JP5532552B2 - Hot-dip Al alloy plated steel - Google Patents

Description

  The present invention relates to a molten metal plated steel material, and more particularly to an Al-based alloy plated steel material.

  Hot-dip aluminum plating has high corrosion resistance, high heat resistance, and excellent appearance and other characteristics, so it is widely used in the building materials field, automotive exhaust system parts, and the like. Usually, in these applications, Al plating is used bare, but when used for a long time, there is a problem that wrinkles are generated on the plating surface due to dust, chipping, etc., and the appearance is deteriorated. Such wrinkles are caused by the low hardness of hot-dip Al plating.

  As shown in Patent Document 1, generally used hot-dip Al plating is Al-Si-based plating having a composition close to pure Al, and the plating layer is mainly composed of an Al phase. The hardness is as low as about 50 to 100 in Hv, and is very easy to wrinkle. For this reason, until now, it has been impossible to maintain the excellent appearance for a long time in a hot-dip Al-plated steel sheet having a soft plating layer, and this improvement in scratch resistance has been strongly desired.

  Generally, in order to increase the hardness of the Al plating layer, an alloy element that forms an intermetallic compound with Al may be added. There are many elements that form an intermetallic compound with Al. If a hard intermetallic compound is selected from these, and if it can be contained in the plating layer at a certain volume fraction, the increase in plating layer hardness will be Is possible.

  However, since the known Al-containing intermetallic compound has a high melting point, if the alloy element concentration is increased without any guidelines for the purpose of increasing the hardness, the melting point of the Al alloy increases, or the metal in the plating bath increases. Since the intermetallic compound becomes a precipitate, it is impossible to contain the alloy element in the plating layer. Therefore, the addition of elements to the Al plating bath requires selection of element types and guidelines for the amount of element addition, but no such studies have been made so far for Al-based plating.

  Up to now, the elements added to Al plating are limited to some element types such as Zn, Mg, and Si as shown in Patent Document 2, and the characteristics of Zn and Mg are low melting points. Although it is relatively easy to add, the corrosion resistance is inferior to that of Al, and these additions lose the excellent corrosion resistance of Al. On the other hand, like Zn and Si, two-phase separation with Al is performed, and intermetallic compounds are formed. In any case, it was not possible to obtain the necessary characteristics with elements that were not formed, such as inability to increase the plating layer hardness efficiently.

Japanese Patent Laid-Open No. 10-265928 JP-A-2005-133151

  The problem to be solved by the present invention is to provide a molten Al alloy-plated steel material having both high corrosion resistance and scratch resistance in a molten Al-based plated steel material.

  The inventors of the present invention have studied the increase in hardness due to the addition of alloy elements as a means for obtaining scratch resistance in hot-dip Al plating. As a result of examining various additive elements, it was found that the hardness of the plating layer can be increased by adding Ni at a high concentration, and the scratch resistance is improved as compared with conventional Al-Si plating. . Moreover, rare earth elements, such as Y, La, and Ce, and Ca were discovered as an element which acts like Ni.

  Furthermore, in a specific plating layer composition range, the structure of the plating layer can be a fine crystal, in particular, a fine crystal containing an intermetallic compound, or a structure containing an amorphous phase. It was found that it can be further enhanced.

  In addition to rare earth elements such as Y, La, and Ce, and Ca, Si is further added to form a harder intermetallic compound composed of element group X and Si, thereby effectively improving hardness. Found that is possible. Furthermore, since Si has a ternary eutectic composition with Al and element group X and lowers the melting point of the plating bath, it has also been found that the addition of Si improves the productivity of plating.

  The present invention has been made based on such findings, and the gist thereof is as follows. All compositions are expressed in atomic%. Hereinafter, in the description, even when there is no description of an atom, “%” in composition display means “atomic%”.

(1) When the element group X is {Ni, element group A (where element group A is La, Ce, Y), Ca}, one or two elements selected from element group X 1 atom% or more and 30 atom% or less in total (where Ni contains 1 atom% or more and 15 atom% or less as an essential component, and the total of elements selected from element group A is 0 .5 atomic% or more and 10 atomic% or less, Ca satisfies 0.5 atomic% or more and 15 atomic% or less, and when simultaneously adding an element selected from element group A and Ca, each concentration is Molten Al, which does not exceed 5 atomic%), further contains 0.1 atomic% or more and 40 atomic% or less of Si, and the balance has a plating layer made of Al and inevitable impurities. Alloy plated steel.

( 2 ) When the plating layer further sets the element group B to {Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Zr, Nb, and Mo}, the element group B The molten Al alloy-plated steel material according to (1) above, containing one or more selected elements in a total of 0.1 atomic% or more and 10 atomic% or less.

( 3 ) The molten Al alloy plated steel material according to any one of (1) to ( 2 ), wherein the plating layer contains an amorphous phase in a volume fraction of 5% or more.

