JPH04259363A - Hot dip aluminized steel sheet excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a hot dip aluminized steel sheet, at the time of applying the hot dip coating of an Al-Si allay to the surface of a steel sheet, by adding a specified amt. of Mn to the hot dip Al series allay. CONSTITUTION:At the time of applying the hot dip coating of an Al-Si alloy having a compsn. of Al-10% Si to the surface of a cold rolled steel sheet degreased and cleaned and finished with annealing, Al series hot dip coating is applied by using a hot dip coating bath mixed with 0.01 to 1.5% Mn. An Al allay hot dip coated steel sheet having extremely high corrosion resistance in the field of a severe corrosive environment can be obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip aluminized steel plate with excellent corrosion resistance.

0002

[Prior Art] Conventionally, hot-dip aluminized steel sheets have excellent corrosion resistance and heat resistance, so they have been widely used as materials in fields exposed to corrosion and heat, such as household heated furniture and automobile exhaust system materials. Publication No. 57-47861, “T in steel”
"Aluminized steel plate containing i", JP-A-63-184
No. 043, “Aluminized steel sheet containing small amounts of C, Si, Cu, Ni, and Cr in steel”, JP-A-63-2
There are many types of aluminized steel sheets, such as "aluminum-plated steel sheets containing a large amount of Cr and Al in the steel" as disclosed in Japanese Patent No. 13658. Generally, these aluminized steel sheets are
An annealing process in which a cold-rolled sheet is heated in a non-oxidizing or weakly oxidizing atmosphere to burn off oil adhering to the surface, and then heated in a reducing atmosphere to activate the surface. It is manufactured by dipping it in a hot-dip aluminum plating bath. Regarding the aluminum plating layer, in addition to the pure aluminum plating bath, by adding 10% or less Si to the aluminum plating bath, the growth of the Fe-Al alloy layer, the diffusion of the aluminized metal into the steel, and the F eluted from
e component, etc., and improves plating adhesion, heat resistance, and corrosion resistance. In addition, in recent years, as a measure to extend the life of automobile exhaust system materials, for example, Japanese Patent Laid-Open Publication No. 63-18
``Steel plate containing 1.8 to 3.0% Cr'' in Publication No. 043, and ``Steel plate containing 3 to 2% Cr'' in JP-A-63-47456.
Many types of Cr-containing steel sheets have been developed in which Cr is added to the steel, such as "Steel sheets containing 0% Cr." Furthermore, in recent years, as automobile exhaust systems have become more sophisticated, hot-dip aluminized steel sheets have been manufactured using stainless steel as the plating original sheet. However, the aluminum plating layer of hot-dip aluminized stainless steel sheets containing a large amount of Cr is corroded earlier than the plated original sheet, so high-grade stainless steel with high corrosion resistance is used as a long-life exhaust system material. There was a problem that it had to be used for plated original plates.

0003

OBJECTS OF THE INVENTION The present invention advantageously solves these problems, and has excellent corrosion resistance, especially in an automobile exhaust gas atmosphere, while being used in many fields. The purpose is to provide inexpensive hot-dip aluminized steel sheets.

0004

[Means for Solving the Problems] That is, the gist of the present invention is to provide a plated original plate (steel plate to be plated) with an Mn of 0.01 to 1.
．． This is a hot-dip aluminized steel sheet with excellent corrosion resistance, coated with a hot-dip aluminium-plated layer containing 5%.

[0005]

