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Due to the special nature of large stamping parts such as car covers, the primary components of car cover stamping molds (hereinafter referred to as molds) are large or even super large castings. The length, width, and weight of each individual component of the mold are generally over 2 X 2 meters and 3 tons, respectively. Some large body parts such as stretching molds, trimming and punching molds, such as truck door frames, bus roof covers, and overall side panels of sedans, can reach a length, width, and width of over 4 X 3 meters. The weight of individual components such as convex molds, concave molds, press rings, and upper and lower bottom plates of the mold exceeds 10 tons, making it a difficult and technically challenging large-scale, super large investment casting in the casting industry. At the moment, these large castings usually adopt the process of making full mold with foam first and then investment casting. Once casting defects occur, the castings will be scrapped, and the loss is not only the various costs and material costs in the casting process, but also the production costs of foam full mold (now multiple integrated layered numerical control, high machining costs), and the more profound impact on the entire mold cost and delivery date, which has very serious consequences. Therefore, to reduce the occurrence of casting waste, reasonably reduce the mold cost, it is necessary to correctly select pig iron materials, and reasonably preset the mold casting structure according to the casting performance and mechanical properties of various pig iron materials.
The common materials for mold castings are as follows:
1. Molybdenum chromium pig iron MTMoDr (Japanese trademark GM241, French trademark FGL240HB)
It belongs to a type of high chromium white cast iron in the nickel hard white cast iron system. Due to its eutectic structure consisting of M7D3 type carbides and other austenite transformations, its matrix can exhibit high wear resistance after annealing into martensite. At the same time, the alloy elements such as molybdenum, manganese, and copper contained in it can effectively improve its hardenability, and the hardness after quenching is HRD 50 or above. Based on the above performance, it is very suitable for drawing convex dies and pressing rings (commonly used for inner surface parts and outer surface parts made of alloy QT600, as described in detail later); For areas where high wear resistance is required for surface cutting such as flanged plastic molding material boards and integral casting large convex molds (without trimming), the author has previously selected this material for three sets of wheel cover drawing molds, convex molds, concave molds, and pressing rings. Due to its good castability, mature casting process, and limited material requirements for mold structure, and moderate (10000/ton, 2006.10, RMB) heat treatment punishment conditions: annealing+flame surface quenching, hardness performance: HRD50-55 Note: (Drawing forming is essentially achieved by the pressure generated by the slider on the press and the pressure generated by the press support rod acting simultaneously on the concave die and the press ring, causing the edge of the metal sheet sandwiched between the two to experience frictional force from the combination of the concave die and the press ring, resulting in a slightly unsightly internal "normal flow" of the sheet metal. At the same time, the middle part of the sheet metal is subjected to the forming force of the convex die and undergoes permanent normal deformation according to the shape of the convex die, becoming the desired part shape. Nowadays, with a production volume of up to 200000 to 300000 parts, the wear resistance of the mold material is very important for the entire production cycle of the part.)