  The alloy-plated steel material of the present invention is a plated steel material having sufficient corrosion resistance equal to or higher than that of conventional hot-dip aluminum plating and having excellent scratch resistance. It can be used for building materials and automobile exhaust system members that are used, and contributes to industrial development by extending the life of these members, reducing maintenance labor, and reducing costs.

  Moreover, it is possible to apply also to a member for which higher resistance to scratching is required, where application of a hot-dip Al plating material has conventionally been postponed from the viewpoint of resistance to scratching. In this case, the conventional performance is shown at a lower material cost than the conventional material.

  In order to improve the corrosion resistance of Al-based plating with excellent corrosion resistance, the present inventors examined methods for increasing hardness by adding various elements to the Al-based plating layer, and obtained many useful findings. The present invention has been reached. Hereinafter, the present invention will be described in detail.

  The requirement of the present invention is to increase the hardness by forming a fine and hard intermetallic compound in the Al plating layer. For this purpose, an element that forms a fine and hard intermetallic compound with Al may be added to the Al plating bath.

  From the viewpoint of the hardness of the intermetallic compound to be formed and the temperature rise of the Al plating bath, the most suitable elements for forming the intermetallic compound are Ni, rare earth elements Y, La, Ce, and Ca. is there. These elements are collectively referred to as an element group X, and rare earth elements Y, La, and Ce are collectively referred to as an element group A.

  The plating hardness of Al plating and Al-Si plating, which are ordinary Al plating, is about 50 to 100 Hv in Vickers hardness and is about the hardness of mild steel, but Al is selected from element group X If one or more elements are contained in a total of 1% or more, the Vickers hardness of the plating can be set to 100 Hv or more, and the scratch resistance is increased. This is because, as described above, Ni and rare earth elements form a hard intermetallic compound with Al and precipitate finely in the plating layer.

  In addition, since these elements all have a eutectic composition with Al, there is an operational advantage that the eutectic composition can be added while lowering the melting point of Al. For this reason, it is necessary to determine the addition conditions (concentrations) of the elements from the viewpoints of the precipitation of the intermetallic compound and the melting point of the Al plating bath.

For example, when Ni is added to the Al plating bath, a hard intermetallic compound called NiAl ₃ is finely dispersed and deposited in the plating layer. This intermetallic compound is formed when Ni is added to Al in an amount of 0.5% or more. In order to increase the hardness to 100 Hv or more by adding Ni alone, it is necessary to add 1% or more. Ni is an element that can be added up to 5% while keeping the melting point low. Preferably, 6% or more of Ni is added to 150 Hv or more.

  As the amount of Ni increases, the hardness of the plating layer increases. However, if the amount of Ni exceeds 15%, the melting point of the plating bath exceeds 850 ° C., resulting in difficult operating conditions. The upper limit of the amount is 15%. In order to make the melting point of the plating bath 800 ° C. or lower in order to facilitate the plating operation, the addition amount of Ni is preferably 11% or less in the Al—Ni system. For reference, FIG. 1 shows a phase diagram of Al—Ni reported in the past.

  In addition, since Ni is excellent in corrosion resistance, it is suitable also as an element contained in the plating layer in this respect. In the above-described 0.5 to 15% addition concentration range, the higher the addition concentration, the higher the addition concentration. Shows good corrosion resistance.

When Y, Ce, La of element group A is added to the Al-based plating layer, hard intermetallic compounds such as YAl ₃ , Ce ₃ Al ₁₁ , La ₃ Al ₁₁ are finely dispersed in the plating layer. Precipitates and the hardness of the plating layer increases.

  These intermetallic compounds are formed when an element selected from element group A is added to Al in an amount of 0.5% or more. In order to make the hardness 100 Hv or more by adding an element selected from the element group A or only the element group, addition of 1% or more is necessary. Up to 5% can be added while keeping the melting point low. The present inventors believe that this is caused by having a eutectic composition with Al at a concentration of about 5%, which is almost the same as Ni.

  More preferably, it is preferable to add 6% or more of an element selected from the element group A to 150 Hv or more. If it exceeds 5%, the melting point starts to rise again, and if it exceeds 10%, the melting point exceeds 850 ° C., resulting in difficult operation conditions, so the upper limit of the amount of addition of these elements or element groups alone is 10%. And

  In order to make the plating bath melting point 800 ° C. or less in order to facilitate the plating operation, the additive amount of the element selected from the element group A is 8% or less in the Al- (element group A) system. Is preferred. For reference, FIG. 2, FIG. 3, and FIG. 4 show the Al—Y state diagram, Al—La state diagram, and Al—Ce state diagram reported in the past, respectively.

Ca is also an element that works very similar to the elements of Ni and element group A. That is, a hard intermetallic compound called CaAl ₄ generated by the addition of Ca is finely dispersed and precipitated in the plating layer, and the effect of improving the hardness of the plating layer can be obtained. This intermetallic compound is produced when Ca is added to Al in an amount of 0.5% or more.

