JPS60106681A - Production of clad steel plate - Google Patents

Abstract

PURPOSE:To obtain a clad steel plate of which the surface of the cladding metal after rolling is flaw-less, has a metallic gloss and <=100mu in roughness in a titled process for production using a (semi)sandwich type rolling and joining method by using boron nitride as a separating material. CONSTITUTION:Both surfaces of the original plates for cladding metals 2 are cleaned and <=70mu surface roughness is assured on one surface, on which boron nitride 3 is coated. The sandwich type composite in which the surfaces of such metals 2 coated with said boron nitride are positioned to face each other and in which the respective joint surfaces of the base steels 1 and the metals 2 face each other is prepd. The semisandwich type composite in which the surfaces of the metals 2 coated with said boron nitride and a dummy steel 13 are positioned to face each other and in which the joint surfaces of the steels 1 and the metals 2 face each other is otherwise prepd. Such composite is hot-rolled by which the flaw-less surface having a metallic gloss is provided to the surface of the cladding metal 2 after rolling and <=100mu surface roughness is provided to the metal 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a clad steel plate in which alloy steel or non-ferrous alloy of any thickness is firmly bonded 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. Demand for advanced materials, ie corrosion resistance.

It is a composite metal material that can meet strict requirements for heat resistance, abrasion resistance, crack resistance, etc., and is widely used in oil plants, seawater desalination equipment, pressure vessels, etc.

Up until now, clad steel sheets have been manufactured using the explosion bonding pressure welding method.

Overlay rolling methods, rolling joining methods (open sandwich type, sandwich type, semi-sandwich type), etc. have been used, but these techniques have the following drawbacks, and are not necessarily satisfactory bonding methods. I can't say that.

■ Oxidized scale is not only formed on the surface of the laminate of clad steel plates produced by manufacturing methods such as explosion rolling, overlay rolling, and open sandwich inch rolling joining, but also during the rolling process. The surface quality of the laminated material is extremely poor due to the occurrence of flaws or indentation flaws in the steel.

■ In the sand inch type rolling joining method and the semi-sand inch type rolling joining method, deterioration of the surface quality of the laminate due to the separation material occurs, that is, indentation defects of the separation material during the rolling process or rolling Inability of the separating material to follow deformation over time, i.e., increase in surface roughness due to poor lubrication of the separating material, and damage to the surface material of the joining material due to intrusion of the separating material itself or gas released from the separating material into the joining material. Deterioration of properties and further surface cracking of the laminated material caused by these deteriorations occurred. In addition, defective joints between the laminate material and the base material occurred due to gas released from the separation material.

■ Due to ■ and ■, in conventional manufacturing technology, repair processes such as scale flaws and cracks on the surface of the cladding material, or defective joints between the cladding material and the base steel, and a polishing process of the surface of the cladding material are unavoidable. Therefore, at the slab design stage, it was necessary to ensure in advance the amount of polishing needed to remove the 9 cracks and scale. For this reason, there was an economical disadvantage that the yield was lowered and the manufacturing cost of the clad steel sheet could not be reduced.

■ Furthermore, when welding and repairing cracks or joint defects, it is necessary to ensure the same material properties as the laminate, especially corrosion resistance. In order to keep the welding heat input as low as possible, it is not only necessary to reduce the welding heat input, but also to secure a certain number of laminated layers by adopting a multi-bus welding method. 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, there are minor surface cracks.

In the surface polishing process for removing scratches, scales, etc., the amount of polishing cannot be strictly controlled due to initial deformation of the clad steel plate and distortion induced during polishing. Therefore, not only is there a risk that the laminated material thickness tolerance may not be partially satisfied, but also it is impossible to perform welding repair in the case of a clad steel plate formed with an extremely thin laminated material.

In addition, in the production of clad steel sheets, the repair and polishing processes described above are unavoidable with the current technology, which makes it impossible to manufacture clad steel sheets with a thin coating thickness. There were also challenges.

(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 formation on the surface of the laminated material, attention is paid to the Santo Inch type and semi-Sand Inch 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. As a result, by adopting a sandwich-inch or semi-sand-inch rolling joining method as a manufacturing method, and placing BN in the gap between the laminate and laminate, or between the laminate and the dummy steel, which are separated after rolling, it is possible to The technical and economical difficulties faced by the project were solved all at once.

