SU1452849A1 - Method of controlled rolling of thick plate - Google Patents

Abstract

The invention relates to ferrous metallurgy, namely, to the production of thick plate, and can be used to produce high-quality pipe billet, for example, for pipes operating under low-temperature (up to -60 ° C) temperatures at high (up to 100 atm) pressures. The purpose of the invention is to increase productivity and improve the quality of rolled products. Steel 09G2FB billet, obtained by continuous casting of steel, with a cross section of 300 x 1650 mm and a length of 2.8 m, is heated in a furnace to 1200 C and rolled in a roughing stand, and then rolled up is intensively cooled for 15 seconds at a rate of 8 amp ° C / s from the top and bottom, and then within 12 s at a speed of 1.5 S / s. After that, the tackle temperature is equal from above, below 865 C, in the middle of 900 ° C. Then the tackle is cooled for 24 s with an intensity of over 600 –7t, and below it is 1300, M Ohm 1–. then cooled in air for 9 s. The temperature above, below, in the middle. Then the tackle is rolled out in the finishing stand and cooled with a GKO ratio of 8 ° C / s, ensuring the completion of the deformation at 730 ° C. The cooling time is 60 s, which improves the productivity of the mill. 2z.p. f-ly, 2 tab. with S (L with:;: СЛ to 00 u CD

Description

The invention relates to ferrous metallurgy, to the production of thick plate and can be used to produce high-quality pipe billet, for example, for pipes operating under conditions of low (up to -60 ° C) temperatures at high (up to 100 atm) pressures.

The aim of the invention is to increase mill productivity and improve the quality of rolled products.

A billet of 09G2FB steel, obtained by continuous casting of steel, with a cross section of 300 x 1650 mm and a length of 2.8 m, is heated in a furnace to 1200 C and fed into a roughing stand, where it is rolled out to 8 mm thickness in 8 passes and leaves the roughing stand. On the transport roller table, the tackle is fed to the intensive cooling sections, where for 15 seconds (with a total cooling time of 60 seconds — 0.25) it is cooled at a speed of 8 degrees / s from the top and bottom, and then for 12 seconds. (0.20 at a rate of 1.5 degrees / s (an estimate of the intensity is based on the surface temperature). After that, the tackle temperature is 850 C above, 865 C below, in the middle (thickness). Then the roll comes in the cooling control section, where cools for 24 s (0.4 C) with an intensity above 600, and below 1300 W / m2-C, after which is cooled in the air on a rolling field for 9 seconds (0.15-2). The temperature above is 740 ° C, below is 740 in the middle, and the prepared roll is rolled in a finishing stand in 5 passes to a thickness of 14.2 mm, and During the 4th and 5th aisles, with deformation, the tackle is cooled with an intensity of 8 degrees / s, o6ecnettoB completion of the deformation at 730 C.

The numerical values of the time and the intensity of each of the cooling periods in the interdeformation period are determined under laboratory conditions simulating the real process of controlled rolling of a thick plate. The results of laboratory studies are given to the real parameters are given in table. 1 and 2. As a criterion for evaluating the operational parameters, choose the value of austenitic grain in the rolled metal, as well as the degree of temperature unevenness over the sheet thickness (rolled).

Analysis of the research results makes it possible to conclude that it is inexpedient to increase the intensity of cooling more and the duration of intensive cooling is more than 0.4 times the interdeformation period (H) due to the high degree of irregularity of temperatures across the sheet thickness (more than 40 ° C) and the impossibility of cooling with intensity below 3 deg / s and time less than 0.11 due to incomplete recrystallization of austenite, which determines the large size (40 microns) of the initial grain.

The quench time (0.2–0.52) is determined from the condition of cooling the rolled stock to 850–780 ° C (the temperature of the completion of recrystallization in the steel of the type 09-10G2FB), as well as from the thermal conditions to ensure temperature equalization for the rolled stock 40–80 mm

Temperature control during adjustment is carried out on the upper surface of the sheet at a level of 720 s. Analysis table. 2 shows the appropriateness of the assigned cooling parameter limits. .

The sheet rolled according to the proposed method has high mechanical properties (2 kg / mm2, ff 26%), and the cooling time (60 s) is consistent with the rolling rate in the cages and ensures the mill's productivity at the highest possible technical level.

Claims (3)

1. A method of controlled rolling of a thick sheet, including rough and numerical rolling and controlled cooling during the interdeformation period, characterized in that, in order to increase mill productivity and improve rolling quality, after rough rolling, two-sided cooling of the tackle is performed at a speed of 5 ... 10 deg / s for 0.1 ... 0.3 C, then for O, 2 ... O, 57 with a speed of not more than 3.0 degrees / s, the subsequent cooling of the rolled at various speeds above and below for 0.1 ... 0.4 - and air cooling before finishing rolling in echenie 0.1 ... 0.3 S. 3 1452849 - 2. The method according to p. 1, about t l and h a 3. The method according to claim 1, characterized in that the flow rate of the refrigerant and with the fact that when finishing that on the lower cooling in the control-rolling cooling is performed, this period is 2.0 ... 4, O - speed of 5 ... 15 degrees / s with the advantage of the upper cooling. In the last 1 ... 3 passes. Table 1 note, the size of the cooling time is in fraction from C. Table