JPH07166329A - Production of material plated with al-cr alloy by vacuum deposition - Google Patents

Abstract

PURPOSE:To stably and continuously produce a material plated with an Al-Cr alloy by vacuum deposition and excellent in the appearance and quality by regulating the temp. of a material to be plated before and after plating at the time of continuous plating with the Al-Cr alloy by vacuum deposition. CONSTITUTION:A material to be plated is pretreated by reduction and activation or the like, Al-Cr mixed vapor is generated from an alloy bath in a single evaporating vessel in a vacuum vessel and at least one side of the material to be plated is continuously plated with an Al-Cr alloy by vacuum deposition. In this vacuum deposition method, the temp. of the material to be plated is controlled to >=200 deg.C before the beginning of plating and to <=400 deg.C at the end of plating. By this temp. control, the crystal structure of the resultant plating layer is preferentially oriented parallel to the substrate to prevent the tarnish of the surface of the plating layer such as blackening and to obtain high luster, and the satisfactory appearance and quality are secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing an Al-Cr alloy vapor-deposited plating material having excellent appearance quality. The material to be plated to which the present invention is applied includes ordinary steel, stainless steel, and various alloy steels,
Non-ferrous materials such as Al, Cu and Ti and alloy materials thereof are included. In the present invention, the most general purpose steel plate will be mainly described. The shape of the material to be plated is not particularly limited, and may be plate-shaped, rod-shaped, tubular, or the like.

[0002]

2. Description of the Related Art Hot-dip Al-plated steel sheets have excellent properties such as heat resistance, corrosion resistance, and heat reflectivity, and their production costs are relatively low. Therefore, they are used for automobile mufflers, home appliances, and building materials. , Has been widely used for incinerator members. However, in an environment where a large amount of halide ions such as Cl ⁻ ions exist in the Al-plated steel sheet, the passive film on the Al surface is easily destroyed by the halide ions, and pitting corrosion may occur in the plating layer. Many. White rust containing Al (OH) ₃ , which is a corrosion product of Al, as a main component is generated in the vicinity of the portion where the generated pitting corrosion occurs. Further, when pitting corrosion further progresses in the plating thickness direction and reaches the base steel sheet, there is a problem that red rust occurs due to corrosion of the steel sheet. For this reason,
For the purpose of improving the corrosion resistance, studies have been made on adding various metals such as Zn to the Al bath, but there are limits to the types and amounts of metals that can be added to the Al bath, and satisfactory results have not been obtained.

Further, a method of electrodepositing Al or Al alloy from a non-aqueous solution by the electroplating method has been studied.
Combined with the fact that the plating density is low due to the extremely low current density during electrodeposition and the plating bath is electrically unstable, many problems remain for practical use on an industrial scale. .

On the other hand, so-called continuous vacuum vapor deposition plating has been put to practical use, in which vaporized raw materials are heated and vaporized in a vacuum or a dilute gas atmosphere to continuously vapor-deposit the surface of a material to be plated that is running. As a method for heating and evaporating the evaporation raw material, an electric resistance heating method or a high frequency induction heating method can be adopted. However, by adopting a high energy source such as an electron beam, an ion beam or a laser beam, various refractory metals In addition to materials, it can be applied to non-metallic materials such as ceramics.

Such continuous vacuum deposition plating technique is
Studies have been carried out to improve the corrosion resistance of l-based plating materials. For example, in JP-A-64-21060 and JP-A-1-127665, Al and Cr are separately vacuum-deposited to form an Al-Cr alloy. A technique for obtaining a plated steel sheet, and Japanese Patent Laid-Open No. 1-188666 discloses a laminated vapor-deposited steel sheet in which a Cr plating layer is the bottom layer, an Al-Cr alloy plating layer is the middle layer, and an Al plating layer is the top layer. It has been disclosed and has succeeded in improving corrosion resistance.

However, these conventional Al-Cr vapor deposition plating methods require two evaporation source tanks for Al and Cr, and the evaporation rate must be controlled individually, but this control is extremely difficult. It was difficult, and the coating weight and alloy composition often varied. Cr is a sublimable substance that evaporates as a solid without forming a molten bath,
The means for replenishing the reduced amount of raw material by evaporation has not been established especially in the case of continuous vapor deposition, and the batch method in which the plating is interrupted when the raw material runs out has to be adopted.

In order to solve such a problem, the inventors of the present invention directly apply A to the Al--Cr alloy bath in a single evaporation tank.
We have found a method of vacuum evaporation of l-Cr mixed vapor and continuous vapor deposition, and are studying further improvement of corrosion resistance. For example, in Japanese Patent Application No. 5-36940, there is a result that corrosion resistance is improved by forming a crystal structure of a plating layer of α (Al) phase single phase in which Cr is solid-soluted in supersaturation, and Japanese Patent Application No. 5-6280.
No. 4 consists of α (Al) phase and θ (Al ₁₃ Cr ₂ ),
Moreover, the diffraction peak in X-ray diffraction has a surface spacing of 2.29 to
It has been shown that the workability and the red rust resistance were successfully improved by using two plating layer crystal structures existing in the range of 2.34Å.

