ASTM A554 MT-304 Stainless Steel Welded Tube for Architectural Purposes

What Is ASTM A554?

ASTM A554 covers welded stainless steel mechanical tubing produced from flat-rolled strip or sheet by automatic welding without the addition of filler metal. It is a mechanical tubing standard, not a pressure piping standard: the tube is intended for structural, architectural, automotive and furniture applications where surface quality, dimensional accuracy, mechanical properties and corrosion resistance are the primary requirements. Grades covered include the austenitic types MT-301, MT-304, MT-304L, MT-316 and MT-316L, and the ferritic types MT-429, MT-430 and MT-430Ti. The designation MT-304, widely referred to in the market as TP304, corresponds to Type 304. Equivalent designations include JIS G3446 SUS304TK and CNS 5802 304TK.

The composition limits below follow ASTM A554 for MT-304.

	MT-304
	0.08
	2.0
	0.045
	0.030
	1.0
	18.0-20.0
	8.0-10.5

Minimum tensile requirements per ASTM A554 for the MT-304 grade are listed below.

	MT-304
	515
0.2% yield strength, min (MPa)	205
Elongation in 50 mm, min (%)	35

Because A554 is a mechanical tubing standard, the tube is not rated for internal pressure service; pressure-containing piping should be specified to ASTM A312, A269 or the applicable ASME code.

MT-304 tube is manufactured by roll-forming strip into a tubular shape and joining the edges by automatic welding, typically high-frequency electric resistance welding. The weld seam is then cold worked or annealed to refine the structure, and the tube is straightened, cut to length and finished. Because the standard is used mainly for visible architectural and furniture components, surface quality is critical; common finishes are satin, brushed and mirror-polished, and decorative shapes such as square, rectangular, round and oval sections are produced in a wide range of sizes, including round diameters from about 95 mm to 140 mm and larger structural sections with wall thicknesses from about 0.6 mm to 3.05 mm.

ASTM A554 tube is available in round, square and rectangular sections, and special shapes on request. Typical applications include handrails and guardrails, balustrades, architectural framing, shop fronts and display fixtures, furniture frames, automotive trim and exhaust components, food service equipment frames, and light structural members where the appearance of stainless steel is required. When choosing between MT-304 and MT-316, apply the same rule as for the parent grades: MT-304 for dry interior and mildly corrosive service, and MT-316 for coastal, marine or chloride-exposed locations.

Is ASTM A554 tube suitable for pressure service? No. A554 is a mechanical tubing standard for structural and architectural use; pressure applications require ASTM A312, A269 or ASME code pipe.

What does MT mean in MT-304? MT denotes mechanical tubing in ASTM A554; the grade carries the same chemistry as Type 304 with minimum mechanical properties for structural use.

What is the difference between MT-304 and TP304? MT-304 is the A554 mechanical tubing designation; TP304 is the A312 pressure pipe designation. The chemistry is similar but the service ratings differ.

Satin, brushed and mirror-polished finishes are standard, with the choice depending on the architectural or functional requirement.

Can A554 tube be welded during installation? Yes, the austenitic grades weld readily with standard techniques; the tube itself is produced by automatic welding without filler metal.

JIS G3446 SUS304TK and CNS 5802 304TK are the Japanese and Taiwanese equivalents of MT-304.

Q1. Which grades are covered by ASTM A554?
The austenitic types MT-301, MT-304, MT-304L, MT-316 and MT-316L, and the ferritic types MT-429, MT-430 and MT-430Ti.

Q2. How is MT-304 tube manufactured?
Strip is roll-formed into a tubular shape and the edges are joined by automatic welding, typically high-frequency electric resistance welding; the weld seam is then cold worked or annealed.

Q3. What is the chemical composition of MT-304?
Carbon 0.08 max, manganese 2.0 max, silicon 1.0 max, chromium 18.0-20.0 and nickel 8.0-10.5.

Q4. When should MT-316 be selected over MT-304?
MT-304 suits dry interior and mildly corrosive service, while MT-316 is chosen for coastal, marine or chloride-exposed locations, following the same rule as the parent grades.

Q5. What are the minimum tensile requirements of MT-304?
Tensile strength 515 MPa min, 0.2% yield strength 205 MPa min and elongation 35% min in 50 mm.