PROCESS OF PRODUCING STEEL STRIPS SUITABLE FOR AN OXIDATION-RESISTING SURFACE COATING
A process is described for producing steel strips suitable for receiving a surface coating which is resisting to oxidation, in particular tin plating, of medium productivity, that does not require for its execution plants extended of a large areas or involving high economical investments. It comprises, starting from pickled hot strips having a thickness >0.7 mm, preferably obtained from thin-slab plants, a single cold rolling step by passing through not more than three stands of the Sendzimir 6Zhi type for the cold reduction of thickness to less than 0.25 mm and subsequent annealing. It is possible to obtain final thicknesses <0.18 mm both by simple reduction, which only provides subsequent skin-passing and finishing steps, and by double reduction on half-raw strip, which provides subsequent passes for thickness reduction of 30%.
The present invention relates to a process for manufacturing steel strips adapted to receive a surface coating which is resisting to oxidation by using anti-oxidizing elements such as aluminum, chromium or nickel, copper, etc., and in particular tin for producing tin-plate. As it is known, for depositing the above-mentioned coating metals use is made of the electrolytic method or, whenever possible, heat treatment methods.
High productivity, large plants of this type are known for which considerably large areas and very burdensome investments are required, while a valid alternative thereto is provided by medium-productivity plants (about 200,000 tons/year), which are suitable for being combined with Mini-Mills type plants, and this is the technology which the present invention is directed to, rather than to the plants and relevant high production processes of known type, with the strips for obtaining the tin-plate generally produced starting from hot strips having a thickness of about 2 mm and subsequently brought to the final thickness through two distinct cold rolling steps, one first of which by means of big “High-Four” tandem-type rolling mills with 4-5 stands, either aligned with the pickling line, or off-line, as disclosed by patent GB 1,027,495, still with the same type and number of stands. The second cold rolling step occurs after annealing with 2-3 stands of the “High-Four” type to bring the strip to the final thickness of 0.14-0.18 mm before tin coating. A plant of this type is schematically shown in
It is true that could be advantageous to use, as starting material for the production of tin-plate, hot strips such as those preferably obtained, even not exclusively, by means of in-line systems of the thin-slab type, such as the one described in the published international patent application No. WO 2004/026497, in the name of the present applicant. A diagram of such a system of endless rolling is represented in
Object of the present invention is that of providing a medium-productivity process for ultrathin strips adapted to receive an oxidation-resisting surface coating that does not require to be carried out in plants extended over too large areas, and consequently involving high investments costs.
This object of the present invention is obtained with a production process the steps of which are listed in claim 1.
Further objects, advantageous and features of the process according to the invention will result more clearly from the following detailed description with reference to the annexed drawings in which:
According to the present invention, as already mentioned above, the strips used as a substrate for the surface coating, preferably for producing tin-plate, are ultrathin hot strips of 0.7-1.0 mm thickness, obtained from a “thin-slab” plant, such as of the type schematically shown in
With reference to
It should be noted that, unlike as the High-Four type stands, the Sendzimir stands are more compact and allow more sensible reductions, as much smaller rolls are used to this effect, whereby the contact cross-section is reduced and the specific pressure, for the same value of applied force, is higher. On the contrary the prior art had used (while adopting the corresponding processes) plants in which, like in
Such a technical prejudice will be fully removed when considering that the starting hot strips which are used according to the present invention and manufactured in thin-slab plants according to
Furthermore it is noted, still with reference to
Claims
1.-4. (canceled)
5. A process for producing steel strips adapted to receive an oxidation resisting surface coating, comprising:
- providing a pickled hot strip having a thickness≧0.7 mm;
- performing a single cold rolling step by passing through not more than three stands of a Sendzimir 6Zhi type to obtain a cold reduction of the thickness to less than 0.25 mm; and
- performing a subsequent annealing step.
6. The process of claim 5, wherein the steel strips are simple reduction (SR) steel strips, and wherein
- the single cold rolling step is carried out until a thickness≦0.18 mm is reached, and
- the annealing step is followed only by skin-passing and finishing steps.
7. The process of claim 5, wherein the steel strips are half-raw double reduction (DR) steel strips, and wherein
- the single cold rolling step is carried out until a thickness between 0.20 mm and 0.25 mm is reached, and
- upon annealing, the thickness is reduced to less than 0.18 mm.
8. The process of claim 5, wherein the pickled hot strip having a thickness≧0.7 mm is obtained through a thin-slab plant.
9. The process of claim 5, wherein the steel strips are half-raw double reduction (DR) steel strips, and wherein
- the single cold rolling step is carried out until a thickness between 0.20 mm and 0.25 mm is reached, and
- upon annealing, the thickness undergoes a reduction of about 30%.
Type: Application
Filed: Jan 26, 2006
Publication Date: Sep 30, 2010
Inventor: Giovanni Arvedi (Cremona)
Application Number: 12/161,675
International Classification: B21B 1/28 (20060101); B21B 13/14 (20060101); C21D 8/02 (20060101);