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SAE J2833-2018: High Strength Low Alloy Steel Hydraulic Tubing for Bending, Flaring, and Brazing
Scope and Key Specifications
SAE J2833-2018 covers stress relieved annealed electric resistance welded and cold-drawn single-wall high strength low alloy steel hydraulic tubing. The material achieves a minimum 690 MPa tensile strength through micro-alloy composition and controlled processing. The tubing is intended for bending, flaring, cold forming, and brazing in hydraulic pressure lines. Nominal reference working pressures are listed in ISO 10763 for metric sizes and SAE J1065 for inch sizes.
The manufacturing process begins with electric resistance welding of a formed steel strip, followed by cold drawing over a mandrel with a minimum wall reduction of 8%. Finally, the tubing is stress relieved annealed to meet mechanical requirements. Dimensional tolerances for outside diameter (OD) and inside diameter (ID) are specified based on nominal OD, as shown in Table 1. Tolerances apply to OD and wall thickness unless otherwise agreed between purchaser and producer.
| Nominal Tubing OD (mm) | Tube OD and ID Tolerance (mm) |
|---|---|
| Up to 10 | ±0.05 |
| Over 10 to 16 | ±0.06 |
| Over 16 to 50 | ±0.08 |
| Over 50 to 60 | ±0.10 |
| Over 60 to 80 | ±0.13 |
| Over 80 to 110 | ±0.15 |
Wall thickness tolerances are also defined in the standard for different OD ranges. For common tube sizes and wall thicknesses, refer to ISO 10763 (metric) and SAE J1065 (inch).
🛠️ Global Standardization: SAE J2833 promotes the use of metric tube sizes to unify systems, guide users toward preferred sizes, reduce complexity, and eliminate inventory duplications.
Design and Fabrication Considerations
Engineers must account for the effect of thermal processes when designing with SAE J2833 tubing. The material is sub-critically annealed, meaning it has been heat treated below the lower critical temperature (AC1) to achieve strength. Welding, brazing, or other operations that expose the tube to temperatures near or above AC1 can initiate isothermal transformation and locally reduce strength in the heat-affected zone.
⚠️ Thermal Processing Caution: If the tubing is welded or brazed, the nominal working pressures from ISO 10763 or SAE J1065 may not be applicable. Users and fabricators must validate the assembly design and pressure ratings. Performance testing per SAE J2551-2 is recommended to confirm system integrity.
Design Insight: Cold forming tube end connections is the preferred method because it avoids compromising the structural integrity of the tube. Thermal joining methods like brazing and welding introduce potential strength degradation and may require qualification testing per ISO 19879. By using cold forming, designers can bypass additional qualification steps and maintain reliable performance. The standard also encourages metric tube sizes to simplify global sourcing and reduce inventory complexity.
Frequently Asked Questions
What are the nominal reference working pressures for SAE J2833 tubing?
Nominal working pressures are provided in ISO 10763 (metric) and SAE J1065 (inch) for the tubing in its as-delivered condition. These values may change if the tube is subsequently welded or brazed, requiring revalidation.
How does welding or brazing affect the strength of this tubing?
Thermal processes at or near the AC1 temperature can cause local annealing, reducing tensile strength in the heat-affected zone. Cold forming eliminates this risk entirely.
What tests are required for assemblies that include brazed or welded joints?
Assemblies with brazed or welded joints may need qualification testing per ISO 19879. Performance testing per SAE J2551-2 can help develop suitable protocols for the specific design.
Why does the standard recommend metric tube sizes?
Metric sizing aligns with global practices, simplifies inventory, and reduces complexity. SAE J2833 encourages metric adoption to support international competitiveness and standardization.
