KR830000808B1 - Method for manufacturing composite strip by continuous casting - Google Patents

Abstract

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Description

Method for manufacturing composite strip by continuous casting

1 is an overall view of a continuous casting apparatus for producing a composite strip according to the present invention.

2 is a longitudinal sectional view of a composite strip plated on one side to show solidified dendritic texture.

The present invention continuously adjusts Al between two rolls, and inserts a metal plating strip between a driving roll and molten Al, so that a metal having a much higher melting point and greater mechanical strength than Al is used as one or both sides of Al. It relates to a method for producing a composite strip consisting of a core coated with (Core). The invention also relates to a composite strip obtained by the above method. The term 'Al' will be used both in pure Al or in alloys based on Al.

French Patent No. 1,364,758, issued May 19, 1964, describes the principle of a continuous casting process in which a still molten metal is inserted between two cooled rolls and a metal plating strip is inserted between the molten metal and the drive roll. will be. The metal plating strip is then placed on a continuously rolled molten metal, thereby plating on the molten metal.

The main object of the present invention is to make Al surface exhibiting coarse texture even in slight processing into Al strip having excellent corrosion resistance, and also suitable for good quality, especially anodizing or polishing treatment. Plating to have surface conditions. However, French Patent No. 1,364,758 mentioned above did not allow plating with metals very different in properties from Al. That is, for example, it was not allowed to plate with stainless steel, for example, with sufficient adhesion to withstand further processing of the composite strip. Several methods of continuous casting of Al between rolls are known. French Patent No. 1,198,006, filed on June 8, 1959, describes a supply tank receiving molten metal from a foundry and a device composed of nozzles with flat sides to form a strip of metal. will be.

The ends of the nozzles are fixed between two parallel rolls which are separated from each other. The molten metal from the nozzle is cooled, solidified by contact with the cooled roll, and converted into a strip under constant pressure due to the bending of the roll. Once the strip reaches the face of the roll shaft, the strip is wound on the winder. From an economic point of view, the above method is carried out only in the manufacture of aluminum stiffness, which ranges in thickness from 1.5 mm to 20 mm.

An object of the present invention is a metal having a much higher melting point and mechanical strength than Al, and a thickness of between 1.5 mm and 20 mm, plated on one or both sides with a thickness between 0.1-1 mm to obtain good adhesion of the two components. A plating strip comprising an Al core is obtained at the exit of the roll by continuous casting.

The present invention makes it possible to produce a composite strip that can withstand later processing such as, for example, a mold, and, under good conditions, is very competitive in price compared to other plating methods.

The process according to the invention has the following characteristics.

(a) In contact with the roll, the plated metal strip shall be at least in contact with the part between the bus bar close to the nozzle end and the face of the roll shaft, and preferably at least 30 ° between the bus bar and the face of the roll shaft.

(b) The gap between the nozzle and the plated metal insert shall not exceed the thickness of the plated metal strip by more than 1 mm.

(c) The casting speed is lower than the elongation when Al is solidified, but the elongation of the plated metal is 1% or more.

Cu or stainless steel may be used as the plating metal. In the case of stainless steel, the elongation of the strip is usually between 3 and 10%. Applicants also observed that the special texture of the solidified Al layer from the rolls was obtained by unique casting conditions, which ensured good adhesion to the plated portions. The longitudinal cross-sectional layer thus obtained was represented by solidified dendritic structure of a slender pattern which forms an angle of 85 degrees or less in a direction opposite to the strip traveling direction, and particularly forms an angle of 75 degrees or less with a strip surface. This tissue is very evident when the surface of the cross section is treated with conventional reagents for visual inspection.

Needless to say, when plating both sides of the strip in the same shape and thickness, the heat exchange conditions between the strip and the two rolls are almost the same. In this case, the dendritic phase becomes almost symmetrical to the center of the Al layer. When plating only on one side, such symmetry is not apparent. In this case, the connecting line at the center of the dendritic tissue no longer coincides with the center surface and moves to the plating surface.

