ASTM A350 Standard

ASTM A350 Fittings

Forging:

ASTM A350 LF1 and LF2 grades would ideally be forged at around 2250-2300ºF(1230-1260ºC) and not forged below 1650-1700ºF(900-925ºC.) LF3 grade would be forged at around 2150-2200ºF (1175-1205ºC) and not forged below 1700ºF (925ºC.)

Welding/Heat Treatment:

Heat treatment of pipeline steels will no doubt be done on a continuous basis, and after welding. The structure of these steels will be initially determined by the rolling/forging process. The pipeline itself will be supplied from hot-rolled steels, the flanges etc. from forgings. The actual welding process will be primordial in ensuring the suitability and security of the pipeline and its subsequent performance. Preheat and postheat treatments are essential.

Machinability:

In the case of forged fittings and flanges, these grades may be machined as required, and ongoing experience will determine if machining is best done on an as-forged structure, a normalized structure or an annealed structure. In either case, in view of the critical nature of the end use, advice should be taken from a recognized heat treatment company.

Chemical Composition (%) of ASTM A350

Element	LF1	LF2	LF3	LF5	LF6	LF9	LF787
C	0.30	0.30	0.20	0.30	0.22	0.20	0.07
Mn	0.60-1.35	0.60-1.35	0.90 max	0.60-1.35	1.15-1.50	0.40-1.06	0.40-0.70
P	0.035	0.035	0.035	0.035	0.025	0.035	0.025
S	0.040	0.040	0.040	0.040	0.025	0.040	0.025
Si	0.15-0.30	0.15-0.30	0.20-0.35	0.20-0.35	0.15-0.30	-	0.40 max
Ni	0.40 max	0.40 max	3.3-3.7	1.0-2.0	0.40 max	1.60-2.24	0.70-1.00
Cr	0.30 max	0.30 max	0.30 max	0.30 max	0.30 max	0.30 max	0.60-0.90
Mo	0.12 max	0.12 max	0.12 max	0.12 max	0.12 max	0.12 max	0.15-0.25
Cu	0.40 max	0.40 max	0.40 max	0.40 max	0.40 max	0.75-1.25	1.00-1.30
Nb	0.02 max	0.02 max	0.02 max	0.02 max	0.02 max	0.02 max	0.02 min
V	0.08 max	0.08 max	0.03 max	0.03 max	0.04-0.11	0.03 max	0.03 max
N	-	-	-	-	0.01-0.030	-	-

Referenced Documents:

A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A788/A788M Specification for Steel Forgings, General Requirements
A961/A961M Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts for Piping Applications
600 Steel Gate Valves with Flanged or Butt-Welding Ends
602 Compact Design Carbon Steel Gate Valves for Refinery Use
605 Large Diameter Carbon Steel Flanges
A5.1 Mild Steel Covered Arc-Welding Electrodes
A5.5 Low-Alloy Steel Covered Arc-Welding Electrodes
B16.10 Face-to-Face and End-to-End Dimensions of Ferrous Valves
B16.11 Forged Steel Fittings, Socket-Welding and Threaded
B16.30 Unfired Pressure Vessel Flange Dimensions
B16.34 Valves-Flanged, Threaded, and Welding End
B16.47 Large Diameter Steel Flanges
B16.5 Steel Pipe Flanges and Flanged Fittings
B16.9 Factory-Made Wrought Steel Butt-Welding Fittings
Section IX Welding Qualifications

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