Contents
What is the influence of cooling rate on the properties of cast iron?
Increasing the cooling rate significantly influences the as-cast structure (refines both the graphite size and matrix structure) and therefore the mechanical properties and increase the chilling tendency, which result in a higher hardness, decrease the strength and castings machinability can be severely impaired.
How much does iron shrink when cast?
There are three types of shrinkage: shrinkage of the liquid, solidification shrinkage and patternmaker’s shrinkage….Solidification shrinkage.
| Metal | Percentage |
|---|---|
| Low carbon steel | 2.5–3.0 |
| High carbon steel | 4.0 |
| White cast iron | 4.0–5.5 |
| Gray cast iron | −2.5–1.6 |
What is ductile iron castings?
Its mechanical properties are similar to steel, and far exceed those of standard cast irons. Ductile iron castings are solid metal objects that result from molten ductile iron being poured into voids in a mold. The ductile iron subsequently cools and solidifies in the shape of the void it occupies.
How do you make cast iron ductile?
Using a blast furnace, the pig iron is melted down and has carbon forced into the material beyond its normal capacity. Silicon, sulfur, and manganese help the excess carbon form the spherical graphite nodules as the metal cools in its cast. This process creates a durable, wear-resistant metal.
What is the most desirable pattern of graphite flakes in gray cast iron?
Grey cast irons are softer with a microstructure of graphite in transformed-austenite and cementite matrix. The graphite flakes, which are rosettes in three dimensions, have a low density and hence compensate for the freezing contraction, thus giving good castings free from porosity.
What property of GREY cast iron has?
While grey cast iron has less tensile strength and shock resistance than most other castings or even steal, it has compressive strength that is comparable to low- and medium-carbon steel. These mechanical properties are controlled by the size and shape of the graphite flakes present in the microstructure.
What is the difference between GREY cast iron and ductile cast iron?
While gray iron does not have a measurable yield strength, the range for tensile strength is 20,000 psi – 60,000 psi. Impact – Ductile iron has a greater resistance to impacts, and is able to resist a minimum of 7 foot pounds of impact (versus 2 pounds of impact for gray iron).
Is stainless steel better than ductile iron?
Ductile iron is also significantly less likely to corrode than cast iron. Stainless steel is a shiny, silver-colored metal that is minimally porous and very durable. These ferrous stainless steels alloys may have magnetic properties and be less resistant to corrosion and lose ductile strength.
What is the composition of GREY cast iron?
This material is a ternary Fe-C-Si alloy. Grey cast iron is characterized by its graphitic microstructure. Most cast irons have a chemical composition of 2.5 to 4.0% carbon, 1 to 3% silicon, and the remainder is iron.
What reduces ductility of a GREY cast iron?
Large graphite flakes reduce the strength and ductility, so inoculants are used to promote fine flakes. Gray cast iron is named after its gray fractured surface, which occurs because the graphitic flakes deflect a passing crack and initiate countless new cracks as the material breaks.
Why are quality controls more critical on ductile iron?
Quality Controls More Critical On Ductile Iron (Executive Overview) The meet structural expectations of ductile iron, more in -process controls, closer iron control, and more analyses and tests are necessary. These are briefly suggested below and explained in more detail under process steps.
Is there an OW N certification for ductile iron?
Manu purchasers of ductile iron castings have developed their ow n certification standards for auditing potential suppliers. The certification process has been extended to suppliers of materials to ductile iron producers. RESEARCH PROJECTS OF THE DIS have been directed toward knowledge helpful toward better quality.
What kind of tensile strength does ductile iron have?
Figure 3.1 illustrates the wide range of strength, ductility and hardness offered by conventional Ductile Iron. The high ductility ferritic irons shown on the left provide elongation in the range 18-30 per cent, with tensile strengths equivalent to those found in low carbon steel.
What are the purposes of the ductile iron Society?
Ductile Iron Society Purposes of Quality Assurance Guide The primary objective of this guide is to assist producers of ductile iron castings in obtaining higher levels of quality reliability. It is not intended to be a complete textbook or handbook on ductile iron; these are available from several sources.