JP4654346B2 - Method for producing hot dip galvanized steel sheet having zinc phosphate coating - Google Patents

Description

  The present invention relates to a method for producing a hot dip galvanized steel sheet having excellent lubricity, which is used for improving press formability in the automotive field and the like. More specifically, the present invention represents operability in a continuous galvanized steel sheet production line. The present invention relates to a method for producing a hot dip galvanized steel sheet having a zinc phosphate coating capable of improving productivity.

  In recent years, application of hot dip galvanized steel sheets has been expanding as a rust prevention measure for steel sheets used in automobiles. When a hot dip galvanized steel sheet is used in an automobile, most of the hot dip galvanized steel sheet is used after being formed into a predetermined shape by press molding. However, the hot dip galvanized steel sheet has a problem in press formability as compared with the conventionally used cold rolled steel sheet. This is because the soft η phase remains in the case of hot dip galvanized steel sheets, and the soft ζ phase remains in the case of alloyed hot dip galvanized steel sheets. This is considered to be inferior.

  In order to solve this problem, Patent Document 1 discloses a technique for improving lubricity by further providing an iron-zinc alloy electroplating film on the hot-dip zinc-based plating film. In addition, from the viewpoint of manufacturing cost reduction, a technique for producing a hot-dip galvanized steel sheet having excellent lubricity by eliminating the plating film as described in Patent Document 1 and making the upper layer a zinc phosphate film is disclosed in Patent Document 2 is disclosed. This comprises a zinc-containing metal-plated steel plate composite having excellent high-speed press formability at the time of manufacturing an automobile body, for example, by providing a zinc phosphate coating.

  However, in the production of steel sheets having these zinc phosphate coatings, various pretreatment steps are required because the desired performance cannot be obtained unless pretreatment is performed. For example, in Patent Document 2 and Patent Document 3 described above, when the steel sheet is produced on the continuous hot dip galvanized steel sheet production line, the pre-treatment agent is prevented from being brought into the zinc phosphate aqueous solution. Have.

  Patent Documents 4 and 5 disclose that the substrate is washed and then immersed in a surface conditioner such as a titanium colloid aqueous solution for surface adjustment before contacting with the zinc phosphate aqueous solution.

Japanese Unexamined Patent Publication No. 1-319661 JP-A-7-138864 JP 2001-98383 A JP 2005-54220 A JP 2005-54203 A

  However, in the production methods described in Patent Documents 1 to 4, when washing with water, water is brought into the step of supplying a zinc phosphate aqueous solution when not washing with water, and a treatment agent is used. The composition balance of a certain zinc phosphate aqueous solution is changed. In addition, when not washed with water, the steel sheet is activated with a surface conditioner, etc., so that the reaction with the treatment liquid and the like in the subsequent process is promoted, and the galvanized film from the steel sheet, in particular, the elution of the zinc component is large. The variation in the composition balance of the treatment liquid was increased. Usually, the capacity of tanks for storing processing agents is limited, and in order to keep the composition balance of the changed processing agents constant, there is a method of adding a replenisher while discharging a part of the processing agent as a drain. Often taken. Therefore, replenishment costs and discharge facilities for the zinc phosphate aqueous solution are required, and since waste liquid of P increases, it is necessary to provide drainage facilities and the like.

  In view of environmental considerations in recent years, there is a social demand to suppress the waste liquid of P as much as possible. Further, conventionally, it has been common knowledge that the surface of an aqueous treatment is not dried. This is due to the fact that when dried, the surface oxidizes and the reactivity becomes poor and the performance deteriorates.

  Therefore, the present invention aims to provide a method for producing a hot-dip galvanized steel sheet having a zinc phosphate coating that can keep the composition balance of the treatment agent constant, reduce the production cost, and reduce the environmental impact. And

As a result of intensive studies, the present inventors have obtained the following knowledge in order to solve the above problems, and have developed a method for producing a hot dip galvanized steel sheet having the zinc phosphate coating of the present invention.
(A) By bringing the surface conditioner into a dry state before the step of supplying the zinc phosphate solution, it is possible to prevent the surface conditioner from being brought into the zinc phosphate solution. This is because the activation of the galvanized surface can be suppressed by drying the surface conditioner. Here, the surface conditioner is an aqueous liquid containing a crystal nucleating agent of zinc phosphate. For example, an aqueous liquid in which Ti colloid is dispersed in an aqueous solution of sodium pyrophosphate, or particles of zinc phosphate are dispersed. An aqueous liquid or the like.
(B) Among the surface conditioners, by using an aqueous liquid in which zinc phosphate particles are dispersed and drying the aqueous liquid, it is possible to suppress fluctuations in the composition balance of the aqueous zinc phosphate solution that is the treatment agent. it can. By drying the aqueous liquid containing zinc phosphate particles, the zinc phosphate particles can be adsorbed on the surface of the hot dip galvanized plating without agglomerating while maintaining the particle size, and the particle morphology can be maintained. And it is because it becomes possible to make a plating surface react at the following drying process, suppressing the oxidation reaction of the steel plate surface to a processing agent process by the effect | action like a protective film. On the other hand, in the case of an aqueous liquid in which Ti colloid is dispersed in an aqueous solution of sodium pyrophosphate, the crystal nucleation agent may be dried and aggregated.

  The present invention will be described below.

