AMS 6346
AMS 6346 is the SAE Aerospace Material Specification covering SAE 4130 chromium-molybdenum steel in the seamless tubing product form. The specification sets requirements for chemical composition, mechanical properties, dimensional tolerances, and non-destructive inspection of 4130 steel seamless tubing produced by hot or cold working processes. Tubing is available in outside diameters from 0.375 inch to 10.500 inches with wall thicknesses from 0.028 inch to 2.000 inches, supplied in the annealed, normalized, or quenched and tempered condition.
SAE 4130 seamless tubing to AMS 6346 is one of the most widely used materials in aircraft structural fabrication. Its thin-wall capability, weldability, and forming properties make it ideal for welded space-frame fuselages, control system push-pull tubes, hydraulic system hard lines, and landing gear drag braces in light aircraft, military trainers, and experimental aircraft.
AMS 6346 requires a minimum 90,000 psi tensile strength and 70,000 psi yield strength in the normalized condition, with measured values typically 10–20% higher. Tubing produced to AMS 6346 undergoes mandatory hydrostatic or eddy current non-destructive testing at the mill to verify wall integrity. The seamless manufacturing process eliminates the longitudinal weld seam present in welded tube, providing uniform circumferential properties critical for pressurized aircraft hydraulic applications.
- Aircraft welded tube-frame fuselage structures
- Control system push-pull tubes and bellcranks
- Aircraft hydraulic hard lines and accumulators
- Landing gear drag braces and V-struts
- Engine mount tubular framework
- Aerospace ground support equipment structural members
Certified Material for Critical Service
AMS 6346 tubing is certified to chemical composition, mechanical properties (tensile and yield strength, elongation), dimensional tolerances (OD, wall thickness, straightness), and hydrostatic or eddy current inspection results. Mill test reports are provided per heat and lot. For aircraft applications governed by Federal Aviation Regulations, 4130 tubing must additionally comply with applicable FAA-approved material data in the Type Certificate Data Sheet or Supplemental Type Certificate.