An aluminum alloy includes more than or equal to 1.0 mass% and less than or equal to 1.8 mass% of Si, more than or equal to 0.5 mass% and less than or equal to 1.2 mass% of Mg, more than or equal to 0.3 mass% and less than or equal to 0.8 mass% of Fe, more than or equal to 0.1 mass% and less than or equal to 0.4 mass% of Cu, more than or equal to 0.2 mass% and less than or equal to 0.5 mass% of Mn, more than or equal to 0 mass% and less than or equal to 0.3 mass% of Cr, at least one of more than or equal to 0.005 mass% and less than or equal to 0.6 mass% of Ni and more than or equal to 0.005 mass% and less than or equal to 0.6 mass% of Sn, Al, and an inevitable impurity.

A bolt of the present invention has a composition comprising: 0.50 mass % or greater and 0.65 mass % or less of carbon (C), 1.5 mass % or greater and 2.5 mass % or less of silicon (Si), 1.0 mass % or greater and 2.0 mass % or less of chromium (Cr), 0.2 mass % or greater and 1.0 mass % or less of manganese (Mn), 1.5 mass % or greater and 5.0 mass % or less of molybdenum (Mo), wherein a total amount of phosphorous (P) and sulfur (S) as impurities is 0.03 mass % or less, the remaining is iron (Fe), and the bolt comprises an iron based oxide film with a film thickness of 3 μm or greater and 20 μm or less on the surface thereof. The bolt has excellent delayed fracture resistance and reliably provides a fastening axial force.

The invention relates to a method for producing a screw, having the following steps: (a) rolling a screw wire made of low-alloy carbon steel to produce screw (10) having a thread; (b) heating the entire screw (10) to an austenitizing temperature under a carbon atmosphere and/or nitrogen atmosphere and maintaining the temperature; (c) quenching the entire screw (10) to a bainitizing temperature and maintaining the bainitizing temperature until the screw has a bainitic structure over its cross-section. The invention is characterized in that the screw (10) is subsequently hardened locally at its tip (22), by the tip (22) being heated to an austenitizing temperature and the screw (10) being subsequently quenched to a temperature below the martensite starting temperature (MS).

A method of manufacturing a stainless steel fastener includes following operations. Firstly, a stainless steel blank is prepared and contains from 1 to 3.5 wt % molybdenum, from 10 to 16 wt % chromium, from 0.5 to 3.5 wt % nickel, from 0.05 to 0.3 wt % nitrogen, carbon which is not more than 0.2 wt %, iron, and other inevitable compositions. Initially, a steel crystalline structure of the blank is martensite whose hardness ranges from 230 to 350 HV. Then, the blank is annealed to transform a partial crystalline structure of the steel crystalline structure into ferrite. The annealed blank experiences a cutting operation, a head forming operation, and a thread forming operation sequentially. Thereafter, a heat treating operation is executed to transform the partial crystalline structure from ferrite into martensite to complete a stainless steel fastener whose hardness is increased and is at least 500 HV, which facilitates a direct drilling effect.

Provided are: a boron-added high strength steel for bolt excellent in delayed fracture resistance even having a tensile strength of 1100 MPa or more without addition of large amounts of expensive alloy elements such as Cr and Mo: and a high strength bolt made from the boron-added high strength steel for bolt. The high strength steel for bolt contains C of 0.23% to less than 0.40%, Si of 0.23% to 1.50%, Mn of 0.30% to 1.45%, P of 0.03% or less (excluding 0%), S of 0.03% or less (excluding 0%), Cr of 0.05% to 1.5%, V of 0.02% to 0.30%, Ti of 0.02% to 0.1%, B of 0.0003% to 0.0050%, Al of 0.01% to 0.10%, and N of 0.002% to 0.010%, with the remainder being iron and inevitable impurities. The steel has a ratio ([Si]/[C]) of the Si content [Si] to the C content [C] of 1.0 or more and has a ferrite-pearlite mixed microstructure.

A steel wire for high-strength bolts is used for a non heat-treatment bolt with an excellent cold forgeability for which quenching and tempering steps have been omitted after bolt formation, and which has a tensile strength of 1200 MPa or more and an excellent delayed fracture resistance. The steel wire includes C, Si, Mn, P, S, Cr, Al, N, and B, at least one selected from the group consisting of Ti, V, and Nb with the balance consisting of iron and inevitable impurities. The steel wire has a microstructure wherein ferrite and perlite have a total area rate of 98% or more, perlite lamellar spacing is 250 nm or less, and an area rate of the perlite is more than 40%, and 80% or less. The steel wire has a tensile strength of 1300 MPa or less.

Steel for a high-strength bolt contains: from 0.50 mass % to 0.65 mass % carbon, from 1.5 mass % to 2.5 mass % silicon, 1.0 mass % or more chromium, 0.4 mass % or less manganese, greater than 1.5 mass % molybdenum, 0.03 mass % or less phosphorus and sulfur combined, and balance iron and inevitable impurities.

A high-strength bolt is formed using steel for a high-strength bolt that contains: from 0.50 mass % to 0.65 mass % carbon, from 1.5 mass % to 2.5 mass % silicon, 1.0 mass % or more chromium, 0.4 mass % or less manganese, greater than 1.5 mass % molybdenum, 0.03 mass % or less phosphorus and sulfur combined, and balance iron and inevitable impurities.

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.

An NPR steel material for rock bolt and a production method thereof are disclosed. The NPR steel material for rock bolt has a composition, in weight percent, consisting of: C: 0.4-0.7%, Mn: 15-20%, Si: ≤0.1%, Cu: ≤0.03%, Cr: ≤0.01%, Ni: ≤0.02%, S: ≤0.001%, P: ≤0.001%, and the rest being Fe and unavoidable impurity elements. The NPR steel material for rock bolt and the production method thereof effectively solve the problem that rock bolts in the prior art have low tensile strength and low effective elongation. The NPR steel material for rock bolt has a yield strength adjustable in the range of 500-1100 MPa, and an elongation adjustable in the range of 10-80%.

A member (10), for bearing a load, including a load receiving portion (12) at which the load is applicable to the member. A strainable portion (14) is connected to the load receiving portion to be strained by the load. A datum (16a) is defined and an elongate portion (18) defines another datum (18a). The datums are arranged such that relative displacement therebetween indicates an amount by which the strainable portion is strained. The strainable portion defines the datum.