A chassis component for a motor vehicle is disclosed. The chassis component (1) is manufactured at least partially from a multi-layer steel sheet (10, 20, 30). The multi-layer steel sheet (10, 20, 30) includes at least three steel layers, including two outer steel layers (11, 12; 21, 22; 31, 32) and one inner steel layer (13, 23, 33). At least one outer steel layer (11, 12; 21, 22; 31, 32) of the multi-layer steel sheet (10, 20, 30) has a tensile strength of at least 1200 MPa. A method for producing a chassis component for a motor vehicle, in particular a wheel (1) or a part thereof, is also disclosed.

A high-efficient rolling process for magnesium alloy sheet. The process is a rolling process for rolling billets. Parameters of the rolling process are: the rolling speed of each rolling pass is 1050 m/min, the rolling reduction of each rolling pass is controlled to be 4090%, and both the preheating temperature before rolling and the rolling temperature of each rolling pass are 250450 C. A preparation method for magnesium alloy sheet. The method comprises the steps of: 1) preparing rolling billets; 2) high-efficient hot rolling: controlling the rolling speed of each rolling pass to be 1050 m/min, controlling the rolling reduction of each rolling pass to be 4090%, and controlling both the preheating temperature before rolling and the rolling temperature of the each rolling pass to be 250450 C.; and 3) performing annealing. By means of the rolling process, mechanical performance of the sheet can be also effectively improved, and especially, the strength and ductility of the sheet can be greatly improved.

Warming a metastable steel after coating and before or during cold rolling suppresses the transformation of austenite to martensite, resulting in lower mill loads and higher amounts of reduction at similar loads. As-warm rolled steel has enhanced mechanical properties when compared to steel reduced the same amount by cold rolling at room temperature.

The present invention provides a method for the fabrication of a steel sheet with a completely martensitic structure which has an average lath size of less than 1 micrometer and an average elongation factor of the laths is between 2 and 5. The elongation factor of a lath is defined as a maximum dimension l.sub.max divided by and a minimum dimension l.sub.min. The steel sheet has a yield stress greater than 1300 MPa and a mechanical strength greater than (3220(C)+958) megapascals. A composition of a semi-finished steel product includes, expressed in percent by weight, is, 0.15%C0.40%, 1.5%Mn3%, 0.005%Si2%, 0.005%Al0.1%, 1.8%Cr4%, 0%Mo2%, whereby: 2.7% 0.5 (Mn)+(Cr)+3(Mo)5.7%, S0.05%, P0.1%, optionally: 0%Nb0.050%, 0.01%Ti0.1%, 0.0005%B0.005%, 0.0005%Ca0.005%. The semi-finished product is reheated to a temperature T.sub.1 in the range between 1050 C. and 1250 C., then subjected to a roughing rolling at a temperature T.sub.2 in the range between 1000 and 880 C., with a cumulative rate of reduction .sub.a greater than 30%, to obtain a sheet with a completely recrystallized austenitic structure with an average grain size less than 40 micrometers and preferably less than 5 micrometers. The sheet is then partially cooled to prevent a transformation of the austenite at a rate V.sub.R1 greater than 2 C./s to a temperature T.sub.3 between 600 C. and 400 C. in the metastable austenitic range, and subjected to a finishing hot rolling at the temperature T.sub.3 of the partially cooled sheet, with a cumulative rate of reduction .sub.b greater than 30% to obtain a sheet that is then cooled at a rate V.sub.R2 which is greater than the critical martensitic quenching rate.

The present disclosure relates to production lines and methods for hot rolling steel strips. Example production lines may include a hot rolling line that comprises a plurality of rolling stands through which a steel strip passes in a conveying direction. The production line may also include a cooling section for intensively cooling the steel strip as the steel strip exits a final rolling stand of the rolling line. The steel strips may be deformed so as to have a thickness of more than 15 mm and to comply with the most stringent requirements with respect to, for example, toughness. Further, at least a portion of the cooling section may overlap with a portion of the hot rolling line.

