Heat treatment of cast iron

Apr 9 13:31 2013 David Yvon Print This Article

Cast iron is cost low, the production process is simple and has excellent casting and cutting performance, also has high wear-resisting, less friction and eliminate shock resistance and low notch sensitivity, at present, is still one of the most important materials in the machinery manufacturing industry.

Cast iron is the earlier used material in the history,Guest Posting also one of the cheapest metal materials. Such as machine bed, headstock, tailstock, internal combustion engine cylinder block, cylinder liner, piston rings and camshafts, crankshafts are made of cast iron, in agricultural machinery, automobiles, machine tools and other industries, the cast iron is total account for 40%-90%. The same as steel, cast iron is mainly used the Fe, C elements as iron-based material, but has a high carbon content (more than 2.11%), also containing more sulfur, phosphorus and other impurity elements. According to metal powder supplier, in order to further improve the mechanical properties or special properties of cast iron, also can be add chromium, molybdenum, vanadium, copper, aluminum and other alloying elements, or improve the content of silicomanganese phosphorus and other elements, this cast iron is referred to as alloy cast iron. Common alloy cast iron has cast iron, heat-resistant cast iron, corrosion-resistant cast iron.

The cast iron that hard to be wear is called wear-resistant cast iron, general can be formed certain amount of hardening phase to improve the wear-resistance by adding some alloying elements in cast iron. According to their working conditions, wear resistant cast iron can be divided into antifriction cast iron and wear-resistant cast iron two categories.

Antifriction cast iron is refered to as the wear-resistant cast iron work in the lubrication conditions. Although the ordinary gray cast iron has good wear-resistance, but for Machine tool, engine cylinder liners and piston rings and other parts, this is still far failed to meet the requirements. The way to increase antifriction cast iron is mainly through alloying and inoculation, common alloying elements has Cu, Mo, rare earth, Mn, Si, P, Cr, Ti, etc. , the common used inoculant is ferrosilicon. Common antifriction cast iron has phosphorus-containing cast iron, vanadium and titanium cast iron, boron cast iron three types and other antifriction cast iron developed on the basis of them. Most of these cast iron were by improving the organization of the cast iron to improve the wear resistance of the cast iron.

The wear-resistance of antifriction cast iron is closed to the substrate organization. Its organization is generally distributed hard particles in a soft matrix, theoretically, the higher the hardness of the matrix, the better the abrasion resistance, but high hardness of the substrate is not conducive to the film formation of graphite. In cast iron, the pearlite is an ideal organization. Wherein the ferrite is the soft substrate, cementite is hard particle, while the flake graphite has lubrication role, in order to further improve the wear resistance of pearlitic gray cast iron, can increase the mass fraction of phosphorus element to 0.4%-0.7%, formed of high phosphorus cast iron. The morphology of pearlite is better the flake. In granular pearlite, carbide is easy to fall off to form of abrasive, so that its wear resistance is worse than pearlite, generally do not want this kind of organization.

Boron is a rich alloying element in China, the total storage is accounted for fifth in the world. Boron is a special element, atomic number is five, between metal and nonmetal, both can combine with the metal and the non-metallic. Adding a small amount of boron powder (0.01 to 0.1%) in cast iron can effectively improve the hardness of the cast iron, corrosion and wear resistance, therefore, the emergence of boron cast iron also caused great importance around the world, particularly industrial countries. Cast iron boron as antifriction material put into industrial, only have 50 years history. The application of boron cast iron in China is late, started to develop in the early 1970s, and applied to cars and tractors cylinder liner and piston rings, get good results.

Source:http://www.mhcmp.com

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