According to one aspect of the present invention, a method for producing a hot-dip galvanized steel sheet having zinc phosphate coating continuously, the surface conditioning agent supply process for supplying a surface conditioning agent to the surface of the hot dip galvanized in the step after the surface conditioning agent supply process, and before drying step of drying the surface modifier, before the step after the drying step, a treatment agent containing zinc phosphate solution in a roll coating method on the surface of the hot dip galvanized The said subject is solved by providing the manufacturing method of the hot dip galvanized steel plate which has a zinc-phosphate membrane | film | coat including the processing agent supply process to supply.

  Here, the “hot-dip galvanized steel sheet” is a concept including “alloyed hot-dip galvanized steel sheet” in addition to “hot-dip galvanized steel sheet”.

  Invention of Claim 2 solves the said subject when the surface conditioner of the surface conditioner supply process of Claim 1 is the aqueous liquid containing a zinc phosphate particle.

  Invention of Claim 3 is the average particle diameter of the zinc phosphate particle contained in the surface conditioner of the surface conditioner supply process of the manufacturing method of the hot dip galvanized steel sheet which has the zinc phosphate film of Claim 2 Is 10 μm or less.

  Invention of Claim 4 is an average particle diameter of the zinc phosphate particle | grains contained in the surface conditioner of the surface conditioner supply process of the manufacturing method of the hot dip galvanized steel sheet which has a zinc phosphate film | membrane of Claim 2. Is 10 μm or less, and the pH of the surface conditioning agent is 5 or more.

  The invention according to claim 5 is a zinc phosphate phosphate in the surface conditioner supplying step of the method for producing a hot dip galvanized steel sheet having the zinc phosphate coating according to any one of claims 1 to 4. Contains more than 0 mol / L and 0.5 mol / L or less of particles, and contains at least 0.3 mol / L or less selected from the group consisting of Li, Na, K, Be, Mg and Ca in total It is characterized by that.

  The invention according to claim 6 is characterized in that the treatment agent in the treatment agent supplying step of the method for producing a hot dip galvanized steel sheet having the zinc phosphate coating according to any one of claims 1 to 5 has a phosphate group of 0.0. It contains 001-0.7 mol / L, and contains zinc ions having a molar ratio of 0.7 or less with respect to the phosphate radical.

  The invention according to claim 7 is a zinc phosphate aqueous solution as a treatment agent in the treatment agent supply step of the method for producing a hot dip galvanized steel sheet having the zinc phosphate coating according to any one of claims 1 to 6. It contains zinc ions and phosphate radicals, has a pH of 4 or less, and, in addition to zinc ions and phosphate radicals, a nitrate ratio of 0.2 or less in molar ratio with respect to phosphate radicals, 0.2 or less nitrite radicals, 0.1 It contains one or more selected from the group consisting of the following strong electrolyte anions of the following hydrofluoric acid radicals and 0.05 or less sulfuric acid radicals.

Invention of Claim 8 is hot-dip zinc by the surface-conditioner supply process and the processing agent supply process of the manufacturing method of the hot dip galvanized steel sheet which have a zinc-phosphate coating as described in any one of Claims 1-7. P attached to the surface of the system plating is adjusted to 30 to 500 mg / m ² in terms of P.

  Here, the P adhesion amount in “P conversion” can be calculated from measurement by chemical dissolution or measurement by fluorescent X-rays. In the chemical dissolution method, a galvanized steel sheet having a predetermined area is dissolved with a predetermined amount of strong acid (for example, hydrochloric acid), and the P concentration in the solution is adjusted by ICP (inductively coupled plasma emission analysis). Measure and convert. On the other hand, in the method using fluorescent X-rays, samples with various amounts of P attached are prepared, the fluorescent X-ray intensity resulting from PKα is measured by the fluorescent X-ray method, and the amount of P attached is obtained by the method using the above chemical dissolution. By preparing a calibration curve, fluorescent X-ray intensity is obtained for the subsequent samples in the same manner. According to this, it is possible to determine the P adhesion amount in a non-destructive manner.

According to the first aspect of the present invention, since the surface conditioner is not brought into the treatment agent supply step as a liquid agent, and the surface conditioner is not mixed in the treatment agent, the composition balance of the treatment agent is maintained over a long period of time. . As a result, it is possible to obtain effects such as a reduction in manufacturing cost, a reduction in the amount of processing agent supplied, a reduction in the amount of waste liquid discharged, and an improvement in productivity. Furthermore, a hot-dip galvanized steel sheet having a zinc phosphate coating in consideration of the environment can be manufactured. Therefore, since the reduction of the treatment agent is only the amount adhering to the plate, it is possible to establish a manufacturing process that only requires replenishment of the reduced treatment agent, and the zinc phosphate coating is continuously molten zinc in a closed system. It can be formed on a system plating line.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the crystal nucleating agent contained in the surface conditioner does not dry and agglomerate. Can be formed.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, the operability and stability of the surface conditioner can be improved.

  According to invention of Claim 4, in addition to the effect of the invention as described in any one of Claims 1-3, it becomes possible to further improve the operativity and stability of a surface conditioning agent.

  According to invention of Claim 5, in addition to the effect of the invention as described in any one of Claims 1-4, improving the stability of a surface conditioning agent and reaction of the substrate surface in a predrying process Can be made more uniform.

  According to invention of Claim 6, in addition to the effect of the invention as described in any one of Claims 1-5, the operativity and stability of a processing agent can be improved.

  According to the invention described in claim 7, in addition to the effect of the invention described in any one of claims 1 to 6, it is possible to further improve the stability of the treatment agent and improve the homogeneity of the film. it can.

  According to the invention described in claim 8, since P is supplied from two supply sources in addition to the invention described in any one of claims 1 to 7, the adjustment can be easily performed. Can be accurately adjusted.

