Engaged in machining, high-precision mechanical parts manufacturing, the selection of blanks to determine, not only affect the economy of the manufacture of blanks, but also affect the economics of machining. Therefore, in determining the blank, both the hot processing aspects should be considered, as well as economic aspects, but also to take into account the requirements of cold processing, in order to determine the blank from this link, to reduce the manufacturing cost of parts.
First. Castings
The shape of complex parts blank, it is appropriate to use casting methods of manufacture. Most of the current castings with sand casting, which is divided into wooden mold manual modeling and metal mold machine modeling. Wooden mold hand-shaped castings with low accuracy, processing surface allowance, low productivity, suitable for single-piece small batch production or large parts of the casting. Metal mold machine molding high productivity, casting accuracy, but the high cost of equipment, the weight of the casting is also limited, suitable for mass production of small and medium-sized castings. Second, a small number of small castings with high quality requirements can be used for special casting, such as pressure casting, centrifugal manufacturing and investment casting.
Second, forgings
Mechanical strength requirements of high steel parts, generally to use forging blanks. Forgings are free forging forgings and die forgings of two kinds. Free forging forgings can be manually forged (small blanks), mechanical hammer forging (medium-sized blanks) or press press forging (large blanks) and other methods to obtain. The accuracy of such forgings is low, the productivity is not high, the machining allowance is large, and the structure of the parts must be simple, suitable for single and small batch production, as well as the manufacture of large forgings.
The accuracy and surface quality of the forgings are better than the free forgings, and the shape of the forgings can also be more complex, and thus can reduce the machining allowance. The production efficiency of die forging is much higher than that of free forging, but it needs special equipment and forging die, so it is suitable for small and medium-sized forgings with large batches.
Three, profiles
Profiles can be divided into: round steel, square steel, hexagonal steel, flat steel, angle steel, channel steel, I-beam and other special cross-sectional profiles according to the shape of the section. Profiles have two types of hot-rolled and cold-drawn. Hot-rolled profiles have low accuracy, but are inexpensive and used for general parts of the blank; cold-drawn profiles are smaller in size, high in accuracy, easy to achieve automatic feeding, but higher in price, and are used for larger batch production, suitable for automatic machine tool processing.
Fourth, the welded parts
Welded parts are obtained by welding method, the advantages of welding is simple manufacturing, short cycle time, saving materials, the disadvantage is poor vibration resistance, deformation, need to be processed by aging before mechanical processing.