying the metal(s) and/or intermetallic compound(s) on the plating layer in a melted state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Zn-based plated steel sheet excellent in corrosion resistance and workability, which is used as a material for automobiles, building materials, home appliances, and other devices and machines, and a method for producing the same.

  Since Zn is electrochemically lower than Fe, zinc itself corrodes and prevents corrosion of Fe (sacrificial rust prevention). Therefore, Zn plating is widely used to improve the corrosion resistance of iron products.

  In order to maintain the sacrificial rust prevention effect of Zn plating over a long period of time, it is most effective to increase the adhesion amount of Zn plating. However, increasing the adhesion amount of Zn plating has an adverse effect on plating weldability. This is not practically preferable.

In order to avoid this harmful effect and improve the corrosion resistance with a small amount of adhesion, it is effective to perform Zn-Al alloy plating, and the corrosion resistance is improved by several steps compared to the conventional Zn plating. Furthermore, when Mg ₂ Si (intermetallic compound) is dispersed in the Zn—Al alloy plating, the corrosion resistance is remarkably improved (see Patent Document 1).

The method for obtaining a Zn—Al alloy plating in which Mg ₂ Si is dispersed is basically based on depositing the plating on the surface of the steel sheet through the steel sheet in a Zn plating bath in which Al, Mg, and Si are dissolved and precipitated.

  If the amount of intermetallic compound in the plating increases, the corrosion resistance improves. Therefore, in order to increase the amount of dissolution and precipitation of the intermetallic compound in the plating bath, the intermetallic compound powder is supplied to the plating bath by gas. A method and a method of supplying a Zn—Al-based ingot in which intermetallic compound powder is dispersed to a plating bath have been proposed (see Patent Document 2).

  However, the method for dissolving and precipitating intermetallic compounds in the plating bath requires replacement of peripheral equipment such as a plating bath and a roll in the bath for each type of plating, including conventional Zn plating. This replacement requires complicated work, and the cost required for the replacement is enormous.

  Moreover, the plating product in which the intermetallic compound is dispersed in the Zn-Al alloy plating layer by the method of dissolving and precipitating the intermetallic compound powder in the plating bath is attributed to the fact that the matrix phase of plating hardens. The problem is that plating breaks during bending and pressing.

  As a plating method to solve this problem, after plating a steel sheet in a plating bath, the particles of intermetallic compounds are put into a plating layer in the solidification process by using a gas for gas wiping (controlling the amount of plating). A method has been proposed in which an intermetallic compound having a higher melting point than that of plating is dispersed without being melted in the plating layer (see Patent Documents 3 and 4).

  However, in the above method, it is difficult to control the speed of the gas carrying the intermetallic compound particles within an appropriate range. If the gas speed is too high, Zn (matrix) is scattered, while the gas speed is low. And the said particle | grain does not enter in a plating layer, and content of the intermetallic compound in a plating layer is not stabilized after all.

  Further, in this method, even if intermetallic compound particles enter the plating layer, they are segregated only on the surface layer portion of the plating layer, and the oxide layer remaining on the surface of the intermetallic compound particles forms Zn (matrix) and metal. There has been a problem that it becomes difficult to inhibit the binding of intermetallic compounds and sufficiently improve the press workability.

  In addition, immediately after dipping the steel strip in a metal bath, pulling it up and applying gas wiping, by spraying molten fine particles of a metal different from the plating in the metal bath on the entire surface of the steel strip, i) Plating layer in which two types of molten metal are completely mixed, (ii) Plating layer in which compositions of two types of molten metal are mixed in an inclined manner, (iii) Plating layer in which two types of molten metal are separated into two layers A method and an apparatus for forming the film are disclosed (see Patent Documents 5 and 6).

  However, in this method, a large-scale facility is used to make molten metal fine particles by pressurizing a metal different from plating in an oxygen-free or reducing atmosphere and a metal pump in a champ maintained at or above the melting point of the molten metal. Therefore, the equipment cost is inevitably increased, and it is difficult to say that this is an industrially preferable method.

