All Gray Iron castings in ASTM A278 are suitable for use up to 450°F (230°C), and class 40, 45, 50, 55 and 60 castings are suitable above 450-650°F(230-350°C). it also need heat treatment but other gray iron don’t require stress relieving. lity.com
Reference Casting Standards:
ASTM A278: Standard Specification for Gray Iron Castings for Pressure-Containing Parts for Temperatures Up to 650°F (350°C)
Gray Iron castings can be produced in Casting Quality Industrial:
- Sand Casting
- Shell Casting
- Lost Form Casting
- Centrifugal casting
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- Sand Casting
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Sand Casting is a popular metal form method, are suitable for all materiel, such as grey iron, ductile iron, malleable iron, carbon steel, stainless steel, aluminum and bronze.
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also named as precision lost wax casting, mainly suitalbe for carbon steel and stainless steel parts. We also provide grey iron and ductile iron and aluminum and bronze parts by investment casting. It can achieve the best appearance with good tolerance
- Shell Casting
Shell casting method is a good option to replace investment casting and sand casting. the quality is better than sand casting parts, suitable for bulk production.
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Gray iron standard grades in ASTM A278:
| Tensile Requirements, min | Tensile Requirements (Si), min | ||
| Casting Grade | Tensile Strength, ksi,min | Casting Grade | Tensile Strength, Mpa,min |
| ASTM A278 Class No.20 | 20 | ASTM A278 Class No.150 | 150 |
| ASTM A278 Class No.25 | 25 | ASTM A278 Class No.175 | 175 |
| ASTM A278 Class No.30 | 30 | ASTM A278 Class No.200 | 200 |
| ASTM A278 Class No.225 | 225 | ||
| ASTM A278 Class No.35 | 35 | ASTM A278 Class No.250 | 250 |
| ASTM A278 Class No.40 | 40 | ASTM A278 Class No.275 | 275 |
| ASTM A278 Class No.45 | 45 | ASTM A278 Class No.300 | 300 |
| ASTM A278 Class No.325 | 325 | ||
| ASTM A278 Class No.50 | 50 | ASTM A278 Class No.350 | 350 |
| ASTM A278 Class No.55 | 55 | ASTM A278 Class No.380 | 380 |
| ASTM A278 Class No.60 | 60 | ASTM A278 Class No.415 | 415 |
Chemical Requirements in ASTM A278: castingquality.com
Not defined details in standard. But the chemical composition need Carbon Equivalent:
ASTM A278 Class 40, 45, 50, 55 and 60 castings intended for service above 450°F (230°C) shall have a maximum carbon equivalent of 3.8 % as calculated from the equation CE = %C +0.3 (%Si + %P). The maximum phosphorus and sulfur contents shall be 0.25 % and 0.12 %, respectively. castingquality.com
ASTM A278 Class 275, 300, 325, 350, 380, and 415 castings intended for service above 230°C shall have a maximum carbon equivalent of 3.8 % as calculated from the equation CE = %C + 0.3 (%Si + %P). The maximum phosphorus and sulfur contents shall be 0.25 % and 0.12 %, respectively.
ASTM A278 Gray Iron Heat treatment requirement: it’s very important for ATM A278 material
- Stress Relieving process: A278 Castings intended for use above 450°F (230°C) shall be stress-relieved by placing them in a suitable furnace at a temperature not exceeding 400°F (200°C) and heating them uniformly to the temperatures and for the times. The heating and cooling rates shall be uniform and shall not be more than 400°F/h (250°C/h) for castings of 1 inch (25 mm) maximum section. For heavier sections the maximum heating and cooling rates in degrees Fahrenheit per hour shall be 400 divided by the maximum section thickness.
| ASTM A278 CLASS | Metal Temperature, °F | Holding Time, hours | |
| 40, 45, 50, 55, 60 | 1050 to 1200 °F | 2 hours, (min) | 12 hours (max) |
| (275, 300, 325, 350, 380, 415) | 565 to 650 °C | ||
- Heat Treatment and Cooling Rate: castingquality.com
- A278 Castings of Class 45,50,55, and 60, which are to be used at temperatures below 450°F, may be heat treated in accordance stress relieving proces or they shall be cooled in the mold to 500°F at an average rate of not more than 100°F/h for castings up to 1 in. in section. For heavier sections the maximum cooling rate in degrees Fahrenheit per hour shall be 100 divided by the maximum section thickness.
- A278 Castings of Class 275, 300, 325, 350, 380, and 415, which are to be used at temperatures below 230°C, may be heat treated in accordance with stress relieving or they shall be cooled in the mold to 250°C at an average rate of not more than 5O°C/h for castings up to 25-mm in section. For heavier sections the maximum cooling rate in degrees Celsius per hour shall be 1250 divided by the maximum section thickness.castingquality.com
ASTM A278 Gray Iron Typical Casting Application: castingquality.com
Heat Exchange equipment, such as bonnet and connection parts. castingquality.com
No detailed requirement about chemistry in ASTM A278 Standards, but we will suggest the chemistry as our experience in Casting industry; pls follow the material ASTM A48
