JPH0371957B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing rolled clad steel sheets. In the present invention, titanium, titanium alloy, zirconium, zirconium alloy, or chromium-containing steel is used as the laminating material, and steel with a carbonate content of 0.12% or more and 0.7% or less is used as the base material. (Prior art) Japanese Patent Application Laid-Open No. 100890/1989 as a conventional technology,
No. 55-128390, No. 56-122681, No. 57
The method for producing cladding materials described in Publication No. 109587 involves forming a base material, a laminate material, and
Although the laminate material and the base material are stacked in this order, or the covering material, the laminate material, and the base material are stacked in this order, there is no intermediate material between the laminate material and the base material to prevent diffusion of carbon from the base material. Furthermore, JP-A-60-203377 states that ferritic stainless steel or martensitic stainless steel is used as a joining intermediate material, but in this case, carbides are formed due to the chromium in the stainless steel and the carbon in the base material. It forms and becomes brittle, causing shear test values to vary to a low level and bending test results to deteriorate. In addition, when the heating temperature is low and the steel reaches the Ar ₃ transformation point during rolling, the thickness of the warpage prevention material and the base material,
If the width and length are not equal, significant warping will occur, and in passes near the rolling finish, significant warping will occur toward the side where the thickness of the anti-warp material and the thickness of the base material are smaller. (Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing clad steel that has excellent joint strength and that causes little warping during rolling. (Means for Solving the Problems) The gist of the present invention is to use titanium, titanium alloy, zirconium, zirconium alloy, or chromium-containing steel as a laminated material, and to have a carbon content of 0.03% by weight.
The following steel plates are used as intermediate materials and the thickness of the clad product is 100 μm or more, and the carbon content is
Use steel of 0.12% by weight or more and 0.7% by weight or less as a base material, clean the mating surfaces, stack them in layers, further overlap the warping prevention member on the laminated material, and apply any of these on the opposing surfaces of the warp prevention member and the mating material. With the above oxide interposed, inert gas is blown inside the interlayers of the warpage prevention member, the intermediate material, and the base material, the surroundings are welded and fixed, and the inside is sealed by reducing the pressure, and the facing surfaces of these to be joined are The rolled material is isolated from external sources of contamination, heated to a temperature range of 650°C or higher and 900°C or lower, and rolled with the thinner side of the warpage prevention member and base material as the lower surface, so that the rolled structure of the steel remains. A method for producing a rolled clad steel sheet having a carbon concentration distance of 20 μm or less at a joint boundary, characterized in that rolling is completed at a temperature of 830° C. or less. (Operation of the invention) The basic constituent elements of the present invention and their operation can be summarized as follows. (1) The present invention is a rolled clad steel plate made of titanium, titanium alloy, zirconium, zirconium alloy, or chromium-containing steel as a base material and made of high-strength steel with a carbon content of 0.12% or more and 0.7% or less. By suppressing the formation of carbides at the bonding boundary, a clad steel plate with excellent bonding performance can be obtained. For this purpose, a steel plate with a carbon content of 0.03% or less and a thickness of 100 μm or more in the finished product is interposed as an intermediate material between the laminated material and the base material. The thickness of this intermediate material when it is a raw material is approximately twice the rolling ratio of the thickness when it is a product, that is, when the rolling ratio (=thickness before rolling/thickness after rolling) is 5, it is 500 μm or more. The upper limit of the heating temperature of the material is Ac ₃ points, or approximately 900
It is ℃. When the heating temperature exceeds this temperature, the diffusion of carbon from the intermediate material to the laminate material and the diffusion of laminate metal elements from the laminate material to the intermediate material become active, increasing the amount of metal carbide produced and the distance at which it is formed. , which is not preferable because it makes the joint part brittle. The carbide is found in titanium and titanium alloys.
TiC. Mainly ZrC in zirconium and zirconium alloys, and Cr ₇ C ₃ or Cr ₂₃ C ₆ in chromium-containing steels. The lower limit of the heating temperature is 650°C, which is the temperature at which the material becomes significantly softer than room temperature.
