Development Of Brake Lever For Vehicle With High Strength And High Plasticity Ductile Iron

Among the components of the vehicle,the brake lever is the connection device of the brake,which enables the entire brake system to be combined in an orderly manner,and is one of the important links for ensuring the safety of the vehicle.Due to the existence of multiple thin-walled holes in the brake lever,friction loss is easily generated at the joint,so it is required to have high strength and good wear resistance;the impact force generated during the braking process is large,in order to Avoid deformation under the action of external force,and have high requirements on the plasticity of the material.Therefore,the development of high-strength and high-plastic vehicle brake levers is imminent.Because the graphite in the ductile cast iron is spherical,the splitting effect between the crystal grains is greatly reduced,the stress concentration is small,so the strength is greatly improved,and at the same time,it has a certain plasticity,so it becomes a high strength and high plasticity.The best choice for lever materials for vehicle braking.At present,there are three main methods for improving the strength of ductile cast iron,heat treatment,casting process and alloying.However,the former two methods have high cost,complicated process and low yield.Therefore,the alloying method is used to strengthen the performance of ductile iron.The research goal is to obtain high strength and high plasticity QT600-7 nodular cast iron in the as-cast state.The graphite size rating should be≥5 and the spheroidization level should be≥3.Firstly,the effects of different contents of Mn on the microstructure and mechanical properties of ductile cast iron were studied,and the suitable content was optimized.When the plasticity meets the requirements,the tensile strength is lacking.Because Cu and Ni can promote the formation of pearlite and improve the tensile strength of the material,on this basis,different content of Cu element and appropriate amount of Ni element are further added.After sufficient alloy strengthening,the microscopic study of ductile iron is studied.Changes in microstructure and mechanical properties,and found that the material meets the performance requirements of high strength and high plasticity.In the end,the subject reached the following conclusions:(1)The effects of different contents of Mn on the microstructure and mechanical properties of ductile cast iron were studied.It was found that within a certain range,with the increasing content of Mn,the harmful S element in the molten iron was consumed,which indirectly promoted the precipitation of graphite.At the same time,the pearlite content has also increased,and the corresponding mechanical properties have been continuously improved.When the content of Mn is 0.6%,it is a turning point.At this time,the spheroidization rate is 85%,the spheroidization grade is 3,the tensile strength is 576 MPa,and the elongation is 7.5%.Further research found that Mn element continues on this basis.When increased,the precipitation of graphite will be inhibited and the spheroidization rate will be reduced.Excessively high content of Mn will lead to the appearance of free cementite in the matrix structure,which will reduce the mechanical properties of ductile iron.(2)The effects of different content of Cu on the microstructure and mechanical properties of ductile cast iron were studied.It was found that the contribution of Cu to graphitization was weak.After increasing the content of Cu,the amount and size of graphite in the microstructure were not much different.The grade is grade 3 and meets the production requirements.Cu element has a strong role in promoting the formation of pearlite.When the content of Cu element is 0.5%,it can produce a ferrite-pearlite mixed matrix of ductile iron,but the tensile strength is low;as the content of Cu increases to 1.2%When left and right,the pearlite in the iron matrix can reach more than 90%.At this time,the tensile strength of the ductile iron is 870 MPa,the elongation is 2.5%,and the plasticity is poor,which cannot meet the demand for use.After the Ni element was added on the basis of 0.5%Cu content,the pearlite in the matrix structure was sufficiently refined.The tensile strength of the ductile iron was found to be 642 MPa,the elongation was 7.5%,and the mechanical properties reached QT600-7 requirements.(3)The spheroidal graphite cast iron was tested for friction and wear samples.It was found that after strengthening by alloying method,the average friction coefficient of the sample was lower,the hardness was higher,and the wear resistance was better.Among them,the ductile iron after adding the Ni element has the best wear resistance,and the material after the abrasion test loses the least weight.After observing the worn surface of the material,it can be known that the ductile iron strengthened by the alloying method has a higher amount of graphite balls,and the spherical graphite can have a good lubricating effect in the friction,so the wear resistance is higher.