National Conference on
emerging research trend in science and technology
September 27th – 29th, 2018
HJD Institute of Technical Education & Research
Gajod, At. Kera, Kutch, Gujarat, India
Effect of Centrifugal Force and Speed in Casting of Aluminium alloy – a Review
Hirak Naik1*, Misal Gandhi2, Milan Patel3 , Rikesh Prajapati4
[email protected]*, [email protected], [email protected], @gmail.com4
1Research Scholar of Mechanical Engineering, S. N. Patel Institute of Technology & Research centre, Umrakh, Dist. Surat, Gujarat, INDIA
2,3,4Department of Mechanical Engineering, S. N. Patel Institute of Technology & Research centre, Umrakh, Dist. Surat, Gujarat, INDIA
This review is about to focus on effects of centrifugal forces and various rotational speeds as well as metal flow in casting on microstructures and mechanical properties of different alloy formed under different centrifugal casting conditions in graphite molds. Various mold rotating rates were adopted in the experiment. Results show that grain size and lamellar thickness decrease with the decreasing of casting modulus or the increasing of centrifugal force, while tensile strengths are considerably enhanced. It is found that the grain size or thickness in the two molds shows effect with the cooling rate, and the quantitative relationships between structures and cooling rates have been obtained. The solidification rate affects the microstructure and mechanical properties of the castings. Also the grain size is directly depending on the solidification rate of the casting. Grain size has been measured for the gravity castings at different cooling rates and using this result rate of solidification of the centrifugal casting is determined which are carried out at different rotational speeds
Keywords: Centrifugal Force, Gravity Die Casting, Cooling rate, Rotational speed, Rotational time
Centrifugal casting process has been mainly used for obtaining cylindrical parts. There are two types of centrifugal casting processes: horizontal type and vertical type. horizontal type which rotate about horizontal axis and vertical type which rotates about a vertical axis. Horizontal centrifugal casting machines are generally used to make pipe, tube, bushing, cylinder sleeves (liners), and cylindrical or tubular casting that are simple in shape. The application of vertical centrifugal casting machines is considerably wider: gear blanks, pulley sheaves, wheels, impellers, electric motor rotors, valve bodies, plugs, yokes, brackets. Casting that are not cylindrical, or even symmetrical, can be made using vertical centrifugal casting. Centrifugally cast parts have better cleanliness and microstructures.1
Centrifugal casting is one of the techniques in material processing in which the flow pattern of the molten metal strongly affects the quality of the final product. it should be possible to produce a true uniform cylinder when the mould is rotated at low speeds but, depending upon the conditions of the molten metal, the mould has to be accelerated to a certain speed to obtain a uniform cylinder.2
In centrifugal casting, achieving higher cooling rate depends on the fluidity of the molten metal, which again depends on the mold rotation. Hence, the cast tubes needs to be processed with different rotational speed of the mold to understand the effect of cooling rate and in turn mechanical properties.3
2. Literature Survey
Li Xinlei et al.4 , had investigated the effect of rotational speed in counter-gravity die casting of A357 aluminum alloy. They performed the experiment on different rotational speed range of 0, 50, 150 rpm with vibration. The results show that counter-gravity die casting has better feeding capacity than the vacuum suction casting; and effect of mechanical vibration surpass the growth of dendrites, and improve the mechanical properties By increasing rotational speed upto 150 rpm will resulted into fine grain and higher strength. However, Rotational speed above 150 rpm it will resulted into the decrease mechanical properties as well appear the defects.
Li Changyun et al.5, concluded that the castings obtained in the centrifugal field are better than that obtained in the gravity field. In this research paper investigate on coriolis force and centrifugal force. effect of force will resulted in that, melt sticks to the wall which is opposite to the rotational direction to fill in the runner. As increasing the rotational velocity further decreasing the casting defects.A. Shailesh Rao, et al.3, studied on the flow of molten metal and effect of centrifugal force in Al-2Si alloy. cast is generated in the vertical mold at the various rotational speeds of the mold. At 600, 800, 1200 rpm rotational speed, shape of tube irregular. However at 1000 rpm uniform spreading of melt and proper shape of the tube. Higher rotational speed will resulted into the decrease in fluidity of molten metal and cooling rate forming coarse grain structure across the tube.
