Posted 28 Dec 2010 23:25
Gray cast iron is a consumer good shock resistance, wear resistance, mechanical properties and casting performance, cast iron and low cost birth, in the casting is widely used. To get qualified casting blank, subject to grind sand - modeling - melting - casting - clean - test such links, to ensure the quality of casting has to control all aspects of casting process. First, the grinding process control sand sand performance will directly affect the quality of the casting, therefore, the sand should have good air permeability, wet strength, mobility, plasticity, and yield and so on. Size should be used in green sand 55/1O0, 75/150, 100/200 polygonal or round natural stone sand, so you can get better strength and sand of the surface. In the same clay content, bentonite clay than the average tensile strength of high heat and moisture. Type of clay in the wet sand by adding an appropriate amount of pulverized coal, sawdust, etc., can improve the ability of anti-sand and prevent sand, sand and get sticky and smooth surface castings. Sand as the water about 6% to make it a better overall performance. Strict accordance with the charging order: Sand - New sand - clay - coal - water. The mixing time set at 6 ~ 7min, about 5h after the mixing around and mix thoroughly. Mix thoroughly after the screening, playing loose and then used to make a loose sand to improve permeability, mobility. Second, the melting process control production gray iron casting, the furnace must be strictly controlled and the people who package the quality of materials, their composition, degree of physical and chemical properties of the block to be required for inspection and acceptance. Birth is a flake graphite cast iron gray cast iron, cast iron is different manufacturing principles with the general increase of breeding process. In the low-carbon, silicon content of hot metal in the amount of inoculant added to suppress the excessive graphite. In general, the original carbon content of molten iron at 2.8 to 3.0%, and the low carbon iron birth, adding more people to charge a sufficient number of scrap. Silicon content of 0.9 ~ 1.5%, in order to increase the added amount of inoculant to improve the mechanical properties of castings. Sulfur, manganese 0.08 to 0.12%, respectively, and 0.9 to 1.2% range, if the manganese content is too high, appeared cementite in cast iron. Phosphorus content of less than 0.12%, if their content will affect the casting strength. Third, the modeling process control modeling casting process control is the key to the process of generating a direct impact on the quality of the casting. Major attention to the following aspects: 1) appearance: appearance is the main casting production technology and equipment, is the first casting process, while ensuring the geometry. Should also consider the scale of production and ease of use. First, in the production process is the process to consider the structure and performance. On the one hand to improve productivity, on the other hand to ensure quality. In the course look like to test the integrity, to ensure defect-free use. If there are defects repaired before we can use to go through. To the attention of percussion from the intensity model, aluminum block to pad the percussion mode to reduce the extent of the damage aluminum mold. 2) reasonable process: the operator must operate in strict accordance with process, the calendar looks like manufacturers seeking to make casting simple structure, so that the small number of sub-surface, with Taper Angle, sand ****, few have a reasonable thickness , the connection must transition. Reasonable choice of gating system, the casting solidification, to obtain homogeneous castings. 3) co-box: a box is an important part can not be ignored, the floating sand mold surface should be cleaned up by mark on together, pay attention to the wrong container volume, is to reduce the casting an important means of partial boxes. 4), the ****: The next **** when smooth, clean floating sand. The location of the sand **** in case you want to put a good partial **** generation. 5) Drying: The drying process of dry-mode shape, according to operating procedures to operate, drying time is more than 8h to prevent drying opacity caused by sand, porosity and other defects. Fourth, control of casting process for the above link, you can be casting. Cast before pouring water on the breeding and slag processing. In the casting process to keep current, stable, to avoid the formation of red sand and trachoma. Running time the fire blocked the drain when the water casting parts, and make up the cast in water, to reduce the cooling compartment, lack of water and other defects. V. control the liquidation process after the cleaning process is the casting cooled casting from the mold in the clean-up in order to obtain defect-free surface of the castings. (1) falling sand: cast must be cast to cool to Bachu and generally require no less than 3h. If time is too short, will occur leaving the surface hardness of cold shock caused by cutting difficult. Casting may produce large thermal cracking stress is large castings, could easily lead to deformation of casting dimensions. (2) sand: To obtain a good casting surface finish, small pieces of live drum removed by cleaning the surface of the sand. Great deal of live parts for shot blasting to remove the surface of the sand. Non-processed surface of the sticky sand must be clean, to prevent the movement into the finished product, after falling into the bearing interior, and adversely affect the use of bearings. (3) aging: general aging of castings should be carried out to reduce the stress of the castings to obtain good performance. (4) testing process control: By inspection, feedback casting defects, find and analyze the causes and take timely measures to reduce casting defects. Control through the above links to make casting a qualified product, requires that each process of mutual cooperation and mutual coordination, only pay attention to detail in order to better control and improve the quality of each process, to ensure the quality of castings.