JPH0361554B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a method for producing a multilayer cladding having excellent corrosion resistance, bonding properties, and surface properties of the laminated material, which is made by firmly bonding alloy steel or non-ferrous metal having excellent corrosion resistance to the surface of a steel material. This is related to. [Prior art] Clad steel sheets, which are made by forming alloy steel or nonferrous metal layers with excellent corrosion resistance on the surface of steel materials such as carbon steel, low alloy steel, and high alloy steel, can meet the high demands of corrosive environments. It is widely used as a composite metal material in the shipbuilding industry, petrochemical industry, industrial machinery industry, etc. Until now, clad steel sheets have been produced using explosion rolling, overlay rolling, and rolling joining methods (open sandwich type, sandwich type, semi-sanded type).
However, these manufacturing techniques and the clad steel sheets manufactured by these techniques have the following technical difficulties. Oxidized scales are formed on the surface of clad steel sheets produced by methods such as explosion rolling, build-up rolling, and open sandwich-type rolling joining, due to heating, but also due to the rolling process. As scale flaws or steel indentation flaws occur, the surface quality of the laminate becomes extremely poor. In the sandwich-type rolling joining method and the semi-sanding Germany-type rolling joining method, the surface quality of the laminated material deteriorated due to the separation material. In other words, indentation of the separating material during the rolling process, increased surface roughness due to poor wetting of the separating material during rolling, and intrusion of the separating agent itself or gas released from the separating material into the joining material. Deterioration of material surface properties and surface cracking of the laminated material occurred. In addition, defective joints between the laminate material and the base material occurred due to gas released from the separation material. Therefore, in conventional manufacturing technology, repair processes such as scale flaws and cracks on the surface of the laminate, or poor bonding between the laminate and the base steel, as well as polishing processes on the surface of the laminate are unavoidable. It was necessary to secure an allowance in advance for repairing defects and cracks and for polishing to remove scale. For this reason, there was an economic difficulty in that the yield was lowered and the manufacturing cost of the clad steel sheet could not be reduced. Furthermore, in order to guarantee the same material properties as the laminated material, especially corrosion resistance, in welding repair parts of flaws, cracks, or poor joints, it is necessary to
In order to keep component dilution from the base steel as low as possible, it is inevitable to use a multi-pass welding method with low heat input to ensure a certain number of layers or more, and as a result, the quality assurance of the welded repair part mentioned above cannot be guaranteed. The lower limit of the possible thickness of the laminate was limited. In addition, in the surface polishing process to remove minor surface cracks, scratches, scale, etc., the amount of polishing cannot be strictly controlled due to the initial deformation of the clad steel plate and the strain induced during polishing. There was a risk that some parts would not meet the material tolerances. As shown in 1 to 3, with the current manufacturing technology, a clad steel plate having a thin coating laminate cannot be manufactured because a repair process and a polishing process are unavoidable. In addition to these technical problems, conventional clutch steel plates only exhibit excellent corrosion resistance in a corrosive environment when the laminate covers the entire surface of the base steel plate, resulting in scratches, scratches, and scratches. If the base steel is exposed due to damage to the cladding material, such as a crack or crack, a galvanic cell is formed at a corrosion potential with the noble cladding material serving as the cathode electrode and the base steel serving as the anode electrode. As a result, so-called galvanic corrosion occurs, in which the base steel is selectively corroded at a significantly high rate. This corrosion progresses in the base steel both in the direction parallel to the joint surface and in the thickness direction, but the progression of corrosion in the thickness direction is especially a very serious problem. In other words, when corrosion progresses in the thickness direction, through holes are formed in the base steel, allowing corrosive substances to leak or enter, which not only causes the structure to lose its functionality, but also causes environmental pollution and human disasters. There was a serious problem of triggering. If the coating thickness is thin, the base steel will be exposed more frequently due to damage