  In order to increase the hardness to 100 Hv or more by adding Ca alone, it is necessary to add 1% or more. Up to 8% of Ca can be added while keeping the melting point of the plating bath low. The present inventors believe that this is caused by the fact that Ca has a eutectic composition with Al at a concentration of about 8%.

  Preferably, 11% or more of Ca is added to make the hardness 150 Hv or more. When the addition amount exceeds 8%, the melting point of the plating bath starts to rise again. When the addition amount exceeds 15%, the melting point exceeds 850 ° C., which is a difficult operation condition, so the upper limit of the addition amount of Ca alone is 15%. And

  In order to make the plating operation easy, in order to set the melting point of the plating bath to 800 ° C. or lower, in the Al—Ca system, the Ca addition amount is preferably 13% or less. For reference, FIG. 5 shows a phase diagram of Al—Ca reported in the past.

  It is also possible to form an intermetallic compound by adding Ni and an element selected from element group A in combination. In this case, since the eutectic composition exists in the vicinity where the addition amount of Ni is 10% and the total addition amount of the element group A is 5%, more elements can be added during Al plating. A hard plating layer can be obtained.

  When used in combination, both Ni and element group A are added by 0.5% or more. With this combined addition, an intermetallic compound of Al and each is generated in the plating layer, and the effect of improving hardness is obtained.

  Preferably, 3% or more of Ni and 3% or more of an element selected from the element group A are added to make the hardness 150 Hv or more. If the Ni addition amount exceeds 15% or the addition amount of the element group A exceeds 10% in total, the melting point of the plating bath exceeds 850 ° C., resulting in difficult operation conditions, so the upper limit of Ni addition amount Is 15%, and the upper limit of the total amount of element group A is 10%.

  In order to facilitate the plating operation, in order to set the melting point of the plating bath to 800 ° C. or less, in the Al—Ni— (element group A) system, the additive amount of Ni is selected from 11% or less and the element group A. The amount of element added is preferably 8% or less.

  Similarly, it is possible to form an intermetallic compound by using Ni and Ca together. Also in this case, since the eutectic composition exists in the vicinity where Ni is 10% and Ca is 8%, more elements can be added during the Al plating than when adding alone, and a harder plating layer can be formed. Can be obtained. When used in combination, both Ni and Ca are added at 0.5% or more. By the combined use, an intermetallic compound is generated in the plating layer, and the effect of improving the hardness is obtained.

  Preferably, Ni is added to 3% or more and Ca is added to 3% or more to make the hardness 150 Hv or more. If the Ni addition amount exceeds 15% or the Ca addition amount exceeds 15%, the melting point of the plating bath exceeds 850 ° C., which is a difficult operation condition, so the upper limit of the Ni addition amount is 15%, Ca The upper limit of the addition amount is 15%.

  In order to make the melting point of the plating bath 800 ° C. or less in order to facilitate the plating operation, the addition amount of Ni is preferably 11% or less and the addition amount of Ca is preferably 6% or less in the Al—Ni—Ca system.

  Since simultaneous addition of element group A and Ca to Al does not take the eutectic composition of the Al- (element group A) -Ca system, the melting point of the plating bath increases as the addition amount increases. Although simultaneous addition of high concentration to the plating is difficult, there is no problem if both are added up to 5%. When both of them exceed 5%, the melting point of the plating bath exceeds 850 ° C., which makes it difficult to operate. Therefore, the upper limit of the addition amount of the element selected from the element group A is 5%, and the addition amount of Ca The upper limit is 5%.

  It is also possible to form an intermetallic compound by using Ni, an element selected from the element group A, and Ca together. When both Ni, the total of elements selected from the element group A, and Ca are added in an amount of 0.5% or more, an intermetallic compound is generated in the plating layer, and an effect of improving hardness is obtained. Preferably, 3% or more of Ni and an element selected from element group A or 3% or more of Ca are added to make the hardness 150 Hv or more.

  However, in this case, since an element selected from A and Ca are used in combination, both are added up to 5%. Moreover, since melting | fusing point of a plating bath will exceed 850 degreeC and it will become difficult operation conditions when Ni addition amount exceeds 15%, the upper limit of the addition amount of Ni shall be 15%.

  The addition of Si to Al also has a slight effect on increasing the hardness of the plating layer. However, the addition of Si together with Ni, element group A, Ca, etc., increases the hardness of the plating layer rather than adding it alone. It is possible to improve more effectively. This is because Si does not form an intermetallic compound with Al, but easily forms an intermetallic compound with additive elements such as Ni, element group A, and Ca. Si also has the effect of lowering the melting point of the Al-based plating bath.

  Since the Si concentration is 12% and it takes a eutectic composition with Al, up to this range, the hardness of the plating layer is increased while lowering the melting point of the plating bath. The melting point drop is observed when the Si concentration is 0.1% or more.

