A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid is provided. The method includes a fluid medium and nanoparticles. A thickness/lateral size ratio of the nanoparticles is below 0.00044. The nanoparticles do not include carbon nanotubes.

A thick steel plate for high heat input welding and having great heat-affected area toughness and a manufacturing method therefor, comprising the steps of smelting, casting, rolling, and cooling. Also, the chemical composition of the steel plate satisfies 1Ti/N6 and (Ca+REM+Zr)/Al0.11, where the effective S content in steel=S-0.8Ca-0.34REM-0.35Zr. and the effective S content in steel: 0.0006-0.005%; finely dispersed inclusions may be formed, and the amount of composite inclusion CaO+Al.sub.2O.sub.3+MnS+TiN in the steel plate is at a proportion of 12%. With respect to welding in which the thickness of the steel plate is 50-70 mm, the tensile strength of a base material is 510 MPa. and welding input energy is 200-400 kJ/cm, the average Charpy impact work of a welding heat-affected area of the steel plate at 40 C. is 100 J or more, and at the same time, the average Charpy aging impact work of the base material of thickness at 40 C. is 46 J or more.

A thick steel plate for high heat input welding and having great heat-affected area toughness and a manufacturing method therefor, comprising the steps of smelting, casting, rolling, and cooling. Also, the chemical composition of the steel plate satisfies 1Ti/N6 and (Ca+REM+Zr)/Al0.11, where the effective S content in steel=S-0.8Ca-0.34REM-0.35Zr. and the effective S content in steel: 0.0006-0.005%; finely dispersed inclusions may be formed, and the amount of composite inclusion CaO+Al.sub.2O.sub.3+MnS+TiN in the steel plate is at a proportion of 12%. With respect to welding in which the thickness of the steel plate is 50-70 mm, the tensile strength of a base material is 510 MPa. and welding input energy is 200-400 kJ/cm, the average Charpy impact work of a welding heat-affected area of the steel plate at 40 C. is 100 J or more, and at the same time, the average Charpy aging impact work of the base material of thickness at 40 C. is 46 J or more.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid including a fluid medium, hydrophobic nanoparticles having a lateral size between 26 and 50 m and a dispersing agent is provided. The nanoparticles concentration/dispersing agent concentration ratio in weight is between 3 and 18 and the nanoparticles do not include carbon nanotubes. A heat transfer fluid is also provided.

A method of heat transfer between a metallic or non-metallic item and a heat transfer fluid including a fluid medium, hydrophobic nanoparticles having a lateral size between 26 and 50 m and a dispersing agent is provided. The nanoparticles concentration/dispersing agent concentration ratio in weight is between 3 and 18 and the nanoparticles do not include carbon nanotubes. A heat transfer fluid is also provided.

A method of heat treatment of a non-metallic or metallic item is provided. The method includes at least one step of heat transfer between the item and a heat transfer fluid A. The heat transfer fluid A includes a fluid medium and nanoparticles having a lateral size between 26 and 50 m. The heat transfer fluid has a heat transfer coefficient below the heat transfer coefficient of water.

A method of heat treatment of a non-metallic or metallic item is provided. The method includes at least one step of heat transfer between the item and a heat transfer fluid A. The heat transfer fluid A includes a fluid medium and nanoparticles having a lateral size between 26 and 50 m. The heat transfer fluid has a heat transfer coefficient below the heat transfer coefficient of water.

A heavy weight drill pipe may include a tube body formed of AISI 1340 alloy steel, and first and second tool joints at respective ends of the tube body, and which are formed of an AISI 41XX series alloy steel. The first and second tool joints may be welded to the tube body at a weld line within a weld region. A Charpy impact toughness at the weld line or surrounding weld region may be least 12 ft-lbs. (16.5 N-m). Yield and tensile strengths at the weld line or weld region may be at least 65 ksi (448.0 MPa) and at least 106 ksi (731.0 MPa), respectively. Material properties at the weld line or weld region may be achieved by heat treating after welding. Heat treating may include austenitizing, quenching, and tempering the weld line and/or the surrounding weld region.

A heavy weight drill pipe may include a tube body formed of AISI 1340 alloy steel, and first and second tool joints at respective ends of the tube body, and which are formed of an AISI 41XX series alloy steel. The first and second tool joints may be welded to the tube body at a weld line within a weld region. A Charpy impact toughness at the weld line or surrounding weld region may be least 12 ft-lbs. (16.5 N-m). Yield and tensile strengths at the weld line or weld region may be at least 65 ksi (448.0 MPa) and at least 106 ksi (731.0 MPa), respectively. Material properties at the weld line or weld region may be achieved by heat treating after welding. Heat treating may include austenitizing, quenching, and tempering the weld line and/or the surrounding weld region.

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.