Valve material introduction and material selection (1)

Here mainly introduces the body material, other materials will be added in later articles: 1, cast iron mainly by the iron, carbon and silicon alloy composition. In these alloys, carbon content exceeds the eutectic temperature can be retained in the austenite solid solution classification: ① gray cast iron. Carbon content is higher (2.7% ~ 4.0%), carbon is mainly in the form of flake graphite, gray fracture, referred to as gray iron. Low melting point (1145 ~ 1250 ℃), when the shrinkage of small solidification, compressive strength and hardness close to the carbon steel, good shock absorption. For the manufacture of machine bed, cylinder, box and other structural parts. ② white cast iron. Carbon and silicon content is lower, carbon is mainly in the form of cementite, the fracture is silvery white. Shrinkage when solidified, easy to produce shrinkage, cracks. High hardness, brittleness, can not withstand the impact load. Used as a malleable cast iron parts and wear-resistant parts. ③ malleable iron. Obtained from the white cast iron annealed, graphite was flocculent group distribution, referred to as tough iron. Its uniform organizational performance, abrasion resistance, good ductility and toughness. For the manufacture of complex shapes, can withstand strong dynamic load parts. ④ ductile iron. The gray cast iron molten iron obtained by the ball after the precipitation of graphite was spherical, referred to as ductile iron. More than the average gray cast iron has high strength, good toughness and plasticity. For the manufacture of internal combustion engines, auto parts and farm machinery and so on. ⑤ compacted graphite iron. The gray cast iron hot metal obtained after the vermicular treatment, precipitated graphite was worm-like. Mechanical properties and ductile iron similar casting performance between the gray cast iron and ductile iron. Used to make car parts. ⑥ alloy cast iron. Ordinary cast iron by adding the right amount of alloying elements (such as silicon, manganese, phosphorus, nickel, chromium, molybdenum, copper, aluminum, boron, vanadium, tin, etc.). Alloying elements of the matrix of cast iron changes, which have the corresponding heat, wear resistance, corrosion resistance, low temperature or non-magnetic properties. For the manufacture of mines, chemical machinery and instruments, meters and other components. 1.1 gray iron (cast iron) its strength, wear resistance, heat resistance are good, good vibration damping, casting superior performance, the need for artificial aging treatment. Can be used to require high strength and corrosion resistance of a certain pump casing, containers, tower, flange, packing box body and gland, carbonation tower, nitrification tower, etc .; also make machine bed, column, cylinder, gear and need Gray cast iron valves for surface-hardened parts are gray cast iron valves for water, steam, air, kerosene and oil media with a nominal pressure of PN ≤1.0 MPa and an operating temperature of 10 to 200 ° C. The advantage is lower cost, Own material defects, fragile characteristics of the limited scope of its application. 1.2 ductile iron GJS-400-15 (nodular iron GJS-400-15) ductile iron production costs lower than the cast steel, the mechanical properties of cast iron is better than normal, So now it has been widely used. Plays the role of iron and steel.Dubbling is a good wear-resistant material, its wear resistance is better than gray cast iron and carbon steel. Different tensile strength, the product has a great impact, the higher the tensile strength, the more able to withstand greater external forces and fatigue stress, not easily damaged. So a wide range of applications. 1.3 ductile iron GJS-500-7 (nodular iron GJS-500-7) ductile iron GJS-500-7 ductile iron GJS-400-15 greater strength, good wear resistance, resistance Pull ability.