JPH0371954B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing rolled clad steel. (Prior art) Conventionally, as a manufacturing method for rolled clad steel, JP-A-56-12268 discloses that titanium or A method of manufacturing titanium clad steel by rolling has been proposed, and Japanese Patent Application Laid-Open No. 58-65589 discloses a method in which dummy materials are overlapped, welded, and rolled in order to prevent peeling due to the difference in linear expansion coefficient between the base material and the laminate. In addition, Japanese Patent Application Laid-open No. 55-100890, No. 55-128390, No. 56-122681, and No. 57-109587 all disclose methods for forming the base material, laminate material, and laminate material in a sandwich pattern. Methods have been proposed in which rolling is carried out in the following order: material and base material, or covering material, laminate material, and base material in this order. However, when using these methods, warpage occurs during rolling even if the material is symmetrical in the thickness direction, and if the warp becomes large, it cannot be sent to the next process, and there is a problem in that the material cannot be sent to the next process. There are many problems such as the inability to obtain thickness accuracy, especially the plate thickness accuracy of laminated materials, buckling during straightening or destruction of the part to be joined, or excessive diffusion of the joining boundary and deterioration of material properties. is holding. (Problems to be Solved by the Invention) An object of the present invention is to provide a method for producing clad steel with strong joint strength. A second object of the present invention is to provide a method for manufacturing clad steel that can reduce warpage after rolling. A third object of the present invention is to provide a method for manufacturing clad steel which has excellent plate thickness accuracy of the laminate and which does not cause buckling or destruction of the parts to be joined during straightening. Furthermore, a fourth object is to provide a method for promoting separation of the anti-warp material. (Means for Solving the Problems) The present invention provides a laminated assembly member of a plurality of metal plates, which includes a base material and a laminated plate, and is configured such that the member to be separated from the cladding material after hot rolling is steel. A method of hot rolling a material to obtain a clad material, in which the material is heated to a temperature higher than the _A1 transformation point of steel,
Rolling is performed to complete the final pass at a temperature below the _A1 transformation point of the steel, and then the material is forcedly cooled to a temperature of 650°C or below under conditions that prevent warping, and at a temperature of 200°C to 500°C. The gist of the present invention is a method for manufacturing rolled clad steel, which is characterized by performing at least one reciprocation of straightening in the area. The basic constituent elements of the present invention and their effects will be explained. (1) In the present invention, the steel is heated to a temperature higher than the _A1 transformation point, that is, 726°C or higher, and the temperature change during rolling is kept small using the heat of transformation. At the same time, by rolling across this transformation point, fluctuations in deformation resistance due to temperature unevenness are reduced, and clad steel with excellent dimensional accuracy is rolled. (2) The final rolling pass is completed at a temperature below the _A1 transformation point, and the warpage that tends to occur during the _A1 transformation is corrected by rolling, and the occurrence of warpage due to the transformation during cooling is avoided. (3) Once rolling bonding is completed, in order to minimize diffusion at the bonding boundary, forced cooling is performed to a temperature at which the diffusion rate is sufficiently low, that is, 650°C or less. Since warping is likely to occur during this forced cooling process, this is done while repeating straightening. (4) If it is necessary to promote separation between steel members, perform at least one round trip of straightening at the blue brittle temperature, that is, 200°C or more and 500°C or less, to spread the fracture on the surface to be separated over the entire surface. The base material of the material used in the present invention is steel, but the bonding material may be stainless steel, iron-based superalloy, nickel-based superalloy, titanium or its alloy, copper or its alloy, or the melting point is _A1 transformation point of steel. Any metal with the above-mentioned values may be used. The assembly structure of the materials is not particularly limited, and for example, as shown in Figures 1 and 2 of JP-A No. 59-225892, a filler material is built in between the base material and the scrap material (or covering material). As shown in Figures 3 to 5, two laminates are built in between the base metals and the laminates are separated after rolling, or the peripheries of the base metal and laminate are welded together. 3 to 5 of this specification.
The structure shown in the figure can be used. Next, the most desirable method of assembling the material used in the present invention and its structure will be explained. FIG. 1 shows the process up to the middle of implementing this invention. In the embodiment shown in FIG. 1, a laminate material 2 is stacked on a base material 1, and a covering material 3, which has been welded around the periphery in advance to accommodate the laminate material, is superimposed on this, and the covering material 3 is attached to the base material 1 with a fillet. It is fixed with welding 8. When performing this fillet welding, use nozzle 9 or 9'.
Blow inert gas such as argon or helium. If the bonding material is not an active metal, inexpensive nitrogen or carbon dioxide gas can be substituted for an inert gas such as argon or helium. FIG. 2 shows a case in which the end of the covering material is bent and fillet welded to the base material, and the rest is the same as FIG. 1. After that, when welding and fixing the anti-warping material around this layered assembly material, if there is a nozzle 9', close this nozzle 9', heat the surface 11 of the covering material 3 to 100 degrees Celsius or higher, and close the nozzle 9'. from 9
It is desirable to reduce the pressure to 10 ^-1 torr or less. FIG. 3 shows a process in which the anti-warping material 4 is fitted to the assembled material shown in FIG. 1 and the gap 12 with the base material 1 is welded.
During this welding, welding heat is used to
It is desirable to continue reducing the pressure to 10 ^-1 torr or less. The rolled material thus obtained is heated to a predetermined temperature and hot rolled, and then the rolled material is cut to separate the anti-warp material 4. Subsequently, the covering material 3 is removed by cutting, grinding, or pickling to expose the surface of the laminate material 2 to obtain a cladding material. In the embodiment of the invention shown in FIG.
pieces of assembly material on at least one of the covering material surfaces 11.
Either generate an oxide layer of 30 μm or more in advance, or use Al ₂ O ₃ , SiO ₂ , TiO ₂ , Cr ₂ O ₃ ,
A powder containing one or more of Fe ₂ O ₃ and Fe ₃ O ₄ as a main component is coated and dried to a thickness of 10 μm or more using a resin as a vehicle, and the two are brought together on the surface 11 of the covering material, and then combined with the base material 1. 12 is welded to the base material 7, and it is desirable to reduce the pressure to 10 ^-1 torr or less through the nozzles 9 and 10 during welding. In the embodiment shown in FIG. 4, the mutual base materials 1 and 7 function as warpage prevention materials. FIG. 5 shows the same structure except that the assembly materials shown in FIG. 2 are used and the distant piece 13 is inserted between the covering materials 3 and 5 to prevent the covering materials 3 and 5 from being damaged by welding. It is the same as Figure 4. These third
The rolling material shown in FIG. 4 or 5 is hot rolled after the nozzle 9 is closed by forge welding or welding with the pressure reduced to 10 ^-1 torr or less, heated, and then hot rolled. After hot rolling, the material is cut and separated between the faces of the shroud, and the shroud is then removed by cutting, grinding, or pickling to expose the cladding material to obtain a two-piece rolled cladding material. In the material having the structure shown in FIGS. 3 to 5 described above, as a method for reducing warping during and after rolling, the surface to be separated (covering material surface) 11
It is effective to join them locally and incompletely by rolling. If the members to be separated are made of steel, in order to join them locally incompletely, the total thickness of the oxide scale must be 10 μm or less locally, or Al ₂ O ₃ , SiO ₂ must be formed locally. , TiO ₂ ,
It is desirable to provide a place where separation agents such as Cr ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ are not applied. Even if such parts are apparently joined by rolling, they are likely to be destroyed by contaminants or contaminants that have invaded from the surrounding area. In order to separate this, if the members to be separated are both made of steel, straightening is performed at least once in the blue brittle temperature range of steel, that is, from 200°C to 500°C, to prevent destruction of the surface to be separated. Expand to full size. (Example) Table 1 shows examples. All except for the laminated materials
Carbon steel with C0.18% is used. Although the comparative method has improvements in material assembly compared to the prior art, it is inferior to the method of the present invention. The structure of the rolled material in the comparative method is shown in Fig. 4 without providing the cover material 3, but the conditions of inert gas injection during welding and subsequent pressure reduction are kept as much as possible in Examples 1 to 5. . In Examples 1 and 2 of the comparative method, the temperature in the final pass is above the A ₁ transformation point of the steel, and the A ₁ transformation occurs during the cooling process, resulting in large warpage after cooling.
In Examples 3 to 5 of the method of the present invention, the final pass of rolling is performed at a temperature lower than the _A1 transformation point of 726°C, so that the _A1 transformation is almost completed during rolling, and warping during the cooling process is small. In addition, since the method of the present invention utilizes _A1 transformation heat during rolling, the amount of temperature drop during rolling is small, and by keeping the variation in deformation resistance within a small range, the thickness deviation of the laminate (= maximum thickness - minimum thickness) is getting smaller. Furthermore, in the method of the present invention, the shear test results and side bending test results are improved by rapidly cooling after the completion of rolling to suppress diffusion at the joint boundary. This effect of minimizing diffusion was first proposed by the applicant and others, and by utilizing this effect, it is possible to produce clad steel with unprecedented superior performance. It became.

