What is Gray Cast Iron?
Gray cast iron, also known as grey cast iron, it refers to the cast iron with flake graphite, which is called gray cast iron because the fracture surface is dark gray. The mechanical properties of gray cast iron are related to the structure of matrix and the morphology of graphite. The flake graphite in gray cast iron splits the matrix seriously, and it is easy to cause stress concentration at the graphite sharp corner, which makes the tensile strength, ductility and toughness of gray cast iron far lower than that of steel, but its compressive strength is equivalent to that of steel. It is the lowest cost of common cast iron.
Common Gray Cast Iron Grades in Maple
| China | USA | Germany | Japan | UK |
| GB/T 9439 | ASTM A48 | DIN 1691 | G5501 | BS1452 |
| HT150 | Class 20 | GG15 | FC15 | Cr.150 |
| HT200 | Class 30 | GG20 | FC20 | Cr.180 |
| HT250 | Class 35 | GG25 | FC25 | – |
| HT300 | Class 45 | GG30 | FC30 | Cr.300 |
| HT350 | Class 50 | GG35 | FC35 | Cr.350 |
| – | Class 60 | GG40 | – | Cr.400 |
Tip: In Chinese standard, grade HT250 refers to gray cast iron with minimum tensile strength of 250Mpa for φ 30mm test bar.
Gray Iron Casting Process
Sand casting is the most traditional casting process, and also the main process of gray iron casting in Maple. Its biggest advantage is its low production cost. Maple has been committed to providing customers with high quality and competitive prices of gray iron castings, and can quickly respond to customer requirements.
Lost Foam Casting is another process for Maple to cast gray iron parts. Compared with sand casting, lost foam casting has the advantages of low pattern cost and high production efficiency, which is suitable for the production of small parts. We usually use this process to help customers make parts with better surface and higher accuracy and save machining costs.
Application of Gray Cast Iron
Although the strength, plasticity and toughness of gray cast iron are lower than other cast iron, it has excellent shock absorption, low notch sensitivity and high wear resistance.
HT150: Castings with medium load, such as: prop, base, gear box, tool holder, bearing seat, bearing sliding seat, working table, gear and sprocket wheel with non machined tooth surface, intake pipe, exhaust pipe and oil inlet pipe of hydraulic pump of automobile and tractor.
HT200/HT250: Castings with big load and gas tightness requirements, such as cylinder, gear, frame, flywheel, lathe tool, cylinder block, cylinder sleeve, piston, gearbox, brake wheel, coupling disc, medium pressure valve body, etc.
HT300/HT350: castings with heavy load, wear resistance and high air tightness, such as machine tool, frame, high-pressure hydraulic parts, piston rings, gears, cams and liners with large force, crankshaft, cylinder block, cylinder head of large engine, etc.