Hangbo Alloy Group
Shanghai · Est. 2012
Bolts, studs, nuts, washers and threaded rod in Inconel, Hastelloy, Monel and Incoloy - produced to ASTM B446, B564, A193 and A194 and compliant with NACE MR0175 / ISO 15156.
A flanged joint is only as corrosion-resistant as its weakest component, and in aggressive service that component is usually the bolting. Fasteners carry the preload that keeps the gasket seated, they sit in a crevice where oxygen is depleted and chlorides concentrate, and they are frequently threaded through a dissimilar flange material that sets up a galvanic couple. Hangbo Alloy Group manufactures nickel alloy fasteners from bar and forging stock drawn from the same melt programme as our other product forms, so chemistry, strength and corrosion behaviour are consistent throughout the assembly.
Our fastener range covers the complete stud bolt and nut set used with nickel alloy flanges to ASME B16.5 and B16.47, heavy hex nuts, through-hardened washers, continuous and double-end studs, socket head cap screws, hex head bolts and threaded rod. Sizes span M6 to M64 metric and 1/4" to 2-1/2" imperial (UNC / 8UN series), with non-standard lengths, fine threads and special head configurations produced to drawing.
Principal applications are sour oil and gas wellheads and manifolds requiring NACE MR0175 / ISO 15156 compliance, subsea and topside marine bolting, chemical reactor and heat exchanger covers, desalination plant, FGD scrubber internals, and high-temperature furnace and turbine casings where relaxation resistance governs bolt life.
Fasteners are manufactured to the material and dimensional standards that the end user's piping class or equipment specification calls for:
Thread forms are produced to ASME B1.1 unified coarse and 8-pitch series, ASME B1.13M metric, or ISO 228-1 / ASME B1.20.1 pipe threads where applicable. Roll threading is used wherever the alloy's work-hardening behaviour permits it, because the cold-worked root and the continuous grain flow it produces give measurably better fatigue performance than cut threads - an important consideration on vibrating equipment and subsea risers. Threads on precipitation-hardenable grades such as Inconel 718 are rolled in the solution-treated condition and the fastener is aged afterwards.
Grade selection for bolting is driven by three constraints: the required minimum yield strength at design temperature, the environmental cracking resistance, and the galvanic relationship with the flanges being clamped.
Where the environment is dominated by chlorides, grade selection should be checked against the pitting resistance equivalent number of the flange material as well, so that the bolting is not made the anode of the couple. Our chloride stress corrosion cracking guide sets out the practical thresholds.
Raw material is nickel alloy bar and forging billet to ASTM B446, B166, B160, B473 or B564, sourced from approved mills with full melt certification. Bar is centreless-ground or peeled to remove surface decarburisation and seams before processing, then cut to slug length.
Heads are formed by hot forging on horizontal upsetters or by cold heading for the smaller diameters, followed by heat treatment: solution anneal and rapid quench for solid-solution alloys, and solution treatment plus a controlled double or single age for precipitation-hardenable grades such as Inconel 718 and Monel K500. Ageing is carried out in calibrated, furnace-uniformity-surveyed equipment with chart-recorded cycles, because a few degrees of overshoot on the ageing temperature measurably reduces the final yield strength.
Threads are rolled rather than cut wherever the alloy permits. Nuts are tapped or, for the harder grades, produced by hot forging and machining. Where the service requires it, fasteners are supplied with a controlled surface finish, and thread lubricant compatibility is reviewed at the enquiry stage - nickel alloys are prone to galling, and specifying the right anti-seize compound is essential to achieving the target preload without thread pick-up.
Manufacture and inspection take place under a quality management system certified to ISO 9001:2015, GJB 9001C and GOST R. Each lot is released against an EN 10204 3.1 certificate; EN 10204 3.2 certification with third-party witness by BV, SGS, TUV, DNV or Lloyd's Register can be arranged for sour service and subsea packages.
Routine verification covers dimensional and thread gauging to the applicable ASME or ISO standard, hardness testing on each lot, tensile testing on a per-heat and per-lot basis, positive material identification by XRF, and visual and dye penetrant inspection of forged heads. For NACE MR0175 / ISO 15156 orders we document the maximum hardness achieved and confirm that the heat treatment condition falls inside the qualified envelope for the specified environmental severity.
Fastener markings are applied by low-stress dot peening or rolling - never by methods that create a stress raiser or breach the passive film - and identify the grade, the manufacturer and, for A193/A194 bolting, the grade symbol. Studs and nuts are packed as matched sets with a lot certificate, and full heat traceability is retained from the melt through to the finished fastener.
ASTM B446 covers nickel-chromium-molybdenum-columbium alloy (UNS N06625) rod and bar - the normal starting stock for machined and rolled studs and bolts. ASTM B564 covers nickel alloy forgings, and is the appropriate specification where the fastener or a large-diameter bolting component is produced by closed-die forging rather than from bar. In practice, small and medium diameter studs are typically B446 bar, while very large diameter or heavily headed components may be quoted to B564. Both are acceptable when specified correctly on the enquiry.
Fasteners in Inconel 718 and Inconel 625 can be supplied to meet NACE MR0175 / ISO 15156 requirements for sour service, provided the heat treatment condition and maximum hardness fall within the qualified limits for the grade and the environmental severity specified. We document the achieved hardness and the heat treatment cycle on the inspection certificate, and third-party verification by BV, SGS, TUV, DNV or Lloyd's Register can be added. The required severity level should be stated at the enquiry stage so that the correct ageing cycle is applied.
Yes. We routinely supply matched sets - stud bolts or hex bolts, heavy hex nuts and washers - manufactured from the same alloy family and released under a single lot certificate, which simplifies both procurement and joint integrity documentation for the end user. Sets can be assembled to the flange rating and bolt circle of the associated ASME B16.5 or B16.47 flange order.
Send us your grade, diameter, length, quantity, and any special requirements. Our team responds within 10 minutes during business hours.