ASTM A213 T22 Seamless Tubes

ASTM A213 T22 seamless tubes are a specific type of alloy steel tube designed for high temperature service, commonly used in power plants for the fabrication of steam line boilers, superheaters, reheaters, heat exchangers, as well as headers (to distribute steam or water to various parts of the boiler). Designated as UNS K21590 with nominal composition of 2.25Cr-1Mo, Grade T22 of ASTM A213 is an important family member of the chromium-molybdenum heat-resistant steels. The chromium provides improved oxidation and corrosion resistance, and the molybdenum increases strength at elevated temperatures.

Sizes & Dimensions

ASTM A213 T22 seamless tubes, (OD)50.8mm x (WT)6mm x (L) 6000mm, supplied to Brazil.

ASTM A213 T22 seamless tubes are usually furnished with outside diameter ranging from 1/4” [6.35 mm] to 5” [127 mm] and minimum wall thickness ranging from 0.015” [0.4 mm] to 0.500” [12.7 mm]. Sometimes the wall thickness may be specified in accordance with the Birmingham Wire Gauge (B.W.G) designation. When specified in the purchase order, Grade T22 tubing may be furnished with average wall thickness. The maximum length we can manufacture is 16 meters.

Chemical Composition Requirements

The composition of ASTM A213 T22 tubes is precisely defined to ensure optimal performance under high-temperature conditions. The primary elements and their typical ranges are:

• Chromium (Cr): 1.90-2.60%
• Molybdenum (Mo): 0.87-1.13%
• Carbon (C): 0.05-0.15%
• Manganese (Mn): 0.30-0.60%
• Phosphorus (P): ≤ 0.025%
• Sulfur (S): ≤ 0.025%
• Silicon (Si): 0.50% max

Mechanical Properties

ASTM A213 T22 tubes stored in warehouse to be delivered to Indonesia.

The mechanical properties of ASTM A213 T22 tubes ensure their suitability for high-stress environments:

• Tensile Strength: ≥ 415 MPa (60 ksi)
• Yield Strength: ≥ 205 MPa (30 ksi)
• Elongation: ≥ 30% (in 50 mm gauge length)
• Hardness: ≤ 85 HRB (Rockwell B) or 163 HBW (Brinell)

Manufacture & Heat Treatment

The manufacturing of ASTM A213 T22 seamless tubes involves the following steps: (1) Melting and Casting: The alloy is melted and cast into billets. (2) Billet Preparation: High-quality steel billets are selected and cut to the required length. (3) Heating: The billets are heated to a high temperature to make them malleable. (4) Piercing: The heated billets are pierced to create a hollow tube (rough tube). (5) Extrusion: The hollow billets are then extruded to form the seamless tubes. This process involves forcing the billet through a die to achieve the desired tubing shape and size. (6) Cold Drawing or Rolling: To achieve precise dimensions and improve mechanical properties, the tubes may undergo multi-pass cold drawing or rolling.

The fabrication of ASTM A213 T22 seamless tubes, (OD)38.1mm x (WT)5mm x (L)11800mm, in the packaging workshop of our pipe mill.

ASTM A213 T22 seamless tube may be subjected to one of the two main heat treatment processes to achieve the desired mechanical properties and performance characteristics for high-temperature applications: (1) Full or isothermal annealing: The tubes are heated to a temperature range of 900-950℃ (1652-1742℉) and held at this temperature to allow for complete transformation. They are then cooled slowly, usually in the furnace. This process helps to relieve internal stresses, improve ductility, and refine the grain structure. (2) Normalizing and tempering: The tubes are heated to a temperature above their critical range, typically around 920-960℃ (1688-1760℉), and then air-cooled. Normalizing refines the grain structure, enhances mechanical properties, and improves machinability. After normalizing, the tubes are tempered at a temperature of 675℃ (1247℉) or higher. Tempering reduces brittleness, increases toughness, and enhances the overall mechanical properties of the tubes.

Test & Inspection

Heat analysis, tensile test, hardness test, flattening test, flaring test, hydrostatic test, eddy current test, dimensional examination, and visual inspection.

Maximum Temperature & Allowable Stress

ASTM A213 T22 seamless tubes are designated with P Number 5A and Group Number 1. The use of T22 tubes are endorsed by a series of ASME Codes. The maximum temperatures for the use of these tubes under different conditions are listed below:

• • ASME B31.1 Power Piping: 1100℉
  • ASME BPVC Section I: 1200℉
  • ASME BPVC Section III Class 2 & 3: 700℉
  • ASME BPVC Section VIII, Division 1: 1200℉
  • ASME BPVC Section VIII, Division 2: 1200℉

The maximum allowable stress values for ASTM A213 T22 seamless tubes for various metal temperatures are listed in below tables for design reference.