  Such an operation and effect of the present invention will become apparent from the best mode for carrying out the invention described below.

  The best mode of the present invention and preferred ranges thereof will be described below.

  First, a hot dip galvanized steel sheet, which is a base material processed by the method for producing a hot dip galvanized steel sheet having a zinc phosphate coating of the present invention, will be described. The base material is a hot dip galvanized steel sheet having a base material that is a steel plate and a layer that is a hot dip galvanizing coating coated on the surface of the base material.

  Here, the kind of steel plate used as a base material is not specifically limited, All kinds of cold-rolled steel plates and hot-rolled steel plates can be applied. Therefore, the chemical composition of the base material is not particularly limited, and is extremely low carbon steel or low carbon steel containing Ti, Nb or the like as required, or Si, Mn, P, Cr, Ni, A high-strength steel or a high-strength steel containing Cu, V, or the like as appropriate can be applied.

  There are two types of hot-dip galvanized steel sheets that serve as substrates: hot-dip galvanized steel sheets (GI steel sheets) that are not subjected to alloying treatment by heating and galvannealed steel sheets (GA steel plate) that have been subjected to alloying treatment by heating. Can be mentioned. Here, it is preferable that the GI steel sheet contains Fe in an amount of 2% by mass or less in the hot dip galvanizing. This is because when the content exceeds 2% by mass, a part of the Fe—Zn alloy layer appears on the surface, which is not preferable in appearance. The GA steel sheet preferably contains 7 to 15% by mass of Fe in the galvannealed alloy. This is because when the Fe content is less than 7% by mass, the η phase remains in the vicinity of the surface of the plating layer, which may be undesirable in appearance. More preferably, it is 8 mass% or more. On the other hand, if the Fe content exceeds 15% by mass, powdering tends to occur during press molding. More preferably, it is 13 mass% or less.

  Furthermore, you may contain 0.05-0.5 mass% Al in the said hot dip zinc type plating layer. Thereby, the adhesiveness of a plating layer and a base material can be improved. Moreover, Cu, Ni, Cr, Si, Mn, Pb, Sb, Sn, misch metal, etc. may be contained or added in a small amount to the hot dip galvanized layer.

Also, the type of alloy phase constituting the hot dip galvanized layer is not particularly limited, and GI steel sheet has η phase, ζ phase, δ phase, GA steel sheet has ζ phase, δ1 phase, Γ1 phase, Γ phase. It may be mixed. And the adhesion amount of hot dip galvanizing is not specifically limited, either. From the viewpoint of workability, weldability and productivity, it is preferably 150 g / m ² or less.

  The manufacturing method of the hot dip galvanized steel sheet as the base material is not particularly limited. This can include, for example, a method of immersing in a plating bath and cooling as it is to obtain a GI steel sheet. Regarding the GA steel sheet, a method of alloying after immersion in a plating bath can be mentioned. Moreover, you may add processes, such as temper rolling (skin pass) and a planarization process (leveler), as appropriate. Although the surface form of the steel sheet is variously changed by the skin pass and the leveler, the present invention is not affected at all by these.

  The present invention is applied to the substrate. Below, the manufacturing method of the hot dip galvanized steel sheet which has a zinc phosphate membrane | film | coat of this invention is demonstrated.

  The flow of the manufacturing method of the hot dip galvanized steel plate which has the zinc phosphate film | membrane of this invention concerning one embodiment in FIG. 1 was shown. This manufacturing method includes a surface conditioning agent supplying step (S1) for supplying a surface conditioning agent to a substrate, a pre-drying step (S2) for drying the supplied surface conditioning agent, and a processing agent supplying step for supplying a processing agent. (S3) and a post-drying step (S4) for drying after the treatment agent supply step (S3). Each step will be described below.

The surface conditioning agent supply step (S1) is a step of supplying the surface conditioning agent to the substrate. Here, the surface conditioner is an aqueous liquid containing a crystal nucleating agent of zinc phosphate. For example, an aqueous liquid in which Ti colloid is dispersed in an aqueous solution of sodium pyrophosphate, or an aqueous liquid in which particles of zinc phosphate are dispersed. Etc. The method for supplying the surface adjusting agent in the surface adjusting agent supplying step (S1) is not particularly limited. Examples thereof include a method of dipping in a surface conditioner, a method of spraying on a substrate (including a method of squeezing with a ringer roll after spraying), a method of applying with a roll coater, and the like. The adhesion amount of the surface conditioner is preferably less than 30 mg / m ² . This is because at 30 mg / m ² or more, surface treatment spots may occur and the appearance may be impaired. Preferably it is 15 mg / m ² or less, more preferably 10 mg / m ² or less. Moreover, the upper limit is preferable because the effect as a base treatment is saturated even if it is further adhered, and conversely it may affect the treatment agent in the subsequent process.

  Among the surface conditioners supplied to the substrate in the surface conditioner supply step (S1), “an aqueous liquid in which zinc phosphate particles are dispersed” means an aqueous turbid liquid in which particulate zinc phosphate is dispersed. The zinc phosphate particles are preferably crystalline. The aqueous liquid preferably has a pH of 5 or more. The aqueous liquid preferably has a particle size of 10 μm or less. Moreover, it is preferable that this aqueous liquid contains this zinc phosphate particle at greater than 0 and 0.5 mol / L or less. Further, it is preferable that the aqueous liquid contains at least one or two or more selected from alkali metals of Li, Na, and K and alkaline earth metals of Be, Mg, and Ca in a total amount of 0.3 mol / L or less. .

