ASTM A511 Tubing is a specification covering seamless stainless steel mechanical tubing intended for structural and precision mechanical applications. Unlike pressure pipe standards, ASTM A511 focuses on dimensional accuracy, surface finish, hardness control, and machinability rather than pressure containment.
ASTM A511 tube is manufactured strictly as seamless mechanical tubing and supplied in hot finished (HF) or cold finished (CF) condition. The ASTM A511 specification includes austenitic, ferritic, and martensitic stainless steel grades such as MT304, MT316, MT410, MT430, MT347, and others. ASTM A511 mechanical tubing is widely used for hydraulic cylinders, hollow bar machining, rollers, shafts, and precision structural components where tight tolerances and surface quality are critical.
ASTM A511 Tubing Specifications
Standard: ASTM A511 / A511M
Type: Seamless only
Manufacturing Process: Cold Finished (CF) or Hot Finished (HF)
Shapes: Round, square, rectangular, hollow bar
Grades Covered:
- MT304 / MT304L
- MT316 / MT316L
- MT309S / MT310S
- MT317
- MT321
- MT347
- MT410, MT430, MT446
- Ferritic & Martensitic grades
ASTM A511 Grade MT304 Chemical Composition
| Element | Carbon | Manganese | Phosphorus | Sulfur | Silicon | Chromium | Nickel |
|---|---|---|---|---|---|---|---|
| MT304 (%) | ≤ 0.08 | ≤ 2.00 | ≤ 0.040 | ≤ 0.030 | ≤ 1.00 | 18.0 – 20.0 | 8.0 – 11.0 |
MT304 is the most commonly used ASTM A511 tubing grade due to its cost efficiency, corrosion resistance, and excellent machinability.
ASTM A511 Grade MT316 Chemical Composition
| Element | Carbon | Manganese | Phosphorus | Sulfur | Silicon | Chromium | Nickel | Molybdenum |
|---|---|---|---|---|---|---|---|---|
| MT316 (%) | ≤ 0.08 | ≤ 2.00 | ≤ 0.040 | ≤ 0.030 | ≤ 1.00 | 16.0 – 18.0 | 11.0 – 14.0 | 2.0 – 3.0 |
MT316 ASTM A511 tube offers improved resistance to chloride environments and enhanced resistance to pitting and stress corrosion cracking compared to MT304.
Mechanical Properties of ASTM A511 Seamless Mechanical Tubing
| Grade | Tensile Strength (Min) | Yield Strength (Min) | Hardness (Max HBW) |
|---|---|---|---|
| Austenitic Grades | 75 ksi | 30 ksi | 192 |
| MT410 | 70 ksi | 40 ksi | 207 |
| MT430 | 65 ksi | 30 ksi | 190 |
Cold-worked tubing is available for higher strength applications.
Cold Finished ASTM A511 Tubing Tolerances
Cold-worked ASTM A511 mechanical tubing provides superior surface finish and tighter dimensional accuracy compared to hot finished material. The following table outlines permissible variations for outside diameter (OD), wall thickness, ovality, and cut length.
| Size (Inches) | OD Tolerance (Over/Under) | Wall Thickness Tolerance (%) | Cut Length (Inches) | Ovality (Double OD Tol. when wall is:) |
|---|---|---|---|---|
| Under 1/2 | 0.005" | 15% | +1/8, –0 | Less than 0.015" |
| 1/2 to 1-1/2 excl. | 0.005" | 10% | +1/8, –0 | Less than 0.065" |
| 1-1/2 to 3-1/2 excl. | 0.010" | 10% | +3/16, –0 | Less than 0.095" |
| 3-1/2 to 5-1/2 excl. | 0.015" | 10% | +3/16, –0 | Less than 0.150" |
| 5-1/2 to 8 excl. | 0.030" | 10% | +3/16, –0 | Less than 0.240" |
| 8 to 8-5/8 excl. | 0.045" | 10% | +3/16, –0 | Less than 0.300" |
Hot Finished ASTM A511 Tubing Tolerances
Hot-finished tubing is an economical choice for applications where the tightest tolerances are not required, but mechanical strength is essential.
Permissible Variations in Wall Thickness (%)
| Outside Diameter (In.) | OD Tol. (Over/Under) | ≤ 0.109" Wall | 0.109–0.172" Wall | 0.172–0.203" Wall | > 0.203" Wall | Cut Length (Over/Under) |
|---|---|---|---|---|---|---|
| Under 3 | 0.023" | 16.5% | 15% | 14% | 12.5% | 3/16" / 0 |
| 3 to 5-1/2 excl. | 0.031" | 16.5% | 15% | 14% | 12.5% | 3/16" / 0 |
| 5-1/2 to 8 excl. | 0.047" | — | 14% | 14% | 12.5% | 3/16" / 0 |
| 8 to 10-3/4 excl. | 0.047" | — | — | — | 12.5% | 3/16" / 0 |
| 10-3/4 to 12-3/4 | 0.063" | — | — | — | 12.5% | 3/16" / 0 |
ASTM A511 Seamless Mechanical Tube Dimensions
Finish: H.F
| Size OD, Inches | Wall Inches | Wall Decimal | ID | Weight Lbs./Ft. |
|---|---|---|---|---|
| 1 | 3/16 | 0.188 | 0.624 | 1.630 |
| 1/4 | 0.250 | 0.500 | 2.003 | |
| 1-1/4 | 3/16 | 0.188 | 0.874 | 2.132 |
| 1/4 | 0.250 | 0.750 | 2.670 | |
| 1-1/2 | 3/16 | 0.188 | 1.124 | 2.634 |
| 1/4 | 0.250 | 1.000 | 3.338 | |
| 3/8 | 0.375 | 0.750 | 4.506 | |
| 1-3/4 | 3/16 | 0.188 | 1.374 | 3.136 |
| 1/4 | 0.250 | 1.250 | 4.005 | |
| 3/8 | 0.375 | 1.000 | 5.507 | |
| 2 | 3/16 | 0.188 | 1.624 | 3.638 |
| 1/4 | 0.250 | 1.500 | 4.673 | |
| 3/8 | 0.375 | 1.250 | 6.508 | |
| 1/2 | 0.500 | 1.000 | 8.010 | |
| 2-1/8 | 3/16 | 0.188 | 1.749 | 3.889 |
| 1/4 | 0.250 | 1.625 | 5.006 | |
| 5/16 | 0.313 | 1.500 | 6.057 | |
| 7/16 | 0.438 | 1.250 | 7.891 | |
| 2-1/4 | 3/16 | 0.188 | 1.874 | 4.140 |
Applications of ASTM A511 Tube
- Hydraulic cylinder barrels
- Rollers & shafts
- Hollow machined components
- Food processing equipment
- Marine structural parts
- Wastewater systems
- Industrial fixtures
Contact us for ASTM A511 tubing, ASTM A511 tube hollow bar, or MT304 / MT316 mechanical tubing requirements, submit your specifications including OD, wall thickness, finish, and length requirement.
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