Automotive engine oil pan 1, defects that appear The product is an essential part of the car engine, the working environment is harsh, and it is required not to leak oil. We mainly encounter the sensor hole air holes in the production of this product that can not meet the requirements, large plane local air holes into pepper powder, it is difficult to lift. 2, the reasons for the generation 1) Oil sump is a deep cavity part, aluminum liquid from the water mouth to the water tail, the process is long, easy to produce cold material. And the sensing air hole is an isolated part, which is not conducive to the discharge of cold material. 2) The principle of product die-casting release agent is manual spraying, the amount of spraying changes every time, and there are more unstable factors, causing the product to be easily deformed. 3) Bad exhaust. 3, Solution 1) Open a slag collection bag in the sensor part to facilitate the discharge of cold material in this part. 2) Use ABB robots to ensure stable and fast spraying. 3) Open an exhaust block on the mold to get the best exhaust effect. Thermostat housing 1, Defects that occur The product needs not to show water under high temperatures and pressure, so the sealing groove of the product is required to be very strict. Product sealing slot requirements do not allow air holes, such as in production, the end of the product often appear pepper-like air holes, will cause the product scrap; and the proportion of air leakage caused by more. 2, the reasons for the generation 1) complex structure of the product, more tabs in the middle, the aluminum liquid is not smooth in the flow, at the end of the product is easy to produce rolled gas. 2) The wall thickness of the product varies too much, the smallest place is only 4 mm, but the thickest place can reach 30 mm, and it is easy to produce shrinkage and shrinkage holes in the wall thickness. 3) There is an 85 mm long sliding block on the product, which is easy to pull on and crack the product, causing air leakage. 3, Improvement measures 1) Add a vacuum exhaust device to the mold to reduce the amount of gas in the mold cavity. 2) Open a partial extrusion pin at the product wall thickness to reduce the product shrinkage and shrinkage hole. 3) Make program changes to the machine, set core extraction spraying, and spray lubrication to the oblique extraction core to reduce the phenomenon of strain and cracking. Aluminum alloy base 1, defects The problem of casting inlet buckling, buckling crack, and deformation after cooling occurs during the trial production of the product. 2, Causes of occurrence 1) Casting heat sink with the thin and narrow wall, in order to cast water tail heat sink forming good and take high speed and high-pressure molding, resulting in a large impact on the inlet port buckling die buckling crack. 2) The casting is too long, uneven wall thickness, different crystallization strength of each part, and the shrinkage in cooling have different differences causing distortion and deformation. 3, improvement measures 1) Do surface cloaking treatment at the inlet of the mold to improve the buckling mold. 2) Take vacuum die-casting, not to reduce the inner gate speed and improve the internal quality when reducing the injection speed and pressure, so as to reduce the impact on the inlet port during the injection and improve the buckling mold. 3) Adopt cooling without water spout to reduce the deformation by pulling the casting during cooling. 4) Pre-align the product in the condition of semi-cooling of the casting, when the internal stress of the product is not completely released. Gear chamber 1, Defective problem Air leakage was found during product air inspection. 2, Cause Analysis The casting structure is complex, and in order to achieve a good appearance and required strength, the filling speed is up to about 60m/s and the specific pressure is more than 820kg/cm2. Therefore, a great impact on the part shown, so that the product surface burns, sticky aluminum; at the same time, due to the large difference in wall thickness of the part, the cooling rate is not the same and will lead to shrinkage, shrinkage crack, and these defects will lead to air leakage in the product in the gas inspection. 3, solution 1) Adopt point cooling method for die cooling in the corresponding part, which increases the local cooling effect; adopt local extrusion pin process to solve the problem of shrinkage. 2) Do surface cloaking treatment at the inlet of the mold to improve the buckling die and solve the burn. The gas station connection body 1, defect problem Casting both sides of the core extraction cavity buckling injury and lamination, the fixed mold forming surface of the two fixed columns has water lines or cold separation. 2, cause analysis 1) Due to the thin and long cores on both sides, the casting is wrapped by aluminum liquid, the temperature rises quickly, causing the cores to adhere to the inner cavity of the casting, and strains when taking off the mold. 2) After closing the mold, the core and the mold with a gap, resulting in feeding, forming a flying edge, after opening the mold, the core extraction, the flying edge can not be normal off, was caught in the mold, after closing the mold, the flying edge with the core inserted, the next filling, aluminum liquid in the flying edge on both sides of the molding, forming a sandwich. 3) The two fixed pillars on the molding surface of the fixed mold extend into the mold 35 mm, and are slender, with cooling water inside the mold, the top of the pillar is closer to the cooling water channel, after opening the mold, the pillar position cools down faster, and when spraying, the mold release agent is easy to remain because of the small space in the cavity of the pillar. 3, Solution 1) Install additional cooling points inside the extractor core on both sides of the mold to take away the heat from the end properly. 2) Polish the surface of the extractor core to stick to aluminum and cloak it to prevent the flying edge from sticking. Enable deceleration, deceleration position 525 mm to prevent flying edge. 3) Open 1/3 of the cooling water at the two pillars after normal, reduce the mold temperature appropriately, and blow out the residual mold release agent in the inner cavity after spraying in the fixed mold.

