JPH02290961A - Production of vapor-deposition aluminized steel sheet excellent in workability - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and formability by preheating a base steel sheet, vapor-depositing Cr, Ti, and Ni onto the above steel sheet, and then applying vapor-deposition aluminizing to the above. CONSTITUTION:One or more metals selected from Cr, Ti, and Ni are vapor- deposited onto a preheated cold rolled steel sheet to >=0.1g/m<2> thickness by using continuous vacuum vapor deposition plating equipment, etc. Successively, vapor-deposition aluminizing is applied to the above. Undercoat plating is applied for the purpose of preventing diffusion between the base steel sheet and the aluminizing layer, and it is desirable to reduce the thickness of this undercoat plating layer so far as its functions can be maintained. When the film thickness of the undercoat plating layer is small, this undercoat plating layer is alloyed with the aluminizing layer and transformed into a thin Al-alloy plating layer. This Al-alloy layer has superior adhesive strength to the base steel sheet as well as to the Al layer.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention is heat resistant. The present invention relates to a method for producing a vapor-deposited Al-plated steel sheet having excellent corrosion resistance and formability.

[Prior Art] Al-plated steel sheets are surface-treated steel sheets that have excellent properties such as heat resistance, corrosion resistance, heat reflection, and aesthetics, and are relatively inexpensive to produce, so they are used in automobile mufflers. Incinerator parts. It is widely used in home appliances, building materials, etc. In other words, Al-plated steel sheets utilize the various properties of Al to protect and beautify the surface of steel, and hot-dip plating and vapor deposition plating are currently in practical use as manufacturing methods. Electroplating methods are also under development.

As described above, although Al-plated steel sheet is a material with considerably excellent properties such as corrosion resistance, it has the following problems with regard to heat resistance and workability.

For example, a hot-dip Al-plated steel plate is manufactured by running the steel plate while immersing it in a molten Al bath, so the surface temperature of the steel plate rises to about 700°C. As a result, a thick Fe-Al intermetallic compound such as Fe2Al5 is formed at the bonding interface between the steel sheet base and the Al plating layer, and this intermetallic compound is brittle and has poor workability. However, when a forming process such as bending, particularly a strong forming process, is performed on an Al-plated steel sheet, a problem arises in that the Al-plated layer easily peels off.

Therefore, in order to suppress the formation of Fe-Al intermetallic compounds, molten Al-S was added with about 9% St in the molten Al bath.
A t-alloy plated steel sheet was proposed.

In other words, Al-Si alloy plated steel sheets retain Fe even in high-temperature environments.
-Since no Al intermetallic compounds are generated, it has superior formability and high-temperature oxidation resistance compared to Al-plated steel sheets. However, the Al-SL alloy plated steel sheet has a drawback in that the addition of Si reduces the corrosion resistance of Al. In addition, if it is used continuously in a high temperature environment of 600℃ or higher, or if it is used in an environment where heating and cooling are repeatedly repeated even at a temperature of less than 600℃, a rapid oxidation reaction will proceed, and eventually It cannot be said that it is necessarily sufficient in terms of heat resistance and the like.

On the other hand, in the case of vapor-deposited Al-plated steel sheets, the steel sheet temperature during plating is kept low, so there is less formation of Fe-Al intermetallic compounds at the interface between the base steel sheet and the plating layer, and there is generally no problem with workability. It is said that

However, recently, with the aim of further improving heat resistance and corrosion resistance,
There is a growing demand for increasing the thickness of Al plating (that is, the amount of coating), and in particular for thick Al-plated steel sheets with good workability, and this demand tends to become stronger.

It is not very difficult to obtain such a thick Al-plated steel sheet by hot-dip plating, but as the thickness increases, the formation of Fe-Al intermetallic compounds becomes more pronounced, so hot-dip plating is not practical. Can not do it.

