Classification analysis of spring requirements in the hardware mold industry
1, cold extrusion die
Cold extrusion is divided into positive extrusion, reverse extrusion and composite extrusion. The cold extrusion punch is subjected to a large dynamic load. To prevent the early fatigue failure of the mold, excessive stress concentration should be avoided, and the stability of the punch should be noted. The length to diameter ratio (L:D) of the punch should not be too large. When extruding steel, L: D ≤ 3: 1, extruded copper and its alloy L: D ≤ 5: 1, extruded aluminum and its alloy L: D ≤ 10: 1. When the stress on the mold exceeds σ0.2/2 of the material, the pre-stress ring should be added to the die, and the taper (0.5°~1°) or hot press fit (red sleeve) can be used between the die and the pre-stress ring.
Cold extrusion dies for low and medium carbon steels require high hardness (59 to 66 HRC), high compressive yield strength and appropriate toughness. Commonly used mold materials include Cr12MoV, Cr12Mo1V1, W6Mo5Cr4V2 steel and base steel. The inner prestressed ring is usually made of 4Cr5MoVSi and 4Cr5MoV1Si steel (46~48HRC), and the outer prestressed ring is usually made of 4Cr5MoVSi, 5CrNiMo and other steels.
2, aluminum alloy cold extrusion die
It can be made of steels such as T7A, T10A, Cr12, Cr12MoV, GCr15, 9SiCr and CrWMn.
Molds with good materials, correct structural design, good hot and cold processing, and reasonable heat treatment may still fail early in the service process due to improper adjustment and operation of the machine. Machine adjustment and operating factors include machine tool accuracy, rigidity, clearance adjustment, misalignment, and accidental overload. Taking these factors seriously will help to find out the real cause of mold failure. The large fluctuations in the life of the mold are often related to the adjustment and use of machine tools, and must be given enough attention.
3, cold die
Cold heading is a cold forging process in which part of the metal of the blank is machined into a specific cross-sectional shape by one or more impacts. The blank is mainly a wire or a bar. Cold heading is widely used to produce fasteners such as screws and rivets. Suitable materials for cold heading are low carbon steel wire or bar (75-78HRB), copper and copper alloy, aluminum and aluminum alloy, stainless steel and medium carbon steel wire with less than 0.44% carbon (spheroidizing annealing). The cold die is divided into a punch (or hammer) and a die. The die has an integral die and an open die. The die can be made of one material or two materials. The cavity portion is made of different materials to form a die insert. The open die consists of two modules with a groove on the surface, and the two modules are combined to form a die. Slot the different surfaces of the module and then form a number of new slots by flipping the module.
The surface of the cold heading mold requires high hardness (≥60HRC), and the cold heading die of the hard material should be hardened as a whole to prevent collapse; under the premise of ensuring no collapse, in order to make the mold have sufficient toughness, prevent cracking, cold heading The hardness of the core of the mold is preferably 40 to 50 HRC.
The commonly used cold heading die steels are T10A, 9SiCr, 9Cr2, Cr12MoV, etc. The die inserts can be made of Cr12MoV, W6Mo5Cr4V2, WC (including 13% to 25% Co) and W18Cr4V steel. The punches with complex shapes and large impact can be used. Impact resistant steel 5CrW2Si, 60Si2Mn and base steel.