JP2000246461A - Manufacture of stainless steel/aluminum clad plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably manufacture a stainless steel/aluminum clad plate which is high in bonding strength. SOLUTION: One material is formed of a stainless steel plate 2 which is surface-finished through the pickling treatment using nitric acid or hydrofluoric acid, or the electrolytic pickling treatment using nitric acid, and the other material is formed of an aluminum plate 1 of 35-60 N/mm2 in flow stress. Both materials are lapped and continuously rolled to manufacture a stainless steel/ aluminum clad plate high in bonding strength. Because of using the aluminum plate 1 of specified flow stress, the aluminum plate 1 is rolled in a first half of a zone Z1 and a zone Z2, its active surface is exposed, and the joined interface is activated by the relative slip between the aluminum plate 1 and the stainless steel plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stainless steel / aluminum clad plate having high joining strength and good workability.

[0002]

2. Description of the Related Art A clad plate in which dissimilar metals having different properties are combined has been used in a wide range of fields such as kitchenware, building materials, electronic components, and piping as materials having the advantages of the dissimilar metals. Above all, a stainless steel / aluminum clad plate obtained by combining stainless steel having excellent corrosion resistance and strength with aluminum having good thermal conductivity is widely used for electromagnetic cookers. The stainless steel / aluminum clad plate is manufactured by a method such as diffusion bonding or roll bonding, but roll bonding is widely used for efficiently manufacturing a thin clad plate. In rolling joining, an oxide film is removed from the surface of the steel plate by polishing the stainless steel plate with a wire brush or the like in advance in order to improve the bondability between the stainless steel plate and the aluminum plate. When the polished stainless steel plate is heated, it is joined to the aluminum plate via the activated surface.

[0003]

When the surface of stainless steel is activated with a wire brush, the degree of brushing tends to fluctuate in the width direction of the plate. Fluctuations in the degree of brushing cause variations in the bonding strength in the width direction after bonding to the aluminum plate. Variations in bonding strength appear more as the polishing processing speed is increased in order to increase productivity. Therefore, the present inventors have found that an active surface suitable for bonding to an aluminum plate can be obtained when the surface of stainless steel is finished by pickling or electrolytic pickling instead of brushing. -167915. When a stainless steel sheet is surface-finished by pickling using a mixed acid of nitric acid / hydrofluoric acid or electrolytic pickling using nitric acid, an oxide film mainly composed of Fe ₂ O _{3 in the} outer layer and Cr ₂ O _{3 in the} inner layer is formed on the surface of the steel sheet. It is formed. The stainless steel plate that has been pickled or electrolytically pickled is likely to have cracks in the oxide film due to plastic working at the time of joining, and exposes an active substrate. Joined with the aluminum plate of the material.

[0004]

SUMMARY OF THE INVENTION The present invention is a further improvement of the rolling joining proposed in the prior application, wherein the rolling joining is performed by specifying an aluminum plate as a mating material in consideration of plastic deformation during rolling. An object of the present invention is to sometimes activate a joining interface between a stainless steel plate and an aluminum plate by frictional heat to obtain a stainless steel / aluminum clad plate having high joining strength and good workability. In order to achieve the object, the production method of the present invention provides a stainless steel sheet surface-treated by pickling treatment using a mixed acid of nitric acid and hydrofluoric acid or electrolytic pickling treatment using nitric acid to form a deformation resistance of 35 to 60 N / mm ^2. Characterized in that the aluminum plates are superposed and joined to a stainless steel plate by continuous rolling.

[0005]

The improvement of the bondability of a stainless steel plate to an aluminum plate by pickling treatment using a mixed acid of nitric acid / hydrofluoric acid or electrolytic pickling treatment using nitric acid is disclosed in Japanese Patent Application No. 9-16 / 1997.
It was just introduced in Issue 7915. However, from the results of subsequent research by the present inventors, the material of the aluminum plate as the mating material also has a great effect on the bondability, and the aluminum plate whose deformation resistance has been adjusted to the range of 35 to 60 N / mm ² has been used. It has been found that when used, a stainless steel plate and an aluminum plate are roll-bonded with good bonding strength.

The reason why the bonding strength changes due to the deformation resistance of the aluminum plate is presumed as follows. As shown in FIG. 1 showing the inside of the roll bite, when the aluminum plate 1 is superimposed on the stainless steel plate 2 and passed between the rolling rolls 3 and 4, the yield starting point P ₁ which varies depending on the difference in deformation resistance. and plastic deformation of the aluminum plate 1 and a stainless steel plate 2 starts at P _2. That is, the roll bite inlet side as viewed from the rolling direction D has an area Z ₁ where the aluminum plate 1 is selectively rolling, region Z ₂ to the aluminum plate 1 and a stainless steel plate 2 is rolled simultaneously in the region Z ₁ in the process of. In region Z _1, elongation of the aluminum plate 1 occurs, to generate a relative sliding between the stainless steel plate 2 by selective rolling. Relative sliding due to deformation difference is occurring in the first half of the rolling direction D viewed from region Z _2, joining the aluminum plate 1 is a stainless steel plate 2 in the second half of the region Z ₂ to the plastic deformation of the stainless steel plate 2 is increased The same material speed.

