South Korean steel giant POSCO has contracted Fives for its reversible cold rolling mill DMS 20Hi EcoMill to process GIGA steel - Ultra Advance High Strength Steel (U-AHSS) and TWIP (twinning-induced plasticity) – for automotive applications.

According to Fives, it is challenging for steelmakers and plant builders to produce the highest tensile strength steel with 2,000 MPa to behave properly in terms of crash behaviour and better formability. Tensile strength refers to the maximum amount of stress a material can withstand while being stretched or pulled without breaking, and is measured in MPa, as a force per unit area - the unit being a pascal (Pa)/megapascal (MPa).

Since 2016, POSCO has been developing its GIGA steel for automotive application due to its unparalleled properties. The steelmaker claims that GIGA steel is stronger than aluminium and, therefore, meets the most stringent safety standards. High formability means it can produce complex auto parts without any special processing and its ultra light weight reduces emissions, it is claimed. Lighter vehicle body weight and a significant reduction of CO2 emissions have been major drivers for carmakers.

Cold rolling mills are essential to reduce strip thickness while guaranteeing strip surface quality, says Fives. With more than 100 references worldwide over last 60 years, DMS 20Hi cold rolling mills from Fives are claimed to be proven for applications in stainless and silicon steels. In view of the fact that the mechanical properties of UHSS or GIGA steel are similar to those of stainless steel, DMS 20Hi EcoMill was a silver bullet for GIGA steel processing.

According to Fives, the 'robust monobloc housing and a fully controlled manufacturing process guarantee fabrication of the strongest cold rolling mill ever'. The equipment will have 180kt production capacity, and will process ultra-high strength steel from 0.5 mm to 2.5 mm thickness on a strip width from 800mm to 1,650mm.

In addition, DMS 20Hi EcoMill combines several advances:

• Enhanced productivity thanks to the advanced strip wiping and strip cooling technologies

• Push-push 1st intermediate roll shifting system to reduce the risk of broken parts

• Improved strip surface quality due to an advanced strip cooling and flatness control system

• Quick and safe maintenance with minimal downtime due to easy access

Fives has already supplied a record number of references to POSCO worldwide: DMS 20Hi cold rolling mills for stainless steel to POSCO’s facilities in China, Vietnam and Turkey, as well as vertical annealing furnaces for continuous galvanising lines at its Gwangyang Steelworks.