The molten metal is poured into a mold, and after it cools and solidifies, a part of the desired shape and size is obtained. Cast parts are called castings. In order to make a mold, a desert mold with a shape similar to the part must be made first. The mold is filled with sand, and a sand mold with a certain cavity is made after the mold is taken out. This sand mold is called a mold. Components. It is very convenient to use casting to make mechanical parts, but it takes a long time to make models and the price is high. When the number of production parts is large, it is more economical to use the casting method. When the production number is small, the price of the model accounts for a large proportion of the production cost of the parts, so it is very important to reduce the production cost of the model. Due to the uneven shape of the casting during the solidification process, the size is not so accurate, so most of the castings need to be cut and ground.
It is a processing method of pressing a metal blank with a hammer press to deform it to obtain a forging of the desired shape and size. As the temperature increases, the metal is easily deformed, so the metal is often heated to a high temperature for forging. Forging is divided into model forging and free forging. Model forging is a method of placing a heated blank into a forging mold cavity and deforming under pressure to obtain a forging. Free forging is a method of pressing and deforming a blank between the upper and lower anvils to obtain a forging. During forging, the metal blank is deformed under compression, the metal structure is dense, the strength is increased, and the durability is increased. Die forging is used when the number of forgings is large, and free forging is used when the number of forgings is small.
It is a method of compressing powder into a desired shape, heating it to a high temperature below the melting point, and sintering the powder into a solid. Parts made by powder metallurgy are called powder metallurgy parts. The powder is mainly composed of iron series and copper series metals, and is used to make parts such as gears and oil bearings. It can also be sintered with tungsten carbide and cobalt to make hard box blades, and refractory materials and metals are sintered into cermets. Due to the limitation of forming, the strength of powder metallurgy parts is lower than that of castings and forgings, but powder metallurgy can produce porous parts and parts that cannot be cast and forged.
It is a processing method of cutting, bending and stretching the sheet according to the desired shape. It is very important to keep the cut surface clean when cutting with a knife. When bending, use the tool to bend the workpiece to the necessary angle. Since the workpiece will have rebound deformation after bending, this must be considered when selecting the bending angle. Stretching is a forming process that uses a die to create a seamless bottomed container. Since the deformation of one stretch cannot be too large, several stretches must be carried out when making deeper containers with flat plates. Stretching parts such as car bodies have different curvatures in the front, rear, left and right sides, which not only prevents wrinkles, but also ensures the integrity of the shape. Therefore, special efforts are required when stretching.
It is a method of permanently connecting sheets (or bars). The joined sheet or bar is called the parent material. Fusion welding is to melt the connection part of the base metal to generate common grains to realize the connection. Electricity is applied to the electrode, and it is in instant contact with the base metal to generate an arc, and the heat generated by the arc melts the connection between the electrode and the base metal. This welding method is called arc welding. In addition, there is a welding method in which both heat and pressure are applied to the connection part of the base metal, and the welding rod is not used at this time. In addition, the base metal does not melt, but the molten low melting point metal flows into the connection part of the base metal to realize the connection method (brazing) welding can connect the sheets into various shapes, and the application is very convenient. Using welding method to make zero can save material and can make large objects. Welding is used in ships, bridges, vehicles and other machinery manufacturing sectors.
Parts with relative motion (rotation, sliding) on ​​the machine, joint surfaces between parts and other parts require small surface roughness and high dimensional accuracy. Therefore, these parts are cut with a cutting tool and ground with a grinding wheel. The cutting tool is made of materials that are harder than the blank material, such as tool steel, cemented carbide, ceramics, etc. In order to carry out cutting processing, various machine tools are used. The machine tools include lathes (for processing rotary surfaces), drilling machines, hearths (mainly for processing holes), gantry machines (for processing larger planes), planers (for processing planes), and milling machines (for milling Knife machining grooves, planes, etc.), grinders (using grinding wheels to process internal and external rotating surfaces, planes), etc. In addition, there are various gear machine tools for processing gears. Various types of Numerically Controlled (NC) machine tools can automatically process.
A special method for machining hard, difficult-to-cut materials. The methods to be processed include: electrical discharge machining, electron beam machining, laser machining, plasma arc machining, electrolytic machining, explosive machining, etc. The processing energy of special processing is very concentrated, which is used for cutting, drilling, grooving and other processing of materials.
The metal material is heated, kept warm and then cooled. Due to the difference in the heating temperature and the cooling rate, the metal material can be given special properties. For example, high carbon steel is heated to a high temperature and then rapidly cooled, the steel sinks and hardens (called quenching), and the steel becomes soft when slowly cooled in the furnace (called annealing), and the rapidly cooled and hardened steel is reheated to a certain temperature. , its hardness has decreased, and its toughness has increased (called tempering). This change in performance is often used in machine manufacturing to improve the mechanical properties of parts. For example, hardening the tooth surface of gears for wear resistance, and softening work-hardened materials to improve pod machinability. The audible heat treatment described above is an important treatment method in machine manufacturing.