  Regarding that the pH is preferably 5 or more, when the pH is less than 5, the dissolution of hot dip zinc plating by etching may occur in the surface conditioner supply step (S1), the composition balance fluctuates, and zinc phosphate This is because the dispersion state of the particles is disturbed and the stability of the aqueous liquid may be lowered. The upper limit of the pH is not particularly limited, but the pH is preferably less than 11. This is because when the pH is 11 or more, in order to maintain the dispersion of the aqueous liquid, a large amount of alkali must be added, which increases the cost. Further, when the pH is 11 or more, dissolution reaction of the zinc phosphate particles in the aqueous phase occurs, the particle form and dispersion state are impaired, and there is a possibility that the uniform film formation during the treatment agent process may be hindered.

  The reason why the particle diameter of zinc phosphate is preferably 10 μm or less is that when the particle diameter exceeds 10 μm, the dispersion becomes unstable and the life of the aqueous liquid may be reduced. Preferably, it is 5 μm or less, more preferably 3 μm or less. The lower limit of the particle diameter is not particularly limited, but is preferably 0.1 μm or more from the viewpoint of the viscosity of the aqueous liquid.

The content of zinc phosphate particles is 0.5 mol / L or less. This is because when the concentration of the zinc phosphate particles is higher than 0.5 mol / L, the content of the dispersion becomes too high, which may reduce the life of the aqueous liquid. From the viewpoint of the stability of the aqueous liquid, it is preferably 0.3 mol / L or less. The content of zinc phosphate particles, by measuring the concentration of zinc, can be converted from atomic weight as Zn ₃ (PO _{4) 2.}

By adding at least one or two or more selected from alkali metals of Li, Na and K and alkaline earth metals of Be, Mg and Ca to the aqueous liquid, the substrate in the pre-drying step described later is thereby added. This is because the surface reaction becomes more uniform and a stable hot dip galvanized steel sheet can be produced. The concentration of the alkali metal and alkaline earth metal is 0.3 mol / L or less in total of the alkali metal and alkaline earth metal. This is because, if a large amount is added exceeding 0.3 mol / L, these additives adhere to the substrate surface and carry over, and the stability of the processing agent and the like in the subsequent step may be lowered. The alkali metal and alkaline earth metal can be added as orthophosphate, metaphosphate, pyrophosphate, orthosilicate, metasilicate, carbonate, bicarbonate, borate and the like. Moreover, you may use ammonium salt or aqueous ammonium solution for pH adjustment. Furthermore, metal or metal salt particles such as Fe, Co, Ni, Cu, Mn, and Cr may be contained as long as the total is about 0.05 mol / L or less. In addition, it is preferable that a pH buffer or the like is mixed in the aqueous liquid. For example, a buffer solution composed of K ₂ HPO ₄ and NaOH can be mentioned. As a result, the pH change is reduced, and stable production may be possible. As the aqueous liquid, if the above composition is satisfied, a commercially available surface conditioner used for coating surface treatment or the like can be used.

  By having the surface conditioning agent supply step (S1) for supplying the aqueous liquid to the base material, it can be combined with the steps described later to provide a method for producing a hot dip galvanized steel sheet having the zinc phosphate coating of the present invention.

  Next, the pre-drying step (S2) will be described. The pre-drying step (S2) is a step of drying the surface conditioner supplied to the substrate surface without washing with water. Although a drying temperature is not specifically limited, It is preferable that it is less than 200 degreeC by the steel plate highest ultimate temperature from a viewpoint of manufacturing cost. More preferably, it is less than 150 degreeC. The drying time is not particularly limited, but is preferably less than 30 seconds from the viewpoint of surface appearance and productivity. More preferably, it is less than 10 seconds. The method for drying is not particularly limited, and can be appropriately selected. Examples thereof include an air knife, a dryer, and an oven.

  There is no possibility that the surface conditioning agent is brought into the processing agent supply step (S3), which will be described later, in the predrying step (S2) as a liquid agent, and the surface conditioning agent to the processing agent that is circulated and used in the processing agent supply step (S3). It is possible to reduce the fluctuation of the composition balance of the treatment agent by suppressing the mixing of the composition. As a result, it becomes possible to suppress replenishment and discharge of the treatment agent, which was conventionally necessary to maintain the composition balance of the treatment agent.

  This is because the activation of the hot-dip galvanized steel sheet can be stopped once by drying after supplying the surface conditioner. In addition, the zinc phosphate particles can be adsorbed on the surface of the hot dip galvanized plating without agglomerating while maintaining the particle size by the drying, and the particle morphology can be maintained, and the treatment agent process can be performed by the action like a protective film It is also possible to react the plating surface in the next drying step while suppressing the oxidation reaction on the steel sheet surface.

  Next, the treatment agent supply step (S3) will be described. The treatment agent supply step (S3) is a step of supplying a treatment agent for forming a zinc phosphate film on the substrate on which the pre-drying step (S2) has been performed. Examples of the method for supplying the treatment agent to the substrate include a spray ringer method and a roll coating method. Among these, the combination with the above-mentioned pre-drying step (S2) can effectively simplify the equipment, and preferably applies the treatment by the roll coating method from the viewpoint that a hot-dip galvanized steel sheet can be produced at a lower cost. It is possible. From the viewpoint of the operability of the treatment agent, treatment by a roll coat method is most preferable. Furthermore, the entry material temperature when the steel sheet that has undergone the pre-drying step (S2) enters the treatment material supply step (S3) is preferably less than 80 ° C. This is because when the steel plate temperature is high, the activation of the steel plate is higher than the protective film-like action of the surface conditioner, and the galvanized film may be eluted into the treatment material. Preferably it is less than 60 degreeC. The lower limit is preferably 30 ° C. or higher. This is because if it is less than 30 ° C., the reaction due to heating in the drying step after the treatment step does not sufficiently occur, and the film formation may be nonuniform. The adjustment of the temperature of the entry material can be achieved by providing a cooling section of the steel sheet, but temperature control by roll cooling such as a water cooling roll is also possible.

