JPH0336250A - Production of hot-dip aluminized cr-containing steel sheet - Google Patents

Abstract

PURPOSE:To obtain a steel sheet excellent in aluminizing suitability and adhesive strength of aluminizing by simplified equipment and operations by exerting Ni-type plating of specific coating weight prior to reduction and also specifying the composition of an Al bath at the time of subjecting a Cr-containing steel sheet to reduction and then to dipping in a molten Al bath. CONSTITUTION:Ni or Ni-Fe alloy plating is applied to both sides of a sheet of steel containing 5-40wt.% Cr by 0.01-20g/m<2> coating weight per side. This steel sheet is heated in a reducing atmosphere and then subjected to hot dipping in an Al bath having a composition consisting of 0.15-0.9% each of Cu and Ni and the balance Al. Since the formation of various oxides on the steel-sheet surfaces can be prevented by the presence of the above Ni-type plating layer at this time, H2 concentration in the atmospheric gas at the time of aluminizing can be reduced and equipment and operations can be facilitated. Moreover, the formation of CrN causing uncoating can be prevented even if N2 is contained in the gas at the time of reduction, and further, aluminizing suitability and adhesive strength of aluminizing can be improved by the above-mentioned restriction of the composition of the Al bath.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> Kinei 1 relates to a method for producing a hot-dip Al-plated Cr-containing steel sheet with good Al plating properties and good Al plating adhesion.

<Prior Art> As iron-based materials that provide properties such as corrosion resistance, I1 heat resistance, and oxidation resistance, H1-coated steel sheets, stainless steel, and the like are conventionally known. Of this, Al-coated ordinary steel sheets account for 7%.
It has the above-mentioned properties almost equivalent to steel containing a certain amount of Cr, and can be manufactured at low cost.For example, it requires heat resistance, 1II4 heat resistance, and oxidation resistance, such as in automobile exhaust gas pipes. It is used in areas where

However, with the worsening of environmental pollution in recent years, the environment in which Al-coated ordinary steel sheets are used has become harsher, and as the performance required of automobiles increases,
There has been a demand for a shrine that has 1 food, 1 heat, and 1 oxidation.

In particular, regarding corrosion resistance, there was a problem that when l+iE entered the plating part, the underlying metal part of the plating was exposed, rusting occurred from that part, and in some cases, pitting corrosion occurred in a short period of time. Improving corrosion resistance is becoming important.

Therefore, 11% Cr, which has good corrosion resistance, can be manufactured at low cost as automotive exhaust gas pipe parts that require corrosion resistance.
, 13% Cr stainless steel is mainly used in North America. However, this is especially true in the welded areas after the exhaust gas pipe processing for automobiles. As with the coated sleeve 1' steel plate, there is a problem in that red rust forms in a relatively short period of time.

On the other hand, U.S. Patent No. 4,675,214 discloses a hot-dip aluminum-plated stainless steel 1 in which stainless steel 1, which has excellent surface corrosion resistance or oxidation resistance, is used as a material and hot-dip aluminum plating is formed on the jal plate. has been done.

This conventional hot-dip Al-plated stainless steel has excellent corrosion resistance at the base metal IFfl)W mountain portions and welded portions when defects occur during plating removal.

<Problems to be Solved by the Invention> The hot-dip aluminum-plated stainless steel shown in the above U.S. characteristics suffers from oxidation of Cr, Si, Mn, etc. that is concentrated and generated on the surface of the steel sheet during heat treatment during plating. It is manufactured by reducing the material in a reducing gas atmosphere to clean the surface layer of the steel sheet, and then immersing it in a molten halogen bath. ” In order to reduce the oxide, it is essential to control the reducing atmosphere to a high-concentration hydrogen gas, low commercial point, and low-concentration oxygen gas atmosphere. However, in order to achieve such a reducing atmosphere, the installation and operation of the reduction atmosphere become complicated.