(Structure of the Invention) In the present invention, in the rolling joining method of clad steel plates, both surfaces of a mating original plate 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 three cylinder original plates facing each other and the joining surfaces of the base steel and the cladding material facing each other, or by applying the same to the surface of the original plate of the cladding material. A semi-sandwich type composite in which the surfaces of the dummy steel and the base steel face each other and the joint surfaces of the base steel and the laminate face each other is hot rolled at a rolling reduction rate of 3 to 35% per pass. 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 sandwich type composite assembly in manufacturing a clad steel plate according to the present invention. In Figure 1, ■ is the base material steel slab, 2
3 is a separate phase, i.e. BN, 4 is an insert metal, 5 is an oxide nitride forming substance such as Zr or Ti, 6 is a frame material, 7 is an exhaust port, 8 is an exhaust pipe, 9 is a shield Welded portions 10 indicate welded portions of laminate materials. In addition,
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 μIl+ or less.

First, as shown in Fig. 1, B
Place N3. After bonding, one side of the base steel 1 is cleaned, and as shown in FIG.
The laminated material 2 and the base key steel 1 are arranged so that their respective clean surfaces face each other. Z in the gap between frame material 6.6 and laminate material 2
After charging the gas-absorbing substances 5, 5 such as R, Ti, etc., and shield-welding the frame material 6 and the base steel 1, the exhaust is forcibly exhausted through the exhaust lower and the exhaust pipe 8, thereby blocking the inside of the composite from the outside air. do. 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 joint stronger, (1) an insert metal 4 is inserted between the mating piece 2 and the base steel 1;

(2) To keep the bonding surface between the cladding material 2 and the base steel 1 cleaner, and also to eliminate the residual force inside the composite and the emitted force during heating, which can cause poor bonding. In addition, gas absorption by the gas absorbing material 5 and forced exhaust through the exhaust lower are used together. As a result, sound bonding can be achieved during the hot rolling process.

FIG. 2 is a schematic cross-sectional view of a semi-sand inch type knot. Among the clean front and back surfaces of the laminated material 2, the surface roughness of one surface 12, which will be the separation surface, is 7° μm or less. In this assembly 14), the BN 3 is placed in the gap between the mating piece 2 and the dummy steel 13. After binding, base material II
One side of the shrine is cleaned and placed so as to face the clean side 11 of the mating shrine 1. Force-absorbing substances 5, 5 are charged into the gap between the frame huts 6, 6 and the mating mat 2, and the frame material 6, base material steel 1, and dummy steel 13 are shield welded. Thereafter, the exhaust is forcibly exhausted through the exhaust lower and the exhaust pipe 8, thereby blocking 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 be explained mainly regarding clad steel plates made by the sandwich-inch rolling joining method.
The following is merely a description of typical examples, and all modifications within the scope of the claims are included within the scope of the present invention.

For example, in the production of single-sided clad steel plates or two or more layer clad steel plates using the semi-sand inch type of rolling joining method, the following method can be followed or partially modified. It goes without saying that they are included in the present invention.

(Example) Example 1 First, as a result of conducting research on an appropriate separated phase to be placed in the gap between the mating mill and the mating material or the mating material and the dummy steel to be separated after rolling, we found that It was found that the following power characteristics are (a) to (e).

(,) It is chemically stable in the hot heating temperature range, and there is no reaction with or intrusion into the ashoku.

(l)) There is no gas released during heating, which causes a decrease in bondability.

(c) It has lubricity under high temperature and high pressure during rolling and straightening.

(d) During rolling, the surface quality should not be deteriorated, that is, the rolling process should not cause defects or increase in surface roughness.

(e) Separability between the dowel and the dummy steel after rolling is good.

Considering these points, various separation materials were tested in order to select an appropriate separation phase. 907 as a laminating material
10 Cypronickel original plate (CN, 2.5III+ thickness)
and a base steel slab (3M41.B) as the matrix.

15n+m 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 adjustment thickness + 90/10 cupronickel thickness) is (4.3m).
m+0.7+nm).

The total reduction ratio is 3.5. The finished product is a thinly coated CN clad steel plate with CNNO3.7mm.