Therefore, thick Al-plated steel sheets are manufactured using the vapor deposition plating method, but even if the coating weight of the Al plating is large, some Fe-Al intermetallic compounds may form between the Al plating layer and the substrate. Formed at the interface of steel plates. This is because in the vapor deposition Al plating method, when Al vapor is deposited on a base steel plate, the steel plate temperature rises due to the sensible heat and latent heat of the Al vapor, and when this temperature exceeds a certain value, the gap between the Al plating layer and the base steel plate increases. This is because this causes diffusion of Al and Fe. Furthermore, in the vapor deposition plating method, it is common to preheat the base steel plate for the purpose of improving adhesion, but this has a considerable effect on the formation of Fe-Al intermetallic compounds.

In other words, the vapor deposition Al plating method can obtain Al-plated steel sheets with better workability compared to the hot-dip Al plating method, but it does not always yield Al-plated steel sheets with satisfactory performance, especially thick Al-plated steel sheets. In the production of Fe-
The formation of Al intermetallic compounds cannot be avoided.

[Problems to be Solved by the Invention] The present invention has been made in view of these circumstances, and has been developed to provide a vapor-deposited aluminum-plated steel sheet that has better corrosion resistance and workability than hot-dip aluminum-plated steel sheets. In manufacturing, F
Vapor deposition with excellent workability that reliably suppresses the formation of e-Al intermetallic compounds and allows production of aluminum-plated steel sheets with a large Al coating weight without generating Fe-Al intermetallic compounds. The object of the present invention is to provide a method for manufacturing an Al-plated steel sheet.

[Means for Solving the Problems] According to the method of the present invention which has achieved the above object, when producing an Al-plated steel plate by a vapor deposition plating method, a material selected from the group consisting of Cr and TiNi is applied onto a preheated base steel plate. The gist lies in that one or more metals are vapor-deposited to a thickness of 0.1 g/+' or more, followed by Al vapor-deposited plating.

[Function] The present inventors investigated the following four methods as means for suppressing the formation of Fe-Al intermetallic compounds due to mutual diffusion between the base steel sheet and the Al plating layer.

(2) Lower the preheating temperature of the base steel plate to prevent the temperature of the base steel plate from rising excessively during or after forming the vapor-deposited Al plating layer.

■ Immediately after forming the vapor-deposited Al plating layer,
Cool the plated steel plate.

(2) An alloying element capable of suppressing diffusion between the base steel sheet and the Al plating layer is contained in the Al plating layer to prevent the formation of Fe-Al intermetallic compounds.

■Before forming the Al plating layer on the base steel plate,
An element or alloy that can prevent the diffusion of Al and Fe is vapor-deposited and plated, and this is used as a barrier layer to suppress the reaction between the Al plating layer and the base steel sheet.

Among the above four methods, (1) the method of lowering the preheating temperature of the base steel sheet lowers the temperature of the steel sheet after vapor deposition Al plating by the lower preheating temperature, and the diffusion of Fe and Al is promoted by the increase in the steel sheet temperature. That is, the formation of Fe-Al intermetallic compounds can be suppressed. However, if the preheating temperature of the steel sheet is lowered, the adhesion of the plating layer on the obtained vapor-deposited Al-plated steel sheet will deteriorate, and the surface appearance of the Al-plated steel sheet will change from silvery white to a slightly grayish dark gray, resulting in poor aesthetics. The commercial value of Al-plated steel sheets, which are characterized by Because of these drawbacks, method
There is a problem with the method of manufacturing l-plated steel sheets.

Next, the method (1) of immediately cooling the Al-plated steel sheet after forming the vapor-deposited Al plating layer suppresses the formation of Fe-Al intermetallic compounds by immediately lowering the temperature of the steel plate after vapor deposition, similar to the method (2). The present inventors installed water-cooled rolls in multiple stages in the post-processing part of the vapor deposition plating chamber, and adopted a method of bringing the vapor-deposited Al-plated steel sheet into contact with the water-cooling rolls to rapidly lower the sheet temperature. I considered it.

