Alloy 904L is a low carbon, high alloy austenitic stainless steel which is widely used in applications where the corrosion properties of AISI 316L and AISI 317L are not adequate.

The addition of copper to this grade gives it corrosion resistant properties superior to the conventional chrome nickel stainless steels, in particular to sulfuric, phosphoric and acetic acids.

Heat Resistance

Good resistance to oxidation, but like other highly alloyed grades suffers from structural instability (precipitation of brittle phases such as sigma) at elevated temperatures. 904L should not be used above about 400°C.

Heat Treatment

Solution Treatment (Annealing) - heat to 1090-1175°C and cool rapidly. This grade cannot be hardened by thermal treatment.

Welding

904L can be successfully welded by all standard methods. Care needs to be taken as this grade solidifies fully austenitic, so is susceptible to hot cracking, particularly in constrained weldments. No pre-heat should be used and in most cases post weld heat treatment is also not required. AS 1554.6 pre-qualifies Grade 904L rods and electrodes for welding of 904L.

Fabrication

904L is a high purity, low sulphur grade, and as such will not machine well. Despite this the grade can be machined using standard techniques.

Bending to a small radius is readily carried out. In most cases this is performed cold. Subsequent annealing is generally not required, although it should be considered if the fabrication is to be used in an environment where severe stress corrosion cracking conditions are anticipated.

Applications

Typical applications include:

· Processing plant for sulphuric, phosphoric and acetic acids

· Pulp and paper processing

· Components in gas scrubbing plants

· Seawater cooling equipment

· Oil refinery components

· Wires in electrostatic precipitators

Chemical Composition

Table 1.Composition ranges for 904L grade of stainless steel.

Grade		C	Mn	Si	P	S	Cr	Mo	Ni	Cu
904L	min. max.	- 0.020	- 2.00	- 1.00	- 0.045	- 0.035	19.0 23.0	4.0 5.0	23.0 28.0	1.0 2.0

Product Specifications

ASTM A213/A269, ASME SA213 AVG wall, NACE MR0175/MR0103

ALLOY 904L (UNS N08904) CHEMICAL COMPOSITION % (MAX.)
Cr Chromium	Ni Nickel	C Carbon	Mo Molybdenum	Mn Manganese	Si Silicon	P Phosphorous	S Sulfur	N Nitrogen	Cu Copper
19.0-23.0	23.0-28.0	.02	4-5%	2.0	1.0	0.04	0.03	0.1	1.0-2.0

THEORETICAL BURST PRESSURE
OD	WALL	ID	PSI
0.250	0.035	0.180	16,898
0.250	0.049	0.152	23,657
0.250	0.065	0.120	31,382
0.375	0.035	0.305	11,265
0.375	0.049	0.277	15,771
0.500	0.035	0.430	8,946
0.500	0.049	0.402	12,524
0.500	0.065	0.370	16,614
0.750	0.065	0.620	11,076
1.000	0.065	0.870	8,307
DIMENSIONAL TOLERANCES
OUTSIDE DIAMETER (OD)		OD TOLERANCE	WALL TOLERANCE
UP TO 1/2"		+/- .005"	+/- 15%
1/2" to 1-1/2" EXCL.		+/- .005"	+/- 10%
TYPICAL APPLICATIONS Acid Production, Fertilizer Processing, Oil Refining, Pulp and Paper Processes, Gas Scrubbers, Seawater Cooling Equipment, Control and Instrumentation

SIZE RANGE
Outside Diameter (OD)	Wall Thickness
1/4"- 1"	.035" - .065"
Cold Finished and Bright Annealed Tube
MECHANICAL PROPERTIES
YIELD STRENGTH 0.2% OFFSET (MINIMUM KSI)	31
TENSILE STRENGTH (MINIMUM KSI)	71
ELONGATION (MINIMUM 2 INCHES)	35%
FABRICATION
Alloy 904L is non-magnetic in all conditions and has excellent formability and weldability. The austentic structure also give this grade excellent toughness, even down to cryogenic temperatures.

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