Study And Development Of Material About Vanadium And Titanium Vermicular Cast Iron Automobile Brake Drum And Casting Design

Automobile brake drum is the most common brake equipment,is also an important guarantee for safe driving.As the car becoming more high-speed and heavy, the existing material can not meet the growing demand,so develop new material which owns good comprehensive performance is necessary. V-Ti vermicular cast iron has acquired by V-Ti iron, which owns good comprehensive performance and can reach the requirement of atomobile brake drum.This paper have researched the method of acquiring V-Ti vermicular cast iron with using V-Ti iron, vermicular agent and inoculation, tested the mechanical properties, microstructure, wear resistance, thermal conductivity, thickness sensitivity thickness, vermicularity recession of V-Ti vermicular cast iron, designed the gating system of V-Ti vermicular cast iron brake drum,compared the mechanical properties, microstructure, wear resistance and thermal conductivity between V-Ti vermicular cast iron and V-Ti gray cast iron.Mechanical test results showed that the tensile strength of V-Ti vermicular cast iron were above 350MPa, Brinell hardness were 230 ~ 280HBW, extension rate were more than 1.42%. It owned superior mechanical properties than V-Ti gray cast iron and reached the requrement of RuT340. By observing microstructure we have known that the graphite morphology of ervery furnace V-Ti vermicular cast iron was worm-like and spherical, vermicular graphite were more than 60%. The matrix of V-Ti vermicular cast iron were pearlite, ferrite, a small amount cementite and alloy compounds, the amout of pearlite were more than 50%.The effect of alloy elements in vermicular cast iron such as vanadium and titanium and fracture mechanisms by scanning electron microscopy (SEM) and energy dispersive (EDS). The results showed that vanadium and titanium existed in forms of carbide which like block, multilateral shape, riangular shape, or solid solution in cementite. Since the dispersion strengthening of vanadium and titanium compounds, solid solution strengthening vanadium and titanium cementite, the role of grain refinement and refining graphite of vanadium and titanium, the strength and hardness of V-Ti vermicular cast iron had been improved. But when the alloying elements existed or enriched inprecipitate grain boundaries as precipitate phase, the strength and plastic of compacted graphite cast iron will be reduced. The crack of V-Ti vermicular cast iron originated from graphite accumulation area, the fracture morphology were small amount of shallow dimples and river patterns which existed as mixed ductile - brittle.The thermal conductivity and wear properties of V-Ti vermicular cast iron and V-Ti gray cast iron had been tested by laser thermal constant analyzer and reciprocating friction and wear tester. The results have shown that V-Ti vermicular cast iron owned high a high thermal conductivity, especially at high temperatures can still maintain a relatively high thermal conductivity, the thermal conductivity at high temperatures even higher than V-Ti gray cast iron. The wear resistance of V-Ti vermicular cast iron were superior to gray cast iron, which wear rate were 27% to 35% lower than V-Ti gray cast iron and wear coefficient were 40%to 55% higher than V-Ti gray cast iron.The study on thickness sensitivity of V-Ti vermicular cast iron shown that the hardness increase and organizational change were not obvious during the thickness changed between 50mm to 15mm, the hardness increased and organizational changed obviously during the thickness changed between 15mm to 8mm. Generally speaking, the thickness sensitivity of V-Ti vermicular cast iron was not obvious. The research on vermicularity recession shown that mechanical properties of V-Ti vermicular cast iron which poured at different times after treatment, but when the puring time was within 15 min, the vermicularity recession was not obvious.The mechanical properties and microstructure of different times depended on the value ofβ, which reflected the integrated effects of residual rare earth , residual magnesium content and residual sulfur to the rate of vermicular graphite,the value was more larger, the rate of ductile iron increased, the rate of vermicular graphite delined.