JP2012176422A - Laser cladding method, laminated structure, and corrosion-resistant metal clad steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply corrosion resistance treatment to a carbon steel without adjusting respective content ratios of chromium, nickel, and molybdenum in metal powder.SOLUTION: The laser cladding method includes a layer forming step in which the metal powder which comprises SUS312L and is supplied to a surface 2a side of the carbon steel 2 is melted by the laser irradiated to the surface 2a side to form clad layers 3A and 3B on the surface 2a side. The layer forming step is repeated by a plurality of times to stack the clad layers 3A and 3B on the surface 2a side, thereby forming a laminate structure 4 comprising a plurality of layers of clad layers 3A and 3B. At the second and later layer forming steps, melting by laser is held back at the clad layers 3A and 3B formed in the previous layer forming step.

Description

  The present invention relates to a laser cladding method, a laminated structure, and a corrosion-resistant metal clad steel.

Conventionally, as a method for improving the corrosion resistance of carbon steel, for example, a laser cladding method as shown in Patent Document 1 below is known. In this method, a low-melting-point metal and a high-melting-point metal in a metal component are alloyed into a powder, and a fired coating in which a metal powder composed of a chromium-based composite material containing the alloy powder and a binder are mixed is applied to the surface of the carbon steel. Forming a clad layer by firing the film to be fired by laser irradiation.
The metal powder is formed by pulverizing an Fe-based alloy, and contains iron as a main component, and also contains chromium, nickel, and molybdenum. Each content ratio of chromium, nickel, and molybdenum in the cladding layer is a certain value or more with respect to the content ratio of iron. As a result, the cladding layer has corrosion resistance, and the carbon steel can be subjected to corrosion resistance treatment.

JP-A-5-306475

By the way, since the melting point of molybdenum is higher than the melting point of iron, in order to form a clad layer by firing the fired film by laser irradiation using the conventional laser cladding method, the fired film and carbon steel are laser-fired. It is necessary to heat above the melting point of iron by irradiation. Then, the carbon steel is melted and mixed with the fired film so that the fired film is diluted with the carbon steel, and the content ratios of chromium, nickel, and molybdenum in the cladding layer are compared to the content ratios in the metal powder. Will be reduced.
Therefore, in the conventional laser cladding method, the content ratios of chromium, nickel, and molybdenum in the metal powder are increased in advance so that the content ratios of chromium, nickel, and molybdenum in the cladding layer are equal to or higher than a certain value. Therefore, SUS312L having high corrosion resistance could not be used as a raw material for the metal powder when the components were not adjusted.

  The present invention has been made in view of the above-described circumstances, and the purpose thereof is a laser capable of performing corrosion resistance treatment on carbon steel without adjusting the content ratios of chromium, nickel and molybdenum in the metal powder. It is to provide a build-up method.

In order to solve the above problems, the present invention proposes the following means.
The laser cladding method according to claim 1 of the present application is a layer in which a metal powder made of SUS312L and supplied to the surface side of carbon steel is melted by a laser that irradiates the surface side, and a cladding layer is formed on the surface side. Forming a stacking structure including a plurality of clad layers by repeating the layer forming step a plurality of times and laminating the clad layer on the surface side, and forming the layer forming step for the second and subsequent layers. At this time, the melting by the laser is kept until the clad layer formed in the immediately preceding layer forming step.

According to the present invention, the layer formation process is repeated a plurality of times, and the clad layer is laminated on the surface side of the carbon steel, thereby forming a laminated structure composed of a plurality of clad layers. The content ratios of chromium, nickel, and molybdenum in the outermost cladding layer positioned can be made closer to the content ratios in SUS312L.
That is, among the multiple clad layers, the innermost clad layer located on the innermost side and formed on the carbon steel is diluted with carbon steel, and each content ratio of chromium, nickel and molybdenum in the innermost clad layer Becomes lower than each content ratio in SUS312L.
However, since the innermost clad layer is disposed between the innermost clad layer and the carbon steel, the innermost clad layer is melted by a laser when forming the laminated clad layer. By retaining the innermost cladding layer, the influence of dilution by carbon steel can be suppressed. Therefore, each content ratio of chromium, nickel, and molybdenum in the laminated clad layer can be increased as compared with each content ratio in the innermost clad layer, and can be brought close to each content ratio in SUS312L.
In this way, in the second and subsequent layer forming steps, the melting by the laser is kept up to the cladding layer formed in the immediately preceding layer forming step, so that the layered structure is gradually moved from the inside to the outside. The effect of dilution with carbon steel can be weakened, and the content ratios in SUS312L can be brought close to each other. Thereby, each content ratio of chromium, nickel and molybdenum in the outermost cladding layer can be brought close to each content ratio in SUS312L.

