Class 40 cast iron typically refers to gray cast iron with a tensile strength of approximately 400 MPa.
Common grades include German GG40 (corresponding to EN-GJL-150). This type of cast iron belongs to the category of high-grade cast iron, and its mechanical properties are improved by adjusting the chemical composition or adding alloying elements (such as chromium, nickel, and molybdenum).
The carbon in gray cast iron mainly exists in the form of flake graphite, resulting in a gray fracture surface. It possesses good casting properties, shock absorption, and wear resistance, but its strength and toughness are relatively low. The typical chemical composition range of Class 40 cast iron is 2.9%–3.8% carbon, 1.8%–2.4% silicon, and ≤0.8% manganese, and its properties can be further optimized through heat treatment.
Its main applications include manufacturing simple castings that bear light loads, such as machine tool beds, housings, covers, outer covers, trays, oil pans, handwheels, base plates, handles, and other structural components. Compared to ordinary sand-cast iron, Grade 40 cast iron profiles have higher compressive strength, fatigue resistance (fatigue ratio can reach over 60%), and can reduce machining allowances and tool consumption.
What about the heat resistance of Grade 40 cast iron?
The heat resistance of Grade 40 cast iron mainly depends on its specific type and alloy composition. The following are key analyses:
1. General Characteristics of Heat-Resistant Cast Iron
Heat-resistant cast iron forms a dense oxide film (such as Cr₂O₃, Al₂O₃) by adding elements such as silicon, chromium, and aluminum, exhibiting oxidation resistance and growth resistance at high temperatures. Typical requirements include:
Oxidation resistance: Oxidation rate after 150 hours of heating < 0.5 g/(m²·h)
Growth resistance: Volume expansion < 0.2%
2. Heat Resistance of Grade 40 Cast Iron
Silicon-based cast iron: When the silicon content is 5-6%, a SiO₂ protective layer can be formed, with a heat resistance temperature reaching 800-950℃. However, excessive silicon content increases brittleness.
Chromium-based cast iron: Heat resistance can reach 600-900℃, possessing both high-temperature strength and oxidation resistance.
Aluminum-based cast iron: Good heat resistance, but poor mechanical properties; suitable for environments below 650℃.
The above is an introduction to the characteristics of Grade 40 cast iron. Of course, if you have large-scale custom cast iron parts needs, you can choose to cooperate with Mulan Metal. Mulan Metal has 13 years of experience in metal casting production and processing, and has helped clients in more than 30 countries complete various custom casting commissions, receiving consistent praise. We look forward to your cooperation inquiries.
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