Selection overview
ASTM A513 tubing types
The type designation communicates manufacturing route. It should be explicit on a purchase order rather than inferred from a trade nickname.
On this page
The short answer
A513 tubing types are lettered and numbered manufacturing routes, not quality grades. Type 1a is as-welded from hot-rolled strip carrying mill scale; Type 1b is as-welded from hot-rolled pickled-and-oiled strip. Type 2 is as-welded from cold-rolled strip. Types 3 and 4 are sink-drawn routes — Type 3 from hot-rolled steel and Type 4 from cold-rolled steel. Type 5 (DOM) is cold drawn over a mandrel for the tightest dimensional relationships in the family. Type 6 is the special smooth inside diameter (SSID) route, produced for applications where the ID surface condition is the controlling requirement.
Higher type numbers are not automatically better — they are different processes with different capabilities and costs. Choose the least-processed route that reliably meets the finished part's requirements.
How the types differ
Types 1a, 1b, and 2 are as-welded routes differentiated by starting strip: hot-rolled with mill scale, hot-rolled pickled-and-oiled, and cold-rolled respectively. Types 3 and 4 are sink drawn — through a die without an internal mandrel — from hot-rolled and cold-rolled steel respectively. Type 5 is drawn over a mandrel. Type 6 is the special smooth inside diameter route.
- Do not describe DOM as seamless: it begins as welded tubing
- Cold work can change dimensions, surface, and mechanical response
- Availability depends on size, shape, grade, and producer capability
| Route | Process family | Typical distinguishing character | Typical relative cost |
|---|---|---|---|
| Type 1a | As-welded, hot-rolled strip (mill scale) | Baseline for the family | Lowest |
| Type 1b | As-welded, hot-rolled pickled-and-oiled strip | Scale-free surface vs 1a | Low |
| Type 2 | As-welded, cold-rolled strip | Generally tighter than Type 1 | Low |
| Type 3 | Sink drawn, hot-rolled steel | OD-focused drawn control | Moderate |
| Type 4 | Sink drawn, cold-rolled steel | OD-focused control, cleaner start | Moderate |
| Type 5 (DOM) | Welded then drawn over mandrel | Tightest in the family | Highest |
| Type 6 (SSID) | Special smooth inside diameter | ID surface condition | High |
Selection questions
Ask what the finished component needs: outside- and inside-diameter control, wall consistency, surface quality, weld-zone behavior, formability, machinability, or lowest viable conversion cost.
Then ask the supplier what their equipment actually holds for your size, shape, and grade. Published capability and demonstrated capability are not the same thing, and the standard allows negotiated requirements that exceed its defaults.
Common specification mistakes
The most frequent errors we see: ordering by nickname (“DOM” or “HREW”) without a type designation; assuming a higher type number guarantees a specific tolerance without stating it; and carrying a type from an old drawing into a new size range where a different route would be more economical or more available.
Sources and limitations
- ASTM A513/A513M — Standard Specification for Electric-Resistance-Welded Carbon and Alloy Steel Mechanical Tubing — ASTM International. Controlling specification for types, tolerances, and ordering requirements. Purchase the current edition for all normative values.
These sources inform the qualitative guidance on this page. This publication does not reproduce their text, tables, numerical settings, or acceptance criteria. Normative requirements come only from the purchased current edition of the governing standard and your supplier agreement.