The lower limit of carbon content in the base steel is 0.12% to ensure the strength of the base metal, and the upper limit of 0.7% is within the range of hypo-eutectoid steel that does not produce pro-eutectoid cementite, which has poor workability. Carbon content as an intermediate material between base material and laminate material
Using steel with a content of 0.03% or less not only suppresses the formation of carbides with the laminate metal within a harmless range, but also absorbs the difference in deformation characteristics between the laminate and the base metal in the product state, making it easier to perform bending processes, etc. It has the effect of preventing joint failure due to plastic working. Furthermore, steel with a carbon content of 0.03% or less is mass-produced as steel plate for deep drawing, is inexpensive, and as such can withstand extremely large plastic deformations. (2) If the heating temperature is above the _A1 transformation point of the steel, i.e. 720°C, ferrite begins to transform into austenite, and during rolling, the opposite reaction occurs due to the temperature drop, resulting in significant warping. do. General steel materials are not rolled in such a temperature range, and rolling is completed in the austenite single phase range.
The occurrence of warpage becomes significant when the material or structure is vertically asymmetrical with respect to the center of the plate thickness. In the present invention, when the structure is asymmetrical with respect to the center of plate thickness as shown in Fig. 1 or 2, rolling is performed with the thinner side of the anti-warp material and the base material as the lower surface to prevent the material from warping towards the thinner side. Rolling is performed while restraining warpage using a roller table. That is, the material that is prevented from warping downward by the front and rear roller tables, which are only several tens of millimeters lower than the upper surface of the lower rolling roll, is rolled between the rolls and is deformed so as not to warp as a result. In this way, it is possible to finish rolling at a temperature below 830° C., where warpage is likely to occur, and it is possible to obtain a highly tough joint that suppresses recrystallization of the steel and has less carbide formation. Next, a method of assembling the materials used in the present invention and its structure will be explained. In FIG. 1, a laminate material 1, an intermediate material 3, and a base material 6 are stacked in layers and preferably fixed by welding 11. This welded part is not expected to have any strength, but is intended to prevent contamination of the surface to be joined from the outside. A warp prevention material 7 is placed on the laminate 1, and between the two 8 are oxides of the laminate, oxides of the warp prevention material, Al ₂ O ₃ ,
One or more of SiO ₂ , TiO ₂ , and Cr ₂ O ₃ is present to facilitate separation of the two after rolling. A detance piece 9 is inserted around the base material 6 and the anti-warp material 7, and the welding is performed integrally while preventing contamination of the surfaces to be joined during welding. The surfaces to be joined are preferably under reduced pressure to prevent oxidation during heating. Fig. 2 shows that the anti-warp material 7 in Fig. 1 is the laminated material 1',
This is the case where the intermediate portion 3' and the base material 6' are replaced, and the separating agent 8 is interposed between the laminates 1 and 1' as in the case of FIG. Separation planned position 8' in Figure 2
If the thicknesses of the base materials 6 and 6' are different between the upper and lower parts of the base material, the thinner side is turned downward and rolled. In the case of FIG. 2, an intermediate material 3 is sandwiched between the laminate material 1 and the base material 6, and an intermediate material 3' is sandwiched between the laminate material 1' and the base material 6'. (Example) Table 1 shows examples.

【table】

[Table] 0.17% carbon steel was used as the steel base material, and 0.01% ultra-low carbon steel was used as the intermediate material. The assembled material is a small test piece with a width of 150 mm and a length of 200 mm, which is sufficient to evaluate the production rolling conditions and quality. All test pieces were welded using the MIG welding method, and argon gas was blown into the surfaces to be joined to prevent welding contamination during welding, and after welding, the interior was heated to 10 ^-2 torr to prevent oxidation of the surfaces to be joined.
It is depressurized and sealed. Any heating temperature
It is 800℃. In example 1 of the conventional method, a 6 mm thick steel base material is used for a 20 mm thick steel base material.
