Stress Relieved 4130 Tubing
Stress relieving is a low-temperature heat treatment. It removes the internal stresses left by cold drawing or welding without changing the structure of the steel, so the tube keeps most of its cold-worked strength.
When Stress Relief is Specified
Stress relief is specified for 4130 tubing when:
- The tube has been cold drawn and the residual stresses from drawing may cause dimensional instability during or after machining
- The tube has been welded and the heat-affected zone residual stresses must be reduced without full re-normalising
- A precision component requires dimensional stability and cannot tolerate stress redistribution during machining
For most structural applications (roll cages, airframes), stress relief alone is not specified — normalizing or as-drawn are the standard conditions.
Stress Relief vs. Annealing vs. Normalizing
These three processes achieve different outcomes:
| Process | Temperature Range | Primary Effect |
|---|---|---|
| Stress relief | Below Ac1 (~550–650°C) | Reduces residual stress; minimal property change |
| Annealing | Above Ac3 (~870–900°C) | Full microstructure change — softest, most ductile |
| Normalizing | Above Ac3, air cool | Uniform microstructure, intermediate properties |
| Note | Specific temperatures depend on the 4130 composition of the heat | Verify with heat treater |
When to Specify Stress Relieved Tube
Cold drawn tube holds locked-in stress. When such a tube is machined, slit or cut along its length, the stress is released unevenly and the part can move. Stress relieving first reduces that distortion, which is valuable for precision machined components.
It is also the usual treatment after welding a 4130 assembly where full re-heat-treatment is impractical: the welded zone is heated to a temperature below the transformation range and cooled slowly to reduce residual stress. It does not refine the grain the way normalizing does, and it does not soften the tube as far as annealing. If a structure will be welded, normalized tube is normally preferred as the starting material. The conditions are set side by side in the heat treatment guide; see also normalized 4130 tubing.
Frequently Asked Questions
Does stress relief change the mechanical properties of 4130?
Stress relief performed below Ac1 does not significantly change the yield or tensile strength of the material — the microstructure is unchanged. However, ductility (elongation) may improve slightly due to stress relaxation. This is why stress relief is used when properties must be preserved but dimensional stability must be improved.
Is stress relieved tube stronger than normalized?
Often, because it keeps much of the strength from cold drawing, but with lower ductility.
Should a welded 4130 assembly be stress relieved?
It depends on wall thickness and the application. Follow the governing specification or weld procedure.
At what stage is stress relieving done?
After cold drawing at the mill, or after welding or rough machining in fabrication.
Does stress relieving change the tube dimensions?
Only slightly. Its purpose is to stop the part moving later during machining.
Enquire for Stress-Relieved 4130 Tubing
Specify ASTM A519, Grade 4130, Stress-Relieved condition, OD, wall, and MTC.
- Standard: ASTM A519
- Grade: 4130
- Condition: Stress-Relieved
- OD & Wall
- Footage
- MTC
- Delivery