Study On The Effect Of Composite Powder On The Mechanical Properties Of QT400-18

Since the invention of nodular cast iron in the 1950s,its relatively high cost performance has been rapidly applied to various fields in industrial production and is one of the most widely used metallic materials in the modern casting industry.In the field of automobile manufacturing,the cylinder block,crankshaft,rear axle housing,and all kinds of brackets of large engines are made of ductile iron.In the field of wind power generation,most of the key castings are also made of ductile iron.With the improvement of industrial technology on the mechanical properties of ductile iron,the mechanical properties of ductile iron have not been satisfied.Therefore,some new research methods are needed to improve the mechanical properties of ductile iron.The high melting point,high hardness of the composite powder and its good compatibility with the liquid metal can play an important role in the field of ductile cast iron strengthening and toughening.This article takes QT400-18 as the research object,discusses the effect of adding different mass percentages of composite powder on its microstructure,tensile strength,elongation,impact properties and hardness,and comparative analysis of the results of the organization and performance testing,preliminary discussion of composite powder Body toughening mechanism.With the change of the amount of composite powder added in QT400-18,its spheroidization rate increased from 82.71%to 95.56%in the microstructure,the grade of graphite increased from 3 to 1 and the pearlite content decreased from 21.85%to 11.43%,matrix structure has been refined;mechanical properties,QT400-18 tensile strength increased from 493.03MPa to 526.52MPa,an increase of 6.7%,elongation from 18.67%to 21.49%,an increase of 11.54%;In the hardness test,the Brinell hardness of QT400-18 changed little,with an average value of 140HB;in the Vickers hardness test,the Vickers hardness value of the substrate increased from 212.85HB to 236.57HB;in the impact test,the impact toughness increased from 10.13J to 12.98J,an increase of 28%.In this paper,the preliminary study on the strengthening mechanism of QT400-18 composite powder is given.After the composite powder is added to QT400-18,the influence on the tensile strength may be caused by the following reasons:Firstly,more heterogeneous cores may be formed.,The increase in the number of crystal grains,grain growth inhibition,play a role in grain refinement;Secondly,the graphite sphere diameter,distribution and pearlite content,distribution may be refined,adding more similar to the second The phase material particles form more dislocations;in the end,it may play a role of increasing "cold iron" in the molten iron,increase the degree of supercooling of the molten iron,and promote grain refinement.