KR100336424B1 - THE METHOD FOR MANUFACTURING STEEL PLATE COATED WITH Al-Si ALLOY AND ITS PRODUCTS - Google Patents

Abstract

The present invention relates to a method for producing an aluminum-silicon-based alloy plated steel sheet and a product produced thereby, further comprising 0.3 to 1.5% by weight of any one or more of Cr, Mn, Ti, and Zr components in the plating bath molten metal. It characterized in that the plated treatment, the steel sheet produced by this is a multi-layer structure of the cross-sectional structure of the plated layer is composed of the first alloy layer, the first overlay layer, the second alloy layer, the second overlay layer and the pure plating layer from the base steel sheet It is characterized by having a structure of a type.

Description

Manufacturing method of aluminum-silicon alloy plated steel sheet and its products {THE METHOD FOR MANUFACTURING STEEL PLATE COATED WITH Al-Si ALLOY AND ITS PRODUCTS}

Aluminum plated steel sheet has a high corrosion resistance and heat resistance compared to hot dip galvanized steel sheet has been applied to automobile muffler, home appliances heat-resistant materials. Aluminum-plated steel, first manufactured in the Sandzimir line in 1939, began to become commonplace in the late 1950s when it was applied to muffler steel in American automobile companies.

The aluminum plated steel sheet is significantly degraded in workability due to rapid diffusion alloying layer formation between aluminum and iron. In order to suppress this, about 5 to 11 wt% of silicon is added to control the formation of an alloy layer that degrades workability. It is roughly classified into a mold and a second mold composed of a pure aluminum-only plating layer.

Type 1 aluminum plated steel sheet is widely used in heat-resistant parts such as muffler, water heater, heater or rice cooker endothelium of automobiles. It is used.

However, the aluminum plated steel sheet of the first type has a disadvantage in that the added silicon acts as a factor that inhibits the surface appearance, in order to compensate for the disadvantage of workability deterioration by forming an alloy layer of aluminum and iron. The second type aluminum plated steel sheet has excellent appearance characteristics, but the plated plate and aluminum react rapidly to generate a thick intermetallic compound, resulting in extremely poor moldability. There is a disadvantage in that it is limited to the use of decorative materials that do not require molding.

Another disadvantage is that the work life is remarkably reduced as the life of the sink roll assisting the progress of the steel plate in the plating bath due to the rapid aluminum diffusion reaction.

The present invention relates to a method for producing an aluminum-silicon alloy plated steel sheet excellent in corrosion resistance and workability, and a steel sheet produced thereby.

1 is a schematic diagram of a simulator for explaining the method of the present invention.

Figure 2a is a cross-sectional enlarged micrograph of a conventional aluminum plated steel sheet (type 1), Figure 2b is a cross-sectional electron micrograph of a coating layer for explaining the effect of the present invention.

The present invention is to solve the above problems, an object of the present invention, by adding any one or more of Cr, Mn, Ti and Zr components known to be excellent in corrosion resistance and heat resistance while forming an alloy with aluminum easily The present invention provides a method for producing an aluminum-silicon-based alloy plated steel sheet excellent in corrosion resistance and workability in which an alloy layer is formed in a multilayer structure.

In the method for producing an aluminum-silicon alloy plated steel sheet according to the present invention, in the conventional hot dip plating method, plating is performed by further including 0.3 to 1.5% by weight of any one or more of Cr, Mn, Ti, and Zr components in the plating bath melt. It is characterized by the process.

In the manufacture of the conventional aluminum plated steel sheet, it is essential to contain 5 weight% or more of silicon for the purpose of controlling alloy layer growth in bath property. On the contrary, when the content of silicon is 11% by weight or more, a large amount of silicon cannot be supplied to control the alloy layer because the plate-like silicon phase precipitates in the plating layer, thereby significantly lowering the workability of the plating layer itself.

Therefore, in the present invention, among the elements which are generally known as grain refining elements in molten metals, the sequin refining effect is large, and the affinity with Al, that is, the solid solubility is stable, and the elements which are easily purchased and economically industrially. Cr, Mn, Ti, and Zr were selected as the third alloying elements based on the condition that the one would be satisfied.

