Embodiments of the present disclosure are directed to coiled steel tubes and methods of manufacturing coiled steel tubes. In some embodiments, the final microstructures of the coiled steel tubes across all base metal regions, weld joints, and heat affected zones can be homogeneous. Further, the final microstructure of the coiled steel tube can be a mixture of tempered martensite and bainite.

A steel strip for an electric-resistance-welded steel pipe or tube having a strength of X70 grade or more and excellent HIC resistance and SSC resistance is provided. A steel strip for an electric-resistance-welded steel pipe or tube has a chemical composition containing, in mass %: C: 0.02% to 0.06%; Si: 0.1% to 0.3%; Mn: 0.8% to 1.3%; P: 0.01% or less; S: 0.001% or less; V: 0.04% to 0.07%; Nb: 0.04% to 0.07%; Ti: 0.01% to 0.04%; Cu: 0.1% to 0.3%; Ni: 0.1% to 0.3%; Ca: 0.001% to 0.005%; Al: 0.01% to 0.07%; and N: 0.007% or less, with a balance being Fe and incidental impurities, contents of C, Nb, V, and Ti satisfying the following Expression (1)

[C]−12([Nb]/92.9+[V]/50.9+[Ti]/47.9)≦0.03%  (1),

wherein a ferrite area ratio is 90% or more.

There is provided a high-strength steel material for oil well having a chemical composition consisting, by mass percent, of C: 0.70-1.8%, Si: 0.05-1.00%, Mn: 12.0-25.0%, Al: 0.003-0.06%, P: ≦0.03%, S: ≦0.03%, N: ≦0.10%, V: >0.5% and ≦2.0%, Cr: 0-2.0%, Mo: 0-3.0%, Cu: 0-1.5%, Ni: 0-1.5%, Nb: 0-0.5%, Ta: 0-0.5%, Ti: 0-0.5%, Zr: 0-0.5%, Ca: 0-0.005%, Mg: 0-0.005%, B: 0-0.015%, the balance: Fe and impurities, satisfying [0.6≦C-0.18V-0.06Cr<1.44], wherein a metal micro-structure is consisting essentially of an austenite single phase, V carbides having circle equivalent diameters of 5 to 100 nm exist at a number density of 20 pieces/μm.sup.2 or higher, and a yield strength is 654 MPa or higher.

A process for manufacturing a bellows, made of austenitic high-grade steel with high compressive strength and fatigue strength, forms a single-layer or multilayer sleeve into a bellows with hydraulic forming. The pressure resistance and fatigue strength are improved by the bellows being cleaned after the forming and by the bellows being exposed to a surrounding area containing carbon and/or nitrogen atoms at temperatures between 100° C. and 400° C., preferably 200° C. to 320° C. With this a hardening of the bellows takes place by means of the diffusing in of carbon and/or nitrogen atoms. A bellows made of austenitic high-grade steel with one or more layers created in this manner has the edge layer hardened by the incorporation of carbon and/or nitrogen atoms up to a hardening depth of at least 5% of the wall thickness.

This disclosure describes new high temperature, radiation-resistant, ferritic-martensitic steel compositions. The new steels generally contain 9.0-12.0 wt. % Cr, 0.001-1.0 wt. % Mn, 0.001-2.0 wt. % Mo, 0.001-2.5 wt. % W, and 0.1-0.3 wt. % C, with the balance being primarily Fe. More specifically, steels having from 10.0-12.0 wt. % Cr are considered particularly advantageous. Small amounts of N, Nb, V, Ta, Ti, Zr, and B may or may not also be present, depending on the particular embodiment. Impurities may be present in any embodiment, in particular impurities of less than 0.01 wt. % S, less than 0.04 wt. % P, less than 0.04 wt. % Cu, less than 0.05 wt. % Co, and less than 0.03 wt. % As are contemplated. Examples of these steels exhibit improved fracture toughness and reduced thermal creep and swelling.

The present invention discloses a machining technology of a low-temperature high-strength-ductility high manganese steel, high manganese steel plate, and high manganese steel tube, and a high manganese steel comprises the following components in percentage by weight: Mn 30%-36%, C 0.02%-0.06%, S≦0.01%, P≦0.008% and the balance being Fe. Smelted steel ingots are subject to solution treatment and are rolled and homogenized to obtain a high manganese steel plate or are drawn to form a high manganese steel tube. The hot-rolled or cold-rolled steel plate after being hot-rolled has tremendous application value in the fields of low-temperature applications, such as the steel plate used for a low temperature pressure container.

Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, more than 0.6% and 1.7% or less Cr, more than 1.0% and 3.0% or less Mo, 0.01 to 0.30% V, 0.001% or more and less than 0.01% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (X.sub.Si+X.sub.Mn+X.sub.Mo)+1.2X.sub.P is set to less than 65.

Sensitive hollow blocks or tubes are elongated in a hot-forming elongator while maintaining, if possible, the internal structure that is present or that forms immediately after casting, and thereby, in the case of suitable method management, even thin-walled tubes or tubes rolled from centrifugally cast hollow blocks can be made available to a sufficiently operationally reliable extent. As a result, for the first time, it is possible for rolled centrifugally cast composite material tubes to be made available and for composite material hollow. blocks produced using centrifugal casting to be utilized for the production of a seamless tube.

The austenitic stainless steel that does not cause defects such as aging crack or delayed fracture even after the expansion and curling process of 5 steps or more is disclosed. In accordance with an aspect of the present disclosure, an austenitic stainless steel with excellent pipe expanding workability and aging crack resistance includes, in percent (%) by weight of the entire composition, C: 0.01 to 0.04%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.0%, Cr: 16 to 20%, Ni: 6 to 10%, Cu: 0.1 to 2.0%, Mo: 0.2% or less, N: 0.035 to 0.07%, the remainder of iron (Fe) and other inevitable impurities, and the C+N satisfies 0.1% or less, the product of the Md30 (° C.) value and average grain size (μm) satisfies less than −500.

A hollow screw and related process of making is provided, wherein the hollow screw is formed from a generally circular corrosion resistant stainless steel disk cut from flat roll stock. The hollow screw includes a head and an elongated and hollow shaft having a wall thickness between about 0.2 to about 0.7 millimeters extending therefrom and defining a shank portion and a threaded portion having a plurality of threads thereon with a rotational drive mechanism configured to facilitate tightening via the threads. The process involves annealing to soften the stamped hollow screw, followed by thread rolling, and then age hardening the hollow screw. As such, the resultant hollow screw is relatively lightweight, about 50% the mass of a solid core screw made from the same material, with a sufficient thread strength to meet most aerospace applications and contributes to important aircraft fuel economy.