  In addition, since the metal powder is melted by a laser having a smaller heat input than TIG welding or the like, the solidification time required for the molten pool to solidify and become a clad layer can be suppressed in a short time during the layer formation process. be able to. Therefore, even if it is Fe base alloy with small solid solution amount of Mo like SUS312L, it can suppress that a molybdenum segregates when a molten pool solidifies.

  The laminated structure according to claim 2 of the present application includes a plurality of clad layers laminated on the surface side of carbon steel, and the clad layer is made of SUS312L, and the metal powder supplied to the surface side is made of It is formed by melting with a laser that irradiates the surface side, and the melting by the laser when forming the second and subsequent layers from the inside is held up to the clad layer formed immediately before Features.

According to this invention, since it has a plurality of clad layers laminated on the surface side of carbon steel, each content ratio of chromium, nickel and molybdenum in the outermost clad layer located on the outermost side of the laminated structure Can be brought close to the respective content ratios in SUS312L.
That is, among the multiple clad layers, the innermost clad layer located on the innermost side and formed on the carbon steel is diluted with carbon steel, and each content ratio of chromium, nickel and molybdenum in the innermost clad layer Becomes lower than each content ratio in SUS312L.
However, since the innermost clad layer is disposed between the innermost clad layer and the carbon steel, the innermost clad layer is melted by a laser when forming the laminated clad layer. By retaining the innermost cladding layer, the influence of dilution by carbon steel can be suppressed. Therefore, each content ratio of chromium, nickel, and molybdenum in the laminated clad layer can be increased as compared with each content ratio in the innermost clad layer, and can be brought close to each content ratio in SUS312L.
In this way, by keeping the melting by the laser when forming the second and subsequent clad layers from the inside up to the clad layer formed immediately before, the carbon dioxide gradually increases from the inside to the outside of the laminated structure. The influence of dilution with steel can be weakened, and it can be brought close to each content ratio in SUS312L. Thereby, each content ratio of chromium, nickel and molybdenum in the outermost cladding layer can be brought close to each content ratio in SUS312L.

  In addition, since the metal powder is melted by a laser having a smaller heat input than TIG welding or the like, when forming each cladding layer, the solidification time required for the molten pool to solidify to become the cladding layer is shortened. Can be suppressed. Therefore, even if it is Fe base alloy with small solid solution amount of Mo like SUS312L, it can suppress that a molybdenum segregates when a molten pool solidifies.

  The laminated structure according to claim 3 of the present application includes, as the clad layer, two layers including an inner clad layer formed on the carbon steel and an outer clad layer laminated on the inner clad layer from the outside. The outer cladding layer is thicker than the inner cladding layer.

In this case, since the outer cladding layer exhibiting corrosion resistance is thicker than the inner cladding layer, the outer cladding layer can be reliably provided with corrosion resistance, and the corrosion resistance treatment to the carbon steel can be made more reliable.
In addition, since the inner cladding layer is thinner than the outer cladding layer, it is possible to prevent the entire laminated structure from becoming thick while making the corrosion resistance treatment to the carbon steel more reliable as described above.

  Moreover, the corrosion-resistant metal clad steel according to claim 4 of the present application is characterized by including carbon steel and the laminated structure.

According to the laser cladding method according to claim 1 of the present application, each content ratio of chromium, nickel, and molybdenum in the outermost cladding layer can be brought close to each content ratio in SUS312L. High corrosion resistance can be achieved, and the carbon steel can be subjected to corrosion resistance treatment without adjusting the content ratios of chromium, nickel and molybdenum in the metal powder.
Moreover, since it can suppress that a molybdenum segregates when a molten pool solidifies, the corrosion-resistant process to carbon steel can be ensured.
Furthermore, since it is possible to suppress segregation of molybdenum even in the case of SUS312L as described above, it is not necessary to use a Ni-based high-cost welding material (for example, Inconel 625). You can also plan.