  In addition, the plated product obtained by this method has a plating layer of mixed plating of two kinds of metals, gradient plating, and two-layer plating, and hardening is caused by melting of a metal different from Zn (matrix). Corrosion resistance is low compared to the case where different types of metals are dispersed in a granular form.

JP-A-11-240947 Japanese Patent Laid-Open No. 2002-4022 JP 2002-285212 A JP 2004-107695 A JP-A-7-173599 JP-A-7-292482

  In view of the above problems, the present invention provides a Zn-based plated steel sheet excellent in corrosion resistance and workability, and a manufacturing method capable of manufacturing the steel sheet without replacing peripheral equipment such as a plating bath and a roll in a bath. Objective.

  The present inventor has paid attention to the fact that cracks in the plating layer are caused by the oxide layer remaining on the surface of the intermetallic compound, and put the intermetallic compound uniformly in the plating layer with the oxide layer remaining as little as possible. We studied earnestly about the method to incorporate.

  As a result, the metal and / or intermetallic compound is sprayed onto the plating layer in the solidification process, that is, the metal and / or intermetallic compound is sprayed into the plating layer in the form of droplets and dispersed. I found a technique to incorporate.

  This invention was made | formed based on the said knowledge, The summary is as follows.

(1) In the Zn-based hot-dip galvanized steel sheet,
(A) A metal having a higher ionization tendency than Zn having a particle diameter of 0.5 to 50 μm in terms of an average equivalent circle diameter formed by thermal spraying in a plating layer applied to the surface of a steel sheet and / or the metal The intermetallic compound consisting of is present dispersed in an average volume% of 0.2 to 30% with respect to the entire plating layer, and
(B) A Zn-based plated steel sheet excellent in corrosion resistance and workability, wherein the maximum depth of craters existing on the surface of the plating layer is less than 20% of the average plating layer thickness.

  (2) Zn having excellent corrosion resistance and workability as described in (1) above, wherein the metal is one or more of alkali metal, alkaline earth metal, rare earth metal, and Al Plated steel sheet.

(3) The intermetallic compound includes one or more of Mg ₂ Si, Ca ₂ Si, CaSi, and CaSi ₂ , and the corrosion resistance according to (1) or (2) above, Zn-plated steel sheet with excellent workability.

  (4) The metal is mass%, Al: 13 to 42%, Ca: 1 to 5%, Zn: 0 to 65%, the total amount of Al and Zn is 42% or less, and The total amount of Al, Ca and Zn is 49% or less, and the balance is excellent in corrosion resistance and workability according to any one of (1) to (3), wherein the balance is Mg alloy Zn-based plated steel sheet.

  (5) The metal is mass%, Al: 42 to 78%, Ca: 1 to 5%, Zn: 0 to 65%, the total amount of Al and Zn is 78% or less, and The total amount of Al, Ca, and Zn is 79% or less, and the balance is an Mg alloy made of Mg, which is excellent in corrosion resistance and workability according to any one of the above (1) to (3) Zn-based plated steel sheet.

(6) In the method for producing a Zn-based hot dipped galvanized steel sheet,
(A) For a plating layer in a molten state immediately after the plating layer is applied to the surface of the steel sheet, a metal having a higher ionization tendency and / or an intermetallic compound composed of the metal compared to Zn has a droplet velocity at the time of collision. Thermal spraying is performed at 100 to 300 m / sec.
(B) Zn-based plating excellent in corrosion resistance and workability characterized by dispersing and solidifying the metal and / or intermetallic compound comprising the metal in the molten layer in the molten layer A method of manufacturing a steel sheet.

  (7) In the said thermal spraying, the aspect of a thermal spray raw material is a powder, a wire, or the melt in a molten metal, The Zn-type plated steel plate excellent in the corrosion resistance and workability as described in said (6) characterized by the above-mentioned. Production method.

  (8) The method for producing a Zn-based plated steel sheet having excellent corrosion resistance and workability according to (6) or (7), wherein the thermal spraying is performed after adjusting the plating layer thickness.

  (9) The Zn-based plated steel sheet having excellent corrosion resistance and workability according to any one of (6) to (8), wherein the plated layer is re-melted after the Zn-based hot-plated layer is solidified Manufacturing method.