2. Grey pig iron HT250, HT300 (Japanese trademark FD250, FD300, French trademark FGL215HB
Gray mouthed pig iron is a common type of pig iron, primarily used in molds for components such as upper and lower base plates that do not directly participate in molding. It has good casting performance and is not limited by mold structure. Its mechanical properties are also good, and it is cheap (5600/ton)
3 ductile iron QT600 QT700 QT800 (Japanese trademarks FDD55, FDD70, French trademark FGL240HB)
Ductile iron, commonly used in molds, is a pearlite ductile iron with pearlite as the matrix and ferrite as the remainder. It has high strength and hardness, as well as certain toughness and good wear resistance, making it particularly suitable for parts that can withstand heavy loads and friction wear. The number after QT represents the tensile strength of this type of ductile iron. The higher the number, the better the strength of the castings produced. As molds are often only subjected to static loads, alloys QT700 and QT800 are sufficient to replace cast steel materials when used as mold materials to reduce costs. Due to its superior performance, ductile iron is commonly used in molds for the pressing ring of drawing dies, the pressing plate of convex dies and trimming dies, as well as the upper and lower bottom plates, which have poor mechanical properties due to the mold structure. However, due to the significant shrinkage of ductile iron during the casting process, slight unevenness in wall thickness can lead to casting defects such as shrinkage porosity and loose holes, and can also cause the casting to be scrapped under tension. Therefore, attention should be paid to the preset mold structure to maintain a uniform wall thickness and a smooth transition between thick and thin areas. To achieve a hardness of HRD50-55 after annealing and flame quenching, QT600 needs to be added with alloying elements such as molybdenum, copper, nickel, chromium, and tungsten, as well as trace elements such as Ti, Bs, Pb, BL, Dr, Sn, and Sb during casting, in order to improve its wear resistance. Therefore, its production cost is much higher than ordinary QT600, which is only used to enhance mechanical properties and does not require high wear resistance. For example, when producing upper and lower base plates with poor strength but not directly involved in forming, alloying elements do not need to be added, and its production cost will naturally decrease significantly. When using QT600, it is important to distinguish casting conditions, such as whether alloy elements need to be added. The author once designed a set of drawing dies with a split structure for the convex die, and the lower base plate does not include the profile. The length by width is 3.2X 2.5m, but the thickness is only 160mm in large areas. The HT300 was used at the beginning, but considering that the thickness of the base plate is relatively thin and there are many hollow holes such as support rods in the middle, the strength is not good enough. However, the entire casting wall thickness is relatively uniform, so it is changed to QT600. The heat treatment penalty is to retreat (without adding alloy elements), and its strength will be much better than the previous HT300, but only increased by 1550 X 4=6200 yuan. However, if the alloy elements are not distinguished and added incorrectly, it will increase the basis of 6200 yuan. We need to increase the material cost by nearly ten thousand yuan again!! Compared to QT600, QT700 has better performance, but due to casting reasons, its usage is relatively more than double (ordinary QT600 7500/ton, alloy QT700 13600/ton). Alloy QT700 has similar performance to cast steel, but is cheaper and has a shorter casting cycle. Therefore, it is commonly used in high-strength components in molds, such as the pressure plate of the flanging mold plastic mold, large convex molds that require cast steel materials (such as ZDH-1 air-cooled steel). (Note: QY700 is all alloy QT700) Currently, QT800 cannot be used by domestic casting manufacturers to produce large castings. They need to place orders with casting factories in South Korea, Japan, and other countries. Therefore, they do not consider using QT700 or other cast steel materials after consultation with customers. The above are three common types of mold casting materials. In the increasingly competitive and profit reducing mold industry, choosing the right casting material is a very useful way to reasonably reduce costs.
The common materials for mold castings are as follows:
1. Molybdenum chromium pig iron MTMoDr (Japanese trademark GM241, French trademark FGL240HB)
It belongs to a type of high chromium white cast iron in the nickel hard white cast iron system. Due to its eutectic structure consisting of M7D3 type carbides and other austenite transformations, its matrix can exhibit high wear resistance after annealing into martensite. At the same time, the alloy elements such as molybdenum, manganese, and copper contained in it can effectively improve its hardenability, and the hardness after quenching is HRD 50 or above. Based on the above performance, it is very suitable for drawing convex dies and pressing rings (commonly used for inner surface parts and outer surface parts made of alloy QT600, as described in detail later); For areas where high wear resistance is required for surface cutting such as flanged plastic molding material boards and integral casting large convex molds (without trimming), the author has previously selected this material for three sets of wheel cover drawing molds, convex molds, concave molds, and pressing rings. Due to its good castability, mature casting process, and limited material requirements for mold structure, and moderate (10000/ton, 2006.10, RMB) heat treatment punishment conditions: annealing+flame surface quenching, hardness performance: HRD50-55 Note: (Drawing forming is essentially achieved by the pressure generated by the slider on the press and the pressure generated by the press support rod acting simultaneously on the concave die and the press ring, causing the edge of the metal sheet sandwiched between the two to experience frictional force from the combination of the concave die and the press ring, resulting in a slightly unsightly internal "normal flow" of the sheet metal. At the same time, the middle part of the sheet metal is subjected to the forming force of the convex die and undergoes permanent normal deformation according to the shape of the convex die, becoming the desired part shape. Nowadays, with a production volume of up to 200000 to 300000 parts, the wear resistance of the mold material is very important for the entire production cycle of the part.)