Furthermore, even if some oxides remain on the surface of the stainless steel plate for plating, the oxides on the surface layer of the steel plate are reduced by the strong reducing power of At when immersed in the Al bath, and the surface of the steel plate becomes clean as a result. However, if the gas 11 during reduction contains nitrogen, CrN0 will be formed on the surface layer of the steel sheet. This CrN accelerates the formation of an Al--Fe alloy layer on the surface of the steel plate when the S plate is immersed in an Al bath, thereby causing non-plating.

Therefore, in view of the above, it was necessary to reduce the nitrogen gas concentration in the atmospheric gas while increasing the hydrogen gas concentration.

-・Ko, Japanese Patent Application Publication No. 1983. -2723) 19, JP11I'
! 63-47356 and Japanese Patent Publication No. 63-44825, Ni or old alloy plating is used as a base treatment for molten Al plating! The i-zugoto is disclosed. However, JP-A-612723 F+ 9, JP-A-6
3-47356, the hot-dip plating bath is basically Al.
-Si alloy, and also
Publication No. 5 discloses that the purpose of performing pretreatment plating is to remove the raw material when hot-dipping a steel sheet containing a large amount of Cr, such as stainless steel. The purpose is to suppress the growth of the secondary alloy layer without stopping the unplated coating.
This is not a technique for melt-dipping pure Al onto a steel sheet containing a large amount of aluminum.

On the other hand, Japanese Patent Application Laid-Open No. 60-262950 discloses that the steel plate heating atmosphere does not require a high u2e4 degree but a normal N2
A technique has been disclosed in which a high Cr-containing steel sheet that has been previously plated using a pure Al plating bath in a 112 atmosphere is subjected to two-melt dipping. It became clear that there were unplated areas, the density and density of 71 were not good, and it was not possible to obtain satisfactory melt M plating properties in terms of I-min.

Furthermore, the [ICA
Since it is more fragile than the l-based alloy layer ↓, for example, during bending, the plating fAl] i! ! lf
is born and a hole is opened 1lJj fj! There is a possibility that ll may occur.

In order to solve the above problems of the conventional hot-dip Al-plated stainless steel sheet, the present invention aims to improve Al plating property and A
f Easy installation of single-sided corroding steel plate with good plating adhesion (11
1i, molten Al, which can be produced by the operating method
The objective is to provide a method for producing a plated Cr-containing copper-containing steel sheet.

<Means for Solving the Problems> The present invention provides a method for producing a hot-dip Al-plated Cr-containing steel plate by applying hot-dip Al plating to a Cr-containing steel plate containing 5 to 40% by weight of Cr. N1 plating or Nl with a basis weight of 0.01 to 20 g/rrr per side
After applying Fe alloy plating on both sides, the steel plate is heated in a reducing atmosphere, and then CuO, ], 55 to 0.9% by weight
This is a method for producing a hot-dip Al-plated Cr-containing steel sheet, characterized in that hot-dip Al plating is carried out using an Al melt containing 15 to 0.9 % of NiO, with the remainder being Al and inevitable impurities.

According to the present invention, since hot-dip Af plating is performed after forming a Ni or Ni-1'e plating layer on the surface of the r-containing steel sheet, heat treatment during hot-dip M plating is Various oxides are not generated on the surface of the steel sheet even when melting A.
The concentration of hydrogen gas in the atmospheric gas during plating is low (
There is no particular problem. On the other hand, even if nitrogen gas is present in the atmospheric gas, CrN, which causes unplating, is generated, which eliminates the problem. ) will be improved.

Moreover, the Pe-Ni-M alloy layer produced by Ni or Nj-Fe plating and hot-dip Al plating is Ni or Ni-1
'Al-Fe produced by conventional methods without e-plating
Since the adhesion is better than that of the alloy layer, it is possible to prevent the plating from peeling off due to bending or scratches.

Moreover, compared to the conventional Pe-M alloy layer, Fe-Nl
The Af alloy layer has superior corrosion resistance, and the resulting molten M.I. The corrosion resistance of the Cr-containing steel plate is significantly better than that of conventional materials.

