An electric resistance welded steel pipe which has sufficient strength and low-temperature toughness and a low yield ratio and which is suitable as a line pipe to be laid in depths of the sea, characterized in that: the composition of the base material contains, in mass %, 0.05 to 0.10% of C, 1.00 to 1.60% of Mn, and 0.005 to less than 0.035% of Nb, and has a Ceq value of 0.23 to 0.38; and the metal microstructure of the base material contains 3 to 13% of martensite in area fraction with the balance being ferrite.

An electric resistance welded steel pipe which has sufficient strength and low-temperature toughness and a low yield ratio and which is suitable as a line pipe to be laid in depths of the sea, characterized in that: the composition of the base material contains, in mass %, 0.05 to 0.10% of C, 1.00 to 1.60% of Mn, and 0.005 to less than 0.035% of Nb, and has a Ceq value of 0.23 to 0.38; and the metal microstructure of the base material contains 3 to 13% of martensite in area fraction with the balance being ferrite.

A conveyor belt configured for a direction of travel, the conveyor belt including a plurality of connecting rods; and a spiral overlay; wherein each of the connecting rods has a flattened oblong cross section. In addition, a method a manufacturing a connector rod for a conveyor, belt includes providing a connector rod having a circular cross section; rolling the connector rod along a longitudinal axis thereof, and thereby producing a flattened oblong cross section.

Method and system for thermal treatment by heat induction of a metal piece on a targeted zone. According to the method, the thermal treatment is carried out using a thermal element mounted on a robotic system for moving the thermal element along a cyclical trajectory on the targeted zone so as to heat the target zone and minimize the temperature deviations over the targeted zone.

Method and system for thermal treatment by heat induction of a metal piece on a targeted zone. According to the method, the thermal treatment is carried out using a thermal element mounted on a robotic system for moving the thermal element along a cyclical trajectory on the targeted zone so as to heat the target zone and minimize the temperature deviations over the targeted zone.

A martensitic steel including the following elements, expressed in percentage by weight 0.1%≤C≤0.4%; 0.2%≤Mn≤2%; 0.4%≤Si≤2%; 0.2%≤Cr≤1%; 0.01%≤Al≤1%; 0%≤S≤0.09%; 0%≤P≤0.09%; 0%≤N≤0.09%; and can contain one or more of the following optional elements 0%≤Ni≤1%; 0%≤Cu≤1%; 0%≤Mo≤0.1%; 0%≤Nb≤0.1%; 0%≤Ti≤0.1%; 0%≤V≤0.1%; 0.0015%≤B≤0.005%; 0%≤Sn≤0.1%; 0%≤Pb≤0.1%; 0%≤Sb≤0.1%; 0%≤Ca≤0.1%; the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of said steel having microstructure by area percentage including cumulative presence of residual austenite and bainite between 0% and 25%, the remaining microstructure being martensite at least 70%, and with an optional presence of ferrite between 0% and 10%.

A martensitic steel including the following elements, expressed in percentage by weight 0.1%≤C≤0.4%; 0.2%≤Mn≤2%; 0.4%≤Si≤2%; 0.2%≤Cr≤1%; 0.01%≤Al≤1%; 0%≤S≤0.09%; 0%≤P≤0.09%; 0%≤N≤0.09%; and can contain one or more of the following optional elements 0%≤Ni≤1%; 0%≤Cu≤1%; 0%≤Mo≤0.1%; 0%≤Nb≤0.1%; 0%≤Ti≤0.1%; 0%≤V≤0.1%; 0.0015%≤B≤0.005%; 0%≤Sn≤0.1%; 0%≤Pb≤0.1%; 0%≤Sb≤0.1%; 0%≤Ca≤0.1%; the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of said steel having microstructure by area percentage including cumulative presence of residual austenite and bainite between 0% and 25%, the remaining microstructure being martensite at least 70%, and with an optional presence of ferrite between 0% and 10%.

The present invention relates to a steel material used as materials for building structures, ship structures, offshore structures, or the like and, more specifically, to a steel material having low yield ratio and excellent weld heat affected zone toughness and a manufacturing method therefor.

This application relates to a resistance spot weld, a resistance spot welding method, a resistance spot welded joint, and a method for manufacturing the resistance spot welded joint. In the resistance spot weld, at least one of steel sheets is a high-strength steel sheet having a prescribed chemical composition. In at least one of a nugget edge region corresponding to a faying interface, the nugget edge region has a metal microstructure including tempered martensite as a main phase. The hardness Hv of the nugget edge region and the hardness Hmw of martensite in the nugget as a whole satisfy formula (4). In at least one of a strong HAZ region corresponding to the faying interface, the hardness Hh of the strong HAZ region and the hardness Hmh of martensite in a prescribed steel sheet satisfy formula (8).

[00001]$\begin{array}{cc}\mathrm{Hv}\le \mathrm{Hmw}-40& \left(4\right)\\ \mathrm{Hh}<\mathrm{Hmh}-25& \left(8\right)\end{array}$

A system for air quenching a heat treated element comprises a tubular component, an internal air quench device moveably disposed within the interior of the tubular component, and an external air quench device moveably disposed about the tubular component. The internal air quench device comprises a nozzle configured to induce an airflow within the tubular component. The external air quenching device can comprise an annular ring disposed about the tubular component that is configured to generate a cone of air about the tubular component.