ASTM A403 Standard Specification

ASTM A403 Standard specification covers the standard for wrought austenitic stainless steel fittings for pressure piping applications. ASTM A403 / A403M Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings.

The material for fittings shall consist of forgings, bars, plates, or seamless or welded tubular products. Forging or shaping operations shall be performed by hammering, pressing, piercing, extruding, upsetting, rolling, bending, fusion welding, machining, or by a combination of two or more of these operations. All fittings shall undergo heat-treatment. Chemical and product analyses shall be performed and shall conform to the required chemical composition in carbon, manganese, phosphorus, sulfur, silicon, chromium, molybdenum, and titanium. Tension test shall be done on the fitting material to determine the tensile properties such as yield strength and tensile strength. Fittings supplied under this specification shall be examined visually for surface discontinuities, surface checks, and mechanical marks.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

Wrought Austenitic Stainless Steel Piping Fittings

Chemical Composition (%)

Grade C Mn P S Si Ni Cr Mo
WP 304 0.08 2 0.045 0.03 1 8.0-11.0 18.0-20.0
WP 304L 0.035 2 0.045 0.03 1 8.0-13.0 18.0-20.0
WP 316 0.08 2 0.045 0.03 1 10.0-14.0 16.0-18.0 2.00-3.00
WP 316L 0.035 2 0.045 0.03 1 10.0-16.0 16.0-18.0 2.00-3.00

All values are maximum unless otherwise indicated.

Mechanical properties

Tensile and Elongation Requirements WP304, WP316 WP304L, WP316L
Yield Strength, min, ksi [MPa] 30[205] 25[170]
Tensile Strength, min, ksi [MPa] 75[515] 70[485]
Elongation (1) Longitudinal 28 28
Transverse 20 20

General Scope

1.1 This specification covers wrought stainless steel fittings for pressure piping applications.

1.2 Several grades of austenitic stainless steel alloys are included in this specification Grades are designated with a prefix, WP or CR, based on the applicable ASME or MSS dimensional and rating standards, respectively.

1.3 For each of the WP stainless grades, several classes of fittings are covered, to indicate whether seamless or welded construction was utilized. Class designations are also utilized to indicate the nondestructive test method and extent of nondestructive examination (NDE). Table 1 is a general summary of the fitting classes applicable to all WP grades of stainless steel covered by this specification. There are no classes for the CR grades. Specific requirements are covered elsewhere.

1.4 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.6 This specification does not apply to cast steel fittings. Austenitic stainless steel castings are covered in Specifications A351/A351M, A743/A743M, and A744/A744M.

TABLE 1 Fitting Classes for WP Grades
Class Construction Nondestructive Examination

S Seamless None
W Welded Radiography or Ultrasonic
WX Welded Radiography
WU Welded Ultrasonic

--- Hot flanges by Sunny Steel ---

  • Blind Flanges, BL Flange, BLRF
    The blind flange is used to close ends of piping systems.