to the cladding, and there is a risk of galvanic corrosion.Thinly coated clad steel sheets should not be used in structures that are used in corrosive environments. Very difficult. Despite the serious technical problems with conventional manufacturing techniques and the clad steel plates manufactured using these techniques, it has been proven that the clad metal with excellent corrosion resistance can be firmly bonded to the base steel. At present, emphasis is placed only on [Objective of the Invention] An object of the present invention is to use a rolling joining method to improve the surface quality of the laminate of clad steel plates after rolling, and to ensure that the laminate does not deteriorate during transportation of the clad steel plates, construction of structures, or use. It is an object of the present invention to provide a method for manufacturing a multilayer clad steel plate having extremely excellent corrosion resistance and having a structure capable of preventing the progression of corrosion to the base steel due to galvanic corrosion when damaged, particularly corrosion progression in the thickness direction. [Summary of the Invention] In the present invention, attention is paid to the sandwich type and semi-sand Germany type rolling joining methods from among the conventional techniques, and the joint method is placed in the gap between the cladding material to be separated after rolling or the dummy steel and the dummy steel. As a separation material,
Boron nitride (BN) is excellent, and by arranging boron nitride as a separating material, the surface of the laminated material after rolling is free of defects and has a metallic luster, and its surface roughness is
It was revealed that the thickness could be controlled to 100 μm or less. On the other hand, with regard to galvanic corrosion, we focused on the fact that the laminated material is electrochemically more noble than the base steel, and developed a method to reliably prevent galvanic corrosion from progressing to the plate thickness method. , the cross-sectional structure of the clad steel plate in the plate thickness direction is as shown in the example below. It was revealed that a multilayer structure in which the noble metal is located on the steel side is effective. As a result, we adopted a sandwich-type or semi-sandwich-type rolling joining method as a manufacturing method, and placed boron nitride in the gap between the laminate original plate and the laminate original plate, or between the laminate original plate and the dummy steel, which were separated after rolling. By arranging at least one set of metals that are more noble at galvano potential than the steel between the original material plate and the base steel, such that the noble metal is located on the base steel side,
The major technical and economical problems of the prior art and the clad steel sheets produced using that technology have been solved at once. This has made it possible to produce a clad steel sheet with a multilayer structure that has excellent laminate surface quality and prevents the progression of galvanic corrosion in the thickness direction. In addition, it is now possible to manufacture thinly coated clad steel sheets, which were outside the range that could be manufactured with conventional technology, and since it has a multilayer structure that prevents galvanic corrosion from progressing in the thickness direction, the thickness of the laminated material can be made thinner. Even with this new technology, it has become possible to meet more advanced demands in more severe corrosive environments. In the present invention, metal materials nobler than steel at galvanic potential include Cu, Ni, Fe, Cr, Mo, Ti,
A metal consisting of one or more elements such as Zr, Ta, and Nb is effective. For example, acidic, seawater,
In a corrosive environment such as fresh water, metals that are more noble than steel include the following metals. Pure metals such as Cu, Ni, Mo, Ti, Zr, and Nb, and Ni-based alloys such as Hastelloy and Inconel.
Copper alloys such as 90/10 Cypronickel, 70/30 Cypronickel, Monel, etc. Ferritic, austenitic, and martensitic stainless steels and Fe-Cr-Ni-Mo steel As is clear from the above, the present invention improves corrosion resistance. The surface roughness of the cladding material is 70 μm or less, and at least one metal layer consisting of steel and a metal more noble than this steel is provided between the cladding material and the base steel, and the noble metal is on the base steel side. Then, boron nitride is placed between the above-mentioned laminate material and the laminate material or dummy steel that is overlapped facing this laminate material to form a sanderch type or semi-sanderch type composite. The present invention provides a method for producing a multilayer clad steel sheet with excellent corrosion resistance, characterized in that after forming, hot rolling is performed to separate the layers between layers in which boron nitride is present. In this case, the amount of boron nitride is 0.3gr/ ^m2 .
