JPS63100192A - Double-layer played steel sheet - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a two-layer plated steel sheet having an Al alloy layer on the surface and having excellent heat resistance and corrosion resistance, which can be manufactured industrially by electroplating.

(Conventional technique + Fi) Al and M alloy plated steel sheets (hereinafter referred to as Al-based plated steel sheets) exhibit corrosion resistance superior to ordinary Zn-plated steel sheets, and are also highly effective in preventing oxidation of steel at high temperatures.
Used as an economical heat-resistant or corrosion-resistant material.

However, conventional Al-based plating is mostly done by molten metal immersion plating, and the amount of plating deposited is 2 on one side.
Only comparatively thick Al-plated steel sheets of 0 to 100 g/r/m were manufactured. In addition, since Al-based hot-dip plating is performed at high temperatures of 700°C or higher, it has a negative effect on the base material, and furthermore, there is a possibility that brittle Fe may be formed between the plating film and the steel sheet base.
- There was a serious problem in that the Al alloy layer developed and the workability of the steel sheet inevitably deteriorated.

On the other hand, it has been considered for some time that Al-based plating can be performed using electroplating methods that can be operated at low temperatures, but since Al cannot be completely electrodeposited from an aqueous solution, aluminum chloride (AI2C23) is mainly used. Electroplating in a molten salt bath using mixed chlorides with alkali chloride added as a flux has been considered as a practical Al-based electroplating method (for example, Japanese Patent Publications No. 45-29085 and No. 48- (See Publication No. 38064).

As pointed out in the above-mentioned Japanese Patent Publication No. 48-38064, when the HeQ electroplated steel sheet is used as a heat-resistant material at high temperatures, the Al plating film forms an alloy layer with the base material Fe. Adhesion deteriorates, and alloying spreads over the entire plating layer due to long-term use, resulting in Fe-Al alloy reaching the surface.

Although this Fe-A2 alloy film is effective in preventing high-temperature oxidation of steel, its corrosion resistance at room temperature is inferior to that of pure Al. Therefore, in the method described in the above publication, electrolytic Ni plating is performed using a sulfamine nickel bath as a base treatment, and by interposing a Ni plating layer as a lower layer, alloying of Al and Fe is prevented and The aim is to prevent deterioration of heat resistance due to the use of However, this base N
The thickness of the i-layer is 5 to 10 μ-, which corresponds to about 40 to 80 g/d when converted to a coating weight, and is quite thick, so it is not only expensive, but also difficult to coat with the upper and lower plating layers. It was found that the adhesion with the steel sheet decreased and the end face corrosion resistance was poor.

By the way, electrolytic Q plating using a molten salt bath cannot produce a beautiful, high-quality plating film unless it is operated at a low current density. In operation in the above practical current density range, the plating film becomes dendritic or powdery, and this deterioration in plating quality also deteriorates corrosion resistance. In order to overcome these drawbacks of electroplating with Al, it has been proposed to add Mn salt to a molten salt bath to form a Q-Mn alloy electroplating film. This Al-Mn
Alloy plating is said to have heat resistance comparable to M plating, and its corrosion resistance is even better than Al.

(Problems to be Solved by the Invention) The present inventors investigated the use of Al-Mn alloy coated steel sheets as heat-resistant materials and found that Q-Mn alloy plating is similar to pure Al plating. However, when exposed to high temperatures, Al forms an alloy layer with the underlying Fe, resulting in poor corrosion resistance.Moreover, at high temperatures of 500°C or higher, the alloy between the underlying Fe and Al forms within a relatively short period of about 30 minutes. I started to notice the formation of a layer and found that there were cases where the adhesion deteriorated.

An object of the present invention is to provide an Al Mn alloy plated steel sheet with excellent heat resistance and corrosion resistance, which does not easily deteriorate in corrosion resistance and adhesion even when used at high temperatures.

(Means for solving the problem) In order to achieve the above objective, we focused on the pre-plating method and found that one or more metals from N1, Cr and Co were applied in a relatively low amount as a base treatment. discovered that the formation of an alloy layer of Al and Fe at high temperatures could be suppressed by forming a two-layer plated steel sheet by applying Q-Mn alloy plating in a molten salt bath after plating with aluminum, and completed the present invention. I let it happen.

