1 failure form of aluminum extrusion die failure, production will be due to the impact of the mold cracking, plastic deformation, adhesion and premature wear and hot cracking, neck or pull off, bending and other phenomena appear early failure, will also Due to technical problems, nitride problems and other damage caused by the mold, but also due to mold problems caused by pressure plugging, gaps, expansion, parallel port and other failures, but the failure of the extrusion mold mainly as wear, cracking, deformation of the three normal failure modes .
(1) In case of wear failure, during the extrusion process, the aluminum extrusion material is pressed through the open part of the mold cavity under high temperature and high pressure without lubrication processing, and the surface of the aluminum profile is in direct contact with the sizing belt, sliding sideways, resulting in very The large frictional force causes the cavity surface and the sizing belt surface to wear out and fail. At the same time, during the friction process of the mold, some blank metal is adhered to the working surface of the mold, so that the geometrical shape of the mold is changed and cannot be used. It is also considered as a wear failure, which is expressed in the form of blade passivation, rounding of edges and corners, plane subsidence, Surface grooves, peeling, sticking mold and so on.
The root cause of wear failure is friction. The specific form of mold wear is related to many factors such as the speed of the friction process, such as the chemical composition and mechanical properties of the mold material and the processed blank, the surface roughness of the mold and the blank, and the pressure, temperature, and speed in the extrusion process. relationship. Aluminum extrusion die wear is mainly thermal wear, thermal wear is friction, the metal surface due to temperature rise and softening and mold cavity surface are caused by the mutual engagement, the mold cavity surface softening at high temperature, its reduced wear resistance . The thermal wear process is very complicated. It is obvious that the temperature is the main factor affecting the thermal wear. The higher the temperature, the more severe the thermal wear.
(2) Cracking failure occurs. In actual production, cracks are distributed in certain parts of the mold. After a certain service period, it initiates small cracks and gradually expands to the depth. After the cracks are extended to a certain size, the load on the mold will be seriously weakened. The ability to cause breakage, or microcracks have been generated during the original heat treatment and processing to make the mold, so that the mold is easy to expand during service and early cracking occurs. The reason for the failure is mainly the design of the die strength and the selection of fillet radii at the transition; the manufacturing is mainly the pre-inspection of the material and the attention of the surface roughness and damage during processing, as well as the influence of heat treatment and surface treatment quality. In use, it mainly pays attention to mold preheating, extrusion ratio and temperature control of the billet, as well as the extrusion speed and the metal deformation flow.
(3) failure of deformation, deformation failure is the use of the mold in the use of cantilever eccentricity, subsidence, diversion mold in the use of the mold in the eccentric tongue and the lower mold cavity collapse, hole bulging, angular collapse and other failures, The main reason is that the material strength is not high; or the mold material is selected correctly, but the heat treatment process is not correct, and the toughness of the mold steel is not fully used; or the design of the flow splitter is not proper, the flow velocity is uneven, and the lateral force to the tongue is uneven However, the eccentricity is produced. However, the design of the splitter die is correct, but the level of processing and manufacturing is not high, so that the flow velocity into each split hole is uneven, resulting in different lateral forces resulting in eccentricity.
2 main measures to improve the life of aluminum extrusion die Many factors affect the life of aluminum extrusion die, in addition to the structural design and strength of the die compared to nuclear, mold materials, cold and hot processing and electrical processing technology, heat treatment and surface treatment processes and other internal factors The impact is related to the external factors such as the extrusion process and conditions of use, mold maintenance and repair, extrusion product material properties and shapes, specifications, and the management of the mold science. At the same time, the impact factor is not a single, but a Complex multi-factor synthesis issues. However, based on the analysis of the above failure modes and their causes, we have thoughts and methods in how to improve the life of the aluminum extrusion die. The author believes that the life of the die should be improved mainly from the following aspects:
(1) Properly designing the mold and properly designing the mold is an important part of extending its service life. Correctly designed mold structure should ensure that there is no possibility of impact cracking and stress concentration under normal conditions of use. Therefore, when designing the mold, all parts should be made as even as possible, and care should be taken to avoid sharp corners, concave corners, and poor wall thickness. Disparity, thin-walled cross-section, etc., in order to avoid excessive stress concentration, causing heat treatment deformation, cracking and brittle fracture during use or early thermal cracking. At the same time, the standardized design is conducive to the exchange, storage and maintenance of the mold. In general, reasonable mold structure design and reliable strength comparison core, as well as continuous innovation of mold design theory and methods, the use of computer-aided design is the main way to improve the extrusion mold design and increase the service life.