However, the Al-- produced by the above method
Cr alloy vapor deposition plated products still have the problem that the product appearance is likely to change depending on the plating manufacturing conditions, and have a beautiful appearance that is one of the most important quality requirements in the fields of automobiles, home appliances, building materials, etc. At present, stable production of products has not been achieved yet.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and provides a method for stably continuously producing an Al-Cr alloy vapor deposition plated material having excellent appearance quality. The main purpose is to provide.

[0010]

The method for producing an Al—Cr alloy vapor deposition plated material according to the present invention, which has achieved the above-mentioned object, comprises a continuous pretreatment of at least one surface of the material to be plated with Al—Cr continuously. In the vacuum vapor deposition method for performing alloy vapor deposition plating, the point is to control the temperature of the material to be plated before starting vapor deposition plating to 200 ° C. or higher and to control the temperature of the plating material at the end of vapor deposition plating to 400 ° C. or lower.

[0011]

The present invention will be described in detail below along with the background to the achievement of the present invention. The present inventors used the continuous vapor deposition plating equipment shown in FIG. 1 to manufacture an Al—Cr alloy vapor deposition plated (hereinafter “plating” means “vapor deposition plating” unless otherwise specified) steel sheet. The manufacturing conditions and the obtained plating quality were examined.

FIG. 1 is an explanatory view showing an example of continuous plating equipment. In the figure, 1 is a steel plate as a material to be plated which moves in the direction of arrow A. The steel sheet 1 whose surface has been reduced and activated in the reduction furnace 2 is cooled to a predetermined temperature in the gas cooling zone 3 and then the atmospheric pressure is increased by the two connection chambers 41 and 42 and the inlet side vacuum seal device 5. It is introduced into the vacuum deposition chamber 6 after being reduced from atmospheric pressure to vacuum. After the plating, the pressure is returned to atmospheric pressure by the connection chambers 43 and 44 and the outlet-side vacuum seal device 7.

The inventors of the present invention have conducted various studies on the plating quality with the above-mentioned apparatus, and when the Al--Cr alloy vapor-deposited plating layer becomes defective due to a decrease in surface gloss, when the plating layer surface is blackened, In addition, we found that both of them may occur at the same time, and based on this finding, we investigated the cause of gloss reduction and the cause of blackening, and as a result, the temperature of the plated material before the start of vapor deposition plating was 200 ° C or higher, Moreover, it has been found that if the plating material temperature at the end of vapor deposition plating is controlled to 400 ° C. or lower, the surface quality does not deteriorate.

First, the surface temperature of the material to be plated before the start of vapor deposition plating must be 200 ° C. or higher. FIG. 2 shows the relationship between the temperature of the steel sheet before plating and the surface glossiness.
It can be seen that when the temperature is lower than 200 ° C., the lower the plate temperature before plating is, the significantly lower the surface gloss after plating. It was also clarified that when the temperature is lower than 200 ° C, the surface gloss remains low even when the plate temperature rises during or after the vapor deposition plating. At 200 ° C. or higher, it is possible to stably obtain a high glossiness. When the surface temperature of the material to be plated before plating is less than 200 ° C. and there is a non-uniform temperature distribution in the plate width direction, there arises a disadvantage that the temperature distribution position becomes uneven in gloss.

The reason why the surface temperature of the material to be plated before plating has a great influence on the surface gloss of the plating layer is considered as follows. Generally, the crystal grains of the plating layer obtained by vapor deposition plating should be columnar crystals with a fine diameter, but if fine irregularities due to individual columnar crystals are generated on the surface of the plating layer, the surface gloss decreases Conceivable. The cause of the unevenness is that the individual crystal grains forming the plating layer have various crystal orientations, or the growth rate of the crystal grains becomes non-uniform. When the crystal grains forming the plating layer have various crystal orientations, even if the plate temperature before plating decreases and the crystal grain growth rate becomes uneven, the gloss level of the plating layer only gradually decreases. Therefore, it is considered that the gloss does not decrease remarkably as studied by the present inventors.

Usually, the Al-Cr alloy vapor deposition plating layer contains Cr in the plating layer, and therefore crystals having a strong preferential orientation such that the (111) plane of the α (Al) phase is parallel to the substrate. It becomes a structure and shows high glossiness. However, if the plate temperature before plating decreases, the α (Al) phase (1
11) The degree of preferential orientation of the plane parallel to the substrate is reduced, and at the same time, individual grain growth rates are also non-uniform.
The reason why the growth rate becomes non-uniform is thought to be because the presence of Cr, which is a supersaturated solid solution in the plating layer, prevents the raw material vapor from moving to a stable position and condensing. Eventually, these factors are synergized to form fine irregularities on the surface of the plating layer, which reduces the surface gloss, and these effects are caused by the plate temperature before plating being 2%.
It appears remarkably when the temperature is lower than 00 ° C. Therefore, in the present invention, the surface temperature of the material to be plated before the start of vapor deposition plating must be 200 ° C. or higher.

