KR20040058613A - Manufacturing Method of Cu-Al-Stainless Steel Clad Plate - Google Patents

Abstract

PURPOSE: A method for manufacturing copper-aluminum-stainless steel clad materials is provided to prevent work hardening by proper pretreatment and heating and rolling conditions and to secure excellent bonding strength. CONSTITUTION: A method for manufacturing copper-aluminum-stainless steel clad materials is composed of steps for removing pollutants on the surface of a copper sheet(1a) by heating the copper sheet within 100¯200 deg.C; removing scales by acid-treating the copper sheet and an aluminum sheet(1b) and washing a stainless steel sheet(1c); forming uneven units on the copper and aluminum sheets, respectively; successively laying and heating the copper sheet, the aluminum sheet, and the stainless steel sheet within 200¯400 deg.C; and rolling and joining a heated copper-aluminum-stainless layered sheet(1) below 3m per minute at the percentage reduction in thickness of 15¯30%.

Description

Manufacturing Method of Cu-Al-Stainless Steel Clad Plate

The present invention relates to a cladding material, and more particularly, to a method for producing a copper-aluminum-stainless steel cladding material for producing a triple cladding sheet made of copper, aluminum and stainless steel by a rolling process.

Clad material is defined as a laminated composite material in which the surfaces of two or more metal materials are joined by metal bonding. These clad materials are economically advantageous because they can maximize the performance of materials and save expensive materials by using various combinations of appropriate materials. Therefore, the combination of materials is gradually diversified and the field of application is expanded. have.

Among the cladding materials, the most widely used materials for home appliances are stainless steel-aluminum cladding materials, which are used to properly combine the advantages of stainless steel and aluminum, and have low specific gravity, high thermal conductivity, and stainless steel. It has the advantages of excellent corrosion resistance and workability of steel. For this reason, it is used for general household cooking containers, electronic cooking utensils, etc., and it is partially applied also to building materials, heat exchanger materials used for a plant, a motor vehicle, a ship, etc.

Since clad material can be used for various purposes, it is highly likely to replace the existing single material in each field. The replacement of such materials is rapidly progressing in kitchen containers, and existing single materials such as stainless steel or aluminum are rapidly being replaced by stainless steel-aluminum or stainless steel-aluminum-stainless steel cladding.

In addition, in recent years, the use of less dangerous and environmentally friendly induction heating device instead of using gas as a heat source has gradually increased, and thus, an austenitic stainless steel-aluminum-ferrite which can evenly conduct heat and conduct heat to a suitable material. The use of system stainless steel cladding materials is increasing. In order to heat by induction heating method, the material must be magnetic, so in case of double plate, the outside is made of ferritic stainless steel, and the inside which is in contact with food is coated with resin on aluminum. In the case of the triple plate, the outside is made of ferritic stainless steel, the center is made of aluminum, and the inside is made of austenitic stainless steel.

In addition, recently, in order to fully utilize induction heating characteristics, carbon steel having excellent magnetic properties is used, such as stainless steel-aluminum-carbon steel-aluminum-stainless steel cladding material or aluminum-carbon steel-aluminum cladding material.

Along with these clad materials, the demand for copper-aluminum clad material with high added value, beautiful appearance and excellent heat transfer characteristics is gradually increasing around Europe. Compared with stainless steel, heat transfer performance and heat diffusion performance are very good. Therefore, when copper-clad cladding material is used as a material for cooking utensils, the cooking time can be shortened, and energy saving can be performed accordingly. In addition, copper-aluminum cladding material is valuable for decoration because of its beautiful appearance, and can be used as a heat sink material.

On the other hand, as a manufacturing method of the clad material currently used, there exist an explosion joining, the diffusion joining, the rolling method, the build-up welding, etc., and these methods are often used in combination.

Among them, explosion bonding cannot be applied because the noise is high at the time of joining, so that it is difficult to obtain a working place, the work is dangerous, and the surface shape deteriorates with respect to the thin plate material.

In addition, diffusion bonding can produce a product having excellent bonding strength, but it takes a lot of time, and has high manufacturing cost, and thus it is not economical as a general industrial material manufacturing process excluding expensive components.

In addition, the wet welding cannot be directly applied between copper-aluminum and aluminum-stainless steel, and thus cannot be applied to the manufacturing process of copper-aluminum-stainless steel clad material.

Therefore, among the methods for manufacturing the clad material mentioned above, the most economical mass production method can be said to be a rolling method.

In particular, the method of manufacturing the clad by hot rolling is a kind of solid state bonding, and surface treatment before bonding to remove foreign substances such as scale, oil, and dirt present on the bonding surface is very important. At the time of joining, care must be taken to prevent the formation of an oxide film at the joining interface. By the way, in the commercial process of mass-producing a product, in order to protect an interface, it is difficult to roll in a vacuum atmosphere or to roll in a reducing gas atmosphere. Therefore, even if the plate is surface treated, an oxide film is formed again when the plate is heated, which causes problems in bonding.

On the other hand, the following looks at some of the prior art related to the production of copper-aluminum cladding material.

First, in the data published in "Sheet Metal Industry" Vol. 60, No. 5 (1983), copper and aluminum were rolled in a temperature range of 100 to 150 ° C. under a rolling reduction of 55% or more. A method of post-heat treatment in the temperature range of 260-300 degreeC is disclosed. By using this method, the joining of the two materials is possible, but the hardening of the work is so large that the plate breaks or the cleavage of the joint occurs during plastic processing for processing into a final product such as a kitchen vessel. When the product is heat-treated at a temperature of 200 to 400 ° C. as is known, aluminum may have an effect of alleviating the processing hardness. However, since copper has a melting point of about 1100 ° C., it is difficult to soften the copper. .

Next, Korean Patent Laid-Open Publication No. 2001-091951 discloses a manufacturing technique of copper and aluminum cladding material, which uses pure aluminum as an insert metal in joining an oxygen-free copper and an aluminum alloy plate. have. That is, after cold-rolling an oxygen-free copper and a pure aluminum plate on the conditions of 40 to 70% of a reduction ratio, this clad material is cold-rolled again with an aluminum alloy or hot-rolled in the temperature range of 100-350 degreeC. However, this technique also causes problems in the joints in subsequent processes as described above, and also in terms of economics because of the use of intermediate materials.

In addition, although it is not a publicly known technique, in recent years, aluminum-copper clad products manufactured by joining nickel or plated on copper or aluminum plates have been produced. However, since nickel plating significantly increases the production cost, it is not only a clad material but also a final product. There is a problem of lowering the price competitiveness of the product.

Recently, Korean Patent Laid-Open Publication No. 2002-052087 discloses a method of manufacturing a copper-aluminum clad material by heating copper and aluminum at different temperatures, and then laminating and rolling them. However, this method can produce a cladding material that can secure plastic workability, but productivity is lower than that of laminating two materials and heating them at the same time, and in the case of joining stainless steel other than copper and aluminum, The disadvantage is that it is difficult to apply.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned general problems, and an object thereof is to provide a method for producing a copper-aluminum-stainless steel clad material having excellent productivity while securing plastic workability for processing into a final product. To provide.

1 is a view briefly showing a method for producing a cladding material according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1: Cu-Al-STS laminated sheet 1a: copper plate

1b: aluminum sheet 1c: stainless steel sheet

2: heating furnace 3: rolling mill

Method for producing a copper-aluminum-stainless steel clad material according to the present invention for achieving the above object, the step of heating the copper plate in the range of 100 ~ 200 ℃ to remove contaminants on the surface; Pickling the copper plate and the aluminum plate to remove scale and washing the stainless steel plate; Forming irregularities on surfaces of the copper plate and the aluminum plate, respectively; Stacking the copper plate, the aluminum plate, and the stainless steel plate in sequence and heating them in a range of 200 to 400 ° C .; The technical subject matter includes the step of joining the heated copper-aluminum-stainless steel laminate at a rate of 3 meters per minute or less with a rolling reduction of 15-30%.

In particular, the irregularities formed on the surfaces of the copper plate and the aluminum plate, respectively, are preferably formed with a width of 0.5 mm or less.

Moreover, it is preferable that the unevenness | corrugation formed in the surface of the said copper plate and the said aluminum plate, respectively is formed by the iron brush whose wire diameter is 0.5 mm or less.

Hereinafter, a method of manufacturing a copper-aluminum-stainless steel cladding material according to the present invention will be described in detail.

The cladding material of the present invention is obtained by laminating a copper plate, an aluminum plate, and a stainless steel plate in sequence, and first, heating the copper plate to remove contaminants such as oil and dirt present on the surface of the copper plate. This is because the copper plate is much more sensitive to oxidation than aluminum or stainless steel when heated at high temperatures, and particularly when contaminants remain on the surface, oxidation occurs severely at that portion, resulting in poor bonding at the time of joining. In particular, the contaminants on the surface of the copper plate are difficult to be completely removed even if subjected to chemical treatment such as pickling, but heating to about 100 to 200 ° C. can almost eliminate the contaminants.

Next, the scale of the copper plate and the aluminum plate is removed. In this case, pickling is most preferable. For example, in the case of copper plate, the scale can be removed by immersion in nitric acid or sulfuric acid solution for a certain time, and in the case of aluminum, it is immersed in sodium hydroxide solution and then petroleum ether solution. You may wash. On the other hand, the stainless steel sheet is not sensitive to surface oxidation, so it does not need to be treated separately, and it is suitable only to clean the surface.

In the next step, irregularities are formed on the surfaces of the copper plate and the aluminum plate, respectively, and the size of the irregularities is preferably formed to be 0.5 mm or less in width. This is because if the size of the unevenness is larger than 0.5 mm, marks may remain on the surface after rolling. As a method of forming the unevenness, it is preferable to use an iron brush having a wire diameter of 0.5 mm or less. If the iron brush is applied to the copper plate and the aluminum plate, fine grooves are formed on the surface of the material, so that the grooves increase the joint area. Bonding is made.

Next, after laminating the copper plate and the aluminum plate in which the irregularities are formed as described above together with the stainless steel sheet, and then heated to a temperature range of 200 ~ 400 ℃. The temperature range is limited in this way, if the heating temperature exceeds 400 ° C., the thickness of the surface oxide layer of the copper plate is rapidly increased, so that the bonding becomes difficult. This is because it requires a lot of load, so that it is difficult to secure workability required in subsequent processing steps as in normal temperature bonding.

In the next step, the laminated sheet of copper-aluminum-stainless steel (Cu-Al-STS) heated as above is joined by hot rolling. Typically, in order to make a clad material of copper and aluminum, aluminum and stainless steel by such hot rolling, diffusion must occur between the atoms on the surfaces of the two materials, and the diffusion is affected by the rolling speed. In the present invention, it is preferable to control the rolling speed to 3 meters per minute or less for such diffusion. If the rolling speed is faster than 3 meters per minute, the time required for diffusion is so short that bonding does not occur. On the other hand, the reduction ratio is preferably controlled to 15 to 30%. If it is less than 15%, sufficient bonding force cannot be applied. If the reduction rate is greater than 30%, the sheet material, especially stainless steel sheet, is severely deformed, resulting in work hardening. It becomes difficult to process the produced clad material by using a kitchen container.

In producing the clad material of the present invention as described above, the copper plate used is most preferably copper oxide free, and the aluminum plate and the stainless steel plate may be used as a common clad material.

