JPH05117830A - Hot dip zinc-aluminum alloy plating method - Google Patents

Abstract

PURPOSE:To provide the method capable of forming a high-aluminum-content galvanized layer which prevents the generation of non-plated parts, remarkably decreases a rough surface feel and can prevent the generation of burnt deposits. CONSTITUTION:The extreme-purity zinc ground metal is melted. An aluminum ground metal and a manganese ground metal are weighed and are respectively added thereto to prepare a plating bath consisting of 3 to 10wt.% aluminum - 0.01 to 1.0wt.% manganese - the balance zinc and unavoidable impurities. This bath is held at 480 to 600 deg.C and a rolled steel sheet for general structural purposes is immersed therein and is subjected to a plating treatment. The generation of the non-plated parts is obviated in this way and the rough surface plats are <5% of the entire part and are remarkably decreased. The plating layer free from the generation of the burnt deposits is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides hot-dip zinc-aluminum plating for preventing corrosion of steel materials used as structural members such as automobile parts and building members, which has no unplated portion and is rough. The present invention relates to a hot dip zinc-aluminum alloy plating method which can be obtained as an extremely small plated layer.

[0002]

2. Description of the Related Art In order to prevent corrosion of steel materials which have been widely used as structural members such as automobile parts and building members, galvanizing treatment has been frequently carried out, and the method is as follows. The hot dip galvanizing method and the electroplating method are generally used. However, recently, instead of pure zinc plating, which has been the mainstream until now,
It is known that the corrosion resistance of the plating layer is dramatically improved by using a plating bath of an alloy containing zinc in an amount of 3 to 10% by weight, and the method using this alloy bath seems to be the mainstream.

[0003]

In the hot dip galvanizing treatment, the plating layer adheres to the iron of the base material because it causes an alloying reaction between the iron and zinc, and the iron is formed between the plating layer and the base material. -It is strongly adhered by forming a zinc alloy layer, but when the content of aluminum in the zinc bath as a plating bath exceeds 1% by weight, the alloying reaction between iron and zinc is hindered. Therefore, there is a problem that the iron-zinc layer is not sufficiently formed on the surface of the plated member, and the non-plated portion is likely to occur.

On the other hand, when zinc-aluminum alloy plating containing aluminum in an amount of 3 to 10% by weight is applied, an iron-aluminum alloy layer or an iron-aluminum alloy layer is formed during solidification.
There is a problem that so-called roughness, which is formed of a zinc alloy layer, is formed on the surface of the plated product, and the appearance is significantly impaired.

The present invention provides a hot dip coating method capable of preventing the occurrence of non-plating on the surface of a plated product and significantly reducing the roughness formed on the surface of the plated product when the steel material is plated with a zinc-aluminum alloy. It is intended to be provided.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems and achieve the above objects, the present inventors have used a hot dip zinc-aluminum alloy plating bath containing manganese in a specific amount. The inventors have found that the purpose can be achieved by performing a plating treatment at a specific treatment bath temperature, and completed the present invention. That is, the present invention is 3-10% aluminum and 0.01-1.0% by weight.
Hot-dip zinc-aluminum alloy to be subjected to plating treatment at a plating bath temperature of 480 to 600 ° C., using a hot-dip alloy plating bath containing manganese and a balance of zinc and unavoidable impurities. It is a plating method.

Each of the alloy plating baths as described above has 9
It is preferably prepared using high purity zinc, aluminum and manganese of 9.9% or more.

[0008]

As described above, in the present invention, the plating bath composition is limited as described above, but the reason why the aluminum content is 3 to 10% by weight is that the corrosion resistance of the plating layer is maintained when the aluminum content is less than 3% by weight. This is because the effect is small, and even if it exceeds 10% by weight, it is difficult to further improve the corrosion resistance, and the melting point of the plating bath becomes high, which deteriorates the workability. Further, the manganese is added in an amount of 0.01 to 1.0% by weight in order to prevent the surface roughness of the plated product when the zinc-aluminum alloy plating is applied, and its mechanism is clearly stated. I can't, but 0.0
Addition of less than 1% by weight has no effect of preventing roughness.
Even if added over 0% by weight, there is no further effect,
Moreover, excess manganese forms oxides with iron, aluminum, zinc, etc. on the surface of the plating bath, and floats as dross.

As described above, the plating treatment is 480-6.
Performed in the temperature range of 00 ° C. This is because when the plating bath temperature when dipping the material in the molten alloy bath is lower than 480 ° C, the alloying reaction between zinc and iron is suppressed by the effect of aluminum present in the bath, and The non-plated part of the plating is likely to occur, and a product that can withstand long-term use in a corrosive atmosphere cannot be obtained. If the temperature exceeds 600 ° C, the reaction between iron and zinc is promoted, and zinc-aluminum-iron 3 By reaching the product surface of the original alloy,
This is because the phenomenon that the surface gloss of the plated product is lost, that is, a phenomenon generally called burn, is observed, and the mechanical strength of the steel material that is the raw material deteriorates.

The plating treatment time is preferably in the range of 1 to 5 minutes.

[0011]

EXAMPLES Next, examples of the present invention will be described. Example 1 1) Preparation of material specimen Rolled steel plate for general structure (SS400) having a thickness of 3 mm and a width of 7
5mm, 150mm high material sample, this sample 6
Degreasing was performed in a 10% aqueous solution of sodium orthosilicate for 10 minutes at 0 ° C., and then a pickling treatment was performed for 30 minutes in a 15% sulfuric acid aqueous solution, followed by heating at 70 ° C.
Flux treatment was performed by immersing in a 0% zinc chloride aqueous solution to prepare a test piece.

