Improving the Rolling Technology at Mill 450 OJSC "MMK" to Reduce the Level of Alloying of 09G2S Steel Designed for Strength Class up to 440 MPa

Abstract

Nowadays, the technology of shape-rolled steel production defines the quality and strength of common purpose and critical building structures. To provide for all the necessary mechanical characteristics, it is necessary to pay attention to each phase of steel production: melting, casting, reheating, rolling and cooling. Often, due to poor production equipment and lack of appropriate technologies steel alloying is applied. This deteriorates steel weldability and significantly increases the cost of the rolled product. The article reviews the final stage properties formation – water quenching stage after the rolling mill. Now, at mill 450 of OJSC Magnitogorsk Iron and Steel Works (MMK) vanadium is used for microalloying during the production from 09G2S steel, which provides for the specified technical properties of steel. The developed quenching technology provides for a possibility to decrease the level of microalloying. The following mathematical simulation was carried-out: steel section cooling down during quenching; heat treatment of section steel using DEFORM 3D + Heat Treatment software and further physical simulation to define convective heat transfer temperature coefficients, find tendencies to hardening and dynamics analysis which made it possible to develop a three section module located after dividing shears consisting of 176 nozzles (44 nozzle blocks). As for the proposed design of water cooling line, regimes which provides strength classes 345, 390 and 440 MPa are developed for L-steel with sizes from 40x40x4 to 125x125x16 mm, channel steel from 50 to 180 mm web length and strip (of equivalent thickness).