  According to the present invention, a Zn-based plated steel sheet having excellent corrosion resistance and workability can be manufactured and provided at low cost without replacing peripheral equipment such as a plating bath and a bath roll.

  The Zn-based plated steel sheet (present invention steel sheet) excellent in corrosion resistance and workability of the present invention is obtained by spraying a metal and / or an intermetallic compound on a plated layer in a molten state immediately after the plating layer is applied to the steel sheet surface. A formed metal having an average equivalent circle diameter of 0.5 μm or more and 50 μm or less and having a higher ionization tendency than Zn and / or an intermetallic compound composed of the metal is present in the plating layer in a dispersed manner. It is characterized by.

  Although Zn-based plating is originally excellent in corrosion resistance, it is formed in the plating layer by thermal spraying, and the particle diameter is 0.5 μm or more and 50 μm or less in terms of average equivalent circle diameter, and has a higher ionization tendency than Zn. Due to the presence of metal and / or intermetallic compounds composed of the metal dispersed in the plating layer, the workability is significantly improved compared to a plating layer in which a different kind of metal is sprayed and contained in a solid state. In addition, a Zn-based plated steel sheet (the steel sheet of the present invention) having excellent corrosion resistance and workability can be obtained.

  That is, a plating layer in which particles of metal and / or intermetallic compound are dispersed is known (see [Background Art], see section), but in the steel sheet of the present invention, it is dispersed in the plating layer. The particles are particles obtained by spraying a metal having a higher ionization tendency than Zn and / or an intermetallic compound made of the metal into the plating layer in a molten state (droplet state) and solidifying (hereinafter referred to as “thermal spray forming particles”). ”).

  And it is important that the particles dispersed and present in the plating layer are spray-forming particles in order to ensure both excellent corrosion resistance and workability.

  The reason why the workability is remarkably improved when the spray-forming particles are dispersed in the plating layer as compared with the conventional dissimilar metal dispersion plating layer is as follows.

  The metal and / or intermetallic compound powder particles contained in the zinc-based plating layer for improving the corrosion resistance are usually covered with an oxide layer, and the powder particles are dispersed in the molten plating layer as they are. The oxide layer obstructs the bond between the Zn-based alloy matrix (hereinafter abbreviated as Zn) and the powder particles, and easily forms the starting point of cracking.

  In contrast, the thermal spray forming particles of the steel sheet of the present invention are particles formed in the plating layer through a molten state (droplet state) using thermal spraying, but the powder particles of metal and / or intermetallic compound are melted. When it reaches the state, the surface oxide layer also melts and eventually disappears, so when it enters and solidifies in the molten Zn, it is firmly bonded while being alloyed with the molten Zn.

  In particular, if a non-oxidizing gas is used as a shielding gas during thermal spraying, the amount of surface oxidation can be drastically reduced if the thermal spray particles (in the form of droplets) and oxygen in the atmosphere are blocked. The strong bonding effect between the particles and the Zn matrix is great.

  Also, the molten Zn matrix solidifies while containing droplets of the molten metal and / or intermetallic compound, so that the molten Zn matrix is different from the dissimilar metal powder particles in the solid state as in the conventional method. Compared with the case of solidifying while encapsulating, distortion is accumulated in the matrix, particularly around the dissimilar metal powder particles, and hardening is suppressed, and as a result, the workability of the plated steel sheet is improved.

  Therefore, the Zn-based hot-dip galvanized steel sheet coated with a coating layer in which the spray-forming particles of the present invention are dispersed does not peel off or crack even during severe bending or pressing, and is extremely excellent in workability. is there.

  In the present invention, the metal and / or intermetallic compound in the plating layer formed by thermal spraying, that is, the particle size of the thermal spray-forming particles is an average equivalent circle diameter in order to ensure improvement in corrosion resistance and workability. 0.5 μm or more and 50 μm or less.

  In addition, since the form of particle | grains changes with a thermal spraying method and thermal spraying conditions, it is not restricted to a spherical shape. The form of the particles may take various forms such as flat particles and elliptical particles, but the particle size when the particles are not spherical is the maximum length of the particles in the plating thickness direction.

