Thermomechanical processing routes in compact strip production of high-strength low-alloy steel

Abstract

Process for hot rolling of high-strength low-alloy steel cast in Compact Strip Production as a thin slab. The strain and temperature at initial roll stands where deformation occurs allows full recrystallization, and at latest roll stands where deformation occurs there is no recrystallization. Deformation is absent at strains and temperatures where partial recrystallization would occur, allowing increased recrystallization over conventional CSP rolling. The result may be beneficial for microalloyed high-strength low-alloy steel in permitting accurate ultrasonic testing of welds. The time allowed between deformation at passes through roll stands may be increased by eliminating deformation at one or more central roll stands. Combined with increased strain at the initial roll stands where the temperature of the steel is in the full recrystallization region, the process may result in a relatively fine and uniform austenite grain size.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from co-pending provisional patent application Ser. No. 60 / 458,153, filed Mar. 27, 2003, the entire contents of which are hereby incorporated by reference.BACKGROUND OF INVENTION [0002] The present invention relates to the field of high-strength low-alloy steel, and more particularly to methods of thermomechanical processing for making high-strength low-alloy steel that is thin slab cast. [0003] Conventional thick slab casting is performed in an integrated plant, where steel is made from pig iron and scrap metal in a Basic Oxygen Furnace. Thin slab casting is an improvement over conventional thick slab casting, is performed in a Compact Strip Production (CSP) plant, and may use metal melted in an Electric Arc Furnace. Both thick and thin slab casting may be done as continuous casting processes. Thin slabs are cast in thicknesses generally ranging from 25 to 100 mm, while thick slabs are generally from 20...

AI Technical Summary

Benefits of technology

[0011] The present invention is directed to hot rolling of high-strength low-alloy (HSLA) steel cast in Compact Strip Production as a thin slab. The strain and temperature for a particular steel at initial roll stands where deformation occurs may allow full recrystallization and at latest stands where deformation occurs may not allow recrystallization. Deformation may be absent in the region of strain and temperature where partial recrystallization would occur. The time allowed between deformation at passes through roll stands may be increased by eliminating deformation at one or more central stands that conventionally may be used to apply strain to the thin slab. Eliminating deformation in the partial recrystallization region may allow increased recrystallization over conventional CSP casting, which may result in a relatively fine and uniform austenite grain size that may allow accurate ultrasonic testing of welds.

Problems solved by technology

The strain and temperature for a particular steel at initial roll stands where deformation occurs may allow full recrystallization and at latest stands where deformation occurs may not allow recrystallization.

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