JPH0363512B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a clad steel plate with excellent corrosion resistance and bondability, which is obtained by firmly bonding alloy steel or non-ferrous metal having excellent corrosion resistance to the surface of a steel material. (Prior art) Clad steel sheets are made by forming a layer of highly corrosion-resistant laminate material (alloy steel or nonferrous metal) on the surface of steel materials (carbon steel, low alloy steel, high alloy steel, etc.), and are resistant to corrosion in corrosive environments. As a composite metal material that can meet advanced demands,
It is widely used in the shipbuilding industry, petrochemical industry, industrial machinery industry, etc. By the way, conventional clad steel sheets only exhibit excellent corrosion resistance in a corrosive environment when the laminate covers the entire surface of the base steel sheet. There was a very serious technical problem in that the base metal would corrode extremely quickly if exposed. Scratches, scratches, and indentation scratches on laminate materials during the transportation process. Cracks in the laminate during welding work. Defects that occur during use of a structure. Generally, when dissimilar metals come into contact in a corrosive solution, the metal side that is base in the corrosion potential (galvanic potential) series depending on the corrosive environment to which the metal material is exposed is used as the anode electrode, and the metal side that is noble is used as the cathode electrode. A galvanic cell is formed as an electrode, and the base metal is severely corroded. This corrosion behavior is called galvanic corrosion. Clad steel sheet is a composite material made by metallurgically joining different metals, and since the base steel sheet is less base in the corrosion potential series compared to the laminated metal, which has excellent corrosion resistance, it is If the base metal is exposed due to damage and placed in the same corrosive environment as the clad metal, the galvanic corrosion described above will occur, and the base steel, which is less base than the clad metal, will selectively corrode. It corrodes. In this case, corrosion progresses in both parallel and perpendicular directions (thickness direction) to the surface of the laminate, and the corrosion rate is usually several to several hundred times that of the base steel alone. Become. In structures using clad steel plates, when galvanic corrosion progresses and penetrates the base steel, corrosive substances leak or enter, causing the structure to lose its functionality. Furthermore, even if penetration does not occur, that portion becomes a stress concentration area, inducing failure such as fatigue fracture or brittle fracture, and similarly causes the structure to lose its function. Loss of functionality of these structures may eventually lead to environmental pollution or human disasters. Therefore, in order to use a clad steel plate in a corrosive environment, it is necessary to solve the serious technical problem of preventing galvanic corrosion, particularly preventing the progression of galvanic corrosion in the thickness direction. However, at present, emphasis is placed only on bonding a laminating metal with excellent corrosion resistance to a base steel plate, and no technical consideration is given to the problem of preventing galvanic corrosion. (Objective of the Invention) The object of the present invention is to have a structure that not only exhibits the excellent corrosion resistance of the laminated material but also can prevent corrosion of the base steel due to galvanic corrosion, particularly corrosion in the plate thickness direction. An object of the present invention is to provide a multilayer clad steel sheet with extremely excellent corrosion resistance. The present invention focuses on the fact that galvanic corrosion occurs because the laminated material is electrochemically more noble than the base steel, and has conducted various research studies on methods to prevent the progression of galvanic corrosion in the thickness direction. This is the result obtained by doing this. (Structure of the Invention) The multilayer clad steel sheet according to the present invention includes a pair of ordinary steel and a metal whose galvanic potential is nobler than that of the ordinary steel, between the base steel and the laminated material (corrosion-resistant metal layer).
It is characterized in that at least one set of noble metals is interposed so as to be located on the base steel side. In the present invention, the types of steel to be inserted include:
It is made of so-called ordinary steel that does not become passivated in a corrosive environment. Also, metals that are more noble than steel include
Metals consisting of one or more of the following elements are effective: Cu, Ni, Cr, Mo, Ti, Zr, Ta, Nb, etc. For example, in corrosive environments such as acidic, seawater, and fresh water, the following ~ Metal corresponds. Pure metals such as Cu, Ni, Cr, Mo, Ti, Zr, Ta, Nb, etc. Ni-based alloys such as Hastelloy and Inconel and 90/
10 Kyupronitskel, 70/30 Kyupronitskel,
Copper alloys such as Monel. Ferritic, austenitic, and martensitic stainless steels and Fe-Cr-Ni-Mo
steel. (Function) The multilayer clad steel sheet according to the present invention not only exhibits excellent corrosion resistance of the laminated material (corrosion-resistant metal layer), but even if the laminated material is damaged, the steel layer remains in the direction parallel to the base steel. The progress of corrosion in the plate thickness direction is reliably prevented by the noble metal layer interposed between the steel and the base steel. Therefore, the above-mentioned technical problems of conventional clad steel sheets have been solved at once, and it has become possible to meet more advanced requirements in severe corrosive environments. (Example) An example of the present invention will be described below based on the attached drawings. Note that the following is merely a description of typical examples, and all modifications and implementations within the scope of the scope of the claims are included in the technology of the present invention. FIGS. 1a, b, and c show the thickness cross-sections of multilayer clad steel sheets manufactured by the rolling bonding method, diffusion bonding method, explosion bonding rolling method, etc. according to the present invention.
Here, 1 is a corrosion-resistant metal composite material, 2 is a base steel plate, 3 is an insert metal, 4 is ordinary steel, and 5 is a metal material whose corrosion potential (galvanic potential) is nobler than ordinary steel 4. Figure 1 a and 1
In the single-sided clad steel shown in FIG.
In the latter case, two sets are arranged. In the double-sided clad steel plate shown in Fig. 1c, ordinary steel 4 and ordinary steel 4
A metal 5 which is more noble than the metal 5 is arranged. Metal 3 inserted between cladding material 1 and steel 4
are arranged to form a stronger bond. Depending on the type of metal 5, which is nobler than ordinary steel, proper bonding may be necessary between ordinary steel 4 and metal 5, or between metal 5 and base steel 2, to ensure sound bonding. It may be necessary to place insert metal. It goes without saying that clad steels in which three or more sets of ordinary steel 4 and metal 5 nobler than ordinary steel 4 are arranged are also included in the scope of the present invention. Next, the effects of the present invention will be explained based on specific examples. 90/10 Cypronickel as the mating material, SM41B as the base steel plate, pure nickel as the insert metal to strengthen the joint, SM41B as the steel.
Using pure nickel as a metal whose corrosion potential in seawater is more noble than steel, a 90/10 Cypro nickel clad steel plate having a multilayer structure described in the structure of the present invention was manufactured by a sand-deutsch type rolling joining method.
The thickness of each layer of this 90/10 Cypronickel clad steel sheet after rolling is, starting from the cladding material side, 90/10 Cypronickel thickness (cladding material) 0.8mm, Nickel foil thickness (insert metal) 2 to 3μm, steel thickness 1.5mm. mm, nickel thickness (metal nobler than steel) 15μm, base steel thickness
It is 10mm. On the other hand, a conventional 90/10 Cypronickel clad steel plate was manufactured using 90/10 Cypronickel as the cladding material, SM41B as the base steel, pure nickel as the insert metal, and similarly using the sand-deutsch type rolling joining method. The base metal thickness of this conventional clad steel plate was 12 mm, and the 90/10 Cypronickel thickness was 0.8 mm. The nickel foil thickness of the insert metal is 6 μm. Using these multi-layer clad steel plates according to the present invention and conventional clad steel plates as test materials, test pieces were prepared by artificially adding round holes with a diameter of 3 mm to the composite material of each clad steel plate, and the test pieces were subjected to an actual seawater immersion test. was carried out to investigate the behavior of galvanic corrosion in seawater. The test results for immersion periods of 45 days and 60 days are shown in the table. FIG. 2a is a partial sectional view schematically showing the corroded part of the multilayer clad steel plate according to the present invention, and shows the hole 3
1 is given to the corrosion-resistant metal 1 and reaches the steel layer 4. After being immersed in seawater for 45 days and 60 days, the steel 4 near the hole 31 is corroded, and the corrosion holes 32 caused by the corrosion develop only in the longitudinal direction, and the corrosion in the thickness direction is similar to the steel 4. The base steel 2 was completely prevented from being corroded by the metal 5, which is more noble than the steel 4, interposed between the base steel 2, and the base steel 2 was not corroded at all. On the other hand, FIG. 3 is a schematic partial sectional view of a corroded portion of a conventional clad steel plate. Here, hole 36
was given to the corrosion-resistant metal 1, and the corrosion holes 37 caused by corrosion in seawater had spread widely in the base steel 2 both in the direction parallel to the steel plate surface and in the plate thickness direction. As shown in the table, in the case of the present invention material, the progress of galvanic corrosion in the plate thickness direction is
and the thickness of the steel 4 interposed between the base steel 2, i.e.