[0007] The region Z ₁ and the region Z in which relative slip occurs.
_In the first half of ₂ , the rolled and extended aluminum plate 1 exposes an active new surface, and metal atoms at the joint interface between the aluminum plate 1 and the stainless steel plate 2 are activated by frictional heat. As a result, the bondability between the aluminum plate 1 and the stainless steel plate 2 is improved. The relative positional relationship between the region Z ₁ and the region Z ₂ changes according to the deformation resistance of the aluminum plate 1. When the deformation resistance of the aluminum plate 1 is increased, the yield starting point P ₁ moves to the exit side, an aluminum plate 1
And the relative slip generated between the stainless steel plate 2 and the stainless steel plate 2 are reduced, and the speed difference of the relative slip is also reduced. Therefore, the frictional heat generated by the relative slip is reduced, and the joining property is reduced.
Conversely, when the deformation resistance is small, the aluminum plate 1 in the passing is meandering, and the thickness variation easily occurs at the time of rolling and joining,
Manufacturing conditions are not stabilized.

The deformation resistance of the aluminum plate 1 is determined according to JIS.
It is evaluated with a 0.2% proof stress specified in Z2241. According to the study by the present inventors, the deformation resistance (0.2% proof stress) is 35 to 60, as is clear from the examples described later.
When the aluminum plate 1 in the range of N / mm ² is selected as a material to be joined, the first half of the region Z ₁ and the region Z ₂ where relative slip occurs is appropriately maintained, and the aluminum plate 1 is made of stainless steel with good joining strength. It was found that the steel sheet 2 was roll-joined.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum plate 1 is not particularly limited in terms of material as long as its deformation resistance is in the range of 35 to 60 N / mm ² , but it is A1000 series, A3000.
A system or the like is used. Stainless steel plate 2, the deformation resistance in comparison to an aluminum plate 1 is much larger, without the addition of material constraints first half relative sliding region Z ₁ and region Z ₂ during rolling bonding occurs. However, in the case of an excessively hard stainless steel plate 2, an excessive load is applied to the rolling rolls 1 and 2, and the balance of plastic deformation between the aluminum plate 1 and the stainless steel plate 2 is lost, which may cause breakage or cracks. Become stronger. In this regard, the deformation resistance is 400 N / mm
Ferritic, austenitic, martensitic stainless steels of ² or less are preferred.

The stainless steel plate 2 is surface-finished by pickling using a mixed acid of nitric acid / hydrofluoric acid or electrolytic pickling using nitric acid. The oxide film on the surface of the stainless steel plate 2 is
The outer layer is made of Fe ₂ O ₃ and the inner layer is made of Cr by pickling or electrolytic pickling.
Tempered to an oxide film mainly composed of ₂ O ₃ . The tempered oxide film is difficult to ductile, and therefore, when the stainless steel plate 2 is plastically deformed during rolling joining, cracks are likely to be formed on the surface of the steel plate. As a result, the active steel surface is exposed, and the bondability is improved. As the pickling condition, for example, a condition in which a stainless steel plate is immersed in a mixed acid of 6.0% nitric acid, 0.5% hydrofluoric acid and 50 to 60 ° C. for 30 to 60 seconds is adopted. Electrolytic pickling conditions include, for example, immersing the stainless steel plate 2 in a nitric acid aqueous solution having a concentration of 5% and a temperature of 50 to 60 ° C., and a current density of 5 A / m 2.
Conditions for performing cathodic electrolysis at m ² are employed.

