ASTM A312 TP316L Seamless Pipe: Specification and Data
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What Is ASTM A312 TP316L Seamless Pipe?
ASTM A312 is the standard specification for seamless, welded and heavily cold-worked austenitic stainless steel pipe for general corrosive service. TP316L is the low-carbon grade of 316, designated UNS S31603, with a carbon limit of 0.035 percent maximum. The low carbon content prevents chromium carbide precipitation during welding, preserving corrosion resistance in the heat-affected zone, while the molybdenum content of 2.0 to 3.0 percent provides outstanding resistance to pitting and crevice corrosion in chloride environments. ASME SA312 is the identical specification adopted for pressure vessel and piping code applications.
Seamless pipe of this grade is manufactured from solid round billets by hot piercing and then cold rolling or cold drawing to the finished size, which gives higher dimensional accuracy and a uniform wall than welded equivalents. It is widely stocked in schedules from SCH5 to SCH160 and XXS, in forms including round, square, rectangular, U-shape and coiled tubes.
Chemical Composition
The chemical requirements for TP316L pipe to ASTM A312 are listed below.
| Element | Composition, % |
|---|---|
| Carbon, max | 0.035 |
| Manganese, max | 2.00 |
| Phosphorus, max | 0.045 |
| Sulfur, max | 0.030 |
| Silicon, max | 1.00 |
| Chromium | 16.0 - 18.0 |
| Nickel | 10.0 - 14.0 |
| Molybdenum | 2.00 - 3.00 |
Mechanical Properties and Heat Treatment
In the solution-annealed condition, TP316L pipe must meet the tensile requirements below.
| Property | ksi | MPa |
|---|---|---|
| Tensile strength, min | 70 | 485 |
| Yield strength, min | 25 | 170 |
The pipe is furnished in the annealed condition; the standard solution annealing temperature is 1900 F, equivalent to 1040 C, followed by water quenching or another rapid cooling method. For welded pipe, the filler metal is normally ER316L to AWS A5.9, which matches the base metal in composition and corrosion resistance.
Sizes, Schedules and Finishes
Outside diameter: from 6.0 mm up to 250 mm, or up to 12 inch nominal bore for standard stock.
Wall thickness schedules: SCH5, SCH10, SCH40, SCH40S, SCH80, SCH80S, SCH160, XXS and all intermediate schedules.
Lengths: single random, double random or cut to length.
Surface finishes: 2B, No.1, No.4 and No.8 mirror finish.
Delivery conditions: annealed and pickled, polished, or bright annealed.
Typical Applications
Chemical and petrochemical process piping handling chlorides and mild acids.
Seawater and coastal cooling water systems.
Food, beverage and pharmaceutical processing lines.
Pulp and paper bleach plants.
Oil and gas utility and instrumentation lines.
Selection, Testing and Marking Points
Confirm that the pipe is ordered to ASTM A312 or ASME SA312 with the grade TP316L and the required schedule and surface finish. Before delivery the pipe should be hydrostatically tested or non-destructively tested by eddy current or ultrasonic methods, and mechanical tests and chemical analysis should be reported on the mill certificate. Marking must comply with ASTM A1016/A1016M and include the standard, grade, size, heat number and batch number, together with the indication of whether the pipe is hot-worked or cold-worked. Where a high degree of surface cleanliness is required, polishing, electropolishing or pickling can be specified as a value-added operation.
Frequently Asked Questions
What does TP316L stand for?
TP indicates tubing or pipe grade in the ASTM designation system, 316 is the base austenitic grade, and L stands for low carbon, meaning the maximum carbon content is limited to 0.035 percent.
Is TP316L the same as UNS S31603?
Yes. TP316L is the ASTM grade name and UNS S31603 is the unified numbering system designation for the same material.
What is the maximum continuous operating temperature of 316L pipe?
316L is suitable for continuous service up to about 925 C in oxidising atmospheres for non-pressure parts, but for pressure-retaining design the allowable stress at the service temperature must be checked against the applicable code; at high temperatures the low carbon grade has lower creep strength than 316H.
Does 316L pipe require post-weld heat treatment?
No. The low carbon content avoids sensitisation, so welded 316L pipe can be placed in service without post-weld heat treatment in most corrosive environments.
How can I verify the grade of delivered 316L pipe?
Check the stencil marking required by ASTM A1016/A1016M, which identifies the standard, grade, size, heat number and batch number, and cross-check with the mill certificate and chemical analysis.
