Disclosed are a case hardened steel which is suitable as a material for producing mechanical structural parts having high rotating bending fatigue strength and impact fatigue strength at a relatively low cost, and a method of producing the same. The case hardening steel has a chemical composition containing, by mass %, C, Si, Mn, P, S, Cr, Mo, B, Ti, N, and O within a range satisfying a predetermined relationship, and Al in at least a predetermined amount in relation to the B, N, and Ti contents, with the balance being Fe and inevitable impurities, wherein √I≤80 is satisfied, where I represents an area in μm.sup.2 of an oxide-based inclusion located at the center of a fish-eye on a fracture surface of the case hardening steel after being subjected to carburizing-quenching and tempering and subsequently to a rotating bending fatigue test.

A process for manufacturing compact coils of ultra-fine grained, martensite-free steel bars, the process comprising the following stages:

a) rolling a steel billet by means of a roughing rolling mill producing a steel bar;

b) performing at least one first cooling stage so that the steel bar has a surface temperature higher than the martensite start temperature, and performing at least one first equalization stage in air;

c) rolling the steel bar by means of at least one intermediate rolling mill;

d) performing at least one second cooling stage always maintaining the surface temperature higher than the martensite start temperature, and performing at least one second equalization stage in air;

e) rolling the steel bar by means of a finishing rolling mill in a non-recrystallization temperature range, maintaining the whole cross-section of the steel bar within said non-recrystallization temperature range, and with a total reduction between 25 and 50% with respect to the cross-section of the steel bar at the entry of the finishing rolling mill, in order to obtain an ultra-fine-grained austenitic matrix;

f) winding the steel bar in a compact coil, by means at least one spooling device, so that the ultra-fine-grained austenitic matrix transforms in a mixture of ferrite and pearlite.

After the winding operation is completed, the compact coil can be transferred to a storage area through a transferring device, for example a walking beam, where a natural or forced or retarded cooling is applied to the coil.

A high-strength and corrosion-resistant sucker rod and a preparation process thereof are disclosed. Raw materials for preparing the high-strength and corrosion-resistant sucker rod include, by weight percent, Mn: 0.70% to 1.20%, Cr: 9.50% to 13.50%, Ni: 0.65% to 1.10%, Mo: 0.10% to 0.90%, Cu: 0.28% to 0.56%, C: ≤0.07%, Si: ≤0.50%, P: ≤0.08%, and S: ≤0.005%, the balance is Fe and unavoidable impurities. The sucker rod prepared by the new process has an actual grain size equal to or greater than grade 8, excellent mechanical properties that meet the standard of grade HL specified in SY/T5029 Sucker Rods, and excellent corrosion fatigue resistance. The preparation process is simple and easy for operation, and suitable for large-scale promotion.

Steel for a crankshaft includes 0.37 to 0.42 wt % of carbon (C), 0.55 to 0.70 wt % of silicon (Si), 1.45 to 1.65 wt % of manganese (Mn), 0.025 wt % or less (excluding 0 wt %) of phosphorus (P), 0.020 to 0.035 wt % of sulfur (S), 0.15 to 0.30 wt % of chromium (Cr), 0.035 to 0.055% of vanadium (V), and the remainder of Fe and other inevitable impurities. The steel for a crankshaft has strength that is maintained high even when reducing the amount of vanadium.

Provided is a dehydrogenation method capable of efficiently reducing hydrogen content in steel for thick or complexly-shaped steel materials and steel products in general. In a dehydrogenation method for a steel material, in a series of steel material production process including: a process of supplying a steel raw material; a process of subjecting the steel raw material to hot working; a process of inspecting a steel material obtained from the steel raw material; and a process of shipping the steel material, at least one of the steel raw material and the steel material at any stage from the supply process to the shipment process is subjected to, at least once, a sound wave irradiation treatment so that a sound pressure level at a surface of the at least one of the steel raw material and the steel material will be 30 dB or more.

Provided are a steel wire having excellent straightness quality and a method of manufacturing the steel wire, wherein the steel wire includes a wire, after undergoing a drawing operation, undergoing a heating operation of performing heating in a state in which tension is applied, and undergoing a cooling operation, wherein, when winding the wire around a winding portion having a diameter greater than a diameter of the wire for a preset period of time and then measuring straightness of the wire of 400 mm, the straightness of the wire is less than or equal to 30 mm, and the method includes a wire preparation operation, a heating operation, a cooling operation, and a straightness measurement operation.

The present disclosure relates to a duplex stainless steel comprising in weight % (wt %): C less than 0.03; Si less than 0.60; Mn 0.40 to 2.00; P less than 0.04; S less than or equal to 0.01; Cr more than 30.00 to 33.00; Ni 6.00 to 10.00; Mo 1.30 to 2.90; N 0.15 to 0.28; Cu 0.60 to 2.20; Al less than 0.05; balance Fe and unavoidable impurities. The present disclosure also relates to a component or a construction material comprising the duplex stainless steel. Additionally, the present disclosure also relates to a process for manufacturing a component comprising said duplex stainless steel.

The invention relates to a steel wire suitable for making a spring or medical wire products which remarkably improve the performance of conventional stainless steel wire. The steel comprises (in wt. %): C: 0.02 to 0.15, Si: 0.1 to 0.9, Mn: 0.8 to 1.6, Cr 16 to 20, Ni: 7.5 to 10.5, Mo: ≤3, Al: 0.5 to 2.5, Ti: ≤0.15, N: ≤0.05, optional elements, and impurities, balance Fe, wherein the total amount of Cr and Ni is 25 to 27 wt. %, and wherein the steel has a microstructure including, in volume % (vol. %), martensite: 40 to 90, austenite: 10 to 60, and delta ferrite: ≤5.

An embodiment of the present invention provides a wire rod and a steel wire which are for springs and have excellent corrosion fatigue resistance properties, and a method for producing same, the wire rod and steel wire containing, in wt %, 0.40-0.70% of C, 1.20-2.30% of Si, 0.20-0.80% of Mn, 0.20-0.80% of Cr, 0.015% or less of P, 0.015% or less of S, and 0.010% or less of N, with the remainder comprising Fe and other unavoidable impurities, along with at least one among 0.01-0.20% of V and 0.01-0.10% of Nb, wherein the V and Nb satisfy relational expression 1 below, the average grain size of prior austenite is no greater than 20 μm, and the surface decarburization depth is no greater than 0.1 mm. [Relational expression 1] [V]+[Nb]≥0.08 (where the V and Nb contents are in wt %).

A method of manufacturing a magnetostrictive torque sensor shaft (100) to which a sensor portion (2) of a magnetostrictive torque sensor (1) is mounted. The method includes heat treatment step of subjecting an iron-based shaft member to a carburizing, quenching, and tempering process, and a shot peening step of performing shot peening using a steel shot media having a Vickers hardness at least equal to 1100 and at most equal to 1300 and being free of boron, at least in a position on the shaft member, after the heat treatment step, to which the sensor portion is to be attached.