321 stainless steel pipe

321 stainless steel pipe



Product Description

321 Stainless Steel Pipe

321 Stainless Steel Pipe

Grades 321 and 347 are the basic austenitic 18/8 steel (Grade 304) stabilised by Titanium (321) or Niobium (347) additions. These grades are used because they are not sensitive to intergranular corrosion after heating within the carbide precipitation range of 425-850°C.

321 stainless steel pipe is the grade of choice for applications in the temperature range of up to about 900°C, combining high strength, resistance to scaling and phase stability with resistance to subsequent aqueous corrosion.Grade 321H is a modification of 321 with a higher carbon content, to provide improved high temperature strength.A limitation with 321 is that titanium does not transfer well across a high temperature arc, so is not recommended as a welding consumable. In this case grade 347 is preferred – the niobium performs the same carbide stabilisation task but can be transferred across a welding arc. Grade 347 is therefore the standard consumable for welding 321.

Grade 347 is only occasionally used as parent plate material.Like other austenitic grades, 321 and 347 have excellent forming and welding characteristics, are readily brake or roll formed and have outstanding welding characteristics.

 

Applications of 321 stainless steel pipe:

Typical compositional ranges for grade 321 stainless steel pipe are given in table 1.
Table 1. Composition ranges for 321 grade stainless steel

 Grade  C  Mn  Si  P  S  Cr  Mo  Ni  N  Other
 321  min.
max
 –
0.08
 2.00  0.75  0.045  0.030  17.0
19.0
 -  9.0
12.0
 0.10 Ti=5(C+N)
0.70
 321H  min.
max
 0.04
0.10
 2.00  0.75  0.045  0.030  17.0
19.0
 -  9.0
12.0
 -  Ti=4(C+N)
0.70
 347  min.
max
 0.08  2.00  0.75  0.045  0.030  17.0
19.0
 -  9.0
13.0
 - Nb=10(C+N)
1.0

Typical mechanical properties for grade 321 stainless steel pipe are given in table 2.
Table 2. Mechanical properties of 321 grade stainless steel

 Grade  Tensile Strength (MPa) min  Yield Strength 0.2% Proof (MPa) min  Elongation (% in 50mm) min  Hardness
 Rockwell B (HR B) max  Brinell (HB) max
 321  515  205  40  95  217
 321H  515  205  40  95  217
 347  515  205  40  92 201