ASTM A312 is a standard specification specifically for seamless and welded austenitic stainless steel pipes. It is intended for use in high-temperature and corrosive environments, commonly applied in industries such as chemical processing, oil, and gas. This standard defines the chemical composition, mechanical properties, dimensional requirements, and other inspection methods for the materials. A312 includes various grades of stainless steel, such as TP304 and TP316, to meet different usage requirements and conditions.
Scope of ASTM A312 Pipe
ASTM A312 specification covers:
Seamless, straight-seam welded, and heavily cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service.
ASTM A312 Pipe Manufacture
| Process Options |
| – The pipe shall be manufactured by one of the following processes: |
| – Seamless (SML) pipe shall be made by a process that does not involve welding at any stage of production. |
| – Welded (WLD) pipe shall be made using an automatic welding process with no addition of filler metal during the welding process. |
| – Heavily cold-worked (HCW) pipe shall be made by applying cold working of not less than a 35% reduction in the thickness of both the wall and the weld to a welded pipe prior to the final anneal. |
| – No filler shall be used in making the weld. |
| – Prior to cold working, the weld shall be 100% radiographically inspected in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, latest revision, Paragraph UW-51. |
| Weld Requirements |
| – Welded pipe and HCW pipe of NPS 14 and smaller shall have a single longitudinal weld. |
| – Welded pipe and HCW pipe larger than NPS 14 shall have a single longitudinal weld or shall be produced by forming and welding two longitudinal sections of flat stock when approved by the purchaser. |
| – All weld tests, examinations, inspections, or treatments shall be performed on each weld seam. |
| Finish Options |
| – At the option of the manufacturer, the pipe shall be either hot finished or cold finished. |
| Cleanliness Requirements |
| – The pipe shall be free of scale and contaminating exogenous iron particles. |
| – Pickling, blasting, or surface finishing is not mandatory when the pipe is bright annealed. |
| – The purchaser is permitted to require that a passivating treatment be applied to the finished pipe. |
ASTM A312 Pipe Heat Treatment
All pipe shall be furnished in the heat-treated condition in accordance with the requirements
| Grade or UNS Designation | Heat Treating Temperature | Cooling/Testing Requirements |
| TP304H, TP316H | ||
| Cold finished | 1900°F [1040°C] | Quenched in water or rapidly cooled by other means. |
| Hot finished | 1900°F [1040°C] |
ASTM A312 Pipe Chemical Composition
| Grade | UNS Designation | Chemical Composition,% | ||||||||
| Carbon | Manganese | Phosphorous | Sulfur | Silicon | Chromium | Nickel | Molybdenum | Nitrogen | ||
| TP304 | S30400 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-11.0 | ||
| TP304L | S30403 | 0.035 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-13.0 | ||
| TP316 | S31600 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 16.0-18.0 | 11.0-14.0 | 2.00-3.00 | |
| TP316L | S31603 | 0.035 | 2.00 | 0.045 | 0.030 | 1.00 | 16.0-18.0 | 10.0-14.0 | 2.00-3.00 | |
| TP321 | S32100 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 17.0-19.0 | 9.0-12.0 | 0.10 | |
ASTM A312 Tensile Requirements
| Grade | UNS Designation | Tensile Strength, min ksi [MPa] | Yield Strength, min ksi [MPa] |
| TP304 | S30400 | 75 [515] | 30 [205] |
| TP304L | S30403 | 70 [485] | 25 [170] |
| TP304H | S30409 | 75 [515] | 30 [205] |
| TP316 | S31600 | 75 [515] | 30 [205] |
| TP316L | S31603 | 70 [485] | 25 [170] |
| TP316H | S31609 | 75 [515] | 30 [205] |
ASTM A312 Pipe Permissible Variations in Dimensions
Permitted Variations in Wall Thickness
The wall thickness for seamless and welded pipe at any point shall be within the tolerances specified in Table 1, except that for welded pipe the weld area shall not be limited by the “Over” tolerance. The wall thickness and outside diameter for inspection for compliance with this requirement for pipe ordered by NPS and schedule number is shown in Dimensions of Welded and Seamless Stainless Steel Pipe PDF
| Table 1 | Tolerance, % from Nominal | |
| NPS Designator | Over | Under |
| ⁄8 to 21⁄2 incl., all t/D ratios | 20.0 | 12.5 |
| 3 to 18 incl., t/D up to 5 % incl. | 22.5 | 12.5 |
| 3 to 18 incl., t/D > 5 % | 15.0 | 12.5 |
| 20 and larger, welded, all t/D ratios | 17.5 | 12.5 |
| 20 and larger, seamless, t/D up to 5 % incl. | 22.5 | 12.5 |
| 20 and larger, seamless, t/D > 5 % | 15.0 | 12.5 |
- where:
- t= Nominal Wall Thickness
- D= Ordered Outside Diameter
Lengths
- All sizes from NPS 1⁄8 to and including NPS 8 are available in lengths up to 24 ft ，with a permissible range of 15 to 24 ft.
- Short lengths are acceptable, and the number and minimum length must be agreed upon between the manufacturer and the purchaser.
- If definite cut lengths are desired, they should be specified in the order.
- No pipe shall be less than the specified length and not more than 1⁄4 in. [6 mm] over that specified.
- No jointers are permitted unless otherwise specified.
Marking Requirements
In addition to the marking specified in Specification A 999/A 999M, the marking shall include the following:
- NPS (nominal pipe size) or outside diameter and schedule number or average wall thickness
- Heat number
- NH when hydrotesting is not performed
- ET when eddy-current testing is performed
- UT when ultrasonic testing is performed
- Manufacturer’s private identifying mark
- Marking requirement of 12.3, if applicable
- Indication of whether the pipe is seamless (SML), welded (WLD), or heavily cold-worked (HCW)
For Grades TP304H, TP316H, TP321H, TP347H, TP348H, and S30815, the marking shall also include the heat number and heat-treatment lot identification. If specified in the purchase order, the marking for pipe larger than NPS 4 shall include the weight.
Ordering Requirements
When placing orders for material to this specification, the following details should be included as necessary to adequately describe the desired material:
1.Quantity: Specify in feet, centimeters, or number of lengths.
2.Name of Material: Indicate “austenitic steel pipe.”
3.Process: Specify “seamless (SML),” “welded (WLD),” or “heavily cold worked (HCW).”
4.Grade: Refer to Table 1 for the specific grade.
5.Size: Provide NPS or outside diameter, along with schedule number or average wall thickness.
6.Length: Indicate whether specific or random.
7.End Finish: Refer to the section on ends in Specification A 999/A 999M.
8.Optional Requirements: Include product analysis or hydrostatic/nondestructive electric test.
9.Test Report Required: Specify certification as per the Certification Section of Specification A 999/A 999M.
10.Specification Number: Include the relevant specification number.
11.Special Requirements: List any special or supplementary requirements selected, or both.
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FAQ
These pipes are commonly used in industries such as chemical processing, oil and gas, power generation, and food processing.
Yes, testing methods such as hydrostatic testing, eddy-current testing, and ultrasonic testing may be specified, depending on the application.
Pipes are available in various sizes, generally ranging from NPS 1/8 to NPS 30 or larger, depending on the grade and manufacturer.
Ensure that the supplier provides certification and documentation proving that the pipes meet the ASTM A312 specifications.
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