As a result, according to the present invention described in Section 2, there is no need to increase the hydrogen concentration and lower the nitrogen gas concentration in the atmospheric gas during molten F plating, and there is no need to lower the n point. With simple equipment and operations, it is possible to produce hot-dip Al-plated Cr-containing steel sheets with good Al plating properties, Al plating adhesion, and corrosion resistance.

Next, a description will be given of the reason why the number of Ni and 1li-Fe pre-applied layers is limited to one view in the present invention.

The basis weight of the Ni, Ni-Fe plating layer is 0.0 per side.
If it is less than 01g/++f, At plating property and E
Since plating adhesion and corrosion resistance are not improved, the lower limit is set to 0.
01 g/1rI. On the other hand, Ni, Ni-@e
If the amount of the plating layer exceeds 20 g/- per lunar surface, the adhesion of the plating at the bending part will decrease, so the upper limit should be set at 20 g/-.
g/rd.

In the present invention, whether the pre-applied layer is Ni or N1-
Although the same characteristics can be obtained with Fe alloys, Ni-F
In e-alloy plating, good characteristics can be obtained when the Pe concentration is preferably 40% or less.

Further, in the present invention, the Cr content is limited to the above range for the following reason.

As is well known, Crl is an element that contributes to the corrosion resistance, oxidation resistance and heat resistance properties of the steel sheet. However, when trying to obtain good eating habits,
A minimum of 5T3ff1% (hereinafter simply referred to as %) of Cr is required. On the other hand, if the Cr content exceeds 40%, weak C phases such as σ phase are likely to occur during the production of the base steel sheet, and not only will the formability and workability deteriorate significantly, but the steel sheet and Ni Alternatively, the adhesion with the Ni-Fe alloy plating layer may be reduced, resulting in a reduction in plating adhesion after hot-dip Al plating, so the upper limit of the Cr content was set to 40%.

The hot-dip Al-plated Cr-containing steel sheet according to the present invention, which has a Cr content of 5 to 40%, can have the following various elements added to it as needed, and the content of the elements is as follows: It is preferably within the following range.

C: O, t% or less When the content of C becomes large, the corrosion resistance and mechanical properties of the galvanized steel sheet deteriorate, and when it exceeds 0.1% by weight, the effects become particularly pronounced, so the upper limit should be set to the above value. was selected.

TiXNb, Zr, V: 1.0% or less Ti,
Nb, Zr, ■ are strong carbonitride-forming elements, and depending on the application in which the m-plate is used, Ti, Nli, Zr,
By adding V, excellent formability, toughness and workability of the welding affected zone can be obtained, but if the amount exceeds 1.0%, the carbonitrides and inclusions generated will become HY-like or coarse, which will adversely affect the forming process. Since the properties and corrosion resistance also deteriorate, the upper limit of the content was set at 1.0%.

Mo: 2.5% Mo increases the n-resistance and heat resistance of the plated plate, but if its content exceeds 2.5%, not only will the bottom shape be inferior, but also Ni or Ni-Fe alloy Since the adhesion of the plating when plating is performed is reduced, the content of "21" was set as above (fixed).

Si: 2.0% or less Si is an effective element for improving the corrosion resistance and heat resistance of plating materials, but if its content exceeds 2.0%, the formability and toughness of the material itself will decrease significantly. Therefore, the upper limit of the content was set to 2.0%.

Mn:2. 0% or less When the content of Mn becomes high, it has a negative effect on the corrosion resistance and heat resistance of elemental hydrogen, and in particular, when it exceeds 2.0%, SUI occurs, so the limit should be kept at 2.0%. .

CIl: 4.0% or less Cu has a low melting point, and if it exceeds 4.0% at 1.V, it will cause a high temperature bladder at 1°, and the 2nd limit will be 4.0%.

In addition, there is Ni as a main additive element, but the present invention
Since Austety 1-series and two-phase stainless steel are also included, their amounts are not particularly specified.

