In the aluminum production enterprises, the cost of extrusion die in the cost of production accounted for about 35%. Mold is good or bad and whether the mold can be reasonably used and maintained, directly determines whether the enterprise can be normal, qualified to produce profiles to. Extrusion die extrusion profile in the production of working conditions is very bad, both in high temperature, high pressure under severe friction, wear, and also need to withstand the role of cyclical load. This requires the mold has a high thermal stability, thermal fatigue resistance, thermal wear resistance and sufficient toughness. To meet the above requirements, the current domestic high-quality 4Cr5MoSiV1 (US grade H13) alloy steel, and the use of vacuum heat treatment quenching, etc. to produce molds to meet the aluminum production requirements.

However, in the actual production, there are still some of the mold in the extrusion did not meet the scheduled output, serious even less than 20 bars or on the machine less than 2 times on the early retirement, resulting in the use of expensive die steel production Mold is far from achieving its due benefits. This phenomenon in many domestic aluminum production enterprises are currently widespread. The causes, need to start from the following aspects.

First, the aluminum section itself is ever-changing, and the development of aluminum extrusion industry today, aluminum alloy with light weight, good strength and other important advantages, there are already many industries to replace the original aluminum material. As a result of some of the profiles of the special profile of the mold due to special, design and production of more difficult. If the use of conventional extrusion method is often difficult to achieve the rated output of the mold, must use a special process, strictly control the production process parameters in order to normal production. And some mold because of their profile profile of the special mold itself or the quality of the problem, which led to the mold can not be squeezed to the rated output, which requires sales staff in the order with the technical department and mold factory full communication. At the same time die design production department needs to constantly optimize the mold design technology, improve the accuracy of mold production, improve mold quality.

Second, select the appropriate extrusion models for production. Extrusion production before the need to fully calculate the profile section, according to profiles of the complexity of the cross-section, wall thickness and extrusion coefficient λ to determine the size of the extruder tonnage. In general, λ> 7-10. When λ> 8-45, the mold life is longer, profile production process more smoothly. When λ> 70-80 after the more difficult to squeeze profiles, mold generally shorter life expectancy. The more complex product structure, the more likely to lead to local rigid mold is not enough, the mold cavity of the metal flow is difficult to uniform, and with the local stress concentration. When the profile is easy to mold and boring cars or the formation of distorted waves, the mold is prone to elastic deformation, serious plastic deformation will occur directly to the mold scrapped.

Third, a reasonable choice of billet and heating temperature. To strictly control the extrusion alloy composition of ingot billet. At present, enterprises generally require ingot grain size to achieve a standard to enhance the plastic and reduce the opposite sex. When the ingot has pores, loose tissue or a central crack, the sudden release of gas during extrusion like "blasting", making the local work with a sudden load shedding and loading, the formation of local huge impact load, the impact of the mold is very Big. Conditional enterprises can be homogenized on the billet, 550 ~ 570C 8 hours after the forced cooling, break pressure can be reduced by 7-10%, extrusion speed can be increased by about 15%.

Fourth, optimize the extrusion process. To extend the life of the mold, the rational use of mold production can not be ignored is one aspect. As the extrusion die working conditions are extremely bad, in the extrusion production must take reasonable measures to ensure that the organization of the mold performance. (1) take the appropriate extrusion speed. In the extrusion process, when the extrusion speed is too fast, it will cause the metal flow is difficult to uniform, aluminum metal flow and mold cavity wall friction caused by increased friction with the die working with wear accelerated, the actual mold temperature is higher and so on. If the metal deformation of the waste heat can not be taken away in time, the mold may be due to local overheating and failure. If the extrusion speed is appropriate, you can avoid the occurrence of adverse consequences, extrusion speed should generally be controlled at 25mm / s or less. (2) a reasonable choice of extrusion temperature. The extrusion temperature is determined by the mold heating temperature, the mandrel temperature and the bar temperature. Aluminum bar temperature is too low easily lead to increased squeeze pressure or the phenomenon of stuffy car, mold prone to local trace of elastic deformation, or stress concentration in parts of the mold cracks caused by the early retirement. Aluminum rod temperature is too high will soften the metal structure, which makes adhesion to the surface of the mold with the work even block (seriously when the die under high pressure collapse), the uneven heating temperature of the ingot in the 460-520 ° C, homogenized Ingot reasonable heating temperature in the 430-480 ° C.