Further, according to the laminated structure according to claim 2 of the present application, each content ratio of chromium, nickel and molybdenum in the outermost cladding layer can be brought close to each content ratio in SUS312L. The carbon steel can be subjected to corrosion resistance treatment without adjusting the content ratios of nickel and molybdenum.
Moreover, since it can suppress that a molybdenum segregates when a molten pool solidifies, the corrosion-resistant process to carbon steel can be ensured.
Furthermore, since it is possible to suppress segregation of molybdenum even in the case of SUS312L as described above, it is not necessary to use a Ni-based high-cost welding material (for example, Inconel 625). You can also plan.

Further, according to the laminated structure according to claim 3 of the present application, since the outer cladding layer exhibiting corrosion resistance is thicker than the inner cladding layer, the corrosion resistance treatment to the carbon steel is made more reliable, and the entire laminated structure Can be prevented from becoming thick.
Furthermore, according to the corrosion-resistant metal clad steel according to claim 4 of the present application, since the laminated structure is provided, corrosion resistance can be reliably provided.

It is sectional drawing of the corrosion-resistant metal clad steel which concerns on one Embodiment of this invention. It is a side view of the principal part of the building-up apparatus used for the laser building-up method which concerns on one Embodiment of this invention. It is a top view which shows the shape on the carbon steel of the laser used with the build-up apparatus shown in FIG. It is sectional drawing of the carbon steel in the stage before an inner cladding layer is formed. It is sectional drawing of the carbon steel in which the single layer clad layer was formed in the surface.

Hereinafter, a corrosion-resistant metal clad steel according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the corrosion-resistant metal clad steel 1 includes a carbon steel 2 and a laminated structure 4 including a plurality of clad layers 3 </ b> A and 3 </ b> B laminated on the surface 2 a side of the carbon steel 2. . This corrosion-resistant metal clad steel 1 is employed in, for example, an offshore structure.

  The clad layers 3A and 3B are formed by melting metal powder made of SUS312L and supplied to the surface 2a side of the carbon steel 2 with a laser L (see FIG. 2) that irradiates the surface 2a side. In the present embodiment, the laminated structure 4 includes an inner cladding layer 3A (innermost cladding layer) formed on the carbon steel 2 as the cladding layers 3A and 3B, and an outer cladding layer 3B (layered on the inner cladding layer 3A). The outermost cladding layer and the laminated cladding layer). That is, the inner cladding layer 3A is located on the innermost side among the plurality of cladding layers 3A and 3B, and the outer cladding layer 3B is located on the outermost side among the plurality of cladding layers 3A and 3B.

Further, the inner clad layer 3A is disposed over the entire area between the carbon steel 2 and the outer clad layer 3B by being formed by a laser cladding method described later.
Further, the outer cladding layer 3B is thicker than the inner cladding layer 3A, and the thickness T of the laminated structure 4 is, for example, about 0.1 to 0.5 mm, preferably about 0.1 to 0.5 mm as a whole, including the plurality of cladding layers 3A and 3B. Is about 0.2 mm to 0.3 mm.

Next, a laser cladding method for manufacturing the corrosion-resistant metal clad steel 1 configured as described above will be described.
First, the overlay apparatus used for this method will be described.

As shown in FIG. 2, the overlay apparatus 10 includes a head 11 that irradiates a laser L, and a powder nozzle 12 that supplies metal powder.
The head 11 is arranged to face the carbon steel 2 in the vertical direction, and moves in one direction X of the horizontal direction while irradiating the surface 2a side of the carbon steel 2 with the laser L.

  As shown in FIG. 3, the laser L emitted from the head 11 onto the carbon steel 2 is a rectangle that is long in a direction orthogonal to the one direction X when the carbon steel 2 is viewed from above along the vertical direction. It has a shape. In the illustrated example, the size L1 along the one direction X in the top view shape of the laser L is, for example, about 1.0 to 2.5 mm, and is orthogonal to the one direction X in the top view shape of the laser L. For example, the size L2 along the direction is about 12 mm.

