Casting Technology and Processes Steel parts are required for higher machine parts for strength, ductility and toughness. Cast steel production after cast iron, accounting for about 15% of total casting output.

The main castings of the Great Wall Machinery Cast Steel:Girth Gear for Ball Mill&rotary kiln,Slag Pot,Grinding Roller for Vertical Mill,Grinding Table for Vertical Mill,Rotary Kiln Tyre and so on.

一、according to the chemical composition Cast steel can be divided into two categories of carbon steel and alloy steel. One of the most widely used carbon cast steel, accounting for more than 80% of the total output of cast steel.

1, carbon steel In general, the melting point of low carbon steel, casting performance is poor, only used in the manufacture of motor parts or carburizing parts; medium carbon steel, cast iron with a higher than the overall performance, namely, high strength, Has excellent plasticity and toughness, it is suitable for the manufacture of complex shapes, strength and toughness demanding parts, such as train wheels, forging hammer and anvil rack, roll and high pressure valves, carbon cast steel is the most used one Class; high carbon steel low melting point, its casting performance is better than carbon steel, but its poor plasticity and toughness, only for the manufacture of a small number of wear parts.

2, alloy steel According to the total amount of alloying elements, alloy steel can be divided into two low-alloy steel and high alloy steel. Low-alloy steel, the main application of manganese, manganese and silicon-based Department of chromium and so on. Used to manufacture gears, hydraulic press work and hydraulic turbine rotor parts, with wear, heat or corrosion resistance and other special properties. Such as high manganese steel, is an anti-wear steel, mainly used in the manufacture of dry friction working conditions of the parts; chromium nickel stainless steel and chromium stainless steel, nitric acid corrosion resistance is high, mainly used in the manufacture of chemical, oil , Chemical fiber and food and other equipment on the parts.

二、the cast steel casting process measures:

1, due to the poor fluidity of molten steel, in order to prevent cold castings and cold castings cast inadequate, cast steel wall thickness can not be less than 8mm; casting system to simple structure, and the cross-sectional size larger than cast iron; Or hot cast; appropriate to improve the pouring temperature, generally 1520 ° ~ 1600 ° C, because the pouring temperature is high, the superheat of molten steel to maintain a long time liquid, fluidity can be improved. But the temperature is too high, will cause coarse grain, hot crack, porosity and sticky sand and other defects. So the general small, thin-walled and complex shape of the casting, the casting temperature is about the melting temperature of steel + 150 ℃; large, thick-walled castings pouring temperature higher than its melting point of about 100 ℃.

2, in order to prevent the casting shrinkage, shrinkage defects in the casting process are mostly riser and cold iron and subsidies and other measures to achieve the order of solidification. In addition, in order to prevent the steel castings shrinkage, shrinkage, porosity and crack defects, should make the wall thickness uniform, to avoid sharp corners and right angle structure, in the mold sand with sawdust, add coke in the core, and The use of hollow core and oil sand core, etc. to improve the sand or core of the concession and permeability.

三、the heat treatment of steel castings

Steel castings shall be used after heat treatment. Because of the cast steel under the existence of the internal stomata, cracks, shrinkage and shrinkage, grain size, uneven organization and residual internal stress and other casting defects, so that the strength of steel, especially plasticity and toughness greatly reduced. For grain refinement, uniform organization and elimination of internal stress, steel castings must be normalized or annealed. Normalized steel, the mechanical properties than the high after annealing, the cost is low, so the application of more. However, due to normalizing treatment will cause a larger annealing internal stress, only applies to carbon content of less than 0.35% of the steel castings. Because the low-carbon steel castings good plasticity, cooling is not easy to crack. In order to reduce internal stress, steel castings in normalizing, the high-temperature tempering should be carried out. For the carbon content ≥ 0.35%, the structure is complex and easy to crack steel castings, can only be annealed. Steel castings should not be quenched, or easily cracked.

四、the melting of cast steel

Cast steel smelting generally use open hearth furnace, electric arc furnace and induction furnace. Open hearth furnace is characterized by large capacity, the use of scrap as raw materials, can accurately control the composition of steel and can melt high-quality steel and low-alloy steel, used for melting quality requirements of large, large steel with steel casting. Three-phase electric arc furnace open and shut down the furnace easy to operate, to ensure the composition and quality of molten steel, the burden of less stringent requirements, easy to heat, it can be refined high-quality steel, advanced alloy steel and special steel, is the production molding Casting of the commonly used equipment. In addition, the use of frequency or IF induction furnace, can melt a variety of high alloy steel and carbon content of very low steel. Induction furnace smelting fast, little burning alloy elements, low energy consumption, and high quality steel, impurity content is small, less inclusion, suitable for small cast steel workshop.