The Differences between ASTM A403 and WP304 Fittings

A403 is ASTM standard for forged austenitic stainless steel pipe fittings.  WP304 is a kind of material in ASTM A403 standard. In ASTM A403 standard, according to the size and pressure grade of ASME or MSS standard, the grade of stainless steel pipe parts is expressed with prefix WP or CR.

Let's start with the details of ASTM A403 standard.There are several grades of austenitic stainless steel alloys areincluded in this specification Grades are designated with aprefix, WP or CR, based on the applicable ASME or MSS dimensional and rating standards, respectively.

Fitting Classes for WP Grades：

The Common Names：

Manufacture Specification in ASTM A403

• All fittings shall be heat treated in accordance.

• Grade WP fittings ordered as Class S shall be of seamless construction and shall meet all requirements of ASME B16.9, B16.28, or MSS SP-79.

• Grade WP fittings ordered as Class W shall meet the requirements of ASME B16.9 or B16.28.

• Grade WP fittings ordered as Class WX and Class WU shall meet the requirements of ASME B16.9 or B16.28 and shall have all welds, whether made by the fitting manufacturer or the starting material manufacturer,radiographically examined throughout their entire length.

• Class WP-W—Radiographic inspection of the welds,

• made with the addition of filler metal, is required .

• Class WP-WX— Radiographic inspection of all welds, made with or without the addition of filler metal, is required .

• Class WP-WU— Ultrasonic inspection of all welds,made with or without the addition of filler metal, is required.

• Class CR nondestructive examination is not required.

Specific Requirements 

Tensile Properties

Grade 304 Steel Materials

 Characteristics and Data  for WP304 stainless Steel 

• Tensile strength σb (MPa)≥520

• Conditional yield strength σ0.2 (MPa)≥205

• Elongation δ5 (%)≥40

• Shrinkage ratio of cross-section (%)≥60

• Hardness: ≤187HBW;  90 HRB or less;  200 hv or less

• Density (20℃, g/cm3) : 7.93

• Melting point (℃) : 1398~1454

• Specific heat capacity (0~100℃, KJ·kg-1K-1) : 0.50

• Thermal conductivity (W·m-1·K-1) : (100℃) 16.3, (500℃) 21.5

• Linear expansion coefficient (10-6·K-1) : (0~100℃) 17.2, (0~500℃) 18.4

• Resistivity (20℃, 10-6Ω·m) : 0.73

• Longitudinal modulus of elasticity (20℃, KN/mm2) : 193

  
  

  
  

WP304 stainless steel is suitable for a wide range of pipe fittings, such as butt welded  fittings, socket weld fittings, threaded pipe fittings, steel pipe, forged steel outlet, forged flange, etc.