As shown in FIG. 2, the powder nozzle 12 is positioned on the one direction X side with respect to the optical axis O, and is inclined with respect to the optical axis O in the one direction X. Moreover, the discharge port 12a of the metal powder in the powder nozzle 12 is arranged away from the surface 2a of the carbon steel 2 in the vertical direction, for example, by about 3 mm. As a result, the metal powder discharged from the powder nozzle 12 passes through the optical axis O, and is then supplied to a portion located on the other direction side facing the opposite to the one direction X on the carbon steel 2.
Further, the powder nozzle 12 moves in the one direction X as the head 11 moves in the one direction X.

Next, a laser overlay method using the overlay apparatus 10 will be described.
In this method, the metal powder supplied to the surface 2a side of the carbon steel 2 is melted by the laser L, and a layer forming process is performed to form the cladding layers 3A and 3B on the surface 2a side.
In the present embodiment, the laminated structure 4 is formed by repeating the layer formation step a plurality of times and laminating the cladding layers 3A and 3B on the surface 2a side.

  In the above process, first, an inner cladding layer forming step for forming the inner cladding layer 3A on the carbon steel 2 is performed. At this time, the metal powder is supplied from the powder nozzle 12 while irradiating the surface La of the carbon steel 2 with the laser L, and the head 11 and the powder nozzle 12 are moved in the one direction X. Then, the carbon steel 2 and the metal powder are respectively melted by the laser L, and a molten pool (not shown) formed by mixing them is formed. Thereafter, the molten pool is solidified to form an inner cladding layer 3A as shown in FIG.

  As described above, the molten pool is formed by mixing the carbon steel 2 and the metal powder, and the carbon steel 2 is diluted in the inner cladding layer 3A. Therefore, each of chromium, nickel and molybdenum in the inner cladding layer 3A is contained. The ratio is lower than the respective content ratios in SUS312L.

  As shown in FIG. 4, before the inner cladding layer 3 </ b> A is formed on the carbon steel 2, the surface 2 a of the carbon steel 2 is a rough surface having irregularities of about 40 μm, for example. And in the case of an inner clad layer formation process, this surface 2a becomes flat surface shape by fuse | melting the carbon steel 2 as mentioned above. Note that a virtual surface 2b indicated by a broken line in FIG. 1 represents an average position of the unevenness of the rough surface 2a before the inner cladding layer 3A is formed on the carbon steel 2.

  Thereafter, an outer cladding layer forming step of forming the outer cladding layer 3B on the inner cladding layer 3A is performed. At this time, the metal powder is supplied from the powder nozzle 12 while irradiating the surface La of the carbon steel 2 with the laser L, and the head 11 and the powder nozzle 12 are moved in the one direction X. Then, the inner cladding layer 3A and the metal powder are respectively melted by the laser L, and a molten pool (not shown) formed by mixing them is formed. At this time, melting by the laser L is kept up to the inner cladding layer 3A. Thereafter, the molten pool is solidified to form an outer cladding layer 3B as shown in FIG.

Thus, since the inner cladding layer 3A is disposed between the outer cladding layer 3B and the carbon steel 2, the melting by the laser L when the outer cladding layer 3B is formed up to the inner cladding layer 3A. By retaining, the influence of dilution by the carbon steel 2 can be suppressed. Therefore, the content ratios of chromium, nickel, and molybdenum in the outer cladding layer 3B can be increased compared with the content ratios in the inner cladding layer 3A, and can be brought close to the content ratios in SUS312L.
Further, in this way, by keeping the melting by the laser L when forming the outer cladding layer 3B up to the inner cladding layer 3A, the inner cladding layer 3A is interposed between the carbon steel 2 and the outer cladding layer 3B. It will be formed over the entire area.

  As explained above, according to the laser cladding method and the laminated structure 4 according to the present embodiment, by laminating the cladding layers 3A and 3B on the surface 2a side of the carbon steel 2 by repeating the layer forming process a plurality of times Since the laminated structure 4 composed of a plurality of clad layers 3A and 3B is formed, in the second and subsequent layer forming steps, the melt by the laser L is melted and the clad layers 3A and 3B formed in the immediately preceding layer forming step. By staying up to the above, the influence of dilution by the carbon steel 2 can be gradually weakened from the inside to the outside of the laminated structure 4. As a result, the content ratios of chromium, nickel and molybdenum in the outer cladding layer 3B can be brought close to the respective content ratios in SUS312L, and the outer cladding layer 3B can be provided with high corrosion resistance. The carbon steel 2 can be subjected to a corrosion resistance treatment without adjusting the content ratios of nickel and molybdenum.

