RU2399442C2 - Method for production of semi-finished rolled products for hot-galvanised steel - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method includes cold rolling of strips on multiple-stand continuous rolling mill in rolls with prepared surface and tension of specified value. Production of items with defect-free surface, which do not have scratches, "imprints", without corrugation of edges, is provided by the fact that rolling in fourth stand of mill is carried out in polished rolls with transfers in every 2500 t or in notched rolls after preliminary rolling of 1000 t of metal of other purpose, at the same time rolling of strips with thickness of h≤0.6 mm is carried out with thickened front ends in amount of 2…3 turns per drum of reel, and tension T on reel motor is established for strips with thickness h≤0.7 equal to 1.2 × T_max, and for strips of thickness h>0.7 mm equal to 1.3 × T_max, where T_max - maximum permissible value of tension in process of rolling metal not intended for hot galvanisation.

EFFECT: invention is intended to improve quality of hot galvanised steel.

2 ex

Description

The invention relates to the processing of metals by pressure and can be used in the technology of producing tackle for hot dip galvanized steel with a thickness of at least 0.48 mm

One of the main operations in the production of such steel is to obtain a rolling stock going to a continuous hot dip galvanizing unit (ANGC). The production technology of galvanized sheet steel is described in sufficient detail, for example, in the reference book edited by V.I. Zyuzin and A.V. Tretyakov, "Rolling production technology," vol. 2, M.: Metallurgy, 1991, pp. 718-725. Tackle for ANGC is usually obtained on multicell (for example, 4 cage) cold rolling mills.

A known method of manufacturing a steel sheet for subsequent coating, including hot rolling with predetermined temperatures, cold rolling and tempering of strips with predetermined crimps (see US Pat. RF No. 2165809, class B21B 1/22, publ. BI No. 12, 2001 ) However, this method is only suitable for obtaining a stable enameled sheet.

The closest analogue to the claimed object is the technology of cold rolling of sheet steel, described in the book by S. P. Efimenko and V. P. Slednev "Roller sheet rolling mills." M .: "Metallurgy", 1980, p.230-238.

This technology consists in the sequential rolling of strips in the stands of a continuous mill and is characterized by the fact that the mill rolls have a pre-prepared surface with its required cleanliness and hardness and is characterized by the fact that the compression mode (values) are determined by the thickness and strength of the rolled steel and the tension between the last stand mill and coiler is determined by the type of mill and its assortment. A disadvantage of the known technology is the uncertainty of its parameters in the preparation of hot-dip galvanized steel, which will not allow to obtain high-quality galvanized sheet steel.

An object of the present invention is to provide high-quality hot-dip galvanized steel with a thickness of at least 0.48 mm.

To solve this problem, a method is proposed for the production of hot rolled galvanized steel with a thickness of at least 0.48 mm by cold rolling of strips in rolls with a prepared surface on a four-stand continuous mill with a predetermined tension and winding, unlike the closest analogue, rolling in the fourth mill stand polished rolls with transhipments every 2500 tons or in notched rolls after preliminary rolling of 1000 tons of metal for other purposes, while rolling strips with a thickness of h≤0.6 mm are made with thickened the front ends with a length of 2 ... 3 turns on the drum of the coiler, and the tension on the coiler is set for strips with a thickness h≤0.7 mm equal to 1.2 × 2.3 t, and for strips with a thickness h> 0.7 mm equal to 1.3 × 3.2 t.

The given rolling parameters are obtained experimentally and are empirical.

The essence of the proposed technical solution is to optimize the production of rolled rolling for ANSC. As a result of this, the necessary properties of the finished galvanized sheet are provided and, above all, its flatness.

An experimental verification of the proposed method was carried out on a four-stand cold rolling mill 2500 of OJSC Magnitogorsk Iron and Steel Works. To this end, when rolling strips of various assortments for the ANSC, its claimed parameters were varied, evaluating the results of the yield of a finished galvanized quality sheet.

The best results (maximum yield of such a sheet) were obtained using the proposed technology. Deviations from its claimed parameters worsened the achieved indicators.

For example, transshipment after rolling in polished rolls of more than 2500 tons led both to a deterioration of the surface of the rolled stock and to an increase in its flatness, which negatively affected the quality of galvanized steel, reducing the yield of sheets of the required quality (against the maximum achieved) by 7 ... 12%. At the beginning of the rolling of the tackle for galvanizing in the notched rolls of the IY (last) mill stand 2500 earlier than after 1000 tons of preliminary rolling, the unsatisfactory condition of the tackle worsened the surface quality of galvanized steel.

When rolling strips with a thickness of less than 0.6 mm without thickened front ends (or when extending to the length of one revolution on the winder), it was not possible to form bushings on the rolls without surface defects from segments of the winder drum (the presence of a “fingerprint” defect). An increase in the tension of the strips between the IVth stand and the coiler led either to the appearance of unacceptable longitudinal scratches on the metal or to the waviness of the edges of the strips. Reducing the same tension (less than recommended values) in some cases brought the thickness of the tackle beyond the permissible values.

The cold rolling technology, taken as the closest analogue, was not tested in the experiments due to the uncertainty of its main parameters (see above). Thus, an experimental verification confirmed the acceptability of the technical solution found to achieve the goal and its advantage over a known object.

The feasibility study showed that the use of the present invention for producing rolled galvanized steel at mills similar to mill 2500 of OJSC MMK will increase the yield of high-quality galvanized steel at ANGC by at least 5% with a corresponding increase in profits from the sale of rolled products.

Case Studies

1. At the cold rolling mill 2500 in the polished rolls of its IVth stand, strips with a thickness of h = 0.55 mm and a width of 1200 mm are rolled.

Tranch rolls are transshipped every 2500 tons of rolled metal. The front ends of the strips with a length equal to the length of 2 turns on the drum of the mill winder are thickened, with h = 0.58 mm, the tension on the winder is set equal to 1.2 × T _max = 1.2 × 2.3≅2.8 t .

2. In the IV-th stand of the same mill on rolled grooves rolled tackle for ANGC thickness h = 0.75 mm, width 1300 mm Its rolling starts after preliminary rolling of 1000 tons of strip steel for stamping. The magnitude of the tension: T = 1.15 × T _max = 1.3 × 3.2≅4.16.

Claims (1)

A method of manufacturing a rolled product for hot dip galvanized steel with a thickness of at least 0.48 mm by cold rolling strips in rolls with a prepared surface on a four-stand continuous mill with a predetermined tension and winding, characterized in that the rolling in the fourth mill stand is carried out in polished rolls with transhipments every 2500 tons or in notched rolls after preliminary rolling 1000 tons of metal for other purposes, while rolling strips with a thickness of h≤0.6 mm is carried out with thickened front ends with a length of 2 ... 3 turns on reel coiler and tension on the reel is set for strips h≤0,7 mm thickness equal to 1.2 × 2.3 m, and the thickness for strips h> 0,7 mm - equal to 1.3 × 3.2 m.