[Operation] The present invention will be explained in detail below. The steel plate to be plated used in the present invention is produced by melting molten steel using a normal melting furnace such as a converter or electric furnace, or other refining equipment, and processing it into slabs through an ingot decomposition method or continuous casting method. Alternatively, it is produced by a general manufacturing process for thin steel sheets, in which the steel slab is heated to a high temperature, hot rolled, pickled, and cold rolled. The steel composition of the steel plate to be plated is not particularly limited, and steel plates of various compositions are used depending on the required properties and purpose, such as aluminum killed steel, Ti-added steel, Cr-containing steel, and even stainless steel. The cold-rolled sheet produced in this way is used as a plated steel sheet,
Hot-dip aluminum plating is applied using the non-oxidizing furnace method or the Sendzimer method. The hot-dip aluminum plating bath in the present invention is a pure aluminum plating bath or a conventional aluminum plating bath with 10% or less of Si added, and Mn: 0.01 to 1.5%. 1.5% or less of M
n, which further improves the corrosion resistance of aluminized steel sheets manufactured using conventional aluminizing baths. That is, Mn in the aluminum plating bath is mixed into the plating layer, and has the effect of significantly improving the corrosion resistance of the plating layer, particularly the corrosion resistance against automobile exhaust gas corrosion. However, if the amount of Mn added in the aluminum plating bath is small, less than 0.01%, the amount mixed into the plating layer is too small to improve corrosion resistance. Furthermore, as the amount of Mn added increases, the Mn content mixed into the plating layer also increases, which significantly improves corrosion resistance.
Addition of a large amount of n also causes problems in that the effect of improving corrosion resistance reaches a saturation range and that the plating bath temperature also rises, posing a problem in the maintenance management of the plating equipment and its auxiliary equipment. Therefore, in the present invention, the amount of Mn added to the aluminizing bath is 0.
It was regulated at 0.01 to 1.5%. The molten aluminized steel sheet produced as described above has excellent corrosion resistance and can be used as a material in fields with severe corrosive environments.

[0006]

[Example] Next, an example of the present invention will be explained. Example 1 A plating bath with an Al-10% Si bath as the basic bath composition and 0.001 to 2% Mn added thereto was prepared in a continuous plating line using a non-oxidizing furnace using the plating original plates shown in Table 1. Then, aluminum plating was performed and the area weight was adjusted to 80 g/m2 using the gas wiping method. The obtained sample was immersed in a test liquid simulating exhaust gas condensate in a semi-immersed state to evaluate its corrosion resistance. The corrosion resistance evaluation results are shown in Figure 1. These results show that when the amount of Mn in the plating bath is 0.01% or more, the corrosion loss of each steel type is significantly reduced and the corrosion resistance is improved.Moreover, the corrosion loss tends to gradually decrease depending on the amount of Mn added, but when it is 1.5% or more, The additive effect is saturated. As described above, the corrosion resistance of aluminized steel sheets plated with the aluminum plating bath of the present invention with Mn added in an amount of 0.01% or more is significantly higher than in comparative examples in which no Mn is added or the amount of added Mn is less than 0.01%. It is excellent. Furthermore, when Cr steel or stainless steel is plated with a Mn-added bath, the effects are superimposed.

Example 2 [0007] Using a plating original plate of A (low carbon steel) in Table 1, hot-dip aluminum plating was applied in a continuous plating line using a non-oxidizing furnace. At this time, the amount of Si in the plating bath was changed between 0 and 10%, and the amount of Mn
Hot-dip aluminum plating was carried out using a bath without addition (comparative example) and a bath in which 0.1% was added (invention), and the basis weight was adjusted to 80 g/m2 by a gas wiping method. The resulting samples were immersed in a test liquid simulating exhaust gas condensate in a semi-immersed state to evaluate their corrosion resistance. The evaluation results are shown in Figure 2, and the results show that when aluminum plating is performed using the Mn-added bath of the present invention, the corrosion resistance is significantly superior to that of the comparative example, and the corrosion resistance is improved regardless of the amount of Si in the plating bath. It shows. Corrosion Resistance Test The test material was semi-immersed in an aqueous solution containing 10 g/l of HCl and 1 g/l of H2SO4, adjusted to pH 8 with NH4OH, and tested in a semi-closed state at 80°C for 30 days. CrO320g/l, H3PO4
It was immersed in a 32 g/l solution at 88° C. for 10 minutes and removed to determine the corrosion loss.

[0008]

[Table 1]

[0009]

[Effects of the Invention] As described above, the hot-dip aluminized steel sheet of the present invention has extremely excellent corrosion resistance.
In particular, it is possible to extend the life of household thermal furniture and automobile exhaust materials used in fields with highly corrosive environments.

0010

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of Mn added to the plating bath and the corrosion loss by immersion test when each steel type is aluminized in various Mn-added aluminum plating baths;

FIG. 2 is a diagram showing the influence of presence or absence of Mn addition on corrosion loss when the amount of Si in the plating bath is changed.

Claims (1)

[Claims] [Claim 1] The steel plate to be plated has Mn: 0.01 to 1.
．． A hot-dip aluminized steel sheet with excellent corrosion resistance characterized by being coated with a hot-dip aluminium-plated layer containing 5%.