The above is preferable in order to ensure good separation properties and surface properties. The amount of boron nitride as a separating agent per ^m2
If it is less than 0.3 gr, separation may not be possible, or a partial crimped portion on the separation surface may break, resulting in rough surface roughness at that portion. Further, it is preferable that the rolling reduction rate per pass in the hot rolling be 3 to 35% in order to ensure good surface quality and sound bondability. Reduction rate per pass in hot rolling is 3%
If it is less than 35%, the shear strength may vary to a low level, and on the other hand, if the reduction rate per pass is
If the weld exceeds this value, the restraint weld of the composite may be damaged during rolling, and in that case, high-temperature air may enter the composite, resulting in non-bonded areas or oxidation of the surface of the laminate. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In Fig. 1, which shows the assembly structure of a sandwich-architecture composite for multilayer clad steel, 1, 1 is a base steel slab, 2, 2 is a laminated original plate with excellent corrosion resistance,
3 is interposed between the laminate original plates 2 and 2 and is made of boron nitride BN as a separating material; 4 and 4 are interposed in the next layer of the laminate original plates 2 and 2 in order to receive corrosion on behalf of the base steel 1 and 1. Steel materials 5, 5 are metal materials more noble than steel interposed between the steel material 4 and the base steel 1, 6, 6, 7,
7, 7', and 7' are used to ensure mutual bonding between the original plate 2 and the steel material 4, between the steel material 4 and the metal material 5, and between the metal material 5 and the base steel 1, respectively. This is an insert metal material that is inserted to increase the height. In addition, 8 indicates Zr and Ti introduced into the composite.
9, 9 is a frame material located between the base steel 1, 1 and holding the laminated material original plates 2, 2, etc., 10
is an exhaust port, 11 is an exhaust pipe attached to the outer end of the exhaust port 10, 12 is a mounting weld for fixing the exhaust pipe 11 to the frame member 9, and 13, 13 are both ends of the separation part 3. 14, 14, ... is a shield welding part that shields 15, 1
5 is a separation plane, and 16, 16, . . . are constrained welds. Next, a method of assembling the above composite will be explained. First, among the clean front and back surfaces of each laminate material original plate 2,
The surface roughness of one surface, which becomes the separation surface 15, is 70 μm or less. Next, the separation surface 1 of each laminated material original plate 2
The boron nitride 3 is placed in the gap between 5 and 15. After that, one surface of the base steel 1, the steel material 4, and the front and back surfaces of the metal material 5, which is nobler than the steel in the galvano potential series, are cleaned, and as shown in FIG. are arranged so that their clean surfaces face each other with the insert metal material 6 in between, and the more noble metal material 5 and the base steel 1 are similarly placed in a manner that the clean surfaces face each other through the insert metal material 7' in the galvano potential series. Place them so that they are facing each other. A gas absorbing substance 8 such as Zr or Ti is charged into the gap between each frame material 9 and each laminated material original plate 2, and after shield welding the frame material 9 and base material steel 1, it is forced through the exhaust port 10 and the exhaust pipe 11. Vent the air and isolate the inside of the composite from outside air. Next, the metal is heated to a temperature below the melting point of the metal constituting the multilayer structure, and hot rolled at a reduction rate of 3 to 35% per pass. Here, in order to make the joint stronger, (1) an insert metal material 6 is inserted between the base material plate 2 and the steel material 4; Insert metal materials 6, 7, 7' are inserted between each. However, depending on the type of the blank material 2 and the metal material 5 nobler than steel, it is possible to omit the insertion of the insert metal material 6 or 7, 7'. (2) Keep the bonding surfaces of the original plate 2, the base steel 1, the steel 4, and the metal 5 nobler than the steel cleaner, and prevent residual gas inside the composite that may cause poor bonding. In order to remove the gas released during heating, absorption of the gas by the gas absorbing material 8 and forced exhaust through the exhaust port 10 are used together. (3) As shown in Fig. 1, the laminated materials of the laminated material original plate 2, steel material 4, metal material more noble than steel 5, and insert metal materials 6, 7, and 7' are partially restrained welded to prevent rolling. This prevents the occurrence of non-joined portions at the leading and trailing ends that may occur due to deviation of each material in the rolling direction during rolling. As a result, sound bonding can be achieved during the hot rolling process. Figure 2 shows a schematic cross-sectional view of a semi-sandwich type composite. As is clear from the comparison with Fig. 1, there is no difference in the assembly structure except that one side is made of dummy steel material 17.