In order to achieve good adhesion of the components under the above-mentioned casting conditions, it was found that the range of movement of the dendritic tissue centerline from the center side should not exceed 10% at half the thickness of the Al layer.

The following detailed description of the accompanying drawings in the present invention will further enhance the understanding of the present invention.

FIG. 1 shows a casting apparatus consisting of a chute 1 containing molten aluminum 2 fed to an outlet 3 and a float 4 holding metal at a constant level in the feed tank 5. will be. The supply tank 5 is connected to a nozzle 6 which tapers gradually toward the end, which is connected through an outlet tube 7 between the two rolls 8 and 9 to make the strip the desired thickness. Drain the molten metal.

The plated metal strip 10 is brought into contact with the roll 9 as an arc contact 11 which must be at least equal to the arc generated between the bus bar 12 close to the end of the nozzle and the face 13 of the roll shaft. To be solved. It is noteworthy that the contact arc should be large enough to heat the plating strip 10 and remove moisture from the surface.

The surface of the strip is pretreated by methods known in the art such as degreasing, pickling, brushing, polishing, etc. in order to facilitate plating revolution. In this way, the strip 10 can be degreased and polished, for example, by brushing, to obtain roughness on the surface to be coated with Al on the order of 0.1 to several microns CLA before contacting Al.

It has been found that it is desirable to carry out the polishing operation immediately before plating rather than in pretreatment. On the other hand, the other side to be in contact with the roll should be as high as smooth as possible so as not to be damaged by thermal changes. Of course the strip 10 has a frictional force of, for example, 5-100 Mpa so as to be in good contact with the roll 9. The gap between the end of the nozzle and the roll 9 on which the strip 10 is wound should be maintained at a sufficient gap to prevent damage to the nozzle and large friction that may interfere with the flow of the roll without the strip wound. . However, this spacing should be limited to about 1 mm in order to prevent the instability of the unevenness of Al, which adversely affects the adhesion, from occurring in this spacing.

×100은 일반적으로 10-40%사이에 있게 된다.This spacing is limited by a pre-stresing of the cast mill stand to a value similar to the stress value that balances the spacing caused by deformation during operation. Al gradually solidifies as it passes between rolls. If Al is completely solidified to a thickness of E before exiting the roll, a rolling is performed to reduce the thickness to e. Rolling rate between nozzle outlet and roll outlet

× 100 is typically between 10-40%.

The plated metal is rolled slightly as it passes between the rolls.

One of the conditions for normal plating is less than Al and elongation between the end of the solidification and the hole filed, but the elongation of the plating strip is 1% and the actual speed of the strip is also an important factor. The theoretical maximum speed of continuous casting between rolls is the speed at the start of solidification located near the plane of the roll axis. When casting Al without actually plating, a slightly slower rate than this theoretical rate is applied. When inserting the plating strip, it has been found that further limiting the speed is necessary for good plating to maintain a proper reduction ratio of the base metal. At high speeds, it has been found that the plating strip folds, especially when the plating strip is thin, which tends to fold more easily because it solidifies only near the center and the strip does not insert well into the roll. The composite strip is cooled by air only at the exit of the roll.

Due to the difference in expansion coefficient between Al and stainless steel, the method of French Patent No. 1,364,758 does not require rapid cooling of the strip because the stress of the interface between the two metals increases due to the cooling when the stainless steel is used as a plating metal. Thus, it is desirable to cool slowly to a temperature between about 250-450 ° C. so that it can be reabsorbed by the creep phenomenon of the expanded Al. Since this method is carried out in a temperature range which gives little change in the two metal phases, if the plating metal is a Cu alloy, it must be cooled quickly without any risk of brittle fracture that can occur between the two metal phases. Rolling after cooling the strip is advantageous because it has excellent adhesion to the plated metal and the properties of mild steel, and is generally better than that of the cast metal and also affects Al. If the composite strip has to be subjected to further processing, for example tooling, it is not necessary to cool the plated metal too badly. However, in order to obtain a fairly thin composite strip between 1.5-6 mm by this method, the composite strip can be used directly without going through a rolling process, unlike the conventional method.

