Die casting mold finishing process

A die-casting mold is made up of a large number of parts, the quality of the parts directly affect the quality of the mold, and the final quality of the parts is finished by the finishing to ensure that the control of finishing the relationship between the major.
In most of the domestic die-casting mold manufacturing enterprises, finishing the method used in general grinding, electrical processing and fitter processing. At this stage to control the parts deformation, internal stress, shape tolerance and dimensional accuracy and many other technical parameters, in the specific production practice, the operation more difficult, but there are still many effective experience is worth learning.

1. Die-casting mold finishing process control
Die casting mold parts processing, a general guiding ideology is for different materials, different shapes, different technical requirements for adaptive processing, it has a certain plasticity, through the control of processing, to achieve good processing results.
According to the appearance of different parts of the shape, the parts can be divided into three categories: shaft, plate and shaped parts, the common process is roughly: rough processing - heat treatment (quenching, quenching and tempering) Processing - fitter (surface treatment) - with processing.

2. Parts heat treatment
Parts of the heat treatment process, so that parts required to obtain the required hardness at the same time, the need for internal stress control to ensure that the size of parts processing stability, different materials have different treatment. With the development of mold industry in recent years, the use of the types of materials increased, in addition to Cr12, 40Cr, Cr12MoV, carbide, the work of some of the high strength, stress harsh convex, die, optional new material powder alloy steel , Such as V10, ASP23, etc., such materials have a high thermal stability and good state of the organization.
For Cr12MoV as the material of the parts, after the roughing of the quenching process, quenching after the workpiece there is a lot of retention stress, easily lead to finishing or working in the crack, parts quenching should be hot after tempering to eliminate quenching stress. Quenching temperature control at 900-1020 ℃, and then cooled to 200-220 ℃ baked air-cooled, followed by rapid return 220 ℃ tempering, this method is called a hardening process, you can get a higher strength and wear resistance, for wear As the main failure form of the mold effect is better. Production encountered some corner of the more complex shape of the workpiece, tempering is not enough to eliminate the quenching stress, finishing before the need for stress annealing or multiple aging treatment, the full release of stress.
For V10, APS23 and other powder alloy steel parts, because it can withstand high temperature tempering, quenching can be used secondary hardening process, 1050-1080 ℃ quenching, and then high temperature tempering at 490-520 ℃ and carried out several times, you can get more High impact toughness and stability, to chipping the main form of failure for the mold is very applicable. The cost of powder alloy steel is higher, but its performance is good, is the formation of a wide range of trends.

3. Grinding of parts
There are three main types of machine tools for grinding: surface grinder, internal and external grinder and tool abrasive. Finishing grinding to strictly control the grinding deformation and grinding cracks, even a very small crack, in the subsequent processing will be used to reveal. Therefore, the grinding of the feed to be small, not large, coolant to full, size tolerance within 0.01mm parts to try to constant temperature grinding. It can be seen from the calculation, 300mm long steel parts, the temperature difference of 3 ℃, the material has about 10.8μm change, 10.8 = 1.2 × 3 × 3 (per 100mm deformation of 1.2μm / ℃), the finishing process must be fully considered this A factor of influence.
Fine grinding when the choice of a good grinding wheel is very important for high-molybdenum steel mold high molybdenum situation, the choice of GD single crystal corundum grinding wheel is more applicable, when processing carbide, quenching high hardness of the material, the preferred use of organic bonding In recent years, with the application of new materials, CBN grinding wheel, that is, cubic boron nitride grinding wheel show that the diamond grinding wheel, organic binder grinding wheel self-grinding, grinding out the workpiece rough up to Ra = 0.2μm, Very good processing effect, in the NC molding mill, coordinate grinding machine, CNC internal and external grinder finishing, the effect is better than other types of grinding wheel. Grinding, we should pay attention to the timely repair of grinding wheel, to maintain the sharp wheel, when the wheel passivation, the workpiece surface will be rubbed, squeezed, causing the workpiece surface burns, reduced strength.
Most of the processing of plate parts using surface grinding machine processing, often encountered in the processing of a long thin sheet parts, such parts of the processing more difficult. Because the processing, the magnetic force in the adsorption, the workpiece deformation, close to the table surface, when you get the workpiece, the workpiece will produce a return to deformation, consistent thickness measurement, but parallelism can not meet the requirements, Can be used magnetic grinding method, grinding to the contours of the block in the workpiece below the four-dimensional block to death, processing a small infeed, multi-beam knife, processing a good side, no longer pad and other high block, direct adsorption processing , Which can improve the grinding effect, to achieve parallelism requirements.