JPS5956569A - Production of one-side plated steel sheet - Google Patents

Abstract

PURPOSE:To obtain a one-side plated steel sheet, which has an excellent plating stop-off property, preventivenss for sticking of molten metal on the coating film, by coating an aq. slurry contg. MgO of the grain sizes regulated according to raw materials and calcining conditions and subjecting the steel sheet to hot dipping after drying and heating. CONSTITUTION:A six-component type slurry contg. >=1 kinds among MgO, alkali silicate, boric acid, alkali metal hydroxide and titania and further compds. contg. of >=1 kinds among alumina, Al(OH)3 and alumina sol is coated on the one side of a steel sheet. It is an essential requiement in this case to regulate the grain size of the raw material for MgO of a stop-off agent component, that is, Mg(OH)2 at >=0.1mum and to use the MgO prepd. by calcining the assemblage thereof at 950 deg.C. The steel sheet coated with the above-mentioned stop-off agent slurry is dipped in a zinc hot dipping bath after drying and annealing whereby only the one side of the steel sheet is plated. Thereafter the plating stop-off agent is quickly cooled from about >=100 deg.C temp., whereby the coating film of stop-off agent is easily stripped and the intended one-side plated steel sheet is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a single-sided plated steel sheet using a plating inhibitor.

Recently, steel sheets for use in automobiles, home appliances, and construction equipment (1st grade) have been applied to one side of the steel sheet (with this graining and polishing to achieve the necessary corrosion resistance), and have been designed to improve the properties of CC10. The point 97 of the single-sided plated steel sheet was strongly bent. Single-sided plated steel plate can be manufactured by electroplating.1;-Although it can be manufactured by the electroplating method, the plating speed is slow (= + strike height), so if there are many plated seams. It is particularly advantageous to use the hot-dip plating method. Conventionally, the hot-dip plating method was used to produce I'+1i+i coated steel sheets. A method of combining 4 pieces, welding and plating both ends, and then cutting off both ends, [7-ru and curtain flow miri J] A method of applying molten zinc to one side of a steel plate, both sides. (The method is to remove the IF lead on one side by grinding or ILV, or by coating and plating the ILF lead on one side of the steel plate in advance with a galling inhibitor.) Many proposals have been made, including methods of removing the paint film, and methods of elevating the surface of the C plating bath using ultrasonic waves or electromagnetic pumps to coat only one side. However, these methods However, there are very few examples of successful production of roses in commercial frameworks, as they have drawbacks such as technical difficulties and difficult implementation, and low production costs.

Since the present invention relates to a method of ft ITJ using plating inhibitors, we will particularly focus on the method of lunar surface!1■1 lead plating that has been proposed in the past regarding methods using plating 1" and 11 inhibitors. and plating lsf, l, +L agent, water slurry (Japanese Patent Publication No. 39-4204), alkali metal silicate acid filling, water slurry containing ammonium silicate as the main component (Japanese Patent Publication No. 53-48 (No. 129) ), non-plating treatment agent whose main component is silicone resin (/r￥Koshō 51-81
01), an aqueous slurry of a synthetic scale-like silicic acid compound (JP-A-54-64026'+j), or an alkaline earth metal oxide (US Pat. No. 3121019). However, these conventional techniques have the following drawbacks.

1) Reducing atmosphere annealing (approximately 700℃) before plating
In the continuous hot-dip galvanizing method ([, plating prevention,% 11 coating I snout decomposes during annealing or peels off from each sheet surface in some parts, Completely prevent plating adhesion (2 is a problem! Since it is an IC, the steel plate may become 1ψ in the atmosphere after being silica-plated, so this oxide must be returned 1) and fJ Mechanical removal is necessary.
,i,i'ill iTherefore, the coating film formed on one side of the steel plate is generally not good, so the appearance of the steel plate surface is completely removed. It was almost impossible to do so, and the removal of the bipartite film required a high cost. As an easy plating N1 stopper agent, a water slurry (JP-A-52-14673 (No. 1)) containing Magnesi T, boric acid, Alka IJ jd and Kei rβ Alka IJ t'44-14 components was used. Then, a five-component slurry (1986-1983) was prepared by adding one of these four components titania and titanium hydroxide.
L19157), but even in these cases, the following drawbacks still remain.

