Inconel 625 Tubing — Seamless & Welded for Heat Exchangers & Subsea Systems

Single-grade focus means single-grade expertise. At Changzhou DLX Alloy Co., Ltd., Inconel 625 is not one line item in a catalog — it is the nickel-chromium-molybdenum alloy we know best. Our tubing is cold drawn from solution-annealed hollows through multi-pass precision reduction, delivering the exact outside diameter, wall thickness, and surface finish your heat exchanger design, subsea hydraulic system, or chemical injection line demands. Seamless to ASTM B444 or welded to ASTM B704 — both produced under the same ISO9001 system with full EN 10204 3.1 MTC traceability.

• Cold drawn to your exact OD and wall — Multi-pass precision drawing with inter-pass annealing achieves your specified dimensions without the wall thickness variation of hot-finished tube. OD tolerance typically ±0.10 mm or better on standard sizes.
• Choose seamless or welded based on your application, not our capability — Seamless for pressure integrity and heavy-wall requirements. Welded for tighter wall tolerance on thin-wall applications and longer continuous lengths. We manufacture both to ASME SB-444 and SB-704 respectively — you choose what your design needs.
• Solution-annealed and rapid-quenched — Every tube solution treated and quenched to dissolve all secondary phases. Clean microstructure with no sigma, no Laves, no sensitization. Verified by ASTM grain size and microstructural examination before shipment.
• Coil-length seamless to 2000m — For subsea umbilical and control line applications where every field joint is a potential leak path. Our long-length capability eliminates intermediate welds in your system design.
• Eddy current + hydrostatic tested as standard — 100% eddy current per ASTM E426 on every tube. Hydrostatic test to 1.5* design pressure or per your specification. Test reports included with your EN 10204 3.1 MTC.
• Heat exchanger U-bend capability — Tubes supplied in straight lengths or U-bent to your bend radius specification. Solution annealed after bending to restore corrosion resistance in the bend zone. No sensitized U-bends that fail first.

When you specify Inconel 625 tubing, you are paying for the nickel, the chromium, and the molybdenum — and you are betting that the processing was done right. Cold worked too much without intermediate annealing, and the tube cracks during flare testing. Annealed at the wrong temperature, and sigma phase precipitates, destroying corrosion resistance. Quenched too slowly, and sensitization creates a tube that corrodes exactly where it shouldn't — in the heat-affected zone of your weld.

At DLX, every Inconel 625 tube is cold drawn with pass-by-pass reduction control, inter-stage solution annealing at precisely 1090–1150°C, and rapid water quenching. Our operators know that rushing the quench by two seconds can mean the difference between a tube that passes ASTM B444 and one that doesn't. Since 2002, this attention to nickel alloy processing has been our only business.

• 12,000 m² facility with dedicated nickel alloy cold drawing, bright annealing, and NDT lines — your 625 tubing never shares processing equipment with carbon steel or stainless
• Seamless from 6mm to 76mm OD; welded from 12mm to 114mm OD — standard and non-standard dimensions
• U-bending, coiling, cut-to-length — secondary processing in-house means your order ships complete, not in pieces from three different shops
• ISO9001 with full heat traceability; SGS-accredited; BV and TÜV third-party inspection available

Source: DLX Alloy product catalog. EN 10204 3.1 MTC with full composition included on every shipment.

Third-party witnessing by SGS, BV, or TÜV available. All shipments fully traceable to hollow heat number.

Seamless for maximum pressure integrity, heavy-wall applications, and when your design code requires it. Thin-wall welded when you need tight wall tolerance, longer continuous lengths, or lower cost at thinner gauges. Both meet the same chemistry and tensile requirements. Our technical team can review your operating pressure and recommend.

Up to 2000m in a single seamless length depending on OD and wall. This is critical for subsea umbilical tubing where every field weld is a cost, a schedule delay, and a potential leak path. We verify continuous length by eddy current from end to end.

Yes. Specify your bend radius (typically 1.5* to 2.5* OD), leg length, and whether you need the bend zone solution annealed after forming. We U-bend in-house and can supply with post-bend annealing to restore full corrosion resistance in the bend region.

Every seamless tube is eddy current tested 100%. Hydrostatic testing is performed to your specified test pressure or per ASTM B829 as standard. For subsea applications, we can hydrotest to API 5CRA requirements. Test pressure and hold time per your order specification.

We target mid-range chemistry — not just "within spec." For Inconel 625, we aim Ni ≥60%, Mo ≥9%, Cr ~21.5% — tighter than the ASTM B444 minimums. This means consistent PREN, consistent tensile, and consistent corrosion performance regardless of which heat your tube came from.