Fifth, the use of pre-extrusion mold must be a reasonable mold surface nitriding process. Surface nitriding treatment can make the mold to maintain sufficient toughness under the premise of greatly improving the surface hardness of the mold to reduce the use of the mold to produce thermal wear. Note that the surface nitriding is not a time to complete, in the mold during service must be repeated 3-4 times nitriding treatment, the general requirements of nitriding layer thickness of 0.15mm or so. A suitable nitriding process is the first nitriding after the in-mold inspection. At this point because the nitride layer is not stable, should be squeezed 5-10 bar again nitriding. After the second nitriding, 40-80 bars can be extruded. After the third nitriding to not more than 100-120 bar is appropriate. Nitriding work with the former must be polished, mold cavity to clean up, not residual alkali residue or foreign particles. In general, the number of nitriding of the mold is not more than 4-5 times, because at this time if the nitride layer is not the work belt is strained, then repeated nitriding and extrusion production, nitride layer organization has been relatively stable. It should be noted that the pre-nitriding to go through the appropriate production process can only be nitriding, the number of nitriding can not be too frequent, or work with easy delamination.

6, die on the machine before the belt must be grinding and polishing, working with the general requirements of polishing to the mirror. Check the flatness and verticality of the tooling strip before assembly. Nitride quality to a certain extent determines the quality of the work with polished finish. Mold cavity must be high-pressure gas and brush clean, no dust or impurities foreign body, or easily driven in the metal flow under the work of pulling the strip, the extruded profile products appear rough or crossed defects.

7, extrusion die insulation time is generally 2-3 hours, but not more than 8 hours, or die with a nitride layer hardness will lead to lower when the machine is not wear-resistant profiles caused by rough surface, a serious cause Crossed and other defects. When using the mold, there must be a mold support, mold sleeve and bearing pad matched with the mold, so as to avoid too much contact hole between the die exit surface and the bearing pad due to the too large inner hole of the bearing pad, so that the mold is deformed or broken. Mold, extrusion tube, squeeze the axis of the three concentric, concentricity of ± 3mm or less, or easy to produce eccentric load and mold parts of the design flow rate changes, affecting the profile molding.

Eight, using the correct caustic washing (boiling mold) method. If the temperature of the mold is lower than 500 ° C, the temperature of the alkaline water will be much lower than that of the mold. If the temperature of the mold drops rapidly, the mold will be easily cracked. The correct way is to wait after the mold unloading in the air placed in the 100 ° -150 ° C and then immersed in alkaline water. Ordinary split shunt die in the mold before the draft operation, can greatly reduce the amount of cooking mold work, shorten the cooking time. The specific approach is to squeeze the end of the extrusion tube before the extrusion tube back, the pressure remained in the extrusion tube, and then extrusion tube back, while the mold shunt part of residual aluminum along with the pressure more than pull out, then And then alkaline cooking. Some shunt combination core is very small, even more than the pen is also thin, this type of mold extrusion is not allowed after draft, cook mold open mold must be clearly seen before the mold structure, mold cavity must be residual aluminum Basically boiled to open mold. Otherwise a little inattentive will be the core head off, resulting in die scrapped.

Nine, the use of mold from low to high and then use the low intensity. Die just entered the service period, the performance of the internal metal is still in the floating phase, during which low-intensity operation program should be used to make the transition to a smooth mold. Die use of medium-term, due to the performance of the mold has been basically in a stable state, similar to just after the run-in period of the car, may be appropriate to improve the use of strength. To the late, the mold metal structure has begun to deteriorate, fatigue strength, stability and toughness after long-term production service has begun to fall into the curve, this time should be appropriate to reduce the use of the mold until the die scrapped.

10, to strengthen the mold in the extrusion process of the use of maintenance records, improve the tracking and recording of each set of mold files and management. Extrusion die from the factory acceptance to die end of use, the middle of a short time a few months, up to a year or more. Basically, the use of mold records also records the various sections of the production process. Extrusion die a large number of varieties, the use of each mold to manage the process, help mold library administrators, mold users and mold design and manufacturing personnel to understand the real situation of each mold inventory. The tracking records of the mold include:

(1) mold manufacturing information, including each set of mold design drawings, production records, inspection records (accuracy, hardness) and so on.

(2) the process information of each die extrusion process, such as heating time, aluminum bar temperature, mold temperature, extrusion speed, extrusion pressure, break pressure, the length of aluminum rod, qualified product count, profile linear density, Finished rate and so on.

(3) the first three times per mold repair mode program, nitriding time, access to mold base time, scrap or return to the mold factory maintenance time and reason, the collection of these records to improve mold management, accounting mold costs, optimize the mold Design and repair mold, mold quality assessment of good and bad, to improve the stability of extrusion production, the rational use of molds, molds to determine the minimum inventory and other work has a direct impact.

Aluminum market competition intensifies, forcing the aluminum extrusion enterprises in the extrusion die of the procurement, use, maintenance and management of huge investment, which requires companies to change before the extensive production management at the same time change their own ideas, from the details Grasp, do a good job of mold statistical analysis and cost management, in order to adapt to the new market situation in the market to seize the initiative.