Why GREY cast iron is brittle and weak in tension?
Gray cast irons are comparatively weak and brittle in tension due to its microstructure; the graphite flakes have tips which serve as points of stress concentration. Strength and ductility are much higher under compression loads.
What causes gray brittle cast iron?
In grey cast iron, most of the carbon is present in the form of graphite flakes, which make the material softer, more machinable and less brittle than white cast iron.
Is gray iron brittle?
cast iron is either so-called gray iron or white iron, the colours shown by fracture. Gray iron contains more silicon and is less hard and more machinable than is white iron. Both are brittle, but a malleable cast iron produced by a prolonged heat treatment was developed in France in…
What are the advantages and disadvantages of the GREY cast iron alloys?
Gray cast iron can be made into pipes.
- Advantages. Gray iron’s high carbon content makes it easy to melt, weld, machine and cast using common metalworking processes.
- Disadvantages. Gray cast iron’s extremely low tensile strength makes it a poor shock resistor relative to newer, less rigid iron alloy varieties.
- Density.
What is the amount of carbon in gray cast iron?
The presence of graphite gives a grey shade to the fractured surface of cast iron. Therefore, when all the carbon in cast irons is in the form of graphite, it is called Grey cast Iron. Grey cast iron with a carbon content of 2.4\% – 3.8\%.
Which cast iron is most brittle and not machinable?
White cast irons
White cast irons are hard and brittle; they cannot easily be machined. They are unique in that they are the only member of the cast iron family in which carbon is present only as a carbide. White cast iron has a light appearance due to the absence of graphite.
Is gray cast iron ductile or brittle?
Compared to the more modern iron alloys, gray iron has a low tensile strength and ductility; therefore, its impact and shock resistance is almost non-existent.
Is cast iron brittle?
Cast iron is harder, more brittle, and less malleable than wrought iron. It cannot be bent, stretched, or hammered into shape, since its weak tensile strength means that it will fracture before it bends or distorts. It does, however, feature good compression strength.
What are the relative advantages of gray cast iron over other types of iron?
Advantages of Gray Cast Iron
- Low Cost.
- Good Vibration/Damping Capability.
- Excellent Compressive Strength.
- Ability to Withstand Thermal Cycling.
- Tensile Strength.
- Deformation Resistance.
- Low Melting Point.
- Oxidation Resistance.
Which process is convenient for extrusion of highly brittle materials like gray cast iron Mcq?
The brittle material is extruded in the hydrostatic pressure extrusion process. Whereas ductile metal can be extruded through normal operations.
What is the carbon percentage in cast iron?
Cast iron is an alloy with a high carbon content (at least 1.7\% and usually 3.0–3.7\%), making it relatively resistant to corrosion.
Does cast iron contains a lower percentage of carbon than high carbon steel?
Cast iron typically contains more than 2 percent carbon, while cast steel often contains between 0.1–0.5 percent carbon.
Why is greygrey cast iron brittle?
Grey cast iron is brittle because of the graphite flakes present in it. The flakes with pointed ends act as stress raisers.These flakes then behave as cracks causing brittle fracture when load is applied.
Why is grey carbon steel brittle?
Grey C.I. is brittle because of graphite flakes.If the microstructure is observed one can find graphite flakes distributed in a matrix of ferrite or pearlite.Since graphite is having poor strength as well as sharp corners the ductility is reduced and makes G.C.I. brittle. One small correction.
What is the strength of gray cast iron?
The strength of gray cast iron depends on the matrix in which graphite (free carbon) is embedded. The matrix can range from ferrite to pearlite and various combinations of the two phases. Large graphite flakes reduce the strength and ductility, so inoculants are used to promote fine flakes.
How does heat treatment affect the mechanical properties of grey cast iron?
This heat-treatment reduces substantially the mechanical properties; for example, it reduces the properties of grade 40 grey iron to grade 30. The extent of reduction depends on the annealing temperature, time at that temperature and the alloying elements present in grey cast iron.