That is, continuous hot-dip galvanizing method in which annealing is carried out in a reducing atmosphere before plating.When the pulling speed of the steel sheet from the molten zinc bath is high, or in order to obtain a 1fij lead-plated steel sheet with excellent workability, galvanizing method A1 is used. If annealing is carried out at a temperature above the transformation point, zinc will adhere to the coating of the plating inhibitor, resulting in not only an economical disadvantage, but also the layered zinc may be deposited in the middle of the steel sheet production line. F2 is often contaminated. Therefore, the present invention adds at least a compound selected from the group consisting of alumina, aluminum hydride, and alumina sol to one of the previously invented magnesia-boric acid-alkali-silicate salt-titania and titanium hydroxide. The added water slurry improves plating resistance, molten metal adhesion prevention properties, and pricking properties during firing, and improves the cleanliness of the steel plate surface after peeling. , phosphate chemical treatment 11! It improves sex.

The plating inhibitor of the present invention includes magnesia, alkali silicate (MmO・n5101・m, l-110, where M indicates total alkali concentration), nitric acid, total alkali concentration σ) hydroxide, titania, and At least one type of titanium hydroxide, θ)・), and at least one type of compound among aluminum hydroxide, aluminum hydroxide, and alumina sol. 1. The present inventors applied an inhibitory slurry consisting of the above six components to a steel plate, and removed the inhibitor after single-sided plating. It has been my experience that some products have poor phosphate treatment properties. After conducting a detailed voltage check to find out the cause of this, one person 11 +L- agent peeled 301 g/? on the steel plate surface? 1111 lead is 7) J IF・
E4 and phosphorus 6'Jl 1'A after phosphate treatment;
(It was found that there are cases where the crystals are large and partially covered with f4゛ (the same as the first 1i (i).
When the residual zinc on the surface of the steel plate exceeds 30■/- (45~/
Figure 2 shows the phosphate treatment status of R), and the residual zinc is 30■
/n? Figure 3 shows the phosphate treatment condition when the temperature is less than (10~/rr?), but from a comparison of the two,
Figure 3) shows that the crystals are small and the coverage is good.

Reasons why zinc remains on the surface of the steel plate after removing the inhibitor (J,
This was because the B11 +) agent film applied during the annealing process before plating cracked or part of the blocking film peeled off.

As mentioned above, we have conducted repeated research to improve the quality defects of f' and f', and have found that the factors that affect cracks and local sludge during the annealing process before the plating of the inhibitor film are as large as f'. ,
It was found that it is a property of magnesia in the inhibitor.

The magnesia used in Fuinbanko is made by adding slaked lime directly to bittern recovered from seawater or 4i% water to convert it into magnesium hydroxide, or by blowing CO and gas into bittern to turn it into magnesium carbonate. After conversion, filter
It is a general term for powder mainly composed of magnesium oxide, which is produced by pulverizing and classifying the powder fired in a rotary kiln or batch furnace. Magnesia has different characteristics, such as particle size, surface area, and reactivity, depending on the form of the raw material, firing method, firing temperature, and so on.

Therefore, we changed the production conditions of magnesium hydroxide, which is the raw material for magnesia, to reduce its secondary particle size (the smallest particle unit obtained from strain measurement using the X-ray in-broadening method) to 0.
．． 01-1. (Various raw materials that have been changed to IflWL,
An inhibitor using magnesia calcined in the range of 800°C to 1100'C'' was prepared, and a single-sided plating production experiment was conducted to obtain the following result S: At this time, the inhibitor i11 composition was magnesia 65 (l f/t, caustic soda 150-150 f/l, boric acid 300-400 l/l
/=, water glass 400-500f/ /=, ditania 150-250f/l- and alumina 150-2
It is a 50 f/l water slurry. J(1) particle size is o,
When magnesylanohydroxide under L pnt u is aged, sintering occurs between the particles on both the outer surface and the outer surface of the sintering temperature. If the adhesion force is low, part of the film will peel off during the annealing process before plating, and lead will be adsorbed onto the plate due to fine work in the plating bath. phenomenon was observed, and the firing flow rate of magnesyl hydroxide l,σ) was 9 F) o
If the temperature exceeds ℃, the zinc residue on the steel plate surface after peeling will be 3 nmf
- Phosphate treatability deteriorates beyond -.

(2) Regardless of the particle size, the viscosity of the inhibitor is high (more than 20 voids) when fired at 950°C, causing fine cracks in the film during annealing before plating, and causing voids in the plating bath. Zinc penetrates from q・11 and the zinc residue after separation is 30~/
ff1')1i(get).

(3) When magnesilanohydroxide with a particle size of Q, l pm or more is used as a raw material, the firing temperature is 9 Fi O
Sintering is slow even when the temperature exceeds ℃, the adhesion to the steel plate hardly deteriorates, and the viscosity of the 15J4 and L17 agents is 5.
-20 voids, there were almost no cracks during annealing before plating, the zinc residue after peeling was less than 30 rny/ze, and the phosphate treatment was good. It should be noted that if the grain size is O,], 11yLμ, it is large, but if the culm size is 10μm, it is disadvantageous in terms of cost.