2) Preparation of plating bath A pure zinc ingot specified in JIS H 2107 was used as a zinc raw material, a predetermined amount was weighed, put into a graphite crucible charged in an electric furnace and heated. After melting, a predetermined amount of aluminum ingot and magnesium ingot each having a purity of 99.9% or more are weighed and put into a zinc melt to be melted,
A plating bath containing 5% by weight of aluminum, 0.05% by weight of manganese, the remaining zinc and inevitable impurities was prepared.

3) Plating treatment The plating bath prepared in 2) was maintained at a bath temperature of 490 ° C., and the material sample prepared in 1) was immersed for 60 seconds to apply hot dip zinc alloy plating to the base sample. .. The plated material sample pulled up from the plating bath was cooled with water after 30 seconds passed from the pulling. When immersing the base test piece in the plating bath, remove the dross existing on the surface of the plating bath and then immerse it, and also remove the dross before pulling up to remove the plated surface of the base test piece. Care was taken to avoid contamination with dross.

4) Various tests The surface of the obtained plated green test piece was visually observed, and the appearance of the non-plated portion of the plating layer and the degree of roughness were evaluated. If the degree of roughness was less than 5% of the total A age,
5 to less than 10% was evaluated as B, and 10% or more was evaluated as C. As a result, no unplated part was observed, and the roughness was A, indicating that a good zinc alloy plated product was obtained. The results are shown in Table 1 together with the processing conditions. Comparative Example 1 A plating process was performed in the same manner as in Example 1 except that the bath temperature was set to 450 ° C., which was outside the temperature range of the plating bath of the present invention, and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1, but no unplated portion was observed and the roughness evaluation was C. Example 2 A plating bath was prepared in the same manner as in Example 1 except that the plating bath was prepared so that the manganese content was 0.10% by weight, and the bath temperature was 510 ° C. The test was conducted. The results obtained are shown in Table 1. Comparative Example 2 A plating process was performed in the same manner as in Example 2 except that the plating bath temperature was 450 ° C., and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1. Example 3 The plating treatment was performed in the same manner as in Example 2 except that the plating bath was prepared so that the manganese content was 0.20% by weight, and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1. Example 4 A plating bath was prepared so that the manganese content was 0.50% by weight, and the plating treatment was performed in the same manner as in Example 1 except that the plating bath temperature was 520 ° C., and various tests were performed in the same manner as in Example 1. Was done. These results are also shown in Table 1. Example 5 A plating bath was prepared so that the aluminum content was 7% by weight, and the plating treatment was performed in the same manner as in Example 1 except that the plating bath temperature was 540 ° C., and various tests were performed in the same manner as in Example 1. I did. These results are also shown in Table 1. Example 6 A plating bath was prepared in the same manner as in Example 5 except that the plating bath was prepared so that the manganese content was 0.20% by weight, and the plating bath temperature was 560 ° C. Various tests were conducted. These results are also shown in Table 1. Example 7 A plating bath was prepared in the same manner as in Example 1 except that the plating bath was prepared so that the manganese content was 0.70% by weight, and the plating bath temperature was 580 ° C. The test was conducted. These results are also shown in Table 1. Comparative Example 3 A plating treatment was performed in the same manner as in Example 1 except that manganese was not added and the plating bath temperature was 460 ° C., and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1. Comparative Example 4 A plating process was performed in the same manner as in Comparative Example 3 except that the plating bath temperature was 520 ° C., and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1. Comparative Example 5 A plating process was performed in the same manner as in Comparative Example 3 except that the plating bath was prepared so that aluminum was 7% by weight and manganese was 0.50% by weight, and various tests were performed in the same manner as in Example 1. I did. These results are also shown in Table 1. Comparative Example 6 A plating treatment was performed in the same manner as in Comparative Example 5 except that manganese was not added and the plating bath temperature was set to 580 ° C., and various tests were performed in the same manner as in Example 1. These results are also shown in Table 1.
Shown in. Comparative Example 7 A plating bath was prepared in the same manner as in Comparative Example 5 except that the plating bath was prepared so that the manganese content was 0.05% by weight and the plating bath temperature was 630 ° C. Various tests were conducted. These results are also shown in Table 1,
Although there was no non-plated portion and the roughness was A as well, the occurrence of burns was recognized, and it is understood that defects occur even when the composition of the plating bath is within the range of the present invention and the bath temperature is outside the range of the present invention.

From these results, according to the present invention, a product having a good hot-dip galvanized layer without the formation of non-plated parts, the surface of the plated product having a markedly small roughness phenomenon, and the occurrence of the burn phenomenon are not produced. You can see that you can get it.

[0016]

[Table 1]

[0017]

The present invention provides a zinc-aluminum alloy,
Further, using a bath to which a specific amount of manganese has been added, the plating treatment is performed at a specific plating bath temperature, so in hot dip galvanizing with a high aluminum content, there is no unplated portion, and the roughness is also significantly less, It is possible to obtain a plating layer that does not cause burns,
Excellent effect is recognized.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Takano 2-7-8 Oe, Otsu City, Shiga Prefecture (72) Inventor Tetsuya Nakata 551 Senriokachu, Suita City, Osaka Prefecture

Claims (1)

[Claims] 1. A molten alloy plating bath having a composition containing 3 to 10% by weight of aluminum and 0.01 to 1.0% of manganese, and the balance being substantially zinc and unavoidable impurities. Is used to perform a plating treatment at a plating bath temperature of 480 to 600 ° C.
Aluminum alloy plating method.