Volatility of molten Al plating is well-known] 1. There are Type I which is made of substantially 1-3i and Type I which is made of substantially pure Al, but from the viewpoint of corrosion resistance which is the main focus of the present invention. It is well known that the latter Typell type is superior. Therefore, it is assumed that the molten Al plating bath is made of substantially pure Al.

Furthermore, from the point of view of melt plating properties, which is the main focus of this application, 0.15-09% C11 and 0.15-0.9% Ni
It must contain ◆J above l. The reason for this is based on the fact that the actual path 0 is exactly the same as the following.

CJI is less than 0.15% or N1-ffl is 0.
In the case of a 15% human disaster, even if N is used as a steel plate F ground treatment.
Even with i or NiFe alloy plating, it is 1! , II
Since the main objective of improving hot-dip plating properties is insufficient, Cu and Nifi in the Al hot bath are each 0.15
% or more.

On the other hand, Cul in the Al hot bath is 0.9% and l+iil is 0.9%.
If it exceeds 9%, Ni or Ni must be used as a base pretreatment.
Even if -Fe alloy plating was applied, the plating adhesion +11 after molten Al plating was poor, so -J two limits were each set at 09%.

At present, the cause of this is not clear, but
Probably due to the "two precepts" behavior of the alloy layer, A! Cu contained in hot bath
, Ni has some influence 1. If I, it is considered that

Next, embodiments of the present invention will be explained.

<Example> (Example A) Chemical composition is 0015%C-0,3%Si-0,3%
Mn112%Cr-0,0312%P-0005%S
-0,01%N02 Plate thickness containing 20%Ti 1,0
Using a +nm Cr-containing cold-rolled steel sheet, the Kippatsu 1!11 method was implemented.

N1 coating method 1; Ni (:l 2・611202008/1.-
l-11c! 1008/, i! 30~I in aqueous solution
Cathode electrode i'+A' treatment is carried out at a current density IA of BOr, /cl to remove Ni. In addition, for some things (,
Yo Ni coating thickness! Electrolytic treatment of the front hole ■11
], then 2110 t: / E nilyl sulfate +50
To/E chloride, ;・7 Kelu (Publisher 0 [, #2 is cathode type in 8 solution) 1 treatment is performed and 0.01 per side.
~20 g/nr of N1 oxidation was performed.

(Actually!ii!i Example B) The method of the present invention was carried out using a steel plate having the composition described in the above examples.

Ni-Pc alloy plating method; 100 [X/E Nisokel sulfate-1-70g/f2 dichloride, Nonoru 140[,, #1L oxalic acid aqueous solution Yoju 206/E ferrous sulfate aqueous solution] A cathodic electrolytic treatment was performed to coat one side with a Ni-Fe alloy of 001 to 20 [x/rK]. This 11. The FO content in the plating layer of v is 5 to 25%.

Next, the Ni or Ni-Fe alloy plated test piece was carried into a vertical plating apparatus and subjected to hot-dip Al plating. Melt sealing 11) Al plating strip (1 is as follows.

4 in the m1 diagram is atmospheric gas introduction I], and 0 to 20% 11□10 N2 gas was introduced from this part. Reference numeral 2 in Figure 1 is an infrared heating device, which heats the test piece 1 suspended above the plating equipment in the heat pattern shown in Figure 2 at an atmospheric gas dew point of -120 to -30°C. Heat (700~9
50'C). After this? Bono I, a member of Yoyu Corporation
690-720° mainly composed of Al maintained at 3◆
A molten metal bath heated to C (composition f - 0.03% Fe
-0.17%Cu-0.01%h-0.18%Ni)
Then, immerse the test piece] intermittently for 1 to 30 seconds.
After holding the sample J1 from the bath, it was cooled in the gas atmosphere.

When this cooling was completed, test Ll was visually inspected for unplated areas, and no unplated areas were found. The results show that the plating properties are good.

