JPH0322479B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a Zn-based composite electroplated steel sheet,
More specifically, it has excellent corrosion resistance and is suitable for various uses.
For example, the present invention relates to a Zn-based composite electroplated steel sheet containing metal powder that can be used as a steel sheet for automobiles. [Conventional technology and problems] In general, the corrosion resistance of automotive steel sheets in a corrosive environment includes not only bare corrosion resistance, but also painted corrosion resistance, that is, paint film adhesion, puncture resistance, hot water immersion adhesion of the paint film, Red rust resistance, etc. is required. For example, JP-A-56-133488 can be seen.
Conventionally used galvanized steel plates, such as the Zn-Fe two-layer plated steel plate and the Zn-Ni plated steel plate seen in Japanese Patent Publication No. 50-29821, have excellent corrosion resistance, but users As the required performance becomes more sophisticated, there is still room for improvement in terms of the puncture resistance of the external rust-resistant processed part. Furthermore, in Japanese Patent Publication No. 54-30649, a composite plated steel sheet in which A powder is dispersed in a Zn plated layer is
JP-A-60-211095 discloses a surface-treated steel sheet containing chromium, alumina, silica, and titania in the Zn-Ni alloy plating layer, but in order to satisfy the current performance requirements, It is still insufficient. [Means for Solving the Problems] In view of the above circumstances, the present inventors have conducted various experiments and found that Zn containing chromate-treated metal powder of a predetermined size, singly or in combination, within a predetermined amount. It has been found that composite galvanized steel sheets made of Zn alloy alone or made of Zn alloy have particularly improved external rust resistance and hole resistance in machined parts, and have better workability than conventional alloy coated steel sheets. . This is thought to be due to the fact that the elution rate of the metal powder contained in the plating layer is controlled by the barrier effect of the chromate treatment film, and the corrosion resistance is improved by creating a film of corrosion products with excellent corrosion resistance. It is thought that the chromate treatment film improved the compatibility between the metal powder and the matrix-plated metal, so the workability was also good. In addition, a composite plating layer formed of Zn alone or a Zn alloy containing metal powder subjected to chromate treatment can be used not only as a single layer plating but also as a lower layer of a plating layer having a two-layer structure. Or when used as an upper layer plating, due to its corrosion resistance,
It was also found to be extremely effective. [Structure and operation of the invention] The present invention has been made based on the above knowledge, and its gist is to provide a metal with an average grain size of 5μ or less that is chromate-treated on one or both sides of a steel plate. Contains 0.01-30% by weight of powder
A Zn-based composite electroplated steel sheet containing metal powder, characterized by having a Zn or Zn alloy plating layer. And on one or both sides of the steel plate, a chromate-treated metal powder with an average particle size of 5μ or less is applied as a lower layer.
Zn containing metal powder characterized by having a Zn or Zn alloy plating layer containing 0.01 to 30% by weight, and having a Zn or Zn alloy plating layer as an upper layer.
Composite electroplated steel sheet. and Zn or Zn alloy plating, which has a Zn or Zn alloy plating layer as the lower layer on one or both sides of the steel plate, and the upper layer contains 0.01 to 30% by weight of metal powder with an average particle size of 5μ or less that has been subjected to chromate treatment. Containing metal powder characterized by having a layer
Found in Zn-based composite electroplated steel sheets. The present invention will be explained in detail below. First, in the present invention, as the matrix plating layer containing metal powder, Zn alone, Zn-Ni, Zn-Fe, Zn-Co, Zn-Ni-
Co, Zn−Ni−Fe, Zn−Ni−Fe−Cr, Zn−Fe−
Co, Zn-Fe-Cr, Zn-Cr, Zn-Mn, Zn-Ti,
Zn alloy plating such as Zn-Sn, Zn-Cu, Zn-Pb, Zn-Cd, etc. is used. The plating thickness is not particularly limited, but from the viewpoint of the metal powder content or size and shape described later, a thickness of about 0.1 to 20 μm is effective. Note that alloy plating systems are effective in improving coating film adhesion. Next, the main point of the present invention is that the plating layer contains chromate-treated metal powder alone or in combination. In this case, the metal powder contained is A
, Ti, Nb, Ta, V, Mg, Fe, Cr, Ni, Co,
Powders of single metals such as Mo, W, Mn, Pb, Sn, Cu, and Zn, or alloy powders containing these elements as main components, each surface of which is subjected to chromate treatment, can be used. These are effective when used alone or in combination. In addition to improving corrosion resistance, the effects of the chromate treatment film applied to metal powder are to prevent dissolution of the metal powder in the plating bath, suppress the formation of a hydroxide film on the surface of the metal powder, and thereby improve matrix-plated metal and metal powder. The aim is to improve the familiarity of The effects of these chromate-treated films make it possible to stably and easily produce metal powder-containing Zn-based composite galvanized steel sheets with high corrosion resistance and good workability. In addition, in order to fully demonstrate these effects, the amount of chromate film applied to the metal powder must be 10 to 10%.
It is preferable to set it as 10000mg/ ^m2 . In addition, by setting the composition of the chromate film, that is, the weight ratio of Cr ³⁺ and Cr ⁶⁺ to Cr ³⁺ / (Cr ⁶⁺ + Cr ³⁺ ) = 0.5 to 1.0, it improves the puncture resistance and external rust resistance. There is a further improvement effect on Chromate treatment can be carried out by dipping, electrolyzing, spraying, brushing, etc. using an aqueous solution containing mainly chromic acid, which is a source of Cr ⁺⁶ , but it is difficult to uniformly form a chromate film on the metal powder. As a method for this purpose, a dipping method or an electrolytic method is more effective. In the case of the immersion method, a chromate treatment solution containing silica sol or Cr ³⁺ in addition to chromic acid may be used. In the case of electrolysis, it is preferable to electrolyze by contact with a cathode, for example, by placing metal powder in a metal cage and electrolyzing in a chromate treatment solution while using the cage itself as a cathode and moving the cage. In both the immersion method and the electrolytic method, SO ₄ ^2- , SiFe ^2- ,
