JPH031114B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a clad steel plate, which is formed by firmly joining alloy steel or non-ferrous alloy of any thickness to the surface of a steel material. (Prior art) Clad steel sheets are made by forming layers of other alloy steels or non-ferrous alloys on the surface of steel materials such as carbon steel, low carbon steel, and high alloy steel. It is a composite metal material that can meet the strict requirements for advanced materials, such as corrosion resistance, heat resistance, abrasion resistance, and crack resistance, and is widely used in oil plants, seawater desalination equipment, pressure vessels, etc. ing. Until now, clad steel sheets have been produced using explosion bonding, pressure welding, overlay rolling, and rolling joining methods (open sandwich German trench type, sand German trench type, semi-sand German trench type).
However, these techniques have the following difficulties and cannot be said to be necessarily satisfactory methods. Oxidized scales are formed on the surface of clad steel plates made by manufacturing methods such as explosion rolling, overlay rolling, and open-sand Germany-type rolling joining, due to heating, and 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 laminate material deteriorates due to the separation material, that is,
Indentation flaws in the separating material during the rolling process, or inability of the separating material to follow deformation during rolling, i.e., increased surface roughness due to insufficient lubrication of the separating material;
Deterioration of the surface material properties of the laminate due to the separation material itself or the intrusion of gas released from the separation material into the laminate, and further surface cracking of the laminate due to these deteriorations occurred. In addition, defective joints between the laminate material and the base material occurred due to gas released from the separation material. For this reason, in conventional manufacturing technology, repair processes such as scale flaws, cracks, or poor bonding between the laminate and base steel on the surface of the laminate, and a polishing process on the surface of the laminate are unavoidable. At the design stage, it was necessary to secure an allowance for cleaning flaws and cracks and for polishing to remove scale. This results in a decrease in yield,
There was an economic difficulty in not being able to reduce the manufacturing cost of clad steel sheets. Furthermore, when repairing defects, cracks, or joint defects by welding, material properties equivalent to those of laminated materials,
In particular, since it is necessary to guarantee corrosion resistance, when repairing these welds, it is necessary not only to reduce the welding heat input in order to keep the dilution of components from the base steel as low as possible, but also to use multi-pass welding methods. When adopted, it becomes inevitable to secure a certain number or more of laminated layers. As a result, the lower limit of the thickness of the laminate material that can guarantee the quality of the welded repair portion described above is limited. In addition, in the surface polishing step for removing minor surface cracks, scratches, scales, etc., the amount of polishing cannot be strictly controlled due to initial deformation of the clad steel plate, strain induced during polishing, and the like. Therefore, not only is there a risk that some parts may not satisfy the laminate thickness tolerance, but also welding repair is not possible in the case of a clad steel plate formed with an extremely thin laminate. In addition, in the production of clad steel sheets, the repair and polishing processes described above are unavoidable with the current technology, so there was an extremely large technical problem in that it was impossible to manufacture clad steel sheets with a thin coating thickness. . (Object of the Invention) An object of the present invention is to provide a method for manufacturing clad steel plates in which the surface quality of the laminated material of the clad steel plates after rolling is excellent in the rolling joining method. In the present invention, from the viewpoint of preventing scale generation on the surface of the laminated material, attention is paid to the sanderch type and semi-sanderch type rolling joining methods from among the conventional techniques. As shown in the examples below, boron nitride (BN) has been found to be excellent as a separating material to be placed in the gap between the laminate and dummy steel or between the laminate and dummy steel to be separated after rolling. the result,
By adopting the sandwich type or semi-sand German style rolling joining method as the manufacturing method, and placing BN in the gap between the laminate and the laminate, or between the laminate and the dummy steel, which are separated after rolling, the technology of the conventional technology can be improved. The economic difficulties were solved all at once. (Structure of the Invention) In the present invention, in the rolling joining method of clad steel sheets, both surfaces of the original laminate sheet are cleaned, and boron nitride is applied to one of the two surfaces with a surface roughness of 70 μm or less. After coating, a sandwich-type composite is formed by placing the surfaces of the two original sheets of cladding material facing each other and the joining surfaces of the base steel and the cladding material facing each other, or by applying a dummy composite to the one surface of the original cladding material sheet. 3 to 35% per pass of a semi-sand German composite with the steel surface facing each other and the joint surfaces of the base steel and laminate facing each other.