In addition, as a water-cooled roll, a 50 μm thick A is applied to the roll surface.
A steel roll on which a 1 2 0 3 + Z r O 2 ceramic film was thermally sprayed was used, and the roll had a structure in which cooling water circulated.

Although the above cooling method succeeded in rapidly lowering the plate temperature after vapor deposition plating and suppressing the formation of Fa-Al intermetallic compounds to some extent, the suppressing effect was insufficient, and Al pickup on the surface of the water-cooled roll did not occur. A phenomenon occurs and this is A
This caused pressure scratches on the surface of the L-plated steel plate, making long-term operation virtually impossible. That is, the vapor-deposited Al-plated steel sheet obtained by the method (2) has a poor appearance, and there are practical problems even if workability is maintained.

■The method of forming an Al alloy plating layer containing elements that can prevent the diffusion of Fe and Al on a base steel plate is being researched by the present inventors,
1060, JP-A-64-21062, etc. According to research by the present inventors, the alloying elements include Cr, Ti, Ni, Cu. St and the like are effective, and the addition of these alloying elements can achieve considerable results in preventing the formation of Fe-Al intermetallic compounds.

However, with the above vapor-deposited Al alloy plated steel sheet, it is difficult to stably form vapor-deposited Al alloy plating on the base steel sheet.
, Control of vapor amount of Al and alloying elements, Steam mixing technology. Various control techniques are required, such as controlling the Al alloy plating composition. In addition, Al-plated steel sheets have a silvery white surface and are characterized by excellent aesthetics.
In the Al alloy plated steel sheet, the color tone of the Al plating changes as the content of alloying elements increases, approaching dark gray. Therefore, although the processability is satisfactory, there are problems with stable productivity and appearance, and there is room for improvement.

As described above, all of the methods (1) to (2) have some kind of problem, and it is not possible to obtain an aluminum-plated steel plate (particularly a thick aluminum-plated steel plate) with satisfactory characteristics. On the other hand, the present invention attempts to solve the above-mentioned problem by adopting the method (2) of forming a barrier plating layer on the base steel plate and then applying Al vapor deposition plating. The purpose is to eliminate the shortcomings of the prior application method. In other words, considering that the formation of Fe-Al intermetallic compounds always proceeds at the interface between the base steel sheet and the Al plating layer, in order to prevent the Fe-Al diffusion reaction that occurs at the interface, it is necessary to provide such a function only to the interface. The thin barrier layer was formed at the interface between the base steel sheet and the Al-plated layer, based on the idea that it would be sufficient to use a material with performance similar to or better than that of a normal vapor-deposited Al-plated steel sheet except at the interface. It is something.

Further requirements for these barriers include (a) Fe-
exhibits the effect of inhibiting the formation of Al intermetallic compounds, (b
) The barrier layer has good adhesion to the Al-plated layer and the base steel sheet, and the barrier layer itself does not deteriorate workability; (C) does not impair the corrosion resistance of the vapor-deposited Al-plated steel sheet; (d) ) The aesthetic appearance of the vapor-deposited Al-plated steel sheet is not impaired.

The inventors of the present invention have repeatedly studied a configuration that satisfies all of these barrier conditions, and as a result, they have arrived at the method of the present invention that satisfies the above-mentioned requirements.

That is, in the present invention, after first applying one or more elements selected from the group consisting of Cr, Ti, and Ni as a base plating on a preheated base steel plate by a vacuum evaporation method,
Subsequently, Al vapor deposition plating is applied, and since the base plating is to prevent diffusion of the base steel sheet and the Al plating layer, making it thicker than necessary does not meet the purpose of the present invention. In addition, the Kowara base plating does not have to remain as it is after applying Al plating;
It is also possible to form an alloy by causing interdiffusion with the Al plating layer.

