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.
| ELEMENT | CONTENT % |
| Iron, Fe | 97.345 – 98.22 |
| Chromium, Cr | 0.80 – 1.20 |
| Manganese, Mn | 0.40 – 0.80 |
| Carbon, C | 0.27 – 0.33 |
| Silicon, Si | 0.15 – 0.30 |
| Molybdenum, Mo | 0.15 – 0.25 |
| Sulfur, S | 0.025 (max) |
| Phosphorous, P | 0.025 (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.
| ELEMENT | CONTENT % |
| Iron, Fe | 96.785 – 97.77 |
| Manganese, Mn | 0.75 – 1.0 |
| Chromium, Cr | 0.80 – 1.10 |
| Carbon, C | 0.37 – 0.44 |
| Silicon, Si | 0.15 – 0.30 |
| Molybdenum, Mo | 0.15 – 0.25 |
| Sulfur, S | 0.025 (max) |
| Phosphorous, P | 0.025 (max) |
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.
| ELEMENT | CONTENT % |
| Iron, Fe | 96.745 – 98.02 |
| Chromium, Cr | 0.40 – 0.60 |
| Manganese, Mn | 0.65 – 0.95 |
| Nickel, Ni | 0.35 – 0.75 |
| Carbon, C | 0.28 – 0.33 |
| Silicon, Si | 0.15 – 0.30 |
| Molybdenum, Mo | 0.15 – 0.25 |
| Sulfur, S | 0.025 (max) |
| Phosphorous, P | 0.025 (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.
| ELEMENT | CONTENT % |
| Iron, Fe | 96.875 – 99.3 |
| Chromium, Cr | 0.30 max (1-2) |
| Manganese, Mn | 0.60-1.05 |
| Carbon, C | 0.35 max |
| Silicon, Si | 0.10 – 0.35 |
| Molybdenum, Mo | 0.12 max (1-2) |
| Sulfur, S | 0.04 max |
| Phosphorous, P | 0.035 max |
| Copper | 0.40 max (1) |
| Nickel | 0.40 max (1) |
| Vanadium | 0.03 max |
(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
| ELEMENT | CONTENT % |
| Iron, Fe | 83.53 – 87.75 |
| Chromium, Cr | 11.5 – 13.5 |
| Manganese, Mn | 1.0 max |
| Carbon, C | 0.15 max |
| Silicon, Si | 1.0 max |
| Sulfur, S | 0.025 max |
| Phosphorous, P | 0.025 max |
| Nickel | 0.75 |
ASTM 182, Type AISI 316L Stainless Steel
Used as a weld inlay material for API Ring Grooves.
| ELEMENT | CONTENT % |
| Iron, Fe | 62.175 – 72.0 |
| Chromium, Cr | 16.0 – 18.0 |
| Manganese, Mn | 2.0 max |
| Carbon, C | 0.08 max |
| Silicon, Si | 1.0 max |
| Molybdenum, Mo | 2.0 – 3.0 |
| Sulfur, S | 0.03 max |
| Phosphorous, P | 0.040 max |
| Nickel, Ni | 10.0 – 14.0 |
UNS N06625, 625 Inconel
CRA used increasingly as the choice weld inlay material for API Ring Grooves.
| ELEMENT | CONTENT % |
| Iron, Fe | 5.0 max |
| Chromium, Cr | 20.0 – 23.0 |
| Manganese, Mn | .50 max |
| Cobalt, Co | 1.00 max |
| Columbium Nb, Tantalum, Ta | 3.15 – 4.15 |
| Aluminum, Al | 0.4 max |
| Titanium, Ti | 0.4 max |
| Carbon, C | 0.1 max |
| Silicon, Si | 0.5 max |
| Molybdenum, Mo | 8.0 – 10.0 |
| Sulfur, S | 0.015 max |
| Phosphorous, P | 0.015 max |
| Nickel, Ni | 58.0 – Balance |