Hot rolled at a reduction rate of . This method is characterized in that the surface of the laminated material after rolling is free from defects and has a metallic luster, and the roughness of the surface is controlled to 100 μm or less. FIG. 1 is a schematic cross-sectional view showing an example of a sandwich-arche composite assembly for producing a clad steel plate according to the present invention. In Figure 1, 1
2 is the base material steel slab, 2 is the original plate for the laminate material, 3 is the separation material, i.e. BN, 4 is the insert metal, 5 is the oxide-nitride forming substance such as Zr or Ti, 6 is the frame material, 7 is the exhaust port, 8
Reference numeral 9 indicates an exhaust pipe, 9 indicates a shield welded portion, and 10 indicates a welded portion between laminated materials. Note that 11 is a joint surface, and 12 is a separation surface. First, the surface roughness of one of the clean front and back surfaces of the laminated material 2, which will be the separation surface, is set to 70 μm. first,
As shown in Figure 1, in the gap between the separated surfaces of the laminate 2,
Place BN3. Thereafter, one surface of the base steel 1 is cleaned, and the mating material 2 and the base steel 1 are placed so that their respective clean surfaces face each other with the insert metal 4 in between, as shown in FIG. Frame material 6,
Gas absorbing substances 5, 5 such as Zr and Ti are charged into the gap between the frame material 6 and the laminated material 2, and after shield welding the frame material 6 and the base material steel 1, forced exhaust is passed through the exhaust port 7 and the exhaust pipe 8. , to isolate the interior of the composite from outside air.
Then, it is heated and hot rolled at a reduction rate of 3 to 35% per pass. After rolling, both ends are cut to separate the two clad steel plates. Here, in order to make the bond stronger,
(1) Insert metal 4 between laminate material 2 and base steel 1. (2) In order to keep the bonding surface between the laminate 2 and the base steel 1 cleaner, and to remove residual gas inside the composite and gas released during heating, which can cause poor bonding, Gas absorption by the absorbing substance 5 and forced exhaust through the exhaust port 7 are used together. As a result, in the hot rolling process,
A healthy bond can be achieved. FIG. 2 is a schematic cross-sectional view of a semi-sandwich type composite. Of the clean front and back surfaces of the laminate material 2, the surface roughness of one surface 12, which will be the separation surface, is
Should be 70μm or less. In assembling this composite, the gap between the cladding material 2 and the dummy steel 13 is
Place BN3. Thereafter, one surface of the base steel 1 is cleaned and placed so as to face the clean surface 11 of the laminate 1. Gas absorbing substances 5, 5 are charged into the gap between the frame members 6, 6 and the laminate member 2, and the frame member 6, base material steel 1, and dummy steel 13 are shield welded. Thereafter, the exhaust is forcibly exhausted through the exhaust port 7 and the exhaust pipe 8 to shut off the inside of the composite from outside air. Next, hot rolling is performed to produce a clad steel plate. In the following, specific examples will mainly be explained about clad steel plates formed by the Sand-German-tied rolling joining method. However, the following is merely a description of typical examples, and changes may be made within the scope of the scope of the claims. are all included within the scope of the present invention.
For example, in the production of single-sided clad steel plates or two or more layers of clad steel plates using other types of rolling joining methods, such as the semi-sandwich type,
It goes without saying that the method described below can be carried out in accordance with or with some modifications, and these methods are included in the present invention. (Example) Example 1 First, as a result of conducting research on an appropriate separating material to be placed in the gap between the laminate and the laminate, or between the laminate and the dummy steel, which are to be separated after rolling, it was found that It was found that the power characteristics are the following (a) to (e). (a) It is chemically stable in the hot heating 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 and pressure during rolling and straightening. (d) During rolling, the surface quality should not deteriorate, that is, it should not cause defects or increase in surface roughness. (e) Separability between laminates or dummy steel after rolling is good. From these viewpoints, various separation materials were tested in order to select an appropriate separation material. 90/10 Cypronickel base plate (CN, 2.5mm) as a laminating material
thickness) and base material steel slab (SM41B, 15
mm thickness), assemble the composite as shown in Figure 1 according to the procedure described in the structure of the invention, and the finished product thickness (base material steel thickness + 90/10 Cypronickel thickness) is (4.3
mm + 0.7 mm). The total reduction ratio is 3.5. The finished product is a thinly coated CN clad steel plate with a CN thickness of 0.7 mm. 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 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 due to rolling was the lowest among the various separation materials tested. Furthermore, the bondability fully satisfies the JIS standard (lower limit standard value 10 kgf/mm ² ). From the above results, it is clear that the appropriate

