Sihe Steel
Sihe Steel
Explore our technical-grade seamless and welded stainless steel tubing products engineered for oil, gas, chemical processing, and aerospace engineering.
An authoritative analysis of metallurgical processing, structural performance, and application engineering of high-alloy pipelines from Liaocheng Sihe Stainless Steel Material LTD.
Austenitic stainless steel grade AISI 304 (UNS S30400) remains the bedrock of modern industrial fluid transportation systems. Synthesized with a nominal chemical layout of 18% chromium and 8% nickel, it forms a passive chromium oxide protective barrier that provides exceptional resistance to atmospheric oxidation and mild corrosive agents. In high-demand environments, preventing localized failure requires strict control over the carbon content. While standard AISI 304 operates optimally up to 800°F (427°C), it undergoes sensitization in the heat-affected zone (HAZ) during welding, leading to chromium carbide precipitation at grain boundaries and intergranular corrosion.
For applications involving structural welding, we utilize AISI 304L (UNS S30403) with a carbon limit capped strictly at 0.030%. This low-carbon design prevents sensitization and maintains ductility in extreme welding processes, making it critical for thick-walled heat exchangers and heavy pressure pipelines. Conversely, for high-temperature operations, AISI 309S and AISI 310S are optimized with elevated chromium and nickel content to resist scaling at temperatures up to 2000°F (1093°C).
Comparing the mechanical thresholds, chemical layout, and corrosion capabilities of common austenitic, duplex, and super-alloy grades manufactured in our factory.
| Alloy Grade | UNS Designator | Nominal Chemical Composition (%) | Yield Strength (MPa min) | Tensile Strength (MPa min) | Pitting Resistance (PREN) | Primary Environment Compatibility |
|---|---|---|---|---|---|---|
| AISI 304 | UNS S30400 | 18Cr - 8Ni - 0.08C max | 205 | 515 | 18 - 20 | Freshwater, food processing, organic acids, light chemicals. |
| AISI 316L | UNS S31603 | 16Cr - 10Ni - 2Mo - 0.03C max | 170 | 485 | 23 - 25 | Chloride-bearing environments, marine air, pharmaceuticals. |
| Duplex 2205 | UNS S32205 | 22Cr - 5Ni - 3Mo - 0.18N | 450 | 620 | 34 - 36 | High stress, sour gas wells, high chloride chemical processing. |
| Super Duplex 2507 | UNS S32750 | 25Cr - 7Ni - 4Mo - 0.28N | 550 | 750 | 41 - 43 | Subsea umbilicals, desalination, highly concentrated inorganic acids. |
| Incoloy 825 | UNS N08825 | 21Cr - 42Ni - 3Mo - 2Cu - Ti | 220 | 550 | 31 - 33 | Sulfuric & phosphoric acids, acid gas recovery systems. |
| Inconel 625 | UNS N06625 | 21Cr - 61Ni - 9Mo - 3.6Nb | 415 | 825 | 46 - 50 | Extreme temperature exhaust, subsea production, high pressure steam. |
Liaocheng Sihe is equipped with six high-efficiency production lines that support customized physical geometries, thermal treatments, and mechanical processing.
Our drawing systems produce coiled tubing from 0.125 inch (3.175 mm) outer diameter up to 1 inch (25.4 mm) outer diameter. Wall thicknesses can be drawn up to 0.165 inch (3.0 mm) with continuous lengths reaching 32,800 feet (10,000 meters) without orbital welds. This is ideal for subsea control systems and chemical injection umbilicals.
We utilize online protective atmosphere bright annealing furnaces operating with high-purity hydrogen. This thermal treatment relieves internal stress in cold-worked tubes and prevents the formation of scale, leaving a bright, mirror-like inner and outer finish that optimizes fluid dynamics.
Using automatic laser cutting and multi-roll precision straightening machinery, we guarantee straightness tolerances down to 0.5 mm/m and clean, burr-free end cuts. This is critical for capillary lines and instruments that require tight fits and orbital welding.
