What is metalworking?
Metalworking is the production activity of applying various processes to metallic materials to create the required parts, line components or overall large structures. From many large-scale projects such as oil rigs, ships, bridges to small parts such as engines, to jewelry, etc. are manufactured by metal processing. Therefore, it is necessary to use a wide range of techniques, processes, tools to deal with metals and finally obtain the desired results.
The process of metal processing is roughly divided into three categories, namely metal forming, metal cutting and metal joining.
What are the methods of processing metals?
- Die casting (note that die casting is not short for pressure casting) is a metal casting process characterized by the use of a mold cavity to apply high pressure to molten metal. Molds are usually machined from stronger alloys, a process somewhat similar to injection molding.
- Sand casting is the use of sand to make molds. Sand casting involves placing a finished part model or a wooden model (pattern) in the sand, then filling the pattern with sand over the weekend, and unpacking the pattern to form a mold. In order to take out the model before pouring the metal, the mold should be made into two or more parts; during the mold making process, the holes and vent holes for pouring the metal into the mold must be left to synthesize the pouring system. The mold is kept for an appropriate time after the metal liquid is poured until the metal solidifies. After the parts were taken out, the molds were destroyed, so a new mold had to be made for each casting.
- Investment casting, also known as lost wax casting, includes processes such as wax pressing, wax repairing, tree grouping, dipping, wax melting, molten metal casting and post-processing. Lost wax casting is to use wax to make a wax mold of the part to be cast, and then coat the wax mold with mud, which is a mud mold. After the clay mold is dried, it is fired into a pottery mold. Once fired, all the wax molds are melted and lost, leaving only the pottery molds. Generally, the pouring port is left when the mud mold is made, and then the molten metal is poured from the pouring port. After cooling, the required parts are made.
- Die forging is a forging method that uses a die to form a blank on a special die forging equipment to obtain a forging. According to different equipment, die forging is divided into hammer die forging, crank press die forging, flat forging machine die forging, friction press die forging, etc. Roll forging is a plastic forming process in which the material is plastically deformed under the action of a pair of counter-rotating dies to obtain the desired forging or forging blank. It is a special form of forming rolling (longitudinal rolling).
Forging is a processing method that uses a forging machine to apply pressure to a metal blank to plastically deform it to obtain a forging with certain mechanical properties, certain shape and size, and is one of the two major components of forging (forging and stamping). Through forging, defects such as as-cast looseness produced by the metal during the smelting process can be eliminated, and the microstructure can be optimized. At the same time, due to the preservation of the complete metal streamline, the mechanical properties of forgings are generally better than those of castings of the same material. For important parts with high load and severe working conditions in related machinery, forgings are mostly used in addition to rolling plates, profiles or welded parts with simple shapes.
- Rolling Also known as calendering, refers to the process of passing a metal ingot through a pair of rollers to shape it. If the temperature of the metal exceeds its recrystallization temperature during rolling, the process is called “hot rolling”, otherwise it is called “cold rolling”. Calendering is the most commonly used method in metal processing.
- The essence of die casting is to fill the cavity of the die-casting mold (die-casting mold) with liquid or semi-liquid metal at a high speed under the action of high pressure, and to form and solidify under pressure to obtain a casting.
- Low pressure casting is a casting method in which liquid metal fills the mold and solidifies into a casting under the action of low pressure gas. Low-pressure casting was initially mainly used for the production of aluminum alloy castings, and was further expanded to produce copper castings, iron castings and steel castings with high melting points.
- Centrifugal casting is a technology and method for injecting liquid metal into a high-speed rotating mold, so that the molten metal fills the mold and forms a casting under the action of centrifugal force. The mold used in centrifugal casting, according to the shape, size and production batch of the casting, can choose non-metallic mold (such as sand mold, shell mold or investment shell mold), metal mold or coating layer or resin sand layer in the metal mold. of casting.
- Lost foam casting is to bond and combine paraffin or foam models similar in size and shape to castings into model clusters. After brushing refractory paint and drying, they are buried in dry quartz sand for vibration modeling, and poured under negative pressure to vaporize the model. , a new casting method in which liquid metal occupies the model position and solidifies and cools to form a casting. Lost Foam Casting is a new process with nearly no margin and precise forming. This process does not require mold taking, no parting surface, no sand core, so the casting has no flash, burr and draft angle, and reduces the number of mold cores due to core loss. Dimensional error caused by combination.
- Squeeze casting, also known as liquid die forging, is to inject molten metal or semi-solid alloy directly into an open mold, and then close the mold to generate a filling flow to reach the outer shape of the part, and then apply high pressure to make the solidified The metal (shell) is plastically deformed, the unsolidified metal is subjected to isostatic pressing, and high-pressure solidification occurs at the same time, and finally the product or blank is obtained. The above is a direct squeeze casting; there is also indirect squeeze casting. The solid alloy is injected into a closed mold cavity through a punch, and high pressure is applied to make it crystallize and solidify under pressure, and finally a method of obtaining a product or blank.
- Continuous casting is a casting method in which liquid metal is continuously poured into one end by a through mold, and the molding material is continuously pulled out from the other end.
