Cast iron is made of iron, carbon and silicon and other components of the alloy. It contains more than carbon sulfur, phosphorus and other impurity elements. In order to further improve the properties of cast iron or special performance, can also add chromium, molybdenum, vanadium, copper, aluminum and other alloy elements, silicon, manganese, phosphorus or increase the content of the element such as iron, this is called alloy cast iron.
The classification of cast iron
According to carbon in cast iron and existing form of different forms, can be divided into:
In 1, white cast iron — C sparingly soluble in F. The remaining 3 are Fe C form, fracture blue white. This type of cast iron is present in the eutectic ledeburite, properties of hard and brittle, hard cutting, rarely used for machinery parts, steel main steelmaking raw materials or malleable iron casting blank. Also sometimes use it hard and wear-resistant characteristics, casting into a chilled cast iron. Cold moraine cast iron used as some of the requirements for wear resistant workpieces, such as roll, ball mill grinding ball.
In 2, gray iron — C mainly sheet free G exists, because the fracture is dull black.
3, mottled cast iron — it is the carbon to form part of the cementite; another part of the graphite form of cast iron, the fracture was gray and white. This type of cast iron is much hard and brittle, so the application of little.
According to the cast iron graphite morphology of cast iron can be divided into:
1, malleable cast iron — G to clusters exist.
2, vermicular cast iron — G to circle in the sheet and globular intermediate between a worm-like shape.
3, ductile iron — G to globular existence.
In 4, gray iron — it is in the form of flake graphite.
Gray cast iron
One, the iron composition, microstructure and properties.
1 components of Wc=2.6~3.5% Wsi=1.0~2.2% WMn=0.5~1.3%, Ws ≤ 0.15% Wp ≤ 0.3%
2, species and tissues
Organizational characteristics: G distribution on metal substrate
Three types: F based on distribution of a thick sheet of G; P+F consisting of base distribution of thin G films; P matrix on distribution of fine and uniform G
( a ) in cast iron and steel by G:
1 in the presence of G local equivalent hole, crack it not only destroyed the base of continuous, reducing the matrix stress effective area, and the G tip to form stress concentration, causes the material to form a brittle, gray iron tensile is only the same matrix steel B 1 / 3~ 1 / 5, A,ψKU low.
2 pull pressure is B and steel approach, as is 4 times that of B ( tensile ), G does not produce a reduced effective area and notch stress concentration.
3 matrix effects: F grey cast iron high plastic, P is B higher gray cast iron. F+P ash ranging between two.
( two) other properties:
1 excellent casting performance: volume larger G, partially compensating shrinkage.
2 good cutting properties: G friction and lubrication.
3 excellent shock resistance: G soft, shock absorption, hinder the spread is 10 times that of steel.
4 good abrasion resistance: G lubrication, formed Kong Run and store up the lubricating oil, thus reducing friction is low.
5 notch sensitivity: G holes and cracks. Notch sensitivity of small.