  If the particle size of the thermal spray-forming particles of the metal and / or intermetallic compound is less than 0.5 μm in terms of the average equivalent circle diameter, the effect of improving the corrosion resistance of the plating layer cannot be sufficiently secured. The lower limit of the average circle equivalent diameter was 0.5 μm.

  On the other hand, if the upper limit of the spray-forming particles of the metal and / or intermetallic compound exceeds the average equivalent circle diameter of 50 μm, the mass of the droplet particles at the time of spraying increases and the kinetic energy becomes excessive. As a result, a crater having a large depth is formed or a molten plating matrix is blown away, which may result in deterioration of the corrosion resistance and workability of the plated steel sheet.

  For this reason, the upper limit of the particle diameter of the spray-forming particles of the metal and / or intermetallic compound is limited to an average equivalent circle diameter of 50 μm.

  Furthermore, when the particle size of the thermal spray forming particles exceeds the thickness of the plating layer, the portion of the thermal spray forming particles that is exposed from the surface without completely entering the plating layer is increased. Once adhered to the plating layer, the adhered thermal spray forming particles are easily detached from the plating layer, and the workability of plating is lowered.

  Therefore, it is more preferable that the upper limit of the particle size of the thermal spray forming particles be less than the plating layer thickness.

  However, even if the particle size of the thermal spray forming particles exceeds the plating layer thickness, if the plating layer thickness is 1.2 times or less, the thermal spray forming particles exposed from at least the plating layer surface are remelted by heating or the like, The bond between the spray formed particles and the plating layer surface can be strengthened, and the problem of desorption of the spray formed particles can be solved.

  Moreover, in this invention, in order to improve the corrosion resistance and workability of a plated steel plate reliably, the thermal spray formation particle | grains of a metal and / or an intermetallic compound are 0.2-30% by the average volume% with respect to the whole plating layer. It is made to contain in a plating layer in a ratio.

  When the thermal spray forming particles of the metal and / or intermetallic compound in the plating layer are less than 0.2% in average volume% with respect to the entire plating layer, the effect of improving the corrosion resistance of the plating layer cannot be sufficiently ensured. Therefore, the lower limit of the average volume% of the thermally sprayed particles with respect to the entire plating layer is set to 0.2%.

  On the other hand, if the thermal spray forming particles of the metal and / or intermetallic compound exceed 30% in terms of the average volume% with respect to the plating layer, plating cracks are likely to occur during bending, and the workability of the plated steel sheet is deteriorated. Therefore, the upper limit of the average volume% of the thermal spray forming particles with respect to the entire plating layer is set to 30%.

  In particular, in the case of a plated steel sheet that requires high workability, it is preferable to set the upper limit of the average volume% of the spray-formed particles to the entire plating layer to 10%.

  In the present invention, the metal and / or intermetallic compound dispersed and present in the plating layer is a metal having a higher ionization tendency than Zn and / or in order to ensure the improvement of the corrosion resistance of the plated steel sheet. It is set as the intermetallic compound which consists of this metal.

  When a metal having a higher ionization tendency than Zn and / or an intermetallic compound composed of the metal is dispersed in the Zn-based hot-plated layer, the corrosion resistance of the plated layer is affected by sacrificial anticorrosive action against Zn in a corrosive environment. Can be increased.

  In particular, the metal is preferably one or more of alkali metals, alkaline earth metals, rare earth metals, and Al, which have a high sacrificial anticorrosive action against Zn in a corrosive environment.

In addition, as an intermetallic compound composed of the above metal, Mg ₂ Si, Ca ₂ Si, which is a kind of intermetallic compound composed of the above metal and Si, in order to further enhance the sacrificial anticorrosive action against Zn in a corrosive environment, Those containing one or more of CaSi and CaSi ₂ are preferred.

Of the alkaline earth metal elements, Mg is particularly preferred because it has a high effect in order to significantly improve the corrosion resistance of the underlying plating layer. In addition, when Mg is sprayed using Mg ₂ Si which is an intermetallic compound with Si described above, explosion does not easily occur, but when spraying using a metal such as pure Mg or Mg alloy, Since the ignition temperature of Mg is lower than the melting point, there is a risk of explosion (dust explosion) before melting.