  If the addition is 12% or more, the melting point starts to increase, but the hardness of the plating layer further increases. When the addition amount of Si is 40% or more, the melting point of the plating bath becomes 850 ° C., which is a difficult operation condition, so the upper limit of the addition amount of Si is 40%.

  When Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Zr, Nb, and Mo are element group B, one or more elements selected from element group B By containing 0.1% or more, it is possible to further increase the hardness of the plating layer. It is possible to improve the hardness of the plating layer more effectively by adding these elements together with Ni, element group A, Ca, Si, or the like rather than adding them alone.

For example, Mg is strongly associated with Si, and when added, Mg ₂ Si, which is a hard intermetallic compound, is formed and finely precipitated, which is effective in increasing the hardness of the plating layer. However, if the addition amount of one or more of Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Zr, Nb, and Mo exceeds 10%, the melting point of the plating bath is 850. Since it is difficult to operate under a temperature exceeding ℃, the upper limit of the addition amount of the element group B is 10%. Note that the addition of these elements has almost no influence on the later-described amorphous forming ability.

  The present inventors studied to control the crystal structure by adding elements to the plating layer for the purpose of further increasing the hardness of the plating layer. As a result, it has been found that the hardness of the plating layer can be increased by refining the crystal grains of the forming phase of the plating layer or by including an amorphous phase in the plating layer.

  If the amorphous phase can be contained in the plating layer, the plating hardness increases, and the increase effect is obtained by the presence of 5% or more of the amorphous phase in the plating layer.

  The effect of improving the corrosion resistance by containing the amorphous phase can be predicted most easily by measuring the corrosion current density or the like by electrochemical measurement. When the volume fraction is 5% or more, the corrosion current density at the corrosion potential starts to decrease. It is also possible to perform a salt spray test and a combined cycle corrosion test to improve the corrosion resistance, but originally, Al-based plated steel sheets have a low corrosion weight loss and it may be difficult to find this effect. is there.

  However, even in the above test, since the effect of improving the corrosion resistance can be confirmed in plating with a high volume fraction of the amorphous phase, the plating containing the amorphous phase is equivalent to or higher than the crystalline material. It can be obtained from the corrosion resistance data close to the real environment that it has corrosion resistance.

  Although the detailed factor about the improvement effect of corrosion resistance by containing an amorphous phase is not clarified, this may be due to the fact that the ingredients are homogeneous and the coupling cell formation is suppressed. The inventors are thinking.

  A composition in which the structure is easily refined and a composition in which an amorphous phase is easily obtained are compositions that are difficult to crystallize and that can easily be supercooled during solidification, that is, a eutectic composition that can maintain a liquid state at a lower temperature. Since the composition of the present invention is a component range based on the eutectic composition, it is a component system that can obtain an amorphous phase if a cooling method having a high cooling rate is performed.

  The composition in which an amorphous phase is easily obtained varies depending on the selection of the constituent atoms. In general, it is known that a larger difference in atomic radii and a multi-element system are more convenient for amorphous formation. Therefore, a ternary system is usually preferable to a binary system.

  As described above, the binary component system does not have a large amorphous forming ability, but if the thickness is about several μm like a plating layer, even in the binary component system, by controlling the cooling condition, It is possible to obtain an amorphous phase, and it is possible to increase the precipitation concentration of the amorphous phase by selecting a component condition and a concentration range with good amorphous forming ability in the above component system.

  In the Al—Ni system, the amorphous forming ability increases in the vicinity where Ni becomes 10%. In order to facilitate the formation of amorphous, it is preferable to add 5% or more and 15% or less of Ni to Al.

  In plating in which one or more elements selected from the element group A are added to Al, the amorphous forming ability is increased in the vicinity where the elements selected from the element group A are 10% in total. In order to facilitate the formation of an amorphous layer, it is preferable to add a total of 2% to 10% of elements selected from the element group A.

  In plating in which Ca is added to Al, the amorphous forming ability is increased in the vicinity where Ca is 8%. In order to facilitate the formation of an amorphous layer, Ca is preferably added in an amount of 5% to 13%.

  In the plating in which Si is added to Al, the eutectic composition is obtained in the vicinity where Si becomes 12%, but the composition that is most easily formed amorphous is not the eutectic composition. In the amorphous formation theory, it is general that the composition having the highest amorphous forming ability is shifted to the high melting point metal side (reference material: Y. Li: JOM, vol 57, n3, March 2005, p. 60). -63).

  Therefore, according to this theory, in a system that does not form an intermetallic compound and has a very large melting point difference, such as an Al—Si system, the composition that easily forms an amorphous phase is greatly shifted to the high Si concentration side.

On the other hand, Al-Ni, Al-element group A, Al-Ca, and the like are formed of intermetallic compounds (NiAl ₃ , La ₃ Al _11, etc.) and have a eutectic composition with Al. Is small.

  According to this theory, the present inventors have searched for a composition that can obtain an amorphous phase. As a result, the amount of Si added to obtain an amorphous phase is 25% or more, and the amount of Si added is around 35%. It has been found that it is easier to form.