The fine addition element is dispersed in the plating layer after the iron plate is plated in A1- 5-15 wt% Si molten metal to form a myriad of nucleation, thereby interfering between grain boundaries during the solidification of the plating material. It serves to control the growth of grains. Thus, it exhibits a fine surface appearance while suppressing intergranular corrosion to enhance corrosion resistance, and the multilayer alloy plating layer serves to suppress and block penetration by various elements of the external environment.

In addition, by inhibiting the growth of the alloy layer by acting as a barrier to the formation of an alloy layer of aluminum and iron, a plated coating layer excellent in workability is formed.

The reason why these additive elements are limited within the range of 0.3 to 1.5% by weight is that when a large amount is added, the intermetallic compound of Cr, Mn, Ti, and Zr is coarsened and the surface appearance of the plating layer is damaged. This is also because there is a problem in the solubility of various additive elements in the molten aluminum.

2A is an electron micrograph of a cross section of a conventional aluminum plated steel sheet (type 1, Pohang Plated Steel Sheet Co., Ltd. product, trade name ALCOSTA) which is conventionally used, and FIG. 2B is an electron micrograph of a cross section of a product according to the present invention. Photomicrograph.

As shown, the aluminum-silicon-based alloy plated steel sheet according to the present invention, the first alloy layer 20, the first overlay layer 21, the second alloy layer 22 sequentially on the base steel sheet 11 And the second overlay layer 23 are sequentially formed, that is, the multilayer alloy layer is formed, and the pure plating layer 30 is formed thereon. That is, the multilayer alloy and the plating layer in this way significantly increases the corrosion resistance to external environmental conditions.

In the method for producing an aluminum-silicon-based alloy plated steel sheet according to the present invention, it is appropriate that the plating deposition amount is in a range of 20 to 200 g / m 2 based on one side. The reason for this is that if the coating weight is less than 20g / m2, the air pressure of the air knife equipment controlling the coating weight is excessively increased and the coating surface weight in the molten metal is increased along with the variation of the coating weight on the plate surface. This is because adhesion of the oxide dross occurs, and when it is 200 g / m 2 or more, workability is remarkably inferior due to excessive formation of the alloy layer.

In addition, in the method for producing an aluminum-silicon-based alloy plated steel sheet according to the present invention, it was confirmed that the temperature of the molten plating bath is 650 to 700 degrees Celsius.

The reason is that when the bathing temperature of the base steel sheet is below 650 ℃, the appearance of the plating film is poor and coating adhesion is deteriorated, and when the temperature is above 700 ℃, thermal diffusion of the base steel sheet is accelerated, resulting in abnormal growth of the alloy layer, resulting in processability. This is because the oxide layer in the molten metal is over-produced.

For the present invention was used a hot-dip plating simulator, Figure 1 shows a schematic diagram thereof.

The apparatus comprises a specimen moving device 1, an infrared heating furnace 2, which is a heat treatment furnace, a gate valve 3, a cooling device 4, an air wiper 5, a plating bath 6 and the like.

The gas supply device may be connected to the main body to automatically supply various gases to the main body, and in particular, heat treatment may be performed in a reducing atmosphere using the vacuum pump 9 and the H 2 and N 2 gases. The specimen 7 used in this experiment was a cold rolled steel sheet (CQ) having a thickness of 0.6 to 1.0 mmT degreased before the experiment, and was cut into a size of approximately 100 × 200 mm 2.

The specimens were thoroughly cleaned with acetone before mounting on the simulator. After mounting the simulator, annealing was carried out in the infrared heating furnace 2 to remove the organic material and the oxide layer attached to the specimen.

In the test method, first, a thermocouple (not shown) is bonded to a specimen 7 after pretreatment using a spot welder, and then the specimen 7 is fixed to the specimen holder of the specimen moving device 1. After closing the door of the container loaded with the specimen (7) to establish a vacuum state using a vacuum pump (9) and purge nitrogen gas on the upper portion through the gas supply device.

On the other hand, the specimen (7) is placed in the infrared heating furnace (2) position by the specimen moving device (1) and blows the gas mixed with nitrogen and hydrogen by the gas supply device, and then heat treatment according to a predetermined cycle .

