EP0190083A1 - Four-high mill for rolling bright flat products - Google Patents

Abstract

The invention relates to a four-high mill for obtaining strips or sheets of aluminium or alloys thereof of "high brightness" quality. At least one of these work rolls comprises a central annular groove whose roughness is low and controlled. <IMAGE>

Description

The technical field of the invention relates to the rolling of metal sheets or strips, in particular of Al or its alloys, with a glossy surface condition using a suitable quarto rolling mill.

It is known that obtaining flat products with a glossy surface condition requires working rolls having a very good surface condition and suitable lubrication.

So far, the first factor indicated above has always prohibited the use of quarto rolling mills to obtain such products, the surface condition of the working cylinder being rapidly deteriorated by the support and / or the relative sliding of the working cylinder on the support cylinder or the introduction of metallic particles or not, between these two cylinders, by the cylinder itself, the lubricating agent or in any other way.

The problem that we propose to solve is therefore the use of quarto rolling mills (much more widespread than the duo) for this purpose, despite the major up to now insurmountable drawbacks, mentioned above.

• - soit un cylindre de travail plan "normal".
• - soit un cylindre à gorge semblable au premier.
• - soit un cylindre de travail dont la partie centrale comporte un relief annulaire de hauteur égale aux 2/3 environ de la profondeur de la gorge de l'autre cylindre sur une longueur inférieure à celle de cette gorge, l'état de rectification de ce cylindre étant quelconque.

According to the invention, the quarto rolling mill comprises two working rolls, at least one of which has a central annular groove with a depth less than the final thickness of the desired product and whose length is greater than the width of the product, the machining of the central part being such that the surface roughness Ra is less than 0.07 µm, the other cylinder being:

• - either a "normal" working cylinder.
• - or a grooved cylinder similar to the first.
• - or a working cylinder, the central part of which has an annular relief of a height equal to approximately 2/3 of the depth of the groove of the other cylinder over a length less than that of this groove, the state of rectification of this cylinder being arbitrary.

The machining of the normal working cylinder and the ends of the modified working cylinder (s) is such that the roughness reaches a usual Ra value, close to 0.35 µm.

The range of these working cylinders on the corresponding support cylinder along a generator must preferably be greater than 25% of the length of the support cylinder, to ensure sufficient training of the former.

• . la figure 1 représente une vue en coupe schématique suivant la ligne I-I de la figure 2 d'un laminoir quarto selon l'invention,
• . la figure 2 représente une élévation schématique du laminoir représenté à la figure 1,
• . la figure 3 représente une vue en coupe schématique suivant la ligne III-III de la figure 4 d'une variante d'un laminoir quarto selon l'invention,
• . la figure 4 représente une élévation schématique du laminoir représenté à la figure 3.

The invention will be better understood with the aid of the following illustrations and examples:

• . FIG. 1 represents a schematic sectional view along line II of FIG. 2 of a quarto rolling mill according to the invention,
• . FIG. 2 represents a schematic elevation of the rolling mill shown in FIG. 1,
• . FIG. 3 represents a schematic sectional view along line III-III of FIG. 4 of a variant of a quarto rolling mill according to the invention,
• . FIG. 4 represents a schematic elevation of the rolling mill shown in FIG. 3.

The quarto rolling mill conventionally comprises two working rolls (1a, 1b) supported by 2 support rolls (2a, 2b). In the case shown in fig. 1 and 2, the support cylinders (2a, 2b) and one of the working cylinders (1b) are smooth while the second working cylinder (la) is provided with a central annular groove (3) whose depth is less than the final thickness of the product to be laminated (4). The bottom of this annular groove is rectified to a roughness less than Ra - 0.07 µm.

In the case shown in Figures 3 and 4, the cylinder (la) is machined as described above and the cylinder (1b) has an annular relief (5) whose height reaches substantially 2/3 of the depth of the throat (3). Of course. ie the corresponding support cylinder (2b) has the corresponding annular groove (6). This makes it possible to laminate products (4) of relatively smaller thickness.

The following examples illustrate the invention. The surface condition of the products obtained is generally characterized by the value of the specular reflectance R measured using a Hunterlab device with an incidence of 20 ° in a transverse plane (Tête de Lange) with the following classes:

EXAMPLE 1

Cold rolling of a 1200 alloy blank (according to the designation of the Aluminum Association) 1.6 mm thick and 1210 mm wide, with the following passes: 1.6 ---> 1.2 - -> 0.8 ° ---> 0.6 mm, the central part of the cylinder being machined with a roughness Ra ≃ 0.07 µm.

We obtain sheets whose quality is BI, from the second pass.

EXAMPLE 2

Cold rolling of a preform in 1050 (according to the designation of the Aluminum Association) 1.6 mm thick and 1030 mm wide with the following passes: 1.6 ---> 1.25 ---> 1 ---> 0.8 ---> 0.6 mm; the central part of the working cylinder has been machined with a roughness Ra of 0.05 µm; the evolution of the reflector and the veil are as follows:

The surface finish obtained achieves the "glossy finish" quality.

• . elle permet de cumuler les avantages du laminoir duo en ce qui concerne la qualité de surface de cylindres et ceux du laminoir quarto en ce qui concerne l'utilisation des automatismes de contrôle de la planéité, de la précision et de la régularité d'épaisseur:
• . elle permet d'utiliser des laminoirs quarto existants, sans investissement;
• . elle permet d'obtenir des bandes ou tôles de grande largeur (par exemple 1500 mm de large) avec une bonne planéité;
• . elle permet d'obtenir sur la surface non brillante des états de surface divers (grenaillés, motifs décoratifs, etc...).

The invention has the following advantages:

• . it allows you to combine the advantages of the duo rolling mill with regard to the surface quality of rolls and those of the quarto rolling mill with regard to the use of automatic controls for flatness, precision and regularity of thickness:
• . it allows the use of existing quarto rolling mills, without investment;
• . it makes it possible to obtain strips or sheets of large width (for example 1500 mm wide) with good flatness;
• . it makes it possible to obtain various surface states on the non-shiny surface (shot blasted, decorative patterns, etc.).

Claims (4)

_the. Quarto rolling mill for rolling shiny flat products, characterized in that the central zone of at least one of the two working rolls (la, lb) has an annular groove (3) whose depth is less than the final thickness of the desired product (4), whose length is less than the final width of the product and whose roughness Ra is less than or equal to 0.07 µm. 2. Quarto rolling mill, characterized in that the central zone of one of the working rolls (la) has an annular groove (3) whose length is less than the final width of the product (4) and whose roughness is less or equal to 0.07 µm and in that the other working cylinder (lb) is provided with a cylindrical relief (5) whose length and height are respectively less than the length and the height of the groove ( 4) of the first working cylinder. 3. Quarto rolling mill according to claim 2, characterized in that the height of the relief of the working cylinder reaches 2/3 of the depth of the groove of the other working cylinder. 4. Quarto rolling mill according to one of claims 1 to 3, characterized in that the effective range of the working rolls on the corresponding bearing rolls represents at least 25% of the length of the common generator.

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