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怎么预防压铸模具损坏

来源:    发布时间:2019-04-08 13:52:53    点击:

  一、造成压铸生产模具损坏的原因:
  1. Causes of die casting die damage:
  在压铸生产中,模具损坏比较常见的形式是裂纹、开裂。应力是导致模具损坏的主要原因。热、机械、化学、操作冲击都是产生应力之源,包括有机械应力和热应力,应力产生于:
  In die casting production, the most common form of die damage is cracking. Stress is the main cause of die damage. Thermal, mechanical, chemical and operational shocks are all sources of stress, including mechanical and thermal stresses, which arise from:
  (一).在模具加工制造过程中
  (1) In the process of mould manufacturing1、毛坯锻造质量问题
  1. Quality Problems of Blank Forging
  有些模具只生产了几百件就出现裂纹,而且裂纹发展很快。有可能是锻造时只保证了外型尺寸,而钢材中的树枝状晶体、夹杂碳化物、缩孔、气泡等疏松缺陷沿加工方法被延伸拉长,形成流线,这种流线对以后的然后的淬火变形、开裂、使用过程中的脆裂、失效倾向影响极大。
  Some dies produce only a few hundred pieces, and cracks develop rapidly. It is possible that the forging process only ensures the shape and size, while the dendritic crystals, inclusions of carbides, shrinkage holes, bubbles and other loose defects in steel are stretched along the processing method to form a streamline, which has a great impact on the final quenching deformation, cracking, brittle cracking and failure tendency in the use process.
  2、在车、铣、刨等终加工时产生的切削应力,这种应力可通过中间退火来消除。
  2. The cutting stress produced in turning, milling and planer finishing can be eliminated by intermediate annealing.
  3、淬火钢磨削时产生磨削应力,磨削时产生摩擦热,产生软化层、脱碳层,降低了热疲劳强度,容易导致热裂、早期裂纹。对h13钢在精磨后,可采取加热至510-570℃,以厚度每25mm保温一小时进行消除应力退火。
  3. Grinding stress occurs during grinding of quenched steel, friction heat occurs during grinding, softening layer and decarbonization layer occur, which reduces thermal fatigue strength and easily leads to hot cracking and early cracking. After finishing grinding, H13 steel can be heated to 510-570 (?) C and annealed for stress relief with a thickness of 25 mm for one hour.
  4、电火花加工产生应力。模具表面产生一层富集电极元素和电介质元素的白亮层,又硬又脆,这一层本身会有裂纹,有应力。电火花加工时应采用高的频率,使白亮层减到比较小,必须进行抛光方法去除,并进行回火处理,回火在三级回火温度进行。
  4. Stress produced by EDM. The die surface produces a white layer enriched with electrode elements and dielectric elements, which is hard and brittle. The layer itself will have cracks and stress. In order to minimize the white layer, the frequency should be used in EDM. The polishing method must be used to remove the white layer, and the tempering process must be carried out at the third tempering temperature.
  (二).模具处理过程中
  (2) Mould processing
  热处理不当,会导致模具开裂而过早报废,特别是只采用调质,不进行淬火,再进行表面氮化工艺,在压铸几千模次后会出现表面龟裂和开裂。
  Improper heat treatment will lead to die cracking and scrap prematurely. Especially, surface cracking and cracking will occur after thousands of die casting times, when only tempering, quenching and surface nitriding are used.
  钢淬火时产生应力,是冷却过程中的热应力与相变时的组织应力叠加的结果,淬火应力是造成变形、开裂的原因,固必须进行回火来消除应力。
  The stress produced during quenching of steel is the result of superposition of thermal stress in cooling process and microstructural stress in phase transformation. The quenching stress is the cause of deformation and cracking. The stress must be eliminated by tempering.
  (三).在压铸生产过程中
  (3) In the process of die casting production1、模温
  1. Mold temperature
  模具在生产前应预热到一定的温度,否则当高温金属液充型时产生激冷,导致模具内外层温度梯度增大,形成热应力,使模具表面龟裂,甚至开裂。
  Die should be preheated to a certain temperature before production, otherwise, when high temperature liquid metal filling, chilling will occur, leading to the increase of temperature gradient inside and outside the die, forming thermal stress, making the die surface crack, or even crack.
  在生产过程中,模温不断升高,当模温过热时,容易产生粘模,运动部件失灵而导致模具表面损伤。
  In the process of production, the temperature of the die keeps rising. When the temperature of the die is overheated, it is easy to produce viscous die. The failure of the moving parts results in the surface damage of the die.
  应设置冷却温控系统,保持模具工作温度在一定的范围内。
  The cooling temperature control system should be set up to keep the working temperature of the die within a certain range.
  2、充型
  2. Filling type
  金属液以高压、高速充型,必然会对模具产生激烈的冲击和冲刷,因而产生机械应力和热应力。在冲击过程中,金属液、杂质、气体还会与模具表面产生复杂的化学作用,并加速腐蚀和裂纹的产生。当金属液裹有气体时,会在型腔中低压区先膨胀,当气体压力升高时,产生内向爆破,扯拉出型腔表面的金属质点而造成损伤,因气蚀而产生裂纹。