  In addition, since the metal powder is melted by the laser L having a smaller heat input than TIG welding or the like, the solidification time required for the molten pool to solidify and become the cladding layers 3A and 3B in the layer forming process. It can be suppressed in a short time. Therefore, even for Fe-based alloys such as SUS312L with a small amount of solid solution of Mo, it becomes possible to suppress segregation of molybdenum when the molten pool solidifies, and the corrosion resistance treatment to the carbon steel 2 Can be ensured.

Furthermore, since it is possible to suppress segregation of molybdenum even in the case of SUS312L as described above, it is not necessary to use a Ni-based high-cost welding material (for example, Inconel 625). You can also plan.
The amount of heat input by the laser L is, for example, about 1000 to 3000 J / cm, and the amount of heat input during Tig welding is, for example, about 9000 J / cm.

Further, since the outer cladding layer 3B exhibiting corrosion resistance is thicker than the inner cladding layer 3A, the outer cladding layer 3B can be reliably provided with corrosion resistance, and the corrosion resistance treatment to the carbon steel 2 can be made more reliable. .
Further, since the inner cladding layer 3A is thinner than the outer cladding layer 3B, it is possible to prevent the entire laminated structure 4 from being thickened while making the corrosion resistance treatment to the carbon steel 2 more reliable as described above. it can.

  And according to the corrosion-resistant metal clad steel 1 which concerns on this embodiment, since the said laminated structure 4 is provided, it can comprise corrosion resistance reliably.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the outer cladding layer 3B is thicker than the inner cladding layer 3A, but the present invention is not limited to this.
Moreover, in the said embodiment, although the laminated structure 4 shall be a 2 layer structure, it is not restricted to this, A 3 or more layer laminated structure may be sufficient.

  In addition, it is possible to appropriately replace the constituent elements in the embodiment with known constituent elements without departing from the spirit of the present invention, and the above-described modified examples may be appropriately combined.

(Verification test)
Next, the verification test about the effect of the laser cladding method shown by the said embodiment was done.
In this verification test, a total of 8 types of laser overlaying methods of Comparative Examples 1 to 5 and Examples 1 to 3 were performed.

In Comparative Examples 1 to 4, as shown in FIG. 5, a single clad layer was formed without repeating the layer formation step.
In Comparative Example 5 and Examples 1 to 3, the layer formation step was repeated twice to perform an inner cladding layer formation step and an outer cladding layer formation step. Among these, in Comparative Example 5, the surface side of the carbon steel was melted by laser until reaching the carbon steel in the outer cladding layer forming step. On the other hand, in Comparative Examples 1 to 3, melting by laser was stopped up to the inner cladding layer.
Here, the conditions of each laser overlaying method are shown in Table 1. In addition, the powder in Table 1 means the metal powder.

  Next, each content ratio of chromium, nickel and molybdenum in the outermost clad layer located on the outermost side among the clad layers formed by the laser cladding methods of Comparative Examples 1 to 5 and Examples 1 to 3 is measured. did.

Here, the outermost clad layer is a clad layer when the clad layer is a single layer as in Comparative Examples 1 to 4, and the clad layer is 2 as in Comparative Example 5 and Examples 1 to 3. When laminated on a layer, it is an outer cladding layer.
Then, each content ratio of chromium, nickel and molybdenum in each outermost cladding layer was measured by EPMA analysis of each outermost cladding layer.
The results are shown in Table 2 and Table 3.

  Table 2 shows the content ratios of chromium, nickel, and molybdenum in the outermost cladding layer formed by each overlaying method of Comparative Example 1 and below. In addition, the row | line | column of the metal powder in Table 2 represents each content rate of chromium, nickel, and molybdenum in the metal powder which consists of SUS312L.

Table 3 also shows the content ratios of chromium, nickel and molybdenum in the outermost cladding layer formed by the overlaying methods of Comparative Example 1 and below divided by the content ratios of chromium, nickel and molybdenum in the metal powder. The residual ratio (%) of each component is shown. As the residual ratio of each component is closer to 100, the content ratios of chromium, nickel, and molybdenum in the outermost cladding layer are closer to the content ratios in SUS312L.
In addition, the average residual ratio shown in Table 3 is calculated by weighted average of the residual ratio of each component.

