JPH03170659A - Vapor deposition zn-cr plating material excellent in workability and its production - Google Patents

Abstract

PURPOSE:To form a Zn-Cr alloy plating layer free from peeling at the time of working, such as press forming, and excellent in corrosion resistance by vapor-depositing a Zn-Cr alloy reduced in oxygen content and having a specific composition onto the surface of a metallic member. CONSTITUTION:A steel sheet or a nonferrous metal sheet is placed in a vacuum vapor deposition apparatus and Zn and Cr in the apparatus are heated and evaporated by means of an electron beam, by which a vapor-deposition plating layer of Zn-Cr alloy consisting of 1-40wt.% Cr and the balance Zn is formed on the surface of the steel sheet, etc. At this time, O2 content in the Zn-Cr vapor deposition plating layer is regulated to <=100ppm by holding O2 concentration in the vapor deposition chamber at <=20ppm, by which a Zn-Cr vapor deposition plated steel sheet free from the occurrence of the peeling of plating, such as powdering, at the time of working, such as press forming, and excellent in corrosion resistance can be produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable in the field of application of anti-corrosion materials such as vehicles, electrical equipment, and construction materials, especially in the field of application of anti-rust materials such as vehicles, electrical equipment, and construction materials. This invention relates to a vapor-deposited Zn-Cr plating material that has excellent workability and is free of metal oxides.The plating base materials used in the present invention include iron and iron-based alloys, as well as non-ferrous metals such as copper and aluminum, and alloys thereof. Although there are no examples, and the shape may be plate-shaped, corrugated plate-shaped, tubular-shaped, rod-shaped, etc., the following explanation will mainly be based on the most typical steel plate.

[Conventional technology] Zn plating has been widely used as a plating method with high rust prevention effects. However, there is an increasing demand for improved corrosion resistance, and conventional Zn-plated steel sheets are no longer able to fully meet the demands of customers.

Against this background, Zn-Ni, Zn-Fe. Zn-
Mn. Various Zn alloy coated steel sheets such as Zn-Cr and Zn-A1 have been developed by electroplating method and hot-dip plating method C.
Among them, Zn-Cr alloy plating by electroplating method (
JP-A-63-243295) showed excellent corrosion resistance. The present inventors focused on the corrosion resistance of Cr and tried manufacturing it by the steam-refreshing method. As a result, we found that when the Cr content was 1 to 70% by weight and the X-ray diffraction pattern of the plating layer was 3.
It was discovered that Zn-Cr plating, which shows two or more diffraction peaks in addition to the peak of the Zn (002) plane within the range of 0 to 50 degrees, has particularly excellent corrosion resistance.
1111864) L/ta.

[Problems to be Solved by the Invention] In the above-mentioned applications, molding is often performed after plating, and therefore workability is also one of the important required characteristics. However, in conventional electroplating methods, Cr tends to eutectoid in the form of oxides and hydroxides during plating, and although these oxides and hydroxides do not have a negative effect on corrosion resistance, they cannot be processed during processing such as press forming. If this is added, there is a problem in that plating peeling such as bordering is likely to occur. As a countermeasure against this, attempts have been made to add formate, amino group-containing compounds, etc. to the plating as complex ion forming agents or antioxidants to increase the precipitation ratio as metal Cr, but this is not yet sufficient. On the other hand, vapor deposition plating is known as a general-purpose plating method other than electroplating, but even this method does not provide satisfactory workability at present.

The present invention has been made in view of the above-mentioned circumstances, and is particularly intended to improve vapor deposition plating, and to provide a vapor deposited Zn-Cr plating material with excellent workability and a method for producing the same. It is something to do.

[A Thousand Steps to Solve the Problem] The vapor-deposited Zn-Cr plating material according to the present invention has a Cr content in the plating layer of 1 to 401i%, and an oxygen content of 10 to 401i% in the plating layer. The point is that it is 0 ppm or less. Further, the above-mentioned plating material can be manufactured by controlling the oxygen concentration in the vapor deposition chamber to 20 ppm or less.

[Function] As a result of repeated studies from the viewpoint of workability, the present inventors have found that the amount of powdering during processing changes depending on the Cr content in the vapor-deposited Zn-Cr plating layer and manufacturing conditions.

Therefore, a more detailed investigation revealed that Zn-C varies depending on the oxygen concentration in the deposition chamber during plating.
It has been found that the oxygen concentration in the r-plating layer has a large effect on workability.