  For this reason, when spraying using a metal such as pure Mg or Al-Mg alloy, in order to avoid dust explosion, a method of spraying in a low oxygen atmosphere environment, Ca, Al or Zn in Mg alloy It is preferable to use a method using an Mg alloy in which the ignition point and melting point of the Mg alloy are adjusted.

  Ca raises the ignition temperature of the Mg alloy, and Al and Zn lower the melting point of the Mg alloy. Therefore, they are added within a range that does not impair the corrosion resistance of the Mg alloy, and the ignition point of the Mg alloy with respect to the melting point. The risk of explosion during spraying can be reduced by adjusting the height to be higher.

  From the viewpoint of improving the corrosion resistance of the plated steel sheet with Mg alloy and the explosion resistance at the time of thermal spraying, the composition of Ca, Al and Zn in the Mg alloy is more preferably defined as follows.

Composition (I): Al: 13 to 42% by mass, Ca: 1 to 5% by mass, Zn: 0 to 3% by mass, the total amount of Al and Zn is 42% or less, and the total amount of Al, Ca and Zn: 49 % By mass or less, balance: Mg
Composition (II): Al: 42 to 78 mass%, Ca: 1 to 5 mass%, Zn: 0 to 65 mass%, total amount of Al and Zn: 78% or less, total amount of Al, Ca and Zn: 79 % By mass or less, balance: Mg

  In the Mg alloys having the above compositions (I) and (II), the ignition point of the Mg alloy increases to the melting point because the ignition point is increased by the addition of Ca and the melting point is decreased by the addition of Al and Zn. On the other hand, since it is kept high, explosion during spraying is prevented. Since the composition (I) has a higher Mg content than the composition (II), when an Mg alloy of this composition is sprayed onto a Zn-based hot-dip steel sheet by spraying, the corrosion resistance improving effect of the steel sheet is improved in the composition (II). Compared to higher.

  Further, since the composition (II) has a lower Mg content than the composition (I), the effect of improving the corrosion resistance of the steel sheet is slightly inferior to the composition (I). However, since the composition (II) has a higher content of Al and Zn than the composition (I), the melting point of the Mg alloy is lower than that of the composition (I), and the temperature difference with respect to the melting point of its ignition point is Since it is larger than the composition (I), the risk of explosion is extremely reduced during thermal spraying.

In addition, in order to obtain high corrosion resistance and good bending workability in the steel sheet characteristics by spraying these spray-forming particles onto the molten Zn-based plating layer by thermal spraying, the Zn-based plating layer and the above composition are used. As the overall composition of the Mg alloy, the Zn adhesion amount is 20 to 150 g / m ² , the Mg adhesion amount is 0.5 to 10 g / m ² , and the Ca adhesion amount is 0.05 to 0.7 g / m ² . It is preferable to thermally spray the Mg alloy having the above composition on the Zn-based plating layer.

  When each adhesion amount is less than the lower limit value, the corrosion resistance is deteriorated, and when the upper limit value is exceeded, the bending workability is deteriorated.

  Moreover, in this invention, in order to ensure the improvement of the corrosion resistance and workability of the plated steel sheet, the maximum depth of the crater existing on the plated layer surface is set to less than 20% with respect to the average plated layer thickness.

  In addition, the maximum depth of the crater existing on the plating layer surface is measured by observing the cut cross section of the plated steel sheet with an optical microscope, measuring the maximum depth of each crater existing on the plating layer surface from the plating layer surface, and the measured value. The maximum value of is evaluated.

  The crater present on the surface of the plating layer, when spraying the spray forming particles to the molten plating layer, (a) When the droplet particles of the thermal spray raw material is large, (b) When the gas spray rate is high, or ( c) It tends to occur when the droplet velocity is high.

  If the maximum crater depth on the plating layer surface is 20% or more of the average plating layer thickness, it will cause plating cracking during processing, and there are many craters with such a large depth. In this case, the corrosion resistance deteriorates, which is not preferable.

