The ASTM A269 tubing refers to series of seamless or welded austenitic stainless steel tubing for general corrosion-resisting and low- or high-temperature service. The tubing or tube is generally furnished with round cross section in either straight-cut length or coil. Among all austenitic stainless steels, TP304, TP304L, TP316 and TP316L are the most widely used grades and are often found available in stock.
The tubing sizes and thicknesses usually furnished to ASTM A269 are 1/4″ [6.4 mm] in inside diameter and larger and 0.020″ [0.51 mm] in nominal wall thickness and heavier. The wall thickness is normally given in decimal parts of an inch rather than as a fraction or gauge number. When gauge numbers are given without reference to a system, Birmingham wire gauge (BWG) is implied. Conventional outside diameters available are 0.250″, 0.312″, 0.375″, 0.500″, 0.625″, 0.750″, 0.875″, 1.000″, 1.250″, 1.500″, 2″. And some prevalent wall thicknesses are 0.035″[BWG 20], 0.049″[BWG 18], 0.065″[BWG 16], 0.083″[BWG 14], 0.095″[BWG 13], 0.109″[BWG 12], 0.120″[BWG 11].
ASTM A269 tubing, made of grades TP304 and TP316 as well as their low carbon version TP304L and TP316L, exhibits good corrosion resistance in atmospheric industrial and marine environments as well as some oxidizing chemical environments. Especially, TP316 & TP316L offer enhanced resistance to pitting corrosion in chloride solution. The low carbon version TP304L or TP316L reduces sensitization significantly and provides much better welding performance. The tubing has outstanding impact toughness at low or cryogenic temperatures. It maintains long life span at elevated temperatures and under other severe conditions.
The ASTM A269 tubing are widely used in instrumentation piping to connect various piping, valves, instruments and apparatuses, or to measuring equipment. They may be used for high purity gas piping, fine chemical engineering, sampling & analysis system, hydraulic line, chemical and petrochemical process control, coal processing, as well as automotive engineering. Especially, grades TP304, TP304L, TP316 and TP316L of ASTM A269 are listed and endorsed by ASME B31.3 – process piping.
ASTM A269 tubes are generally furnished in seamless type. The starting austenitic stainless steel shall be made by a continuous casting process, which usually involves an electric melting process and an argon oxygen process. The seamless tubing shall be made by a seamless process, in which the mandrel piercing through the billet between the rolls of a rotary piercing mill is treated is conducted for several passes. The finished tubing shall be solution annealed at a temperature no less than 1900°F [1040°C] and soaks for a time long enough to dissolve all carbides, followed by a quench in cold water. Generally, solution annealing shall be done in vacuum or cracked ammonia atmosphere, which is known as bright annealing. It helps to obtain a smooth (bright) and aesthetic surface appearance. If the tubing is not bright annealed, good surface finish may be obtained from a mechanical or electrochemical polishing process.