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ASTM A350 Carbon and Low-Alloy Steel Forgings

ASTM A350 is the standard specification covering carbon and low-alloy steel forged or ring-rolled flanges, forged fittings and valves intended primarily for low-temperature service and requiring notch toughness testing. They are manufactured to corresponding ASME or API dimensional standards. The forgings may be made from ingots, blooms, billets, slabs or bars through hot-forging process. The steel shall be fully killed and fine-grain. ASTM A350 covers several grades and classes: Grade LF1, Grade LF2, Grade LF3, Grade LF5, Grade LF6, Grade LF9, Grade LF787; and Class 1, Class 2, Class 3. All the forgings supplied by Metals-Piping will be ultrasonically tested.

Long welding neck flange(LWN), 2" 900#, ASTM A350 LF3.

Long welding neck flange(LWN), 2″ 900#, ASTM A350 LF3 CL1.

1. ASTM A350 Chemical Composition Requirements

ElementComposition, w.t % Grades
*1. When vacuum carbon-deoxidation is required, the silicon content shall be 0.12% maximum.
*2. For grades LF1, LF2 & LF6, the sum of Cu, Ni, Cr, V and Mo shall not exceed 1.00 % on heat analysis.
*3. For all grades except grade LF787, the sum of Cr and Mo shall not exceed 0.32 % on heat analysis.
*4. For grades LF1 & LF2, the limit for Cb may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
*5. The carbon equivalent C.E = [C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15] shall not exceed 0.45%.

2. ASTM A350 Mechanical Properties

Grade/ClassTensile StrengthYield Strength, min.Elongation, min.Hardness, max.
LF1 CL160-85415–5853020525197
LF5 CL160-85415–5853020525197
LF2 CL170–95485–6553625022197
LF2 CL270–95485–6553625022197
LF3 CL170–95485–65537.526022197
LF3 CL270–95485–65537.526022197
LF5 CL270–95485–65537.526022197
LF6 CL166–91455–6305236022197
LF6 CL275–100515–6906041520197
LF6 CL375–100515–6906041520197
LF787 CL265-85450-5855538020197
LF787 CL375-95515-6556545020197
*1. The elongation values are on the basis of standard round specimen, or small proportional specimen, min % in 4D gauge length.
*2. The yield strength shall be determined by either the 0.2 % offset method or the 0.5 % extension under load method.

3. ASTM A350 Charpy V-Notch Impact Properties

Charpy V-Notch Energy Requirements for 10x10 mm Specimens
Grade/ Class*A*B
LF1 and LF913181014
LF2 CL115201216
LF3 CL115201216
LF5 CL1 & CL215201216
LF787 CL2 & CL315201216
LF6 CL115201216
LF2 CL220271520
LF3 CL220271520
LF6 CL2 & CL320271520
*A denotes minimum impact energy required for average of each set of three specimens.
*B denotes minimum impact energy permitted for one specimen only of a set.

Standard Impact Test Temperature for 10x10 mm Specimens
Grade/ ClassTest Temperature
LF2 CL1-50-46
LF2 CL2-0-18
LF3 CL1 & CL2-150-101
LF5 CL1 & CL2-75-59
LF6 CL1 & CL2-60-51
LF6 CL3-0-18
LF787 CL2-75-59
LF787 CL3-100-73
* Applicable for specimens representing forging material with thickness ≥ 10 mm.

Minimum Equivalent Absorbed Energy for Various Specimen Sizes. ft·lbf [J]
Standard Size3/4 Size2/3 Size1/2 Size1/3 Size1/4 Size
10x10 mm10x7.5 mm10x6.6 mm10x5 mm10x3.3 mm10x2.5 mm
15 [20]12 [16]10 [14]8 [11]5 [7]4 [6]
13 [18]10 [14]9 [12]7 [10]5 [7]4 [6]
12 [16]10 [14]9 [12]7 [10]4 [6]3 [5]
10 [14]8 [11]7 [10]5 [7]3 [5]3 [5]
* Straight-line interpolation for intermediate values is permitted.

4. Heat Treatment & Welding Process

As specified by ASTM A350, after hot working and before reheating for heat treatment, the forging shall be allowed to cool substantially below the transformation range. Forgings of grades other than Grade LF787 shall be furnished in the normalized, or normalized and tempered, or quenched and tempered condition. All quenched forgings shall be then tempered at 1100 °F [590 °C], minimum, holding at temperature a minimum of 30 min/in. [30 min/25 mm] of maximum thickness, but in no case less than 30 min.  Grade LF787 forgings shall be furnished in either the normalized-and-precipitation heat treated condition or in the quenched-and-precipitation heat treated condition.

API 602 forged gate valves in A350 LF2 body

API 602 forged gate valves, body: ASTM A350 LF2 Class1, trim: SS 316, 2″ 900# SW.

For Grade LF1 and LF2 forgings, the weld metal shall be deposited using carbon steel electrodes E 7015, E 7016, or E 7018, complying with AWS A 5.1. For Grade LF2 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 7015-A1; E 7016-A1, or E 7018-A1 complying with AWS 5.5; for Grade LF3 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 8016-C2 or E 8018-C2 complying with AWS A 5.5; for Grades LF5, LF9, and LF787 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 8016-C1 or E 8018-C1 complying withAWS A 5.5. For Grade LF6, the electrodes shall be low-hydrogen, E-XX15, E-XX16, or E-XX18 complying with AWS A 5.1 or A 5.5, as applicable.

5. Product Forms & Dimensional Standards

The Dimensional Standards for ASTM A350 Forgings
ASME B16.5 Steel Pipe Flanges and Flanged Fittings
ASME B16.9Factory-MadeWroughtSteelButt-WeldingFittings
ASME B16.11Forged Steel Fittings, Socket-Welding and Threaded4
ASME B16.34Valves-Flanged, Threaded, and Welding End
ASME B16.47Large Diameter Steel Flanges
API 600Steel Gate Valves with Flanged or Butt-Welding Ends
API 602Compact Design Carbon Steel Gate Valves for Refinery Use
API 605Large Diameter Carbon Steel Flanges

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Carbon & Low Alloy Steels

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    Hebei Metals Industrial Limited
    (Shijiazhuang Metalsin Pipeline Tech Co., Ltd)
    No. 176, Zhonghua South Street, Shijiazhuang, China.
    Tel: +86-311-89642206