The same parts as those in the figures are given the same numbers and redundant explanations will be omitted. Next, the effects of the present invention will be explained based on specific examples, but the following is merely a description of typical examples, and as mentioned above, changes and implementations may be made within the scope of the scope of the claims. within the scope of the invention. In the following, we will first test a conventional type of clad steel sheet and demonstrate that boron nitride BN functions extremely effectively in ensuring excellent surface quality after rolling, and then manufacture the multilayer clad steel sheet according to the present invention. This shows that boron nitride BN is effective as a separation material even when Thereafter, it will be clarified that the thickness cross-sectional structure of the multilayer clad steel sheet manufactured based on the technology of the present invention can reliably prevent the progression of galvanic corrosion in the thickness direction in the case of damage to the laminate. (b) About the separating material As a result of research on the appropriate separating material to be placed in the gap between the laminate and the laminate, or between the laminate and dummy steel, which are to be separated after rolling, the characteristics that the separating material should have were found. However, it was found that the following (a) to (e) were true. (a) It is chemically stable in the heating hot rolling temperature range and does not react with or invade the laminate. (b) There is no gas released during heating, which causes a decrease in bondability. (c) It has lubricity under high temperature instep pressure during rolling and straightening. (d) No deterioration of surface quality during rolling, i.e.
Do not cause defects or increase surface roughness. (e) The separability of the laminate material or the dummy steel from the laminate material after rolling, and the removal of the separation material shall be good. Based on these points of view, various types of separation materials were tested in order to select an appropriate separation material. Using a 90/10 Cypronickel base plate (CN, 2.5 mm thick) as the laminating material and a base steel slab (SM41B, 15 mm thick) as the base material, we created a conventional sandwich type for clad steel plates as shown in Figure 3. After assembling the composite, the finished product thickness (base material steel thickness + 90/10 Cypronickel thickness) was (4.3 mm).
+0.7mm). The total reduction ratio is 3.5. The finished product is a conventional type thinly coated CN clad steel plate with a CN thickness of 0.7 mm. In Fig. 3, 20 and 20 are base metal steel, 21 and 21 are 90/10 Cypronickel as a joining material, and 23 is boron nitride as a separating material.
BN, 24, 24 is used as insert metal material
Ni foil, 25, 25 is the frame material, 26 is the gas absorbing material, 27, 27 is the shield welding part for the laminated material 21, 21, 28, 28, ... is the shield welding part between the base material steel 21 and the frame material 25. be. After rolling, both ends were cut, and the separability of the upper and lower clad steel plates, the removability of the separating material, the surface condition of the laminated material, the deterioration of surface roughness, and the bondability were investigated. The results are shown in Table 1. It can be seen that boron nitride BN is the most excellent separation material. That is, it has excellent lubricity under high temperature and high pressure during rolling, has good separability and removability, and the surface appearance of the laminated material (CN) after rolling maintains a metallic luster. Furthermore, there were no scratches, cracks, etc. on the surface of the laminate, and the surface roughness of the laminate after rolling was the lowest among the various separating materials tested. Furthermore, JIS standards for bondability (lower limit standard value 10Kgf/mm ² )
I am fully satisfied. Based on the above results, if boron nitride BN is selected as an appropriate separating material for use in the sandwich type or semi-sand Germany type rolling joining method,
As mentioned above, it has been found that it is possible to produce a clad steel plate in which the surface of the laminate material after rolling maintains a metallic luster and is also defect-free. Therefore, boron nitride BN was selected as the separation material.

