1. Composition design
In order to understand the influence of vanadium, titanium, carbon and silicon content on the microstructure and properties of gray cast iron, four kinds of vanadium titanium gray cast iron with different composition were designed (as shown in the table). Because vanadium and titanium are carbide forming elements, the free carbon in gray cast iron is reduced. In order to obtain more graphite structure, higher carbon content is required. However, in order to obtain more pearlite and improve the strength of gray cast iron, ferrite and coarse graphite in gray cast iron need to be reduced, and the carbon content can not be too high. Therefore, the carbon content in gray cast iron is determined to be 3.00% ~ 3.30%. At the same time, in order to ensure the good fluidity of gray cast iron and reduce the tendency of shrinkage cavity, porosity and white mouth, the carbon equivalent is controlled at about 4.0%, in which the silicon content is designed to be 1.70% ~ 1.85%, the manganese content is designed to be 0.80%, and the contents of phosphorus and sulfur are controlled within 0.10% and 0.06% respectively.
2. Experimental method
Samples were cut from the brake drum body actually produced by an enterprise in Luoyang, of which the metallographic sample size was 10 mm × 10 mm × 10 mm. After preparing the sample, use olympusg respectively × The graphite morphology of vanadium titanium gray cast iron with different composition was observed by type 51 metallographic microscope. The thermal conductivity and thermal diffusivity of gray cast iron were measured by laser flash method. Hb-3000 Brinell hardness tester is used for hardness testing. Five standard tensile samples are processed according to GB / t9439-2010. The tensile strength of vanadium titanium gray cast iron is measured on rgm-4300 electronic tensile testing machine, and the tensile rate is 2 mm / min.