Talk:Ductile iron

A link should be added to Malleable Iron as well as specific Nodular Iron types

Machinability

Does adding cerium to ductile iron make ductile iron more difficult to machine?

The atomic radius of Cerium is about 25% greater than that of Iron, so the addition of Cerium to Iron would probably make it more difficult to machine. —Preceding unsigned comment added by 131.215.115.31 (talk) 22:42, 19 December 2008 (UTC)

Note that cerium is added to grey cast iron to make it into ductile iron. Here is a link discussing machinability of ductile iron: http://www.americanmachinist.com/304/Issue/Article/False/9129/Issue Wizard191 (talk) 23:04, 19 December 2008 (UTC)

The process is more sophisticated than adding Cerium (Ce) to gray iron, to make ductile iron. Ductile iron is an iron alloy of itself, meaning the base iron has to be properly prepared and of the proper chemical composition to make ductile iron, by either the addition of magnesium or cerium. In general the sulfur content has to be reduced to a very low level in comparison to gray iron, else the cerium will combine very readily with the sulfur and would not be available for modularization. In addition, most ductile iron is made with magnesium as the agent for nodularization with cerium also added. The addition of cerium will allow the use of less Magesium. The cerium may be in the master alloy for other functions, such as tying up subversive (to ductile iron) elements present in the scrap used for melting. In heavy sections, Cerium is used with caution due to possibility of chunky graphite and graphite flotation. It's basic function is to improve graphite structure.

It would be difficult to say whether cerium alone would influence machinability of ductile iron. If all other things were constant, then perhaps a level change of cerium alone would change graphite structure and thus influence machinability. Cerium itself does not act in interstitial sites in iron as a substitutional element in the atomic structure. It usually would form a compound with other elements. Mfields1 (talk) 14:50, 22 December 2008 (UTC)

References needed

Applications section needs reference. Nnaylime113 (talk) 15:34, 29 July 2008 (UTC)

Photomicrograph

It is good to see someone has added a photomicrograph for readers who may not have seen ductile iron microstructures. I'm interested in a citation for the term 'carbon islanding effect' - I have never heard this term before. Could the editor be referring to the 'bulls eye' microstructure where in a ferritic-pearlitic grade of ductile iron, the carbon in the austenite diffuses to the graphit nodules thus depleting the rgion and causing the retention of ferrite, surrounded by pearlite? PErhaps a set of ductile iron photomicrographs could be added. I'd be willing to add some good quality photomicrographs. Also the original would possibly be at 100x but a scalar bar might help readers gage the size of the graphite nodules.

Rewrite of main paragraph

The main paragraph contained misleading statements about how ductile irons are produced, and did not inform the reader that ductile iron is a generalized description of many grades of material which can be produced, all of which have the common microstructural property of graphite formed into a spheroidal or spherical shape through chemical and process methods. Also there was a nice paragraph about heat treating grey iron to make a form of malleable iron. Nicely written but out of character in this article. Not included was a description that literally 30 to 50 grades of ductile irons exist (including the various standards world wide) which grades are acheived through control of the matrix surrounding the graphite nodules. I have been making ductile iron for 33 years and to the new reader a lot of misinformation was being given. I suggest as a guidline the page at the Ductile Iron Society site would be a worthy basis for improvement to the artilce which is extremely brief. However, it is best to keep the article accurate in its description lest a badly written article could cause misleading information to be passed on to readers completely unfamiliar with the material. Mfields1 (talk) 02:42, 3 December 2009 (UTC)

Sorry about the mistake about how ductile iron starts as grey iron. I was trying to pare down the info on grey iron and got the impression that it started off as grey iron so it was definitely my mistake. But that's also why I put a {{cn}} template on that portion of the text. Wizard191 (talk) 15:14, 3 December 2009 (UTC)

np we're all working on this together. Mfields1 (talk) 03:10, 5 December 2009 (UTC)

Corrected some errors, sorry if I was rude

Current China export ban on Rare Earth metals is partly due to decline of US Steel Industry in the 1970's. The minimally processed metal content of Rare Earth Ores, Misch metal, was used extensively to convert high carbon pig iron (cast iron) to Ductile Iron. This was added to Iron making through Misch metal /Iron alloy: hence "Ronson" lighter flints. US Rare Earth Ores generally have a substantial part of metal content as Cerium and it usually contains a few percent Thorium, which I believe was also used as a nodulizer. The Chinese Rare Earth mines are co-located with their Steel Industry. Rare Earth metals are quite common however their separation is expensive, hence applications like Steel did not merit separation. Yttrium is also in the Misch metal melange so that should provide some reference for Yttrium.

The composition information needs to be clarified. The composition listed is similar to that of a local, Seattle Steel, Mill which takes recycled Steel (typically crushed Autos) and resells as rebar mostly. That would explain the metals content listed, there are no ores and no call for that high a copper content (it promotes corrosion). Steel composition information is based on Alloy type and may or may not be labeled. Steel containing less than 1% Manganese does not require Mn content to be listed, yet US Iron (Masabi range) runs about .9% Mn. Phosphorus and Sulfur below a threshold are included in the Carbon percentage. Chinese ore contains no Mn but high levels of Phosphorus and Sulfur are unreported in their steel. The Magnesium number is ridiculous and seems to be a fabrication from the source: MAGNESIUM VAPOR has limited solubility in molten Iron.

I thought it should be noted Magnesium BOILS 400 degrees C BELOW Irons melting temperature, and cannot be added as an alloy (like Tellurium) because it is not soluble in Iron. The maximum concentration of Magnesium reached is 50PPM. Tellurium is obviously expensive but functions at PPM levels, I think it was first nodulizer used at start of 1900's. At one time Cerium may have been separated for addition to steel, but it was unnecessary, see Misch metal article. Cerium (1000PPM) and Thorium(?ppm), like almost every other Iron alloying material affects Iron carbide formation.

I worked for an Industrial Testing Laboratory an a picture showing the flake carbon would help illustrate the improvement. I still have pictures of the etched microphotographed samples I prepared, although I suppose that only open source pictures are allowed. It would be nice if there was some reference as to how the samples were prepared.

Shjacks45 (talk) 13:01, 24 July 2011 (UTC)

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