Up to now, the method of plating on one side of the Al strip has been described. When plating both sides of the Al strip, the metal strip should be loosened on the roll 8 in the same way as the strip 10 is loosened on the roll 9. The casting speed in this case is somewhat slower than when plating on only one side.

This method can be used despite the inclination of the roll axis with respect to the vertical line.

FIG. 2 shows the longitudinal cross section of the composite strip in detail with a fluorochromonitrile reagent to visually see the composite Al-stainless strip. In the Al layer, a solid resinous structure with a pattern of slits that forms an angle of 75 ° or less with the center of the strip is shown. Due to the asymmetry of the plated part, the center line of the resinous phase moves to the plated surface but moves with an eccentricity of less than 20%.

The process according to the invention is a composite Al-metal strip plated with a metal having a much higher melting point and mechanical strength than Al and a composite Al, which can be used in the manufacture of an inevitable tool or heat exchanger, in particular economically advantageous conditions. It is possible to make Cu strips or composite Al-stainless strips. Moreover, the adhesive force of the composite strip manufactured by this method was also excellent. The invention can also be described by several specific embodiments.

Example 1

In a continuous casting method on a roll having a diameter of 600 mm, 1050 Al having a thickness of about 10 mm was plated with an austenitic stainless steel called AISI 304 having a thickness of about 0.3 mm. After degreasing the stainless strip, it was corrected with a wire brush to obtain roughness on the order of micron CLA, and the strip was inserted into a gap of about 1 mm formed between the roll and the Al feed exposure end. A stainless strip enclosed the roll by about 90 °.

During the plating process, the stainless strip increased by about 8%. Rigid Al was about 5% off center, and the angle to the center of the dendritic tissue was about 15˚. The adhesion of the produced product was good.

Example 2

In a continuous casting method between the rolls having a diameter of 600 mm, 1050 Al having a thickness of about 2.6 mm was plated with a ferrite stainless steel called AISI 434 having a thickness of about 0.4.

After degreasing the stainless strip, it was corrected with a wire brush to obtain roughness on the order of 1 micron CLA, and the strip was inserted into a gap of about 0.6 mm formed between the roll and the end of the Al feed nozzle. A stainless strip enclosed the roll by about 90 °. During the plating, the stainless strip increased by about 3%. The elevation of the solidified Al was about 5% off center and the angle to the center of the dendritic tissue was about 60˚. The adhesion of the produced product was good. The product produced could be pressed into a 30% reduction ratio after cold working.

Example 3

Cu having a thickness of 0.5 mm was plated on 1050 Al having a thickness of 6 mm by a continuous casting method between rolls having a diameter of 600 mm.

After Cu was degreased, it was corrected with a wire brush to obtain roughness of about 1.5 micron CLA, and the strip was inserted into a gap of about 1 mm formed between the roll and the Al feed end.

The Cu plate surrounded the roll by about 30 degrees.

Cu plating increased by 10.5% during plating.

The elevation of the solidified Al was about 1% off center and the angle to the center of the dendritic tissue was about 30 °.

The adhesion of the produced product allowed for the continuous cold rolling with a thickness reduction of 3.25 mm, ie 45% reduction ratio.

Claims (1)

Al is continuously cast between two rolls spaced in parallel by a nozzle having a width equal to the width of the strip to be cast located on the flat side and near the roll, and on one or both sides of Al or Al alloy having a thickness of 1.5-20 mm. In a method for producing a composite strip by continuous casting in which Al is continuously plated by inserting a strip having a thickness of 0.1-1 mm having a much higher mechanical strength and melting point into a gap formed between a roll and molten Al, the plated metal strip At least at an angle of at least 30 ° between the bus bar close to the end of the nozzle and the bus bar located on the side of the roll, and the spacing between the nozzle and the roll into which the plated metal is inserted is less than 1 mm, the thickness of the plating strip, Composite casting by continuous casting, characterized in that the casting rate is adjusted to be greater than the elongation of the plating strip greater than 1%, less than the elongation after Al solidified. The method of tripping.

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