Factors affecting the size of die castings are broadly the following. 1, molding compression is caused by the size of the error. Molding shrinkage is the main factor affecting the size of die castings. Because molding compression is a complex process, so the shrinkage rate has a wide range of choices. According to the external shape of the die casting and structural characteristics, respectively, select the size of each part of the appropriate molding shrinkage and determine the size of the molding, is to ensure that the die casting size accuracy of the key issues. 2, the manufacturing error of molding parts. 2.1, the molding parts of the insert, mold processing datum, and the impact of processing technology. 2.2, machining errors of molded parts. 2.3, assembly errors of molded parts. 2.4, the error caused by the slope of the molded parts of the mold. 3, the influence of fluctuations in molding shrinkage during die-casting. 3.1, the influence of die-casting molding process parameters, such as press injection ratio pressure and internal gate speed. 3.2, the effect of mold temperature. 3.3, the effect of the temperature of the die casting when the mold is removed. Die castings in the shrinkage process, broadly divided into the following three stages. a, liquid shrinkage, after die casting, still in the liquid metal liquid temperature reduction caused by shrinkage; b, solidification shrinkage, in the cooling and solidification process, the metal liquid from the liquid to solid crystallization stage shrinkage; c, solid shrinkage, metal completely solidified when the crystallization is completed stage and out of the mold body shrinkage. In die casting, because the superheat temperature of the metal liquid is not high, so the volume shrinkage in the liquid shrinkage stage is not large; shrinkage in the solidification stage, although larger, but is completed in the mold forming parts, and therefore by the molding parts, especially the core of the resistance limit. When the die-casting die temperature decreases and can reach the temperature of the mold, die castings from the mold body, only after the free shrinkage state, that is, the solid-state shrinkage stage. This shrinkage process has continued until the die casting reaches room temperature before the basic end. Therefore, it can be said that the temperature of the mold of the final shrinkage of the die casting plays an important role in determining the amount. 4, the error caused by the phase time movement of the structural parts. 4.1, mold closing errors. 4.2, the movement error of the side-drawing core and the movable core. 4.3, the error caused by the precision of the die-casting machine and the instability of the process performance. 5, punching error. 5.1, molding parts by the impact of pressure injection deformation caused by the error. 5.2, forming parts surface by the metal liquid or impurity erosion generated by the error. 5.3, subject to pressure injection stamping, template, or forming parts to produce elastic deformation or plastic deformation and the formation of forming part of the size error.

1, structural process analysis of die casting 1.1 The reasonable choice of materials used in die casting. Aluminum alloy because of its good die-casting performance, specific strength, and specific stiffness is high, high and low-temperature mechanical properties are also good, its surface has a dense oxide film, and certain corrosion resistance and in the production of die castings are used in large quantities, widely. 1.2 The minimum wall thickness of the die casting is 3mm, and the minimum wall thickness is also by the process requirements, and the 3mm*54mm rib on the two long sides, 8mm*4mm rectangular hole, R4mm flange, etc. are also by the requirements of the die casting process. 1.3 Because of the strong affinity between aluminum alloy and iron at high temperatures, it is easy to bond with the pressure chamber, and the die-casting mold design should use a cold chamber die-casting machine as far as possible. 2, the choice of parting surface According to the middle shell for the long frame hollow parts, both sides of the long side have different side convex, step, small rectangular hole structure characteristics. The die casting parting surface of this die casting, except for the horizontal parting between the moving die and the fixed die, is chosen in the upper face of the shell, and the forming of both long sides needs to adopt the lateral parting mold structure form (i.e. the form of lateral core extraction of the inclined pin slider). 3, the determination of the pouring system Due to the thin wall thickness of the four sides of the intermediate shell and the difference between the plant and width dimensions, to prevent cold separation and ensure the thermal balance of the mold, the pouring system uses side gates. The molten alloy is pressed in simultaneously from both ends of the long side of the casting, and a larger overflow slot is set at the part where the metal liquid meets or is likely to produce eddy currents. A larger overflow slot can be set both exhaust role and can set slag and conducive to the thermal balance of the mold. 4, the choice of die-casting machine The middle shell is no insert die-casting, can choose horizontal cold room die-casting machine, according to the actual production of enterprises to choose the appropriate die-casting machine, to meet the actual production requirements. 