  Therefore, a preferable Si addition amount is 25% or more from the viewpoint of formation of amorphous. In addition, since melting | fusing point of a plating bath will exceed 850 degreeC and it will become difficult operation conditions when Si addition amount exceeds 40%, Si addition amount upper limit shall be 40%.

  Heretofore, the composition that increases the amorphous forming ability of the binary system has been described.

  As described above, by using Ni, element group A, Ca element, or Si together to form a ternary component system, the amorphous forming ability can be made higher than that of the binary component system. As the number of element species increases, it becomes difficult to move between atoms to form a regular lattice structure, and the amorphous forming ability is improved.

  However, if the additive concentration of the element is low, the effect of making it difficult to move between atoms for taking this regular lattice structure cannot be obtained sufficiently. Therefore, at least one element has a certain concentration or more. It is preferable to add. For example, when adding elements of Ni, element group A, Ca and Si, Ni is 5% or more, element group A is 2% or more in total, Ca is 5% or more, and Si is 25% or more. It is preferable to satisfy one of these.

  Further, Si does not form an intermetallic compound with Al, but the amorphous forming ability of the plating bath increases when the intermetallic compound is easily formed. For this reason, when obtaining more amorphous phases in a plating bath with a high Si concentration, an element selected from Ni or element group A, such as Ca, which is an element that easily forms an intermetallic compound with Al or Si, Further addition is preferable.

  Hereinafter, the characteristic component system of the ternary system of the present invention will be described.

  First, by adding 0.5 to 10% or less in total of elements selected from the element group A to a composition in which Ni is added to Al (preferably, 5% or more of Ni is added). By increasing the number of atoms to make the atoms difficult to move, it is possible to stabilize the liquid state and make it easier to form an amorphous phase.

  The optimum amount of addition varies depending on the element, but about 5% is optimum for the element group A. That is, the eutectic composition exists in the vicinity of the Al-10% Ni-5% (element group A) composition.

  If the total amount of elements added in element group A is less than 0.5%, the effect of improving the amorphous forming ability cannot be expected. If the content is 0.5% or more, the amorphous volume fraction in the plating layer is increased, and the amount of exothermic peak during crystallization can be detected in the differential scanning calorimetry (about 0.5 J / g). Change of degree). If it exceeds 10%, the melting point becomes high and it becomes difficult to operate as described above, so the upper limit of the total amount of addition of one or more elements selected from element group A is 10%.

  Moreover, the Al—Ni—Ca system using Ca instead of the element group A can also increase the amorphous forming ability, and the optimum addition amount of Ca is about 8%. That is, the eutectic composition exists in the vicinity of the Al-10% Ni-8% Ca composition.

  If Ca is less than 0.5%, an effect on the amorphous forming ability cannot be expected. If the content is 0.5% or more, the amorphous volume fraction in the plating layer increases, and it can be detected as a peak amount of heat generated during crystallization by differential scanning calorimetry (about 0.5 J / g). Changes occur). If it exceeds 15%, as described above, the melting point becomes high and it becomes difficult to operate, so the upper limit of the Ca addition amount is 15%.

  The simultaneous addition of element group A and Ca to Al has almost no effect of increasing the amorphous forming ability by lowering the melting point because the Al- (element group A) -Ca system does not take a eutectic composition. If the addition is up to about 5%, the plating bath temperature is 850 ° C. or lower and the plating operation can be performed. Therefore, plating having an amorphous forming ability equivalent to that of binary plating can be produced.

  Si is added to a binary system in which any one of Ni, element group A, and Ca is added to Al, or a ternary system in which two or more elements are added to increase the number of constituent atoms. By making it difficult to move, it is possible to stabilize the liquid state and make it easier to form an amorphous phase.

  Since Si is an element capable of lowering the melting point of the plating bath, the liquid state can be maintained at a lower temperature. Therefore, Si is particularly preferable in forming an amorphous phase. If the amount of Si added is less than 0.1%, it cannot be expected to improve the amorphous forming ability.

  If it is contained in an amount of 0.1% or more, the amorphous volume fraction in the plating layer increases, and the amount of exothermic peak during crystallization can be detected by differential scanning calorimetry (about 0.5 J / g). Changes occur). If it exceeds 40%, as described above, the melting point becomes high and it becomes difficult to operate, so the upper limit of the amount of Si is 40%.

  In particular, in the Al-Ni-Si system, eutectic composition exists in Al-10% Ni-15% Si, and those having a high melting point when Ni alone is added have an alloy melting point of 700 ° C or lower. It is possible. With this composition, the amorphous forming ability is very high, and an amorphous phase can be obtained even when the alloy is cooled by water or high pressure mist, which is convenient for producing amorphous plating.

  In addition, this composition is preferable in improving the corrosion resistance as plating because the amorphous forming ability is improved without relying on the active metal Ca and rare earth elements.

