347HFG is fine-grain strengthened niobium-stabilized high-carbon austenitic heat-resistant stainless steel bright bar. Its base chemical composition is identical to standard 347H: C 0.04%~0.10%, Cr 17~19%, Ni 9~13%, Nb≥10×C. The core difference lies in proprietary fine grain technology (FG = Fine Grain): high-temperature pre-solution + heavy deformation rolling + double-stage solution annealing, grain size strictly controlled ASTM 7~10 grade, while conventional 347H only reaches 4~7 coarse grain grade.
Niobium preferentially binds carbon to form stable NbC, blocking chromium depletion at grain boundaries during 425~850℃ long-term heating, eliminating intergranular corrosion under repeated thermal cycles. High carbon delivers solid-solution hardening, combined with fine grain & nano NbC dispersion strengthening. Its stress rupture strength and creep life at 600~650℃ are 20%~30% higher than standard 347H, with vastly superior high-temperature fatigue, steam oxidation and anti-scaling spalling performance.

Chemical element content (%)

Specification：1.00~300.00mm

Application: It is mainly used to manufacture pressure-bearing mandrels for supercritical & ultra-supercritical boiler superheaters/reheaters, high-temperature header bolts and flanges, 600~650℃ steam pipe fasteners for thermal power plants, high-temperature heat exchange valve stems for waste incineration waste heat boilers, stressed bars for petrochemical medium-high temperature cracking furnaces, medium-high temperature heat exchange tooling for solar thermal power stations, support shafts for chloride-free carburizing furnaces, high-temperature hot circulation valve bodies, load-bearing standard parts for power plant medium-high temperature auxiliary machines, connectors for high-pressure steam reactor equipment, etc.
Widely applied in ≥600MW supercritical thermal power units, waste incineration waste heat boilers, petrochemical medium-high temperature cracking units, solar thermal heat exchange systems, industrial carburizing furnaces, high-temperature high-pressure steam pipelines, high-temperature reactor equipment with chloride-free media and other industries.

Core Advantages Over Competitors

1. High quality stability: Full closed-loop production with dual online spectral & metallographic inspection strictly controls C, Cr, Ni, Nb key elements and implements proprietary two-stage fine-grain solution process, grain size stably maintained 7~10 grade. Uniform dispersed NbC precipitates ensure negligible batch fluctuation of high-temperature creep strength, steam oxidation resistance and weldability for consistent mass production of power station high-pressure high-temperature components.

2. Excellent surface quality: Dedicated high-precision cold drawing and centerless grinding lines produce bars free of peeling, oxide scale, scratches and pits with mirror finish. Smooth surface reduces alternating thermal stress concentration under high-temperature steam service to greatly extend fatigue life of parts operating long-term at 600℃; secondary polishing is unnecessary for most precision machining.

3. Ultra-high dimensional accuracy: Precision cold rolling mills and automatic online dimension detectors narrow tolerance range with tiny single-bar error and strong batch uniformity. Unified part specifications during automatic mass production significantly raise finished yield and machining precision.

4. Rich product variety: According to market demand and customer's special requirements, customized products are provided to meet the use requirements under various complex working conditions, providing customers with more choices.

5. Perfect after-sales service: The perfect after-sales service system can respond to customer needs and feedback in a timely manner. For problems encountered by customers during use, technical support and solutions are provided to customers quickly.

We mainly engage in cold heading wire, bar, peeled bar, and profiled bar; our products cover 11 series and more than 300 grades, and we continue to develop a variety of professional steels. We can provide all-round solutions such as cold heading finishing line manufacturing and high-precision bright bar customization, and provide one-stop procurement services and package procurement solutions for global customers. The website displays some grades. If you don’t have the grade you need, please contact us by phone or email.