- Drawing is a plastic processing method in which an external force acts on the front end of the drawn metal to pull a metal blank from a die hole smaller than the blank section to obtain a product of the corresponding shape and size. Because drawing is mostly carried out in a cold state, it is also called cold drawing or cold drawing.
- Stamping is a forming and processing method that applies external force to sheets, strips, pipes and profiles by means of presses and dies to cause plastic deformation or separation, thereby obtaining workpieces (stamping parts) of the required shape and size.
- Metal Injection Molding (MIM) is a new type of powder metallurgy near-net forming technology derived from the plastic injection molding industry. It is well known that plastic injection molding technology produces various complex shapes at low prices, but plastic The strength of the product is not high. In order to improve its performance, metal or ceramic powder can be added to the plastic to obtain a product with high strength and good wear resistance. In recent years, the idea has evolved to maximize the solids content and completely remove the binder and densify the green body during the subsequent sintering process. This new powder metallurgy forming method is called metal injection molding.
Turning means that lathe processing is a part of mechanical processing. Lathe machining mainly uses turning tools to turn the rotating workpiece. Lathes are mainly used to process shafts, discs, sleeves and other workpieces with revolving surfaces, and are the most widely used type of machine tool in machinery manufacturing and repair factories. Turning is a method of cutting a workpiece on a lathe using the rotation of the workpiece relative to the tool. The cutting energy of turning is mainly provided by the workpiece rather than the tool. Turning is the most basic and common cutting method and plays a very important role in production. Turning is suitable for machining rotary surfaces. Most workpieces with rotary surfaces can be processed by turning methods, such as inner and outer cylindrical surfaces, inner and outer conical surfaces, end faces, grooves, threads, and rotary forming surfaces. The tools used are mainly turning tools.
- Milling Milling is to fix the blank, and use a high-speed rotating milling cutter to move on the blank to cut out the required shapes and features. Conventional milling is used more for simple shapes/features such as contours and slots. CNC milling machines can process complex shapes and features. The milling and boring machining center can perform three-axis or multi-axis milling and boring processing for machining, molds, inspection tools, tire tools, thin-walled complex surfaces, artificial prostheses, blades, etc. When selecting CNC milling processing content, the advantages and key roles of CNC milling machines should be fully utilized.
- Planing is a cutting method in which a planer is used to make a horizontal relative linear reciprocating motion on the workpiece, which is mainly used for the shape processing of parts. The precision of planing processing is IT9~IT7, and the surface roughness Ra is 6.3~1.6um.
- Grinding Grinding refers to the processing method of removing excess material on the workpiece with abrasives and abrasive tools. Grinding is one of the most widely used cutting methods.
- Selective Laser Melting In a tank filled with metal powder, a computer-controlled high-power carbon dioxide laser selectively sweeps the surface of the metal powder. Wherever the laser goes, the metal powder on the
- surface is completely melted and bonded together, and the powdery state remains where it is not illuminated. The whole process needs to be carried out in a sealed chamber filled with inert gas.
- Selective laser sintering is the SLS method that uses infrared lasers as the energy source, and the modeling materials used are mostly powder materials. During processing, the powder is first preheated to a temperature slightly lower than its melting point, and then the powder is flattened under the action of a leveling stick; the laser beam is selectively sintered according to the layered section information under computer control, and one layer is completed. Then the next layer of sintering is carried out, and after all the sintering is completed, the excess powder is removed, and a sintered part can be obtained. At present, the mature process materials are wax powder and plastic powder, and the process of sintering with metal powder or ceramic powder is still under study.
Metal deposition Somewhat similar to “squeeze cream” style fused deposition, but instead spray metal powder. While spraying metal powder materials, the nozzle also provides high-power laser and inert gas protection. This will not be limited by the size of the metal powder box, and can directly manufacture larger-volume parts, and it is also very suitable for repairing partially damaged precision parts.
- Roll Forming Roll forming is the use of a series of continuous stands to roll stainless steel into complex shapes. The sequence of rolls is designed so that the roll profile of each stand continuously deforms the metal until the desired final shape is obtained. If the shape of the part is complex, up to thirty-six racks can be used, but for parts with a simple shape, three or four racks are sufficient.
- Die forging refers to a forging method that uses a die to form a blank on a special die forging equipment to obtain a forging. The forgings produced by this method are accurate in size, small in machining allowance, complex in structure and high in productivity.
- Die-cutting is the blanking process. The film formed in the previous process is positioned on the male die of the punching die, and the excess material is removed by closing the die, retaining the 3D shape of the product and matching the mold cavity.
- Die Cutting Process – Die Die Cutting process of die cutting, the film panel or circuit is positioned on the bottom plate, the die is fixed on the upper template of the machine, and the force provided by the machine’s downward pressure is used to control the blade to cut the material. The difference between him and the punching die is that the incision is smoother; at the same time, by adjusting the cutting pressure and depth, theindentation, half-break and other effects can be punched out. At the same time, the low-cost operation of the mold is more convenient, safe and fast.