STAINLESS STEEL TUBE & PIPE   

The physical properties of Types 321 and 347 are quite similar and, for all practical purposes, may be considered to be the same. The values given in the table may be used to apply to both steel.

When properly annealed, the Alloys 321 and 347 stainless steel pipe consist principally of austenite and carbides of titanium or columbium. Small amounts of ferrite may or may not be present in the microstructure. Small amounts of sigma phase may form during long time exposure in the 1000°F to 1500°F (593°C to 816°C) temperature range.

The stabilized Alloys 321 and 347 stainless steel are not hardenable by heat treatment.

The overall heat transfer coefficient of metals is determined by factors in addition to thermal conductivity of the metal. In most cases, film coefficients, scaling, and surface conditions are such that not more than 10 to 15% more surface area is required for stainless steel tubing than for other metals having higher thermal conductivity. The ability of stainless steel to maintain clean surfaces often allows better heat transfer than other metals having higher thermal conductivity.

Magnetic Permeability
The stabilized Alloys 321 and 347 are generally non-magnetic in the annealed condition with magnetic permeability values typically less than 1.02 at 200H. Permeability values may vary with composition and will increase with cold work. Permeability of welds containing ferrite will be higher.

Back to 321/321H

Physical Properties of Stainless Steel