Here, the present invention provides a method of depositing at least one metal selected from Ni, Cr and Co in an amount of 0.5 to 20 g.
2N plating with excellent heat resistance and corrosion resistance, which has a lower plating layer of /d and an upper plating layer of Al-Mn alloy plating layer with a coating weight of 1 to 100 g/ryf on one or both sides of the steel sheet. It is a steel plate.

(effect) The present invention will be explained in detail below.

In the two-layer plated steel sheet of the present invention, the lower layer is coated with M O,
The plating layer is made of at least one metal selected from NrsCr and Co at a rate of 5 to 20 g/rd. Regarding the effect of suppressing Al--Fe alloy formation by the base plating treatment, N1 shows the most excellent effect, but Cr and Co can also provide a practically sufficient and substantial suppressing effect.

When alloy plating is used for the lower layer, it is preferable to use alloy plating of a metal selected from these three types of metals, but it is also possible to use alloy plating in which a small amount of other metal is present, if necessary.

If the coating weight of the lower plating layer is less than 0, s g/m, the formation of an alloy layer between the upper layer Al and the base material Fe cannot be effectively suppressed. Even if plating is carried out, no further improvement in the above-mentioned alloy formation suppressing effect is observed, and it is also disadvantageous in terms of cost.
Furthermore, if the lower plating layer becomes too thick, the adhesion of the plating generally tends to decrease. Furthermore, if the coating weight of the lower layer exceeds 20g/=, if the underlying metal is Ni, the corrosion of the upper Al-Mn alloy layer will progress easily and the end face corrosion resistance will deteriorate because Ni is the culprit metal. On the other hand, when the lower layer metal is Cr or Co, the workability deteriorates as will be shown later in the examples, and Co is particularly expensive.
Since a high coating weight is economically disadvantageous, the coating weight of the lower plating layer is limited to 0.5 to 20 g/cd.

The lower layer can be formed by a conventional method using a known N+, Cr or Co electroplating bath.

The upper layer is attached to m t -too g/rrr Q-M
This is an n-alloy plating layer. Adhesion amount 1g/r+? less than
The good corrosion resistance and heat resistance exhibited by sub-base plating cannot be obtained at all, and on the other hand, if the upper layer's adhesion exceeds 100 g/r+f, the workability of the steel sheet will deteriorate significantly.

The upper layer Al-Mn alloy plating is a well-known AlC12s-
It can be carried out similarly to conventional molten salt electroplating using an electroplating bath in which Mn is also added as chloride to an XC2 (X is an alkali metal) mixed molten salt bath. Mn content in Al-Mn alloy is 0.5-50% by weight
Outside this range, the appearance of the plating tends to deteriorate, and if the Mn content is too low, the corrosion resistance will drop significantly, and conversely, if the Mn content increases beyond 50%, the workability will decrease. . A particularly preferable Mn content is 10
-40% by weight.

In addition, alloying elements other than Mn and Mn can also be added in small amounts (usually 1.0% by weight or less in total) as long as they do not adversely affect the performance of the plated steel sheet. Examples of such other alloying elements include, but are not limited to, Fe, Crs Nis T+, etc. (Also, two or more such other alloying elements may be added. It is also preferable to add the element as a chloride to the molten salt bath.

Generally, the plating temperature for Al-Mn alloy plating using a mixed molten salt bath is about 150 to 200°C, and the current density is 2
0 to 100 A/dn (approximately).

As is well known, in Al-Mn alloy electroplating using a molten salt bath, avoiding moisture contamination is important for plating efficiency and maintaining plating quality.
Before applying alloy electroplating, the base-plated steel plate is thoroughly washed with water and then heated and dried to completely remove moisture. When a bare steel plate is heated and dried in the air, an oxide film is formed on the surface, which significantly impairs the adhesion of the Al-based plating film. Since it is plated, no decrease in adhesion due to heat drying is observed.

The base steel plate of the two-layer plated steel plate of the present invention is generally a cold-rolled steel plate, but a hot-rolled steel plate may also be used, or one that has been subjected to chemical conversion treatment in advance.The two-layer plated steel plate of the present invention includes:
The above two-layer plating may be provided on either one side or both sides of the steel plate.

In the case of double-sided coating, the coating amounts of the lower layer and upper layer mentioned above are both for one side.

