Study on Machinability of gray cast iron for engine block

1.The designed and manufactured three-dimensional force mounting calibration device can calibrate the stress-strain system simply, quickly and accurately when measuring the turning force. The calibration device is easy to use, directly uses the standard weight as the reference, and can realize the accurate force application in three mutually perpendicular directions; When the wear of short-distance cutting tools is negligible, the change of cutting force caused by blade reassembly and replacement is less than 2%, and the change of cutting force caused by overall tool reassembly is as high as about 11%. When evaluating the machining performance of materials with cutting force, the tool holder tool can be used to replace the blade, but the tool rod needs to be installed at one time.

2.The mechanical properties of gray cast iron are significantly improved by alloying. The compound addition of alloy elements Cu and Cr not only promotes the graphitization process of molten iron, but also reduces the white tendency of gray cast iron, and refines the pearlite matrix of gray cast iron. Cu and Cr alloying can improve the uniformity of pearlite structure and microhardness, reduce the cutting force of gray cast iron in the machining process, and improve the machinability of gray cast iron.

3.The tensile strength of gray cast iron treated with multi-element alloy additives meets the requirements of HT300. When the cutting depth is 3.0 mm, 3.5 mm and 4.0 mm, the cutting force of gray cast iron treated with multi alloy additive is 12.9%, 11.5% and 17.3% lower than that of gray cast iron alloyed with copper, respectively. The wear degree of cutting tools used for cutting samples treated with multi-element alloy additives is not serious as a whole. The sample obtained by copper alloying has large mesh cracks at the cutter head, wide wear area of the blade, serious uneven wear and tear on the tool surface. The experimental results show that the multi-element alloy additive alloying treatment is better than copper alloying in mechanical properties and machinability.

4.Two groups of different samples were prepared with low titanium pig iron and z14 as raw materials. The tensile strength of the two groups of samples was basically the same, with a difference of 1.01%. Under the same cutting conditions, the cutting resistance of gray cast iron samples melted with low titanium pig iron is 4.09% lower than that of z14 cast gray cast iron. The wear area of cutting tools for the two groups of samples is similar, but the damage degree of rake face is quite different. The overall wear of z14 casting gray cast iron tool is more serious, the tool surface is seriously damaged, and the roughness of the wear area is large.

5.Inoculating gray cast iron with four different inoculants, the results show that high-performance cast iron ht350 can be obtained by low alloying and effective inoculation with appropriate inoculants. The gray iron castings inoculated with sisR (80%) + 75fesi (20%) composite inoculant have the highest hardness, but their section sensitivity is large. From the comparison of microstructure photos of castings after inoculation treatment, it can be seen that the graphite of gray iron castings treated with composite inoculation treatment is smaller and bent than that of gray iron castings treated with single inoculation treatment, the uniformity of matrix structure is good, and its mechanical properties and processability are better. Under the same strength, the three-dimensional cutting force and cutting force of the gray cast iron sample inoculated with basi are significantly higher than those inoculated with SRSI.