ASTM A515 Grade 70 (often abbreviated as A515 Gr. 70 or SA515 Gr. 70) is a high-strength carbon-silicon steel plate primarily used for intermediate and higher-temperature service in welded boilers and other pressure vessels.
ASTM A515 Grade 70 Plates Specifications
|
Specifications |
ASTM A515 |
|
Thickness |
8-100mm |
|
Width |
1500-3500mm |
|
Length |
3000-8000mm |
|
Surface |
2B, 2D, BA, NO.1, NO.4, NO.8, 8K, mirror, checkered, embossed, hair line, sand blast, Brush, etching, etc |
|
Finish |
Hot rolled plate (HR), Cold rolled sheet (CR) |
|
Form |
Coils, Foils, Rolls, Plain Sheet, Shim Sheet, Strip etc. |
Chemical Composition( %):
|
Grade/ Material |
Element |
Composition( Max-A, Min-I) |
|
A515 Grade 70/ A515 Gr70 |
C |
A:0.31 |
|
Mn |
A:1.20 |
|
|
Si |
0.15-0.40 |
|
|
P |
A:0.035 |
|
|
S |
A:0.035 |
Mechanical Properties( Mpa)
|
Grade/ Material |
Tensile Test |
Ksi/MPa |
|
A515 Grade 70/ A515 Gr70 |
Tensile Strength |
70-90/485-620 |
|
Yield Strength |
38/260 |
|
|
Elongation |
17% |
|
|
Impact Test( if any) |
|
Comparison with Other ASTM A515 Grades
|
Property |
A515 Grade 60 |
A515 Grade 65 |
A515 Grade 70 |
|---|---|---|---|
|
Carbon Content (Max %) |
0.24-0.31 |
0.28-0.33 |
0.30-0.35 |
|
Manganese (Max %) |
0.98 |
0.98 |
1.30 |
|
Yield Strength (Min Mpa) |
220 |
240 |
260 |
|
Tensile Strength (Mpa) |
415-550 |
450-585 |
485-620 |
|
Elongation (Min %, 200mm) |
21 |
19 |
17 |
processing flow
1. Steelmaking & Casting
Melting: Produced via Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF).
Ladle Refining: Precise chemical adjustment and vacuum degassing to ensure purity.
Deoxidation: The steel must be Killed Steel (镇静钢).
Grain Practice: Manufactured to a Coarse Austenitic Grain Size practice (grain size 1 to 5) to improve high-temperature creep resistance.
2. Rolling & Heat Treatment
Reheating: Slabs are heated in a furnace to approximately 1100°C–1250°C.
Hot Rolling: Multi-pass rolling to achieve the final thickness and mechanical properties.
Heat Treatment Conditions:
Thickness
≤ 50 mm (2 in): Typically supplied in As-Rolled condition.
Thickness > 50 mm (2 in): Must be Normalized (加热至 900–950°C 后空冷) to refine the grain structure and ensure uniform properties.
3. Fabrication Processing
Cutting: Using Oxy-propane flame, Plasma, or Laser cutting.
Forming:
Cold Forming: Suitable for moderate bending and shaping.
Hot Forming: Recommended for heavy sections, typically performed between 900°C and 1100°C.
Machining: Conventional drilling, milling, and turning (similar to AISI 1330 performance).
4. Welding Process
Filler Metals: Typically use E7018 (SMAW) or compatible wires like ER70S-6 (GMAW).
Preheating: Preheating to 95°C–150°C is often required, especially for thicker plates, to prevent hydrogen-induced cracking.
PWHT (Post-Weld Heat Treatment): Stress-relief annealing is usually required by ASME codes after welding to reduce residual stresses.
5. Inspection & Testing
Mechanical Testing:
Tensile Test: Minimum 485 MPa (70 ksi).
Yield Test: Minimum 260 MPa (38 ksi).
Non-Destructive Testing (NDT):
Ultrasonic Examination (UT): Performed according to ASTM A435 or A578.
Magnetic Particle (MT) / Radiographic Testing (RT): Used to verify weld integrity.
Surface Conditioning: Shot blasting, pickling, or painting.
advantages
1. Superior High-Temperature Performance
Unlike ASTM A516, which is optimized for low-temperature toughness, A515 Gr.70 is manufactured to coarse grain practices.
Creep Resistance: Coarse grains provide better resistance to creep deformation at elevated temperatures.
Graphitization Prevention: This structure helps minimize graphitization, making it ideal for steam piping and high-temperature pressure vessels.
2. High Strength and Durability
As the highest strength grade in the A515 series, Grade 70 provides:
High Tensile Strength: Typically between 485–620 MPa (70–90 ksi), allowing components to withstand high internal pressures and external stresses.
Structural Integrity: Its durability and toughness ensure longevity in demanding environments like power generation and petrochemical processing.
3. Excellent Fabricability
Good Weldability: It can be readily welded using standard methods such as SMAW (e.g., E7018 electrodes), TIG, and MIG.
Formability & Machinability: Despite its strength, it maintains good ductility, supporting effective cold forming and standard machining processes similar to plain carbon steels.
4. Cost-Effectiveness
Economical Choice: Compared to specialized high-alloy or exotic materials, A515 Gr.70 offers a reliable balance of performance and relatively low material cost, making it ideal for cost-sensitive projects requiring high-temperature service.
5. Versatility across Industries
Its properties make it a standard choice for:
Boilers & Heat Exchangers: Industrial steam systems and thermal equipment.
Pressure Vessels: Storage tanks and containers for the oil, gas, and chemical industries.
Structural Applications: Manufacture of high-strength fasteners and bolts.
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.
What marking requirements apply to A515 Grade 70 plates?
Each plate must be marked with grade, heat number, thickness, manufacturer's logo and ASTM A515 compliance for traceability.
What is the as-rolled condition of A515 Grade 70?
As-rolled means natural cooling after rolling without extra heat treatment, meeting basic needs for general applications.
How does normalization improve the performance of A515 Grade 70?
Normalization (heat above critical temp, hold, air-cool) refines grains, reduces stress and improves toughness and microstructure uniformity.
What is the maximum sulfur (S) content allowed for A515 Grade 70?
Max S content is 0.035% by weight. Excess S causes hot brittleness and impairs the steel's weldability.
Can A515 Grade 70 be used in low-temperature environments below -20°F (-29°C)?
Not recommended. Below -20°F (-29°C), its toughness drops sharply, increasing the risk of brittle fracture.
What is the function of continuous casting in A515 Grade 70 production?
It turns molten steel into slabs continuously, improving efficiency, reducing waste and ensuring uniform material quality.
What post-weld heat treatment is recommended for A515 Grade 70?
Stress relief annealing is recommended to reduce residual welding stress, prevent cracking and stabilize joint performance.
How is oxide scale removed from A515 Grade 70 plates after rolling?
Shot blasting (abrasive particles) or pickling (acidic solutions) are used to remove oxide scale from the plate surface.
Is A515 Grade 70 suitable for high-pressure service?
Answer: Yes, for moderate-high pressure, provided it meets ASTM A515's thickness and mechanical property requirements for the application.
Why is ultrasonic testing (UT) essential for A515 Grade 70 plates?
Answer: UT detects invisible internal defects, ensuring the plate's internal integrity for boiler and pressure vessel use.