JPH0414174B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is particularly aimed at obtaining a material that has excellent corrosion resistance and does not peel or crack in the plating layer even when subjected to bending, by melt plating the surface of a steel material. Highly corrosion resistant and workable Zn for hot-dip plating
It concerns alloys. [Prior Art] In general, as a cheap and simple method for improving the corrosion resistance of steel materials, it is known that hot-plating Zn or Zn alloys is applied to the surface of steel materials. have been proposed. [Problems to be solved by the invention] It is true that steel materials have relatively good corrosion resistance through hot-dip plating of these conventional Zn alloys, but if this material is placed in a harsh use environment, However, it does not necessarily show sufficient corrosion resistance, and there is usually brittleness between the base material and the matte material.
Since a Fe--Zn alloy layer is formed, when this is subjected to bending, peeling and cracking of the plating layer cannot be avoided. [Means for Solving the Problems] Therefore, from the above-mentioned viewpoints, the present inventors have discovered that the glazed layer exhibits excellent corrosion resistance even under severe usage conditions, and that the glazed layer remains intact even after bending. In order to reliably and easily obtain hot-dip plating products that do not cause peeling or cracking, we conducted research on Zn alloys for hot-dip plating, and found that one of Ni and Co was added to Zn.
When one species or two species are contained, it combines with Zn and becomes Zn.
-Ni alloy, Zn-Co alloy, and Zn-Ni-Co alloy are formed, and since these alloys all have good compatibility with Ti, the range of Ti content in Zn has been expanded, Furthermore, Ni and Co components include Ti.
In addition to having the effect of uniformly dispersing and precipitating compounds,
The Zn alloy has the effect of refining the crystal grains of the alloy itself, and the Ti content has increased due to the inclusion of Ni and Co, and the crystals have become finer.
It has extremely good corrosion resistance, and
On the other hand, when Al and, if necessary, Si are further included, the formation of Fe-Zn and Fe-Ti alloy layers between the plating layer and the substrate is significantly suppressed.
During bending, there is no phenomenon of plating layer peeling or cracking caused by the earlier Fe-Zn or Fe-Ti alloy layer, and when Mg is added, the viscosity of the plating layer increases and the plating film As the Ti content increases, the thickness of the plating film also increases, which improves the corrosion resistance of the plating film, and reduces the effect of Al, which has the opposite effect to Mg, that is, the viscosity of the plating film. This reduces the Ti content in the plating film and at the same time prevents the action of Al, which reduces the thickness of the plating film. It was found that the addition of Al increases the thickness of the plating film against the action of Al, in other words, the thickness of the plating film can be controlled by controlling the amount of addition. Therefore, this invention was invented based on the above-mentioned knowledge, and in weight% (hereinafter, unless otherwise specified, all percentages mean weight%), Ti: 0.1 to 2%, One or two of Ni and Co: 0.1 to 1.6
%, Al: 0.08 to 5.0%, Mg: 0.01 to 0.8%, and if necessary, Si: 0.01 to 0.3%, with the remainder consisting of Zn and unavoidable impurities, especially When used for melt plating the surface of a steel material, it enables stable use over a long period of time in a severe corrosive environment of the steel material, and enables bending without peeling or cracking of the plating layer. This is a Zn alloy with high corrosion resistance and high workability for hot-dip plating. Next, the reason why the composition range of the Zn alloy of the present invention is limited as described above will be explained. (a) Ti The Ti component has the effect of imparting excellent corrosion resistance that satisfies even under severe corrosive environments, but if its content is less than 0.1%, the desired excellent corrosion resistance cannot be achieved. If the content exceeds 2%, the plating workability will be impaired, and therefore, in order to maintain the plating workability in a good condition, the molten plating bath temperature must be considerably high, and as a result, the Since the plating material dissolves in the plating bath and significantly disturbs the bath composition, its content was determined to be 0.1 to 2%. (b) Ni and Co As mentioned above, these components increase the solid solubility of Ti in the Zn matrix and refine the crystal grains and partially dispersed precipitated Ti compounds.
It has the effect of uniformly distributing Ti compounds and improving corrosion resistance, and when one or both of Ni and Co are added, the content increases.
If the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 1.6%, the toughness of the alloy will be extremely deteriorated and the plating layer will be more likely to crack or peel. The content was set at 0.1-1.6%. (c) Al The Al component includes Fe-Zn, which is brittle between the surface of the substrate and the plating layer during melt plating as described above.
It suppresses the formation of an Fe-Ti alloy layer, prevents peeling and cracking of the plating layer caused by the Fe-Zn and Fe-Ti alloy layers during bending, and contains Ni and Co. It has the effect of mitigating the hardening of the plating layer due to
If the content is less than 0.08%, the desired effect cannot be obtained, while if the content exceeds 5.0%, the corrosion resistance will decrease.
It was set at 0.08-5.0%. (d) Mg The Mg component prevents intergranular corrosion, prevents the formation of the Fe-Zn and Fe-Ti alloy layers mentioned above through interaction with Al, and prevents these during bending. In addition to preventing peeling and cracking of the plating layer caused by the alloy layer, as mentioned above, the viscosity of the plating bath is increased to increase the thickness of the plating film, and the concentration of Ti dissolved in the film is increased. Since the Mg component has the effect of improving the corrosion resistance of the plating film, it is added not only to improve the workability and corrosion resistance described above, but also to adjust the thickness of the plating film. If the content is less than 0.01%, the desired effect cannot be obtained, while if the content exceeds 0.8%,
Since the viscosity of the plating bath would increase too much and the plating workability would be impaired, its content was set at 0.01 to 0.8%. (e) Si The Si component not only improves the fluidity of the plating bath to form a smooth and glossy plating layer, but also
It has the effect of further suppressing the formation of Fe-Zn and Fe-Ti alloy layers and dramatically improving corrosion resistance, so it is included as necessary when these characteristics are particularly required. If it is less than 0.01%, the desired effect of improving the above action cannot be obtained;
On the other hand, if the content exceeds 0.3%, the plating properties will be impaired, so the content should be adjusted accordingly.
It was set at 0.01-0.3%. Next, the Zn alloy of the present invention will be explained using examples and comparing with comparative examples. [Example] Zn alloys 1 to 15 of the present invention, comparative Zn alloys 1 to 4, conventionally plated metal Zn, and conventionally plated alloy Zn-0.2Al, each having the composition shown in Table 1.
A molten plating bath was prepared, and then ZnCl ₂ -
The Zn alloy plated steel plates 1 to 1 of the present invention are prepared by immersing a steel plate with a thickness of 0.4 mm pretreated with NH ₄ Cl-based flux for 5 seconds to form a plating layer with a thickness of 13 μm on one side on the surface of the steel plate. 15. Comparative Zn alloy plated steel plates 1 to 4, conventional pure Zn plated steel plates, and Zn-0.2L alloy steel plates were manufactured, respectively. In addition,
Comparative Zn alloys 1 to 4 all have compositions in which the content of one of their constituent components (marked with * in Table 1) is outside the scope of the present invention. Next, for each of these steel plates, JIS/
A salt spray test based on Z2371, a hammer test based on JIS/H0401, and a bending test based on JIS/Z2248 were conducted. The presence or absence of peeling and lifting of the plating layer due to impact was examined. If there was no peeling or lifting of the plating layer at all, mark ◎, and if peeling or lifting was observed in the plating layer, mark ×. In addition, in the bending test, the state of the plating layer on the bent surface was observed, and if there was no peeling or cracking in the plating layer, it would be marked ◎, and if there was no peeling or cracking in the plating layer, it would be evaluated as ◎. ○ if there is a case
Peeling and cracking are observed on the markings and plating layer.

