Stainless Steel 310S Tubes | Welded & Seamless | UNS S31008

Stainless steel 310S tubes refers to welded (ASTM A249) or seamless (ASTM A213) boiler, superheater, heat-exchanger and condenser tubes made from austenitic stainless steel TP310S. It is a modified version from 304 stainless steel with increased chromium and nickel for improved strength and better oxidation resistance at elevated temperatures. The primary feature of TP310S tubes is their excellent oxidation and corrosion resistance, especially at high temperatures up to 1500°F [816°C]. Type 310S welded or seamless tubes are widely used in applications requiring excellent heat and corrosion resistance, including furnaces for radiant tubes and burner parts, heat exchangers in petrochemical and chemical processing, and power generation for superheaters and reheaters. They are also utilized in the high-temperature sections of cement kilns and in the petrochemical industry where high temperatures and corrosive environments demand durable, heat-resistant tubing. Moreover, 310S stainless steel is considered to be metallurgically stable for all conditions of cryogenic exposure. Therefore, it is used for instrument tubing in which maximum stability and a high degree of toughness are required at cryogenic temperatures.

Chemical Composition Requirements

ASTM A249 TP310S welded tubes in straight length, supplied to Saudi Arabia.

Designated as 25Cr-20Ni, 310S stainless steel tubes has the UNS number S31008. It shall meet the following composition requirements:

• Chromium (Cr): 24.0–26.0%
• Nickel (Ni): 19.0–22.0%
• Carbon (C): 0.08% max
• Manganese (Mn): 2.00% max
• Silicon (Si): 1.00% max
• Phosphorus (P): 0.045% max
• Sulfur (S): 0.030% max
• Iron (Fe): Balance

Mechanical Properties

The tensile and hardness test results of Type 310S tubes made to ASTM A249 or ASTM A213 shall meet the following requirements:

• Tensile Strength (min): 515 MPa (75 ksi)
• Yield Strength (min): 205 MPa (30 ksi)
• Elongation in 2″ (min): 35%
• Hardness (max): 192 HBW; 200 HV; 90 HRB

Manufacture & Inspection

Type 310S seamless stainless steel tubes shall be made by the seamless process and shall be either hot rolled or cold rolled in accordance with ASTM A213. Type 310S welded stainless steel tubes shall be made from flat-rolled steel strips by an automatic welding process with no addition of filler metal. Solution treatment shall be performed as the final heat treatment, in which the Type 310S tubes are heated to a temperature higher than 1900°F [1040°C], holding for sufficient long time, and then rapidly cooled by water.

ASTM A213 TP310S seamless U tubes, supplied to a heat-exchanger manufacturer in Romania.

A set of tests and inspection shall be conducted to ensure the quality of Type 310S welded or seamless tubes: visual examination, dimensional inspection, tensile test, hardness test, chemical analysis, flattening test, flaring test, flange test (for welded), reverse-bend test (for welded), eddy current test, complete X-ray inspection on the welding seam, ultrasonic test, and hydrostatic test.