After the heat treatment is completed, the test piece is moved to the cooling device 4 through the gate valve 3, cooled by nitrogen gas, and then deposited and plated in the plating bath 6. The specimen 7 after plating is adjusted to an appropriate plating thickness while passing through the air wiper 5. Thereafter, the specimen is moved to a cooling stand or a specimen container, cooled, and then taken out at room temperature. During the experiment, the temperature of the specimen 7 is measured by means of thermocouples attached to the specimen, the plating bath temperature is measured by thermocouples installed in the plating bath, and the dew point is continuously recorded by the dew point meter 8 in the reducing gas atmosphere. do.

The following examples were applied to various additive elements as the aluminum-silicon alloy plated steel sheet produced by the method of the present invention in the above simulator to evaluate the characteristics.

The comparative material is an aluminum-silicon alloy plated steel sheet (type 1) free from additive elements (Cr, Mn, Ti, and Zr).

The characteristics evaluation and comparison items were evaluated the initial red blue development time and adhesion processability by salt spray. Corrosion resistance was compared with the initial red blue development time (5%) in 5% and 35 ℃ NaCl salt spray test atmosphere, and the surface appearance was observed by the visual uniformity of the film, and the workability was subjected to 180 degree (0T) bending test. Then, the width of the fracture surface was observed by a three-dimensional microscope at 30 and 50 magnification, and the width of the fracture surface was measured and compared, and the results are shown in Table 1.

Evaluation results of various molten aluminum plated steel sheets Example No. Additional element (wt%) Steel plate bathing temperature (℃) Plating bath temperature (℃) Coating Weight (g / ㎡) Corrosion Resistance (hours) Machinability (breaking width) Remarks Example 1 Cr 0.3 670 660 40 2,500 10 ~ 15㎛ 2 0.5 3,000 〃 3 0.6 3,000 〃 4 0.7 3,000 〃 5 Mn 0.5 900 〃 6 0.8 1,000 〃 7 1.0 1,200 〃 8 1.2 1,500 〃 9 Ti 0.3 1,000 〃 10 0.5 1,500 〃 11 0.6 1,600 〃 12 0.7 1,800 〃 13 Zr 0.3 900 〃 14 0.5 1,000 〃 15 1.0 1,200 〃 16 1.2 1,400 〃 Comparative Material 1 450 20 ~ 30㎛ Comparative Material 2 45 900 30 ~ 45㎛

Example 1

This embodiment is a case where an aluminum-silicon alloy plated steel sheet containing 0.3 wt% Cr is manufactured. In this case, the specimen 7 used was a cold rolled steel sheet having a thickness of 0.9 mm degreased before the experiment, and used a size of 100 × 200 mm. The plating bath adjusted pure weight A1 (99.8%) metal and A1-25 weight% Si alloy by weight ratio, and Cr used A1-5 weight% Cr alloy ingot. The specimen 7 was annealed at 800 ° C. by pretreatment prior to plating. The bath temperature of the steel sheet was set at 670 ° C., and the plating bath temperature was maintained at 620 to 680 ° C., so that the plating deposition amount was 40 g / m 2 (one sided). It is a product when it plated on a steel plate as much as possible.

(Examples 2 to 4)

It is the same as Example 1, but the product when it processed so that the content of Cr may be 0.5, 0.6, or 0.7 weight%, respectively.

(Example 5)

This embodiment is a case in which an aluminum alloy plated steel sheet to which Mn is added is 0.5% by weight. In this case, the specimen 7 used was a cold rolled steel sheet having a thickness of 0.9 mm degreased before the experiment, and used a size of 100 × 200 mm. The plating bath adjusted pure weight A1 (99.8%) metal and A1-25 weight% Si alloy by weight ratio, and Mn used A1-20 weight% Mn alloy ingot. The specimen 7 was annealed at 800 ° C. by pretreatment prior to plating. The bath temperature of the steel sheet was set at 670 ° C., and the plating bath temperature was maintained at 620 to 680 ° C., so that the plating deposition amount was 40 g / m 2 (one sided). It is a product when it plated on a steel plate as much as possible.

(Examples 6 to 8)

It is the product similar to Example 5, when processed so that the addition content of Mn may be 0.8, 1.0, or 1.2 weight%, respectively.

