Influence of Tempering on Microstructure and Performance of Gray Cast Iron
Abstract
This article clarifies the influence of tempering on the microstructure and performance of gray cast iron. Grey cast iron is a cast iron alloy with a rich graphite in the microstructure, so it has good machinability and good casting performance, which is widely used in the production and life. In the actual production process, tempering treatment after casting and other processing steps is a very important step, which has a great influence on the properties of the Gray cast iron. Through literature research and experimental research, this article first introduces the properties and classification of gray iron, then details the influence of tempering on gray cast iron microstructure and performance. The main contents are as follows:
1. The influence of air tempering and oil tempering on the microstructure of grey iron.
2. The effect of tempering on the mechanical properties of gray iron.
3. The effect of tempering on the corrosion resistance and wear resistance of gray iron.
Through the study of tempering treatment of gray iron, it is more feasible to choose the heat treatment process reasonably and make the best use of the properties of gray iron. It is beneficial to provide a reference for the tempering of gray iron in actual production.
Keywords: Gray cast iron, tempering treatment, microstructure, mechanical properties, corrosion resistance
1 Introduction
Gray cast iron is a cast iron alloy which contains a high amount of graphite flakes in the microstructure. It is a commonly used manufacturing material due to its good machinability and castability. In the actual production process, tempering treatment is an important processing technology for gray iron, which can greatly improve its performance. Through this article, the influence of tempering on the microstructure and performance of gray cast iron is described in detail.
2 Gray Cast Iron Properties and Classification
Gray cast iron is an alloy composed of iron, carbon and silicon. It is formed by graphite flake in the microstructure. Graphite is an insulator and lubricant, which makes gray cast iron have good machinability and good casting performance. Gray cast iron can be divided into three categories according to the composition of graphite in the microstructure: nodular graphite cast iron, flake graphite cast iron and compacted graphite cast iron. The mechanical properties and application fields of the three types of gray iron are quite different. Nodular graphite cast iron has good mechanical properties and is mainly used in automobile manufacturing, such as crankshafts and connecting rods. Flake graphite cast iron has good machinability and is mainly used in manufacturing manhole covers, valves and other components. Compacted graphite cast iron (Compacted Graphite Iron, CGI) has good wear resistance and is mainly used in manufacturing heavy-duty and high-temperature components, such as cylinder liners and gears [1].
3 The Influence of Air Tempering and Oil Tempering on the Gray Cast Iron Microstructure and Performance
3.1 Air Tempering
Air tempering is mainly used for gray cast iron parts with a thickness of 5-8mm. Air tempering has a significant effect on the properties of gray iron. Air tempering can increase the hardness of gray cast iron, and also increase the toughness and wear resistance of gray iron. Moreover, tempering can also homogenize the structure of gray iron and refine the pearlite, ferrite and graphite surface, which is beneficial to improve the machinability and other performance of gray iron [2].
3.2 Oil Tempering
Oil tempering treatment can be used for parts with lower thickness. The performance of oil tempering is similar to that of air tempering, which can also improve the hardness, toughness and wear resistance of gray iron and make the structure of gray iron more homogeneous. In addition, oil tempering also has the advantage of low production cost [3].
4 Conclusion
Tempering is an important technology of gray cast iron heat treatment, which can effectively improve the microstructure and performance of gray iron. Through the study, air tempering and oil tempering are adopted for the tempering of gray cast iron. Through air tempering or oil tempering, the hardness, toughness and wear resistance of gray iron can be improved, and the structure of gray iron also can be homogenized. Combined with the actual application, it is more reasonable to choose the tempering process of gray iron, so as to make the best use of the properties of Gray cast iron.
References
[1] WANG Jun-feng, TANG Bao-qun. Centrifugal casting technology of gray cast iron[J]. World Foundry, 2009, 14(04):
[2] ZHOU Xian-hong, LUO Xue-lin, YUAN Xin-li. Study on air tempering ductile iron[J]. Metal Technology, 2006, 35(06):
[3] TANG Shao-jun, WEN Qi-guo, LIU Jing-hua. Study on air tempering of gray cast iron[J]. Metallurgical Research＆Technology, 2018, 33(01):