5, die-casting mold forming parts working size calculation and determination By die-casting alloy comprehensive shrinkage rate list data can be seen: aluminum alloy shrinkage rate in the free shrinkage rate of 0.50%-0.75%; hindered shrinkage rate of 0.40%-0.65%. After separate analysis and calculation, it is determined. 6, die-casting process protocol The process protocol is mainly to determine the process parameters of die-casting production. Die-casting production process parameters mainly include die-casting with new, old material reasonable ratio (old material is impossible to abandon, new, old material unreasonable ratio will affect the material performance and shrinkage rate), determine the die-casting production process protocol, equipment, the correct use of paint (because it has the role of improving the working conditions of the mold, improve molding conditions, improve the quality of castings and extend the life of the mold and essential), etc. 7, die-casting mold assembly design There are two structural options in the design of die assembly. Program one: die-casting forming castings, the shape of the inner cavity mold forming part are designed into the form of the overall structure; program two: forming castings, the shape of the mold work parts are designed into the set, set block set combination of structural form. After analysis and comparison, although program one uses less material, good strength, short processing cycle, but the mold manufacturing accuracy is difficult to ensure that the mold damage and wear are not easy to repair. While the second option increases the use of alloy steel, the processing cycle is extended, but the precision of the working parts of the mold is easy to ensure, and the size adjustment of the working parts of the mold and the wear and damage formed after a certain period of production is also convenient to repair and replace. In the assembly structure of the mold, the fixed mold insert and the fixed mold insert of the fixed mold part are set into the fixed mold plate in the form of grouping. For the moving side, the moving die insert and the moving die insert are inserted into the moving template in a group. The die plate is made of medium carbon steel. The working parts are made of hot work die steel for die casting, the strength, and processing accuracy of the die can be guaranteed, and the adjustment of each forming size is also convenient. Because the hollow shell of die casting has long sides of rectangular holes, flanges, convex tendons, and other structures respectively. So both sides need to use different slider structure forming, tilt pin core parting, wedge tight block locking lateral forming form. Considering the thin wall thickness around the middle shell, and the size of the overflow groove has been enlarged, so pushrods are set on the overflow groove and the cross sprue, and 8 rectangular sheet pushrods are set on both sides of the long side of the die casting to ensure the smooth and synchronous launch of the overflow groove, cross sprue and die casting. The mold is reset by the reset rod to push the pushrod fixed plate to reset.

In the ordinary casting process, the initial crystal grows in the way of dendrites, and when the solid phase rate reaches about 20% the dendrites form a continuous network skeleton and lose macroscopic mobility. If strong stimulation is applied during the solidification of metal, the dendritic network skeleton easily formed during ordinary casting will be broken into dispersed particles suspended in the remaining liquid phase, and this alloy prepared by stirring is generally called a non-dendritic semi-solid alloy. This semi-solid alloy still has good fluidity when the solid phase rate reaches 50%-60% and can be formed using conventional forming processes such as pressure casting, extrusion casting, continuous casting, vacuum casting, etc. to achieve metal forming. 1, Preparation of semi-solid alloys To realize the semi-solid die-casting, first of all, we must prepare the semi-solid alloy slurry with the non-dendritic organization. The current preparation methods of semi-solid alloy slurry mainly include mechanical stirring method, electromagnetic stirring method, strain-induced melting activation method, jet casting method, semi-solid isothermal heat treatment method, near liquid phase line casting method, and chemical grain refinement method, etc. 2, The application of semi-solid die-casting It is expected that the main market for semi-solid die-casting is the automobile industry for quite a long period of time, and aluminum alloy and magnesium alloy are the main materials for semi-solid die-casting in the automobile manufacturing industry. Through the die-casting process real-time control research, so that the whole die-casting process is under dynamic monitoring, improve the performance of die-casting, reduce die-casting scrap, and can make an ordinary die-casting machine for semi-solid metal die-casting forming. Automotive wheel hubs are mostly made of steel, to reduce the quality of the car now increasingly use aluminum alloy, its forming process is mainly low-pressure casting, but low-pressure casting has a high scrap rate, low productivity shortcomings. The use of semi-solid die-casting forming, can customer service the above disadvantages, and improve the strength of the product, reduce the quality. The semi-solid metal forming process has various characteristics and advantages that traditional processing and forming technology does not have, in the past decade, the rapid development of semi-solid forming technology, has gradually become a new field of competition, known as a new generation of emerging metal forming technology.

