Continuous casting graphite mold
Mold is a basic process equipment used in industrial production, and the mold industry is the basic industry of the national economy. In modern industrial production, the product parts are widely used in stamping, forging forming, die casting, extrusion forming, plastic injection or other forming processing methods, and matching with the forming mold to form the blank into parts that meet the requirements of the product. The tools and products we use in daily production and life range from the base of the machine tool to the outer casing of the machine, to a small screw, button and shell of various household appliances, all of which have a close relationship with the mold. The shape of the continuously cast graphite mold determines the shape of these products, and the quality and precision of the molds determine the quality of these products. In recent years, the mold industry has developed rapidly. Graphite materials, new processes and increasing mold factories continue to impact the mold market. Continuous casting of graphite molds has gradually become the material of choice for mold making with its good physical and chemical properties.
? ?1. Excellent thermal and electrical conductivity;
? ?2. Low thermal expansion coefficient and thermal shock resistance; 3. Chemical resistance is difficult to react with most metals;
? ?4. At high temperatures (above most copper matrix carcass sintering temperatures above 800 ° C) the strength increases with increasing temperature;
? ?5. Has good lubrication and wear resistance;
? ?6. Easy to process, good machining performance, can be made into a mold with complex shape and high precision.
? Application of graphite mold:
? ? ?1. Graphite Mold for Continuous Casting and Semi-Continuous Casting of Non-Ferrous Metals: In recent years, advanced production methods such as direct or continuous (or semi-continuous) manufacture of rods or pipes by molten metal state are being promoted at home and abroad. Domestically, this method has been adopted in copper, copper alloy, aluminum, and aluminum alloy. Artificial graphite is considered to be the most suitable material for continuous casting or semi-continuous casting of non-ferrous metals. Production practice proves that due to the use of graphite mold, because of its good thermal conductivity (thermal conductivity determines the solidification speed of metal or alloy), the self-lubricating properties of the mold and other factors not only improve the speed of the mold, but also the size of the ingot Accurate, smooth surface, uniform crystal structure, can be directly processed in the next process. This not only greatly improves the yield, reduces the loss of waste, but also greatly improves the quality of the product. Continuous casting methods include vertical continuous casting and horizontal continuous casting.
? ? ?2. Die for Pressure Casting: Artificial graphite materials have been successfully used for pressure casting of non-ferrous metals. For example, castings of zinc alloys and copper alloys produced by a mold for pressure casting made of artificial graphite materials have been used for automotive parts and the like.
3. Graphite mold for centrifugal casting: Graphite mold has been successfully applied to centrifugal casting. The United States has used artificial graphite molds with a wall thickness of 25 mm or more to centrifugally cast bronze casings. In order to prevent the burning of the artificial graphite mold, certain anti-oxidation measures can be taken. After casting a certain number of castings, if the inner surface of the mold is found to be burnt, the inner hole of the mold can be enlarged to be used for casting a large-sized sleeve.
4. Hot pressing die: The artificial graphite hot pressing die has the following characteristics for the pressure sintering of cemented carbide: First, if the pressing temperature is increased to 1350-1450 degrees, the required unit pressure can be reduced to 67-100 kg/cm2 (that is, 1/10 of the cold pressing pressure); second, pressurization and heating are carried out in the same process, and a compact sintered body can be obtained by short-time sintering.
?5. Mold for glass forming: Since graphite material has chemical stability, it is not easily infiltrated by molten glass, does not change the composition of glass, graphite material has good thermal shock resistance, and its size changes little with temperature, so it has been in glass in recent years. It is an indispensable mold material in manufacturing, which can be used to make glass tubes, elbows, funnels and other various types of shaped glass bottles.
? ? ?6. Sintered molds and other diamond sintered molds: The use of artificial graphite materials with extremely small thermal deformation, the manufacture of sintered molds and supports for transistors has been widely used, and it has become an indispensable material for the development of the semiconductor industry. In addition, graphite molds are also used in cast iron molds, durable molds for various non-ferrous metals, cast steel molds, molds for heat-resistant metals (titanium, zirconium, molybdenum, etc.) and aluminum for welded rails. Heat-welded type of mold, etc. The graphite die for hot-pressed sintered diamond tools plays the dual role of heating elements and mold support in the manufacturing process of diamond tools. The quality of graphite molds directly affects the dimensional accuracy and appearance of diamond tools.
? ? ?Hot pressing sintering process requirements: temperature reaches (1000 ± 2) ° C, molding pressure 16 ~ 50MPa, holding pressure holding time is 15 ~ 30min, the environment is non-vacuum state. Under this working condition, the graphite mold which requires molding and heating elements has conductivity, high electrical resistivity, sufficient mechanical strength, and good oxidation resistance and long service life to ensure diamond. The dimensional accuracy and superior performance of the tool. At present, graphite mold materials for diamond tool manufacturing in western developed countries are mainly ultrafine particle structures, high purity and high graphitization graphite materials, and the average particle size is required to be less than 15 μm or even 10 μm, and the medium pore size is less than 2 μm. The graphite mold made of the carbon material has small porosity, compact structure, high surface smoothness and strong oxidation resistance, and the average service life can reach 30 to 40 times. The diamond mold requires high hardness, good oxidation resistance and high processing precision. The use of high-quality graphite raw materials greatly prolongs the service life of the mold and improves the oxidation resistance.