The double-layer plated steel sheet of the present invention has good heat resistance and corrosion resistance, so it can be used as is as a corrosion-resistant or heat-resistant steel sheet, but depending on the purpose of use, it can be further coated, and the adhesion of the coating film is also good. Therefore, a coated steel machine with excellent coating corrosion resistance can be obtained. In addition, prior to painting,
Chromate treatment can be performed by a conventional method.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example) After cleaning the surface of a cold-rolled steel plate with a thickness of 0.8fi, a width of Loom, and a length of 200mm by degreasing and pickling, various coating amounts of Ni, Cr, and Ni were coated under the following plating conditions. Co
, or electroplated with Ni-Cr or Ni-Co alloy on one side.

Plating bath composition: N15O*・7HtO270g/
lNiC11・6Hz0 50 g/IHsB(h
35 g/1 pH: 5.5 Bath temperature: 50°C Current density: 5A/di 1 λ plating bath composition: Crys 250 g/1!1
．． so, 2.5 gil Bath temperature: 45℃ Current density: 5A/dmr Electrolytic Co plating conditions Plating bath composition: CO3O4・7Hz0 450 g/
12) 1sBOs 40 g/jICo
C1x ・6uto 45 g/ff1KCI
20 g/ItpH: 4.0 Bath temperature: 37°C Current density: 5A/dn? In the case of Ni-Cr or Ni-Co alloy plating, Crys(N
i-Cr alloy) or CO3O4' 7HtO (
In the case of Ni-Co alloy), use a plating bath containing
Electroplating was performed under conditions similar to the Ni plating conditions described above.

Next, this base-plated steel plate was thoroughly washed with water, dried for 1 minute in a hot air dryer at 70°C to completely remove moisture, and immediately subjected to A treatment using a mixed molten salt bath under the following conditions.
It was subjected to l-Mn alloy plating treatment.

Al-Mn plating bath composition: Ala2374.1% by weight NaG?
14.1% by weight and C211.8m! t% Bath temperature: 200°C Current density: 40A/drrr Regarding Mn, during the 0 current application time when Mnα8 was added to the molten salt bath so that the Mn content in the plating film was a predetermined weight%, the upper layer deposition amount was In the case of 20g/td, it is about 60 seconds. This molten salt electroplating was carried out using a flow cell exclusively for molten salt [Inconel 600 (manufactured by Illi, a registered trademark)].

The obtained two-layer plated steel sheet was tested for corrosion resistance and adhesion after heating, and workability in the following manner. The test results are shown in Tables 1 to 5 below, along with the plating type and coating amount of each of the lower and upper layers.

After heating at 500℃ in the atmosphere for 24 hours, a salt spray test (JIS-Z2371) was conducted.
Evaluation was made based on the number of days until red rust appeared.

S/, after heating at 600°C in the atmosphere for 30 minutes, a DuPont impact test (ball head diameter: inch, energy: 0.8 kgf-■) was conducted, and the tape! ! Adhesion was evaluated based on the peeling condition after 1 release.

(1) After close bending with a bending radius of 0.8 degrees, a tape peeling test was conducted, and the adhesion was evaluated based on the peeling condition.

For comparison, an Al-Mn single-layer plated steel sheet omitting the lower layer plating or a two-layer plated steel sheet with various conditions outside the scope of the present invention were similarly prepared and tested.
It is also shown in Tables 5 to 5.

Table 1 (Danken All adhesion amounts are in dd.

Table 2 Table 3 συ　＊　All adhesion amounts are in GOD.

Table 4 Table 5 συ　Umbrella　All adhesion amounts are in &/rd.

(Effects of the Invention) As can be seen from the results in the above tables, the second-layer 9-hardened steel plates of the present invention have excellent corrosion resistance and adhesion after heating,
It also has good workability.

Specifically, Table 1 shows the changes in the adhesion amount of the lower layer when the lower layer is Ni plating (Arashi 1 to 8) and the upper layer Al-Mn plating.
The amount of deposited Ni plating on the lower layer is 0.5 to 20g/
Excellent corrosion resistance and adhesion after heating are obtained within the range of td. If Nl plating is not performed or the amount of Nl plating is less than 0.5 g/rr1, both corrosion resistance and adhesion after heating are insufficient.

When the amount of N1 plating is 30.0g/cd (llh
8) The corrosion resistance and adhesion after heating are good, but since Ni is the culprit, if the Ni layer is this thick, the corrosion of the base M in the upper layer will easily progress from the end face, and the end face corrosion resistance will deteriorate. If the amount of Q-Mn alloy plating on the upper layer is less than 0.1 g/rrr, corrosion resistance will be extremely deteriorated, and conversely, if it is less than 100 g/n? It can be seen that good workability cannot be obtained when the value exceeds .