  As described above, the increase in the hardness of the plating layer due to the inclusion of the hard intermetallic compound or the amorphous phase due to the addition of Ni, element group A, Ca, Si element has been described. As described above, Ni, element group A, Ca, In addition to Si, there is an element group B that is effective in increasing the hardness of the plating layer. By containing 0.1% or more of one or more selected from the element group B consisting of Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Zr, Nb, and Mo. It is possible to further increase the hardness of the plating layer.

  In particular, element group B can improve the hardness of the plating layer more effectively by adding together with Ni, element group A, Ca, Si, or the like, rather than adding alone, The addition of these elements has almost no influence on the amorphous forming ability.

  The plating alloy is basically prepared using pure metal (purity 99% or more). A predetermined amount of the metal to be used is mixed and completely melted by using a high frequency induction furnace, an arc furnace or the like in a vacuum or an inert gas replacement state to obtain an alloy.

  However, when adding a low boiling point metal such as Mg and Zn and a high melting point metal such as Ti and V at the same time, an alloy of the high melting point metal and Al is prepared first, compared to the high melting point pure metal. After forming an alloy bath having a low melting point, pure metal, Al—Zn, Al—Mg alloy or the like is added to adjust the components.

  In addition, it is preferable to use the plating bath in which the alloy components are completely dissolved and the components are adjusted as it is, without solidifying as much as possible. Once solidified, the high melting point intermetallic compound precipitates and segregates, causing component separation and remelting, and the high melting point metal may form a bottom dross.

  For this reason, also in the Example of this invention, the molten metal which adjusted the component was moved to the crucible only for metal plating, and was used as a plating bath, hold | maintaining more than melting | fusing point.

  There is no restriction | limiting in particular about the base material at the time of producing a plated steel plate. Al killed steel, ultra low carbon steel, high carbon steel, various high tensile steels, Ni, Cr-containing steel, etc. can be used. There is no particular limitation on the pretreatment processing of the steel material such as the steel making method, the strength of the steel, the hot rolling method, the pickling method, and the cold rolling method.

  As for the plating production method, Sendzimir method, pre-plating method, two-step plating method, flux method and the like are applicable. As the pre-plating type before the Al plating of the present invention, Al-Si plating or the like is optimal as the first-stage plating type of Ni pre-plating and two-step plating.

The bath temperature of the plating bath is 850 ° C. or lower, and a range higher by 10 to 50 ° C. than the melting point is preferable. When producing a crystalline plating, after immersing in a plating bath, the basis weight is adjusted by wiping using N ₂ gas, and then air cooling is performed. When obtaining an amorphous phase, after plating, the basis weight is adjusted by wiping using N ₂ gas, and then water cooling or high pressure mist cooling is performed.

  In the present invention, Cu press quenching was performed in a system with low amorphous forming ability. This is a technique in which a plated steel sheet immediately after hot dipping is pressed and rapidly cooled with a Cu mold cooled to 0 ° C. Unlike water cooling, the effect of decreasing the cooling rate such as nucleate boiling or film boiling by water vapor can be eliminated, so that the cooling rate can be obtained efficiently.

In the cooling rate survey conducted by the present inventors, the water cooling is about 10 ³ ° C / s, whereas the Cu press rapid cooling has a cooling rate of about 10 ⁵ ° C / s.

  Formation of the amorphous phase can be confirmed by obtaining a halo pattern in the X-ray diffraction image of the plating layer. In the case of a single amorphous phase, only a halo pattern (when the plating adhesion amount is small, an Fe diffraction peak of a steel material is also detected) is obtained.

  However, this method cannot be used when crystal phases are mixed. When the amorphous phase and the crystalline phase are mixed, that is, when the amorphous volume fraction is low, a differential thermal analyzer is used to detect the exothermic peak when the amorphous phase crystallizes during temperature rise, Confirm that the amorphous phase is present in the plating layer.

  The calorific value of the exothermic peak is proportional to the volume fraction of the amorphous phase in the plating layer, which is convenient for confirming the effect of improving the amorphous forming ability.

  Using an Al-based alloy prepared in advance, an amorphous ribbon ribbon with an amorphous phase volume fraction of 100% is prepared by a single roll method, a DSC sample is taken, and heat generated during crystallization of this amorphous phase Record the peak temperature and calorific value. By taking a DSC sample from the steel plate plated with the Al alloy and measuring the calorific value at the temperature under the same measurement conditions, it is possible to easily estimate the amorphous volume fraction in the plating layer.

  If the existence of a non-equilibrium phase other than amorphous (supersaturated solid solution or high-temperature stable phase) is suspected, the cross section of the plated steel material is cut, polished and etched, and the surface plating layer is examined with an optical microscope (hereinafter optical microscope). Observe. No structure is observed in the amorphous part even by etching, but in the part where the crystal phase remains, the structure due to the crystal grain boundaries, sub-grain boundaries, precipitates, and the like is observed.