[Table] (B) Regarding the charging amount of boron nitride In order to investigate the required charging amount of boron nitride, 90/10CN original plate was used as the composite material and SM41B was used as the base steel, as shown in Figure 3. Composite slabs for conventional clad steel plates were fabricated and hot rolled. At this time, the composite assembly conditions and rolling conditions are shown in Table 2. Table 2 also shows the results of separability, surface condition of the laminate material after rolling, and surface roughness. FIG. 4 shows the relationship between the amount of separating material charged and the surface roughness of the laminated material after rolling. As is clear from Table 2 and Figure 4, by setting the charging amount of boron nitride to 0.3 gr or more per 1 m ² , the separability after rolling is good, and the surface of the laminate material after rolling has a metallic luster. The surface has no flaws or cracks, and the surface roughness of the laminate after rolling is 75 μm or less, which is an extremely excellent surface quality.

[Table] (c) Regarding the surface roughness of the laminating material original plate 90/10CN as a laminating material of composite material
Original plate or SUS304 as base material steel SM41B
Using BN as a separating material, a conventional sandwich-type composite slab for clad steel as shown in FIG. The controllable range of the surface roughness of the laminate after rolling was investigated. The composite assembly conditions and rolling conditions for this purpose are as shown in Table 3. Also, the longitudinal direction (L) and transverse direction of the laminated material after rolling.
Table 3 shows the measurement results of surface roughness in (C). FIG. 5 shows the relationship between the surface roughness of the separated surface of the original plate of the laminate before rolling and the surface roughness of the laminate after rolling. As is clearer from Table 3 and Figure 5, by making the surface roughness of the laminate original sheet 70 μm or less and charging 0.3 gr or more of boron nitride as a separating material per 1 m ² , the laminate material after rolling is Surface roughness 100μm
You can do the following. In addition, there are no scratches or cracks on the surfaces of thinly coated clad steel sheets with coating thicknesses of 0.4 mm and 0.7 mm, and thickly coated clad steel plates with coating thicknesses of 3 mm or more, and the surface appearance is , maintains a metallic luster. As a result of the above, the surface polishing process and repair process that were necessary in the conventional technology can be omitted.
It has become possible to manufacture clad steel sheets with a thin coating and a laminated material thickness that was previously impossible to manufacture.

【table】

[Table] (d) Corrosion resistance 90/10 Kiypronickel as the base material for laminating material.
SM41B is used as the base steel plate, SM41B is used as the steel, pure nickel is used as a metal that is more noble than steel in terms of corrosion potential in seawater, and pure nickel is used as the insert metal material to strengthen the bond between the base plate and the steel. Using the above-selected boron nitride (charging amount 0.3gr/ ^m2 or more) as a separating material placed between the laminate original sheets and the laminate original sheets, the multilayer structure 90/
A sandwich-type composite slab for 10 Cypronickel multilayer clad steel was fabricated and hot rolled. At this time, boron nitride was charged so as to satisfy the required amount. The composite assembly conditions, hot rolling conditions, surface condition of the laminate after rolling, and measurement results of the surface roughness are as shown in Table 4.