[Table] It is only 1.5mm, and there is no corrosion in the thickness direction of base steel 2, which can be controlled by the combination of steel and noble metal that mediates galvanic corrosion in the thickness direction. It shows. In addition, FIG. 4a is a micrograph showing the structure of the multilayer clad steel sheet according to the present invention under corrosion conditions (immersion period: 45 days), and FIGS. 4b and 4c are A of FIG. 2a, respectively. This is an enlarged micrograph (x200) of the bottom of a galvanic corrosion hole corresponding to parts 1 and 2.
As clearly shown in these photographs, in the clad steel plate according to the present invention, galvanic corrosion occurs only in the steel placed between the laminate and the base steel, and the base steel is not corroded at all. The noble metal placed between the steel and the base steel completely prevents galvanic corrosion from progressing in the thickness direction. From the above, the multilayer clad steel sheet according to the present invention has
It has been found that this method works extremely effectively to reliably prevent galvanic corrosion from progressing in the thickness direction, which was a serious technical problem with conventional clad steel plates. (Effects of the Invention) In the multilayer clad steel sheet according to the present invention having a laminating material with excellent corrosion resistance in the surface layer, when the laminating material is damaged, corrosion progresses to the base steel due to galvanic corrosion, especially corrosion in the thickness direction. Progress can definitely be stopped. As a result, the multilayer clad steel sheet according to the present invention can sufficiently meet more advanced requirements under severe corrosion ring mirrors than conventional clad steel sheets.

