ASTM A403 Stainless Steel Pipe Fittings refers to the material of forged and rolled austenitic stainless fittings for pressure pipes. Common grades are WP304/L, WP316/L. They can be used into many fields as engineering industry, energy conversion plants etc.

ASTM A403 Standard Scope

The standard includes several grades of austenitic stainless steel alloys, and uses the WP or CR prefix to mark the grade of steel, depending on the applicable ASTM or MSS size and rated pressure standards.

ASTM A403 is designed for forged steel pipe fittings, Cast pipe fittings are not suitable. (Austenitic stainless steel castings are included in these standard, A351/A351M, A743/A743M and A744/A744M.)

ASTM A403 Pipe Fittings is a standard specification for steel pipe fittings. These pipe fittings have very good ductility, good weldability. These pipe fittings are manufactured in both seamless and welded forms such as elbow, tee, reducers, cap, bend, stub-end, collar, cross, etc. The welding of pipe is done through shielded metal arc welding (SMAW), gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW). In GMAW process an inert gas such as argon, helium, carbon dioxide or a mixture of them are used to prevent atmospheric contamination of the weld. The shielding gas is allowed to flow through the weld gun. The electrode used here is, in a wire form, fed continuously at a fixed rate. 

WP Grade Stainless Steel Pipe Fittings

Material under this standard named as WP Grade, and for each WP grade stainless steel, several categories of pipe fittings are included, to indicate that a seamless or welded structure is used. Class designations are also used to indicate non-destructive testing methods and the extent of non-destructive testing (NDE).

Stainless Steel Pipe Fittings Material

The material used for the pipe fittings shall be the forgings, bars, plates, seamless or welded tubular products specified in the chemical composition table.

Manufacture of Stainless Steel Pipe Fittings

Forming

The forging or forming operation may be performed by hammer forging, press forging, perforating, extrusion, upsetting, rolling, bending, welding or machining, or two or more methods at the same time. The forming process should ensure that no harmful defects are produced on the pipe fittings.

Heat treatment of  Stainless Steel Pipe Fittings

For H grade steel, separate solution heat treatment are required for solution annealing. All pipe fittings should be supplied in heat treated condition. All welding work should be done before heat treatment. Fitting that have been machined directly from solution annealed forgings and bar stocks do not need to be annealed again.

Chemical Composition of Stainless Steel Pipe Fittings

The chemical composition of each cast or furnace steel shall be determined and shall comply with the chemical composition requirements for each grade of material listed in the chemical composition table.

Surface Finish of Stainless Steel Pipe Fittings

Pipe fittings supplied in accordance with this standard shall be visually inspected. The depth of a typical surface discontinuity should be measured.

• Surface crack (fish scales) deeper than 1/64 inch (0.4 mm) should be removed.

• Mechanical flaws deeper than 1/16 inch (1.6 mm) should be removed.

• Except for the above two, the pipe fittings shall not have a surface discontinuity deeper than 5% of the specified nominal wall thickness, and shall have a good machined surface.