  The filling of liquid metal at high pressure and high speed will inevitably produce intense impact and erosion on the die, resulting in mechanical stress and thermal stress. In the impact process, the metal liquid, impurities and gases will also have complex chemical interaction with the surface of the die, and accelerate the corrosion and crack generation. When the liquid metal is wrapped with gas, it will expand in the low pressure area of the cavity first. When the gas pressure rises, it will produce inward blasting, pull out the metal particles on the surface of the cavity and cause damage, resulting in cracks due to cavitation.
  3、开模
  3, mold opening
  在抽芯、开模的过程中,当某些元件有形变时,也会产生机械应力。
  In the process of core pulling and die opening, mechanical stress will also occur when some components are deformed.
  4、生产过程
  4. Production process
  在每一个压铸件生产过程中,由于模具与金属液之间的热交换,使模具表面产生周期性温度变化,引起周期性的热膨胀和收缩,产生周期性热应力。如浇注时模具表面因升温受到压应力,而开模顶出铸件后,模具表面因降温受到拉应力。当这种交变应力反复循环时,使模具内部积累的应力越来越大,当应力超过材料的疲劳极限时,模具表面产生裂纹。
  In each production process of die casting, due to the heat exchange between the die and liquid metal, periodic temperature changes occur on the die surface, resulting in periodic thermal expansion and contraction, and periodic thermal stress. For example, when casting, the die surface is subjected to compressive stress due to temperature rise, and when the die is ejected from the casting, the die surface is subjected to tensile stress due to temperature drop. When the alternating stress is repeated, the accumulated stress in the die becomes larger and larger. When the stress exceeds the fatigue limit of the material, the surface of the die will crack.
  二、预防模具损伤的措施:
  2. Measures to prevent mould damage:
  1.良好的铸件结构设计
  1. Good Casting Structure Design
  铸件壁厚尽可能均匀,避免产生热节,以减少模具局部热量集中产生的热疲劳。铸件的转角处应有适当的铸造圆角,以避免模具上有尖角位导致应力产生。
  The wall thickness of the castings is as uniform as possible to avoid hot spots, so as to reduce the thermal fatigue caused by local heat concentration of the die. Appropriate casting roundness should be provided at the corner of the casting to avoid the stress caused by sharp corners on the die.
  2.合理的模具结构设计
  2. Reasonable die structure design
  1)模具中各元件应有足够的刚度、强度,以承受压力而不变形。模具壁厚要足够,才能减少变形。
  1) Each component in the die should have sufficient stiffness and strength to withstand pressure without deformation. Die wall thickness should be enough to reduce deformation.
  2)浇注系统设计尽量减少对型芯冲击、冲蚀。
  2) The design of the gating system minimizes the impact and erosion on the core.
  3)正确选择各元件的公差配合和表面粗糙度。
  3) Correct selection of tolerance fit and surface roughness of each element.
  4)保持模具热平衡。
  4) Keep the thermal balance of the die.
  3.规范热处理工艺
  3. Standardize heat treatment process
  通过热处理可改变材料的金相组织,保证必要的强度、硬度、高温下尺寸稳定性、抗热疲劳性能和材料切削性能。
  The metallographic structure of the material can be changed by heat treatment to ensure the necessary strength, hardness, dimensional stability at high temperature, thermal fatigue resistance and cutting performance of the material.
  正确的热处理工艺,才会得到比较好的模具性能,而钢材的性能是受到淬火温度和时间、冷却速度和回火温度控制。
  Correct heat treatment process can get the best die performance, and the properties of steel are controlled by quenching temperature and time, cooling speed and tempering temperature.
  4.压铸生产过程控制
  4. Control of Die Casting Production Process1)温度控制:模具的预热温度和工作温度;合金浇注温度,在保证成型良好前提下,用较低的浇注温度。
                                         山东模具
  1) Temperature control: preheating temperature and working temperature of the die; casting temperature of the alloy, on the premise of ensuring good moulding, with a lower pouring temperature.
  2)合理的压铸工艺:比压、充填速度。
  2) Rational die casting process: specific pressure and filling speed.
  3)调整机器的锁模力,使模具受力均匀。注意清扫模具表面的残削碎片,以免合模时这些多余物使模具表面受力不均匀,引起变形。
  3) Adjust the clamping force of the machine to make the force of the die uniform. Attention should be paid to cleaning the debris on the surface of the die so as not to cause uneven force and deformation on the surface of the die when closing the die.
  4)对合金熔炼严格控制,减少金属液中气体。
  4) Strict control of alloy smelting and reduction of gas in liquid metal.
  5.模具的维护与保养
  5. Mould Maintenance and Maintenance
  1)定期消除应力
  1) Regular stress relief
  2)模具修补
  2) Die Repair
 
 
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