The treatment agent supplied in the treatment agent supply step (S3) is a zinc phosphate aqueous solution. The aqueous zinc phosphate solution is an aqueous solution containing phosphate groups and zinc ions. Here, the phosphate group is a general term for H ₂ PO ₄ ⁻ , HPO ₄ ²⁻ , and PO ₄ ³⁻ , and is represented by [PO ₄ ³⁻ ]. The zinc phosphate aqueous solution contains 0.001 to 0.7 mol / L of phosphate radicals [PO ₄ ³⁻ ], and contains zinc ions having a molar ratio of 0.7 or less with respect to the phosphate radicals. Furthermore, the zinc phosphate aqueous solution has a pH of 4 or less, and in addition to zinc ions and phosphate radicals, the molar ratio with respect to phosphate radicals is 0.2 or less nitrate, 0.2 or less nitrite radical, and 0.1 or less hydrofluoric acid radical. Or an aqueous solution containing at least one strong electrolyte anion having a sulfate group of 0.05 or less. And the P adhesion amount is set to 30 to 500 mg / m ^{2 in} terms of P in total with the surface conditioning agent supplied in the surface conditioning agent supply step (S1).

  The reason why the phosphate radical concentration range is 0.001 to 0.7 mol / L is that if the phosphate radical is increased beyond 0.7 mol / L, the stability of the treatment agent may be lowered. On the other hand, if it is less than 0.001 mol / L, the pH of the treatment agent becomes high, and the reaction may be hindered to obtain desired performance. The reason why the zinc ion is contained in a molar ratio of 0.7 or less with respect to the phosphate radical is that a homogeneous crystalline film can be formed by containing the zinc ion.

The pH of the zinc phosphate aqueous solution was set to 4 or less because when the pH exceeds 4, the treatment agent becomes unstable and sludge is generated, the surface quality is deteriorated, and the reaction does not proceed smoothly. This is because the desired performance may not be obtained. Here, “sludge” is obtained by solidifying Zn ₃ (PO ₄ ) _{2 in an} aqueous solution. In addition, the reason why the molar ratio of zinc to phosphate radicals is 0.7 or less is that sludge is generated in the same manner, which may impair the surface quality. The pH of the zinc phosphate aqueous solution is preferably 3.5 or less from the viewpoint of surface quality, and the molar ratio of zinc ions to phosphate groups is 0.5 or less.

In addition to zinc ion and phosphate radical, nitrate radical (NO ₃ ⁻ ) is 0.2 or less, nitrite radical (NO ₂ ⁻ ) is 0.2 or less, and hydrofluoric acid radical (F ⁻ ) in molar ratio with respect to phosphate radical. The addition of one or more strong electrolyte anions of 0.1 or less and sulfate radicals (SO ₄ ²⁻ ) of 0.05 or less reacts with the treatment agent in order to stably improve the film uniformity. This is to make it happen. Specifically, an etching action and an oxidation action can be obtained by the reaction. When the amount of the strong electrolyte anion is added more than the above upper limit, the stability of the treatment agent is lowered and the life of the treatment agent may be shortened.

  In addition, an ammonium salt or an aqueous ammonium solution may be added to the aqueous zinc phosphate solution for pH adjustment. The concentration of ammonium ions is preferably 0.02 or less in molar ratio with respect to the phosphate radical. Moreover, as long as the structure of the said zinc phosphate aqueous solution is satisfied, other metal ions other than zinc may be mixed. At this time, the total molar ratio of the metal ions to phosphate groups is preferably 0.2 or less.

The adhesion amount of the zinc phosphate aqueous solution is converted to P in the total amount of the surface adjustment agent supply step (S1) and the treatment agent supply step (S3) described above in the film adhesion amount finally formed, and 30 it is preferably to 500 mg / ^{m 2.} This lubricating effect of the film is less than 30 mg / m ² is not reflected in the formability of the steel sheet, the effect exceeds 500 mg / m ² is to saturate. More preferably from 30 to 400 mg / ^{m 2.}

  By providing the pre-drying step (S2), which is a pre-step of the treatment agent supply step (S3), the surface conditioning agent is not brought into the treatment agent supply step (S3) as a liquid agent, and the balance of the treatment agents Can be properly maintained over a long period of time. Thereby, processing agent management and drainage can be simplified.

  Next, the post-drying step (S4) will be described. The post-drying step (S4) is a step of drying the treatment agent supplied to the substrate surface without washing it with water. Although a drying temperature is not specifically limited, It is preferable that the steel plate highest achieved temperature is less than 250 degreeC from a viewpoint of manufacturing cost. More preferably, it is less than 180 degreeC. The drying time is not particularly limited, but is preferably less than 100 seconds after coating from the viewpoint of surface appearance and productivity. More preferably, it is less than 50 seconds. The method for drying is not particularly limited, and can be appropriately selected. Examples thereof include an air knife, a dryer, and an oven. A homogeneous zinc phosphate crystal film is formed by the post-drying step (S4).