Addition of small amounts of anions such as SeO ₄ ^2- and NO ₃ ^- is an effective method for increasing the amount of chromate film.
It goes without saying that it is better to perform a treatment such as pickling to remove an oxide film on the surface of the metal powder before the chromate treatment. The metal powder must have an average particle size of 5 μm or less, and from the viewpoint of processability, smaller particle sizes are preferred. If it exceeds 5μ, galvanic action between the metal powder and the matrix-plated metal becomes obvious, leading to local corrosion and poor fitting, resulting in processing defects. Moreover, the dispersibility in the plating bath becomes poor and sedimentation tends to occur. Note that the average particle size means the particle size with the largest distribution among all metal powders, and the particle size when the shape of the metal powder is other than spherical means the maximum diameter, for example, when the metal powder is scaly. It means maximum length, not thickness. Further, the content of metal powder in the plating layer is required to be 0.01 to 30% by weight. If it is less than 0.01% by weight, corrosion resistance will not improve, and if it exceeds 30% by weight, workability will deteriorate rapidly. Note that a more preferable upper limit is 10% by weight or less in terms of processability. Contains chromate-treated metal powder
Two composite plating layers made of Zn alone or Zn alloy
When plating the lower layer or upper layer of layer plating,
For other upper or lower layer plating, Zn alone or Zn alloy plating is used, similar to the matrix plating metal of the composite plating layer. There is no particular limit to this weight, but from the viewpoint of puncture resistance, 10
~150g/ ^m2 is desirable. Note that a Zn alloy plating layer is effective in improving coating film adhesion. The production of the galvanized steel sheet of the present invention is carried out using ordinary electric Zn
This is possible with plating lines. For example, using a sulfate bath or chloride bath with a pH of 1 to 3.0, the current density is 10 to
It can be manufactured under plating conditions of 200 A/dm ² and line speed of 10 to 250 m/min. As the base steel plate,
Various materials can be used, such as A-killed steel and high-tensile steel plates. Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples. [Example] Table 1 shows the chromate treatment (method, Cr adhesion amount) of metal powder, plating layer composition, corrosion resistance test, and workability test results of representative steel sheets of the present invention.
They are summarized in Tables 2 and 3. Table 1 shows the composite plating layer containing metal powder, Table 2 shows the lower layer of the two-layer plating is the composite plating layer, and the upper layer is Zn or Zn.
When the alloy plating layer is used, Table 3 shows the case where the lower layer of the two-layer plating is a Zn or Zn alloy plating layer, and the upper layer is the composite plating layer. The basis weight is 5±0.5μ as the plating thickness for a single layer of composite plating, 3±0.3μ for the thickness of the composite plating layer for two-layer plating, and the adhesion amount of the Zn or Zn alloy plating layer. , 10±0.5g/ ^m2 . For the chemical conversion treatment, we used a normal Zn phosphate dip type treatment and applied cationic ED coating. As a corrosion resistance test, cold cycle corrosion test (CCT:
Salt spray test 4 hours → dry 70℃, RH 60%, 2 hours → wet 49℃, RH 95%, 2 hours → cool -20℃,
One hour is one cycle. ) was carried out. In addition,
A hem-shaped laminated material was used as a sample for the hole resistance test of the processed part. On the other hand, workability was examined by a tape test for powdering properties after deep drawing cylindrical molding. The evaluation criteria for the test are as follows. (Corrosion resistance) Puncture resistance of machined parts…Maximum perforation depth after 50 cycles of CCT Less than 0.1mm 〇 0.1mm or more and less than 0.2 △ If more than 0.2mm × External rust resistance…Red rust resistance of cross cut portion Excellent 〇 Average △ Poor × Paint film adhesion...Maximum bulge width at cross cut after cross cut after 50 cycles of CCT Less than 3mm 〇 3mm to 5mm △ If more than 5mm × (Workability) Powling property...Degree of blackening in tape test after deep drawing cylindrical molding Less than 10% ◎ 10 % or more and less than 25% 〇 25% or more × (Overall evaluation) Best ◎ Good △ Excellent 〇 Poor ×

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〔Effect of the invention〕

As described above, the metal powder-containing Zn-based composite electroplated steel sheet of the present invention is a high-performance galvanized steel sheet with not only high corrosion resistance but also excellent workability, and its practical value is truly great.

Claims (1)

[Scope of Claims] 1. A metal characterized by having a Zn or Zn alloy plating layer containing 0.01 to 30% by weight of chromate-treated metal powder with an average particle size of 5μ or less on one or both sides of a steel plate. Powder-containing Zn-based composite electroplated steel sheet. 2. A Zn or Zn alloy plating layer containing 0.01 to 30% by weight of chromate-treated metal powder with an average particle size of 5 μ or less as a lower layer on one or both sides of the steel plate, and a Zn or Zn alloy plating layer as an upper layer. Containing metal powder characterized by having a layer
Zn-based composite electroplated steel sheet. 3 Zn as a lower layer on one or both sides of the steel plate.
Or metal powder-containing, characterized by having a Zn alloy plated layer and a Zn or Zn alloy plated layer containing 0.01 to 30% by weight of metal powder with an average particle size of 5μ or less that has been subjected to chromate treatment as the upper layer.
Zn-based composite electroplated steel sheet.