There are no particular restrictions on the thickness of the base plating layer, but if it is too thick, problems will occur with bending workability, etc., while if it is too thin, the above functions are not guaranteed, so it should be determined within an appropriate range. However, in normal cases, it is desirable that the thickness be as thin as possible while still maintaining the above functions. In other words, when the thickness of the base plating layer, that is, the basis weight is small, it changes into a thin Al alloy plating layer that is alloyed with the subsequently applied Al plating layer, and this thin Al alloy plating layer Since it has excellent adhesion with the plating layer and also maintains good adhesion with the base steel sheet, the resulting Al-plated steel sheet has very good plating adhesion overall and exhibits excellent workability. Furthermore, the Al alloy plating layer formed in this way exhibits a potential electrochemically closer to that of the Al plating layer than a single base plating layer of Cr, Ti, Ni, etc.
There is a very small electrochemical potential difference between the two and the galvanic layer in a corrosive environment.
Corrosion (potential corrosion) is less likely to occur, and vapor-deposited Al
The corrosion resistance of plated steel sheets can be improved. Also, Al
Although the influence of the base plating layer on the appearance of the plated steel sheet is not so great, it is preferable that the base plating layer is thinner.

For the reasons stated above, the thickness of the base plating layer such as Cr, Ni, Ti, etc. needs to have a basis weight of 0.1 g/n' or more, but it is desirable to make it as small as possible. The basis weight is 0.1g/
If it is less than m', the formation of Fe-Al intermetallic compounds cannot be completely suppressed, while if the basis weight is increased too much,
There is no point in increasing the basis weight unnecessarily, since not only the above-mentioned problems may occur, but also lead to an increase in cost. If I had to dare to say it, the upper limit is 1-5g/Il1
2nd place is appropriate.

The vapor deposition plating method employed in the present invention is not particularly limited, but a vacuum vapor deposition plating method using an electron beam (EB) heating method is preferred. Electron beams have a high output and are fully capable of depositing not only Al but also Cr, Ti, and Ni, and are excellent in productivity from an industrial perspective. It is also preferable to employ a so-called ion plating method, in which each of the metal vapors mentioned above is ionized using radio frequency waves or the like and deposited on a base steel plate to which a bias voltage is applied. The Al-plated steel sheet obtained by the ion-blating method has stronger adhesion between the steel sheet and the plating layer, and the plating layer itself is free from pinholes, so it is preferable in terms of corrosion resistance. Also, Cr, Ti
, Ni, when vapor-depositing only one of the above elements, prepare one crucible etc. suitable for each element and vapor-deposit only one element on the base steel plate. That's fine. On the other hand, when applying alloy plating such as a Cr-Ni alloy plating layer, the metals to be plated are evaporated from separate crucibles, mixed in a gas phase and then deposited, or alloyed in advance. It is also possible to evaporate from one crucible in a state in which the

Furthermore, as mentioned above, electron beam (EB) heating is preferable as the heating method for plating these metals or alloys, but since the amount of plating deposited is much smaller than that of Al plating, electron beam (EB) heating is preferable. The output of the wire does not need to be so large compared to that for evaporating Al, and therefore, the production of vapor-deposited Al-plated steel sheets by the method of the present invention has the same equipment cost and running cost as conventional methods, and is cost-effective. There is no problem.

[Example] The content of the present invention will be explained below using examples.

Using the continuous vacuum evaporation plating equipment shown in FIG.
1) Apply base vapor deposition plating of Cr, Ni, etc. in Step 2, and then pass through the connection duct to the vapor deposition chamber (No. 2) 1
Vapor-deposited Al plating was performed within 0.

The amount of plating deposited in each vapor deposition chamber was controlled by the output of the electron beam that heats and evaporates each metal and the line speed of the steel plate.

The following evaluations were performed on the various vapor-deposited Al-plated steel sheets obtained.

(Suppressing effect on the formation of Fe-Al intermetallic compounds) The cross section of the obtained vapor-deposited Al-plated steel sheet was observed, and the difference in the suppressing effect depending on the thickness of the Fe-Al intermetallic compound formed between the plating layer and the base steel sheet. investigated.

Table 1 shows the results.

The symbols have the following meanings.

