China Supplier Precision Casting Company - Grey Cast Iron Sand Casting Part – RMC Foundry

Grey cast iron products by sand mould casting process and CNC machining.

Grey cast iron is named after the gray color of the fracture it forms. The gray cast iron is used for housings where the stiffness of the component is more important than its tensile strength, such as internal combustion engine cylinder blocks, pump housings, valve bodies, electrical boxes, counter weights and decorative castings. Grey cast iron’s high thermal conductivity and specific head capacity are often exploited to make cast iron cookware and disc brake rotors.

A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1 to 3% silicon by weight. Graphite may occupy 6 to 10% of the volume of grey iron. Silicon is important to making grey iron as opposed to white cast iron, because silicon is a graphite stabilizing element in cast iron, which means it helps the alloy produce graphite instead of iron carbides; at 3% silicon almost no carbon is held in chemical combination with the iron.

The graphite takes on the shape of a three-dimensional flake. In two dimensions, as a polished surface will appear under a microscope, the graphite flakes appear as fine lines. The tips of the flakes act as preexisting notches; therefore, it is brittle. The presence of graphite flakes makes the Grey Iron easily machinable as they tend to crack easily across the graphite flakes. Grey iron also has very good damping capacity and hence it is mostly used as the base for machine tool mountings.

Sand casting uses green sand (moist sand) or dry sand to form the molding systems. The green sand casting is the oldes casting process used in history. When making the mold, the patterns made of wood or metal should be produced in order to form the hollow cavity. The molten metal then pour into the cavity to form the castings after cooling and solidification. Sand casting is less expensive than other casting processes both for mold development and unit casting part. The sand casting, always mean the green sand casting (if no special description). However, nowadays, the other casting processes are also use the sand to make the mold. They have their own names, such as shell mold casting, furan resin coated sand casting (no bake type), lost foam casting and vacuum casting.

 The Advantages of Sand Casting:

• ✔ Lower Cost due to its cheap and recyclable mold materials and simple production equipment.
• ✔ Wide range of unit weight from 0.10 kg to 500 kgs or even bigger.
• ✔ Various Structure from simple type to complex type.
• ✔ Suitable for production requirements of various quantity.

Tolerance That Sand Castings Achieve:
The casting tolerances are divided into Dimensional Casting Tolerances (DCT) and Geometrical Casting Tolerances (GCT). Our foundry would like to talk with you if you have special request on the required tolerances. Here in the following are the general tolerances grade we could reach by our green sand casting, shell mould casting and no-bake furan resin sand casting:

• ✔ DCT Grade by Green Sand Casting: CTG10 ~ CTG13
• ✔ DCT Grade by Shell Mold Casting or Furan Resin Sand Casting: CTG8 ~ CTG12
• ✔ GCT Grade by Green Sand Casting: CTG6 ~ CTG8
• ✔ GCT Grade by Shell Mold Casting or Furan Resin Sand Casting: CTG4 ~ CTG7