Effect of microstructure and mechanical properties on cutting force of different cast irons with similar tensile strength

Abstract

Flake graphite iron, compacted graphite iron and spheroidal graphite iron with various tensile strengths were cast. They were selected and grouped according to roughly the same tensile strength, and then the main cutting force in each group was measured and compared. The microstructures of different cast irons were characterized. The relationship between the cutting force and microstructure was established. Results show that the graphite morphology in cast irons determines the strength. In order to obtain the same strength of the cast iron with sharply edged graphite, more or finer pearlite in the matrix is needed. Graphitic cast irons with high pearlite content and smaller pearlite interlamellar spacing have higher hardness. For the cast irons with different graphite morphologies, but almost the same tensile strength, the main cutting force is obviously different, along with the hardness. Harder cast irons have a greater cutting force, but the difference in cutting force is not proportional to hardness.

Effects of Microstructure, Mechanical and Physical Properties on Machinability of Graphite Cast Irons

“…The HT250 (FGI) with higher hardness and lower tensile strength had a higher cutting force compared with QT450 (SGI). In [5] (our previous work), the cutting force of FGI was also higher with higher hardness and lower tensile strength than CGI and SGI. FGI with 250 HB hardness and 347 MPa tensile strength had 1438 N cutting force at 2.5 mm cutting depth, whereas CGI with 162 HB hardness and 345 MPa tensile strength had 1156 N cutting force, and SGI with 181 HB hardness and 525 MPa tensile strength had 1254 N cutting force.…”

“…In the turning process, the main cutting force was measured in real-time. The used lathe (Shenyang First Machine Tool Factory, Shenyang, China), a cutting tool (Sumitomo Electric Industries Ltd, Osaka, Japan), and measurement system of the cutting force (Donghua Testing Technology Co. Ltd., Taizhou, China) were the same as that in the previous paper [5]. Luis Norberto López de Lacalle et al [16] adopted the dynamometric table KISTLER 9255B to measure the cutting force.…”

“…system of the cutting force (Donghua Testing Technology Co. Ltd., Taizhou, China) were the same as that in the previous paper [5]. Luis Norberto López de Lacalle et al [16] adopted the dynamometric table KISTLER 9255B to measure the cutting force.…”

“…Seker et al [4] reported that austempering heat treatment of SGI significantly improved the surface quality and resulted in a relatively small change in cutting forces in the turning process. For various cast irons with equal tensile strength, Ren et al [5] investigated the effects of microstructure and mechanical properties on the cutting force of different cast irons with similar tensile strength in the turning process. Results showed that there is a positive correlation between the cutting force, hardness, and pearlite content for cast irons with equal tensile strength.…”

“…In addition, contrasting the machinability of FGI and SGI, some literature reports gave inconsistent results. For example, the authors of both [3,7] reported that FGI has a lower cutting force compared to SGI, but the authors of [5] reported that FGI has a higher cutting force. Thus, the machinability comparison of two or more graphite cast irons still needs further research.…”