◎: Effect of suppressing the formation of Fe-Al intermetallic compounds: (*O
: : Good △ : : Slightly inferior × : : Inferior (workability) The obtained vapor-deposited Al-plated steel sheet was subjected to bending and unbending processing tests, and evaluated by the amount of plating peeled off.

Table 1 shows the results.

The symbols in the table have the following meanings.

O: No peeling of plating △: 〃 Slightly present ×:〃 Yes (corrosion resistance) The obtained vapor-deposited Al-plated steel sheet was extruded using an Erichsen tester (extrusion] t7 m+n), and then a salt water spray test was conducted to confirm the corrosion of the Erichsen extruded part. Evaluation was made based on the time it took for red rust to develop from the steel plate. The evaluation method was based on how the red rust generation time changed compared to when Erichsen extrusion was not performed, and the presence or absence of deterioration of the corrosion resistance of the processed part was evaluated.

Table 1 shows the results.

The symbols in the table have the following meanings.

○: Compared to the corrosion resistance of the unprocessed part: Equal △: 〃: Slightly inferior ×: 〃: Inferior Comparative materials were also subjected to the same evaluation test as above, and the results are also listed in Table 1.

As is clear from Table 1, Experiment No. 1 showing an example of the present invention. 1
~3 or experiment no. For Nos. 5 to 11, a thin Al alloy plating layer was formed between the vapor-deposited Al plating layer and the base steel plate (however, for No. 7 and No. 9, a part of the Al alloy plating layer was not formed but a Ti alloy layer was formed). (or Ni remains), this layer exerts a parrying effect and prevents the formation of Fe-Al intermetallic compounds. Therefore, good results were shown in workability and corrosion resistance (corrosion resistance after processing).

Although not shown in the table, it was confirmed by microscopic cross-sectional observation that the Al alloy plating layer was not diffused or alloyed with the Fe of the base steel sheet, although it was thin.

Also, experiment no. As shown in Experiment No. 4, when the thickness of the base brushing film before applying the vapor-deposited Al plating layer is lower than the lower limit of the range of the present invention, or as shown in Experiment No. In the case of direct vapor deposition Al plating on the base steel plate as in No. 12, the formation of Fe-Al intermetallic compounds was insufficiently suppressed, and therefore the workability was clearly inferior to the example of the present invention. Furthermore, in the case of hot-dip Al-plated steel sheets (Experiment Nos. 13 to 15)
), Fe-Al is applied to the Al plating layer and the red part of the base steel plate
-The formation of a Si-based intermetallic compound layer is clearly enhanced,
The workability is inferior to that of the inventive example. Regarding corrosion resistance, in the case of the present invention example, there was almost no difference in the time taken for red rust to develop on the steel plate from the processed part compared to the unprocessed part, indicating excellent corrosion resistance. Although the details of the reason for this are unknown, it is thought that the thin Al alloy plating layer formed at the interface with the base steel plate contributes to maintaining corrosion resistance.

[Effects of the Invention] The present invention is configured as described above, and a vapor-deposited Al-plated steel sheet, particularly a thick vapor-deposited Al-plated steel sheet, excellent in heat resistance, corrosion resistance, and formability can be manufactured at a low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an apparatus for carrying out the method of the present invention. 1... Cold rolled steel plate 2... Vapor deposition chamber (No. 1)
3...Dissolution tank (No.1) 4...Evaporation raw material (Cr etc.) 5...Exhaust device 6...Deposition chamber (No.1) Person side roll 7...Connection duct entry side roll 8...Connection duct 9...Vaporization chamber (No. 2) Person side roll lO...Vaporization chamber (No. 2) 11...Dissolution tank (No. 2) 12...Evaporation raw material (Al )

Claims (1)

[Claims] When producing Al-plated steel sheets by vapor deposition plating, one or more metals selected from the group consisting of Cr, Ti, and Ni are applied to a preheated base steel sheet at a thickness of 0.1 g/m^2 or more. A method for producing a vapor-deposited Al-plated steel sheet with excellent workability, which comprises performing vapor deposition plating and then applying Al vapor deposition plating.