【table】

〔Effect of the invention〕

From the results shown in Table 1, the present invention Zn alloy 1
Each of the present invention was melt-plated by ~15
Zn alloy plated steel sheets 1 to 15 all exhibit excellent corrosion resistance, and the invention alloys 1 to 15 form a plated layer with excellent adhesion that does not peel or crack at all even when bent or hit. In contrast, in comparative Zn alloy plated steel sheets 1 to 4, each of which was hot-dip plated with comparative Zn alloys 1 to 4 having a composition in which the content of any one of the constituent components was outside the scope of the present invention. is corrosion resistance,
This shows poor results in at least one of the formation of the alloy layer and the bending evaluation. Further, in the conventional Zn-plated steel sheets 1 and 2, a Fe--Zn alloy layer was formed, and the corrosion resistance and adhesion of the plating layer were significantly deteriorated. Furthermore, as seen in the Zn alloy plated steel sheets 1 to 3 of the present invention, a predetermined amount of one or two of Ni and Co is added.
It can be seen that the higher the Ti content in the presence of seeds, Al and Mg, and in some cases Si, the better its corrosion resistance. In addition, in addition to hot-plating with the Zn alloy of the present invention,
It was confirmed that further chromate treatment further improves corrosion resistance. As mentioned above, according to the highly corrosion-resistant Zn alloy for hot-dip plating of the present invention, excellent corrosion resistance can be ensured even under severe usage conditions, especially by hot-plating the surface of steel materials. It also has extremely good adhesion to the surface of steel materials and is brittle.
Since there is almost no formation of Fe-Zn or Fe-Ti alloy layers, there is no peeling or cracking of the plating layer during bending, and the thickness of the plating film can be easily adjusted, which is generally compared to sheet materials. However, it is also suitable for shapes such as angles that require a thick plating layer.
Various industrially useful effects are brought about by being able to apply a sufficiently thick plating layer having the above characteristics.

Claims (1)

[Claims] 1 Ti: 0.1 to 2%, one or two of Ni and Co: 0.1 to 1.6
%, Al: 0.08 to 5.0%, Mg: 0.01 to 0.8%, with the remainder consisting of Zn and unavoidable impurities (weight %), with high corrosion resistance and high workability for hot-dip plating. Zn alloy. 2 Ti: 0.1-2%, one or two of Ni and Co: 0.1-1.6
%, Al: 0.08 to 5.0%, Mg: 0.01 to 0.8%, and further contains Si: 0.01 to 0.3%, with the remainder consisting of Zn and unavoidable impurities (weight %). Highly corrosion resistant and highly workable Zn alloy for hot-dip plating.