We offer surface preparation techniques including acid pickling, passivation, and mechanical polishing. We also provide electropolishing (EP) to reduce the inner surface roughness (Ra) down to ≤ 0.25 μm, meeting the standards required for semiconductor fabrication and pharmaceutical manufacturing.
Our flanging and end-forming services are designed for heavy automotive exhaust pipes, high-vibration engine manifolds, chemical supply lines, and precision diagnostic instruments, ensuring tight, leak-proof connections.
How Liaocheng Sihe supports deep-sea exploration and high-risk extraction projects with reliable corrosion-resistant materials.
As offshore oil and gas operations expand into deeper waters and high-pressure reservoirs, safety requirements become increasingly strict. Critical hydraulic control lines, chemical injection pipelines, and umbilical systems are exposed to high pressure, internal chemical attack, and external seawater corrosion. These environments demand reliable corrosion-resistant alloys.
Liaocheng Sihe manufactures coiled tubing in high-alloy grades, including Duplex 2205, Super Duplex 2507, Incoloy 825, and Inconel 625. These alloys are chosen for their resistance to chloride-induced stress corrosion cracking (SCC), hydrogen embrittlement, and localized pitting. By using continuous cold-drawn, orbital-weld-free manufacturing processes, we minimize potential weak points, ensuring the reliable operation of control systems in subsea environments.
Our AISI 304 and high-alloy tubes are used in critical applications across eight primary industrial sectors.
Optimized thermal performance and corrosion resistance for high-pressure industrial shell and tube configurations.
Continuous coiled tube paths reduce leak risks in commercial air conditioning and heat pump systems.
Designed to withstand aggressive acids, chlorides, and high-temperature processing environments.
FDA-compliant, highly polished inner surfaces prevent bacterial attachment and support sanitation cycles.
Ultra-clean capillary tubes matching ASME BPE standards prevent cross-contamination.
Withstands the high temperatures and pressures of boilers, steam feeds, and condenser systems.
Resistant to H2S sour gas environments, oil field chemical corrosion, and high pressures.
Precision tubes designed for high-vibration fuel lines, hydraulic systems, and exhaust manifolds.
Our production plant complies with GB, ASTM, ASME, JIS, and EN standards. Every batch undergoes strict testing, including flaring, flattening, hardness, and air tightness tests.
We maintain strict quality control throughout our manufacturing process. We conduct 100% pneumatic testing on all capillary and heat exchanger tubes to ensure seal integrity. Mechanical testing, including tensile strength, yield strength, and elongation, verifies that each batch meets engineering specifications. Visual inspection systems check outer dimensions to keep outer diameter (OD) and wall thickness (WT) within tolerances of ±0.05 mm.
We perform destructive tests, such as flaring and flattening, in accordance with ASTM A1016 standards to verify ductility and weld integrity. For corrosion verification, we conduct intergranular corrosion testing (ASTM A262 Practice A or E) to ensure that the bright annealing process has removed sensitization from the grain boundaries, which prevents corrosion during field installation.
The development of alloy pipelines is driven by the requirements of hydrogen energy, ultra-deepwater exploration, and low-carbon manufacturing.
The growth of the green hydrogen sector requires transport piping with minimal susceptibility to hydrogen embrittlement. Liaocheng Sihe is optimizing AISI 316L and Incoloy alloy structures with controlled grain sizes to improve resistance to high-pressure hydrogen penetration.
To meet the requirements of deepwater projects (down to 3,000 meters), we are updating our drawing machines to produce single-run seamless coiled tubing up to 15,000 meters without joints. This helps operators minimize installation risks and cut down on offshore welding costs.
We are integrating automated eddy current testing (ECT) and laser telemetry into our production lines. This allows us to track internal and external dimensional variations in real time, creating an end-to-end digital twin of the tubing for traceability.
Technical and logistics answers for global engineering procurement construction (EPC) agents and industrial engineers.
Our product line includes high-temperature resistance pipes, capillary tubes, and duplex lines designed to meet demanding industrial specifications.