After rolling, both ends were cut, and the separability of the upper and lower clad steel plates, 1 the removability of the separating material, 9 the combined benefits, the surface condition, 9 the deterioration of the surface roughness, the bondability, etc. were investigated. The results are shown in Table 1.

It can be seen that BN is the most excellent separating material. That is, it has excellent lubricity under high temperature and high pressure during rolling, and has good separability and removability, and the surface appearance of the laminated material (CN) after rolling maintains a metallic luster. In addition, no scratches or cracks were generated on the surface of the laminated material, and the surface roughness of the laminated grain formed by rolling was the lowest in the case of BN among the various separation materials tested. Furthermore, the bondability fully satisfies the JIS standard (lower limit standard value 10 kgf/mm2).

From the above results, B
It has been found that by selecting N, as described above, it is possible to produce a clad steel sheet in which the surface of the laminated mill after rolling maintains a metallic luster and is free from defects. Therefore, boron nitride was selected as the separation material.

Example 2 A 90/10CN original plate or a high carbon steel original plate (850C) was used as a composite material, and 5M was used as the base material steel.
41B base steel slab using BN as a separating material,
A sandwich-type composite slab was produced in the same manner as in Example 1, and then hot rolled to investigate the controllable range of the surface roughness of the laminated mill after rolling. The assembly conditions and rolling conditions for this pot are as shown in Table 2. Table 2 also shows the measurement results of the surface roughness in the longitudinal direction (L) and the transverse 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, when the surface roughness of the laminate original plate is set to 70 μm or less, the laminate surface after rolling increases
The U degree can be reduced to 100μI11 or less. Further, the surfaces of all the rolled clad steel plates have no scratches or cracks, and the surface appearance maintains a metallic luster. Therefore, the surface polishing step can be omitted.

From the above, in the sandwich-type rolling joining method, the surface roughness of the separation surface of the laminated material original plate is set to 70 μm1 or less, and
If hot rolling is carried out using BN having the above properties (,) to (e) as a separated phase under hot rolling conditions with a rolling reduction of 3 to 35%/pass, the It was found that the surface of the laminated material was free of defects and had a metallic luster appearance, and that the surface hardness of the laminated material could be controlled to 100 μm or less.

(Effects of the Invention) In the present invention, BN having the above characteristics is used as a separated phase.
In addition, the separation part is isolated from the outside air, etc., so that hot rolling can be performed in the range of a rolling reduction of 3 to 35%/pass, and the BN functions effectively. The surface of the laminated material of the produced clad steel plate has a metallic luster, no scratches or cracks occur on the surface, and the surface of the laminated steel sheet tIt
The thickness can be reduced to 100 μm or less. As a result, the surface polishing process of the mating mill and the surface welding repair process in the production of clad steel sheets can be omitted, and it has also become possible to manufacture thinly coated clad steel plates, which could not be manufactured using conventional technology. .

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a sand inch type knot. FIG. 2 is a schematic cross-sectional view of a semi-sand inch composite. FIG. 3 is a graph showing the change in surface roughness of the mating hole 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 (the surface of bonding material after rolling), 13... Dummy steel . Patent applicant: Kobe Steel, Ltd. Patent attorney: Aoyo Aoki and two others Figure 1 Figure 2 IIIZ t:i Figure 3 Ni Tsuna de Ya ◆ City ~ b1

Claims (1)

[Claims] (1) After cleaning both surfaces of the original laminate sheets and placing boron nitride on one of the two surfaces with a surface roughness of 70 μm or less, clean the surface of the two original laminate sheets. A sandwich type composite is formed in which the joint surfaces of the base steel and the cladding material face each other, or the surface of the base material steel and the dummy steel surface face each other and the base steel and the cladding material face each other. A semi-sandwich type composite with each joint surface facing each other is hot rolled, and as a result,
A method for producing a clad steel sheet with excellent bonding properties that does not require surface polishing, characterized in that the surface of the laminate material after rolling is free of defects and has a metallic luster, and the roughness of the surface is controlled to 100 μI or less. . (2. In the method for manufacturing a clad steel sheet as set forth in claim 1, the reduction rate per pass in hot rolling of the sandwich-type or semi-sandwich-type composite is set to 3 to 35%. A manufacturing method for a clad steel sheet characterized by: