JP3695063B2 - Manufacturing method of stainless steel strip for clad material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a stainless steel strip as a material for a clad material produced by rolling joining.
[0002]
[Prior art]
The demand for clad materials in which different types of metal plates are joined has increased rapidly in the fields of industrial and daily necessities because they exhibit characteristics that cannot be obtained with a single metal plate.
[0003]
There are several methods for producing the clad material, but the rolling joining method is suitable for mass production. As a general method for producing a stainless steel-aluminum clad material by a pressure welding method, a cold rolling joining method in which a stainless steel strip and an aluminum strip are overlapped and pressure-welded at room temperature, and the two strips are 200 to 500 are combined. There is a method of superimposing by heating to ° C., and rolling and joining them hot.
Conventionally, a stainless steel strip as a cladding material is manufactured by the following two methods.
[0004]
That is, the stainless steel strip that has been cold-rolled is continuously annealed in a continuous annealing pickling line that is called an AP line, which includes an annealing furnace part, an alkali molten salt bath (chemical descaling) part, and a pickling part. After descaling
1) A method of temper rolling with a rolling reduction of 0.3%, and further polishing and cleaning using a polishing belt having a grain size of # 120
2) A method of performing temper rolling with a rolling reduction of 0.3% and dry-polishing the joining interface of the raw material using a wire brush on the entry side of the clad joining rolling mill.
[0005]
However, this method has the following drawbacks.
In the method 1), since the three steps of temper rolling, belt polishing, and washing are included between the annealing-descaling process and the clad bonding rolling process, the lead time becomes longer. In addition, sufficient bonding strength cannot be obtained for the clad material even by roll bonding.
[0006]
In the method 2), the joining interface is polished with a wire brush on the entry side of the clad bonding rolling mill, so that polishing scraps adhere to the material, and indentation flaws occur in the clad steel strip as a product. Also, the bonding strength is not sufficient.
[0007]
The temper rolling is performed in order to reduce the scale and facilitate removal of the scale in subsequent polishing.
Each of them has the above-mentioned problems, and the present situation is that it is impossible to produce a stainless steel strip for a clad material that is excellent in surface properties and bondability at a low production cost.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a stainless steel strip that can omit the steps as much as possible after the annealing-descaling process and can increase the bonding strength of the clad material.
[0009]
[Means for Solving the Problems]
The present inventor investigated the cause of the low bonding strength of the clad material using the stainless steel strip for clad material produced by the above-mentioned conventional method, conducted various experiments for the countermeasure, and obtained the following knowledge as a result of repeated studies. It was.
[0010]
(1) After the annealing-descaling treatment step, a temper rolling is performed, and then the surface of the steel strip polished with a polishing belt or a wire brush has a film mainly composed of Fe ₂ O _3. Since it has ductility, the film cannot be destroyed during clad bonding rolling, and the new surface is not exposed on the surface of the steel strip, so that the bonding with the laminated material becomes insufficient.
[0011]
(2) In order to remove the film mainly composed of Fe ₂ O _3, it is preferable to polish with a brush roll without performing temper rolling. The film mainly composed of Fe ₂ O ₃ is removed and Cr ₂ O ₃ is applied to the surface. It should be exposed.
[0012]
(3) When a stainless steel strip having Cr ₂ O ₃ exposed on the surface is bonded and rolled, Cr ₂ O ₃ is destroyed and a new surface appears, and the bonding strength with the laminated material is improved.
[0013]
The present invention has been made on the basis of such knowledge. The gist of the present invention is that "the cold-rolling , annealing and descaling treatments are performed to form an oxide film mainly composed of Fe ₂ O ₃ and its underlying Cr ₂ O _3. The surface of the stainless steel strip having the main oxide film on the surface is a depth at which the Fe ₂ O ₃ main oxide film is removed using the brush roll as it is to expose the Cr ₂ O ₃ main oxide film. The method of manufacturing a stainless steel strip for a clad material characterized by polishing .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
The material of the stainless steel strip is not particularly limited and can be austenitic stainless steel or ferritic stainless steel. SUS 304 and SUS 430 are suitable for combination with aluminum or titanium.
[0015]
For the annealing of the stainless steel strip and the removal of the oxide scale, it is efficient to perform the treatment continuously in an AP line comprising an annealing furnace, an alkali molten salt bath, and a pickling bath as in the conventional method described above. However, it is not always necessary to perform the treatment on the AP line, and annealing and descaling may be performed on separate lines.
[0016]
The annealing temperature is about 1050 to 1150 ° C. for austenitic stainless steel and about 800 to 980 ° C. for ferritic stainless steel.
The dimensions of a stainless steel strip suitable as a material for the clad material are a plate thickness of 0.2 to 1.0 mm, a width of 750 to 900 mm, and a plate passing speed adjusted to 10 to 20 m / min according to annealing conditions. To do.
[0017]
Next, the brush roll is used to polish the surface of the stainless steel strip by removing the film mainly composed of Fe ₂ O ₃ existing on the surface of the stainless steel strip, and mainly using the Cr ₂ O ₃ existing thereunder. This is to expose the film to be exposed on the surface. Since the thickness of the coating layer mainly composed of Fe ₂ O ₃ is about 100 to 150 angstroms, it may be polished to such an extent that the coating layer can be removed. Too much polishing results in faster brush wear and is not economical.
The polishing of the material by the brush roll exerts the effect of increasing the bonding strength of the clad material because the stress concentrates on the irregularities on the surface of the stainless steel strip generated by the brush roll polishing during the bonding rolling, and Cr ₂ O _It is assumed that the film mainly composed of ₃ is destroyed and the new surface is exposed.
[0018]
For removal of the Fe ₂ O ₃ main film on the surface of the steel strip, we tried polishing with a wire brush or belt without temper rolling, but these means could not remove it, but the reason is not clear Absent.
[0019]
As a matter of course, it is only necessary to polish the surface on which the laminated materials are stacked.
FIG. 1 is a side view of an example facility used to carry out the method of the present invention.
From the payoff reel 1 to the pickling tank 7 in the figure is an AP line that performs annealing and descaling. A cold-rolled stainless steel strip S, which is a material before clad bonding rolling, is wound around a payoff reel 1. The steel strip S is unwound and the leading end or the trailing end is cut by the shear 2 on the entry side, and then welded to the leading coil or the trailing coil in the welder 3. And it conveys to the annealing furnace 5 through the entrance side loop 4, and anneals at predetermined temperature.
[0020]
Oxide scale is generated on the surface of the steel sheet after annealing. In order to remove the oxide scale layer, as a pretreatment, the steel strip is immersed in an alkali molten salt bath 6 mainly composed of sodium hydroxide (NaOH), and then the reaction product remaining on the surface is removed. The steel strip S is immersed in a pickling tank 7 containing sulfuric acid, hydrofluoric acid or the like. The surface of the steel strip after the pickling treatment is passivated, and a coating mainly composed of Fe ₂ O ₃ exists on the surface layer. Thereafter, the steel strip is conveyed to the brush roll polishing apparatus 8 and the surface of the steel strip S is polished in order to remove Fe ₂ O ₃ present on the surface.
[0021]
Next, the steel strip S is cut into a predetermined size by the split shear 2 through the exit loop 9 and wound on the tension reel 11.
FIG. 2 is an enlarged side view of the brush roll polishing apparatus.
[0022]
The steel strip S after pickling is drained with an inlet ringer roll 12 and washed with an inlet water spray nozzle 13. Next, the steel strip S is polished with the brush roll 14. The lower surface of the steel strip is supported by a rubber-lined backup roll 15. This polishing is wet polishing by the intermediate water spray nozzle 16. Polishing debris adhering to the surface of the steel strip S after polishing is washed away by the outlet water spray nozzle 17. Further, the steel strip S is drained by the ringer roll 18 on the exit side of the brush roll polishing apparatus.
[0023]
FIG. 3 is a front view of the polishing section, and the steel strip S is polished while being sandwiched between a brush roll 14 on the upper surface side and a backup roll 15 of a rubber lining on the lower surface side.
Since the steel strip does not pass through both ends of the backup roll, it is barrel-cut and prevented from being polished by the brush roll.
A preferred brush roll polishing apparatus and its operating conditions are as follows.
[0024]
(1) Brush roll polishing apparatus The brush roll has brush hair made of SiC or Al ₂ O ₃ abrasive, particle size is # 100 to # 120, brush diameter is 1.2 to 1.5 mm, hair length is 30 to 35 mm, brush The roll diameter is about 380 to 420 mm, and the roll barrel width is about 1200 to 1300 mm.
[0025]
(2) Brush roll polishing apparatus operating conditions Steel strip moving speed: 10 to 20 m / min
Brush roll rotation speed: 800-1000rpm
Pressing pressure (rolling down): About 3-4mm below the threading plate height The rolling brush roll is rotated in the opposite direction (upcut method) to the sheeting steel strip. It is better to set the above level. The pressing pressure (referred to as “reduction”) lowers the brush roll, and further lowers the position where the brush roll tip contacts the surface of the sheet steel strip, that is, the pass line, by about 3 mm (hereinafter referred to as “3 mm reduction”).
[0026]
The load current of the brush roll is preferably controlled by an inverter so that a constant reduction is always maintained.
The clad material stainless steel strip prepared according to the present invention is clad into, for example, an aluminum plate or a copper plate, and the conditions may be in accordance with conventional conditions.
In the case of the raw material according to the present invention, it is not necessary to perform temper rolling in particular.
[0027]
[Example 1]
With the equipment shown in FIG. 1, ferritic stainless steel SUS304 cold rolled steel strip having a thickness of 0.6 mm and a width of 900 mm is used for annealing and descaling under the following conditions, and then the brush roll shown in FIG. 2. The material for the clad material was manufactured by polishing with a polishing apparatus under the following conditions.
[0028]
Annealing temperature: 970 ° C
Sheeting speed during annealing: 19m / min
Descaling: Pickled brush roll diameter: 400 mm with alkali molten salt and sulfuric acid-nitric acid aqueous solution
Roll barrel width: 1300mm
Brush bristle material: SiC
Brush hair length, diameter: 30mm, 1.2mm
Brush granularity: # 100
Brush rotation speed: 1000rpm
Reduction: 3 mm
In addition, a part of the descaled cold-rolled steel strip was used as a conventional example (a) after temper rolling with a rolling reduction of 0.3%, followed by polishing with a belt of grain size # 120, washing with water, and comparative example (B) The material of the clad material was manufactured by two methods of polishing and washing with a belt of grain size # 120 without temper rolling.
[0029]
The chemical composition of the surface layer portion of the cold-rolled steel strip subjected to brush roll polishing and belt polishing manufactured in this manner was determined by a micro-partial chemical analyzer (ESCA). Moreover, after applying a tensile elongation of 10% to these clad materials, the state of cracking of the oxide film on the surface of the steel strip was observed with an optical microscope. This tension simulates elongation in joint rolling.
[0030]
As a result of analysis of chemical components on the surface of each steel strip, the surface of the steel strip manufactured by the method of the present invention polished with a brush roll was an oxide mainly composed of Cr ₂ O ₃ . In addition, the surfaces of the steel strips belt-polished after temper rolling of the conventional example and the steel strips belt-polished without temper rolling of the comparative example were both oxide films mainly composed of Fe ₂ O ₃ . In addition, the surface observation result after applying the tensile force showed that the film mainly composed of Cr ₂ O ₃ had large cracks, but the oxide film mainly composed of Fe ₂ O ₃ had no cracks. There wasn't.
[0031]
In the actual production of the clad material, at the time of rolling joining, not only the above-described tension but also the compressive force acts on the convex portions generated by polishing, so the destruction of the oxide film mainly composed of Fe ₂ O ₃ , Become more prominent.
[0032]
Next, the cold rolled steel strip, which is the material of the clad material polished by the above-mentioned brush roll polishing and belt polishing, and the aluminum (JIS A1100) plate having a thickness of 2.0 mm are overlapped and subjected to joint rolling under the following conditions. A material was manufactured, and a peel test was performed in accordance with the provisions of JIS K 6854 (test piece width: 5 mm) to evaluate the bondability of the clad material. Three peel test pieces were prepared for each.
[0033]
Stainless steel strip heating temperature: 450 ° C
Heating temperature of aluminum plate: 440 ° C
Bond rolling reduction ratio: 23%
Sheet thickness after joint rolling: 2.0 mm
The result of the peeling test of the clad material using the material of the present invention subjected to brush roll polishing is an average peel strength of 25 N / mm, and the clad material using the belt polished material after temper rolling in the conventional example is 18 N / mm. The clad material that was not temper-rolled in mm and the comparative example was 15 N / mm.
[0034]
As described above, the clad material using the stainless steel strip polished with the brush roll polishing apparatus has greatly improved the bonding strength as compared with the clad material using the conventional temper rolled and belt polished stainless steel strip. I understand that Moreover, the clad material using the steel strip polished by belt without temper rolling in the comparative example had the best bonding strength because there was no temper rolling effect.
[0035]
【The invention's effect】
According to the method for producing a stainless steel strip for a clad material according to the present invention, the production process such as temper rolling can be simplified, so that the production cost of the clad material can be reduced and the clad material having excellent bonding strength. Is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an example facility used to carry out the method of the present invention.
FIG. 2 is a side view of the brush roll polishing apparatus.
FIG. 3 is a front view of a polishing unit.
[Explanation of symbols]
S Stainless Steel Strip 11 Tension Reel 1 Payoff Reel 12 Incoming Ringer Roll 2 Shear 13 Incoming Water Spray Nozzle 3 Welder 14 Brush Roll 4 Incoming Loop 15 Backup Roll 5 Annealing Furnace 16 Intermediate Water Spray Nozzle 6 Alkaline Molten Salt Tank 17 Out Side water spray nozzle 7 Pickling tank 18 Outlet ringer roll 8 Brush roll polishing device 9 Outlet loop

Claims (1)

The surface of the stainless steel strip having the Fe ₂ O ₃ main oxide film and the underlying Cr ₂ O ₃ main oxide film on the surface as a result of cold rolling , annealing and descaling treatment is directly applied to the brush roll. A method for producing a stainless steel strip for a clad material , comprising polishing to a depth at which the Fe ₂ O ₃ based oxide film is removed and the Cr ₂ O ₃ based oxide film is exposed .

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