  Thereby, since the area | region of an amorphous part and a crystal | crystallization part is distinguished clearly, it can convert into a volume ratio by the line segment method or image analysis. When the structure is too fine and measurement with a light microscope is difficult, a thin piece is produced from the cross section of the plating layer and observed with a transmission electron microscope, so that the measurement can be performed in the same manner.

  In the case of a transmission electron microscope, it is also possible to confirm an amorphous structure by a halo pattern of an electron beam diffraction image in a region where a tissue is not observed.

  If the structure is not observed on the entire surface, or if there is a part of the structure that is not observed in the light microscope, if there is a suspicion that the crystal grains are coarse and have no distortion, a thin piece for electron microscopy should be further collected. It is desirable to confirm the amorphous phase by observing a halo pattern without a diffraction spot in the electron diffraction pattern.

  In both the light microscope and the electron microscope, it is desirable that the area ratio is obtained by image processing with a computer for 10 or more different fields of view, and these are averaged to obtain the volume ratio.

  The scratch resistance evaluation of the plating is evaluated by performing a scratch test and a Vickers test. In the scratch test, a sapphire test needle with a tip radius of 0.05 mm was pressed vertically against the test material with a load of 2 to 20 gf (19.6 to 196 mN), and the test material was run 20 mm, and then visually observed for the presence of scratches. The lightest load with wrinkles is the weight with wrinkles.

  In addition, a Vickers test is performed in combination with this test. The Vickers test is a test that can most easily measure the hardness of the plating layer, and has a very high correlation with the scratch test. In other words, when the Vickers hardness is 100 or more, it is found that in the scratch test, the wrinkle load is approximately 10 gf (98 mN) or more, and has a wrinkle resistance higher than that of the current Al-Si plated steel sheet.

  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.

Example 1
A cold-rolled steel sheet having a thickness of 0.6 mm, a plated steel sheet having Ni pre-plated thereon, a steel sheet having Al-10 mass% Si plated for use in two-stage plating, and a meat plating bath having the composition shown in Tables 1 to 4 Surface treatment using an equilateral angle steel having a thickness of 10 mm and a side length of 10 cm and a hot-rolled steel sheet having a thickness of 10 mm (both equilateral angle steel and hot-rolled steel sheet were pre-plated with Ni) as a base material A steel material was produced.

  After adjusting Al and other necessary component elements to a predetermined composition, they were melted in an Ar atmosphere using a high-frequency induction furnace or an arc melting furnace to obtain an Al-based alloy. From the prepared alloy, a solution obtained by collecting chips and dissolving the acid was quantified by ICP (inductively coupled plasma emission) spectroscopic analysis, and it was confirmed that the prepared alloy matched the compositions shown in Tables 1 to 4. This alloy was used as a plating bath.

Cold-rolled steel sheets (thickness 0.6 mm) were cut into 10 cm × 10 cm, and then plated with a batch type hot-dip plating test apparatus manufactured by Reska. The basis weight was adjusted by N ₂ gas wiping, and then cooled to room temperature with nitrogen gas.

  The equilateral mountain-shaped steel was cut into a square of 10 cm in the longitudinal direction and the hot-rolled steel plate was cut into a square of 10 cm × 10 cm, immersed in an Al-based alloy bath of the present invention by soaking plating, and naturally cooled by air.

  In this experiment, since any plated steel sheet was produced using natural air cooling, an amorphous phase was not obtained. They indicated “x” when the volume fraction of the amorphous phase was 5% or less. Those for which plated steel sheets could not be produced are indicated by “−”.

  The corrosion resistance of the plated steel sheet was evaluated by carrying out 21 cycles of a method based on automobile standards (JASO M 609-91, 8 hours / cycle, 50% wet / dry time ratio). However, 0.5% salt water was used as the salt water. Corrosion resistance was evaluated by corrosion weight loss converted from corrosion weight loss after test and plating layer density.

  Corrosion thickness was less than 0.5 μm as “◎”, 0.5-1 μm as “◯”, and 1 μm or more as “x”. In Table 1, those not subjected to the corrosion resistance evaluation are indicated by “−”.

  A Vickers test was used to evaluate the scratch resistance of the plating layer. The hardness of the plating layer surface was measured with a load of 10 g. The Vickers hardness was the 10-point average hardness of the plating layer. When the hardness of the plating layer is 300 or more, “◎”, 250-300 or more is “◯”, 200-250 or more is “◇”, 150-200 or more is “□”, 100-150 The above were marked with “Δ” and those less than 100 were marked with “x”. In Table 1, those not subjected to the Vickers test are indicated by “−”.

  In FIG. The XRD result of 59 plating layers is shown. By adding Ni and Si to Al, an intermetallic compound is generated, and the hardness of the plating layer is increased.

(Example 2)
Based on a cold-rolled steel sheet having a thickness of 0.6 mm, a plated steel sheet having Ni pre-plated thereon, and a steel sheet having Al-10 mass% Si plated for use in two-stage plating, in a bath having a plating composition shown in Tables 5 to 8. As the material, a surface-treated steel material was produced.