As shown in the second result, the zinc residue is 307η/rr?
In order to obtain a single-sided hot-dip galvanized steel sheet with excellent phosphating properties and having the following steel sheet surface, an aggregate of magnesium hydroxide particles with a grain size of 01 μm or more is fired at a temperature of 95()℃ or higher. It was found that it was necessary to use a β-former arsenic agent containing magnesia.

In the present invention, first, the above-mentioned six-component water slurry is applied to the surface of a well-degreased steel plate and dried preferably at a temperature below 200°C. Any method such as brushing is preferred; the amount of application is 5 to 300 P/ff/ after drying.
It is an indulgence. If the coating amount is too small and the coating is incomplete, or if it is too large and the coating film cracks when drying, it will not be possible to completely prevent plating on the coated surface. In addition, it is desirable to evaporate the moisture in the coating film by drying at a low temperature of 200°C or less, but this is done to keep the subsequent annealing atmosphere reducing and to prevent cracking or peeling of the coating film due to rapid high-temperature heating. It's for a reason.

After forming a uniform dry coating film on one side, the steel plate is annealed (approximately 70 min.
0 to 900°C), the humidity of the steel sheet is cooled to near the plating bath temperature (460°C in the case of a galvanizing bath), and then immersed in the plating bath. During this time, the coating film partly flows and becomes glassy during annealing, and then becomes a solid coating during cooling or in the plating bath, preventing contact between the steel plate surface and the molten metal in the bath. A steel plate pulled up from the plating bath is plated on only one side, and the other side is not plated and is covered with a coating film.

This coating film has extremely poor tendency to rub against the molten metal, so
Although molten metal rarely adheres to the coating film, dross may occasionally adhere to it, so it is best to gas wipe it after applying it. This gas wiping also uses combustion gases such as butane and propane.
Illusive. However, since this coating film is extremely dense, it completely prevents the formation of air on the steel plate after it is removed from the plating bath. If the coating film was not removed from the steel plate after plating, the IK would be 14°, but when the plating inhibitor of the present invention was used (J, the steel plate removed from the plating bath
It has been found that the coating film can be easily separated by rapid cooling from a temperature of about 100° C. or higher. The rapid cooling may be performed before the plating solidifies as well as the F+I"J adjustment of the spangle size, or after the plating hardens, or even after being slowly cooled and then reheated at a convenient time. You can go.

As a rapid cooling method, immersion in water is easy and effective. It has been found through experiments that the coating film is completely peeled off from the steel sheet surface by rapid cooling in water, and is not oxidized at all, resulting in a steel sheet surface that is as it was rolled.

Furthermore, in addition to the 15 method using tλ water cooling as described above, the coating film can be easily peeled off and removed by repeated bending, grinding, and polishing. After removing the paint film using this method, if you perform the general final treatment by washing with water and light brushing, you can obtain a complete single-sided plated steel sheet. '? It will be done.

According to the present invention, it is possible to solve the problem of conventional 11-inhibitor <1
．． ++ Remove the zinc residue on the surface of the steel plate after separation using magnesia J9.
30 nTf/1 depending on the temperature and firing conditions
r? The following, complete f with excellent phosphate chemical treatment properties,
f A single-sided plated steel plate can be easily obtained.

Next, the present invention will be explained using Examples and Comparative Examples.

〔Example〕

0-1, 0, 3, which is aged in one or multiple stages by adding lime to bittern collected from seawater and adjusting the temperature and concentration.
Magnesia calcined at 1000°C with magnesium hydroxide 5-1.1-targyrin having a particle size of 0,6,0,Q pm, 650°C. / l, Nori soda 20
A filtrate slurry was prepared from 0 f/l, boric acid 35 (l f//-1 water glass 450 g/11 titania 200 f/1. and alumina 20 (If/l). The viscosity of this slurry was 5 to It was 20 voices.

This water slurry was applied to one side of a cold-rolled steel sheet that had been cleaned by water washing and alkali removal (dealkaliization of the neck J1-). j=. After coating, t at 150°C in an open air oven.
Low flow drying for 1 minute at h't, rrr, 10% 11. −＋
-90% N, at a temperature of 700°C for about 2 minutes,
Nail 1 was continuously cooled to approximately 530°C in the same atmosphere in this order, and then the steel plate was heated to molten F'pHl! dipped in galvanized m.

Regarding the plating conditions, the bath composition was 0.18% At-Zn, the bath temperature was 465±5°C, and the immersion time was 3 seconds.

After plating, the steel plate was removed from the plating bath, and the plating quality was adjusted using a nitrogen gas wiper directly above the plating bath.Then, when the steel plate temperature reached approximately 300°C, the steel plate was placed in water at approximately 20°C. It collapsed and cooled down rapidly. The surface of the steel plate after separation from q・11 exhibits a transparent surface with metallic luster;
Residual zinc on the plate surface is 0~25η/n? Met.

