Grades of Stainless Steel - Grade 309

SX 309 Technical Data

Summary

SX 309 is a highly alloyed austenitic stainless steel used for its excellent oxidation resistance, high temperature strength and creep resistance.  The lower nickel content of SX309 improves resistance to sulphur attack at high temperatures.  It is tough and ductile, and can be readily fabricated and machined.  SX 309S is the low-carbon version of SX 309, and is recommended for applications where sensitisation, and subsequent corrosion by high temperature gases or condensates during shutdown may pose a problem.
SX 309 is manufactured to ASTM A 167 and SX 309S to ASTM A240 specifications.

Typical Applications
SX 309 / 309S is used exclusively for its high temperature oxidation resistance.  It is common for SX 309, 310 and 321 to be used in the same piece of equipment in the various temperature regions.

Chemical Composition (ASTM A240)
 

SX	C	Mn	P	S	Si	Cr	Ni
309 309S	0.20 max 0.08 max	2.00 max	0.045 max	0.030 max	1.00 max	22.0 - 24.0	12.0 - 15.0

 
Typical Properties in the Annealed Condition
The properties quoted in this publication are typical of mill production and unless indicated should not be regarded as guaranteed minimum values for specification purposes.

1.    Mechanical Properties at Room Temperature
 

	SX 309		SX 309S
	TYPICAL	MIN	TYPICAL	MIN
Tensile Stength       MPa	560	515	540	515
Proof Stress (0.2% Offset)                    MPa	285	205	280	205
Elongation  (Percent in 50 mm)	54	40	54	40
Hardness (Brinell)	164		159
Endurance (fatigue) limit                       MPa	260		260

2.    Properties at Elevated Temperatures
The values quoted are those for SX 309
Short Time Elevated Temperature Tensile Stress
 

Temperature	oC	550	650	750	850	950	1 050
Tensile Stress	MPa	440	360	240	150	70	30

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

Time	TemperatureoC	550	600	650	700	750	800
10 000 h 100 000 h	Stress MPa  Stress MPa	100 75	80 50	60 30	30 20	25 10	10 5

Creep Rupture Stress
 

Time	Temperature oC	600	700	800	900	1 000
1 000 h 10 000 h 100 000 h	Stress MPa Stress MPa Stress MPa	180 150 100	90 50 40	35 30 20	20 10 5	5 2 -

Maximum Recommended Service
Temperature
(Oxidising Conditions)

Continuous                            1 100^oC
Intermittent                                980^oC
 

Thermal Processing
1.    Annealing.  Heat between 1 050^oC and 1 150^oC and water quench.  This treatment ensures that all carbides are in solution.
2.    Stress Relieving  250-400^oC for 1 hour.
3.    Hot Working
Initial forging and pressure                            1 150-1 200^oC
Finishing temperature                                           1 000^oC

Note:  Soaking times to ensure uniformity of temperature are up to 12 times that required for mild and carbon steels.

Info By  :  http://www.askzn.co.za/tech/tech_grade_309.htm