  After adjusting Al and other necessary component elements to a predetermined composition, they were melted in an Ar atmosphere using a high-frequency induction furnace or an arc melting furnace to obtain an Al-based alloy. From the prepared alloy, a solution obtained by collecting chips and dissolving the acid was quantified by ICP (inductively coupled plasma emission) spectroscopic analysis, and it was confirmed that the prepared alloy matched the composition shown in Tables 5-8. This alloy was used as a plating bath.

  A cold-rolled steel sheet (plate thickness 0.6 mm) was cut into 10 cm × 10 cm, and plated with a batch type hot-dip plating test apparatus manufactured by Reska. The amount of basis weight was adjusted by air wiping, and then submerged in water at 0 ° C. and cooled with water, cooled with high pressure mist from a close range, or Cu pressed to quench.

  Amorphous formation of the plating layer surface layer was determined by the presence or absence of a halo pattern by measuring the diffraction pattern with an X-ray diffractometer using Cu Kα rays. When the amorphous volume and the crystalline phase coexist and the amorphous volume fraction is low, a differential thermal analyzer is used to detect the exothermic peak during crystallization from the amorphous phase during the temperature rise. The presence or absence of a phase was confirmed.

  Using an Al-based alloy prepared in advance, an amorphous ribbon ribbon is produced by a single roll method, a DSC sample is taken, and the temperature of the exothermic peak that appears during crystallization of this amorphous phase, and the calorific value The DSC sample was taken from the steel sheet plated with the Al-based alloy, the calorific value at a predetermined temperature was measured in the same manner, and the amorphous volume fraction in the plating layer was estimated.

  In the amorphous volume fraction, the proportion of the amorphous phase in the plating layer is 50% or more “以上”, 35% or more, less than 50% “◯”, 25% or more, less than 35% “◇”, 15 % Or more, less than 25% is “□”, 5% or more, less than 15% is “Δ”, and less than 5% is “x”.

  The corrosion resistance of the plated steel sheet was evaluated by carrying out 21 cycles of a method based on automobile standards (JASO M 609-91, 8 hours / cycle, 50% wet / dry time ratio). However, 0.5% salt water was used as the salt water. Corrosion resistance was evaluated by corrosion weight loss converted from corrosion weight loss after test and plating layer density.

  Corrosion thickness was less than 0.5 μm as “◎”, 0.5-1 μm as “◯”, and 1 μm or more as “x”. In Table 2, those not subjected to the corrosion resistance evaluation are indicated by “−”.

    A Vickers test was used to evaluate the scratch resistance of the plating layer. The Vickers hardness was the 10-point average hardness of the plating layer. When the hardness of the plating layer is 300 or more, “◎”, 250-300 or more is “◯”, 200-250 or more is “◇”, 150-200 or more is “□”, 100-150 The above were marked with “Δ” and those less than 100 were marked with “x”.

  In FIG. The differential thermal analysis result of 32 plating layers is shown. A crystallization peak representing the presence of an amorphous phase appears between 250 ° C and 350 ° C.

  In FIG. The differential thermal analysis result of 45 plating layers is shown. A crystallization peak representing the presence of an amorphous phase appears between 220 ° C and 300 ° C.

It is a figure which shows an Al-Ni phase diagram. It is a figure which shows an Al-Y phase diagram. It is a figure which shows an Al-La phase diagram. It is a figure which shows an Al-Ce phase diagram. It is a figure which shows an Al-Ca phase diagram. No. in Table 1 It is a figure which shows the XRD result of 59 plating layers. No. in Table 2 It is a figure which shows the differential thermal analysis result of 32 plating layers. No. in Table 2 It is a figure which shows the differential thermal analysis result of 45 plating layers.

Claims (3)

When element group X {Ni, element group A (where element group A is La, Ce, Y), Ca}, one or more elements selected from element group X are 1 atomic% or more and 30 atomic% or less in total (However, Ni contains 1 atomic% or more and 15 atomic% or less as an essential component, and the total of elements selected from element group A is 0.5 atomic%. As described above, 10 atomic% or less and Ca satisfy 0.5 atomic% or more and 15 atomic% or less, and when simultaneously adding an element selected from element group A and Ca, each concentration is 5 atomic%. A molten Al alloy-plated steel material, further comprising a Si layer containing 0.1 atomic% or more and 40 atomic% or less and the balance being Al and inevitable impurities.   The plating layer is further selected from the element group B when the element group B is {Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Zr, Nb, and Mo}. 2. The molten Al alloy-plated steel material according to claim 1, comprising one or more elements in a total amount of 0.1 atomic% or more and 10 atomic% or less.   The molten Al alloy plated steel material according to any one of claims 1 to 2, wherein the plating layer contains an amorphous phase in a volume fraction of 5% or more.

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