A low-cost and high-formability 1180 MPa grade cold-rolled annealed dual-phase steel plate and a manufacturing method thereof are provided. The dual-phase steel plate has the following chemical composition by mass percentages: C: 0.1%-0.125%, Si: 0.4%-0.8%, Mn: 2.6%-2.9%, Al: 0.01%-0.05%, Nb: 0.01%-0.03%, and Ti: 0.01%-0.03%, the remainder being Fe and unavoidable impurities. By reasonable design of alloy elements and manufacturing processes, the dual-phase steel plate of the invention achieves a strength of 1180 MPa grade at a low cost, obtains a fine and uniform martensite-ferrite dual-phase structure that ensures excellent elongation rate and cold bending performance, and has good formability. The dual-phase steel plate has a yield strength of more than 850 MPa, a tensile strength of more than 1180 MPa, an elongation rate of 8% or more, and a parameter (R/t), characterizing the 90-degree cold bending performance, of 2.5 or less.

Metal components subject to wear or contact fatigue in a first area, and subject to bending, axial and/or torsional stress loading in a second area comprise a surface hardened, first surface layer in the first area; and a surface compressive-stress treated, second surface layer in the second area. The second surface layer has a material hardness different from, and typically lower than the first surface layer, and induced residual compressive stress to improve fatigue strength. Example components described include a gear, a cog, a pinion, a rack, a splined shaft, a splined coupling, a torquing tool and a nut driving tool. A hybrid manufacturing process is described, including area-selective surface hardening combined with a process to add compressive stress to fatigue failure prone areas.

A method of heating for hot stamping is configured to heat a plated metallic material while conveying the plated metallic material. A heating device for hot stamping comprises: a first heating tank provided in a conveyance path for the plated metallic material; and a second heating tank provided downstream of the first heating tank in the conveyance path. A heating amount provided by the second heating tank is configured such that a temperature of the plated metallic material becomes equal to or higher than Ac3 point and less than a boiling point of a plating of the plated metallic material, and a heating amount provided by the first heating tank is configured to be larger than the heating amount provided by the second heating tank.

Methods of selectively cooling and quenching surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise selectively cooling at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to selective cooling, the component has a microstructure comprising about 5% by volume retained austenite in a matrix of martensite. The selective cooling is conducted at a temperature of about 40 C. and forms at least one quenched region comprising about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.

To provide a technique capable of preventing or suppressing fatigue failure of a vehicle underbody part material by 3DQ. A vehicle underbody part material relating to this disclosure includes: a quenched and bent steel pipe; and a plating film layer provided on a surface of the steel pipe and containing 30 mass % or more of Al and having an AlFe alloy existing in a surface thereof.

A sample holder for annealing apparatus and electrically assisted annealing apparatus using the same are provided. The sample holder includes a heat conductive shell, high thermal conductive and electrical insulation blocks, first and second electrodes. The heat conductive shell includes a base frame and a top cover. The high thermal conductive and electrical insulation blocks are adjacent to the base frame and the top cover, respectively, and a sample pallet is sandwiched therebetween. Length and width of the sample pallet is smaller than that of the high thermal conductive and electrical insulation blocks. The first and the second electrodes are fixed to two sides of the sample pallet, and are connected to electrifying wire respectively. Thickness of the first and the second electrodes is smaller than that of the sample pallet, while the width of the first and the second electrodes is longer than that of the sample pallet.

Embodiments include a heating device for heating a workpiece, comprising a furnace defining a closed space insulated from exterior and surrounded by a heat insulator, a heater disposed in the furnace to heat a workpiece, at least one support element for supporting a workpiece in the furnace, and a base holding the at least one support element. The base may comprise a mounting portion, a support element retaining portion for each support element, the retaining portion horizontally offset from the mounting portion, and a reinforcement portion configured to increase the strength of the base against deformation due to a load of the workpiece and/or support element applied through the support element retaining portion.

Embodiments include a heating device for heating a workpiece, comprising a furnace defining a closed space insulated from exterior and surrounded by a heat insulator, a heater disposed in the furnace to heat a workpiece, at least one support element for supporting a workpiece in the furnace, and a base holding the at least one support element. The base may comprise a mounting portion, a support element retaining portion for each support element, the retaining portion horizontally offset from the mounting portion, and a reinforcement portion configured to increase the strength of the base against deformation due to a load of the workpiece and/or support element applied through the support element retaining portion.

A heating furnace includes a bolt inserted through an insertion hole in a part of a heater and further inserted into a hole on a tip surface of an electrode rod. A first washer is between a bearing surface of the bolt and one face of the heater. A second washer is between another face of the heater and the tip surface. The relation of: |L.sub.0.Math..sub.0(T.sub.H.Math..sub.H+T.sub.B.Math..sub.B+T.sub.E.Math..sub.E)|.Math.T0.15(T.sub.B+T.sub.E) is satisfied, where L.sub.0 is an interval between the bearing surface and the tip surface, .sub.0 is a linear expansion coefficient (LEC) of the bolt, T.sub.H, T.sub.B and T.sub.E are thicknesses of the part, first and second washers and .sub.H, .sub.B and .sub.E are their LECs, respectively, and T is a temperature increment quantity of a part where the heater and the electrode rod are fastened by the bolt.

Method for forming a metallic component surface to achieve lower electrical contact resistance. The method comprises modifying a surface chemical composition and creating a micro-textured surface structure of the metallic component that includes small peaks and/or pits. The small peaks and pits have a round or irregular cross-sectional shape with a diameter between 10 nm and 10 microns, a height/depth between 10 nm and 10 microns, and a distribution density between 0.4 million/cm.sup.2 and 5 billion cm.sup.2.