(Example 9)

This embodiment is a case in which an aluminum alloy plated steel sheet containing 0.3 wt% of Ti is manufactured. In this case, the specimen 7 used was a cold rolled steel sheet having a thickness of 0.9 mm degreased before the experiment, and used a size of 100 × 200 mm. The plating bath adjusted pure weight A1 (99.8%) metal and Al-25 weight% Si alloy by the weight ratio, and Ti used Al-10 weight% Ti alloy ingot. The specimen 7 was annealed at 800 ° C. by pretreatment prior to plating. The bath temperature of the steel sheet was set at 670 ° C., and the plating bath temperature was maintained at 620 to 680 ° C., so that the plating deposition amount was 40 g / m 2 (one sided). It is a product when it plated on a steel plate as much as possible.

(Examples 10 to 12)

It is the same as Example 9, but it is a product when it is processed so that the addition content of Ti may be 0.5, 0.6, or 0.7 weight%, respectively.

(Example 13)

This embodiment is a case in which an aluminum alloy plated steel sheet containing 0.3 wt% of Zr is manufactured. In this case, the specimen 7 used was a cold rolled steel sheet having a thickness of 0.9 mm degreased before the experiment, and used a size of 100 × 200 mm. The plating bath adjusted the pure Al (99.8%) metal and A1-25 weight% Si alloy by weight ratio, and Zr used A1-10 weight% Zr alloy ingot.

In addition, the annealing heat treatment of the specimen (7) at 800 ℃ by pretreatment before plating, the bath temperature of the steel sheet is set to 670 ℃, the plating bath temperature is maintained in the range of 620 ~ 680 ℃ plating amount 40g / ㎡ (one side) It is a product when it is plated on a steel plate so that).

(Examples 14 to 16)

The product is the same as in Example 13 except that the amount of Zr added is 0.5, 1.0, or 1.2% by weight, respectively.

(Comparative Material 1)

This is a case where an aluminum alloy plated steel sheet of the first type without any additional elements (Cr, Mn, Ti, or Zr) is produced in the simulator. In this case, the specimen 7 used was a cold rolled steel sheet having a thickness of 0.9 mm degreased before the experiment, and used a size of 100 × 200 mm. The plating bath was used to adjust the pure A1 (99.8%) metal and A1-25% by weight Si alloy in a weight ratio so that the Si component was 25%. The specimen 7 was annealed at 800 ° C. by pretreatment prior to plating. The bath temperature of the steel sheet was set at 670 ° C., and the plating bath temperature was maintained at 620 to 680 ° C., so that the plating deposition amount was 40 g / m 2 (one sided). It is a product when it plated on a steel plate as much as possible.

(Comparative Material 2)

It is currently produced by Pohang Coated Steel Co., Ltd. (trade name ALCOAT), which is a molten aluminum plated steel sheet with an Si component of 8 to 12% and a plating adhesion amount of 45 g / m 2 (one sided).

According to the above-described examples and the evaluation table of Table 1, it was found that the corrosion resistance is much superior to the conventional products compared, and also the processability of the product according to the present invention was nearly two times better.

According to the present invention, by adding Cr, Mn, Ti, or Zr to the existing aluminum-plated steel sheet tubing, it is possible to manufacture an aluminum-silicon alloy plated steel sheet having an improved surface appearance by controlling nucleation between grain boundaries.

In addition, according to the present invention, as the result is excellent in corrosion resistance after processing by reducing the peeling of the plating layer and the degree of cracking of the coating film appearing in the molding process, it is possible to further improve the durability in applications such as automotive muffler or heat-resistant home appliances. Can be.

Claims (4)

In the method of manufacturing an aluminum-silicon alloy plated steel sheet, the aluminum-silicon system is characterized in that the plating bath contains at least 0.3 to 1.5% by weight of at least one selected from the group consisting of Cr, Mn, Ti, and Zr components. Manufacturing method of alloy plated steel sheet. The method of manufacturing an aluminum-silicon alloy plated steel sheet according to claim 1, wherein the plating amount is in a range of 20 to 200 g / m 2 on a one-side basis. The method of claim 1, wherein the silicon component of the plating bath molten metal is 5 to 15% by weight, and the temperature of the plating bath is 650 to 700 degrees Celsius. The aluminum-silicon alloy plated steel sheet produced by the method according to any one of claims 1 to 3, wherein the aluminum-silicon alloy plated steel sheet has a cross-sectional structure of the plated layer from the base steel sheet 11 to the first alloy. Aluminum-silicon system having a multi-layered structure consisting of the layer 20, the first overlay layer 21, the second alloy layer 22, the second overlay layer 23 and the plating layer 30 Alloy plated steel sheet.