In addition, test) 1 was subjected to an adhesion bending test (o'r test), and the part 1 was observed using a 20x magnifying glass, and the f1'I'r recognition of plating adhesion was determined by whether or not the crank was struck. When I went there, there was no cranking at all. The fact that no cranking occurs indicates that the plating adhesion is good.

(Comparative example A) The cultivated steel plate explained in the above actual hiE example A was coated with ○ to 95% I without plating with old or Ni-1'c alloy.
I z N 2 dust atmosphere, n point -i, O ~ -50
Hot-dip Al plating was carried out using the apparatus shown in Fig. 1 and the pattern shown in Fig. 2 at a temperature of When the properties were tested, the non-plating rate was about 15% or more, and -
It was confirmed that large racks had occurred in some of the test specimens.

(Comparative Example B) One plate of one nail and one nail explained in the previous example was coated with 95 to 10 plating without Ni or Ni-1'e alloy plating.
0% l12 NdJ' atmosphere, n point -10 to -5
Hot-dip Al plating was carried out under the same conditions as in School Precept A using 0'C (7) strips (11゛ and J for the rest. Then, after plating, under-plating and plating adhesion tests were conducted. As a result, no defects were found. Although the plating rate was reduced to 1%, cracks appeared in a considerable number of test pieces, indicating that the plating adhesion was poor.

(Comparative Example C) n; J Example 1y] A steel plate with a thickness of 11% was coated using the method described above. Ni-Fe alloy plated, O~20%llz N2 gas atmosphere,
Hot-dip Al plating was carried out at a dew point of +20 to -30°C using the apparatus shown in Fig. 1 and according to the heat pattern shown in Fig. 2. When the unplated rate was measured using the cooled test piece, it was found that the Ni, N1-FD alloy plating A; J amount was 0.0.
When it was less than 1 g/rrT, 1% or more of unplated material remained. In addition, more than 20g/bo of N
In the case of Ni or Ni-Fe alloy plating, cracks were found in the scratched parts.

Analysis of the following Examples and Comparative Examples reveals the following.

In Examples A and B, Ni or N11'e was applied to the steel plate base surface.
Since an alloy plating layer is formed and further Al plating is performed, the Al plating property and Al plating adhesion are improved as described in the above section.

In the first case, the high concentration of nitrogen gas in the reducing gas causes CrN, which is the cause of non-plating, to be deposited on the surface of the plate, resulting in a high non-plating rate.

In Comparative Example 13, since the nitrogen gas concentration in the reducing gas was low (hydrogen gas concentration was high), the generation of CrN, which is the cause of non-plating, was suppressed, but alloy +11 formed by Al plating was weak Fe- It is Af. As a result, bending process 11. It is thought that this was due to poor Al plating adhesion.

In Comparative Example C, Ni or Ni-Fe alloy plating [1 background is 0. If it is less than OIg/nf,
The effect described in the column is small, and when it is more than 20 g/nK, the plating adhesion decreases.

(Comparative Example 1) On the above-mentioned length h1! 1 example 8, the theory 191 was 3.0 strength steel plate,
0.01-20 g of Ni or Ni-Fe alloy plating
/r+ (application, 0-50% 11.-N, gas atmosphere,
Using the apparatus shown in Fig. 1 at a frost point of -1-20°C to -40°C, and using the heat pattern shown in Fig. 2 (to l-0.03°C),
%Fe-0.10%Cu-0.01%M.

Hot-dip Al plating was performed in a Hal bath containing 0209%Ni).

When this particular non-plating rate was measured, about 1 to 3% of non-plating occurred. Therefore, even if the pre-applied layer is coated with JI or Nr-Fe, which is the NiV required range of Mokumyo, if Cu and N1Ji in the Al bath are less than 0.15%, it is sufficient to obtain 2i. j:) I understand that it is difficult.

4it = As can be seen from Examples A and B above, 1L was heated in a relatively high temperature atmosphere with a low hydrogen gas temperature, melting and closing 1
Even if plating is performed, no unplated parts will occur, and the plating will not peel off even in the processed areas.

