JPS6280262A - Plated steel sheet and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a corrosion and heat resistant plated steel sheet having superior workability by successively forming a Ti film and a titanium oxide film of a prescribed thickness on the surface of a steel sheet before plating with Al. CONSTITUTION:The surface of a steel sheet 1 is cleaned and the steel sheet 1 is fed to a heating chamber 4 through a differential pressure chamber 3 provided with sealing rolls 2 on the inlet side. After the steel sheet 1 is heated in the chamber 4, it is fed to a vapor deposition chamber 5, where Ti particles evaporated from a crucible 6 are ionized to plate the surface of the steel sheet 1 with Ti. The steel sheet 1 is fed to an oxidation chamber 7, where a titanium oxide film of <=0.1mum thickness is formed on the surface of the Ti layer with gaseous O2 blown from a nozzle 8. The steel sheet 1 is then fed to a vapor deposition chamber 9, where the surface of the titanium oxide film is plated with Al evaporated from a crucible 10, and the steel sheet 1 is coiled around a roll 12 through a differential pressure chamber 11 on the outlet side.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to improvements in aluminum-plated steel sheets.

[Prior art and its problems]

Hot dip aluminum plated steel sheets are well known as plated steel sheets with excellent corrosion resistance and heat resistance. However, when a pure At bath is used for hot-dip aluminum plating, a brittle Fe--At alloy layer grows significantly between the steel sheet and the At layer, and the plating layer peels off due to intense processing.

Therefore, a small amount of St is added to the At bath and At-8i alloy plating is performed to suppress the formation of the Fe-A1 alloy layer. This hot-dip At-81 alloy plated steel sheet has improved workability compared to hot-dip At-plated steel sheets, and
It has excellent high temperature oxidation resistance at temperatures below 00°C. However, when the temperature reaches 700 to 800°C, oxidation rapidly progresses and the heat resistance deteriorates.

For this reason, attempts have been made to improve the high-temperature oxidation resistance at 700 to 800°C by using an ultra-low carbon Cr-Ti killed steel plate as the base steel plate.

However, since these plated steel sheets are all made by hot dipping, it is inevitable that an alloy layer will be formed between the plating layer and the steel sheet, resulting in poor workability. Moreover, the film thickness of the plated steel sheet is as thick as several tens of micrometers or more, which is not economical.

Therefore, At plating by vacuum deposition has been developed in place of hot-dip plating. Vacuum deposition plating is a plating method in which At is heated and evaporated in a vacuum, and the vapor is condensed on a steel plate to form a highly pure At film on the steel plate. According to this method, no Fe-A1 alloy layer is formed between the At film and the steel sheet, and the resulting At-plated steel sheet can have excellent adhesion and workability.

However, in a vacuum-deposited At-plated steel sheet, there are many pinholes in the At film, and a corrosion current flows between the At layer near the pinholes and the Fe in the underlying steel sheet, causing M to rapidly dissolve. For this reason, sufficient corrosion resistance cannot be obtained. Moreover, 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.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and its object is to obtain a plated steel sheet that has corrosion resistance, heat resistance, and excellent workability.

[Structure of the invention]

The present invention is a plated steel sheet in which a titanium film, a titanium oxide film with a thickness of 0.1 μm or less, and an aluminum film are deposited on the surface of the steel sheet.

In addition, this invention performs ion plating or vacuum evaporation of titanium on the surface of a steel plate in a vacuum, and then spraying oxygen gas or an oxygen-containing gas or ion plating in an oxygen atmosphere! This is a method in which a titanium oxide film with a thickness of 0.1 μm or less is formed, and then aluminum is vacuum-deposited.

[Detailed description of the invention]

First, a titanium film is formed on the surface of the steel plate after cleaning it. Ion plating in a high vacuum or vacuum evaporation is preferable for forming a titanium film, and ion plating in a high vacuum is particularly suitable when a thin film thickness is to be obtained.

Note that ion plating in low or medium vacuum using an introduced gas such as DC discharge ion plating or high frequency discharge ion grating may also be used, but this method is less effective than high vacuum in terms of film adhesion and density. Inferior to ion plating. In this way, a dense film with few pinholes and good adhesion is produced. The thickness of this titanium film is preferably Q, 02 to 5 μm, particularly preferably 0.5 to 3.0 μm.

Next, oxygen gas or oxygen-containing gas is sprayed onto the titanium film to form a titanium oxide film. Alternatively, oxygen gas or oxygen-containing gas may be sprayed into the atmosphere in the latter half of the step of forming the titanium layer. Alternatively, a titanium oxide film may be formed by ion grating in an oxygen atmosphere.

The thickness of this titanium oxide layer is 0.1 μm or less.

This is because if the film thickness exceeds this, the adhesion and corrosion resistance after processing will decrease.

After that, an aluminum film is formed on the titanium oxide film. The preferred formation method is ion plating or vacuum deposition. This results in an aluminum film that is dense, has excellent workability, and has good adhesion to the base. The thickness of this film is preferably 0.5 to 20 μm, particularly preferably 2 to 8 μm.

According to this configuration, even if a pinhole exists in the aluminum film, it does not directly reach the underlying steel plate, improving corrosion resistance. In particular, the insulating titanium oxide film prevents corrosion current from flowing between the aluminum film and the Fe in the base steel sheet, so it can suppress the dissolution of At, and as a result, corrosion resistance can be significantly improved. .

