Gray Cast Iron - Micro Structure 1) Will there be any difference in microstructure of a Grey Iron component, if it is made with two different charge mix on Induction, provided chemical composition, pouring temperature & other things are same? Two different charge mix are – a) 10 % Pig iron, 40 % RR & balance Cast iron scrap & b) 10 % Pig iron, 40 % RR & balance CRC 2) Yes charge mix plays improve micro 3) Yes. As steel reduces &c.i.inceases iron tends to be softer. It does reflect on micro. Either the ferrite increases or tends to get formed. Pearlite becomes coarser. (If the alloying elements in general &pearlite stabilisers in particular are constant 4) CI produced with charge containing higher MS scrap exhibits finer flakes, higher Strength associated with higher BHn. 5) What about flake distribution 6) With Pig less stress on inoculant. 7) It will be normal with proper inoculation . 8) Both charge mixes have equal % of pig iron We are observing around 70 % A type flakes in charge mix with CRC whereas in charge mix have cast iron scrap we generally observe around 85 % What is the reason? 9) Formetion of flakes drpends on the available sites of nucliation. M'S scrap is Killed steel and has lower O2 content as compared to Pig Iron and CI scrap hence the difference in % of flakes. 10) Perhaps need to work on right mix because steel to the extent of 50% is quite a high percentage and is prime factor for creating under cooling leading to D and E types of flakes and lower pearlite in matrix 11) Pl pour cooling curve cup for each of them and you shall read the degree of undercooling...also this could be seen in wedge test...After inoculation. .. 12) One needs to maintain strength and BHN in casting for the given grade ..to achieve consistency. .It experienced that a min of 40% steel scrap is essential... 13) Most of foundries don't have cooling curve facility and if someone has and knows to analyse should not face problem 14) 50% seem more
15) We have to upgrade with time...Most of the CE meter suppliers have this facility these days... 16) For what section thickness and grade? It's relative... 17) Need to convert non measurable to measurable.... 18) One can get predominately A type even with 40/ 50 %steel. Please look at your inoculant type and/ or method of addition. However it is recommended to use 40%and not more steel for so many reasons. 19) Vinit ji, Microstructure in terms of graphite type and ferrite depends predominantly on inoculation and very much less on charge mix. 20) Very often charge mix is given too much of importance. Wedge control and now cooling curve analysis are very important in cast iron merallurgy 21) For such not too modern foundries wedge control is good enough. Lack of adequate control on chemistry and inoculation use of 0.04% Tin Addition is very good to always get full pearlite. 22) For such not too modern foundries wedge control is good enough. Lack of adequate control on chemistry and inoculation use of 0.04% Tin Addition is very good to always get full pearlite. 23) What is the max 24) Ti content permitted in PI 25) 0.04% is good enough. More is not harmful but unnecessary due to cost 26) FG 260, average section thickness around 25 mm 27) Currently getting desired pearlite and hardness, problem is only not getting desired A type graphite consistently 28) The inconsistency is caused by proper addition of inoculant and temperature. Holding too long and at high temperature causes inadequate inoculation and hence degenerate graphite flakes. 29) Inoculant and additions being the same, Inconsistency because of... 1. Change if source of MS scrap 2. Change of source of CI boring if used 3. Temp and Degree of holding of Bath 4. Variations in mixing of inoculated
5. Holding of metal after inoculation 6. Trace elements... 30) Most of them affect the degree of nucleation of Bath. ..