2. Grey pig iron HT250, HT300 (Japanese trademark FD250, FD300, French trademark FGL215HB
Gray mouthed pig iron is a common type of pig iron, primarily used in molds for components such as upper and lower base plates that do not directly participate in molding. It has good casting performance and is not limited by mold structure. Its mechanical properties are also good, and it is cheap (5600/ton)
3 ductile iron QT600 QT700 QT800 (Japanese trademarks FDD55, FDD70, French trademark FGL240HB)
Ductile iron, commonly used in molds, is a pearlite ductile iron with pearlite as the matrix and ferrite as the remainder. It has high strength and hardness, as well as certain toughness and good wear resistance, making it particularly suitable for parts that can withstand heavy loads and friction wear. The number after QT represents the tensile strength of this type of ductile iron. The higher the number, the better the strength of the castings produced. As molds are often only subjected to static loads, alloys QT700 and QT800 are sufficient to replace cast steel materials when used as mold materials to reduce costs. Due to its superior performance, ductile iron is commonly used in molds for the pressing ring of drawing dies, the pressing plate of convex dies and trimming dies, as well as the upper and lower bottom plates, which have poor mechanical properties due to the mold structure. However, due to the significant shrinkage of ductile iron during the casting process, slight unevenness in wall thickness can lead to casting defects such as shrinkage porosity and loose holes, and can also cause the casting to be scrapped under tension. Therefore, attention should be paid to the preset mold structure to maintain a uniform wall thickness and a smooth transition between thick and thin areas. To achieve a hardness of HRD50-55 after annealing and flame quenching, QT600 needs to be added with alloying elements such as molybdenum, copper, nickel, chromium, and tungsten, as well as trace elements such as Ti, Bs, Pb, BL, Dr, Sn, and Sb during casting, in order to improve its wear resistance. Therefore, its production cost is much higher than ordinary QT600, which is only used to enhance mechanical properties and does not require high wear resistance. For example, when producing upper and lower base plates with poor strength but not directly involved in forming, alloying elements do not need to be added, and its production cost will naturally decrease significantly. When using QT600, it is important to distinguish casting conditions, such as whether alloy elements need to be added. The author once designed a set of drawing dies with a split structure for the convex die, and the lower base plate does not include the profile. The length by width is 3.2X 2.5m, but the thickness is only 160mm in large areas. The HT300 was used at the beginning, but considering that the thickness of the base plate is relatively thin and there are many hollow holes such as support rods in the middle, the strength is not good enough. However, the entire casting wall thickness is relatively uniform, so it is changed to QT600. The heat treatment penalty is to retreat (without adding alloy elements), and its strength will be much better than the previous HT300, but only increased by 1550 X 4=6200 yuan. However, if the alloy elements are not distinguished and added incorrectly, it will increase the basis of 6200 yuan. We need to increase the material cost by nearly ten thousand yuan again!! Compared to QT600, QT700 has better performance, but due to casting reasons, its usage is relatively more than double (ordinary QT600 7500/ton, alloy QT700 13600/ton). Alloy QT700 has similar performance to cast steel, but is cheaper and has a shorter casting cycle. Therefore, it is commonly used in high-strength components in molds, such as the pressure plate of the flanging mold plastic mold, large convex molds that require cast steel materials (such as ZDH-1 air-cooled steel). (Note: QY700 is all alloy QT700) Currently, QT800 cannot be used by domestic casting manufacturers to produce large castings. They need to place orders with casting factories in South Korea, Japan, and other countries. Therefore, they do not consider using QT700 or other cast steel materials after consultation with customers. The above are three common types of mold casting materials. In the increasingly competitive and profit reducing mold industry, choosing the right casting material is a very useful way to reasonably reduce costs.