Hereinafter, the copper-aluminum-stainless steel cladding material prepared according to the manufacturing method according to the present invention and the cladding material not otherwise described will be described.

First, the copper plate was heated in a heating furnace to remove contaminants on the surface, and then immersed in nitric acid solution for 10 minutes to remove scale. The aluminum plate was immersed in sodium hydroxide solution for several seconds, and then washed with petroleum ether solution to remove scale. In addition, the foreign matter on the surface of the stainless steel sheet was removed with acetone, and then washed with warm water.

Subsequently, the descaling copper plate and the aluminum plate were brushed with an iron brush made of a wire having a diameter of 0.2 mm to form irregularities on each surface.

Then, as shown in FIG. 1, the copper plate 1a, the aluminum plate 1b, and the stainless steel plate 1c are sequentially laminated and heated in the heating furnace 2, and then the laminated plate 1 is rolled into a rolling mill 3. ) To prepare a clad material (not shown 4 is a roller table).

For the clad material manufactured in this manner, various examples and comparative examples were applied to the pretreatment conditions, the heating temperature in the furnace, and the hot rolling conditions, and the joint strength and workability (drawing properties) were evaluated accordingly. The results are shown in Table 1. Here, the criterion of the good bonding state in terms of the bonding strength was set to 100 N / cm, which is a typical experience value.

As can be seen from Table 1, the cladding materials of Examples 1 to 4 bonded according to the conditions of the present invention had both good bonding strength and drawability. However, when the surface of the copper plate was decontaminated by chemical treatment without heat treatment as in Comparative Example 1, the bonding strength of the copper-aluminum interface was low, and the phenomenon of the interface peeling during subsequent molding occurred. When the heating temperature is higher than 400 ° C as in Comparative Examples 2 and 4, the peeling phenomenon occurred at the copper-aluminum interface. When the heating temperature is lower than 200 ° C as in Comparative Example 3, the stainless steel sheet was Severe work hardening caused plate failure. In addition, as in Comparative Example 5, when the rolling speed was increased to about 4 meters per minute, the bonding strength of the copper-aluminum interface was lowered, and the surface defects appeared partially during molding. In addition, when the reduction ratio was higher than 30% as in Comparative Example 6, the plate fracture occurred due to the work hardening of the stainless steel sheet, and when the reduction ratio was lower than 15% as in Comparative Example 7, the bond strength was significantly decreased.

Note) O: Good, △: Partial defect, X: Poor

As described above, according to the method for producing a copper-aluminum-stainless steel cladding material according to the present invention, copper-aluminum-stainless steel having excellent bonding strength and workability without causing work hardening by appropriate pretreatment, heating, and rolling conditions. In addition to being able to manufacture steel cladding materials, each material is not heated to a separate temperature, and thus excellent effects are also exhibited in productivity.

Claims (3)

Heating the copper plate in a range of 100 to 200 ° C. to remove contaminants on the surface; Pickling the copper plate and the aluminum plate to remove scale and washing the stainless steel plate; Forming irregularities on surfaces of the copper plate and the aluminum plate, respectively; Stacking the copper plate, the aluminum plate, and the stainless steel plate in sequence and heating them in a range of 200 to 400 ° C .; A method of manufacturing a copper-aluminum-stainless steel clad material comprising the step of bonding the heated copper-aluminum-stainless steel laminate at a rate of less than 3 meters per minute and a rolling reduction of 15 to 30%. The method of claim 1, The unevenness | corrugation formed in the surface of the said copper plate and the said aluminum plate, respectively, is 0.5 mm or less in width, The manufacturing method of the copper- aluminum-stainless steel cladding material characterized by the above-mentioned. The method according to claim 1 or 2, The unevennesses formed on the surfaces of the copper plate and the aluminum plate, respectively, are formed by iron brushes having a wire diameter of 0.5 mm or less, characterized in that the copper-aluminum-stainless steel cladding material manufacturing method.