The atmospheric gas need not be a high hydrogen gas atmosphere, but may be hydrogen gas, 100% nitrogen gas, or other non-oxidizing gas atmosphere.

Next, an embodiment in which the present invention is applied to continuous plating equipment will be described.

Melting M plating was carried out using the continuous plating apparatus shown in Fig. 3 using a cold-rolled finish sintering machine with a plate width of 60 mm, plate thickness of 0.7 mm, and a coil electric power of 30 kg, having the toughness shown in Table 1 below. I did it. The hot-dip Al plating bath composition at this time was (Al-0,02%Fe-0,19%Cu-0,20
%Ni -0.03%h).

To explain Figure 3, Mekkikawa's steel plate material is Jl.
It is continuously supplied from a coil, and is passed through multiple tanks to be described next by a conveying roller, and is subjected to 1!11 surface treatments each.

First, for the tIA plate, 11 surfactants were added to 2. Alkaline degreasing is performed in a 2.5% Na0Il aqueous solution tank 12 containing -/ffi, and water washing is performed in a water tank 13. After washing with water, 200
g/l N1Cz2・6+120-)-100g#
! Activated nickel strike plating was applied to the W4 temporary base material in a nickel strike plating tank 14 of llCf.

After that, wash with water in the water tank 15, and perform 1. L, 280
g/l nickel sulfate - 1-50g/f nickel chloride +4
0g/e Ni
Perform plating. Thereafter, the steel plate is washed with water in a water tank 17, and then dried in a dryer 18.

Next, in heating step 19, the steel plate is heated to 700-950°C and melted A! The steel sheet is immersed in the bot 20, the nitrogen gas wiper 21 on the exit side controls the weight of Al, and after cooling, the coiler 22 melts the Al! Wind up the steel plate.

Table 2 shows the plating conditions at this time.

9 Comparative examples are shown for those in which the element + A component exceeds the range of the present invention, those in which the pre-applied thickness is outside the range of the present invention, and those hot-dipped at a conventional high 112 concentration.

The thus obtained hot-dip Al-plated Cr-impregnated ML plate was subjected to a carpet test regarding the following points.

(1) Measurement of unplated rate if melting A! Optionally Loam X from plated steel plate
A 4 cm test piece was cut out, the area of the unplated portion was visually measured, and the unplated rate, which is the ratio of the area of the unplated portion to the total surface area, was calculated. The results are shown in Table 3.

(ii) Plating adhesion A steel plate was tightly bent (OT) and the erupted portion was observed using a 20x magnifying glass, and the plating adhesion was evaluated based on whether there were any cracks. No cracks occurred/
B: Some cracks occurred; C: Significant cracks occurred. The evaluation results are shown in Table 3.

0 ℃ Plate (period) Jiryuha 9 Be semi-placement □ Placing a tribute, placing a mausoleum on a diamond, leaping into the sky, and placing a tribute on the shrine. 8 e Hamashi carvingsho [ 过き會〜 Base stationary sun tears sum; ρ hat, beshichiha! i': U□ Yoichito l, = U〕 □ Return 1, = Yo~ +1 + 8 Ward Return Fukio 1, Hesenji 1 Issou\ Concave 8 Keitagon Shimi = ℃ Tani~ Enbo□ □ Genus 5 ~ = ~ ~ Hokyureitsu■ ~ Kurewan Cicada - 匣媚■ = Kurewan 0 Kuretsumi■ Tribute 1---Once sent, 11~ Midori Saisuke~ Fuyusousou = Chanui Mill 23 As can be seen from Table 3 above, the hot-dip M-plated Cr-containing steel 41F produced by the method of the present invention has excellent plating density @bamboo and also has good hot-dip M plating properties. As shown in the comparative example, when hot-dip Al plating is performed using the conventional method, if the heating atmosphere prior to hot-dip plating is set to high hydrogen gas and low dew point, hot-dip Al-coated steel containing Cr will not form uncoated. Furthermore, it can be seen that the plating adhesion is poor due to the Fe-E alloy layer generated during melt-dip plating (Comparative Example 3.4).Also, even if the method of the present invention is used, the Cr It can also be seen that when the amount exceeds the range of 1!11, the plating receptivity decreases (Comparative Example 1).

