Stainless Steel 347/347H Fasteners Manufacturer, Stockist & Exporter

Both are niobium-stabilised austenitic grades, but 347H carries a higher controlled carbon range of 0.04–0.10% (versus 0.08% max for 347). That extra carbon gives 347H superior creep and stress-rupture strength at elevated temperature, so it is preferred for long-term hot bolting above roughly 540 °C, while 347 suits general stabilised-grade service.

They provide reliable service up to approximately 815 °C, with 347H retaining useful creep strength at the top of that range. The grade was specifically developed for the 425–815 °C window where unstabilised 304 fasteners are vulnerable to intergranular attack.

Niobium combines preferentially with carbon to form stable niobium carbides. This stops chromium from forming chromium carbides at grain boundaries during welding or high-temperature exposure, keeping chromium available to protect the steel and preventing intergranular (weld-decay) corrosion.

Yes. UNS S34700 is the Unified Numbering System designation for SS 347, equivalent to Werkstoff 1.4550, JIS SUS 347 and EN X6CrNiNb18-10. SS 347H corresponds to UNS S34709 / 1.4961 / X6CrNiNb18-13.

Bolts are supplied to ASTM A193 (ASME SA193) and nuts to ASTM A194 (ASME SA194). We also certify to DIN, EN, BS, IS and JIS equivalents when your drawing calls for them.

Standard stock runs M3–M56 (and 3/16″ to 2″), with custom sizes up to M100. Threads are available in metric coarse/fine, UNC, UNF, BSW and BSF, with lengths from 3 mm to 200 mm and custom lengths to order.