Jia Limin, et al6, Ti-6Al-4V alloy formed under different vertical centrifugal casting conditions in graphite molds. Mold rotating rates of 0, 110 and 210 r/min were adopted in the experiment. Results show that by increasing the centrifugal force, grain size decreasing and mechanical properties, including tensile strength and yield strength are considerably enhanced.
Madhusudhan, at el7, investigated on cooling rate, solidification rate and rotational speed in vertical centrifugal casting. The cooling rate is mainly depending upon the temperature of the die and metal. Since the study of slow rate of solidification gives coarse grains and faster rate of solidification gives fine equi-axed grains. At around 400 rpm the slow rate of solidification gives fine grains and at 800 rpm the rate of solidification is slightly slower hence gives coarse grains.
3. Effect of rotational speed on mechanical properties
Figure 1. Effect of rotational speed on tensile strength on horizontal bar 1
Fig 2. Effect of rotational speed on tensile strength on vertical bar 1
The graph in Figure-1 & 2 shows the rotational effect on casting product. When the rotation speed is 0, the differences in tensile strength of the four groups are not large. After the application of the centrifugal speed, the tensile strength has been improved. For the one particular sample, whose speed is 150 rpm, the tensile strength reaches 315 N/mm2. These were higher by 11.2% than the VSC samples. This is caused by the effect of the centrifugal force and the feeding direction being in the same direction. This improves the feeding ability of casting solidification, make the cast metal more compact, and improves the mechanical properties.1
Figure 3. Rockwell hardness value vs position at a rotational speed for 600 rpm3
Figure 4. Rockwell hardness value vs position at a rotational speed for 800 rpm3
Figure 5. Rockwell hardness value vs position at a rotational speed for 1000 rpm3
Figure 6. Rockwell hardness value vs position at a rotational speed for 1000 rpm3
There are various effects on mechanical properties of cast material due to rotational speed which can be observed with the help of graphs
Figure 3, 4, 5, 6, shows the different Hardness value for the cast tubes using the Rockwell Hardness Tester. The Rockwell hardness test is carried out at 5 points having equal distance along the axis for all the cast tubes and at various speeds. It is observed that high values of hardness are seen in the cast tube produced at 1000 rpm. Due to the non-uniform distribution of the melt, variation in the hardness value is observed for below and above 1000 rpm.
In this present review paper the effect of centrifugal force and rotational(centrifugal) speed is measured. The variation in speed and centrifugal force is done. The variation in speed directly affects the mechanical properties of cast product. The better rotation range gives the best mechanical properties and fine grain structure. As well the rotational speed crosses such limit decrease of mechanical properties occurs and coarse grain structure formed.
IJDI-ERET International Journal of Darshan Institute on Engineering Research and Emerging Technology
Cs – Saturation concentration of dissolved oxygen in water (mg/L).
Rpm Revolution per minutes.
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P. G. Mukunda1, Shailesh Rao A1,*, and Shrikantha S Rao, Influence of Rotational Speed of Centrifugal Casting Process on Appearance, Microstructure, and Sliding Wear Behaviour of Al-2Si Cast Alloy. Met Mater Int, 16, 1, pp. 137~143, 2010.
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A. Shailesh Rao, Mahantesh S. Tattimani, and Shrikantha S. Rao, Effect of Rotational Speeds on the Cast Tube During Vertical Centrifugal Casting Process on Appearance, Microstructure, and Hardness Behavior for Al-2Si Alloy. The Minerals, Metals & Materials Society and ASM International, 46, 2, pp 793–799, April 2015.
Jia Limin, Liang Zhimin, Xu Daming, Guo Jingjie, Effects of Centrifugal Forces and Casting Modulus on Structures and Mechanical Properties of Ti-6Al-4V Alloy. Rare Metal Materials and Engineering, 45, 3, 2016.