  For this reason, the maximum depth of the crater existing on the plating layer surface is set to less than 20% with respect to the average plating layer thickness.

  The plating layer may be any plating layer formed by Zn-based plating, and may of course be a Zn—Al alloyed plating layer or a Zn—Al—Mg— (Si) alloy plating layer.

  Next, a method for manufacturing a Zn-based plated steel sheet having excellent corrosion resistance and workability according to the present invention (method of the present invention) will be described.

  FIG. 1 shows an embodiment of an apparatus for carrying out the method of the present invention.

  After the steel plate 2 is immersed in the plating bath 3 accommodated in the plating tank 1 and the direction is changed by the roll 4, the steel plate 2 is pulled up from the plating bath 3. The plating bath is a Zn-based plating bath.

  A molten Z-based plating layer is formed on the steel plate 2 immediately after being pulled up from the plating bath 3, and the plating layer thickness (or plating adhesion amount) is further adjusted by the film thickness controller 5.

  The film thickness control device 5 need not be limited to a specific device, but includes means for adjusting the layer thickness by spraying, for example, an inert gas (argon, nitrogen, etc.) on the unsolidified plating layer of the steel plate 2. Is used.

  After adjusting the thickness of the plating layer, a metal having a higher ionization tendency than Zn and / or an intermetallic compound (spraying material) made of the metal is sprayed from the spraying device 6 to the plating layer still in a molten state.

  A cross section of the plated steel sheet thus obtained is schematically shown in FIG.

  A Zn-based hot dipped plating layer 7 is formed on the surface of the base steel of the steel plate 2, and all or a part of the spray particles 8 are dispersed in the Zn-based hot dipped plating layer 7.

  In order to improve the bonding property between the Zn-based hot-dip plating layer 7 and the thermal spray-forming particles 8, 80% or more of the thermal spray particles 8 are present in the Zn-based hot-plating layer, and a portion exposed from the surface of the plating layer is present. Less is preferred.

  In the present invention, the material form of the metal to be sprayed and / or the intermetallic compound (spraying material) is not particularly limited to a specific form, but powder or wire is preferable. Moreover, you may spray a metal and / or an intermetallic compound (spraying material) in the molten material in a molten metal.

  In addition, when using a powdery material as the thermal spray material, if the particle size of the powdery material is smaller than 5 μm, it aggregates when supplying particles of the powder material, it becomes difficult to supply a stable powder material during thermal spraying, Productivity of the plated steel sheet decreases. Therefore, when a powdery material is used as the thermal spray material, it is more preferable that the particle size of the powdery material is 5 μm or more.

  The particle size of the thermal spray forming particles in the plating layer formed by thermal spraying depends on the kinetic energy of the thermal spray forming particles when colliding with the plating layer, and in particular, the droplet velocity of the thermal spray forming particles when colliding with the plating layer. Is more affected.

  When the velocity of the droplet when colliding with the plating layer is less than 100 m / sec at the time of thermal spraying, the droplet of the molten thermal spray forming particle does not enter the molten Zn-based plating layer, and the thermal spray forming particle Since the effect of improving the corrosion resistance of the plating layer cannot be obtained sufficiently, the lower limit of the droplet speed is set to 100 m / sec.

  On the other hand, when the droplet velocity during thermal spraying exceeds 300 m / sec, the possibility of forming a crater having a large depth on the surface of the plating layer increases, and plating cracks occur during the processing of the plated steel sheet, thereby degrading workability. For this reason, the upper limit of the droplet velocity during spraying is set to 300 m / sec.

  The droplet velocity at the time of thermal spraying can be adjusted mainly by adjusting the velocity of the gas flow for conveying the thermal spray material according to the form of the thermal spray material.

  The speed of gas flow during spraying, the size of metal and / or intermetallic compound (spraying material) droplets, and the spraying temperature are not particularly limited, and the speed of gas flow during spraying and the size of droplets are not limited. By adjusting the droplet velocity during spraying to the above range depending on the spraying temperature, the sprayed particles are uniformly dispersed in the molten Zn-based plating layer, and the generation of craters with a large depth on the surface of the plating layer is generated. Can be prevented.

