JPS62109967A - Heat resistant plated steel sheet - Google Patents

Abstract

PURPOSE:To obtain a plated steel sheet having superior corrosion and heat resistances and workability by successively forming a plated Cr film and a plated Al film on the surface of a steel sheet by vacuum deposition and by specifying the total thickness of the films and the proportion of the thickness of the Cr film. CONSTITUTION:A plated Cr film and a plated Al film are successively formed on the surface of a steel sheet by vacuum deposition. At this time, the total thickness of the films is regulated to 0.5-20mum and the thickness of the Cr film to <=50% of the total thickness, preferably to about 0.05-5mum. Thus, a plated steel sheet having superior workability and adhesion and also having superior corrosion and heat resistances is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plated steel sheet with excellent corrosion resistance, heat resistance and workability.

[Prior art and its problems]

BACKGROUND ART Hot-dip aluminum-plated steel sheets are well known as toughened steel sheets with excellent heat resistance and heat resistance. However, when hot-dip aluminum-plated steel sheets are manufactured using a pure aluminum bath, a brittle Fe-At alloy layer grows significantly between the steel sheet and the aluminum layer during hot-dip plating, and if the steel sheet is subjected to strong processing, The plating layer will peel off.

Therefore, a method has been used in which a small amount of St is added to the U bath and the steel plate is plated with Al-81 alloy to suppress the formation of the Fe-k1 alloy layer. Molten kt-S produced by this method
The i-alloy plated steel sheet has improved workability compared to the hot-dip At-plated steel sheet, and has excellent high-temperature oxidation resistance at 600° C. or lower. However, this steel plate has a resistance of 700 to 800
It is known that when the temperature reaches ℃, oxidation rapidly progresses and heat resistance deteriorates (Nissin Steel Technique No. 32).

In order to solve this problem, we developed ultra-low carbon C as the base steel plate.
Using r-Ti killed steel plate, this gives 700 to 80
Attempts have been made to improve high temperature oxidation resistance at temperatures as high as 0°C (Nissin Steel Technique No. 43). However, since these galvanized steel sheets are all hot-dip galvanized steel sheets,
Regardless of the presence or absence of additive elements in the At bath or the type of base steel sheet, it is inevitable that an alloy layer will be formed between the plating layer and the steel sheet, resulting in poor workability.

Furthermore, all of the plated steel sheets have a film thickness of several + titn or more, which poses an economical problem.

To solve these problems, At
By plating, F is created between the plating layer and the steel plate.
A method has been proposed that does not generate an e-At alloy layer, has excellent adhesion and workability, and allows thin plating (9
th, Vacuum Metal Conf.

of America Vac, Soc, +19
66) o However, vacuum-deposited At-plated steel sheets have many pinholes in the A/ film, and At
Corrosion current flows between the layer and the Fe in the base steel plate, and AA rapidly dissolves, so that sufficient corrosion resistance cannot be obtained. Further, at high temperatures, At and Fe are significantly alloyed, and oxidation of the base steel sheet progresses from the peeled portion of the alloy layer, resulting in a problem in that sufficient heat resistance cannot be obtained.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a plated steel sheet that utilizes vacuum evaporation plating and has excellent workability and adhesion, as well as excellent corrosion resistance and heat resistance.

[Means for solving problems]

In this invention, a chromium plating film and an aluminum plating film are formed in advance on the surface of a steel sheet, and the total thickness of both films is in the range of 0.5 to 20 fkm, and the thickness of the chromium plating film is in the range of 0.5 to 20 fkm. It is a heat-resistant plated steel sheet whose total film thickness is 50 times or less. The total thickness of the plating film on this steel plate is 0.5 to 201/rrL, preferably 2 to 8μ.
The range of m is good. If it is less than 0.5#1, sufficient corrosion resistance and heat resistance cannot be obtained, while if it exceeds 20#1, the temperature of the underlying steel plate may rise during film formation, which may impair the mechanical properties of the steel plate. It's not economical.

The thickness of the chrome plating film is 50% of the total film thickness.
less than or equal to This is because if it exceeds 50%, excellent corrosion resistance and heat resistance cannot be obtained.

This was confirmed from the experimental results of the present inventors.

The thickness of the chromium plating film is preferably 0.051
/I'n to 5 μm, particularly preferably 013 to 38 m. This is because the thinner the film, the smaller the effect, and the thicker the film, the worse the workability.

A plated steel sheet having this configuration is preferably manufactured, for example, as follows. A chromium plating film is formed on the surface of a steel plate by ion blating or vacuum deposition in a high vacuum, and an aluminum plating film is further formed on this chromium plating film by vacuum deposition. By performing ion derating or vacuum deposition in a high vacuum, a dense chromium plating film with few pinholes and good adhesion can be formed. Ion derating in a high vacuum is particularly desirable when making the chromium plating film thin. Note that ion brating in low to medium vacuum using introduced gas, such as DC discharge ion brating and high frequency discharge ion grating, is inferior to ion brating in high vacuum in terms of film adhesion and density. . Furthermore, when applying an aluminum plating film, in order to improve adhesion to the underlying chromium plating film, it is necessary to use a high vacuum that does not impair the activity of the chromium plating film surface. It should be noted that ion derating is not necessarily required because vacuum deposition provides an aluminum plating film that is dense, has excellent workability, and has excellent adhesion to the underlying chromium plating film.

