ASTM A210 Grade C (ASME SA210 Grade C) is a medium-carbon seamless steel tube specifically designed for use in the manufacture of boiler tubes and boiler flues, including safety ends, furnace wall and support tubes, and superheater tubes.
Grade C has good mechanical properties, with a tensile strength of 485 MPa and a yield strength of 275 MPa.These properties, along with a suitable chemical composition, make ASTM A210 Grade C tubes well-suited for use in high-temperature and high-pressure environments and capable of withstanding the pressures generated by boiler operation.
The tubes shall be made by the seamless process and shall be either hot-finished or cold-finished.
Below is a flow chart of the manufacturing process for cold-finished seamless steel pipe:
So what's the difference between hot-finished and cold-finished seamless steel pipe and how do you choose?
Hot-finished seamless steel pipe is a steel pipe that is rolled or pierced at a high temperature and other processes and then cooled directly to room temperature. Steel pipes in this state usually have better toughness and some strength, but the surface quality may not be as good as cold-finished steel pipes because the heat treatment process may lead to oxidation or decarburization of the surface of the steel pipe.
Cold-finished seamless steel pipe refers to the final processing of steel pipe by cold drawing, cold rolling, and other processes at room temperature. Cold-finished steel pipe has higher dimensional accuracy, and good surface quality, and because cold processing can improve the strength and hardness of the steel pipe, the mechanical properties of cold-finished steel pipe are usually better than those of hot-finished steel pipe. However, a certain amount of residual stress may be generated inside the steel pipe during cold working, which needs to be eliminated by subsequent heat treatment.
Hot-finished steel pipe does not require heat treatment.
Cold-finished tubes shall be subcritical annealed, fully annealed, or normal heat treated after the final cold finishing process.
| Grade | Carbon A | Manganese | Phosphorus | Sulfur | Silicon |
| ASTM A210 Grade C ASME SA210 Grade C |
0.35% max | 0.29 - 1.06% | 0.035% max | 0.035% max | 0.10% min |
A For each reduction of 0.01% below the specified carbon maximum, an increase of 0.06% of manganese above the specified maximum will be permitted up to a maximum of 1.35%.
Tensile Property
| Grade | Tensile strength | Yielding strength | Elongation |
| min | min | in 2 in or 50 mm, min | |
| ASTM A210 Grade C ASME SA210 Grade C |
485 MPa [70 ksi] | 275 MPa [40 ksi] | 30% |
Flattening Test
Tears or breaks occur at the 12 oг 6 o'clock positions on Grade C tubing with sizes of 2.375 in. [60.3 mm] in outside diameter and smaller shall not be considered a basis for rejection.
Specific requirements can be viewed in ASTM A450, item 19.
Flaring Test
Specific requirements can be viewed in ASTM A450, item 21.
Hardness
Grade C: 89 HRBW (Rockwell) or 179 HBW (Brinell).
Each steel pipe shall be subjected to a hydrostatic pressure test or non-destructive electrical test.
Hydrostatic pressure-related test requirements are in accordance with ASTM 450, item 24.
Non-destructive electrical-related experimental requirements are in accordance with ASTM 450, item 26.
Forming operations are necessary for boiler tubes to ensure that the tubes meet the specific needs of the boiler system.
When inserted in the boiler, tubes shall stand expanding and beading without showing cracks or flaws. When properly manipulated, superheater tubes shall stand all forging. welding. and bending operations necessary for application without developing defects.
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