  Further, it is not necessary to particularly limit the supply rate of the thermal spray material at the time of thermal spraying, depending on the thermal spraying method and the form of the thermal spray material, the plating layer of the thermal spray forming particles of the metal and / or intermetallic compound defined in the present invention. Adjust to an average volume% range.

  Thus, according to the present invention, without changing the plating bath or peripheral equipment, the type of metal and / or intermetallic compound to be sprayed and the thermal spraying conditions are changed, and the surface of various steel sheets has corrosion resistance and processing. It is possible to form a plating layer having a desired composition with excellent properties.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  The thermal spraying method shown in Table 1 and the Zn plating layer (GI: Zn, SD: Zn-5Al, Zn-55Al, SD: Zn-11Al-3Mg-0.5Si) in the molten state of the steel sheet pulled up from the Zn plating bath and The sprayed material was sprayed under the spraying conditions to produce a plated steel sheet. In addition, low-temperature metal spraying was performed as a comparative example.

  About the obtained plated steel sheet, while measuring the maximum depth of the crater on the surface of the plating layer shown in Table 2 (continuation of Table 1), the particle diameter and volume ratio of the thermal spray forming particles in the plating layer, Corrosion resistance and processability were evaluated.

  The maximum depth of the crater is determined by observing the cut section of the plated steel sheet with an optical microscope, measuring the maximum depth of each crater from the plating layer surface on the plating layer surface, and determining the maximum depth relative to the average plating layer thickness. Is 20% or more when no crater is present, and ○ when it is present.

  Moreover, the volume ratio of the thermal spray formation particle | grains in a plating layer converted the area ratio of the thermal spray formation particle | grains obtained by measuring from the cross-sectional photograph 20 sheets of a plating layer into the volume ratio.

  The corrosion resistance evaluation was calculated from the corrosion amount after 100 hours of the salt spray test, and the workability was determined from the 3R bending test result of the obtained plated steel sheet (the thickness of the base steel was 1.6 mm). In addition, as for corrosion resistance and workability, the grade 4 or more was made favorable.

  No. in Table 1 and Table 2. In the invention examples shown in Nos. 1 to 17, the thermal spraying method and conditions satisfy the specified range of the present invention, and the plating layer applied to the steel sheet surface also satisfies the specified range of the present invention. Thus, a plated steel sheet having excellent corrosion resistance and workability is obtained.

  On the other hand, no. The comparative examples shown in 18 to 25 are comparative examples in which the thermal spraying method and conditions, and the obtained plating layer are out of the specified range of the present invention.

  No. No. 18, the droplet velocity at the time of collision is high from the specified range of the present invention, the molten Zn plating is scattered, and a crater having a maximum depth outside the specified range of the present invention is formed on the plating layer surface. Therefore, the corrosion resistance and workability were poor.

  No. No. 19, the droplet velocity at the time of collision is lower than the specified range of the present invention, the droplet cannot enter the molten plating, and the spray-formed particles cannot be sufficiently dispersed in the plating layer, resulting in poor corrosion resistance. It was.

  No. No. 20, the droplet velocity at the time of collision is higher than the specified range of the present invention, the molten Zn plating scatters, and a crater is formed on the surface of the plating layer with the maximum depth deviating from the specified range of the present invention. Therefore, the corrosion resistance and workability were poor.

  No. In No. 21, the suitability of the liquid at the time of collision increases, so that the molten Zn plating scatters, the spray-formed particle diameter in the plating layer becomes larger than the specified range of the present invention, and the maximum depth is formed on the surface of the plating layer. However, as a result of the formation of a crater that deviated from the predetermined range of the present invention, the corrosion resistance and workability of the plated steel sheet were poor.

  No. In No. 22, since the powder material used for thermal spraying was Ni, which has a lower ionization tendency than Zn, the corrosion resistance of the plated steel sheet was insufficient.

  No. No. 23 is an example of thermal spraying using the same thermal spraying method as No. 5, but since the supply rate of the thermal spray material at the time of thermal spraying was too high, the volume percentage of the thermal spray forming particles in the plating layer is within the specified range of the present invention. It became higher and the workability of plating was lowered.