For this steel plate surface, a phosphate treatment using Bonderite #3004 made by E1 Parr Lusing)]! and scan the condition of the phosphoric acid film. 1. The size of the crystals and the degree of coverage were determined by observation using a microscope. As a result, the size of the crystals was 2 to 6 (rm), and the specimen was complete.

[Comparative example J]

Bitterness recovered from seawater? ++ Particle size 0.05 which is aged in one stage or in multiple stages by adding lime and adjusting the temperature, concentration, etc.
11m and 0.4pm of hydroxide 7gnesium, calcined in a rotary kiln at 880℃ and )40℃, 2509/l of magnesia, 250/l of sodium hydroxide /l
,,boric acid 300Y/l, water glass 500y7t, titania 1.50? A water slurry consisting of 250 f/L of alumina and 250 f/L of alumina was prepared. The viscosity and IW of this slurry is 2
5 and 30 l? (There was a ``C''.

This water slurry was coated on one side by method b of Example 1, and after that, the inhibitor coating was removed. [
The steel plate surface after f・11 distance is 71N, and has a gold gloss f''
I have an enviable side of f :・) However, the surface roller of this steel plate surface has residual zinc of 35■/ty/ and 45+
It was Nj/m'.

This steel plate surface was subjected to phosphoric acid treatment and observed.
It is large at 12/IN, and one of the steel plates is insufficiently coated.
However, it had poor phosphate treatment properties.

[Comparison Icl 2] River water (・Particle size aged by adding surface lime (), 0
4 pm magnesium hydroxide in a rotary kiln
7 gnesia calcined at 000℃ 2502/11 caustic soda 15 (l r /l, nitric acid 400?/1, hydraulic strength 400 f//, titania 250y7t, alumina i 50 f/1. A slurry was prepared.The viscosity of this slurry was 3 voids.

This water slurry was plated on one side in the same manner as in the example,
After plating, the inhibitor film was released f11. q・! Visually, the surface of the steel plate after 1 separation was as beautiful as Y-sawa 4-I1, but when this steel plate surface was analyzed, the residual zinc was 40ml /ff1'.

When this steel plate was subjected to the same phosphate treatment as in Example No., it was observed that the phosphate crystals were large, ranging from 6 to 9777+1, and there were places where the a-covering was insufficient and the steel plate was visible. Processability was poor.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the residual zinc on the detuning plate surface of the plating prevention film Mllll, the size of phosphate crystals in phosphate treatment, and the steel plate coating condition J=. Figures 2 and 3 are for metal Figure 2 is an 850x electron micrograph of the treated surface of the steel plate, and shows that the residual zinc on the surface of the steel plate is 45μ/n? Figure 3 of Noyoshikino is an 850x electron microscope photograph of Noyoshikino of 10~/-. , Patent applicant Kawasaki Steel Co., Ltd. Representative Patent Attorney Nozomi Watanabe・71′・＼、10
Blood Office 11; (No change in 1) State post 1 Remains of steel plate surface after removal of group. March 70, ↑11 Mr. Kazuo Wakasugi, Director-General of the License Agency] 111 indications Showa 5 Fi I Patent y (I No. 166176 2 Title of the invention Method for manufacturing single-sided plated steel sheet 3, Relationship with the person making the amendment fI) Patent applicant (1”1; 1 1-28 Kitahonmachi-dori, Chuo-ku, Kobe, Hyogo Prefecture Yl + 1 (2 mountains) (125) Kawasaki Yotetsu Co., Ltd. 4, Agent 〒 101 Telephone 258
-18fi88 Contents of correction as attached

Claims (1)

[Claims] Magnesia, alkali silicate (Mto・n5iO,-
mH, o, in the formula M is alkali metal (-), boric acid, alkali metal hydroxide, titanium oxide, and a small amount of titanium hydroxide (at least one kind, and also alumino-alpenium hydroxide and - of alumina sol) 6. A water slurry containing at least one type of Metsu Naga l511 4--Apply it to one side of the steel plate, dry it for 1 coat, and then dry it for a while.
The steel plate is plated on only one side of the steel plate by dipping in a lead plating bath, and then the metal plated steel plate is peeled off to form a single-sided plated steel plate. ! (At this time, the particle size of magnesylanohydroxide, which is the raw material for magnesia, is
By using magnesia which has been fired at 950°C or higher, the residual zinc on the non-plated surface E after removing the plating inhibitor II-agent is set to 30~/ff/ or less. A method for manufacturing single-sided plated steel sheets.