Fully Threaded Rods

Fully threaded rods, also called threaded bars or stud bolts, are headless cylindrical fasteners with full-length continuous threading—those over 1m are threaded rods, and ≤1m are threaded bars. Available in M3-M64 metric and 4#-40UNC American standard specifications, they are essential industrial fastening components for their easy installation, stable connection and precise preload adjustability, and serve as core connectors for high-pressure extreme conditions like oilfields and chemical engineering.
 
For application scenarios, ordinary carbon steel rods fit light-duty uses such as furniture assembly and storage racking, while high-strength grades (8.8 and above) apply to automobile chassis and heavy machine tools. Special-grade rods like B7 and L7 are custom-engineered for high-pressure oilfield environments, widely used in oil and gas drilling platforms, high-pressure oil pipelines, hydrogenation reactors and LNG cryogenic storage tanks. They resist high temperature and pressure, severe corrosion and extreme temperature differences, acting as key parts for oilfield wellhead equipment and manifold flange connections; modified versions are also suitable for sour oil and gas production with wet hydrogen sulfide.
 
In terms of materials and grades, mainstream rods fall into carbon/alloy steel and stainless steel. Carbon steel is graded 4.8 to 12.9 by strength, and stainless steel is mainly A2-70 and A4-70. High-pressure oilfields primarily use ASTM standard chromium-molybdenum alloy steel: B7 (ASTM A193) has a tensile strength ≥860MPa, temperature resistance up to 450℃, and excellent creep and relaxation resistance for conventional high-temperature and high-pressure oilfield conditions; B7M, its modified version, features strict hardness control, enhanced impact toughness and sulfide stress corrosion cracking resistance for hydrogen sulfide-containing sour oilfields. L7 (ASTM A320) shares a similar composition with B7, and after cryogenic treatment, it withstands -101℃ with a tensile strength ≥860MPa, suitable for low-temperature high-pressure oilfields and LNG pipelines; L7M further optimizes low-temperature corrosion resistance. Quenched and tempered, these materials reach 8-10 grade grain size and ＜0.3% deformation rate, meeting oilfield fastening requirements under pressure above 10MPa.
 
For standards, Chinese rods follow GB15389 and GB/T901 (60° thread angle, metric M series), and German ones comply with DIN975/976 (metric threads compatible with Chinese standards, higher precision). High-pressure oilfield rods mainly adhere to American ASTM A193 (high temperature) and ASTM A320 (low temperature), paired with ANSI B18.31.2 inch-thread standard, and must pass oil industry certifications like API 20E and NORSOK M650. The petrochemical industry also requires compliance with SH/T 3404 to ensure compatibility with oilfield flanges, pipes and valves.
 
Overall, via flexible material and grade matching, fully threaded rods meet general industrial basic fastening needs, and realize safe adaptation to oilfield high-pressure extreme conditions with B7, L7 and other special materials, making them indispensable key components in cross-field industrial connections.