[Brief explanation of drawings]

FIGS. 1a and 1b are schematic partial sectional views of a single-sided clad steel plate according to the present invention, and FIG. 1c is a schematic partial sectional view of a double-sided clad steel plate according to the present invention. FIG. 2a is a schematic partial sectional view of a corroded part of a multilayer clad steel plate according to the present invention.
FIGS. 2b and 2c are partially enlarged cross-sectional views of portions A and B in FIG. 2a, respectively. FIG. 3 is a schematic partial sectional view of a corroded portion of a conventional clad steel plate. Figure 4 a, b, and c show corrosion experiments (immersion period 45
FIG. 4a, b, and c correspond to FIG. 2, a, b, and c, respectively. 1...Corrosion-resistant metal (laminated material), 2...Base material steel, 3...
Insert metal, 4... Steel layer, 5... Metal layer nobler than steel, 31... Artificial flaw imparted to laminate material, 32...
Corrosion hole, 36...Artificial flaw added to the laminated material, 37...
Corrosion holes.

Claims (1)

[Claims] 1. Between the corrosion-resistant laminate and the base steel, there is a pair of ordinary steel and a metal whose galvanic potential is nobler than that of the ordinary steel, so that at least one pair of the noble metal is located on the side of the base steel. A multilayer clad steel sheet with excellent corrosion resistance and galvanic corrosion prevention properties in the thickness direction.