Control of chilling tendency in grey cast iron reuse

Abstract

In grey cast iron remelt and recycling, white iron can result in the cast product if careful control of the chilling tendency is not ensured. Many jobbing foundries are constrained in furnace types and available foundry additives that the operation always results in white irons. This study is towards ensuring grey iron is reproduced from cast iron scrap auto engine blocks, when using a diesel fired rotary furnace and a FeSi alloy for structural modification (inoculation). With varying addition rate of the FeSi alloy to the tapped molten metal, chill wedge tests were performed on two different wedge samples of type W (according to ASTM A367-wedge test) with cooling modulus of 0.45 cm (W 3½ ) and 0.54 cm (W 4 ). The carbon equivalents for the test casts were within hypoeutectic range (3.85 wt. (%) to 4.11 wt. (%)). In the W 4 wedge sample, at 2.0 wt. (%) addition rate of the FeSi alloy, the relative clear chill was totally reduced to zero from 19.76%, while the relative mottled chill was brought down to 9.59% from 33.71%. The microstructure from the cast at this level of addition was free of carbidic phases; it shows randomly oriented graphite flakes evenly distributed in the iron matrix. Hardness assessment shows that increasing rate of FeSi addition results in decreasing hardness, with maximum effect at 2.0 wt. (%) addition. With equivalent aspect ratio (cooling modulus) in a target cast product, this addition rate for this FeSi alloy under this furnace condition will attain graphitized microstructure in the cast product.

Application of Alloyed Cast Iron to Increase the Durability of Products of the Mining and Metallurgical Industry

“…The analysis of the main phases of cast iron: titanium carbide, phosphide eutectic and perlite matrix was performed using microstructure analysis [3]. Working out the optimal chemical composition it is necessary to try to obtain a favorable microstructure of cast iron for each specific case [3][4][5][6][7][8][9][10]. The naturally alloyed cast iron was found to have all the characteristics necessary to increase the service life of wear-resistant and heat-resistant products: high strength and wear resistance, and in the presence of phosphide eutectic, also good fluidity.…”

“…The effect of titanium and vanadium is not being studied enough. It is not enough both in studies of the properties of white cast irons and optimally doped gray heat-resistant cast irons [2][3][4].…”

Influence of Steel Scrap in the Charge on the Properties of Gray Cast Iron

“…Conventional GCI has a pearlite matrix and a tensile strength ranging from 140 to 400 MPa. 9,10) Inoculation causes significant improvements in mechanical properties because the microstructure of the alloy is modified.…”

Processing and Effect of Heat treatment on Mechanical Properties of Gray Cast Iron

“…It is an alloy of iron, carbon and silicon that has been melted and poured into a mould to form a shape. If molten iron is allowed to cool normally the carbon comes out of solution and forms flakes of graphite which run through the ferrite/pearlite matrix [2][3][4][5]. Although, ferrous casting may have superior properties, gray iron offers a unique versatility at lower cost that can be obtained through microstructure control.…”