Ductile ironalso referred to as spheroidal or nodular ironis actually a group of irons that exhibit high strength flexibility durability and elasticity due to their unique microstructure. Cast ductile iron normally contains over 3 percent carbon it can be bent twisted or deformed without fracturing. Its mechanical properties are similar to steel and far exceed those of standard cast irons.Get A Quote
Ductile ironalso referred to as spheroidal or nodular ironis actually a group of irons that exhibit high strength flexibility durability and elasticity due to their unique microstructure. Cast ductile iron normally contains over 3 percent carbon it can be bent twisted or deformed without fracturing. Its mechanical properties are similar to steel and far exceed those of standard cast irons.
Ductile iron castingsare 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.
Invented in 1943 ductile iron is a modern iteration of cast iron. Cast iron and ductile iron have contrasting physical properties caused by differences in their microstructures.
The graphite and carbon contained in cast iron occur as flakes cast iron exhibits positive compressive load capabilities but tensile loading above its natural tensile strength can cause cracks to form and propagate rapidly out from stress points within the flaked graphite microstructure. As a result cast iron has virtually no elongation. It is a brittle material and therefore limited in its use in tensile and shock loading applications.
The graphite within ductile iron occurs as spheroids so it is sometimes referred to asspheroidal graphite. Similarly the termnodular ironstems from the fact that the carbon contained in ductile iron is held in the form of nodules. This unique microstructure causes ductile iron to withstand bending and shock loading far better than traditional cast iron.
While ductile iron can be produced from steel or iron scrap pig iron is the primary source of infeed for most modern ductile iron foundries.Pig ironrefers to the primary iron production of a blast furnace that contains over ninety percent iron.
The term pig iron arose from the old-fashioned method of casting blast furnace iron into molds arranged in sand beds in such a manner that they could be fed from a common runner. Because the groups of molds resembled a litter of suckling pigs the individual pieces of iron were referred to as pigs and the runner was referred to as a sow. Modern pigs are produced by a continuous pig casting machines.
Pig iron is used in ductile iron production as a primary source of pure iron. It offers a number of unique advantages pig iron contains low residual or harmful elements has a consistent chemistry promotes optimal slag conditions and improves process control by providing consistent charge properties. Demand for pig iron has increased in recent years as ductile iron foundries utilize its advantages over alternate iron sources such as iron scrap or melting steel scrap and adding carbon.
There are several advantages that ductile iron provides designers
Ductile Iron is a type of cast iron known for its impact and fatigue resistance elongation and wear resistance due to the spherical round graphite structures in the metal. Ductile Iron is also called ductile cast iron spheroidal graphite cast iron or nodular cast iron.
Both ductile iron and cast iron have graphite within. If you look closely with a high-power microscope with 100x magnification or more at regular cast iron gray iron you will see the graphite bits look like squiggly lines called flakes. When you look at the graphite in ductile cast iron however they look like little spheres or nodules thus the spheroidal graphite iron and nodular iron names.
We give Keith Millis credit for creating ductile iron way back in 1943. He and his buddies Albert Gagnebin and Norman Pilling received US patent 2485760 and US Patent 2485761 for making ductile iron using magnesium Mg in the metallurgy the metal composition or what was in the secret recipe to get the graphite to line up into spheres.
Millis was not the first to strengthen normal cast iron. We still cast Meehanite castings today. Augustus Meehan patented the Meehanite process back in January of 1931. Meehan used calcium silicide to also produce similar nodules to what is in ductile iron.
Yet it is ductile iron that has become one of the most popular types of iron casting. Development of ductile iron continued into the 1950s making the process of ductile iron casting better leading to acceptance of ductile iron acceptance proven out by the nine-fold increase in use during the 1960s as an engineered material for commercial applications.
Most of the magic in making ductile iron happens in the furnace with the molten iron. You start with the iron of course and then add more carbon than the iron would normally be able to absorb into the structure. Explaining the iron-carbon relationship in another way it is like adding so much salt to your water that you reach a point no more salt will dissolve. By the way this is what makes ductile iron different than steel. Steel only has as much carbon as the iron can absorb.
Silicon Sulphur manganese and oxygen all do their part in the mix to help the carbon to form into spherical graphite structures as the iron cools. This admittedly is an oversimplification of the process after all we are not training you for a metallurgical degree though if you want one we like the Engineering Degrees found in Wisconsin dont mind our geographic bias.
If you were to do a chemical analysis of ductile iron this is what you would normally find
To improve the strength of ductile iron additional tin or copper can be added. To improve corrosion resistance copper nickel or chromium can replace anywhere from 15-30 of the iron.
Ductile iron castings are very strong compared to regular cast iron gray iron. The tensile strength of cast iron is 20000 60000 psi while ductile iron starts at 60000 psi and can go to 120000 psi. The yield strength for ductile iron is generally 40000 90000 psi but the yield strength of cast iron is so low it is considered not measurable.
Apr 10 2017nbsp018332Ductile iron castings for the applications mentioned earlier are normally produced by sand casting or shell moulding processes with cores used to create hollow internal sections. Sand casting is the most common process due to the relatively low cost of production as compared to other manufacturing techniques.
The austempering process was first commercially applied to ductile iron in 1972 and by 1998 worldwide production was approaching 100000 tonnes annually. In many cases the composition of an ADI casting differs little from that of a conventional ductile iron casting the alteration in properties being achieved by the addition of alloys like .
Baker Casting Division produces gray and ductile iron castings for OEMs and machine shops. Our customers compliment us on our quality workmanship metallurgical capabilities process control and timely delivery. Contact our iron casting experts today to discuss your needs or browse our site to learn more about our services 1-608-882-5100.
A leading producer of high quality gray and ductile iron castings Aarrowcast Inc. proudly provides innovative custom cast metal solutions to customers in a wide array of industries. Located in Shawano Wisconsin Aarrowcast is one of the most modern iron foundries of its kind and is capable of producing more than 50000 tons of gray and .
Visitors who tour a McWane Ductile facility are often surprised by how much work goes into making Ductile iron pipe. The pipe starts out as scrap metalfromold cars and demolished buildings that ismelted down and given a new lease on life. Up to 95of our product is made from recycled material.
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