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How to solve the quality problem of diecasting die casting factory

Essai Industries Co.,Ltd | Updated: Jun 15, 2017

Die-casting manufacturers of the die castings mainly include the appearance of quality, internal quality and use of quality. Appearance quality refers to the surface roughness, surface defect, dimension deviation, shape deviation and weight deviation of castings; internal quality mainly refers to the chemical composition of castings, physical properties, mechanical properties, metallographic structure and the holes existing in the castings. Crack, inclusion, segregation and so on; using the quality of the castings under different conditions of work durability, including wear, corrosion resistance, heat shock, fatigue, shock absorption and other properties as well as cutting, solderability and other process properties.
Die Casting Manufacturers
Casting quality of die casting manufacturers has a great impact on the performance of mechanical products. For example, machine tool castings wear resistance and dimensional stability, directly affect the accuracy of the machine tool maintenance life; the impeller, Shell and the size of the inner cavity of the hydraulic parts the accuracy and surface roughness of the line directly affect the efficiency of the pump and the hydraulic system, the development of energy consumption and cavitation, and the strength of the cylinder body, cylinder head, cylinder liner, piston ring, exhaust pipe and so on, which directly affect the working life of the engine.
There are many factors affecting the quality of castings, the first is the design process of castings. In the design, in addition to the working conditions and metal properties to determine the shape of the casting geometry, in addition to the size, the rationality of the design must be considered from the angle of casting alloy and casting process characteristics, that is, the apparent size effect and solidification, shrinkage and stress problems, so as to avoid or reduce the defects such as segregation, deformation and cracking of castings. The second must have a reasonable casting process. According to the casting structure, weight and size, casting alloy characteristics and production conditions, select the appropriate fractal surface and modelling, core-making methods, reasonable to set the casting bar, iron, riser and gating system. To ensure the quality of castings. The third is the quality of raw materials for foundry. Metal burden, refractory material, fuel, flux, metamorphic agent and casting sand, sand binder, paint and other materials of substandard quality, will cause the casting pores, pinhole, slag, sticky sand and other defects, affecting the appearance of castings and internal quality, serious will make castings scrap. The Forth is the process operation, should make the reasonable craft operating procedure, enhances the worker's technical level, causes the craft procedure to be carried on correctly.
Die casting manufacturers in the casting process, the quality of the castings should be controlled and inspected. The first step is to develop a process code and technical specifications for control and inspection of raw materials, auxiliary materials and each specific product. Each procedure is strictly controlled and inspected according to the technical rules and specifications. Finally, the quality of finished castings is inspected. should be equipped with reasonable testing methods and suitable testers. Generally, the appearance quality of castings can be used to judge the surface roughness of castings, and the microscopic cracks can be examined by coloring and magnetic powders. The internal quality of castings can be examined and judged by means of audio, ultrasonic, Eddy Current, X-ray and gamma rays.
Sand casting casting defects are: cold insulation, insufficient watering, pores, sticky sand, sand-trap, sand hole, such as swelling.
1. Cold separation and pouring insufficient liquid metal filling capacity is insufficient, or the filling condition is poor, before the cavity is filled, the metal liquid will stop flowing, will cause the casting to cast insufficient or cold insulation defects. When the casting is insufficient, the castings can not get the complete shape, while the castings can obtain the complete shape, the mechanical properties of the castings are seriously damaged because of the incomplete fusion.
Prevent insufficient and cold insulation: increase pouring temperature and pouring speed.
2. The pore gas is not escaping in time before the metal liquid crust, and the holes in the casting are defective. The inner wall of the stomata is smooth, bright or with a slight oxidation color. The effective bearing area will be reduced when the blowhole is produced in the casting, and the stress concentration will be reduced around the blowhole and the impact resistance and fatigue resistance of the castings can be decreased. The porosity also reduces the density of castings, resulting in the scrap of castings that are required to withstand hydrostatic tests. In addition, the porosity has bad effect on the corrosion resistance and heat-resistant of castings.
To prevent the production of stomata: Reduce the gas content in the metal liquid, increase the permeability of sand type, and add the vent at the top of the cavity.
3. Sticky sand casting surface is sticky with a layer of hard to clear sand particles called sticky sand. Sticky sand not only affects the appearance of castings, but also increases the work load of casting cleaning and cutting, and even affects the life of the machine. For example, when the surface of the cast teeth is prone to damage, the pump or engine, such as machine parts if there is sticky sand, will affect the fuel oil, gas, lubricants and cooling water and other fluid flow, and will tarnish and wear the entire machine.
Prevent sticking sand: add pulverized coal in molding sand, and paint anti adhesive sand coating on mold surface.
4. The groove and scar defects formed on the surface of the casting are very easy to be produced in the wet casting of thick plate castings.
The parts of the casting that produce the sand are mostly in contact with the upper surface of the sand type, the surface of the cavity is affected by the radiant heat of metal liquid, which is easy to arch and warp, and when the sand layer is washed by the molten metal, it may break and break, remain in place or be taken into other parts. The larger the upper surface of the casting, the larger the volume expansion of the sand, the greater the tendency of the sand-forming.
5. Sand holes in the castings or the surface of the hole-like defects.
6. The casting mold wall moves under the pressure of the molten metal, and the defects of the local swelling of the castings are formed. In order to prevent the expansion of sand, it is necessary to improve the sand-type strength, the rigidity of the sand box, the pressure box force or the fastening force of the box, and to reduce the pouring temperature, so that the metal liquid surface early crust, in order to reduce the metal liquid on the mold pressure.