  As shown in Table 3, in Examples 1 to 3, the average residual rate in the outermost cladding layer and the residual rates of chromium, nickel and molybdenum exceeded 90%, and chromium and nickel in the outermost cladding layer It was confirmed that the respective content ratios of molybdenum and molybdenum approached the respective content ratios in SUS312L. On the other hand, in Comparative Examples 1-5, it was confirmed that each said residual rate is lower than Examples 1-3.

  As described above, the inner clad layer forming step and the outer clad layer forming step are performed, and the single-layer clad layer is formed by keeping the melting by the laser in the outer clad layer forming step up to the inner clad layer. In the case of the outer clad layer forming step, each content ratio of chromium, nickel and molybdenum in the outermost clad layer is compared with the case where the surface side of the carbon steel is melted by laser until reaching the carbon steel by laser. It was confirmed that the content ratio can be brought close to each of the above.

(simulation)
Here, in Examples 1 to 3 in the verification test, the layer formation process was repeated twice, and as a result of laminating two clad layers, the average residual rate of the outermost clad layer which is the second clad layer was It was confirmed that it exceeded 90%, but the layer formation process was repeated three times, and three clad layers were laminated to form the third outermost clad layer, whereby chromium and nickel in the outermost clad layer were formed. It is considered that the content ratios of molybdenum and molybdenum can be made closer to the content ratios in SUS312L.

Therefore, a simulation was performed to calculate the expected value of the average content of the outermost cladding layer when the layer formation step was repeated three times.
In this simulation, the average remaining rate of the outermost cladding layer in the two types of laser cladding methods of Reference Examples 1 and 2 was calculated.

In each laser cladding method of Reference Examples 1 and 2, in the layer forming process, in the cladding layer formed in the layer forming process (hereinafter referred to as a formed cladding layer), carbon steel serving as a base of the formed cladding layer or An expected value of the average residual ratio in each cladding layer was calculated after making the content ratio (% by weight) including the base component, which is a component of the cladding layer, constant.
The conditions and results are shown in Table 4.

  As a result, the average remaining rate of the second cladding layer in Reference Examples 1 and 2 is 91 to 94%. Here, since the average residual ratio of the outermost cladding layer (second cladding layer) in Examples 1 to 3 in the verification test is also 91 to 94%, the laser cladding method of Examples 1 to 3 Under the above conditions, it is considered that the content ratio of the base component in the formed clad layer was 25 to 30% by weight.

  In Reference Examples 1 and 2, which are considered to be the same conditions as in Examples 1 to 3, the average residual rate of the outermost cladding layer, which is the third cladding layer, exceeds 97%. It is considered that the respective content ratios of chromium, nickel and molybdenum in the outermost cladding layer are closer to the respective content ratios in SUS312L, and the carbon steel 2 can be reliably provided with corrosion resistance.

DESCRIPTION OF SYMBOLS 1 Corrosion-resistant metal clad steel 2 Carbon steel 2a Surface 3A Inner clad layer 3B Outer clad layer 4 Laminated structure L Laser

Claims (4)

A metal powder supplied from the surface side of carbon steel made of SUS312L is melted by a laser that irradiates the surface side, and includes a layer forming step of forming a cladding layer on the surface side,
By laminating the clad layer on the surface side by repeating the layer forming step a plurality of times, a laminated structure composed of a plurality of layers of the clad layer is formed,
In the second and subsequent layer forming steps, laser melting is performed until the cladding layer formed in the immediately preceding layer forming step is melted by a laser. Provided with multiple clad layers laminated on the surface side of carbon steel,
The clad layer is formed by melting the metal powder made of SUS312L and supplied to the surface side with a laser that irradiates the surface side,
A laminated structure in which melting by a laser when forming the second and subsequent clad layers from the inside is held up to the clad layer formed immediately before. The laminated structure according to claim 2,
The clad layer has a two-layer structure comprising an inner clad layer formed on the carbon steel and an outer clad layer laminated on the inner clad layer from the outside,
The laminated structure, wherein the outer cladding layer is thicker than the inner cladding layer.   A corrosion-resistant metal clad steel comprising carbon steel and the laminated structure according to claim 2.

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