It can also be seen that plating adhesion deteriorates when Ni pre-plating (fiJ amount) exceeds 20 g/nl (Comparative Example 2).

In the above embodiment, the old plating tank was formed by electrolytic plating, but the Ni plating tank can also be formed by other plating methods, such as electroless plating.

4 Furthermore, although hydrogen-nitrogen gas was used as the atmosphere gas for molten Al plating in the above embodiment, in the present invention, there is no need to use high concentration hydrogen gas as the atmosphere gas for M plating, and low f) F! 1.1 Hydrogen gas may also be used,
Other non-oxidizing gases such as 100% nitrogen gas may also be used. Most importantly, this does not preclude the use of a reducing gas.

Next, using the same period of time as in the example, the surface of the steel plate was similarly coated with a 2 g/nY lli or Ni-10%Fe alloy plating layer, and A! Cu in bath, N1jl
Figure 4 shows the relationship between the unplatedness rate, Cu, and Ni when melt JV plating is performed with various values. From Figure 4, it can be seen that molten M
1; From the viewpoint of plating properties, it is found that it is essential to contain 0.1 jl or more of Cu and 0.1 jl or more of Ni in the /V bath.

In addition, in the present invention, if the steel contains 5 to 40% of Cr,
It can be applied to various hole bottoms.

Furthermore, the steel manufactured by Akihiro Kinei can be manufactured into various shapes other than plate-like ones, such as tubular ones.

The hot-dip Al-plated Cr-containing steel sheet obtained by the Kinoe 191 method can be used for various parts that require corrosion resistance, heat resistance, and oxidation resistance, such as tJ gas vibrators for automobiles.

Effect of First Effect> As explained above, according to the present invention, since Ni or Ni-Fe alloy plating is performed before hot-dip Al plating, the atmosphere at the time of this hot-dip/V plating is elevated. reducing gas,
Hot-dip Al-plated Cr-containing steel can be produced using simple equipment and simple operations without requiring a low dew point.

Moreover, N1 or Ni-Fe alloy plating prevents the formation of Cr nitride, which causes non-plating, and forms Fe-Ni-M alloy layers with good adhesion to each other. Hot-dip Al-plated Cr-containing steel with good greenness can be produced.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the configuration of a vertical hot-dip plating device, Figure 2
The figure shows the heat pattern of heat treatment when performing hot-dip Al plating, Figure 3 is a cross-sectional view showing the configuration of a continuous plating equipment, and Figures 4 (1) and (2) show the amount of Cu in the Al hot bath, respectively. It is a graph showing the relationship between the unplated rate and the relationship between the amount of N1 in the Al hot bath and the unplated rate. l...sample, 2...infrared heat, 3...molten metal pot, 4...atmospheric gas inlet, 11...coil, 12...Na0
11 Aqueous solution, 13.15, ]6.17 Water tank, 14 Nickel strike plating tank, 1st Dryer, 19 Heating furnace, 20 Melting A
T pot, 21...nitrogen gas wiper 22...
coiler

Claims (1)

[Claims] Molten Al is applied to a Cr-containing steel plate containing 5 to 40% by weight of Cr.
When plating is applied to produce a hot-dip M-plated Cr-containing steel sheet, the Cr-containing steel sheet is preliminarily coated with a basis weight of 0.0 per side.
After applying Ni plating or Ni-Fe alloy plating of 1 to 20 g/m^2 on both sides, the steel plate is heated in a reducing atmosphere, and then Cu0.15 to 0.9% by weight and Ni0.15
1. A method for producing a hot-dip Al-plated Cr-containing steel sheet, characterized in that hot-dip Al plating is performed using an Al solution containing ~0.9% by weight and the remainder consisting of M and unavoidable impurities.