1.1 This specification covers seamless stainless tubing for use in mechanical applications or as hollow bar for use in the production of hollow components such as, but not limited to nozzles, reducers, and couplings by machining where corrosion-resistant or high-temperature strength is needed. The grades covered are listed in Table 1, Table 2, and Table 3.

(A) For small diameter or thin wall tubing or both, where many drawing passes are required, a maximum of 0.040 % carbon is necessary in grades MT-304L and MT-316L. Small outside diameter tubes are defined as those under a 0.500 in. [12.7 mm] outside diameter and light-wall tubes as those under a 0.049 in. [1.2 mm] average wall thickness (0.044 in. [1.1 mm] min wall thickness).
(B) Iron shall be determined arithmetically by difference of 100 minus the sum of the other specified elements.
(C) The range of (Al + Ti) shall be within 0.85–1.20 %.
(D) The terms Niobium (Nb) and Columbium (Cb) are alternate names for the same element.
(A) MT446-2 is a lower carbon version of MT446-1, that has a lower tensile strength but improved ductility and toughness.
(B) Carbon plus nitrogen = 0.025 max %.
(A) Maximum, unless a range or minimum is indicated. Where ellipses (…) appear in this table, there is no requirement and analysis for the element need not be determined or reported.
(B) % Cr + 3.3 X % Mo + 16X % N ≥ 40.
1.2 This specification covers seamless cold-finished mechanical tubing and hollow bar and seamless hot-finished mechanical tubing and hollow bar in sizes up to 123/4 in. [325 mm] in outside nominal diameter (for round tubing) with wall thicknesses or inside diameters as required.

1.3 Tubes for mechanical applications shall be furnished in one of the following shapes, as specified by the purchaser: round, square, rectangular, or special. Tubes to be used as hollow bar shall be furnished in round shape.

1.4 Optional supplementary requirements are provided and when desired, shall be stated in the order.

1.5 The values stated in inch-pound units are to be regarded as the standard. Within the text, the SI units are shown in square brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other.

ASTM Standards

A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
A1016/A1016M Specification for General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes
A1058 Test Methods for Mechanical Testing of Steel Products--Metric
E112 Test Methods for Determining Average Grain Size

Military Standards

MIL-STD-129 Marking for Shipment and Storage

Federal Standard

Fed. Std. No. 123 Marking for Shipments (Civil Agencies)