Stainless steel (SUS304) laminates are directly fillet welded. In this example, the material warped significantly toward the stainless steel side during rolling, and the thickness deviation of the laminate (=maximum thickness - minimum thickness) was as large as 0.33 mm. The shear strength is low and the bending test results are also poor. Example 2 of the conventional method has a structure without intermediate members 3 and 3' in FIG. 2, but the shear strength is low and the side bending test results are also poor. Examples 3 and 4 of the present invention have the structures shown in FIGS. 1 and 2, respectively, and are asymmetrical in the thickness direction to make warping more noticeable, but unlike the present invention, the base material or warpage prevention material is Since the thinner side is used as the bottom surface during rolling, the warpage is within an acceptable range. Furthermore, the thickness deviation of the laminate, the shear strength of the base material and the laminate, and the side bending test results are all good. The shear strength and side bending test results are related to the distribution thickness of carbides enriched near the joint boundary. Carbides are mainly TiC when the bonding material is titanium or titanium alloy, and are mainly Cr ₇ C ₃ and Cr ₂₃ C ₆ when the bonding material is stainless steel. These carbides were collected using a Shimadzu EPMA (model name: EMX-SM) at an accelerating voltage of 20 kV, a sample current of 0.01 μA, and a beam diameter of 1 μm.
When line analysis of carbon is performed perpendicularly across the cross section of the joint, and when the count number 0.5k is the full width of the recording paper, the carbon concentration distance at the joint boundary is measured as shown in Figure 3. This carbon enrichment distance is related to the shear strength, and in the case of titanium clad steel, the shear value of 14Kg specified by JIS G3603 is shown in Figure 4.
f/mm ² can be satisfied if the carbon concentration distance is 20 μm or less. Such carbide concentration at the titanium-steel joint interface is TiC, which improves shear strength if it is in a small amount, but when the carbon concentration distance is 20 μm
If TiC is formed to an extent that exceeds the above, it becomes brittle, and low shear values are mixed. The above is the same when stainless steel or zirconium is used as a composite material, and stainless steel has Cr ₇ C ₃ ,
Cr ₂₃ C ₆ is formed in the same way as ZrC in the case of zirconium, and exhibits similar behavior. (Effects of the Invention) According to the present invention, a clad steel with strong joint strength can be obtained. In addition, even though the hot rolling temperature of steel is abnormally low and warping during rolling becomes a problem, by setting the direction of warping downward, the roller table can prevent warping. It becomes like this. Furthermore, conventionally, when the carbon content of the base material exceeded 0.12%, the shear strength varied to a low level, but it was revealed that one of the causes of this was the formation of carbides, and according to the present invention, the shear strength
By using 0.03% or less steel as an intermediate material, it is possible to provide a clad steel plate that is inexpensive and has excellent workability.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of an example of the assembly structure of the rolling material of the present invention, Figure 3 is an explanatory diagram of the carbon concentration distance, and Figure 4 is the carbon concentration distance and shear strength showing the effects of the present invention. It is a relationship diagram. 1: Laminated plate, 3, 3': Intermediate material, 6, 6': Base material, 7: Warp prevention material, 8: Separation material, 8': Separation position, 9: Distance piece, 10: Four-periphery welded part.

Claims (1)

[Claims] 1 Titanium, titanium alloy, zirconium, zirconium alloy, or chromium-containing steel are used as laminated materials, and a steel plate with a carbon content of 0.03% by weight or less is used as an intermediate material so that the thickness of the clad product is 100 μm or more, and the carbon content is is 0.12% by weight or more, 0.7% by weight
The following steels are used as a base material, their mating surfaces are cleaned and stacked in layers, a warp prevention member is further layered on the mating material, and one of these oxides is interposed on the opposing surfaces of the warp prevention member and the mating material. , While blowing an inert gas into the interior of the warpage prevention member, intermediate material, base material, and interlayers, the surroundings are welded and fixed, the interior is sealed by reducing the pressure, and the facing surfaces to be joined are isolated from external contamination sources and rolled. material and heat it to 650℃ or higher, 900℃
℃ or less, rolling is performed with the thinner side of the warpage prevention member and the base material as the lower surface, and the rolling is completed at a temperature of 830℃ or less at which the rolled structure of the steel remains. The carbon concentration distance of is 20μm
The following method of manufacturing rolled clad steel sheet.