The chemical compositions of the steels most commonly used for the manufacturing of API Spec 6A, API Spec 16A and API Spec 17D  equipment, appear below.

AISI 4130 Alloy Steel

Steel most commonly used for API Spec 6A, API Spec 16A and API Spec 17D, 60K and 75K, Bodies, Bonnets and End and Outlet Connections.

API Spec 6A Material Class AA,BB,DD,EE.

ELEMENTCONTENT %
Iron, Fe97.345 – 98.22
Chromium, Cr0.80 – 1.20
Manganese, Mn0.40 – 0.80
Carbon, C0.27 – 0.33
Silicon, Si0.15 – 0.30
Molybdenum, Mo0.15 – 0.25
Sulfur, S0.025 (max)
Phosphorous, P0.025 (max)

AISI 4140 Alloy Steel

Used for API Spec 6A, API Spec 16A and API Spec 17D, 60K and 75K  Bodies, Bonnets and End and Outlet Connections.

API Spec 6A Material Class AA,BB,DD,EE.

ELEMENTCONTENT %
Iron, Fe96.785 – 97.77 
Manganese, Mn0.75 – 1.0 
Chromium, Cr0.80 – 1.10
Carbon, C0.37 – 0.44
Silicon, Si0.15 – 0.30
Molybdenum, Mo0.15 – 0.25
Sulfur, S0.025  (max)
Phosphorous, P0.025  (max)
AISI 4140- Not a welding friendly steel.

AISI 8630 Alloy Steel

Used for API Spec 6A, API Spec 16A and API Spec 17D, 60K and 75K  Bodies, Bonnets and End and Outlet Connections.

API Spec 6A Material Class AA,BB,DD,EE.

ELEMENTCONTENT %
Iron, Fe96.745 – 98.02
Chromium, Cr0.40 – 0.60
Manganese, Mn0.65 – 0.95
Nickel, Ni0.35 – 0.75 
Carbon, C0.28 – 0.33
Silicon, Si0.15 – 0.30
Molybdenum, Mo0.15 – 0.25
Sulfur, S0.025 (max)
Phosphorous, P0.025  (max)

ASTM A105

Steel used for API Spec 6A, Type 6B 45K weld neck flanges and bodies.

API Spec 6A Material Class AA,BB,DD,EE.

ELEMENTCONTENT %
Iron, Fe96.875 – 99.3
Chromium, Cr0.30 max (1-2)
Manganese, Mn0.60-1.05
Carbon, C0.35 max
Silicon, Si0.10 – 0.35
Molybdenum, Mo0.12 max (1-2)
Sulfur, S0.04  max
Phosphorous, P0.035  max
Copper0.40 max (1)
Nickel0.40 max (1)
Vanadium0.03 max
(1) The sum of copper, nickel, chromium, molybdenum and vanadium shall not exceed 1.00%.
(2) The sum of chromium and molybdenum shall not exceed 0.32%.
Note: For each reduction of 0.01% below the specified carbon maximum (0.35%), an increase of 0.06% manganese above the specified maximum (1.05%) will be permitted up to a maximum of 1.35%.
ASTM A105- A welding friendly steel.

UNS S41000, Grade 410 Stainless Steel

Used for API Spec 6A and API Spec 17D, 60K and 75K  Bodies, Bonnets and End and Outlet Connections.

API Spec 6A Material Class  CC and FF

ELEMENTCONTENT %
Iron, Fe83.53 – 87.75
Chromium, Cr11.5 – 13.5
Manganese, Mn1.0 max
Carbon, C0.15 max
Silicon, Si1.0 max
Sulfur, S0.025  max
Phosphorous, P0.025  max
Nickel0.75
UNS S41000, Grade 410 Stainless – Not a welding friendly steel.

ASTM 182, Type AISI 316L Stainless Steel

Used as a weld inlay material for API Ring Grooves.


ELEMENTCONTENT %
Iron, Fe62.175 – 72.0
Chromium, Cr16.0 – 18.0
Manganese, Mn2.0 max
Carbon, C0.08 max
Silicon, Si1.0 max
Molybdenum, Mo2.0 – 3.0
Sulfur, S0.03  max
Phosphorous, P0.040  max
Nickel, Ni10.0 – 14.0
Weld wire chemistry will vary.

UNS N06625, 625 Inconel

CRA used increasingly as the choice weld inlay material for API Ring Grooves.


ELEMENTCONTENT %
Iron, Fe5.0 max
Chromium, Cr20.0 – 23.0
Manganese, Mn.50 max
Cobalt, Co1.00 max
Columbium Nb, Tantalum, Ta3.15 – 4.15
Aluminum, Al0.4 max
Titanium, Ti0.4 max
Carbon, C0.1 max
Silicon, Si0.5 max
Molybdenum, Mo8.0 – 10.0
Sulfur, S0.015  max
Phosphorous, P0.015  max
Nickel, Ni58.0 – Balance
Weld wire chemistry will vary.

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