【table】

[Table] (Effects of the Invention) According to the present invention, rolled clad steel with strong joint strength can be obtained. Although the present invention has been described with reference to plates, it can also be applied to tubes or strips. Furthermore, the material of the base material is limited to steel because it utilizes the heat of _A1 transformation of steel, but it can be applied to all rolling methods for clad materials that generate heat of transformation during cooling. As a laminating material, the base material
It can be applied to rolled cladding made of materials with a melting point above the _A1 transformation temperature, such as stainless steel, iron-based alloy steel, titanium or its alloys.

[Brief explanation of drawings]

1 and 2 are diagrams showing an intermediate stage of assembling a rolling material according to the present invention, and FIGS. 3, 4, and 5 are views showing the state after assembly of a rolling material according to the present invention. FIG. 1, 7: Base material, 2, 6: Laminating material, 3, 5: Covering material, 4: Warp prevention material, 8: Fillet welded part, 9,
9', 10: Nozzle, 11: Covering material surface, 12:
Weld between base metal and anti-warp material or between base metals, 1
3: Distance piece.

Claims (1)

[Claims] 1. A method for obtaining a cladding material by hot rolling a laminated assembly member of a plurality of metal plates including a base material and a laminated plate, and configured such that the member to be separated from the cladding material after hot rolling is steel. The material is heated to a temperature above the A ₁ transformation point of steel, rolled to complete the final pass in a temperature range below the A ₁ transformation point of steel, and then the material is rolled to a temperature below 650°C. In addition to forced cooling under conditions that inhibit
A method for manufacturing rolled clad steel characterized by performing reciprocating straightening.