A387 Grade 5 Class 1 is a chromium-molybdenum alloy steel plate designed for use in welded pressure vessels and high-temperature service. It offers good strength and creep resistance at elevated temperatures, along with excellent weldability and toughness. This grade is commonly employed in the oil and gas, petrochemical, and power generation industries for components that must withstand both high pressure and high temperature over extended periods.
Equivalents
| BS | EN | ASME | DIN |
| ... | ... | A387-5-1 | ... |
Specifications ASTM A387 Grade 5 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 5 | 5.00% | 0.50% |
Tensile Requirements for ASTM A387 Grade 5 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 5 |
|
A387 Grade 5 |
Tensile strength, ksi [MPA] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 45 [310] | |
| Elongation in 8 in. [200mm], min % | ... | |
| Elongation in 2 in. [50mm], min, % | 18 | |
| Reduction of area, min % | 45 (measured on round specimen) 40 (measured on flat specimen) |
Chemical Requirements for ASTM A387 Grade 5 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| A 387 Grade 5 | ||
| Carbon: | Heat Analysis: | 0.15 max |
| Product Analysis: | 0.15 max | |
| Manganese: | Heat Analysis: | 0.30 - 0.60 |
| Product Analysis: | 0.25 - 0.66 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.030 |
| Product Analysis: | 0.030 | |
| Silicon: | Heat Analysis: | 0.50 max |
| Product Analysis: | 0.55 max | |
| Chromium: | Heat Analysis: | 4.00 - 6.00 |
| Product Analysis: | 3.90 - 6.10 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.65 |
| Product Analysis: | 0.40 - 0.70 |
processing
1. Material Preparation
Surface Cleaning: Shot blasting or pickling to remove mill scale and rust.
NDE Inspection: Ultrasonic Testing (UT) to ensure there are no internal laminations or defects before cutting.
2. Cutting & Edge Preparation
Thermal Cutting: CNC Flame (Oxy-fuel) or Plasma cutting to size.
Beveling: Mechanical machining or grinding to create welding bevels (U-groove or V-groove).
Grinding: Removal of the hardened heat-affected zone (HAZ) from the cut edges.
3. Forming
Cold Rolling: Bending into cylindrical shells or cones (suitable for Class 1 due to high ductility).
Hot Forming: For heavy thicknesses (over 50mm), heating to 900°C–1050°C followed by a full re-heat treatment (Normalizing & Tempering).
4. Welding
Preheating: Maintaining a consistent temperature of 150°C–250°C.
Welding Methods: SAW (Submerged Arc), GTAW (TIG), or SMAW (Stick) using matching Cr-Mo fillers (e.g., E8018-B6).
Interpass Control: Keeping the temperature stable to prevent cold cracking.
5. Post-Weld Heat Treatment - PWHT
Stress Relieving: Heating the fabricated vessel to 700°C–760°C and holding for a specific duration (e.g., 1 hour per inch of thickness) to soften the weld and HAZ.
6. Final Inspection & Testing
Radiographic Testing (RT): X-ray inspection of weld seams for internal integrity.
Hardness Testing: Ensuring the maximum hardness (typically below 225 HBW) to prevent brittle failure.
Hydrostatic Test: Pressure testing the completed vessel to verify structural safety.
7. Surface Finishing
Final Coating: Applying heat-resistant primers or anti-corrosive coatings for transport and site installation.
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What is A387 Grade 5 Class 1 mainly composed of?
Its main components are iron, 4.00-6.00% chromium, 0.45-0.65% molybdenum, 0.15-0.25% carbon, with trace manganese and silicon for stability.
What is the standard specification for A387 Grade 5 Class 1?
It follows ASTM A387, a standard for chromium-molybdenum alloy steel plates used in welded pressure vessels and high-temperature services.
What is the minimum yield strength of A387 Grade 5 Class 1?
The minimum yield strength is 275 MPa (40 ksi), ensuring it can withstand high pressure and load in industrial applications without deformation.
What's the difference in chemical composition between A387 Grade 5 Class 1 and A387 Grade 11 Class 1?
Grade 11 Class 1 has 1.00-1.50% chromium, while Grade 5 Class 1 has 4.00-6.00% chromium, enhancing the latter's high-temp performance.
What is the standard specification for A387 Grade 5 Class 1?
It follows ASTM A387, a standard for chromium-molybdenum alloy steel plates used in welded pressure vessels and high-temperature services.
What is the minimum yield strength of A387 Grade 5 Class 1?
The minimum yield strength is 275 MPa (40 ksi), ensuring it can withstand high pressure and load in industrial applications without deformation.
How does the ductility of A387 Grade 5 Class 1 differ from A516 Grade 70?
A516 Grade 70 has higher ductility (elongation ≥21%) than A387 Grade 5 Class 1 (≥18%), but the latter is more heat-resistant.
What is the melting point range of A387 Grade 5 Class 1?
Its melting point ranges from 1420-1480°C, similar to other chromium-molybdenum steels, suitable for high-temperature fabrication.
Is A387 Grade 5 Class 1 suitable for cryogenic services?
No, it is not ideal for cryogenic use. Its toughness decreases at low temps; cryogenic steels like A353 are preferred instead.
What is the molybdenum content of A387 Grade 5 Class 1?
The molybdenum content is 0.45-0.65%, which enhances high-temperature strength, creep resistance, and corrosion resistance.
What distinguishes the application scope of A387 Grade 5 Class 1 from A242 Type 1?
Grade 5 Class 1 is for high-pressure boilers and vessels, while A242 Type 1 is for structural use, differing in pressure and temp resistance.