quality chrome molybdenum steel of A387 Grade 12 Class 2
A387 Grade 12 Class 2 is a high quality chrome molybdenum steel which is ideal for elevated temperature service and offers excellent anti corrosion characteristics. Chrome molybdenum steel has a wide range of uses including industrial boilers and pressure vessels, especially in environments where high temperature levels are common.
Different Grades of ASTM / ASME Grade 12 Chromium Molybdenum Steel
Masteel's range of ASTM / ASME A387 Grade 12 Chromium Molybdenum Steel products are available in different grades listed in the following.
ASTM A387 Grade 12 Class 2
ASME SA387 Grade 12 Class 2
Equivalent Grades of A387 Grade 12 Chromium Molybdenum Steel
The equivalent grades of A387 Grade 12 Chromium Molybdenum Steel are as follows:
|
BS |
EN |
ASTEM/ASME |
DIN |
|
620B |
3 CRMO 45 |
A387-12-2 |
13 CRMO 44 |
Chromium and Molybdenum Composition of A387 Grade 12 Chromium Molybdenum Steel
The chromium and molybdenum contents of A387 Grade 12 Chromium Molybdenum Steel (according to the ASTM specification) are outlined in the following table.
|
Designation |
Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
|
A387 Grade 12 |
1.00% |
0.50% |
Tensile Requirements for A387 Grade 12 Chromium Molybdenum Class 2 Plates
The tensile requirements for A387 Grade 12 Chromium Molybdenum Class 2 Plates are listed in the following table.
|
Designation |
Requirement |
Grade 12 |
|
A387 Grade 12 |
Tensile strength, ksi [MPA] |
65 to 85 [450 to 585] |
|
Yield strength, min, ksi [MPa]/(0.2% offset) |
40 [275] |
|
|
Elongation in 8 in. [200mm], min % |
19 |
|
|
Elongation in 2 in. [50mm], min, % |
22 |
|
|
Reduction of area, min % |
- |
Chemical Composition of A387 Grade 12 Chromium Molybdenum Steel
The chemical composition of A387 Grade 12 Chromium Molybdenum Steel from heat and product analysis is summarised in the following table.
|
Element |
Analysis |
Chemical Composition (%) inc. Grade & UNS No. |
|
Grade 12 (UNS: K11757) |
||
|
Carbon: |
Heat Analysis: |
0.05 - 0.17 |
|
Manganese: |
Heat Analysis: |
0.40 - 0.65 |
|
Phosphorus: |
Heat Analysis: |
0.035 |
|
Sulphur (max): |
Heat Analysis: |
0.035 |
|
Silicon: |
Heat Analysis: |
0.15 - 0.40 |
|
Chromium: |
Heat Analysis: |
0.80 - 1.15 |
|
Molybdenum: |
Heat Analysis: |
0.45 - 0.60 |
Tensile Test Requirements for Chromium Molybdenum Steel
The material shall be tested using a test specimen will confirm to the tensile requirements as outlined in tensile requirements for A387 Grade 12 Chromium Molybdenum Class 2 Plates above.
1. What is the typical post-weld heat treatment (PWHT) temperature and hold time for A387 Gr.12 Cl.2?
For A387 Grade 12 Class 2, the typical recommended Post-Weld Heat Treatment (PWHT or stress relief) temperature range is 1100°F to 1250°F (595°C to 675°C). The holding time is usually a minimum of 1 hour per inch (25 mm) of thickness, with a common minimum of 1 hour total. This process is critical to relieve welding stresses, temper the heat-affected zone (HAZ), and restore corrosion resistance, ensuring the integrity of the fabricated pressure vessel component.
2. Why is preheating mandatory before welding A387 Gr.12 Cl.2 steel?
Preheating, typically in the range of 300°F to 450°F (150°C to 230°C), is mandatory for welding A387 Grade 12 Class 2 to prevent hydrogen-induced cracking (HIC), also known as cold cracking. This alloy's hardenability can lead to a brittle microstructure in the weld zone upon rapid cooling. Preheating slows the cooling rate, allowing hydrogen to diffuse out and reducing the risk of forming crack-susceptible martensite, thereby ensuring a sound, defect-free weld.
3. What is the maximum continuous service temperature for A387 Gr.12 Cl.2 plates?
The maximum recommended continuous service temperature for ASTM A387 Grade 12 Class 2 plates is generally up to 1000°F (540°C). At this elevated temperature range, the chromium content provides improved resistance to oxidation (scaling) and corrosion, while the molybdenum enhances strength and reduces creep. For service above this temperature, grades with higher chromium content (like Grade 11 or 22) are typically considered.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