[0011]

[Example] Deformation resistance (0.2% proof stress) 250 N / mm
^2. An SUS430 stainless steel plate having a thickness of 0.6 mm was used as one material, and A1100 aluminum plates having various deformation resistances were used as the other material. Four types of stainless steel plates A to D were prepared. As the aluminum plate, a plate whose deformation resistance was adjusted to a range of 30 to 160 N / mm ² by changing heat treatment conditions after cold rolling was used. A) Mixed acid solution of 6.0% nitric acid and 0.5% hydrofluoric acid (60 ° C)
B) dipped in an aqueous solution of 5% nitric acid and dipped in an aqueous solution of 5% nitric acid to obtain a current density of 5 A / dm ²
Stainless steel sheet finished by electrolytic pickling in step C) Stainless steel sheet finished by polishing using a wire brush D) Stainless steel sheet finished by temper rolling with an elongation of 0.2%

After heating a stainless steel plate to 300 ° C.,
The sheet was overlapped with an aluminum plate and passed through a four-high rolling mill.
By continuously rolling a stainless steel plate and an aluminum plate at a rolling reduction of 40%, a stainless steel / aluminum clad plate having a thickness of 1.2 mm was manufactured. A test piece having a diameter of 400 mm was sampled from the center of the obtained stainless steel / aluminum clad plate in the plate width direction and subjected to a forming test. In the molding test, the diameter was 200 mm and the shoulder radius was 50.
mm punch, inner diameter 202.9 mm, shoulder radius 10 mm
Using a die, set the aluminum side of the test piece with the lubricant applied to both sides to the punch side, and set the wrinkle pressing force to 4 N / m.
Deep drawing was performed at m ² .

With respect to the test piece subjected to the deep drawing, the joint interface between stainless steel and aluminum was observed, and the presence or absence of peeling was examined. The investigation results are shown in Table 1 together with the bonding strength and the production stability. The bonding strength was evaluated by a peel test. In the peeling test, a peeling test piece having a width of 15 mm and a length of 100 mm was used. A test piece from which the stainless steel and aluminum at the tips were peeled off by about 20 mm in advance was attached to a chuck of a tensile tester, and the stainless steel and aluminum were peeled off while being pulled in a T-shape at a speed of 0.17 mm / sec. The tensile load was measured. The measured value was converted to the width of the test piece, which was taken as the bonding strength. In addition, the production stability was determined by observing the passing state of the sheet material at the time of rolling and joining, and determining the meandering, sheet thickness variation, and the like that adversely affect the joining property. As shown in Table 1, when a stainless steel plate subjected to pickling or electrolytic pickling and an aluminum plate having a deformation resistance in the range of 30 to 60 N / mm ² are continuously rolled and joined, the stainless steel / aluminum can be formed by deep drawing. No peeling occurred at the bonding interface. The obtained stainless steel / aluminum clad plate has a high bonding strength of 20 N / mm or more, which is comparable to a stainless steel / aluminum clad plate manufactured by rolling and joining an aluminum plate to stainless steel polished with a wire brush, and There was no variation in bonding strength in the plate width direction observed when using a wire brush. The thickness of the clad plate is 1.2 mm ± 0.0
It was within the range of 2 mm.

On the other hand, when an aluminum plate having a deformation resistance of less than 35 N / mm ² is used, the aluminum plate during the passing is easy to meander, and the obtained stainless steel / aluminum clad plate has a thickness of 1.2 mm. It varied greatly within a range of ± 0.1 mm. When an aluminum plate having a deformation resistance exceeding 60 N / mm ² was used, the bonding strength was insufficient, and peeling occurred at the stainless steel / aluminum bonding interface by deep drawing.

[0015]

[0016]

As described above, according to the present invention, a stainless steel plate surface-finished by pickling or electrolytic pickling and an aluminum plate having a specified deformation resistance are overlapped and roll-joined. There is no variation in the joining strength in the width direction, and a clad plate in which stainless steel and aluminum are joined with high joining strength is manufactured. The obtained clad plate does not generate defects such as peeling or cracks at the joint interface even when it is deep drawn, so it utilizes the features of both stainless steel and aluminum to make kitchen parts, various building materials, electronic parts, and home appliances. Used in a wide range of fields as casing, piping materials, etc.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating deformation of a material in a roll bite when a stainless steel plate and an aluminum plate are overlapped and roll-joined.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 103: 20 (72) Inventor Kenji Hara 1 Tsurumachi, Amagasaki City, Hyogo Prefecture Nisshin Steel Corporation Technology F-term in the laboratory (reference) 4E067 AA03 AA05 BD02 DA03 4F100 AB04A AB10B BA02 EC01 EJ15A GB07 GB41 GB48 GB71 JK06 JK14 JK20B JL01 YY00B 4K053 PA03 PA12 QA01 RA15 RA16 RA17 SA06 TA06 TA15 TA16 XA41

Claims (1)

[Claims] 1. An aluminum plate having a deformation resistance of 35 to 60 N / mm ² is superimposed on a stainless steel plate whose surface has been finished by pickling treatment using a mixed acid of nitric acid and hydrofluoric acid or electrolytic pickling treatment using nitric acid, followed by continuous rolling. A method for manufacturing a stainless steel / aluminum clad plate, comprising joining an aluminum plate to a stainless steel plate by using the method described above.