Casting is a production method in which molten metal is poured into the cavity of casting mold and cooled and solidified to obtain products. In the process of automobile manufacturing, many parts are made of cast iron, accounting for about 10% of the weight of the whole vehicle, such as cylinder block, transmission housing, steering gear housing, rear axle housing, brake drum and various supports. Sand molds are usually used to make iron castings. The raw material of sand mold is mainly sand, mixed with binder and water. The sand mold material must have a certain bonding strength, so that it can be molded into the required shape and can resist the erosion of high-temperature molten iron without collapse. In order to create a cavity in the sand mold that conforms to the shape of the casting, it is necessary to make a wooden mold, which is called a wooden mold. Hot molten iron will shrink in volume after cooling. Therefore, the size of the wooden mold needs to be increased according to the shrinkage rate on the basis of the original size of the casting, and the surface to be processed will be thickened accordingly. Hollow castings need to be made into sand cores and corresponding core wood molds (core boxes). With the wooden mold, you can turn over the cavity sand mold (casting is also called "turning over sand"). When making sand molds, it is necessary to consider how to separate the upper and lower sand boxes to take out the wooden mold, where the molten iron flows in, and how to fill the cavity to obtain high-quality castings. After the sand mold is finished, it can be poured, that is, molten iron is poured into the cavity of the sand mold. When pouring, the temperature of molten iron is 1250~ 1350℃, and the temperature is higher when melting.
forge
Forging is widely used in automobile manufacturing. Forging is divided into free forging and model forging. Free forging is a processing method (called "strike while the iron is hot") in which a metal blank is placed on an anvil to bear impact or pressure. The blank of automobile gear and shaft is processed by free forging. Die forging is a processing method of putting metal blank into the cavity of forging die to bear impact or pressure. Forging model is a bit like the process of dough being pressed into biscuit shape in the mold. Compared with free forging, die forging has more complex shape and more accurate size. Typical examples of automobile die forgings are: engine connecting rod and crankshaft, automobile front axle, steering knuckle, etc.
driller
Cold stamping or metal plate stamping is a processing method in which the metal plate is cut or formed by pressure in a mold. Daily necessities, female aluminum pot, lunch box, washbasin, etc. It is made of cold stamping. For example, to make a lunch box, you must first cut out a rectangular blank with four rounded corners (experts call it blanking), and then press the blank into a concave die with a punch (experts call it drawing). In the process of painting, the flat plate becomes box-shaped, its four sides bend vertically upwards, and the materials at the four corners pile up together, so folds can be seen. Automobile parts processed by cold stamping include: engine oil pan, brake bottom plate, automobile frame and most body parts. These parts are generally formed by blanking, punching, stretching, bending, flanging, trimming and other processes. In order to manufacture cold stamping parts, a stamping die must be prepared. Usually, the stamping die is divided into two pieces, one is installed above the press and can slide up and down, and the other is installed below the press and fixed. During production, the blank is placed between two stamping dies, and the upper and lower dies are closed to complete the stamping process. The productivity of stamping is very high, and parts with complex shapes and high precision can be manufactured.
weld
Welding is a processing method to connect two metals by local heating or simultaneous heating and pressure. We ordinary workers hold a mask in one hand and an electrode holder connected to the wire in the other. Covered electrode's welding method is called manual arc welding, which uses the high temperature generated by arc discharge to melt covered electrode and weldment, so as to combine them. Manual arc welding is not widely used in automobile manufacturing. Spot welding is widely used in automobile body manufacturing. Suitable for spot welding of thin steel plate. In operation, the two electrodes apply pressure to the two steel plates to make them join, and at the same time, heat and melt the joint (a circle with a diameter of 5~6mm) with current to make it firmly join. When two car body parts are welded, their edges are welded at a distance of 50~ 100mm, which makes the two parts form discontinuous multi-point connection. It usually takes thousands of welds to weld the whole car body. The strength of solder joints is very high, and each solder joint can bear a tensile force of 5kN. Even if the steel plate is torn, the solder joints cannot be separated. Gas welding is a common method in repair shops. Combustion of acetylene and oxygen produce high-temperature flame, which makes covered electrode fuse with weldment. This high-temperature flame can also be used to cut metal, which is called gas cutting. The application of gas welding and gas cutting is flexible, but the heat affected zone of gas welding is large, which leads to welding deformation, metallographic structure change and performance degradation. Therefore, gas welding is rarely used in automobile manufacturing.
heat treatment
Heat treatment is a method of reheating, preserving heat or cooling solid steel to change its structure and meet the use requirements or process requirements of parts. Heating temperature, holding time and cooling rate will cause different microstructure changes of steel. Steels heated by blacksmiths can be quickly cooled by immersion in water (which experts call quenching) to improve their hardness. This is an example of heat treatment. Heat treatment includes annealing, normalizing, quenching and tempering. Annealing is to heat the steel for a certain period of time, and then slowly cool it with the furnace, so as to obtain a finer and more uniform structure, reduce the hardness and be beneficial to cutting. Normalization is to heat the steel, keep the temperature, then take it out of the furnace and cool it in the air, which is suitable for refining low carbon steel. Quenching is to heat steel parts, keep them warm, and then quickly cool them in water or oil to improve their hardness. Tempering is usually a subsequent process of quenching. Quenched steel is heated and cooled after heat preservation to stabilize microstructure and eliminate brittleness. There are many automobile parts, which not only need to maintain the toughness of the core, but also need to change the surface structure to improve the hardness, so it is necessary to adopt surface high-frequency quenching or carburizing, cyaniding and other heat treatment processes.
201May September 15-17, Guangzhou International Casting, Die Casting and Forging Industry Exhibition 20 15 hosted by Guangzhou Guangya Frankfurt Exhibition Co., Ltd. will be held in Guangzhou "China Import and Export Fair Exhibition Hall". The rapid development of die casting and casting industry has attracted much attention. It is reported that this exhibition will display a series of exhibits including castings and forgings, die-casting equipment, die-casting raw materials and accessories, die-casting molds and technologies, casting equipment and industrial furnaces, forging equipment and technologies. , bringing together sellers and buyers from automobile industry, household appliances industry, medical equipment, instruments and equipment, lighting, electronic appliances and other industries. The number of exhibitors and visitors exceeded 10000, far exceeding the previous scale. This is the annual industry event of die casting industry. Now the exhibition is in full swing. Please consult online customer service to reserve a booth!