(2) Reasonable choice of mold materials. Extrusion molds are operated under high temperature and high pressure, and they are subjected to periodic loads. The working conditions and environment are very harsh. Therefore, the performance requirements for mold steel are quite high, and the materials for mold making should be good. The thermal stability, thermal fatigue resistance, thermal wear resistance and sufficient toughness. At present, the domestic commonly used mold materials are 4Cr5MoSiV1?H13 steel and 3Cr2W8V steel, but in recent years due to the low toughness of 3Cr2W8V steel, fatigue strength is not good, even if the high temperature quenching and other processing measures can not meet the requirements, the early mold failure is more serious , The new steel 4Cr5MoSiV1?H13 steel has good hardenability, thermal strength, wear resistance and plasticity, high impact toughness, resistance to cold and heat fatigue, small heat treatment deformation, good resistance to crack propagation, can improve extrusion The surface roughness of the profile, easy mold repair and good high-temperature comprehensive performance and the organization contains more Cr, Mo elements, nitriding treatment can generate rich and stable nitride and diffuse distribution and other outstanding features, so gradually replaced Cr2W8V steel has become the preferred material for extrusion dies. Practical data also show that the same type of mold is made of 4Cr5MoSiV1 steel and 3Cr2W8V steel. The service life of 4Cr5MoSiV1 is 3 to 5 times longer than that of 3Cr2W8V. , Has become a standard mold material. Of course, the choice of mold materials is also a very complex issue, involving a wide range, only the development of new materials, improve the quality of the material itself and research new heat treatment process and surface strengthening process organically combined, is an effective way to improve life.
(3) To improve the quality of heat treatment and surface treatment, the service life of the extrusion die depends largely on the quality of the heat treatment. Therefore, advanced heat treatment methods and heat treatment processes, as well as toughening and surface strengthening treatments are particularly important for improving the service life of the die. At the same time, strictly control the heat treatment and surface hardening process, prevent heat treatment defects, adjust the quenching and tempering process parameters, increase the number of pretreatment, stabilization treatment and tempering, pay attention to temperature control, heating and cooling intensity, adopt new quenching media and study Toughening treatment, a variety of surface hardening processes and other new processes, new equipment, are conducive to the improvement of mold life.
(4) Improve the quality of processing in mold making. In the processing of molds, common machining methods include machining, wire cutting, and electric discharge machining. Machining is an indispensable process in the mold processing process. It not only changes the appearance of the mold, but also directly affects the quality of the profile and the service life of the mold. The wire cutting mold hole is a widely used process method in the mold processing, which improves the Processing efficiency and processing accuracy, but also brought some special problems, such as warp cutting die, if not directly tempered directly for production, easy to produce dregs, peeling and other phenomena, will reduce the life of the die. Therefore, fully tempering the die after wire cutting can improve the surface tension state, reduce the residual stress, and increase the service life of the die. Stress concentration is the main cause of die fracture. Within the allowable range of drawing design, the larger the diameter of the wire is, the better it is. This will not only improve the processing efficiency, but also greatly improve the distribution of stress and prevent the occurrence of stress concentration; EDM It is an electric corrosion process that is performed by the superposition of vaporization, melting of the material, and evaporation of the processing fluid during discharge. The problem is that due to the thermal effects of heating and cooling and the electrochemical action of the machining fluid, strains and strains are formed at the degraded layer at the processing site, and carbon atoms decomposed by the combustion of the oil when the processing fluid is oil. Diffusion and carburizing to the processed surface, while the thermal stress of the modified layer is increased, it is easy to produce cracks due to brittleness and hardness, and at the same time it forms residual stress and adheres to the workpiece. This will result in reduced fatigue strength, accelerated fracture, stress corrosion, etc. . Therefore, in the processing process, the above problems should be prevented as much as possible and the processing quality should be improved.
(5) Improvement of working conditions and improvement of extrusion process conditions. Extremely poor working conditions of the extrusion die and very harsh environments. Therefore, improvement of the extrusion process method and process parameters, and improvement of working conditions and working environment are favorable for improving die life. Therefore, we must carefully formulate the extrusion program before extrusion, select better equipment systems and billet specifications, and formulate better extrusion process parameters (such as extrusion temperature, speed, extrusion coefficient, and extrusion pressure, etc.) and improvement. The working environment during extrusion (such as water cooling or nitrogen cooling, full lubrication, etc.) reduces the work load of the mold (such as reducing the extrusion force, reducing the chilling heat and alternating load, etc.), establishing and improving the technical operating procedures and Safe use procedures.
3 Conclusions During the actual production and working process, the service life of the extrusion die is a comprehensive technical problem. The five aspects described above are only the main ones. Reasonable use and maintenance of the die and scientific management are necessary to extend extrusion. The service life of the mold is also crucial.
Shaped Parts
Shaped Parts,Hardware Fasteners Rivet,Coarse Thread Bolts,M20 Anchor Bolt
Handan Changlan fasteners manufacturing ,.Co ltd , https://www.hdchanglanjgj.com