Views: 0 Author: Site Editor Publish Time: 2022-07-29 Origin: Site
Cast iron still occupies a place in automotive materials because of its many advantages in performance and cost.
(1) Ductile iron
Ferritic Ductile iron has a tensile strength of 500MPa and high toughness, so it is mostly used for chassis parts, and some models are even used as safety parts such as steering knuckle.
Pearlitic ductile iron has higher strength and can replace forged steel parts in some parts. The crankshaft of 4-cylinder car engine with balance weight adopts nodular cast iron and fillet rolling strengthening, which has become the standard process of automobile manufacturers in the United States, Germany, France and other countries. Because the density of nodular iron is about 10% less than that of steel, substituting nodular iron for steel can produce a certain lightweight effect.
ADI austempered ductile iron has high strength and ductility. The highest strength grade of ADI manufactured according to American and German standards reaches 1400MPa, which exceeds the strength level of quenched and tempered steel and carburized steel. ADI can be used instead of steel to manufacture automobile hubs, all wheel drive tandem rods, steering knuckle arms, engine timing gears, crankshafts, connecting rods, etc. Through physical measurement, the weight of crankshaft made of forged steel can be reduced by 10%, and the weight of truck hub made of aluminum alloy can be reduced by 0.5kg each.
(2) Vermicular graphite cast iron
Vermicular graphite cast iron is also called compact graphite cast iron. Its mechanical physical properties and casting process performance are between gray cast iron and ductile cast iron. It is very suitable for manufacturing parts with high strength requirements and bearing thermal cycle load, such as cylinder block, cylinder head, exhaust manifold and brake drum.
The discovery of vermicular cast iron is at the same time as nodular cast iron, but its application is limited due to the difficulty of vermicular process control. Sinter cast process control system opens up a broad prospect for the application of vermicular cast iron. The weight of vermicular iron cylinder block is 16% lower than that of gray cast iron cylinder block, and the structural stiffness is increased by 12%~25%. Using vermicular iron to make cylinder block can also improve friction and wear performance, reduce vibration and noise, and improve emissions.
Powder metallurgy materials
Due to the large degree of freedom of composition of powder metallurgy materials and the near net shape characteristics of powder sintering process, its application in automobiles has an increasing trend, especially the application of iron-based powder sintering materials in complex structural parts requiring high strength is more and more.
Assembled powder metallurgy hollow camshaft is a new product in recent years. It is made of iron-based powder metallurgy materials and then fixed on the hollow steel pipe by sintering or mechanical methods. Compared with conventional forged steel or cast iron parts, the weight can be reduced by 25% - 30%. This kind of camshaft has been used in high-speed gasoline engine, with? With the increasingly severe service conditions of diesel engine camshaft, powder metallurgy hollow camshaft has the trend to be promoted to diesel engine.
Powder forged connecting rods have been successfully applied. The production cost of the once sintered powder metallurgy connecting rod technology developed in recent years is low, and 11% light weight can be achieved.