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321 TP321 stainless steel seamless pipe tube tubing
Stainless steel seamless pipes Written by admin on 04/24/2010 – 4:52 pm 
Grades of Stainless Steel Semaless pipe- Grade 321
SX 321 Technical Data

Summary

SX 321 is a titanium-stabilised version of SX 304, used in particular applications within the sensitizing temperature range.  Its resistance to sensitization, coupled with its higher strength at high temperature makes it suitable in application where SX 304 will become sensitized, or where SX 304L has insufficient hot strength.  It is not subject to weld decay (intergranular corrosion) when exposed to mildly corrosive environments.  However, welded SX 321 must never be used in highly oxidising environments as it is liable to ‘Knife-line’ attack.

Typical Applications

SX 321 is today used almost exclusively for service within the sensitizing temperature range (450-850oC).  In welded ambient temperature applications it has been replaced by SX 304L.  Some typical areas of application are:
                Furnace components.
                Superheater and afterburner parts.
                Compensators and expansion bellows.

Chemical Composition (ASTM A240)
 

  C Mn P S Si Cr Ni Ti
SX Analysis 0.08 max 2.0 max 0.045 max 0.030 max 1.0 max 17.0 – 19.0 9.0 – 12.0 5X%C min
0.5 max
Typical 0.06  1.2 0.020 0.020 0.5 17.5 9.4 0.48

Typical Properties in the Annealed Condition

The properties quoted in this publication are typical of mill products.  Unless otherwise indicated they should not be regarded as guaranteed minimum values for specification purposes.

1. Mechanical Properties at Room Temperature
 

  Typical  Minimum
Tensile Strength, MPa 580 515
Proof Stress (0.2 % offset), MPa 280 205
Elongation (Percent in Lo = 5.65 So) 60 40
Hardness (Brinell) 163 -
Endurance (fatigue) limit, MPa 260 -

2. Properties at Elevated Temperatures
Short Time Elevated Temperature Tensile Strength

Temperature, oC 600 650 700 750 800 850
Tensile Strength, MPa 390 329 280 230 190 140

Creep data
Stress to develop a creep rate of 1% in the indicated time at the indicated temperature.

Time Temperature oC 550 600 650 700 800
10 000 h Stress MPa 180 100 70 40 10
100 000 h Stress MPa 120 80 50 25 5

Creep Rupture Stress

Time Temperature oC 500 600 650 700 800
1 000 h Stress MPa 270 180 140 70 30
10 000 h Stress MPa 240 130 90 50 10
100 000 h Stress MPa 200 90 50 15 5

Recommended Maximum Service Temperature
(Oxidising Conditions)

Continuous Service            950oC
Intermittent Service             870oC

Thermal Processing
1.    Annealing Heat  from 1050 to 1150oC and cool in air.  This ensures maximum ductility of the steel.
2.    Stress Relieving SX 321 can be stress-relief annealed within the sensitization temperature range
       450-800oC without carbide precipitation occurring, thus avoiding the possibility of intergranular corrosion.
3.     Hot working
        Initial forging and pressing temperature:              1150  – 1250oC
        Finishing temperature:                                                           950oC
 
Note:  Soaking times to ensure uniformity of temperature are up to 12  times that required for carbon steel.  Care must be exercised with this grade, and long soaking times to ensure even distribution of carbides should be employed.  The initial reductions must be light to allow dispersion of carbides in the flow pattern during forging.

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