  No. In No. 24, since the particle size of the powder sprayed material is low at the time of thermal spraying, the supply capability of the powder particles is inferior, and the powder spraying particle size in the plating layer is not sufficient in the molten plating layer. As a result of being lower than the specified range, the corrosion resistance was low.

  No. In No. 25, since the metal was sprayed into the plating layer by low temperature spraying without using thermal spraying, the bond strength between the thermal spray forming particles and the Zn plating was insufficient, resulting in poor workability of the plated steel sheet.

  As described above, according to the present invention, a Zn-based plated steel sheet excellent in corrosion resistance and workability can be produced and provided without replacing peripheral equipment such as a plating bath and a bath roll.

  Therefore, the present invention expands the use of Zn-based plated steel sheets as materials for automobiles, building materials, home appliances, and other equipment / machines, and has great industrial applicability.

It is a figure which shows the one aspect | mode of the apparatus which enforces the method of this invention. It is a figure which shows typically the cross-sectional structure of the plated steel plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plating tank 2 Steel plate 3 Plating bath 4 Roll 5 Film thickness control device 6 Thermal spraying device 7 Zn system hot dipping layer 8 Thermal spray formation particle

Claims (9)

In Zn-based hot dipped galvanized steel sheet,
(A) A metal having a higher ionization tendency than Zn having a particle diameter of 0.5 to 50 μm in terms of an average equivalent circle diameter formed by thermal spraying in a plating layer applied to the surface of a steel sheet and / or the metal The intermetallic compound consisting of is present dispersed in an average volume% of 0.2 to 30% with respect to the entire plating layer, and
(B) A Zn-based plated steel sheet excellent in corrosion resistance and workability, wherein the maximum depth of craters existing on the surface of the plating layer is less than 20% of the average plating layer thickness.   2. The Zn-based plated steel sheet having excellent corrosion resistance and workability according to claim 1, wherein the metal is one or more of alkali metal, alkaline earth metal, rare earth metal, and Al. _3. The Zn having excellent corrosion resistance and workability according to claim 1, wherein the intermetallic compound contains one or more of Mg ₂ Si, Ca ₂ Si, CaSi, and CaSi _2. Plated steel sheet.   The metal contains, by mass%, Al: 13 to 42%, Ca: 1 to 5%, Zn: 0 to 65%, the total amount of Al and Zn is 42% or less, and Al, Ca The Zn-based plated steel sheet having excellent corrosion resistance and workability according to claim 1, wherein the total amount of Zn and Zn is 49% or less, and the balance is Mg alloy composed of Mg.   The metal contains, in mass%, Al: 42 to 78%, Ca: 1 to 5%, Zn: 0 to 65%, the total amount of Al and Zn is 78% or less, and Al, Ca The Zn-based plated steel sheet having excellent corrosion resistance and workability according to claim 1, wherein the total amount of Zn and Zn is 79% or less, and the balance is Mg alloy composed of Mg. In the method for producing a Zn-based hot-dip steel sheet,
(A) For a plating layer in a molten state immediately after the plating layer is applied to the surface of the steel sheet, a metal having a higher ionization tendency and / or an intermetallic compound composed of the metal compared to Zn has a droplet velocity at the time of collision. Thermal spraying is performed at 100 to 300 m / sec.
(B) Zn-based plating excellent in corrosion resistance and workability characterized by dispersing and solidifying the metal and / or intermetallic compound comprising the metal in the molten layer in the molten layer A method of manufacturing a steel sheet.   In the said thermal spraying, the aspect of a thermal-spraying raw material is a powder, a wire, or the melt in a molten metal, The manufacturing method of the Zn type plated steel plate excellent in corrosion resistance and workability of Claim 6 characterized by the above-mentioned.   The method for producing a Zn-based plated steel sheet excellent in corrosion resistance and workability according to claim 6 or 7, wherein the thermal spraying is performed after adjusting the thickness of the plating layer.   The method for producing a Zn-plated steel sheet having excellent corrosion resistance and workability according to any one of claims 6 to 8, wherein the plated layer is re-melted after the Zn-based hot-plated layer is solidified.

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