In the present invention, in addition to the regulation of the plate temperature before plating,
It is also an essential requirement that the surface temperature of the plated material at the end of vapor deposition plating is 400 ° C or lower. If the temperature of the plated material after plating exceeds 400 ° C., the plated surface remarkably becomes black, which is not preferable. This is for the following reasons. During vapor deposition plating, the temperature of the material to be plated rises due to heat of vapor condensation and radiant heat from the evaporation tank during plating, but at this time, the residual oxidizing gas components in the vapor deposition chamber and the outermost surface of the plating layer React to form an oxide film. In the case of pure Al plating, the degree of blackening is small even if an oxide film is formed, but in the case of Al-Cr alloy plating, an Al-Cr-O-based composite oxide film is formed on the outermost surface of the plating layer. As a result, the degree of blackening becomes severe. It was revealed that this oxide film discolors significantly black when the temperature of the plated material after plating exceeds 400 ° C.
In the present invention, the surface temperature of the plated material at the end of vapor deposition plating is 40
Specified below 0 ° C.

The blackening of the oxide film on the surface of the plating layer not only deteriorates the appearance of the product, but the chemical conversion treatment performed as necessary after plating cannot be performed well, or the plastic deformation of the plating layer itself. It is very important to prevent blackening, because it causes problems such as deterioration of workability and deterioration of workability and poor adhesion. Further, if there is a part of 400 ° C. or higher in the plate width direction after plating, only that part will be black, and a band-shaped black pattern will be present in the traveling direction of the plated material. It is preferable to avoid temperature distribution in the plate width direction as much as possible.

In order to satisfy the temperature regulation conditions of the present invention, the temperature of the steel sheet before plating in the gas cooling zone 3 in FIG. 1 is controlled to be 200 ° C. or higher. Further, in the vapor deposition chamber 6, the steel plate temperature rises with an increase in the vapor deposition plating amount.
Do not exceed 0 ° C. Further, it is also an effective means to install the radiation thermometer 8 in the connection chambers 42 and 43 before and after the vacuum deposition chamber 6 in FIG.

[0020]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All modifications and implementations that do not depart from the spirit of the description below are included in the technical scope of the present invention. Example 1 Using the continuous vapor deposition plating equipment shown in FIG. 1, an Al—Cr alloy vapor deposition plated steel sheet was manufactured by changing the vapor deposition conditions as shown below and in Table 1, and the quality of the obtained plated material was examined. A study was conducted. The main manufacturing conditions other than those shown in Table 1 are as follows.

<Main manufacturing conditions> ・ Band material to be plated: Ultra low carbon Ti killed steel plate (plate thickness 0.6 mm) ・ Evaporation plating: Pierce type electron gun (maximum output: 3
(00 kW) was used as a heating source to perform vacuum deposition from an Al-Cr alloy bath.・ Deposition degree of vapor deposition chamber: 5 × 10 ^-3 to 2 × 10 ^-2 Pa ・ Method of measuring steel plate temperature before and after plating: Measured by radiation thermometers installed in connection chambers on the inlet and outlet sides of the vapor deposition chamber ・ Appearance evaluation standard・ Gloss ○: High gloss △: Medium gloss ×: Low gloss or uneven gloss ・ Blackening ○: No blackening part △: Light blackening part ×: Dark blackening part Table 1 The results are also shown.

[0022]

[Table 1]

Examples satisfying the conditions specified in the present invention
It can be seen that (Nos. 1 to 10) have high gloss, no blackened portion is observed, and exhibit excellent surface quality.

[0024]

The present invention is constituted as described above, and A
In continuously producing the 1-Cr alloy vapor deposition plated material, by regulating the surface temperature of the material to be plated before and after vapor deposition,
It has become possible to consistently obtain products with excellent appearance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of continuous vapor deposition plating equipment.

FIG. 2 is a graph showing the relationship between the surface temperature of a steel sheet before plating and the surface gloss of the plating layer.

[Explanation of symbols]

 1 material to be plated 2 gas reduction furnace 3 gas cooling zone 41, 42, 43, 44 connection chamber 5 inlet vacuum seal device 6 vacuum deposition chamber 7 outlet vacuum seal device 8 radiation thermometer 9 outlet gas cooling zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junji Kawafuku 2222 Ikeda, Ikeda, Ikeda, Onoe Town, Kakogawa City, Hyogo Prefecture 1 Kobe Steel Works, Kakogawa Research Area

Claims (1)

[Claims] 1. A vacuum vapor deposition method in which Al-Cr alloy vapor deposition plating is continuously performed on at least one surface of a pre-plated material surface to be plated, the temperature of the material to be plated before starting vapor deposition plating is 200 ° C. or higher, and Al-characterized by controlling the temperature of the plating material at the end of vapor deposition plating to 400 ° C or lower
Method for producing Cr alloy vapor deposition plated material.