The present invention provides a method for the fabrication of a steel sheet with a completely martensitic structure which has an average lath size of less than 1 micrometer and an average elongation factor of the laths is between 2 and 5. The elongation factor of a lath is defined as a maximum dimension 1.sub.max divided by and a minimum dimension 1.sub.max. The steel sheet has a yield stress greater than 1300 MPa and a mechanical strength greater than (3220(C)+958) megapascals. A composition of a semi-finished steel product includes, expressed in percent by weight, is, 0.15%C0.40%, 1.5%Mn3%, 0.005%Si2%, 0.005%Al0.1%, 1.8%Cr4%, 0%Mo2%, whereby: 2.7%0.5 (Mn)+(Cr)+3(Mo)5.7%, S0.05%, P0.1%, optionally: 0%Nb0.050%, 0.01%Ti0.1%, 0.0005%B0.005%, 0.0005%Ca0.005%. The semi-finished product is reheated to a temperature T.sub.1 in the range between 1050 C. and 1250 C., then subjected to a roughing rolling at a temperature T.sub.2 in the range between 1000 and 880 C., with a cumulative rate of reduction .sub.a greater than 30%, to obtain a sheet with a completely recrystallized austenitic structure with an average grain size less than 40 micrometers and preferably less than 5 micrometers. The sheet is then partially cooled to prevent a transformation of the austenite at a rate V.sub.R1 greater than 2 C./s to a temperature T.sub.3 between 600 C. and 400 C. in the metastable austenitic range, and subjected to a finishing hot rolling at the temperature T.sub.3 of the partially cooled sheet, with a cumulative rate of reduction .sub.b greater than 30% to obtain a sheet that is then cooled at a rate V.sub.R2 which is greater than the critical martensitic quenching rate.

The invention describes a dual-phase steel comprising 8-12 wt. % Mn, 0.3-0.6 wt. % C, 1-4 wt. % Al, 0.4-1 wt. % V, and a balance of Fe. The steel has martensite and retained austenite phases, and may include vanadium carbide precipitations. A method for making the dual-phase steel involves the steps of (a) hot rolling the ingots of the composition to produce a plurality of thick steel sheets, (b) treating the steel sheets by an air cooling process, (c) warm rolling the steel sheets at a temperature in the range of 300-800 C. with a thicknesses reduction of 30-50%, (d) annealing the steel sheets a first time at a temperature in the range of 620-660 C. for 10-300 min, (e) cold rolling the steel sheets at room temperature with a thickness reduction of 10-30% to generate hard martensite, and (f) annealing the steel sheets a second time at a temperature in the range of 300-700 C. for 3-60 min to form the dual-phase steel.

A press hardening steel by a thin slab casting and direct rolling has a tensile strength of 1500 MPa or more. The press hardening steel has a components by weight percent: C: 0.21-0.25%, Si: 0.26-0.30%, Mn: 1.0-1.3%, P0.01%, S0.005%, Als: 0.015-0.060%, Cr: 0.25-0.30%, Ti: 0.026-0.030% or Nb: 0.026-0.030% or V: 0.026-0.030%, or a mixture of two or more of the above in any proportion; B: 0.003-0.004%, and N0.005%. A method for producing the press hardening steel includes following steps: hot metal desulphurization; electric-furnace or converter smelting and refining; continuous casting; descaling, then entering a soaking furnace; heating and soaking; high-pressure water descaling, then entering a rolling mill; hot rolling; cooling; coiling; austenitizing; die deforming and quenching.

A press hardening steel by a thin slab and having a tensile strength of 1900 MPa or more includes following components by weight: C: 0.31-0.40%, Si: 0.36-0.44%, Mn: 1.6-2.0%, P0.006%, S0.004%, Als: 0.015-0.060%, Cr: 0.36-0.49%, Ti: 0.036-0.045% or Nb: 0.036-0.045% or V: 0.036-0.045% or a mixture of any two or more of the above in any proportion, B: 0.004-0.005%, Mo: 0.26-0.35%, and N0.005%. A method for producing the press hardening steel includes following steps: molten iron desulphurization; smelting and refining by an electric furnace or converter; continuous casting; descaling treatment before entering a soaking furnace; heating and soaking; high pressure water descaling before entering a rolling mill; hot rolling; cooling; coiling; austenitizing; die deforming and quenching.

A chassis component for a motor vehicle is disclosed. The chassis component (1) is manufactured at least partially from a multi-layer steel sheet (10, 20, 30). The multi-layer steel sheet (10, 20, 30) includes at least three steel layers, including two outer steel layers (11, 12; 21, 22; 31, 32) and one inner steel layer (13, 23, 33). At least one outer steel layer (11, 12; 21, 22; 31, 32) of the multi-layer steel sheet (10, 20, 30) has a tensile strength of at least 1200 MPa. A method for producing a chassis component for a motor vehicle, in particular a wheel (1) or a part thereof, is also disclosed.