  As described above, the operability of the treatment agent can be improved by eliminating the need for discharging the treatment agent in the treatment agent supply step by the hot dip galvanizing production process of the present invention. Thereby, the manufacturing method of the hot dip galvanized steel sheet which has the zinc phosphate membrane | film | coat which is simple and reduces the influence on an environment and can be operated stably can be provided.

In the following, the embodiment will be described in more detail.
Example 1
As Example 1, an ultra-low carbon steel plate GI steel plate having a thickness of 0.8 mm and 200 mm × 250 mm (plating adhesion amount 90 g / m ² , coating Al concentration: 0.4 mass%, Fe concentration: 1.5 mass) %) And GA steel sheets (plating adhesion amount 60 g / m ² , coating Al concentration: 0.30 mass%, Fe concentration: 9.5 mass%), operability evaluation and lubricity evaluation I did it. In this example, the evaluation based on the presence or absence of the pre-drying step in the case where the component of the surface conditioner and the component of the treatment agent are changed is performed. Table 1 shows the components of the surface conditioner, and Table 2 shows the components of the treatment agent.

Moreover, the conditions of each process are as follows.
Surface modifier supply process Surface modifier supply method: spray or roll coater Adhesion amount: 3 mg / m ^{2 in} terms of P
Pre-drying process Drying equipment: Dryer Drying temperature: Maximum steel sheet temperature 60 ° C
Drying time: 10 seconds Treatment agent supply process Supply method: Roll coater (intrusion material temperature 50 ° C.)
Total adhesion amount: 80 mg / m ^{2 in} terms of P
Post-drying process Drying equipment: Oven Drying temperature: Maximum steel sheet temperature 70 ° C
Drying time: 30 seconds

Moreover, the case where the conventional alkali and the acid wash | clean was performed as a prior art example. In this case, specifically, the base material washed with water after the washing is introduced into the treatment agent supplying step. In this example, the presence or absence of a drying step before being introduced into the treatment agent supply step after washing with water was also shown. The conditions are shown below.
Pre-cleaning conditions: 7% by weight NaOH and 2% by weight H ₂ SO ₄ (Nos. 13 and 14 in Table 1)
Immersion condition: Immerse in 7% NaOH aqueous solution (70 ° C) for 5 seconds
Immerse in 2% H ₂ SO ₄ aqueous solution (50 ° C) for 5 seconds

(1) Evaluation item Based on the above conditions, the evaluation described below was performed.
(1-1) Evaluation of operability The operability is from the surface conditioner in the treatment agent when the treatment agent is supplied to a base of 10 m ² (the total area of the cut plates is 10 m ² ) with respect to 10 L of the treatment agent. The concentration of zinc mainly contained in the carry-in component (alkali metal of the surface conditioner) and the treatment agent was measured, and the change in concentration before supply of the treatment agent was evaluated. The evaluation criteria for operability are as follows. The need for concentration adjustment in the following evaluation criteria means that water washing equipment, replenishers, and waste liquid treatment equipment are unnecessary.
○: Concentration increase of alkali metal and zinc in the treatment agent is 2% by mass or less of the initial concentration (concentration adjustment unnecessary)
Δ: Concentration increase of alkali metal and zinc in the treatment agent exceeds 2% by mass of initial concentration and 4% by mass or less (concentration adjustment is almost unnecessary)
X: Concentration increase of alkali metal and zinc in the treatment agent exceeds 4% by mass of the initial concentration (concentration adjustment required)

(1-2) Lubricity Evaluation Method Using a pin-on-disk type frictional wear tester on the hot dip galvanized steel sheet having the zinc phosphate coating, the following conditions were applied. The friction coefficient was measured at, and the lubricity was evaluated by the friction coefficient. The evaluation criteria for the friction coefficient are as follows.
Test conditions
Load: 30kN
Slider material: SKD steel Slider shape: Steel spherical surface with a diameter of 5 mm Test temperature: 60 ° C
Turning radius: 10mm
Sliding speed: 1rpm
Test rotation speed: 20 times Number of measurement points: 1 average value is calculated from 12 measurement values per rotation, and the average value is 20 times.
Evaluation criteria A: Friction coefficient less than 0.12 (very good lubrication)
○: Friction coefficient 0.12 or more and less than 0.15 (good as a lubrication treatment)
X: Coefficient of friction of 0.15 or more (unsuitable for lubrication)

(1-3) Stability of surface conditioner and treatment agent The stability of each surface conditioner and treatment agent was obtained by a 40 ° C. × 7 day test. This is to keep each adjusting agent and treating agent at 40 ° C. for 7 days. Evaluation of the stability of the surface conditioner and the treatment agent is as follows.
Surface conditioner ○: Maintain dispersion state
×: Precipitation occurs Treatment agent ○: No generation of sludge
×: Sludge is generated

(2) Evaluation result The result about Example 1 evaluated based on the above conditions is demonstrated below.
(2-1) Operability and lubricity Table 3 lists the results.

  As seen from this, when the surface conditioning agent is supplied and dried in the pre-drying step, the operability of the treatment agent is high, and the lubricity of the obtained hot dip galvanized steel sheet is also good. The effect of the invention is remarkably exhibited. Furthermore, it turns out that it does not depend on the supply method of a surface conditioning agent.

  On the other hand, only the operability of the treatment agent is good due to the pre-drying step even in the case of using the conventional cleaning shown by the symbol R26 to R29 as a conventional example. This means that the pre-drying step has a great effect on improving the operability of the treatment agent. However, it can be seen that the surface conditioner must be supplied because the desired lubricity is not obtained in the hot dip galvanized steel sheet under the conditions of the symbols R26 to R29.