[Table] As is clear from Table 4, the surface roughness of the laminated material of the multilayer clad steel sheet after rolling is as follows: The surface roughness of the laminated material original plate is 70μm or less, and the boron nitride as a separating material is 0.3gr/m. By charging ² or more, the surface roughness of the laminate material after rolling can be made 100 μm or less. In addition, there were no scratches or cracks on the surface of either the thinly coated clad steel sheets (laminated material thickness: 0.4 mm, 0.8 mm) or the thickly coated clad steel sheets (laminated material thickness: 2.0 mm). , and maintains a metallic luster. Next, the above 0.8 manufactured according to the technology of the present invention
By hot rolling a multilayer clad steel plate with a coating thickness of mm and a composite having the structure according to Fig. 3,
The manufactured conventional clad steel plates were used as test materials, and the diameter of each clad steel plate was artificially set to 3
A test piece with a mm round hole was prepared and an actual seawater immersion test was conducted. Table 5 shows the test results for immersion periods of 45 days and 60 days. Further, FIGS. 6 and 7 schematically show the corrosion state after the immersion test of a conventional clad steel plate and a clad steel plate according to the method of the present invention, respectively. As is clear from these tables and figures, in conventional 90/10 Cyprus clad steel sheets, galvanic corrosion progresses in the base steel in both directions parallel to the steel sheet surface and in the thickness direction. . On the other hand, 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. It is clear that the noble metal completely prevents galvanic corrosion from progressing through the thickness of the plate.

[Table] From the above, it can be seen that the technology of the present invention is functioning extremely effectively in solving the serious technical and economical problems inherent in conventional manufacturing technology and clad steel sheets manufactured using that technology. found. In other words, in the rolling joining method, the surface roughness of the separation surface of the laminated original plate, which has excellent corrosion resistance, is set to 70 μm.
As per the following, 0.3 gr/m 2 or ^more of boron nitride per 1 m ² shall be placed as a separating material in the separation surface gap between the laminate material original plate and the laminate material original plate, or the separation surface gap between the laminate material original plate and dummy steel, and the base material steel A composite slab for multi-layered clad steel is formed by arranging one or more pairs of steel and a metal more noble than the steel between each joint surface of the original plate of the laminated material, and is heated to below the melting point of each material. Clad steel sheets produced by hot rolling have a laminate surface with no defects and a metallic luster, the surface roughness is controlled to 100 μm or less, and there is no damage in the thickness direction due to damage to the laminate. It has become clear that the plate has a cross-sectional structure with a thickness that can reliably prevent the progress of galvanic corrosion. [Effects of the Invention] As is clear from the above, according to the present invention, the surface quality of the laminated material after rolling is excellent, and
Multilayer clad steel sheets with excellent corrosion resistance can be easily produced.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of the assembly structure of the Sanderch type composite according to the present invention, and FIG.
The figure is an explanatory cross-sectional view showing an example of the assembly structure of a semi-sandier arch type composite, Figure 3 is an explanatory cross-sectional view showing the assembled structure of a conventional sandwich arch type composite, and Figure 4 is an explanatory cross-sectional view showing the assembled structure of a semi-sandier arch type composite. A graph showing the relationship between the surface roughness of the laminate material, and FIG. 5 a graph showing the relationship between the surface roughness of the laminate original plate and the surface roughness of the laminate material after rolling. A cross-sectional explanatory diagram schematically showing the corrosion situation after the test,
FIGS. 6b and 6c are enlarged cross-sectional explanatory views of parts A and B of FIG. 6a, respectively, and FIG. 7 is a cross-sectional explanatory view showing the corrosion state of a conventional product after an immersion test.

Claims (1)

[Scope of Claims] 1. The surface roughness of the cladding material having corrosion resistance is 70 μm or less, and at least one set of metals consisting of steel and a metal nobler than the steel is provided between the cladding material and the base steel. After arranging the layers so that the above-mentioned noble metal is located on the base steel side, 1 m 2 of boron nitride is placed between the above-mentioned laminate material and the laminate material or dummy steel that is overlapped facing this laminate ^material. Place 0.3gr or more per unit,
After forming a sanderch type or semi-sanderch type composite, it is hot rolled and separated between layers with boron nitride present.It has excellent corrosion resistance and galvanic corrosion prevention properties in the plate thickness direction. A method for producing multilayer clad steel sheets. 2. The method for manufacturing a multilayer clad steel sheet according to claim 1, wherein the rolling reduction per pass in the hot rolling is 3 to 35%.