[Operation and effect of the invention]

According to this plated steel sheet, even if a pinhole exists in the aluminum plating film, since there is a chrome plating film below it, it will not directly reach the underlying thin plate.
Corrosion resistance is significantly improved. Particularly during high-temperature heating, chromium plating diffuses into the base steel sheet and at the same time precipitates on the surface layer through the aluminum plating layer, forming a complete oxide protective film. This prevents oxygen from diffusing into the underlying steel sheet and significantly improves high-temperature oxidation resistance.

〔Example〕

Next, embodiments of the invention will be described.

FIG. 1 shows an example of the manufacturing process of a plated steel sheet.

First, pretreatment was performed using an At-killed Kasohita '1zAr ion yK board with a thickness of 0.8 mm. This preprocessing is 1
．． A high-frequency discharge is generated in an Arf atmosphere of 0x10 Torr, and a negative voltage of 1 kV is applied to the -blade steel plate to cause Ar ions to collide with the steel plate, removing oxides etc. on the steel plate surface and leaving a clean steel plate surface. This is a pretreatment method to obtain

Next, the steel plate is heated to 300°C and then plated with chromium.

At this time, the atmospheric pressure was 1.0 x 10 to 5 Torr or less, the chromium-plated material was placed in a water-cooled steel crucible, and the pressure was 10 kV.
It is heated and evaporated by an electron beam of 200 to 300 mA. The evaporated chromium particles are ionized by a molybdenum electrode to which a positive voltage of 20 V is applied, and plated on a steel plate to which a negative voltage of -5 oov is applied.

Subsequently, aluminum is plated on the chromium plating film at the same atmospheric pressure. This is done by putting the plating material aluminum in a ceramic crucible and applying 10kV, 300~
Plating is performed by heating and evaporating with an electron beam of 10,100 O.

By the method described above, a plated steel sheet is obtained in which a chromium plating film 2 and an aluminum plating film 3 are sequentially formed on a steel sheet 1 as shown in FIG. Here, a plated steel plate according to the present invention and a plated steel plate of a comparative example outside the scope of the present invention were manufactured by changing the thicknesses of the chromium plating film and the aluminum plating film. These plated steel sheets were examined for adhesion, corrosion resistance after processing, corrosion resistance, corrosion resistance after cutting, and heat resistance. The results are shown in Table 1.

Adhesion was evaluated by a bending tape peel test. This is done by performing a tape peel test every time a 180°at bend is performed, and repeating this until the base material breaks.
This is a test to check for peeling of the plating layer.

Evaluation of adhesion after processing is Erichsen processing (7a extrusion)
Corrosion resistance was evaluated by performing a post-tape peeling test to determine whether the plating layer peeled off or not, and by performing a 5-chip salt spray test.

The corrosion resistance after processing was evaluated by a 5-chip salt spray test after Erichsen processing (7 crrL extrusion).

Heat resistance was evaluated by oxidation weight increase when a heating cycle of heating at 800° C. for 48 hours in the air and air cooling to room temperature was repeated twice.

Adhesion and adhesion after processing■...No peeling×...Peeling Corrosion resistance and corrosion resistance after processing■...No red rust after 200 hours△...Red rust occurs after 100 to 200 hours×・・・１０
Red rust occurs within 0 hoursHeat resistance ■...Oxidation tank 9501//m" or lessΔ...50-100g/m2 ×...100!!/m2 or more As is clear from Table 1, adhesion In terms of corrosion resistance and post-processing adhesion, both Examples and Comparative Examples are excellent.On the other hand, the corrosion resistance and #f corrosion resistance after processing are excellent for the plated steel sheet of the present invention, which is A, but the single-layer plated steel sheet with the same film thickness (Al , A6. Haruka 9) and double-layer plated steel sheets (45, A8) in which the ratio of the thickness of the chromium plating film to the total film thickness exceeds 50% are deteriorated.

Regarding heat resistance, the plated steel sheet of the present invention has superior heat resistance compared to the plated steel sheet of the comparative example.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an example of a method for manufacturing a heat-resistant plated steel sheet of the present invention, and FIG. 2 is a sectional view showing an example of a heat-resistant plated steel sheet of the present invention. 1...1.1 plate, 2...chrome plated steel plate, 3...
・Aluminium-plated steel plate. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Commissioner of the Patent Office Michibe Uga 1, Indication of the case Japanese Patent Application No. 1988-250498 2, Name of the invention Heat-resistant plated steel plate 3, Amendments to be made Relationship with the case Patent applicant (412) Nippon Shogi Co., Ltd. 4, Agent 6, Specification subject to amendment 7, Contents of amendment (1) “2” on page 12, lines 7 to 8 of the specification・・・
・Correct the phrase ``chromium-plated steel sheet, 3...aluminum-plated steel sheet'' to ``2...chromium plating layer, 3...aluminum plating layer.''

Claims (1)

[Claims] A chromium plating film and an aluminum plating film are sequentially formed on the surface of a steel sheet, and the total thickness of both films is in the range of 0.5 to 20 μm, and the thickness of the chrome plating film is the sum of the thicknesses of both films. Heat-resistant plated steel sheet with a heat resistance of 50% or less.