Knowledge of Graphite Mold
In recent years, the mold industry has developed rapidly. Graphite materials, new processes and increasing mold factories continue to impact the mold market. Graphite has gradually become the material of choice for mold making with its good physical and chemical properties.
Introduction of 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 our daily production and life range from the base of the machine tool to the outer casing of the machine. It is small enough to have an embryo screw, a button and a shell of various household appliances, all of which have a close relationship with the mold. The shape of the mold determines the shape of these products, and the quality and precision of the mold determines 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. Graphite has gradually become the material of choice for mold making with its good physical and chemical properties.
Excellent performance
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-based 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 complex shape, high precision mold
7. Widely used in continuous and semi-continuous casting of non-ferrous metals
8. Graphite formation type is fast, the size is accurate, the surface is smooth, the crystal structure is uniform, and the scrap rate is low.
Application
At present, graphite molds have been widely used in the following aspects:
Graphite mold for continuous casting and semi-continuous casting of non-ferrous metals
In recent years, advanced production methods such as the production of rods or pipes directly and continuously (or semi-continuously) from the state of molten metal 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.
Pressure casting mold
Artificial graphite materials have been successfully used in pressure casting of non-ferrous metals. For example, zinc alloys and copper alloy castings produced by a pressure casting mold made of an artificial graphite material have been used for automotive parts and the like.
Graphite mold for centrifugal casting
Graphite molds have 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.
Hot pressing die
The artificial graphite hot press 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 dense sintered body can be obtained by sintering for a short time.
Glass forming mold
Because graphite material has chemical stability, it is not easy to be 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 become an indispensable mold in glass manufacturing in recent years. Material, which can be used to make glass tubes, elbows, funnels and other molds for various shaped glass bottles.
Sintered die and other diamond sintering 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 molds, 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. The hot pressing sintering process requires: the temperature reaches (1 000±2) °C, the molding pressure is 16~50 MPa, the holding pressure is 15~30 min, and the environment is non-vacuum. 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.
Processing technology
First of all, it is designed by the mold designer according to the requirements of the product (parts), the mold structure is designed, the drawings are drawn and then processed by the skilled workers according to the drawings (such as lathes, planers, milling machines, grinding machines, electric sparks, Various equipment such as wire cutting) Make each part on the mold and assemble and debug it until it can produce a qualified product.
Status and development
Today, the graphite mold industry plays a vital role in the life and development of human beings. The development of many industrial sectors (such as electromechanical, automotive, home appliance light industry, electrical instrumentation, communication, ordnance, etc.) depends on the technological improvement and development of the mold industry. All countries in the world have invested a lot of human and financial resources to develop the graphite mold industry. Sikri, like Germany, and Japan's Toyo Carbon have taken a leading position in the international graphite mold industry. China also attaches great importance to the development of the mold industry. The level of mold production technology has become an important indicator to measure the level of product manufacturing in a country, because the mold determines the quality, efficiency and development ability of new products to a large extent. . Since 1997, China's relevant departments have begun to attach importance to and support the development of the graphite mold industry, and vigorously foster the development of Chinese local enterprises in the graphite mold industry. Now they have achieved good results and contributed to China's export foreign exchange earnings. For the future development trend of the mold industry, who can complete the mold production in the shortest time, who won the customer and won the market. Graphite molds (graphite electrodes) have established an important leading position and future development trend in the mold industry due to their superior performance in all aspects.
