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Machinability of Materials
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
Finally, the machinability of P/M parts can be increased through the use of free machining additives [184,186,187]. Additives are effective for P/M materials for essentially the same reasons they are effective in cast irons and wrought steels; they result in the formation of inclusions in the material matrix, which serve to lubricate the tool—chip contact and reduce cutting friction and temperature. Additives also generally reduce cutting forces, reduce BUE formation, improve surface finish, and increase chip breakability. For P/M steels, manganese sulfide is the most common and effective additive, followed by sulfur and lead. Bismuth, graphite, tellurium, and selenium are also usually effective. Adding copper is also effective when it results in a significant increase in thermal conductivity. Iron—copper P/M steels are used extensively in automotive applications for bearing caps, connecting rods, and valve seats and guides; care should be taken in these applications in reducing copper content to reduce costs, as this may result in greatly reduced tool life. Many contemporary valve seat alloys are infused with copper to reduce porosity and increase heat conduction; these alloys have high hardness, however, and are normally difficult to machine.
Flow of Solid-Liquid Mixture in Pipe (Slurry Pipelines)
Published in Henry Liu, Pipeline Engineering, 2017
Plug valves, ball valves, gate valves, and check valves are all used in slurry pipelines. The main difference between valves for slurry and for water is that the former must be more rugged and protected against wear. For slurry pipelines that must be pigged (it is a good idea to design slurry pipelines with the ability to pass pigs), full-bore valves must be used to allow free passage of the pigs. This eliminates plug valves, which cannot have full bore. Full-bore ball valves are always the best for slurry pipelines except that they are more expensive than gate valves. Globe valves and butterfly valves should not be used because they block the passage of slurry and can wear rapidly. Most commercial slurry valves contain mechanisms for flushing the valve with clean water periodically. This keeps the gap between the valve body and the valve seat free of solid particles, thereby minimizing valve wear and optimizing valve operation. Otherwise, the valves will soon be worn out or even be jammed during operation.
The reciprocating piston petrol engine
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
Valve seat inserts for aluminium alloy cylinder heads are produced from either a nickel alloy iron casting, or a sintered powder metal the composition of which can be tailor-made to impart the desired hot strength, hardness and corrosion resistance, together with a matching coefficient of expansion. Metal sintering is later explained in Section 1.7 in relation to engine connecting rods.
Dynamic characteristics evaluation of balance valve for seawater hydraulic variable ballast system considering the depth variation
Published in Ships and Offshore Structures, 2022
Zhenyao Wang, Yinshui Liu, Qian Cheng, Hao Pang, Yunxiang Ma, Shendan Zhao, Wei Wang, Defa Wu
As shown in Figure 1, the balance valve is mainly composed of a valve seat, a bolt, a ball, a push rod, a spring and two valve bodies. In order to prevent seawater from corroding materials (Rajput et al. 2020), all parts in the balance valve are made of anti-corrosion materials (Wang et al. 2014). The bolt, valve body, and spring are made of stainless steel (316L). The push rod is made of polyether-ether-ketone (PEEK). The material of the ball is ceramic (Si3N4). And the valve seat is made of stainless steel (316L) and polyamide (PA66).