1, Thermal fatigue cracking Die casting production, die repeatedly by the role of cold and heat, forming surface and its internal deformation, mutual involvement and repeated cycles of thermal stress, resulting in structural damage and loss of toughness, triggering the emergence of micro-cracking, and continue to expand, once the crack expands, there is molten metal liquid extrusion, coupled with repeated mechanical forces are to accelerate the expansion of the crack. Therefore, in actual production, most of the mold failure is thermal fatigue cracking failure. 2, Brittle cracking Under the action of pressure injection force, the mold will sprout cracks at the weakest point, especially the mold forming surface scribing traces or electric machining traces are not polished, or forming at the angle of inclination will be the first to appear fine cracks, when the grain boundary exists brittle phase or grain coarse, that is easy to fracture. When the brittle fracture is present in the grain boundary or the grain is coarse, it will be easy to fracture. The expansion of the crack is very fast. The brittle failure of the mold is a very dangerous factor, the mold material's plastic toughness is the most important mechanical property corresponding to this phenomenon. 3, Dissolution corrosion Commonly used die casting alloys are zinc alloys, aluminum alloys, magnesium alloys, and copper alloys, but also pure aluminum die casting, Zn, Al, Mg is more active metal elements, they have a good affinity with the mold material, which is due to the combined effect of mechanical and chemical corrosion. Especially Al is easy to bite the mold, molten aluminum alloy shot into the cavity at high speed, resulting in mechanical corrosion of the cavity surface, at the same time, the metal aluminum and mold material to generate brittle iron-aluminum compounds, become a new source of hot crack sprouting, in addition, aluminum filling to the crack and crack wall mechanical action, and superposition with the thermal stress, intensify the tensile stress at the tip of the crack, thus accelerating the expansion of the crack. When the mold hardness is higher, the corrosion resistance is better, and if there are soft spots on the forming surface, it is not good for corrosion resistance. However, in actual production, the dissolution corrosion is only the local place of the mold, generally, the part where the inner gate is directly flushed (core, cavity) is prone to dissolution corrosion, as well as the hardness is soft where the aluminum alloy is prone to sticky mold. Improve the high-temperature strength and chemical stability of the material is conducive to enhance the corrosion resistance of the material.

1, Adjustment content After the die casting mold manufacturing is completed, it should be adjusted after the mold test to choose the correct die casting conditions in order to achieve stable die casting of qualified castings. Before the mold test, mold test personnel should do die casting with alloy materials for inspection, to understand the characteristics of alloy materials and die casting characteristics; should also understand the mold structure, die casting machine performance, die casting conditions, and operating methods. The correct choice of die casting formation conditions is the key to die test adjustment. Often encountered even if the mold design and manufacturing are correct, due to improper selection of die casting forming conditions, the same can not press qualified castings. On the contrary, in some cases, can be used to adjust the die casting forming conditions, to overcome the shortcomings of the mold, press out the qualified castings. For this reason, mold test personnel must be familiar with the role of the die casting molding conditions and the relationship between, mold action principles, in order to correctly select and reasonably adjust the die casting molding conditions. Die casting molding conditions of the adjustment of the following points. 1) Material melting temperature, die temperature, and solution temperature during die casting. 2) The injection pressure of the die casting machine, clamping force, mold opening force, and the required injection ratio pressure, injection speed size, etc. according to the condition of the parts. 3) The condition of the die-cast product should be trimmed in order to get a perfect part. 2, Trial mold process Mold test is the last part of the mold manufacturing, is in the die casting machine on the die casting mold molding effect of the field inspection process. The purpose of the mold test is not only to test the mold design and manufacturing but also to seek the best molding process conditions for formal production. The process of mold trial is divided into three stages: mold loading, mold trial, and adjustment. 1) Mold assembly Mold assembly includes pre-inspection, mold installation, and adjustment, etc. 2) Mold test The main contents of mold trial are as follows: ① mold preheating ② the pouring temperature ③ select the ratio of pressure injection ④ to select the speed of pressure injection ⑤ to determine the filling time 3, Adjustment method Possible defects, causes, and adjustment methods in die casting mold trial