  Further, under the conditions indicated by the symbol R24 and the symbol R25 as a reference example, the operability of the surface treatment agent is not good while the operability of the treatment agent is not affected. This is shown in Table 1 used for symbols R24 and 25, No. The surface treatment agent shown in No. 11 has a pH of 4.5 and is considered to be caused by a lower pH than the others. Therefore, the operability of the surface conditioner can be improved by increasing the pH to at least 4.5.

(2-2) Stability of surface conditioner and treatment agent Next, the results of the stability of each surface conditioner and treatment agent shown in Tables 1 and 2 will be described. Table 4 shows the stability evaluation results of the surface conditioning agent, and Table 5 shows the stability evaluation results of the treatment agent.

  The surface conditioner shown in Table 4 is No. 7, no. 10 and no. 12 was not stable. This is no. Regarding Table 7, as can be seen from Table 1, it is considered that the total of alkali metal and alkaline earth metal has reached 0.401 mol / L. No. 10 and no. Regarding No. 12, the reason is that the particle diameter is large and the zinc phosphate content is large. These do not necessarily affect the operability of the treatment agent, but higher stability is preferred.

  Among the treatment agents shown in Table 5, the stability with respect to g to m was not good. This is considered to be due to the large ratio of zinc ions to phosphate groups for g to i. Moreover, about i, pH is 4.1 and has shown the high value. Regarding j to m, it is considered that the ratio of the added strong electrolyte anion is large. These do not necessarily affect the operability of the treatment agent, but higher stability is preferred.

(Example 2)
As Example 2, in a continuous hot dip galvanized steel sheet production line, a 0.8 mm thick GA steel sheet (very low carbon steel sheet, 45 g / m ² in coating coverage, coating Al concentration: 0.25% by mass, Fe concentration) : 9.0% by mass) was subjected to a skin pass (rolling ratio: 1.0%), and in the surface conditioning agent supplying step, the No. shown in Table 1 was obtained. The surface conditioning agents 1, 4, and 6 were supplied, and in the treatment agent supply step, the zinc phosphate film treatment was performed using the treatment agents a, d, e, and i in Table 2. Conditions for each step are as shown below.
Surface conditioner supply process Supply method: Spray or roll coater Drying equipment: Dryer Adhesion amount: 3 mg / m ^{2 in} terms of P
Pre-drying process Drying temperature: Maximum steel sheet temperature 70 ℃
Drying time: 5 seconds Treatment agent supply process Supply method: Roll coater (intrusion material temperature 50 ° C.)
Post-drying process Drying equipment: Oven Drying temperature: Maximum steel sheet temperature of 80 ° C
Drying time: 30 seconds

  In addition, as a comparative example, a pre-drying step was performed.

(3) Evaluation items Based on the above conditions, the evaluation described below was performed.
(3-1) Evaluability of operation Each component is brought in from the surface conditioner in the treatment agent when the steel plate having a plate thickness of 0.8 mm and a width of 1 m is passed through 100 m of the treatment agent. The concentration of zinc mainly contained in the alkali metal) and the treatment agent was measured, and the change in concentration before supply of the treatment agent was evaluated. The evaluation criteria for operability are as follows. The need for concentration adjustment in the following evaluation criteria means that water washing equipment, replenishers, and waste liquid treatment equipment are unnecessary.
○: Concentration increase of alkali metal and zinc in the treatment agent is 2% by mass or less of the initial concentration (concentration adjustment unnecessary)
Δ: Concentration increase of alkali metal and zinc in the treatment agent exceeds 2% by mass of initial concentration and 4% by mass or less (concentration adjustment is almost unnecessary)
X: Concentration increase of alkali metal and zinc in the treatment agent exceeds 4% by mass of the initial concentration (concentration adjustment required)

(3-2) Lubricity evaluation Using a pin-on-disk type frictional wear tester on the hot dip galvanized steel sheet having the zinc phosphate coating obtained, the rust preventive oil was applied under the following conditions. The friction coefficient was measured, and the validity as a lubrication treatment was evaluated by the friction coefficient. The evaluation criteria for the coefficient of friction are shown below.
Test conditions
Load: 30kN
Slider material SKD steel Slider shape: Steel spherical surface with a diameter of 5 mm Test temperature: 60 ° C
Turning radius: 10mm
Sliding speed: 1rpm
Number of test rotations: 20 times Number of measurement points: An average value is calculated from 12 measurement values per rotation, and the maximum average value of 20 times is obtained.
Evaluation criteria A: Friction coefficient less than 0.12 (very good lubrication)
○: Friction coefficient 0.12 or more and less than 0.15 (good as a lubrication treatment)
X: Coefficient of friction of 0.15 or more (unsuitable for lubrication)

(3-3) Spot Weldability Evaluation Spot welding was performed on the obtained hot dip galvanized steel sheet having a zinc phosphate coating using a spot welder under the following conditions, and the nugget diameter (mm) was 4t ^{1. / 2} (t: steel plate thickness (mm)) The number of hit points was evaluated.
Evaluation conditions Electrode diameter: 6 mm
Electrode tip diameter: 40R dome type Electrode material: 1% by mass Cr-Cu
Applied pressure: 2kN
Upslope: 3 cycles Energizing time: 10 cycles (frequency: 50 Hz)
Cooling flow rate: 3L / min
Welding current: 10.5kA
Evaluation criteria:
○: 2000 points or more (appropriate)
X: Less than 2000 RBI (unsuitable)

(3-4) Corrosion Resistance Evaluation Corrosion resistance evaluation was performed by a method generally used as a performance evaluation method for automobile steel plates and the like. Specifically, after the chemical conversion treatment, electrodeposition was applied, and then a single cut was applied, and the maximum swelling width after 500 hours of a 5 mass% salt spray test was evaluated. The chemical conversion treatment and electrodeposition treatment conditions are shown below.

