Casting is a production method in which molten metal is poured into the cavity of a casting mold and cooled and solidified to obtain a product. In the process of automobile manufacturing, there are many parts made of cast iron, accounting for about 10% of the weight of the entire vehicle, such as cylinder block, transmission housing, steering gear housing, rear axle housing, brake drums, various brackets and so on. Sand molds are commonly used to manufacture cast iron parts. The raw material of sand mold is mainly sand, mixed with binder and water. The sand molding material must have a certain bonding strength so that it can be molded into the desired shape and resist the erosion of high-temperature iron without collapsing. In order to mold a cavity in the sand mold to fit the shape of the casting, it is necessary to make a model of the wood, which is called a wooden mold. Hot iron water shrinks in size as it cools. Therefore, the size of the wooden mold needs to be increased based on the original size of the casting according to the shrinkage rate, and the surface to be machined will be thickened accordingly. Hollow castings need to be made of sand core and the corresponding core wooden mold (core box). With a wooden mold, you can turn the cavity sand mold (casting is also called "sand"). Manufacturing sand, need to consider how to separate the upper and lower sand box to take out the wooden mold, iron from where the inflow, how to fill the cavity, in order to obtain high-quality castings. After the sand mold is done, it can be poured, that is, pour the iron into the cavity of the sand mold. The temperature of the iron is 1250~1350℃ when pouring, and higher when melting.
Forging
Forging is widely used in automobile manufacturing. Forging is divided into free forging and model forging. Free forging is the metal billet on the anvil to bear the impact or pressure of a processing method (called "iron"). The blanks of automobile gears and shafts are processed by free forging. Die forging is the metal billet in the forging mold cavity to withstand the impact or pressure of a processing method. Forging a model is somewhat like the process of dough being pressed into the shape of a cookie in a mold. Compared to free forging, die forging has more complex shapes and more precise dimensions. Typical examples of automotive die forgings are: engine connecting rods and crankshafts, automotive front axles, steering knuckles, and so on.
Drilling Machines
Cold stamping or sheet metal stamping is a process in which a sheet of metal is cut or shaped by pressure in a die. Daily necessities, female aluminum pots, lunch boxes, washbasins, etc. are made by cold stamping. To make a lunch box, for example, a rectangular blank with four rounded corners is first cut out (experts call this a drop), and then a male die is used to press this blank into a concave die to form it (experts call this a drawdown). During the drawing process, the flat plate becomes box-shaped, with its four edges bent vertically upward and the material stacked at the corners with visible folds. Automotive parts processed by cold stamping include: engine oil sumps, brake base plates, automobile frames and most body parts. These parts are generally molded by the processes of drop, punch, stretch, bend, flanging, and trimming. In order to manufacture cold stamped parts, a stamping die must be prepared. Usually the stamping die is divided into two pieces, one is mounted above the press and slides up and down, and the other is mounted below the press and is fixed. During production, the blank is placed between the two stamping dies and the stamping process is completed when the upper and lower dies are closed. Stamping is highly productive and can produce parts with complex shapes and high precision.
Welding
Welding is a process in which two pieces of metal are joined together by localized or simultaneous heating and pressure. Our average worker holds a mask in one hand and an electric welding pliers attached to a wire in the other. The method of welding the electrodes is called manual arc welding, which uses the high temperature generated by the arc discharge to melt the electrodes and the weldments to join them. Manual arc welding is not widely used in automobile manufacturing. Spot welding is widely used in automobile body manufacturing. It is suitable for spot welding of thin steel plates. When operating, two electrodes exert pressure on two steel plates to make them join, and at the same time heat and melt the joining point (a circle with a diameter of 5~6mm) through electric current to make it join firmly. When welding two body parts, their edges are welded at a spacing of 50~100mm, so that the two parts form a discontinuous multi-point connection. Welding the entire body generally requires thousands of welding joints. The strength of the weld joints is required to be very high, and each weld joint can withstand a tensile force of 5kN, so that even if the steel plate is torn, the weld joints cannot be separated. Gas welding, a common method used in repair shops, involves burning acetylene with oxygen to produce a high-temperature flame that melts the welding rod and weldments together. This high-temperature flame can also be used to cut metal, called gas cutting. Gas welding and gas cutting applications are flexible, but the gas welding heat-affected zone is large, resulting in deformation of the weldment, metallurgical organization changes and performance degradation. So automobile manufacturing rarely use gas welding.
Heat treatment
Heat treatment is a method of reheating, holding or cooling solid steel to change its organization and structure to meet the use of parts or process requirements. The heating temperature, holding time and cooling rate can make the steel produce different microstructure changes. Rapid cooling of a blacksmith-heated steel part by immersion in water (called quenching by experts) can increase the hardness of the steel part. This is an example of heat treatment. Heat treatments include annealing, normalizing, quenching, and tempering. Annealing is the process of heating a steel part for a certain period of time and then cooling it slowly with the furnace to obtain a finer, more uniform organization and to reduce the hardness, which facilitates cutting. Normalizing is to heat the steel piece, hold it out of the furnace, and then cool it in the air, suitable for refining low carbon steel. Quenching is to heat the steel piece, hold it, and then cool it rapidly in water or oil to increase the hardness. Tempering is usually a subsequent process to quenching. Quenched steel is reheated, held and then cooled to stabilize the microstructure and eliminate brittleness. There are many automotive 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 use the surface high-frequency quenching or carburizing, cyanide and other heat treatment processes.
September 15, 2015 -17, sponsored by Guangzhou Guangya Messe Frankfurt Exhibition Co., Ltd. 2015 Guangzhou International Foundry, Die Casting and Forging Industry Exhibition will be held in Guangzhou, "China Import and Export Fair Complex," the rapid development of die casting and foundry industry, so that the exhibition has attracted much attention. It is reported that the exhibition will display a series of exhibits including castings and forgings, die casting equipment, die casting raw materials and accessories, die casting molds and technology, casting equipment and industrial furnace, forging equipment and technology. The exhibition will bring together sellers and buyers from the automotive industry, home appliance industry, medical equipment, instrumentation, lighting, electronic appliances and other industries. , exhibitors and visitors more than 10,000 people, far more than the previous scale. It is an annual industry event for the die-casting industry. The exhibition is now in full swing. Please consult online customer service to book a good booth!