[Table] As mentioned above, it was found that by selecting BN as the separating material, it was possible to produce a clad steel sheet in which the surface of the laminate material after rolling maintained a metallic luster and was also defect-free. Therefore, boron nitride was selected as the separation material. Example 2 A 90/10CN original plate or high carbon steel original plate (S50C) was used as the composite material, and an SM41B base steel slab was used as the separation material.
A sandwich-type composite slab was produced using BN in the same manner as in Example 1, and then hot rolled to investigate the controllable range of the surface roughness of the laminate after rolling. The composite assembly conditions and rolling conditions for this purpose are as shown in Table 2. Table 2 also shows the measurement results of the surface roughness in the longitudinal direction L and the lateral direction C of the laminated material after rolling. FIG. 3 shows the relationship between the surface roughness of the separation plane in the original plate of the laminate before rolling and the surface roughness of the laminate after rolling. As is clearer from Table 2 and Figure 3, if the surface roughness of the laminated original plate is 70μm or less, the

【table】

[Table] The surface roughness of the laminate material can be reduced to 100μm or less. Also,
There are no scratches, cracks, etc. on the surfaces of all rolled clad steel sheets, and the surface appearance maintains a metallic luster. Therefore, the surface polishing step can be omitted. From the above, in the sand-deutsch type rolling joining method, the surface roughness of the separation surface of the laminated material original plate is set to 70 μm or less, and BN having the properties (a) to (e) above is used as the separation material, and 3 to 3. If hot rolling is carried out under hot rolling conditions with a rolling reduction rate of 35%, the surface of the laminate after rolling will be free of defects, exhibit a metallic luster appearance, and further improve the surface roughness of the laminate. It was found that it was possible to control the thickness to 100 μm or less. (Effects of the Invention) In the present invention, since BN having the above-mentioned properties is used as the separation material and the separation part is isolated from the outside air, the rolling reduction rate of 3 to 35% pass is reduced. The surface of the laminate material of the manufactured clad steel sheet has a metallic luster, and there are no scratches or cracks on the surface. The surface roughness of the laminated material can be reduced to 100μm or less. As a result, the surface polishing process of the laminate and the surface welding repair process in the production of clad steel sheets can both be omitted, and it has become possible to manufacture thinly coated clad steel plates that could not be manufactured using conventional techniques. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a sanderch type composite. FIG. 2 is a schematic cross-sectional view of a semi-sandwich type composite. FIG. 3 is a graph showing the change in surface roughness of the laminate material in the trial material after rolling. DESCRIPTION OF SYMBOLS 1... Base material steel, 2... Laminating material, 3... Boron nitride, 11... Joint surface, 12... Separation surface (laminating material surface after rolling), 13... Dummy steel.

Claims (1)

[Claims] 1. After cleaning both surfaces of the original laminated materials and placing boron nitride on one of the two surfaces with a surface roughness of 70 μm or less, the two original sheets of laminated materials are cleaned. A sandwich-arch-type composite is formed in which the one surface faces each other and the joint surfaces of the base material steel and the laminate material face each other, or the one surface of the laminate original plate and the dummy steel surface face each other and the base material steel A semi-sand German arch-type composite in which the joint surfaces of the laminate and the laminate face each other is hot-rolled, so that the surface of the laminate after rolling is free of defects and has a metallic luster, and the surface of the laminate is free from defects and has a metallic luster. A method for producing clad steel sheets with excellent bonding properties and omitting surface polishing, characterized by controlling the roughness to 100 μm or less. 2. In the method for producing a clad steel sheet as set forth in claim 1, the reduction rate per pass during hot rolling of the above-mentioned sandwich arch type or semi-sand German arch type composite is set to 3 to 35%. Features: Manufacturing method of clad steel sheet.