For example, Figure 1 shows the relationship between the oxygen content in the plating layer of a vapor-deposited Zn-Cr plated steel sheet and the amount of plating peeled off by a drawbead test. It can be seen that the amount of plating peeling increases rapidly.

Therefore, the oxygen content needs to be 100 ppm or less. Although the cause of this has not been determined theoretically, some of the Cr in the plating layer combines with oxygen, weakening the metal bond, and as a result, the plating layer easily peels off into powder during processing. It is presumed that this was the case.

The Cr content in the plating layer needs to be 1 to 40% by weight. If it is less than 1% by weight, the plating layer is soft and flaking is likely to occur, and no improvement in corrosion resistance can be expected by adding Cr. Moreover, if it exceeds 40% by weight, the plating layer becomes too hard and bacterium tends to occur.

Vapor-deposited Zn-Cr in which the oxygen content in the plating layer is 100 ppm or less and the Cr content is 1 to 401i%
The alloy plating material has excellent workability because the plating layer itself has sufficient intermetallic bond strength and appropriate hardness, and also has excellent corrosion resistance because it contains an appropriate amount of Cr.

To obtain the plating material according to the present invention, the oxygen concentration is 20p.
Zn and Cr can be manufactured by heating and vaporizing Zn and Cr from a crucible in a deposition chamber with a temperature below pm and depositing them on a steel plate placed above the crucible. Oxygen concentration is 2 0 1
If it exceeds 1911, the probability of reaction with evaporated Cr vapor increases, resulting in an increase in the oxygen concentration in the deposited plating layer.
The plating layer will peel off easily. Oxygen concentration 20p
As a method to reduce the pm or less, I
The following methods include a method of reducing the pressure and a method of replacing with argon gas, nitrogen gas, etc. Furthermore, it is preferable to use raw materials for evaporation that have a purity of 99.9% or higher. Furthermore, even if the oxygen concentration in the deposition chamber is the same, if the deposition rate becomes slower, the rate at which evaporated Cr reacts with oxygen in the chamber increases before it is deposited on the substrate, and as a result, the 02 concentration in the deposit increases. It is preferable that the evaporation rate be faster to some extent. [Example] Example and Comparative Example Two crucibles were placed in a vacuum evaporation apparatus, Zn and Cr were charged into each crucible, and the pressure inside the apparatus was reduced to 2 x 10'' Torr.
A steel plate (electrolytic polished steel plate, thickness: 0.6m+o, preheating temperature: 250°C) was prepared by heating and evaporating Zn and C' with an electron beam while maintaining the temperature below r.
A Zn-Cr alloy was deposited on the surface. At this time, Zn and C
The amount of evaporation was adjusted by controlling the output of the electron beam irradiated to r, and the Cr content in the Zn-Cr alloy plating layer was varied in the range of O to 601i%.

Table 1 shows the results of measuring the oxygen concentration in the deposition chamber during vapor deposition, the oxygen content in the obtained plating layer, and workability.

The workability of the plating layer was evaluated as follows based on the amount of plating peeled off by a drawbead test.

○...Plating peeling amount 0.2g/m" or less △...
〃0.2~1.0g/m'×... n
l. Og/tn2 or more Table 1 As shown in Table 1, Comparative Example 1 has a low Cr content and is likely to cause flaking, while Comparative Examples 2 and 3 have a low Cr content.
Due to the high content, the plating layer becomes hard and powdering easily occurs, and in Comparative Examples 4 and 5, the plating layer has a high oxygen content, so it easily peels off into powder, and each has poor workability for some reason. On the other hand, the examples exhibited excellent workability without causing any bagging or the like.

[Effects of the Invention] The present invention is configured as described above, and can provide a Zn-Cr alloy plated material with good workability while ensuring excellent corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the oxygen content in the plating layer of a vapor-deposited Zn-Cr plated steel sheet and the amount of plating peeled off in a drawbead test.

Claims (2)

[Claims] (1) Workability of a vapor-deposited Zn-Cr plating material, characterized in that the Cr content in the plating layer is 1 to 40% by weight, and the oxygen content in the plating layer is 100 ppm or less Vapor-deposited Zn-Cr plating material with excellent properties. (2) A method for producing a vapor-deposited Zn-Cr plating material with excellent workability, which comprises controlling the oxygen concentration in the vapor deposition chamber to 20 ppm or less when producing the vapor-deposited Zn-Cr plating.