ASTM A514 and ASTM A517 are both high-strength, quenched and tempered alloy steels, but they are designed for different applications and have distinct chemical compositions, mechanical properties, and performance characteristics. Below is a detailed comparison:
1. Primary Applications
| ASTM A514 | ASTM A517 |
|---|---|
| Structural applications: bridges, crane booms, construction equipment, mining machinery. | High-pressure applications: pressure vessels, boilers, nuclear containment, chemical reactors. |
| Focus on load-bearing structural parts requiring high yield strength and weldability. | Focus on extreme pressure and temperature resistance with superior toughness. |
2. Chemical Composition
| Element | ASTM A514 Grade B | ASTM A517 Grade B |
|---|---|---|
| Carbon (C) | 0.12–0.21% | 0.10–0.20% |
| Manganese (Mn) | 0.70–1.35% | 0.90–1.35% |
| Chromium (Cr) | 0.30–1.00% | 0.40–0.65% |
| Molybdenum (Mo) | 0.10–0.50% | 0.45–0.60% |
| Boron (B) | Optional (0.001–0.003%) | Not typically specified |
| Silicon (Si) | 0.15–0.35% | 0.15–0.35% |
| Phosphorus/Sulfur | ≤0.035% each | ≤0.035% each |
Key Difference: A517 contains higher chromium and molybdenum for enhanced high-temperature strength and creep resistance.
3. Mechanical Properties
| Property | ASTM A514 Grade B | ASTM A517 Grade B |
|---|---|---|
| Yield Strength | ≥690 MPa (100 ksi) | ≥760 MPa (110 ksi) |
| Tensile Strength | 760–895 MPa (110–130 ksi) | 895–1035 MPa (130–150 ksi) |
| Elongation | ≥16% (in 50 mm) | ≥16% (in 50 mm) |
| Hardness | 235–293 HB | 269–341 HB |
| Impact Toughness | ≥34 J at -40°C (-40°F) | ≥54 J at -18°C (0°F) |
Key Difference: A517 offers higher tensile strength and better toughness at low temperatures due to alloying elements.
4. Heat Treatment
Both grades are quenched and tempered (Q&T).
A517: Requires stricter control of heat treatment to ensure stability under high pressure and temperature.
5. Weldability
| ASTM A514 | ASTM A517 |
|---|---|
| Good weldability with preheating (150–230°C) and post-weld heat treatment (PWHT). | More challenging due to higher alloy content; requires stringent preheating (200–300°C) and PWHT. |
6. Cost and Availability
A514: More cost-effective for structural applications.
A517: Higher cost due to alloy content and specialized use in critical pressure systems.
7. Key Standards
A514: Governed by ASTM A514 (High-Yield-Strength, Quenched and Tempered Alloy steel plate).
A517: Governed by ASTM A517 (Pressure Vessel Plates, Alloy Steel, High-Strength, Quenched and Tempered).
8. Equivalent Grades
| Standard | A514 Grade B | A517 Grade B |
|---|---|---|
| EN (Europe) | S690QL | S890QL |
| JIS (Japan) | SHY685 | SHY685N (modified) |
Summary Table: When to Choose Which?
| Factor | ASTM A514 | ASTM A517 |
|---|---|---|
| Use Case | Structural parts (bridges, cranes). | Pressure vessels, boilers, extreme environments. |
| Strength Needed | High yield strength (690+ MPa). | Ultra-high strength (760+ MPa). |
| Temperature | Room to moderate temperatures. | Elevated temperatures and cyclic loading. |
| Budget | Lower cost for structural projects. | Higher cost justified for critical pressure systems. |
Why the Difference Matters
A514 prioritizes weldability and structural integrity under heavy loads.
A517 emphasizes creep resistance and long-term stability in high-pressure, high-temperature environments.
Always consult the ASTM specifications for project-specific requirements!
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