A method for partial hardening of an austenitic steel by utilizing during cold deformation the TWIP (Twinning Induced Plasticity), TWIP/TRIP or TRIP (Transformation Induced Plasticity) hardening effect. Cold deformation is carried out by cold rolling at least one surface of the steel with forming degree (Φ) of 5≤Φ≤60% in order to achieve in the steel at least two consecutive areas with different mechanical values in thickness, yield strength (R.sub.p0.2), tensile strength (Rm) and elongation, having a ratio (r) between the ultimate load ratio (ΔF) and the thickness ratio (Δt) of 1.0>r>2.0, and in which the areas are mechanically connected to each other by a transition area having a thickness that is variable from the thickness of the first area in the deformation direction to the thickness of the second area in the deformation direction.

Provided is a hot press-formed member having excellent crack propagation resistance and ductility. The hot press-formed member includes: a base steel sheet and a zinc or zinc alloy plating layer on at least one surface of the base steel sheet. The base steel sheet contains, by wt %, carbon (C): 0.08-0.30%, silicon (Si): 0.01-2.0%, manganese (Mn): 3.1-8.0%, aluminum (Al): 0.001-0.5%, phosphorus (P): 0.001-0.05%, sulfur (S): 0.0001-0.02%, nitrogen (N): 0.02% or less, and a balance of iron (Fe) and other impurities. The hot press-formed member comprises 1-30 area % of retained austenite as a microstructure, and a Mn(wt %)/Zn(wt %) content ratio in an oxide layer of 0.5-1.2 μm in a thickness direction from a surface layer of the plating layer is 0.1 or more.

The invention provides a method to obtain a high strength and high toughness yield during production of steel beams by developing a metallurgical model, the method comprising at a tandem mill. In particular, the method comprises rolling a steel beam blank above a non-recrystallization temperature and enhance the RCR value, the beam blank having an austenite grain structure to obtain a rolled beam; and rolling the rolled beam below the non-recrystallization temperature to obtain critical strain accumulation for increased austenite grain refinement to achieve certain CCR value, wherein the non-recrystallization temperature (T.sub.nr). Also provided is a computer implemented method of determining the impact of changes to process parameters on the resulting product.

Provided is a hot press-formed member having excellent crack propagation resistance and ductility. The hot press-formed member includes: a base steel sheet and a zinc or zinc alloy plating layer on at least one surface of the base steel sheet. The base steel sheet contains, by wt %, carbon (C): 0.08-0.30%, silicon (Si): 0.01-2.0%, manganese (Mn): 3.1-8.0%, aluminum (Al): 0.001-0.5%, phosphorus (P): 0.001-0.05%, sulfur (S): 0.0001-0.02%, nitrogen (N): 0.02% or less, and a balance of iron (Fe) and other impurities. The hot press-formed member comprises 1-30 area % of retained austenite as a microstructure, and a Mn(wt %)/Zn(wt %) content ratio in an oxide layer of 0.5-1.2 m in a thickness direction from a surface layer of the plating layer is 0.1 or more.

Provided is a hot press-formed member having excellent crack propagation resistance and ductility. The hot press-formed member includes: a base steel sheet and a zinc or zinc alloy plating layer on at least one surface of the base steel sheet. The base steel sheet contains, by wt %, carbon (C): 0.08-0.30%, silicon (Si): 0.01-2.0%, manganese (Mn): 3.1-8.0%, aluminum (Al): 0.001-0.5%, phosphorus (P): 0.001-0.05%, sulfur (S): 0.0001-0.02%, nitrogen (N): 0.02% or less, and a balance of iron (Fe) and other impurities. The hot press-formed member comprises 1-30 area % of retained austenite as a microstructure, and a Mn(wt %)/Zn(wt %) content ratio in an oxide layer of 0.5-1.2 m in a thickness direction from a surface layer of the plating layer is 0.1 or more.

A steel strip processing system is provided that includes a plurality of microstructure sensors that measure the phase fraction in a steel strip at desired locations in a processing furnace. A process control system includes a plurality of control loops for receiving the outputs of the microstructure sensors to determine the amount of heating and cooling required to achieve a desired phase fraction at the desired locations in the processing furnace. One or more energy systems that receive the output of the process control system to coordinate the heating or cooling of the desired locations to achieve the desired phase fraction.

A method for partial hardening of an austenitic steel by utilizing during cold deformation the TWIP (Twinning Induced Plasticity), TWIP/TRIP or TRIP (Transformation Induced Plasticity) hardening effect. Cold deformation is carried out by cold rolling at least one surface of the steel with forming degree () of 560% in order to achieve in the steel at least two consecutive areas with different mechanical values in thickness, yield strength (R.sub.p0.2), tensile strength (Rm) and elongation, having a ratio (r) between the ultimate load ratio (F) and the thickness ratio (t) of 1.0>r>2.0, and in which the areas are mechanically connected to each other by a transition area having a thickness that is variable from the thickness of the first area in the deformation direction to the thickness of the second area in the deformation direction.

A method for revamping a starting rolling plant, for producing a final strip starting from a slab having a determinate starting thickness, including: at least one heating furnace configured to heat at least the slab to a determinate starting temperature; at least one reversible roughing stand configured to subject the slab to one or more rolling passes in order to obtain an intermediate rolled product; and a rolling train disposed operatively in line with the roughing stand, including at least one pre-finishing stand and a plurality of finishing stands and configured to reduce the thickness of the intermediate rolled product, until the final strip having a determinate final thickness is obtained.