Tables 2 and 3 show that the lower layer is Cr and Co, respectively.
In the case of plating, if the coating weight of the lower layer is less than 0.5 g/n1 or if the lower layer is omitted, both the corrosion resistance and adhesion after heating will be low, and the coating weight of the lower layer will be low. When the amount becomes as high as 30 g/rrr, the deterioration of workability is significant.

Table 4 shows the results when the lower layer plating is Ni-Cr alloy plating and the amount of deposition of the lower layer is changed.
This shows the same trends as in Table 3 and Table 3.

Table 5 shows examples of changing the Mn content of the upper Al-Mn alloy plating layer when the lower layer is a Ni-Co alloy. It can be seen that when the upper layer is made of pure Al, the corrosion resistance after heating is extremely reduced. Moreover, when the Mn content exceeds 50%, good workability cannot be obtained.

In addition, attached FIG. 1(a) shows a plated steel sheet that is outside the scope of the present invention in 臘1 of Table 1 above, that is, an Al-20%Mn alloy plating layer is applied directly to the steel sheet base material at a coating weight of 20 g/rr+. The single-layer plated steel plate provided was heated at 600℃ in the atmosphere for 3
i! showing the cross-sectional structure after heating for 0 minutes! Ji Hui mirror photo, Al-Mn! A Fe-Al alloy layer is already formed between the material and the base metal after only 30 minutes of heating, and as a result,
It can be seen that the plating layer is lifted and peels off easily.

On the other hand, in Figure 1 (bl), the same M-20%h alloy plating layer as above is used as the upper layer, and before that, the lower layer is deposited at
A cross section of the two-layer plated steel sheet of the present invention, in which a Ni plating layer of r was provided under the same conditions as in the above example, was similarly heated in the atmosphere at 600°C for 30 minutes. FIG. By providing a very thin Ni layer in contact with the base material,
It can be seen that the formation of the Fe-Al alloy layer is completely suppressed.

Furthermore, FIG. 2 shows the case where the upper layer is an Al-20%Mn alloy plating layer and there is no lower Ni layer (-1), and the lower layer is coated with a coating amount of 10 g/m. Plating when Ni layer is provided (positive 6)! ! l board,
It is a graph showing the change in the plating appearance depending on the number of days of heating when heated at 400° C. in the atmosphere for a long time, using glossiness as a measure. The decrease in gloss is thought to occur as a result of the formation of surface oxides and the diffusion of base material Fe to the surface, resulting in not only poor appearance but also deterioration in corrosion resistance after heating. Even in the case of long-term heating, as in the case above, if the lower Ni layer is not provided, the gloss will quickly decrease, but if the Ni layer is provided, the rate of decrease will be greatly suppressed, and the It can be seen that the plated steel sheet of the invention has good heat resistance.

As explained above, the 2N-plated steel sheet of the present invention can be produced efficiently (relatively inexpensively) by electroplating, and furthermore, even when used in the atmosphere under heating conditions, deterioration in corrosion resistance and adhesion is suppressed. Since it has good workability, it is useful as a relatively inexpensive heat-resistant or corrosion-resistant material.

[Brief explanation of the drawing]

Figure 1 (al is A12 of 20g/rtr on the surface of the steel plate)
- A cross-sectional micrograph showing the mu weave of an LLI-plated steel sheet with a 20% Mn alloy plating layer after heating at 600°C for 30 minutes in the atmosphere, Fig.
r+? Figure 2 is a cross-sectional micrograph showing the same steel structure after heating of the same two-layer plated steel sheet as above except that a lower Ni layer was provided, and Figure 2 shows the same Al-Mn alloy layer as above as the upper layer and as the lower layer. 10g/n? It is a graph showing the change in plating surface glossiness depending on the number of days of air heating at 400° C. in the case where the Ni plating layer was provided and the case where it was not provided.

Claims (2)

[Claims] (1) At least one selected from Ni, Cr and Co
A lower plating layer consisting of a seed metal with an adhesion amount of 0.5 to 20 g/m^2 and an Al-Mn alloy plating layer with an adhesion amount of 1
2 with excellent heat resistance and corrosion resistance, which has an upper plating layer of ~100 g/m^2 on one or both sides of the steel plate.
Layer plated steel plate. (2) The two-layer plated steel sheet according to claim 1, wherein the Mn content of the Al-Mn alloy of the upper plated layer is 0.5 to 50% by weight.