Effect of vibration frequency on primary phase and properties of grey cast iron fabricated by lost foam casting

The properties of gray cast iron(GCI)are affected by density of matrix,size of flake graphite and primary austenite.In this paper,the Y-type specimen of GCI was prepared by lost foam casting(LFC)with and without vibration,and the influence of vibration frequency on the density of matrix,size of primary phase,and properties of the GCI was studied.The results show that the length of the flake graphite and the size of the primary austenite in GCI firstly decrease and then increase with the increase of the vibration frequency.With a vibration frequency of 35 Hz,the length of the flake graphite is the shortest,the primary austenite is the finest and the density of the matrix is the highest.In addition,the tensile strength,elongation and hardness of the GCI firstly increase and then decrease with the increase of the vibration frequency,due to the refinement of the primary phase and the increase of the matrix density.In order to analyze the refinement mechanism of the primary phase of the GCI fabricated by the LFC with vibration,the solidification temperature fields of the GCI fabricated by the LFC with the vibration frequency of 0 and 35 Hz were measured.The results show that the vibration reduces the eutectic point of the GCI and increases the supercooling degree during the eutectic transformation.As a result,the length of the flake graphite and the size of the primary austenite in GCI fabricated by LFC with the vibration frequency of 35 Hz decrease.

Sliding Wear Behavior of a Grey Cast Iron Surface Remelted by TIG

The sliding wear behavior of a grey cast iron surface remelted by tungsten inert gas （TIG） was studied and compared with the unremelted one in the current work. To evaluate the wear behavior a Pin-on-Disk wear test machine was used. Pins which were prepared from the samples with the remelted layers of different thicknesses of 1.2, 1.8, 2.5 and 3 turn were worn on an AISID3 steel counterface having a hardness of 63HRC under the applied loads of 54, 76 and gg N at a constant sliding velocity of 0.45 m/s. Scanning electron microscopy （SEM） equipped with energy dispersive X-ray analysis （EDS） and X-ray diffraction （XRD） techniques were used to characterize worn surface and subsurface and also wear debris obtained from the wear tests under different test conditions. Results showed that surface remelted grey cast iron have better wear properties for all applied normal loads in comparison with unremelted ones. Microscopic studies on the worn surfaces and subsurfaces of samples revealed that dominant wear mechanism for surface remelted samples was mild oxidative, while it was severe for unremelted samples. Increasing remelted layer thickness and then forming grosser microstructure lead to a decline of wear properties, whereas lower thickness of remelted layer with finer microstructure due to having higher cooling rate through remelting process can withstand better against wear.

THERMAL FATIGUE AND FRACTURE MECHANICS ANALYSIS OF GREY CAST IRON

The in-phase and out-of-phase thermal fatigue,the C-P type and P-C type isothermal fa- tigue of grey cast iron were experimentally studied.The fatigue life was evaluated analytically by using the elastic-plastic fracture mechanics method(mainly J integral).The results of ex- periments and calculations showed that the lifes of in-phase and C-P type fatigue are longer than that of out-of-phase and P-C type fatigue respectively within the same strain range. This is in contrast to the results of other materials such as low carbon steel.On the other hand, the predicted lifes are consistent with experimental results.This suggests that J integral as a mechanics parameter for characterizing the thermal fatigue strength of grey cast iron and the mechanics model and the calculation method developed here are efficient.A parameter ΔW_1 was proposed from energy aspect to characterize the capacity of crack propagation. The isothermal fatigue life is the same as the thermal fatigue life for identical ΔW_1 values.

Research on Welding Test of Grey Cast Iron and Low-Carbon Steel

Grey cast iron’s welding itself is a complex proble m.So proper welding materials must be selected,complex welding techniques such as preheating before weldingslow cooling after welding etc,should be taken. However the carbon component in low-carbon steel is comparatively low,the carbo n of welded joint will diffuse to the low-carbon steel when it is welded with gr ey cast iron,which will cause the component of carbon greatly increased at the low-carbon steel side in HAZ,high carbon martensite and cracks will occur.If p reheating before weldingslow cooling after welding and other welding procedure are taken,the grey cast iron side can probably be qualified.But the carbon wi ll diffuse to HAZ of the low-carbon steel side more easily.Therefore after stud ying the weldabilities of grey cast iron and low-carbon steel,the author develo ped a new type of cast iron electrode considering the demands of factories’prac tices,and the welding technology test of grey cast iron and low-carbon steel ar e carried out. In this paper,a new type of grey cast iron electrode is developed based on the practices in factories,its ingredients and properties are introduced.The w elding tests of grey cast iron and low-carbon steel are practiced.The joint str ucture of the dissimilar metal and the appearance of weld are observed.The hard ness distribution of the welded joint is tested.The results show that the elect rode can meet the welding requirements of the grey cast iron and low-carbon stee l.There are no cracksgas pores and other defects of metallurgy in welded join t,the appearance of welded joint are good.

Molybdenum alloying in cast iron and steel

Metal casting is an important manufacturing technology for efficiently producing massive components with complex shape.A large share of industrial castings is made from iron and steel alloys,combining attractive properties and low production cost.Upgrading of properties in cast iron and steel is mainly achieved by alloying and in fewer cases by heat treatment.Molybdenum is an important alloying element in that respect,increasing strength,hardness and toughness.It also facilitates particular heat treatments such as austempering.The paper describes the metallurgical functionality of molybdenum alloying in iron-based castings and demonstrates its effectiveness for applications in the automotive and mining industry.

Defect elimination in green sand casting using simulation techniques:A case study

The Reynolds number of molten metal flowing mold cavity causes bulk turbulence and is the main cause of defects like shrinkage porosity and sand erosion.Machined housings with shrinkage porosity at critical bearing bores and surface made the casting useless.In old gating casting areas of perimeters 290mm and 264mm of transmission housing,Reynolds numbers were observed as 16307 and 13806,respectively using simulation software.Data were collected from experiments to change casting area perimeters from 785mm and 785mm along with the addition of overlap area.New Reynolds numbers at two locations were observed as 3705 and 3393,respectively.Molten metal pressure,velocity and temperature results were related for final shrinkage results of the components on full production.The purpose of the study is to reduce shrinkage and porosity defects in green sand casting part using MAGMAS simulation software.High outcome was the reduction of casting machining rejection in transmission housing casting from 5.8%0.7%with savings of approximately 0.13 million USD over the period of 14 months.Implications of this work include casting defects study and reduction in different grades and weight range.