How to improve the mechanical properties of cast gray iron?
Gray cast iron is an iron-carbon alloy in which the section surface is gray. Through the control of the composition and the solidification process, the carbon mainly appears in the form of flake graphite. The metallographic structure of gray cast iron is mainly composed of flake graphite, metal matrix and grain boundary eutectic.
The existence of flake graphite in gray cast iron destroys the basic continuity of the metal and makes gray cast iron a brittle material. But gray cast iron is one of the earliest and most widely used metal materials. Gray cast iron castings have many properties. For a long time, in production practice, we have summarized some common measures to improve the tensile strength of gray cast iron. Under certain conditions, we can also improve the cutting performance, wear resistance and shock absorption performance of gray cast iron.
In actual casting production, the vast majority of gray cast iron is hypoeutectic. Therefore, in order to improve its tensile strength, the following points should be done as much as possible:
1) Guarantee the gray cast iron has more and more developed primary austenite dendrites during solidification
2) Reduce the amount of eutectic graphite and make it evenly distributed with fine A-type graphite
3) Increase the number of eutectic clusters
4) During the austenite eutectoid transformation, all transform into a fine pearlite matrix
In the actual production of gray cast iron castings, we often use the following measures to achieve the above results:
1) Choose reasonable chemical composition
2) Change the composition of the charge
3) Overheated molten iron
4) Inoculation treatment
5) Trace or low alloying
6) Heat treatment
7) Increase the cooling rate during eutectoid transformation
The specific measures to be taken depend on the type of gray cast iron castings, the required properties and the specific production conditions. However, it is often necessary to take two or more measures to achieve the desired performance of cast iron.
Post time: Dec-28-2020