Furthermore, during high-temperature heating, the titanium film and titanium oxide film prevent the Fs in the base steel sheet from diffusing into the aluminum film, and at the same time, oxygen diffusing from the surface layer combines with titanium to form oxides, so the titanium film and titanium oxide film prevent the Fs in the base steel sheet from diffusing into the aluminum film. Prevent diffusion to steel plates. As a result, high temperature oxidation resistance is significantly improved.

[Example] First, an At-killed steel plate having a thickness of 0.8 wz was pretreated with an Ar ion gompard. Namely 1. OX 10”-
A high frequency discharge is generated in an Ar gas atmosphere of 3 Torr,
At the same time, a negative voltage of -1 kV is applied to the steel plate to cause Ar ions to collide with the steel plate, thereby removing oxides and the like on the steel plate surface, thereby obtaining a clean steel plate surface.

Next, the steel plate is heated to 200°C and plated with titanium.

This process consists of 1. Put the titanium plated material into a water-cooled copper crucible at an atmospheric pressure of OX 10-” Torr or less,
The titanium particles were heated and evaporated by an electron beam of kV, 300 to 10,100 O, and the evaporated titanium particles were ionized by a molybdenum electrode to which a positive voltage of 20 V was applied, and -500 V was applied.
This is done by plating a steel plate to which a negative voltage of .

Further, oxygen gas is sprayed onto the surface of the steel sheet immediately after titanium plating to form a titanium oxide film.

After that, the atmospheric pressure was increased to 1. OX 10-5 Tor
Plate aluminum at a temperature below r. This process is
Place aluminum in a ceramic crucible, apply 10kV,
It is heated and evaporated with an electron beam of 300 to 10,100 O to plate a steel plate.

An example of an apparatus that performs such processing is the one shown in the figure. In Jin's apparatus, a coiled steel plate 1 is passed through an inlet differential pressure chamber 3 equipped with seal rolls 2 , heated in a heating chamber 4 , and then passed through a titanium deposition chamber 5 . Here, the titanium particles evaporated from Haruppo 6 are ionized and plated on the surface of the steel plate 1. After this, the steel plate 1 is passed through the oxidation chamber 7.

Here, the gas spraying forms a titanium oxide film on the surface of the titanium plating layer using oxygen gas sprayed from the nozzle 8. Next, the steel plate 1 is passed through an aluminum vapor deposition chamber 9. Here, aluminum evaporated from the crucible lθ is plated on the surface of the titanium oxide film. Then, the steel plate 1 is passed through the outlet side differential pressure chamber 11 and wound onto a winding roll 12.

By the above-mentioned plating treatment, plated steel sheets having a titanium film, a titanium oxide film, and an aluminum film were manufactured by changing the thickness of each film. In addition, for comparison, a plated steel sheet having a titanium film and an aluminum film without forming a residual titanium oxide film was manufactured.

These steel plates were examined for adhesion, adhesion after processing, corrosion resistance, corrosion resistance after processing, and heat resistance. Table 1 shows the results.
Shown below.

Adhesion was evaluated by a folded tape peel test.

In this test, a tape peeling test is performed every time a 180° OT bend is performed, and this is repeated until the base material breaks, and the presence or absence of peeling of the plating film is examined.
evaluated.

Adhesion after processing is Erichsen processing (7 crn extrusion)
Thereafter, a tape peel test was conducted to determine whether or not the plating layer peeled off.

Corrosion resistance was evaluated by a 5% salt spray test.

Corrosion resistance after processing was evaluated by a 5% salt spray test after Erichsen processing (7α extrusion).

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

However, adhesion and adhesion after processing○...No peeling×...Peeling Heat resistance○...Oxidation increase 5097m2 or less△...50-100g/n2 ×...10097m2 Corrosion resistance and corrosion resistance after processing ○...No red rust occurs after 300 hours Δ...Red rust occurs after 100-300 hours×...10
Red rust occurs within 0 hours The above table shows that the plated steel sheet of the present invention exhibits excellent adhesion and adhesion after working, but when the titanium oxide film exceeds 0.1 μm, the aluminum film peels off. It can also be seen that the plated steel sheet of the present invention has better corrosion resistance and post-processing corrosion resistance than the aluminum single-layer plated steel sheet and the aluminum/titanium double-layer plated steel sheet. Furthermore, it can be seen that when the titanium oxide film exceeds 0.1 μm, the corrosion resistance after processing deteriorates. Furthermore, it can be seen that the plated steel sheet of the present invention has excellent heat resistance.

[Brief explanation of drawings]

The drawing is an explanatory view of a plated steel sheet manufacturing apparatus showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... HA plate, 2... Seal roll, 3... Inlet side differential pressure chamber, 4... Heating chamber, 5... Titanium vapor deposition chamber, 6...
...Titanium crucible, 7...Oxidation chamber, 8...Nozzle for gas spraying, 9...Aluminum deposition chamber, 10...Aluminum crucible, 11...Output side differential pressure chamber, 12...
Take-up roll O

Claims (2)

[Claims] (1) A plated steel sheet formed by sequentially forming a titanium film, a titanium oxide film with a thickness of 0.1 μm or less, and an aluminum film on the surface of the steel sheet. (2) After ion plating or vacuum evaporating titanium on the surface of the steel sheet in vacuum, spray oxygen gas or oxygen-containing gas or ion plate it in an oxygen atmosphere to form a titanium oxide film with a thickness of 0.1 μm or less. A method for manufacturing a galvanized steel sheet, in which aluminum is formed and then vacuum-deposited with aluminum.