The chemical conversion treatment is performed in the order of chemical conversion treatment (zinc phosphate treatment) after alkali degreasing, water washing and surface conditioning. The conditions in each order will be described next.
Alkaline degreasing: Fine cleaner E2001 (Nihon Parkerizing Co., Ltd.) 200 g / L solution (50 ° C.), 2 minutes immersion Water washing: 30 seconds Surface adjustment: Percolen Z (Nihon Parkerizing Co., Ltd.) 1 g / L solution (room temperature) immersion for 10 seconds Chemical conversion treatment: PB-L3080 (manufactured by Nihon Parkerizing Co., Ltd., liquid temperature 43 ° C.) sprayed for 2 minutes

Subsequent to the chemical conversion treatment, GT-10 (cationic electrodeposition coating: 20 μm) was electrodeposited.
The evaluation criteria are as follows.
Evaluation criteria: Maximum bulge width on one side ○: Less than 3 mm (suitable)
×: 3 mm or more (unsuitable)

(4) Evaluation Results The results for the above conditions and evaluation items will be described. Table 6 shows the results.

  As can be seen from Table 6, the operability of the treating agent is good for those having the pre-drying step shown in the remarks as examples of the present invention. On the other hand, the operability of the treatment agent is not good for any of those having no pre-drying (described as a comparative example in the remarks). Therefore, it can be said that the effect of the present invention is remarkably exhibited.

  Moreover, it can be said that various performances in the presence of the pre-drying step are generally good. Regarding the symbol Z11 and the symbol Z16, the reason why the lubricity is not good is that the adhesion amount of P is small. This is not affected by the presence or absence of the pre-drying step included in the present invention.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein. The method of manufacturing a hot-dip galvanized steel sheet having a zinc phosphate coating, which can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. It should be understood as being included in the technical scope of the invention.

It is the figure which represented typically the flow of the manufacturing method of the hot dip galvanized steel plate which has a zinc phosphate membrane | film | coat of this invention.

Explanation of symbols

S1 Surface conditioning agent supply step S2 Pre-drying step S3 Treatment agent supply step S4 Post-drying step

Claims (8)

A method for continuously producing a hot dip galvanized steel sheet having a zinc phosphate coating,
A surface conditioning agent supply process for supplying a surface conditioning agent to the surface of the hot-dip galvanized,
In a subsequent step of the surface conditioning agent supply step, a pre-drying step of drying the surface conditioning agent,
Wherein in the step after the previous drying step, the molten zinc-based with a treatment agent supply process for supplying a roll coating method treating agent containing zinc phosphate solution to the hot-dip galvanized surface, a zinc phosphate film containing plating A method of manufacturing a steel sheet.   The method for producing a hot-dip galvanized steel sheet having a zinc phosphate coating according to claim 1, wherein the surface conditioner in the surface conditioner supply step is an aqueous liquid containing zinc phosphate particles.   The average particle diameter of the zinc phosphate particles contained in the surface conditioner in the surface conditioner supply step is 10 µm or less, The production of a hot dip galvanized steel sheet having a zinc phosphate film according to claim 2 Method.   The average particle diameter of the zinc phosphate particles contained in the surface conditioner in the surface conditioner supply step is 10 µm or less, and the pH of the surface conditioner is 5 or more. A method for producing a hot-dip galvanized steel sheet having a zinc phosphate coating.   The surface conditioner in the surface conditioner supply step contains zinc phosphate particles in an amount of more than 0 mol / L and not more than 0.5 mol / L, and is selected from the group consisting of Li, Na, K, Be, Mg and Ca. 1 or more types are contained in total 0.3 mol / L or less, The manufacturing method of the hot dip galvanized steel sheet which has a zinc phosphate membrane | film | coat as described in any one of Claims 1-4 characterized by the above-mentioned.   The treatment agent in the treatment agent supply step contains 0.001 to 0.7 mol / L of a phosphate radical and contains 0.7 or less zinc ions in a molar ratio with respect to the phosphate radical. The manufacturing method of the hot dip galvanized steel plate which has a zinc phosphate membrane | film | coat as described in any one of claim | item 1 -5.   The aqueous zinc phosphate solution of the treatment agent in the treatment agent supply step contains zinc ions and phosphate radicals, has a pH of 4 or less, and has a molar ratio of 0.2 or less with respect to the phosphate radicals other than the zinc ions and phosphate radicals. It contains at least one selected from the group consisting of a strong electrolyte anion of nitrate radical, 0.2 or less nitrite radical, 0.1 or less hydrofluoric acid radical and 0.05 or less sulfate radical. The manufacturing method of the hot dip galvanized steel plate which has a zinc phosphate membrane | film | coat as described in any one of 1-6. The P adhering to the surface of the hot dip galvanizing by the surface adjusting agent supplying step and the treating agent supplying step is adjusted to 30 to 500 mg / m ² in terms of P. 8. The manufacturing method of the hot dip galvanized steel plate which has a zinc phosphate membrane | film | coat as described in a term.

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